Toll-Like Receptor Signaling and SIGIRR in Renal Fibrosis Upon Unilateral Ureteral Obstruction
Total Page：16
File Type：pdf, Size：1020Kb
Toll-Like Receptor Signaling and SIGIRR in Renal Fibrosis upon Unilateral Ureteral Obstruction Veronika Skuginna1., Maciej Lech1., Ramanjaneyulu Allam1, Mi Ryu1, Sebastian Clauss1,2, Heni Eka Susanti1, Christoph Ro¨ mmele1, Cecilia Garlanda3, Alberto Mantovani3, Hans-Joachim Anders1* 1 Department of Nephrology, Medizinische Poliklinik, University of Munich, Munich, Germany, 2 Medizinische Klinik und Poliklinik I Grosshadern, University of Munich, Munich, Germany, 3 Istituto Clinico Humanitas and Fondazione Humanitas per la Ricerca, Rozzano, Italy Abstract Innate immune activation via IL-1R or Toll-like receptors (TLR) contibutes to acute kidney injury but its role in tissue remodeling during chronic kidney disease is unclear. SIGIRR is an inhibitor of TLR-induced cytokine and chemokine expression in intrarenal immune cells, therefore, we hypothesized that Sigirr-deficiency would aggravate postobstructive renal fibrosis. The expression of TLRs as well as endogenous TLR agonists increased within six days after UUO in obstructed compared to unobstructed kidneys while SIGIRR itself was downregulated by day 10. However, lack of SIGIRR did not affect the intrarenal mRNA expression of proinflammatory and profibrotic mediators as well as the numbers of intrarenal macrophages and T cells or morphometric markers of tubular atrophy and interstitial fibrosis. Because SIGIRR is known to block TLR/IL-1R signaling at the level of the intracellular adaptor molecule MyD88 UUO experiments were also performed in mice deficient for either MyD88, TLR2 or TLR9. After UUO there was no significant change of tubular interstitial damage and interstitial fibrosis in neither of these mice compared to wildtype counterparts. Additional in-vitro studies with CD90+ renal fibroblasts revealed that TLR agonists induce the expression of IL-6 and MCP-1/CCL2 but not of TGF-b, collagen-1a or smooth muscle actin. Together, postobstructive renal interstitial fibrosis and tubular atrophy develop independent of SIGIRR, TLR2, TLR9, and MyD88. These data argue against a significant role of these molecules in renal fibrosis. Citation: Skuginna V, Lech M, Allam R, Ryu M, Clauss S, et al. (2011) Toll-Like Receptor Signaling and SIGIRR in Renal Fibrosis upon Unilateral Ureteral Obstruction. PLoS ONE 6(4): e19204. doi:10.1371/journal.pone.0019204 Editor: Christos Chatziantoniou, Institut National de la Sante´ et de la Recherche Me´dicale, France Received December 21, 2010; Accepted March 28, 2011; Published April 22, 2011 Copyright: ß 2011 Skuginna et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: Grants from the Deutsche Forschungsgemeinschaft (AN371/10-1 and GRK1202) to ML and HJA. VS CR and RA were graduate fellows of the GRK 1202. SC was supported by the Molecular Medicine program of the Medical Faculty, University of Munich, Germany. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: [email protected] . These authors contributed equally to this work. Introduction tissue remodeling [7,8]. Interestingly, TLRs can trigger inflam- mation and tissue remodeling also in the absence of pathogens or Chronic kidney disease is usually associated with diffuse PAMPs [9]. Dying cells were found to elicit identical immune remodeling of the tubulointerstitial compartment. Tubular activation by the release of endogenous ‘danger-associated atrophy and interstitial fibrosis represent a common terminal molecular patterns’ (DAMP) that have immunostimulatory effects pathway of various types of kidney diseases involving numerous and act as endogenous immune adjuvants [10]. As such TLRs pathomechanisms and effector elements [1] such as loss of seem to functionally act as universal danger recognition receptors peritubular vasculature and ischemia [2], epithelial-mesenchymal that alert the immune system to tissue damage independent of the transition [3], recruitment of circulating fibrogenic progenitor cells type of injury [10]. This universal mechanism also applies to [4], the release of growth factors and proapoptotic molecules [5], kidney diseases [11]. For example, postischemic renal inflamma- and interstitial inflammation driven by chemokine-mediated tion and tubular damage are significantly reduced in mice leukocyte recruitment [6]. The factors that orchestrate the onset, deficient for TLR2, TLR4 or MyD88, the main adaptor molecule resolution or progression of renal fibrosis remain unclear. for these TLRs [12,13,14,15,16]. Data from other acute kidney Generally, tissue remodeling is the result of a danger response