Atorvastatin Reduces High Glucose Toxicity in Rat Peritoneal Mesothelial Cells

IL-17A as a Potential Therapeutic Target for Patients on Peritoneal Dialysis

Chronic kidney disease (CKD) is a health problem reaching epidemic proportions. There is no cure for CKD, and patients may progress to end-stage renal disease (ESRD). Peritoneal dialysis (PD) is a current replacement therapy option for ESRD patients until renal transplantation can be achieved. One important problem in long-term PD patients is peritoneal membrane failure. The mechanisms involved in peritoneal damage include activation of the inflammatory and immune responses, associated with submesothelial immune infiltrates, angiogenesis, loss of the mesothelial layer due to cell death and mesothelial to mesenchymal transition, and collagen accumulation in the submesothelial compact zone. These processes lead to fibrosis and loss of peritoneal membrane function. Peritoneal inflammation and membrane failure are strongly associated with additional problems in PD patients, mainly with a very high risk of cardiovascular disease. Among the inflammatory mediators involved in peritoneal damage, cytokine IL-17A has recently been proposed as a potential therapeutic target for chronic inflammatory diseases, including CKD. Although IL-17A is the hallmark cytokine of Th17 immune cells, many other cells can also produce or secrete IL-17A. In the peritoneum of PD patients, IL-17A-secreting cells comprise Th17 cells, γδ T cells, mast cells, and neutrophils. Experimental studies demonstrated that IL-17A blockade ameliorated peritoneal damage caused by exposure to PD fluids. This article provides a comprehensive review of recent advances on the role of IL-17A in peritoneal membrane injury during PD and other PD-associated complications.

The role of Resveratrol-induced mitophagy/autophagy in peritoneal mesothelial cells inflammatory injury via NLRP3 inflammasome activation triggered by mitochondrial ROS

It has been suggested that continuous exposure of peritoneal mesothelial cells (PMCs) to high glucose-containing peritoneal dialysis (PD) solutions may result in peritoneal inflammatory injury and impairment of local peritoneal host defence. Here, we investigated the effect of glucose-based PD solutions on mitochondrial reactive oxygen species (ROS) and nod-like receptor 3 (NLRP3) inflammasome activation in human PMCs (HPMCs). Exposure of HPMCs to high glucose-based PD solutions resulted in ROS production, which can trigger NLRP3 activation, leading to IL-1β secretion. Additionally, resveratrol (RSV) treatment induced mitophagy/autophagy via adenosine monophosphate-activated protein kinase (AMPK) activation. Increased mitochondrial ROS concentrations and IL-1β upregulation were confirmed following inhibition (siRNA against Beclin1 and ATG5 or autophagy inhibitor 3MA), but not induction (RSV), of mitophagy/autophagy. Furthermore, we observed that ATG5 and Beclin1 downregulation sensitised cells to IL-1β release induced by MSU or nigericin, which is an NLRP3 inflammasome activator. RSV treatment attenuated this effect. Taken together, this study may provide a potential therapeutic strategy for peritoneal inflammatory injury via NLRP3 inflammasome activation triggered by mitochondrial ROS.

Fluvastatin inhibits the expression of fibronectin in human peritoneal mesothelial cells induced by high-glucose peritoneal dialysis solution via SGK1 pathway

BACKGROUND

Previous studies showed that statins may have protective effects on peritoneal mesothelial cells (PMC) cultured in high glucose. However, the mechanisms are not clear yet. Several studies demonstrated that serum- and glucocorticoid-inducible kinase 1 (SGK1) is implicated in tissue fibrosis of liver, lung and kidney by regulating the expression of many profibrogenic cytokines and extracellular matrix (e.g., fibronectin). However, few available reports elucidated whether the SGK1 is involved in the pathogenesis of peritoneal fibrosis (PF) in patients with peritoneal dialysis (PD). So far, there is no study about the interaction between the statins and SGK1 in PMC. The purpose of this study was to identify whether fluvastatin may decrease the expression of fibronectin (FN) in human peritoneal mesothelial cells (HPMC) cultured with high-glucose peritoneal dialysis solution (HGPDS) by affecting SGK1 signal pathway.

