Features of kidney structural changes in IgA-nephropathy with isolated detection of IgA class antibodies to deamidated gliadin peptides in the serum

IgA Nephropathy

BACKGROUND AND AIMSSeveral models have been proposed to describe the pathogenesis of Immunoglobulin A nephropathy (IgAN) and, among them, the multihit model where the gut-microbiota may play an important role. These models explain the pathogenesis of IgAN caused by the production of aberrant IgA, but it is believed that further predisposing factors are present, including immunological, genetic, environmental or nutritional factors.Recently, the role of IL-6 in IgAN pathogenesis is becoming increasingly important. It is essential for the deposition of glomerular immunoglobulin A and the development of renal disease in Cd37-deficient mice, although the pathogenetic mechanisms that determine its increase are not well known.A possible hypothesis emerges from our recent work on genome-wide DNA methylation screening in patients with IgAN, which identified, among other findings, a hypermethylated region comprising Vault 2–1 RNA (VTRNA2-1), a non-RNA coding also known as a precursor of miR-886 (pre-mi-RNA). Consistently, VTRNA2-1 expression was found downregulated in IgAN patients.Here we studied the involvement of the VTRNA2-1/PKR/CREB/IL-6 pathway in IgAN.METHODTotal RNA were isolated from PBMCs of IgAN patients, transplanted IgAN patients (TP-IgAN), non-IgAN transplanted patients (TP) and healthy subjects (HS). VTRNA2-1, CREB and PKR transcripts were evaluated by RT-PCR. Total and phosphorylated PKR, CREB and Il-6 proteins were evaluated by ELISA. Poly (I: C), a synthetic analogue of dsRNA and Pfizer-BioNTech COVID-19 COMIRNATY vaccine were used to transfect patient PBMCs. PKR inhibitor imoxin (C16) 1 µM was used to stimulate patient PBMCs.RESULTSHere we confirm that VTRNA2-1 transcript was down-regulated in native and transplanted IgAN subjects compared to HS and non IgAN transplanted patients, with a decrease of 30- and 100-folds, respectively (P < 0.05, and P < 0.0001). IgAN patients with downregulated VTRNA2-1 showed a PKR overactivation (fold increase of phosphorilation of 2.6- in IgAN and 2-folds in TP-IgAN patients; P < 0.05), coherently with the role played by VTRNA2-1 that binds to PKR and inhibits its phosphorylation. Then, we found that PKR causes the activation of CREB, a classical cAMP-inducible CRE-binding factor (fold increase of phosphorilation of 3- in IgAN and 2.67-folds in TP-IgAN patients; P < 0.01). CREB, interacting with a region of the IL-6 promoter, led to IL-6 production. Indeed, in IgAN patients we showed a IL-6 mean increase to 120 pg/mL compared to the respective controls (P < 0.05). Moreover, the IL-6 levels correlated with CREB and PKR phosphorylation (r = 0.97; P = 0.0006 and r = 0.89; P = 0.0064, respectively, for IgAN and TP-IgAN patients).Since PKR is normally activated by bacterial and viral RNA, we hypothesized that these microorganisms can further activate the PKR/CREB/IL-6 pathway leading to an excess of IL-6 production. This may explain both the high levels of IL-6, and infection involvement in the disease, and cases of IgAN associated with COVID-19 infection or with COVID-19 RNA-vaccination, and recent data showing microbiota involvement in IgAN. Effectively, we found that IgAN PMBCs stimulated with RNA poly(I: C) or the COVID-19 RNA-vaccine showed a significant increase in IL-6 levels compared to not-stimulated PBMCs (P < 0.05), supporting the pathogentic role played by viral RNA in IgAN pathogenesis and explaining the cases of IgAN patients developing episodes of macrohematuria after a COVID-19 infection or vaccination.Finally, we showed that the IL-6 secretion can be reduced by the PKR inhibitor imoxin (fold decrease of 5-folds in IgAN and TP-IgAN patients; P < 0.05).CONCLUSIONIn conclusion, the discovery of the upregulated VTRNA2-1/PKR/CREB/IL-6 pathway in IgAN patients may provide a new pathogenic mechanism in IgAN and may be useful for the development of novel therapeutic approaches, likely by modulating the VTRNA2-1 methylation level in IgAN patients.

