Rosiglitazone via PPARγ-dependent suppression of oxidative stress attenuates endothelial dysfunction in rats fed homocysteine thiolactone

S-nitrosylation of AMPKγ impairs coronary collateral circulation and disrupts VSMC reprogramming

Collateral circulation is essential for blood resupply to the ischemic heart, which is dictated by the contractile phenotypic restoration of vascular smooth muscle cells (VSMC). Here we investigate whether S-nitrosylation of AMP-activated protein kinase (AMPK), a key regulator of the VSMC phenotype, impairs collateral circulation. In rats with collateral growth and development, nitroglycerin decreases coronary collateral blood flow (CCBF), inhibits vascular contractile phenotypic restoration, and increases myocardial infarct size, accompanied by reduced AMPK activity in the collateral zone. Nitric oxide (NO) S-nitrosylates human recombinant AMPKγ1 at cysteine 131 and decreases AMP sensitivity of AMPK. In VSMCs, exogenous expression of S-nitrosylation-resistant AMPKγ1 or deficient NO synthase (iNOS) prevents the disruption of VSMC reprogramming. Finally, hyperhomocysteinemia or hyperglycemia increases AMPKγ1 S-nitrosylation, prevents vascular contractile phenotypic restoration, reduces CCBF, and increases the infarct size of the heart in Apoe-/- mice, all of which is rescued in Apoe-/-/iNOSsm-/- mice or Apoe-/- mice with enforced expression of the AMPKγ1-C130A mutant following RI/MI. We conclude that nitrosative stress disrupts coronary collateral circulation during hyperhomocysteinemia or hyperglycemia through AMPK S-nitrosylation.

Diagnostic ultrasound-mediated microbubble cavitation dose-dependently improves diabetic cardiomyopathy through angiogenesis

Ultrasound-mediated microbubble cavitation (UMMC) induces therapeutic angiogenesis to treat ischemic diseases. This study aimed to investigate whether diagnostic UMMC alleviates diabetic cardiomyopathy (DCM) and, if so, through which mechanisms. DCM model was established by injecting streptozocin into rats to induce hyperglycemia, followed by a high-fat diet. The combined therapy of cation microbubble with low-intensity diagnostic ultrasound (frequency = 4 MHz), with a pulse frequency of 20 Hz and pulse length (PL) of 8, 18, 26, or 36 cycles, was given to rats twice a week for 8 consecutive weeks. Diagnostic UMMC therapy with PL at 8, 18, and 26 cycles, but not 36 cycles, dramatically prevented myocardial fibrosis, improved heart functions, and increased angiogenesis, accompanied by increased levels of PI3K, Akt, and eNOS proteins in the DCM model of rats. In cultured endothelial cells, low-intensity UMMC treatment (PL = 3 cycles, sound pressure level = 50%, mechanical index = 0.82) increased cell viability and activated PI3K-Akt-eNOS signaling. The combination of diagnostic ultrasound with microbubble destruction dose-dependently promoted angiogenesis, thus improving heart function through PI3K-Akt-eNOS signaling in diabetes. Accordingly, diagnostic UMMC therapy should be considered to protect the heart in patients with diabetes.

COX/iNOS dependence for angiotensin-II-induced endothelial dysfunction

Vascular dysfunction induced by angiotensin-II can result from direct effects on vascular and inflammatory cells and indirect hemodynamic effects. Using isolated and functional cultured aortas, we aimed to identify the effects of angiotensin-II on cyclooxygenase (COX) and inducible nitric oxide synthase (iNOS) and evaluate their impact on vascular reactivity. Aortic rings from mice were incubated overnight in culture medium containing angiotensin-II (100 nmol/L) or vehicle to induce vascular disfunction. Vascular reactivity of cultured arteries was evaluated in a bath chamber. Immunofluorescence staining for COX-1 and COX-2 was performed. Nitric oxide (NO) formation was approached by the levels of nitrite, a NO end product, and using a fluorescent probe (DAF). Oxidative and nitrosative stress were determined by DHE fluorescence and nitrotyrosine staining, respectively. Arteries cultured with angiotensin-II showed impairment of endothelium-dependent relaxation, which was reversed by the AT₁ receptor antagonist. Inhibition of COX and iNOS restored vascular relaxation, suggesting a common pathway in which angiotensin-II triggers COX and iNOS, leading to vasoconstrictor receptors activation. Moreover, using selective antagonists, TP and EP were identified as the receptors involved in this response. Endothelium-dependent contractions of angiotensin-II-cultured aortas were blunted by ibuprofen, and increased COX-2 immunostaining was found in the arteries, indicating endothelium release of vasoconstrictor prostanoids. Angiotensin-II induced increased reactive oxygen species and NO production. An iNOS inhibitor prevented NO enhancement and nitrotyrosine accumulation in arteries stimulated with angiotensin-II. These results confirm that angiotensin-II causes vascular inflammation that culminates in endothelial dysfunction in an iNOS and COX codependent manner.

Peroxisome proliferator-activated receptor gamma is essential for stress adaptation by maintaining lipid homeostasis in female fish

Reduction of lipid synthesis often causes free fatty acid (FFA) overload, resulting consequential oxidative stress and health damage. Environmental stresses also induce cellular oxidative stress in organisms. The functional peroxisome proliferator-activated receptor gamma (pparg) gene is essential for lipid synthesis and homeostatic lipid maintenance. However, the relationship between the pparg-mediated lipid synthesis and environmental stress adaptation awaits full elucidation. Here, we generated a pparg-knockout zebrafish model. The conversion of free fatty acids into triglycerides in the female pparg mutants was hampered by reduced esterification efficiency, thus induced lipotoxicity, as evidenced by high oxidative stress and damaged health in these mutants, which led to reduced resistance to cold, heat and ammonia nitrogen stresses. Activating pparg in the wild-type female fish via dietary supplementation with rosiglitazone (a pparg agonist), or reducing oxidative stress in the female pparg mutants via dietary supplementation with N-acetylcysteine (an antioxidant), or promoting mitochondrial fatty acid β-oxidation in the female pparg mutants via dietary supplementation with l-carnitine, resulted in significantly reduced cellular injury, and improved environmental stress resistance. Collectively, our findings reveal that the regulative function of pparg in FFA esterification is important in stress resistance in female fish, and highlight the tight correlation existing between lipotoxicity and environmental adaptation.