METHODS

Cultured HPMC were divided into groups of control, high-glucose peritoneal dialysis solution (HGPDS), HGPDS with fluvastatin (10(-8) mol/L ~ 10(-6) mol/L) or GSK650394 10(-5) mol/L (the competitive inhibitor of SGK1), fluvastatin 10(-6) mol/L or GSK650394 10(-5) mol/L alone. The expression of SGK1 and FN was detected by RT-PCR, western immunoblotting or ELISA.

RESULTS

Compared with the control, the mRNA and protein expression of SGK1 and FN increased significantly in HPMC treated with HGPDS (p < 0.05). GSK650394 significantly decreased the upregulated mRNA and protein expression of SGK1 and FN induced by HGPDS (p < 0.05), and fluvastatin had the same effects as GSK650394 in a dose-dependent manner (p < 0.05).

CONCLUSIONS

Expression of SGK1 and FN increased in HPMC induced by HGPDS. Treated with fluvastatin and the SGK1-inhibitor GSK650394, abnormalities of SGK1 and FN could be corrected partially, which suggested that the SGK1 pathway was implicated in the pathogenesis of PF, and that fluvastatin might decrease the expression of SGK1 so as to meliorate the progression of PF.

Hydrogen sulfide ameliorates high-glucose toxicity in rat peritoneal mesothelial cells by attenuating oxidative stress

BACKGROUND/AIMS

Continuous exposure of the peritoneal membrane to high-glucose (HG) peritoneal dialysis fluids (PDFs) can produce peritoneal mesothelial cells (PMCs) injury. It has been demonstrated that hydrogen sulfide (H2S), the third endogenous gaseous mediator identified after nitric oxide and carbon monoxide, exhibits a potent protective effect on cell activity. We studied the toxic effects of HG PDFs and their reversal by H2S on cultures of rat PMCs.

METHODS

Synchronized confluent rat PMCs were incubated with 2.5% glucose PDFs with or without NaHS, an H2S donor. Cell viability was assessed by methyl thiazolyl tetrazolium assay and flow cytometry. The level of phospho-p38 mitogen-activated protein kinase (MAPK) was analyzed by immunoblotting. p53, Bax and Bcl-2 mRNA expressions by rat PMCs were detected by real-time PCR. The levels of reactive oxygen species (ROS), superoxide dismutase (SOD) activity and caspase-3 activity were measured.

RESULTS

Exposure of rat PMCs to 2.5% glucose PDFs for 24 h resulted in a significant induction of apoptosis, which was attenuated by NaHS. NaHS also restored the 2.5% glucose PDF-induced increase in phospho-p38 MAPK (indices of cellular toxicity). Further investigation of the apoptotic mechanisms in rat PMCs demonstrated that HG activated caspase-3 and upregulated Bax, while it downregulated Bcl-2. All the above responses were prevented by pretreatment with NaHS. Moreover, NaHS reversed the 2.5% glucose PDF-induced increase in ROS generation and decrease in SOD activity.

CONCLUSIONS

These findings suggest that HG PDFs significantly inhibit rat PMC viability, leading to peritoneal injury. H2S exhibits a potent anti-apoptotic ability by attenuating oxidative stress and inhibiting caspase-3 activation, which in turn restores peritoneal injury.

Aliskiren prevents the toxic effects of peritoneal dialysis fluids during chronic dialysis in rats

The benefits of long-term peritoneal dialysis (PD) in patients with end-stage renal failure are short-lived due to structural and functional changes in the peritoneal membrane. In this report, we provide evidence for the in vitro and in vivo participation of the renin-angiotensin-aldosterone system (RAAS) in the signaling pathway leading to peritoneal fibrosis during PD. Exposure to high-glucose PD fluids (PDFs) increases damage and fibrosis markers in both isolated rat peritoneal mesothelial cells and in the peritoneum of rats after chronic dialysis. In both cases, the addition of the RAAS inhibitor aliskiren markedly improved damage and fibrosis markers, and prevented functional modifications in the peritoneal transport, as measured by the peritoneal equilibrium test. These data suggest that inhibition of the RAAS may be a novel way to improve the efficacy of PD by preventing inflammation and fibrosis following peritoneal exposure to high-glucose PDFs.