Advances in our understanding of the pathogenesis of immunoglobulin A nephropathy (IgAN) have led to the identification of novel therapeutic targets and potential disease-specific treatments. Specifically, a proliferation-inducing ligand (APRIL) has been implicated in the pathogenesis of IgAN, mediating B-cell dysregulation and overproduction of pathogenic galactose-deficient IgA1 (Gd-IgA1). Animal and clinical studies support the involvement of APRIL in the pathogenesis and progression of IgAN. An elevated level of APRIL is found in IgAN when compared with controls, which correlates with the level of Gd-IgA1 and associates with more severe disease presentation and worse outcomes. Conversely, anti-APRIL therapy reduces pathogenic Gd-IgA1 and IgA immune complex formation and ameliorates the severity of kidney inflammation and injury. Genome-wide association studies in IgAN have identified TNFSF13 and TNFRSF13B, a cytokine ligand-receptor gene pair encoding APRIL and its receptor, respectively, as risk susceptibility loci in IgAN, further supporting the causal role of the APRIL signalling pathway in IgAN. Several novel experimental agents targeting APRIL, including atacicept, telitacicept, zigakibart and sibeprenlimab, are currently under investigation as potential therapies in IgAN. Preliminary results suggest that these agents are well-tolerated, and reduce levels of Gd-IgA1, with corresponding improvement in proteinuria. Further studies are ongoing to confirm the safety and efficacy of anti-APRIL approaches as an effective therapeutic strategy in IgAN.

Background. Immunoglobulin A nephropathy (IgAN) is a serious medical problem reported to be one of the most common causes of terminal renal failure. Current research increasingly focuses on the role of intestinal mucosa-associated lymphoid tissue (MALT) in IgAN pathogenesis, especially under the effect of food antigens, such as gluten. Patients with IgAN often have IgA antibodies to deamidated gliadin peptides (antiDGP IgA). Studying their isolated carriage can help in the development of new diagnostic and therapeutic methods aimed at regulating intestinal immune response and managing the highly active course and progression of IgAN.Objective: To establish the clinical and diagnostic role of anti-DGP IgA in IgAN patients for the development of additional personalized clinical approaches and optimization of treatment strategies.Material and methods. A total of 105 IgAN patients aged 18 to 64 years participated in the controlled, prospective, comparative, cohort study. Demographic, anamnestic, clinical, and treatment data were used. The blood of patients was tested for celiac-specific antibodies: anti-DGP IgA, IgA antibodies to tissue transglutaminase (anti-TTG IgA), IgA antibodies to endomysium. As a result, patients were divided into two groups depending on the presence of anti-DGP IgA: the main group (n=20) comprising IgAN patients with detected antibodies and the control group (n=85) consisting of patients seronegative for celiac antibodies. One patient was seropositive for both anti-DGP and anti-TTG IgA.Results. As compared to the control group, the patients of the main group exhibited higher IgAN activity, which was assessed in terms of morning proteinuria (0.96 [0.70–1.60] g/l; p=0.005), daily proteinuria (1.50 [0.70–2.50] g/day; p=0.014), erythrocyturia (20.00 [15.00–25.00] per high power field; p=0.015), as well as levels of systolic (147.65±12.06 mm Hg; p=0.001) and diastolic (94.35±12.78 mm Hg; p=0.006) blood pressure. The detection of anti-DGP IgA was associated with a high concentration of serum IgA (4.35±1.06 g/l; p &lt; 0.001). The direct correlation between anti-DPG IgA and IgA (ρ=0.247; p=0.020) can most likely be attributed to the hyperreactivity of IgA-producing B-lymphocytes of the intestinal mucosa in response to gluten. In the main group, the risk of a 50% decrease in the estimated glomerular filtration rate or progression to terminal renal failure within 5 years after the performed renal biopsy was statistically significantly higher than in the control group (15.05% [9.32–20.91] vs. 7.99% [4.97–11.73]; p=0.015).Conclusion. The obtained results indicate the possibility of using anti-DGP IgA as a potential risk marker for IgAN progression. Further studies into the effect of food antigens on the immune response in IgAN opens up new prospects for the development of effective treatment methods.

