Molecular mechanisms of caffeine-mediated intestinal epithelial ion transports.

BACKGROUND AND PURPOSE

As little is known about the effect of caffeine, one of the most widely consumed substances worldwide, on intestinal function, we aimed to study its action on intestinal anion secretion and the underlying molecular mechanisms.

EXPERIMENTAL APPROACH

Anion secretion and channel expression were examined in mouse duodenal epithelium by Ussing chambers and immunocytochemistry. Ca imaging was also performed in intestinal epithelial cells (IECs).

KEY RESULTS

Caffeine (10 mM) markedly increased mouse duodenal short-circuit current (I ), which was attenuated by a removal of either Cl or HCO , Ca -free serosal solutions and selective blockers of store-operated Ca channels (SOC/Ca release-activated Ca channels), and knockdown of Orai1 channels on the serosal side of duodenal tissues. Caffeine induced SOC entry in IEC, which was inhibited by ruthenium red and selective blockers of SOC. Caffeine-stimulated duodenal I was inhibited by the endoplasmic reticulum Ca chelator (N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine), selective blockers (ruthenium red and dantrolene) of ryanodine receptors (RyR), and of Ca -activated Cl channels (niflumic acid and T16A). There was synergism between cAMP and Ca signalling, in which cAMP/PKA promoted caffeine/Ca -mediated anion secretion. Expression of STIM1 and Orai1 was detected in mouse duodenal mucosa and human IECs. The Orai1 proteins were primarily co-located with the basolateral marker Na , K -ATPase.

CONCLUSIONS AND IMPLICATIONS

Caffeine stimulated intestinal anion secretion mainly through the RyR/Orai1/Ca signalling pathway. There is synergism between cAMP/PKA and caffeine/Ca -mediated anion secretion. Our findings suggest that a caffeine-mediated RyR/Orai1/Ca pathway could provide novel potential drug targets to control intestinal anion secretion.