Hang Yuan

Involvement of p300/CBP and epigenetic histone acetylation in TGF-β1-mediated gene transcription in mesangial cells

Transforming growth factor-β1 (TGF-β1)-induced expression of plasminogen activator inhibitor-1 (PAI-1) and p21 in renal mesangial cells (MCs) plays a major role in glomerulosclerosis and hypertrophy, key events in the pathogenesis of diabetic nephropathy. However, the involvement of histone acetyl transferases (HATs) and histone deacetylases (HDACs) that regulate epigenetic histone lysine acetylation, and their interaction with TGF-β1-responsive transcription factors, are not clear. We evaluated the roles of histone acetylation, specific HATs, and HDACs in TGF-β1-induced gene expression in rat mesangial cells (RMCs) and in glomeruli from diabetic mice. Overexpression of HATs CREB binding protein (CBP) or p300, but not p300/CBP-activating factor, significantly enhanced TGF-β1-induced PAI-1 and p21 mRNA levels as well as transactivation of their promoters in RMCs. Conversely, they were significantly attenuated by HAT domain mutants of CBP and p300 or overexpression of HDAC-1 and HDAC-5. Chromatin immunoprecipitation assays showed that TGF-β1 treatment led to a time-dependent enrichment of histone H3-lysine9/14-acetylation (H3K9/14Ac) and p300/CBP occupancies around Smad and Sp1 binding sites at the PAI-1 and p21 promoters. TGF-β1 also enhanced the interaction of p300 with Smad2/3 and Sp1 and increased Smad2/3 acetylation. High glucose-treated RMCs exhibited increased PAI-1 and p21 levels, and promoter H3K9/14Ac, which were blocked by TGF-β1 antibodies. Furthermore, increased PAI-1 and p21 expression was associated with elevated promoter H3K9/14Ac levels in glomeruli from diabetic mice. Thus TGF-β1-induced PAI-1 and p21 expression involves interaction of p300/CBP with Smads and Sp1, and increased promoter access via p300/CBP-induced H3K9/14Ac. This in turn can augment glomerular dysfunction linked to diabetic nephropathy.

Resveratrol Prevention of Diabetic Nephropathy Is Associated with the Suppression of Renal Inflammation and Mesangial Cell Proliferation: Possible Roles of Akt/NF-κB Pathway

The present study was to investigate the protection of resveratrol (RSV) in diabetes associated with kidney inflammation and cell proliferation. Rat mesangial cell and streptozotocin-induced type 1 diabetes mouse model were used. In vitro, RSV attenuated high glucose-induced plasminogen activator inhibitor (PAI-1) expression and mesangial cell proliferation, as well as Akt and nuclear factor-kappa B (NF-κB) activation. The similar results were recaptured in the experiment with Akt inhibitors. In vivo, mice were divided into three groups: control group, diabetes mellitus (DM) group, and RSV-treated DM group. Compared with control group, the kidney weight to body weight ratio and albumin to creatinine ratio were increased in DM group, but not in RSV-treated DM group. Furthermore, the increased expression of PAI-1 and intercellular adhesion molecule-1 in diabetic renal cortex were also reduced by RSV administration. Besides, the kidney p-Akt/Akt ratio and NF-κB were significantly increased in DM group; however, these changes were reversed in RSV-treated DM group. Additionally, immunohistochemistry results indicated that RSV treatment reduced the density of proliferating cell nuclear antigen-positive cells significantly in glomeruli of diabetic mice. These results suggest that RSV prevents diabetes-induced renal inflammation and mesangial cell proliferation possibly through Akt/NF-κB pathway inhibition.

Advances in Murine Models of Diabetic Nephropathy

Diabetic nephropathy (DN) is one of the microvascular complications of both type 1 and type 2 diabetes, which is also associated with a poor life expectancy of diabetic patients. However, the pathogenesis of DN is still unclear. Thus, it is of great use to establish appropriate animal models of DN for doing research on pathogenesis and developing novel therapeutic strategies. Although a large number of murine models of DN including artificially induced, spontaneous, and genetically engineered (knockout and transgenic) animal models have been developed, none of them develops renal changes sufficiently reflecting those seen in humans. Here we review the identified murine models of DN from the aspects of genetic background, type of diabetes, method of induction, gene deficiency, animal age and gender, kidney histopathology, and phenotypic alterations in the hope of enhancing our comprehension of genetic susceptibility and molecular mechanisms responsible for this disease and providing new clues as to how to choose appropriate animal models of DN.