Cytokine gene polymorphisms: Can these differentiate renal disease entities?

Immunoglobulin A nephropathy (IgAN) is the most prevalent glomerulonephritis in the world, and it is one of the leading causes of end-stage kidney disease. It is now believed that the pathogenesis of IgAN is the mesangial deposition of immune complex containing galactose-deficient IgA1, resulting in glomerular injury. Current treatments for IgAN include supportive care and immunosuppressive therapy. A growing number of studies found that the gut microbiota in IgAN was dysregulated. Gut microbiota may be involved in the development and progression of IgAN through three main aspects: destruction of intestinal barrier, changes in metabolites and abnormal mucosal immunity. Interestingly, therapies by modulating the gut microbiota, such as fecal microbiota transplantation, antibiotic treatment, probiotic treatment, Chinese herbal medicine Zhen Wu Tang treatment, gluten-free diet, and hydroxychloroquine treatment, can improve IgAN. In this review, the alteration of gut microbiota in IgAN, potential pathogenic roles of gut microbiota on IgAN and potential approaches to treat IgAN by modulating the gut microbiota are summarized.

IgA nephropathy (IgAN) is one of the most common causes of glomerulonephritis in the world. The proliferative and crescentic forms of IgA are found in up to 30% of cases and are associated with nephritic-range proteinuria, accelerated hypertension, and accelerated decline toward ESRD. Thus, it is important to investigate the mechanism of the onset of IgAN and to identify the most appropriate treatment. We herein review the pathogenesis and treatment of IgA nephropathy. As to the pathogenesis, we found that CB4 provoked exacerbation of renal pathologic findings in HIGA mice via endothelial injury, IFN-gamma production, and dysfunction of the mesangial pathway and could possibly become one of the factors involved in the mechanism of the onset or evolution of human IgAN. As to the treatment of IgAN, we evaluated the efficacy of tonsillectomy plus prednisolone, warfarin, and dipyridamole including methylprednisolone pulse therapy (tonsillectomy plus pulse therapy) and prednisolone, warfarin, and dipyridamole including mizoribine (PWDM) for the treatment of diffuse IgAN in children. These therapies were effective in ameliorating the proteinuria and histological severity of patients with IgAN. Furthermore the detail investigations into the pathogenesis of IgAN and double-blind randomized control studies on children with IgAN will be necessary.

Abnormal IgA1 O-Glycosylation in a Multi-ethnic population of IgA Nephropathy Patients in KwaZulu Natal, South Africa.

