Chronic alcohol feeding and its influence on c-Fos and heat shock protein-70 gene expression in different brain regions of male and female rats

Abstract

Excessive ingestion of the macronutrient, alcohol, causes devastating complications in the brain leading to atrophy and impaired cognitive function with corresponding increases in morbidity and mortality and, consequently, reduced quality of life measures. The pathogenic mechanisms are unknown, but various studies have shown that the immediate early genes and heat shock (ie, stress or chaperone) proteins are increased in alcohol-exposed tissue. However, many of these studies have been performed in vitro or have failed to consider either the nutritional elements in the experimental design by appropriate use of pair-feeding or whether there are regional and/or gender differences. We hypothesized that (1) increased expression of heat shock proteins and/or oncogenes occur as a consequence of alcohol-feeding in vivo, and sensitivities are related to different (2) gender and (3) brain regions. To test this, we fed male and female rats nutritionally complete diets containing ethanol as 35% of total calories (treated) or isocaloric amounts of the same diet in which ethanol was replaced by isocaloric glucose (controls). At the end of 6 weeks, rats were killed and c-Fos and heat shock protein-70 (HSP70) mRNA analyzed in midbrain, cortex, brainstem, and cerebellum by reverse transcription-polymerase chain reaction (RT-PCR) with an endogenous internal standard, beta-actin. The results showed that there were distinct regional differences (P at least <.05) in both c-Fos (cerebellum > cortex > midbrain and brainstem) and HSP70 (brainstem and cerebellum > cortex and midbrain). However, the only significant effect of alcohol feeding occurred in the HSP70 mRNA in midbrain of male rats, which was reduced by approximately 50% (P <.01). In contrast, no corresponding effect of alcohol feeding was observed in c-Fos mRNA levels in either midbrain or other regions of female rats. These data show that chronic ethanol feeding has no demonstrable effect on c-Fos mRNA expression in the brain when using nutritionally complete liquid diet regimens with concomitant pair-feeding. HSP70 mRNA, in contrast, is reduced by alcohol feeding and appears to be regional and gender dependent.