Abstract
Phosphorylated methyl-CpG binding protein2 (p-MeCP2) suppresses the processing of several microRNAs (miRNAs). Homeo-domain interacting protein kinase2 (HIPK2) phosphorylates MeCP2, a known transcriptional repressor. However, it is not known if MeCP2 and HIPK2 are involved in processing of miRNAs implicated in diabetic nephropathy. p-MeCP2 and HIPK2 levels were significantly increased, but Seven in Absentia Homolog1 (SIAH1), which mediates proteasomal degradation of HIPK2, was decreased in the glomeruli of streptozotocin injected diabetic mice. Among several miRNAs, miR-25 and its precursor were significantly decreased in diabetic mice, whereas primary miR-25 levels were significantly increased. NADPH oxidase4 (NOX4), a target of miR-25, was significantly increased in diabetic mice. Protein levels of p-MeCP2, HIPK2, and NOX4 were increased in high glucose (HG)- or TGF-β-treated mouse glomerular mesangial cells (MMCs). miR-25 (primary, precursor, and mature) and mRNA levels of genes indicated in the in vivo study showed similar trends of regulation in MMCs treated with HG or TGF-β. The HG- or TGF-β-induced upregulation of p-MeCP2, NOX4 and primary miR-25, but downregulation of precursor and mature miR-25, were attenuated by Hipk2 siRNA. These results demonstrate a novel role for the SIAH1/HIPK2/MeCP2 axis in suppressing miR-25 processing and thereby upregulating NOX4 in early diabetic nephropathy.
Highlights
Diabetic nephropathy (DN) is a major microvascular complication and the leading cause of end-stage renal disease (ESRD)[1]
These results suggest that glomerular phosphorylated Methyl-CpG binding protein 2 (MeCP2) (p-MeCP2), homeo-domain interacting protein kinase 2 (HIPK2), and NADPH oxidase4 (NOX4) are related to the pathology of DN
Protein levels of t-MeCP2 were not significantly different between the three groups (Fig. 3E and G). We found that these factors were regulated by transforming growth factor (TGF)-β.in TGF-β(10 ng/ml) treated mouse glomerular mesangial cells (MMCs), the mRNA levels of Mecp[2] and Hipk[2] were significantly increased by 6 hr after treatment, and returned below normal by 24 hr compared with the control group (Fig. 4A and B). mRNA expression of Nox[4] was significantly upregulated in the 24 hr TGF-βtreated MMCs compared to control (Fig. 4C)
Summary
Diabetic nephropathy (DN) is a major microvascular complication and the leading cause of end-stage renal disease (ESRD)[1]. Evidence shows that miRNAs regulate the expression of key genes associated with kidney diseases and several miRNAs10–17 These miRNAs were shown to regulate fibrotic gene expression and glomerular hypertrophy via targeting transforming growth factor (TGF)-βsignaling, high glucose (HG) effects and downstream transcription regulators, or extracellular matrix genes. These emerging reports clearly show that several miRNAs are involved in promoting or attenuating the progression of DN by targeting genes related to fibrosis, inflammation, oxidative stress and signal transduction. We previously reported that let-7 miRNA family members are downregulated under diabetic conditions through changes in lin-28b which mediates the processing of let-735 It is not known if MeCP2 and HIPK2 are involved in processing and expression of candidate miRNAs that are downregulated in DN. We assessed whether changes in HIPK2 and p-MeCP2 are observed in glomeruli from diabetic mice, and can affect the processing of miR-25 in renal mesangial cells under diabetic conditions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
