Endogenous antioxidant changes in the myocardium in response to acute and chronic stress conditions

Cardioprotective role of methanolic extract of bark of Terminalia arjuna against in-vitro model of myocardial ischemic-reperfusion injury

BACKGROUND

The present study was designed to investigate the cardio protective role of chronic oral administration of methanolic extract of Terminalia arjuna bark in in-vitro myocardial ischemic reperfusion injury and the induction of HSP72.

MATERIALS AND METHODS

Rats, divided into three groups, and were administered with the methanolic extract of the bark powder of Terminalia arjuna (TAME) by oral gavage (6.75 and 9.75 mg/kg: 6 days/week for 12 weeks). Control and TAME extract treated rat hearts were subjected to in-vitro global ischemic reperfusion injury (5 min perfusion, 9 min noflow and 12 min reperfusion).

RESULTS

Oxidative stress in MIRI was evidenced by, raised levels of myocardial TBARS and depletion of endogenous myocardial antioxidants GSH, SOD and catalase. Western blot analysis showed a single band corresponding to 72 kDa in homogenates of hearts from rat treated with both the doses. In the methanolic extract of the bark powder of Terminalia arjuna treatment groups, both the doses had better recovery of myocardial function, with significant reduction in TBARS, and rise in SOD, GSH, catalase were observed.

CONCLUSION

The results of the present study suggest that the methanolic extract of the bark powder of Terminalia arjuna in rat induces myocardial HSP72 and augments myocardial endogenous antioxidants, without causing any cellular injury and offers better cardioprotection against oxidative stress associated with myocardial IR injury.

Cardioprotective effects of an aminothiazole compound on isoproterenol-induced myocardial injury in mice

Dendrodoine analogue (DA), an aminothiazole compound derived from dendrodoine, present in a marine tunicate, has been shown to possess many beneficial properties. This study was aimed to evaluate its cardioprotective effect against isoproterenol (ISO)-induced myocardial damage in mice. Swiss mice were pretreated with DA for 7 days and then treated with ISO (5 mg/kg BW, for 2 consecutive days). Biochemical assessment of myocardial injury was carried out by measuring marker enzymes, antioxidant enzymes and levels of lipid peroxidation. Histological studies of hearts were also carried out. ISO administration increased the activities of creatine kinase-MB, lactate dehydrogenase and aspartate aminotranferase (AST) in serum. Prior administration of DA restored the levels of these enzymes and the heart coefficient close to normal levels. DA at a concentration of 5 mg/kg BW was most effective in reducing AST, and this concentration was used for further studies. DA also gave significant protection against lipid peroxidation in the heart besides restoring histopathological alterations. DA showed significant reactivity towards superoxide radicals. In conclusion our study indicates that DA can protect mouse myocardium against damage and one of the possible reasons behind this protective effect can be attributed to its antioxidant property.

Mechanisms of cardioprotection resulting from Brown Norway chromosome 16 substitution in the salt-sensitive Dahl rat

The SS-16(BN)/Mcwi consomic rat was produced by the introgression of chromosome 16 from the Brown Norway (BN/NHsdMcwi) rat onto the genetic background of the Dahl salt-sensitive (SS/Mcwi) rat by marker-assisted breeding. We have previously shown that the normotensive SS-16(BN)/Mcwi consomic strain is better protected from developing left ventricular dysfunction and fibrosis with aging than the hypertensive SS/Mcwi parental strain; however, the mechanism of this protection was not clear since the SS-16(BN)/Mcwi had both lowered blood pressure and an altered genetic background compared with SS/Mcwi. Microarray analysis of SS-16(BN)/Mcwi and SS/Mcwi left ventricle tissue and subsequent protein pathway analysis were used to identify alterations in gene expression in signaling pathways involved with the observed cardioprotection on the SS background. The SS-16(BN)/Mcwi rats exhibited much higher mRNA levels of expression of transcription factor JunD, a gene found on chromosome 16. Additionally, high levels of differential gene expression were found in pathways involved with angiogenesis, oxidative stress, and growth factor signaling. We tested the physiological relevance of these pathways by experimentally determining the responsiveness of neonatal cardiomyocytes to factors from identified pathways and found that cells isolated from SS-16(BN)/Mcwi rats had a greater growth response to epidermal growth factor and endothelin-1 than those from parental SS/Mcwi. We also demonstrate that the SS-16(BN)/Mcwi is better protected from developing fibrosis with surgically elevated afterload than other normotensive strains, indicating that gene-gene interactions resulting from BN chromosomal substitution confer specific cardioprotection. When combined with our previous findings, these data suggest that that SS-16(BN)/Mcwi may have an increased angiogenic potential and better protection from oxidative stress than the parental SS/Mcwi strain. Additionally, the early transient idiopathic left ventricular hypertrophy in the SS-16(BN)/Mcwi may be related to altered myocyte sensitivity to growth factors.

Evaluation of antioxidant and immunity function of tetramethylpyrazine phosphate tablets in vivo

The aim of the study was to determine the effect of tetramethylpyrazine phosphate tablets (TPT), a Chinese medicine used for cardiovascular disease, on immunity activity and oxidative injury in rats. Heart failure (HF) was induced by isoproterenol (ISO). After the animal model was established, the rats were administered the TPT by gavage (once a day). The results indicated that TPT improved left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP), ±dP/dt, heart weight/body weight. TPT could decrease the levels of tumor necrosis factor-α (TNF-α) and interleukin 6 (IL-6). Furthermore, it also could raise the activities of catalase, superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), but reduce malonyldialdehyde (MDA) level. The results indicated that TPT improved cardiac function and myocardial fibrosis from myocardial injury, and this cardioprotection might be attributed to a reduction of oxidative stress and regulation of inflammation mediators.

Evaluating the toxic and beneficial effects of jering beans (Archidendron jiringa) in normal and diabetic rats

BACKGROUND

Jering (Archidendron jiringa) is eaten in the tropics and traditionally extolled for treating diabetes, high blood pressure and eliminating bladder stones. Jering contains an unusual amino acid-djenkolic acid (S,S'-methylenebiscysteine)-which may form sharp crystals in the urinary tract, causing pain and haematuria. This study evaluates the beneficial and toxic effects of dietary jering on tissues and organs in normal and diabetic rats.

RESULTS

Dietary jering administered orally to diabetic rats significantly reduced the blood glucose in the streptozotocin-induced diabetic rats to normal levels after about 12 weeks. Jering improved the rats' appetite, body weight, organ oxidative status and number of active islets of Langerhans in both diabetic and normal rats, after 15 weeks of treatment. Although dietary jering showed beneficial effects to diabetic eye lens, lung and pancreas, it caused hypertrophy and lesions to the heart, kidney, liver, lung and pancreas of normal rats.

CONCLUSION

Chronic jering consumption showed toxic effects to the heart, kidney, liver and pancreas of normal rats but produced some beneficial effects to diabetic rats.

