Vegfa promoter gene hypermethylation at HIF1α binding site is an early contributor to CKD progression after renal ischemia

Abstract

Chronic hypoxia is a major contributor to Chronic Kidney Disease (CKD) after Acute Kidney Injury (AKI). However, the temporal relation between the acute insult and maladaptive renal response to hypoxia remains unclear. In this study, we analyzed the time-course of renal hemodynamics, oxidative stress, inflammation, and fibrosis, as well as epigenetic modifications, with focus on HIF1α/VEGF signaling, in the AKI to CKD transition. Sham-operated, right nephrectomy (UNx), and UNx plus renal ischemia (IR + UNx) groups of rats were included and studied at 1, 2, 3, or 4 months. The IR + UNx group developed CKD characterized by progressive proteinuria, renal dysfunction, tubular proliferation, and fibrosis. At first month post-ischemia, there was a twofold significant increase in oxidative stress and reduction in global DNA methylation that was maintained throughout the study. Hif1α and Vegfa expression were depressed in the first and second-months post-ischemia, and then Hif1α but not Vegfa expression was recovered. Interestingly, hypermethylation of the Vegfa promoter gene at the HIF1α binding site was found, since early stages of the CKD progression. Our findings suggest that renal hypoperfusion, inefficient hypoxic response, increased oxidative stress, DNA hypomethylation, and, Vegfa promoter gene hypermethylation at HIF1α binding site, are early determinants of AKI-to-CKD transition.

GCN5 participates in KLF4-VEGFA feedback to promote endometrial angiogenesis

“…Meanwhile, KLF4 promoted the expression of VEGFA in HEMECs, triggered VEGFA secretion and subsequent blood vessel formation ( Figures 4 A–4D and S2 B–S2C). VEGFA promoter contain share considerable binding sites for Sp1/Sp3, AP-1, Egr-1, STAT-3, HIF1α, KLF8, KLF4, YY1 at the proximal region of promoters from various species ( Cheng et al., 2018 ; Sanchez-Navarro et al., 2021 ; Shima et al., 1996 ; Wang et al., 2015 ; Yang et al., 2019 ). In HEMECs, we found that KLF4 bound to ∼0.6 kb region of the VEGFA promoter which contain “CACCC” sites, suggesting that KLF4 can transcriptionally activate VEGFA ( Figure 4 J) and form a positive feedback loop with VEGFA to promote endometrial angiogenesis.…”

Differential Epigenetic Status and Responses to Stressors between Retinal Cybrids Cells with African versus European Mitochondrial DNA: Insights into Disease Susceptibilities

“…The VEGFA levels were decreased after 5-aza-dC treatment in both European-H and African-L cybrids, indicating that its transcription levels are regulated by methylation in the cybrid model. Sanchez-Navarro et al reported that DNA hypermethylation of the VEGFA promoter gene leads to lower levels of HIF-1α/VEGFA signaling [ 58 ]. In the VEGFA promoter region, the HIF1 Binding Site (HBS) is demethylated and the HIF1α/HIF1β complex binds to the promoter to upregulation of VEGF expression [ 59 ].…”

Epigenetic memory contributing to the pathogenesis of AKI-to-CKD transition

“…Eighteen genes with persistent alterations in DNA methylation induced by IRI for 7 days, as well as persistent changes in gene expression, were identified, suggesting that persistent promoter methylation contributes to the pathophysiology of AKI-to-CKD transition ( Zhao et al, 2017 ). Others analyzed DNA methylation and gene expression in a rat model of IRI, focusing on HIF1α/VEGF signaling at 1, 2, 3, and 4 months after IRI ( Sanchez-Navarro et al, 2021 ). Rats that experience IRI exhibit a persistent reduction in global DNA methylation during the entire experiment; and the reduction of HIF1α/VEGF signaling triggered after IRI, which may trigger renal hypoxia, is accompanied by persistent hypermethylation at the HIF-1α binding site of the Vegfα promoter throughout the observational periods ( Sanchez-Navarro et al, 2021 ).…”

“…Others analyzed DNA methylation and gene expression in a rat model of IRI, focusing on HIF1α/VEGF signaling at 1, 2, 3, and 4 months after IRI ( Sanchez-Navarro et al, 2021 ). Rats that experience IRI exhibit a persistent reduction in global DNA methylation during the entire experiment; and the reduction of HIF1α/VEGF signaling triggered after IRI, which may trigger renal hypoxia, is accompanied by persistent hypermethylation at the HIF-1α binding site of the Vegfα promoter throughout the observational periods ( Sanchez-Navarro et al, 2021 ). Thus, DNA methylation, similar to its role in DKD, is a strong candidate for epigenetic memory in AKI-to-CKD transition.…”

“…As described in Section 3.2 and 3.3 , several studies show that epigenetic alterations, including histone modifications and DNA methylation, occur throughout the observational periods that alter the regulation of gene expression during AKI-to-CKD transition ( Zager et al, 2011 ; Zhao et al, 2017 ; Heylen et al, 2018 ; Sanchez-Navarro et al, 2021 ). Further, dynamic phenotypic changes of dedifferentiated tubular epithelial cells, which are required for the initiation of kidney repair, are mediated by epigenetic changes and resultant enhancer and SE dynamics ( Wilflingseder et al, 2020 ).…”