Elevated levels of IL-32 in cerebrospinal fluid of neuro-Behcet disease: Correlation with NLRP3 inflammasome

mTOR activation induces endolysosomal remodeling and nonclassical secretion of IL-32 via exosomes in inflammatory reactive astrocytes

Astrocytes respond and contribute to neuroinflammation by adopting inflammatory reactive states. Although recent efforts have characterized the gene expression signatures associated with these reactive states, the cell biology underlying inflammatory reactive astrocyte phenotypes remains under-explored. Here, we used CRISPR-based screening in human iPSC-derived astrocytes to identify mTOR activation a driver of cytokine-induced endolysosomal system remodeling, manifesting as alkalinization of endolysosomal compartments, decreased autophagic flux, and increased exocytosis of certain endolysosomal cargos. Through endolysosomal proteomics, we identified and focused on one such cargo-IL-32, a disease-associated pro-inflammatory cytokine not present in rodents, whose secretion mechanism is not well understood. We found that IL-32 was partially secreted in extracellular vesicles likely to be exosomes. Furthermore, we found that IL-32 was involved in the polarization of inflammatory reactive astrocyte states and was upregulated in astrocytes in multiple sclerosis lesions. We believe that our results advance our understanding of cell biological pathways underlying inflammatory reactive astrocyte phenotypes and identify potential therapeutic targets.

The regulation and potential role of interleukin-32 in tuberculous pleural effusion

The possible protective effect of interleukin-32 (IL-32) in Mycobacterium tuberculosis (Mtb) infection has been indicated. However, few studies have been focused on IL-32 in tuberculosis patients. Additionally, the regulation of IL-32 production has rarely been reported. In the present study, the production, regulation, and role of IL-32 in tuberculous pleurisy (TBP) were investigated. We found that the content of IL-32 in tuberculous pleural effusion (TPE) was higher than the level in the malignant pleural effusion and transudative pleural effusion. The level of IL-32 mRNA in pleural fluid mononuclear cells (PFMCs) was higher than that in peripheral blood mononuclear cells (PBMCs) of patients with TBP, and this difference was mainly reflected in the splice variants of IL-32α, IL-32β, and IL-32γ. Compared with the PBMCs, PFMCs featured higher IL-32β/IL-32γ and IL-32α/IL-32γ ratios. In addition, lipopolysaccharide (LPS), Bacillus Calmette-Guérin (BCG), and H37Ra stimulation could induce IL-32 production in the PFMCs. IL-32 production was positively correlated with the TNF-α, IFN-γ, and IL-1Ra levels in TPE, whereas IFN-γ, but not TNF-α or IL-1Ra, could induce the production of IL-32 in PFMCs. Furthermore, IL-32γ could induce the TNF-α production in PFMCs. Monocytes and macrophages were the main sources of IL-32 in PFMCs. Nevertheless, direct cell-cell contact between lymphocytes and monocytes/macrophages plays an important role in enhancing IL-32 production by monocyte/macrophage cells. Finally, compared with the non-tuberculous pleural effusion, the purified CD4+ and CD8+ T cells in TPE expressed higher levels of intracellular IL-32. Our results suggested that, as a potential biomarker, IL-32 may play an essential role in the protection against Mtb infection in patients with TBP. However, further studies need to be carried out to clarify the functions and mechanisms of the IFN-γ/IL-32/TNF-α axis in patients with TBP.

IL-38 in Behçet's disease: Gene expression in bronchoalveolar lavage from patients having pulmonary involvement

The etiological complexity of Behçet disease (BD), an immune-mediated rare form of vasculitis characterized by multi-organ involvement, is still elusive due to an incomplete understanding of the synergy between genetic susceptibility, environmental triggers, and an abnormal immune response. The diagnosis of BD relies on clinical symptoms. Lung inflammatory disorders are severe conditions of patients with BD, here we focus on the expression of biomarkers in BD patients with pulmonary manifestations. Aiming to identify additional discriminating biomarker patterns, we measured and compared protein and gene expression of IL-38 and a broad panel of selected genes in bronchoalveolar cells of patients suffering from BD with and without pulmonary involvement compared to controls. ELISA and RT-PCR analysis were applied. The first principal analysis highlighted decreased IL-38 level in BD patients compared to Rheumatoid Arthritis (RA) patients and controls: BD patients expressed lower IL-38 levels, particularly in cases with pulmonary involvement. The area under the curve (AUC) of the receiver-operating characteristic curve showed that IL-38 may be an eventual biomarker for BD. Co-cultured recombinant IL-38 and stimulated memory PBMCs of active BD, were able to suppress IL-17 and NLRP3 inflammasome and ameliorate the secretion of IL-10 and TGFβ. Transcription factors of the IL-1 family (IL-1β, IL-18, IL-32, IL-33 and IL-37) along with IFN-γ, IL-17, RORγt, Foxp3, TGFβ, IL-10 and NLRP3 inflammasome were the parameters that are the main contributor to the segregation between BD with and without lung involvement. Our results indicate that IL-38 might be involved in the pathogenesis of BD and the combined gene expression in BAL suggests distinct mechanisms governing the inflammatory disorders in the lung.

