Hyperbaric oxygen treatment and toll-like receptor 5 in radioprotection of epithelial cells

BACKGROUND: Irradiation of tumours in the pelvic area may lead to adverse effects such as vaginal fibrosis and dyspareunia. We investigated the radioprotective effects of hyperbaric oxygen (HBOT) and toll-like receptor 5 (TLR5) in epithelial cells. METHODS AND MATERIALS: Endothelial cells (HUVEC), urothelial cells (UROtsa), and cervical epithelial cells (HeLa) were irradiated with 6 Gy and subsequently underwent HBOT. Cells were counted and qPCR was performed on HeLa for the expressions of TLR5, downstream signalling molecules, oxidative stress, and cytokines. The effects of the TLR5 agonist flagellin and the TLR5 antagonist TH1020 on radiation-induced cell death and oxidative stress were assessed. RESULTS: HBOT attenuated radiation-induced epithelial cell death. In HeLa, radiation reduced TLR5, TRIF, NRF2, HIF-α and catalase expression. HBOT reversed their expression. The TLR5 agonist flagellin protected against radiation-induced cell death in HeLa and the TLR5 antagonist TH1020 inhibited the radioprotective effects by flagellin. CONCLUSIONS: HBOT antagonizes radiation-induced cell death and normalizes the expressions of antioxidants, TLR5 and connected downstream signalling transcripts. TLR5 signalling contributes to protection from radiation-induced epithelial cell death, which supports further exploration of combined HBOT-TLR5-targeted strategies for mucosal radioprotection.