Current progress on the mechanisms of hyperhomocysteinemia-induced vascular injury and use of natural polyphenol compounds

Cardiovascular disease is one of the most common diseases in the elderly population, and its incidence has rapidly increased with the prolongation of life expectancy. Hyperhomocysteinemia is an independent risk factor for various cardiovascular diseases, including atherosclerosis, and damage to vascular function plays an initial role in its pathogenesis. This review presents the latest knowledge on the mechanisms of vascular injury caused by hyperhomocysteinemia, including oxidative stress, endoplasmic reticulum stress, protein N-homocysteinization, and epigenetic modification, and discusses the therapeutic targets of natural polyphenols. Studies have shown that natural polyphenols in plants can reduce homocysteine levels and regulate DNA methylation by acting on oxidative stress and endoplasmic reticulum stress-related signaling pathways, thus improving hyperhomocysteinemia-induced vascular injury. Natural polyphenols obtained via daily diet are safer and have more practical significance in the prevention and treatment of chronic diseases than traditional drugs.

Morinda citrifolia (Noni) fruit juice promotes vascular endothelium function in hypertension via glucagon-like peptide-1 receptor-CaMKKβ-AMPK-eNOS pathway

Morinda citrifolia (Noni) is extensively used in herbal remedies to prevent and treat various diseases, including hypertension. The purpose of this study was to investigate the vascular effects of noni fruit juice and characterize the upstream signaling pathways. We measured the systolic blood pressure, diastolic blood pressure, 24-hr urinary nitric oxide (NO) metabolite excretion, bodyweight (BW), and urine examination in SHR.Cg-Leprcp/NDmcr (SHR/cp) rats after 6 weeks noni juice (15 ml/kg) treatment. Noni juice significantly decreased blood pressure and 24-hr urinary NO metabolite without change of BW or urine volume. Furthermore, the noni juice extract (NJE) promoted endothelial vasorelaxation in rat aorta rings and NO product through an increase in phosphorylation of endothelial nitric oxide synthase (eNOS) in human umbilical vein endothelial cells (HUVECs). NJE might act on a glucagon like peptide-1 receptor (GLP-1R) via Ca²⁺ /calmodulin-dependent protein kinase kinase β (CaMKKβ)-AMPK signaling with pretreatment of their inhibitors or antagonist in HUVECs. Deacetylasperulosidic acid (DAA) was an active compound in noni juice to improve NO release through same pathway in HUVECs. These results suggested that noni is a novel dietary plant that probably regulates GLP-1R-induced CaMKKβ-AMPK-eNOS pathway to improve endothelium-dependent relaxation, thus reduce the blood pressure probably via one of its responsible ingredient DAA.

High levels of dietary methionine improves sitagliptin-induced hepatotoxicity by attenuating oxidative stress in hypercholesterolemic rats

Background

Both cholesterol (Cho) and methionine (Met, a precursor for homocysteine) are risk factors for fatty liver disease. Since Western diets are rich in Cho and Met, we investigated the hepatic effects of feeding a diet enriched in Met and Cho. Further, based on the reported anti-oxidative and lipid lowering properties of sitagliptin (an antidiabetic drug), we tested whether it could counteract the negative effects of high Cho and Met. We therefore hypothesized that sitagliptin would ameliorate the development of liver pathology that is produced by feeding diets rich in either Cho, Met, or both.

Methods

Male Sprague Dawley rats were fed ad libitum a) control diet, or b) high Met or c) high Cho, or d) high Met + high Cho diets for 35 days. From day 10 to 35, 50% of rats in each dietary group were gavaged with either vehicle or an aqueous suspension of sitagliptin (100 mg/kg/day). Liver samples were harvested for histological, molecular, and biochemical analyses.

Results

The high Cho diet produced significant hepatic steatosis which was unaffected by sitagliptin. Contrary to expectation, sitagliptin exacerbated expression of hepatic markers of oxidative stress and fibrosis in rats fed high Cho. Corresponding increases in 4-hydroxynonenal adducts and collagen deposition were demonstrated by immunohistochemistry and sirius red staining. These hepatic changes were absent in rats on the high Met diet and they were comparable to controls. The inclusion of Met in the high Cho diet resulted in significant reduction of the hepatic steatosis, oxidative stress, and fibrosis produced by high Cho alone.

Conclusion

Sitagliptin exacerbated the effects of high Cho on both oxidative stress and fibrosis, resulting in NASH like symptoms that were significantly reversed by the inclusion of Met.

Rosiglitazone Suppresses Calcium Oxalate Crystal Binding and Oxalate-Induced Oxidative Stress in Renal Epithelial Cells by Promoting PPAR-γ Activation and Subsequent Regulation of TGF-β1 and HGF Expression

Peroxisome proliferator-activated receptor- (PPAR-) γ is a ligand-dependent transcription factor, and it has become evident that PPAR-γ agonists have renoprotective effects, but their influence and mechanism during the development of calcium oxalate (CaOx) nephrolithiasis remain unknown. Rosiglitazone (RSG) was used as a representative PPAR-γ agonist in our experiments. The expression of transforming growth factor-β1 (TGF-β1), hepatocyte growth factor (HGF), c-Met, p-Met, PPAR-γ, p-PPAR-γ (Ser112), Smad2, Smad3, pSmad2/3, and Smad7 was examined in oxalate-treated Madin-Darby canine kidney (MDCK) cells and a stone-forming rat model. A CCK-8 assay was used to evaluate the effects of RSG on cell viability. In addition, intracellular reactive oxygen species (ROS) levels were monitored, and lipid peroxidation in renal tissue was detected according to superoxide dismutase and malondialdehyde levels. Moreover, the location and extent of CaOx crystal deposition were evaluated by Pizzolato staining. Our results showed that, both in vitro and in vivo, oxalate impaired PPAR-γ expression and phosphorylation, and then accumulative ROS production was observed, accompanied by enhanced TGF-β1 and reduced HGF. These phenomena could be reversed by the addition of RSG. RSG also promoted cell viability and proliferation and decreased oxidative stress damage and CaOx crystal deposition. However, these protective effects of RSG were abrogated by the PPAR-γ-specific inhibitor GW9662. Our results revealed that the reduction of PPAR-γ activity played a critical role in oxalate-induced ROS damage and CaOx stone formation. RSG can regulate TGF-β1 and HGF/c-Met through PPAR-γ to exert antioxidant effects against hyperoxaluria and alleviate crystal deposition. Therefore, PPAR-γ agonists may be expected to be a novel therapy for nephrolithiasis, and this effect is related to PPAR-γ-dependent suppression of oxidative stress.

