In vitro silencing of RIP2 in naive CD4+ T cells from lupus-prone mice promotes pathogenic Th17 cell differentiation

OBJECTIVE

This work aims to investigate whether RIP2 silencing in naive CD4+ T cells from lupus-prone mice impacts Th17 cell activity or differentiation in vitro.

METHODS

Naive CD4+ T cells isolation from MRL/lpr mice's spleens. Three RNA interference target sequences of RIP2 were packaged with lentivirus and transfected into naive CD4+ T cells. The shRIP2 with the highest interference efficiency was selected and transfected into naive CD4+ T cells. Naive CD4+ T cells were cultured under conventional (TGF-β1 and IL-6) and pathogenic (IL-6, IL-23, IL-1β) differentiation environments, respectively. Then, RT-qPCR, Western blot or Flow Cytometry were used for measuring the amounts of RIP2 and IL-17 and the differentiation of Th17 cells in two settings.

RESULTS

Under the conventional Th17 (cTh17) cell differentiation environment (TGF-β1 and IL-6), RIP2 deficiency is linked to decreased IL-17A levels (1.00 ± 0.03 vs 0.80 ± 0.03) and attenuated cTh17 cell (2.46 ± 0.08 vs 0.78 ± 0.03) differentiation (all, P < 0.05). Under the pathogenic Th17 (pTh17) cell environment (IL-1β, IL-23, IL-6), RIP2 deficiency is linked to elevated IL-17A levels (1.03 ± 0.05 vs 1.63 ± 0.07) and enhanced pTh17 cell (3.69 ± 0.19 vs 5.49 ± 0.10) differentiation (all, P < 0.05).

CONCLUSION

Our data suggest that RIP2 inhibition induces preferential differentiation of naive CD4+ T cells to pathogenic Th17 cells, while being able to upregulate IL-17A levels in the context of pTh17 cell differentiation. Our study opens up new research areas to reveal the underlying mechanisms and potential therapeutic targets for the prevention and treatment of SLE patients. Key Points • Silencing of RIP2 in naive CD4+ T cells from lupus-prone mice promotes pathogenic Th17 (pTh17) cell differentiation and IL-17A production under pTh17 cell (IL-1β, IL-23, and IL-6) conditions. • RIP2 deficiency in naive CD4+ T cells reduces conventional Th17 (cTh17) cell differentiation and IL-17A production under cTh17 cell (TGF-β1 and IL-6) conditions. • RIP2-deficient naive CD4+ T cells preferentially differentiate towards pTh17 cells rather than cTh17 cells in vitro. • Inhibition of RIP2 may be involved in the development of SLE via effects on Th17/IL-17.

RIPK2 as a promising druggable target for autoimmune diseases

Receptor Interacting Serine/Threonine Kinase 2 (RIPK2) is an essential regulator of the inflammatory process and immune response. In innate immunity, the NOD-RIPK2 signaling axis is an important pathway that directly mediates inflammation and immune response. In adaptive immunity, RIPK2 may affect T cell proliferation, differentiation and cellular homeostasis thereby involving T cell-driven autoimmunity, but the exact mechanism remains unclear. Recent advances suggest a key role of RIPK2 in diverse autoimmune diseases (ADs) such as inflammatory bowel diseases, rheumatoid arthritis, multiple sclerosis, systemic lupus erythematosus, and Behcet's disease. This review aims to provide valuable therapeutic direction for ADs by focusing on the function and modulation of RIPK2 in innate and adaptive immunity, its involvement with various ADs and the application of RIPK2-related drugs in ADs. We raise the notion that drug targeting RIPK2 could be a promising therapeutic strategy for the treatment of ADs, though much work remains to be done for clinical application.

Immune modulating effects of receptor interacting protein 2 (RIP2) in autoinflammation and immunity

Receptor-interacting protein 2 (RIP2) is a kinase that is involved in downstream signaling of nuclear oligomerization domain (NOD)-like receptors NOD1 and 2 sensing bacterial peptidoglycans. RIP2-deficiency or targeting of RIP2 by pharmaceutical inhibitors partially ameliorates inflammatory diseases by reducing pro-inflammatory signaling in response to peptidoglycans. However, RIP2 is widely expressed and interacts with several other proteins suggesting additional functions outside the NOD-signaling pathway. In this review, we discuss the immunological functions of RIP2 and its possible role in autoinflammation and immunity.