IgA nephropathy (IgAN) is a common cause of primary glomerulonephritis worldwide. It is characterised by the deposition of poorly galactosylated IgA1 immune complexes in the renal mesangium, leading to end stage renal damage in 30% of patients. At present, the pathogenesis of IgAN is not well understood. IgAN GWAS studies revealed an association between IgAN and a SNP within the coding sequence of the CARD9 gene. CARD9 is an essential mediator of the innate immune system, however its place in the pathogenesis of IgAN has yet to be defined. The aim of this study was to investigate the role of CARD9 in IgAN.In this project, the expression of CARD9 mRNA was higher in; peripheral blood mononuclear cells (PBMCs) from IgAN patients compared to healthy controls, and in IgAN renal biopsy tissue compared to other renal diseases. rs4077515-T was associated with increased synthesis of IgA and poorly O-galactosylated IgA1 by activated PMBCs from both IgAN patients and healthy subjects. Immunohistochemistry demonstrated CARD9 protein in both the glomerular and tubulointerstitial compartments in IgAN and western blotting revealed the presence of CARD9 in cell lysates from human renal cells. Human mesangial cells with the rs4077515-T allele synthesised significantly more of the pro-inflammatory cytokine IL-6 following exposure to IgA1. Similar increases were seen in mRNA coding for IL-6, IL-6 signal transducer (IL-6ST) and monocyte chemoattractant protein 1(MCP-1), suggesting that the presence of rs4077515-T could result in a greater inflammatory response to mesangial IgA deposition in IgAN. A significant association between rs4077515-T and the likelihood of renal function decline in Chinese IgAN patients was observed.This study provides an insight into the contribution of CARD9 in; the generation of poorly O-galactosylated IgA1 by human PBMCs, the response of mesangial cells to IgA deposition in IgAN, the likelihood of renal function decline in IgAN.

Background: Aberrant O-glycosylation IgA1 production is a major factor in the pathogenesis of IgA nephropathy, but the underlying mechanism is still unclear. IgA1 glycosylation modification is in Golgi, and downregulation of the Golgi peripheral membrane protein Golgi matrix protein 130 (GM130) could lead to glycosylation deficiency. In this study, we aimed to explore the role of GM130 in glycosylate deficiency IgA1 (Gd-IgA1) production. Methods: We enrolled 27 IgA nephropathy patients, 12 patients with chronic tonsillitis, 15 non-IgAN chronic kidney disease patients, and 15 healthy volunteers as healthy control. We explored GM130 expression in Tonsillar tissue by immunofluorescence staining and Western blotting and expression in peripheral blood mononuclear cells (PBMCs) by flow cytometry. The concentration of IgA1 and level of O-glycosylation were determined by ELISA and Vicia Villosa lectin-binding assay. Real-time PCR and Western blot were used to analyze the levels of β1,3-Gal transferase (C1GALT1) and ST6GalNAC2, respectively. To explore the contribution of GM130 in IgA1 O-glycosylation modification, cells were subjected to experiments for evaluation of GM130 silencing by GM130-siRNA transfection. Results: GM130 expression was significantly decreased in tonsil tissues and PBMC of IgAN patients; the expression of C1GALT1 decreased and Gd-IgA1 level increased significantly in patients with IgAN patients. The expression of GM130 was negatively related to Gd-IgA1 production. By siRNA transfection, our results clearly indicated that the downregulation of GM130 can increase IgA1 O-glycosylation deficiency, which is thought to reduce C1GALT1 expression but not affect the expression of ST6GalNAC2. Conclusion: We identified and demonstrated that GM130 plays an important role in IgA1 O-glycans deficiency in IgAN patients, by negatively regulating C1GALT1 expression. We believe that this finding will provide theoretical foundations for a new mechanism of Gd-IgA1 production in IgAN patients.

The Pathogenetic Potential of Environmental Antigens in IgA Nephropathy

IgA nephropathy (IgAN) is one of the most common forms of glomerulonephritis leading to renal failure. MicroRNAs have been shown to play an important role in the pathogenesis and clinical course of IgA nephropathy; therefore, they offer the possibility of noninvasive diagnosis of this disease and have some value in predicting disease prognosis. This study aimed to evaluate the plasma levels of miR-148a-3p, miR-425-3p, and miR-20a-5p in patients with IgA nephropathy and their correlation with selected clinical parameters. This study included 44 patients with IgA nephropathy and 46 control subjects. The results of our study indicated that in patients with IgA nephropathy, the increased plasma levels of miR-148a-3p and miR-425-3p correlated negatively with eGFR values. According to the Haas classification, plasma levels of miR-20a-5p were statistically significantly increased in patients with histopathological changes classified as Stages 3, 4, and 5 compared with patients with histopathological changes classified as Stages 1 and 2. The results of our study suggest the possible involvement of miR-148a-3p, miR-425-3p, and miR-20a-5p in the pathogenesis of IgA nephropathy.

