Genetic relationships between A20/TNFAIP3, chronic inflammation and autoimmune disease

A20 Promoter rs5029924 Concomitant with rs2230926 and rs5029937 May Be a Prognostic Predictor for Joint Deformity or Refractory Rheumatoid Arthritis

Background

There have been several studies regarding the susceptibility of A20 gene SNPs (rs2230926 and rs5029937) in rheumatoid arthritis (RA). However, little is known about the association between polymorphisms in the A20 promoter and RA. The aim of this study was to investigate the characteristics of A20 promoter polymorphisms and the association between these polymorphisms and clinical significance in Chinese RA patients.

Methods

PCR and sequencing were used to identify A20 gene polymorphisms in peripheral blood mononuclear cells (PBMCs) from 123 RA cases and 31 healthy individuals.

Results

Only one SNP (rs5029924) in the A20 gene promoter was identified in RA patients and healthy individuals. 6 patients who carried heterozygous rs5029924 (3918C>T) together with heterozygous rs5029937 (11,571 G>T) and rs2230926 (12,486 T>G, Phe127Cys) suffered from joints deformity or refractory RA.

Conclusion

We reported the A20 promoter polymorphism rs5029924 in RA patients for the first time. rs5029924 concomitant with rs2230926 and rs5029937 may be a prognostic predictor for joint deformity or refractory RA.

Myeloid A20 is critical for alternative macrophage polarization and type-2 immune-mediated helminth resistance

Background

Protective immunity against intestinal helminths requires induction of robust type-2 immunity orchestrated by various cellular and soluble effectors which promote goblet cell hyperplasia, mucus production, epithelial proliferation, and smooth muscle contractions to expel worms and re-establish immune homeostasis. Conversely, defects in type-2 immunity result in ineffective helminth clearance, persistent infection, and inflammation. Macrophages are highly plastic cells that acquire an alternatively activated state during helminth infection, but they were previously shown to be dispensable for resistance to Trichuris muris infection.

Methods

We use the in vivo mouse model A20myel-KO, characterized by the deletion of the potent anti-inflammatory factor A20 (TNFAIP3) specifically in the myeloid cells, the excessive type-1 cytokine production, and the development of spontaneous arthritis. We infect A20myel-KO mice with the gastrointestinal helminth Trichuris muris and we analyzed the innate and adaptive responses. We performed RNA sequencing on sorted myeloid cells to investigate the role of A20 on macrophage polarization and type-2 immunity. Moreover, we assess in A20myel-KO mice the pharmacological inhibition of type-1 cytokine pathways on helminth clearance and the infection with Salmonella typhimurium.

Results

We show that proper macrophage polarization is essential for helminth clearance, and we identify A20 as an essential myeloid factor for the induction of type-2 immune responses against Trichuris muris. A20myel-KO mice are characterized by persistent Trichuris muris infection and intestinal inflammation. Myeloid A20 deficiency induces strong classical macrophage polarization which impedes anti-helminth type-2 immune activation; however, it promotes detrimental Th1/Th17 responses. Antibody-mediated neutralization of the type-1 cytokines IFN-γ, IL-18, and IL-12 prevents myeloid-orchestrated Th1 polarization and re-establishes type-2-mediated protective immunity against T. muris in A20myel-KO mice. In contrast, the strong Th1-biased immunity in A20myel-KO mice offers protection against Salmonella typhimurium infection.

Conclusions

We hereby identify A20 as a critical myeloid factor for correct macrophage polarization and appropriate adaptive mucosal immunity in response to helminth and enteric bacterial infection.

Decoding Toll-like receptors: Recent insights and perspectives in innate immunity

Toll-like receptors (TLRs) are an evolutionarily conserved family in the innate immune system and are the first line of host defense against microbial pathogens by recognizing pathogen-associated molecular patterns (PAMPs). TLRs, categorized into cell surface and endosomal subfamilies, recognize diverse PAMPs, and structural elucidation of TLRs and PAMP complexes has revealed their intricate mechanisms. TLRs activate common and specific signaling pathways to shape immune responses. Recent studies have shown the importance of post-transcriptional regulation in TLR-mediated inflammatory responses. Despite their protective functions, aberrant responses of TLRs contribute to inflammatory and autoimmune disorders. Understanding the delicate balance between TLR activation and regulatory mechanisms is crucial for deciphering their dual role in immune defense and disease pathogenesis. This review provides an overview of recent insights into the history of TLR discovery, elucidation of TLR ligands and signaling pathways, and their relevance to various diseases.

A Pilot Study to Develop Paraneoplastic Cerebellar Degeneration Mouse Model

Modeling paraneoplastic neurological diseases to understand the immune mechanisms leading to neuronal death is a major challenge given the rarity and terminal access of patients' autopsies. Here, we present a pilot study aiming at modeling paraneoplastic cerebellar degeneration with Yo autoantibodies (Yo-PCD). Female mice were implanted with an ovarian carcinoma cell line expressing CDR2 and CDR2L, the known antigens recognized by anti-Yo antibodies. To boost the immune response, we also immunized the mice by injecting antigens with diverse adjuvants and immune checkpoint inhibitors. Ataxia and gait instability were assessed in treated mice as well as autoantibody levels, Purkinje cell density, and immune infiltration in the cerebellum. We observed the production of anti-Yo antibodies in the CSF and serum of all immunized mice. Brain immunoreaction varied depending on the site of implantation of the tumor, with subcutaneous administration leading to a massive infiltration of immune cells in the meningeal spaces, choroid plexus, and cerebellar parenchyma. However, we did not observe massive Purkinje cell death nor any motor impairments in any of the experimental groups. Self-sustained neuro-inflammation might require a longer time to build up in our model. Unusual tumor antigen presentation and/or intrinsic, species-specific factors required for pro-inflammatory engagement in the brain may also constitute strong limitations to achieve massive recruitment of antigen-specific T-cells and killing of antigen-expressing neurons in this mouse model.

METTL14-Mediated m6A Modification of TNFAIP3 Involved in Inflammation in Patients With Active Rheumatoid Arthritis

OBJECTIVE

The aim of the study was to investigate the role of N6 -methyladenosine (m6A) modification in the progression of rheumatoid arthritis (RA).

METHODS

Peripheral blood mononuclear cells (PBMCs) from patients with RA and healthy controls were collected. The expression of m6A modification-related proteins and m6A levels were detected using polymerase chain reaction (PCR), western blot, and m6A enzyme-linked immunosorbent assay (ELISA). The roles of methyltransferase-like 14 (METTL14) in the regulation of inflammation in RA was explored using methylated RNA immunoprecipitation (MeRIP) sequencing and RNA immunoprecipitation assays. Collagen antibody-induced arthritis (CAIA) mice were used as an in vivo model to study the role of METTL14 in the inflammation progression of RA.

RESULTS

We found that m6A writer METTL14 and m6A levels were decreased in PBMCs of patients with active RA and correlated negatively with the disease activity score using 28 joint counts (DAS28). Knockdown of METTL14 downregulated m6A and promoted the secretion of inflammatory cytokines interleukin 6 (IL-6) and IL-17 in PBMCs of patients with RA. Consistently, METTL14 knockdown promoted joint inflammation accompanied by upregulation of IL-6 and IL-17 in CAIA mice. MeRIP sequencing and functional studies confirmed that tumor necrosis factor α induced protein 3 (TNFAIP3), a key suppressor of the nuclear factor-κB inflammatory pathway, was involved in m6A-regulated PBMCs. Mechanistic investigations revealed that m6A affected TNFAIP3 expression by regulation of messenger RNA stability and translocation in TNFAIP3 protein coding sequence.

CONCLUSIONS

Our study highlights the critical roles of m6A on regulation of inflammation in RA progression. Treatment strategies targeting m6A modification may represent a new option for management of RA.

