Elevated expression of NLRP3 in patients with immune thrombocytopenia

The entrenchment of NLRP3 inflammasomes in autoimmune disease-related inflammation

Autoinflammation and autoimmunity are almost "opposite" phenomena characterized by chronic activation of the immune system, 'innate' in the first and 'adaptive' in the second, leading to inflammation of several tissues with specific protean effectors of tissue damage. The mechanism of involvement of multiprotein complexes called 'inflammasomes' within autoimmune pictures, differently from autoinflammatory conditions, is yet undeciphered. In this review we provide a comprehensive overview on NLRP3 inflammasome contribution into the pathogenesis of some autoimmune diseases. In response to autoantibodies against nucleic acids or tissue-specific antigens the NLRP3 inflammasome is activated within dendritic cells and macrophages of patients with systemic lupus erythematosus. Crucial is NLRP3 inflammasome to amplify tissue inflammation with interleukin-1 overexpression and matrix metalloproteinase production at the joint level in rheumatoid arthritis. A deregulated NLRP3 inflammasome activation occurs in the serous acini of salivary and lacrimal glands prone to Sjogren's syndrome, but also in the inflammatory process involving endothelial cells, leucocyte recruitment, and platelet plugging of vasculitides. Furthermore, organ-specific autoimmune diseases such as thyroiditis and hepatitis may display hyperactive NLRP3 inflammasomes at the level of resident immune cells within thyroid or liver, respectively. Therefore, it is not unexpected that preclinical studies have shown how specific inflammasome inhibitors may significantly overthrow the severity of different autoimmune diseases and slow down their trend towards an ominous progression. Specific markers of inflammasome activation could also reveal subclinical inflammatory components escaping conventional diagnostic approaches or improve monitoring of autoimmune diseases and personalizing their treatment.

Efficacy and Safety Results With Rilzabrutinib, an Oral Bruton Tyrosine Kinase Inhibitor, in Patients With Immune Thrombocytopenia: Phase 2 Part B Study

Current treatments for persistent or chronic immune thrombocytopenia (ITP) are limited by inadequate response, toxicity, and impaired quality of life. The Bruton tyrosine kinase inhibitor rilzabrutinib was evaluated to further characterize safety and durability of platelet response. LUNA2 Part B is a multicenter, phase 1/2 study in adults with ITP (≥ 3 months duration, platelet count < 30 × 109/L) who failed ≥ 1 ITP therapy (NCT03395210, EudraCT 2017-004012-19). Oral rilzabrutinib 400 mg bid was given over 24 weeks, with optional long-term extension (LTE). Primary endpoints were safety and platelet counts ≥ 50 × 109/L on ≥ 8 of the last 12 weeks of main treatment without rescue medication. From 22 March2018 to 31 January2023, 26 patients were enrolled. Patients had baseline median platelet count 13 × 109/L, ITP duration 10.3 years, and six prior ITP therapies (46% splenectomized). Nine (35%) patients achieved the primary endpoint. Platelet counts ≥ 50 × 109/L or ≥ 30 × 109/L and doubling from baseline without rescue therapy were sustained for a mean 9.3 weeks. 11 (42%) LTE-eligible patients were ongoing with median LTE platelet > 80 × 109/L. Three (12%) patients received rescue medication during main treatment, none in LTE. Clinically meaningful improvements were observed in fatigue and women's health. With a median treatment duration of 167 days (main treatment), 16 (62%) patients had ≥ 1 treatment-related adverse event (AE), mainly grade 1, including diarrhea (35%), headache (23%), and nausea (15%). There was no treatment-related grade ≥ 2 bleeding/thrombotic events/infections, serious AE, or death. Rilzabrutinib continues to demonstrate durable platelet responses with favorable safety profile in previously treated ITP patients. Trial Registration: NCT03395210, EudraCT 2017-004012-19.

