Physcion prevents high-fat diet-induced endothelial dysfunction by inhibiting oxidative stress and endoplasmic reticulum stress pathways.

High-fat diet (HFD)-induced obesity leads endothelial dysfunction and contributes to cardiovascular diseases. Palmitic acid (PA), a free fatty acid, is the main component of dietary saturated fat. Physcion, a chemical ingredient from Rhubarb, has been shown anti-hypertensive, anti-bacteria, and anti-tumor properties. However, the effects of physcion on endothelial dysfunction under HFD-induced obesity have not been reported. The purpose of the present study was to define the protective effect of physcion on HFD-induced endothelial dysfunction and its mechanisms involved. Obesity rat model was induced by HFD for 12 weeks. A rat thoracic aortic ring model was used to investigate the effects of physcion on HFD-induced impairment of vasorelaxation. Endothelial cell injury model was constructed in human umbilical vein endothelial cells (HUVECs) by treating with PA (0.25 mM) for 24 h. The results revealed that physcion reduced body weight and the levels of plasma TG, prevented impairment of endothelium-dependent relaxation in HFD-fed rats. In PA-injured HUVECs, physcion inhibited impaired viability, apoptosis and inflammation. Physcion also suppressed PA-induced both oxidative stress and ER stress in HUVECs. Furthermore, physcion increased PA-induced decrease in the activation of eNOS/Nrf2 signaling in HUVECs. These findings suggest that physcion has a significant beneficial effect on regulating HFD-induced endothelial dysfunction, which may be related to the inhibition of oxidative stress and ER stress through activation of eNOS/Nrf2 signaling pathway.

Emodin protects against homocysteine-induced cardiac dysfunction by inhibiting oxidative stress via MAPK and Akt/eNOS/NO signaling pathways.

Elevated levels of plasma homocysteine (Hcy) causes severe cardiac dysfunction, which is closely associated with oxidative stress. Emodin, a naturally occurring anthraquinone derivative, has been shown to exert antioxidant and anti-apoptosis activities. However, whether emodin could protect against Hcy-induced cardiac dysfunction remains unknown. The current study aimed to investigate the effects of emodin on the Hcy-induced cardiac dysfunction and its molecular mechanisms. Rats were fed a methionine diet to establish the animal model of hyperhomocysteinemia (HHcy). H9C2 cells were incubated with Hcy to induce a cell model of Hcy-injured cardiomyocytes. ELISA, HE staining, carotid artery and left ventricular cannulation, MTT, fluorescence staining, flow cytometry and western blotting were used in this study. Emodin significantly alleviated the structural damage of the myocardium and cardiac dysfunction from HHcy rats. Emodin prevented apoptosis and the collapse of MMP in the Hcy-treated H9C2 cells in vitro. Further, emodin reversed the Hcy-induced apoptosis-related biochemical changes including decreased Bcl-2/Bax protein ratio, and increased protein expression of Caspase-9/3. Moreover, emodin suppressed oxidative stress in Hcy-treated H9C2 cells. Mechanistically, emodin significantly inhibited the Hcy-activated MAPK by reducing ROS generation in H9C2 cells. Furthermore, emodin upregulated NO production by promoting the protein phosphorylation of Akt and eNOS in injured cells. The present study shows that emodin protects against Hcy-induced cardiac dysfunction by inhibiting oxidative stress via MAPK and Akt/eNOS/NO signaling pathways.

Decreased gene expression of KACh and KATP channels in hyperthyroid rabbit atria.

Cardiac hypertrophy is a common myocardial structural abnormality which may cause heart failure. Many studies have shown that cardiac hypertrophy can be induced by hyperthyroidism. Ligand-gated potassium channels have been reported to be involved in various biological processes in the cardiovascular system, such as GPCR coupled KACh and metabolism sensor KATP channel. It is unclear whether the gene expression of KACh and KATP was altered in hyperthyroid rabbit atria. We aimed to investigate the expression of KACh and KATP genes in rabbit atria in our experimental model. We established an effective hyperthyroidism-induced cardiac hypertrophy animal model through an injection of T4. H&E staining and RT-PCR were used to observe the histomorphological damages and alteration of gene expression. The results showed that the heart weight, heart rate significantly increased in T4-treated rabbits. The systolic pressure increased from 115.60 mmHg to 152.6 mmHg in T4-treated rabbits. The expression of KACh and KATP genes was decreased in the atria of hyperthyroidism-induced cardiac hypertrophied rabbits. These findings indicated that the decreased gene expression of KACh and KATP may be related to hyperthyroidism-induced cardiac hypertrophy and atrial fibrillation.

