Elevated expression of interleukin-6 (IL-6) and serum amyloid A (SAA) in the skin and the serum of recessive dystrophic epidermolysis bullosa: Skin as a possible source of IL-6 through Toll-like receptor ligands and SAA.

The effect of persistent skin inflammation on extracutaneous organs and blood is not well studied. Patients with recessive dystrophic epidermolysis bullosa (RDEB), a severe form of the inherited blistering skin disorder, have widespread and persistent skin ulcers, and they develop various complications including anaemia, hyperglobulinaemia, hypoalbuminaemia and secondary amyloidosis. These complications are associated with the bioactivities of IL-6, and the development of secondary amyloidosis requires the persistent elevation of serum amyloid A (SAA) level. We found that patients with RDEB had significantly higher serum levels of IL-6 and SAA compared to healthy volunteers and patients with psoriasis or atopic dermatitis. Both IL-6 and SAA were highly expressed in epidermal keratinocytes and dermal fibroblasts of the skin ulcer lesions. Keratinocytes and fibroblasts surrounding the ulcer lesions are continuously exposed to Toll-like receptor (TLR) ligands, pathogen-associated and damage-associated molecular pattern molecules. In vitro, TLR ligands induced IL-6 expression via NF-κB in normal human epidermal keratinocytes (NHEKs) and dermal fibroblasts (NHDFs). SAA further induced the expression of IL-6 via TLR1/2 and NF-κB in NHEKs and NHDFs. The limitation of this study is that NHEKs and NHDFs were not derived from RDEB patients. These observations suggest that TLR-mediated persistent skin inflammation might increase the risk of IL-6-related systemic complications, including RDEB.

"Input/output cytokines" in epidermal keratinocytes and the involvement in inflammatory skin diseases.

Considering the role of epidermal keratinocytes, they occupy more than 90% of the epidermis, form a physical barrier, and also function as innate immune barrier. For example, epidermal keratinocytes are capable of recognizing various cytokines and pathogen-associated molecular pattern, and producing a wide variety of inflammatory cytokines, chemokines, and antimicrobial peptides. Previous basic studies have shown that the immune response of epidermal keratinocytes has a significant impact on inflammatory skin diseases. The purpose of this review is to provide foundation of knowledge on the cytokines which are recognized or produced by epidermal keratinocytes. Since a number of biologics for skin diseases have appeared, it is necessary to fully understand the relationship between epidermal keratinocytes and the cytokines. In this review, the cytokines recognized by epidermal keratinocytes are specifically introduced as "input cytokines", and the produced cytokines as "output cytokines". Furthermore, we also refer to the existence of biologics against those input and output cytokines, and the target skin diseases. These use results demonstrate how important targeted cytokines are in real skin diseases, and enhance our understanding of the cytokines.

Co-occurrence of non-alcoholic steatohepatitis exacerbates psoriasis associated with decreased adiponectin expression in a murine model.

Introduction: Clinical studies have suggested a bidirectional association between non-alcoholic steatohepatitis (NASH) and psoriasis, affecting each other's development and severity. Here, we explored bidirectional causal linkages between NASH and psoriasis using a murine model. Methods: NASH was induced in mice by streptozotocin injection at 2 days of age and by high-fat diet feeding (STAM™ model). Psoriasis was induced by topical application of imiquimod (IMQ) on the ear. The severities of liver damage and psoriatic skin changes were determined using histological analysis. Gene expression in the skin tissues was evaluated using quantitative PCR analysis. Serum cytokine levels were determined using enzyme-linked immunosorbent assay. To examine the innate immune responses of normal human epidermal keratinocytes (NHEKs), the cells were treated with interleukin (IL)-17A, tumor necrosis factor (TNF)-α, and AdipoRon, an adiponectin receptor agonist. Results and Discussion: There were no differences in the degree of liver tissue damage (fat deposition, inflammation, and fibrosis) between NASH mice with and those without psoriasis. Conversely, the co-occurrence of NASH significantly augmented psoriatic skin changes, represented by epidermal hyperplasia, in psoriatic mice. Pro-inflammatory cytokines were expressed in the inflamed skin of psoriatic mice, and the expression of genes, especially Il23a, Il1b, Il36g, and Mip2, was significantly upregulated by the co-occurrence of NASH. The expression of keratinocyte activation marker genes Defb4b and Krt16 was also upregulated by the co-occurrence of NASH. The serum TNF-α and IL-17 levels were increased by the co-occurrence of NASH and psoriasis. The serum adiponectin levels decreased in NASH mice compared with that in non-NASH mice. In NHEK culture, TNF-α and IL-17A synergistically upregulated CXCL1, CXCL8, and IL1B expression. The upregulated pro-inflammatory gene expression was suppressed by AdipoRon treatment, reflecting the anti-inflammatory capacity of adiponectin. Conclusion: The co-occurrence of NASH exacerbated psoriatic skin changes associated with increased serum inflammatory cytokine levels and decreased serum adiponectin levels. Combined with in vitro findings, increased inflammatory cytokine levels and decreased adiponectin levels likely promote innate immune responses in epidermal keratinocytes in psoriatic skin lesions. Overall, therapeutic intervention for co-occurring NASH is essential to achieve a favorable prognosis of psoriasis in clinical practice.

Coexpression of natural killer cell antigens by T-cell large granular lymphocytes in hydroa vacciniforme lymphoproliferative disorder and the involvement of Vδ1 + epithelial-type γδT cells.

Hydroa vacciniforme lymphoproliferative disorder (HV-LPD) is a cutaneous variant of chronic active Epstein-Barr virus disease. We examined the coexpression of T- and natural killer (NK)-cell antigens in five patients with classic HV (cHV) and five with systemic HV (sHV). T-cell receptor (TCR) repertoire analysis was performed with high­throughput sequencing. All five cHV patients had increased γδT cells (> 5%), whereas five sHV patients showed γδT- and αßT-cell dominance in two patients each, and a mixture of abnormal γδT and αßT cells in one. Circulating CD3 + T cells expressed CD16/CD56 at 7.8-42.3% and 1.1-9.7% in sHV and cHV, respectively. The percentage of CD16/CD56 + T cells was higher in the large granular lymphocyte or atypical T-cell fractions in sHV, but no TCR Vα24 invariant chain characteristic of NKT cells was detected. Considerable numbers of CD3 + cells expressing CD56 were observed in sHV skin infiltrates. Of the circulating γδT cells tested, TCR Vδ1 + cells characteristic of the epithelial type of γδT cells were dominant in two sHV cases. Thus, atypical αßT and γδT cells in HV-LPD can express NK-cell antigens, such as CD16 and CD56, and Vδ1 + epithelial-type γδT cells are a major cell type in some HV-LPD cases.