Impact of house dust mite in vitiligo skin: environmental contribution to increased cutaneous immunity and melanocyte detachment.

BACKGROUND: Vitiligo is an autoimmune skin disorder characterized by loss of melanocytes. Protease-mediated disruption of junctions between keratinocytes and/or keratinocyte intrinsic dysfunction may directly contribute to melanocyte loss. House dust mite (HDM), an environmental allergen with potent protease activity, contributes to respiratory and gut disease but also to atopic dermatitis and rosacea. OBJECTIVES: To verify if HDM can contribute to melanocyte detachment in vitiligo and if so, by which mechanism(s). METHODS: Using primary human keratinocytes, human skin biopsies from healthy donors and patients with vitiligo, and 3D reconstructed human epidermis, we studied the effect of HDM on cutaneous immunity, tight and adherent junction expression and melanocyte detachment. RESULTS: HDM increased keratinocyte production of vitiligo-associated cytokines and chemokines and increased expression of toll-like receptor (TLR)-4. This was associated with increased in situ matrix-metalloproteinase (MMP)-9 activity, reduced cutaneous expression of adherent protein E-cadherin, increased soluble E-cadherin in culture supernatant and significantly increased number of suprabasal melanocytes in the skin. This effect was dose-dependent and driven by cysteine protease Der p1 and MMP-9. Selective MMP-9 inhibitor, Ab142180, restored E-cadherin expression and inhibited HDM-induced melanocyte detachment. Keratinocytes from patients with vitiligo were more sensitive to HDM-induced changes than healthy keratinocytes. All results were confirmed in a 3D model of healthy skin and in human skin biopsies. CONCLUSIONS: Our results highlight that environmental mite may act as an external source of pathogen-associated molecular pattern molecules in vitiligo and topical MMP-9 inhibitors may be useful therapeutic targets. Whether HDM contributes to the onset of flares in vitiligo remains to be tested in carefully controlled trials.

Ceramide AD™ Restores Skin Integrity and Function following Exposure to House Dust Mite.

Ceramides are epidermal lipids important for normal skin barrier function. Reduced Ceramide content is associated with atopic dermatitis (AD). House dust mite (HDM) has been localized in AD skin where it plays an exacerbator role. We set to examine the impact of HDM on skin integrity and the effect of three separate Ceramides (AD™, DS, Y30) on HDM-induced cutaneous damage. The effect was tested in vitro on primary human keratinocytes and ex vivo on skin explants. HDM (100 µg/mL) decreased the expression of adhesion protein E-cadherin, supra-basal (K1, K10) and basal (K5, K14) keratins and increased matrix metallopeptidase (MMP)-9 activity. The presence of Ceramide AD™ in topical cream inhibited HDM-induced E-cadherin and keratin destruction and dampened MMP-9 activity ex vivo which was not seen for the control cream or cream containing DS or Y30 Ceramides. The efficacy of Ceramide AD™ was tested in a clinical setting on moderate to very dry skin (as surrogate for environment-induced skin damage). When applied topically for 21 days, Ceramide AD™ significantly reduced transepidermal water loss (TEWL) in patients with very dry skin compared to their TEWL baseline data. Our study demonstrates Ceramide AD™ cream to be effective in restoring skin homeostasis and barrier function in damaged skin and warrants testing in larger clinical trials for possible treatment of AD and xerosis.

Analysis of Matched Skin and Gut Microbiome of Patients with Vitiligo Reveals Deep Skin Dysbiosis: Link with Mitochondrial and Immune Changes.

