Astragaloside IV protects cardiomyocytes from anoxia/reoxygenation injury by upregulating the expression of Hes1 protein.

Astragaloside IV (ASI), a traditional Chinese medicine, is a main active ingredient of Astragalus membranaceus. Many clinical studies have found that ASI protects cardiomyocytes in cardiovascular diseases, but the underlying mechanisms remain obscure. The aim of this study was to investigate the molecular mechanisms responsible for the protective effects of ASI in cardiomyocytes from anoxia/reoxygenation (A/R) injury. According to the previous studies, we hypothesized that the cardioprotective effects of ASI against A/R injury might be associated with Notch1/Hes1 signaling pathway. In this study, neonatal rat primary cardiomyocytes were preconditioned with ASI prior to A/R injury. Our results showed that ASI effectively increased the cell viability, decreased the content of MDA, decreased the activities of CPK and LDH, increased the activities of GSH-Px and SOD, and reduced the reactive oxygen species (ROS) generation and the loss of mitochondrial membrane potential (Δψm). ASI inhibited the mitochondrial permeability transition pore (mPTP) opening and activation of caspase-3, and finally decreased the cell apoptosis in cardiomyocytes. Furthermore, ASI upregulated Hes1 protein expression. However, pretreatment with DAPT, a Notch1 inhibitor, effectively attenuated the cardioprotective effects of ASI against A/R injury, except MDA, SOD, GSH-Px, and the ROS generation. Taken together, we demonstrated that ASI could protect against A/R injury via the Notch1/Hes1 signaling pathway.

Triptolide alleviates isoprenaline-induced cardiac remodeling in rats via TGF-ß1/Smad3 and p38 MAPK signaling pathway.

Triptolide (TPL) is a diterpene triepoxide with potent immunosuppressive and anti-inflammatory properties. It is the main effective component of the traditional Chinese herb Tripterygium wilfordii Hook F and has been used in China for centuries to treat immune-related disorders. The present study was conducted to investigate the effects of TPL on cardiac remodeling in rats. Age matched male Wistar rats were used in this study. Cardiac remodeling rat model was established by hypodermic injection of isoprenaline for ten days. The rats were treated with TPL (20 or 100 µg/kg/d) for six consecutive weeks. At the end of the study, the cardiac function, collagen volume fraction, perivascular collagen area and hydroxyproline concentration were studied. Echocardiography, Masson staining, immunohistochemistry, western blot and real-time polymerase chain reaction were performed. The protein and mRNA expression of transforming growth factor-ß1 (TGF-ß1), drosophila mothers against decapentaplegic protein 3 (Smad3) and p38 mitogen activated protein kinase (p38 MAPK) were analyzed. The results indicated that TPL treatment significantly reduced the collagen volume fraction, perivascular collagen area, ventricular weight/body weight ratio and hydroxyproline concentration in myocardial tissue compared with the model group. In addition, it also improved the cardiac function. TPL attenuated cardiac remodeling in rats by down-regulating the p38 MAPK and TGF-ß1/Smad3 signaling pathways. TPL treatment significantly attenuated cardiac fibrosis and improved cardiac function through suppressing the p38 MAPK and TGF-ß1/Smad3 signaling pathway in isoprenaline-induced cardiac remodeling rats. Our findings suggested that TPL might be a novel complementary medicine in the treatment of chronic heart failure.

Curcumin protects against regional myocardial ischemia/reperfusion injury through activation of RISK/GSK-3ß and inhibition of p38 MAPK and JNK.

