Protective role of Galectin-7 for skin barrier impairment in atopic dermatitis.

BACKGROUND: Atopic dermatitis (AD) patients have a barrier disorder in association with Th2 dominant skin inflammation. Galectin-7 (Gal-7), a soluble unglycosylated lectin, is highly expressed in the stratum corneum of AD patients. However, the biological significance of increased Gal-7 expression in AD skin lesions remains unclear. OBJECTIVE: We aimed to investigate the production mechanism and functional role of Gal-7 in AD patients and IL-4/IL-13-stimulated epidermal keratinocytes. METHODS: We assessed the Gal-7 expression levels in skin lesions and sera from AD patients. Gal-7 levels were also measured in monolayered normal human epidermal keratinocytes (NHEKs) and 3-dimensional (3D)-reconstructed epidermis in the presence or absence of IL-4/IL-13 with or without Stat3, Stat6 or Gal-7 gene silencing. RESULTS: Gal-7 was highly expressed in the stratum corneum or intercellular space of AD lesional epidermis as assessed by the stratum corneum proteome analysis and immunohistochemistry. A positive correlation was noted between serum Gal-7 level and transepidermal water loss in patients with AD. These clinical findings were corroborated by our in vitro data, which showed that IL-4/IL-13 facilitated the extracellular release of endogenous Gal-7 in both monolayered NHEKs and 3D-reconstructed epidermis. This machinery was caused by IL-4/IL-13-induced cell damage and inhibited by knockdown of Stat6 but not Stat3 in NHEKs. Moreover, we performed Gal-7 knockdown experiment on 3D-reconstructed epidermis and the result suggested that endogenous Gal-7 serves as a protector from IL-4/IL-13-induced disruption of cell-to-cell adhesion and/or cell-to-extracellular matrix adhesion. CONCLUSION AND CLINICAL RELEVANCE: Our study unveils the characteristic of Gal-7 and its possible role as an alarmin that reflects the IL-4/IL-13-induced skin barrier impairment in AD.

Decreased expression of suprabasin induces aberrant differentiation and apoptosis of epidermal keratinocytes: Possible role for atopic dermatitis.

BACKGROUND: Suprabasin (SBSN), a secreted protein, is expressed in various epithelial tissues. The role of SBSN in epidermal differentiation and atopic dermatitis (AD) pathology remains largely unknown. OBJECTIVE: To evaluate the effects of SBSN on epidermal keratinocytes and its role in AD. METHODS: We examined the SBSN expression levels in the stratum corneum and the epidermis by proteome analysis and immunohistochemistry, respectively. The serum SBSN concentration was measured by ELISA. These values were compared between AD and healthy control. Morphological changes in the epidermis were investigated in SBSN-knockdown three-dimensional human living skin equivalent (LSE) model with or without IL-4/IL-13. RESULTS: Epidermal SBSN expression was decreased in AD lesional skin compared to healthy skin, as assessed by the stratum corneum proteome analysis and immunohistochemistry. The SBSN serum levels were significantly lower in AD patients than in normal subjects (P<0.05). The SBSN-deficient LSE exhibited compact stratum corneum, immature stratum granulosum, and increased keratinocyte apoptosis. Th2 cytokines, IL-4 and IL-13, did not affect SBSN expression in LSE. There were no differentiation-associated makers that were affected by the SBSN knockdown. SBSN deficiency-induced apoptosis of keratinocytes was exaggerated by IL-4/IL-13, and accordingly, the addition of recombinant SBSN induced significant keratinocyte proliferation (P<0.05). CONCLUSION: Our data demonstrated that SBSN regulates normal epidermal barrier. Th2 cytokines unaffect SBSN expression in keratinocytes, but promote SBSN deficiency-induced apoptosis. It is suggested that SBSN has an anti-apoptotic activity, and its deficiency is involved in the pathogenesis of AD.

Repeated Amblyomma testudinarium tick bites are associated with increased galactose-α-1,3-galactose carbohydrate IgE antibody levels: A retrospective cohort study in a single institution.

