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The Dark Side of Extracellular ATP in Kidney Diseases

† †‡ Anna Solini,* Vera Usuelli, and Paolo Fiorina

*Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy; †Division of Transplant Medicine, San Raffaele Hospital, Milan, Italy; and ‡Nephrology Division, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts

ABSTRACT Intracellular ATP is the most vital source of cellular energy for biologic systems, unknown, signaling function on the whereas extracellular ATP is a multifaceted mediator of several cell functions via its cell membrane, by binding and activat- interaction, in an autocrine or paracrine manner, with P2 purinergic receptors ing membrane-anchored ionotropic expressed on the cell surface. These ionotropic and metabotropic P2 purinergic P2X (P2XRs) and metabotropic P2Y receptors modulate a variety of physiologic events upon the maintenance of a highly (P2YRs), purinergic receptors that are sensitive “set point,” the derangement of which may lead to the development of key likely ubiquitous. The eight G protein– pathogenic mechanisms during acute and chronic diseases. Growing evidence sug- coupled P2YRs (P2Y1,P2Y2,P2Y4,P2Y6, gests that extracellular ATP signaling via P2 purinergic receptors may be involved in and P2Y11–P2Y14)areactivatedbya different renal pathologic conditions. For these reasons, investigators and pharma- range of native agonists (e.g., ATP, ADP, ceutical companies are actively exploring novel strategies to antagonize or block UTP, and UDP). Aside from the crucial these receptors with the goal of reducing extracellular ATP production or acceler- role exerted by P2Y12 in platelet aggre- ating extracellular ATP clearance. Targeting extracellular ATP signaling, particularly gation, the targeting of which has yielded 8 through the P2X7 receptor, has considerable translational potential, given that novel successful therapeutic strategies, addi- fl P2X7-receptor inhibitors are already available for clinical use (e.g., CE224,535, tional functions of P2Y12 (e.g., in uenc- AZD9056, and GSK1482160). This review summarizes the current evidence regard- ing microglial motility and stimulating ing the involvement of extracellular ATP and its P2 purinergic receptor–mediated ciliary movement and secretion of epi- signaling in physiologic and pathologic processes in the kidney; potential therapeu- thelial cells) have been discovered.9 In tic options targeting extracellular ATP purinergic receptors are analyzed as well. addition to the activation of purinergic signaling, the effect of extracellular ATP J Am Soc Nephrol 26: 1007–1016, 2015. doi: 10.1681/ASN.2014070721 (eATP) relies upon the activity of ecto- nucleotidases (e.g., CD39 and CD73), which deg rade eATP to ADP, AMP, ATP is the most important source of small fraction of ATP is released from and adenosine, all of which are capable energy for intracellular reactions,1 in- the cells into the extracellular space themselves of exerting P1R- and 10 cluding synthesis and degradation of bi- through a series of finely tuned pro- P2R-mediated functions. The P2XRs ologic molecules, muscle contraction, cesses. For instance, in nonexcitable (ligand-gated ion channels), of which fi and membrane transport.2 Intracellular cells, ATP release occurs through exocy- sevenhavebeenidenti ed thus far – ATP (iATP) levels, which are regulated tosis, ion channels, gap junction hemi- (P2X1 P2X7), bind ATP as their princi- by mitochondrial oxidative phosphory- channels, nucleotide transporters, and pal ligand and are involved in a variety of lation,3 reflect cell activity and viability, the cystic fibrosis transmembrane con- and a decline in iATP levels is associated ductance regulator.7 The extracellular A.S and V.U. contributed equally to this work. with cell death.4 ATP is then exported releaseofATPcanbetriggeredbya from the mitochondrial matrix to the wide range of stimuli such as mechanical Published online ahead of print. Publication date cytoplasm, across the inner mitochon- stress, cell membrane damage, inflam- available at www.jasn.org. drial membrane by the ADP/ATP carrier mation, hypoxia, and excitation of neu- Correspondence: Dr. Paolo Fiorina, Division of protein.3 The release of cytoplasmic ATP ral tissue, and by cell growth and death.7 Nephrology, Boston Children’sHospital,Harvard Medical School, 300 Longwood Avenue, Enders occurs as a physiologically regulated Although the concentration of ATP ex- Building, Fifth Floor, Room En511, Boston, MA mechanism; indeed, ATP, given that it tracellularly is 1000-fold lower com- 02115. Email: paolo.fi[email protected] is a highly charged molecule, does not pared with the intracellular space, it Copyright © 2015 by the American Society of cross the plasma membrane.5,6 Only a can still exert precise, albeit partially Nephrology

