Baicalein ameliorates high-altitude hypoxic lung injury via macrophage polarization remodeling by downregulating ALOX15 pathway in ferroptosis.

BACKGROUND

Ferroptosis has been reported to be involved in the pathogenesis of high-altitude hypoxic acute lung injury (ALI). This study investigated baicalein's protective role, focusing on alveolar macrophage polarization, ferroptosis, and inflammatory responses via arachidonate 15-lipoxygenase (ALOX15).

METHODS

Twenty-four male rats were divided into control, ALI, ferrostatin-1(Fer-1) control, baicalein (40 mg/kg or 80 mg/kg) control group, Fer-1 ALI, baicalein (40 mg/kg or80 mg/kg) ALI groups. Proteomic analysis was performed to screen out key pathways of ALI. Lung injury, inflammatory response, lipid peroxidation and ferroptosis pathway related proteins, macrophage polarization in ALI rat lung tissue were evaluated to assess the preventative effect of baicalein. Then human lung epithelial cell line (BEAS-2B) and human monocytic leukemia cell (THP-1) cell line were co-cultured under hypoxia condition (1 % O2) to simulate hypoxia environment in vitro. Knock-down of ALOX15,15-HpETE rescue experiments and pre-treatment with baicalein was performed to evaluate how ferroptosis via ALOX15 affect macrophage polarization.

RESULTS

Proteomic analysis revealed a significant enrichment of the ferroptosis pathway in ALI lung. There was a notable increase in ALOX15 expression within ALI lung tissue, accompanied by a reduction in glutathione (GSH) levels and superoxide dismutase (SOD) activity, elevated reactive oxygen species (ROS) levels, malondialdehyde (MDA) content, iron (Fe2+) accumulation, and decreased ferroptosis-negative regulators, including SLC7A11, GPX4, and FTH1, all of which could be alleviated by the administration of Fer-1. Baicalein was screened out through molecular docking that specifically target ALOX15, which was also effective in mitigating ferroptosis, elevating the M2 macrophage proportion and decreasing inflammation in both in vivo and in vitro ALI model. Knockdown of ALOX15 encouraged the shift of M1 to M2 macrophages through regulating ferroptosis and then alleviated ALI. However, exogenous administration of 15-HpETE under ALOX15 knockdown conditions partially reversed this protective effect.

CONCLUSIONS

ALOX15 could exacerbates high-altitude hypoxic ALI inflammatory responses by promoting both macrophage ferroptosis and M1 polarization. Identification of baicalein as an ALOX15 inhibitor mitigates ferroptosis, shifts macrophages to the M2 phenotype, and reduces inflammation, offering a promising preventative strategy for high-altitude hypoxic lung injury.