Streptococcus salivarius ameliorates the destructive effect on the epithelial barrier by inhibiting the growth of Prevotella melaninogenica via metabolic acid production.

BACKGROUND: Oral lichen planus (OLP) is one of the most common oral mucosal diseases, exhibiting a higher prevalence in women than men, but its pathogenesis is still unclear. Current research suggests that microbial dysbiosis may play an important role in the pathogenesis of OLP. Our previous research has found that the increase of Prevotella melaninogenica and decrease of Streptococcus salivarius have been identified as a potential pathogenic factor in OLP. Consequently, the objective of this study is to examine whether S. salivarius can counteract the detrimental effects of P. melaninogenica on the integrity of the epithelial barrier function. MATERIALS AND METHODS: Epithelial barrier disruption was induced by P. melaninogenica in human keratinocytes (HaCaT cells). HaCaT cells were pretreated with S. salivarius(MOI = 20) or cell-free supernatant for 3 h, followed by treatment with P. melaninogenica (MOI = 5) for 3 h. The epithelial barrier integrity of HaCaT cells was detected by FD4 permeability. The mRNA level of tight junction protein was detected by quantitative real-time polymerase chain reaction (PCR). Immunofluorescence and Western Blot were used to detect the protein expression of zonula occludin-1 (ZO-1). The serial dilution-spotting assay was applied to monitor the viability of P. melaninogenica at the end of 8 and 24 h incubation. RESULTS: Challenge by P. melaninogenica decreased the levels of tight junction proteins, including occludin, ZO-1, and claudin in HaCaT cells. S. salivarius or its cell-free supernatant inhibited the down-regulation of ZO-1 mRNA and protein expression levels induced by P. melaninogenica and thus improved the epithelial barrier function. The inhibitory effect of the cell-free supernatant of S. salivarius on the growth of P. melaninogenica is associated with metabolic acid production rather than with bacteriocins and hydrogen peroxide. CONCLUSIONS: These results suggest that live S. salivarius or its cell-free supernatant significantly ameliorated the disruption of epithelial tight junctions induced by P. melaninogenica, likely through the inhibition of P. melaninogenica growth mediated by metabolic acid production.

Bibliometric analysis of recent research on the association between TRPV1 and inflammation.

TRPV1 channel is a sensitive ion channel activated by some noxious stimuli and has been reported to change many physiological functions after its activation. In this paper, we present a scientometric approach to explore the trends of the association between TRPV1 channel and inflammation and our goal is to provide creative directions for future research. The related literature was retrieved from Web of Science Core Collection and then analyzed by CiteSpace and VOSviewer. A total of 1533 documents were screened. The most productive country, institution, journal, author, cited journal, cited author, and references were the United States, University of California, San Francisco, Pain, Lu-yuan Lee, Nature, Michael J. Caterina, and Caterina MJ (Science, 2000), respectively. The most influential country and institution were Switzerland and University of California, San Francisco, respectively. The cooperation among countries or institutions was extensive. Amounts of documents were distributed in molecular, biology, genetics. TRPV1-associated neurons, neuropeptides, neuropathic pain, neuroinflammation, and neurogenic inflammation were mainly hotspots in this field. The research has presented valuable data about previous studies in the link of TRPV1 channel and inflammation.

Function of normal oral mucosa revealed by single-cell RNA sequencing.

The functions of oral mucosa include barrier, sensation, and secretion. The barrier protection function is particularly important, which includes physical barrier and immunological barrier. Few studies have revealed the function of oral mucosa by displaying the map of normal oral mucosal cells from the perspective of single cells. Here, single-cell transcriptome sequencing was used to bring a relatively comprehensive map of the normal oral mucosal cells. In total, 26,398 cells from three cases of normal oral mucosa were analyzed by single-cell RNA-sequencing and 14 distinct cell groups were defined, 7 of which were immune cells. We performed subgroup classification and heterogeneity analysis of epithelial cells, T cells, and macrophagocytes, which found a subpopulation of epithelial cells with high expression of major histocompatibility complex class II molecules, a subpopulation CD8+ GZMK+ T cells, and two kinds of active macrophagocytes. Meanwhile, we identified ligand-receptor pairs among the major cell types to explore the interactions and how they maintain the homeostasis of normal oral mucosa. Based on these results, the epithelial barrier function, immunological barrier function, and potential maintenance function of stromal cells in the oral mucosa were described at the single-cell level, which provides basic data resources for further studies of oral mucosal diseases.

