Mycophenolic acid reverses IgA1 aberrant glycosylation through up-regulating Cosmc expression in IgA nephropathy. Int Urol Nephrol. 2013;45:571-579. [PMID: 23136028 DOI: 10.1007/s11255-012-0313-y]

Efficacy and safety of low-dose corticosteroids combined with leflunomide for progressive IgA nephropathy: a systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

The effectiveness of immunosuppressive and corticosteroid treatments for Immunoglobulin A (IgA) nephropathy (IgAN) remains thoroughly evaluated. We undertook a meta-analysis to investigate the efficacy and safety of low-dose corticosteroids plus leflunomide for progressive IgA nephropathy.

METHODS

Eligible studies were obtained from PubMed, Embase, and Cochrane Library databases. We also searched the references of the included studies. Our protocol followed the preferred reporting items for systematic reviews and meta-analyses (PRISMA) checklist. Eligibility criteria were defined using a PICOS framework.

RESULTS

Our study included three articles presenting 342 patient cases. Findings revealed that low-dose corticosteroids combined with the leflunomide group were effective in relieving urine protein excretion (UPE) [mean difference (MD) = -0.35, 95% confidence interval (CI): -0.41 to -0.30, P < 0.00001] compared with the full-dose corticosteroids group. Regarding serum creatinine (SCr), estimated glomerular filtration rate (eGFR), complete remission rate, and overall response rate, there was no difference between the groups (p > 0.05). Regarding safety, low-dose corticosteroids combined with leflunomide significantly reduced the risk of serious adverse events [odds ratio (OR): 0.11, 95% CI: 0.01 to 0.91, P = 0.04]. Besides, no significant differences were observed between the two groups in the incidence of respiratory infection, abnormal liver function, diarrhea, herpes zoster, alopecia, pruritus, insomnia, pneumonia, diabetes, and urinary tract infection (P > 0.05).

CONCLUSIONS

Low-dose corticosteroids combined with leflunomide are a safe and effective treatment for progressive IgA nephropathy.

TRIAL REGISTRATION

The PROSPERO registration number is CRD42022361883.

COSMC expression as a predictor of remission in IgA nephropathy

PURPOSE

The impact of core 1,3-galactosyltransferase-specific molecular chaperon (COSMC) gene expression and methylation profile on clinical progression of IgA nephropathy (IgAN) is unclear. The aim of this study was to determine the clinical significance and the relation of the COSMC gene expression and methylation pattern with the progression of IgAN.

METHODS

Thirty-nine biopsy-confirmed IgAN patients, 11 healthy relatives and 20 healthy controls were recruited. The COSMC mRNA levels and methylation profile of COSMC gene promoter were measured using the quantitative real-time PCR. The galactose-deficient IgA1 (Gd-IgA1) levels were measured using ELISA in serum and cell culture supernatant. The effect of IL-4 and AZA on COSMC expression and methylation and the correlation of COSMC gene expression and methylation levels with baseline kidney function tests, histology and long-term outcomes were examined.

RESULTS

The mean COSMC mRNA level was significantly lower, and serum Gd-IgA1 level was higher in IgAN patients compared with the control groups (p < 0.001, and p =  < 0.001, respectively). The COSMC mRNA levels were correlated with intensity of hematuria (r = - 0.41, p = 0.009), serum creatinine level (r = - 0.37, p = 0.002) and eGFR (r = 0.36, p = 0.002). The COSMC methylation levels were correlated with age (r = 0.25, p = 0.04) and baseline eGFR (r = - 0.326, p = 0.006). Twenty IgAN patients (51.3%) reached to complete (5, 12.8%) or partial remission (15, 38.5%) after a median of 34.5 months (IQR, 13.75-71). In multivariable Cox regression analysis, COSMC mRNA expression (adjusted HR (aHR) 1.871, 95% CI 1.287-2.722, p = 0.001) and Oxford T score (aHR 0.355, 95% CI 0.146-0.859, p = 0.022) predicted the remission.

CONCLUSION

COSMC mRNA level is a novel biomarker candidate to predict the remission in IgAN patients.

