Effect ofbax deletion on ethanol sensitivity in the neonatal rat cerebellum

Abstract

The developing cerebellum is highly sensitive to ethanol during discrete neonatal periods. This sensitivity has been linked to ethanol-induced alterations in molecules of the Bcl-2 survival-regulatory gene family. Ethanol exposure during peak periods of cerebellar sensitivity, for example, results in increased expression of proapoptotic proteins of this family, while overexpression of the antiapoptotic Bcl-2 protein in the nervous system protects against ethanol neurotoxicity. For the present study, neonatal mice with a targeted deletion of the proapoptotic bax gene were used to determine whether elimination of this protein would mitigate ethanol toxicity. bax knock-out and wild-type mice pups were exposed to ethanol via vapor inhalation during the maximal period of neonatal cerebellar ethanol sensitivity and cerebellar tissue was subsequently assessed for Purkinje and granule cell number and ethanol-mediated generation of reactive oxygen species (ROS). The results revealed that: (1) ethanol exposure during the peak period of cerebellar vulnerability resulted in substantial loss of Purkinje cells in wild-type animals, but not in bax knock-outs; (2) granule cells in the bax gene-deleted animals were not similarly protected from ethanol effects; and (3) levels of ROS following acute ethanol exposure were appreciably enhanced in the wild-type animals but not in the bax knock-outs. These results imply that Bax is important to ethanol-induced Purkinje cell death during critical neonatal periods, but that ethanol effects on granule cells may function at least partially independent of this apoptosis agonist. Amelioration of ethanol-mediated increases in ROS production in the knock-outs may contribute to the observed effects.

Brain DNA damage and behavioral changes after repeated intermittent acute ethanol withdrawal by young rats

“…The present results show that chronic exposure to ethanol in rats cause DNA single-strand damage in all brain structures analyzed, including the striatum, which differs from a previous study in mice (Guo et al 2007). It has been considered that differences in the ethanol-induced ROS effects could be due to tissue differences and to diverse experimental conditions that modulate the attempts at counterbalancing the ethanol insult through antioxidant systems, successfully or not (Heaton et al 2006). Although ethanol-induced DNA damage can be repaired by the body in a short time, there is a potential increase in the incidence of mistakes during the DNA repair process.…”

“…More studies have already shown that ethanol may increase DNA damage in animal models (Heaton et al 2006;Guo et al 2007;Deng and Deitrich 2008;Bustamante et al 2012). Most of these studies use moderate to very high doses of ethanol in animals, corresponding to different alcoholic states in humans.…”

“…Neuronal dendritic shrinkage has also been associated with alcohol consumption and this dendritic shrinkage has been shown to be reversible in an experimental model following a prolonged period of abstinence (reviewed by Harper 2009). Oxidative stress with excessive production of reactive oxygen species (ROS) has been proposed as an important cause of ethanol-induced neuronal damage (Heaton et al 2006;Bustamante et al 2012;Wang et al 2012;Fowler et al 2014).…”

Alcohol and thiamine deficiency trigger differential mitochondrial transition pore opening mediating cellular death

“…These findings suggest that ethanol-related oxidative stress provokes partial opening of MPT pore [66]. Following these observations, ethanol-induced death of neonatal granule cells would be partially shared between proapoptotic Bax and ethanolincreased ROS production [70]. However, literature does not provide any evidence that Bax is an undisputed component of MPT pore.…”

Ethanol exposure of neonatal rats does not increase biomarkers of oxidative stress in isolated cerebellar granule neurons

“…These include: altered neuronal metabolism (de la Monte et al, 2005;Li et al, 2002), glutamate excitotoxicity (Ikonomidou et al, 2000), disruption of apoptotic regulators (Heaton et al, 2006;Siler-Marsiglio et al, 2005a), limited neurotrophin support (Heaton et al, 2000b;Light et al, 2002b;Light et al, 2001), restricted synaptic development (Klintsova et al, 2002;West et al, 1994), and oxidative stress (Heaton et al, 2003;Heaton et al, 2002;Henderson et al, 1995;Ramachandran et al, 2003;Reyes et al, 1993;Siler-Marsiglio et al, 2005b;Smith et al, 2005). Oxidative stress can cause mitochondrial membrane depolarization, which is followed by cytochrome c release, caspase activation, and apoptosis (Bernardi et al, 2006;O'Rourke et al, 2005).…”