BACKGROUND: Curcumin, the active ingredient of turmeric (Curcuma longa), is known to have anti-inflammatory and antioxidative properties. The present study was aimed to determine the effect of curcumin in regional myocardial ischemia/reperfusion (I/R) injury and its underlying mechanisms involving the role of prosurvival kinases and apoptotic kinases. METHODS: Sprague-Dawley rats (n = 109) subjected to a 30-minute left anterior descending coronary artery (LAD) occlusion followed by reperfusion were assigned to receive saline (control), curcumin (100 mg/kg), wortmannin (inhibitor of phosphatidylinositol-3-OH kinase [PI3K]-Akt), wortmannin + curcumin, U0126 (inhibitor of extracellular signal-regulated kinase [ERK1/2]), U0126 + curcumin, SB216763 (inhibitor of glycogen synthase kinase [GSK-3ß]), and SB216763 + curcumin 20 minutes before LAD occlusion. Infarct size was measured after 2 hours of reperfusion by triphenyl tetrazolium chloride staining. The phosphorylation of Akt, ERK1/2, GSK-3ß, p38, and c-Jun N-terminal kinases (JNK) was determined by immunoblotting after 10 minutes of reperfusion. RESULTS: Curcumin significantly reduced the infarct size compared with the control (33.1% ± 6.2% vs 50.1% ± 3.9%; P < .05). Wortmannin or U0126 alone did not affect the infarct size but abolished the curcumin-induced cardioprotective effect. Curcumin significantly enhanced the phosphorylation of Akt, ERK1/2, and GSK-3ß, while it reduced that of p38 and JNK. Wortmannin or U0126 abolished enhanced phosphorylation of GSK-3ß induced by curcumin. SB216763 alone or combined with curcumin reduced the infarct size and enhanced phosphorylation of GSK-3ß compared with the control. CONCLUSIONS: Preconditioning by curcumin effectively protects against regional myocardial I/R injury through the activation of prosurvival kinases involving PI3K-Akt, ERK1/2, and GSK-3ß, and attenuation of p38 and JNK.

Reversal of isoflurane-induced depression of myocardial contraction by nitroxyl via myofilament sensitization to Ca2+.

Isoflurane (ISO) is known to depress cardiac contraction. Here, we hypothesized that decreasing myofilament Ca(2+) responsiveness is central to ISO-induced reduction in cardiac force development. Moreover, we also tested whether the nitroxyl (HNO) donor 1-nitrosocyclohexyl acetate (NCA), acting as a myofilament Ca(2+) sensitizer, restores force in the presence of ISO. Trabeculae from the right ventricles of LBN/F1 rats were superfused with Krebs-Henseleit solution at room temperature, and force and intracellular Ca(2+) ([Ca(2+)](i)) were measured. Steady-state activations were achieved by stimulating the muscles at 10 Hz in the presence of ryanodine. The same muscles were chemically skinned with 1% Triton X-100, and the force-Ca(2+) relation measurements were repeated. ISO depressed force in a dose-dependent manner without significantly altering [Ca(2+)](i). At 1.5%, force was reduced over 50%, whereas [Ca(2+)](i) remained unaffected. At 3%, contraction was decreased by ∼75% with [Ca(2+)](i) reduced by only 15%. During steady-state activation, 1.5% ISO depressed maximal Ca(2+)-activated force (F(max)) and increased the [Ca(2+)](i) required for 50% activation (Ca(50)) without affecting the Hill coefficient. After skinning, the same muscles showed similar decreases in F(max) and increases in Ca(50) in the presence of ISO. NCA restored force in the presence of ISO without affecting [Ca(2+)](i). These results show that 1) ISO depresses cardiac force development by decreasing myofilament Ca(2+) responsiveness, and 2) myofilament Ca(2+) sensitization by NCA can effectively restore force development without further increases in [Ca(2+)](i). The present findings have potential translational value because of the efficiency and efficacy of HNO on ISO-induced myocardial contractile dysfunction.

Nicorandil preserves myocardial function following brain death in rats by mitochondrial adenosine triphosphate-sensitive potassium channel-dependent mechanism.