Co-delivery of p38α MAPK and p65 siRNA by novel liposomal glomerulus-targeting nano carriers for effective immunoglobulin a nephropathy treatment

Glomerulonephritis related renal failure is a frequent cause of end-stage renal disease, and immunoglobulin A nephropathy (IgAN) is the most frequent type of primary glomerulonephritis. As damage induced by IgAN mostly attributes to inflammation responses, inhibiting inflammation in glomerulus can protect normal renal function and delay the onset of renal failure. Hence, reducing levels of p38 MAPK and p65 which are essential regulators in p38 MAPK and NF-κB related inflammation responses could be effective against IgAN. Here, we rationally designed and constructed size- and surface charge- dependent glomerulus-targeting liposomal nanoparticles which are loaded with both p38α MAPK and p65 siRNA. Experiments show that our nanoparticles successfully crossed fenestrated endothelium, accumulated in mesangial cells and endothelial cells, efficiently silenced p38α MAPK and p65 genes, and eventually alleviated proteinuria, inflammation and excessive extracellular matrix deposition in mouse IgAN models. This siRNA co-delivery system thus represents a promising treatment option for IgAN and offers a versatile platform for other glomerular problems. Our work also highlights a novel strategy of glomerulus-targeting and an encouraging therapeutic route for other inflammatory diseases.

CDG and immune response: From bedside to bench and back

Glycosylation is an essential biological process that adds structural and functional diversity to cells and molecules, participating in physiological processes such as immunity. The immune response is driven and modulated by protein-attached glycans that mediate cell-cell interactions, pathogen recognition and cell activation. Therefore, abnormal glycosylation can be associated with deranged immune responses. Within human diseases presenting immunological defects are congenital disorders of glycosylation (CDG), a family of around 130 rare and complex genetic diseases. In this review, we have identified 23 CDG with immunological involvement, characterized by an increased propensity to-often life-threatening-infection. Inflammatory and autoimmune complications were found in 7 CDG types. CDG natural history(ies) and the mechanisms behind the immunological anomalies are still poorly understood. However, in some cases, alterations in pathogen recognition and intracellular signaling (eg, TGF-β1, NFAT, and NF-κB) have been suggested. Targeted therapies to restore immune defects are only available for PGM3-CDG and SLC35C1-CDG. Fostering research on glycoimmunology may elucidate the involved pathophysiological mechanisms and open new therapeutic avenues, thus improving CDG patients' quality of life.

Efficacy and safety of leflunomide in IgA nephropathy: a systematic review and meta-analysis

BACKGROUND

The optimal therapy for immunoglobulin A nephropathy (IgAN) remains uncertain. Leflunomide (LEF) is an immunosuppressive drug which may reduce deposition of glomerular autoantibodies and immune complexes. Several clinical trials were designed to evaluate the efficacy of LEF, but their results were controversial.

METHODS

Ovid Medline, Embase, the Cochrane Library, PubMed, and CNKI were systematically searched. Search terms included ("glomerulonephritis" OR "nephritis") AND ("immunoglobulin A" OR "IgA") AND "leflunomide". Studies in which patients were diagnosed with IgAN based on renal biopsy were included. Studies needed to report clinical outcomes via either short- or long-term clinical examination, remission rate, or complication rate.

RESULTS

Forty-four studies encompassing 1802 patients were included, of which 35 were randomized controlled trials. Results of 24 h post-treatment urine protein tests and serum creatinine tests were significantly lower in patients treat with LEF and corticosteroids (CS) or valsartan (ACEI) (CS + LEF or CS + ACEI) compared with patients treated with CS or ACEI alone (P < 0.05). More patients treated with CS + LEF (31.2%) achieved complete remission (CR) than patients treated with CS alone (22.2%) (RR = 0.71, 95% CI 0.59-0.85, P < 0.05). Although there was no significant difference in CR between patients treated with cyclophosphamide and CS (CS + CTX) and those treated with CS + LEF, the complication rate in the former group was higher (28.4%) than in the latter one (11.4%) (RR = 2.46, 95% CI 1.47-4.13, P < 0.005).

CONCLUSION

LEF appears to improve renal function while decreasing loss of urine protein. Combination regimens including LEF were better and safer compared with CS or ACEI alone or combinations including CTX.

