-Induced MiRNAs Regulate CCL20 Responses in Human Oral Epithelial Cells

The mechanisms through which oral commensal bacteria mitigates uncontrolled inflammatory responses of the oral mucosa remain unknown. Here, we show that representative oral bacterial species normally associated with oral health [S. gordonii (), V. parvula (), (), C. sputigena (), and N. mucosa ()] enhanced differential chemokine responses in oral epithelial cells (OECs), with some bacteria () inducing higher chemokine levels (CXCL1, CXCL8) than others (). Although all bacterial species (except ) increased CCL20 mRNA levels consistent with protein elevations in cell lysates, only , induced higher CCL20 secretion, similar to the effect of the oral pathogen F. nucleatum . In contrast, most CCL20 remained associated with OECs exposed to and negligible amounts released into the cell supernatants. Consistently, attenuated -induced CCL20. MiR-4516 and miR-663a were identified as -specifically induced miRNAs modulating validated targets of chemokine-associated pathways. Cell transfection with miR-4516 and miR-663a decreased - and -induced CCL20. MiRNA upregulation and attenuation of -induced CCL20 by were reversed by catalase. Up-regulation of both miRNAs was specifically enhanced by oral streptococci HO-producers. These findings suggest that CCL20 levels produced by OECs in response to bacterial challenge are regulated by -induced miR-4516 and miR-663a in a mechanism that involves hydrogen peroxide. This type of molecular mechanism could partly explain the central role of specific oral streptococcal species in balancing inflammatory and antimicrobial responses given the critical role of CCL20 in innate (antimicrobial) and adaptive immunity (modulates Th17 responses).