Tubulointerstitial fibrosis is a hallmark of advanced diabetic kidney disease that is linked to a decline in renal function, however the pathogenic mechanisms are poorly understood. Microparticles (MPs) are 100–1000 nm vesicles shed from injured cells that are implicated in intercellular signalling. Our lab recently observed the formation of MPs from podocytes and their release into urine of animal models of type 1 and 2 diabetes and in humans with type 1 diabetes. The purpose of the present study was to examine the role of podocyte MPs in tubular epithelial cell fibrotic responses. MPs were isolated from the media of differentiated, untreated human podocytes (hPODs) and administered to cultured human proximal tubule epithelial cells (PTECs). Treatment with podocyte MPs increased p38 and Smad3 phosphorylation and expression of the extracellular matrix (ECM) proteins fibronectin and collagen type IV. MP-induced responses were attenuated by co-treatment with the p38 inhibitor SB202190. A transforming growth factor beta (TGF-β) receptor inhibitor (LY2109761) blocked MP-induced Smad3 phosphorylation and ECM protein expression but not p38 phosphorylation suggesting that these responses occurred downstream of p38. Finally, blockade of the class B scavenger receptor CD36 completely abrogated MP-mediated p38 phosphorylation, downstream Smad3 activation and fibronectin/collagen type IV induction. Taken together our results suggest that podocyte MPs interact with proximal tubule cells and induce pro-fibrotic responses. Such interactions may contribute to the development of tubular fibrosis in glomerular disease.
s e25 P = 0.041, P = 0.028, and P = 0.002, respectively). Expression was observed in macrophages, foam cells, endothelial cells, and smooth muscle cells. Moreover, unstable plaques from men demonstrated greater features of plaque instability compared to unstable plaques from women, including hemorrhage, large lipid core, abundance of inflammatory cells, and fibrous cap infiltration by inflammatory cells (P < 0.05 for all). Conclusion: Our preliminary findings indicate a possible association betweenandrogens and the androgen receptor pathway and plaque instability. With further investigations, our ongoing work will unravel the underlying mechanisms, and may ultimately lead to hormone-specific therapies aimed at stabilizing plaques and reducing the incidence of stroke for men and women.
Objective: Endothelial dysfunction plays a central mechanistic role in the pathogenesis of hypertension and diabetes. However, the molecular determinants of endothelial dysfunction are not fully understood. Peptidylarginine deiminases (PADs) irreversibly convert arginine to citrulline in protein, generating neoantigens that are unrecognizable to the immune system. PAD4, an isoform predominantly expressed in neutrophils is upregulated in autoimmune and coronary artery disease. PAD4 activation, in turn, promotes vascular injury through the formation of neutrophil extracellular traps (NETs), networks of chromatin and protein-containing extracellular fibres released to fight infection. Whether PAD4 activity is altered in hypertension and diabetes and whether this contributes to disease pathogenesis is not known. The objective of the present study was to examine the effect of angiotensin II on formation of neutrophil extracellular traps in vitro and in an animal model of hypertension and diabetes. Design and method: Neutrophil-like cells were generated from differentiation of the HL-60 cell line and then treated with angiotensin II (10-7 M) for 24 hours. NET formation was assessed by Western blot analysis of citrullinated histone H3 (a primary component of NETs). We further assessed NET formation in mice expressing human renin under the control of the transthyretin promoter (TTRhRen) intercrossed with OVE26 diabetic mice [i.e. hypertensive-diabetic, HD mice] and compared with wild-type (WT) FVBN/J mice. We examined levels of citrullinated histone H3, neutrophil elastase, and PAD4 expression in the kidney of HD and WT mice by immunohistochemistry. Results: Treatment of neutrophil-like cells with angiotensin-II increased levels of citrullinated histone H3 by ∼2-fold. Similarly, in HD mice we observed a significant increase in citrullinated histone H3 (P < 0.0001), in neutrophil elastase (P < 0.0001), and in PAD4 protein levels (P < 0.0001) compared with WT. Increased PAD4 activity was associated with the presence of albuminuria, renal interstitial fibrosis and reduced glomerular filtration rate. Conclusions: Taken together these data suggest that angiotensin II induces NET formation leading to renal accumulation in hypertension and diabetes. PAD4 may therefore play a role in target organ injury in hypertension and diabetes.
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