Trimethylamine-N-oxide (TMAO) and basic fibroblast growth factor (bFGF) are possibly involved in corticosteroid resistance in adult patients with immune thrombocytopenia

PURPOSE

Immune thrombocytopenia (ITP) is an autoimmune disease characterized by accelerated platelet clearance. Gut dysbiosis was associated with its pathogenesis, but the underlying mechanisms have not been fully elucidated. Patients with ITP exhibit varying degrees of responsiveness to corticosteroid treatment. Therefore, prognostic indexes for corticosteroid responsiveness in ITP could offer valuable guidance for clinical practices.

METHODS

The present study examined the signature of six types of gut-microbiota metabolites and forty-eight types of cytokines, chemokines, and growth factors and their clinical significance in patients with ITP.

RESULTS

Both patients with good and poor corticosteroid responsiveness exhibited significantly elevated/suppressed secretion of twenty-two cyto(chemo)kins/growth factors in comparison to healthy controls. Additionally, patients with ITP demonstrated a significant decrease in plasma levels of trimethylamine-N-oxide (TMAO), which was found to be negatively correlated to circulating platelet counts, and positively correlated with Interleukin (IL)-1β and IL-18. Notably, patients who exhibited poor response to corticosteroid treatment displayed elevated levels of TMAO and basic fibroblast growth factor (bFGF) in comparison to responders. Additionally, we found that the amalgamation of TMAO, bFGF and interleukin (IL)-13 could serve as a valuable prognostic tool for predicting CS responsiveness.

CONCLUSION

Patients with ITP were characterized overall by an imbalanced secretion of cyto(cheo)kins/growth factors and inadequate levels of TMAO. The varying degrees of responsiveness to corticosteroid treatment can be attributed to different profiles of basic FGF and TMAO that might be related to overburdened oxidative stress and inflammasome overactivation, and ultimately mediate corticosteroid resistance.

Pyroptosis in platelets: Thrombocytopenia and inflammation

OBJECTIVE

The purpose of this manuscript was to conclude the role of platelets in immune inflammation and discuss the complex mechanisms of pyroptosis in platelets as well as their related diseases.

METHODS

This article reviewed the existing literature to see the development of pyroptosis in platelets.

RESULTS

Platelets have been shown to be capable of activating inflammasomes assembled from NOD-like receptor family pyrin domain containing 3 (NLRP3), apoptosis-associated speck-like protein containing a CARD (ASC) and caspase-1. Recently, they were also implicated in pyroptosis. Cleaved by caspase-1, N-terminal gasdermin D (N-GSDMD) could form pores in the cell membrane, inducing nonselective intracellular substance release. This programmed cell death induced thrombocytopenia and inflammatory cytokine release such as IL-1β and IL-18, promoting platelet aggregation, vaso-occlusion, endothelial permeability and cascaded inflammatory response.

CONCLUSION

Pyroptosis in platelets contributes to thrombocytopenia and inflammation.

Novel Biomarkers for Diagnosis and Monitoring of Immune Thrombocytopenia

Lower-than-normal platelet counts are a hallmark of the acquired autoimmune illness known as immune thrombocytopenia, which can affect both adults and children. Immune thrombocytopenia patients' care has evolved significantly in recent years, but the disease's diagnosis has not, and it is still only clinically achievable with the elimination of other causes of thrombocytopenia. The lack of a valid biomarker or gold-standard diagnostic test, despite ongoing efforts to find one, adds to the high rate of disease misdiagnosis. However, in recent years, several studies have helped to elucidate a number of features of the disease's etiology, highlighting how the platelet loss is not only caused by an increase in peripheral platelet destruction but also involves a number of humoral and cellular immune system effectors. This made it possible to identify the role of immune-activating substances such cytokines and chemokines, complement, non-coding genetic material, the microbiome, and gene mutations. Furthermore, platelet and megakaryocyte immaturity indices have been emphasized as new disease markers, and prognostic signs and responses to particular types of therapy have been suggested. Our review's goal was to compile information from the literature on novel immune thrombocytopenia biomarkers, markers that will help us improve the management of these patients.