Interleukin-17 promotes the production of underglycosylated IgA1 in DAKIKI cells

Background: Interleukin 17 (IL-17) plays an important role in the pathogenesis of autoimmune diseases and might be associated with IgA nephropathy (IgAN). This study aimed to investigate the effect of IL-17 on autoimmune pathogenesis in IgA nephropathy.

Methods: DAKIKI cells were cultured and stimulated with IL-17 to perform dose-dependent and time-dependent experiments. Cell proliferation was examined by cell counting and the Cell Counting Kit-8 (CCK-8) assay. The IgA concentration and the degree of galactosylation in the supernatant were tested using ELISA and a helix aspersa (HAA) lectin binding assay, respectively. To study the mechanism of O-glycosylation, cells were stimulated with IL-17, lipopolysaccharide (LPS) or 5-azacytidine (5-AZA) + IL-17 for 48 h, and the levels of C1GALT1 and its molecular chaperone Cosmc were measured by western blot and real-time PCR.

Results: The cell counting and CCK-8 results suggested that B lymphocyte proliferation increased significantly with increased IL-17 concentration. IL-17 affected the quantity of IgA1 and its glycosylation status. HAA revealed that IL-17 promoted IgA1 underglycosylation. Mechanistically, the expression of C1GALT1 and Cosmc was significantly lower in cells stimulated by IL-17 or LPS than in the 5-AZA + IL-17 or the control group.

Conclusions: Our results suggested that IL-17 stimulates B lymphocyte to promote B-cell proliferation, which leads to increased IgA1 production in vitro accompanied by underglycosylation of IgA1. The molecular mechanism for the IgA1 underglycosylation induced by IL-17 was similar to that of LPS; however, 5-AZA inhibited IgA1 underglycosylation. IL-17 might participate in IgAN pathogenesis by influencing the production and glycosylation of IgA1 in B-cells.

Mycophenolate mofetil following glucocorticoid treatment in Henoch-Schönlein purpura nephritis: the role of early initiation and therapeutic drug monitoring

BACKGROUND

Henoch-Schönlein purpura (HSP) is the most common vasculitis in childhood and traditionally considered as a self-limiting disease. However, renal involvement can unfavorably determine long-term prognosis. The reported regimens to treat HSP nephritis (HSPN) are diverse, indicating that the most effective treatment remains controversial.

METHODS

This retrospective, single-center study involved 18 patients presenting with HSPN and nephrotic-range proteinuria. We aimed to investigate the efficacy and safety of mycophenolate mofetil (MMF) and identify a cut-off level for estimated mycophenolic acid area under the curve (eMPA-AUC_0-12h) values, which can predict complete remission with high sensitivity.

RESULTS

Despite prior insufficient therapeutic response to corticosteroids, 89% of patients showed a significant decrease in proteinuria after 1 month of MMF treatment. None of them relapsed during treatment; however, two children relapsed after discontinuation. Based on results of a receiver operating characteristic (ROC) analysis, an eMPA-AUC_0-12h >56.4 mg*h/l was a predictor for complete remission within 3 months (80% sensitivity, 83.3% specificity, p = 0.035). During MMF administration, we encountered no adverse event requiring discontinuation of treatment.

CONCLUSION

Our study demonstrates that MMF is a safe and potentially effective secondary treatment option for children with HSPN to achieve and maintain long-term remission without serious side effects. To achieve complete remission within 3 months, resolve severe inflammatory glomerular lesions, and avoid progression to chronic kidney disease, we propose timely diagnosis and early initiation of MMF with an eMPA-AUC_0-12h value of 56.4 mg*h/l.

MiR-320 promotes B cell proliferation and the production of aberrant glycosylated IgA1 in IgA nephropathy