Bacopa monniera protects rat heart against ischaemia–reperfusion injury: role of key apoptotic regulatory proteins and enzymes

Objectives

Rat isolated hearts were perfused in a Langendorff model to study the cardioprotective effects of Bacopa monniera, a medicinal herb used in the Indian system of medicine, on cardiomyocyte apoptosis and antioxidant status following ischaemia–reperfusion (I-R) injury.

Methods

Forty-eight rats were randomly divided into four groups (12 in each group): sham group (no ischaemia–reperfusion injury), B. monniera control group (orally fed B. monniera at a dose of 75 mg/kg, for three weeks); ischaemia–reperfusion control group(subjected to ischaemia–reperfusion-induced myocardial injury) and B. monniera-treated group (same protocol as ischaemia–reperfusion control group except that rats also fed B. monniera).

Key findings

Post-ischaemic reperfusion injury resulted in significant cardiac necrosis, apoptosis, depression of heart rate, decline in antioxidant status and elevation in lipid peroxidation. Oral administration of B. monniera per se for three weeks to healthy rats caused augmentation of myocardial antioxidants, superoxide dismutase, catalase and glutathione, along with induction of heat shock protein 72 (HSP72). Ischaemia–reperfusion-induced biochemical and histopathological perturbations were significantly prevented by B. monniera (75 mg/kg) pre-treatment. Interestingly, B. monniera also restored the antioxidant network of the myocardium and reduced myocardial apoptosis, caspase 3 and Bax protein expression.

Conclusions

Histopathological studies and myocardial creatine phosphokinase content further confirmed the cardioprotective effects of B. monniera (75 mg/kg) in the experimental model of ischaemia–reperfusion injury. The study provides scientific basis for the putative therapeutic effect of B. monniera in ischaemic heart disease.

Peripheral benzodiazepine receptor ligand Ro5-4864 inhibits isoprenaline-induced cardiac hypertrophy in rats

Oxidative stress plays a significant role in the pathogenesis of cardiac hypertrophy. Peripheral benzodiazepine receptors are ubiquitously expressed in various tissues, including the heart. Peripheral benzodiazepine receptors have been reported to be involved in the protection of cells against oxygen radical damage. The present study was designed to determine whether Ro5-4864 (a peripheral benzodiazepine receptor ligand) can inhibit isoprenaline-induced cardiac hypertrophy. Male Wistar rats (body weight 150-200g) were administered, isoprenaline (5mg/kg, body weight, subcutaneously) alone or along with Ro5-4864 (0.1 and 0.5mg/kg, body weight, intraperitoneally) once daily for 14days. Control rats received normal saline subcutaneously (1.0ml/kg). Isoprenaline-induced changes in heart weight to body weight ratio, left ventricular wall thickness (M-mode echocardiography and gross morphometry) and myocyte size were significantly prevented by both the doses of Ro5-4864. Ro5-4864 also attenuated isoprenaline-induced increase in interstitial fibrosis, lipid peroxidation and changes in endogenous antioxidants (glutathione, superoxide dismutase and catalase). Isoprenaline-induced cardiac hypertrophy was associated with increased expression of beta myosin heavy chain, which was also prevented by Ro5-4864. This is the first study to demonstrate a salutary effect of Ro5-4864 in experimental cardiac hypertrophy.

Protective effect of propyl gallate against myocardial oxidative stress-induced injury in rat

This study was designed to investigate the effect of chronic administration of propyl gallate on myocardial oxidative stress-induced injury. Propyl gallate was administered orally to Wistar albino rats (150–200 g) in three different doses, by gastric gavage (250 mg kg−1 (P1), 500 mg kg−1 (P2) and 750 mg kg−1 (P3)), 6 days a week for 5 weeks. At the end of this period, all the rats, except the normal untreated rats that served as the control group, were administered isoproterenol (ISO), 85 mg kg−1 subcutaneously, for 2 consecutive days to induce myocardial injury. After 48 h, rats (n = 6 per group) were anaesthetized with anaesthetic ether, sacrificed and the hearts were harvested for the estimation of thiobarbituric acid reactive substances (TBARS), endogenous antioxidants (reduced glutathione (GSH), superoxide dismutase (SOD) and catalase) and for the assessment of histological changes. In the P2 BL group (BL = baseline), there was a significant (P < 0.001) rise in baseline TBARS and SOD when compared with the saline-treated group, while no such changes were observed in the other baseline-treated groups. However, there was a significant (P < 0.001) increase in TBARS and endogenous anti-oxidants (GSH, SOD and catalase) in the P2 ISO and P3 ISO groups, when the hearts were subjected to in-vivo myocardial oxidative stress-induced injury. We observed no such changes in the P1 ISO group. This study showed that propyl gallate modulates the levels of endogenous antioxidants present at the myocardial site. Whether these modifications are a result of direct interference at this site or a remote effect is not immediately clear. In conclusion, from the results it could be stated that chronic administration of 500 mg kg−1 of propyl gallate offers significant protection against myocardial oxidative stress-induced injury.

Cardioprotective effect of SMND-309, a novel derivate of salvianolic acid B on acute myocardial infarction in rats

(2E)-2-{6-[(E)-2-carboxyvinyl]-2,3-dihydroxyphenyl}-3-(3,4-dihydroxyphenyl) propenoic acid, a novel compound designated SMND-309, is a new derivate of salvianolic acid B. The present study was designed to investigate the cardioprotective potential of SMND-309 and to elucidate the possible mechanisms on the basis of biochemical, histopathological and immunohistochemical studies in a rat model of acute myocardial infarction induced by permanent ligation of the left coronary artery. The results showed that treatment with SMND-309 via tail vein at doses of 10 and 20 mg/kg significantly prevented the elevation in ST segment level and the increase in serum creatine kinase-MB, lactate dehydrogenase, alanine aminotransferase and cardiac troponin T content. Meanwhile, SMND-309 significantly increased the activities of superoxide dismutase, catalase and glutathione peroxidase, decreased the content of malondialdehyde in myocardium, and reduced the myocardium necrosis scores and the number of apoptosis cardiocytes in accordance with the up-regulated expression of anti-apoptotic protein, Bcl-2 and the down-regulated expression of proapoptotic protein, Bax. Moreover, SMND-309 exhibits significantly higher potency compared to salvianolic acid B at the same mg/kg but not the same mol/kg. These findings indicate that SMND-309 has a protective potential against myocardial infarction injury and the protective effects may be due to its scavenging lipid peroxidation products, increasing endogenous antioxidant defence enzymes and attenuating cardiocyte apoptosis.