Reduced intracellular antioxidant capacity in platelets contributes to primary immune thrombocytopenia via ROS-NLRP3-caspase-1 pathway

Primary immune thrombocytopenia (ITP) is a common acquired autoimmune hemorrhagic disease characterized by a low platelet count and increased risk of bleeding. However, some patients do not respond well to current therapeutic approaches. Further studies on pathogenesis and pathophysiology of ITP are needed to discover new therapeutic targets. We explored the role of enhanced intracellular oxidative stress and NLRP3 inflammasome activation of platelets in ITP. The expression of NLRP3 inflammasome was assessed in platelets from active ITP patients and healthy donors. Both the mRNA and protein expression level of platelet NLRP3 inflammasome was upregulated in ITP patients compared with healthy donors. Besides, the elevated caspase-1 activity and increased co-localization of NLRP3 and its adaptor molecule ASC indicated activation of NLRP3 inflammasome in ITP platelets. Significantly decreased intracellular antioxidant capacity was observed in ITP platelets. H₂O₂ supplementation elevated the expression of NLRP3 inflammasome and increased IL-1β secretion in ITP platelets. Preincubating ITP platelets with NAC down-regulated the expression of NLRP3 inflammasome. Pretreating ITP platelets with NLRP3 inhibitor MCC950 or caspase-1 inhibitor Z-YVAD-FMK significantly reduced the proportion of pyroptotic cells in H₂O₂-treated ITP platelets and suppressed IL-1β secretion in supernatants. Hence, platelet NLRP3 inflammasome activation resulted from reduced intracellular antioxidant capacity plays a critical role in ITP and might have potential diagnostic or therapeutic implications.

Engineered Pigs Carrying a Gain-of-Function NLRP3 Homozygous Mutation Can Survive to Adulthood and Accurately Recapitulate Human Systemic Spontaneous Inflammatory Responses

The NLRP3 inflammasome is associated with a variety of human diseases, including cryopyrin-associated periodic syndrome (CAPS). CAPS is a dominantly inherited disease with NLRP3 missense mutations. Currently, most studies on the NLRP3-inflammasome have been performed with mice, but the activation patterns and the signaling pathways of the mouse NLRP3 inflammasome are not always identical with those in humans. The NLRP3 inflammasome activation in pigs is similar to that in humans. Therefore, pigs with precise NLRP3-point mutations may model human CAPS more accurately. In this study, an NLRP3 gain-of-function pig model carrying a homozygous R259W mutation was generated by combining CRISPR/Cpf1-mediated somatic cell genome editing with nuclear transfer. The newborn NLRP3 R259W homozygous piglets showed early mortality, poor growth, and spontaneous systemic inflammation symptoms, including skin lesion, joint inflammation, severe contracture, and inflammation-mediated multiorgan failure. Severe myocardial fibrosis was also observed. The tissues of inflamed skins and several organs showed significantly increased expressions of NLRP3, Caspase-1, and inflammation-associated cytokines and factors (i.e., IL-1β, TNF-α, IL-6, and IL-17). Notably, approximately half of the homozygous piglets grew up to adulthood and even gave birth to offspring. Although the F1 heterozygous piglets showed improved survival rate and normal weight gain, 39.1% (nine out of 23) of the piglets died early and exhibited spontaneous systemic inflammation symptoms. In addition, similar to homozygotes, adult heterozygotes showed increased delayed hypersensitivity response. Thus, the NLRP3 R259W pigs are similar to human CAPS and can serve as an ideal animal model to bridge the gap between rodents and humans.

