The Cardioprotective Effects of Remote Ischemic Conditioning in a Rat Model of Acute Myocardial Infarction.

BACKGROUND Cardiac remote ischemic conditioning (RIC) is a noninvasive cardioprotective method in ischemia-reperfusion injury and acute myocardial infarction (AMI). The aims of this study were to investigate the effects of RIC in a rat model of AMI. MATERIAL AND METHODS Adult male Sprague-Dawley rats included the AMI group that underwent ligation of the left anterior descending (LAD) coronary artery (n=24), the RIC group that consisted the AMI rat model treated with RIC once daily in the left hind limb until days 1, 7 and 14 (n=24), and the sham group (n=24). Myocardial infarct size was measured by routine histology with triphenyltetrazolium chloride (TTC) and Masson's trichrome histochemical staining for myocardial necrosis and fibrosis, respectively. Serum levels of Bcl-2, Bax, caspase-3, and inducible nitric oxide synthase (iNOS) were measured by enzyme-linked immunosorbent assay (ELISA). The apoptosis index was detected using the TUNEL assay. Spectrophotometry of the myocardium was used to identify mitochondrial complexes and myocardial ATP. RESULTS The RIC group showed improved cardiac hemodynamics, reduced the size of the myocardial infarction, upregulated expression of Bcl-2, and down-regulation of the levels of Bax, caspase-3, and iNOS, and reduced cardiac myocyte apoptosis and inhibited the opening of the mitochondrial permeability transition pore (MPTP). CONCLUSIONS In a rat model of AMI, RIC improved the hemodynamic index, reduce the levels of apoptosis and myocardial injury, and improved mitochondrial function.

Taurine-magnesium coordination compound, a potential anti-arrhythmic complex, improves aconitine-induced arrhythmias through regulation of multiple ion channels.

Taurine-magnesium coordination compound (TMCC) exhibits antiarrhythmic effects in cesium-chloride-and ouabain-induced arrhythmias; however, the mechanism underlying these effects on arrhythmia remains poorly understood. Here, we investigated the effects of TMCC on aconitine-induced arrhythmia in vivo and the electrophysiological effects of this compound in rat ventricular myocytes in vitro. Aconitine was used to induce arrhythmias in rats, and the dosages required to produce ventricular premature contraction (VPC), ventricular tachycardia (VT), ventricular fibrillation (VF), and cardiac arrest (CA) were recorded. Additionally, the sodium current (INa) and L-type calcium current (ICa,L) were analyzed in normal and aconitine-treated ventricular myocytes using whole-cell patch-clamp recording. In vivo, intravenous administration of TMCC produced marked antiarrhythmic effects, as indicated by the increased dose of aconitine required to induce VPC, VT, VF, and CA. Moreover, this effect was abolished by administration of sodium channel opener veratridine and calcium channel agonist Bay K8644. In vitro, TMCC inhibited aconitine-induced increases in INa and ICa,L. These results revealed that TMCC inhibited aconitine-induced arrhythmias through effects on INa and ICa,L.

[Anti-arrhythmic effects of taurine-magnesium coordination compound on torsades de pointes].

