Free radicals and myocardial injury: pharmacologic implications

Mitochondria-derived methylmalonic acid aggravates ischemia-reperfusion injury by activating reactive oxygen species-dependent ferroptosis

Ferroptosis is a regulatory cell death process pivotal in myocardial ischemia-reperfusion (I/R) injury. However, the precise mechanism underlying myocardial ferroptosis remains less known. In this study, we investigated the pathophysiological mechanisms of methylmalonic acid (MMA) associated with ferroptosis activation in cardiomyocytes after I/R. We found an increase level of MMA in patients with acute myocardial injury after reperfusion and AC16 cells under hypoxia/reoxygenation (H/R) condition. MMA treatment was found to be associated with excessive oxidative stress in cardiomyocytes, leading to ferroptosis-related myocardial injury. In mice with I/R injury, MMA treatment aggravated myocardial oxidative stress and ferroptosis, which amplified the myocardial infarct size and cardiac dysfunction. Mechanistically, MMA promoted NOX2/4 expression to increase reactive oxygen species (ROS) production in cardiomyocytes, aggravating myocardial injury. Notably, the increased ROS further activated ferroptosis by inhibiting solute carrier family 7 member 11 (SLC7A11) and glutathione peroxidase 4 (GPX4) expression. In addition, MMA decreased the ectopic nuclear distribution of nuclear factor E2-related factor 2 (NRF2) by increasing the interaction between NRF2 and kelch-like ECH-associated protein 1 (KEAP1). This impeded the activation of GPX4/SLC7A11, downstream of NRF2, activating ferroptosis and aggravating myocardial cell injury. Collectively, our study indicates that MMA activates oxidative stress and ROS generation, which induces ferroptosis to exacerbate cardiomyocyte injury in an I/R model. These findings may provide a new perspective for the clinical treatment of I/R injury and warrant further investigation.

A Cardiac-Targeted Nanozyme Interrupts the Inflammation-Free Radical Cycle in Myocardial Infarction

Severe systemic inflammation following myocardial infarction (MI) is a major cause of patient mortality. MI-induced inflammation can trigger the production of free radicals, which in turn ultimately leads to increased inflammation in cardiac lesions (i.e., inflammation-free radicals cycle), resulting in heart failure and patient death. However, currently available anti-inflammatory drugs have limited efficacy due to their weak anti-inflammatory effect and poor accumulation at the cardiac site. Herein, a novel Fe-Cur@TA nanozyme is developed for targeted therapy of MI, which is generated by coordinating Fe3+ and anti-inflammatory drug curcumin (Cur) with further modification of tannic acid (TA). Such Fe-Cur@TA nanozyme exhibits excellent free radicals scavenging and anti-inflammatory properties by reducing immune cell infiltration, promoting macrophage polarization toward the M2-like phenotype, suppressing inflammatory cytokine secretion, and blocking the inflammatory free radicals cycle. Furthermore, due to the high affinity of TA for cardiac tissue, Fe-Cur@TA shows an almost tenfold greater in cardiac retention and uptake than Fe-Cur. In mouse and preclinical beagle dog MI models, Fe-Cur@TA nanozyme preserves cardiac function and reduces scar size, suggesting promising potential for clinical translation in cardiovascular disease.

The Effect of Cerium Oxide on Lung Tissue in Lower Extremity Ischemia Reperfusion Injury in Sevoflurane Administered Rats

INTRODUCTION

We aimed to investigate the effects of cerium oxide, applied before the sevoflurane anesthesia, on lung tissue in rats with lower extremity ischemia-reperfusion (IR).

MATERIALS AND METHODS

A total of 30 rats were randomly divided into five groups as; control (C), IR, cerium oxide-IR (CO-IR), IR-sevoflurane (IRS), and cerium oxide-IR-sevoflurane (CO-IRS). In the CO-IR group, 30 minutes after the injection of cerium oxide (0.5 mg/kg, intraperitoneal (i.p)), an atraumatic microvascular clamp was placed on the infrarenal abdominal aorta for 120 minutes. Then, the clamp was removed and reperfused for 120 minutes. Sevoflurane was applied in 100% oxygen at a rate of 2.3% at 4 L/min during IR. The blood samples were taken for biochemical analysis and the lung tissue samples were taken for histological analysis.

RESULTS

Neutrophil infiltration/aggregation was significantly higher in the IR group than in the C and CO-IRS groups. The alveolar wall thickness and total lung injury scores were significantly higher in the IR group than in the C, IRS, CO-IR and CO-IRS groups.

DISCUSSION

We determined that the administration of 0.5 mg/kg dose of cerium oxide with sevoflurane reduces the oxidative stress and corrects IR-related damage in lung tissue. Our results show that the administration of cerium oxide before IR and the administration of sevoflurane during IR have a protective effect in rats.