Vasculitis and the NLRP3 inflammasome

PURPOSE OF REVIEW

Vasculitis are a group of heterogeneous conditions characterized by chronic inflammation of blood vessels, leading to tissue destruction and organ failure. Vasculitis is an inflammatory process in which immune effector cells infiltrate blood vessels and surrounding tissues. The involvement of inflammasomes seems to occur during inflammatory processes.

RECENT FINDINGS

Studies have emphasized that genetic susceptibility is an important aspect of the pathogenesis of vasculitis. The innate immune system is a major contributor to these inflammatory diseases, suggesting that the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome plays a key role. NLRP3 activation causes the assembly of a large multiprotein and leads to the secretion of bioactive interleukin (IL)-1β and IL-18 as well as the induction of inflammatory cell death, termed pyroptosis. Accumulating evidence confirms the involvement of this cascade in sterile inflammatory diseases and other vascular diseases.

SUMMARY

In this review, we will summarize the current state of knowledge regarding the role of NLRP3 inflammasome in vascular diseases, and discuss the potential of the NLRP3 inflammasome as a therapeutic target.

Behçet's syndrome: recent advances to aid diagnosis

Behçet's syndrome is a recurring inflammatory multiorgan disorder affecting the skin, mucosa, eyes, joints, stomach, and central nervous system. Behçet's syndrome epidemiology varies greatly among populations (0.64-420/100,000), and Behçet's syndrome has gained increasing international acclaim in the recent 50 years due to raising awareness of the syndrome, although it is rare in most population. In addition to the unclear etiology of the syndrome, the diagnosis of Behçet's syndrome is complicated by a vague clinical presentation, phenotypic heterogeneity and/or incomplete representation, and the lack of any specific laboratory, radiographic, or histological findings. There exists a dire need to elucidate factors that contribute to disease pathogenesis and/or are associated with clinical features of Behçet's syndrome and the classification of different forms of the syndrome. The identification of such molecular, cellular, and/or clinical factors are crucial for timely diagnosis and efficacious management of Behçet's syndrome. We discuss recent advances in the clinical diagnosis of Behçet's syndrome and related contributions of genetics, epigenetics, microbiome, inflammasomes, and autoantibodies to the improved diagnosis, management, and understanding of Behçet's syndrome.

Innate immune responses in Behçet disease and relapsing polychondritis

Behçet disease (BD) and relapsing polychondritis (RP) are chronic multisystem disorders characterized by recurrent flare-ups of tissue inflammation. Major clinical manifestations of BD are oral aphthae, genital aphthous ulcers, skin lesions, arthritis, and uveitis. Patients with BD may develop rare but serious neural, intestinal, and vascular complications, with high relapse rates. Meanwhile, RP is characterized by the inflammation of the cartilaginous tissues of the ears, nose, peripheral joints, and tracheobronchial tree. Additionally, it affects the proteoglycan-rich structures in the eyes, inner ear, heart, blood vessels, and kidneys. The mouth and genital ulcers with inflamed cartilage (MAGIC) syndrome is a common characteristic of BD and RP. The immunopathology of these two diseases may be closely related. It is established that the genetic predisposition to BD is related to the human leukocyte antigen (HLA)-B51 gene. Skin histopathology demonstrates the overactivation of innate immunity, such as neutrophilic dermatitis/panniculitis, in patients with BD. Monocytes and neutrophils frequently infiltrate cartilaginous tissues of patients with RP. Somatic mutations in UBA1, which encodes a ubiquitylation-related enzyme, cause vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic syndrome (VEXAS) with severe systemic inflammation and activation of myeloid cells. VEXAS prompts auricular and/or nasal chondritis, with neutrophilic infiltration around the cartilage in 52-60% of patients. Thus, innate immune cells may play an important role in the initiation of inflammatory processes underlying both diseases. This review summarizes the recent advances in our understanding of the innate cell-mediated immunopathology of BD and RP, with a focus on the common and distinct features of these mechanisms.

