BNIP3/BNIP3L-Dependent Mitophagy Protects Against Hippocampal Neuronal Damage and Apoptosis in a Model of Vascular Dementia.

Abstract

Mitophagy serves as an essential quality control mechanism that maintains mitochondrial homeostasis through selective autophagic clearance of damaged organelles. Vascular dementia (VD) has been increasingly associated with mitophagy dysregulation in recent studies. However, the precise molecular mechanisms underlying mitophagy's involvement in VD pathogenesis remain poorly characterized. To elucidate the role of mitophagy in VD, we systematically examined the expression of key mitophagy pathways in hippocampal neurons of bilateral common carotid artery occlusion (BCCAO) rats and in oxygen-glucose deprivation (OGD)-treated HT22 cells. Intriguingly, under autophagy-deficient conditions, both BNIP3 and BNIP3L were markedly downregulated, whereas FUNDC1 expression increased; PINK1/Parkin levels remained unaltered. To further dissect the functional contributions of BNIP3 and BNIP3L, we administered the mitochondrial fission inhibitor Mdivi-1 to BCCAO model rats. Histopathological analysis revealed pronounced neuronal damage and apoptosis in the hippocampal region, which was further exacerbated upon Mdivi-1 treatment. In vitro, BNIP3 silencing significantly compromised cell viability, elevated reactive oxygen species (ROS) accumulation, disrupted mitochondrial membrane potential (ΔΨm), suppressed mitophagy, and increased apoptotic rates. Conversely, BNIP3 overexpression reversed these detrimental effects. Notably, treatment with the autophagy inhibitor 3-methyladenine (3-MA) diminished LC3B-Tomm20 colocalization and intensified apoptosis, reinforcing the critical role of BNIP3-mediated mitophagy in neuronal survival. Similarly, BNIP3L overexpression enhanced cell viability, attenuated ROS production, restored ΔΨm, and mitigated apoptosis, while 3-MA treatment again impaired mitophagic flux and worsened cell death. Collectively, these findings underscore the critical and distinct roles of BNIP3 and BNIP3L in maintaining mitochondrial homeostasis and neuronal survival under ischemic conditions.