Cardioprotection of CAPE-oNO2 against myocardial ischemia/reperfusion induced ROS generation via regulating the SIRT1/eNOS/NF-κB pathway in vivo and in vitro

Caffeic acid phenethyl ester (CAPE) could ameliorate myocardial ischemia/reperfusion injury (MIRI) by various mechanisms, but there hadn’t been any reports on that CAPE could regulate silent information regulator 1 (SIRT1) and endothelial nitric oxide synthase (eNOS) to exert cardioprotective effect. The present study aimed to investigate the cardioprotective potential of caffeic acid o-nitro phenethyl ester (CAPE-oNO₂) on MIRI and the possible mechanism based on the positive control of CAPE. The SD rats were subjected to left coronary artery ischemia /reperfusion (IR) and the H9c2 cell cultured in hypoxia/reoxygenation (HR) to induce the MIRI model. Prior to the procedure, vehicle, CAPE or CAPE-oNO₂ were treated in the absence or presence of a SIRT1 inhibitor nicotinamide (NAM) and an eNOS inhibitor Nω-nitro-L-arginine methyl ester (L-NAME). In vivo, CAPE and CAPE-oNO₂ conferred a cardioprotective effect as shown by reduced myocardial infarct size, cardiac marker enzymes and structural abnormalities. From immunohistochemical and sirius red staining, above two compounds ameliorated the TNF-α release and collagen deposition of IR rat hearts. They could agitate SIRT1 and eNOS expression, and consequently enhance NO release and suppress NF-κB signaling, to reduce the malondialdehyde content and cell necrosis. In vitro, they could inhibit HR-induced H9c2 cell apoptosis and ROS generation by activating SIRT1/eNOS pathway and inhabiting NF-κB expression. Emphatically, CAPE-oNO₂ presented the stronger cardioprotection than CAPE both in vivo and in vitro. However, NAM and L-NAME eliminated the CAPE-oNO₂-mediated cardioprotection by restraining SIRT1 and eNOS expression, respectively. It suggested that CAPE-oNO₂ ameliorated MIRI by suppressing the oxidative stress, inflammatory response, fibrosis and necrocytosis via the SIRT1/eNOS/NF-κB pathway.

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CAPE-oNO₂ exerting cardioprotective potential was firstly synthesized.

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IR-induced ROS increase aggravates inflammation, fibrosis and necrocytosis.

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The SIRT1/eNOS/NF-κB pathway is contributed to MIRI both in vivo and in vitro.

Simultaneous Bilateral Carotid Endarterectomy: A Revision of Concepts and Strategies

The results of 156 bilateral cases of carotid endarterectomy are reported: 71 patients had staged operations and 85 patients had simultaneous endarterectomies.

The results in these two groups of bilateral cases were very similar. In each of the two groups no patient died and the major neurologic complications (stroke) were less than 2% in regard to patient risk, and therefore less than 1% in regard to procedure risk.

Indications for and against bilateral carotid surgery as a simultaneous or a staged procedure are discussed. The parameters for selecting patients likely to undergo simultaneous surgery are indicated. The main parameter to consider is the probability for the patient to have a serious post-operative hyperperfu sion, especially if a cerebral ischemia coexists.

Impact of Carotid Endarterectomy Critical Pathway on Surgical Outcome and Hospital Stay

Carotid endarterectomy (CEA) is associated with substantial consumption of hospital days and other resources. Although surgical outcomes in their practice compared favorably with published benchmarks, the authors were concerned that postoperative stays were unnecessarily long and that patients were receiving unnecessary tests and pharmaceuticals. Recent studies suggest that within the bounds of safe practice, efforts to standardize care may increase quality and patient satisfaction and reduce consumption of resources. They examined their practice of CEA in an effort to discover the potential for quality improvement and decreased utilization of resources.

A CEA critical pathway (CP) was designed, the primary goal of which was elimination of a possibly unnecessary second postoperative hospital day for most patients and superfluous perioperative testing and medications. Data were recorded prospectively both for Pre-CP patients during the year prior to CP initiation and for subsequent CP patients during the subsequent 13-month period. CP patients were interviewed and the pathway was described prior to surgery.

Pre-CP and CP patients were indistinguishable with respect to indications for CEA and medical comorbidities. A single operative death occurred due to myocardial infarction (Pre-CP). Perioperative stroke and other complications occurred in similar numbers of Pre-CP and CP patients. CP resulted in a 0.5-day decrease in hospital stay overall. CP was also associated with a 22% decrease in direct costs. One early readmission for neck hematoma on postoperative day 2 (1 day postdischarge) might have been preventable. A second readmission on postoperative day 2 was secondary to a drug reaction and would likely have occurred prior to initiation of the CP as well.

CP resulted in significant decreases in resource utilization and with the possible exception of a single readmission did not appear to adversely affect outcome. Preoperative education and expectation that patients will be ready for discharge 1 day after CEA are critical to patient acceptance and satisfaction. Further modification of the CP may further decrease utilization of resources. CP is an excellent mechanism to understand how surgeons practice and it facilitates quality improvement.

Comparison of Shenfu Injection () and epinephrine on catecholamine levels in a porcine model of prolonged cardiac arrest

OBJECTIVE

To compare the effects of Shenfu Injection (SFI) and epinephrine (EPI) on catecholamine levels in a porcine model of prolonged cardiac arrest (CA).

METHODS

After 8 min of untreated ventricular fibrillation, 24 Wuzhishan miniature pigs were randomly assigned to one of the three groups (n=8 per group) and received central venous injection, respectively: SFI group (1 mL/kg), EPI group (20 μg/kg EPI), and normal saline (NS) group. Cardiac output (CO), maximum rate of increase/decrease in left ventricular pressure (±dp/dt), serum levels of EPI, norepinephrine (NE), and dopamine (DA) were determined at baseline and at 0.5, 1, 2, and 4 h after restoration of spontaneous circulation.

