Luteolin Attenuates Hypoxia-Induced Ferroptosis in Human Brain Microvascular Endothelial Cells Through Modulation of the PPARγ/FABP5/ALOX15 Signaling Pathway

Abstract

Background: Hypoxia-induced oxidative stress and ferroptosis contribute to blood–brain barrier dysfunction and neurovascular injury associated with ischemic stroke and neurodegenerative diseases. Luteolin, a naturally occurring flavonoid with potent antioxidant and anti-inflammatory activities, has emerged as a potential neuroprotective agent; however, its effects on hypoxia-induced ferroptosis in brain microvascular endothelial cells remain unclear. This study investigated the protective effects of luteolin and its association with changes in the PPARγ/FABP5/ALOX15 signaling pathway during hypoxia-induced ferroptotic injury. Methods: Human brain microvascular endothelial cells (HBEC-5i) were exposed to cobalt chloride (CoCl2) to establish an in vitro hypoxia model and subsequently treated with luteolin. Cell viability was assessed using the MTT assay. Intracellular Fe2+ accumulation, reactive oxygen species (ROS), malondialdehyde (MDA), and glutathione (GSH/GSSG) levels were determined using biochemical assays. The expression of ferroptosis- and hypoxia-related proteins, including GPX4, ALOX15, FABP5, PPARγ, HIF-1α, and VEGF, was evaluated by Western blotting. Results: CoCl2-induced hypoxia significantly reduced cell viability and increased intracellular Fe2+ accumulation, ROS generation, lipid peroxidation, and ferroptosis-associated signaling in HBEC-5i cells. Hypoxic conditions upregulated ALOX15 and FABP5 expression while suppressing GPX4 and PPARγ levels. Luteolin treatment markedly attenuated these effects by restoring GSH/GSSG homeostasis, enhancing GPX4 expression, reducing ALOX15-mediated lipid peroxidation, and suppressing HIF-1α and VEGF expression. In addition, luteolin modulated the PPARγ/FABP5 signaling pathway, suggesting its involvement in the regulation of hypoxia-induced ferroptosis. Conclusions: Luteolin attenuates hypoxia-induced ferroptosis-associated changes in human brain microvascular endothelial cells by restoring redox homeostasis and is associated with coordinated modulation of the PPARγ/FABP5/ALOX15 pathway. These findings extend previous reports of the anti-ferroptotic effects of luteolin by providing evidence in brain microvascular endothelial cells under hypoxia-mimetic stress.