J Am Soc Nephrol 26: 1007–1016, 2015 ISSN : 1046-6673/2605-1007 1007 BRIEF REVIEW www.jasn.org biologic responses, mainly related to based on mRNA expression, which does renal tubular transport of solute and wa- inflammation, tissue damage and cell not necessarily imply an increased func- ter.24 In the thick ascending limb, ATP re- proliferation, and the graft-versus-host tional activity of these receptors. The lease may activate basolateral (via P2XRs) 10 response. Among these P2XRs, P2X7R lack of availability of adequate antibod- and luminal (via P2YRs) membrane and appears particularly intriguing due to its ies as well as the complexity of the P2R stimulate nitric oxide production, thus emerging role in NLRP3/ASC/caspase1 structure may have caused uncertainty regulating NaCl absorption25 and poten- inflammasome activation11,12 as well as in their immunohistochemical evalua- tially modulating the activity of the epi- its involvement in acute allograft rejec- tion. It can be also hypothesized that thelial sodium channel in the collecting tion.13 eATP-P2Rs signaling modulates some of these receptors, particularly duct26 (Figure 2). eATP may therefore several aspects of normal kidney function, P2X7R, are scarcely expressed in physio- control extracellular fluid volume status but it is also implicated in the develop- logic conditions but can be upregulated and BP,26,27 and maintenance of these reg- ment of renal damage during chronic dis- during inflammation. The localization ulatory functions appears to be performed eases such as diabetes and hypertension, of ionotropic and metabotropic recep- by the connexin 30 hemichannel (Cx30) as well as in inherited conditions includ- tors in the kidney is reported in Table 1. in the collecting duct.28 Cx30 knockout ing polycystic kidney disease (PKD), (KO) mice, with a salt retention pheno- although the precise mechanisms under- type in response to acute elevations in BP, lying the involvement of these receptors is EFFECTS OF eATP SIGNALING VIA have a reduced ability to excrete urinary not fully understood.14 The present re- PURINERGIC RECEPTORS salt and water.28 Interestingly, Cx30 KO view addresses the pathophysiologic roles mice showed reduced luminal ATPrelease exerted in the kidney by eATP and by P2 Effects on Renal Hemodynamics in vitro28 and in vivo,suggestingthat purinergic receptors. eATP exerts a fundamental role in the Cx30-dependent purinergic intracellular regulation of renal hemodynamics and calcium signaling may control the regula- microcirculation19 (Figure 2). For in- tion of salt and water reabsorption.29 THE eATP/P2Rs AXIS IN THE stance, the intrarenal infusion of ATP Consistent with the aforementioned ob- KIDNEY in canine kidneys in vivo produces vaso- servations, upon injection of ATP agonists dilation through P2XR and P2YR activa- (a,b-methylene ATP and b,g-methylene eATP Production in the Kidney tion and stimulation of endothelial ATP) into the femoral vein of rat, there is Sources of eATP in the kidney include release of nitric oxide.20 However, some an increase in diuresis and sodium excre- perivascular and peritubular nerve termi- studies suggest that eATP-mediated vaso- tion,30 while pyridoxalphosphate-6- nals, aggregating platelets, circulating ery- constriction may occur in juxtamedullary azophenyl-29,49-disulfonic acid (PPADS), throcytes, and resident endothelial and nephron preparations in vitro and that a nonselective P2 antagonist,30 abolished epithelial cells.15 In renal epithelial cells, de- eATP may induce preglomerular vasocon- this effect. In conclusion, taken together, rived from human nephron segments, ATP striction of afferent arterioles.21 Another these findings confirm that eATP has an release occurs in both the apical and baso- eATP-mediated effect on renal hemody- important role in the regulation of renal lateral membrane, with apical release pre- namics may stem from tubuloglomerular hemodynamics, salt, and water reabsorp- dominating.16 eATP has been also found in feedback, which is operated by the macula tion, thus contributing to the maintenance the interstitial fluid of canine renal cortex, densa. Indeed, macula densa releases of normal BP, body fluid, and electrolyte possibly released by macula densa cells in eATP in response to increased luminal balance (Figure 2). response to BP-induced changes in renal NaCl concentration, thus regulating the vascular resistance.17 The effective amount GFR and renal blood flow22 (Figure 2). Effects on Permeation of eATP found in the extracellular space Recent relevant contributions have iden- could be influenced by several factors, in- Effects on Tubular Transport tified and characterized P2YRs in podo- cluding the activity of the hydrolyzing en- Function cytes.31,32 eATP activates podocyte TRPC6 zymes ectoapyrases18 (Figure 1). Mechanical stimulation of renal tubules, Ca2+-permeable channels, thus influenc- either by cell swelling or by an increase in ing foot process effacement and subse- Expression of Purinergic Receptors tubular flow, promotes ATP release by quent changing in glomerular basement in the Kidney renal epithelial cells, which in turn acti- membrane permeability.33 Mechanical- eATP exerts effects on the kidney in vates P2 receptors in the apical and induced podocyte injuries appear to be both a paracrine and autocrine manner, basolateral membrane, thus modulating mediated, at least in part, by P2Rs, in- 23,24 32 via the activation of all P2Xs and some renal tubular transport. In the absence cluding P2Y2. P2Ys receptors.15 These receptors are ex- of fluid flow, primary cilium, expressed by pressed in the cortical and in the medul- renal epithelial cells, protrudes perpendic- Effects on Cell Proliferation and lary renal compartments14,15; however, ularly into the tubular lumen, while fluid Extracellular Matrix Deposition upon stringent analysis, some of these flow triggers cilium bending that elicits Extracellular nucleotides may regulate renal results appear controversial and mainly tubular release of eATP and inhibits the fibroblast proliferation and activity, thus

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hypertension by inducing a proinflam- matory setting, in addition to influenc- ing NaCl and water reabsorption.18,43,44 P2X7R KO mice were used to investigate the role of P2X7R in a deoxycorticoster- one acetate high-salt diet–induced hy- pertension murine model.43 Although P2X7R mRNA and protein expression increased after treatment in the kidney of wild-type mice, P2X7RKOmiceshowed reduced BP, renal injury, urinary albumin excretion, and renal interstitial fibrosis compared with controls43 (Table 2). Furthermore, a recent article suggested that CD73 and adenosine A2B receptor mRNA/protein and mRNA expression, re- spectively, were augmented in kidneys of angiotensin II–infused mice.45 Despite these interesting observations, very few human studies, mostly genetic, have thus Figure 1. The purinergic system in the glomerular cells. eATP has a short life depending on far explored the link between purinergic the activity of ectonucleotidases that degrade eATP to generate ADP, AMP, and adenosine. signaling and BP control. An association The purinergic receptors P2YR, P2XR, and P1R bind extracellular nucleotides and nu- between BPand the single nucleotide poly- cleosides, and their activation causes a cascade of signaling. Such an effect may promote fi cellular proliferation or apoptosis of mesangial cells. Ado, adenosine; PLC, phospholipase morphism rs591874 in the rst intron of 46 C; DAG, diacylglycerol; PKC, protein kinase C; IP3, inositol 1,4,5-triphosphate; AC, ad- the P2X7R gene was found (Table 2). enylate cyclase; PL, phospholipase. However, another study found no rela- tionship between two single nucleotide polymorphisms of the P2X7R gene, influencing fibroblast-to-myofibroblast adenosine) in mice have been found to be Glu496Ala and His155Tyr, and endothelial transformation, confirming the existence associated with more severe diabetic ne- function or arterial stiffness in essential hy- of an interesting P2R-mediated cross-talk phropathy.40 Increased eATP signaling via pertensive patients.47 Taken together, these 34,35 between epithelial cells and fibroblasts. P2X4R due to hyperglycemia induces acti- studies suggest that altered eATP signal- eATP also increases the proliferation of vation of the NLRP3 inflammasome, thus ing may contribute to hypertension by human mesangial cells, via P2YR-mediated stimulating IL-1b and IL-18 release, with controlling vascular tone and by favoring activation of the Ras-Raf-MAPK42/44 signal development of tubulointerstitial inflam- Na+ retention (Table 2). transduction pathway.36 mation41,42 (Table 2). Two studies revealed that in individuals with type 2 diabetes and GN diabetic nephropathy, P2X4R, P2X7R, and An increase in glomerular P2X7RmRNA PATHOLOGIC ROLE OF eATP IN NLPR3 are upregulated compared with and protein expression was observed in rat KIDNEY DISEASES controls, and that tubular P2X4Rexpres- and murine models of GN compared with sion colocalized in confocal analysis with controls, as well as in renal biopsies ob- Diabetic Nephropathy NLRP3, IL-1b, and IL-18 expression.12,41 tained from individuals with lupus ne- 48 Preclinical studies on the role of eATP This is in agreement with the results from phritis. P2X7Rdeficiency was shown to signaling in diabetic nephropathy are lim- in vitro studies in HK-2 cells, in which be renoprotective in an experimental ited by the lack of suitable murine models high-glucose challenge increased protein model of antibody-mediated GN, with 37,38 of the disease. In the CD39 (the main expression of NLRP3 and augmented the P2X7R KO mice displaying a reduction vascular ectonucleotidase)–null diabetic release of IL-1b and IL-1841 (Table 2). in glomerular thrombosis by 60%, in pro- mouse model, glomerulosclerosis is Thus, the activation of eATP signaling teinuria by 52% and in serum creatinine more severe than in age-matched diabetic may play a crucial role in the development by 38% compared with wild-type49 (Table wild-type animals, thus suggesting a pro- of diabetic nephropathy by enhancing in- 2). Renal expression of the P2X7/NLRP3 tective role against inflammation of this flammation. inflammasome pathway and IL-1b are eATP-hydrolyzing enzyme.39 More significantly increased in a mouse model recently, the genetic deletions of the Hypertension of lupus nephritis, and P2X7 inhibition adenosine A2B receptor and of CD73 Some studies have suggested that reduces immune complex deposition (a key enzyme that produces extracellular P2X7Rs may be relevant in the onset of in the kidneys as well as the levels of

