The Trpa1 Agonist Cinnamaldehyde Induces The Secretion Of Hco3- By The Porcine Colon

A therapeutic potential of the TRPA1 channel agonist cinnamaldehyde for use in inflammatory bowel disease is emerging, but the mechanisms are unclear. Semi-quantitative qPCR of various parts of the porcine gastrointestinal tract showed that mRNA for TRPA1 was highest in the colonic mucosa. In Ussing chambers, 1 mmol center dot L-1 cinnamaldehyde induced increases in short circuit current (Delta I-sc) and conductance (Delta G(t)) across the colon that were higher than those across the jejunum or after 1 mmol center dot L-1 thymol. Lidocaine, amiloride or bumetanide did not change the response. The application of 1 mmol center dot L-1 quinidine or the bilateral replacement of 120 Na+, 120 Cl- or 25 HCO3- reduced Delta G(t), while the removal of Ca2+ enhanced Delta G(t) with Delta I-sc numerically higher. Delta I-sc decreased after 0.5 NPPB, 0.01 indometacin and the bilateral replacement of 120 Na+ or 25 HCO3-. The removal of 120 Cl- had no effect. Cinnamaldehyde also activates TRPV3, but comparative measurements involving patch clamp experiments on overexpressing cells demonstrated that much higher concentrations are required. We suggest that cinnamaldehyde stimulates the secretion of HCO3- via apical CFTR and basolateral Na+-HCO3- cotransport, preventing acidosis and damage to the epithelium and the colonic microbiome. Signaling may involve the opening of TRPA1, depolarization of the epithelium and a rise in PGE2 following a lower uptake of prostaglandins via OATP2A1.