Regulation of central angiotensin type 1 receptors and sympathetic outflow in heart failure

Angiotensin type 1 receptors (AT(1)Rs) play a critical role in a variety of physiological functions and pathophysiological states. They have been strongly implicated in the modulation of sympathetic outflow in the brain. An understanding of the mechanisms by which AT(1)Rs are regulated in a variety of disease states that are characterized by sympathoexcitation is pivotal in development of new strategies for the treatment of these disorders. This review concentrates on several aspects of AT(1)R regulation in the setting of chronic heart failure (CHF). There is now good evidence that AT(1)R expression in neurons is mediated by activation of the transcription factor activator protein 1 (AP-1). This transcription factor and its component proteins are upregulated in the rostral ventrolateral medulla of animals with CHF. Because the increase in AT(1)R expression and transcription factor activation can be blocked by the AT(1)R antagonist losartan, a positive feedback mechanism of AT(1)R expression in CHF is suggested. Oxidative stress has also been implicated in the regulation of receptor expression. Recent data suggest that the newly discovered catabolic enzyme angiotensin-converting enzyme 2 (ACE2) may play a role in the modulation of AT(1)R expression by altering the balance between the octapeptide ANG II and ANG- (1-7). Finally, exercise training reduces both central oxidative stress and AT(1)R expression in animals with CHF. These data strongly suggest that multiple central and peripheral influences dynamically alter AT(1)R expression in CHF.

Pharmacological activation of soluble guanylate cyclase protects the heart against ischemic injury

BACKGROUND

The role of the nitric oxide/cGMP/cGMP-dependent protein kinase G pathway in myocardial protection and preconditioning has been the object of intensive investigations. The novel soluble guanylate cyclase activator cinaciguat has been reported to elevate intracellular [cGMP] and activate the nitric oxide/cGMP/cGMP-dependent protein kinase G pathway in vivo. We investigated the effects of cinaciguat on myocardial infarction induced by isoproterenol in rats.

METHODS AND RESULTS

Rats were treated orally twice a day for 4 days with vehicle or cinaciguat (10 mg/kg). Isoproterenol (85 mg/kg) was injected subcutaneously 2 days after the first treatment at an interval of 24 hours for 2 days to produce myocardial infarction. After 17 hours, histopathological observations and left ventricular pressure-volume analysis to assess cardiac function with a Millar microtip pressure-volume conductance catheter were performed, and levels of biochemicals of the heart tissues were measured. Gene expression analysis was performed by quantitative real-time polymerase chain reaction. Isolated canine coronary arterial rings exposed to peroxynitrite were investigated for vasomotor function, and immunohistochemistry was performed for cGMP and nitrotyrosine. The present results show that cinaciguat treatment improves histopathological lesions, improves cardiac performance, improves impaired cardiac relaxation, reduces oxidative stress, ameliorates intracellular enzyme release, and decreases cyclooxygenase 2, transforming growth factor-beta, and beta-actin mRNA expression in experimentally induced myocardial infarction in rats. In vitro exposure of coronary arteries to peroxynitrite resulted in an impairment of endothelium-dependent vasorelaxation, increased nitro-oxidative stress, and reduced intracellular cGMP levels, which were all improved by cinaciguat. A cardioprotective effect of postischemic cinaciguat treatment was shown in a canine model of global ischemia/reperfusion.

CONCLUSIONS

Pharmacological soluble guanylate cyclase activation could be a novel approach for the prevention and treatment of ischemic heart disease.

Evaluation of Pringle Maneuver During Liver Resection in a Rat Model of Surgical Obstructive Jaundice

Temporary portal triad clamping (Pringle maneuver) during liver resection reduces intraoperative blood loss. A normal liver can safely tolerate normothermic ischemia for up to 60 min. However, its safety in patients with surgical obstructive jaundice (SOJ) is not known. Therefore, we investigated the effect of hepatic ischemia in an experimental rat model of SOJ created by ligating the bile duct. Four groups of rats were created: Group I (sham operation, 10 days later, liver resection); Group II (sham operation, 10 days later, liver resection with 5 min of hepatic ischemia); Group III (bile duct ligation, 10 days later, liver resection); and Group IV (bile duct ligation, 10 days later, liver resection with 5 min of hepatic ischemia). The ischemic injury was assessed by the survival of rats, liver tissue malondialdehyde and total glutathione (markers of free radical injury), serum alanine aminotransferase, aspartate aminotransferase, and liver histology. The results showed decreased survival (47.6% vs. 90% [p = .046]), increased liver tissue malondialdehyde (161 +/- 35 vs. 129 +/- 33 microg/gm liver tissue [p = .05]), and decreased liver tissue total glutathione (565 +/- 169 vs. 1075 +/- 276 nmol/gm liver tissue [p = .05]) in rats with SOJ subjected to hepatic ischemia when compared to nonjaundiced rats. The changes in serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase showed an increasing trend in the SOJ group but were not statistically significant. Ischemic changes in liver histology were seen more often in the SOJ group but were not statistically significant. These data suggest that temporary portal triad clamping in an experimental model of SOJ is detrimental to the outcome of liver resection.

Propofol limits rat myocardial ischemia and reperfusion injury with an associated reduction in apoptotic cell death in vivo

Propofol, a rapidly acting, short duration, intravenous hypnotic anesthetic induction agent, is often used in clinical situations where myocardial ischemia/ reperfusion (I/R) injury is a threat. The aim of the present study was to evaluate the protective effect of propofol on myocardial I/R injury in rat due to apoptosis. Myocardial I/R injury were induced by occluding the left anterior descending (LAD) coronary artery for 25 min followed by either 2 h or 6 h reperfusion. Apoptosis was evaluated by Western blot analysis (Bcl-2, Bax expression), DNA strand breaks, TUNEL analysis and measuring myocardial caspase-3 activity. Propofol significantly reduced infarct size and improved I/R-induced myocardial contractile dysfunction by improving left ventricular diastolic pressure and positive and negative maximal values of the first derivative (+dp/dt) of left ventricular pressure. Propofol increased Bcl-2/Bax expression ratio and decreased caspase-3 activity in I/R rat hearts, which resulted in reduction of myocardial apoptosis as evidenced by TUNEL analysis and DNA laddering experiments. In an in vitro study, propofol increased H9c2 cell viability against oxidative stress induced by glucose oxidase (GOX) in a dose-dependent manner. These data suggest propofol limits I/R injury with an associated reduction in apoptotic cell death in vivo.

The antioxidant tempol attenuates pressure overload-induced cardiac hypertrophy and contractile dysfunction in mice fed a high-fructose diet

We have previously shown that high-sugar diets increase mortality and left ventricular (LV) dysfunction during pressure overload. The mechanisms behind these diet-induced alterations are unclear but may involve increased oxidative stress in the myocardium. The present study examined whether high-fructose feeding increased myocardial oxidative damage and exacerbated systolic dysfunction after transverse aortic constriction (TAC) and if this effect could be attenuated by treatment with the antioxidant tempol. Immediately after surgery, TAC and sham mice were assigned to a high-starch diet (58% of total energy intake as cornstarch and 10% fat) or high-fructose diet (61% fructose and 10% fat) with or without the addition of tempol [0.1% (wt/wt) in the chow] and maintained on the treatment for 8 wk. In response to TAC, fructose-fed mice had greater cardiac hypertrophy (55.1% increase in the heart weight-to-tibia length ratio) than starch-fed mice (22.3% increase in the heart weight-to-tibia length ratio). Treatment with tempol significantly attenuated cardiac hypertrophy in fructose-fed TAC mice (18.3% increase in the heart weight-to-tibia ratio). Similarly, fructose-fed TAC mice had a decreased LV area of fractional shortening (from 38+/-2% in sham to 22+/-4% in TAC), which was prevented by tempol treatment (33+/-3%). Markers of lipid peroxidation in fructose-fed TAC hearts were also blunted by tempol. In conclusion, tempol significantly blunted markers of cardiac hypertrophy, LV remodeling, contractile dysfunction, and oxidative stress in fructose-fed TAC mice.