Vitiligo is an autoimmune disease characterized by patchy, white skin owing to melanocyte loss. Commensal cutaneous or gut dysbiosis has been linked to various dermatological disorders. In this study, we studied the skin and gut microbiota of patients with vitiligo compared with those of healthy controls. We obtained swabs and biopsies from both lesional and nonlesional skin as well as stool and blood samples from each individual. We detected reduced richness and diversity of microbiota in the stools of subjects with vitiligo compared with the stools of the controls (P < 0.01). Skin swabs had greater α-diversity than biopsies (P < 0.001); swabs from lesional sites were primarily depleted of Staphylococcus compared with those from nonlesional sites (P < 0.02). Sampling deeper layers from the same patients showed differences in both α- and ß-diversity between samples with decreased richness and distribution of species (P < 0.01) in the lesional site. Biopsy microbiota from the lesional skin had distinct microbiota composition, which was depleted of protective Bifidobacterium and Bacteroides but was enriched in Proteobacteria, Streptococcus, Mycoplasma, and mtDNA (P < 0.001); the latter increased in the same patients with heightened innate immunity and stress markers in their blood (P < 0.05). These data describe vitiligo-specific cutaneous and gut microbiota and a link between skin dysbiosis, mitochondrial damage, and immunity in patients with vitiligo.

FBXO32 links ubiquitination to epigenetic reprograming of melanoma cells.

Ubiquitination by serving as a major degradation signal of proteins, but also by controlling protein functioning and localization, plays critical roles in most key cellular processes. Here, we show that MITF, the master transcription factor in melanocytes, controls ubiquitination in melanoma cells. We identified FBXO32, a component of the SCF E3 ligase complex as a new MITF target gene. FBXO32 favors melanoma cell migration, proliferation, and tumor development in vivo. Transcriptomic analysis shows that FBXO32 knockdown induces a global change in melanoma gene expression profile. These include the inhibition of CDK6 in agreement with an inhibition of cell proliferation and invasion upon FBXO32 silencing. Furthermore, proteomic analysis identifies SMARC4, a component of the chromatin remodeling complexes BAF/PBAF, as a FBXO32 partner. FBXO32 and SMARCA4 co-localize at loci regulated by FBXO32, such as CDK6 suggesting that FBXO32 controls transcription through the regulation of chromatin remodeling complex activity. FBXO32 and SMARCA4 are the components of a molecular cascade, linking MITF to epigenetics, in melanoma cells.

Innate lymphocyte-induced CXCR3B-mediated melanocyte apoptosis is a potential initiator of T-cell autoreactivity in vitiligo.

T-cells play a crucial role in progression of autoimmunity, including vitiligo, yet the initial steps triggering their activation and tissue damage remain unknown. Here we demonstrate increased presence of type-1 innate lymphoid cells (NK and ILC1)-producing interferon gamma (IFNγ) in the blood and in non-lesional skin of vitiligo patients. Melanocytes of vitiligo patients have strong basal expression of chemokine-receptor-3 (CXCR3) isoform B which is directly regulated by IFNγ. CXCR3B activation by CXCL10 at the surface of cultured human melanocytes induces their apoptosis. The remaining melanocytes, activated by the IFNγ production, express co-stimulatory markers which trigger T-cell proliferation and subsequent anti-melanocytic immunity. Inhibiting the CXCR3B activation prevents this apoptosis and the further activation of T cells. Our results emphasize the key role of CXCR3B in apoptosis of melanocytes and identify CXCR3B as a potential target to prevent and to treat vitiligo by acting at the early stages of melanocyte destruction.

Uncovering and deciphering the pro-invasive role of HACE1 in melanoma cells.

HACE1 is an E3 ubiquitin ligase described as a tumour suppressor because HACE1-knockout mice develop multi-organ, late-onset cancers and because HACE1 expression is lost in several neoplasms, such as Wilms' tumours and colorectal cancer. However, a search of public databases indicated that HACE1 expression is maintained in melanomas. We demonstrated that HACE1 promoted melanoma cell migration and adhesion in vitro and was required for mouse lung colonisation by melanoma cells in vivo. Transcriptomic analysis of HACE1-depleted melanoma cells revealed an inhibition of ITGAV and ITGB1 as well changes in other genes involved in cell migration. We revealed that HACE1 promoted the K27 ubiquitination of fibronectin and regulated its secretion. Secreted fibronectin regulated ITGAV and ITGB1 expression, as well as melanoma cell adhesion and migration. Our findings disclose a novel molecular cascade involved in the regulation of fibronectin secretion, integrin expression and melanoma cell adhesion. By controlling this cascade, HACE1 displays pro-tumoural properties and is an important regulator of melanoma cell invasive properties.

