Letter to the Editor

Life-threatening NLRC4-associated hyperinflammation successfully treated with IL-18 inhibition

Chronic pain has been proven to be an independent disease, other than an accompanying symptom of certain diseases. Interleukin-18 (IL-18), a pro-inflammatory cytokine with pleiotropic biological effects, participates in immune modulation, inflammatory response, tumor growth, as well as the process of chronic pain. Compelling evidence suggests that IL-18 is upregulated in the occurrence of chronic pain. Antagonism or inhibition of IL-18 expression can alleviate the occurrence and development of chronic pain. And IL-18 is located in microglia, while IL-18R is mostly located in astrocytes in the spinal cord. This indicates that the interaction between microglia and astrocytes mediated by the IL-18/IL-18R axis is involved in the occurrence of chronic pain. In this review, we described the role and mechanism of IL-18 in different types of chronic pain. This review provides strong evidence that IL-18 is a potential therapeutic target in pain management.

NLRC4 gain-of-function variants are known to cause various autoinflammatory phenotypes, including familial cold autoinflammatory syndrome (FCAS4) and NLRC4 macrophage activation syndrome (NLRC4-MAS). However, to date, no study has linked NLRC4 gain-of-function variants to systemic lupus erythematosus (SLE). In this study, we identified a novel NLRC4 W655S variant in an SLE patient and her son, who had neonatal lupus complicated with macrophage activation syndrome. Our in vitro experiments demonstrated that the W655S NLRC4 increased ASC speck formation and mature IL-1β secretion compared to the wild-type NLRC4. In addition, the patient had elevated levels of IL-1β and IL-18 in both serum and PBMCs. RNA sequencing showed that NF-κB and interferon signaling pathways were significantly activated in the patient compared to healthy controls. Furthermore, gene set enrichment analysis revealed upregulation of NLRC4-related pathways in patient PBMCs. In conclusion, our study identified the NLRC4 W655S variant in a patient with SLE. This is the first report linking inflammasomopathy to monogenic SLE. Our findings suggest that inflammasome activation may be a critical driver in the pathogenicity of lupus, and autoinflammatory pathways may play important roles in the development of the disease.

IL-18 and IL-1β play a central role in the pathogenesis of systemic juvenile idiopathic arthritis and its life-threatening complication, macrophage activation syndrome (MAS).

This study aimed to clarify the role of IL-18 and IL-1β in the pathogenesis of MAS.

We developed a mouse model to evaluate the role of each cytokine with Toll-like receptor 9 stimulation after continuous infusion with IL-18, IL-1β, and a combination of both for 7 days. The symptoms and laboratory findings were compared among the IL-18, IL-1β, and combination (IL-18+IL-1β) groups.

Body weight was significantly decreased in the IL-1β and combination groups. Splenomegaly was observed in all groups, whereas hepatomegaly was noted in the IL-18 group only. Decreased T-cell numbers, anemia, and thrombocytopenia were observed in the combination group. IFN-γ, CXCL9, and IL-12A mRNA levels were upregulated and IL-10 mRNA levels in the spleen were downregulated in the IL-18 group. Hepatomegaly and splenomegaly in the IL-18 group were observed in a dose-dependent manner. TNF-α, CXCL9, and IL-12A mRNA levels were upregulated only in those mice with extremely elevated plasma IL-18 levels.

IL-18 and IL-1β have distinct roles in the pathogenesis of MAS. Dual blockade of IL-18 and IL-1β might be necessary to treat MAS.

Cold urticaria is a chronic condition causing episodic symptoms of cold-induced wheals or angioedema in response to direct or indirect exposure to cold temperatures. Whereas symptoms of cold urticaria are typically benign and self-limiting, severe systemic anaphylactic reactions are possible. Acquired, atypical, and hereditary forms have been described, each with variable triggers, symptoms, and responses to therapy. Clinical testing, including response to cold stimulation, helps define disease subtypes. More recently, monogenic disorders characterized by atypical forms of cold urticaria have been described. Here, we review the different forms of cold-induced urticaria and related syndromes and propose a diagnostic algorithm to aid clinicians in making a timely diagnosis for the appropriate management of these patients.