Neuroprotective Effects of Simvastatin Pre-treatment Against Alcohol-Induced Brain Damage in Adolescent Mice

Abstract

Adolescence is a critical period of brain development characterised by increased vulnerability to alcohol-induced neurotoxicity, particularly in the hippocampus and prefrontal cortex, regions essential for memory, executive function, and emotional regulation. In South Africa, adolescent alcohol misuse is widespread and contributes significantly to long-term neurocognitive and structural impairments. Chronic alcohol exposure during adolescence disrupts neurogenesis and induces oxidative stress and neuroinflammation, with sex-specific differences in susceptibility driven by hormonal and developmental factors. Drug repurposing offers a promising intervention strategy, and simvastatin, a lipid-lowering agent with known antioxidant and anti-inflammatory properties, has shown potential for neuroprotection. This study investigated the neuroprotective potential of simvastatin against alcohol-induced brain damage in adolescent C57BL/6J mice, with a focus on oxidative stress, neuroinflammation, and neurogenesis in the hippocampus and prefrontal cortex. Four-week- old male and female mice were grouped separately and assigned to treatment conditions. Mice received daily intraperitoneal alcohol (20% v/v) for 28 days, alone or in combination with oral simvastatin (5 or 15 mg). Control groups received simvastatin only or remained untreated. Biochemical assays measured oxidative stress markers (MDA, GSH-Px, SOD) in the hippocampus and prefrontal cortex. Immunohistochemistry assessed neurogenesis (PcNA, DCX), neuronal and glial populations (NeuN, GFAP), and cortical laminar structure (Nissl stain). RT-PCR was used to examine hippocampal expression of IL-6, IL-10, CREB1, and BDNF. Alcohol exposure increased hippocampal GSH-Px activity, a response attenuated by simvastatin in a dose- and sex-dependent manner, particularly in females. Neurogenesis in the dentate gyrus was suppressed by alcohol and partially restored by simvastatin, with high-dose treatment more effective in females and low-dose treatment in males. Although NeuN-positive neuronal populations and dentate gyrus volume remained stable, GFAP expression revealed marked sex-specific astrocytic responses: alcohol-induced astrocyte reactivity in females was reduced by simvastatin, whereas in males, simvastatin exacerbated alcohol-induced GFAP loss. In the prefrontal cortex, simvastatin enhanced alcohol-induced increases in Nissl- and NeuN- positive cell densities in females but not in males. Molecular analyses revealed divergent IL-6, IL-10, and CREB expression patterns across sexes, while BDNF levels remained unchanged. vii These findings highlight simvastatin’s capacity to mitigate alcohol-related neurotoxicity in adolescence through antioxidant, neurogenic, and anti-inflammatory mechanisms that are both sex- and region-specific. The study highlights the importance of glial modulation in early alcohol-induced neuropathology and positions simvastatin as a candidate for sex-specific neuroprotective intervention. By integrating biochemical, molecular, and stereological analyses, this research offers a comprehensive framework for understanding adolescent alcohol neurotoxicity and informs future translational efforts aimed at protecting neurodevelopmental health in at-risk youth.