TNFα-induced IP3R1 expression through TNFR1/PC-PLC/PKCα and TNFR2 signalling pathways in human mesangial cell.

Background. Little information is available regarding the mechanisms involved in cytokine-induced type 1 inositol 1,4,5-trisphosphate receptor (IP(3)R1) expression in human mesangial cells (HMCs) in the occurrence of hepatorenal syndrome (HRS). Over-expression of IP(3)R1 would enhance both IP3-binding activity and sensitivity. We hypothesize that it is possible that increased IP(3)R1, induced by TNF alpha, would lead to increased IP3 sensitivity in response to a variety of vasoconstrictors, and promote HMC contraction and thus lead to reduced GFP, promoting HRS occurrence and development. Methods. Quantitative real-time polymerase chain reaction and immunoblot assay were used to examine the effects of TNF alpha on IP(3)R1 mRNA and protein expression. Several inhibitors of kinases, depletion PKC, over-expression of dominant-negative mutant of PKC and non-radioactive PKC assay were used to examine the mechanism of signal transduction of TNF alpha-regulated IP(3)R1 in HMCs. Results. TNF alpha increased IP(3)R1 mRNA and protein expression in HMCs, an effect that was blocked by prolonged incubated chronic PMA, D609, safingol and also by transfection with domain-negative PKC alpha construct. TNF alpha activated and promoted autophosphorylation of the PKC alpha. In addition, both anti-TNFR1 and anti-TNFR2 antibodies blocked TNF alpha-induced IP(3)R1 protein expression, while only anti-TNFR1 antibodies but not anti-TNFR2 antibodies attenuated TNF alpha-induced PKC alpha activity. Conclusions. TNF alpha increased the expression of IP(3)R1, and this was mediated, at least in part, through the TNFR1/PC-PLC/PKC alpha and TNFR2 signalling pathways in HMCs.