IgA nephropathy (IgAN) is one of the most common primary glomerulonephritis. However, the etiology of this disease is complex and the pathogenesis of IgAN is still unknown. MicroRNAs (miRNAs) play important roles in a lot of pathological and physiological processes. In this study, we showed that the expression of miR-320 was significantly upregulated in renal tissues and urinary of IgAN patients. Moreover, the intra-renal expression level of miR-320 had significant correlation with miR-320 expression in the urinary of IgAN patients. Overexpression of miR-320 increased B cell proliferation and promoted cyclin D1 expression. Furthermore, we identified that PTEN was direct target gene of miR-320 in the B cell. Ectopic expression of miR-320 suppressed PTEN expression. Overexpression of miR-320 decreased Cosmc expression in the B cell. In addition, we demonstrated that Cosmc expression was significantly downregulated in the renal tissues and urinary of IgAN patients. The intra-renal expression level of Cosmc had significant correlation with Cosmc expression of urinary in IgAN patients. We proved that the expression level of Cosmc was negatively correlated with the expression of miR-320 in the renal tissues of IgAN patients. Overexpression of miR-320 promoted the B cell proliferation through suppressing PTEN expression. Taken together, these data suggested that miR-320 acted an important role in the development of IgAN.

Short-term anti-proteinuric effect of tacrolimus is not related to preservation of the glomerular filtration rate in IgA nephropathy: A 5-year follow-up study

BACKGROUND

The immunosuppressive drug tacrolimus has the short-term effect of reducing proteinuria in patients with immunoglobulin A nephropathy (IgAN). Our study investigated the effects on proteinuria and kidney function after discontinuation of tacrolimus.

METHODS

Patients with biopsy-proven IgAN were included in the study and randomly divided into two treatment groups. There was a corresponding control group for each treatment group. The first group included patients treated with tacrolimus (Tac vs non-Tac group) and the second group included patients with a renin angiotensin system blocker (RASi vs non-RASi group). The Tac group received treatment for up to 16 weeks, with the administration of tacrolimus being ceased at the final visit (trial phase). We tracked the patients at 12, 24, 52, and 240 weeks (observational phase). The primary outcomes examined were the percentage change (from the trial phase to the observational phase) of time-averaged proteinuria (TA-proteinuria; g/g creatinine [cr]) and the estimated glomerular filtration rate (eGFR). Time-averaged proteinuria was defined as the average of urine protein to creatinine ratio (UPCR), measured every 3 months during both the trial and observational phases of the study.

RESULTS

A significant reduction in UPCR was observed in the Tac group compared to non-Tac group at the 4 and 8 week visits during the trial phase (p = 0.023 and p = 0.003, respectively). However, the difference between the Tac group and non-Tac group was not evident in the other review periods, estimated by linear mixed effect model. The percentage change in TA-proteinuria was greater in the Tac group than that in the corresponding control group (116 ± 96% vs. 63 ± 239%, p = 0.004). Therefore, during the observational phase, TA-proteinuria was not significantly different between the Tac group and the non-Tac group (1.150 ± 0.733 g/g cr vs. 1.455 ± 2.017 g/g cr, p = 0.775). The levels of eGFR throughout the observational phase were not significantly different between the two groups. Furthermore, the mean rate of eGFR change throughout both phases of the study was -6.4 ± 5.9 mL/min/1.73 m2/year in the non-Tac group and -5.4 ± 7.9 mL/min/1.73 m2/year in the Tac group (p = 0.988).

CONCLUSION

The anti-proteinuric effect of tacrolimus was promptly reversed 3 months after discontinuing the drug. The use of tacrolimus for a short period of time for patients with IgAN temporarily reduces proteinuria, but the data showed no long-term efficacy regarding proteinuria reduction and improvement of renal function.

Efficacy and safety of calcineurin inhibitor treatment for IgA nephropathy: a meta-analysis

Background

IgA nephropathy is the most common progressive glomerular disease to end stage renal failure worldwide. Calcineurin inhibitors (CNIs) is a selective immunosuppressant widely used in organ transplantation. The efficacy and safety of calcineurin inhibitors for the treatment of IgA nephropathy remain uncertain.

Methods

We performed a systematic literature search using the PubMed, Embase, Science Citation Index, Ovid evidence-based medicine, Chinese Biomedical Literature (CBM) and Chinese science and technology periodicals (CNKI, VIP, and Wan Fang) for randomized, controlled trials of CNIs therapy of IgA nephropathy. Complete remission rate (CR) was defined as proteinuria less than 0.5 or 0.3 g/d. Partial remission rate (PR) was defined as proteinuria reduced to at least half of the baseline measurement and an absolute value of >0.5 or 0.3 g/d.

