Defective activation of the MAPK/ERK pathway, leading to PARP1 and DNMT1 dysregulation, is a common defect in IgA nephropathy and Henoch-Schönlein purpura

The Role of Clonal Hematopoiesis of Indeterminant Potential and DNA (Cytosine-5)-Methyltransferase Dysregulation in Pulmonary Arterial Hypertension and Other Cardiovascular Diseases

DNA methylation is an epigenetic mechanism that regulates gene expression without altering gene sequences in health and disease. DNA methyltransferases (DNMTs) are enzymes responsible for DNA methylation, and their dysregulation is both a pathogenic mechanism of disease and a therapeutic target. DNMTs change gene expression by methylating CpG islands within exonic and intergenic DNA regions, which typically reduces gene transcription. Initially, mutations in the DNMT genes and pathologic DNMT protein expression were found to cause hematologic diseases, like myeloproliferative disease and acute myeloid leukemia, but recently they have been shown to promote cardiovascular diseases, including coronary artery disease and pulmonary hypertension. We reviewed the regulation and functions of DNMTs, with an emphasis on somatic mutations in DNMT3A, a common cause of clonal hematopoiesis of indeterminant potential (CHIP) that may also be involved in the development of pulmonary arterial hypertension (PAH). Accumulation of somatic mutations in DNMT3A and other CHIP genes in hematopoietic cells and cardiovascular tissues creates an inflammatory environment that promotes cardiopulmonary diseases, even in the absence of hematologic disease. This review summarized the current understanding of the roles of DNMTs in maintenance and de novo methylation that contribute to the pathogenesis of cardiovascular diseases, including PAH.

Transmembrane signaling molecules play a key role in the pathogenesis of IgA nephropathy: a weighted gene co-expression network analysis study

BACKGROUND

Immunoglobulin A nephropathy (IgAN) is one of the most common primary glomerulonephritis and a serious health concern worldwide; though still the underlying molecular mechanisms of IgAN are yet to be known and there is no efficient treatment for this disease. The main goal of this study was to explore the IgAN underlying pathogenic pathways, plus identifying the disease correlated modules and genes using the weighted gene co-expression network analysis (WGCNA) algorithm.

RESULTS

GSE104948 dataset (the expression data from glomerular tissue of IgAN patients) was analyzed and the identified differentially expressed genes (DEGs) were introduced to the WGCNA algorithm for building co-expression modules. Genes were classified into six co-expression modules. Genes of the disease's most correlated module were mainly enriched in the immune system, cell-cell communication and transmembrane cell signaling pathways. The PPI network was constructed by genes in all the modules and after hub-gene identification and validation steps, 11 genes, mostly transmembrane proteins (CD44, TLR1, TLR2, GNG11, CSF1R, TYROBP, ITGB2, PECAM1), as well as DNMT1, CYBB and PSMB9 were identified as potentially key players in the pathogenesis of IgAN. In the constructed regulatory network, hsa-miR-129-2-3p, hsa-miR-34a-5p and hsa-miR-27a-3p, as well as STAT3 were spotted as top molecules orchestrating the regulation of the hub genes.

CONCLUSIONS

The excavated hub genes from the hearts of co-expressed modules and the PPI network were mostly transmembrane signaling molecules. These genes and their upstream regulators could deepen our understanding of IgAN and be considered as potential targets for hindering its progression.

IgA Vasculitis: Etiology, Treatment, Biomarkers and Epigenetic Changes

IgA, previously called Henoch-Schönlein vasculitis, is an essential immune component that drives the host immune response to the external environment. As IgA has the unique characteristic of a flexible response to broad types of microorganisms, it sometimes causes an autoreactive response in the host human body. IgA vasculitis and related organ dysfunction are representative IgA-mediated autoimmune diseases; bacterial and viral infections often trigger IgA vasculitis. Recent drug developments and the presence of COVID-19 have revealed that these agents can also trigger IgA vasculitis. These findings provide a novel understanding of the pathogenesis of IgA vasculitis. In this review, we focus on the characteristics of IgA and symptoms of IgA vasculitis and other organ dysfunction. We also mention the therapeutic approach, biomarkers, novel triggers for IgA vasculitis, and epigenetic modifications in patients with IgA vasculitis.