Physcion, a tetra-substituted 9,10-anthraquinone, prevents homocysteine-induced endothelial dysfunction by activating Ca2+- and Akt-eNOS-NO signaling pathways.

BACKGROUND: Homocysteine (Hcy) induced vascular endothelial dysfunction is known to be closely associated with oxidative stress and impaired NO system. 1,8-Dihydroxy-3-methoxy-6-methylanthracene-9,10-dione (physcion) has been known to has antioxidative and anti-inflammatory properties. PURPOSE: The purpose of the present study was to define the protective effect of physcion on Hcy-induced endothelial dysfunction and its mechanisms involved. STUDY DESIGN AND METHODS: Hyperhomocysteinemia (HHcy) rat model was induced by feeding 3% methionine. A rat thoracic aortic ring model was used to investigate the effects of physcion on Hcy-induced impairment of endothelium-dependent relaxation. Two doses, low (L, 30 mg/kg/day) and high (H, 50 mg/kg/day) of physcion were used in the present study. To construct Hcy-injured human umbilical vein endothelial cells (HUVECs) model, the cells treated with 3 mM Hcy. The effects of physcion on Hcy-induced HUVECs cytotoxicity and apoptosis were studied using MTT and flow cytometry. Confocal analysis was used to determine the levels of intracellular Ca2+. The levels of protein expression of the apoptosis-related markers Bcl-2, Bax, caspase-9/3, and Akt and endothelial nitric oxide synthase (eNOS) were evaluated by western blot. RESULTS: In the HHcy rat model, plasma levels of Hcy and malondialdehyde (MDA) were elevated (20.45 ± 2.42 vs. 4.67 ± 1.94 µM, 9.42 ± 0.48 vs. 3.47 ± 0.59 nM, p < 0.001 for both), whereas superoxide dismutase (SOD) and nitric oxide (NO) levels were decreased (77.11 ± 4.78 vs. 115.02 ± 5.63 U/ml, 44.51 ± 4.45 vs. 64.18 ± 5.34 µM, p < 0.001 and p < 0.01, respectively). However, treatment with physcion significantly reversed these changes (11.82 ± 2.02 vs. 20.45 ± 2.42 µM, 5.97 ± 0.72 vs. 9.42 ± 0.48 nM, 108.75 ± 5.65 vs. 77.11 ± 4.78 U/ml, 58.14 ± 6.02 vs. 44.51 ± 4.45 µM, p < 0.01 for all). Physcion also prevented Hcy-induced impairment of endothelium-dependent relaxation in HHcy rats (1.56 ± 0.06 vs. 15.44 ± 2.53 nM EC50 for ACh vasorelaxation, p < 0.05 vs. HHcy). In Hcy-injured HUVECs, physcion inhibited the impaired viability, apoptosis and reactive oxygen species. Hcy treatment significantly increased the protein phosphorylation levels of p38 (2.26 ± 0.20 vs. 1.00 ± 0.12, p <0.01), ERK (2.11 ± 0.21 vs. 1.00 ± 0.11, p <0.01) and JNK. Moreover, physcion reversed the Hcy-induced apoptosis related parameter changes such as decreased mitochondrial membrane potential (MMP) and Bcl-2/Bax protein ratio, and increased protein expression of caspase-9/3 in HUVECs. Furthermore, the downregulation of Ca2+, Akt, eNOS and NO caused by Hcy were recovered with physcion treatment in HUVECs. CONCLUSION: Physcion prevents Hcy-induced endothelial dysfunction by activating Ca2+- and Akt-eNOS-NO signaling pathways. This study provides the first evidence that physcion might be a candidate agent for the prevention of cardiovascular disease induced by Hcy.

Protective effects of oxymatrine on homocysteine-induced endothelial injury: Involvement of mitochondria-dependent apoptosis and Akt-eNOS-NO signaling pathways.

