Expression of nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 6 in human dental pulp tissues and cells

Objective: This study aims to investigate the expression pattern of nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 6 (NLRP6) in human dental pulp tissues and cells, and roughly explore the role of NLRP6 in dental pulp immunity. Methods: Immunohistochemistry and immunofluorescence double staining were performed to determine the expression and localization of NLRP6 in healthy and inflamed pulp tissues. The expression of NLRP6 in human dental pulp cells (HDPCs) was investigated by immunocytofluorescence. Furthermore, reverse transcription polymerase chain reaction (RT-PCR) and western blot were used to evaluate the impact of lipopolysaccharide (LPS) stimulation on NLRP6 expression in HDPCs. Last, NLRP6 gene was silenced by lentiviral short hairpin RNA to explore the impact of NLRP6 on LPS-induced interleukin (IL)-1 beta. Results: NLRP6 was predominantly expressed in odontoblasts layer and blood vessels of healthy dental pulp, as well as infiltrated immune cells and fibroblasts of inflamed pulp. Further immunofluorescence double staining showed that pericytes and endothelial cells in the dental pulp blood vessels, macrophages and T cells as well as fibroblasts in the inflamed pulp expressed NLRP6. NLRP6 was also basically expressed in cultured HDPCs and upregulated by LPS stimulation. Knockdown of NLRP6 in HDPCs significantly inhibited the LPS-induced IL-1 beta expression. Conclusions: Our study revealed the expression and distribution of NLRP6 in human dental pulp tissues. Furthermore, NLRP6 was also basically expressed in cultured HDPCs, which could be upregulated by LPS stimulation, indicating the involvement of NLRP6 in dental pulp immune response.