Verapamil prevents isoproterenol-induced cardiac failure in the rat

7-Hydroxy Frullanolide Ameliorates Isoproterenol-Induced Myocardial Injury through Modification of iNOS and Nrf2 Genes

Myocardial infarction (MI) is the principal cause of premature death. Protecting myocardium from ischemia is the main focus of intense research. 7-hydroxy frullanolide (7-HF) is a potent anti-inflammatory agent, showing its efficacy in different acute and chronic inflammatory disorders such as atherosclerosis, suggesting it can be a potential cardioprotective agent. For the induction of MI, Sprague-Dawley rats (n = 5) were administered isoproterenol (ISO) 85 mg/kg s.c at 24 h intervals for two days. The potential cardioprotective effect of 7-HF and its mechanisms were explored by in vivo and in vitro methods. 7-HF significantly prevented the extent of myocardial injury by decreasing the infarct size, preserving the histology of myocardial tissue, and reducing the release of cardiac biomarkers. Further, 7-HF increased the mRNA expression of cardioprotective gene Nrf2 and reduced the mRNA expression of iNOS. 7-HF also improved cardiac function by decreasing the cardiac workload through its negative chronotropic and negative ionotropic effect, as well as by reducing peripheral vascular resistance due to the inhibition of voltage-dependent calcium channels and the release of calcium from intracellular calcium stores. In conclusion, 7-HF showed cardioprotective effects in the MI model, which might be due to modulating the expression of iNOS and Nrf2 genes as well as improving cardiac functions.

L-carnitine protects cardiac damage by reducing oxidative stress and inflammatory response via inhibition of tumor necrosis factor-alpha and interleukin-1beta against isoproterenol-induced myocardial infarction

BRIEF INTRODUCTION

Myocardial infarction (MI) is a common manifestation of certain cardiac diseases where oxidative stress and fibrosis aggravate the condition markedly.

MAIN OBJECTIVE OF THE STUDY

Investigation of L-carnitine's cardioprotective roles and mechanism of action in a rat model of MI.

METHODS

To develop a MI animal model, Isoproterenol (ISO) was administered in male Long Evans rats where animals were divided into five groups (six rats/group). The oxidative stress and antioxidant enzyme activities were determined by different biochemical tests. The real-time PCR was performed to determine the expression of TNF-α and Il-1β. Histopathological observations by hematoxylin-eosin and Masson trichrome were made to observe the tissue damage and fibrosis in heart and kidney.

SIGNIFICANT FINDINGS FROM THE STUDY

The ISO-treated rats showed increased levels of troponin I and lipid peroxidation and lower antioxidant enzyme activity in heart and kidney tissues. The levels of TNF-α and IL-1β were also increased in ISO-rats. Co-administration of L-carnitine with ISO reversed all these parameters. The elevated levels of uric acid and creatinine kinase and ALP, AST and ALT activities in ISO-rats were also significantly reduced by L-carnitine administration. L-carnitine markedly decreased the infiltration of inflammatory cells and improved the tissue architecture in heart and kidney. Control animals did not show any appreciable response upon L-carnitine administration.

RELEVANT CONTRIBUTION TO KNOWLEDGE

These results suggest that L-carnitine plays a defensive role against cardiac and renal damage in ISO-treated MI rat model via suppressing oxidative stress and increasing antioxidant enzyme functions through inhibition of TNF-α and IL-1β.

Protective and therapeutic effects of dexpanthenol on isoproterenol-induced cardiac damage in rats

