Ethanol induced alterations in plasma membrane protein phosphorylation of neurons and astrocytes

Ethanol can modify the effects of certain free radical-generating systems on astrocytes

The central nervous system is vulnerable to oxidative stress, especially when a toxicant can modify the physiological balance between anti- and pro-oxidant mechanisms. Among brain cells, astrocytes seem less vulnerable than neurons, but their impairment can dramatically affect neurons because of their protective role toward neurons. Ethanol is able to stimulate the formation of reactive oxygen species and modify the activity of most of the antioxidant agents. However, ethanol can react with the OH* radical to form the alpha-hydroxyethyl radical, which is considered to be less toxic. Ethanol also can stimulate H2O2 degradation through catalase activation. This study, therefore, sought to determine whether ethanol affected the sensitivity of astrocytes exposed to various free radical-generating systems. The cellular impact of such exposure was assessed by assays exploring cytotoxicity (i.e., NR (neutral red) and MMT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetiazolium bromide) reduction assays) and genotoxicity (comet assay) induced by these treatments. DNA alterations were evaluated by single-cell gel electrophoresis (comet assay), considered a precocious biomarker of intracellular alterations. After concomitant exposure to H2O2 and ethanol, the viability of astrocytes decreased significantly whereas the mean percentage of DNA in the tail increased,reflecting DNA damage (H2O2 was either directly added to the culture medium or endogenously produced from menadione). Ethanol also reduced the loss of viability and DNA alterations after exposure to OH* radicals produced by a Fenton system. The exposure to a xanthine/xanthine oxidase system had the same effect.

Effect of alcohol on energy storage of primary astrocytes and C6-glioma cells in vitro

The present experiments were conducted to investigate the direct effects of ethanol on the energy metabolism of astrocytes and C6-glioma cells. Primary astrocytes were prepared from cerebral cortices of neonatal rats, and C6-glioma cells were purchased from American Type Culture Collection (ATCC). These cells were exposed to different concentrations of alcohol (100 mM, 200 mM, and 300 mM) for 15 minutes and 24 hours. The amount of ATP and PCr was measured by the method of Lowry and Passonneau (1972). Following 15 minutes treatment with different doses of ethanol the amount of ATP and PCr increased, in both cell types. Only the increase of ATP concentration with varying doses of ethanol (100 mM, 200 mM, and 300 mM) was statistically significant. Following 24 hours treatment of astrocytes with different doses of ethanol the concentration of ATP and PCr decreased. The decrease in concentration of ATP was significant with all three doses of ethanol, but the decrease of PCr concentration was only statistically significant with 300 mM ethanol. Following 24 hours treatment of C6-glioma cells to varying doses of ethanol, the concentration of PCr and ATP decreased. The decrease of PCr was statistically significant with all three doses of ethanol and the decrease of ATP concentration was only significant with 300 mM ethanol.

Effect of ethanol on nuclear casein kinase II activity in brain

Casein kinase II (CK II) plays an important role in serine/threonine dependent protein phosphorylation. In brain it is associated with long term potentiation besides its involvement in DNA, RNA and protein metabolism. Ethanol has been shown to induce cognitive impairment and affects DNA, RNA and protein metabolism at various steps. Since CK II is central in all these events, which are specifically affected by ethanol, the role of nuclear CK II is investigated in the present study. Total nuclear casein kinase activity was unaffected while heparin sensitive nuclear casein kinase II activity showed a 30% decrease in the brain from chronic alcohol fed rats. Cytosolic CK II activity was also unaffected. Immunological detection by western analysis using CK II antibodies showed no alteration in the quantity of enzyme. The decrease in nuclear casein kinase II might be responsible for ethanol induced cognitive impairment in the brain.