Oxidative stress, caspase-3 activation and cleavage of ROCK-1 play an essential role in MeHg-induced cell death in primary astroglial cells.
Methylmercury is a toxic environmental contaminant that elicits significant toxicity in humans. The central nervous system is the primary target of toxicity, and is particularly vulnerable during development. Rho-associated protein kinase 1 (ROCK-1) is a major downstream effector of the small GTPase RhoA and a direct substrate of caspase-3. The activation of ROCK-1 is necessary for membrane blebbing during apoptosis. In this work, we examined whether MeHg could affect the RhoA/ROCK-1 signaling pathway in primary cultures of mouse astrocytes. Exposure of cells with 10 μM MeHg decreased cellular viability after 24 h of incubation. This reduction in viability was preceded by a significant increase in intracellular and mitochondrial reactive oxygen species levels, as well as a reduced NAD+/NADH ratio. MeHg also induced an increase in mitochondrial-dependent caspase-9 and caspase-3, while the levels of RhoA protein expression were reduced or unchanged. We further found that MeHg induced ROCK-1 cleavage/activation and promoted LIMK1 and MYPT1 phosphorylation, both of which are the best characterized ROCK-1 downstream targets. Inhibiting ROCK-1 and caspases activation attenuated the MeHg-induced cell death. Collectively, these findings are the first to show that astrocytes exposed to MeHg showed increased cleavage/activation of ROCK-1, which was independent of the small GTPase RhoA.
['Dos Santos|Alessandra Antunes|AA|', 'López-Granero|Caridad|C|', 'Farina|Marcelo|M|', 'Rocha|João B T|JBT|', 'Bowman|Aaron B|AB|', 'Aschner|Michael|M|']
D000818:Animals D001253:Astrocytes D053148:Caspase 3 D053453:Caspase 9 D016923:Cell Death D002478:Cells, Cultured D004789:Enzyme Activation D054461:Lim Kinases D008767:Methylmercury Compounds D008810:Mice, Inbred C57BL D043263:Myosin-Light-Chain Phosphatase D018384:Oxidative Stress D010766:Phosphorylation D059748:Proteolysis D054460:rho-Associated Kinases
Oxidative stress Caspase-3 ROCK-1 Primary astroglial cells Methylmercury