Regulation of Carbonic Anhydrase Expression in Experimental Colitis: A Possible Mechanistic Link with Na‐H Exchanger

Abstract

In this study we investigated a role and regulation of carbonic anhydrase (CA) and a possible mechanistic link with the NHE expression in experimental colitis. Intra‐rectal instillation of trinitrobenzenesulphonic acid was used to induce colitis in rats. On day 6 post‐TNBS, colon and ileal segments were taken out and used to measure expression levels of the CA‐I, ‐II and ‐IV isoforms by ECL western blot analysis. These isoforms together with NHE‐1 were significantly suppressed in the inflamed colon. Immunoprecipitation and confocal immunofluorescence demonstrated co‐localization of CA‐I and CA‐II, but not the CA‐IV isoform with NHE‐1 in the colon. However, the binding of CA isoforms with NHE‐1 was more suppressed as compared to their expression level in inflamed colon. Only CA‐I was found to interact with an 83 aa long NHE‐1 C‐terminal peptide. Ex‐vivo studies demonstrated suppression of CA‐I and CA‐II isoforms by TNF‐alpha treatment of control colon segments. Inflammation in the colon was confirmed by measuring body weight, myeloperoxidase activity, colon hypertrophy, mucus staining and inflammatory cells infiltration. These findings demonstrate inflammation‐induced reduction in the expression of CA isoforms which is regulated by TNF‐alpha. Reduction in the binding of CA isoforms with NHE‐1 C‐terminal peptide suggest inflammation‐induced uncoupling of the two transporters. Interaction of CA with the NHE‐1 is important to ensure availability of H+ for NHE‐1 activity. In conclusion both expression and coupling of CA and NHE‐1 are altered and may account for the suppression of NHE‐1 activity in inflamed colon.Support or Funding InformationFinancial support through a grant (MB 03/15) by the Research Sector, Kuwait University.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.