BACKGROUND:This study aimed to explore the effects of TNF-a on the expression of IP3R1mRNA and protein in human mesangial cells（HMCs）,and to elucidate the mechanism of TNF-a relating to IP3R1 expression in the occurrence of hepatorenal syndrome（HRS）.METHODS:HMCs were stimulated by tumor（TNF-a） with 100 ng/mL for different hours（2,4,8,and 24 hours）.The expression changes of IP3R1 mRNA and protein were detected by quantitative real-time polymerase chain reaction and immunoblotting.Several inhibitors including D609,U73122,PP1,safingol,rottlerin and non-radioactive protein kinase C（PKC） were used to examine the mechanism of signal transduction ofTNF-a-regulated IP3R1 in HMCs.RESULTS:The levels of IP3R1 mRNA at 2 hours after TNF-a exposure were significantly enhanced and peaked at 8 hours in HMCs（P<0.01）,then descended at 24 hours（P<0.01）.The levels of IP3R1 protein at 4 hours after TNF-a exposure were obviously increased and peaked at24 hours after TNF-a exposure（P<0.01）.Compared to the control group,safingol（PKCa inhibitor）and D609（phosphatidylcholine-specific phospholipase C inhibitor） significantly blocked the TNF-ainduced expression of IP3R1 mRNA（3.30±0.81 vs.1.95±0.13,P<0.05;2.10±0.49,P<0.01） and IP3R1protein（3.09±0.13 vs.1.86+0.39,P<0.01;1.98±0.02,P<0.01）.TNF-a promoted PKCa activation with maximal PKCa phosphorylation that occurred 8 hours after stimulation measured by non-radioactive PKC assay,and the effect was markedly attenuated by pretreatment with D609 or safingol.CONCLUSION:TNF-a increased the expression of IP3R1 and this was mediated,at least in part,through the PC-PLC/PKCa signaling pathways in HMCs.
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