Preserved Expression of Mrna Coding Von Willebrand Factor–Cleaving Protease ADAMTS13 by Selenite and Activated Protein C
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Preserved Expression of mRNA Coding von Willebrand Factor–Cleaving Protease ADAMTS13 by Selenite and Activated Protein C Michael L Ekaney,1,2 Clemens L Bockmeyer,3 Maik Sossdorf,1,2 Philipp A Reuken,1,2 Florian Conradi,2 Tobias Schuerholz,4 Markus F Blaess,1,2 Scott L Friedman,5 Wolfgang Lösche,1,2 Michael Bauer,1,2 and Ralf A Claus1,2 1Center for Sepsis Control and Care, and 2Clinic for Anaesthesiology and Intensive Care Medicine, Jena University Hospital, Jena, Germany; 3Department of Nephropathology, and 4Department for Interdisciplinary Intensive Care, University Hospital Aachen, Aachen, Germany; and 5Mount Sinai School of Medicine, New York, New York, United States of America In sepsis, the severity-dependent decrease of von Willebrand factor (VWF)–inactivating protease, a disintegrin and metallo- proteinase with thrombospondin motifs 13 (ADAMTS13), results in platelet aggregation and consumption, leading to sepsis- associated thrombotic microangiopathy (TMA) and organ failure. Previous reports assessing its functional deficiency have pin- pointed involvement of autoantibodies or mutations to propagate thrombotic thrombocytopenic purpura (TTP). However, mechanisms of acquired ADAMTS13 deficiency during host response remain unclear. To enhance understanding of ADAMTS13 deficiency in sepsis, we evaluated changes in expression of mRNA coding ADAMTS13 during septic conditions using primary cel- lular sources of the protease. We hypothesized that proinflammatory cytokines and constituents of serum from septic patients af- fect the transcriptional level of ADAMTS13 in vitro, and previously recommended therapeutic agents as adjunctive therapy for sepsis interact therewith. Cultured hepatic stellate cells (HSCs), endothelial cells (HMEC) and human precision-cut liver slices as an ex vivo model were stimulated with sepsis prototypic cytokines, bacterial endotoxin and pooled serum obtained from septic pa- tients. Stimulation resulted in a significant decrease in ADAMTS13 mRNA between 10% and 80% of basal transcriptional rates. Cos- timulation of selenite or recombinant activated protein C (APC) with serum prevented ADAMTS13 decrease in HSCs and in- creased ADAMTS13 transcripts in HMEC. In archived clinical samples, the activity of ADAMTS13 in septic patients treated with APC (n = 5) increased with an accompanying decrease in VWF propeptide as surrogate for improved endothelial function. In conclu- sion, proinflammatory conditions of sepsis repress mRNA coding ADAMTS13 and the ameliorating effect by selenite and APC may support the concept for identification of beneficial mechanisms triggered by these drugs at a molecular level. Online address: http://www.molmed.org doi: 10.2119/molmed.2014.00202 INTRODUCTION ing from a systemic inflammatory re- Central to these responses are alter- Despite therapy with appropriate an- sponse to infection (5). The continuum ations in endothelial cell function and a tibiotics and intensive supportive care, of sepsis pathophysiology involves a shift to a proinflammatory and procoag- sepsis carries a persistently high mor- complex integrated response involving ulant surface, which amplifies the initial bidity and mortality (1–4). Sepsis is a immune cell activation, inflammatory signal intensity (6,7). Alterations in mi- progressive injurious process aggravat- mediators and the coagulation system. crocirculation and microvascular perme- ability precede early tissue injury and organ failure (8). However, pathogenic mechanisms and messengers involved Address correspondence to Ralf A Claus, Center for Sepsis Control and Care, and Clinic in processes resulting in remote organ for Anaesthesiology and Intensive Care Therapy, Jena University Hospital, Erlanger Allee injury require further investigation. 101, D-07747 Jena, Germany. Phone: +49-(0)-3641-9325860; Fax: +49-(0)-3641-9325862; During sepsis, von Willebrand factor E-mail: [email protected]. (VWF), a multimeric acute phase pro- Submitted October 9, 2014; Accepted for publication April 3, 2015; Published Online tein, is abundantly secreted into plasma (www.molmed.org) April 3, 2015. by activated endothelial cells and platelets (9,10). VWF in its native, ultralarge isoform (ulVWF) is only de- tectable in conditions of an activated MOL MED 21:355-363, 2015 | EKANEY ET AL. | 355 ADAMTS13 EXPRESSION IN INFLAMMATION endothelium (11) and functions as a de- induced mortality because the complete with 100 ng/mL of endotoxin as de- terminant of platelet activation and ag- absence of its regulating protease had scribed previously) (40). The stimulation gregation (12,13). ADAMTS13 is a only a minor impact in the murine sep- period was limited to a maximum of 