Genetic association of miRNA-146a with systemic lupus erythematosus in Europeans through decreased expression of the gene

The Yin and Yang of microRNAs: leukemia and immunity

Yin and Yang are two complementary forces that together describe the nature of real-world elements. Yin is the dark side; Yang is the light side. We describe microRNAs having both Yin and Yang characteristics because they can contribute to normal function (Yang) but also to autoimmunity, myeloproliferation, and cancer (Yin). We have been working on a number of microRNAs that have these dual characteristics and here we focus on two, miR-125b and miR-146a. We have concentrated on these two RNAs because we have very extensive knowledge of them, much of it from our laboratory, and also because they provide a strong contrast: the effects of overexpression of miR-125b are rapid, suggesting that it acts directly, whereas the effects of miR-146a are slow to develop, suggesting that they arise from chronic alterations in cellular behavior.

Down-regulation of inflammation-protective microRNAs 146a and 212 in monocytes of patients with postpartum psychosis

BACKGROUND

Postpartum psychosis (PP) is thought to belong to the bipolar spectrum. Recently we described an immune activation signature in monocytes of patients with PP using gene expression profiling. Immune activation genes are regulated by microRNAs (miRNAs). We therefore profiled miRNA expression in monocytes of PP patients to identify differentially expressed miRNAs between PP and the healthy state.

METHODS

In a profiling study we carried out miRNA profiling using TaqMan array human microRNA A cards v2.0 and monocytes of 8 PP patients. Data were analyzed against monocytes of healthy postpartum women (CP). Nine miRNAs were selected and tested using individual Q-PCR in a larger validation study on monocytes of 20 PP patients, 20 CP and 20 healthy non-postpartum women (HC).

RESULTS

In the validation study miR-146a expression was significantly down-regulated in the monocytes of first onset PP patients as compared to CP and HC; miR-212 expression was significantly down-regulated in PP patients with prior bipolar disorder. In silico miR-146a targeted 4 genes of the previously described monocyte activation signature in bipolar disorder; miR-212 targeted 2 of such genes. In a correlation study decreased expression of miR-146a in monocytes was related to decreased natural T regulator cells in PP patients; decreased miR-212 was correlated to increased Adrenomedulin and decreased IL-6 expression in monocytes and to higher Th2 cell levels.

CONCLUSIONS

This study identified changes in miR-146a and -212 expression in PP. Since these miRNAs are linked to inflammation, the study strengthens the view that PP is an inflammation-like condition.

Negative regulation of human mononuclear phagocyte function

At mucosal surfaces, phagocytes such as macrophages coexist with microbial communities; highly controlled regulation of these interactions is essential for immune homeostasis. Pattern-recognition receptors (PRRs) are critical in recognizing and responding to microbial products, and they are subject to negative regulation through various mechanisms, including downregulation of PRR-activating components or induction of inhibitors. Insights into these regulatory mechanisms have been gained through human genetic disease-association studies, in vivo mouse studies utilizing disease models or targeted gene perturbations, and in vitro and ex vivo human cellular studies examining phagocytic cell functions. Although mouse models provide an important approach to study macrophage regulation, human and mouse macrophages exhibit differences, which must be considered when extrapolating mouse findings to human physiology. This review discusses inhibitory regulation of PRR-induced macrophage functions and the consequences of dysregulation of these functions and highlights mechanisms that have a role in intestinal macrophages and in human macrophage studies.

Association of MicroRNA-146a with autoimmune diseases

MicroRNAs (miRNAs) are a group of approximately 20-22-nucleotide-long non-coding RNAs that repress target gene expression through mRNA degradation and translation inhibition. MiRNA (miR)-146a, located in the second exon of the LOC285628 gene on human chromosome 5, is a negative regulator in immune and inflammatory responses. Studies have indicated that miR-146a is associated with the pathogenesis of several autoimmune diseases, such as systemic lupus erythematosus, rheumatoid arthritis, and Sjögren's syndrome. In this review, emphasis will be laid on the recent progress in the functional roles of miR-146a in these autoimmune diseases.

MicroRNA control in the development of systemic autoimmunity

Mammalian immune responses are intended to eradicate microbial pathogens and thus protect individuals from the harmful effects of such infections. However, unresolved inflammation can be devastating to the host and cause tissue damage and organ malfunction. Immune responses can even mistakenly target self-antigens and mediate autoimmune inflammation. Consequently, a variety of cellular and molecular mechanisms have evolved to control the inflammatory responses, and many of these safeguards or triggers are perturbed in the setting of autoimmunity. In this review, we discuss the emerging roles of cellular non-coding RNAs, and in particular microRNAs (miRNAs), in the regulation of autoimmune inflammation. How miRNAs function to impact the onset, magnitude, and resolution of inflammatory responses and recent observations regarding links between miRNAs and specific autoimmune disorders will be addressed. Finally, the diagnostic and therapeutic relevance of miRNAs involved in autoimmunity will be considered. It is clear that, taken together, mammalian miRNAs are integral to the pathogenesis of mammalian autoimmune diseases and may be effective targets of next-generation therapeutics aimed at eradicating tissue inflammation.