Disorders of ubiquitylation: unchained inflammation

Ubiquitylation is an essential post-translational modification that regulates intracellular signalling networks by triggering proteasomal substrate degradation, changing the activity of substrates or mediating changes in proteins that interact with substrates. Hundreds of enzymes participate in reversible ubiquitylation of proteins, some acting globally and others targeting specific proteins. Ubiquitylation is essential for innate immune responses, as it facilitates rapid regulation of inflammatory pathways, thereby ensuring sufficient but not excessive responses. A growing number of inborn errors of immunity are attributed to dysregulated ubiquitylation. These genetic disorders exhibit broad clinical manifestations, ranging from susceptibility to infection to autoinflammatory and/or autoimmune features, lymphoproliferation and propensity to malignancy. Many autoinflammatory disorders result from disruption of components of the ubiquitylation machinery and lead to overactivation of innate immune cells. An understanding of the disorders of ubiquitylation in autoinflammatory diseases could enable the development of novel management strategies.

Advanced glycation end products alter the m6A-modified RNA profiles in human dermal fibroblasts

Background: To explore advanced glycation end products (AGEs)-induced m⁶A modification in fibroblasts and its potential role in photoaging. Methods: We studied m⁶A modification in AGEs-bovine serum albumin-treated fibroblasts with m⁶A-mRNA & lncRNA epitranscriptomic microarray and bioinformatics analysis. The m⁶A modification level was also investigated in skin samples. Results: m⁶A methylation microarray analysis revealed m⁶A modification profiles in AGEs-treated fibroblasts. Gene ontology, Kyoto Encyclopedia of Genes and Genomes, protein-protein interaction and competing endogenous RNA network analysis indicated that the genes of differentially methylated mRNAs and lncRNAs were mainly related to inflammation processes. We also found that AGEs-bovine serum albumin dose-dependently increased the m⁶A level and METTL14 expression in both fibroblasts and sun-exposed skin. Conclusion: Our study provided novel information regarding alterations of m⁶A modifications in AGEs-induced dermal fibroblasts and potential targets for treatment of photoaging.

Impact of TNFAIP3 Genetic Polymorphisms on Primary Immune Thrombocytopenia in Egyptian Adults: Case-control Study

BACKGROUND: Immune Thrombocytopenia (ITP) is a common acquired hematological disease. Genetic polymorphisms play an important role in ITP pathogenesis and prognosis. TNF-α-induced protein 3 (TNFAIP3) is a negative regulator of NF-kB in many signaling pathways. Several variants of TNFAIP3 have been associated with various inflammatory autoimmune disorders. AIM: Our study aimed to study the association of TNFAIP3 single nucleotide polymorphisms (SNPs); rs2230926 & rs5029939 with ITP susceptibility, as well ITP prognosis by follow up the cases for 18 months. METHODS: One hundred and ten ITP patients as well 110 matched unrelated normal controls were enrolled in our study. The polymorphisms were assessed by real-time polymerase chain reaction (real time PCR). RESULTS: There were a significant difference between cases and control groups regarding rs2230926 T>G and rs5029939 C>G frequencies with p < 0.05. Linkage disequilibrium (LD) analysis of the two variants revealed that there was a significant LD (p < 0.001). Non-cutaneous bleeding manifestations were observed mainly in the mutant genotypes of rs2230926 and rs5029939. The ITP patients with mutant genotypes of rs5029939 showed more need to use 2nd line immunosuppressive therapy as well the mutant genotypes of rs2230926 showed more steroid dependence and less complete recovery. CONCLUSION: Our data concluded the presence of LD between rs5029939 and rs2230926. The mutant genotypes of both variants were associated with increase the susceptibility to ITP and accompanied by worse clinical manifestations and poor response to the treatment in the adult Egyptian patients.

A20 deficiency in myeloid cells protects mice from diet-induced obesity and insulin resistance due to increased fatty acid metabolism

Obesity-induced inflammation is a major driving force in the development of insulin resistance, type 2 diabetes (T2D), and related metabolic disorders. During obesity, macrophages accumulate in the visceral adipose tissue, creating a low-grade inflammatory environment. Nuclear factor κB (NF-κB) signaling is a central coordinator of inflammatory responses and is tightly regulated by the anti-inflammatory protein A20. Here, we find that myeloid-specific A20-deficient mice are protected from diet-induced obesity and insulin resistance despite an inflammatory environment in their metabolic tissues. Macrophages lacking A20 show impaired mitochondrial respiratory function and metabolize more palmitate both in vitro and in vivo. We hypothesize that A20-deficient macrophages rely more on palmitate oxidation and metabolize the fat present in the diet, resulting in a lean phenotype and protection from metabolic disease. These findings reveal a role for A20 in regulating macrophage immunometabolism.

Serum Proteomic Analysis of Cannabis Use Disorder in Male Patients

Cannabis use has been growing recently and it is legally consumed in many countries. Cannabis has a variety of phytochemicals including cannabinoids, which might impair the peripheral systems responses affecting inflammatory and immunological pathways. However, the exact signaling pathways that induce these effects need further understanding. The objective of this study is to investigate the serum proteomic profiling in patients diagnosed with cannabis use disorder (CUD) as compared with healthy control subjects. The novelty of our study is to highlight the differentially changes proteins in the serum of CUD patients. Certain proteins can be targeted in the future to attenuate the toxicological effects of cannabis. Blood samples were collected from 20 male individuals: 10 healthy controls and 10 CUD patients. An untargeted proteomic technique employing two-dimensional difference in gel electrophoresis coupled with mass spectrometry was employed in this study to assess the differentially expressed proteins. The proteomic analysis identified a total of 121 proteins that showed significant changes in protein expression between CUD patients (experimental group) and healthy individuals (control group). For instance, the serum expression of inactive tyrosine protein kinase PEAK1 and tumor necrosis factor alpha-induced protein 3 were increased in CUD group. In contrast, the serum expression of transthyretin and serotransferrin were reduced in CUD group. Among these proteins, 55 proteins were significantly upregulated and 66 proteins significantly downregulated in CUD patients as compared with healthy control group. Ingenuity pathway analysis (IPA) found that these differentially expressed proteins are linked to p38MAPK, interleukin 12 complex, nuclear factor-κB, and other signaling pathways. Our work indicates that the differentially expressed serum proteins between CUD and control groups are correlated to liver X receptor/retinoid X receptor (RXR), farnesoid X receptor/RXR activation, and acute phase response signaling.

Bavachin exerted anti-neuroinflammatory effects by regulation of A20 ubiquitin-editing complex

Neuroinflammation is a major pathophysiological contributor to the progression of the central nervous system disorders. Bavachin is a natural product belonging to the flavonoid class. The anti-neuroinflammatory effect and the molecular mechanisms are not well understood. In this study, we found bavachin can exert anti-neuroinflammatory effect via inhibition of nuclear factor-kappa B (NF-κB) signaling. We found that bavachin can obviously upregulate the expression of A20 (TNFAIP3) in microglial cells. Further studies suggested siRNA-A20 knockdown treatment can attenuate the inhibitory effects of bavachin on neuroinflammation. We further found bavachin can increase the interaction of ubiquitin-editing enzyme A20 complex including A20, Tax1-binding protein 1 (TAX1BP1) and Itch, the subsequently downregulated the K63-ubiquitination of TNF receptor associated factor 6 (TRAF6) and NF-κB signaling pathway. Altogether, our results indicated that bavachin exerted anti-neuroinflammatory effects through inhibition of NF-κB signaling mediated by regulation of ubiquitin-editing enzyme A20 complex. Our finding has important clinical significance for the potential application of bavachin in the treatment of neurological disorders.

Nrf2 Regulates Anti-Inflammatory A20 Deubiquitinase Induction by LPS in Macrophages in Contextual Manner

The aberrant regulation of inflammatory gene transcription following oxidant and inflammatory stimuli can culminate in unchecked systemic inflammation leading to organ dysfunction. The Nrf2 transcription factor dampens cellular stress and controls inflammation by upregulating antioxidant gene expression and TNFα-induced Protein 3 (TNFAIP3, aka A20) deubiquitinase by controlling NF-kB signaling dampens tissue inflammation. Here, we report that Nrf2 is required for A20 induction by inflammatory stimuli LPS in monocyte/bone marrow derived macrophages (MDMΦs) but not in lung-macrophages (LDMΦs). LPS-induced A20 expression was significantly lower in Nrf2^-/- MDMΦs and was not restored by antioxidant supplementation. Nrf2 deficiency markedly impaired LPS-stimulated A20 mRNA expression Nrf2^-/- MDMΦs and ChIP assays showed Nrf2 enrichment at the promoter Nrf2^-/- MDMΦs upon LPS stimulation, demonstrating that Nrf2 directly regulates A20 expression. Contrary to MDMΦs, LPS-stimulated A20 expression was not largely impaired in Nrf2^-/- LDMΦs ex vivo and in vivo and ChIP assays showed lack of increased Nrf2 binding at the A20 promoter in LDMΦ following LPS treatment. Collectively, these results demonstrate a crucial role for Nrf2 in optimal A20 transcriptional induction in macrophages by endotoxin, and this regulation occurs in a contextual manner.