Amorphous nano-selenium quantum dots improve endothelial dysfunction in rats and prevent atherosclerosis in mice through Na+/H+ exchanger 1 inhibition

AIM

Selenium, a trace element involved in important enzymatic activities inside the body, has protective effects against cardiovascular diseases including atherosclerosis. The safe dose of selenium in the organism is very narrow, limiting the supplementation of selenium in diet. The aim of this study is to explore whether selenium quantum dots (SeQDs) prevent atherosclerosis and to investigate the potential mechanisms.

METHODS

An amorphous form of SeQDs (A-SeQDs) and a crystalline form of SeQDs (C-SeQDs) were prepared through self-redox decomposition of selenosulfate precursor. Endothelial dysfunction was induced by balloon injury plus high fat diet (HFD) in rats. Atherosclerotic model was established by feeding Apoe^-/- mice with HFD.

RESULTS

Administrations of A-SeQDs but not C-SeQDs dramatically improved endothelium-dependent relaxation, and accelerated would healing in primary endothelial cells isolated from rats, which was comprised by co-treatment of LiCl. Lentivirus-mediated knockdown of Na⁺/H⁺ exchanger 1 (NHE1) abolished LiCl-induced endothelial dysfunction in rats. In cultured endothelial cells, A-SeQDs, as well as cariporide, inhibited NHE1 activities, decreased intracellular pH value and Ca²⁺ concentration, and reduced calpain activity increased by ox-LDL. These protective effects of A-SeQDs were reversed by LiCl treatment in endothelial cells. In Apoe^-/- mice feeding with HFD, A-SeQDs prevented endothelial dysfunction and reduced the size of atherosclerotic plaque in aortic arteries. Further, lentivirus-mediated NHE1 gene overexpression abolished the protective effects of A-SeQDs against endothelial dysfunction and atherosclerosis in Apoe^-/- mice.

CONCLUSION

A-SeQDs prevents endothelial dysfunction and the growth of atherosclerotic plaque through NHE1 inhibition and subsequent inactivation of Ca²⁺/calpain signaling. Clinically, the administration of A-SeQDs is an effective approach to treat atherosclerosis.

A minimally invasive approach to induce myocardial infarction in mice without thoracotomy

Acute myocardial infarction (MI) is a leading cause of morbidity and mortality in the world. Traditional method to induce MI by left coronary artery (LCA) ligation is typically performed by an invasive approach that requires ventilation and thoracotomy, causing serious injuries in animals undergoing this surgery. We attempted to develop a minimally invasive method (MIM) to induce MI in mice. Under the guide of ultrasound, LCA ligation was performed in mice without ventilation and chest-opening. Compared to sham mice, MIM induced MI in mice as determined by triphenyltetrazolium chloride staining and Masson staining. Mice with MIM surgery revealed the reductions of LVEF, LVFS, E/A and ascending aorta (AAO) blood flow, and the elevations of S-T segment and serum cTn-I levels at 24 post-operative hours. The effects of MI induced by MIM were comparable to the effects of MI produced by traditional method in mice. Importantly, MIM increased the survival rates and caused less inflammation after the surgery of LCA ligation, compared to the surgery of traditional method. Further, MIM induced angiogenesis and apoptosis in ischaemic hearts from mice at postoperative 28 days as similarly as traditional method did. Finally, the MIM model was able to develop into the myocardial ischaemia/reperfusion model by using a balloon catheter with minor modifications. The MI model is able to be efficiently induced by a minimally invasive approach in mice without ventilation and chest-opening. This new model is potentially to be used in studying ischaemia-related heart diseases.

Citronellal prevents endothelial dysfunction and atherosclerosis in rats

BACKGROUND

Atherosclerosis is a chronical inflammatory disease in arterial walls, which is involved in oxidative stress and endothelial dysfunction. Aromatherapy is one of the complementary therapies that use essential oils as the major therapeutic agents to treat several diseases. Citronellal (CT) is a monoterpene predominantly formed by the secondary metabolism of plants, producing antithrombotic, antiplatelet, and antihypertensive activities.

AIM

The aim of the present study is to explore whether aromatherapy with CT improves endothelial function to prevent the formation of atherosclerotic plaque in vivo.

METHODS

An AS model in carotid artery was induced by balloon injury and vitamin D3 injection in rats fed with a high-fat diet. The size of the carotid atherosclerotic plaque was determined by ultrasound, oil red, and hematoxylin-eosin staining. Endothelial function was assessed by measuring acetylcholine-induced vessel relaxation in an organ chamber.

RESULTS

Administrations of CT (50, 100, and 150 mg/kg) as well as lovastatin dramatically reduced the size of carotid atherosclerotic plaque in rats in a dose-dependent manner, compared with atherosclerotic rats fed with a high-fat diet plus balloon injury and vitamin D3. Mechanically, CT improved endothelial dysfunction, increased cell migration, and suppressed oxidative stress and inflammation in vascular endothelium in rats feeding on the high-fat diet plus balloon injury. Further, CT downregulated the protein levels of sodium-hydrogen exchanger 1 in rats with atherosclerosis.

CONCLUSION

CT improves endothelial dysfunction and prevents the growth of atherosclerosis in rats by reducing oxidative stress. Clinically, CT is potentially considered as a medicine to treat patients with atherosclerosis.

