Hypoxia-Inducible Factor-1α Regulates BNIP3-Dependent Mitophagy and Mediates Metabolic Reprogramming Through Histone Lysine Lactylation Modification to Affect Glioma Proliferation and Invasion.

Objective: Gliomas are the predominant form of malignant brain tumors. We investigated the mechanism of hypoxia-inducible factor-1α (HIF-1α) affecting glioma metabolic reprogramming, proliferation and invasion.

Methods: Human glioma cell U87 was cultured under hypoxia and treated with small interfering (si)HIF-1α, si-B cell lymphoma-2/adenovirus E1B 19-kDa interacting protein 3 (siBNIP3), si-YT521-B homology domain 2 (siYTHDF2), 3-methyladenine and 2-deoxyglucose, with exogenous sodium lactate-treated normally-cultured cells as a lactate-positive control. Cellular hexokinase 2, lactate dehydrogenase A and pyruvate dehydrogenase kinase 1 enzyme activities, glucose uptake, and levels of lactic acid and adenosine triphosphate (ATP), and HIF-1α, glycolysis-related proteins, mitophagy-related proteins, histone H3 lysine 18 lactylation (H3K18la) and YTHDF2 were determined by ELISA, 2-NBDG, kits, and Western blot. Extracellular acidification rate (ECAR), and cell proliferation, invasion, apoptosis and mitophagy were evaluated by extracellular flux analysis, CCK-8, Transwell, flow cytometry, and immunofluorescence staining. H3K18la-YTHDF2 relationship and YTHDF2-BNIP3 interaction were assessed by ChIP and Co-IP assays.

Results: Hypoxia-induced highly-expressed HIF-1α in glioma cells increased glycolysis-related protein levels, glycolytic enzyme activities, glucose uptake, lactic acid production, ATP level and ECAR, thereby promoting metabolic reprogramming, invasion and proliferation. HIF-1α mediated metabolic reprogramming, proliferation and invasion through BNIP3-dependent mitophagy, which were partly negated by mitophagy inhibition. HIF-1α induced histone Kla modification to upregulate YTHDF2. YTHDF2 downregulation impeded YTHDF2-BNIP3 interaction and inhibited HIF-1α-induced BNIP3-dependent mitophagy, curbing glioma cell metabolic reprogramming, proliferation and invasion.

Conclusions: Hypoxia-induced high HIF-1α expression upregulated YTHDF2 through hH3K18la modification, enhanced YTHDF2-BNIP3 interaction, and regulated BNIP3-dependent mitophagy-mediated metabolic reprogramming to affect glioma proliferation and invasion.