Dextran sulfate sodium-induced chronic colitis attenuates Ca^sup 2+^-activated Cl^sup -^ secretion in murine colon by downregulating TMEM16A

• Published in: American Journal of Physiology: Cell Physiology 2018-07, Vol.315 (1), p.C10
• Main Authors: Rottgen, Trey S, Nickerson, Andrew J, Minor, Emily A, Stewart, Amanda B, Harold, Abby D, Rajendran, Vazhaikkurichi M
• Format: Article
• Language: English
• Subjects: Acetylcholine receptors; Acetylcholine receptors (muscarinic); Calcium channels; Carbachol; Colitis; Colon; Cystic fibrosis; Cystic fibrosis transmembrane conductance regulator; Dextran; Dextran sulfate; Epithelium; Inflammatory bowel disease; Membranes; Polarity; Rodents; Secretion; Sodium; Surgical apparatus & instruments; Transcription; Western blotting
• ISSN: 0363-6143; 1522-1563

Attenuated Ca2+-activated Cl− secretion has previously been observed in the model of dextran sulfate sodium (DSS)-induced colitis. Prior studies have implicated dysfunctional muscarinic signaling from basolateral membranes as the potential perpetrator leading to decreased Ca2+-activated Cl− secretion. However, in our chronic model of DSS-colitis, cholinergic receptor muscarinic 3 (Chrm3) transcript (1.028 ± 0.12 vs. 1.029 ± 0.27, P > 0.05) and CHRM3 protein expression (1.021 ± 0.24 vs. 0.928 ± 0.09, P > 0.05) were unchanged. Therefore, we hypothesized that decreased carbachol (CCH)-stimulated Cl− secretion in DSS-induced colitis could be attributed to a loss of Ca2+-activated Cl− channels (CaCC) in apical membranes of colonic epithelium. To establish this chemically-induced colitis, Balb/C mice were exposed to 4% DSS for five alternating weeks to stimulate a more moderate, chronic colitis. Upon completion of the protocol, whole thickness sections of colon were mounted in an Ussing chamber under voltage-clamp conditions. DSS-induced colitis demonstrated a complete inhibition of basolateral administration of CCH-stimulated Cl− secretion that actually displayed a reversal in polarity (15.40 ± 2.22 μA/cm2 vs. −2.47 ± 0.25 μA/cm2). Western blotting of potential CaCCs, quantified by densitometric analysis, demonstrated no change in bestrophin-2 and cystic fibrosis transmembrane regulator, whereas anoctamin-1 [ANO1, transmembrane protein 16A (TMEM16A)] was significantly downregulated (1.001 ± 0.13 vs. 0.510 ± 0.12, P < 0.05). Our findings indicate that decreased expression of TMEM16A in DSS-induced colitis contributes to the decreased Ca2+-activated Cl− secretion in murine colon.