Nicotine regulates autophagy of human periodontal ligament cells through α7 nAchR that promotes secretion of inflammatory factors IL-1β and IL-8

Background: Nicotine is an important risk factor and the main toxic component associated with periodontitis. However, the mechanism of nicotine induced periodontitis is not clear. To investigated the mechanism through which nicotine regulates autophagy of human periodontal ligament cells (hPDLCs) through the alpha7 nicotinic acetylcholine receptor (alpha 7 nAChR) and how autophagy further regulates the release of IL-1 beta and IL-8 secretion in hPDLCs. Methods: HPDLCs were obtained from root of extracted teeth and pre-incubated in alpha-bungarotoxin (alpha-BTX) or 3-Methyladenine (3-MA), followed by culturing in nicotine. We used a variety of experimental detection techniques including western blotting, immunofluorescence, enzyme-linked immunosorbent assay (ELISA), transmission electron microscopy (TEM) and RT-qPCR to assess the expression of the LC3 protein, autolysosome, and release of IL-1 beta and IL-8 from hPDLCs. Results: Western blots, immunofluorescence and TEM results found that the nicotine significantly increased the autophagy expression in hPDLCs that was time and concentration dependent and reversed by alpha-BTX treatment (p < 0.05). RT-qPCR and ELISA results revealed a noticeable rise in the release of inflammatory factors IL-1 beta and IL-8 from hPDLCs in response to nicotine. RT-qPCR and ELISA results showed that nicotine can significantly up-regulate the release of inflammatory factors IL-1 beta and IL-8 in hPDLCs, and this effect can be inhibited by 3-MA (p < 0.05). Conclusions: Nicotine regulated autophagy of hPDLCs through alpha 7 nAChR and in turn the regulation of the release of inflammatory factors 1L-1 beta and 1L-8 by hPDLCs.