Mogroside V Alleviates Lipopolysaccharide-Induced Neuroinflammation via Inhibition of TLR4-MyD88 and Activation of AKT/AMPK-Nrf2 Signaling Pathway

As innate immune effector cells in the central nervous system (CNS), microglia not only are essential for the normal development of nervous system but also act on different neurological diseases, including Alzheimer's disease (AD), Huntington's disease (HD), and other neuroinflammatory diseases. Mogroside V (Mog), a natural plant active ingredient and isolated form of Momordica grosvenori, has been shown to possess anti-inflammatory action, but few studies were carried out to investigate the effects of Mog on neuroinflammation. This study aimed to investigate the role of Mog in lipopolysaccharide- (LPS-) induced neuroinflammation and neuronal damage, revealing the underlying mechanisms. Our data indicated that Mog significantly inhibited the LPS-induced production of proinflammatory factors, such as tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-18, IL-6, cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), and high mobility group box 1 (HMGB1) in BV-2 cells. We found that Mog also suppressed toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), the phosphorylation of mitogen-activated protein kinases (MAPKs), adenosine 5'-monophosphate- (AMP-) activated protein kinase (AMPK), nuclear factor kappa-B (NF-κB), and protein kinase B (AKT). Moreover, Mog also enhanced the expression of γ-glutamyl cysteine synthetase catalytic subunit (GCLC), modifier subunit (GCLM), heme oxygenase-1 (HO-1), and quinine oxidoreductase 1 (NQO1) proteins, mostly depending on the nuclear translation of nuclear factor erythroid-2 related factor 2 (Nrf2). In contrast, pretreatment with inhibitors of AKT can suppress the phosphorylation of AMPK, Nrf2, and its downstream proteins expression. In summary, Mog might play a protective role against LPS-induced neurotoxicity by inhibiting the TLR4-MyD88 and activation of AMPK/AKT-Nrf2 signaling pathway.

Single nucleotide polymorphism rs5029937 in TNFAIP3 gene is correlated with risk of rheumatoid arthritis

Background: Rheumatoid arthritis (RA) is a progressive and common autoimmune disease with multifactorial etiology. Several pieces of research show that genetic factors play a major role in the incidence of RA. Several genome-wide association studies (GWAS) have identified the tumor necrosis factor alpha inducible protein 3 (TNFAIP3) genes as one of the candidate loci. The TNFAIP3 gene encoding ubiquitin-editing protein A20 witch restricts B cell survival and prevents autoimmunity. Previous studies have indicated that single nucleotide polymorphisms (SNPs) in the TNFAIP3 gene are correlated with several autoimmune disorders. In the present study, we assessed the possible association between SNP rs5029937 (intronic variant) in the TNFAIP3 gene with RA risk in the Iranian population.

Methods: A case-control study using 50 RA patients and 50 control subjects was undertaken to evaluate rs5029937 (G>T) genotypes using real-time PCR high resolution melting method (HRM). The SPSS22 was used for statistical analyses and the significance level was set at P<0.05.

Results: Logistic regression analysis demonstrates that homozygous TT + heterozygous TG genotypes compared with GG genotype increase the risk of RA (TT+TG vs GG; P= 0.004, OR= 3.46; 95%CI [1.492-8.075]). Also, individuals with allele T were more frequently affected with RA than subjects with G allele (T vs G; P= 0.004, OR= 2.61; 95%CI [1.382-4.919]).

Conclusion: Our findings propose a substantial correlation between rs5029937 (G>T) polymorphism and RA risk in Iranian population.

Candidate Genes Identified in Systemic Sclerosis-Related Pulmonary Arterial Hypertension Were Associated with Immunity, Inflammation, and Cytokines

Background

Pulmonary complications of systemic sclerosis (SSc), including pulmonary arterial hypertension (PAH), are the leading causes of patient death. However, the precise molecular mechanisms of its etiology are unclear. This study's objective was to identify the candidate genes involved in the progression of SSc-PAH and investigate the genes' function.

Methods

The gene expression profiles of GSE33463 were obtained from the Gene Expression Omnibus (GEO) database. A free-scale gene coexpression network was constructed using the weighted gene coexpression network analysis (WGCNA) to explore the association between gene sets and clinical features and identify candidate biomarkers. Then, gene ontology analysis was performed. A second dataset was used, GSE19617, to validate the hub genes. The verified hub genes' potential function was further explored using gene set enrichment analysis (GSEA).

Results

Through average link-level clustering, a total of seven modules were classified. A total of 938 hub genes were identified in the key module, and the key module's function mainly enriched was related to chemokine activities. Subsequently, four candidate genes, BTG3, CCR2, RAB10, and TMEM60, were filtered. The expression levels of these four hub genes were consistent in the GSE19617 and GSE33463 datasets. We plotted the ROC curve of the hub genes (all AUC > 0.70). Furthermore, the results of the GSEA for hub genes were correlated with complement and inflammatory responses.

Conclusions

The hub genes (BTG3, CCR2, RAB10, and TMEM60) performed well in distinguishing the SSc-PAH patients from controls, and some biological functions, related to immunity, inflammation, and cytokines, might pave the way for follow-up studies on the diagnosis and treatment of SSc-PAH.

Tumor necrosis factor induced protein 3 gene polymorphism and the susceptibility to chronic primary immune thrombocytopenia in Egyptian children: a case-control study

Background

Primary immune thrombocytopenia (PIT) is an acquired auto-immune disease characterized by decreased platelet count with increased bleeding tendency. The tumor necrosis factor associated induced protein-3 (TNFAIP3) codes for the ubiquitin-modifying enzyme that is indispensable for limiting inflammation. TNFAIP3 single-nucleotide polymorphisms (SNP) has been implicated in the susceptibility to multiple auto-immune diseases. We aimed to study the distribution of TNFAIP3 (rs5029939 C>G) SNP and the possible association of the studied polymorphism with the susceptibility to chronic PIT and the response to treatment in a sample of the Egyptian pediatric chronic PIT patients. This is a case-control study performed on 40 chronic PIT patients and 50 age- and gender-matched healthy controls. DNA samples from both groups were tested for TNFAIP3 (rs5029939 C>G) SNP using polymerase chain reaction-restriction fragment length polymorphism assay.

Results

TNFAIP3 (rs5029939 C>G) genotype distribution showed no statistically significant difference between PIT cases and controls [CC 77.5% vs. 82.5%, and CG 22% vs. 18%, respectively; OR (95% CI), 1.323 (0.470–0.723); p, 0.596]. The minor allele frequency (MAF) of rs5029939-G was comparable between the 2 groups (0.11 vs. 0.09) [OR (95% CI), 1.282 (0.484–3.397); p, 0.617]. No statistically significant difference was observed between chronic PIT patients carrying the mutant heterozygous genotype (CG) achieving complete response and those with no response [OR (95% CI), 1.667 (0.165-16.810); p > 0.05]. The MAF of rs5029939-G was comparable between both groups [OR (95% CI), 1.571 (0.175–14.111); p > 0.05].

Conclusion

This study showed no liability of patients carrying TNFAIP3 (rs5029939 C>G) polymorphism to develop chronic course of the disease or to achieve complete response to treatment. TNFAIP3 (rs5029939 C < G) SNP plays no role in either susceptibility to chronic PIT in the studied sample of Egyptian pediatric population or their response to treatment.