Withania somnifera provides cardioprotection and attenuates ischemia-reperfusion induced apoptosis

BACKGROUND & AIMS

The present study was undertaken to evaluate the cardioprotective mechanisms of Withania somnifera (Ws), in the setting of ischemia and reperfusion (IR) injury.

METHODS

Wistar rats were divided into three groups and received orally saline (sham, control IR) and Ws-50 mg/kg (Ws-IR), respectively, for 1 month. On the 31st day, in the rats of control IR and Ws-IR group, LAD coronary artery occlusion was undertaken for 45 min followed by 1 h reperfusion. Subsequently, all the animals were sacrificed for biochemical, immunohistochemical {Bax and Bcl-2 protein}, terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) positivity and histopathological studies.

RESULTS

Post-ischemic reperfusion injury resulted in significant cardiac necrosis, apoptosis, decline in antioxidant status and elevation in lipid peroxidation in the IR control group as compared to sham. Ws prior-treatment favorably restored the myocardial oxidant-antioxidant balance, exerted marked anti-apoptotic effects {upregulated Bcl-2 (p<0.001) protein, decreased Bax (p<0.01) protein, and attenuated TUNEL positivity (p<0.01)}, and reduced myocardial damage as evidenced by histopathologic evaluation.

CONCLUSIONS

The antioxidant and anti-apoptotic properties of Ws may contribute to the cardioprotective effects.

Coenzyme Q10 in cardiovascular disease

In this review we summarise the current state of knowledge of the therapeutic efficacy and mechanisms of action of CoQ(10) in cardiovascular disease. Our conclusions are: 1. There is promising evidence of a beneficial effect of CoQ(10) when given alone or in addition to standard therapies in hypertension and in heart failure, but less extensive evidence in ischemic heart disease. 2. Large scale multi-centre prospective randomised trials are indicated in all these areas but there are difficulties in funding such trials. 3. Presently, due to the notable absence of clinically significant side effects and likely therapeutic benefit, CoQ(10) can be considered a safe adjunct to standard therapies in cardiovascular disease.

Cardioprotective effect of the Hibiscus rosa sinensis flowers in an oxidative stress model of myocardial ischemic reperfusion injury in rat

BACKGROUND

The present study investigates the cardioprotective effects of Hibiscus rosa sinensis in myocardial ischemic reperfusion injury, particularly in terms of its antioxidant effects.

METHODS

The medicinal values of the flowers of Hibiscus rosa sinensis (Chinese rose) have been mentioned in ancient literature as useful in disorders of the heart. Dried pulverized flower of Hibiscus rosa sinensis was administered orally to Wistar albino rats (150-200 gms) in three different doses [125, 250 and 500 mg/kg in 2% carboxy methyl cellulose (CMC)], 6 days per week for 4 weeks. Thereafter, rats were sacrificed; either for the determination of baseline changes in cardiac endogenous antioxidants [superoxide dismutase, reduced glutathione and catalase] or the hearts were subjected to isoproterenol induced myocardial necrosis.

RESULTS

There was significant increase in the baseline contents of thiobarbituric acid reactive substances (TBARS) [a measure of lipid per oxidation] with both doses of Hibiscus Rosa sinensis. In the 250 mg/kg treated group, there was significant increase in superoxide dismutase, reduced glutathione, and catalase levels but not in the 125 and 500 mg/kg treated groups. Significant rise in myocardial thiobarbituric acid reactive substances and loss of superoxide dismutase, catalase and reduced glutathione (suggestive of increased oxidative stress) occurred in the vehicle treated hearts subjected to in vivo myocardial ischemic reperfusion injury.

CONCLUSION

It may be concluded that flower of Hibiscus rosa sinensis (250 mg/kg) augments endogenous antioxidant compounds of rat heart and also prevents the myocardium from isoproterenol induced myocardial injury.

Cardioprotective effect of grape seed proanthocyanidins on isoproterenol-induced myocardial injury in rats

PURPOSE

To investigate whether grape seed proanthocyanidins (GSP) might protect the heart against myocardial injury (MI) induced by isoproterenol (ISO), in a rat model.

METHODS

GSP was administered orally to Wistar albino rats (150-180 g) in three different doses, by gastric gavage (50, 100 and 150 mg kg(-1) GSP), 6 days a week for 5 weeks. At the end of this period, all the rats, except the normal untreated rats that served as the control group, were administered ISO, 85 mg kg(-1) subcutaneously, for 2 consecutive days to induce myocardial injury. After 48 h, rats (n=6 per group) were anaesthetized with anesthetic ether, sacrificed and the levels of biochemical and histological observations of the heart tissues were performed.

RESULT

Our results suggest that prior administration of GSP maintained the levels of the marker enzymes (AST, ALT, LDH and CK) in all the treatment groups (GSP-50-ISO, GSP-100-ISO and GSP-150-ISO) when compared to ISO-injected rats. The entire baseline groups also showed no significant alterations in serum marker enzyme levels in comparison to that of control group. Interestingly, in this study, there was no significant change in the basal levels of myocardial TBARS, GST, SOD and CAT on administration of GSP in all the three dosages (GSP-50-BL, GSP-100-BL and GSP-150-BL). However, a significant decrease occurred in the levels of GSH and GPx in group GSP-50-BL, which in the absence of any cellular injury (as evidenced by histological studies), is considered to be non-lethal. In the ISO-injected group there was a significant rise in TBARS and a significant decrease in GSH, GPx, GST, SOD and CAT when compared to group control. The administration of GSP maintained the activities of these enzymes close to normal levels when compared to group ISO, which proves the stress stabilizing action of GSP. The biochemical and histological evidence from this study shows that 100 and 150 mg kg(-1) of GSP protected against ISO-induced myocardial injury.

CONCLUSION

This study demonstrates that GSP has a significant effect in the protection of heart against MI induced by ISO. We believe that pretreatment with GSP may contribute to developing novel strategies in the prevention and treatment of cardiotoxic effects of elevated levels of catecholamine.

Effect of Curcuma longa and Ocimum sanctum on myocardial apoptosis in experimentally induced myocardial ischemic-reperfusion injury

Background

In the present investigation, the effect of Curcuma longa (Cl) and Ocimum sanctum (Os) on myocardial apoptosis and cardiac function was studied in an ischemia and reperfusion (I-R) model of myocardial injury.