Homocysteine (Hcy) is an independent risk factor in the development of cardiovascular diseases (CVD). Hyperhomocysteinemia (HHcy), induces the injury of vascular endothelial cells via oxidative stress. Oxymatrine (OMT), one of the main components of Sophora flavescens, has displayed anti-inflammatory, anti-oxidant and anti-apoptotic activity. However, the effect of OMT on the Hcy-induced endothelial injury is not clearly defined yet. The aim of this study was to determine the protective effect of OMT on the Hcy-induced endothelial injury and its mechanisms involved. Human umbilical vein endothelial cells (HUVECs) were cultured in vitro. Methyl thiazolyl tetrazolium assay (MTT), fluorescence staining, flow cytometry and western blotting were used in this study. OMT prevented the Hcy-induced toxicity and apoptosis in HUVECs. Moreover, OMT suppressed Hcy-induced increases in reactive oxygen species, lactate dehydrogenase, malondialdehyde levels and increased superoxide dismutase levels. OMT reversed the Hcy-induced decrease in the protein expression of nuclear factor erythroid-2-related factor 2 (Nrf2). In addition, OMT reversed the Hcy-induced apoptosis related biochemical changes such as decreased mitochondrial membrane potential and Bcl-2/Bax protein ratio, and increased protein expression of caspase-9 and caspase-3. Furthermore, OMT elevated the phosphorylation levels of Akt and eNOS, and the formation of nitric oxide (NO) in injured cells. These results suggest that OMT prevents Hcy-induced endothelial injury by regulating mitochondrial-dependent apoptosis and Akt-eNOS-NO signaling pathways concomitantly with accentuation of Nrf2 expression.

Emodin accentuates atrial natriuretic peptide secretion in cardiac atria.

Emodin, an active anthraquinone constituent isolated from the rhubarb, a traditional Chinese herbal medicine which is widely used in clinical treatment, has cardiovascular protective properties. However, it remains unclear whether the cardiovascular protective actions of emodin are related to an activation of cardiac natriuretic hormone secretion. The purpose of the present study was to explore the effect of emodin on the secretion of ANP, a member of the family of cardiac natriuretic hormones, and its mechanisms involved. Experiments were performed in isolated perfused beating rabbit atria allowing measurement of ANP secretion, atrial pulse pressure, and stroke volume. Emodin increased ANP secretion concomitantly with a decrease in atrial pulse pressure and stroke volume in a concentration-dependent manner. These effects were reversible. Inhibition of K(+) channels with tetraethylammonium and glibenclamide attenuated the emodin-induced changes in ANP secretion and atrial dynamics. Furthermore, the emodin-induced changes in ANP secretion and atrial dynamics were attenuated by inhibition of L-type Ca(2+) channels with nifedipine. Atropine, methoctramine, tertiapin-Q, and pertussis toxin had no significant effect on the emodin-induced changes in ANP secretion and mechanical dynamics. The present study demonstrates that emodin increases ANP secretion via inhibition of L-type Ca(2+) channels through an activation of K(+)ATP channel in isolated beating rabbit atria. The results also provide a rationale for the use of emodin in the treatment of impairment of the regulation of the cardiovascular homeostasis.

Vasorelaxant action of an ethylacetate fraction of Euphorbia humifusa involves NO-cGMP pathway and potassium channels.

ETHNOPHARMACOLOGICAL RELEVANCE: Euphorbia humifusa Willd. (EH) is an important traditional Chinese medicine that has commonly been used for treating bacillary dysentery and enteritis in many Asian countries for thousands of years. EH has a wide variety of pharmacological actions such as antioxidant, hypotensive, and hypolipidemic effects. However, the mechanisms involved are to be defined. AIM OF THE STUDY: The present study was performed to evaluate the cardiovascular effects of EH in rats. MATERIALS AND METHODS: Methanol extract of EH (MEH) and ethylacetate fraction of the MEH (EEH) was examined for their vascular relaxant effects in phenylephrine-precontracted aortic rings. Effects of EEH on systolic blood pressure and heart rate were tested in Sprague-Dawley rats. RESULTS: MEH and EEH induced vasorelaxation in a concentration-dependent manner. Endothelium-denudation abolished the EEH-induced vasorelaxation. Pretreatment of the endothelium-intact aortic rings with N(G)-nitro-L-arginine methylester (L-NAME) and 1H-[1,2,4]-oxadiazolo-[4,3-α]-quinoxalin-1-one (ODQ) significantly inhibited the EEH-induced vasorelaxation. EEH increased cGMP levels of the aortic rings in a concentration-dependent manner and the effect was blocked by L-NAME or ODQ. Extracellular Ca(2+) depletion and treatments with thapsigargin, Gd(3+), and 2-aminoethyl diphenylborinate significantly attenuated the EEH-induced vasorelaxation. Wortmannin markedly attenuated the EEH-induced vasorelaxation. In addition, tetraethylammonium, iberiotoxin, and charybdotoxin, but not apamin, attenuated the EEH-induced vasorelaxation. Glibenclamide, indomethacin, atropine, and propranolol had no effects on the EEH-induced vasorelaxation. Furthermore, EEH decreased systolic blood pressure and heart rate in a concentration-dependent manner in rats. CONCLUSIONS: The present study demonstrates that EEH induces endothelium-dependent vasorelaxation via eNOS-NO-cGMP signaling through the modification of intracellular Ca(2+), Ca(2+) entry, and large- and intermediate-conductance KCa channel homeostasis. The data also suggest that the Akt-eNOS pathway is involved in the EEH-induced vasorelaxation. EEH induces hypotension and bradycardia in vivo.

