Potential roles of nucleotide-binding oligomerization domain 2 in the pathogenesis of systemic lupus erythematosus

NOD-like receptors in autoimmune diseases

Autoimmune diseases are chronic immune diseases characterized by dysregulation of immune system, which ultimately results in a disruption in self-antigen tolerance. Cumulative data show that nucleotide-binding and oligomerization domain (NOD)-like receptors (NLRs) play essential roles in various autoimmune diseases, such as inflammatory bowel disease (IBD), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), psoriasis, multiple sclerosis (MS), etc. NLR proteins, consisting of a C-terminal leucine-rich repeat (LRR), a central nucleotide-binding domain, and an N-terminal effector domain, form a group of pattern recognition receptors (PRRs) that mediate the immune response by specifically recognizing cellular pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs) and triggering numerous signaling pathways, including RIP2 kinase, caspase-1, nuclear factor kappa B (NF-κB), mitogen-activated protein kinase (MAPK) and so on. Based on their N-terminal domain, NLRs are divided into five subfamilies: NLRA, NLRB, NLRC, NLRP, and NLRX1. In this review, we briefly describe the structures and signaling pathways of NLRs, summarize the recent progress on NLR signaling in the occurrence and development of autoimmune diseases, as well as highlight numerous natural products and synthetic compounds targeting NLRs for the treatment of autoimmune diseases.

Nod-like Receptors: Critical Intracellular Sensors for Host Protection and Cell Death in Microbial and Parasitic Infections

Cell death is an essential immunological apparatus of host defense, but dysregulation of mutually inclusive cell deaths poses severe threats during microbial and parasitic infections leading to deleterious consequences in the pathological progression of infectious diseases. Nucleotide-binding oligomerization domain (NOD)-Leucine-rich repeats (LRR)-containing receptors (NLRs), also called nucleotide-binding oligomerization (NOD)-like receptors (NLRs), are major cytosolic pattern recognition receptors (PRRs), their involvement in the orchestration of innate immunity and host defense against bacteria, viruses, fungi and parasites, often results in the cleavage of gasdermin and the release of IL-1β and IL-18, should be tightly regulated. NLRs are functionally diverse and tissue-specific PRRs expressed by both immune and non-immune cells. Beyond the inflammasome activation, NLRs are also involved in NF-κB and MAPK activation signaling, the regulation of type I IFN (IFN-I) production and the inflammatory cell death during microbial infections. Recent advancements of NLRs biology revealed its possible interplay with pyroptotic cell death and inflammatory mediators, such as caspase 1, caspase 11, IFN-I and GSDMD. This review provides the most updated information that caspase 8 skews the NLRP3 inflammasome activation in PANoptosis during pathogen infection. We also update multidimensional roles of NLRP12 in regulating innate immunity in a content-dependent manner: novel interference of NLRP12 on TLRs and NOD derived-signaling cascade, and the recently unveiled regulatory property of NLRP12 in production of type I IFN. Future prospects of exploring NLRs in controlling cell death during parasitic and microbial infection were highlighted.

Strong association of common variants in the miRNA-binding site of NOD2 gene with clinicopathological characteristics and disease activity of systemic lupus erythematosus

INTRODUCTION/OBJECTIVES

Systemic lupus erythematosus (SLE) is a multifactorial systemic autoimmune disease, in which genetic susceptibility plays a pivotal role. The nucleotide oligomerization domain 2 (NOD2) gene is one of the main regulators of chronic inflammatory conditions and could be involved in SLE pathogenesis. Single nucleotide polymorphisms (SNPs) in miRNA binding sites which are located in 3'UTR of the NOD2 gene could be associated with SLE risk by dysregulation of NOD2 expression. In the present study, we assessed the possible association between SNPs rs3135500 and rs3135499 in the NOD2 gene with SLE risk in the Iranian population.

METHODS

A case-control study using 110 SLE patients and 120 control subjects was undertaken to estimate rs3135500 (G > A) and rs3135499 (A > C) genotypes via real-time PCR high-resolution melting method (HRM).

RESULTS

No significant association was observed between allele and genotype frequencies of rs3135500 and rs3135499 polymorphisms and SLE risk in this population (P > 0.05). However, there was an obvious association between rs3135500 (A allele) with laboratory factors that are associated with disease activity (P < 0.05) and some clinical manifestations that are associated with disease severity such as neurological symptoms, skin manifestations, renal involvements, and higher serum concentration of creatinine (P < 0.05). Besides, rs3135499 (C allele) was correlated with renal involvement and also the concentration of creatinine (P < 0.05). Moreover, in the patients group, the risk alleles in these polymorphisms were associated with lower age of onset (P < 0.05).

CONCLUSIONS

Our results suggest a substantial association between NOD2 polymorphisms with clinicopathological characteristics and SLE disease activity. Key Points • Single nucleotide polymorphisms (SNPs) in miRNA binding sites which are located in 3'UTR of the NOD2 gene could be associated with SLE risk by dysregulation of NOD2 expression. • Our results suggested that two miRSNPs (rs3135500 and rs3135499) in the NOD2 gene were meaningfully correlated with clinicopathological characteristics and disease activity of SLE.

Synergistic Activation of Toll-Like and NOD Receptors by Complementary Antigens as Facilitators of Autoimmune Disease: Review, Model and Novel Predictions

Persistent activation of toll-like receptors (TLR) and nucleotide-binding oligomerization domain-containing proteins (NOD) in the innate immune system is one necessary driver of autoimmune disease (AD), but its mechanism remains obscure. This study compares and contrasts TLR and NOD activation profiles for four AD (autoimmune myocarditis, myasthenia gravis, multiple sclerosis and rheumatoid arthritis) and their animal models. The failure of current AD theories to explain the disparate TLR/NOD profiles in AD is reviewed and a novel model is presented that explains innate immune support of persistent chronic inflammation in terms of unique combinations of complementary AD-specific antigens stimulating synergistic TLRs and/or NODs. The potential explanatory power of the model is explored through testable, novel predictions concerning TLR- and NOD-related AD animal models and therapies.