S-Nitrosylation of Prostacyclin Synthase Instigates Nitrate Cross-Tolerance In Vivo

Development of nitrate tolerance is a major drawback to nitrate therapy. Prostacyclin (PGI2) is a powerful vasodilator produced from prostaglandin (PGH2) by prostacyclin synthase (PGIS) in endothelial cells. This study aimed to determine the role of PGIS S-nitrosylation in nitrate tolerance induced by nitroglycerin (GTN). In endothelial cells, GTN increased PGIS S-nitrosylation and disturbed PGH2 metabolism, which were normalized by mutants of PGIS cysteine 231/441 to alanine (C231/441A). Clearance of nitric oxide by carboxy-PTIO or inhibition of S-nitrosylation by N-acetyl-cysteine decreased GTN-induced PGIS S-nitrosylation. Enforced expression of mutated PGIS with C231/441A markedly abolished GTN-induced PGIS S-nitrosylation and nitrate cross-tolerance in Apoe^-/- mice. Inhibition of cyclooxygenase 1 by aspirin, supplementation of PGI2 by beraprost, and inhibition of PGIS S-nitrosylation by N-acetyl-cysteine improved GTN-induced nitrate cross-tolerance in rats. In patients, increased PGIS S-nitrosylation was associated with nitrate tolerance. In conclusion, GTN induces nitrate cross-tolerance through PGIS S-nitrosylation at cysteine 231/441.

Hyperglycemia via activation of thromboxane A2 receptor impairs the integrity and function of blood-brain barrier in microvascular endothelial cells

Diabetes is one of high risk factors for cardio- and cerebra-vascular diseases, including stroke, atherosclerosis and hypertension. This study was conducted to elucidate whether and how thromboxane receptor (TPr) activation contributes to blood-brain barrier (BBB) dysfunction in diabetes. Human brain microvascular endothelial cells (HBMECs) were cultured. The levels of phosphorylated endothelial nitric oxide synthase (eNOS) at Ser¹¹⁷⁷ (p-eNOS) and Akt at Ser⁴⁷³ (p-Akt) were assayed by western blot. Exposure of HBMECs to either high glucose (HG) or thromboxane A₂ (TxA₂) mimetic U46619, significantly reduced p-eNOS and p-Akt. These effects were abolished by pharmacological or genetic inhibitors of TPr. HG/U46619-induced suppressions of eNOS and Akt phosphorylation were accompanied by upregulation of PTEN and Ser³⁸⁰/Thr^382/383 PTEN phosphorylation. PTEN-specific siRNA restored Akt-eNOS signaling in the face of TPr activation or HG. The small GTPase, Rho, was also activated by HG stimulation, and pretreatment of HBMECs with Y27632, a Rho-associated kinase (ROCK) inhibitor, rescued HG-impaired Akt-eNOS signaling. In STZ-injected rats, we found that hyperglycemia dramatically increased the levels of PTEN and PTEN-Ser³⁸⁰/Thr^382/383 phosphorylation, reduced both levels of p-eNOS and p-Akt, and disrupted BBB function assayed by Evans blue staining, which were abolished by SQ29548 treatment. We conclude that hyperglycemia activates thromboxane A2 receptor to impair the integrity and function of blood-brain barrier via the ROCK-PTEN-Akt-eNOS pathway.

Beneficial effects of rosiglitazone and losartan combination in diabetic rats

Diabetes with vascular complication needs strict interventions to retard possible serious complications. This research estimated the possible interaction of rosiglitazone (RGN) with losartan (Los) in diabetic rats. Male Sprague-Dawley rats were randomly divided into nondiabetic rats, diabetic rats, and diabetic rats that received RGN, Los, or a combination of RGN and Los. Measurement of serum glucose, vascular adhesion molecule-1, interleukin-6, tumor necrosis factor-α, aortic lipid peroxide (malondialdehyde), glutathione, superoxide dismutase, and total nitrate/nitrite levels was done. Also, the effects of RGN on the relaxation created by acetylcholine and sodium nitroprusside, contraction of isolated aortic rings provoked by phenylephrine and angiotensin II were determined. Results revealed that RGN or Los had a vasodilating effect to variable degrees indicated by enhanced effects on both acetylcholine-induced relaxation and the antagonistic effect on angiotensin II and phenylephrine-stimulated contraction of diabetic aortas with significant amelioration in serum glucose, vascular adhesion molecule-1, interleukin-6, and tumor necrosis factor-α levels and aortic oxidant/antioxidant balance. Treatment of diabetic rats with a combination of RGN and Los produced a more pronounced effect on the measured parameters compared to the diabetic, RGN-, and Los-treated groups. These findings point out the beneficial effects of RGN and Los combination in diabetic rats.

Lovastatin upregulates microRNA-29b to reduce oxidative stress in rats with multiple cardiovascular risk factors

AIMS

Proteasome-linked oxidative stress is believed to cause endothelial dysfunction, an early event in cardiovascular diseases (CVD). Statin, as HMG-CoA reductase inhibitor, prevents endothelial dysfunction in CVD. However, the molecular mechanism of statin-mediated normalization of endothelial function is not completely elucidated.

METHODS AND RESULTS

Lovastatin time/dose-dependently increased miR-29b expression and decreased proteasome activity in cultured human umbilical vein endothelial cells (HUVECs). Anti-miR-29b or overexpression of PA200 abolished lovastatin-induced inhibition of proteasome activity in HUVECs. In contrast, pre-miR-29b or PA200 siRNA mimics these effects of lovastatin on proteasome activity. Lovastatin inhibited oxidative stress induced by multiple oxidants including ox-LDL, H2O2, TNFα, homocysteine thiolactone (HTL), and high glucose (HG), which were reversed by inhibition of miR-29b in HUVECs. Ex vivo analysis indicated that lovastatin normalized the acetylcholine-induced endothelium-dependent relaxation and the redox status in isolated rat aortic arteries exposure to multiple cardiovascular risk factors. In vivo analysis revealed that administration of lovastatin remarkably suppressed oxidative stress and prevented endothelial dysfunction in rats with hyperglycemia, dyslipidemia, and hyperhomocysteinemia, as well as increased miR-29b expressions, reduced PA200 protein levels, and suppression of proteasome activity in aortic tissues.

CONCLUSION

Upregulation of miR-29b expression is a common mechanism contributing to endothelial dysfunction induced by multiple cardiovascular risk factors through PA200-dependent proteasome-mediated oxidative stress, which is prevented by lovastatin.

Maintained Folic Acid Supplementation Reduces the Risk of Mortality in Continuous Ambulatory Peritoneal Dialysis Patients

BACKGROUND

The association between folic acid (FA) supplementation and mortality in continuous ambulatory peritoneal dialysis (CAPD) patients is unclear.

