Title: Oxidative stress, caspase-3 activation and cleavage of ROCK-1 play an essential role in MeHg-induced cell death in primary astroglial cells.

Authors: Dos Santos, Alessandra Antunes; López-Granero, Caridad; Farina, Marcelo; Rocha, João B T; Bowman, Aaron B; Aschner, Michael

Published In Food Chem Toxicol, (2018 Mar)

Abstract: 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.

PubMed ID: 29428217

MeSH Terms: Animals; Astrocytes/cytology; Astrocytes/drug effects*; Astrocytes/enzymology; Caspase 3/metabolism*; Caspase 9/metabolism; Cell Death/drug effects*; Cells, Cultured; Enzyme Activation; Lim Kinases/metabolism; Methylmercury Compounds/toxicity*; Mice, Inbred C57BL; Myosin-Light-Chain Phosphatase/metabolism; Oxidative Stress*; Phosphorylation; Proteolysis; rho-Associated Kinases/metabolism*