RIPK2 polymorphisms and susceptibility to tuberculosis in a Western Chinese Han population

OBJECTIVE

Host genetic factors play an important role in susceptibility to Mycobacterium tuberculosis (MTB) infection and tuberculosis (TB). Receptor interacting-serine/threonine-protein kinase 2 (RIPK2) is a critical adapter protein for signal propagation of NOD2, dysregulation of which leads to defects in bacterial detection. To investigate the role of RIPK2 on the susceptibility of tuberculosis, we conducted a large sample size case-control study in a Western Chinese Han population.

METHODS

Five single-nucleotide polymorphisms (SNPs) within or near to RIPK2 were genotyped in 1359 TB cases and 1534 controls using the improved multiplex ligation detection reaction method in a case-control study.

RESULTS

Of the five variants, rs39509 was observed to be associated with TB risk in the allelic effects (P = 0.015), additive (P = 0.020) and recessive model (P = 0.005) after Bonferroni correction. Rs39509 might fall in putative functional regions and might be eQTL for the RIPK2 and long non-coding RNA RP11-37B2.1 according to the Genotype-Tissue Expression (GTEx) Project.

CONCLUSIONS

Our findings firstly exhibit that the G allele of rs39509 in nearGene-3 region of RIPK2 might serve as a hazard for TB in this Western Chinese Han population. Further validation studies on a variety of ethnic populations and function experiments are needed to confirm the roles of the variants identified.

RIP2 promotes FcγR-mediated reactive oxygen species production

Receptor-interacting protein 2 (RIP2) is a kinase that mediates signaling downstream of the bacterial peptidoglycan sensors NOD1 and NOD2. Genetic loss or pharmaceutical inhibition of RIP2 has been shown to be beneficial in multiple inflammatory disease models with the effects largely attributed to reducing proinflammatory signaling downstream of peptidoglycan recognition. However, given the widespread expression of this kinase and its reported interactions with numerous other proteins, it is possible that RIP2 may also function in roles outside of peptidoglycan sensing. In this work, we show that RIP2 undergoes tyrosine phosphorylation and activation in response to engagement of the Fc γ receptor (FcγR). Using bone marrow-derived macrophages from WT and RIP2-KO mice, we show that loss of RIP2 leads to deficient FcγR signaling and reactive oxygen species (ROS) production upon FcγR cross-linking without affecting cytokine secretion, phagocytosis, or nitrate/nitrite production. The FcγR-induced ROS response was still dependent on NOD2, as macrophages deficient in this receptor showed similar defects. Mechanistically, we found that different members of the Src family kinases (SFKs) can promote RIP2 tyrosine phosphorylation and activation. Altogether, our findings suggest that RIP2 is functionally important in pathways outside of bacterial peptidoglycan sensing and that involvement in such pathways may depend on the actions of SFKs. These findings will have important implications for future therapies designed to target this kinase.

Association between receptor interacting serine/threonine kinase 2 polymorphisms and gastric cancer susceptibility

The present study aimed to investigate whether single nucleotide polymorphisms in receptor interacting serine/threonine kinase 2 (RIPK2), which encodes a component of the nucleotide binding oligomerization domain containing 2-RIP2 pathway, may compromise the innate immune response to Helicobacter pylori infection, leading to increased susceptibility to gastric cancer in the Japanese population. The present case control study investigated the associations between RIPK2 single nucleotide polymorphisms and gastric mucosal inflammation, atrophy and cancer susceptibility in 528 patients with gastric cancer and 697 patients without gastric malignancies on upper gastro-duodenal endoscopy. Overall, the RIPK2 rs16900627 minor allele was significantly associated with the susceptibility to gastric cancer [OR, 1.37; 95% confidence interval (CI), 1.06-1.77; P=0.016], particularly of the intestinal type (OR, 1.53; 95% CI, 1.13-2.07; P=0.0062). It was also significantly associated with gastric mucosal atrophy (OR, 1.83; 95% CI, 1.14-2.93; P=0.011). When assessing the severity of chronic gastritis using the updated Sydney system, the activity and inflammation scores, as well as atrophy and metaplasia scores, were significantly higher in rs16900627 minor allele carriers compared with wild-type homozygotes. In patients younger than 60 years old, the pepsinogen I/II ratio was significantly lower in rs16900627 minor allele carriers compared with wild-type homozygotes (P=0.037). The rs16900627 minor allele is associated with the severity of gastric mucosal inflammation and the development of gastric mucosal atrophy. Carriers of this allele may have an increased risk for the development of gastric cancer, particularly of the intestinal type.

