RhoA and lysophosphatidic acid are involved in the actin cytoskeleton reorganization of astrocytes exposed to ethanol

Astroglial cells play an important role in maintaining neuronal function in the adult and in the developing nervous system. Ethanol exposure induces profound alterations in the astrogliogenesis process, affecting important cell functions, including intracellular protein trafficking. Because the actin cytoskeleton plays a crucial role in intracellular protein transport, the aim of the present study was to analyze the effects of ethanol on actin cytoskeleton organization and the involvement of the RhoA signaling pathway in these effects. We show that RhoA and lysophosphatidic acid (LPA), an upstream activator of RhoA, stimulate the formation of stress fibers and focal adhesion in cortical astrocytes in primary culture. Exposure of cultured astrocytes to different concentrations of ethanol profoundly disorganizes the actin cytoskeleton, leading to the formation of actin rings at the cell periphery and decreasing the content of focal adhesion proteins. Furthermore, LPA treatment or RhoA transfection revert the ethanol-induced actin alterations in astrocytes, whereas transfection with an inactive mutant of RhoA is unable to revert the actin ring organization. In addition, inhibition of endogenous RhoA by C3 exoenzyme effectively blocks ethanol-induced actin ring formation. These results suggest that the effects of alcohol on actin cytoskeleton organization are mediated by the RhoA signaling pathway. Disruptions in actin organization may impair important astrocyte functions, participating in ethanol-induced astroglial and brain damage during development. (C) 2003 Wiley-Liss, Inc.