Abstract

Connexin hemichannel (Cx HC) opening is involved in physiological and pathological processes, allowing the cellular release of autocrine/paracrine signaling molecules. Linoleic acid (LA) is known to modulate the functional state of connexin46 (Cx46) HCs. However, the molecular mechanism involved in this effect, or whether LA affects HCs constituted of other connexins, remains unknown. Here, we report the effects of LA on HCs in HeLa cells that express Cx26, one of the main Cxs in the cochlear sensory epithelium. Cx26 HC activity (dye uptake) was increased in,a concentration-dependent manner by bath application of LA and inhibited by HC blockers. Moreover, intracellular BAPTA, a Ca2+ chelator, and PI3K/AKT inhibitors were found to reduce the LA-induced Cx26 HC opening, suggesting that the LA effect is mediated by an increase of free intracellular Ca2+ concentration and activation of the PI3K/Akt-dependent pathway. The LA-induced increase in free intracellular Ca2+ concentration was mainly due to Ca2+ influx through Cx26 HCs. In addition, the involvement of -SH groups was ruled out, because dithiothreitol (DTT) did not block the IA-induced dye uptake. LA also increased the membrane current mediated by Cx26 HCs expressed in Xenopus oocytes and the dye uptake in HeLa cells expressing Cxs 32, 43 or 45. Since IA is an essential polyunsaturated fatty acid, its effect on HCs might be relevant to cell growth as well as to cellular functions of differentiated cells such as audition. (C)2012 Elsevier B.V. All rights reserved.