Guanylate-binding protein 5-mediated cell-autonomous immunity suppresses inflammation in dental pulpitis: An in vitro study

Aim: Guanylate-binding protein 5 (GBP5) is an interferon (IFN)-inducible GTPase that plays a crucial role in the cell-autonomous immune response against microbial infections. In this study, we investigated the immunoregulatory role of GBP5 in the pathogenesis of dental pulpitis.Methodology: Gene-set enrichment analysis (GSEA) was utilized to evaluate the IFN-gamma signalling pathway, and the differential expression of GBP mRNA in normal versus inflamed dental pulp tissues was screened, based on Gene Expression Omnibus (GEO) datasets associated with pulpitis. Both normal pulp tissues and inflamed pulp tissues were used for experiments. The expression of IFNs and GBPs was determined by qRT-PCR. Immunoblotting and double immunofluorescence were performed to examine the cellular localization of GBP5 in dental pulp tissues. For the functional studies, IFN-gamma priming or lentivirus vector-delivered shRNA was used to, respectively, overexpress or knock down endogenous GBP5 expression in human dental pulp stem cells (HDPSCs). Subsequently, LPS was used to stimulate HDPSCs (overexpressing or with knocked-down GBP5) to establish an in vitro model of inflammation. qRT-PCR and ELISA were employed to examine the expression of proinflammatory cytokines (IL-6, IL-8 and IL-1 beta) and cyclooxygenase 2 (COX2). Every experiment has three times of biological replicates and three technical replicates, respectively. Statistical analysis was performed using the Student's t-test and one-way ANOVA, and a p-value of <.05 was considered statistically significant.Results: GSEA analysis based on the GEO dataset revealed a significant activation of the IFN-gamma signalling pathway in the human pulpitis group. Among the human GBPs evaluated, GBP5 was selectively upregulated in inflamed dental pulp tissues and predominantly expressed in dental pulp cells. In vitro experiments demonstrated that IFN-gamma robustly induced the expression of GBP5 in HDPSCs. Knockdown of GBP5 expression in HDPSCs significantly amplified the LPS-induced upregulation of inflammatory mediators (IL-6, IL-8, IL-1 beta and COX2) both with and without IFN-gamma priming.Conclusion: Our findings demonstrated that GBP5 partook in the pathogenesis of dental pulpitis. The involvement of GBP5 in pulpitis appeared to coordinate the regulation of inflammatory cytokines. Knockdown of GBP5 contributed to the exacerbation of LPS-mediated inflammation.