Hidradenitis suppurativa - The role of interleukin-17, the aryl hydrocarbon receptor and the link to a possible fungal aetiology

Autoimmune, Autoinflammatory Disease and Cutaneous Malignancy Associations with Hidradenitis Suppurativa: A Cross-Sectional Study

BACKGROUND

Hidradenitis suppurativa (HS) is a debilitating cutaneous disease characterized by severe painful inflammatory nodules/abscesses. At present, data regarding the epidemiology and pathophysiology of this disease are limited.

OBJECTIVE

To define the prevalence and comorbidity associations of HS.

METHODS

This was a cross-sectional study of EPICTM Cosmos© examining over 180 million US patients. Prevalences were calculated by demographic and odds ratios (OR) and identified comorbidity correlations.

RESULTS

All examined metabolism-related, psychological, and autoimmune/autoinflammatory (AI) diseases correlated with HS. The strongest associations were with pyoderma gangrenosum [OR 26.56; confidence interval (CI): 24.98-28.23], Down syndrome (OR 11.31; CI 10.93-11.70), and polycystic ovarian syndrome (OR 11.24; CI 11.09-11.38). Novel AI associations were found between HS and lupus (OR 6.60; CI 6.26-6.94) and multiple sclerosis (MS; OR 2.38; CI 2.29-2.48). Cutaneous malignancies were largely not associated in the unsegmented cohort; however, among Black patients, novel associations with melanoma (OR 2.39; CI 1.86-3.08) and basal cell carcinoma (OR 2.69; CI 2.15-3.36) were identified.

LIMITATIONS

International Classification of Diseases (ICD)-based disease identification relies on coding fidelity and diagnostic accuracy.

CONCLUSION

This is the first study to identify correlations between HS with melanoma and basal cell carcinoma (BCC) among Black patients as well as MS and lupus in all patients with HS.

The role of aryl hydrocarbon receptor in vitiligo: a review

Vitiligo is an acquired autoimmune dermatosis characterized by patchy skin depigmentation, causing significant psychological distress to the patients. Genetic susceptibility, environmental triggers, oxidative stress, and autoimmunity contribute to melanocyte destruction in vitiligo. Due to the diversity and complexity of pathogenesis, the combination of inhibiting melanocyte destruction and stimulating melanogenesis gives the best results in treating vitiligo. The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that can regulate the expression of various downstream genes and play roles in cell differentiation, immune response, and physiological homeostasis maintenance. Recent studies suggested that AhR signaling pathway was downregulated in vitiligo. Activation of AhR pathway helps to activate antioxidant pathways, inhibit abnormal immunity response, and upregulate the melanogenesis gene, thereby protecting melanocytes from oxidative stress damage, controlling disease progression, and promoting lesion repigmentation. Here, we review the relevant literature and summarize the possible roles of the AhR signaling pathway in vitiligo pathogenesis and treatment, to further understand the links between the AhR and vitiligo, and provide new potential therapeutic strategies.

Emerging Treatments and the Clinical Trial Landscape for Hidradenitis Suppurativa Part I: Topical and Systemic Medical Therapies

Hidradenitis suppurativa (HS) is an oftentimes debilitating condition that presents with painful nodules, abscesses, and sinus tracts. This condition is challenging to treat, in part because the pathogenesis of the condition is incompletely understood but also because there are limited therapeutic options. HS research is undergoing explosive growth with multiple new molecular pathways under study, which will hopefully lead to improved disease control for patients. Part I of this review will provide an overview of the emerging topical and systemic therapies under investigation for HS.

Discovering KYNU as a feature gene in hidradenitis suppurativa

BACKGROUND

Hidradenitis suppurativa (HS) is a chronic auto-inflammatory skin condition characterized by nodules, abscesses, and fistulae in skin folds. The underlying pathogenesis of HS remains unclear, and effective therapeutic drugs are limited.

METHODS

We acquired mRNA expression profiles from the Gene Expression Omnibus (GEO) database and conducted differential expression analysis between control and HS samples using R software. Four machine learning algorithms (SVM, RF, ANN, and lasso) and WCGNA were utilized to identify feature genes. GO, KEGG, Metascape, and GSVA were utilized for the enrichment analysis. CIBERSORT and ssGSEA were employed to analyze immune infiltration.

RESULTS

A total of 29 DEGs were identified, with the majority showing up-regulation in HS. Enrichment analysis revealed their involvement in immune responses and cytokine activities. KEGG analysis highlighted pathways such as IL-17 signaling, rheumatoid arthritis, and TNF signaling in HS. Immune infiltration analysis revealed the predominant presence of neutrophils, monocytes, and CD8 T cells. Machine learning algorithms and WCGNA identified KYNU as a feature gene associated with HS. We have also identified 59 potential drugs for HS based on the DEGs. Additionally, ceRNA network analysis identified the MUC19_hsa-miR-382-5p_KYNU pathway as a potential regulatory pathway.