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Table 1. P2XR and P2YR localization in the kidney Receptor Species RNA/Protein Renal Cell Reference

P2X1 Mouse Yes/no Medullary thick ascending limb, inner strip of outer medulla 72 Rat No/yes Vascular networks 73 Pig Yes/no Epithelial cell line (LLC-PK1) 74 Human Yes/no Mesangial cell culture 36

P2X2 Mouse Yes/no Inner strip of outer medulla 72 Human Yes/no Mesangial cell culture 36

P2X3 Mouse Yes/no Inner strip of outer medulla, inner medullary collecting duct cell line 72,75

P2X4 Mouse Yes/no Inner medullary collecting duct cell line, distal convoluted tubule 72,75,76 immortalized cells, inner stripe of the outer medulla, isolated tubules in medullary thick ascending limb Human Yes/no Mesangial cell culture 36

P2X5 Mouse Yes/no Distal convoluted tubule immortalized cells, inner stripe of the outer 72,76 medulla, isolated tubules in medullary thick ascending limb Human Yes/no Mesangial cell culture 36

P2X6 Human Yes/no Mesangial cell culture 36

P2X7 Mouse Yes/no Inner stripe of the outer medulla 72 Rat Yes/yes Mesangial cells and glomeruli 77 Madin-Darby canine Yes/yes Epithelial cells 78 Human Yes/no Mesangial cell culture 36

P2Y1 Mouse Yes/no Inner medullary collecting duct cells 75 Rat Yes/yes Podocytes, proximal convoluted tubule, descending and thin ascending 31,79 limb of Henle’s loop, outer medullary collecting duct Madin- Yes/no Epithelial cells 80 Darby canine Human Yes/no Mesangial cell culture, epithelial cell line (A498) 36,81

P2Y2 Mouse Yes/no Medullary thick ascending limb, inner stripe of the outer medulla, 72,76,82 distal convoluted tubule cells, cortical collecting duct cells Rat Yes/yes Proximal convoluted tubule, descending and thin ascending limb 68,77,79,83 of Henle’s loop, outer medullary collecting duct, mesangial cells and glomeruli, inner medulla collecting duct Human Yes/no Mesangial cell culture, epithelial cell line (A498) 36,81

P2Y4 Rat Yes/no Mesangial cells and glomeruli, proximal convoluted tubule, thin ascending 77,79 limb of Henle’s loop, outer medullary collecting duct Human Yes/no Mesangial cell culture 36

P2Y6 Mouse Yes/no Medullary thick ascending limb, inner strip of the outer medulla 72 Rat Yes/no Mesangial cells and glomeruli, proximal convoluted and straight tubule, thin 68,84 descending limb of Henle’s loop, medullary and cortical thick ascending limb, outer medullary and cortical collecting duct Human Yes/no Mesangial cell culture 36

P2Y11 Madin- Yes/no Epithelial cells 80 Darby canine Human Yes/no Mesangial cell culture, epithelial cell line (A498) 36,81

P2Y12 Mouse Yes/no Inner strip of the outer medulla 72 Human Yes/no Mesangial cell culture 36

P2Y13, P2Y14 Mouse Yes/no Inner strip of the outer medulla 72

circulating anti–double-stranded DNA functional importance need to be further increased P2Y2R, P2Y6R, and P2X7R re- antibodies.50 In a rat model of GN, the elucidated. nal mRNA expression was evident com- 53 activation of adenosine A2A receptors pre- pared with control animals, suggesting a vents renal infiltration of macrophages PKD possible role of these receptors in the dis- and arrests the progression of kidney dis- Accumulating evidence suggests that ease (Table 2). Renal epithelial cells from ease, by inhibiting incoming fibrosis.51 eATP signaling via P2XRs and P2YRs individuals with PKD release higher Therefore, eATP signaling is likely in- could be detrimental with regard to pro- amounts of ATP (from 0.5 mMto2 volved in the pathogenesis of GN; how- gression of PKD.52 In Han:SPRD rats mM) compared with those obtained ever, the underlying mechanisms and its which developed polycystic kidneys, from healthy controls, which then may

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cells degraded 50% of the total ATP in the medium in 20 minutes, 50% of the total ATP was degraded by 3 hours in PKD ep- ithelial cells.54 As far as the involvement of the adenosine receptor in polycystic kidney disease, PKD1-mutated cystic cells express increased levels of adenosine A3A recep- tors.55 Thus, cyst growth and expansion in polycystic kidney disease may be wors- ened by eATPand adenosine-mediated sig- naling, but it remains unclear whether this may lead to a clinically relevant ther- apeutic strategy.

Kidney Allograft Rejection Although the literature is lacking in direct studies on the role of eATP in kidney transplantation, preclinical and clinical studies are available for other models of Figure 2. eATP signaling effects along the nephron. NO, nitric oxide; ENaC, epithelial allotransplantation.10 An increased re- sodium channel; TGF, tubuloglomerular feedback; TRPC6, transient receptor potential lease of ATP is likely to occur in allograft cation channel, subfamily C, member 6. transplantation, possibly due to ischemia/ reperfusion or upon the activation of im- mune cells, thus acting as a danger signal be trapped in the lumen of the cyst.16 In- degradation of eATP in epithelial cells, that may modulate the alloimmune re- terestingly, cyst fluid from PKD kidneys due to lack and/or mislocalization of sponse.10 In models of murine heart, islet, contained large amounts of ATP (up to ecto-ATPases, ectoapyrases, and ectonu- and lung transplantation, P2X1R expres- 10 mM),16 and eATP may augment PKD cleotidases, occurs in individuals with sion was increased in both syngeneic and cyst widening through stimulation of salt PKD; the eATP signal may therefore last allogeneic grafts, whereas intragraft 54 and water secretion across PKD cystic ep- longer in the PKD microenvironment. P2X7R upregulation was observed only ithelia.16 It is possible that a defect in the Indeed, although normal renal epithelial during allograft rejection56 (Table 2).