OBJECTIVES: To investigate the effect of taurine magnesium coordination compound (TMCC) on torsades de pointes (TdP) in isolated guinea pig hearts. METHODS: Healthy male guinea pigs weighting 250~300 g were randomly divided into 4 groups:①TdP model group (n=7):Isolated hearts were perfused by normal K-H solution 20 minutes, then perfused by slowly activated delayed rectifier potassium current(IKs) blocker 10µmol/L Chromanol 293B under hypokalemic solution(1.8 mmol/L) to establish TdP model;②~④ TdP model + TMCC group (n=6):Isolated hearts were perfused by normal K-H solution for 20 minutes, then perfused by IKs blocker 10µmol/L Chromanol 293B under hypokalemic solution(1.8 mmol/L) for 60 minutes, at the same time TMCC which concentration was 1, 2, 4 mmol/L was administered respectively by Langendorff retrograde aortic perfusion method. Cardiac surface electrocardiogram of guinea pigs in vitro was collected and recorded by Biopac electrophysiological recorder. Incidence of TdP, transmural dispersion of repolarization (TDR), instability of QT interval were acquired from Lead Ⅱ electrocardiograph (ECG) wave forms to describe the effect of TMCC on TdP model. Datas were acquired at the time of 20 min and pre-TdP, in case there was no TdP observed, a value of 60 min was entered for calculation purpose. RESULTS: Incidence of TdP in TdP model group was 6/7. TdP incidence could be decreased significantly by 1, 2, 4 mmol/L TMCC, and was 5/6, 1/6, 0/6 respectively. Compared with the pre-drug, Chromanol 293B under hypokalemic solution in TdP model group increased TDR(corrected) evidently(P<0.01). Compared with the pre-drug, 1, 2, 4 mmol/L TMCC in TdP model + TMCC group could decrease the increased TDR(corrected) induced by Chromanol 293B under hypokalemic solution(P>0.05). Compared with the TdP model group, 2, 4 mmol/L TMCC could evidently decrease the instability of QT interval induced by Chromanol 293B under hypokalemic solution(P<0.05). During the establishment of TdP model, P waves in more than one cardiac cycle continuously were disappeared in ECG. However, P wave could always be seen independent in ECG acquired from TdP model + TMCC group. CONCLUSIONS: TMCC can play the role against TdP through decreasing TDR and instability of QT interval, and inhibiting early after depolarization(EAD).

Therapeutic effects of a taurine-magnesium coordination compound on experimental models of type 2 short QT syndrome.

Short QT syndrome (SQTS) is a genetic arrhythmogenic disease that can cause malignant arrhythmia and sudden cardiac death. The current therapies for SQTS have application restrictions. We previously found that Mg· (NH2CH2CH2SO3)2· H2O, a taurine-magnesium coordination compound (TMCC) exerted anti-arrhythmic effects with low toxicity. In this study we established 3 different models to assess the potential anti-arrhythmic effects of TMCC on type 2 short QT syndrome (SQT2). In Langendorff guinea pig-perfused hearts, perfusion of pinacidil (20 µmol/L) significantly shortened the QT interval and QTpeak and increased rTp-Te (P<0.05 vs control). Subsequently, perfusion of TMCC (1-4 mmol/L) dose-dependently increased the QT interval and QTpeak (P<0.01 vs pinacidil). TMCC perfusion also reversed the rTp-Te value to the normal range. In guinea pig ventricular myocytes, perfusion of trapidil (1 mmol/L) significantly shortened the action potential duration at 50% (APD50) and 90% repolarization (APD90), which was significantly reversed by TMCC (0.01-1 mmol/L, P<0.05 vs trapidil). In HEK293 cells that stably expressed the outward delayed rectifier potassium channels (IKs), perfusion of TMCC (0.01-1 mmol/L) dose-dependently inhibited the IKs current with an IC50 value of 201.1 µmol/L. The present study provides evidence that TMCC can extend the repolarization period and inhibit the repolarizing current, IKs, thereby representing a therapeutic candidate for ventricular arrhythmia in SQT2.

Acute and chronic effects of taurine magnesium coordination compound on cardiac sodium channel Nav1.5.

It has been previously demonstrated that taurine magnesium coordination compound (TMCC) produces antiarrhythmic effects in vivo. The present study investigated the acute and chronic effect of TMCC on sodium channels in HEK cells stably expressing human cardiac Nav1.5 sodium channels. The current amplitude, activation and inactivation kinetics, recovery time from inactivation, and use­dependent block of sodium channels were analyzed using the whole­cell patch clamp technique. Western blotting was used to analyze Nav1.5 expression following chronic TMCC treatment. In HEK cells expressing Nav1.5 channels, TMCC acutely inhibited Na+ currents in a dose­dependent manner. In addition, acute application of TMCC shifted the activation and inactivation curves, and prolonged the recovery time from inactivation, but did not exhibit a use­dependent block of Nav1.5. By contrast, chronic TMCC treatment only produced a use­dependent block of Nav1.5 and downregulated Nav1.5 expression. The results of the present study suggested that TMCC may produce antiarrhythmic actions via acute inhibition of sodium channel currents and chronic downregulation of Nav1.5 expression.