Methods

Wistar albino rats were divided into four groups and orally fed saline once daily (sham, control IR) or Cl (100 mg/kg; Cl-IR) or Os (75 mg/kg; Os-IR) respectively for 1 month. On the 31^st day, in the rats of the control IR, Cl-IR and Os-IR groups LAD occlusion was undertaken for 45 min, and reperfusion was allowed for 1 h. The hemodynamic parameters{mean arterial pressure (MAP), heart rate (HR), left ventricular end-diastolic pressure (LVEDP), left ventricular peak positive (+) LVdP/dt (rate of pressure development) and negative (-) LVdP/dt (rate of pressure decline)} were monitored at pre-set points throughout the experimental duration and subsequently, the animals were sacrificed for immunohistopathological (Bax, Bcl-2 protein expression & TUNEL positivity) and histopathological studies.

Results

Chronic treatment with Cl significantly reduced TUNEL positivity (p < 0.05), Bax protein (p < 0.001) and upregulated Bcl-2 (p < 0.001) expression in comparison to control IR group. In addition, Cl demonstrated mitigating effects on several myocardial injury induced hemodynamic {(+)LVdP/dt, (-) LVdP/dt & LVEDP} and histopathological perturbations. Chronic Os treatment resulted in modest modulation of the hemodynamic alterations (MAP, LVEDP) but failed to demonstrate any significant antiapoptotic effects and prevent the histopathological alterations as compared to control IR group.

Conclusion

In the present study, significant cardioprotection and functional recovery demonstrated by Cl may be attributed to its anti-apoptotic property. In contrast to Os, Cl may attenuate cell death due to apoptosis and prevent the impairment of cardiac performance.

Influence of Dietary Curcumin, Capsaicin and Garlic on the Antioxidant Status of Red Blood Cells and the Liver in High-Fat-Fed Rats

BACKGROUND/OBJECTIVE

An animal study was carried out to examine the beneficial influence of known hypolipidemic spice principles - curcumin and capsaicin - and the spice garlic on the antioxidant status of red blood cells and liver tissue in hyperlipidemic rats.

METHODS

Rats were rendered hyperlipidemic by maintaining them on a high-fat (30%) diet for 8 weeks. Spice principles - curcumin (0.2%) or capsaicin (0.015%) - or garlic (2.0%) were included in the diets of separate animal groups. Erythrocytes isolated at the end of the study were analyzed for intracellular antioxidant molecules and antioxidant enzymes.

RESULTS

Intracellular total thiols in the erythrocytes of high-fat-fed rats were depleted significantly (16%). Similarly, the intracellular glutathione content in erythrocytes was depleted in high-fat-fed rats (28%). The concentration of lipid peroxides in the erythrocytes (intracellular as well as membrane) induced by H(2)O(2) was significantly higher in the high-fat-fed group. Curcumin (0.2%) or capsaicin (0.015%) or garlic (2.0%) in the diet which produced the hypotriglyceridemic effect were also effective in reducing oxidant stress, which was indicated by a significant countering of the depleted intracellular antioxidants - total thiols and glutathione - and elevated lipid peroxides in erythrocytes. The elevated lipid peroxide in blood plasma due to the high-fat diet was also significantly countered by the spice treatments. The severely depleted hepatic glutathione in high-fat treatment was also effectively reversed by dietary curcumin, capsaicin and garlic.

CONCLUSIONS

Thus, dietary hypolipidemic spices were effective in reducing the oxidant stress, which was indicated by countering the depleted antioxidant molecules and antioxidant enzymes in erythrocytes and liver, and decreasing the elevated lipid peroxide content.

Chronic oral administration of raw garlic protects against isoproterenol-induced myocardial necrosis in rat

Wistar albino rats (150-200 g) were fed raw garlic homogenate orally in three different doses (125, 250, 500 mg/kg/day) for 30 days. Isoproterenol (85 mg/kg, s.c. 2 doses at 24-h interval, animals sacrificed after 24 h of last injection) induced myocardial necrosis in control rats and after 30 days of garlic feeding. Myocardial oxidative stress was evident following isoproterenol administration by reduction in myocardial superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities along with a rise in plasma thiobarbituric acid reactive substances (TBARS). Myocardial necrosis was evident from the light microscopic and ultrastructural changes, along with a rise in plasma lactate dehydrogenase (LDH). Significant preservation of myocardial SOD activity was observed in all the garlic-fed rats. However, there was no significant change in myocardial reduced glutathione level and GPx activity in any of the treated groups. Significant reduction in plasma TBARS and LDH levels was observed in the 500 mg/kg garlic treated group. Isoproterenol-induced myocardial morphological changes were least in the 250 and 500 mg/kg garlic treated groups. The results suggest that chronic oral administration of raw garlic offered protection against isoproterenol-induced myocardial necrosis and associated oxidative stress.

Cardioprotective effect of the alcoholic extract of Terminalia arjuna bark in an in vivo model of myocardial ischemic reperfusion injury

The present study was designed to investigate the effects of chronic administration of the alcoholic extract of Terminalia arjuna (TAAE) bark on isoproterenol induced myocardial injury. The TAAE was administered orally to Wistar albino rats (150-200 g) in three different doses, by gastric gavage [3.4 mg/kg: (T1), 6.75 mg/kg: (T2) and 9.75 mg/kg: (T3)] 6 days/week for 4 weeks. At the end of this period, all the animals, except the normal untreated rats that served as the control group, were administered isoproterenol (ISO) 85 mg/kg, S.C., for two consecutive days to induce in vivo myocardial injury. After 48 hours rats were anaesthetized with anaesthetic ether, then sacrificed and the hearts were harvested for biochemical and histological studies. A significant rise in myocardial thiobarbituric acid reactive substances (TBARS) and loss of reduced glutathione (GSH), superoxide dismutase (SOD) and catalase (suggestive of increased oxidative stress) occurred in the hearts subjected to in vivo myocardial ischemic reperfusion injury. The 6.75 mg/kg TAAE treatment group (baseline) shows a significant increase in myocardial TBARS as well as endogenous antioxidants (GSH, SOD, and catalase), but not in the other treatment groups. In in vivo ischemic reperfusion injury of the TAAE treated rats there was a significant decrease in TBARS in all the groups. In 6.75 mg/kg treatment group, a significant rise in the levels of GSH, SOD and catalase were observed, and it shows better recovery profile than the other groups subjected to in vivo ischemic reperfusion injury. In histological studies, all the groups, except the isoproterenol treated group, showed preserved myocardium. The present study demonstrates that the 6.75 mg/kg TAAE augments endogenous antioxidant compounds of the rat heart and also prevents the myocardium from isoproterenol induced myocardial ischemic reperfusion injury.