METHODS

FA exposure was calculated as a percentage of cumulative duration of drug usage to total follow-up duration (FA%). A total of 1,358 patients were classified by a cutoff value of FA%. The association of FA with mortality was evaluated using Cox proportional hazards models.

RESULTS

The cutoff value of FA% for predicting mortality was <34% at a median follow-up of 40.7 months. FA ≥34% was associated with decreased risk for all-cause (adjusted hazard ratios [HRs] 95% CI 0.64 [0.48-0.85] and cardiovascular mortality 0.67 (95% CI 0.47-0.97). Moreover, the adjusted HRs per 10% higher FA for all-cause and cardiovascular mortality were 0.925 (95% CI 0.879-0.973) and 0.926 (95% CI 0.869-0.988), respectively.

CONCLUSIONS

Longer period of FA supplementation led to a reduction in risk of both all-cause and cardiovascular mortality in CAPD patients.

Pravastatin activates activator protein 2 alpha to augment the angiotensin II-induced abdominal aortic aneurysms

We have previously reported that activation of AMP-activated kinase alpha 2 (AMPKa2) by nicotine or angiotensin II (AngII) instigates formation of abdominal aortic aneurysms (AAA) in Apoe−/− mice. Statins, used to treat hyperlipidemia widely, activate AMPK in vascular cells. We sought to examine the effects of pravastatin on AAA formation and uncover the molecular mechanism. The AAA model was induced by AngII and evaluated by incidence, elastin degradation, and maximal abdominal aortic diameter in Apoe−/− mice. The phosphorylated levels of AMPKa2 and activator protein 2 alpha (AP-2a) were examined in cultured vascular smooth muscle cells (VSMCs) or in mice. We observed that pravastatin (50 mg/kg/day, 8 weeks) remarkably increased the AngII-induced AAA incidence in mice. In VSMCs, pravastatin increased the levels of pAMPK, pAP-2a, and MMP2 in both basal and AngII-stressed conditions, which were abolished by tempol and compound C. Pravastatin-upregulated MMP2 was abrogated by AMPKa2 or AP-2a siRNA. Lentivirus-mediated gene silence of AMPKa2 or AP-2a abolished pravastatin-worsened AAA formations in AngII-infused Apoe−/− mice. Clinical investigations demonstrated that both AMPKa2 and AP-2a phosphorylations were increased in AAA patients or human subjects taking pravastatin. In conclusion, pravastatin promotes AAA formation through AMPKa2-dependent AP-2a activations.

Folic acid attenuates homocysteine and enhances antioxidative capacity in atherosclerotic rats

Atherosclerosis is a chronic disease that can seriously endanger human life. Folic acid supplementation modulates several disorders, including atherosclerosis, via its antiapoptotic and antioxidative properties. This study investigated whether folic acid alleviates atherogenesis by restoring homocysteine levels and antioxidative capacity in atherosclerosis Wistar rats. To this end, 28 Wistar rats were randomly divided into 4 groups (7 rats/group) as follows: (i) wild-type group, fed only the AIN-93 semi-purified rodent diet (folic acid: 2.1 mg/kg); (ii) high-fat + folic acid-deficient group (HF+DEF) (folic acid: 0.2 mg/kg); (iii) high-fat + normal folic acid group (folic acid: 2.1 mg/kg); and (iv) high-fat + folic acid-supplemented group (folic acid: 4.2 mg/kg). After 12 weeks, histopathological changes in the atherosclerotic lesions of the aortic arch were determined. In addition, serum folate levels, plasma homocysteine levels, plasma S-adenosyl-homocysteine levels, antioxidant status, oxidant status, and lipid profiles were evaluated. The results show aggravated atherosclerotic lesions in the HF+DEF group. Folic acid supplementation increased concentrations of serum folate. Further, folic acid supplementation increased high-density lipoprotein-cholesterol, decreased plasma homocysteine levels, and improved antioxidant capacity in atherogenic rats. These findings are consistent with the hypothesis that folic acid alleviates atherogenesis by reducing plasma homocysteine levels and improving antioxidant capacity in rats fed a high-fat diet.

Hyperhomocysteinaemia and vascular injury: advances in mechanisms and drug targets

Homocysteine is a sulphur-containing non-proteinogenic amino acid. Hyperhomocysteinaemia (HHcy), the pathogenic elevation of plasma homocysteine as a result of an imbalance of its metabolism, is an independent risk factor for various vascular diseases, such as atherosclerosis, hypertension, vascular calcification and aneurysm. Treatments aimed at lowering plasma homocysteine via dietary supplementation with folic acids and vitamin B are more effective in preventing vascular disease where the population has a normally low folate consumption than in areas with higher dietary folate. To date, the mechanisms of HHcy-induced vascular injury are not fully understood. HHcy increases oxidative stress and its downstream signalling pathways, resulting in vascular inflammation. HHcy also causes vascular injury via endoplasmic reticulum stress. Moreover, HHcy up-regulates pathogenic genes and down-regulates protective genes via DNA demethylation and methylation respectively. Homocysteinylation of proteins induced by homocysteine also contributes to vascular injury by modulating intracellular redox state and altering protein function. Furthermore, HHcy-induced vascular injury leads to neuronal damage and disease. Also, an HHcy-activated sympathetic system and HHcy-injured adipose tissue also cause vascular injury, thus demonstrating the interactions between the organs injured by HHcy. Here, we have summarized the recent developments in the mechanisms of HHcy-induced vascular injury, which are further considered as potential therapeutic targets in this condition.

LINKED ARTICLES

This article is part of a themed section on Spotlight on Small Molecules in Cardiovascular Diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.8/issuetoc.

Berberine promotes ischemia-induced angiogenesis in mice heart via upregulation of microRNA-29b

BACKGROUND

Berberine has several preventive effects on cardiovascular diseases. Increased expression of miR-29b has been reported to attenuate cardiac remodeling after myocardial infarction (MI). We hypothesized that berberine via an miR-29b-dependent mechanism promotes angiogenesis and improves heart functions in mice after MI.

METHODS

The MI model was established in mice by ligation of left anterior descending coronary artery. The expression of miR-29b was examined by RT-qPCR. Angiogenesis was assessed by immunohistochemistry.