MicroRNA involvement in lupus: the beginning of a new tale

PURPOSE OF REVIEW

The contributions of microRNA (miRNA) to pathogenesis of autoimmune diseases such as Systemic lupus erythematosus (SLE) are beginning to be uncovered. In this review, we discuss the major progress made in understanding of miRNA biology, as well as novel insights into SLE pathogenesis mediated by miRNAs.

RECENT FINDINGS

MiRNA biogenesis is a deliberately controlled process, which requires multiple layers of regulation involving participation of various protein regulators and posttranscriptional modifications. Its expression regulation is critically modulated by multiple physiopathological factors such as inflammation, stress, Epstein-Barr virus infection and sex hormones. MiRNAs play a crucial role in maintaining immune system development and function, and are implicated in development of numerous immunological disorders. Unique miRNA expression signatures in SLE reveal their clinical relevance. MiRNAs contribute broadly and actively to various aspects of SLE pathogenesis and hold great therapeutic potential.

SUMMARY

The recent findings underscore the potential importance of miRNAs to pathogenesis, diagnosis and treatment of SLE.

Are pre-miR-146a and PTTG1 associated with papillary thyroid cancer?

Papillary thyroid carcinoma (PTC) is the most common endocrine malignancy, with a steadily increasing incidence in the last few decades worldwide. The predisposition to developing this carcinoma by the heterozygous state of rs2910164 within the precursor of the miR-146a has been reported, but recently not confirmed. Interestingly, on the same chromosome, almost 50 kb separate the pre-miR-146a from the pituitary tumor-transforming gene 1 (PTTG1), a proto-oncogene involved in several tumors, including thyroid cancers. In this study, we analyzed, using a case-control design, the genetic association between PTC and the genomic region encompassing pre-miR-146a rs2910164 and PTTG1 rs1862391 and rs2910202. We enrolled 307 affected patients and 206 healthy controls. The possible presence of thyroid nodules in controls was excluded by ultrasonography. All the cases were submitted to single-nucleotide polymorphism (SNP) genotyping of pre-miR-146a and PTTG1, and risk association analyses were carried out. The genotypic and allelic frequencies of pre-miR-146a rs2910164 were not statistically different in the patients and controls, and this SNP was not in linkage disequilibrium with the investigated PTTG1 SNPs. Consistently, meta-analyses, the first including all the affected cases published to date, did not confirm the previously reported association of the heterozygous CG genotype with PTC. The PTTG1 SNPs exhibited the same allelic frequency in the patients and controls and were not associated with the disease. In conclusion, in a well-selected Italian population, neither pre-miR-146a rs2910164 nor PTTG1 rs1862391 and rs2910202 were found to be associated with the risk of developing PTC.

MicroRNAs--novel regulators of systemic lupus erythematosus pathogenesis

Dysregulation of gene expression can cause complex disease phenotypes. MicroRNAs (miRNAs) are well known to fine-tune cellular gene expression to control immune cell development and regulate adaptive and innate immune responses. Discoveries over the past decade have indicated that aberrant expression of miRNAs is associated with the pathogenesis of multiple immunological diseases, including systemic lupus erythematosus (SLE). Indeed, profiling miRNA expression in blood cells, body fluid and target tissues taken from patients with SLE has revealed unique miRNA signatures when compared with healthy individuals or those with other diseases. Moreover, dysregulation of these miRNAs has also been found to be associated with disease activity and major organ involvement. In our opinion, therefore, miRNAs have the potential to act as biomarkers for the diagnosis and assessment of patients with SLE. This Review provides an overview of the novel cellular and molecular mechanisms that seem to underlie the roles of miRNAs in SLE disease processes, as well as the future therapeutic potential of targeting miRNAs in the management of patients with SLE.

MicroRNAs in common human diseases

MicroRNAs (miRNAs) are a class of short non-coding RNA molecules that have attracted tremendous attention from the biological and biomedical research communities over the past decade. With over 1900 miRNAs discovered in humans to date, many of them have already been implicated in common human disorders. Facilitated by high-throughput genomics and bioinformatics in conjunction with traditional molecular biology techniques and animal models, miRNA research is now positioned to make the transition from laboratories to clinics to deliver profound benefits to public health. Herein, we overview the progress of miRNA research related to human diseases, as well as the potential for miRNA to becoming the next generation of diagnostics and therapeutics.