A zebrafish functional genomics model to investigate the role of human A20 variants in vivo

Germline loss-of-function variation in TNFAIP3, encoding A20, has been implicated in a wide variety of autoinflammatory and autoimmune conditions, with acquired somatic missense mutations linked to cancer progression. Furthermore, human sequence data reveals that the A20 locus contains ~ 400 non-synonymous coding variants, which are largely uncharacterised. The growing number of A20 coding variants with unknown function, but potential clinical impact, poses a challenge to traditional mouse-based approaches. Here we report the development of a novel functional genomics approach that utilizes a new A20-deficient zebrafish (Danio rerio) model to investigate the impact of TNFAIP3 genetic variants in vivo. A20-deficient zebrafish are hyper-responsive to microbial immune activation and exhibit spontaneous early lethality. Ectopic addition of human A20 rescued A20-null zebrafish from lethality, while missense mutations at two conserved A20 residues, S381A and C243Y, reversed this protective effect. Ser381 represents a phosphorylation site important for enhancing A20 activity that is abrogated by its mutation to alanine, or by a causal C243Y mutation that triggers human autoimmune disease. These data reveal an evolutionarily conserved role for TNFAIP3 in limiting inflammation in the vertebrate linage and show how this function is controlled by phosphorylation. They also demonstrate how a zebrafish functional genomics pipeline can be utilized to investigate the in vivo significance of medically relevant human TNFAIP3 gene variants.

Toll-like receptors in sepsis-associated cytokine storm and their endogenous negative regulators as future immunomodulatory targets

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Sepsis infects more than 48.9 million people world-wide, with 19.7 million deaths.

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Cytokine storm plays a significant role in sepsis, along with severe COVID-19.

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TLR signaling pathways plays a crucial role in generating the cytokine storm.

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Endogenous negative regulators of TLR signaling are crucial to regulate cytokine storm.

Cytokine storm generates during various systemic acute infections, including sepsis and current pandemic called COVID-19 (severe) causing devastating inflammatory conditions, which include multi-organ failure or multi-organ dysfunction syndrome (MODS) and death of the patient. Toll-like receptors (TLRs) are one of the major pattern recognition receptors (PRRs) expressed by immune cells as well as non-immune cells, including neurons, which play a crucial role in generating cytokine storm. They recognize microbial-associated molecular patterns (MAMPs, expressed by pathogens) and damage or death-associate molecular patterns (DAMPs; released and/expressed by damaged/killed host cells). Upon recognition of MAMPs and DAMPs, TLRs activate downstream signaling pathways releasing several pro-inflammatory mediators [cytokines, chemokines, interferons, and reactive oxygen and nitrogen species (ROS or RNS)], which cause acute inflammation meant to control the pathogen and repair the damage. Induction of an exaggerated response due to genetic makeup of the host and/or persistence of the pathogen due to its evasion mechanisms may lead to severe systemic inflammatory condition called sepsis in response to the generation of cytokine storm and organ dysfunction. The activation of TLR-induced inflammatory response is hardwired to the induction of several negative feedback mechanisms that come into play to conclude the response and maintain immune homeostasis. This state-of-the-art review describes the importance of TLR signaling in the onset of the sepsis-associated cytokine storm and discusses various host-derived endogenous negative regulators of TLR signaling pathways. The subject is very important as there is a vast array of genes and processes implicated in these negative feedback mechanisms. These molecules and mechanisms can be targeted for developing novel therapeutic drugs for cytokine storm-associated diseases, including sepsis, severe COVID-19, and other inflammatory diseases, where TLR-signaling plays a significant role.

Activation of NOTCH1 by Shear Force Elicits Immediate Cytokine Expression in Human Chondrocytes

Osteoarthritis is caused by overloading of joints and is characterized by inflammation-induced disruption of cartilage structure. Current treatment strategy aims to relieve inflammation and prevent further deterioration of joint function. However, how mechanical force leads to inflammation and deterioration of chondrocyte function still remains incompletely understood. To explore the force-regulated molecular mechanism, an in vitro hydraulic shear force experiment to simulate the condition of force loading was required. The result demonstrated that multiple cytokines and immune regulators, including interleukin 8, interferon β, TRAF1 and TNFAIP3, were significantly increased by shear force within two hours of treatment. Moreover, JAG1 and HES1 were drastically upregulated as well, suggesting that NOTCH1 signaling is activated by shear force. Short-term expression of NOTCH1 intracellular domain activated a similar set of cytokines, indicating that NOTCH1 responds to shear force and activates downstream genes. When incubated under the medium conditioned by NOTCH1-activated chondrocyte, osteoblasts expressed higher levels of interferon β and interferon λ. Together, our results indicated that NOTCH1 functions as a force sensor and promotes expression of cytokines and immune regulators from shear-force bearing chondrocytes.

Abnormal miR-214/A20 expression might play a role in T cell activation in patients with aplastic anemia

Aberrant T cell activation is a major cause of aplastic anemia (AA) pathogenesis. Recent studies have shown that miRNAs regulate T cell activation and are involved in AA. A previous study found that miR-214 was significantly up-regulated upon T cell activation in a CD28-dependent fashion by targeting PTEN. However, the expression characteristics of miR-214 and its target genes in AA have not been defined. In this study, target genes for miR-214 were predicted and confirmed by bioinformatics and luciferase reporter assays. The expression levels of miR-214 and target genes were detected in 36 healthy individuals and 35 patients with AA in peripheral blood mononuclear cells by real-time quantitative reverse transcriptase-polymerase chain reaction. Bioinformatics and luciferase reporter assays identified that miR-214 could bind to the A20 3' untranslated regions. Significantly increased miR-214 and the decreased A20 expression level were detected in the AA patients compared with the healthy group. In addition, significantly increased miR-214 was found in non-severe aplastic anemia compared with severe aplastic anemia patients. These results suggested that the A20 gene was a potential target of miR-214, and elevated miR-214 might medicate T cell activation at least in part by regulating A20 expression in AA. We firstly confirmed that miR-214 regulated A20 expression, and aberrant miR-214/A20 expression might contribute to immunopathology in AA. The miR-214 expression might be used as a potential biomarker that assisted in diagnosing AA severity.

Autoimmunity and organ damage in systemic lupus erythematosus

Impressive progress has been made over the last several years toward understanding how almost every aspect of the immune system contributes to the expression of systemic autoimmunity. In parallel, studies have shed light on the mechanisms that contribute to organ inflammation and damage. New approaches that address the complicated interaction between genetic variants, epigenetic processes, sex and the environment promise to enlighten the multitude of pathways that lead to what is clinically defined as systemic lupus erythematosus. It is expected that each patient owns a unique 'interactome', which will dictate specific treatment.

Association of rs610604 in TNFAIP3 and rs17728338 in TNIP1 gene polymorphisms with psoriasis susceptibility: a meta-analysis of case-control studies

BACKGROUND

To date, the fundamental pathophysiology underlying the occurrence and progression of psoriasis are still unanswered questions. Genome-wide association surveys have revealed that TNFAIP3 and TNIP1 were key biomarkers for psoriasis. Here, we intended to conduct a survey on the association between TNFAIP3 and TNIP1 gene polymorphisms and psoriasis risk.

METHODS

A comprehensive search of four online databases-China National Knowledge Infrastructure (CNKI), PubMed, Embase, and Cochrane Library was undertaken up to August 25, 2019. We chose allele genetic model to deal with the original data. Newcastle-Ottawa scale (NOS) was used to evaluate the risk bias of each study. The RevMan 5.3 software was used to calculate the combined odds ratio and 95% confidence interval.

RESULTS

In total, we included 13 case-control studies consist of 13,908 psoriasis patients and 20,051 controls in this work. Our results demonstrated that rs610604 in TNFAIP3 polymorphism was significantly associated with psoriasis risk using random-effect model (G vs. T, OR = 1.19, 95% CI: 1.09-1.31, P = 0.0002), and a significant association between rs17728338 in TNIP1 polymorphism and psoriasis vulnerability using fixed-effect model (A vs. G, OR = 1.69, 95% CI:1.58-1.80, P < 0.00001).

CONCLUSIONS

Our findings indicated that rs610604 in TNFAIP3 and rs17728338 in TNIP1 gene polymorphisms were associated with psoriasis susceptibility.

A20 and Cell Death-driven Inflammation

A20 is a potent anti-inflammatory molecule, and mutations in TNFAIP3, the gene encoding A20, are associated with a wide panel of inflammatory pathologies, both in human and mouse. The anti-inflammatory properties of A20 are commonly attributed to its ability to suppress inflammatory NF-κB signaling by functioning as a ubiquitin-editing enzyme. However, A20 also protects cells from death, independently of NF-κB regulation, and recent work has demonstrated that cell death may drive some of the inflammatory conditions caused by A20 deficiency. Adding to the fact that the protective role of A20 does not primarily rely on its catalytic activities, these findings shed new light on A20 biology.

