Investigating Nickel-Induced Neurotoxicity: Associations with Gut Microbiota Dysbiosis and Ferroptosis

Nickel is a pervasive heavy metal with the potential for multi-route exposure, raising significant concerns regarding systemic toxicity. Although Ni²⁺ has been implicated in nickel sulfate NiSO₄-induced neurotoxicity, its underlying mechanisms remain incompletely elucidated. The present study investigates the role of NiSO₄-induced ferroptosis as a potential contributor to neurotoxicity. C57BL/6 mice were administered NiSO₄ daily via oral gavage at doses of 50, 100, and 200 mg/kg over 28 days. Neurobehavioral assessments, histopathological examination, transmission electron microscopy, and molecular profiling were conducted to evaluate brain injury and ferroptotic activity. Gut microbiota composition and intestinal barrier integrity were systematically evaluated. In vitro, HT22 cells were subjected to NiSO₄ treatment, followed by integrative transcriptomic analysis complemented by pharmacological and genetic manipulation to delineate the contributions of ferroptosis and autophagy. The results demonstrated that NiSO₄ exposure inhibited body weight gain, elicited depression-like behaviors, and initiated ferroptosis, evidenced by ultrastructural mitochondrial damage and dysregulated expression of glutathione peroxidase 4/acyl-CoA synthetase long chain family member 4 (<i>GPX4</i>/<i>ACSL4</i>). Furthermore, NiSO₄ caused gut microbiota dysbiosis and compromised the intestinal barrier, which was correlated with the induction of ferroptosis in neuronal cells of the brain. In HT22 cells, NiSO₄ elicited dose-dependent cytotoxicity and lactate dehydrogenase (LDH) release. KEGG pathway enrichment analysis further revealed that NiSO₄ treatment significantly upregulated pathways associated with ferroptosis, autophagy, and lysosomal function. Moreover, both ferrostatin-1 and rapamycin attenuated NiSO₄-induced cytotoxicity and ferroptosis, indicating that autophagy serves a protective function against ferroptotic cell death. Additionally, overexpression of Transcription Factor EB (<i>TFEB</i>) attenuated NiSO₄-induced ferroptosis by downregulating <i>ACSL4</i>, and upregulating <i>GPX4</i>, implicating the autophagy-lysosome pathway in the protective regulation of this cell death process. In summary, our findings indicated that NiSO₄-induced neurotoxicity was strongly associated with gut microbiota dysbiosis and coincided with ferroptosis in the brain, while stimulation of the autophagy-lysosome pathway conferred neuroprotective effects via modulating <i>TFEB</i>-dependent anti-ferroptotic mechanisms. These findings offer novel insights for risk assessment and therapeutic strategies of nickel-related neurotoxicity.