Angiotensin II type 1 receptor expression is increased via 12-lipoxygenase in high glucose-stimulated glomerular cells and type 2 diabetic glomeruli

BACKGROUNDnAngiotensin II type 1 receptor (AT1) plays an important role in the development of diabetic nephropathy (DN). However, the roles played by 12-lipoxygenase (12-LO) in the AT1 expression in glomerular cells exposed to high glucose (HG) and diabetic glomeruli remain unclear. Our objective in the present study was to investigate the role of 12-LO in the AT1 expression in glomerular cells and glomeruli under diabetic conditions.nnnMETHODSnMesangial cells (MCs), podocytes and glomeruli isolated from rats were used in this study. The rats fed a high fat diet received low-dose streptozotocin to make type 2 diabetes. The 12-LO product 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE] was infused to rats by osmotic mini-pump. Morphometric measurement for glomerular volume, competitive reverse transcription polymerase chain reaction for mRNA expression, western blot and immunohistochemistry for protein expression were performed, respectively.nnnRESULTSnBoth the 12(S)-HETE and HG increased AT1 protein expression in MCs and podocytes. Furthermore, the levels of the AT1 were significantly higher in glomeruli derived from 12(S)-HETE-treated rats compared with control rats. In addition, HG-induced AT1 expression was significantly reduced by the 12-LO inhibitor cinnamyl-3,4-dihydroxy-alpha-cynanocinnamate (CDC). Compared with the non-diabetic controls, DN rats showed significant glomerular hypertrophy and albuminuria. This was associated with significant increases in AT1 protein expression. These abnormalities were prevented by treatment of the CDC.nnnCONCLUSIONSnThese results indicate that AT1 expression is enhanced, at least in part, by 12-LO in the type 2 diabetic glomeruli, and 12-LO inhibition can ameliorate DN progression through downregulation of AT1 expression.

Renal Protective Effect of Sirtuin 1

Silent information regulator 2 (Sir2) is a nicotinamide adenine dinucleotide- (NAD+-) dependent deacetylase. The homology of SIRT1 and Sir2 has been extensively studied. SIRT1 deacetylates target proteins using the coenzyme NAD+ and is therefore linked to cellular energy metabolism and the redox state through multiple signalling and survival pathways. During the past decade, investigators have reported that SIRT1 activity is essential in cancer, neurodegenerative diseases, diabetes, cardiovascular disease, and other age-related diseases. In the kidneys, SIRT1 may inhibit renal cell apoptosis, inflammation, and fibrosis. Therefore its activation may also become a new therapeutic target in the patients with chronic kidney disease including diabetic nephropathy. In this paper, we would like to review the protective functions of sirtuins and the role of SIRT1 in the onset of kidney disease based on previous studies, including diabetic nephropathy, acute renal injury, chronic kidney disease as well as lupus nephritis.

Relationship between five GLUT1 gene single nucleotide polymorphisms and diabetic nephropathy: a systematic review and meta-analysis

So far, case–control studies on the association between glucose transporter 1 (GLUT1) gene single nucleotide polymorphisms (SNPs) and diabetic nephropathy (DN) have generated considerable controversy. To clarify the linkage of GLUT1 SNPs on the risk of DN, a systematic review and meta-analysis was performed. A comprehensive literature search of electronic databases was conducted to obtain relative studies. Nine case–control studies were included. Significant differences were found between XbaI SNP (rs841853) and increased risk of DN in all genetic models. Subgroup analyses for Caucasians population and DN from both type 1 and type 2 diabetes also revealed positive results. For Enh2-1 SNP (rs841847), Enh2-2 SNP (rs841848) and HaeIII SNP (rs1385129), obvious linkages were demonstrated in recessive model. However, analysis for the association between HpyCH4V SNP (rs710218) and the susceptibility of DN showed no significance. Likewise, negative outcome was also found in the assessment for the influence of XbaI or Enh2-2 SNP on the pathogenesis progress of DN. The evidence currently available shows that XbaI, Enh2 and HaeIII SNPs, but not HpyCH4V SNP, in GLUT1 gene may be genetic susceptibility to DN. However, data does not support the association between either XbaI or Enh2-2 SNP and the severity of DN.

Epigenetic Histone Modifications Involved in Profibrotic Gene Regulation by 12/15-Lipoxygenase and Its Oxidized Lipid Products in Diabetic Nephropathy