Age-dependent increase in hydrogen peroxide production by cardiac monoamine oxidase A in rats

Oxidative stress is one of the factors involved in age-related impairment of cardiac function. In the present study, we investigated the role of the catecholamine-degrading enzyme monoamine oxidase (MAO) in H(2)O(2) production in the hearts of young, adult, and old rats. MAO-dependent H(2)O(2) production, measured by a chemiluminescence-based assay, increased with age, reaching the maximum in 24-mo-old rats (7.5-fold increase vs. 1-mo-old rats). The following observations indicate that the age-dependent increase in H(2)O(2) generation was fully related to the MAO-A isoform: 1) at all the ages tested, chemiluminescence production was inhibited by the MAO-A inhibitor clorgyline but not by the MAO-B inhibitor RO-19 6327; 2) enzyme assay, Western blot, and semiquantitative RT-PCR analysis showed an age-dependent increase in cardiac MAO-A activity, immunodetection, and mRNA expression, respectively; and 3) the MAO-B isoform was undetectable by enzyme assay and Western blot analysis. These results suggest that MAO-A could be a major source of H(2)O(2) in the aging heart.

Antioxidant enzyme expression in health and disease: effects of exercise and hypertension

Antioxidant enzymes (superoxide dismutases, catalase and glutathione peroxidase) are components of an organism's mechanisms for combating oxidative stress which is generated in normal metabolism and which may also be a reaction in response to external stimuli. This review identifies the general significance of antioxidant enzymes in health and disease, and some of the diseases that are now believed to have oxidative stress as a component. A discussion is then presented of the molecular mechanisms by which antioxidant enzyme expression is controlled at the transcriptional and post-transcriptional levels. The final sections of the review highlight the effects of exercise and hypertension on antioxidant enzyme expression in a number of different tissues, and the possibilities for future studies in these areas are discussed.

Tissue lipid peroxidation and antioxidant status in patients with adenocarcinoma of the breast

BACKGROUND

Carcinoma of the breast, the third most common cancer worldwide, accounts for the highest morbidity and mortality. The increasing global incidence of breast cancer emphasizes the need to understand the various mechanisms involved in breast tumorigenesis. The present study was undertaken to evaluate the use of lipid peroxidation and antioxidants as biomarkers in human mammary tumors.

METHODS

The extent of lipid peroxidation as evidenced by the formation of thiobarbituric acid reactive substances (TBARS), lipid hydroperoxides (LOOH) and conjugated dienes (CD) as well as the status of the antioxidants superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) in tumor tissues and adjacent normal tissues of 30 breast cancer patients was estimated.

RESULTS

Lipid peroxidation in breast cancer tissues was enhanced compared to the corresponding adjacent uninvolved tissues. This was accompanied by significant elevation in both enzymic and non-enzymic antioxidants.

CONCLUSIONS

We suggest that upregulation of antioxidants induced by oxidative stress confers a selective growth advantage to tumor cells over their adjacent normal counterparts.

A metabolic mechanism for cardiac K+ channel remodelling

1. Electrical remodelling of the ventricle is a common pathogenic feature of cardiovascular disease states that lead to heart failure. Experimental data suggest this change in electrophysiological phenotype is largely due to downregulation of K(+) channels involved in repolarization of the action potential. 2. Voltage-clamp studies of the transient outward current (I(to)) in diabetic cardiomyopathy support a metabolic mechanism for K(+) channel downregulation. In particular, I(to) density is significantly increased in diabetic rat isolated ventricular myocytes treated in vitro with insulin or agents that activate pyruvate dehydrogenase. Recent data suggest this mechanism is not limited to diabetic conditions, because metabolic stimuli that upregulate I(to) in diabetic rat myocytes act similarly in non- diabetic models of heart failure. 3. Depressed I(to) channel activity is also reversed by experimental conditions that increase myocyte levels of reduced glutathione, indicating that oxidative stress is involved in electrical remodelling. Moreover, upregulation of I(to) density by activators of glucose utilization is blocked by inhibitors of glutathione metabolism, supporting the premise that there is a functional link between glucose utilization and the glutathione system. 4. Electrophysiological studies of diabetic and non-diabetic disease conditions affecting the heart suggest I(to) channels are regulated by a redox-sensitive mechanism, where glucose utilization plays an essential role in maintaining a normally reduced state of the myocyte. This hypothesis has implications for clinical approaches aimed at reversing pathogenic electrical remodelling in a variety of cardiovascular disease states.

Garlic-induced alteration in rat liver and kidney morphology and associated changes in endogenous antioxidant status

The effects of chronic garlic intake on various endogenous antioxidant enzymes and lipid peroxidation on two major organs, the liver (L) and kidneys (K), were investigated. Wistar albino rats were fed with fresh garlic homogenate daily by gavage in three different doses (250, 500 and 1000 mg/kg/day) for 30 days. After this period, rats were sacrificed and liver and kidneys were harvested for biochemical estimation. In comparison to saline-treated rats, the 250 mg/kg/day dose significantly (P<0.02) reduced thiobarbituric acid reactive substances (TBARS) (L: 187.48+/-9.23 vs 150.66+/-11.45; K: 177.38 15.88 vs 120.66+/-9.39 nmol/g wet. weight) and glutathione peroxidase (GPx) (L: 0.2438+/-0.05 vs 0.0046+/-0.0005; K: 0.1459+/-0.034 vs 0.0055+/-0.0003 U/mg protein). There was no change in catalase and reduced glutathione (GSH) but superoxide dismutase (SOD) increased significantly (P<0.01) (L: 5.49+/-0.76 vs 18.38+/-2.26; K: 11.47+/-1.48 vs 21.22+/-3.19 U/mg protein). Both 500 and 1000 mg/kg/day doses significantly (P<0.05) reduced endogenous antioxidants (catalase and SOD) without altering TBARS. A 1000 mg/kg/day dose of garlic caused marked histopathological and ultrastructural changes in both liver and kidneys. The results suggest that garlic in low doses has the potential to enhance the endogenous antioxidant status, although at higher doses a reversal of these effects is observed. The present study also highlights the potential ability of a high dose of garlic to induce morphological changes in the liver and kidneys, indicating the need to identify a safe dose range for garlic.

Oxidized low-density lipoprotein is localized in the ventricles of hearts from patients with coronary heart disease

The present study was designed to investigate whether oxidized low-density lipoprotein is accumulated in the left and right ventricular walls of patients with coronary heart disease (n=10) compared with patients with dilated cardiomyopathy (n=9) or healthy heart donors (controls, n=5). Sections from both ventricles of explanted hearts and coronary arteries of the same patients were analyzed by semiquantitative immunohistochemistry for the presence of oxidized low-density lipoprotein. Oxidized low-density lipoprotein was enriched in the left and right ventricular walls from coronary heart disease patients compared with patients with dilated cardiomyopathy (P=0.0012 for left ventricle and P=0.103 for right ventricle) or controls (P=0.0012 for the left ventricle and P<0.05 for the right ventricle). The accumulation of oxidized low-density lipoprotein was higher in the left than in the right ventricles in all three groups. Positive immunoreactivity for oxidized low-density lipoprotein was mainly identified in the endocardium and the subendocardial areas of the ventricles and co-localized with macrophages. Accumulation of oxidized low-density lipoprotein in the ventricles significantly correlated with the enrichment in the respective coronary arteries, whereas only poor correlations were observed between various hemodynamic parameters and ventricular oxidized low-density lipoprotein accumulation. Ventricular accumulation of oxidized low-density lipoprotein seems to be a generalized pathophysiological process which does not exclusively involve the coronary arteries. Higher oxidative stress in combination with impaired oxygen supply in the endocardium could have favored low-density lipoprotein deposition and oxidation.

