Kaempferol activates chloride secretion via the cAMP/PKA signaling pathway and expression of CFTR in T84 cells

Kaempferol is a flavonol identified as the most potent activator of chloride (Cl-) secretion among other flavonoids in airway epithelial cells. This study aimed to investigate the cellular mechanisms by which kaempferol stimulates Cl- secretion in the T84 human colon carcinoma cell line by Ussing chambers and voltage clamp technique. Bilateral addition of kaempferol (1-100 mu M) increased short-circuit current (I-sc ) in a concentration-dependent manner. Ion substitution of Cl- or CFTR inhibitors NPPB and glibenclamide or a Na+/K+/2Cl(-) cotransporter inhibitor bumetanide attenuated kaempferol-induced I sc response. In permeabilized monolayers, selective channel inhibitors CFTRinh-172 and CaCCinh-A01 inhibited kaempferol-induced apical Cl- current (I-Cl ), and K+ blockers BaCl2 and clotrimazole inhibited basolateral K+ current (I-Kb ). The kaempferol-induced I-Cl showed no additive effects with forskolin or 8cpt-cAMP. The kaempferol-induced I-Cl was mostly abolished by protein kinase A inhibitor H89, but not by tyrosine kinase inhibitors, AG490 and tyrphostin A23, or tyrosine phosphatase inhibitor vanadate. Treatment with kaempferol for 24 h increased the expression of CFTR protein as determined by the Western blot analysis. These results demonstrated that kaempferol activates Cl(- )secretion across T84 cells by activating the apical Cl- current and basolateral K+ current. The mechanisms may involve the cAMP/PKA pathway and CFTR expression. Taken together, these findings reveal the beneficial effects of kaempferol to increase fluid secretion which can be used to treat constipation.