Pien Tze Huang alleviate the joint inflammation in collagen-induced arthritis mice

Background

Rheumatoid arthritis (RA) is an autoimmune disease characterized by synovitis. Pien Tze Huang (PZH) is a Chinese patent medicine with anti-inflammatory and immunomodulatory effects. However, whether PZH could be used in RA therapy is still unknown. Therefore, this study aimed to explore the therapeutic effect and the potential mechanism of PZH on collagen-induced arthritis (CIA) mice.

Methods

Male DBA/1J mice were used to establish an animal model of CIA and then treated with different doses of PZH for 4 weeks. The therapeutic effect of PZH on CIA mice was evaluated by arthritis score, pathological staining, and detecting the levels of inflammatory factors in serum and joints. To investigate its possible mechanism, the activity of NF-κB signaling pathway, NLRP3 inflammasome and the level of A20 were detected.

Results

The results showed that PZH could alleviate the erythema and swelling of hind paws of CIA mice, improve the pathological conditions of joint and decrease the production of IL-1β, IL-6 and IL-17 in serum and joints. Furthermore, PZH could significantly inhibit the activity of NF-κB signaling pathway and NLRP3 inflammasome in the ankle joint of CIA mice compared with the model group. It also increased the level of A20 in the ankle joint of CIA mice.

Conclusion

This study indicated that PZH could alleviate the joint inflammation of CIA mice, and the mechanism might be related to the regulation of NF-κB signaling pathway and NLRP3 inflammasome.

Rheumatological manifestations in inborn errors of immunity

Rare monogenetic diseases serve as natural models to dissect the molecular pathophysiology of the complex disease traits. Rheumatologic disorders by their nature are considered complex diseases with partially genetic origin, as illustrated by their heterogeneous genetic background and variable phenotypic presentation. Recent advances in genetic technologies have helped uncover multiple variants associated with disease susceptibility; however, a precise understanding of genotype-phenotype relationships is still missing. Inborn errors of immunity (IEIs), in addition to recurrent infections, may also present with autoimmune and autoinflammatory rheumatologic manifestations and have provided insights for understanding the underlying the principles of immune system homeostasis and mechanisms of immune dysregulation. This review discusses the rheumatologic manifestations in IEIs with overlapping and differentiating features in immunodeficiencies and rheumatologic disorders.

Identification and Classification of Differentially Expressed Genes and Network Meta-Analysis Reveals Potential Molecular Signatures Associated With Tuberculosis

Tuberculosis (TB) is one of deadly transmissible disease that causes death worldwide; however, only 10% of people infected with Mycobacteriumtuberculosis develop disease, indicating that host genetic factors may play key role in determining susceptibility to TB disease. In this way, the analysis of gene expression profiling of TB infected individuals can give us a snapshot of actively expressed genes and transcripts under various conditions. In the present study, we have analyzed microarray data set and compared the gene expression profiles of patients with different datasets of healthy control, latent infection, and active TB. We observed the transition of genes from normal condition to different stages of the TB and identified and annotated those genes/pathways/processes that have important roles in TB disease during its cyclic interventions in the human body. We identified 488 genes that were differentially expressed at various stages of TB and allocated to pathways and gene set enrichment analysis. These pathways as well as GSEA’s importance were evaluated according to the number of DEGs presents in both. In addition, we studied the gene regulatory networks that may help to further understand the molecular mechanism of immune response against the TB infection and provide us a new angle for future biomarker and therapeutic targets. In this study, we identified 26 leading hubs which are deeply rooted from top to bottom in the gene regulatory network and work as the backbone of the network. These leading hubs contains 31 key regulator genes, of which 14 genes were up-regulated and 17 genes were down-regulated. The proposed approach is based on gene-expression profiling, and network analysis approaches predict some unknown TB-associated genes, which can be considered (or can be tested) as reliable candidates for further (in vivo/in vitro) studies.

Ripoptocide - A Spark for Inflammation

The clinical success of biologics that inhibit TNF (Tumor Necrosis Factor) in inflammatory bowel diseases (IBD), psoriasis and rheumatoid arthritis (RA) has clearly established a pathogenic role for this cytokine in these inflammatory disorders. TNF binding to its receptors activates NFκB and MAPK signaling, inducing the expression of downstream pro-inflammatory genes. This is thought to be the primary mechanism by which TNF elicits inflammation. TNF is also a well-known trigger of caspase-dependent apoptosis or caspase-independent necroptosis. Whether cell death has any role in TNF-mediated inflammation has been less clear. Emerging data from animal models now suggest that cellular demise caused by TNF may indeed provoke inflammation. The default response of most cells to TNF stimulation is survival, rather than death, due to the presence of two sequential cell death checkpoints. The early checkpoint is transcription-independent involving the non-degradative ubiquitination of RIPK1 to prevent RIPK1 from becoming a death-signaling molecule. The later checkpoint requires the induction of pro-survival genes by NFκB-mediated transcription. When the early checkpoint is disrupted, RIPK1 initiates cell death and we suggest the term ripoptocide to describe this manner of death (encompassing both apoptosis and necroptosis). The sensitivity of a cell to ripoptocide is determined by the balance between regulatory molecules that enforce and those that disassemble the early checkpoint. As there is evidence suggesting that ripoptocide is inflammatory, individuals may develop inflammation due to ripoptocide brought about by genetic, epigenetic or post-translational alteration of these checkpoint regulators. For these individuals, drugs that reinforce the early checkpoint and inhibit ripoptocide could be useful in ameliorating inflammation.

Expression Pattern of microRNAs, miR-21, miR-155 and miR-338 in Patients with Type 1 Diabetes

BACKGROUND

Type 1 diabetes (T1D) is a multifactorial disease identified by a deficiency in the production of insulin. MicroRNAs (miRNAs) are identified as important epigenetic regulators in T1D. Many studies highlight the differential expression of these small non-coding molecules in the pathogenesis of T1D.

AIM OF THE STUDY

In the present study, the expression pattern of miR-21, miR-155 and miR-338 were analyzed in the peripheral blood mononuclear cells (PBMCs) of T1D patients compared to healthy controls.

METHODS

The expression levels of miR-21, miR-155 and miR-338 were measured in the PBMCs of 30 T1D patients and 11 healthy controls by real time PCR method. The final results were statistically analyzed and ROC curves were created for miRNAs with significant differential expression.

RESULTS

Both miR-155 (p value: 0.021) and miR-21 (p value: 0.05) were upregulated in the PBMCs of T1D patients compared to healthy controls. There was no significant difference in the expression level of miR-338 between patients and controls. Furthermore, ROC curve analysis was performed for miR-21 (AUC: 0.65) and miR-155 (AUC: 0.73) which suggests the potential role of miR-155 as a biomarker in T1D patients. Using integrative computational analysis, a number of dysregulated miR155-mRNA and miR21-mRNA interactions were also suggested.

CONCLUSION

Our findings suggest the significant association between the expression levels of miR-21 and miR-155 with T1D. In addition, miR-155 (AUC: 0.73) could be considered as a possible biomarker to track disease in T1D patients.

A20 as a novel target for the anti-neuroinflammatory effect of chrysin via inhibition of NF-κB signaling pathway

Neuroinflammation is now recognized to be a feature of many neurological disorders. More accumulated evidences suggested chrysin which was contained in honey, propolis, vegetables, fruits and plants can exert biological activities including anti-neuroinflammatory effects. However, the precise molecular mechanisms of anti-neuroinflammatory effects remain unclear. In the present study, we explored a novel molecular mechanism involved in the anti-neuroinflammatory effect of chrysin. Firstly, we investigated the anti-neuroinflammatory effects of chrysin in LPS-induced BV2, primary microglial cells and mice. Next, we found chrysin can inhibit NF-κB pathway and TRAF6 expression, but upregulate the expression of zinc-finger protein A20. Further studies have revealed upregulation of A20 can regulate the inhibitory effects of chrysin on NF-κB pathways via regulation of TRAF6 polyubiquitination. This present study demonstrates that chrysin exerts an anti-neuroinflammatory effect via a novel mechanism, the upregulation of A20 expression, also validates A20 is a novel effective pharmacological target for developing agents in the treatment of neuroinflammation-related diseases.