The mechanism on Prevotella melaninogenica promoting the inflammatory progression of oral lichen planus.

Oral lichen planus (OLP) is a common chronic inflammatory disease occurring in the oral mucosa. Bacteria are a key driver of mucosal immune responses and can induce changes in gene expression and function of epithelial keratinocytes. IL-36γ can induce the expression of antimicrobial peptides, cytokines, and chemokines, and is widely involved in many chronic inflammatory diseases. Our aim is to explore the role of IL-36γ in the pathological process of OLP when Prevotella melaninogenica (P. melaninogenica) invades the oral mucosa. The expression of IL-36γ in OLP lesions and mice was detected by immunohistochemistry. Recombinant human IL-36Gamma (rhIL-36γ) was used to treat oral keratinocytes and the expression levels of inflammatory cytokines were detected by qRT-PCR and ELISA. The expression of IL-36γ and TRPV1 was detected by western blotting following co-culturing P. melaninogenica with oral keratinocytes. The mRNA expression of IL-36γ was detected by qRT-PCR. From our results, IL-36γ was upregulated in OLP lesions. Exogenous rhIL-36γ promoted the expression of pro-inflammatory cytokines and antibacterial peptides in oral keratinocytes. The expression of IL-36γ was significantly increased following the stimulation of P. melaninogenica in oral keratinocytes and mice. TRPV1 activation was induced by P. melaninogenica and its activation enhanced the expression of IL-36γ. IL-36Ra could reduce the inflammation in OLP in vitro. In summary, overexpression of IL-36γ in OLP lesions could promote its pathogenesis by inducing inflammation. P. melaninogenica invasion of oral keratinocytes could induce the expression of IL-36γ by the activation of TRPV1, thereby regulating the interaction between bacteria and oral epithelial cells.

Transcriptome analysis of primary human oral keratinocytes stimulated with Prevotella melaninogenica / 口腔疾病防治

Objective@# To investigate the transcriptomic changes in primary human oral keratinocytes (pHOKs) after coculture with Prevotella melaninogenica (P.m) and to verify the changes in human oral keratinocyte (HOK) cell lines.@*Methods@# pHOK was isolated and cocultured with P.m for 0, 4 and 24 h. Total RNA was extracted, a gene library was constructed, transcriptional sequencing was performed, differentially expressed genes (DEGs) were analyzed, gene ontology (GO) pathway analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed, and the validation of DEGs was performed by qRT-PCR and Western Blot in the HOK and P.m coculture cell model. @*Results @#1 788 DEGs were detected between the 4 h group and control group, including upregulated DEGs such as lymphocyte cytosolic protein 1(LCP1), keratin 7 (KRT7) and Cilia and flagella associated protein 251(CFAP251) and downregulated DEGs such as FERM, ARH/RhoGEF and Pleckstrin domain protein 1 (FARP1), WW domain containing transcription regulator 1(WWTR1) and Discoidin, CUB and LCCL domain-containing protein 2 (DCBLD2). 1 832 DEGs were detected between the 24 h group and control group, including upregulated DEGs such as LCP1, complement C1s(C1S), kynureninase (KYNU) and downregulated DEGs such as phosphoserine aminotransferase 1 (PSAT1), FARP1 and FKBP prolyl isomerase 10 (FKBP10). There were 1 090 common differentially expressed genes (cDEGs) in the 4 h and 24 h groups, including LCP1, KYNU and long intergenic nonprotein coding RNA 958 (LINC00958). The GO pathways were mainly enriched in response to lipopolysaccharide and the molecules of bacterial origin and apical part of the cell. KEGG pathway analysis revealed enrichment in the interleukin-17 (IL-17) signaling pathway, tumor necrosis factor (TNF) signaling pathway, Toll-like receptor (TLR) pathway, etc. We verified the expression of a cDEG, Myosin1B (MYO1B), and qRT-PCR and Western Blot analysis showed that MYO1B expression was significantly upregulated between the control group and the P.m cocultured group (P<0.001), and its expression followed a time-dependent and concentration-dependent manner. @*Conclusion@#P.m played an important role in the transcriptome of oral keratinocytes.