c-Src tyrosine kinase mediates high glucose-induced endothelin-1 expression

Retinal blood flow dysregulation precedes neural retinal dysfunction in type 2 diabetic mice

We investigated and compared the susceptibility of retinal blood flow regulation and neural function in mice developing type 2 diabetes. The longitudinal changes in retinal neuronal function and blood flow responses to a 10-min systemic hyperoxia and a 3-min flicker stimulation were evaluated every 2 weeks in diabetic db/db mice and nondiabetic controls (db/m) from age 8 to 20 weeks. The retinal blood flow and neural activity were assessed using laser speckle flowgraphy and electroretinography (ERG), respectively. The db/db mice had significantly higher blood glucose levels and body weight. The resting retinal blood flow was steady and comparable between two groups throughout the study. Hyperoxia elicited a consistent decrease, and flicker light an increase, in retinal blood flow in db/m mice independent of age. However, these flow responses were significantly diminished in db/db mice at 8 weeks old and then the mice became unresponsive to stimulations at 12 weeks. Subsequently, the ERG implicit time for oscillatory potential was significantly increased at 14 weeks of age while the a-wave and b-wave amplitudes and implicit times remained unchanged. The deficiencies of flow regulation and neurovascular coupling in the retina appear to precede neural dysfunction in the mouse with type 2 diabetes.

Phosphoproteomics analysis of diabetic cardiomyopathy in aging-accelerated mice and effects of D-pinitol

PURPOSE

The molecular mechanisms of diabetic cardiomyopathy (DCM) development and D-pinitol (DP) in its treatment remain unclear. The present study is to explore the underlying mechanism of DCM in an elderly diabetic mouse model and to seek the protective targets of DP by phosphoproteomics.

EXPERIMENTAL DESIGN

We used streptozotocin to induce diabetes in SAMP8 and DP (150 mg/kg/day) intragastrically administrated to diabetic mice for 8 weeks. The heart tissues were harvested for label-free phosphoproteomic analysis from diabetic mice. Some differentially regulated phosphorylation sites were confirmed by parallel reaction monitoring.

RESULTS

Our results showed that 612 phosphorylation sites on 454 proteins had their phosphorylation levels significantly changed in the heart of untreated diabetic mice (DM). Of these phosphorylation sites, 216 phosphorylation sites on 182 proteins were normalized after DP treatment. We analyzed the functional signaling pathways in the heart of DP treated diabetic mice (DMT), including glucagon signaling pathway, insulin signaling pathway, mitophagy, apoptosis, and longevity regulating pathway. Two consensus motifs identified were targeted by Src and epidermal growth factor receptor between DMT and DM groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Our study might help to better understand the mechanism of DCM, provide novel targets for estimating the protective effects of DP.

Activated Histone Acetyltransferase p300/CBP-Related Signalling Pathways Mediate Up-Regulation of NADPH Oxidase, Inflammation, and Fibrosis in Diabetic Kidney

Accumulating evidence implicates the histone acetylation-based epigenetic mechanisms in the pathoetiology of diabetes-associated micro-/macrovascular complications. Diabetic kidney disease (DKD) is a progressive chronic inflammatory microvascular disorder ultimately leading to glomerulosclerosis and kidney failure. We hypothesized that histone acetyltransferase p300/CBP may be involved in mediating diabetes-accelerated renal damage. In this study, we aimed at investigating the potential role of p300/CBP in the up-regulation of renal NADPH oxidase (Nox), reactive oxygen species (ROS) production, inflammation, and fibrosis in diabetic mice. Diabetic C57BL/6J mice were randomized to receive 10 mg/kg C646, a selective p300/CBP inhibitor, or its vehicle for 4 weeks. We found that in the kidney of C646-treated diabetic mice, the level of H3K27ac, an epigenetic mark of active gene expression, was significantly reduced. Pharmacological inhibition of p300/CBP significantly down-regulated the diabetes-induced enhanced expression of Nox subtypes, pro-inflammatory, and pro-fibrotic molecules in the kidney of mice, and the glomerular ROS overproduction. Our study provides evidence that the activation of p300/CBP enhances ROS production, potentially generated by up-regulated Nox, inflammation, and the production of extracellular matrix proteins in the diabetic kidney. The data suggest that p300/CBP-pharmacological inhibitors may be attractive tools to modulate diabetes-associated pathological processes to efficiently reduce the burden of DKD.

