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

Abstract

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‐κB (NF‐κB) pathway in response to C. t. infection, including phosphorylation of the inhibitor of κB (IκB), the nuclear translocation of NF‐κB subunit (NF‐κB‐P65) and the recruitment of NF‐κB‐P65 and RNA polymerase to the NF‐κB 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 IκB kinase and downstream signaling through the canonical NF‐κB pathway. Relevance to chronic inflammatory diseases of the skin and cutaneous oncology is discussed.

Frog Skin-Derived Peptides Against Corynebacterium jeikeium: Correlation between Antibacterial and Cytotoxic Activities

“…Similar data were previously collected for viability assays performed with Esc(1-21) at the same concentrations, except for the greater cytotoxicity against macrophages at 64 µM (i.e., about 50% cell viability) [41]. Lacking the harmful effect of esculentin peptides, particularly for Esc (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) at the antimicrobial concentrations (MIC and MBC values), suggested they are safe compounds, also for long-term treatment.…”

“…However, no studies have been conducted so far for these peptides, as well as for other AMPs, against C. jeikeium. Here, for the first time, we analyzed the effect of some frog skin AMPs against this bacterium and selected the esculentin peptides as the most active molecules with an MIC of 0.125 and 4 µM for Esc and Esc (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18), respectively. This outcome is in sharp contrast with the weaker activity of Esc(1-21) previously recorded against other Gram-positive bacteria (e.g., Staphylococcus aureus, S. epidermidis), where MICs ranging from 1 to 64 µM were found [37].…”

“…In comparison, MICs ranging from 8 to 16 µM were obtained for the other selected AMPs. Unlike temporins and bombinin H2, esculentin peptides are lysine-rich Interestingly, when the most active esculentin peptides were tested for their bactericidal activity, they were found to cause almost the complete killing of the bacterial population with an MBC (i.e., the lowest peptide concentration able to cause a ≥3 log reduction in the number of bacterial cells) 2-fold higher than the corresponding MIC, i.e., 8 µM and 0.25 µM for Esc (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) and Esc(1-21), respectively.…”

“…Esc (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18), Esc , temporin A, temporin B, temporin G, and bombinin H 2 were purchased from Biomatik (USA/Canada). Each peptide was assembled by stepwise solid-phase synthesis and purified via reverse-phase high-performance liquid chromatography to a purity of 98% using a gradient of acetonitrile in 0.1% aqueous trifluoroacetic acid (from 28% to 100% in 30 min) at a flow rate of 1.0 mL/min.…”

“…Corynebacteria are Gram-positive, aerobic, catalase-positive, generally non-motile rods, and this genus comprises Corynebacterium diphtheriae and other different species defined as nondiphtheriae corynebacteria (diphtheroids) [1,2]. Corynebacterium jeikeium (commonly known as group JK corynebacterium by the Centers for Disease Control and Prevention) is part of the human skin flora as Staphylococcus epidermidis and is among the most common bacteria isolated from hospitalized patients [3][4][5]. In particular, its colonization affects groin and axilla where the moist environment favors the formation of malodor substrates leading, in some cases, to an unpleasant body smell [6,7].…”