Peptides antimicrobiens naturels cutanés

Role of the CXCR6/CXCL16 axis in autoimmune diseases

The C-X-C motif ligand 16, or CXCL16, is a chemokine that belongs to the ELR - CXC subfamily. Its function is to bind to the chemokine receptor CXCR6, which is a G protein-coupled receptor with 7 transmembrane domains. The CXCR6/CXCL16 axis has been linked to the development of numerous autoimmune diseases and is connected to clinical parameters that reflect disease severity, activity, and prognosis in conditions such as multiple sclerosis, autoimmune hepatitis, rheumatoid arthritis, Crohn's disease, and psoriasis. CXCL16 is expressed in various immune cells, such as dendritic cells, monocytes, macrophages, and B cells. During autoimmune diseases, CXCL16 can facilitate the adhesion of immune cells like monocytes, T cells, NKT cells, and others to endothelial cells and dendritic cells. Additionally, sCXCL16 can regulate the migration of CXCR6-expressing leukocytes, which includes CD8⁺ T cells, CD4⁺ T cells, NK cells, constant natural killer T cells, plasma cells, and monocytes. Further investigation is required to comprehend the intricate interactions between chemokines and the pathogenesis of autoimmune diseases. It remains to be seen whether the CXCR6/CXCL16 axis represents a new target for the treatment of these conditions.

A topical treatment containing heat-treated Lactobacillus johnsonii NCC 533 reduces Staphylococcus aureus adhesion and induces antimicrobial peptide expression in an in vitro reconstructed human epidermis model

Staphylococcus aureus colonization is thought to contribute to the pathophysiology of atopic dermatitis (AD). AD patients exhibit reduced levels of cutaneous antimicrobial peptides (AMPs), which may explain their increased susceptibility to infections. Using an in vitro reconstructed human epidermis (RHE) model, we sought to determine whether topical application of a non-replicating probiotic, heat-treated Lactobacillus johnsonii NCC 533 (HT La1), could inhibit S. aureus adhesion to skin and boost cutaneous innate immunity. We found that application of HT La1 suspension to RHE samples reduced the binding of radiolabelled S. aureus by up to 74%. To investigate a potential effect of HT La1 on innate immunity, we analysed the expression of nine AMP genes, including those encoding beta defensins and S100 proteins, following topical application of HT La1 in suspension or in a daily moisturizer lotion. Analysed genes were induced by up to fourfold in a dose-dependent manner by HT La1 in suspension and by up to 2.4-fold by HT La1 in the moisturizer lotion. Finally, using ELISA and immunohistochemical detection, we evaluated the expression and secretion of the AMPs hBD-2 and psoriasin and determined that both proteins were induced by topical HT La1, particularly in the stratum corneum of the RHE. These findings demonstrate that a topically applied, non-replicating probiotic can modulate endogenous AMP expression and inhibit binding of S. aureus to an RHE model in vitro. Moreover, they suggest that a topical formulation containing HT La1 could benefit atopic skin by enhancing cutaneous innate immunity and reducing S. aureus colonization.

Expression profile of drosomycin-like defensin in oral epithelium and oral carcinoma cell lines

OBJECTIVE

Drosomycin-like defensin (DLD) is a recently discovered antimicrobial peptide mainly active against filamentous fungi. The present study investigated the expression profile of DLD in oral epithelium and oral squamous cell carcinoma (SCC) cell lines.

METHODS

Tissue sections of human oral mucosa, keratinocytes derived from oral mucosa (NOK) and eight kinds of SCC cell lines were used. In situ hybridization was performed on tissue sections of oral mucosa. Expression levels of DLD in the cells were observed by reverse transcription polymerase chain reaction (RT-PCR) and real-time RT-PCR assays. The cells were treated with IL-1β, IL-8 and TNF-α, and agonists for TLR2, TLR4 and β-glucan. DLD expression in cells was increased and decreased by the DLD gene and its siRNA transfection, respectively. The proliferation rates were assessed by cell counting.

RESULTS

By means of in situ hybridization, DLD mRNA positive staining was detected in the epithelial layer of the oral mucosa. An RT-PCR assay confirmed the expression of DLD mRNA in keratinocytes derived from oral epithelium. Expression of DLD in two out of eight cell lines was significantly lower than in NOK cells. The expression levels of DLD mRNA were not significantly changed in the cells stimulated with any cytokines or agonists. The cell proliferation rate where there was decreased expression of DLD was significantly lower than in the control.

CONCLUSION

DLD may be partially involved in the defence against filamentous fungal infection in the oral mucosa, and may also serve other functions, such as contribution to cell growth.

Psoriasin (S100A7), an antimicrobial peptide, is increased in human middle ear cholesteatoma

CONCLUSION

Increased psoriasin in cholesteatoma epithelium may play a role in epithelial inflammatory response and differentiation.

OBJECTIVES

Cholesteatoma is characterized by excessive keratinocyte differentiation leading to inflammation, granulation tissue, and osteolytic activity. Moreover, psoriasin may act as an antimicrobial peptide, stimulate granulocytes, and control keratinocyte differentiation. The purpose of this study was to investigate the differential expression patterns and the localization of psoriasin in cholesteatoma and in normal external auditory canal skin.

MATERIALS AND METHODS

Expression levels of psoriasin mRNA were evaluated by real-time PCR and Western blotting. Cholesteatoma-affected and normal external auditory canal skin samples were immunostained with monoclonal antibody to psoriasin. Localization of immunoreactivity to psoriasin antibody was then compared.

RESULTS

By real-time PCR, expression levels of psoriasin mRNA in cholesteatoma were significantly higher than in normal external auditory canal skin, and this was confirmed by Western blotting. Immunohistochemical staining revealed that psoriasin protein is mainly expressed in the granular layer and in the upper parts of the spinous layer in cholesteatoma epithelium, but that it is expressed in the superficial layer of normal external auditory canal skin.