Colonization of the skin by Staphylococcus aureus is associated with exacerbation of atopic dermatitis (AD), but any direct mechanism through which dysbiosis of the skin microbiome may influence the development of AD is unknown. Here, we show that proteases and phenol-soluble modulin α (PSMα) secreted by S. aureus lead to endogenous epidermal proteolysis and skin barrier damage that promoted inflammation in mice. We further show that clinical isolates of different coagulase-negative staphylococci (CoNS) species residing on normal skin produced autoinducing peptides that inhibited the S. aureus agr system, in turn decreasing PSMα expression. These autoinducing peptides from skin microbiome CoNS species potently suppressed PSMα expression in S. aureus isolates from subjects with AD without inhibiting S. aureus growth. Metagenomic analysis of the AD skin microbiome revealed that the increase in the relative abundance of S. aureus in patients with active AD correlated with a lower CoNS autoinducing peptides to S. aureus ratio, thus overcoming the peptides’ capacity to inhibit the S. aureus agr system. Characterization of a S. hominis clinical isolate identified an autoinducing peptide (SYNVCGGYF) as a highly potent inhibitor of S. aureus agr activity, capable of preventing S. aureus–mediated epithelial damage and inflammation on murine skin. Together, these findings show how members of the normal human skin microbiome can contribute to epithelial barrier homeostasis by using quorum sensing to inhibit S. aureus toxin production.

Proline oxidase (POX) is a novel mitochondrial tumor suppressor, which can suppress proliferation and induce apoptosis through the generation of reactive oxygen species (ROS) and decreasing hypoxia inducible factor (HIF) signaling. Recent studies have demonstrated the absent expression of POX in human cancer tissues, including renal cancer. However, the mechanism for the loss of POX remains obscure. No genetic or epigenetic variation of POX gene was found. Here, we identified the up-regulated miR-23b* in renal cancer as an important regulator of POX. Ectopic overexpression of miR-23b* in normal renal cells resulted in striking down-regulation of POX, while POX expression increased markedly when endogenous miR-23b* was knocked down by its antagomirs in renal cancer cells. Consistent with POX-mediated tumor suppression pathway, these antagomirs induced ROS, inhibited HIF signaling and increased apoptosis. Furthermore, we confirmed the regulation of miR-23b* on POX and its function in the DLD1 Tet-off POX cell system. Using a luciferase reporter system, we verified the direct binding of miR-23b* to POX mRNA 3′UTR. In addition, pairs of human renal carcinoma and normal tissues showed the negative correlation between miR-23b* and POX protein expression, providing its clinical corroboration. Taken together, our results suggested miR-23b*, by targeting POX, could function as an oncogene; decreasing miR-23b* expression may prove to be an effective way of inhibiting kidney tumor growth.