BACKGROUND: Alpha-gal syndrome is a hypersensitivity reaction to red meat mediated by IgE antibody specific to galactose-α-1,3-galactose carbohydrate (alpha-gal). Amblyomma tick bites are associated with this condition, but the pathophysiology is not understood. OBJECTIVE: To clarify the mechanism of development of alpha-gal syndrome after tick bites. METHODS: We compared alpha-gal antibody levels between patients with and without a history of tick bites and examined histologic stainings of tick bite lesions between patients with and without detectable alpha-gal IgE antibody. RESULTS: Patients who had ≥2 tick bites had higher levels of alpha-gal IgE antibody compared with those with only 1 tick bite or healthy individuals. On histologic investigation, greater numbers of basophils and eosinophils, but not mast cells, were observed infiltrating lesions of patients with ≥2 tick bites compared with those with 1 tick bite. Type 2 cytokine-producing T-cell infiltration was predominantly observed in such patients. LIMITATIONS: The study was conducted at a single institution in Japan. CONCLUSION: In Amblyomma tick bite lesions, basophils; eosinophils; and type 2, cytokine-producing T cells infiltrate the skin and alpha-gal IgE antibodies are produced. These findings provide a potential mechanistic connection between Amblyomma bites and red meat hypersensitivity.

Topical application of a vitamin D3 analogue and corticosteroid to psoriasis plaques decreases skin infiltration of TH17 cells and their ex vivo expansion.

BACKGROUND: Topical combination of a vitamin D3 analogue and corticosteroid is widely used for the treatment of psoriasis, a TH17-mediated disorder, but the underlying mechanism remains unclear. OBJECTIVE: We investigated the effect of this topical applicant, focusing on skin-infiltrating TH17 cells. METHODS: In 10 patients with plaque psoriasis, calcipotriol (Cal), betamethasone dipropionate (Bet), or the calcipotriol and betamethasone dipropionate 2-compound formulation (CB) was applied to 3 different psoriatic plaques with similar severity once a day for 14 days. One nonapplied lesion was used as a control. Four-millimeter biopsy specimens were taken from each site, cut into 2 pieces, and subjected to histologic examination and ex vivo expansion of skin-infiltrating T cells with anti-CD3/CD28 antibodies and IL-2. RESULTS: Clinical, histologic, and IL-17A(+) cell-infiltrate improvement was found in the following order: CB > Cal > Bet > control or CB > Bet > Cal > control. Numbers of ex vivo expanded T cells were decreased by topical application of Bet and CB, and CB exhibited the most suppressive result. Numbers and frequencies of TH17 cells were significantly reduced by CB and Cal, suggesting that Cal has a capacity to preferentially suppress TH17 cells. When the stocked T cells from control samples were stimulated with anti-CD3 antibodies in the presence of Bet, Cal, or both, Cal downmodulated IL-17 and IFN-γ production and tended to upregulate IL-4 and IL-6 without apoptosis, but Bet inhibited production of these cytokines with apoptosis. CONCLUSION: These findings suggest that Cal and Bet have different effects on T cells to normalize psoriatic changes, with decreased TH17 cell expansion in the skin lesions.

Calcipotriol increases hCAP18 mRNA expression but inhibits extracellular LL37 peptide production in IL-17/IL-22-stimulated normal human epidermal keratinocytes.

Interleukins (IL)-17A and -22 are involved in the patho-genesis of psoriasis. Cathelicidin LL37 serves as not only antimicrobial peptide but also as autoinflammatory mediator. 1,25-Dihydroxyvitamin D3 analogues, such as calcipotriol, are used as topical treatment for psoriasis. However, the effect of calcipotriol on the mRNA expression/production of human cathelicidin antimicrobial protein (hCAP18) and LL37 peptide by IL-17A/IL-22-stimulated keratinocytes remains controversial. To evaluate the modulatory action of calcipotriol on the production of hCAP18 and LL37, we analysed hCAP18 mRNA expression and hCAP18/LL37 peptide production in IL-17A/IL-22-stimulated cultured human keratinocytes by real-time qPCR, ELISA, western blotting, and immunocytostaining. By western blotting, hCAP18 protein was detected in keratinocytes cultured for 72 h with IL-17/IL-22. Calcipotriol increased hCAP18 mRNA expression in IL-17/IL-22-stimulated keratinocytes. However, LL37 peptide in the culture supernatants was reduced by calcipotriol. Immunostaining revealed that the overproduced LL37 resides within the cells. LL37 promotes psoriasis via interaction with extracellular DNA, but may suppress psoriasis by interfering cytosolic DNA.