Aim Large conductance Ca2^＋ -activated potassium channel （BK） , expressed in the distal nephron, me- diates potassium secretion. Loss-of-function of renal BK channel is closely related with aldosteronism resulting ...Aim Large conductance Ca2^＋ -activated potassium channel （BK） , expressed in the distal nephron, me- diates potassium secretion. Loss-of-function of renal BK channel is closely related with aldosteronism resulting from renal potassium retention and hyperkalemia. Natural products affecting BK functions are still scarce, especially ac- tivators. Here, the pharmacological characterization of curcumin, one of the compounds isolated from the herb Cur- cuma longa. , on B K channels have been investigated. Methods B K currents were recorded by whole-cell patch- clamp, mRNA expressions of BK were measured by quantitative real-time PCR. The surface and total protein ex- pressions of B K were assessed by surface biotinylation and Western blot. Functional study was performed on aortic rings. Results Curcumin potently increased B K currents in transfected HEK293 cells as well as the current densi- ty in A7r5 cells （ endogenous expressed BK （ α ＋ β1） channels） with ECs0 - （6.76 ± 2.24） μmol · L^-1 and （7.19 ± 0.07） μmol · L^-1, respectively. Curcumin up-regulated B K protein abundance without affecting its mR- NA expression in A7r5 cells. Surface expression and half-life of B K channels were increased by curcumin in HEK293 cells, which were abolished by MG-132, a proteasome inhibitor. Simultaneously, ERK 1/2 phosphoryla- tion was also increased by curcumin. U0126, an inhibitor of ERK, attenuate the curcumin-induced up-regulation of BK protein level. Curcumin-induced relaxation in isolated rat aortic rings was significantly attenuated by paxilline, a BK channel specific blocker. Conclusion Curcumin increased BK currents and protein abundance by inhibiting proteasomal degradation and activating ERK signaling pathway. These findings suggest that curcumin is a potential BK channel activator and provide novel insight into its complicated pharmacological effects and mechanisms.展开更多
文摘Aim Large conductance Ca2^＋ -activated potassium channel （BK） , expressed in the distal nephron, me- diates potassium secretion. Loss-of-function of renal BK channel is closely related with aldosteronism resulting from renal potassium retention and hyperkalemia. Natural products affecting BK functions are still scarce, especially ac- tivators. Here, the pharmacological characterization of curcumin, one of the compounds isolated from the herb Cur- cuma longa. , on B K channels have been investigated. Methods B K currents were recorded by whole-cell patch- clamp, mRNA expressions of BK were measured by quantitative real-time PCR. The surface and total protein ex- pressions of B K were assessed by surface biotinylation and Western blot. Functional study was performed on aortic rings. Results Curcumin potently increased B K currents in transfected HEK293 cells as well as the current densi- ty in A7r5 cells （ endogenous expressed BK （ α ＋ β1） channels） with ECs0 - （6.76 ± 2.24） μmol · L^-1 and （7.19 ± 0.07） μmol · L^-1, respectively. Curcumin up-regulated B K protein abundance without affecting its mR- NA expression in A7r5 cells. Surface expression and half-life of B K channels were increased by curcumin in HEK293 cells, which were abolished by MG-132, a proteasome inhibitor. Simultaneously, ERK 1/2 phosphoryla- tion was also increased by curcumin. U0126, an inhibitor of ERK, attenuate the curcumin-induced up-regulation of BK protein level. Curcumin-induced relaxation in isolated rat aortic rings was significantly attenuated by paxilline, a BK channel specific blocker. Conclusion Curcumin increased BK currents and protein abundance by inhibiting proteasomal degradation and activating ERK signaling pathway. These findings suggest that curcumin is a potential BK channel activator and provide novel insight into its complicated pharmacological effects and mechanisms.