A20 prevents inflammasome-dependent arthritis by inhibiting macrophage necroptosis through its ZnF7 ubiquitin-binding domain

Deficiency in the deubiquitinating enzyme A20 causes severe inflammation in mice, and impaired A20 function is associated with human inflammatory diseases. A20 has been implicated in negatively regulating NF-κB signalling, cell death and inflammasome activation; however, the mechanisms by which A20 inhibits inflammation in vivo remain poorly understood. Genetic studies in mice revealed that its deubiquitinase activity is not essential for A20 anti-inflammatory function. Here we show that A20 prevents inflammasome-dependent arthritis by inhibiting macrophage necroptosis and that this function depends on its zinc finger 7 (ZnF7). We provide genetic evidence that RIPK1 kinase-dependent, RIPK3-MLKL-mediated necroptosis drives inflammasome activation in A20-deficient macrophages and causes inflammatory arthritis in mice. Single-cell imaging revealed that RIPK3-dependent death caused inflammasome-dependent IL-1β release from lipopolysaccharide-stimulated A20-deficient macrophages. Importantly, mutation of the A20 ZnF7 ubiquitin binding domain caused arthritis in mice, arguing that ZnF7-dependent inhibition of necroptosis is critical for A20 anti-inflammatory function in vivo.

Ubiquitin Ligases in Cancer Immunotherapy - Balancing Antitumor and Autoimmunity

Considerable progress has been made in understanding the contribution of E3 ubiquitin ligases to health and disease, including the pathogenesis of immunological disorders. Ubiquitin ligases exert exquisite spatial and temporal control over protein stability and function, and are thus crucial for the regulation of both innate and adaptive immunity. Given that immune responses can be both detrimental (autoimmunity) and beneficial (antitumor immunity), it is vital to understand how ubiquitin ligases maintain immunological homeostasis. Such knowledge could reveal novel mechanisms underlying immune regulation and identify new therapeutic approaches to enhance antitumor immunity and safeguard against autoimmunity.

Increased expression of microRNAs, miR-20a and miR-326 in PBMCs of patients with type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disorder which is characterized by autoimmune attack on β cells of pancreas and lack of insulin. The involvement of microRNAs (miRNAs) in the development of immune system and their differential expression in various autoimmune diseases including T1D have been well established. In this study, the association between expression levels of miR-20a, miR-326 and T1D were evaluated. The expression levels of miR-20a and miR-326 were measured in the PBMCs of 21 T1D patients and 16 healthy controls using qPCR method. In silico analysis was also performed on targetome of miR-20a and miR-326. Both miR-20a (p value: 0.015) and miR-326 (p value: 0.005) were upregulated in the PBMCs of T1D patients compared to healthy controls. Furthermore, different dysregulated miR326-mRNA and miR20a-mRNA interactions were also suggested using integrative computational analysis. The expression level of miR-20a and miR-326 indicates significant association with T1D which suggests the possible regulatory effects of these non-coding RNAs in T1D.

Smoking and drinking influence the advancing of ischemic stroke disease by targeting PTGS2 and TNFAIP3

In the present study, we explored the influence of cigarette smoking and alcohol drinking on gene expression level and related functions and pathways on the development of ischemic stroke (IS) disease. The gene expression profile of E-GEOD-22255 was obtained from 20 IS samples (7 patients without smoking or drinking history and 13 patients with smoking or drinking history) and 20 controls (9 normal controls without smoking or drinking history and 11 controls with smoking or drinking history). The correlation degree between gene expression and grouping were measured by significance analysis of microarray (SAM). Smoking or drinking-related DEGs were screened. GO functional and KEGG pathway enrichment analyses were processed. Based on the KEGG database, a pathway relationship network was constructed. DEGs in significant functions and pathways were inserted and regarded as key DEGs. Gene co-expression network was constructed based on the expression value of key genes. In total, 319 IS-related DEGs, which were induced by smoking and drinking, were screened and enriched in various functions and pathways, including inflammatory response, nuclear factor-κB (NF-κB) signaling pathway and influenza A. Pathway relationship network was constructed with 44 nodes and the hub node was the MAPK signaling pathway. After merging, 87 key DEGs were obtained. The gene co-expression network with 43 node edges was constructed and the hub node was prostaglandin-endoperoxide synthase 2. In IS patients, smoking and drinking may induce different expression of many genes, including PTGS2, TNFAIP3, ZFP36 and NFKBIZ. In addition, these genes participated in various pathways, such as inflammatory response.

A20 ameliorates inflammatory bowel disease in mice via inhibiting NF-κB and STAT3 activation

A20 is a zinc finger protein that effectively inhibits the activation of nuclear factor (NF)-κB to downregulate the expression of tumor necrosis factor-α, interleukin (IL)-1β, and IL-17. A20 also plays a crucial role as a feedback inhibitor of the inflammatory response. Due to its inhibitory role, A20 may be useful in regulating diseases resulting from chronic inflammation and excessive pro-inflammatory cytokine production, such as colitis. Patients with colitis produce high levels of pro-inflammatory cytokines in the intestine. Therefore, this study aimed to investigate whether A20 improves experimental colitis by reducing high levels of inflammation in the intestine. An A20 overexpression vector was administered to mice by intrarectal injection after colitis induction. Histological analysis by immunohistochemistry was used to score sections of the intestine. Confocal laser scanning microscopy was used to identify the expression of IL-17 and forkhead box p (FOXP) 3 protein in spleen tissues. Protein expression induced by STAT3 and NF-κB signaling was analyzed by western blot. We found that A20 reduced the colitis activity index score and the histological score of the intestine. A20 also decreased inflammatory cytokine levels in the intestine and increased colon length. Additionally, A20 overexpression downregulated the activation of NF-kB and STAT3. A20 also reduced IL-17 expression in CD4⁺ T cells from spleen sections. In contrast, A20 overexpression enhanced the expression of FOXP3 in CD4⁺ T cells. These results suggest that A20 may inhibit the progression of colitis by decreasing inflammation via inhibition of NF-κB, phosphorylated STAT3, and IL-17.

A20/Tumor Necrosis Factor α-Induced Protein 3 in Immune Cells Controls Development of Autoinflammation and Autoimmunity: Lessons from Mouse Models

Immune cell activation is a stringently regulated process, as exaggerated innate and adaptive immune responses can lead to autoinflammatory and autoimmune diseases. Perhaps the best-characterized molecular pathway promoting cell activation is the nuclear factor-κB (NF-κB) signaling pathway. Stimulation of this pathway leads to transcription of numerous pro-inflammatory and cell-survival genes. Several mechanisms tightly control NF-κB activity, including the key regulatory zinc finger (de)ubiquitinating enzyme A20/tumor necrosis factor α-induced protein 3 (TNFAIP3). Single nucleotide polymorphisms (SNPs) in the vicinity of the TNFAIP3 gene are associated with a spectrum of chronic systemic inflammatory diseases, indicative of its clinical relevance. Mice harboring targeted cell-specific deletions of the Tnfaip3 gene in innate immune cells such as macrophages spontaneously develop autoinflammatory disease. When immune cells involved in the adaptive immune response, such as dendritic cells or B-cells, are targeted for A20/TNFAIP3 deletion, mice develop spontaneous inflammation that resembles human autoimmune disease. Therefore, more knowledge on A20/TNFAIP3 function in cells of the immune system is beneficial in our understanding of autoinflammation and autoimmunity. Using the aforementioned mouse models, novel A20/TNFAIP3 functions have recently been described including control of necroptosis and inflammasome activity. In this review, we discuss the function of the A20/TNFAIP3 enzyme and its critical role in various innate and adaptive immune cells. Finally, we discuss the latest findings on TNFAIP3 SNPs in human autoinflammatory and autoimmune diseases and address that genotyping of TNFAIP3 SNPs may guide treatment decisions.

