Folic acid supplementation inhibits autophagy-dependent apoptosis in rat brain neural cells and HT-22 neurons via the p53/mTOR signaling pathway.

Folic acid (FA) can modulate neurogenesis and neural cell death, including autophagy and apoptosis, crucial for maintaining neurological homeostasis. Previous studies on the relationship between autophagy and apoptosis were contradictory, and the study aimed to investigate FA's impact on these processes in neural cells and the mechanisms involved. Three-week-old Sprague Dawley (SD) rats were divided into four dietary groups based on FA intake: FA-deficient (<0.1 mg/kg), FA-normal (2 mg/kg), low FA-supplemented (4.0 mg/kg), and high FA-supplemented (8.0 mg/kg), with dietary treatments for 11 months. Neural cell apoptosis was quantified using TdT-mediated dUTP nick end labelling (TUNEL) assay, and autophagy-associated protein microtubule-associated light chain 3 (LC3)/Beclin-1 expression was detected by immunofluorescence (IF). HT-22 neurons were incubated with 1, 10, 20, and 40 µmol/L FA for 2, 4 and 8 d. Cell apoptosis was detected by flow cytometry, autophagic vacuoles were assessed by monodansyl cadaverine (MDC) assay, and the expression of autophagy-related proteins LC3/Beclin-1/p62 and p53/mammalian target of rapamycin (mTOR) pathway was analyzed by Western blotting (WB). In vivo, FA supplementation downregulated the autophagy-associated protein LC3/Beclin-1 expression in rat neural cells, further inhibiting apoptosis, whereas FA deficiency exhibited the opposite effect. In vitro study further revealed that FA supplementation reduced autophagy-dependent apoptosis in HT-22 neurons with decreased p53 expression and increased mTOR expression in a dose-dependent manner within the specific range. These results suggest that FA supplementation may inhibit autophagy-dependent apoptosis in neural cells via the p53/mTOR signaling pathway, whereas FA deficiency produced a significantly negative effect.