RESULTS

The duration of cardiopulmonary resuscitation was shorter in the EPI and SFI groups than in the NS group (P<0.05). The EPI level increased significantly after restoration of spontaneous circulation (ROSC) in all three groups, and was significantly different between the EPI group and the other two groups immediately after ROSC (both P<0.01), but these differences gradually disappeared over time. There were no significant differences in NE or DA levels among the three groups, and there were no correlations between catecholamine levels and CO or dp/dt (P>0.05).

CONCLUSIONS

SFI did not significantly affect endogenous catecholamine levels during cardiopulmonary resuscitation after prolonged ventricular fibrillation. However, SFI improved oxygen metabolism, and produced a better hemodynamic status compared with EPI. SFI might be a potentially vasopressor drug for the treatment of CA.

Dexmedetomidine protects from post-myocardial ischaemia reperfusion lung damage in diabetic rats

OBJECTIVE

Diabetic complications and lipid peroxidation are known to have a close association. Lipid peroxidation commonly occurs at sites exposed to ischaemia, but distant organs and tissues also get damaged during ischaemia/reperfusion (I/R). Some of these targets are vital organs, such as the lung, liver, and kidney; the lung is the most frequently affected. The aim of our study was to investigate the effects of dexmedetomidine on I/R damage in lung tissue and on the oxidant/anti-oxidant system in diabetic rats.

MATERIAL AND METHODS

Diabetes was induced with streptozotocin (55 mg/kg) in 18 Wistar Albino rats, which were then randomly divided into three groups (diabetes control (DC), diabetes plus ischaemia-reperfusion (DIR), and diabetes plus dexmedetomidine-ischaemia/reperfusion (DIRD)) after the effects of diabetes were clearly evident. The rats underwent a left thoracotomy and then ischaemia was produced in the myocardium muscle by a left anterior descending artery ligation for 30 min in the DIR and DIRD groups. I/R was performed for 120 min. The DIRD group received a single intraperitoneal dose of dexmedetomidine (100 µg/kg); the DIR group received no dexmedetomidine. Group DC was evaluated as the diabetic control group and also included six rats (C group) in which diabetes was not induced. These mice underwent only left thoracotomy and were closed without undergoing myocardial ischaemia. Histopathological changes, activities of catalase (CAT) and glutathione-S-transferase anti-oxidant enzymes, and malondialdehyde (MDA) levels were evaluated in the lung tissues of all rats.

RESULTS

Neutrophil infiltration/aggregation was higher in the DIR group than in the C, DC, and DIRD groups (p=0.001, p=0.013, and p=0.042, respectively). The lung injury score was significantly higher in the DIR group than in the C and DC groups (p<0.0001 and p=0.024, respectively). The levels of MDA were significantly higher in the DIR group than in the C and DIRD groups. CAT activity was significantly higher in the DIR group than in the DIRD and C groups.

CONCLUSION

Our results confirm that dexmedetomidine has protective effects against the lung damage resulting from I/R in diabetic rats. Future studies conducted to evaluate the effects of the use of dexmedetomidine on damage to various organs following different I/R durations may help understanding possible protective effects of dexmedetomidine and underlying mechanisms in tissue damage related to I/R injury.

The effect of levosimendan on lung damage after myocardial ischemia reperfusion in rats in which experimental diabetes was induced

BACKGROUND

It is known that diabetic complications and lipid peroxidation are closely associated. During ischemia and reperfusion (IR), injury may occur in distant organs, as well as in tissues next to the region exposed to the ischemia, and the lungs can be one of the most affected of these organs. Therefore, this study investigated the effects of levosimendan on lung tissue and the oxidant-antioxidant system in diabetic rats.

MATERIALS AND METHODS

The study was conducted in 24 Wistar albino rats that were separated into four groups (C, control; DC, diabetic control; DIR, diabetic IR; and DIRL, diabetic IR levosimendan). Diabetes was induced in 18 rats using streptozotocin (55 mg/kg), and the animals were randomly separated into three groups after the effects of the diabetes became apparent. After a left thoracotomy, ischemia was performed on the myocardial muscle with the left main coronary artery (LAD) for 30 min in the DIR and DIRL groups. After ischemia, the LAD ligation was removed, and reperfusion was applied for 120 min. Single-dose intraperitoneal 12 μg/kg levosimendan was administered to group DIRL before the ischemia. Group DC was evaluated as the diabetic control group, and six rats were considered to be the control group (group C), in which thoracotomy was performed and then closed with no induction of myocardial ischemia. We measured the levels of malondialdehyde, as a lipid peroxidation end product, as well as catalase and glutathione S-transferase activities, as antioxidant enzymes in the lung tissue. Tissue samples were also examined histopathologically.

RESULTS

Neutrophil infiltration or aggregation in lung tissue was significantly higher in the DIR group compared with the C, DC, and DIRL groups (P = 0.003, P = 0.026, and P = 0.026, respectively). Alveolar wall thickening in lung tissue was significantly higher in the DIR group compared with the C, DC, and DIRL groups (P = 0.002, P = 0.002, and P = 0.006, respectively). In addition, the lung tissue damage score was significantly higher in the DIR group compared with the C, DC, and DIRL groups (P = 0.001, P = 0.004, and P = 0.007, respectively). Finally, catalase and glutathione S-transferase activity levels were significantly higher in the DIR group compared with those observed in the C, DC, and DIRL groups.