Table 2. Kidney diseases in which a putative role for eATP signaling is claimed Disease Model eATP Signaling Reference

Diabetic nephropathy In vitro Hyperglycemia induces an increase in eATP signaling via P2X4R with NLRP3 activation that 41,42 stimulates IL-1b and IL-18 release and development of tubulointerstitial inflammation

In vitro P2X4R, P2X7R, and NLRP3 are upregulated in individuals with T2D and diabetic 12,41

nephropathy, tubular P2X4R expression colocalizes with NLRP3, IL-1b, and IL-18 In vitro In HK-2 cells, high-glucose challenge increases expression of NLRP3, cleaves caspase-1, 41 and IL-1b and the release of IL-1b and IL-18

Hypertension In vivo In a murine model of hypertension, P2X7R KO mice show reduced BP, renal injury, urinary 43 albumin excretion, and renal interstitial fibrosis

In vivo There is an association between BP and the rs591874 polymorphism of the P2X7Rgene 46 GN In vivo In rat and murine models of GN and in renal biopsies of individuals with lupus nephritis, an 48

increase in glomerular P2X7R expression is observed

In vivo In a model of GN using P2X7R KO mice, P2X7Rdeficiency is renoprotective 49

PKDs In vivo In Han:SPRD rats, renal P2Y2R, P2Y6R, and P2X7R expression is increased 53 In vitro Epithelial cells generated from individuals with PKD release a higher amount of eATP 16,54 compared with healthy controls as well as in a murine model of PKD Kidney allograft rejection In vivo No direct evidence of eATP signaling in kidney transplantation

In murine models of heart, islet, and lung transplantation P2X1R expression increases in 56

syngenic and allogeneic graft, P2X7R upregulation is during allograft rejection

Other kidney diseases In vitro P2X7R is implicated in interstitial inflammation and fibrosis, tubular atrophy, and renal cell 59 apoptosis T2D, type 2 diabetes; NLRP3, NOD-like receptor-family protein 3.

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This may suggest that P2X7R upregulation reduced TGF-b and mesangial extracellu- and proteinuria compared with the is specifically associated with the alloim- lar matrix production by rat mesangial cell vehicle-treated group49 (Table 3). The 42 mune response, whereas P2X1R expres- culture under high-glucose conditions robust proinflammatory role of eATP sion is more related to a peritransplant (Table 3). Targeting of eATP signaling signaling suggests a potential effective inflammatory response and possibly is- may reduce the inflammatory component therapeutic option for its targeting in GN. chemia/reperfusion events.13,57 Interest- of diabetic nephropathy and thus may be ingly, adenosine A2A receptor signaling considered a future novel therapeutic tool PKD may attenuate ischemia-reperfusion in- for diabetic nephropathy.41 In a zebrafish model of PKD, oxidized jury and allogeneic T-cell recognition, ATP and A-438079, P2X7Rantagonists, thus delaying allograft rejection.58 The Hypertension decreased the frequency of the cystic aforementioned data suggested that The involvement of the P2 receptorial phenotype.69 In the growth of Madin- eATP is involved in the regulation of cel- system in the modulation of vascular tone Darby canine kidney-derived cysts, the lular and immunologic process that oc- and arterial pressure is complex and still use of P2XR/P2YR inhibitors (suramin curs during allograft organ rejection. under investigation. Administration of and PPADS) significantly reduced cyst PPADS, a nonselective P2 antagonist, size.70 When ATP was removed from Other Kidney Diseases significantly prevented the development the culture medium using higher con- P2X7Risimplicatedintheonsetofinter- of afferent arteriolar thickening during centrations of apyrase, cyst growth was stitial inflammation, tubular fibrosis, and angiotensin II infusion in rats, as well as also reduced significantly70 (Table 3). atrophy that rapidly occur after unilateral reduced the increase in a-actin expres- eATP signaling may thus promote cyst 59 62 ureteral obstruction, whereas P2X4Rhas sion in mesangial cells (Table 3). In vitro growth and its targeting may slow the recently unveiled protective properties in exposure to a P2XR antagonist (NF279) progression of the disease. the above-described setting.60 Extracellular prevented vasoconstriction of afferent adenosine has recently been regarded as an arteriolar diameter, increasing renal per- Kidney Allograft Rejection intriguing novel modulator of AKI through fusion pressure in rodents.63 In vivo inhi- In heart, islet, and lung transplantation its renal signaling. The A1A,A2A,A3A bition of P2X1RwithPPADSorIP5I models, targeting of eATP/P2X7Rsignal- adenosine receptors have different bene- inhibits autoregulatory control of whole- ing has been associated with long-term ficial effects against ischemia-reperfusion kidney blood flow,64 whereas the infusion graft function, thus potentially repre- injury and AKI, by modulating metabolic of Brilliant Blue G, a P2X7R antagonist, to senting an intriguing therapeutic target demand and leukocyte-mediated renal Fischer rats and Dahl salt-sensitive rats re- in kidney transplantation.10,56 Heart inflammation, as well as by decreasing duced arterial BP and decreased renal vas- grafts of periodate-oxidized ATP–treated necrosis, apoptosis, and tissue damage.61 cular resistance.65,66 On the other hand, mice showed mild graft lymphocyte in- The activation of adenosine receptors is P2Y2Rmodulates,via paracrine signaling, filtration and reduced coronaropathy needed for efficient kidney protection, renal sodium excretion in the distal nephron compared with untreated animals.13 and the clinical availability of adenosine in mice, thus playing a pivotal role in main- Analogous results were obtained in a may suggest a fast-track for this com- taining arterial BP within a normal range.67 murine model of islet transplantation, pound to be translated into the clinical In conclusion, although it is difficult to an- wherein treatment with eATP targeting setting when supplementation is needed. ticipate the net effect of modulating eATP showed a significant synergism with signaling on arterial BP, a reduction in va- rapamycin in reducing the alloimmune soconstriction tone and in renal salt and response57 (Table 3). CD39 and CD73 ec- TARGETING eATP AND ITS water homeostasis suggests a potential ben- toenzymes may represent future thera- RECEPTORS IN THE KIDNEY efitinhypertension. peutic targets as well.10 Genetic ablation of CD39 and CD73 enhanced hypoxic in- Diabetic Nephropathy GN jury in kidney and liver transplantation The enzyme apyrase, the P2 receptor PPADS, a nonselective P2 antagonist, in- murine models and reduced cardiac allo- 10 antagonist suramin, the P2X4R selective jected intravenously and intraperitoneally graft survival (Table 3). Clinical studies antagonist 5-BDBD, and silencing of in vivo in the anti-Thy1 model of rat me- in kidney transplant recipients are under- the P2X4R gene are all able to nearly nor- sangial proliferative GN reduced glomer- way and will clarify whether eATP can malize NLRP3 expression and reduce the ular mesangial cell proliferation, without serve as a therapeutic target. release of IL-1b and IL-18, which is in- affecting the proliferative activity of non- creased by high glucose in HK-2 cells in mesangial cells (i.e., mainly endothelial Other Kidney Diseases vitro41 (Table 3). In another study, the in- cells and monocytes/macrophages).68 Depletion of eATP with apyrase or in- creased expression of NLRP3 and IL-18 In a rat model of antibody-mediated hibition of the P2XR with PPADS hasbeen releasewereattenuatedbyP2X7R silencing GN, administration of A-438079 de- shown to reduce the extent of necrosis- in murine podocytes.12 Furthermore, the creased glomerular thrombosis and re- associated inflammation.35 Furthermore, P2X7R inhibitor periodate-oxidized ATP duced glomerular macrophage infiltration treatment with A438079, a highly selective

