Chitinase-3-like Protein 1 (YKL-40) Is Expressed in Lesional Skin in Hidradenitis Suppurativa

Cytokine-Mediated Molecular Pathophysiology of Hidradenitis Suppurativa: A Narrative Review

Background

Hidradenitis suppurativa (HS) is a chronic inflammatory condition of the skin that mainly affects the apocrine gland-rich intertriginous areas. The disease manifests as painful nodules, abscesses, and pus-filled tunnels, which can severely impact patient's quality of life. While diagnosis is clinical, successful treatment options for this condition are limited. There has been an increase in research and clinical trials focusing on biomarkers and cytokines for clinical use. Understanding the potential biomarkers and cytokines implicated in HS pathogenesis may allow efficacious and safe treatment options.

Summary

A literature review was conducted on nine biomarkers and cytokines. IL-1, IL-10, IL-17, IL-23, TNF-α, YKL-40, G-CSF, NOD2, and the complement system were identified due to their potential clinical utilization and pathophysiological involvement in HS.

Key Messages

With further research expanding our understanding of the pathophysiology of HS and the roles these cytokines and biomarkers play, there is potential for utilization as diagnostic markers or development of antagonists against these specific agents for HS management.

Hidradenitis Suppurativa and Comorbid Disorder Biomarkers, Druggable Genes, New Drugs and Drug Repurposing-A Molecular Meta-Analysis

Chronic inflammation and dysregulated epithelial differentiation, especially of hair follicle keratinocytes, have been suggested as the major pathogenetic pathways of hidradenitis suppurativa/acne inversa (HS). On the other hand, obesity and metabolic syndrome have additionally been considered as an important risk factor. With adalimumab, a drug has already been approved and numerous other compounds are in advanced-stage clinical studies. A systematic review was conducted to detect and corroborate HS pathogenetic mechanisms at the molecular level and identify HS molecular markers. The obtained data were used to confirm studied and off-label administered drugs and to identify additional compounds for drug repurposing. A robust, strongly associated group of HS biomarkers was detected. The triad of HS pathogenesis, namely upregulated inflammation, altered epithelial differentiation and dysregulated metabolism/hormone signaling was confirmed, the molecular association of HS with certain comorbid disorders, such as inflammatory bowel disease, arthritis, type I diabetes mellitus and lipids/atherosclerosis/adipogenesis was verified and common biomarkers were identified. The molecular suitability of compounds in clinical studies was confirmed and 31 potential HS repurposing drugs, among them 10 drugs already launched for other disorders, were detected. This systematic review provides evidence for the importance of molecular studies to advance the knowledge regarding pathogenesis, future treatment and biomarker-supported clinical course follow-up in HS.

Chitinase-3-like Protein 1 (YKL-40): A New Biomarker of Inflamma-tion in Pyoderma Gangrenosum

Pyoderma gangrenosum (PG) is a rare, neutrophil-ic dermatosis with unclear aetiopathology, considered as an autoinflammatory disease, associated with other immune-mediated disorders. Chitinase-3-like protein 1 (YKL-40) is an inflammatory biomarker secreted by a wide variety of cells, including neutrophils. To evaluate YKL-40 serum level in relation to clinicopathological data, 48 patients with PG and 40 healthy controls were enrolled in the study. Skin lesions were measured to calculate the affected area. Inflammatory parameters (C-reactive protein, white blood cell count with neutrophils) were determined from blood samples. YKL-40 and IL-6 levels were measured in serum by enzyme-linked immunosorbent assay. YKL-40 serum level was significantly higher in patients with PG than in controls (58.4 vs 36.4 ng/ml, respectively; p < 0.00001). The positive correlation between YKL-40 level and IL-6 level was observed (r=0.48, p = 0.0006) along with a trend towards significance of relationship between YKL-40 level and C-reactive protein (r=0.28, p = 0.052). YKL-40 can be considered a valuable biomarker of inflammation in PG.

Potential predictive biomarkers of adalimumab response in patients with hidradenitis suppurativa

BACKGROUND

Adalimumab provides significant efficacy for patients with hidradenitis suppurativa (HS), which was demonstrated by at least 50% of patients achieving a clinical response by week 12 that was maintained through to week 168 in the PIONEER trials.

OBJECTIVES

To identify whether there are biomarkers that could predict adalimumab response, as well as markers that differentially respond to adalimumab in patients with HS.

METHODS

Baseline and week-12 plasma samples from the PIONEER studies were used to assess the levels of circulating proteins by multiplex and enzyme-linked immunosorbent assays.

RESULTS

Analyses revealed significantly higher high-sensitivity C-reactive protein (hs-CRP) and chemokine (C-C motif) ligand (CCL) 16 (HCC-4) levels in nonresponders at baseline and identified a multivariate response signature of calprotectin, fractalkine and HCC-4, reaching an 86% predictive accuracy rate for adalimumab response. Additionally, post-treatment reduction of plasma C-X-C motif chemokine ligand (CXCL)9, CXCL8 (interleukin-8) and CCL19 (macrophage inflammatory protein 3β) were greater in adalimumab super-responders than in nonresponders (P = 0·026, P = 0·044 and P = 0·026, respectively). These cytokines are involved in the recruitment of innate and adaptive inflammatory cells, and/or stimulation of certain inflammatory responses, suggesting that these pathways could be disease drivers in adalimumab nonresponders.

CONCLUSIONS

These initial results suggest HCC-4, calprotectin and fractalkine could be potential predictive biomarkers of adalimumab response in HS and identified possible tumour necrosis factor-independent disease pathways.