Effects of non-invasive remote ischemic conditioning on rehabilitation after myocardial infarction.

Recent studies have demonstrated that remote ischemic conditioning (RIC) creates cardioprotection against ischemia/reperfusion injury and myocardial infarction (MI); however, the effects of non-invasive remote ischemic conditioning (nRIC) on prognosis and rehabilitation after MI (post-MI) remain unknown. We successfully established MI models involving healthy adult male Sprague-Dawley rats. The nRIC group repeatedly underwent 5 min of ischemia and 5 min of reperfusion in the left hind limb for three cycles every other day until weeks 4, 6, and 8 after MI. nRIC improved cardiac hemodynamic function and mitochondrial respiratory function through increasing myocardial levels of mitochondrial respiratory chain complexes I, II, III, IV, and adenosine triphosphate (ATP) and decreasing the activity of nitric oxide synthase (NOS). nRIC could inhibit cardiomyocytes apoptosis and reduce myocardium injury through raising the expression of Bcl-2 and reduced the content of creatine kinase-MB, cardiac troponin I and Bax. The results indicated that long-term nRIC could accelerate recovery and improve prognosis and rehabilitation in post-MI rats.

Mitochondrial events responsible for morphine's cardioprotection against ischemia/reperfusion injury.

Morphine may induce cardioprotection by targeting mitochondria, but little is known about the exact mitochondrial events that mediate morphine's protection. We aimed to address the role of the mitochondrial Src tyrosine kinase in morphine's protection. Isolated rat hearts were subjected to 30 min ischemia and 2h of reperfusion. Morphine was given before the onset of ischemia. Infarct size and troponin I release were measured to evaluate cardiac injury. Oxidative stress was evaluated by measuring mitochondrial protein carbonylation and mitochondrial ROS generation. HL-1 cells were subjected to simulated ischemia/reperfusion and LDH release and mitochondrial membrane potential (ΔΨm) were measured. Morphine reduced infarct size as well as cardiac troponin I release which were aborted by the selective Src tyrosine kinase inhibitors PP2 and Src-I1. Morphine also attenuated LDH release and prevented a loss of ΔΨm at reperfusion in a Src tyrosine kinase dependent manner in HL-1 cells. However, morphine failed to reduce LDH release in HL-1 cells transfected with Src siRNA. Morphine increased mitochondrial Src phosphorylation at reperfusion and this was abrogated by PP2. Morphine attenuated mitochondrial protein carbonylation and mitochondrial superoxide generation at reperfusion through Src tyrosine kinase. The inhibitory effect of morphine on the mitochondrial complex I activity was reversed by PP2. These data suggest that morphine induces cardioprotection by preventing mitochondrial oxidative stress through mitochondrial Src tyrosine kinase. Inhibition of mitochondrial complex I at reperfusion by Src tyrosine kinase may account for the prevention of mitochondrial oxidative stress by morphine.

[The effects of dioscin on myocardial contraction and sodium-cal-cium exchanger].