NLRP3 Attenuates Intraocular Inflammation by Inhibiting AIM2-Mediated Pyroptosis Through the Phosphorylated Salt-Inducible Kinase 1/Sterol Regulatory Element Binding Transcription Factor 1 Pathway

OBJECTIVE

The NLRP3 inflammasome has been shown to be involved in the development of uveitis, but the exact mechanism remains elusive. This study was undertaken to explore the role of NLRP3 in the development of uveitis.

METHODS

First, Nlrp3-deficient mice were used to study the role of NLRP3 in experimental autoimmune diseases, such as experimental autoimmune uveitis (EAU) and experimental autoimmune encephalomyelitis (EAE). Next, the gathering of ASC, activation of caspase 1 and gasdermin D, and secretion of lactate dehydrogenase and interleukin-1β were detected to confirm macrophage pyroptosis and AIM2 activation in the Nlrp3^-/- mice. Additionally, RNA sequencing and chromatin immunoprecipitation-polymerase chain reaction were used to investigate the phosphorylated salt-inducible kinase 1 (p-SIK1)/sterol regulatory element binding transcription factor 1 (SREBF1) pathway, which regulates the transcription of Aim2. Finally, overexpression of Nlrp3 was applied to treat EAU.

RESULTS

Surprisingly, our findings show that NLRP3 plays an antiinflammatory role in 2 models of EAU and EAE. Additionally, macrophages show an increased M1 activation and pyroptosis in Nlrp3^-/- mice. Further experiments indicate that this pyroptosis of macrophages was mediated by the up-regulated transcription of Aim2 as a result of Nlrp3 deficiency. In mechanistic studies, Nlrp3 deficiency was implicated in the down-regulation of p-SIK1 and subsequently the up-regulation of SREBF1, which binds to Aim2 and then promotes the latter's transcription. Finally, Aim2 deficiency, RNA silencing of Aim2 or Srebf1, and overexpression of Nlrp3 resulted in attenuated inflammation of EAU.

CONCLUSION

Our data demonstrate that NLRP3 inhibits AIM2 inflammasome-mediated EAU by regulating the p-SIK1/SREBF1 pathway, highlighting the therapeutic potential of targeting Nlrp3.

Regulation of NLRP3 inflammasome by zinc supplementation in Behçet's disease patients: A double-blind, randomized placebo-controlled clinical trial

BACKGROUND

Overproduction of NLRP3 inflammasome complex is one of the causes of Behcet's disease's (BD) auto-inflammatory nature. The aim of current study was to examine the effect of zinc supplementation on NLRP3 inflammasome expression; as well as clinical manifestations of BD.

METHODS

In this double-blind parallel placebo-controlled randomized clinical trial, 50 BD patients were randomly allocated into either zinc gluconate (30 mg/day elemental zinc) or placebo groups for 12 weeks. The mRNA expression of NLRP3 and caspase-1 in the leukocytes, serum level of zinc and IL-1β, anthropometric measures, and clinical manifestations of patients were collected at pre- and post-intervention phase. The Iranian Behçet's disease dynamic activity measure (IBDDAM) was scored to measure the treatment effect using the calculation of number needed to treat (NNT). Analysis of covariance was performed to obtain the corresponding effect sizes.

RESULTS

Zinc gluconate led to a significant improvement in genital ulcer (P = 0.019). Zinc supplementation decreased NLRP3 and caspase-1 genes expression compared with placebo group (baseline-adjusted P-value = 0.046 for NLRP3 and P-value = 0.003 for caspase-1), even after adjustment for the effect of confounding factors (baseline- and confounders-adjusted P-value = 0.032 for NLRP3 and P-value = 0.004 for caspase-1). Baseline and confounders adjusted effect size demonstrated that zinc was effective in reducing the serum level of IL-1β (P = 0.046). The NNT [95 %CI] for the rate of IBDDAM improvement was 3 [1.7-8.5].

CONCLUSIONS

Zinc gluconate supplementation (30 mg/day) for a 3-month period can be considered as an adjuvant therapy in alleviating inflammation and genital ulcer among BD patients.