title: Apelin-13 inhibits large-conductance Ca2+-activated K+ channels in cerebral artery smooth muscle cells via a PI3-kinase dependent mechanism.
abstract: Apelin-13 causes vasoconstriction by acting directly on APJ receptors in vascular smooth muscle (VSM) cells; however, the ionic mechanisms underlying this action at the cellular level remain unclear. Large-conductance Ca(2+)-activated K(+) (BKCa) channels in VSM cells are critical regulators of membrane potential and vascular tone. In the present study, we examined the effect of apelin-13 on BK(Ca) channel activity in VSM cells, freshly isolated from rat middle cerebral arteries. In whole-cell patch clamp mode, apelin-13 (0.001-1 μM) caused concentration-dependent inhibition of BK(Ca) in VSM cells. Apelin-13 (0.1 µM) significantly decreased BK(Ca) current density from 71.25 ± 8.14 pA/pF to 44.52 ± 7.10 pA/pF (n=14 cells, P<0.05). This inhibitory effect of apelin-13 was confirmed by single channel recording in cell-attached patches, in which extracellular application of apelin-13 (0.1 µM) decreased the open-state probability (NPo) of BK(Ca) channels in freshly isolated VSM cells. However, in inside-out patches, extracellular application of apelin-13 (0.1 µM) did not alter the NPo of BK(Ca) channels, suggesting that the inhibitory effect of apelin-13 on BKCa is not mediated by a direct action on BK(Ca). In whole cell patches, pretreatment of VSM cells with LY-294002, a PI3-kinase inhibitor, markedly attenuated the apelin-13-induced decrease in BK(Ca current density. In addition, treatment of arteries with apelin-13 (0.1 µM) significantly increased the ratio of phosphorylated-Akt/total Akt, indicating that apelin-13 significantly increases PI3-kinase activity. Taken together, the data suggest that apelin-13 inhibits BK(Ca) channel via a PI3-kinase-dependent signaling pathway in cerebral artery VSM cells, which may contribute to its regulatory action in the control of vascular tone.
authors.affiliation: Department of Pharmaceutical Sciences, North Dakota State University, Fargo, North Dakota, United States of America.
authors.forename: Amit
authors.initials: A
authors.lastname: Modgil
authors.affiliation: Department of Pathophysiology, College of Basic Medical Sciences, Jilin University, Changchun, Jilin, China ; Department of Pharmaceutical Sciences, North Dakota State University, Fargo, North Dakota, United States of America.
authors.forename: Lirong
authors.initials: L
authors.lastname: Guo
authors.affiliation: Department of Pharmaceutical Sciences, North Dakota State University, Fargo, North Dakota, United States of America.
authors.forename: Stephen T
authors.initials: ST
authors.lastname: O'Rourke
authors.affiliation: Department of Pharmaceutical Sciences, North Dakota State University, Fargo, North Dakota, United States of America.
authors.forename: Chengwen
authors.initials: C
authors.lastname: Sun
mesh_terms: D000818:Animals; D000073861:Apelin; D020013:Calcium Signaling / Q000187:drug effects; D002536:Cerebral Arteries / Q000166:cytology / Q000187:drug effects; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology / Q000502:physiology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D037342:Pertussis Toxin / Q000494:pharmacology; D058539:Phosphatidylinositol 3-Kinase / Q000502:physiology*; D024681:Potassium Channels, Calcium-Activated / Q000037:antagonists & inhibitors*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000073861:Apelin; C498579:Apln protein, rat; D036341:Intercellular Signaling Peptides and Proteins; D024681:Potassium Channels, Calcium-Activated; D037342:Pertussis Toxin; D058539:Phosphatidylinositol 3-Kinase