OBJECTIVE: To investigate the inotropic effects of dioscin (Dio)in rat isolated-heart and intracellular free calcium concentration in isolated rat ventricular myocytes and to explore its mechanism preliminarily. METHODS: Left ventricle contractile function was measured using the Langendorff non-recirculating mode of isolated rat heart perfusion. Effects of dioscin and dioscin+SEA0400, sodium-calcium exchanger (NCX) inhibitor, were investigated by measuring left ventricular systolic pressure (LVSP) and left ventricular end diastolic pressure (LVEDP). Also, heart rate (HR), peak rate of rise/fall of left ventricular pressure (±dp/dtmax) of isolated rat heart were calculated; Effects of dioscin and SEA0400 on intracellular free calcium concentration in rat H9c2 cells were measured by Fluo3-AM and then detected the fluorescence intensity with confocal microscopy. RESULTS: With 1 µmol/L dioscin, LVSP was significantly increased by 19.7% (P<0.01) and dp/dtmax was increased by 9.6%; With 1 µmol/L dioscin, the relative fluorescence intensity of intracellular free calcium concentrations were strong significantly(P<0.01). While in presence of SEA0400, the relative fluorescence intensity was changed to 17.09±0.63 (P<0.01) by 1 µmol/L dioscin. With 1 µmol/L dioscin, the relative fluorescence intensity was weak(P<0.01) without calcium or sodium in the extracellular fluid. CONCLUSIONS: Dioscin shows positive inotropic effect on isolated rat heart, enhancing the LVSP and +dp/dtmax; Dioscin increases the intracellular concentration of Ca2+ in the cardiac myocytes by increasing Na+ influx and facilitating the reverse mode of the sodium-calcium exchanger.

NFATc3 pathway participates in the process that 15-LO/15-HETE protects pulmonary artery smooth muscle cells against apoptosis during hypoxia.

Hypoxia activates nuclear factor of activated T cells isoforms c3 (NFATc3), a Ca(2+)-dependent transcription factor in murine pulmonary arteries (PAs), and NFATc3 has been proved to be implicated in hypoxia-induced pulmonary arterial smooth muscle cells (PASMCs) proliferation, but it remains unclear whether NFATc3 acts on the apoptosis of PASMCs, an important step in PAs remodeling. Our laboratory has demonstrated that 15-hydroxyeicosatetraenoic acid (15-HETE) is a key factor in hypoxia-induced PA remodeling and can increase PASMC intracellular Ca(2+) ([Ca(2+)](i)) in rats. It is possible that NFATc3 is related with the function of 15-HETE anti-apoptosis during hypoxia. Our results identified that NFATc3 was mainly localized in rat PASMCs and was upregulated in PAs during hypoxia-induced rat pulmonary hypertension (PH), while this effect was inhibited by administration of nordihydroguaiaretic acid (NDGA), a 15-lipoxygenase (15-LO) inhibitor. Moreover, hypoxia and exogenous 15-HETE promoted the expression and nuclear translocation of NFATc3 in PASMCs, which was inhibited by NDGA or small interfering RNA targeted to rat 15-LO1 or 15-LO2. Furthermore, endogenous 15-HETE induced by hypoxia and exogenous 15-HETE suppressed serum deprivation-induced loss of rat PASMCs survival and prevented annexin V binding, mitochondrial membrane potential depolarization, DNA nick end labeling and chromatin condensation. Although all these effects were suppressed after the cells were treated with cyclosporin A (a calcineurin/NFAT inhibitor), it aggravated the apoptosis induced by serum deprivation. Thus, all these results indicate that 15-HETE-mediated PASMCs anti-apoptosis in hypoxic PH via the Ca(2+)-NFATc3 pathway.

Assessment of effects of IR and IPC on activities of cytochrome P450 isozymes in rats by a five-drug cocktail approach.

BACKGROUND AND OBJECTIVE: To evaluate the effects of ischemia and reperfusion (IR) and ischemic preconditioning (IPC) on the metabolic activities of cytochrome P450 (CYP) isozymes in rats by a five-drug cocktail approach. METHODS: Cocktail approach was used to evaluate the influence of IR and IPC on the activities of CYP1A2, CYP2C9, CYP2E1, CYP2D6 and CYP3A4, which were reflected by the changes of pharmacokinetic parameters of five specific probe drugs: caffeine, chlorzoxazone, tolbutamide, metoprolol and midazolam, respectively. Rats were randomly divided into IR, IPC and sham groups, and then injected the mixture of five probe drugs. Blood samples were collected at a series of time-points and the concentrations of probe drugs in plasma were determined by a HPLC method with UV detection. The pharmacokinetic parameters were calculated by the software of DAS 2.0. RESULTS: The parameters including t(1/2ß), CLs, AUC, MRT and K10 exhibited a similar tendency for both IR and IPC groups. Compared with sham group, CLs and K10 of five probe drugs were significantly lower (p < 0.05), AUC and t(1/2ß) of five or some probe drugs were significantly increased in IR and IPC groups (p < 0.05). Compared with IPC group, CLs of five probe drugs were decreased and AUC were significantly increased in the IR group (p < 0.05). CONCLUSION: IR can variably decrease the activities of CYP isozymes in rats and this decrease can be attenuated by IPC.

