Tetrandrine attenuates hypoxia-induced microglial M1 polarization and microglia-mediated photoreceptor cell injury through modulation of NF-κB/p65 signaling.

Abstract

Diabetic retinopathy (DR), a primary cause of working-age vision loss, is characterized by neuroinflammation, in which microglial polarization toward the proinflammatory M1 phenotype serves as a pivotal driver. Reprogramming microglia toward an anti-inflammatory and reparative phenotype may therefore represent a promising therapeutic strategy. This study investigated the effects of tetrandrine (Tet) on hypoxia-induced microglial activation and explored the underlying mechanisms. We established a chemical hypoxia model using CoCl2 and evaluated inflammatory mediators and associated molecules by qRT-PCR, western blotting, and immunofluorescence. Microglial migratory and phagocytic functions were assessed by scratch wound and phagocytosis assays, respectively. Potential drug targets were identified through an integrative approach combining network pharmacology, molecular docking, and cellular thermal shift assay (CETSA). Tet suppressed CoCl2-induced M1-associated inflammatory gene expression in BV2 cells and attenuated p65 activation and cytotoxic responses in HMC3 cells. Functionally, Tet restored impaired phagocytic capacity, attenuated aberrant migration, and mitigated microglia-mediated injury to 661W photoreceptor-derived cells. Mechanistic analyses showed that Tet reduced p65 phosphorylation and apparent nuclear accumulation, thereby limiting activation of the HIF-1α/NF-κB signaling axis; docking and CETSA findings further supported a potential interaction between Tet and p65. In summary, Tet alleviates hypoxia-induced microglial M1 polarization and microglia-mediated photoreceptor cell injury, at least partly through modulation of NF-κB/p65 signaling. These findings identify Tet as a candidate compound for further preclinical investigation in retinal neuroinflammation associated with DR.