Hypoxia-induced inflammation and protective autophagy in dental pulpitis

Autophagy is critical for cellular homeostasis and may participate in the pathogenesis of pulpitis, although its underlying mechanisms remain unclear. This study investigated hypoxia-induced autophagy in human dental pulp cells (HDPCs) and its molecular basis.

HDPCs were exposed to hypoxic conditions (1% O₂). Cell proliferation, apoptosis, inflammatory cytokine levels, and autophagy markers and autophagic flux were evaluated with or without 3-methyladenine (3-MA) treatment. RNA sequencing was performed to compare healthy and inflamed human dental pulp tissues.

Hypoxia significantly inhibited HDPCs proliferation, promoted cell apoptosis, and enhanced the secretion of tumor necrosis factor-alpha, interleukin-6, and interleukin-1β. Meanwhile, hypoxia activated autophagic flux, as evidenced by increased autophagosome formation, elevated microtubule-associated protein 1 light chain 3 beta II (LC3B-II) levels, and reduced sequestosome-1 (SQSTM1/p62) expression; these effects were reversible by 3-MA treatment. Autophagy inhibition exacerbated hypoxic damage to HDPCs, confirming its protective role. RNA- sequencing revealed enrichment of autophagy-related pathways (Mitophagy-animal; Autophagy-animal) in inflamed pulp and identified two core upregulated genes: BCL2 interacting protein 3 pseudogene 11 (BNIP3P11) and cathepsin B (CTSB) were identified.

Hypoxia elicits cytoprotective autophagy in HDPCs under pulpitis-associated stress. The BNIP3P11-CTSB axis may regulate autophagic flux and cellular homeostasis, representing a potential therapeutic target for pulpitis.