UPLC-DAD/Q-TOF-MS Based Ingredients Identification and Vasorelaxant Effect of Ethanol Extract of Jasmine Flower.

Chinese people commonly make jasmine tea for recreation and health care. Actually, its medicinal value needs more exploration. In this study, vasorelaxant effect of ethanol extract of jasmine flower (EEJ) on isolated rat thoracic aorta rings was investigated and [Ca(2+)] was determined in vascular smooth muscle cells by laser scanning confocal microscope (LSCM). The result of aorta rings showed that EEJ could cause concentration-dependent relaxation of endothelium-intact rings precontracted with phenylephrine or KCl which was attenuated after preincubation of the rings with L-NAME and three different K(+) channel inhibitors; however, indomethacin and glibenclamide did not affect the vasodilatation of EEJ. In addition, EEJ could inhibit contraction induced by PE on endothelium-denuded rings in Ca(2+)-free medium as well as by accumulation of Ca(2+) in Ca(2+)-free medium with high K(+). LSCM also showed that EEJ could lower the elevated level of [Ca(2+)] induced by KCl. These indicate that the vasodilation of EEJ is in part related to causing the release of nitric oxide, activation of K(+) channels, inhibition of influx of excalcium, and release of calcium from sarcoplasmic reticulum. A total of 20 main ingredients, were identified in EEJ by UPLC-DAD/Q-TOF-MS. The vasodilation activity should be attributed to the high content of flavonoid glycosides and iridoid glycosides found in EEJ.

Biological evaluation of a cytotoxic 2-substituted benzimidazole copper(II) complex: DNA damage, antiproliferation and apoptotic induction activity in human cervical cancer cells.

Exploring novel chemotherapeutic agents is a great challenge in cancer medicine. To that end, 2-substituted benzimidazole copper(II) complex, [Cu(BMA)Cl2]·(CH3OH) (1) [BMA = N,N'-bis(benzimidazol-2-yl-methyl)amine], was synthesized and its cytotoxicity was characterized. The interaction between complex 1 and calf thymus DNA was detected by spectroscopy methods. The binding constant (K b = 1.24 × 10(4 )M(-1)) and the apparent binding constant (K app = 6.67 × 10(6 )M(-1)) of 1 indicated its moderate DNA affinity. Complex 1 induced single strand breaks of pUC19 plasmid DNA in the presence of H2O2 through an oxidative pathway. Cytotoxicity studies proved that complex 1 could inhibit the proliferation of human cervical carcinoma cell line HeLa in both time- and dose-dependent manners. The results of nuclei staining by Hoechst 33342 and alkaline single-cell gel electrophoresis proved that complex 1 caused cellular DNA damage in HeLa cells. Furthermore, treatment of HeLa cells with 1 resulted in S-phase arrest, loss of mitochondrial potential, and up-regulation of caspase-3 and -9 in HeLa cells, suggesting that complex 1 was capable of inducing apoptosis in cancer cells through the intrinsic mitochondrial pathway.

Arctigenin, a potential anti-arrhythmic agent, inhibits aconitine-induced arrhythmia by regulating multi-ion channels.