CONCLUSIONS

KYNU emerged as a feature gene associated with HS, and the ceRNA network analysis identified the MUC19_hsa-miR-382-5p_KYNU pathway as a potential regulator.

Aryl Hydrocarbon Receptors: Evidence of Therapeutic Targets in Chronic Inflammatory Skin Diseases

The aryl hydrocarbon receptor (AhR), a ligand-dependent transcription factor, is important for xenobiotic metabolism and binds to various endogenous and exogenous ligands present in the skin. AhR is known to be associated with diseases in various organs; however, its functions in chronic inflammatory skin diseases, such as atopic dermatitis (AD) and psoriasis (PS), have recently been elucidated. Here, we discuss the molecular mechanisms of AhR related to chronic inflammatory skin diseases, such as AD and PS, and the mechanisms of action of AhR on the skin immune system. The importance of AhR molecular biological pathways, clinical features in animal models, and AhR ligands in skin diseases need to be investigated. In conclusion, the therapeutic effects of AhR ligands are demonstrated based on the relationship between AhR and skin diseases. Nevertheless, further studies are required to elucidate the detailed roles of AhR in chronic inflammatory skin diseases.

Role of Aryl Hydrocarbon Receptor Activation in Inflammatory Chronic Skin Diseases

Aryl Hydrocarbon Receptor (AhR) is an evolutionary transcription factor which acts as a crucial sensor of different exogenous and endogenous molecules Recent data indicate that AhR is implicated in several physiological processes such as cell physiology, host defense, proliferation and differentiation of immune cells, and detoxification. Moreover, AhR involvement has been reported in the development and maintenance of several pathological conditions. In recent years, an increasing number of studies have accumulated highlighting the regulatory role of AhR in the physiology of the skin. However, there is evidence of both beneficial and harmful effects of AHR signaling. At present, most of the evidence concerns inflammatory skin diseases, in particular atopic dermatitis, psoriasis, acne, and hidradenitis suppurativa. This review exam-ines the role of AhR in skin homeostasis and the therapeutic implication of its pharmacological modulation in these cutaneous inflammatory diseases.

Insights into the Pathogenesis of HS and Therapeutical Approaches

Hidradenitis suppurativa (HS) is a debilitating, chronic, (auto)inflammatory disease primarily affecting apocrine gland-rich areas of the body. Although pathogenic mechanisms responsible for HS have not yet been fully elucidated, it is a multifactorial process whose main target is the terminal follicle. The role of the inflammatory process (and consequently of cytokine milieu) and of several other factors (genetics, lifestyle, hormonal status, microbiome, innate and adaptive immune systems) involved in HS pathogenesis has been investigated (and often defined) over the years with a view to transferring research results from bench to bedside and describing a unique and universally accepted pathogenetic model. This review will update readers on recent advances in our understanding of HS pathogenesis and novel (potential) medical therapies for patients with moderate-to-severe HS.

Contribution of mycobiota to the pathogenesis of spondyloarthritis

This review lists current evidences for a contribution of gut mycobiota to the pathogenesis of SpA and related conditions. Gut mycobiota has a small size as compared to bacterial microbiota, but an even greater inter- and intra-individual variability. Although most fungi (brought by food or air) are only transitory present, a core mycobiota of gut resident fungi exists, and interplays with bacteria in a complex manner. A dysbiosis of this gut mycobiota has been observed in Crohn's disease and sclerosing cholangitis, with decreased proportion of Saccharomyces cerevisiae and outgrowth of more pathogenic gut fungi. Fungal-induced lower number of commensal gut bacteria can promote translocation of some bacterial/fungal antigens through mucosae, and live fungi can also cross the epithelial border in Crohn's disease. This dysbiosis also lower the ability of bacteria to metabolize tryptophan into regulatory metabolites, consequently enhancing tryptophan metabolism within human cells, which might contribute to fatigue. Translocation of mycobiotal antigens like curdlan (beta-glucan), which plays a major role in the pathogenesis of SpA in the SGK mice, has been observed in humans. This translocation of fungal antigens in human SpA might account for the anti-Saccharomyces antibodies found in this setting. Contribution of fungal antigens to psoriasis and hidradenitis suppurativa would fit with the preferential homing of fungi in the skin area most involved in those conditions. Fungal antigens also possess autoimmune uveitis-promoting function. As genes associated with SpA (CARD9 and IL23R) strongly regulate the innate immune response against fungi, further studies on fungi contribution to SpA are needed.