The purpose of the study was to explore the protective and therapeutic effects of dexpanthenol (DEX) on isoproterenol (ISO)-induced cardiac damage. Forty rats were distributed into four groups: group I (Control); group II (ISO); ISO (150 mg/kg/day) was given to rats once a day for 2 consecutive days with an interval of 24 h; group III (DEX+ISO): DEX (250 mg/kg) was applied 30 min before the first ISO administration and continued in the next two days after second ISO administration; group IV (ISO+DEX): After the ISO treatment at 1st and 2nd days, DEX was given at 3rd and 4th days. Rats were monitored for mean arterial blood pressure (BP), heart rate, oxygen saturation (%SO₂ ), and electrocardiography (ECG). Heart tissue levels of malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), reduced glutathione (GSH), total oxidant status (TOS); total antioxidant capacity (TAC), oxidative stress index (OSI), and caspase-3 were determined. BP and SO₂ values indicated a significant decrease in the ISO group. Also, T wave negativity was observed in 6 of 10 rats, SOD, CAT, and GPX levels were significantly lower in ISO group than control group. ISO administration increased TOS and OSI levels, whereas DEX treatment significantly reduced these parameters. Also, ISO-induced morphological alterations such as disorganization of cardiomyocytes, loss of myofibrils and cytoplasmic vacuolization whereas these histological damages were significantly decreased in ISO+DEX and DEX+ISO groups when compared to the ISO group. This study implies the cardioprotective effects of DEX on ISO-induced cardiotoxicity.

Inhibition of NADPH oxidase by apocynin promotes myocardial antioxidant response and prevents isoproterenol-induced myocardial oxidative stress in rats

Preventive and/or therapeutic interventions for ischemic heart disease have gained considerable attention worldwide. We investigated the mechanism(s) underlying cardioprotection of apocynin (APO) and whether it attenuates isoproterenol (ISO)-induced myocardial damage in vivo. Thirty-two male Wistar Albino rats were randomised into four groups (n = 8 for each group): Group I (Control); Group II (ISO), ISO was given intraperitoneally (ip) (150 mg/kg/d) daily for 2 consecutive days; Group III (APO + ISO), APO was applied ip 20 mg/kg 30 min before the first ISO administration and continued for the next 2 d after the second ISO administration; Group IV (ISO + APO), after the ISO treatment on days 1 and 2, 20 mg/kg APO was given ip on days 3 and 4. Cardioprotective effects of APO were evaluated by biochemical values, histopathological observations and the antiapoptotic relative proteins. Mean blood pressure, heart rate, and electrocardiography (ECG) were also monitored. Malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH), total oxidant status (TOS), total antioxidant capacity (TAC), oxidative stress index (OSI), caspase-3 and connexin 43 levels were determined. Major ECG changes were observed in the ISO-treated rats. MDA, TOS, OSI and creatine kinase levels decreased and SOD, CAT, GSH and TAC levels increased, indicating that APO reduced cardiac injury and oxidative stress compared with controls. APO also decreased the number of cardiomyocytes with pyknotic nuclei, inflammatory cell infiltration, intracytoplasmic vacuolisation and myofibrils. APO provides preventive and therapeutic effects on ISO-induced myocardial injury in rats by inhibiting reactive oxygen species production, blocking inflammation and enhancing antioxidant status.

Anthocyanin rich extract of Brassica oleracea L. alleviates experimentally induced myocardial infarction

Cardioprotective potential of anthocyanin rich red cabbage extract (ARCE) was assessed in H₂O₂ treated rat neonatal cardiomyoblasts (H9c2 cells) and isoproterenol (ISO) induced rodent model of myocardial infarction. H₂O₂ treated H9c2 cells recorded cytotoxicity (48–50%) and apoptosis (57.3%), the same were reduced in presence of ARCE (7–10% & 12.3% respectively). Rats pretreated with ARCE for 30 days followed by ISO treatment recorded favourable heart: body weight ratio as compared to ISO treated group. Also, the mRNA levels of enzymatic antioxidants (sod and catalase) and apoptotic genes (bax and bcl-2) in ARCE+ISO treated group were similar to the control group suggesting that ARCE pretreatment prevents ISO induced depletion of enzymatic antioxidants and apoptosis. Histoarchitecture of ventricular tissue of ISO treated group was marked by infracted areas (10%) and derangement of myocardium whereas, ARCE+ISO treated group (4.5%) recorded results comparable to control (0%). ARCE+ISO treated group accounted for upregulation of caveolin-3 and SERCA2a expression as compared to the ISO treated group implying towards ARCE mediated reduction in membrane damage and calcium imbalance. Molecular docking scores and LigPlot analysis of cyanidin-3-glucoside (-8.7 Kcal/mol) and delphinidin-3-glucoside (-8.5 Kcal/mol) showed stable hydrophobic and electrostatic interactions with β₁ adrenergic receptor. Overall this study elucidates the mechanism of ARCE mediated prevention of experimentally induced myocardial damage.

