Association of glomerular DNA damage and DNA methylation with one-year eGFR decline in IgA nephropathy

Abstract

Accumulation of DnA double-strand breaks (DSBs) is linked to aging and age-related diseases. We recently reported the possible association of DnA DSBs with altered DnA methylation in murine models of kidney disease. However, DSBs and DnA methylation in human kidneys was not adequately investigated. this study was a cross-sectional observational study to evaluate the glomerular DnA DSB marker γH2AX and phosphorylated Ataxia Telangiectasia Mutated (pATM), and the DNA methylation marker 5-methyl cytosine (5mC) by immunostaining, and investigated the association with pathological features and clinical parameters in 29 patients with IgA nephropathy. To evaluate podocyte DSBs, quantitative long-distance pcR of the nephrin gene using laser-microdissected glomerular samples and immunofluorescent double-staining with WT1 and γH2AX were performed. Glomerular γH2AX level was associated with glomerular DnA methylation level in igA nephropathy. podocytopathic features were associated with increased number of WT1(+)γH2AX(+) cells and reduced amount of pcR product of the nephrin gene, which indicate podocyte DnA DSBs. Glomerular γH2AX and 5mC levels were significantly associated with the slope of eGFR decline over one year in IgA nephropathy patients using multiple regression analysis adjusted for age, baseline eGfR, amount of proteinuria at biopsy and immunosuppressive therapy after biopsy. Glomerular γH2AX level was associated with DNA methylation level, both of which may be a good predictor of renal outcome in igA nephropathy. Various stresses, including UV radiation, chemicals, reactive oxygen species (ROS), DNA replication errors and mechanical stress, cause DNA damage 1. Although various types of DNA damage have been reported, DNouble-strand breaks (DSBs) are biologically important because of the repair difficulty 2. Accumulation of DNA damage is linked to aging and age-related diseases, such as cancer. Recent studies reported that increased DNA damage and reduced DNA repair capacity also play roles in the pathogenesis of cardiovascular and metabolic diseases 3. Angiotensin II and aldosterone are key factors in kidney disease that cause DNA damage, such as DSBs, and DNA base modification, such as 8-OHdG 4,5. However, the association of DNA DSBs in human kidneys with clinical parameters and pathological findings has not been adequately elucidated. Previous in vitro studies suggested that DNA DSBs and their repair processes induced altered DNA methylation 6-8. We recently investigated the association of DNA DSBs with altered DNA methylation status in glomerular podocytes using murine models of diabetic nephropathy 9. Increased DNA DSBs in podocytes due to both decreased levels of the DNA repair factor KAT5 and increased DNA damage induced by high-glucose conditions increased DNA methylation in the nephrin promoter region. However, the association of DNA DSBs with DNA methylation status in human kidneys was not investigated. IgA nephropathy is the most common glomerulonephritis in many countries, especially countries in Asia...

Monozygotic Twins Discordant for Immunoglobulin A Nephropathy Display Differences in DNA Methylation and Gene Expression

“…Previous studies showed that epigenetic modifications play important roles in multiple autoimmune diseases, such as type 1 diabetes [4] and rheumatoid arthritis (RA) [5]. As for IgAN, there is a lot of evidence, suggesting that DNA methylation participates in the development of IgAN [6][7][8][9]. For example, DNA hypermethylation in promoter region of Cosmc and the molecular chaperone of core 1 β1,3-galactosyltransferase in peripheral blood mononuclear cells (PBMCs) of IgAN patients were shown to be because of low expression of the gene and increased level of aberrantly glycosylated IgA1 [7].…”

Loss of genome maintenance accelerates podocyte damage and aging

“…The same holds true for factors involved in other forms of DNA maintenance such as the KEOPS complex (Braun et al, 2017; Hecker et al, 2009) or KAT5, a contributor to DNA methylation and non-homologous endjoining repair (Hishikawa et al, 2019). The Itoh group further linked the proteinuric phenotype to DNA double strand breaks and methylation in the promotor region of slit diaphragm protein nephrin and established an association of DNA double strand breaks in glomeruli of patients suffering from IgA nephropathy (Hayashi et al, 2020; Hishikawa et al, 2020). Our analysis adds considerably to this body of evidence, as we identify multiple factors of DNA maintenance, in particular of NER, to be transcriptionally altered in glomeruli of various renal diseases involving pronounced podocyte damage and loss.…”

“…Likewise, glomerular DNA damage was found to be associated with declining kidney function 12 and cells isolated from the urine of patients suffering from diabetes and hypertension showed increased levels of DNA strand breaks 13 . However, a link between DNA damage and podocyte loss, to date, remains unclear.…”

“…Mutations in the kinase, endopeptidase and other proteins of small size (KEOPS) complex genes caused proteinuria and induced DNA damage response (DDR) in vitro (Braun et al, 2017). Likewise, glomerular DNA damage was found to be associated with declining kidney function (Hayashi et al, 2020) and cells isolated from the urine of patients suffering from diabetes and hypertension showed increased levels of DNA strand breaks (Hishikawa et al, 2020). First evidence of nucleotide excision repair (NER) as an essential pathway in kidney health was recently provided through the identification of Ercc1 mutations causing kidney dysfunction (Apelt et al, 2020).…”

Sirt6-mediated Nrf2/HO-1 activation alleviates angiotensin II-induced DNA DSBs and apoptosis in podocytes

“…These results suggested that renal DNA DSBs may influence renal function of human. 42 However, DSBs in human kidneys have not been adequately investigated so far, and the status of DSBs in the glomeruli of patients with HN has not been reported yet. Our data showed that γH2AX-positive areas in the glomeruli were increased in patients with HN compared to the controls, which indicated that DNA DSB formation might contribute to the pathogenesis of HN.…”