The Effect of FR167653, p38 Mitogen-Activated Protein Kinase (MAPK) Inhibitor, on the Expression of Slit Diaphragm-Associated Proteins in Experimental Diabetic Nephropathy / 대한신장학회지

PURPOSE: This study was undertaken to investigate the effect of a p38 mitogen-activated protein kinase (p38 MAPK) inhibitor, FR167653, on urinary albumin excretion and on the expression of slit diaphragm-associated proteins in diabetic rats. METHODS: Thirty-two Sprague-Dawley rats were injected with diluent [control (C), N=16] or streptozotocin intraperitoneally (DM, N=16). Eight rats from each group were treated with 5 mg/kg/day FR 167653 (C+FR, DM+FR) for 6 weeks. At the time of sacrifice, 24-hour urinary albumin excretion was determined by ELISA. Glomerular nephrin, P-cadherin, and ZO-1 mRNA and protein expression were determined by real-time PCR and Western blot, respectively, with sieved glomeruli. RESULTS: Urinary albumin excretion was significantly higher in DM compared to C rats, and this increase in albuminuria was significantly inhibited by the administration of FR167653 in DM rats. Glomerular phospho-p38 MAPK protein expression was significantly increased in DM rats compared to C rats, and FR167653 treatment significantly attenuated the increase in phospho-p38 MAPK expression in DM glomeruli. Nephrin mRNA and protein expression were higher in 6-week DM compared to C glomeruli, and these increases were significantly abrogated with FR167653 treatment in DM rats. In contrast, FR167653 had no effects on the decrease in P-cadherin expression and the increase in ZO-1 expression observed in DM glomeruli. CONCLUSION: These findings suggest that FR167653, a p38 MAPK inhibitor, reduce the amount of albuminuria in early diabetic nephropathy, and this anti-proteinuric effect seems to be related with the change of glomerular nephrin expression.

The Effect of High Glucose on Renin-Angiotensin System (RAS) in Podocytes / 대한신장학회잡지

The renin-angiotensin system (RAS) plays an important role in the pathogenesis of diabetic nephropathy. Recently, the activation of local RAS in mesangial cells by high glucose has been reported. However, little is known about the changes of RAS in podocytes under diabetic conditions. In this study, we examined whether RAS activation was induced in high glucose- stimulated podocytes. Immortalized mouse podocytes were exposed to medium containing 5.6 mM glucose (NG), NG+24.4 mM mannitol, or 30 mM glucose(HG). mRNA and protein expression of RAS components were determined by real time-PCR and Western blot, respectively. Angiotensin I (AI) and angiotensin II (AII) concentrations, angiotensin-converting enzyme (ACE) levels, and renin activity were also determined. Angiotensinogen (AGT) mRNA expression was significantly increased in HG-stimulated podocytes. In addition, AI and AII concentrations were significantly higher in HG-treated cell lysates and in their conditioned media. However, there were no differences in renin activity and ACE levels among the groups. AII type 1 receptor (AT1R) mRNA and protein expression were also increased by 288% (p<0.01) and 170% (p< 0.05) in HG-stimulated podocytes compared to NG- treated cells. In conclusion, HG induced AGT mRNA expression, resulting in increases in AI and AII levels. These findings suggest that increased AII production along with increased AT1R expression in podocytes under diabetic conditions may well be considered as factors actively involved in the pathogenesis of diabetic nephropathy.