Cytotoxic aldehyde generation in heart following acute iron-loading

Although the mechanism of myocardial failure following acute iron poisoning is not known, excess iron-catalyzed free radical generation is conjectured to play a role. The effects of time (0 to 360 minutes) on total iron concentrations, glutathione peroxidase activity, and cytotoxic aldehyde production in heart of mice (B6D2F1, n = 65) were first investigated following acute iron-loading (20 mg iron dextran i.p./mouse). In a subsequent experiment, the effects of dose (0 to 80 mg iron dextran i.p./mouse, n = 75) on the aforementioned parameters were investigated. Our results show that the concentrations of cytotoxic aldehydes: (1) significantly differ over-time, with corresponding increases in total concentrations of iron (r = 0.93, p < 0.001); and (2) increase parallel to the total dose of iron administered (r = 0.95, p < 0.001). Furthermore, dose-and time-dependent alterations to glutathione peroxidase activity are observed, which is most likely due to an acute up-regulation of the enzyme as an endogenous protective response to increased free radical activity in the heart subsequent to iron-loading. While no single mechanism is likely to account for the complex pathophysiology of acute iron-induced heart failure, our results shown that iron-loading can result in significant free radical generation, as quantified by cytotoxic aldehydes, in heart tissue of mice. This is the first report on the effects of time and dose on cytotoxic aldehyde generation and glutathione peroxidase activity in heart of mice following acute iron-loading.

Sarco/endoplasmic reticulum Ca2+-pump isoform SERCA3a is more resistant to superoxide damage than SERCA2b

Endo/sarcoplasmic reticulum (ER) Ca2+-pumps are important for cell survival and communication but they are inactivated by reactive oxygen species (ROS). We have previously reported that the Ca2+-pump isoform SERCA3a is more resistant than SERCA2b to damage by peroxide. Since peroxide and superoxide differ in their redox potentials, we now report the effects of superoxide on the two Ca2+-pump isoforms. We isolated microsomes from HEK293 cells transiently transfected with SERCA2b or SERCA3a cDNA. We exposed these microsomes to superoxide which was generated using xanthine plus xanthine oxidase and catalase to prevent accumulation of peroxide due to superoxide dismutation. Superoxide damaged the Ca2+-transport activity of both isoforms but SERCA3a was damaged at higher concentrations of superoxide and upon longer periods of exposures than was SERCA2b. Thus the SERCA3a isoform is more resistant than SERCA2b to inactivation by both superoxide and peroxide.

Effect of oxidation on Ca2+ -ATPase activity and membrane lipids in lens epithelial microsomes

Membrane oxidation may contribute to cataractogenesis. In our pursuit to understand the etiology of cataracts, we assessed the effect of membrane oxidation products on the activity of the lens epithelium calcium pump. Microsome preparations from bovine lens epithelium were oxidized to varying degrees with a ferrous and ferric ascorbate system to generate hydrogen peroxide and superoxide. Ca2+ -ATPase activity was measured using a colorometric assay. Lipid oxidation was quantified by infrared spectroscopy. Ca2+ -ATPase activity decreased as a function of ascorbate concentration between 0 and 200 microM. The level of Ca2+ -ATPase inhibition was correlated to both the level of lipid oxidation and the degree of lipid hydrocarbon chain order. At 25 degrees C when lipids are more ordered, the Ca2+ -ATPase activity was similar to that observed in the oxidized system measured at 37 degrees C. Glutathione, mercaptoethanol, and iodoacetate were able to reverse the oxidative inhibition of the calcium pump, suggesting that the ascorbate/iron oxidant directly oxidized the protein sulfhydryl moieties. To further probe the mechanism of Ca2+ ATPase inhibition, hydrogen peroxide was used to oxidize muscle sarcoplasmic reticulum Ca2+ -ATPase reconstituted in its native lipid vesicles, egg phosphatidylcholine, and dihydrosphingomyelin, with saturated hydrocarbon chains. In these systems, oxidation inhibited the Ca2+ -ATPase pump by 60-80%. There was no statistical difference between the level of oxidative inhibition and the percentage of dihydrosphingomyelin. Because dihydrosphingomyelin cannot be oxidized, whereas egg phosphatidylcholine (PC) can, and because the percentage of inhibition was the same for reconstituted systems using either lipid, the mechanism of inhibition is likely not via a secondary process involving oxidation-induced lipid structural changes or products of lipid oxidation.

Effects of peroxide on contractility of coronary artery rings of different sizes

Reactive oxygen species (ROS, free radicals) produced during cardiac ischemia and reperfusion can damage the contractile functions of arteries. The sarcoplasmic reticulum (SR) Ca2+ pump in coronary artery smooth muscle is very sensitive to ROS. Here we show that contractions of de-endothelialized rings from porcine left coronary artery produced by the hormone Angiotensin II and by the SR Ca2+ pump inhibitors cyclopiazonic acid and thapsigargin correlate negatively with the tissue weight. In contrast, the contractions due to membrane depolarization by high KCl correlate positively. Peroxide also produces a small contraction which correlates negatively with the tissue weight. When artery rings are treated with peroxide and washed, their ability to contract with Angiotensin II, cyclopiazonic acid and thapsigargin decreases. Thus, the SR Ca2+ pump may play a more important role in the contractility of the smaller segments of the coronary artery than in the larger segments. These results are consistent with the hypothesis that ROS which damage the SR Ca2+ pump affect the contractile function of the distal segments more adversely than of the proximal segments.

Effects of peroxide on endothelial nitric oxide synthase in coronary arteries

Reactive oxygen species (ROS) are produced in ischemia and reperfusion. Since endothelial nitric oxide synthase (eNOS) is key to the endothelium-dependent vasodilation, we examined the effects of peroxide on this enzyme. We treated cells cultured from pig coronary artery endothelium with different concentrations of hydrogen peroxide, washed them, solubilized them and measured NOS activity by arginine to citrulline conversion. Hydrogen peroxide inhibited the eNOS activity with an IC50 value of 0.85 +/- 0.39 mM. In another experiment, we perfused arteries with solutions containing 0 or 1 mM hydrogen peroxide, washed them, removed the endothelium using a cotton swab, centrifuged and solubilized the endothelium and monitored its NOS activity. Hydrogen peroxide (1 mM) did not affect the NOS activity significantly (p > 0.05) in this assay. We conclude that the inactivation of eNOS by hydrogen peroxide does not play a major role in the ischemia-reperfusion damage because the peroxide concentrations attained during ischemia-perfusion are much lower than those affecting the eNOS activity.