Updates in Lupus Genetics

PURPOSE OF REVIEW

Our understanding on genetic basis of SLE has been advanced through genome-wide association studies. We review recent progress in lupus genetics with a focus on SLE-associated loci that have been functionally characterized, and discuss the potential for clinical translation of genetics data.

RECENT FINDINGS

Over 100 loci have been confirmed to show robust association with SLE and many share with other immune-mediated diseases. Although causative variants captured at these established loci are limited, they guide biological studies of gene targets for functional characterization which highlight the importance of aberrant recognition of self-nucleic acid, type I interferon overproduction, and defective immune cell signaling underlying the pathogenesis of SLE. Increasing examples illustrate a predictive value of genetic findings in susceptibility/prognosis prediction, clinical classification, and pharmacological implication. Genetic findings provide a foundation for better understanding of disease pathogenic mechanisms and opportunities for target selection in lupus drug development.

Therapeutic Effect of Exogenous Truncated IK Protein in Inflammatory Arthritis

Inhibitor K562 (IK) protein was first isolated from the culture medium of K562, a leukemia cell line. It is known to be an inhibitory regulator of interferon-γ-induced major histocompatibility complex class (MHC) II expression. Previously, we found that transgenic (Tg) mice constitutively expressing truncated IK (tIK) showed reduced numbers of pathogenic Th1 and Th17 cells, which are known to be involved in the development of rheumatoid arthritis (RA). Here, we investigated whether exogenous tIK protein has a therapeutic effect in arthritis in disease models and analyzed its mechanism. Exogenous tIK protein was produced in an insect expression system and applied to the collagen antibody-induced arthritis (CAIA) mouse disease model. Injection of tIK protein alleviated the symptoms of arthritis in the CAIA model and reduced Th1 and Th17 cell populations. In addition, treatment of cultured T cells with tIK protein induced expression of A20, a negative regulator of nuclear factor-κB (NFκB)-induced inflammation, and reduced expression of several transcription factors related to T cell activation. We conclude that exogenous tIK protein has the potential to act as a new therapeutic agent for RA patients, because it has a different mode of action to biopharmaceutical agents, such as tumor necrosis factor antagonists, that are currently used to treat RA.

TNFAIP3 gene rs7749323 polymorphism is associated with late onset myasthenia gravis

In this study, we intended to genotype 2 single nucleotide polymorphisms (SNPs) of tumor necrosis factor α-induced protein 3 (TNFAIP3) genes and explore an association of TNFAIP3 genetic polymorphism with the patients of myasthenia gravis (MG) at clinical level. In brief, 215 of adult MG patients were divided into subgroups according to their clinical features, age of onset, thymic pathology, and autoantibodies. Two hundred thirty-five of healthy controls were also divided into subgroups with gender- and age-matched. The allele and genotype frequencies of subgrouped patients were found to be higher than those of healthy controls. The distribution of TNFAIP3 gene rs7749323*A allele of late onset MG (LOMG, with positive acetylcholine receptor antibody and without thymoma) subgrouped patients was also significantly higher than that of gender- and age-matched healthy controls (7.4% vs 2.4%, odds ratio [OR] = 3.27, 95% confidence interval [CI] 1.01-10.6, P = .04). Furthermore, analysis to the genotype frequencies indicates that the carriers of rs7749323*A allele of LOMG group became more frequent than that of age-matched healthy controls (14.9% vs 4.8%, OR = 3.47, 95% CI 1.04-11.6, dominant model: P = .03). It is interesting to notice that there is no significant association between the rs7749323 and susceptibility of other MG subgroups. Therefore, it is suggested that the SNPs in the 3' flanking region (rs7749323) of TNFAIP3 gene and the genetic variations of TNFAIP3 gene may take an important role in the susceptibility of LOMG.

CYLD, A20 and OTULIN deubiquitinases in NF-κB signaling and cell death: so similar, yet so different

Polyubiquitination of proteins has a pivotal role in the regulation of numerous cellular functions such as protein degradation, DNA repair and cell signaling. As deregulation of these processes can result in pathological conditions such as inflammatory diseases, neurodegeneration or cancer, tight regulation of the ubiquitin system is of tremendous importance. Ubiquitination by E3 ubiquitin ligases can be counteracted by the activity of several deubiquitinating enzymes (DUBs). CYLD, A20 and OTULIN have been implicated as key DUBs in the negative regulation of NF-κB transcription factor-mediated gene expression upon stimulation of cytokine receptors, antigen receptors and pattern recognition receptors, by removing distinct types of polyubiquitin chains from specific NF-κB signaling proteins. In addition, they control TNF-induced cell death signaling leading to apoptosis and necroptosis via similar mechanisms. In the case of A20, also catalytic-independent mechanisms of action have been demonstrated to have an important role. CYLD, A20 and OTULIN have largely overlapping substrates, suggesting at least partially redundant functions. However, mice deficient in one of the three DUBs show significant phenotypic differences, indicating also non-redundant functions. Here we discuss the activity and polyubiquitin chain-type specificity of CYLD, A20 and OTULIN, their specific role in NF-κB signaling and cell death, the molecular mechanisms that regulate their activity, their role in immune homeostasis and the association of defects in their activity with inflammation, autoimmunity and cancer.

Upregulation of neuronal zinc finger protein A20 expression is required for electroacupuncture to attenuate the cerebral inflammatory injury mediated by the nuclear factor-kB signaling pathway in cerebral ischemia/reperfusion rats

Background

Zinc finger protein A20 (tumor necrosis factor alpha-induced protein 3) functions as a potent negative feedback inhibitor of the nuclear factor-kB (NF-kB) signaling. It exerts these effects by interrupting the activation of IkB kinase beta (IKKβ), the most critical kinase in upstream of NF-kB, and thereby controlling inflammatory homeostasis. We reported previously that electroacupuncture (EA) could effectively suppress IKKβ activation. However, the mechanism underlying these effects was unclear. Therefore, the current study further explored the effects of EA on A20 expression in rat brain and investigated the possible mechanism of A20 in anti-neuroinflammation mediated by EA using transient middle cerebral artery occlusion (MCAO) rats.

Methods

Rats were treated with EA at the “Baihui (GV20),” “Hegu (L14),” and “Taichong (Liv3)” acupoints once a day starting 2 h after focal cerebral ischemia. The spatiotemporal expression of A20, neurobehavioral scores, infarction volumes, cytokine levels, glial cell activation, and the NF-kB signaling were assessed at the indicated time points. A20 gene interference (overexpression and silencing) was used to investigate the role of A20 in mediating the neuroprotective effects of EA and in regulating the interaction between neuronal and glial cells by suppressing neuronal NF-kB signaling during cerebral ischemia/reperfusion-induced neuroinflammation.

Results

EA treatment increased A20 expression with an earlier peak and longer lasting upregulation. The upregulated A20 protein was predominantly located in neurons in the cortical zone of the ischemia/reperfusion. Furthermore, neuronal A20 cell counts were positively correlated with neurobehavioral scores but negatively correlated with infarct volume, the accumulation of pro-inflammatory cytokines, and glial cell activation. Moreover, the effects of EA on improving the neurological outcome and suppressing neuroinflammation in the brain were reversed by A20 silencing. Finally, A20 silencing also suppressed the ability of EA to inhibit neuronal NF-kB signaling pathway.

Conclusions

Ischemia/reperfusion cortical neurons in MCAO rats are the main cell types that express A20, and there is a correlation between A20 expression and the suppression of neuroinflammation and the resulting neuroprotective effects. EA upregulated neuronal A20 expression, which played an essential role in the anti-inflammatory effects of EA by suppressing the neuronal NF-kB signaling pathway in the brains of MCAO rats.

A20 SNP rs77191406 may be related to secondary cancer for rheumatoid arthritis and systemic lupus erythematosus patients

AIM

An increased risk for malignancy for rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) patients may be related to factors that play a critical role in the regulation of T-cell activation. A20 is an important negative immunoregulatory factor that was found to be associated with lymphoma and the development of numerous solid tumors. Previous studies have implicated the A20 locus in RA susceptibility. In this study, we investigated polymorphisms in the A20 3' UTR and explored whether there was an association between these polymorphisms and malignancy risk in autoimmune diseases.

METHODS

PCR and sequencing were used to identify A20 gene polymorphisms in peripheral blood mononuclear cells (PBMCs) from 99 RA cases, 37 SLE cases and 99 healthy individuals. Pearson's Chi square test was used for statistical analysis.