24 plasma protease primarily synthesized sis model. h because ADAMTS13 mRNA tran- and secreted from hepatic stellate cells To gain insight into mechanisms of scripts remain stable during this period, (HSCs) and is the only enzyme reported ADAMTS13 deficiency in systemic in- therefore providing a threshold to iden- to inactivate ulVWF, thereby reducing flammation and sepsis, we investigated tify significant changes in ADAMTS13 its thrombogenicity (14,15). Congenital the effects of proinflammatory cytokines, transcripts. Longer stimulation times or immunologically induced deficiency endotoxins and constituents of serum ob- may provoke mRNA changes due to ar- of ADAMTS13 has been identified to re- tained from septic patients on tifacts resulting from cellular stress in- sult in thrombotic thrombocytopenic ADAMTS13 expression on a transcrip- duced by starvation and accumulation purpura (TTP) (16). In sepsis, the term tional level. Furthermore, we evaluated of cell debris and not the intended effect thrombotic microangiopathy (TMA) the contribution of selenite and APC as observed by the inflammatory stimuli. A was introduced to characterize throm- adjuvant sepsis therapeutics in regulat- concentration of 5% pooled serum from botic occlusion of arterioles less than ing inflammation-induced ADAMTS13 septic patients (n = 12) was used for 100 μm diameter independent of the changes in transcription. Finally, we stimulation where indicated. Serum underlying pathophysiology (17,18). compared data obtained from in vitro ex- samples were obtained within 24 h after Hence, thrombocytopenia is a risk fac- periments to an observational study co- the patients met the criteria for sepsis or tor for mortality in critically ill patients hort for consistency of our findings. severe sepsis (5). Pivotal parameters of (19) and is also an independent predic- the serum pool were determined as fol- tor of multiple organ failure and death MATERIALS AND METHODS lows (normal values are given in brack- (20–22). Institutional ethical approval by the ets): creatinine 121 μmol/L [44–106], Further evidence suggests ADAMTS13 local ethics committee of the medical fac- blood urea nitrogen 37.2 mg/dL deficiency in patients with systemic in- ulty of Friedrich-Schiller University Hos- [2.6–6.4], γ-glutamyltransferase 80 U/L flammation and severe sepsis (9,23–25). pital in Jena (A-1827-07/06 and A-1840- [6–28], glutamatoxalacetate-transami- This deficiency is associated with an in- 08/06) and written informed consent of nase 209 U/L [<18], lactate dehydroge- crease in ulVWF and is postulated to each patient were obtained. nase 463 U/L [135–223], ammonia cause TMA in patients (9,23,26). The 128 μg/dL [19–94], creatine-phosphoki- impact of ADAMTS13 deficiency in Cell Culture Experiments nase 640 U/L [<174], albumin 2.6 g/dL thrombocytopenia and organ failure is Using cell culture models, an immor- [3,5–5.5], glucose 6.9 mmol/L [3.9–5.6], supported by the observation that talized hepatic stellate cell line (LX-2) IL-6 2282.75 pg/mL, TNFα below detec- plasma exchange reversed organ dys- (37,38) and a human microvascular en- tion limit (10 pg/mL). function in thrombocytopenia-associ- dothelial cell line (HMEC) (39), both of Cells were also coincubated with one ated multiple organ failure in children human origin, were cultured under stan- of the following substances: noradrena- (27) and renal deposition of thrombi en- dard conditions (LX-2: 1% heat inacti- lin (NA), protein C–activated (Eli Lilly, riched from activated platelets and vated fetal calf serum [FCS] in Dul- Indianapolis, IN, USA), arginine vaso- VWF in a porcine sepsis model (28). becco’s Modified Eagle Medium pressin (AVP) or desmopressin Also, an inverse relationship between (DMEM) media, 5% CO2; HMEC: 10% (DDAVP), sodium selenite (biosyn severity of inflammation and heat inactivated FCS in DMEM media, Arzneimittel GmbH, Fellbach, Germany) 6 ADAMTS13 activity is described in 5% CO2). Cells (1 × 10 ) were seeded in and tolvaptan (Sigma-Aldrich, St. Louis, clinical studies (29,30). However, the ac- media supplemented with pooled MO, USA). tual cause for ADAMTS13 deficiency is human AB-serum (1%), equilibrated for controversial, ranging from its con- 2 h and stimulated for 6 or 24 h with Human High Precision–Cut Liver Slices sumption (31), secretion defects (32) or human recombinant cytokines (tumor (HPLS) proteolytic degradation by enzymes cir- necrosis factor-α [TNFα], interferon γ As an established ex vivo model, HPLS culating in plasma of critically ill pa- [IFNγ], interleukin-1β [IL-1β], IL-2 or IL- from patients who underwent liver resec- tients (33,34). Furthermore, an unbal- 6; reconstituted in saline supplemented tion spatially distant to metastases con- anced expression of ADAMTS13 and with 0.1% human albumin) to final con- trolled by macroscopic inspection by two VWF was