Bile acid chenodeoxycholate activation of Cl ‐ transport involves epidermal growth factor receptor signal transduction in human colonic T84 cells (908.4)

A role for EGFR signaling in BA action has been well described in colon cancer, but not as well in BA induced Cl ‐ secretion. Our preliminary report (EB LB 10695, ‘13) showed that the EGFR inhibitor, AG1478, reduced CDCA (500 µM) mediated Cl ‐ secretion by 69%, measured as short circuit current (I sc , µA.cm ‐2 ), in T84 cells. Here we aim to further elucidate this mechanism. To determine if BA action involves matrix metalloproteinases (MMP), CDCA (500 µM) was added to T84 cells ± batimastat (BAT, 20 µM, 30’). CDCA itself increases I sc in 2‐3’ and the effect is sustained for > 20’. BAT inhibited the sustained phase (∆I sc : CDCA: 11.6±1.4; +BAT: 3.9±2.6, n=3). Interestingly the PKA inhibitor H89 has a similar effect (∆I sc : CDCA: 21±4.6; +H89 (30 µM): 1±0.3, n=5), suggesting that EGF and cAMP are involved in sustaining CDCA‐stimulated secretion. The distal steps of EGFR action do not involve Src or MEK as their respective inhibitors PP2 (10 µM, n=3), and PD98059 (20 µM, n=3) did not alter CDCA‐induced I sc . Immunoblotting showed CDCA (5’) increased EGFR (n=1), p38 (n=3), and ERK 1/2 (n=3) phosphorylation. Based on this data we postulate that CDCA stimulates Cl ‐ secretion via MMP‐EGFR‐p38 signaling, but not via Src or the MEK‐ERK pathways. Together with our data (AJP 305:C447‐456, ‘13) that CDCA acts via PKA to activate CFTR, we summarize that CDCA evokes multiple signaling cascades and their cross talk needs further elucidation. Grant Funding Source : Supported by NIH and VA