Results

Seven relevant trials were conducted with 374 patients enrolled. CNIs plus medium/low-dose steroid had a higher CR (RR = 2.51 [95% CI,1.25 to 5.04], P = 0.02) compared to therapy with steroid alone or placebo, but were not significant on PR (RR = 0.87 [95% CI,0.32 to 2.38]; P = 0.78). Also, significant alterations were observed in proteinuria (weighted mean difference, −0.46 g/d,[95% CI:-0.55 to −0.24], P < 0.01) with no differences were found in serum creatinine (SCr) (weighted mean difference, 0.57,95% CI:-4.05 to 5.19; P = 0.78) and estimated glomerular filtration rate (eGFR) (weighted mean difference, 1.13,95% CI:-4.05 to 6.32; P = 0.34) level between the two groups. CNI therapy was associated with an increased risk for adverse events (RR = 2.21,95% CI:1.52 to 3.21, P < 0.01), such as gastrointestinal and neurological symptoms or hirsutism.

Conclusions

CNIs might provide renal protection in patients with IgAN, but at an increased risk of adverse events. Reliably defining the efficacy and safety of CNIs in IgAN requires a high-quality trial with a large sample size.

Aberrant IgA1 Glycosylation in IgA Nephropathy: A Systematic Review

OBJECTIVE

Galactose-deficient IgA1 was evaluated in patients with IgA nephropathy(IgAN) and controls in order to determine the predictive value of galactose-deficient IgA1 in cases of IgA nephropathy.

METHODS

PubMed, EMBASE, Cochrane central register of controlled trials, CNKI, CBM disc, and VIP database were searched to identify eligible studies that evaluated a difference in aberrant IgA1 glycosylation in IgAN patients compared with controls. A meta-analysis was conducted to evaluate the impact of galactose-deficient IgA1(Gd-IgA1) levels in different groups.

RESULTS

A total of 22 studies (n = 1657) met inclusion criteria. The mean Newcastle-Ottawa Scale (NOS) score was 7.2 and ranged from 6 to 8. The standard mean difference(SMD) in the meta-analysis of 20 studies of the level of Gd-IgA1 in the serum and/or supernatant of cultured cells was higher in the IgAN group compared with healthy controls as well as in those with other renal diseases (SMD = 1.76, 95% CI = 1.18-2.34, P<0.00001; SMD = 1.05, 95% CI = 0.05-2.04, P = 0.04). The data synthesis suggested that IgAN patients had similar levels of serum Gd-IgA1, with no significant differences, compared with first-degree relatives and Henoch-Schonlein purpura nephritis (HSPN) patients (MD = 0.04, 95% CI = 0.00-0.08, P = 0.05; MD = -46.03, 95% CI = -217.70-125.64, P = 0.60). In addition, the combined MD of 5 studies indicated that there were no significant differences in Gd-IgA1 levels among patients with varying severities of IgAN (MD = 0.02, 95% CI = -0.02-0.05, P = 0.28).

CONCLUSIONS

The pooled evidence suggests that the level of Gd-IgA1 in the serum or supernatant of cultured cells from peripheral blood or tonsils may be a useful biomarker for predicting IgA nephropathy, though the level of Gd-IgA1 was not significantly associated with disease severity.

Tumor-associated antigens: Tn antigen, sTn antigen, and T antigen

Glycosylation is one of the major posttranslational modifications of proteins. N-glycosylation (Asn-linked) and O-glycosylation (Ser/Thr-linked) are the two main forms. Abnormal O-glycosylation is frequently observed on the surface of tumor cells, and is associated with an adverse outcome and poor prognosis in patients with cancer. O-glycans (Tn, sTn, and T antigen) can be synthesized in the Golgi apparatus with the aid of several glycosyltransferases (such as T-synthase and ST6GalNAc-I) in a suitable environment. The unique molecular chaperone of T-synthase is Cosmc, which helps T-synthase to fold correctly in the endoplasmic reticulum. Dysregulation of these glycosyltransferases, molecular chaperones, or the environment is involved in the dysregulation of O-glycans. Tn, sTn, and T antigen neo- or over-expression occurs in many types of cancer including gastric, colon, breast, lung, esophageal, prostate, and endometrial cancer. This review discusses the major synthetic pathway of O-glycans and the mechanism by which Tn, sTn, and T antigens promote tumor metastasis.