BACKGROUND/AIMS: Arctigenin possesses biological activities, but its underlying mechanisms at the cellular and ion channel levels are not completely understood. Therefore, the present study was designed to identify the anti-arrhythmia effect of arctigenin in vivo, as well as its cellular targets and mechanisms. METHODS: A rat arrhythmia model was established via continuous aconitine infusion, and the onset times of ventricular premature contraction, ventricular tachycardia and death were recorded. The Action Potential Duration (APD), sodium current (I(Na)), L-type calcium current (I(Ca, L)) and transient outward potassium current (I(to)) were measured and analysed using a patch-clamp recording technique in normal rat cardiomyocytes and myocytes of arrhythmia aconitine-induced by. RESULTS: Arctigenin significantly delayed the arrhythmia onset in the aconitine-induced rat model. The 50% and 90% repolarisations (APD50 and APD90) were shortened by 100 µM arctigenin; the arctigenin dose also inhibited the prolongation of APD50 and APD90 caused by 1 µM aconitine. Arctigenin inhibited I(Na) and I(Ca,L) and attenuated the aconitine-increased I(Na) and I(Ca,L) by accelerating the activation process and delaying the inactivation process. Arctigenin enhanced Ito by facilitating the activation process and delaying the inactivation process, and recoverd the decreased Ito induced by aconitine. CONCLUSIONS: Arctigenin has displayed anti-arrhythmia effects, both in vivo and in vitro. In the context of electrophysiology, I(Na), I(Ca, L), and I(to) may be multiple targets of arctigenin, leading to its antiarrhythmic effect.

[Study on the constituents of essential oil of Shunaoxin dropping pills by GC-MS].

OBJECTIVE: To study the constituents of essential oil from Shunaoxin dropping pills by GC-MS. METHODS: The essential oil from Shunaoxin dropping pills were extracted by absolute alcohol and analyzed by GC-MS. RESULTS: 15 components from the essential oil of Shunaoxin dropping pills were identified. CONCLUSION: The main components in the essential oil of Shunaoxin dropping pills are lactones such as Z-ligustilide, senkyunolide A,3-butylphthalide and 3-butylidenephthalide, other components are organic acids such as ethyl linoleate, 9,12-octadecadienoic acid and ethyl palmitate.

Effects of Fufang Biejia Ruangan pills on hepatic fibrosis in vivo and in vitro.

AIM: To explore the protective effect and the relevant mechanisms of Fufang Biejia Ruangan Pills (FFBJRGP) on hepatic fibrosis in vivo and in vitro. METHODS: Hepatic fibrosis was induced by carbon tetrachloride composite factors. Adult Wistar rats were randomly divided into four groups: normal control group; hepatic fibrosis model group; FFBJRGP-treated group at a daily dose of 0.55 g/kg; and colchicine-treated group at a daily dose of 0.1 g/kg. The effects of FFBJRGP on liver function, serum levels of hyaluronic acid (HA), type IV collagen (CIV), type III procollagen (PC III), laminin (LN), histopathology, and expression of transforming growth factor (TGF-ß1) and Smad3 in hepatic fibrosis were evaluated in vivo. The effects of FFBJRGP on survival rate, hydroxyproline content and cell cycle distribution were further detected in vitro. RESULTS: Compared with the hepatic fibrosis model group, rats treated with FFBJRGP showed a reduction in hepatic collagen deposition and improvement in hepatic lesions. Compared with those of the model group, the activities of alanine aminotransferase (62.0 ± 23.7 U/L) and aspartate aminotransferase (98.8 ± 40.0 U/L) in the FFBJRGP-treated group were decreased (50.02 ± 3.7 U/L and 57.2 ± 30.0 U/L, respectively, P < 0.01). Compared with those in the model group, the levels of PCIII (35.73 ± 17.90 µg/mL), HA (563.82 ± 335.54 ng/mL), LN (89.57 ± 7.59 ng/mL) and CIV (29.20 ± 6.17 ng/mL) were decreased to 30.18 ± 9.41, 456.18 ± 410.83, 85.46 ± 7.51 and 28.02 ± 9.45 ng/mL, respectively. Reverse-transcriptase polymerase chain reaction and Western blotting also revealed that expression of TGF-ß1 and Smad3 were down-regulated in vivo. Cell proliferation was inhibited, the level of hydroxyproline was decreased compared with the control group (P < 0.01), and the cell cycle was redistributed when exposed to FFBJRGP in vitro. CONCLUSION: FFBJRGP inhibits hepatic fibrosis in vivo and in vitro, which is probably associated with downregulation of fibrogenic signal transduction of the TGF-ß-Smad pathway.