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Table 3. Preclinical targeting of eATP signaling in different kidney diseases Target Antagonist Preclinical Effect Reference P2Xs/P2Ys PPADS/Suramin Reduces cyst size in Madin-Darby canine kidney-derived cysts 70 P2Xs/P2Ys PPADS Reduces glomerular mesangial cell proliferation in the anti-Thy1 rat model of GN 68 P2Xs/P2Ys PPADS Prevents afferent arteriolar thickening development in angiotensin II infusion in 62 rat Reduces necrosis-associated inflammation 35 P2Xs/P2Ys Suramin Normalizes NLRP3 expression, reducing the release of IL-1b and IL-18 increased 41 by high glucose in HK-2 cells Promotes renal repair after injury when administered with adult renal progenitor 71 cells P2Xs NF279 Prevents vasoconstriction of afferent arteriolar diameter, driving an increase in 63 renal perfusion pressure in rodents P2Xs TNP-ATP Normalizes NLRP3 expression, reducing the release of IL-1b and IL-18 increased 41 by high glucose in HK-2 cells

P2X1 PPADS/IP5I Inhibits autoregulatory control of whole-kidney blood flow 64

P2X4 5-BDBD gene silencing Normalizes NLRP3 expression, reducing the release of IL-1b and IL-18 increased 41 by high glucose in HK-2 cells

P2X7 A-438079 Decreases glomerular thrombosis, glomerular macrophage infiltration and 49 proteinuria in a rat model of GN

P2X7 Brilliant Blue G Causes a reduction in arterial BP and a decrease in renal vascular resistance in the 65,66 Fischer rat

P2X7 A-438079 Diminishes renal fibroblast death 35

P2X7 A-438079/oATP Decreases the frequency of cystic phenotype 69

P2X7 oATP Reduces the mesangial extracellular matrix and TGF-b upregulation in rat 42 mesangial cell culture under high-glucose conditions

P2X7 oATP Prolongs heart and islet graft survival in mouse 13,57

P2X7 P2X7R silencing In murine podocytes, attenuates upregulated expression of NLRP3, pro-caspase 12 1, and release of IL-18 Diminishes renal fibroblast death 35 eATP apyrase Normalizes NLRP3 expression, reducing the release of IL-1b and IL-18 increased 41 by high glucose in HK-2 cells Reduces necrosis-associated inflammation 35 eATP CD39-CD73 genetic deletion Enhances the hypoxic injury in kidney transplantation murine models and 10 reduces cardiac allograft survival NF279, 8,89-(carbonylbis(imino-4,1-phenylenecarbonylimino-4,1-phenylenecarbonylimino))bis(1,3,5-naphthalenetrisulfonic acid); TNP-ATP, 29,39-O-(2,4,6-trini- trophenyl)adenosine 59-triphosphate; IP5I, P1,P5-di(-inosine-5-pentaphosphate) pentasodium salt; 5-BDBD, 5-(3-bromophenyl)-1,3-dihydro-2H-benzofuro[3,2-e]- 1,4-diazepin-2-one); A-438079, 3-[[5-(2,3-dichlorophenyl)-1H-tetrazol-1-yl]methyl]pyridine; oATP, periodate-oxidized ATP; NLRP3, NOD-like receptor-family protein 3.

ACKNOWLEDGMENTS P2X7R inhibitor, or knockdown of the in increasing kidney damage and inflam- P2X7R with small interference RNA di- mation in diabetic nephropathy, as well as minished renal fibroblast death induced in other systemic diseases characterized P.F. was the recipient of a Juvenile Diabetes by supernatant collected from necrotic by a relevant degree of renal inflammatory Research Foundation Career Development cells.35 Mice treated with suramin and response. It is also involved in the path- Award, an American Society of Nephrology murine adult renal progenital cells ogenesisofhypertension,GN,andPKD,as Career Development Award, and an American underwent extensive renal repair after in- well as in the regulation of cellular and DiabetesAssociation Mentor-Based Fellowship jury.71 Both studies suggested that block- immunologic processes that occur during grant. P.F.was also supported by a Translational ing eATP may be a promising therapeutic allograft organ rejection.10,52 P2XR inhib- Research Program grant from Boston Chil- treatment for AKI. itors (e.g., CE224,535, AZD9056, and dren’s Hospital, a Harvard Stem Cell Institute In conclusion, knowledge and under- GSK1482160) are available for clinical grant (“Diabetes Program” DP-0123-12-00), and standing of eATP function in the renal use and are under evaluation as immuno- Italian Ministry of Health grants (RF-2010- system has grown in recent years. eATP modulatory agents.10 Thus, eATP signal- 2303119, RF-2010-2314794, and “Staminali” signaling may modulate renal hemody- ing may be targeted in a wide range of RF-FSR-2008-1213704). namics,microcirculation,BP,andtubular pathologic renal conditions and may transport ofsoluteandfluid.Furthermore, lead to the discovery of clinically relevant DISCLOSURES eATPsignaling may play an important role therapeutic strategies. None.

