Protease-Activated Receptor-2 Expression in IgA Nephropathy

Abstract

ABSTRACT. An increasing body of evidence suggests that proteases may play a key role in the pathogenesis of tissue fibrosis. Protease-activated receptor-2 (PAR-2) is cleaved and activated by trypsin-like proteolytic enzymes, including tryptase and activated coagulation factor X (FXa). Both these soluble mediators have been demonstrated, directly or indirectly, at the interstitial level in progressive renal diseases, including IgA nephropathy (IgAN). PAR-2 mRNA and protein levels were investigated by RT-PCR and immunohistochemistry, respectively, in 17 biopsies from IgAN patients and 10 normal kidneys. PAR-2 expression was also evaluated, by RT-PCR and western blotting, in cultured human mesangial and proximal tubular cells. Finally, gene expression of plasminogen activator inhibitor-1 (PAI-1) and TGF-β, two powerful fibrogenic factors, was evaluated in FXa-, trypsin-, and PAR-2 activating peptide-stimulated human proximal tubular cells by Northern blot. In normal kidneys, PAR-2 gene expression was barely detectable, whereas in IgAN biopsies the mRNA levels for this protease receptor were strikingly increased and directly correlated with the extent of interstitial fibrosis. Immunohistochemical staining demonstrated that PAR-2 protein expression in IgAN biopsies was mainly localized in the proximal tubuli and within the interstitial infiltrate. Proximal tubular cells in culture expressed PAR-2. Activation of this receptor by FXa in tubular cells induced a striking increase in intracellular calcium concentration. In addition, incubation of both cell lines with trypsin, FXa, or PAR-2 activating peptide caused a marked upregulation of PAI-1 gene expression that was not counterbalanced by an increased expression of plasminogen activators. Finally, PAR-2 activation induced a significant upregulation of TGF-β gene and protein expression in both mesangial and tubular cells. On the basis of our data, we can suggest that PAR-2 expressed by renal resident cells and activated by either mast cell tryptase or FXa may induce extracellular matrix deposition modifying the PAI-1/PA balance and inducing TGF-β expression. These molecular mechanisms may underlie interstitial fibrosis in IgAN. E-mail: g.grandaliano@nephro.uniba.it

Protease-Activated Receptor-2 Induces Myofibroblast Differentiation and Tissue Factor Up-Regulation during Bleomycin-Induced Lung Injury

“…In renal interstitial fibrosis, ␣-SM actin and PAR-2 expression are correlated, 25 whereas PAR-2 expression is increased in biopsies of patients with IgA nephropathy. 35 PAR-2 expression is also increased in chronic pancreatitis and in severe fibrosis accompanying pancreatic cancer. 36 Finally, both FXa and PAR-2 are overexpressed in the kidney of rats subjected to experimental glomerulonephritis.…”

Roles of Coagulation Pathway and Factor Xa in the Progression of Diabetic Nephropathy in db/db Mice

“…bular cells. 35) Thrombin and factor Xa activate the PAR family. 14,15) After selective cleavage of the receptors by these serine-proteases, PARs mediate signaling, and thereby exert various cellular effects that induce inflammatory responses to tissue injury.…”

Ischemia-Reperfusion Induces Glomerular and Tubular Activation of Proinflammatory and Antiapoptotic Pathways

“…In this setting, the role of the coagulation cascade in the pathogenesis of interstitial inflammation and in the modulation of tubular cell functions is still largely unclear. Coagulation factors may influence renal resident cell activation interacting with specific cell-surface receptors that belong to the protease-activated receptor (PAR) family (11,12).…”