Pharmacological inhibition of histone deacetylase reduces NADPH oxidase expression, oxidative stress and the progression of atherosclerotic lesions in hypercholesterolemic apolipoprotein E-deficient mice; potential implications for human atherosclerosis

NADPH oxidase (Nox)-derived reactive oxygen species (ROS) are instrumental in all inflammatory phases of atherosclerosis. Dysregulated histone deacetylase (HDAC)-related epigenetic pathways have been mechanistically linked to alterations in gene expression in experimental models of cardiovascular disorders. Hitherto, the relation between HDAC and Nox in atherosclerosis is not known. We aimed at uncovering whether HDAC plays a role in mediating Nox up-regulation, oxidative stress, inflammation, and atherosclerotic lesion progression. Human non-atherosclerotic and atherosclerotic arterial samples, ApoE-/- mice, and in vitro polarized monocyte-derived M1/M2-macrophages (Mac) were examined. Male ApoE-/- mice, maintained on normal or high-fat, cholesterol-rich diet, were randomized to receive 10 mg/kg suberoylanilide hydroxamic acid (SAHA), a pan-HDAC inhibitor, or its vehicle, for 4 weeks. In the human/animal studies, real-time PCR, Western blot, lipid staining, lucigenin-enhanced chemiluminescence assay, and enzyme-linked immunosorbent assay were employed. The protein levels of class I, class IIa, class IIb, and class IV HDAC isoenzymes were significantly elevated both in human atherosclerotic tissue samples and in atherosclerotic aorta of ApoE-/- mice. Treatment of ApoE-/- mice with SAHA reduced significantly the extent of atherosclerotic lesions, and the aortic expression of Nox subtypes, NADPH-stimulated ROS production, oxidative stress and pro-inflammatory markers. Significantly up-regulated HDAC and Nox subtypes were detected in inflammatory M1-Mac. In these cells, SAHA reduced the Nox1/2/4 transcript levels. Collectively, HDAC inhibition reduced atherosclerotic lesion progression in ApoE-/- mice, possibly by intertwined mechanisms involving negative regulation of Nox expression and inflammation. The data propose that HDAC-oriented pharmacological interventions could represent an effective therapeutic strategy in atherosclerosis.

Histone Acetyltransferase-Dependent Pathways Mediate Upregulation of NADPH Oxidase 5 in Human Macrophages under Inflammatory Conditions: A Potential Mechanism of Reactive Oxygen Species Overproduction in Atherosclerosis

Histone acetylation plays a major role in epigenetic regulation of gene expression. Monocyte-derived macrophages express functional NADPH oxidase 5 (Nox5) that contributes to oxidative stress in atherogenesis. The mechanisms of Nox5 regulation are not entirely elucidated. The aim of this study was to investigate the expression pattern of key histone acetyltransferase subtypes (p300, HAT1) in human atherosclerosis and to determine their role in mediating the upregulation of Nox5 in macrophages under inflammatory conditions. Human nonatherosclerotic and atherosclerotic tissue samples were collected in order to determine the expression of p300 and HAT1 isoforms, H3K27ac, and Nox5. In vitro determinations were done on human macrophages exposed to lipopolysaccharide in the absence or presence of histone acetyltransferase inhibitors. Western blot, immunohistochemistry, immunofluorescence, real-time PCR, transfection, and chromatin immunoprecipitation assay were employed. The protein levels of p300 and HAT1 isoforms, H3K27ac, and Nox5 were found significantly elevated in human atherosclerotic specimens. Immunohistochemistry/immunofluorescence staining revealed that p300, HAT1, H3K27ac, H3K9ac, and Nox5 proteins were colocalized in the area of CD45⁺/CD68⁺ immune cells and lipid-rich deposits within human atherosclerotic plaques. Lipopolysaccharide induced the levels of HAT1, H3K27ac, H3K9ac, and Nox5 and the recruitment of p300 and HAT1 at the sites of active transcription within Nox5 gene promoter in cultured human macrophages. Pharmacological inhibition of histone acetyltransferase significantly reduced the Nox5 gene and protein expression in lipopolysaccharide-challenged macrophages. The overexpression of p300 or HAT1 enhanced the Nox5 gene promoter activity. The histone acetyltransferase system is altered in human atherosclerosis. Under inflammatory conditions, HAT subtypes control Nox5 overexpression in cultured human macrophages. The data suggest the existence of a new epigenetic mechanism underlying oxidative stress in atherosclerosis.

Overexpression of Axl reverses endothelial cells dysfunction in high glucose and hypoxia

The receptor tyrosine kinase Axl is involved in diabetic vascular disease. This study aims to investigate the effect of high glucose on endothelial cells injury and Axl expression in hypoxia condition in vitro, and we present details of the mechanism associated with overexpression of Axl rescue the high glucose injury. Our results showed that high glucose impaired both human umbilical vein endothelial cells (HUVECs) and EAhy926 cells angiogenesis in hypoxia condition. In addition, high glucose inhibits Axl and hypoxia-inducible factor 1-α (HIF-1α) protein expression in hypoxia condition. Axl overexpression significantly reversed endothelial cells dysfunction in high glucose/hypoxia. Furthermore, Axl overexpression in EAhy926 cells increases HIF-1α protein synthesis through PI3K/Akt/mTOR/p70 ^S6K signal pathway but not Mek/Erk in high glucose/hypoxia condition. This study demonstrates that high glucose can alter Axl signaling and HIF-1α in hypoxia condition. Overexpression of Axl may rescue endothelial cells dysfunction and HIF-1α expression through its downstream signals in high glucose/hypoxia.

