Nuclear transcription factor kappa B (NF‐kB) mediates ROS and PKC‐induced decrease in TRPC6 protein expression in human glomerular mesangial cells (HMCs)

Abstract

We recently demonstrated that high ambient glucose significantly decreased the expression of TRPC6 at protein level in cultured HMCs through a ROS/PKC pathway. The present study was carried out to examine if NF‐κB is a downstream molecule of ROS/PKC in the pathway of suppressing TRPC6 protein expression in HMCs. Serum‐starved HMCs were treated with 200 μM H2O2 for 6 hours or with 1 μM PMA for 2 hours significantly reduced TRPC6 protein expression. These ROS and PKC effects were significantly prevented by pre‐treating the cells with NF‐κB activation inhibitor at 10 μM for 30 min. Both H2O2 and PMA, but not PMA inactive analog 4α‐PDD phosphorylated the inhibitory κBα (IκBα) and stimulated the degradation of IκBα in a time dependent manner. Furthermore, activation of NF‐κB by knockdown of IκBα using siRNA significantly reduced abundance of TRPC6 protein in HMCs, a reminiscent of H2O2 and PMA effect on TRPC6 protein expression. Importantly, either H2O2 or PMA treatment dramatically increased nuclear expression of NF‐ κB p65/p50 subunits in a time dependent manner in HMCs, suggesting activation of NF‐κB in response to both ROS and PKC activation. These results suggest that NF‐κB is a mediator downstream ROS and PKC for suppression of TRPC6 expression in HMCs.(Supported by NIH)