IgA nephropathy (IgAN) has become the most common form of primary glomerular disease worldwide. So far, it is still not very clear about the exact pathogenesis of IgAN, thus has no specific therapy. Generally mesangial deposition of IgA, especially polymeric IgA1 (pIgA1), suggests to be the initiating event in the pathogenesis of IgAN. In addition to decreased IgA clearance, IgA over production may also participate in the pathogenesis of IgAN. IgA class switching recombination (CSR) played key role during the process of IgA production. Stimulated with hemolytic streptococcus, tonsillar mononuclear cells (TMCs) of patients with IgAN presented with increased levels of Ia-Ca and activation-induced cytidine deaminase (AID), which are significant for IgA CSR. Human B cells and plasmacytoid dendritic cells express Toll-like receptor (TLR)-9, whose natural ligands are unmethylated cytosine–guanine dinucleotide (CpG) motifs characteristic of bacterial DNA (CpG-DNA). Unmethylated deoxycytidylic-deoxyguanosine oligodeoxynucleotide (CpG-ODN) is able to mimic the immunostimulatory activity of microbial DNA. Study found a significant increase in B cell activation factor (BAFF) production when tonsillar mononuclear cells stimulated with CpG-ODN in patients with IgAN. BAFF can induce germline Cα gene expression, AID expression, and IgA class switching in a CD40-independent manner. Therefore, it could be hypothesized that in IgAN there may exist TLR9-BAFF-IgA CSR axis, which induces excessive IgA production. If the hypothesis is correct, it could be of great significance for pathogenesis of IgAN elucidate and IgAN treatment.

IgA nephropathy is the most common primary GN worldwide and is a frequent cause of ESKD, especially in Asia. Work performed over the past few decades has led to significant advances in the understanding of common steps in its pathogenesis. Currently, the best predictors of progression are histologic

Background: We previously reported that glomerulonephritis associated with Staphylococcus aureus infection (SAGN) showed an increased usage of T cell receptor Vβ 5.3 and 8 in peripheral lymphocytes and mesangial IgA and IgG depositions. To elucidate the immunological mechanisms and pathogenesis of IgA nephropathy, we analyzed the usage of TCR Vβ in both peripheral blood lymphocytes (PBLs) and renal infiltrating T cells from IgA-N patients. Methods: In 38 patients with IgA nephropathy and controls, the usage of TCR Vβ in PBLs were analyzed using monoclonal antibodies against Vβ 3.1, Vβ 5.1, Vβ 5.2 + 5.3, Vβ 5.3, Vβ 6.7, Vβ 8, Vβ 12.1, and Vβ 13.1 + 13.3 with three-color flow cytometry. Furthermore, we examined immunohistochemically renal biopsy specimens using antibodies against Vβ 5.3 and Vβ 8. Results: The percentages of DR+CD4+CD8– cells, CD45RO+CD4+ cells, and CD45RO+CD4+DR+ cells in PBLs from IgA nephropathy were significantly higher than controls. The percentages of TCR Vβ 5.3 positive cells and TCR Vβ 8 positive cells in PBLs from patients were 1.3 ± 0.1 and 3.1 ± 0.2%, and both were significantly higher than controls. The percentage of renal interstitial TCR Vβ 5.3 expression was significantly higher than that in PBLs. However, there was no significant difference between the TCR Vβ 8 expression in the interstitium and that in PBLs. Conclusions: TCR Vβ 5.3 and 8 usage and broad CD4+ T cell activation have occurred in IgA nephropathy. These changes were similar but weak compared with formerly reported SAGN.