ADP-ribosylation in evasion, promotion and exacerbation of immune responses

ADP-ribosylation is the addition of one or more (up to some hundreds) ADP-ribose moieties to acceptor proteins. This evolutionary ancient post-translational modification (PTM) is involved in fundamental processes including DNA repair, inflammation, cell death, differentiation and proliferation, among others. ADP-ribosylation is catalysed by two major families of enzymes: the cholera toxin-like ADP-ribosyltransferases (ARTCs) and the diphtheria toxin-like ADP-ribosyltransferases (ARTDs, also known as PARPs). ARTCs sense and use extracellular NAD, which may represent a danger signal, whereas ARTDs are present in the cell nucleus and/or cytoplasm. ARTCs mono-ADP-ribosylate their substrates, whereas ARTDs, according to the specific family member, are able to mono- or poly-ADP-ribosylate target proteins or are devoid of enzymatic activity. Both mono- and poly-ADP-ribosylation are dynamic processes, as specific hydrolases are able to remove single or polymeric ADP moieties. This dynamic equilibrium between addition and degradation provides plasticity for fast adaptation, a feature being particularly relevant to immune cell functions. ADP-ribosylation regulates differentiation and functions of myeloid, T and B cells. It also regulates the expression of cytokines and chemokines, production of antibodies, isotype switch and the expression of several immune mediators. Alterations in these processes involve ADP-ribosylation in virtually any acute and chronic inflammatory/immune-mediated disease. Besides, pathogens developed mechanisms to contrast the action of ADP-ribosylating enzymes by using their own hydrolases and/or to exploit this PTM to sustain their virulence. In the present review, we summarize and discuss recent findings on the role of ADP-ribosylation in immunobiology, immune evasion/subversion by pathogens and immune-mediated diseases.

Association analysis of DNA methyltransferases in IgA nephropathy

DNA methylation, especially DNA methyltransferases (DNMTs), is involved in the pathogenesis of many autoimmune diseases through regulating immune function. This study aimed to explore the potential role of DNMTs in IgA nephropathy (IgAN). We evaluated mRNA expressions of DNMT1, DNMT3A, DNMT3B along with β1,3-galactosyltransferase (C1GALT1) in peripheral blood mononuclear cells (PBMCs), and measured galactose-deficient IgA1 (Gd-IgA1) levels in plasma. The expression intensity of DNMT1 and DNMT3B in the renal specimen of IgAN patients were also detected. Results showed DNMT3B, not DNMT1 or DNMT3A, was notably increased in IgAN patients compared to controls and associated with pathologic types. However, DNMT1 and C1GALT1 were found positively correlated with estimated glomerular filtration rate (eGFR) and negatively correlated with 24 h Urine protein in IgAN patients. No association was found between DNMT1 and Gd-IgA1. The expressions of DNMT3B and DNMT1 were barely observed in IgAN renal biopsy specimens. In conclusion, for the first time, we identified the relations of DNMTs and C1GALT1 to the clinical state and pathology of IgAN patients, which provide new clues for IgAN.

MicroRNA-21-5p participates in IgA nephropathy by driving T helper cell polarization

BACKGROUND

Previous studies have revealed abnormal lymphocyte subsets in IgA nephropathy (IgAN). Some microRNAs have been reported to influence T helper differentiation. Here, we explored the underlying mechanism regarding how miRNAs regulate lymphocyte subsets in IgAN.

METHODS

First, miRNA and mRNA profiles in PBMCs from IgAN patients and controls were obtained by next-generation sequencing and gene expression array. The target miRNAs and mRNAs were identified through combined analysis. Then, in an independent population, we detected the expression of target miRNA in CD3⁺ T cells and CD19⁺ B cells. Next, we detected T helper cell subgroups and plasma IgA1 levels in another independent population and analyzed the correlations between them.

RESULTS

In total, 22 differentially expressed miRNAs were identified between IgAN patients and controls. Among them, microRNA-21-5p (miR-21) showed the highest expression, and SPRY1, SPRY2, and FASLG were chosen as miR-21 target genes. Then, we confirmed elevated miR-21 levels in CD3⁺ T cells of IgAN patients. Accordingly, decreased mRNA levels of SPRY1, SPRY2, and FASLG were found, and miR-21 showed a significant negative correlation with SPRY1 levels in CD3⁺ T cells of IgAN patients. Finally, we revealed that the proportion of Th17 cells was significantly elevated in IgAN patients and negatively correlated with SPRY1 expression. Furthermore, the proportion of Th17 cells showed a positive correlation trend with plasma IgA1 levels.

CONCLUSIONS

Our results suggested that in IgAN, the upregulated miR-21 expression in T lymphocytes inhibited SPRY1 expression and thereby induced Th17 polarization, which might influence the characteristic feature of IgA1 overproduction in IgAN patients.