Activities of a novel Schiff base copper(II) complex on growth inhibition and apoptosis induction toward MCF-7 human breast cancer cells via mitochondrial pathway.

In this study, we investigated the newly synthesized Schiff base copper(II) complex, [Cu(II)(5-Cl-pap)(OAc)(H(2)O)]·2H(2)O (1) (5-Cl-pap=N-2-pyridiylmethylidene-2-hydroxy-5-chloro-phenylamine), inducing growth inhibition and apoptosis in human breast cancer cell line MCF-7 and its potential antitumor mechanism. The results of cytotoxicity research, fluorescence microscopic observation and flow cytometric analysis revealed that complex 1 could significantly suppress MCF-7 cell viability and induce apoptosis. Comet assay indicated that severe DNA fragmentation in MCF-7 cells was induced after treatment with complex 1. Flow cytometric analysis showed that the antitumor effect of complex 1 on MCF-7 cells was associated with the cell cycle arrest. In addition, atomic absorption analyses displayed that complex 1 caused a rapid increase of intracellular copper uptake in MCF-7 cells in a time-dependent manner. The present work suggested that the antitumor mechanism of complex 1 on MCF-7 cells might be via the mitochondrial pathway, based on the up-regulated expression of Bax and activation of caspase-9 and caspase-3.

Effects of taurine-magnesium coordination compound on ionic channels in rat ventricular myocytes of arrhythmia induced by ouabain.

Taurine-magnesium coordination compound (TMCC) has anti-arrhythmic effects. The aim of the present study was to explore the targets of the anti-arrhythmic effect of TMCC and the electrophysiological effects of TMCC on ouabain-induced arrhythmias in rat ventricular myocytes. Sodium current (I(Na)), L-type calcium current (I(ca, L)), and transient outward potassium current (I(to)) were measured and analyzed using whole-cell patch-clamp recording technique in normal rat cardiac myocytes and rat ventricular myocytes of arrhythmia induced by ouabain. In isolated ventricular myocytes, I(Na) and I(to) were blocked by TMCC (100, 200, 400 µM) in a concentration-dependent manner, and the effects of TMCC (400 µM) were equal to that of amiodarone. However, I (ca, L) was moderately increased by TMCC (400 µM) while significantly decreased by amiodarone. Ouabain (5 µM) significantly decreased sodium, L-type calcium, and transient outward potassium currents. TMCC (100 µM) relieved abnormal sodium currents induced by ouabain through facilitation of steady-state inactivation. TMCC (200 and 400 µM) relieved abnormal L-type calcium currents induced by ouabain through facilitation of steady-state activation and retardation of steady-state inactivation. TMCC failed to further inhibit abnormal transient outward potassium currents induced by ouabain. However, amiodarone inhibited the decreasing sodium, L-type calcium, and transient outward potassium currents further. These data suggest that I(Na), I(ca, L), and I(to) may be the targets of the antiarrhythmic effect of TMCC, which can antagonize ouabain-induced changes of ionic currents in rat ventricular myocytes.

Noninvasive delayed limb ischemic preconditioning in rats increases antioxidant activities in cerebral tissue during severe ischemia-reperfusion injury.