RESULTS

Berberine increased miR-29b expression and promoted cell proliferations and migrations in cultured endothelial cells, which were abolished by miR-29b antagomir or AMP-activated protein kinase inhibitor compound C. In mice following MI, administration of berberine significantly increased miR-29b expressional level, promoted angiogenesis, reduced infarct size, and improved heart functions after 14 postoperative days. Importantly, these in vivo effects of berberine were ablated by antagonism of miR-29b.

CONCLUSION

Berberine via upregulation of miR-29b promotes ischemia-induced angiogenesis and improves heart functions.

Activation of thromboxane A2 receptors mediates endothelial dysfunction in diabetic mice

BACKGROUND

Diabetes is one of high-risk factors for cardiovascular disease. Improvement of endothelial dysfunction in diabetes reduces vascular complications. However, the underlying mechanism needs to be uncovered. This study was conducted to elucidate whether and how thromboxane A2 receptor (TPr) activation contributes to endothelial dysfunction in diabetes.

METHODS AND RESULTS

Exposure of human umbilical vein endothelial cells (HUVECs) to either TPr agonists, two structurally related thromboxane A₂ (TxA₂) mimetics, significantly reduced phosphorylations of endothelial nitric oxide synthase (eNOS) at Ser¹¹⁷⁷ and Akt at Ser⁴⁷³. These effects were abolished by pharmacological or genetic inhibitors of TPr. TPr-induced suppression of eNOS and Akt phosphorylation was accompanied by upregulation of PTEN (phosphatase and tension homolog deleted on chromosome 10) and Ser³⁸⁰/Thr^382/383 PTEN phosphorylation. PTEN-specific siRNA restored Akt-eNOS signaling in the face of TPr activation. The small GTPase, Rho, was also activated by TPr stimulation, and pretreatment of HUVECs with Y27632, a Rho-associated kinase (ROCK) inhibitor, rescued TPr-impaired Akt-eNOS signaling. In mice, streptozotocin-induced diabetes was associated with aortic PTEN upregulation, PTEN-Ser³⁸⁰/Thr^382/383 phosphorylation, and dephosphorylation of Akt (at Ser⁴⁷³) and eNOS (at Ser¹¹⁷⁷). Importantly, administration of TPr antagonist blocked these changes.

CONCLUSION

We conclude that TPr activation impairs endothelial function by selectively inactivating the ROCK-PTEN-Akt-eNOS pathway in diabetic mice.

Glycation of paraoxonase 1 by high glucose instigates endoplasmic reticulum stress to induce endothelial dysfunction in vivo

High-density lipoprotein (HDL) modulates low-density lipoprotein and cell membrane oxidation through the action of paraoxonase-1 (PON1). Endoplasmic reticulum (ER) stress has been linked to a wide range of human pathologies including diabetes, obesity, and atherosclerosis. Previous studies have reported that PON1 is glycated in diabetes. The aim of this study is to investigate whether and how PON1 glycation contributes to endothelial dysfunction in diabetes. ER stress markers were monitored by western blot. Endothelial function was determined by organ bath. Incubation of recombinant PON1 proteins with high glucose increased PON1 glycation and reduced PON1 activity. Exposure of HUVECs to glycated PON1 induced prolonged ER stress and reduced SERCA activity, which were abolished by tempol, apocynin, BAPTA, and p67 and p22 siRNAs. Chronic administration of amino guanidine or 4-PBA prevented endothelial dysfunction in STZ-injected rats. Importantly, injection of glycated PON1 but not native PON1 induced aberrant ER stress and endothelial dysfunction in rats, which were attenuated by tempol, BAPTA, and 4-PBA. In conclusion, glycation of PON1 by hyperglycemia induces endothelial dysfunction through ER stress. In perspectives, PON1 glycation is a novel risk factor of hyperglycemia-induced endothelial dysfunction. Therefore, inhibition of oxidative stress, chelating intracellular Ca²⁺, and ER chaperone would be considered to reduce vascular complications in diabetes.

Traditional Chinese medicine xin-mai-jia recouples endothelial nitric oxide synthase to prevent atherosclerosis in vivo

Endothelial dysfunction, which is caused by endothelial nitric oxide synthase (eNOS) uncoupling, is an initial step in atherosclerosis. This study was designed to explore whether Chinese medicine xin-mai-jia (XMJ) recouples eNOS to exert anti-atherosclerotic effects. Pretreatment of XMJ (25, 50, 100 μg/ml) for 30 minutes concentration-dependently activated eNOS, improved cell viabilities, increased NO generations, and reduced ROS productions in human umbilical vein endothelial cells incubated with H₂O₂ for 2 hours, accompanied with restoration of BH4. Importantly, these protective effects produced by XMJ were abolished by eNOS inhibitor L-NAME or specific eNOS siRNA in H₂O₂-treated cells. In ex vivo experiments, exposure of isolated aortic rings from rats to H₂O₂ for 6 hours dramatically impaired acetylcholine-induced vasorelaxation, reduced NO levels and increased ROS productions, which were ablated by XMJ in concentration-dependent manner. In vivo analysis indicated that administration of XMJ (0.6, 2.0, 6.0 g/kg/d) for 12 weeks remarkably recoupled eNOS and reduced the size of carotid atherosclerotic plaque in rats feeding with high fat diet plus balloon injury. In conclusion, XMJ recouples eNOS to prevent the growth of atherosclerosis in rats. Clinically, XMJ is potentially considered as a medicine to treat patients with atherosclerosis.

Resveratrol rescues hyperglycemia-induced endothelial dysfunction via activation of Akt