Citrus medica "Otroj": attenuates oxidative stress and cardiac dysrhythmia in isoproterenol-induced cardiomyopathy in rats

Citrus medica L. commonly known as Otroj, is an important medicinal plant reputed for its nutritious and therapeutic uses. The present work was undertaken to investigate the protective effect of the ethanolic extract of otroj (EEOT) against isoproterenol (ISO)-induced cardiotoxicity in rats. In addition, the antioxidant activity and the phenolic and flavonoidal contents were determined. Rats were administered EETO (250 and 500 mg/kg) or vehicle orally for 15 days along with ISO (85 mg/kg, s.c.) on the 14th and 15th day. ISO induced cardiac dysfunction, increased lipid peroxidation and alteration of myocyte-injury specific marker enzymes. ISO also showed an increase in levels of plasma cholesterol, triglycerides (TG), LDL-C, and VLDL-C. Moreover, the histological investigations showed myocardial necrosis and inflammation. EETO treatment brought the above parameters towards normal level. Moreover, in vitro DPPH radical scavenging and β-carotene-linoleic acid tests of the EEOT exhibited a notable antioxidant activity in both assays used. In addition, histopathological examination reconfirmed the protective effects of EEOT. Thus, the present study reveals that C. medica alleviates myocardial damage in ISO-induced cardiac injury and demonstrates cardioprotective potential which could be attributed to its potent antioxidant and free radical scavenging activity.

Regulation of antioxidant system, lipids and fatty acid β-oxidation contributes to the cardioprotective effect of sodium tanshinone IIA sulphonate in isoproterenol-induced myocardial infarction in rats

OBJECTIVE

Myocardial infarction (MI) is a cause of high morbidity and mortality in the world. Sodium tanshinone IIA sulphonate (STS) has been well used in Oriental medicine for treating cardiovascular diseases, however, the underlying mechanisms remain unclear. Alterations of circulating lipid profiles, increased fatty acid β-oxidation and oxidative stress play most important roles in the pathogenesis of MI. The present study aims to elucidate whether STS possesses cardioprotective effect against MI driven by isoproterenol (ISO), and to investigate its potential mechanisms of action.

METHODS

MI was induced by subcutaneous injection of ISO (85 mg/kg at interval of 24 h for 2 consecutive days) to rats. The rats were randomly divided into 6 groups: (1) control; (2) ISO; (3) STS (16 mg/kg) +control; (4-6) STS (16, 8, 4 mg/kg) +ISO.

RESULTS

Our study showed that STS could ameliorate cardiac dysfunction and variation of myocardial zymogram, up-regulate antioxidant systems, and maintain the levels of circulating lipids driven by supramaximal doses ISO as well. Moreover, modulation of redox-sensitive extracellular signal-regulated kinase1/2 (ERK1/2)/Nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) and AMP-activated protein kinase (AMPK)/acetyl CoA carboxylase (ACC)/carnitine palmitoyltransferase (CPT) 1 pathways were involved in STS induced cardioprotection.

CONCLUSIONS

STS exerts strong favorable cardioprotective action. Additionally, the properties of STS, such as anti-dyslipidemia, anti-oxidant and inhibition of fatty acid β-oxidation, may be the mechanisms underlying the observed results.

Ganoderma lucidum ameliorate mitochondrial damage in isoproterenol-induced myocardial infarction in rats by enhancing the activities of TCA cycle enzymes and respiratory chain complexes

BACKGROUND

Decreased mitochondrial function has been suggested to be one of the important pathological events in isoproterenol (ISO)-induced cardiotoxicity. In this communication, we have evaluated the protective effect of Ganoderma lucidum against ISO induced cardiac toxicity and mitochondrial dysfunction.

METHODS

Cardiac toxicity was assessed by determining the activities of creatine kinase (CK) and lactate dehydrogenases (LDH) after subcutaneous injection of ISO (85 mg/kg) at an interval of 24h for 2 days. The animals were sacrificed 24h after last ISO administration. G. lucidum (100 and 250 mg/kg, p.o.) was given to the rats once daily for 15 days prior to the ISO challenge. Similarly, α-Tocopherol (100mg/kg, p.o) was kept as the standard. To assess the extent of cardiac mitochondrial damage, the activities of Krebs cycle dehydrogenases and mitochondrial complexes I, II, III, and IV as well as the level of ROS and mitochondrial membrane potential (ΔΨmt) were evaluated.