CONCLUSIONS

Although diabetes increases lipid peroxidation, it suppresses antioxidant activity. Our results showed that levosimendan had a protective effect against lung damage secondary to IR in the rats with induced diabetes. We recommend that experimental and clinical studies be conducted to examine the effects of levosimendan at different doses and different IR durations on various organs for clinical use.

Intraperitoneal bilirubin administration decreases infarct area in a rat coronary ischemia/reperfusion model

Bilirubin was previously considered a toxin byproduct of heme catabolism. However, a mounting body of evidence suggests that at physiological doses, bilirubin is a powerful antioxidant and anti-atherosclerotic agent. Recent clinical studies have shown that human beings with genetically-induced hyperbilirubinemia (Gilbert Syndrome) are protected against coronary heart disease. The purpose of this study was to investigate whether administration of exogenous bilirubin to normal rats would convey similar protective effects in an experimental model of coronary ischemia. We hypothesized that intraperitoneal bilirubin administration 1 h before injury would decrease infarct area and preserve left ventricular (LV) systolic function when compared to non-treated rats. Coronary ischemia was induced by temporary (30 min) ligation of the left anterior descending coronary artery in control or bilirubin treated rats, followed by a 1-h period of reperfusion. LV function was estimated by measurements of fractional shortening (FS) and fractional area shortening using echocardiography. LV function decreased in both experimental groups after ischemia and reperfusion, although in bilirubin-treated rats FS was less depressed during the period of ischemia (18.8 vs. 25.8%, p = 0.034). Infarct size was significantly reduced in the bilirubin treated group compared to the non-treated group (13.34 vs. 25.5%, p = 0.0067). Based on the results of this study, bilirubin supplementation appears to provide significant decrease in infarct size although protective effects on LV function were noted only during the period of ischemia. This result also suggests that lipid soluble antioxidant bilirubin prevents the oxidation of cardiolipin and decreases the infarct size in the heart during ischemia.

Protective Effects ofElaeagnus angustifoliaLeaf Extract against Myocardial Ischemia/Reperfusion Injury in Isolated Rat Heart

The purpose of this study is to clarify the cardioprotective property of the aqueous extract ofElaeagnus angustifoliaL. leaf (EA) against myocardial ischemia/reperfusion injury in isolated rat heart. The myocardial ischemia/reperfusion (I/R) injury model of isolated rat heart was set up by the use of improved Langendorff retrograde perfusion technology. Compared with the ischemia/reperfusion (I/R) group, the aqueous extract ofElaeagnus angustifoliaL. leaf (0.5 mg/mL, 1.0 mg/mL) pretreatment markedly improved the coronary flow (CF) and raised left ventricular developed pressure (LVDP) and maximum rise/down velocity (±dp/dtmax). The infarct size of the EA-treated hearts was smaller than that of I/R group. After treatment with EA, the superoxide dismutase (SOD) activity increased; malondialdehyde (MDA) and protein carbonyl content reduced more obviously (P<0.01) than that of I/R injury myocardial tissue.Conclusion. Results from the present study showed that the aqueous extract ofElaeagnus angustifoliaL. leaf has obvious protective effects on myocardial I/R injury, which may be related to the improvement of myocardial oxidative stress states.

Associations of job stress indicators with oxidative biomarkers in Japanese men and women

Some researchers have suggested that oxidative damage may be one of the mechanisms linking job stress with coronary heart disease. The aim of this study was to investigate the association between job stress indicators and oxidative biomarkers. The study included 567 subjects (272 men, 295 women) who answered questionnaires related to their work and underwent a medical examination. Job stress evaluated using the demands-control-support model was measured using the Job Content Questionnaire. Effort-reward imbalance was measured using the Effort-Reward Imbalance Questionnaire. Urinary hydrogen peroxide (H₂O₂) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) were measured by the modified ferrous ion oxidation xylenol orange version-1 method and enzyme-linked immunosorbent assay, respectively. In men, the changes in the odds ratios for high urinary H₂O₂ associated with a 1-standard-deviation (SD) increase in worksite social support were 0.69 (95% confidence interval (CI) 0.53, 0.91) univariately and 0.68 (95%CI 0.51, 0.90) after adjustment for covariates. The change in the odds ratio for high urinary H₂O₂ associated with a 1-SD increase in effort-reward ratio was 1.35 (95% CI 1.03, 1.78) after adjustment for covariates. In women, there were no significant associations of the two job stress indicators with urinary H₂O₂ and 8-OHdG levels after adjustment for covariates (p > 0.05).

Epinephrine in resuscitation: curse or cure?

The use of epinephrine during cardiac arrest has been advocated for decades and forms an integral part of the published guidelines. Its efficacy is supported by animal data, but human trial evidence is lacking. This is partly attributable to disparities in trial methodology. Epinephrine’s pharmacologic and physiologic effects include an increase in coronary perfusion pressure that is key to successful resuscitation. One possible explanation for the lack of epinephrine’s demonstrated efficacy in human trials of out-of-hospital cardiac arrest is the delay in its administration. A potential solution may be intraosseus epinephrine, which can be administered quicker. More importantly, it is the quality of the basic life support, early and uninterrupted chest compressions, early defibrillation and postresuscitation care that will provide the best chance of neurologically intact survival.

