Inhibition of ICl swell impairs TNFα‐dependent activation of NF‐κB (1096.3)

Cytokines such as TNFα drive inflammation via transcription factors including NF‐κB. Biologic agents targeting TNFα modulate disease, but require I.V. administration and cause immune suppression. Thus there is a need to develop oral, titratable therapies. In smooth muscle cells, NF‐κB activation by TNFα depends upon intracellular, endosomal ROS production by Nox1 and deficiency of ClC‐3 disrupts ROS production at this site. TNFα also activates I Cl swell via endosomal ROS. We hypothesized that I Cl swell activity is required for NF‐κB activation by TNFα. We used a luciferase‐NF‐κB reporter to quantify responses to TNFα (10ng/ml). Activation of HEK293 cells was reduced by both Tamoxifen (10μM, 13.9±3.5 to 6.4±2.2 fold) and DCPIB (30μM, 41.5±4.9 to 8.2±0.8 fold, N=6). In addition, inhibition of this channel in HUVECs with tamoxifen resulted in a 40% decrease in NFκB activation (N=6). These data suggest that I Cl swell activation by TNFα may play a role in NF‐κB signaling. I Cl swell has also been hypothesized to allow exit of ROS from the endosome to facilitate downstream cell signaling. Thus, we tested whether inhibition of ROS production would also lead to a decrease in NFκB activation. Inhibition of ROS production by TNFα with DPI resulted in a five‐fold increase in relative NFκB activation (N=4). Identification of the specific role of this anion conductance and localization of its activity to the plasma membrane or endosomes is the subject of ongoing investigation. Grant Funding Source : NIH 5T32HD068256‐03