The Nrf2/HIF-1α/BNIP3 Axis Mediates Mitophagy and Hyperproliferative Behavior in Hypertrophic Scar Fibroblasts

BACKGROUND: Hypertrophic scarring is driven in part by persistent fibroblast activation, but the mechanisms linking hypoxia, mitochondrial dysfunction, and fibrotic behavior remain incompletely defined. In our previous work, abnormal mitophagy and elevated BNIP3 expression were observed in hypertrophic scar fibroblasts. This study investigated whether the Nrf2/HIF-1α/BNIP3 axis contributes to mitophagy and pathologic activation of hypertrophic scar fibroblasts. MATERIALS AND METHODS: Human hypertrophic scar fibroblasts (HHSFC) and normal human dermal fibroblasts (NHDF) were cultured under normoxia (21% O2) or hypoxia (1% O2) for 48 hours. Lentiviral overexpression or knockdown of Nrf2 and siRNA-mediated silencing of HIF-1α or BNIP3 were performed. Mitochondrial ROS, mitochondrial membrane potential, gene and protein expression, cell viability, migration, invasion, and cell-cycle distribution were assessed. RESULTS: Compared with NHDF, HHSFC showed higher basal expression of Nrf2, HIF-1α, BNIP3, and LC3-II. Hypoxia further increased mitochondrial ROS and decreased mitochondrial membrane potential in HHSFC, accompanied by upregulation of Nrf2, HIF-1α, BNIP3, and LC3-II. Nrf2 overexpression increased HIF-1α and BNIP3 expression and promoted HHSFC viability, migration, and invasion, whereas Nrf2 knockdown produced the opposite effects. Silencing HIF-1α reduced BNIP3 expression. Silencing BNIP3 induced G0/G1 arrest and reduced MMP-1, COL1A1, TGF-β1, α-SMA, and LC3-II expression, particularly under hypoxia. CONCLUSION: The Nrf2/HIF-1α/BNIP3 axis is closely associated with hypoxia-driven mitophagy and pathologic activation in hypertrophic scar fibroblasts and may represent a potential therapeutic target for hypertrophic scarring.