Curcumin exerts anti-inflammatory and vasoprotective effects through amelioration of NFAT-dependent endothelin-1 production in mice with acute Chagas cardiomyopathy

BACKGROUND

The anti-inflammatory and cardioprotective properties of curcumin (Cur), a natural polyphenolic flavonoid isolated from the rhizomes of Curcuma longa, are increasingly considered to have beneficial effects on the progression of Chagas heart disease, caused by the protozoan parasite Trypanosoma cruzi.

OBJECTIVE

To evaluate the effects of oral therapy with Cur on T. cruzi-mediated cardiovasculopathy in acutely infected mice and analyse the in vitro response of parasite-infected human microvascular endothelial cells treated with this phytochemical.

METHODS

Inflammation of heart vessels from Cur-treated and untreated infected mice were analysed by histology, with benznidazole (Bz) as the reference compound. Parasitaemia was monitored by the direct method. Capillary permeability was visualised by Evans-blue assay. Myocardial ET-1, IL-6, and TNF-α mRNA expressions were measured by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Microvascular endothelial HMEC-1 cells were infected in vitro with or without addition of Cur or Bz. Induction of the Ca2+/NFAT pathway was assessed by fluorometry, immunoblotting, and reporter assay.

FINDINGS

Oral Cur therapy of recently infected mice reduced inflammatory cell infiltration of myocardial arteries without lowering parasite levels. Compared to that of the phosphate-buffered saline-receiving group, hearts from Cur-treated mice showed significantly decreased vessel inflammation scores (p < 0.001), vascular permeabilities (p < 0.001), and levels of IL-6/TNF-α (p < 0.01) and ET-1 (p < 0.05) mRNA. Moreover, Cur significantly (p < 0.05 for transcript; p < 0.01 for peptide) downregulated ET-1 secretion from infected HMEC-1 cells. Remarkably, Cur addition significantly (p < 0.05 at 27.0 μM) interfered with T. cruzi-dependent activation of the Ca2+/NFATc1 signalling pathway that promotes generation of inflammatory agents in HMEC-1 cells.

CONCLUSIONS

Oral treatment with Cur dampens cardiovasculopathy in acute Chagas mice. Cur impairs the Ca2+/NFATc1-regulated release of ET-1 from T. cruzi-infected vascular endothelium. These findings identify new perspectives for exploring the potential of Cur-based interventions to ameliorate Chagas heart disease.

Epigenetic regulation of vascular NADPH oxidase expression and reactive oxygen species production by histone deacetylase-dependent mechanisms in experimental diabetes

Reactive oxygen species (ROS) generated by up-regulated NADPH oxidase (Nox) contribute to structural-functional alterations of the vascular wall in diabetes. Epigenetic mechanisms, such as histone acetylation, emerged as important regulators of gene expression in cardiovascular disorders. Since their role in diabetes is still elusive we hypothesized that histone deacetylase (HDAC)-dependent mechanisms could mediate vascular Nox overexpression in diabetic conditions. Non-diabetic and streptozotocin-induced diabetic C57BL/6J mice were randomized to receive vehicle or suberoylanilide hydroxamic acid (SAHA), a pan-HDAC inhibitor. In vitro studies were performed on a human aortic smooth muscle cell (SMC) line. Aortic SMCs typically express Nox1, Nox4, and Nox5 subtypes. HDAC1 and HDAC2 proteins along with Nox1, Nox2, and Nox4 levels were found significantly elevated in the aortas of diabetic mice compared to non-diabetic animals. Treatment of diabetic mice with SAHA mitigated the aortic expression of Nox1, Nox2, and Nox4 subtypes and NADPH-stimulated ROS production. High concentrations of glucose increased HDAC1 and HDAC2 protein levels in cultured SMCs. SAHA significantly reduced the high glucose-induced Nox1/4/5 expression, ROS production, and the formation malondialdehyde-protein adducts in SMCs. Overexpression of HDAC2 up-regulated the Nox1/4/5 gene promoter activities in SMCs. Physical interactions of HDAC1/2 and p300 proteins with Nox1/4/5 promoters were detected at the sites of active transcription. High glucose induced histone H3K27 acetylation enrichment at the promoters of Nox1/4/5 genes in SMCs. The novel data of this study indicate that HDACs mediate vascular Nox up-regulation in diabetes. HDAC inhibition reduces vascular ROS production in experimental diabetes, possibly by a mechanism involving negative regulation of Nox expression.