Increased APRIL Expression Induces IgA1 Aberrant Glycosylation in IgA Nephropathy

Aberrant glycosylated IgA1 molecules, mainly galactose-deficient IgA1 (Gd-IgA1), are important causal factors in IgA nephropathy; however, the underlying mechanism for the production of aberrantly glycosylated IgA1 is unknown. A recent genome-wide association study identified a novel IgAN susceptibility gene, TNFSF13, which encoded a proliferation-inducing ligand (APRIL) that promotes lymphocyte proliferation and IgA class switching. We aimed to explore the mechanism of APRIL's involvement in IgAN. We enrolled 166 patients with IgAN and 77 healthy controls and detected the plasma APRIL levels by the ELISA method, identified the mRNA expression of APRIL and its receptors by relative quantitative PCR, and confirmed by in vitro experiment. We identified increased plasma APRIL levels in IgAN, which was further proved by upregulated mRNA expression in B-lymphocytes from 27 IgAN patients. Analysis of the clinical characteristics of patients with IgAN showed that higher plasma APRIL level was associated with more severe clinical presentations (high proteinuria and low eGFR). The plasma APRIL level was positively correlated with Gd-IgA1 levels. Furthermore, exogenous APRIL could induce more production of Gd-IgA1 in cultured lymphocytes from patients with IgAN, compared with that from healthy controls. And, the relative higher expression of receptors of APRIL, that is, BCMA and TACI, in B-lymphocytes from IgAN patients were observed. Our findings implied that in patients with IgAN, increased APRIL is accompanied elevated expression of its receptors in B-lymphocytes, which induces overproduction of Gd-IgA1, ultimately contributing to the pathogenesis of IgAN.

Update on immunoglobulin a nephropathy. Part II: Clinical, diagnostic and therapeutical aspects

Immunoglobulin A nephropathy (IgAN) is characterized by different clinical manifestations and by long-term different outcomes. Major problem for the physicians is to understanding which patients are at risk of a disease evolution and to prescribe the right therapy to the right patients. Indeed, in addition to patients with a stable disease with no trend to evolution or even with a spontaneous recovery, patients with an active disease and patients with a rapidly evolving glomerulonephritis are described. Several histopathological, biological and clinical markers have been described and are currently used to a better understanding of patients at risk, to suggest the right therapy and to monitor the therapy effect and the IgAN evolution over time. The clinical markers are the most reliable and allow to divide the IgAN patients into three categories: The low risk patients, the intermediate risk patients and the high risk patients. Accordingly, the therapeutic measures range from no therapy with the only need of repeated controls, to supportive therapy eventually associated with low dose immunosuppression, to immunosuppressive treatment in the attempt to avoid the evolution to end stage renal disease. However the current evidence about the different therapies is still matter of discussion. New drugs are in the pipeline and are described. They are object of randomized controlled trials, but studies with a number of patients adequately powered and with a long follow up are needed to evaluate efficacy and safety of these new drugs.

The Treatment of IgA Nephropathy

BACKGROUND

IgA nephropathy (IgAN) is a very common glomerulonephritis worldwide. Nevertheless, treatment options for primary IgAN are still largely based on opinion or weak evidence. There is a lack of large randomized controlled trials (RCT) that provide a definitive immunosuppressive protocol for IgAN. The recent KDIGO Clinical Practice Guidelines for Glomerulonephritis have assigned low levels of evidence for almost all recommendations and suggestions related to this nephropathy.

SUMMARY

In this article, we review different treatment options and emphasize that the key to therapeutic decision-making is the assessment of an individual's prognosis. The risk of disease progression is closely related to clinical parameters such as proteinuria, hypertension, and impaired glomerular filtration rate. For patients with minor urinary abnormalities, the mainstay of treatment is long-term regular follow-up to detect renal progression and hypertension. Optimized supportive care aiming to maintain proteinuria <1 g/day is preferred in the typical patient presenting with microhematuria, significant but nonnephrotic proteinuria, hypertension, and variable degrees of renal failure. The atypical patient with overt nephritic syndrome or rapidly progressive kidney injury that represents a vasculitic form of IgAN should be treated with immunosuppression. Finally, the variant of overlapping syndrome of IgAN and lipoid nephrosis that runs a good prognosis should be treated as lipoid nephrosis.

