Excitotoxicity and PANoptosis are examined through endoplasmic reticulum stress of brain in the fat greenling (Hexagrammos otakii) under hypoxic stress.

Hypoxia can cause brain injury in fish, resulting in neurological sequelae of varying severity. This is a key contributor to anorexia, delayed development, and even fish mortality. Endoplasmic reticulum stress (ERS)-mediated PANoptosis is essential for the development of fish brain injury, despite current research to better understand its precise mechanism. This study was conducted to observe ERS and PANoptosis hyperactivation in fish brain injury, followed by a comparison of the neurological damaging effects of hypoxia through modification of the ERS-PANoptosis pathway. A model was constructed using fat greenling (Hexagrammos otakii) exposed to hypoxia for 48 h. Hematoxylin and Eosin (HE) Staining visualized brain tissue pathology, while electron microscopy identified disruptions to the endoplasmic reticulum. Apoptotic cells were detected by TdT-mediated dUTP Nick-End Labeling (TUNEL) staining. The transcriptional and translational levels of ERS/PANoptosis markers were assessed using qPCR and western blotting across time points. Results revealed that hypoxia significantly activated the PERK/ATF4/CHOP pathway and induced ERS, thereby synergistically activating apoptosis, pyroptosis, and necrotic apoptosis, exhibiting typical PANoptotic characteristics. Concurrently, it triggered excitotoxicity manifested as an imbalance in the glutamate (Glu)/γ-aminobutyric acid (GABA) ratio. 4-Phenylbutyric acid (4-PBA) pretreatment effectively alleviated the aforementioned PANoptosis and neurological dysfunction by inhibiting ERS. The ERS-PANoptotic crosstalk link in hypoxia-stress is highlighted in this study, possibly via the regulation of the PERK/CHOP pathway.