Dipropionylcysteine ethyl ester compensates for loss of citric acid cycle intermediates during post ischemia reperfusion in the pig heart

PURPOSE

During reperfusion, following myocardial ischemia, uncompensated loss of citric acid cycle (CAC) intermediates may impair CAC flux and energy transduction. Propionate has an anaplerotic effect when converted to the CAC intermediate succinyl-CoA, and may improve contractile recovery during reperfusion. Antioxidant therapy with N-acetylcysteine decreases reperfusion injury. To synergize the antioxidant effects of cysteine with the anaplerotic effects of propionate, we synthesized a novel bi-functional compound, N,S-dipropionyl cysteine ethyl ester (DPNCE) and tested its anaplerotic and anti-oxidative capacity in anesthetized pigs.

METHODS

Ischemia was induced by a 70% reduction in left anterior descending coronary artery flow for one hour, followed by 1 h of reperfusion. After 30 min of ischemia and throughout reperfusion animals were treated with saline or intravenous DPNCE (1.5 mg x kg(-1) x min(-1), n = 8/group). Arterial concentrations and myocardial propionate, cysteine, free fatty acids, glucose and lactate uptakes, cardiac mechanical functions, myocardial content of CAC intermediates and oxidative stress were assessed.

RESULTS

Ischemia resulted in reduction in myocardial tissue concentration of CAC intermediates. DPNCE treatment elevated arterial propionate and cysteine concentrations and myocardial propionate uptake, and increased myocardial concentrations of citrate, succinate, fumarate, and malate compared to saline treated animals. DPNCE treatment did not affect blood pressure or myocardial contractile function, but increased arterial free fatty acid concentration and myocardial fatty acid uptake. Arterial cysteine concentration was elevated by DPNCE, but there was negligible myocardial cysteine uptake, and no change in markers of oxidative stress.

CONCLUSION

DPNCE elevated arterial cysteine and propionate, and increased myocardial concentration of CAC intermediates, but did not affect mechanical function or oxidative stress.

Safety, feasibility, and hemodynamic and blood flow effects of active compression-decompression of thorax and abdomen in patients with cardiac arrest

OBJECTIVE

During closed chest compression for cardiac arrest, any increase in coronary perfusion pressure accounts for a proportional increase in myocardial blood flow and therefore the resuscitability of the patient. The objectives of this study were to evaluate the safety, feasibility, and hemodynamic effects of phased chest and abdominal compression-decompression and to compare it with mechanical chest compression during cardiopulmonary resuscitation.

DESIGN

In this prospective, single-center, phase II study, we compared patients treated with the Datascope Lifestick Resuscitator with patients who had been treated with mechanical precordial compression.

SETTING

Emergency department of a tertiary care university hospital.

PATIENTS

We included 31 patients with cardiac arrest who had received cardiopulmonary resuscitation in the emergency department.

INTERVENTIONS

The Lifestick device was used in 20 patients. In 11 patients, mechanical chest compression with the Thumper device was used as a control intervention.

MEASUREMENTS AND MAIN RESULTS

We evaluated the safety, feasibility, and hemodynamic effects of both interventions and observed, with the help of echocardiography, the mechanisms through which blood flow was generated. We found no significant difference between the use of the Lifestick device and standard chest compression with the Thumper device in resuscitations. Most operators regarded the Lifestick as a feasible alternative to the Thumper. We could observe a mean increase in coronary perfusion pressure of 9.33 mm Hg (interquartile range, 1.96-14.36; p = .08) and an increase of end-tidal CO2 of 10 mm Hg (interquartile range, 5-16; p = .003) (1333Pa [interquartile range, 665-2133]) during resuscitation with the Lifestick compared with using the Thumper.

CONCLUSION

In this preliminary study, resuscitation with the Lifestick was found to be safe and feasible. The design of the study and small number of patients included in it limit the conclusions about the hemodynamic effects of the Lifestick.

Oxidative injury and antioxidants in coronary artery bypass graft surgery: Off-pump CABG significantly reduces oxidative stress

BACKGROUND

Coronary artery bypass grafting (CABG) can now be performed with or without cardiopulmonary bypass. The former entails global ischemia followed by reperfusion after declamping, whereas the latter does not. In view of growing evidence that reperfusion is associated with oxidative stress, we studied the extent of oxidative stress and antioxidant status in patients undergoing on-pump and off-pump CABG to determine whether the latter significantly reduces oxidative stress.

METHODS

Thirty patients were initially enrolled for the study. The inclusion criteria included patients with atherosclerotic triple vessel disease, undergoing elective CABG, with good LV function, no major risk factors for surgery, with all biochemical investigations within normal limits, having stable angina and no history of previous infarct. Patients with valvular heart disease, ventricular aneurysm, heart failure and poor left ventricular function were excluded. These were alternately posted for on-pump and off-pump CABG. Eight patients were excluded as they developed unforeseen complications during the surgery. Out of the remaining 22 patients, 13 underwent off-pump CABG and 9 underwent on-pump CABG. Five blood samples were collected; baseline, 5, 15, 60 min and 24 h after reperfusion. Samples were analyzed for thiobarbituric acid reactive substances (TBARS), glutathione (G-SH) and catalase (CAT). The results were compared with their preanaesthetic levels in both the groups and also with 20 age- and sex-matched normal healthy individuals.

