[Interventional effects of activating SUR2B/Kir6.1-type KATP channels on renal cells injury and its mechanisms].

Abstract

Objective: To investigate the interventional effects of a new SUR2B/Kir6.1-type K_ATP Channel opener iptakalim on injury renal cells (the renal glomerular endothelial, mesangial and tubular epithelial cells) and its mechanisms. Methods: ①Experimental protocol: control: the cells were treated with with 0 mg/L uric acid for 24 h; model: the cells were treated with with 1 200 mg/L uric acid for 24 h; pretreatment with iptakalim: the cells were pretreated with 0.01,0.1,1,10,100 μmol/L iptakalim for 24 h prior to treatment with 1 200 mg/L uric acid for 24 h; pretreatment with glibenclamide: the cells were preincubated with/without 10 μmol/L glibenclamide for 1 h and then treated with 10 μmol/L iptakalim for 24 h followed by incubation with 1 200 mg/L uric acid for another 24 h. ②The cell viability was measured by MTT assay and flow cytometry; the protein expressions of Kir6.1 and SUR2B and nuclear translocation were detected by immunostaining; the protein expressions of Kir6.1 and SUR2B were determined by Western blot analysis; adhesion of mononuclear cells to endothelial cells were tested by fluorimetric assay; the content of MCP-1 was measured by enzyme linked-immunosorbent assay (ELISA). Results: The renal glomerular endothelial, mesangial and tubular epithelial cells were exposed to 1 200 mg/L uric acid for 24 h. Compared with the control group, 1 200 mg/L uric acid decreased the cell survival rates significantly (P＜0.01, P＜0.01, P＜0.01). Compared with the model group, pretreatment with 0.1, 1, 10, 100 μmol/L iptakalim could remarkably alleviate cellular damages of glomerular endothelium, mesangium cells induced by uric acid (P＜0.05, P＜0.01, P＜0.01, P＜0.01). The K_ATP channel blocker could clearly reduce survival rates of the renal glomerular endothelial, mesangial cells(P＜0.01) and markedly reverse the inhibitory effects of iptakalim on cell death (P＜0.05, P＜0.01), no obvious difference in comparison with the model group (P＞0.05). Compared with the model group, pretreatment with 10, 100 μmol/L iptakalim could notably attenuate cellular damages of tubular epithelial cells induced by uric acid (P＜0.05, P＜0.05). The K_ATP channel blocker could obviously damage the tubular epithelial cells (P＜0.01), no obvious difference in comparison with the model group (P＞0.05). Compared with control group, exposure of renal tubular epithelial, mesangial and glomerular endothelial cells to 1 200 mg/L uric acid for 24 h caused a significant increase in the protein expressions of Kir6.1 and SUR2B(P＜0.05). Compared with the model group, the overexpressions of Kir6.1 and SUR2B were suppressed in presence of iptakalim at a concentration of 10 μmol/L (P＜0.05). These decreases in the expressions of Kir6.1 and SUR2B were prevented by the K_ATP channel blocker, no obvious difference in comparison with the model group (P＞0.05). Compare with the control group, monocytic adhesion to renal glomerular endothelial cells was notably promoted by 1 200 mg/L uric acid for 24 h (P＜0.01). Pretreatment with 10 μmol/L iptakalim for 24 h significantly reduced the monocytic adhesion in comparison with the model group (P＜0.05). It was showed that the inhibitory effects of iptakalim were antagonized by the K_ATP channel blocker, no obvious difference in comparison with the model group (P＞0.05). After stimulating glomerular endothelial cells with 1 200 mg/L uric acid for 24 hours, the secretion of MCP-1 was significantly increased compared to the control group (P＜0.05). Compare with the model group, preincubation with 10 μmol/L iptakalim significantly decreased MCP-1 production (P＜0.05). K_ATP channel blocker suppressed the downregulation of MCP-1 protein synthesis induced by iptakalim. After stimulation with uric acid, translocation of NF-κB from cytoplasms to nuclei of renal glomerular endothelial cells were observed, while that of NF-κB was suppressed in presence of iptakalim at the concentration of 10 μmol/L. This inhibition of NF-κB translocation was clearly prevented by K_ATP channel blocker. Conclusion: These results suggests that a new SUR2B/Kir6.1-type K_ATP channel opener iptakalim plays interventional roles in renal cells damages caused by uirc acid and its mechanism is involved in activating K_ATPchannels .