RESULTS

Administration of G. lucidum and α-tocopherol significantly protected the elevated activities of CK and LDH. Further, the activities of mitochondrial enzymes and the level of ΔΨmt were significantly enhanced and the level of ROS was significantly declined in the G. lucidum and α-tocopherol treatments.

CONCLUSION

The present study concluded that the cardiac mitochondrial enzymes are markedly declined by the ISO challenge and the administration G. lucidum and α-Tocopherol significantly protected mitochondria by preventing the decline of antioxidant status and ΔΨmt or by directly scavenging the free radicals.

Cardioprotective effect of 'Khamira Abresham Hakim Arshad Wala' a unani formulation in isoproterenol-induced myocardial necrosis in rats

The present study was designed to investigate whether Khamira Abresham Hakim Arshad Wala (KAHAW), a preparation of Unani System of Medicine, is able to attenuate the isoproterenol (ISO)-induced myocardial necrosis on the basis of its effects on hemodynamic, antioxidant, histopathological and ultrastructural parameters. Male Wistar albino rats were administered KAHAW (200, 400 and 800mg/kg/day, orally) or vehicle for 14 days with concurrent ISO administration (85mg/kg, subcutaneously, 2 doses at 24h interval) on 13th and 14th day. On the 15th day, vehicle+ISO-treated rats exhibit cardiac dysfunctions as indicated by decrease in systolic, diastolic, and mean arterial pressures, reduction in both maximum positive and maximum negative rates of developed left ventricular pressure (+/-LVdp/dt) and an increase in left ventricular end-diastolic pressure (LVEDP). Biochemical analysis of their heart homogenate presented reduced levels of enzymes viz., superoxide dismutase (SOD), catalase (CAT), lactate dehydrogenase (LDH), creatine kinase-MB (CK-MB) isoenzyme. A marked reduction in reduced glutathione (GSH) levels along with increase in levels of thiobarbituric acid reactive substances (TBARS) was also observed in rat myocardium. Myocardial necrosis, edema and inflammation were evident from the light microscopic and ultrastructural changes. KAHAW at dose of 800mg/kg/day significantly reversed majority of hemodynamic and antioxidant derangements. The protective role of KAHAW on ISO-induced myocardial necrosis was further confirmed by histopathological and ultrastructural examination. There was no significant change in heart rate in all experimental groups. KAHAW per se groups showed no significant change when compared with vehicle control group. The study results thus demonstrated the cardioprotective potential of KAHAW against ISO-induced myocardial necrosis and associated oxidative stress.

Effects of Thalidomide on Isoprenaline-Induced Acute Myocardial Injury: A Haemodynamic, Histopathological and Ultrastructural Study

In the present study, we investigated the cardioprotective effects of thalidomide in a rat model of acute myocardial injury, induced by subcutaneous injection of isoprenaline hemisulphate (85 mg/kg per day for 2 days). Thalidomide (75/150/300 mg/kg) or vehicle (dimethylsulphoxide) or saline (0.9% NaCl) was administered orally for 14 days and isoprenaline injection on the 12th and 13th days. Cardiovascular responses (arterial and left ventricular haemodynamic parameters and heart rate) were obtained in anaesthetized rats on the 14th day. Histopathological and electronmicroscopical analysis of myocardial injury was done. The results showed that thalidomide 300 mg/kg per day orally caused significant improvement in isoprenaline-induced reduction of cardiac function with increases in maximum rate of pressure development (+LVdP/dt, P < 0.001) and maximum rate of pressure decline (-LVdP/dt, P < 0.001) and decreases in left ventricular end-diastolic pressure (P < 0.01), systolic arterial pressure (P < 0.001), diastolic arterial pressure (P < 0.001), mean arterial pressure (P < 0.001) and heart rate (P < 0.001). The myocardial injury caused by isoprenaline was significantly reduced by thalidomide treatment as judged by the reduction of myocardial necrosis, ultrastructural changes such as mitochondria and myofibril damage, 300 mg/kg being the most effective dose. In conclusion, oral administration of thalidomide is able to ameliorate isoprenaline-induced myocardial injury and impaired myocardial function in spite of decreases in systolic arterial pressure, diastolic arterial pressure and mean arterial pressure, which may be due to its depressant effect on the sino-atrial node and sedative action.