RESULTS

Lipid peroxidation was significantly increased after reperfusion in patients undergoing on-pump CABG, maximum increase (p<0.0001) was seen 1 h after reperfusion, whereas off-pump CABG reduces oxidative stress. The G-SH levels were significantly decreased after reperfusion in on-pump and off-pump CABG patients, maximum decrease (p<0.0001) was seen 5 min after reperfusion in on-pump CABG. The catalase activity was significantly increased after reperfusion in on-pump and off-pump CABG patients, maximum increase (p<0.0001) was seen 1 h after reperfusion in on-pump CABG.

CONCLUSION

Significant increase in oxidative stress was seen in patients undergoing on-pump CABG, whereas oxidative stress was less in off-pump CABG patients. The G-SH levels were decreased and Catalase activity was increased significantly in both on-pump and off-pump CABG patients.

Effect of the free radical scavenger MCI-186 on pulmonary ischemia-reperfusion injury in dogs

BACKGROUND

Free radical scavengers and superoxide dismutase have been found to protect against cerebral ischemic damage, and it was suggested that oxygen free radicals contribute to ischemia-reperfusion injury induced by cerebral ischemic damage. MCI-186 (3-methyl-1-phenyl-2-pyrazolin-5-one) is a potent scavenger and inhibitor of hydroxyl radicals and protective agent of peroxidative injury. The purpose of this study was to evaluate the effects of MCI-186 on pulmonary ischemia-reperfusion injury in a simulated transplanted lung model.

METHODS

Fourteen dogs were divided into two groups (n = 7 each). In the MCI group, MCI-186 was continuously administered at 3 mg/kg/hour intravenously (IV) from 30 minutes before reperfusion until 30 minutes after reperfusion (total administration time 1 hour). Vehicle was administered in the control group. Warm ischemia was induced for 3 hours by clamping the left pulmonary artery and veins. Simultaneously, the left stem bronchus was bisected and then anastomosed before reperfusion. The right pulmonary artery was ligated 15 minutes after reperfusion, and the right stem bronchus was then bisected.

RESULTS

The respiratory gas exchange, hemodynamic changes, wet-to-dry weight ratio (WDR) and malondialdehyde (MDA) concentration in the tissue were significantly improved (p < 0.05) in the MCI group. The histologic damage was more severe in the control group and polymorphonuclear neutrophil (PMN) infiltration was reduced in the MCI group.

CONCLUSION

MCI-186 has a protective effect on pulmonary ischemia-reperfusion injury through the inhibition of lipid peroxidation.

The protective role of melatonin in experimental hypoxic brain damage

BACKGROUND

It is known that oxygen-derived free radicals play an important role in the pathogenesis of brain injury. Melatonin is a powerful scavenger of the oxygen free radicals. In this study, the protective effect of melatonin against the damage inflicted by reactive oxygen species during brain hypoxia was investigated in newborn rats using biochemical parameters.

METHODS

For biochemical analyses, the levels of lipid peroxidation product (malondialdehyde ([MDA]), levels of reduced glutathione (GSH) and the activities of superoxide dismutase (SOD) and catalase (CAT) were estimated.

RESULTS

After the third day of brain hypoxia, the brain levels of MDA increased. Pretreatment of animals with melatonin abolished the rise in MDA induced by hypoxia. GSH concentration did not increase by pretreatment with melatonin. Additionally, the activities of two antioxidative enzymes (SOD and CAT) decreased after the experimental period with melatonin only preventing the change of CAT. The activity of SOD was not influenced by melatonin administration as expected.

CONCLUSION

In this experimental study, exogenously administered melatonin effectively protected against brain injury by oxidative stress. This protective effect of melatonin may be due to its direct scavenger activity and activation of CAT. Thus, melatonin may potentially be useful in the treatment of neurodegenerative conditions that may involve free radical production, such as perinatal hypoxia.

Edaravone Prevented Deteriorated Cardiac Function After Myocardial Ischemia-Reperfusion via Inhibiting Lipid Peroxidation in Rat

Edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one) has potent effects in the brain as a free radical scavenger in ischemia-reperfusion as well as in ischemic injuries. However, whether this free radical scavenger prevents deterioration of cardiac function and lethal ventricular arrhythmias after ischemia-reperfusion in rat heart is not clear. We aimed to assess whether free radical scavenging by edaravone maintains cardiac function and suppresses life-threatening ventricular tachyarrhythmia after myocardial ischemia-reperfusion. Twenty-nine 7-week-old male Sprague-Dawley rats had acute myocardial ischemia induced by ligation of the left coronary artery for 5 minutes followed by reperfusion. Eleven were treated by intravenous injection of edaravone at 3 mg/kg 2 minutes after coronary ligation, and 18 were left untreated. The index of systolic function (contractility; end-systolic elastance, Ees) and hemodynamics were measured by pressure-volume relationships every 5 minutes before ligation to 25 minutes after reperfusion. Blood levels of malondialdehyde (MDA) and the ischemic areas were also measured 25 minutes after reperfusion. There were no differences in the ischemic areas between the groups. Lethal reperfusion tachyarrhythmia was observed in 5 untreated rats but not in those having edaravone treatment. Ees was significantly greater in the edaravone-treated than in untreated rats from 5 to 25 minutes after reperfusion (1789 +/- 866 in untreated versus 2809 +/- 273 mm Hg/mL in edaravone-treated rats at 25 minutes, P < 0.001). MDA level was significantly lower in edaravone-treated than in untreated rats (1.44 +/- 0.29 nmol/L in edaravone-treated versus 1.90 +/- 0.28 nmol/L in untreated group, P < 0.05). The results suggest that edaravone treatment before reperfusion prevented lethal reperfusion ventricular tachyarrhythmias and deteriorated cardiac function with ischemia and ischemia-reperfusion injuries through inhibiting lipid peroxidation in terms of scavenging for free radicals.

Urinary biopyrrins levels are elevated in relation to severity of heart failure

OBJECTIVES

We investigated the relationship between the urinary levels of biopyrrins and the severity of heart failure (HF).

BACKGROUND

Oxidative stress is evident in heart disease and contributes to the development of ventricular dysfunction in patients with HF. Biopyrrins, oxidative metabolites of bilirubin, have been discovered as potential markers of oxidative stress.

METHODS

We measured the levels of urinary biopyrrins and plasma B-type natriuretic peptide (BNP) in 94 patients with HF (59 men; mean age 65 years) and 47 control subjects (30 men; mean age 65 years). Urine and blood samples were taken after admission in all subjects. Further urine samples were obtained from 40 patients after treatment of HF.

RESULTS

The urinary biopyrrins/creatinine levels (micromol/g creatinine) were the highest in patients in New York Heart Association (NYHA) class III/IV (n = 26; 17.05 [range 7.85 to 42.91]). The urinary biopyrrins/creatinine levels in patients in NYHA class I (n = 35; 3.46 [range 2.60 to 5.42]) or II (n = 33; 5.39 [range 3.37 to 9.36]) were significantly higher than those in controls (2.38 [range 1.57 to 3.15]). There were significant differences in urinary biopyrrins/creatinine levels among each group. The treatment of HF significantly decreased both urinary biopyrrins/creatinine levels (from 7.43 [range 3.84 to 17.05] to 3.07 [range 2.21 to 5.71]) and NYHA class (from 2.5 +/- 0.1 to 1.7 +/- 0.1). Log biopyrrins/creatinine levels were positively correlated with log BNP levels (r = 0.650, p < 0.001).

CONCLUSIONS

These results indicate that urinary biopyrrins levels are increased in patients with HF and are elevated in proportion to its severity.

Role of adenosine in immunomodulation: Review of the literature

OBJECTIVE

Advances in the understanding of sepsis have failed to deliver satisfactory new treatments aimed at attenuating inflammatory-mediated organ dysfunction. Phagocytic cells play a pivotal role in driving the inflammatory response and causing direct tissue injury. Adenoreceptor stimulation may attenuate such inflammatory-mediated damage by down-regulating phagocytic activity and preventing excessive respiratory burst activation.

DATA

A Medline database was used to perform a literature search for all articles relating to the use of adenosine as an immunomodulatory agent.

CONCLUSION

There is convincing evidence to suggest that adenoreceptor modulation can prevent tissue injury through a variety of pathways. The use of adenosine modulation in ischemia/reperfusion injury has been the subject of considerable investigation, although experience with its use in sepsis is limited.

Cardioselective overexpression of HO-1 prevents I/R-induced cardiac dysfunction and apoptosis

Heme oxygenase (HO)-1 converts heme to bilirubin, carbon monoxide, and iron. Our prior work has suggested a cardioprotective role for HO-1 in heart failure. To test whether HO-1 (heat shock protein 32) prevents cardiomyocyte apoptosis and cardiac dysfunction after ischemia-reperfusion (I/R), we generated transgenic mice overexpressing HO-1 in the heart under the control of the alpha-myosin heavy chain promoter. HO-1 transcript and protein increased markedly in the heart only. In an isolated heart preparation, we observed an enhanced functional recovery during reperfusion after ischemia in the transgenic hearts compared with nontransgenic controls. I/R injury was also performed in intact animals by coronary ligation and reperfusion to assess the protective role of HO-1 overexpression on heart apoptosis. HO-1 overexpression reduced cardiac apoptosis, as evidenced by fewer terminal deoxynucleodidyl transferase-mediated dUTP nick-end labeling-positive or in situ oligo ligation-positive myocytes, compared with nontransgenic mice. Our results indicate that cardioselective overexpression of HO-1 exerts a cardioprotective effect after myocardial I/R in mice, and this effect is probably mediated via an antiapoptotic action of HO-1.