BACKGROUND: To study the protection offered by noninvasive delayed limb ischemic preconditioning (NDLIP) against cerebral ischemia reperfusion (I/R) injury in rats. MATERIALS AND METHODS: Healthy male Wistar rats were randomly divided into four groups. The delayed protection offered by NDLIP was estimated in light of changes in the neural behavior marker and cerebral tissue antioxidative ability. Neurological functions were studied by observing neural behavior. Total superoxide dismutase (T-SOD), manganese-superoxide dismutase (Mn-SOD), glutathione peroxidase (GSH-PX), and xanthine oxidase (XOD) activity in cerebral tissue and malonaldehyde (MDA) content were detected using a spectrophotometer. Mn-SOD mRNA was measured by the reverse transcription polymerase chain reaction method. RESULTS: Cerebral infarct size was diminished in the early cerebral ischemia preconditioning (ECIP)+I/R and NDLIP+I/R groups compared with the I/R group (P < 0.05). The cortical and hippocampal antioxidant enzyme activity and Mn-SOD expression were increased in the ECIP+I/R and NDLIP+I/R groups. In contrast, the cortical and hippocampal XOD activity and MDA content decreased in the ECIP+I/R and NDLIP+I/R groups. CONCLUSIONS: NDLIP decreased cerebral infarct size, increased cerebral antioxidative ability after I/R injury, and decreased peroxidative damage. The antioxidative protection offered by NDLIP was as effective as that offered by ECIP.

The optimal strategy of noninvasive limb ischemic preconditioning for protecting heart against ischemia-reperfusion injury in rats.

BACKGROUND: Limb ischemic preconditioning (LIPC) induced by prior brief periods of ischemia-reperfusion (I/R) to a limb is a simple and convenient strategy to protect the heart from I/R injury. However, the optimal strategy is unknown. Therefore, the present study was conducted to test the most effective method of LIPC for clinical applications. METHODS: Male Wistar rats were randomized into the following groups: control groups, consecutive LIPC groups, intermittent LIPC groups. The control groups, including the sham operation group, the ischemia-reperfusion (I/R)-control group, the myocardial ischemic preconditioning (MIPC) group, the femoral artery ischemic preconditioning (FAIP) group; the consecutive LIPC groups, including continuously using for 1 d, 3 d, and 7 d groups. Each group was tested on the first, third, and fifth d after LIPC; intermittent LIPC groups, including 1-d LIPC + 1-d interval group, 1-d LIPC + 2-d interval group, 3-d LIPC + 3-d interval group, 3-d LIPC + 5-d interval group. Left ventricular function, incidence of ventricular arrhythmia, and ST-segment were measured during I/R. Myocardial infarct size, creatine kinase isoenzyme MB (CK-MB), and cardiac troponins I (cTnI) were determined at the end of experiment. RESULTS: Compared with the I/R-controls, the MIPC, FAIP, continuous LIPC for 3 and 7 d and 1-d LIPC + 1-d interval groups showed amelioration of ventricular arrhythmia, improved left ventricular function, lower ST-segment elevation, reduced myocardial infarct size, decreased CK-MB, and cTnI activity. The protective effects of LIPC persisted for 72 h. CONCLUSIONS: Our results suggest that a 1-d LIPC + 1-d interval provides optimal cardioprotection from I/R.

Inhibition of sodium current by taurine magnesium coordination compound prevents cesium chloride-induced arrhythmias.

The mechanism(s) by which taurine magnesium coordination compound (TMCC) inhibits experimental arrhythmias remains poorly understood. The purpose of this study was to observe the effects of TMCC against cesium chloride-induced arrhythmia in the rabbit heart and find whether the antiarrhythmic activity is related to inhibition of sodium current. Early afterdepolarization was induced by 1.5 mM cesium chloride (1 ml kg(-1)) through intravenous injection. The monophasic action potentials (MAP) and electrocardiograms were simultaneously recorded. The effect of TMCC on functional refractory periods (FRPs) in the left atrium was also observed in vitro. Arrhythmias onset was significantly retarded by TMCC. The number of ventricular premature contractions and incidence of monophasic ventricular tachycardia and polyphasic ventricular tachycardia in 10 min were decreased by TMCC. These effects can be abolished by veratridine (10 µg kg(-1)). MAP duration at 90% repolarization was significantly prolonged by TMCC, which can be prolonged even longer by veratridine (10 µg kg(-1)). In vitro experiments showed that FRPs was prolonged by TMCC which can be cancelled by veratridine (10 µg kg(-1)). TMCC prevents cesium chloride-induced arrhythmias, and inhibition of sodium current, in part, contributes to the antiarrhythmic effect of TMCC.