injury models further support the role of TLRs in renal danger [7]. All cell types can recognize toxic, metabolic, infectious, signaling [17,18]. Does this concept also apply to tissue remodeling mechanic or osmotic types of danger and elicit primary signals that in chronic kidney disease? Only few studies have yet addressed this trigger defense mechanisms and that alert other cells. For example, issue experimentally. Wang, et al. reported that tubulointerstitial pathogens trigger the expression of proinflammatory cytokines and disease was reduced in wildtype kidneys transplanted into TLR2-, chemokines via the activation of Toll-like receptors (TLR) by TLR4-, TLR2/4-, MyD88-, and TRIF-deficient recipients [19]. pathogen-associated molecular patterns (PAMP) like LPS, lipo- These data document a role for TLRs in alloimmunity against a peptides or bacterial DNA [8]. It has now become clear that the renal graft but not necessarily about the role of TLR signaling TLR-dependent innate immune response is essential in mediating inside the donor kidney. The unilateral ureteral obstruction host defense to infection and to infection-related inflammation and (UUO) model is often used in the context of renal fibrosis [20,21] PLoS ONE | www.plosone.org 1 April 2011 | Volume 6 | Issue 4 | e19204 SIGIRR in Renal Fibrosis and data from TLR2– or TLR4-deficient mice propose that TLR induced in obstructed kidneys at day 2 after surgery (Figure 2). All signaling contributes to postobstructive renal inflammation, TLRs were induced only in obstructed kidneys from day 6 after tubular atrophy, and interstitial fibrosis [22,23]. surgery but the expression levels did not further increase at day 10. Negative regulators of TLR signaling limit innate immune Together, surgery increases renal DAMP mRNA expression and activation and thereby prevent inappropriate immunopathology UUO further increases the expression levels for biglycan and [24]. For example, the TIR8 gene encodes for single immuno- HAS2. TLRs are generally induced in obstructed kidneys but the globulin IL-1-related receptor (SIGIRR) [25]. This TLR/IL-1R expression level dynamics do not correlate with those of genes that family member suppresses LPS or IL-1-induced activation of NF- are known to mirror the progression of interstitial fibrosis. kB, a process that protects from immunity-mediated tissue damage upon pathogen challenge or dextran-induced damage of the SIGIRR is expressed in the kidney during UUO intestinal epithelium [25]. Inside the kidney, SIGIRR is expressed As UUO induced the intrarenal expression of many genes by tubular epithelial cells, dendritic cells, and macrophages but related to TLR signaling we questioned whether UUO would also functional activity of SIGIRR is limited to renal immune cells only induce renal SIGIRR expression. However, renal mRNA [26]. SIGIRR was also shown to suppress inflammation and tissue expression of SIGIRR rather declined in UUO versus unobstruct- remodeling in intrarenal immune cells during urinary tract ed kidneys, especially 10 days after UUO (Figure 3A). Western infection [26], lupus nephritis [27,28], and postischemic acute blot confirmed this downmodulation of renal SIGIRR expression renal failure [29,30]. in UUO kidneys 10 days after surgery (Figure 3B). Thus, the We therefore hypothesized that SIGIRR would also suppress intrarenal induction of TLR expression after UUO is associated postobstructive tubular atrophy and renal fibrosis by inhibiting the with a downregulation of SIGIRR. TLR-dependent activation of renal inflammation. We addressed this hypothesis experimentally by inducing UUO in Sigirr(Tir8)- Lack of SIGIRR does not affect the renal expression of deficient mice. In addition, we performed UUO in mice deficient proinflammatory and profibrotic mediators during UUO for either TLR2, TLR9 or MyD88. As SIGIRR suppresses the production of proinflammatory mediators in intrarenal immune cells upon exposure to TLR Results agonists, we expected higher cytokine expression levels in UUO SIGIRR suppresses the activation of intrarenal immune kidneys of Sigirr-deficient mice. But when we compared renal cells mRNA expression levels of MCP-1/CCL2 and RANTES/CCL5 in obstructed and sham-operated kidneys at 2, 6 or 10 days after SIGIRR is known to suppress TLR signaling in antigen- surgery we found their expression levels to be independent of the presenting cells [25]. Therefore, we first determined its potential to SIGIRR genotype (Figure 4). The same was found for the suppress LPS-induced production of proinflammatory and profi- profibrotic cytokines TGF-b and CTGF or for collagen-1a, brotic mediators in renal immune and