Effects of Aluminum Oxide Nanoparticles in the Spinal Cord of Male Wistar Rats and the Potential Ameliorative Role of Melatonin

Aluminum oxide nanoparticles (Al₂O₃ NPs) are widely utilized in vaccine manufacturing and other medical preparations. Melatonin has numerous effects as an antioxidant and anti-apoptotic. The purpose of this study was to examine the beneficial impact of melatonin on Al₂O₃ NPs toxicity in the spinal cord. Forty male rats were divided into four groups: Group I, the negative controls (received standard diet and distilled water); Group II, Al₂O₃ NPs (received 30 mg/kg bw Al₂O₃ NPs); Group III, melatonin and Al₂O₃ NPs (received 30 mg/kg bw Al₂O₃ NPs + 10 mg/kg bw melatonin); Group IV, melatonin (received 10 mg/kg bw melatonin). All treatments were administered daily for 28 days by gastric gavage. After that, all rats were sacrificed, then, the samples from different spinal cords were subjected to histopathological, biochemical, and immunohistochemical analyses. Al₂O₃ NPs markedly elevated malondialdehyde and 8-hydroxydeoxyguanosine while inhibiting superoxide dismutase and catalase. Al₂O₃ NPs also induced histological alterations in both gray and white matter manifested by neuronal degeneration, vacuolation, axonal degeneration, ballooning, and fusion of myelin sheaths. Furthermore, immunohistochemical results displayed a strong positive expression of caspase-3. Conversely, melatonin significantly mitigated the effects of Al₂O₃ NPs by increasing the activities of antioxidant enzymes and inhibiting malondialdehyde and 8-hydroxydeoxyguanosine. Moreover, melatonin alleviated most histological alterations induced by Al₂O₃ NPs and reduced caspase-3 immunoreactivity. Collectively, melatonin could protect the spinal cord and mitigate Al₂O₃ NPs-induced neurotoxicity.