Molecular Mechanism Of Down-regulated Integrin β6 Expression In Epithelial Cells By Porphyromonas Gingivalis Lysate

Objective:Periodontitis is a chronic inflammatory disease mainly caused by the periodontitis pathogens that damage the gums and periodontal tissue.Periodontitis not only is the main cause of adult tooth loss,as well as other systemic diseases such as cardiovascular disease and systemic inflammatory response.Porphyromonas gingivalis is the main pathogen of periodontitis,containing a lot of pathogenic factors.Integrin avβ6 is a cell surface receptor,overexpressed during inflammatory response,tissue damage and repair.avP6 usually is absent in adult epithelial cells,but in the healthy gingival epithelium,avβ6 is constitutively expressed.However in periodontitis,the human gingival epithelium avβ6 expression is decreased,whereas the molecular mechanism for the downregulation of avβ6 remains unclear.The integrin β6 subunit binds only to the integrin av subunit,and the β6 subunit is the key subunit of avβ6.The expression level of β6 subunit represents the level of avβ6.Whether the decrease of avβ6 in the epithelium of human gingival is related with Porphyromonas gingivalis has also not been reported.The aim of current study is to detect the expression of ITGβ6 and the molecular mechanism of ITGβ6 involved after stimulation with Porphyromonas gingivalis in immortalized epithelial cells.Methods:The ITGβ6 mRNA and ITGβ6 protein levels were detected by quantitative real-time RT-PCR and western blot respectively;Transfection the cells with a series of ITGβ6 promoter luciferase reporter gene plasmids to detect the regulating region for ITGβ6 expression in respond to Porphyromonas gingivalis;Bioinformatics analysis was used to predict possible transcription factors in the regulating region;Use conventional PCR techniques,chromatin immunoprecipitation techniques and quantitative real-time RT-PCR to detect whether the predicted transcription factors bind to the ITGP6 promoter region;Overexpression of the transcription factors to detect whether the predicted transcription factors are involved in ITGβ6 expression.RESULTS:In human immortalized epidermal cells,ITGβ6 gene promoter-150/-3 region is the minimal response zone of the binding element of the porphyromonas gingivalis lysate responsed to ITGβ6 expression.This region contains FOXO binding site.Porphyromonas gingivalis lysate decreases the phosphorylation level of FOXO3a,increases the total protein expression of FOXO3a.But Porphyromonas gingivalis lysate has no effect on the phosphorylation level of FOXO and the total protein expression of FOXO1,Porphyromonas gingivalis lysate downregulates the expression of ITGβ6 by increasing transcription factor FOXO3a,but not FOXO1.Conclusion:Porphyromonas gingivalis lysate downregulates the expression of ITGβ6 via upregulation of transcription factor FOXO3a.