Hawthorn Polyphenols Relieve Benzo(a)pyrene-Induced Inflammatory Injury in Respiratory Epithelial Cells

Objective: The objective of this study is to evaluate the cytoprotective activity and potential mechanism of hawthorn bioactive polyphenols (HBPs) using human bronchial epithelial (16HBE) cells exposed to benzo(a)pyrene (BaP). Methods: HBPs were isolated by activity-guided separation, and their cytotoxicity was assessed by the methyl thiazolyl tetrazolium (MTT) method. The cytoprotective activity of HBPs against BaP-induced injury in 16HBE cells was determined by the cell counting kit-8 (CCK-8) method. Enzyme-linked immunosorbent assay (ELISA) was performed to detect the effect of HBP-1 on BaP-induced inflammatory factors such as tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), IL-18, IL-10, IL-6 and reactive oxygen species (ROS) in 16HBE cells. Flow cytometry was utilized to explore the effect of HBP-1 on BaP-induced apoptosis in 16HBE cells. Western blotting was conducted to examine the effect of HBP-1 on protein expression related to the aryl hydrocarbon receptor (AhR) and nuclear factor kappa-B (NF-κB) signaling pathways in BaP-induced 16HBE cells. Results: A total of 10 bioactive phenolic compounds were isolated from hawthorn. Among them, HBP-1 exhibited the most significantly cytoprotective activity against BaP-induced inflammatory injury in 16HBE cells. HBP-1 significantly inhibited the oversecretion of IL-1β, IL-18 and TNF-α and the increase in ROS level and BaP-induced apoptosis in 16HBE cells. Western blotting results indicated that HBP-1 could inhibit the activation of the AhR and NF-κB signaling pathways in 16HBE cells induced by BaP. Conclusion: HBP-1 is able to inhibit BaP-induced oxidative stress and excessive production of inflammatory cytokines in 16HBE cells by suppressing the activation of the AhR and NF-κB signaling pathways, highlighting the cytoprotective effect of HBP-1 against BaP-induced damage.