Resveratrol (RSV), a phytoalexin, has shown to prevent endothelial dysfunction and reduce diabetic vascular complications and the risk of cardiovascular diseases. The aim of this study was to investigate the signaling mechanisms underlying the protecting effects of RSV against endothelial dysfunction during hyperglycemia in vitro and in vivo. Human umbilical vein endothelial cells (HUVECs) were treated with RSV, and then exposed to high glucose (HG, 30 mmol/L). Akt-Ser473 phosphorylation, eNOS-Ser1177 phosphorylation, and PTEN protein levels in the cells were detected using Western blot. For in vivo studies, WT and Akt^-/- mice were fed a normal diet containing RSV (400 mg·kg^-1·d^-1) for 2 weeks, then followed by injection of STZ to induce hyperglycemia (300 mg/dL). Endothelial function was evaluated using aortic rings by assessing ACh-induced vasorelaxation. RSV (5-20 μmol/L) dose-dependently increased Akt-Ser473 phosphorylation, accompanied by increased eNOS-Ser1177 phosphorylation in HUVECs; these effects were more prominent under HG stimulation. Transfection with Akt siRNA abolished RSV-enhanced eNOS phosphorylation and NO release. Furthermore, RSV (5-20 μmol/L) dose-dependently decreased the levels of PTEN, which was significantly increased under HG stimulation, and PTEN overexpression abolished RSV-stimulated Akt phosphorylation in HG-treated HUVECs. Moreover, RSV dramatically increased 26S proteasome activity, which induced degradation of PTEN. In in vivo studies, pretreatment with RSV significantly increased Akt and eNOS phosphorylation in aortic tissues and ACh-induced vasorelaxation, and improved diabetes-induced endothelial dysfunction in wild-type mice but not in Akt^-/- mice. RSV attenuates endothelial function during hyperglycemia via activating proteasome-dependent degradation of PTEN, which increases Akt phosphorylation, and consequentially upregulation of eNOS-derived NO production.

Inhibition of Aberrant MicroRNA-133a Expression in Endothelial Cells by Statin Prevents Endothelial Dysfunction by Targeting GTP Cyclohydrolase 1 in Vivo

Supplemental Digital Content is available in the text.

Background:

GTP cyclohydrolase 1 (GCH1) deficiency is critical for endothelial nitric oxide synthase uncoupling in endothelial dysfunction. MicroRNAs (miRs) are a class of regulatory RNAs that negatively regulate gene expression. We investigated whether statins prevent endothelial dysfunction via miR-dependent GCH1 upregulation.

Methods:

Endothelial function was assessed by measuring acetylcholine-induced vasorelaxation in the organ chamber. MiR-133a expression was assessed by quantitative reverse transcription polymerase chain reaction and fluorescence in situ hybridization.

Results:

We first demonstrated that GCH1 mRNA is a target of miR-133a. In endothelial cells, miR-133a was robustly induced by cytokines/oxidants and inhibited by lovastatin. Furthermore, lovastatin upregulated GCH1 and tetrahydrobiopterin, and recoupled endothelial nitric oxide synthase in stressed endothelial cells. These actions of lovastatin were abolished by enforced miR-133a expression and were mirrored by a miR-133a antagomir. In mice, hyperlipidemia- or hyperglycemia-induced ectopic miR-133a expression in the vascular endothelium, reduced GCH1 protein and tetrahydrobiopterin levels, and impaired endothelial function, which were reversed by lovastatin or miR-133a antagomir. These beneficial effects of lovastatin in mice were abrogated by in vivo miR-133a overexpression or GCH1 knockdown. In rats, multiple cardiovascular risk factors including hyperglycemia, dyslipidemia, and hyperhomocysteinemia resulted in increased miR-133a vascular expression, reduced GCH1 expression, uncoupled endothelial nitric oxide synthase function, and induced endothelial dysfunction, which were prevented by lovastatin.

Conclusions:

Statin inhibits aberrant miR-133a expression in the vascular endothelium to prevent endothelial dysfunction by targeting GCH1. Therefore, miR-133a represents an important therapeutic target for preventing cardiovascular diseases.

Tert-butylhydroquinone lowers blood pressure in AngII-induced hypertension in mice via proteasome-PTEN-Akt-eNOS pathway

Tert-butylhydroquinone (tBHQ), as an antioxidant, has been widely used for many years to prevent oxidization of food products. The aim of this study was to investigate whether tBHQ activates endothelial nitric oxide synthase (eNOS) to prevent endothelial dysfunction and lower blood pressure. The role of Akt in tBHQ-induced eNOS phosphorylation was examined in human umbilical vein endothelial cells (HUVEC) or in mice. tBHQ treatment of HUVEC increased both Akt-Ser473 phosphorylation, accompanied with increased eNOS-Ser1177 phosphorylation and NO release. Mechanically, pharmacologic or genetic inhibition of Akt abolished tBHQ-enhanced NO release and eNOS phosphorylation in HUVEC. Gain-function of PTEN or inhibition of 26S proteasome abolished tBHQ-enhanced Akt phosphorylation in HUVEC. Ex vivo analysis indicated that tBHQ improved Ach-induced endothelium-dependent relaxation in LPC-treated mice aortic arteries, which were abolished by inhibition of Akt or eNOS. In animal study, administration of tBHQ significantly increased eNOS-Ser1177 phosphorylation and acetylcholine-induced vasorelaxation, and lowered AngII-induced hypertension in wildtype mice, but not in mice deficient of Akt or eNOS. In conclusion, tBHQ via proteasome-dependent degradation of PTEN increases Akt phosphorylation, resulting in upregulation of eNOS-derived NO production and consequent improvement of endothelial function in vivo. In this way, tBHQ lowers blood pressure in hypertensive mice.

Berberine activates peroxisome proliferator-activated receptor gamma to increase atherosclerotic plaque stability in Apoe-/- mice with hyperhomocysteinemia

AIMS/INTRODUCTION

An elevated level of plasma homocysteine has long been suspected as a metabolic risk factor for the development of atherosclerotic vascular diseases in diabetes. Berberine (BBR) has several preventive effects on cardiovascular diseases. The effects of BBR on atherosclerotic plaque stability increased by homocysteine thiolactone (HTL) remain unknown.

MATERIALS AND METHODS

The model of atherosclerotic vulnerable plaque was induced by placing a collar around the carotid artery in Apoe^-/- mice. Endothelium-dependent relaxation was assayed by organ chamber.

RESULTS

Homocysteine thiolactone (50 mg/kg/day, 8 weeks) reduced the atherosclerotic plaque stability in the carotid artery of Apoe^-/- mice, which was reversed by BBR administration (1.0 g/kg/day). In vivo and ex vivo experiments showed that HTL dramatically reduced acetylcholine-induced endothelium-dependent relaxation and superoxide dismutase activity, and increased malondialdehyde content, which were inhibited by BBR. Importantly, all effects induced by BBR were abolished by GW9662, an antagonist of peroxisome proliferator-activated receptor-γ. Incubation of cultured endothelial cells with HTL significantly reduced cell viabilities and enhanced production of reactive oxygen species. Pretreatment of cells with BBR dose-dependently reversed HTL-induced detrimental effects, which were GW9662-reversible.

