Pistachio Leaf Extract Modulates Redox-Dependent Mitochondrial and Metabolic Responses in Ethanol-Stressed HepG2 Cells

Ethanol-induced hepatocellular injury is characterized by redox imbalance and mitochondrial dysfunction, which critically determine cellular adaptation to metabolic stress. Rather than acting as simple antioxidants, effective nutraceutical strategies may enhance endogenous adaptive responses that preserve cellular homeostasis. Pistachio (Pistacia vera L.) leaves, an underexplored agricultural by-product, represent a potential source of bioactive compounds with redox-modulating properties. In this study, we investigated the effects of pistachio leaf extract (PLE) in human HepG2 hepatocytes exposed to 1% ethanol (EtOH). EtOH reduced cell viability and increased intracellular and mitochondrial reactive oxygen species (ROS), while triggering compensatory responses including glutathione accumulation and activation of metabolic and inflammatory pathways. PLE alone induced a mild cytosolic ROS signal and increased PGC-1α expression, consistent with transcriptional changes potentially associated with hormetic activation of mitochondrial regulatory pathways. Notably, co-treatment with EtOH and PLE significantly reduced both cytosolic and mitochondrial ROS levels, prevented excessive glutathione accumulation and was associated with transcriptional changes consistent with improved glutathione-related adaptive responses. These effects were associated with transcriptional modulation of genes involved in mitochondrial biogenesis and metabolic adaptation, including PGC-1α, TFAM, SIRT1, PPARα, and UCP2. In parallel, PLE attenuated EtOH-induced IL-6 expression without preventing FAS upregulation, indicating a selective dissociation between inflammatory and lipogenic responses. Overall, our findings suggest that PLE may act as a modulator of redox-dependent signaling rather than as a direct antioxidant and is associated with transcriptional and functional signatures consistent with mitochondrial adaptive responses to ethanol-induced stress. These results support the potential of pistachio leaf-derived phytocomplexes as nutraceutical modulators of hepatocellular adaptive responses.