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REFERENCES receptors in the kidney. Front Physiol 4: 262, mediate flow-induced calcium signaling in 2013 the collecting duct. Front Physiol 4: 292, 15. Vallon V: P2 receptors in the regulation of 2013 1. Burnstock G: Purinergic signalling: Its un- renal transport mechanisms. Am J Physiol 30. Jankowski M, Szamocka E, Kowalski R, popular beginning, its acceptance and its Renal Physiol 294: F10–F27, 2008 Angielski S, Szczepanska-Konkel M: The ef- exciting future. BioEssays 34: 218–225, 2012 16. Wilson PD, Hovater JS, Casey CC, fects of P2X receptor agonists on renal so- 2. Imamura H, Nhat KP, Togawa H, Saito K, Iino Fortenberry JA, Schwiebert EM: ATP release dium and water excretion in anaesthetized R, Kato-Yamada Y, Nagai T, Noji H: Visuali- mechanisms in primary cultures of epithelia rats. Acta Physiol (Oxf) 202: 193–201, 2011 zation of ATP levels inside single living cells derived from the cysts of polycystic kidneys. 31. Ilatovskaya DV, Palygin O, Levchenko V, with fluorescence resonance energy transfer- JAmSocNephrol10: 218–229, 1999 Staruschenko A: Pharmacological character- based genetically encoded indicators. Proc 17. Nishiyama A, Majid DS, Taher KA, Miyatake A, ization of the P2 receptors profile in the po- Natl Acad Sci U S A 106: 15651–15656, 2009 Navar LG: Relation between renal interstitial docytes of the freshly isolated rat glomeruli. 3. Clémençon B, Babot M, Trézéguet V: The ATP concentrations and autoregulation- Am J Physiol Cell Physiol 305: C1050– mitochondrial ADP/ATP carrier (SLC25 fam- mediated changes in renal vascular resistance. C1059, 2013 ily): Pathological implications of its dysfunc- Circ Res 86: 656–662, 2000 32. Burford JL, Villanueva K, Lam L, Riquier- tion. Mol Aspects Med 34: 485–493, 2013 18. Schwiebert EM, Kishore BK: Extracellular Brison A, Hackl MJ, Pippin J, Shankland SJ, 4. Feldenberg LR, Thevananther S, del Rio M, nucleotide signaling along the renal epithe- Peti-Peterdi J: Intravital imaging of podocyte de Leon M, Devarajan P: Partial ATP de- lium. Am J Physiol Renal Physiol 280: F945– calcium in glomerular injury and disease. pletion induces Fas- and caspase-mediated F963, 2001 JClinInvest124: 2050–2058, 2014 apoptosis in MDCK cells. Am J Physiol 276: 19. Inscho EW: ATP, P2 receptors and the renal 33. Roshanravan H, Dryer SE: ATP acting F837–F846, 1999 microcirculation. Purinergic Signal 5: 447– through P2Y receptors causes activation of 5. Gordon JL: Extracellular ATP: Effects, sour- 460, 2009 podocyte TRPC6 channels: Role of podocin – ces and fate. Biochem J 233: 309 319, 1986 20. Majid DS, Inscho EW, Navar LG: P2 purino- and reactive oxygen species. Am J Physiol 6. Falzoni S, Donvito G, Di Virgilio F: Detecting ceptor saturation by adenosine triphosphate Renal Physiol 306: F1088–F1097, 2014 adenosine triphosphate in the pericellular impairs renal autoregulation in dogs. JAm 34. Ponnusamy M, Liu N, Gong R, Yan H, Zhuang space. Interface Focus 3: 20120101, 2013 Soc Nephrol 10: 492–498, 1999 S: ERK pathway mediates P2X7 expression 7. Fields RD: Nonsynaptic and nonvesicular 21. Inscho EW, Mitchell KD, Navar LG: Extracel- and cell death in renal interstitial fibroblasts ATP release from neurons and relevance to lular ATP in the regulation of renal micro- exposed to necrotic renal epithelial cells. Am neuron-glia signaling. Semin Cell Dev Biol vascular function. FASEB J 8: 319–328, 1994 J Physiol Renal Physiol 301: F650–F659, 2011 – 22: 214 219, 2011 22. Komlosi P, Peti-Peterdi J, Fuson AL, Fintha A, 35.PonnusamyM,MaL,GongR,PangM,Chin 8. Tang XF, Fan JY, Meng J, Jin C, Yuan JQ, Rosivall L, Bell PD: Macula densa basolateral YE, Zhuang S: P2X7 receptors mediate del- Yang YJ: Impact of new oral or intravenous ATP release is regulated by luminal [NaCl] eterious renal epithelial-fibroblast cross talk. P2Y12 inhibitors and clopidogrel on major and dietary salt intake. Am J Physiol Renal Am J Physiol Renal Physiol 300: F62–F70, ischemic and bleeding events in patients Physiol 286: F1054–F1058, 2004 2011 with coronary artery disease: A meta-analysis 23. Jensen ME, Odgaard E, Christensen MH, 36. Vonend O, Grote T, Oberhauser V, Von of randomized trials. Atherosclerosis 233: Praetorius HA, Leipziger J: Flow-induced Kügelgen I, Rump LC: P2Y-receptors stimu- – 568 578, 2014 [Ca2+]i increase depends on nucleotide re- lating the proliferation of human mesangial 9. Erlinge D: P2Y receptors in health and dis- lease and subsequent purinergic signaling in cells through the MAPK42/44 pathway. Br J – ease. Adv Pharmacol 61: 417 439, 2011 the intact nephron. JAmSocNephrol18: Pharmacol 139: 1119–1126, 2003 10. Vergani A, Tezza S, Fotino C, Visner G, 2062–2070, 2007 37. Doria A, Niewczas MA, Fiorina P: Can exist- Pileggi A, Chandraker A, Fiorina P: The pu- 24. Praetorius HA, Leipziger J: Intrarenal puri- ing drugs approved for other indications re- rinergic system in allotransplantation. Am J nergic signaling in the control of renal tubular tard renal function decline in patients with – Transplant 14: 507 514, 2014 transport. Annu Rev Physiol 72: 377–393, type 1 diabetes and nephropathy? Semin 11. Baldini C, Rossi C, Ferro F, Santini E, Seccia V, 2010 Nephrol 32: 437–444, 2012 Donati V, Solini A: The P2X7 receptor- 25. Silva G, Beierwaltes WH, Garvin JL: Extra- 38. Fiorina P, Vergani A, Bassi R, Niewczas MA, inflammasome complex has a role in modu- cellular ATP stimulates NO production in rat Altintas MM, Pezzolesi MG, D’Addio F, Chin lating the inflammatory response in primary thick ascending limb. Hypertension 47: 563– M, Tezza S, Ben Nasr M, Mattinzoli D, Ikehata Sjögren’s syndrome. J Intern Med 274: 480– 567, 2006 M, Corradi D, Schumacher V, Buvall L, Yu CC, 489, 2013 26. Pochynyuk O, Bugaj V, Rieg T, Insel PA, Chang JM, La Rosa S, Finzi G, Solini A, 12. Solini A, Menini S, Rossi C, Ricci C, Santini E, Mironova E, Vallon V, Stockand JD: Paracrine Vincenti F, Rastaldi MP, Reiser J, Krolewski Blasetti Fantauzzi C, Iacobini C, Pugliese G: regulation of the epithelial Na+ channel in AS, Mundel PH, Sayegh MH: Role of podo- The purinergic 2X7 receptor participates in the mammalian collecting duct by purinergic cyte B7-1 in diabetic nephropathy. JAmSoc renal inflammation and injury induced by P2Y2 receptor tone. J Biol Chem 283: Nephrol 25: 1415–1429, 2014 high-fat diet: Possible role of NLRP3 in- 36599–36607, 2008 39. Friedman DJ, Rennke HG, Csizmadia E, flammasome activation. J Pathol 231: 342– 27. Rajagopal M, Kathpalia PP, Widdicombe JH, Enjyoji K, Robson SC: The vascular ectonu- 353, 2013 Pao AC: Differential effects of extracellular cleotidase ENTPD1 is a novel renoprotective 13. Vergani A, Tezza S, D’Addio F, Fotino C, Liu ATP on chloride transport in cortical collect- factor in diabetic nephropathy. Diabetes 56: K, Niewczas M, Bassi R, Molano RD, Kleffel S, ing duct cells. Am J Physiol Renal Physiol 2371–2379, 2007 Petrelli A, Soleti A, Ammirati E, Frigerio M, 303: F483–F491, 2012 40. Tak E, Ridyard D, Kim JH, Zimmerman M, Visner G, Grassi F, Ferrero ME, Corradi D, 28. Sipos A, Vargas SL, Toma I, Hanner F, Werner T, Wang XX, Shabeka U, Seo SW, Abdi R, Ricordi C, Sayegh MH, Pileggi A, Willecke K, Peti-Peterdi J: Connexin 30 de- Christians U, Klawitter J, Moldovan R, Garcia Fiorina P: Long-term heart transplant survival ficiency impairs renal tubular ATP release G, Levi M, Haase V, Ravid K, Eltzschig HK, by targeting the ionotropic purinergic re- and pressure natriuresis. JAmSocNephrol Grenz A: CD73-dependent generation of ceptor P2X7. Circulation 127: 463–475, 2013 20: 1724–1732, 2009 adenosine and endothelial Adora2b signal- 14. Birch RE, Schwiebert EM, Peppiatt-Wildman 29. Svenningsen P, Burford JL, Peti-Peterdi J: ing attenuate diabetic nephropathy. JAm CM, Wildman SS: Emerging key roles for P2X ATP releasing connexin 30 hemichannels Soc Nephrol 25: 547–563, 2014