OBJECTIVE: Interventions to preserve myocardial function after brain death may increase the donor pool for heart transplantation. The present study using a brain death model of rats was designed to examine the protective potential of nicorandil, an adenosine triphosphate-sensitive potassium channel opener, on myocardial function after brain death. METHODS: Rats were anesthetized with sevoflurane. A Fogarty catheter was placed intracranially for induction of brain death. The conductance catheter was inserted into the left ventricle for measurement of myocardial function. Rats were assigned randomly to two groups, one receiving nicorandil before brain death and the other receiving saline (control group). Mean blood pressure, heart rate, maximal rate of rise of left-ventricular pressure and ejection fraction were measured every 30 min for 6h after brain death. The same protocol was performed in the presence of nicorandil combined with 5-hydroxydecanoic acid, a mitochondrial adenosine triphosphate-sensitive potassium channel inhibitor. RESULTS: Nicorandil temporally, but significantly, improved ejection fraction compared with the control group. Furthermore, 5-hydroxydecanoic acid inhibited the effects of nicorandil. CONCLUSIONS: Nicorandil was effective to preserve ejection fraction after brain death, and myocardial mitochondrial adenosine triphosphate-sensitive potassium channels may be involved in this action.

Comparative metabolism of cinobufagin in liver microsomes from mouse, rat, dog, minipig, monkey, and human.

Cinobufagin (CB), a major bioactive component of the traditional Chinese medicine Chansu, has been reported to have potent antitumor activity. In this study, in vitro metabolism of CB among species was compared with respect to metabolic profiles, enzymes involved, and catalytic efficiency by using liver microsomes from human (HLM), mouse (MLM), rat (RLM), dog (DLM), minipig (PLM), and monkey (CyLM). Significant species differences in CB metabolism were revealed. In particular, species-specific deacetylation and epimerization combined with hydroxylation existed in RLM, whereas hydroxylation was a major pathway in HLM, MLM, DLM, PLM, and CyLM. Two monohydroxylated metabolites of CB in human and animal species were identified as 1α-hydroxylcinobufagin and 5ß-hydroxylcinobufagin by using liquid chromatography-mass spectrometry and two-dimensional NMR techniques. CYP3A4 was identified as the main isoform involved in CB hydroxylation in HLM on the basis of the chemical inhibition studies and screen assays with recombinant human cytochrome P450s. Furthermore, ketoconazole, a specific inhibitor of CYP3A, strongly inhibited CB hydroxylation in MLM, DLM, PLM, and CyLM, indicating that CYP3A was responsible for CB hydroxylation in these animal species. The apparent substrate affinity and catalytic efficiency for 1α- and 5ß-hydroxylation of CB in liver microsomes from various species were also determined. PLM appears to have K(m) and total intrinsic clearance value (V(max)/K(m)) similar to those for HLM, and the total microsomal intrinsic clearance values for CB obeyed the following order: mouse > dog > monkey > human > minipig. These findings provide vital information to better understand the metabolic behaviors of CB among various species.

Vasoconstrictor and inotropic effects induced by the root bark extracts of Anthocleista schweinfurthii.

The present study was undertaken to investigate the cardiovascular effect of three extracts from the root bark of Anthocleista schweinfurthii Gilg.: an aqueous extract (AE), a dichloromethane extract (DCMR) and a fraction enriched in cardiac glycoside type compounds (CARDAN). In isolated perfused frog heart, bolus injection of the extracts produced a positive inotropic effect. The responses to AE and DCMR, but not to CARDAN, were depressed by propranolol. In isolated rat aorta, DCMR produced a transient increase in contractile tension while AE and CARDAN induced a sustained constriction. AE vasoconstrictor effect was abolished by phentolamine, while contraction evoked by CARDAN was antagonized by verapamil. In aortic rings contracted in low K+ media, the addition of K+ evoked a relaxation, which was abolished by ouabain, depressed by DCMR but not affected by either A(E) or CARDAN. These observations indicate that Anthocleista schweinfurthii contains substances that promote vasoconstriction and increase cardiac contraction. The effect of DCMR was only partially mediated by inhibition of the Na+ pump while the mechanism of action of A(E) and CARDAN was distinct from the inhibition of the Na+, K+ - ATPase pump, but could involve adrenergic receptors, or either direct or indirect activation of L-type calcium channels.

Type II nitric oxide synthase activity is cardio-protective in experimental sepsis.