p38α Mitogen-Activated Protein Kinase Inhibition Improves Cardiac Function and Reduces Myocardial Damage in Isoproterenol-Induced Acute Myocardial Injury in Rats

p38 mitogen-activated protein (MAP) kinase is activated during ischemic/hypoxic myocardial injury. However, the role of activated p38 MAP kinase on cardiac function after myocardial injury is not well understood. In the present study, we investigated the cardioprotective effects of p38 MAP kinase inhibition in a rat model of acute myocardial injury, induced by subcutaneous injection of isoproterenol (ISO, 20 mg/kg/d for 3 days). A synthetic p38 alpha MAP kinase inhibitor, SD-282 (40 mg/kg) or vehicle (0.25% Tween 80 in saline) was given intraperitoneally twice a day for 3 days, concomitant with ISO treatment. Cardiac function, systolic blood pressure, gene expression including collagen I and III, fibronectin and COX-2, and the myocardial injury were analyzed. Results showed that administration of SD-282 remarkably improved ISO-induced reduction of cardiac function with increases in ejection fraction (P < 0.001), cardiac output (P < 0.05), stroke volume (P < 0.001), and cardiac index (P < 0.01). SD-282 abolished ISO-induced reduction of systolic blood pressure (106.7 +/- 2.2 versus 123.1 +/- 5.3 mm Hg, P < 0.05). The ISO-induced expression of COX-2, collagen I and III, and fibronectin genes was reduced significantly (P < 0.05 in all cases) by administration of SD-282. The myocardial injury induced by ISO was significantly reduced by the treatment of SD-282 as judged by the reduction of myocardial necrosis. Data suggest that p38 alpha MAP kinase may be involved in the pathogenesis of cardiac dysfunction in ischemic myocardial injury. Inhibition of this enzyme may improve cardiac function and protect myocardium from ischemic/hypoxic injury that occurs during ischemic heart disease.

Effects of beta-receptor blockade and angiotensin II type I receptor antagonism in isoproterenol-induced heart failure in the rat

The aim of this study was to examine the effects of both angiotensin II type I receptor antagonism using losartan (LOS) and beta-receptor blockade by metoprolol (MP) in isoproterenol-induced cardiac injury in the rat. Two weeks after isoproterenol (ISO) application, 90 ISO and 30 control (CTRL) rats were examined. ISO rats were treated for two weeks with either LOS, MP, or vehicle (n = 30 each group). Compared to CTRL, ISO induced left ventricular hypertrophy (LVH), fibrosis, and overexpression of extracellular matrix proteins. LOS significantly attenuated these changes. MP only reduced LVH, but exerted no effect on structural alterations. LV end-diastolic and mean right atrial pressures were significantly increased in the ISO group and normalized in the LOS and MP group. Mean aortic blood flow velocity was significantly decreased in the ISO group and unaltered in the LOS and MP group versus CTRL. Blood pressure was decreased in ISO and LOS rats. MP treatment had no effect on blood pressure, but significantly lowered heart rate. Isoproterenol induced mild heart failure. Losartan and metoprolol applications in ISO-treated rats were highly effective in attenuating hemodynamic alterations and LVH. Early application of losartan 24 hours after isoproterenol-induced cardiac injury revealed significant beneficial effects on myocardial structure.

Calcium antagonists and heart failure

The systemic vasodilatory actions of the calcium antagonists make them potentially attractive for use as afterload reducing agents in patients with left ventricular failure. However, unlike other vasodilator drugs, these drugs also exert a direct negative inotropic effect on the myocardium. Clinical data suggest a limited role for the calcium antagonists as vasodilator therapy in patients with heart failure.