KEY MESSAGE

The treatment of IgAN should be structured according to the clinical scenario.

DNA methylation in Cosmc promoter region and aberrantly glycosylated IgA1 associated with pediatric IgA nephropathy

IgA nephropathy (IgAN) is one of the most common glomerular diseases leading to end-stage renal failure. Elevation of aberrantly glycosylated IgA1 is a key feature of it. The expression of the specific molecular chaperone of core1ß1, 3galactosyl transferase (Cosmc) is known to be reduced in IgAN. We aimed to investigate whether the methylation of CpG islands of Cosmc gene promoter region could act as a possible mechanism responsible for down-regulation of Cosmc and related higher secretion of aberrantly glycosylated IgA1in lymphocytes from children with IgA nephropathy. Three groups were included: IgAN children (n = 26), other renal diseases (n = 11) and healthy children (n = 13). B-lymphocytes were isolated and cultured, treated or not with IL-4 or 5-Aza-2’-deoxycytidine (AZA). The levels of DNA methylation of Cosmc promotor region were not significantly different between the lymphocytes of the three children populations (P = 0.113), but there were significant differences between IgAN lymphocytes and lymphocytes of the other two children populations after IL-4 (P<0.0001) or AZA (P<0.0001). Cosmc mRNA expression was low in IgAN lymphocytes compared to the other two groups (P<0.0001). The level of aberrantly glycosylated IgA1 was markedly higher in IgAN group compared to the other groups (P<0.0001). After treatment with IL-4, the levels of Cosmc DNA methylation and aberrantly glycosylated IgA1 in IgAN lymphocytes were remarkably higher than the other two groups (P<0.0001) with more markedly decreased Cosmc mRNA content (P<0.0001). After treatment with AZA, the levels in IgAN lymphocytes were decreased, but was still remarkably higher than the other two groups (P<0.0001), while Cosmc mRNA content in IgAN lymphocytes were more markedly increased than the other two groups (P<0.0001). The alteration of DNA methylation by IL-4 or AZA specifically correlates in IgAN lymphocytes with alterations in Cosmc mRNA expression and with the level of aberrantly glycosylated IgA1 (r = −0.948, r = 0. 707). Our results suggested that hypermethylation of Cosmc promoter region could be a key mechanism for the reduction of Cosmc mRNA expression in IgAN lymphocytes with associated increase in aberrantly glycosylated IgA1.

Astragalus membranaceus up-regulate Cosmc expression and reverse IgA dys-glycosylation in IgA nephropathy

Background

Decreased Core I β3-Gal-T-specific molecular chaperone (Cosmc) expression induced IgA1 aberrant glycosylation is the main characteristic of IgA nephropathy (IgAN). This study tried to elucidate the effect of Astragalus membranaceus on Cosmc expression and IgA O-glycosylation of peripheral B lymphocytes in IgAN patients.

Methods

Peripheral B lymphocytes of 21 IgAN patients and 10 normal controls were isolated and cultured with or without lipopolysaccharide (LPS) and Astragalus membranaceus injection (AMI). Cosmc mRNA and protein expression levels were measured by real-time RT-PCR and Western blot. IgA1 and glycosylation level were determined by enzyme-linked immunosorbent assay (ELISA) and VV lectin-binding method.

Results

Cosmc mRNA expression and IgA1 O-glycosylation level in IgAN patients was significantly lower than normal controls at baseline. Treatment of LPS could obviously inhibit Cosmc expression and increase the IgA1 secretion in peripheral B lymphocytes of IgAN patients, which resulted in a significantly increase in IgA1 aberrant glycosylation level. Addition of AMI could remarkably up regulated Cosmc expression, decrease IgA1 secretion, and reverse glycosylation level in a dose related manner.

Conclusion

AMI can up-regulate Cosmc expression of peripheral B lymphocytes and reverse IgA1 aberrant O-glycosylation level, which might be the underlying mechanism of AMI therapy in treating IgAN.

Trial registration

TCTR20140515001 (Registration Date: 2014-05-15)