Corynebacterium tuberculostearicum, a human skin colonizer, induce the canonical nuclear factor-κB inflammatory signaling pathway in the human skin cells

Introduction Corynebacterium tuberculostearicum (C. t.) is a ubiquitous bacterium that colonizes human skin. In contrast to other members of the genus Corynebacterium, such as toxigenic Corynebacterium diphtheriae or the opportunistic pathogen Corynebacterium jeikeium, several studies suggest that C. t. may play a role in skin health and disease. However, the mechanisms underlying these effects remain poorly understood. Methods To investigate whether C. t. induces inflammatory pathways in primary human epidermal keratinocytes (HEKs) and human cutaneous squamous carcinoma cells (SCCs), cell culture, reverse transcription-polymerase chain reaction (PCR), enzyme-linked immunosorbent assay, immunofluorescence microscopy, Western blot, chromatin immunoprecipitation-PCR, small interfering RNA knockdown and luciferase reporter expression system were used. Results Herein, we demonstrate that C. t. upregulates the messenger RNA (mRNA) and protein levels of inflammatory mediators in two human skin cell lines, HEKs and SCCs. We further show activation of the canonical nuclear factor-kappa B (NF-kappa B) pathway in response to C. t. infection, including phosphorylation of the inhibitor of kappa B (I kappa B), the nuclear translocation of NF-kappa B subunit (NF-kappa B-P-65) and the recruitment of NF-kappa B-P-65 and RNA polymerase to the NF-kappa B response elements at the promoter region of the inflammatory genes. Lastly, the data confirm that C. t.-induced tumor necrosis factor mRNA expression in HEKs is toll-like receptor 2 (TLR2) dependent. Conclusion Our results offer a mechanistic model for C. t.-induced inflammation in human keratinocytes via TLR2 and activation of I kappa B kinase and downstream signaling through the canonical NF-kappa B pathway. Relevance to chronic inflammatory diseases of the skin and cutaneous oncology is discussed.