Differential Expression of Proteins Involved in Skin Barrier Maintenance and Vitamin D Metabolism in Atopic Dermatitis: A Cross-Sectional, Exploratory Study

Abstract

Atopic dermatitis (AD) is a chronic inflammatory skin disorder influenced by proteins involved in skin barrier maintenance and vitamin D metabolism. Using an intra-patient design, this study compared protein expression in intra-lesional (IL) and peri-lesional (PL) skin biopsies from AD patients and examined associations between protein levels, vitamin D status, and clinical features. Forty-four biopsies from twenty-two AD patients were analyzed using antibody microarrays targeting twelve proteins. IL samples had significantly higher total protein levels than PL samples, with a mean difference of 77.7% (p < 0.001). Several proteins, including cathelicidin, cingulin, occludin, filaggrin, and the vitamin D receptor, were upregulated in IL samples. Patients with vitamin D levels below 30 ng/mL showed higher expression of CYP24A (p = 0.054), alpha-catenin (p = 0.043), and haptoglobin (p = 0.033). Increased EASI scores (≥16) were associated with elevated expression of CYP24A (p = 0.024), CYP27B (p = 0.044), filaggrin (p = 0.027), occludin (p = 0.049), and claudin-1 (p = 0.052). Multivariate regression analysis identified significant correlations between protein expression, skin prick test positivity, and low vitamin D levels. These findings suggest that proteins related to epithelial barrier function and vitamin D metabolism are highly upregulated in IL skin regions, offering potential therapeutic targets for improving both skin barrier function and overall disease severity in AD patients.

Keywords: atopic dermatitis; protein expression; skin barrier maintenance; vitamin D receptor.

Figure 1

Dendrogram of hierarchical clustering of protein expression profiles from intra-lesional (IL) and peri-lesional (PL) biopsy samples using the complete protein data set. The dendrogram illustrates the clustering of all proteins extracted from PL and IL samples. The x-axis represents individual samples, while the y-axis indicates the distance measure used for clustering. PAZ = patient (identification code assigned to each patient).

Figure 2

Distribution pattern of protein expression in IL and PL samples from patients with AD. The volcano plot presents the adjusted p-values and corresponding log-fold changes (logFCs). The significance level of an adjusted p-value = 0.05 is indicated by a horizontal red line. Vertical lines denote the logFC cutoffs. Proteins with a positive logFC are more abundant in IL samples, whereas those with a negative logFC are more abundant in PL samples. Proteins with |logFC| > 0.5 and a significant adj. p-value are considered differential and are displayed with blue names. Proteins with |logFC| > 0 but not reaching the significance threshold are indicated with green names. PL represents peri-lesional biopsies, and IL corresponds to intra-lesional biopsies. AD = atopic dermatitis; CAMP = cathelicidin; CADH1 = cadherin-1; CING = cingulin; CLD1 = claudin-1; CTNA1 = alpha-catenin; CTNB1 = beta-catenin; CYP24A1 = cytochrome P450 family 24 subfamily A member 1; CYP27B1 = cytochrome P450 family 27 subfamily B member 1; FILA = filaggrin; HPT = haptoglobin; OCLN = occludin.

Figure 3

Heatmap depicting protein expression profiles in intra-lesional (IL) and peri-lesional (PL) skin samples from patients with AD. The heatmap displays the log-fold change (logFC) in protein expression levels, with red hues indicating higher expression and blue hues indicating lower expression. AD = atopic dermatitis; CAMP = cathelicidin; CADH1 = cadherin-1; CING = cingulin; CLD1 = claudin-1; CTNA1 = alpha-catenin; CTNB1 = beta-catenin; CYP24A1 = cytochrome P450 family 24 subfamily A member 1; CYP27B1 = cytochrome P450 family 27 subfamily B member 1; FILA = filaggrin; OCLN = occludin; PAZ = patient (identification code assigned to each patient); VDR = vitamin D receptor.

Figure 4

Image of the thoracic region and abdomen of a male patient with atopic dermatitis. Large erythematous, scaly plaques covering the central trunk are visible. The skin also appears excoriated in some areas. The two regions highlighted with red arrows indicate the sites of intra-lesional and peri-lesional biopsies. The biopsied areas appear slightly erythematous and textured, consistent with the surrounding dermatitis-affected skin. Peri-lesional biopsies were taken approximately 3 cm from the edge of the lesion.