AIMSnEpigenetic mechanisms, including histone post-translational modifications and DNA methylation, are implicated in the pathogenesis of diabetic nephropathy (DN), but the mediators are not well known. Moreover, although dyslipidemia contributes to DN, epigenetic changes triggered by lipids are unclear. In diabetes, increased expression of 12/15-lipoxygenase (12/15-LO) enhances oxidized lipids such as 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE], which promote oxidant stress, glomerular and mesangial cell (MC) dysfunction, and fibrosis, and mediate the actions of profibrotic growth factors. We hypothesized that 12/15-LO and its oxidized lipid products can regulate epigenetic mechanisms mediating profibrotic gene expression related to DN.nnnRESULTSn12(S)-HETE increased profibrotic gene expression and enrichment of permissive histone lysine modifications at their promoters in MCs. 12(S)-HETE also increased protein levels of SET7, a histone H3 lysine 4 methyltransferase, and promoted its nuclear translocation and enrichment at profibrotic gene promoters. Furthermore, SET7 (Setd7) gene silencing inhibited 12(S)-HETE-induced profibrotic gene expression. 12/15-LO (Alox15) gene silencing or genetic knockout inhibited transforming growth factor-β1 (TGF-β1)-induced expression of Setd7 and profibrotic genes and histone modifications in MCs. Furthermore, 12/15-LO knockout in mice ameliorated key features of DN and abrogated increases in renal SET7 and profibrotic genes. Additionally, 12/15-LO siRNAs in vivo blocked increases in renal SET7 and profibrotic genes in diabetic mice.nnnINNOVATION AND CONCLUSIONnThese novel results demonstrate for the first time that 12/15-LO-derived oxidized lipids regulate histone modifications associated with profibrotic gene expression in MCs, and 12/15-LO can mediate similar actions of TGF-β1 and diabetes. Targeting 12/15-LO might be a useful strategy to inhibit key epigenetic mechanisms involved in DN.

Effect of prolonged tacrolimus treatment in idiopathic membranous nephropathy with nephrotic syndrome.

Objective: Tacrolimus has been used for idiopathic membranous nephropathy (IMN) therapy, but most patients who achieved remission showed a high relapse rate when tacrolimus was withdrawn after 6-12 months of therapy. We proposed that a prolonged therapeutic course should help reduce the relapse rate. Methods: A total of 42 patients with nephrotic syndrome caused by IMN were randomly divided into short-term (n = 20) and long-term (n = 22) groups. All patients received initial treatment with tacrolimus and prednisone for 6 months, and afterward only the long-term patient group was tapered with low-dose tacrolimus until 24 months. Results: Over 85% of the patients achieved proteinuria reduction, serum albumin improvement and serum lipid recovery; the probability of remission in both groups was over 80% at 6 months. The remission rate was steady at over 80% after 12 and 24 months in the long-term group, but only 50 and 45%, respectively, in the short-term group. Nine patients (45%) relapsed in the short-term group after tacrolimus withdrawal, while not a single patient suffered recurrence in the long-term group. The concentration of tacrolimus remained similar between the two groups at 5-8 ng/ml during the initial 6 months, and was significantly decreased at 12 months compared to 6 months (p < 0.05), along with reduction of oral administration in the long-term group. Conclusion: Combined therapy of tacrolimus with prednisone can relieve IMN significantly; prolonged tacrolimus treatment at a low blood concentration can alleviate the illness persistently, with a low recurrence rate and gratifying safety.

Combined therapy of low-dose tacrolimus and prednisone in nephrotic syndrome with slight mesangial proliferation

Aim:u2003 Tacrolimus is a calcineurin inhibitor that has been increasingly used in transplant medicine. However, the efficacy and safety of combined therapy of low‐dose tacrolimus and prednisone in the treatment of nephrotic syndrome (NS) with slight mesangial proliferation has not been reported.

Role of histone modification in 12‑lipoxygenase‑associated p21 gene regulation

The aim of the present study was to examine the impacts and mechanisms of 12‑lipoxygenase (12‑LO) and its metabolites on the acetylation and methylation of histone‑3‑lysine (H3K) in the p21 gene. Rat mesangial cells (MCs) were selected for use in the present study. A chromatin immunoprecipitation assay, reverse transcription‑quantitative polymerase chain reaction analysis and a luciferase assay were used to detect transcriptional activities, the acetylation (Ac) of H3K (H3KAc), p21 promoter methylation (Me) and the transcription regions induced by 12xa0(S)‑hydroxyeicosatetraenoic acid (HETE). The cells were transfected to induce the overexpression of p300 to examine changes in 12xa0(S)‑HETE‑associated p21 regulation and epigenetic modifications. 12 (S)‑HETE enhanced p21 transcriptional activity and mRNA expression. In the promoter regions, P1 and P2, and the T1 transcription region, 12 (S)‑HETE induced significant H3K9xa0Ac and H3K4xa0Me1 epigenetic modifications, however, no changes were observed in the T2 region. By contrast, 12xa0(S)‑HETE treatment markedly prevented H3K9Me3 at the p21 promoter, suggesting that complex Me was involved in 12 (S)‑HETE‑associated p21 regulation. Furthermore, the overexpression of p300 markedly enhanced basal and 12xa0(S)‑HETE‑associated p21 transcriptional regulation in the MCs. 12 (S)‑HETE treatment also induced histone acetyltransferase p300 occupancy in the p21 promoter, and reduced the nuclear expression and occupancy of lysine‑specific demethylase (LSD1) in the p21 promoter. 12 (S)‑HETE induced p300 occupancy, and reduced the nuclear expression and occupancy of LSD1 in the p21 promoter. Therefore, enhanced H3K9Ac and H3K4Me1 in the p21 promoter and transcription regions, and decreased H3K9Me3 in the p21 promoter increased the expression of p21.