Multispecies probiotic protects gut barrier function in experimental models.

AIM: To investigate the effect of the probiotic combination Lactibiane Tolerance(®) (LT) on epithelial barrier function in vitro and in vivo. METHODS: The effect of the multispecies probiotic LT was assessed on several models of epithelial barrier function both in vitro (in basal and inflammatory conditions) and in vivo [visceral hypersensitivity induced by chronic stress or by colonic perfusion of a fecal supernatant (FSN) from patients with irritable bowel syndrome (IBS)]. In vitro, we measured the permeability of confluent T84 cell monolayers incubated with or without LT by evaluating the paracellular flux of macromolecules, in basal conditions and after stimulation with lipopolysaccharide (LPS) or with conditioned medium of colonic biopsies from IBS patients (IBS-CM). In vivo, male C57/Bl6 mice received orally NaCl or LT for 15 d and were submitted to water avoidance stress (WAS) before evaluating visceral sensitivity by measuring the myoelectrical activity of the abdominal muscle and the paracellular permeability with (51)Cr-EDTA. Permeability and sensitivity were also measured after colonic instillation of FSN. Tight-junctions were assessed by immunoblotting and TLR-4 expression was evaluated by immunohistochemistry RESULTS: Incubation of T84 cell monolayers with LT in basal conditions had no significant effect on permeability (P > 0.05 vs culture medium). By contrast, addition of LT bacterial bodies (LT) completely prevented the LPS-induced increase in paracellular permeability (P < 0.01 vs LPS 10 ng/mL (LPS 10); P < 0.01 vs LPS 100 ng/mL (LPS 100), P > 0.05 vs culture medium). The effect was dose dependent as addition of 10(9) LT bacterial bodies induced a stronger decrease in absorbance than 10(6) LT (10(9) LT + LPS 10: -20.1% ± 13.4, P < 0.01 vs LPS 10; 10(6) LT + LPS 10: -11.6% ± 6.2, P < 0.01 vs LPS 10; 10(9) LT + LPS 100: -14.4% ± 5.5, P < 0.01 vs LPS 100; 10(6) LT + LPS 100: -11.6% ± 7.3, P < 0.05 vs LPS 100). Moreover, the increase in paracellular permeability induced by culturing T84 cells with conditioned medium of colonic biopsies from IBS patients (IBS-CM) was completely inhibited in the presence of 10(9) LT (P < 0.01 vs IBS-CM). LT also significantly prevented the epithelial disruption induced by intracolonic infusion of fecal supernatant from IBS patients (P < 0.01 vs IBS FSN) or water avoidance stress P < 0.01 vs WAS) in C57/Bl6 mice and increased the expression of occludin in vitro and in vivo, as assessed by immnunoblotting. The WAS-induced effect on visceral sensitivity was prevented by LT treatment since values obtained for all steps of colorectal distension were significantly (P < 0.01) different from the WAS group. Finally, LT down-regulated the response mediated through TLR-4 in vitro (decrease in tumor necrosis factor α secretion in response to LPS: -65.8% for 10(9) LT and -52.5% for 10(6) LT, P < 0.01 vs LPS) and in vivo (inhibition of WAS induced an increase in TLR-4 expression in the LT treated mice colon, P < 0.01 vs WAS). CONCLUSION: The probiotic LT mix prevented the disruption to the epithelial barrier induced by LPS, stress or colonic soluble factors from IBS patients and prevented visceral hypersensitivity.