Imbalanced IL-1B and IL-18 Expression in Sézary Syndrome

Abstract

Sézary syndrome (SS) is a rare and aggressive type of cutaneous T-cell lymphoma, with an abnormal inflammatory response in affected skin. The cytokines IL-1B and IL-18, as key signaling molecules in the immune system, are produced in an inactive form and cleave to the active form by inflammasomes. In this study, we assessed the skin, serum, peripheral mononuclear blood cell (PBMC) and lymph-node samples of SS patients and control groups (healthy donors (HDs) and idiopathic erythroderma (IE) nodes) to investigate the inflammatory markers IL-1B and IL-18 at the protein and transcript expression levels, as potential markers of inflammasome activation. Our findings showed increased IL-1B and decreased IL-18 protein expression in the epidermis of SS patients; however, in the dermis layer, we detected increased IL-18 protein expression. In the lymph nodes of SS patients at advanced stages of the disease (N2/N3), we also detected an enhancement of IL-18 and a downregulation of IL-1B at the protein level. Moreover, the transcriptomic analysis of the SS and IE nodes confirmed the decreased expression of IL1B and NLRP3, whereas the pathway analysis indicated a further downregulation of IL1B-associated genes. Overall, the present findings showed compartmentalized expressions of IL-1B and IL-18 and provided the first evidence of their imbalance in patients with Sézary syndrome.

Keywords: IL-18; IL-1B; Sézary syndrome; erythroderma skin; inflammasome; lymph nodes.

Figure 1

Increased protein levels of epidermal IL-1B and dermal IL-18 in skin of erythrodermic SS. The expression of IL-1B and IL-18 (A) were assessed in the skin biopsies of SS patients (n = 7–8, closed circle), healthy donors (HDs, n = 9–12, open circle), and idiopathic erythroderma (IE, n = 9–13, open triangle) by immunohistochemistry. The analyses were performed on the epidermis (B) and dermis (C). The values are expressed as medians. * p ≤ 0.05 and ** p ≤ 0.01.

Figure 2

High circulating levels of IL-18- and IL-18-binding protein a (BPa) in SS patients. Serum determinations of IL-18 and IL-18BPa were assessed by ELISA (SS, n = 10–19; HD, n = 13–22). The IL18/IL18BP ratios were also calculated. The values are expressed as medians. *** p ≤ 0.001.

Figure 3

Altered inflammasome transcript expressions in peripheral blood mononuclear cells from SS patients. Expressions of NLRP1, NLRP3, NLRP4, pro-IL18, pro-IL1B and CARD8 were analyzed in PBMCs from SS patients (n = 7–10, closed circle), healthy control individuals (n = 5–8, open circle) and in SS cell lines by qRT-PCR. The data were normalized to GAPDH and shown either by median (A) for SS patient samples or by heatmap (B) in SS cell lines. * p ≤ 0.05 and ** p ≤ 0.01.

Figure 4

Decreased IL-1B expression and IL-18 upregulation in lymph nodes at an advanced stage of SS. The expressions of IL-1B and IL-18 were assessed in the lymph-node biopsies of SS patients at stages N1 (n = 4, open circle), N2 (n = 2, pink circle), and N3 (n = 2, closed circle), as well as in idiopathic erythroderma patients (IE, n = 8, open triangle), by immunohistochemistry. (A) Representative images, original magnification ×20. (B) IL-1B expression and IL-18 expression. Data are illustrated by median values. * p ≤ 0.05.

Figure 5

Expression of key genes involved in inflammasome function in the lymph nodes of SS patients. The expression profiles of SS lymph nodes, as compared to IE lymph nodes, were evaluated by RNA sequencing. The absolute FC values of 60 key genes involved in inflammasome function are shown in blue (FC < −1.00) or red (FC > 1.00) bars. The colored background areas represent genes that have either FC ≥ 1.3 or FC ≤ −1.3. * Indicates a p-value significance level of 0.05.

Figure 6

Imbalanced expression of IL-1B and IL-18, as well as their associated regulators of inflammation, in Sézary syndrome.