MicroRNA-122 Enhances Apoptosis Of Keratinocytes In Oral Lichen Planus Though Downregulating VDR Expression

Objective:micro RNA-122(mi R-122),a liver-specific factor,has important biological and cellular roles in human-derived hepatocellular carcinoma(HCC),and its expression is upregulated in response to inflammatory stimuli.Vitamin D receptor(VDR)has been reported to regulate excessive apoptosis of oral keratinocytes,thereby compromising the oral epithelial barrier in oral lichen planus(OLP).Although many studies have shown that mi R-122 has the ability to regulate apoptosis,its effect on OLP development and VDR expression is unclear.In this study,we sought to investigate the effect of mi R-122on VDR expression and apoptosis of keratinocytes in oral lichen planus.Methods:We collected diseased buccal mucosal tissues from recruited patients with oral lichen planus,and healthy buccal specimens from patients with wisdom teeth extraction were served as control groups.The isolated oral epithelial cells from healthy and OLP individuals were used to detect mi R-122 expression.We then examined mi R-122expression in human oral keratinocytes(HOKs)in the setting of endotoxin or supernatant of activated CD4~+T cells challenge separately.To interrogate whether transcription factor nuclear factor-κB(NF-κB)tunes mi R-122 trnascprits,mature mi R-122 status was assessed in HOK with IKKβoverexpression.and This observation was further verified by the Dual-luciferase reporter experiment.Next,we detected the pro-apoptotic functions of mi R-122 in oral keratinocytes.In response to mi R-122 overexpression in HOKs,caspase3 activity measurement was conducted and the protein status of both cleaved caspase3 and cleaved poly(adp-ribose)polymerase(PARP)was monitored.Terminal deoxynucleotidyl transferase d UTP nick end labelling(TUNEL)staining was applied to evaluate cell apoptosis in lesion samples and cell models.Moreover,we examined the the suppression roles of mi R-122 in the m RNA of VDR.Tests of VDR expression of HOK treated by mi R-122 mimics was used and confirmed by Dual-luciferase reporter assay.For better understainding whether apoptosis triggered by mi R-122 relies on VDR,we applied CRISPR/Cas9 system to knockout VDR gene in HOKs,and detected apoptosis in these cells.Finally,the regulatory effect of VDR on mi R-122 expression was investigated.We detected mi R-122 expression in both human and mouse VDRKO oral keratinocytes,and the effect of VDR overexpression on the level of mi R-122 as well as apoptosis was examined in OLP cell models.Results:Herein,we demonstrate that mi R-122 expression is increased in the epithelial layer of OLP.Mechanically,NF-κB could interact withκB binding site located in the promoter fragment of mi R-122 gene to favour gene transcription.Enhanced mi R-122 leads to cell apoptosis in HOKs through degradating VDR m RNA.In oral keratinocytes lacking VDR,mi R-122 can not to booster caspase 3 activity and increase the expression of cleaved caspase 3 and PARP.Furthermore,VDR overexpression is able to reverse lipopolysaccharide(LPS)or activated CD4~+T cell–induced mi R-122 up-regulation and ameliorate mi R-122-stimulated caspase 3 activity.Conclusion:Collectively,our results suggest that mi R-122 promotes oral keratinocytes apoptosis in OLP through decreasing VDR expression.