1014 Journal of the American Society of Nephrology J Am Soc Nephrol 26: 1007–1016, 2015 www.jasn.org BRIEF REVIEW

41. Chen K, Zhang J, Zhang W, Zhang J, Yang J, 52. Rangan G: Role of extracellular ATP and P2 contribute to early mesangial cell trans- Li K, He Y: ATP-P2X4 signaling mediates receptor signaling in regulating renal cyst formation and renal vessel hypertrophy dur- NLRP3 inflammasome activation: A novel growth and interstitial inflammation in poly- ing angiotensin II-induced hypertension. Am pathwayofdiabeticnephropathy.Int J Bio- cystic kidney disease. Front Physiol 4: 218, J Physiol Renal Physiol 294: F161–F169, chem Cell Biol 45: 932–943, 2013 2013 2008 42. Solini A, Iacobini C, Ricci C, Chiozzi P, 53. Turner CM, Ramesh B, Srai SK, Burnstock G, 63. Inscho EW, Cook AK, Imig JD, Vial C, Evans Amadio L, Pricci F, Di Mario U, Di Virgilio F, Unwin RJ: Altered ATP-sensitive P2 receptor RJ: Physiological role for P2X1 receptors in Pugliese G: Purinergic modulation of me- subtype expression in the Han:SPRD cy/+ renal microvascular autoregulatory behavior. sangial extracellular matrix production: Role rat, a model of autosomal dominant poly- JClinInvest112: 1895–1905, 2003 in diabetic and other glomerular diseases. cystic kidney disease. Cells Tissues Organs 64. Osmond DA, Inscho EW: P2X(1) receptor Kidney Int 67: 875–885, 2005 178: 168–179, 2004 blockade inhibits whole kidney autor- 43. Ji X, Naito Y, Weng H, Endo K, Ma X, Iwai N: 54. Schwiebert EM, Wallace DP, Braunstein GM, egulation of renal blood flow in vivo. Am J P2X7 deficiency attenuates hypertension King SR, Peti-Peterdi J, Hanaoka K, Guggino Physiol Renal Physiol 298: F1360–F1368, and renal injury in deoxycorticosterone ace- WB, Guay-Woodford LM, Bell PD, Sullivan 2010 tate-salt hypertension. Am J Physiol Renal LP, Grantham JJ, Taylor AL: Autocrine ex- 65. Menzies RI, Unwin RJ, Dash RK, Beard DA, Physiol 303: F1207–F1215, 2012 tracellular purinergic signaling in epithelial Cowley AW Jr, Carlson BE, Mullins JJ, Bailey 44. Vonend O, Turner CM, Chan CM, Loesch A, cells derived from polycystic kidneys. Am J MA: Effect of P2X4 and P2X7 receptor an- Dell’Anna GC, Srai KS, Burnstock G, Unwin Physiol Renal Physiol 282: F763–F775, 2002 tagonism on the pressure diuresis relation- RJ: Glomerular expression of the ATP- 55. Aguiari G, Varani K, Bogo M, Mangolini A, ship in rats. Front Physiol 4: 305, 2013 sensitive P2X receptor in diabetic and hyper- Vincenzi F, Durante C, Gessi S, Sacchetto V, 66. Ji X, Naito Y, Hirokawa G, Weng H, Hiura Y, tensive rat models. Kidney Int 66: 157–166, Catizone L, Harris P, Rizzuto R, Borea PA, Del Takahashi R, Iwai N: P2X(7) receptor antag- 2004 Senno L: Deficiency of polycystic kidney onism attenuates the hypertension and renal 45. Zhang W, Zhang Y, Wang W, Dai Y, Ning C, disease-1 gene (PKD1) expression increases injury in Dahl salt-sensitive rats. Hypertens Luo R, Sun K, Glover L, Grenz A, Sun H, Tao L, A(3) adenosine receptors in human renal Res 35: 173–179, 2012 Zhang W, Colgan SP, Blackburn MR, cells: Implications for cAMP-dependent sig- 67. Vallon V, Rieg T: Regulation of renal NaCl Eltzschig HK, Kellems RE, Xia Y: Elevated nalling and proliferation of PKD1-mutated and water transport by the ATP/UTP/P2Y2 ecto-59-nucleotidase-mediated increased cystic cells. Biochim Biophys Acta 1792: receptor system. Am J Physiol Renal Physiol renal adenosine signaling via A2B adenosine 531–540, 2009 301: F463–F475, 2011 receptor contributes to chronic hyperten- 56. Liu K, Vergani A, Zhao P, Ben Nasr M, Wu X, 68. Rost S, Daniel C, Schulze-Lohoff E, Bäumert sion. Circ Res 112: 1466–1478, 2013 Iken K, Jiang D, Su X, Fotino C, Fiorina P, HG, Lambrecht G, Hugo C: P2 receptor antag- 46. Palomino-Doza J, Rahman TJ, Avery PJ, Visner GA: Inhibition of the purinergic path- onist PPADS inhibits mesangial cell proliferation Mayosi BM, Farrall M, Watkins H, Edwards way prolongs mouse lung allograft survival. in experimental mesangial proliferative glo- CR, Keavney B: Ambulatory blood pressure is Am J Respir Cell Mol Biol 51: 300–310, 2014 merulonephritis. Kidney Int 62: 1659–1671, associated with polymorphic variation in P2X 57. Vergani A, Fotino C, D’Addio F, Tezza S, 2002 receptor genes. Hypertension 52: 980–985, Podetta M, Gatti F, Chin M, Bassi R, Molano 69. Chang MY, Lu JK, Tian YC, Chen YC, Hung 2008 RD, Corradi D, Gatti R, Ferrero ME, Secchi A, CC, Huang YH, Chen YH, Wu MS, Yang CW, 47. Ghiadoni L, Rossi C, Duranti E, Santini E, Grassi F, Ricordi C, Sayegh MH, Maffi P, Cheng YC: Inhibition of the P2X7 receptor Bruno RM, Salvati A, Taddei S, Solini A: P2X7 Pileggi A, Fiorina P: Effect of the purinergic reduces cystogenesis in PKD. JAmSoc receptor polymorphisms do not influence inhibitor oxidized ATP in a model of Nephrol 22: 1696–1706, 2011 endothelial function and vascular tone in islet allograft rejection. Diabetes 62: 1665– 70. Turner CM, King BF, Srai KS, Unwin RJ: An- neo-diagnosed, treatment-naive essential 1675, 2013 tagonism of endogenous putative P2Y re- hypertensive patients. J Hypertens 31: 58. Sevigny CP, Li L, Awad AS, Huang L, ceptors reduces the growth of MDCK-derived 2362–2369, 2013 McDuffieM,LindenJ,LoboPI,OkusaMD: cysts cultured in vitro. Am J Physiol Renal 48. Turner CM, Tam FW, Lai PC, Tarzi RM, Activation of adenosine 2A receptors at- Physiol 292: F15–F25, 2007 Burnstock G, Pusey CD, Cook HT, Unwin RJ: tenuates allograft rejection and alloantigen 71. Han X, Zhao L, Lu G, Ge J, Zhao Y, Zu S, Yuan Increased expression of the pro-apoptotic recognition. JImmunol178: 4240–4249, M,LiuY,KongF,XiaoZ,ZhaoS:Improving ATP-sensitive P2X7 receptor in experimental 2007 outcomes of acute kidney injury using mouse and human glomerulonephritis. Nephrol Dial 59. Gonçalves RG, Gabrich L, Rosário A Jr, renal progenitor cells alone or in combina- Transplant 22: 386–395, 2007 Takiya CM, Ferreira ML, Chiarini LB, tion with erythropoietin or suramin. Stem 49. Taylor SR, Turner CM, Elliott JI, McDaid J, Persechini PM, Coutinho-Silva R, Leite M Jr: Cell Res Ther 4: 74, 2013 Hewitt R, Smith J, Pickering MC, Whitehouse The role of purinergic P2X7 receptors in the 72. Marques RD, de Bruijn PI, Sorensen MV, DL, Cook HT, Burnstock G, Pusey CD, Unwin inflammation and fibrosis of unilateral ure- Bleich M, Praetorius HA, Leipziger J: Baso- RJ, Tam FW: P2X7 deficiency attenuates re- teral obstruction in mice. Kidney Int 70: lateral P2X receptors mediate inhibition of nal injury in experimental glomerulonephri- 1599–1606, 2006 NaCl transport in mouse medullary thick as- tis. JAmSocNephrol20: 1275–1281, 2009 60. Kim MJ, Turner CM, Hewitt R, Smith J, cending limb (mTAL). Am J Physiol Renal 50. Zhao J, Wang H, Dai C, Wang H, Zhang H, Bhangal G, Pusey CD, Unwin RJ, Tam FW: Physiol 302: F487–F494, 2012 Huang Y, Wang S, Gaskin F, Yang N, Fu SM: Exaggerated renal fibrosis in P2X4 receptor- 73. Chan CM, Unwin RJ, Bardini M, Oglesby IB, P2X7 blockade attenuates murine lupus ne- deficient mice following unilateral ureteric Ford AP, Townsend-Nicholson A, Burnstock phritis by inhibiting activation of the NLRP3/ obstruction. Nephrol Dial Transplant 29: G: Localization of P2X1 purinoceptors by ASC/caspase1pathway.Arthritis Rheum 65: 1350–1361, 2014 autoradiography and immunohistochemistry 3176–3185, 2013 61. Yap SC, Lee HT: Adenosine and protection in rat kidneys. Am J Physiol 274: F799–F804, 51. Garcia GE, Truong LD, Chen JF, Johnson RJ, from acute kidney injury. Curr Opin Nephrol 1998 Feng L: Adenosine A(2A) receptor activation Hypertens 21: 24–32, 2012 74. Filipovic DM, Adebanjo OA, Zaidi M, Reeves prevents progressive kidney fibrosis in a 62. Graciano ML, Nishiyama A, Jackson K, Seth WB: Functional and molecular evidence for model of immune-associated chronic in- DM, Ortiz RM, Prieto-Carrasquero MC, P2X receptors in LLC-PK1 cells. Am J Physiol flammation. Kidney Int 80: 378–388, 2011 Kobori H, Navar LG: Purinergic receptors 274: F1070–F1077, 1998

