The role of mitochondrial dysfunction, oxidative stress, and gender in cardiac fibrosis and vascular remodeling in an induced aged rat model with possible mitigation by eugenol nano-emulsion

Cardiac diseases are strongly associated with aging and pose a major threat to survival. This study evaluated the cardioprotective effects of oral eugenol and its nano-emulsion (20 mg/kg) in a D-galactose-induced aging model (300 mg/kg, i.p.) in male and female rats over 12 weeks. Particle size and zeta potential analyses confirmed the successful development of a stable, well-dispersed nano-emulsion system. At the end of treatment, echocardiography, biochemical assays, histopathology, and immunohistochemistry were performed. Cardiac dysfunction and dilatation were more pronounced in males than females following D-galactose administration, as evidenced by left ventricular internal diameter in diastole (LVIDd) and left ventricular internal diameter in systole (LVIDs), and reduced ejection fraction (EF) and fractional shortening (FS). Both eugenol and its nano-emulsion preserved cardiac architecture and mitigated histopathological alterations, including myofibrillar distortion, necrosis, vascular remodeling, and fibrosis. Treatment significantly reduced oxidative stress and mitochondrial dysfunction by restoring GSH, lowering MDA, and modulating the PINK1/Mfn2 pathway. Furthermore, eugenol and its nano-emulsion attenuated cardiac inflammation, apoptosis, and fibrosis through downregulation of TGF-β1, MMP-9, TNF-α, and caspase-3 expression. In conclusion, eugenol nano-emulsion demonstrates promising anti-aging potential against cardiac complications by regulating mitochondrial dynamics, mitophagy, oxidative stress, inflammatory and apoptotic responses, and the SIRT1/TGF-β/MMP9 signaling pathway.