Gene network analysis of small molecules with autoimmune disease associated genes predicts a novel strategy for drug efficacy

Numerous genes/SNPs in autoimmune diseases (ADs) are identified through genome-wide association studies (GWAS) and likely to contribute in developing autoimmune phenotypes. Constructions of biologically meaningful pathways are necessary to determine how these genes interact with each other and with other small molecules to develop various complex AD phenotypes prior to beginning time-consuming rigorous experimentation. We have constructed biological pathways with genetically identified genes leading to shared AD phenotypes. Various environmental and endogenous factors interact with these AD associated genes suggesting their critical role in developing diseases and further association studies could be designed for assessing the role of these factors with risk allele in a specific gene. Additionally, existing drugs that have been used long before the identification of these genetically associated genes also interact with these newly associated genes. Thus advanced therapeutic strategies could be designed by grouping patients with risk allele(s) in particular genes that directly or closely interact with the specified drugs. This drug-susceptible gene network will not only increase our understanding about the additional molecular basis for effectiveness against these diseases but also indicate which drug could be more effective for those patients carrying risk allele(s) in that gene. Additionally, we have also identified several interlinking genes in the pathways that could be used for designing future association studies.

MicroRNAs and autoimmunity

The role of microRNAs (miRNAs) in the regulation of many physiological and pathological processes has been intensely studied in recent years. Some miRNAs, such as miR-146a and miR-182, play a dominant role in the regulation of the innate and adaptive immune responses, respectively. Many miRNAs are reportedly deregulated in autoimmune diseases, but miR-146a in particular seems to be consistently altered. The overexpression or underexpression of miRNAs can influence specific targets and pathways, leading to autoimmune disease phenotypes, and this is supported also by some in vivo studies. Targeting miRNAs could represent a valid future therapeutic option for autoimmune diseases.

MiR-146a polymorphism is associated with asthma but not with systemic lupus erythematosus and juvenile rheumatoid arthritis in Mexican patients

Extensive research has shown that aberrant expression of microRNAs (miRNAs) plays an important role in innate and adaptive immune responses. The rs2910164 polymorphism has been identified as a functional variant, which affects the transcription and expression level of miR-146a and, thereby, contributes to the pathogenesis of several inflammatory and autoimmune diseases. To investigate whether the rs2910164 G/C polymorphism was associated with asthma, systemic lupus erythematosus (SLE) or juvenile rheumatoid arthritis (JRA), we performed an association study in a pediatric Mexican cohort. We included 979 pediatric patients (asthma: 402, SLE: 367 and JRA: 210) and 531 control subjects without inflammatory or immune diseases. Genotyping was performed using the 5' exonuclease technique. The genotype distribution of the rs2910164 polymorphism was in Hardy-Weinberg equilibrium in each group. No significant differences were detected in the distribution of this polymorphism between cases and controls (P = 0.108, 0.609 and 0.553 for subjects with asthma, JRA and SLE, respectively). However, stratification by gender showed a statistically significant difference between asthmatic and control females, where the C allele was significantly associated with protection to asthma (odds ratio = 0.694, 95% confidence interval 0.519-0.929, P = 0.0138). Our results provide evidence that rs2910164 may play a role in the susceptibility to childhood-onset asthma, but not SLE or JRA in Mexicans. Further association studies may contribute to determining the role of miR-146a single-nucleotide polymorphisms in immune-mediated diseases.

Genetic susceptibility to lupus: the biological basis of genetic risk found in B cell signaling pathways

Over 50 genetic variants have been statistically associated with the development of SLE (or lupus). Each genetic association is a key component of a pathway to lupus pathogenesis, the majority of which requires further mechanistic studies to understand the functional changes to cellular physiology. Whereas their use in clinical practice has yet to be established, these genes guide efforts to develop more specific therapeutic approaches. The BCR signaling pathways are rich in lupus susceptibility genes and may well provide novel opportunities for the understanding and clinical treatment of this complex disease.

miRNA in systemic lupus erythematosus

Since their recent discovery, the small noncoding RNA known as microRNAs (miRNA) have been reported to play a major role in the physiological control of gene expression and in the pathogenesis of malignant, infectious, and autoimmune disorders. In systemic lupus erythematosus (SLE), an autoimmune disease characterized by the presence of autoantibodies to multiple antigens, the role of miRNA as post-transcriptional regulators of different aspects of the disease process has recently emerged. This article reviews the pertinent literature and mechanisms of action of miRNA that have so far been associated with the pathogenesis of SLE.