title: PKCα signaling pathway involves in TNF-α-induced IP3R1 expression in human mesangial cells.
abstract: BACKGROUND
  This study aimed to explore the effects of TNF-α on the expression of IP3R1 mRNA and protein in human mesangial cells (HMCs), and to elucidate the mechanism of TNF-α relating to IP3R1 expression in the occurrence of hepatorenal syndrome (HRS).
  
  
  METHODS
  HMCs were stimulated by tumor (TNF-α) 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 of TNF-α-regulated IP3R1 in HMCs.
  
  
  RESULTS
  The levels of IP3R1 mRNA at 2 hours after TNF-α 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-α exposure were obviously increased and peaked at 24 hours after TNF-α exposure (P<0.01). Compared to the control group, safingol (PKCα inhibitor) and D609 (phosphatidylcholine-specific phospholipase C inhibitor) significantly blocked the TNF-αinduced expression of IP3R1 mRNA (3.30±0.81 vs. 1.95±0.13, P<0.05; 2.10±0.49, P<0.01) and IP3R1 protein (3.09±0.13 vs. 1.86+0.39, P<0.01; 1.98±0.02, P<0.01). TNF-α promoted PKCα activation with maximal PKCα 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.
  
  
  CONCLUSIONS
  TNF-α increased the expression of IP3R1 and this was mediated, at least in part, through the PC-PLC/PKCα signaling pathways in HMCs.
authors.affiliation: Department of Digestion, Jiujiang First People's Hospital, Jiujiang 332000, China.
authors.forename: Yu-Rong
authors.initials: YR
authors.lastname: Wang
authors.affiliation: Department of Digestion, Jiujiang First People's Hospital, Jiujiang 332000, China.
authors.forename: Huan
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Digestion, Jiujiang First People's Hospital, Jiujiang 332000, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Sun
authors.affiliation: Department of Digestion, Jiujiang First People's Hospital, Jiujiang 332000, China.
authors.forename: Pei
authors.initials: P
authors.lastname: Liu
keywords: Hepatorenal syndrome; Human mesangial cells; Phosphatidylcholine-specific phospholipase C; Protein kinase C; TNF-α