Melatonin reduces the increase in 8-hydroxy-deoxyguanosine levels in the brain and liver of kainic acid-treated rats

In the present study, the effect of melatonin on oxidative DNA damage induced by kainic acid (KA) treatment was investigated. 8-hydroxy-deoxyguanosine (8-OH-dG) is a main product of oxidatively damaged DNA and was used as the endpoint in these studies. The levels of 8-OH-dG were found to be elevated in the hippocampus and frontal cortex of rats treated with KA. These elevated levels were significantly reduced in animals that were co-treated with melatonin. Thus, there was no difference in 8-OH-dG levels in the brain of control rats compared to those treated with KA (10 mg/kg) plus melatonin (10 mg/kg). The levels of 8-OH-dG also increased in the liver of rats treated with KA. This rise in oxidatively damaged DNA was also prevented by melatonin administration. Melatonin's ability to reduce KA-induced increases in neural and hepatic 8-OH-dG levels presumably relates to its direct free radical scavenging ability and possibly to other antioxidative actions of melatonin.

Sarcoplasmic reticulum Ca(2+)-pump dysfunction in rat cardiomyocytes briefly exposed to hydroxyl radicals

The effects of hydroxyl radical exposure of intact cardiomyocytes on sarcoplasmic reticulum (SR) function were investigated. For this purpose, isolated rat heart myocytes were exposed briefly (1 min) to the hydroxyl radical generating system (H2O2/FeCl2 or FeSO4) or 5-5'-dithiobis-nitrobenzoic acid (DTNB), a sulfhydryl oxidizing reagent, and following this a SR-enriched fraction was isolated. Marked decreases in the SR calcium uptake activities were seen in the myocytes exposed to either the hydroxyl radical-generating system or DTNB. The exposure of myocytes to the hydroxyl radical, but not DTNB, markedly increased the amount of malonyldialdehyde (MDA) in the subsequently isolated SR. Total sulfhydryl group content in SR was decreased by exposure of myocytes to DTNB. Further, there was a significant decrease in [3H]-NEM binding to SR isolated from the hydoxyl radical-treated myocytes indicating that sulfhydryl groups are affected (oxidized). Both mannitol and catalase were found to offer complete protection against the inhibitory effect of peroxide +/- iron on calcium uptake. Also the above-mentioned alterations in both MDA and sulfhydryl group content were prevented by mannitol and catalase. Exogenously added cyclic AMP-dependent protein kinase (A-PK) or calmodulin (CAM) increased SR calcium uptake activity. In the SR isolated from the treated myocytes, the stimulatory effects of A-PK and CAM were also seen, although under all assay conditions calcium uptakes were of lower magnitude. The findings are consistent with the view that the damaging effect of the hydroxyl radical and DTNB on the functioning of SR occurs rapidly in the intact cardiomyocytes. The hydroxyl radical-provoked damage involves both protein sulfhydryl and lipid oxidation.

Attenuation of myocardial stunning in isolated rat hearts by a 21-aminosteroid lazaroid (U74389G)

The purpose of this study was to evaluate the effects of reperfusion or in vivo pretreatment with a lipid peroxidation inhibitor, lazaroid (U74389G), on attenuating systolic and diastolic alterations occurring during myocardial stunning in isolated rat hearts. Male Sprague-Dawley rats (350-400 g) were randomized into three groups: control animals (n = 13) received no drugs; hearts from reperfused animals (n = 11) received 5 microM U74389G in the reperfusion solution; pretreated animals (n = 11) received 6 mg/kg U74389G by i.v. infusion 30 min before killing. Isolated, isovolumic rat hearts were subjected to 20 min of ischemia at 37 degrees C and subsequent reperfusion for 30 min. Left ventricular isovolumic developed pressure (LVDP), its first derivative (LVDPdP/dt), end-diastolic pressure (LVEDP), and the time constant of diastolic relaxation (tau) were measured. At baseline, no statistically significant differences were detected in systolic or diastolic function in hearts of rats with or without U74389G treatment. After reperfusion, LVDP stabilized at 87 and 92% in both drug-treated groups compared with 52% in the control group (p < 0.01) and dP/dtmax recovered to 101 and 110% of baseline compared with 58% in the control group (p < 0.01). Diastolic dysfunction showed significant improvement in both U74389G pretreatment groups. The increases in LVEDP and tau were 2.0- and 1.2-fold in pretreated hearts and 2,8-fold and 1.5-fold in drug-reperfused hearts, respectively (compared with 6-fold increases in LVEDP and a 2.5-fold increase in tau in controls; p < 0.05). In conclusion, whether administered before ischemia or during reperfusion, U74389G effectively attenuated the systolic and diastolic dysfunction in this model of myocardial stunning, probably protecting cell membranes from peroxidation by oxygen-derived metabolites.

Hypercholesterolemia increases manganese superoxide dismutase immunoreactive macrophages in myocardium

The effect of hypercholesterolemia on manganese superoxide dismutase (MnSOD)-containing macrophages was investigated in male New Zealand white rabbits. Macrophages from control animals, which were marked with the RAM-11 antibody, demonstrated co-localization with MnSOD immunoreactivity, e.g. in the peri- and paravascular space within the myocardium, but not in the bone marrow. In rabbits fed a 0.5% cholesterol-enriched diet for 42 days, a significant increase (P < 0.01) of MnSOD-immunoreactive macrophages within the myocardium was found concomitant to the drastic elevation of serum cholesterol level. In the bone marrow, MnSOD immunoreactivity did not change after cholesterol feeding. Thus in cholesterol-fed rabbits, the increase of MnSOD-containing macrophages seems to parallel that of lipoproteins. MnSOD is considered as being protective against the cytotoxic effects of those superoxide anions, possibly generated in macrophages, which are involved in the metabolism of modified lipoproteins.

Oxidative stress and heart failure

Various abnormalities have been implicated in the transition of hypertrophy to heart failure but the exact mechanism is still unknown. Thus heart failure subsequent to hypertrophy remains a major clinical problem. Recently, oxidative stress has been suggested to play a critical role in the pathogenesis of heart failure. Here we describe antioxidant changes as well as their significance during hypertrophy and heart failure stages. Heart hypertrophy in rats and guinea pigs, in response to pressure overload, is associated with an increase in 'antioxidant reserve' and a decrease in oxidative stress. Hypertrophied rat hearts show increased tolerance for different oxidative stress conditions such as those imposed by free radicals, hypoxia-reoxygenation and ischemia-reperfusion. On the other hand, heart failure under acute as well as chronic conditions is associated with reduced antioxidant reserve and increased oxidative stress. The latter may have a causal role as suggested by the protection seen with antioxidant treatment in acute as well as in chronic heart failure. It is becoming increasingly apparent that, anytime the available antioxidant reserve in the cell becomes inadequate, myocardial dysfunction is imminent.