K+ACh channel activation with carbachol increases atrial ANP release.

Although it has been known that atrial natriuretic peptide (ANP) release is regulated through muscarinic acetylcholine receptors (mAChR), the mechanism by which this neurotransmitter regulates atrial ANP release is largely unknown. This study tested the hypothesis that K(+)(ACh) channels mediate the action of mAChR on atrial myocyte ANP release. Experiments were performed in perfused beating rabbit atria. Carbachol (CCh), an agonist of cardiac mAChR, increased atrial myocyte ANP release concomitantly with a decrease in stroke volume and intra-atrial pulse pressure in a concentration-dependent manner. Isoproterenol, a beta-adrenoceptor agonist, decreased ANP release concomitantly with an increase in cAMP and mechanical dynamics. In the presence of isoproterenol, the CCh-induced increase in ANP release and decrease in cAMP efflux levels and mechanical dynamics were able to be repeated. The CCh-induced changes were blocked by selective M(2) mAChR antagonists. Tertiapin, a selective G-protein-gated K(+)(ACh) channel blocker, attenuated the CCh-induced increase in ANP release and decrease in mechanical dynamics in a concentration-dependent manner, but without a significant effect on the CCh-induced decrease in cAMP efflux levels. The CCh-induced changes in ANP release and atrial dynamics were inhibited in the atria from pertussis toxin-pretreated rabbits. These findings demonstrate that G-protein-gated K(+)(ACh) channels regulate atrial myocyte ANP release. The present study also shows that mAChR and adrenoceptors have opposing roles in the regulation of ANP release.

Altered role of C-type natriuretic peptide-activated pGC-cGMP-PDE3-cAMP signaling in hyperthyroid beating rabbit atria.

The role of C-type natriuretic peptide (CNP) in the pathophysiology of atrial function in hyperthyroidism has not been defined. This study was to define the role of CNP-activated particulate (p) guanylyl cyclase (GC)-cGMP-phosphodiesterase (PDE)3 signaling in the regulation of cAMP levels and contractile and secretory functions in the atria from hyperthyroid rabbits. Experiments were performed in perfused beating rabbit atria. CNP was used to activate pGC. In euthyroid atria from sham-treated rabbits, CNP (100 nM) increased cGMP and cAMP efflux by 176.7+/-17.7 and 55.3+/-10.0%, respectively. CNP decreased stroke volume and pulse pressure and ANP release by 51+/-7 and 41+/-2 and 60.4+/-3.2%, respectively. Pretreatment with milrinone blocked the CNP-induced increase of cAMP but without significant changes in decrease of atrial dynamics and ANP release. In hyperthyroid atria, CNP-induced increase of cGMP levels was accentuated, while CNP-induced increase of cAMP was attenuated. The gain of cAMP, i.e., change in cAMP efflux concentration in terms of cGMP was attenuated in the hyperthyroid compared to euthyroid atria. CNP rather increased atrial dynamics in hyperthyroid atria instead of decrease. CNP-induced decrease in atrial ANP release was attenuated. Pretreatment with milrinone blocked the CNP-induced increase of cAMP levels concomitantly with a decrease of atrial dynamics. The present study demonstrates that altered role of CNP-activated pGC-cGMP-PDE3-cAMP signaling is involved in the pathophysiology of hyperthyroid heart.