Effects of phospholipase inhibitors and calcium antagonists on the changes in myocardial phospholipids induced by isoproterenol

To investigate the change in myocardial phospholipids after the administration of isoproterenol and its prevention by pretreatment with phospholipase inhibitors and calcium antagonists, we determined the phospholipid species in the heart of female Wistar rats. Isoproterenol (40 mg/kg) was administered 24 h before excising the heart, and chlorpromazine, mepacrine (phospholipase inhibitors), nifedipine, verapamil (calcium antagonists) and propranolol (beta-adrenoceptor blocker) were injected intraperitoneally 30 min prior to isoproterenol administration. The phospholipid species were quantified using silica gel precoated thin-layer rods and the hydrogen flame ionization method. Isoproterenol induced significant increases in heart/body weight ratio, myocardial protein/heart weight ratio and lysophosphatidylcholine (LPC), and significant decreases in myocardial total phosphorus, creatine kinase (CK) activity, phosphatidylethanolamine and phosphatidylcholine (PC). The significant decrease in PC and increase in LPC indicated the degradation of myocardial phospholipids. Pretreatment with nifedipine (30 mg/kg), verapamil (50 mg/kg) or propranolol (20 mg/kg) completely prevented the occurrence of myocardial injury through the preservation of myocardial phospholipid composition, total phosphorus, CK activity and heart/body and protein/heart weight ratios. On the other hand, chlorpromazine (30 mg/kg) and mepacrine (50 mg/kg) partially prevented myocardial damage through the preservation of myocardial phospholipid composition, total phosphorus and CK activity. Results suggest that not only calcium influx but also phospholipase activation plays an important role in the development of myocardial injury induced by isoproterenol.

Usefulness of calcium antagonists for congestive heart failure

In patients with congestive heart failure (CHF) due to dilated cardiomyopathy, nifedipine, diltiazem and several of the newer calcium antagonists including nicardipine, nitrendipine, felodipine and PN 200-110 (isradipine) improve left ventricular function. Because of its relatively more pronounced negative inotropic and chronotropic actions, verapamil is generally not tolerated by patients with left ventricular failure. In addition, even relatively vascular-selective agents such as nifedipine can occasionally cause significant left ventricular depression, particularly if combined with beta-adrenergic blocking agents. Comparative studies using nitroprusside to cause an equivalent decrease in arterial pressure indicate that nifedipine acts predominantly on the arterial vasculature, and that a small but significant decrease in contractility occurs, apparently due to a direct myocardial action. Although diltiazem causes a depression in myocardial contractility in dogs with volume overload heart failure, limited data show no significant negative inotropic action in patients with heart failure. The negative inotropic effects, if any, of newer and possibly more vascular-selective agents are not yet known. Calcium antagonists appear to act predominantly on the limb and coronary vasculature, with relatively less effect on renal and hepatic vessels. In patients with CHF, nifedipine causes an increase in coronary blood flow and a decrease in the aorto-coronary sinus oxygen difference indicating an improvement in myocardial energetics. Although nifedipine causes an increase in cardiac index and decreases in systemic vascular resistance and pulmonary capillary wedge pressure during exercise, the limited data available fail to show a short- or long-term increase in exercise capacity. Nifedipine causes an increase in plasma renin activity, possibly due to a direct action on the kidney.(ABSTRACT TRUNCATED AT 250 WORDS)

Protective effect of taurine against isoprenaline-induced myocardial damage

The effect of the sulfur amino acid, taurine, was examined on histological and biochemical changes induced by a toxic dose of isoprenaline in chick hearts. Isoprenaline treatment (80 or 240 mg/kg id twice daily for 4 days) caused a dose-dependent increase in heart weight and decrease in myocardial ATP. Isoprenaline administration (240 mg/kg id twice daily) produced necrotic changes in hearts, such as eosinophilic degeneration, myolysis, interstitial oedema, fibrosis, and inflammatory cell infiltration. Substantial accumulation of calcium was also observed. Taurine content of the heart was not significantly decreased. Parenteral administration of taurine (200 mg/day for 7 days) partially protected against these necrotic changes induced by isoprenaline. It is suggested that the protective effect of taurine against isoprenaline-induced myocardial injury might be due in part to the prevention of the massive overloading with calcium which is thought to cause myocardial cell necrosis.