Receptor-interacting protein 2 (RIP2) gene polymorphisms are associated with increased risk of subclinical atherosclerosis and clinical and metabolic parameters. The Genetics of Atherosclerotic Disease (GEA) Mexican study

The receptor-interacting protein 2 (Rip2) is a serine/threonine kinase involved in multiple nuclear factor-κB (NFκB) activation pathways and is a key regulator of cellular lipid metabolism and cardiovascular disease. The aim of the present study was to evaluate the role of RIP2 gene polymorphisms as susceptibility markers for subclinical atherosclerosis (SA). Using an informatics analysis, four RIP2 gene polymorphisms with predicted functional effects (rs2293808, rs43133, rs431264, and rs16900627) were selected. The polymorphisms were genotyped in 405 individuals with SA (calcium score>0 assessed by computed tomography) and 1099 controls (calcium score=0). Clinical, anthropometric, tomographic and biochemical traits were measured. The association between the RIP2 polymorphisms and SA was evaluated using logistic regression analyses. Pair wise linkage disequilibrium (LD, D') estimations between polymorphisms and haplotype reconstruction were performed with Haploview version 4:1. Under different models adjusted by age, gender, body mass index, hypertension, diabetes mellitus, smoking habit, total cholesterol, HDL-cholesterol, LDL-cholesterol and triglyceride levels, rs43133 (OR=1.43, 95% CI: 1.05-1.94, P=0.022), and rs16900627 (OR=1.59, 95% CI: 1.00-2.54, P_dom=0.048 and OR=1.60, 95% CI: 1.05-2.54, P_add=0.028) were associated with increased risk of developing SA. Moreover, rs2293808, and rs431264 were associated with clinical or metabolic parameters in SA individuals and in healthy controls. The four polymorphisms were in high linkage disequilibrium and the GAAG haplotype was associated with increased risk of developing SA (OR=1.47, P=0.027). This study shows for the first time, that RIP2 polymorphisms are associated with increased risk of SA and with some clinical and metabolic parameters.

Role of Rip2 in development of tumor-infiltrating MDSCs and bladder cancer metastasis

Tumor invasion and metastases represent a complex series of molecular events that portends a poor prognosis. The contribution of inflammatory pathways mediating this process is not well understood. Nod-like receptors (NLRs) of innate immunity function as intracellular sensors of pathogen motifs and danger molecules. We propose a role of NLRs in tumor surveillance and in programming tumor-infiltrating lymphocytes (TILs). In this study, we examined the downstream serine/threonine and tyrosine kinase Rip2 in a murine model of bladder cancer. In Rip2-deficient C57Bl6 mice, larger orthotopic MB49 tumors developed with more numerous and higher incidence of metastases compared to wild-type controls. As such, increased tumor infiltration of CD11b⁺Gr1^hi myeloid-derived suppressor cells (MDSCs) with concomitant decrease in T cells and NK cells were observed in Rip2-deficient tumor bearing animals using orthotopic and subcutaneous tumor models. Rip2-deficient tumors showed enhanced epithelial-to-mesenchymal transition, with elevated expression of zeb1, zeb2, twist, and snail in the tumor microenvironment. We found that the absence of Rip2 plays an intrinsic role in fostering the development of granulocytic MDSCs by an autocrine and paracrine effect of granulocytic colony stimulating factor (G-CSF) expression. Our findings suggest that NLR pathways may be a novel modality to program TILs and influence tumor metastases.

The deubiquitinase A20 in immunopathology of autoimmune diseases

Deubiquitination-mediated regulation is important for homeostatic NF-κB activation. Aberrant NF-κB activation associated with various inflammatory and autoimmune disorders is linked with defects in the deubiquitinase A20. A20 is an important anti-inflammatory molecule that is induced by multiple signals and has numerous targets. Polymorphisms within the A20 locus or its altered expression are thought to contribute in development of autoimmune disorders. Further various studies in mice models underscore the biological importance of A20 in prevention of inflammatory conditions. Dysregulated A20 is also been suggested as a link between prolonged inflammation and cancer by preliminary reports. This review summarizes the existing understanding and focuses on the new developments in the field of A20 biology. These developments highlight the importance of A20 in pathophysiology of autoimmune disorders and its scope as therapeutics and a biomarker.