Overproduction of nitric oxide (NO) via the induction of NO synthase (NOS) II is implicated in the pathogenesis of the refractory hypotension that characterizes septic shock. However, clinical trials of nonselective NOS inhibitors have failed to afford a mortality benefit in patients with sepsis, and in those with depressed left ventricular function, death rates were increased. Such observations have led to the suggestion that a selective inhibitor of NOSII would be more effective in treating septic shock, although precisely how NO modulates cardiac function in these circumstances remains unclear. We therefore used an isolated ejecting rodent heart model to study the effects of NO and experimental sepsis (endotoxin 20 mg kg i.p.) on cardiac functions. Coronary flow and cardiac output and ventricular functions were reduced by LPS, effects that were partially obviated by supplementation of perfusate with the NO substrate, L-arginine. These improvements were partially blocked by the selective NOSII inhibitor N-(3-(aminomethyl)benzyl)acetamidine (1400W) and further reduced by the combined NOSI, II and III inhibitor L-nitro L-arginine methyl ester (L-NAME). These findings suggest that NOSII is cardio-protective in the heart in sepsis and explain why its inhibition in man led to increased mortality in a subpopulation of patients.

S-Isopetasin, a sesquiterpene of Petasites formosanus, allosterically antagonized carbachol in isolated guinea pig atria.

We investigated the antimuscarinic effect of S-isopetasin in isolated guinea pig atria to clarify whether it preferentially acts on muscarinic M 2 or M 3 receptors. The tension changes of isolated atria were isometrically recorded on a polygraph. S-Isopetasin at 50 and 100 microM significantly inhibited baselines of contractile tension and heart rate, but atropine at 1 microM enhanced both. S-Isopetasin (10 - 100 microM) did not significantly alter the concentration-negative inotropic response curves of carbachol (CCh) in left atria. S-Isopetasin (10 - 100 microM) allosterically antagonized negative inotropic and chronotropic responses induced by CCh in spontaneously beating right atria, based on the slopes of Schild plots significantly differing from unity. On the contrary, atropine (0.01 - 1 microM) competitively antagonized all the above responses to CCh. The pA 2 values of S-isopetasin were significantly less than that of S-isopetasin in guinea pig trachealis, suggesting that S-isopetasin may preferentially act on tracheal muscarinic M 3, but not cardiac muscarinic M 2 receptors. However, atropine preferentially acts neither. This finding reveals that S-isopetasin may have benefit in the treatment of asthma.

Uremic sera contain inhibitors that block digitoxin-valproic acid interaction.

BACKGROUND: Digitoxin and valproic acid show strong binding to serum albumin. Thus, when present simultaneously in serum, digitoxin and valproic acid compete for binding sites. We studied digitoxin-valproic acid interaction in normal and uremic sera. METHODS: Fluorescence polarization immunoassays were used for measuring total digitoxin and total valproic acid concentrations. We used a modified protocol of improved sensitivity to measure free digitoxin concentrations. We supplemented 2 normal and 2 uremic pools with digitoxin and then aliquots of these pools were further supplemented with various concentrations of valproic acid. After incubation at 37 degrees C for 2 hours in a water bath, specimens were allowed to re-equilibrate at room temperature for 20 minutes. Free digitoxin concentrations were measured. We also investigated digoxin-valproic acid interaction using 1 normal and 1 uremic serum pool. RESULTS: We observed significant increases in free digitoxin concentrations in normal sera in the presence of valproic acid. In contrast, we observed a slight decline in free digitoxin concentration in the presence of valproic acid in uremic sera. We speculated that uremic sera contained inhibitors that block digitoxin-valproic acid interaction and identified indoxyl sulfate as an inhibitor. However, another uremic compound, hippuric acid showed no inhibitory effect. Interestingly, we observed no significant interaction between digoxin and valproic acid in either normal or uremic serum pool. This is probably because of poor protein binding of digoxin. CONCLUSION: We conclude that valproic acid significantly displaces digitoxin from protein binding sites in normal serum. However, uremic sera contain inhibitors that block digitoxin-valproic acid interaction.