J Am Soc Nephrol 26: 1007–1016, 2015 Extracellular ATP and Kidney Diseases 1015 BRIEF REVIEW www.jasn.org

75. McCoy DE, Taylor AL, Kudlow BA, Karlson K, epithelial cells. Vet Immunol Immunopathol urinary tract. Infect Immun 78: 3609–3615, Slattery MJ, Schwiebert LM, Schwiebert EM, 150: 228–233, 2012 2010 Stanton BA: Nucleotides regulate NaCl transport 79. Bailey MA, Imbert-Teboul M, Turner C, 82. Cuffe JE, Bielfeld-Ackermann A, Thomas J, in mIMCD-K2 cells via P2X and P2Y purinergic Marsy S, Srai K, Burnstock G, Unwin RJ: Axial Leipziger J, Korbmacher C: ATP stimulates receptors. Am J Physiol 277: F552–F559, 1999 distribution and characterization of baso- Cl- secretion and reduces amiloride-sensitive 76. Dai LJ, Kang HS, Kerstan D, Ritchie G, lateral P2Y receptors along the rat renal tu- Na+ absorption in M-1 mouse cortical col- Quamme GA: ATP inhibits Mg(2+) uptake in bule. Kidney Int 58: 1893–1901, 2000 lecting duct cells. JPhysiol524: 77–90, 2000 MDCT cells via P2X purinoceptors. Am J 80. Post SR, Rump LC, Zambon A, Hughes RJ, 83. Kishore BK, Ginns SM, Krane CM, Nielsen S, Physiol Renal Physiol 281: F833–F840, 2001 Buda MD, Jacobson JP, Kao CC, Insel PA: Knepper MA: Cellular localization of P2Y(2) 77. Harada H, Chan CM, Loesch A, Unwin R, ATP activates cAMP production via multiple purinoceptor in rat renal inner medulla and Burnstock G: Induction of proliferation and purinergic receptors in MDCK-D1 epithelial lung. Am J Physiol Renal Physiol 278: F43– apoptotic cell death via P2Y and P2X re- cells. Blockade of an autocrine/paracrine F51, 2000 ceptors, respectively, in rat glomerular me- pathway to define receptor preference of an 84. Bailey MA, Imbert-Teboul M, Turner C, Srai sangial cells. Kidney Int 57: 949–958, 2000 agonist. JBiolChem273: 23093–23097, SK, Burnstock G, Unwin RJ: Evidence for 78. Jalilian I, Spildrejorde M, Seavers A, Curtis 1998 basolateral P2Y(6) receptors along the rat BL, McArthur JD, Sluyter R: Functional ex- 81. Säve S, Persson K: Extracellular ATP and proximal tubule: Functional and molecular pression of the damage-associated molecu- P2Y receptor activation induce a proin- characterization. JAmSocNephrol12: lar pattern receptor P2X7 on canine kidney flammatory host response in the human 1640–1647, 2001

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