Investigation of the Neurotoxicity Mechanisms of Ni²⁺ in Rat Neocortical Neurons Through Transcriptome Analysis

The cytotoxic effects of Ni²⁺ released from nickel-based alloy implants on tissues have been a longstanding research focus in biocompatibility studies. However, investigations into the neurotoxicity of Ni²⁺ remain relatively limited. Building on our previous findings that Ni²⁺ can rapidly affect the excitability of neuronal networks, this study further investigated the neurotoxic effects of prolonged Ni²⁺ exposure. First, the cytotoxicity effects of Ni²⁺ on rat neocortical neurons in vitro were evaluated by MTT cell viability assay, and changes in the length of the axon initial segment of neurons caused by Ni²⁺ exposure were quantified. Next, transcriptome sequencing was employed to identify differentially expressed genes (DEGs) induced by Ni²⁺ treatment, and four DEGs—Hk2, Ldha, Cd9, and Nfasc—were selected for qRT-PCR validation. The ATP content of neurons was measured to assess cellular energy metabolism under Ni²⁺ influence. Finally, by comparing these experimental results with our previous findings, this study explored the neurotoxicity mechanisms of Ni²⁺ and analyzed the correlation between its neurotoxicity and cytotoxicity. This study revealed that the neurotoxicity mechanisms of Ni²⁺ are associated with the concentration of Ni²⁺ and the duration of its action. When at low concentrations or with short exposure times, Ni²⁺ suppresses the excitability of the neuronal networks by rapidly blocking Ca²⁺ channels, whereas at high concentrations or with prolonged exposure, it further inhibits the network’s excitability by activating the HIF-1α pathway and inducing obvious cytotoxicity.