Interleukin-37 reduces inflammation and impairs phagocytosis of platelets in immune thrombocytopenia (ITP)

Immune thrombocytopenia (ITP) is an autoimmune disease characterized by low platelet count with heterogeneous bleeding manifestations. Severe bleeding in ITP is not completely related with low platelet count. Fcγ receptor (FcγR)-mediated platelet destruction is one of the major mechanisms of ITP. Interleukin-37 (IL-37) is a fundamental natural suppressor of innate immunity and inflammatory responses in several autoimmune diseases. However, the role of IL-37 in the pathogenesis of ITP is unknown. In the present study, we identified that IL-37 expression was elevated in ITP patients, which was correlated with platelet count and the severity of bleeding in ITP, indicating that IL-37 could be a candidate in evaluating disease severity of ITP. In the in vitro study, IL-37 initiated an anti-inflammatory effect on monocytes/macrophages from ITP patients by down-regulating the phosphorylation of MAPK, AKT, and NF-κB signaling pathways. Moreover, IL-37 restored the balance of activating and inhibitory FcγRs and decreased antibody-mediated platelet phagocytosis by monocytes/macrophages. Our findings suggest that IL-37 may be a promising indicator of the disease severity and supplementation of IL-37 may be therapeutically beneficial for ITP patients.

NF-κB-94ins/del ATTG Genotype Contributes to the Susceptibility and Imbalanced Th17 Cells in Patients with Immune Thrombocytopenia

Background

The NLRP3 inflammasome plays important roles in the pathogenesis of autoimmune diseases. However, the role of the NLRP3 inflammasome in the pathophysiology of immune thrombocytopenia (ITP) remains unclear.

Methods

RT-PCR was used to examine the polymorphism and expression of genes involved in the NLRP3 inflammasome in ITP patients. T helper cells and apoptosis of PBMC from ITP patients were analyzed by flow cytometry. The antiplatelet autoantibodies in plasma were determined by modified monoclonal antibody-specific immobilization of platelet antigens (MAIPA).

Results

We found that the NF-κB-94ins/del ATTG genotype contributed to the susceptibility of ITP. Furthermore, the platelet counts of ITP patients with the WW genotype or WD genotype were lower than those with the DD genotype of NF-κB-94ins/del ATTG. Compared with controls, NF-κB gene expression was significantly decreased and WW or WD genotype ITP patients displayed higher mRNA expression than DD individuals. Similarly, the mRNA expression of NLRP3 was also increased in the WW genotype. There was a significant gene dose effect of the percentage of Th17 cells for the WW, WD, and DD genotypes (WW < WD < DD) in the unstimulated group and no significant difference was found after being stimulated. The activation of the NLRP3 inflammasome could upregulate Th17 in ITP patients.

Conclusion

The NF-κB-94ins/del ATTG genotype might serve as a novel biomarker and potential target for ITP.

Increased ADAM10 expression in patients with immune thrombocytopenia

Immune thrombocytopenia (ITP) is an autoimmune disease, which is characterized by abnormal of T immunity. A disintegrin and metalloproteinase (ADAM) 10, a member of proteinase family, has been demonstrated to regulate T cell proliferation and effector function. Considering the closely association of dysregulation of T cell function with ITP, whether ADAM10 involves in the pathogenesis of ITP remains unclear. In this study, 54 active ITP patients, 18 ITP in remission and 24 age and gender matched healthy control were enrolled. Peripheral blood mononuclear cells (PBMCs) were isolated from patients and control for isolation of RNA and plasma which were used to measure mRNA level of ADAM10 and tissue inhibitor of metalloproteinase 3 (TIMP3) by quantitative real-time PCR and soluble level of FasL and lymphocyte activation gene-3 (LAG-3) in plasma by ELISA. Meanwhile, T cell activation was measured by flow cytometry. Our results showed significantly higher expression of ADAM10 and lower expression of TIMP3 in active ITP patients compared with control, which were all restored into normal level in remission patients. Consistent with the expression profile of ADAM10, increased soluble plasma level of FasL and LAG-3 were observed in active ITP patients and reduced to normal level in patients in remission. Furthermore, increased T cell activation as demonstrated by higher expression of HLA-DR and CD69 were found in active ITP patients. In conclusion, elevated expression of ADAM10 was associated with the pathogenesis and development of ITP and therapeutically targeting it might be a novel approach for the treatment of ITP.