RESULTS

Only one SNP (rs77191406) and one new mutation (20132 A>G) in A20 gene were identified in RA and SLE patients and healthy individuals. Heterozygous rs77191406 was identified in just 1 of 99 RA patients and 2 of 37 SLE patients. More importantly, a RA patient who was heterozygous for rs77191406 developed colon cancer 10 years after the RA diagnosis. Similarly, two SLE patients carrying rs77191406 (heterozygous) had severe disease or developed bladder cancer 5 years after SLE diagnosis.

CONCLUSIONS

These findings suggest that rs77191406 may be a prognostic marker for a high risk for rapid malignancy progression, poor survival and refractory disease and a new molecular marker associated with autoimmune diseases transforming into a secondary cancer.

TNFAIP3 promotes survival of CD4 T cells by restricting MTOR and promoting autophagy

Autophagy plays important roles in metabolism, differentiation, and survival in T cells. TNFAIP3/A20 is a ubiquitin-editing enzyme that is thought to be a negative regulator of autophagy in cell lines. However, the role of TNFAIP3 in autophagy remains unclear. To determine whether TNFAIP3 regulates autophagy in CD4 T cells, we first analyzed Tnfaip3-deficient naïve CD4 T cells in vitro. We demonstrated that Tnfaip3-deficient CD4 T cells exhibited reduced MAP1LC3/LC3 (microtubule-associated protein 1 light chain 3) puncta formation, increased mitochondrial content, and exaggerated reactive oxygen species (ROS) production. These results indicate that TNFAIP3 promotes autophagy after T cell receptor (TCR) stimulation in CD4 T cells. We then investigated the mechanism by which TNFAIP3 promotes autophagy signaling. We found that TNFAIP3 bound to the MTOR (mechanistic target of rapamycin) complex and that Tnfaip3-deficient cells displayed enhanced ubiquitination of the MTOR complex and MTOR activity. To confirm the effects of enhanced MTOR activity in Tnfaip3-deficient cells, we analyzed cell survival following treatment with Torin1, an MTOR inhibitor. Tnfaip3-deficient CD4 T cells exhibited fewer cell numbers than the control cells in vitro and in vivo. In addition, the impaired survival of Tnfaip3-deficient cells was ameliorated with Torin1 treatment in vitro and in vivo. The effect of Torin1 was abolished by Atg5 deficiency. Thus, enhanced MTOR activity regulates the survival of Tnfaip3-deficient CD4 T cells. Taken together, our findings illustrate that TNFAIP3 restricts MTOR signaling and promotes autophagy, providing new insight into the manner in which MTOR and autophagy regulate survival in CD4 T cells.

Suppression of NLRP3 inflammasome by γ-tocotrienol ameliorates type 2 diabetes

The Nod-like receptor 3 (NLRP3) inflammasome is an intracellular sensor that sets off the innate immune system in response to microbial-derived and endogenous metabolic danger signals. We previously reported that γ-tocotrienol (γT3) attenuated adipose tissue inflammation and insulin resistance in diet-induced obesity, but the underlying mechanism remained elusive. Here, we investigated the effects of γT3 on NLRP3 inflammasome activation and attendant consequences on type 2 diabetes. γT3 repressed inflammasome activation, caspase-1 cleavage, and interleukin (IL) 1β secretion in murine macrophages, implicating the inhibition of NLRP3 inflammasome in the anti-inflammatory and antipyroptotic properties of γT3. Furthermore, supplementation of leptin-receptor KO mice with γT3 attenuated immune cell infiltration into adipose tissue, decreased circulating IL-18 levels, preserved pancreatic β-cells, and improved insulin sensitivity. Mechanistically, γT3 regulated the NLRP3 inflammasome via a two-pronged mechanism: 1) the induction of A20/TNF-α interacting protein 3 leading to the inhibition of the TNF receptor-associated factor 6/nuclear factor κB pathway and 2) the activation of AMP-activated protein kinase/autophagy axis leading to the attenuation of caspase-1 cleavage. Collectively, we demonstrated, for the first time, that γT3 inhibits the NLRP3 inflammasome thereby delaying the progression of type 2 diabetes. This study also provides an insight into the novel therapeutic values of γT3 for treating NLRP3 inflammasome-associated chronic diseases.

Significant lethality following liver resection in A20 heterozygous knockout mice uncovers a key role for A20 in liver regeneration

Hepatic expression of A20, including in hepatocytes, increases in response to injury, inflammation and resection. This increase likely serves a hepatoprotective purpose. The characteristic unfettered liver inflammation and necrosis in A20 knockout mice established physiologic upregulation of A20 as integral to the anti-inflammatory and anti-apoptotic armamentarium of hepatocytes. However, the implication of physiologic upregulation of A20 in modulating hepatocytes' proliferative responses following liver resection remains controversial. To resolve the impact of A20 on hepatocyte proliferation and the liver's regenerative capacity, we examined whether decreased A20 expression, as in A20 heterozygous knockout mice, affects outcome following two-third partial hepatectomy. A20 heterozygous mice do not demonstrate a striking liver phenotype, indicating that their A20 expression levels are still sufficient to contain inflammation and cell death at baseline. However, usually benign partial hepatectomy provoked a staggering lethality (>40%) in these mice, uncovering an unsuspected phenotype. Heightened lethality in A20 heterozygous mice following partial hepatectomy resulted from impaired hepatocyte proliferation due to heightened levels of cyclin-dependent kinase inhibitor, p21, and deficient upregulation of cyclins D1, E and A, in the context of worsened liver steatosis. A20 heterozygous knockout minimally affected baseline liver transcriptome, mostly circadian rhythm genes. Nevertheless, this caused differential expression of >1000 genes post hepatectomy, hindering lipid metabolism, bile acid biosynthesis, insulin signaling and cell cycle, all critical cellular processes for liver regeneration. These results demonstrate that mere reduction of A20 levels causes worse outcome post hepatectomy than full knockout of bona fide liver pro-regenerative players such as IL-6, clearly ascertaining A20's primordial role in enabling liver regeneration. Clinical implications of these data are of utmost importance as they caution safety of extensive hepatectomy for donation or tumor in carriers of A20/TNFAIP3 single nucleotide polymorphisms alleles that decrease A20 expression or function, and prompt the development of A20-based liver pro-regenerative therapies.

Oxytocin opposes effects of bacterial endotoxin on ER-stress signaling in Caco2BB gut cells

BACKGROUND

The neuropeptide neuromodulator and hormone oxytocin (OT) activates signaling pathways involved in mRNA translation in response to endoplasmic reticulum stress and reduces inflammation associated with experimental colitis in rats. The anti-inflammatory effects of OT may serve a vital role in the development, survival and function of newborn-type enterocytes during microbial gut colonization, which coincides with the milk suckling period when OT receptor expression peaks in the gut. Furthermore, mice deficient in the OT receptor have abnormal gut structure and function, underscoring OT's developmental importance.

METHODS

We tested the effect of OT upon lipopolysaccharide (LPS)-induced markers of the inflammatory response in Caco2BB gut cells in vitro using automated immunocapillary electrophoresis.

RESULTS

We demonstrate that OT suppresses NF-κB signaling and presumably inflammatory transcriptional programs, which are unleashed by LPS through the modulation of IκB. We show that OT counteracts LPS-elicited silencing of the unfolded protein response, a pathway limiting endoplasmic reticulum stress by suppressing protein translation. OT selectively activates dsRNA-activated kinase (PKR), X-box binding protein 1 (XBP1), immunoglobulin binding protein (BiP), A20 (TNFα-induced protein 3) and inositol requiring enzyme 1a (IRE1a). OT inactivates eukaryotic translation initiation factor 2a (eIF2a) without significant activation of protein kinase RNA-like endoplasmic reticulum kinase (PERK).

CONCLUSIONS

Mild, preemptive stimulation of endoplasmic reticulum stress sensors by OT may precondition newborn enterocytes to resist apoptosis associated with inflammation and may support their differentiation and development by modulating cellular metabolism.

GENERAL SIGNIFICANCE

OT may protect enterocytes and other cell types, such as neurons, from stress-related complications during postnatal development.