Mechanistic study on nonylphenol-induced depressive-like behavior: PINK1/parkin-mediated mitophagy regulates synaptic remodeling in neurons

Objective: To investigate the role of PINK1/Parkin-mediated mitophagy in regulating synaptic remodeling of neuronal cells in depression-like behaviors induced by nonylphenol (NP). Methods: In vitro experiments: HT-22 neuronal cells were exposed to NP, and mitophagy and Parkin expression were inhibited using specific inhibitors. The cells were categorized into the following groups: (1) control (C) and low-dose NP group (L: 2.5 µM), medium-dose NP group (M: 50 µM), and high-dose NP groups (H: 100 µM); (2) control (C), NP (100 µM), Mdivi-1 (5 µM), and Mdivi-1 + NP (5 µM Mdivi-1 +100 µM NP) groups; (3) control (C), NP (100 µM), AC220 (2 nM), and AC220 + NP (2 nM AC220 +100 µM NP) groups. In vivo experiments: a total of 48 mice, including 24 C57BL/6 wild-type mice and 24 PKRK2 gene-knockout mice, were randomly assigned to the following four groups: control (C), NP (100 mg/kg/day), PKRK2-knockout (KO), and PKRK2-knockout + NP (100 mg/kg/day, KH) groups, with 12 mice in each group. Results: In vitro: With increasing NP concentration, the ATP content reduced and the expressions of synaptic remodeling–related proteins (i.e., PSD-95, BDNF, SYN) decreased. In contrast, the expressions of mitophagy-related proteins and those involved in the PINK1/Parkin-signaling pathway (such as p62, Beclin1, PINK1, Parkin) increased (P < 0.05). Inhibition of mitophagy with Mdivi-1 alleviated the NP-induced changes in synaptic, mitophagy-related, and PINK1/Parkin pathway-related proteins. Similarly, the inhibition of Parkin with AC220 mitigated NP-induced effects on synaptic, mitophagy-related, and PINK1/Parkin-signaling pathway-related proteins and mRNA expression. In vivo: PKRK2 gene-knockout mice exhibited improved NP-induced depression-like behaviors and decreased NP-induced synaptic morphology and mitochondrial ultrastructure changes. Moreover, the gene knockout alleviated the downregulation of synaptic remodeling-related proteins and inhibited the PINK1/Parkin-signaling pathway-mediated mitophagy activated by NP. Conclusion: Mitophagy inhibition or PKRK2 knockout can alleviate NP-induced downregulation of synaptic remodeling-related proteins, protect synaptic morphology and ultrastructure, and improve NP-induced depression-like behaviors.