CONCLUSIONS

Berberine increases atherosclerotic plaque stability in hyperhomocysteinemia mice, which is related to the activation of peroxisome proliferator-activated receptor-γ and subsequent suppression of oxidative stress in endothelial cells.

Suppression of oxidative stress in endothelial progenitor cells promotes angiogenesis and improves cardiac function following myocardial infarction in diabetic mice

Myocardial infarction is a major contributor to morbidity and mortality in diabetes, which is characterized by inadequate angiogenesis and consequent poor blood reperfusion in the diabetic ischemic heart. The aim of the present study was to investigate the effect that oxidative stress in endothelial progenitor cells (EPCs) has on cardiac angiogenesis in diabetic mice. EPCs derived from diabetic mice revealed reductions in superoxide dismutase (SOD) expression levels and activity compared with those from normal mice. An endothelial tube formation assay showed that angiogenesis was markedly delayed for diabetic EPCs, compared with normal controls. EPCs subjected to various pretreatments were tested as a cell therapy in a diabetic mouse model of myocardial infarction. Induction of oxidative stress in normal EPCs by H₂O₂ or small interfering RNA-mediated knockdown of SOD reduced their angiogenic activity in the ischemic myocardium of the diabetic mice. Conversely, cell therapy using EPCs from diabetic mice following SOD gene overexpression or treatment with the antioxidant Tempol normalized their ability to promote angiogenesis. These results indicate that decreased expression levels of SOD in EPCs contribute to impaired angiogenesis. In addition, normalization of diabetic EPCs by ex vivo SOD gene therapy accelerates the ability of the EPCs to promote angiogenesis and improve cardiac function when used as a cell therapy following myocardial infarction in diabetic mice.

Acute effect of rosiglitazone on relaxation responses in hypercholesterolemic corpus cavernosum

Thiazolidinediones (TZDs) improve vascular endothelial dysfunction through non-genomic effects of peroxisomal proliferator-activated receptor γ. This study investigated the acute effect of one of the TZD, rosiglitazone, on endothelium-dependent relaxation response of corpus cavernosum (CC) in hypercholesterolemic rabbits. New Zealand rabbits were divided into two groups randomly as control and cholesterol groups. Hypercholesterolemia was induced by feeding rabbits with 2% cholesterol diet (w/w) for 6 weeks. Endothelium-dependent and -independent relaxation response of CC were evaluated in the presence of rosiglitazone by organ bath studies with cumulative doses of acetylcholine (Ach) and sodium nitroprusside (SNP). Maximal relaxation (Emax) response to Ach significantly decreased owing to hypercholesterolemia in CC tissues. However, in vitro incubation of rosiglitazone with different concentrations (0.1, 1 and 10 μm) did not improve the Ach-dependent Emax responses in hypercholesterolemic rabbit CC. Surprisingly, rosiglitazone caused a significant decrease in Ach-dependent relaxation in healthy CC. Emax responses to SNP did not differ in the presence of rosiglitazone in both the control and hypercholesterolemic groups. Rosiglitazone does not improve hypercholesterolemia-induced endothelial dysfunction in CC tissues while it dose-dependently impairs endothelium-dependent relaxation in healthy CC tissue.

Vitamin B6 Prevents Endothelial Dysfunction, Insulin Resistance, and Hepatic Lipid Accumulation in Apoe (-/-) Mice Fed with High-Fat Diet

Backgrounds. VitB6 deficiency has been associated with a number of adverse health effects. However, the effects of VitB6 in metabolic syndrome are poorly understood. Methods. VitB6 (50 mg/kg/day) was given to Apoe (-/-) mice with hkdigh-fat diet (HFD) for 8 weeks. Endothelial dysfunction, insulin resistance, and hepatic lipid contents were determined. Results. VitB6 administration remarkably increased acetylcholine-induced endothelium-dependent relaxation and decreased random blood glucose level in Apoe (-/-) mice fed with HFD. In addition, VitB6 improved the tolerance of glucose and insulin, normalized the histopathology of liver, and reduced hepatic lipid accumulation but did not affect the liver functions. Clinical and biochemical analysis indicated that the levels of VitB6 were decreased in patients with fatty liver. Conclusions. Vitamin B6 prevents endothelial dysfunction, insulin resistance, and hepatic lipid accumulation in Apoe (-/-) mice fed with HFD. Supplementation of VitB6 should be considered to prevent metabolic syndrome.

Inhibition of NA(+)/H(+) Exchanger 1 Attenuates Renal Dysfunction Induced by Advanced Glycation End Products in Rats

It has been recognized that sodium hydrogen exchanger 1 (NHE1) is involved in the development of diabetic nephropathy. The role of NHE1 in kidney dysfunction induced by advanced glycation end products (AGEs) remains unknown. Renal damage was induced by AGEs via tail vein injections in rats. Function and morphology of kidney were determined. Compared to vehicle- or BSA-treated rats, AGEs caused abnormalities of kidney structures and functions in rats, accompanied with higher MDA level and lower GSH content. Gene expressions of NHE1 gene and TGF-β1 in the renal cortex and urine were also increased in AGEs-injected rats. Importantly, all these detrimental effects induced by AGEs were reversed by inhibition of NHE1 or suppression of oxidative stress. These pieces of data demonstrated that AGEs may activate NHE1 to induce renal damage, which is related to TGF-β1.

Rosiglitazone attenuates renal injury caused by hyperlipidemic pancreatitis

Hyperlipidemic pancreatitis (HP) is a serious inflammatory disease with very high mortality and multiple organ injuries including renal injury. Rosiglitazone (Ros), an agonist of peroxisome proliferator activated receptor-γ (PPAR-γ), was reported to show a protective role against pancreatitis. However, whether Ros has an effect on renal injury caused by HP is not yet clear. In the present study, the function of Ros was explored using ELISA, RT-PCR, western blot, PAS staining and immunohistochemistry. Results of this study showed that Ros could inhibit the activation of NF-κB and MAPK P38 signaling pathways, relieve inflammatory response and inhibit cell apoptosis, thus attenuating renal injury caused by HP. This study suggested that Ros might be a promising drug for the treatment of renal injury caused by HP and also laid theoretical foundation for the development of renal injury treatment.