Epilepsy is a common neurological disease, characterized by repeated seizures (Lopes et al., 2015). At present, the effects of main therapeutic strategy of epilepsy, including anti-epileptic drugs and surgical treatment, are unsatisfactory (d'Orio et al., 2019; Feng et al., 2020; Li et al., 2019; Souza et al., 2013; Yu et al., 2016). Therefore, preventing the development of epilepsy by an in-depth study of epileptogenesis is necessary.

Previous studies indicate that mitophagy is closely related to the development of epilepsy. Mitophagy is activated during epileptogenesis induced by pilocarpine, pentylenetetrazol (PTZ), and kainic acid (Lasarge and Danzer, 2014; Wong 2013; Zhang et al., 2021a). Regulating mitophagy, such as by rapamycin administration, significantly influences the development of epilepsy (Chang et al., 2020; Lasarge and Danzer, 2014; Wong 2013; Zhang et al., 2021a).

Mitophagy, the closely related mitochondrial oxidative stress, and neuronal damage are characteristic features of epileptogenesis (Hattori et al., 2014; Reid et al., 2014; Wu et al., 2018). Due to the heavily dependence on ample oxygen, mitochondria are vulnerable to oxidative stress (Martinc et al.; Wu et al., 2018; Zhang et al., 2020a; Zhang et al., 2021a). The increased levels of oxidative stress that occur during epileptogenesis lead to mitochondrial damage (Jarrett et al., 2008; Martinc et al.; Wu et al., 2018; Zhang et al., 2020a; Zhang et al., 2021a), which trigger clearance of the damaged mitochondria via mitophagy (Limanaqi et al., 2020; Wu et al., 2018; Zhang et al., 2020a, 2021a). However, excessive mitophagy may aggravate neuronal injury and epileptogenesis, promoting the formation of epileptic networks (Limanaqi et al., 2020; Zhang et al., 2020a, 2021a).

PTEN-induced kinase 1 (PINK1) is a major contributor to the mitophagy pathway and is distributed in the brain tissues, myocardial cells, etc. (Cummins and Götz, 2018; Narendra et al., 2012; Rasool et al., 2018a; Unoki and Nakamura, 2001). Autophosphorylation of PINK1 is the main initiator of mitophagy in the mammalian nervous system (Cummins and Götz, 2018; Narendra et al., 2012; Rasool et al., 2018a). In healthy mitochondria, PINK1 that has entered the mitochondrion is degraded by mitochondrial proteolytic enzymes, maintaining basal levels of PINK1 (Jin and Youle, 2012; Narendra et al., 2012; Rasool et al., 2018a).

PINK1 acts as a molecular sensor that rapidly responds to the variations in mitochondrial membrane potential (MMP) (Jin and Youle, 2012; Rasool et al., 2018a). Once MMP is decreased, PINK1 combines with the mitochondrial outer membrane protein transporter (TOM), and its ability to enter the mitochondria is reduced. As the result, full-length PINK1 accumulates on the mitochondrial outer membrane (Okatsu et al., 2012; Rasool et al., 2018b). With the assistance of TOM7 (Hasson et al., 2013; Rasool et al., 2018b), autophosphorylation of PINK1 at Ser-228/Ser-402 site triggers its ubiquitination (Hatano, 2012; Okatsu et al., 2012), and further leads to recruitment of parkin. The activated PINK1 phosphorylates ubiquitin (Ub) molecules on the mitochondrial outer membrane, transmits information about the damaged mitochondria to the cytoplasm, recruits and binds parkin, and further ubiquitinates a large number of mitochondrial substrate proteins, which triggers mitophagy (Jin and Youle, 2012; Kane et al., 2014; Rasool et al., 2018a; Rasool et al., 2018b).

In consideration of the critical role of activated PINK1 in mitophagy, we hypthesized that PINK1 autophosphorylation may be involved in epileptogenesis via PINK1/parkin mitophagic pathway. Therefore, we aimed to investigate changes in PINK1 activity and explore its possible contribution to PTZ-induced epileptogenesis using an animal model, with a view to identify potential therapeutic targets.