Serum thioredoxin (TRX) levels in patients with heart failure

An increase in oxidative stress is thought to be involved in the progression of heart disease, but the serum level of thioredoxin (TRX), which regulates the cellular redox state, has not been investigated in patients with heart diseases. The present study determined serum TRX levels with a sandwich enzyme-linked immunosorbent assay in a total of 39 patients with dilated cardiomyopathy (DCM) (n=5), acute coronary syndrome (ACS) (n=7) or stable angina (n=18), including effort angina (n=7) and vasospastic angina (n=11), and in control subjects (n=7). The serum TRX level in patients with New York Heart Association (NYHA) functional classes III and IV (n=8, 33.3+/-8.6 ng/ml) was significantly higher than in the control subjects (n=7, 14.0+/-4.6 ng/ml). In addition, the serum TRX levels correlated positively with the severity of NYHA class, and negatively with the left ventricular ejection fraction. The serum TRX levels were elevated in patients with ACS and DCM compared with the controls. These results indicate a possible association between TRX concentration and the severity of heart failure.

Cost Containment in Vascular Surgery

In the last decade, the delivery of health care and the role of the physician have undergone radical change. With the ad vent of managed care and the tightening of restrictions by Medicare and insurance companies, physicians have been required to review, re-engineer, and revitalize their role. Increasing financial pressures at the hospital level have caused administrators to cut costs at all levels. It is imper ative that physicians take an active role in cost containment so that the quality of care is not sacrificed. Cost containment in vascular surgery is an urgent priority in health care. Copyright © 2000 by W.B. Saunders Company.

Retrospective analysis of Rt-pa thrombolysis combined with PGE1 in patients with peripheral arterial occlusions

Although thrombolysis has been established for recanalization of acute and in part chronic peripheral artery occlusions, only smaller studies exist regarding the use of long-term rt-pa infiltration-thrombolysis. The objective of this study was to evaluate the benefit of additional long-term thrombolysis in patients with peripheral arterial occlusions for whom acute thrombolysis failed. From 1992 to 1997, 323 patients with peripheral arterial occlusions were treated with rt-pa (recombinant tissue-type plasminogen activator). When the thrombolysis failed during the first 3 hours, the thrombolytic therapy was continued as a long-term treatment with 3 mg rt-pa alternated by PGE1 (2.1 mL/hr for 3 hours, concentration: 20 microg/50 mL NaCl) every 3 hours. Additional heparin was applied in doses of 15,000 IE/24 hr or more to slightly increase the partial thromboplastin time. Angiographic controls were performed every 24 hours. If necessary, a final angioplasty was performed. In 142 of the 323 patients the occlusions were recanalized during the first 3 hours; 119 patients were treated with a long-term thrombolysis and in 72 (61%) a recanalization was ultimately achieved. Thus, the recanalization rate increased to 214 of 323 patients (p < 0.02). Mean treatment time was 2.8 +/- 2.2 days, range: 1 to 13 days. The rates of recanalization were not different in iliac, femoral, or crural arteries. Fibrinogen levels did not decrease during thrombolysis. Severe bleeding (with a decrease of more than 3 g/dL hemoglobin requiring transfusion) occurred in four patients after finishing the thrombolysis with short-term and in six with long-term therapy; two required surgical treatment. The 1-, 2-, and 3-year cumulative patency rates were respectively 90.1%, 74.2% and 64.9%. Patency rates in patients with acute or long-term thrombolysis were not different. A composite thrombolytic treatment using low-dose rt-pa in combination with PGE1 offers significantly better results than an acute thrombolytic treatment alone. It can be an effective and practicable regimen in about 60% of patients in whom acute thrombolysis fails.

Oxidative status and anti-oxidant enzyme activity during calcium paradox in the rat isolated heart

1. The effect of calcium paradox on oxidative status and the activity of anti-oxidant enzymes were studied in the rat isolated heart. Glutathione status, sulphydryl group contents and lipid peroxidation in the myocardium, as well as the release of oxidized and reduced glutathione from the heart, were taken as indices of oxidative events. 2. Reperfusion with calcium after calcium-free perfusion induced a significant decrease in the myocardial content of reduced and oxidized glutathione and non-protein sulphydryl groups. At the same time, a significant release of both forms of glutathione from the heart was observed. However, the ratio of oxidized to reduced glutathione remained unchanged and was not different from control. Increased lipid peroxidation was observed only after 30 min of reperfusion with calcium. 3. Increased anti-oxidant activity during the reperfusion period was observed. Mitochondrial Mn-superoxide dismutase (SOD) activity was increased throughout the reperfusion period, while cytoplasmic Cu,Zn-SOD and glutathione peroxidase activity showed a transient increase at 5 min reperfusion. 4. The results do not support an important role of oxygen free radicals in cell damage observed during calcium paradox in the rat isolated heart. Production of oxygen free radicals may occur during the reperfusion period, but the quantity produced is insufficient to exceed the anti-oxidant capacity of the heart.

Role of high-energy phosphate metabolism in hydrogen peroxide-induced cardiac dysfunction

This study was undertaken to clarify the role of high-energy phosphate metabolism in hydrogen peroxide-induced cardiac dysfunction using phosphorus and fluorine nuclear magnetic resonance spectroscopy. The exposure of a Langendorff-perfused heart to hydrogen peroxide (200-400 micromol/L, 8 min) provoked biphasic contractile dysfunction characterized by a transient depression of left ventricular developed pressure during the administration of hydrogen peroxide and a delayed elevation of left ventricular end-diastolic pressure after the washout of hydrogen peroxide. The initial phase of cardiac dysfunction correlated well with the accumulation of sugar phosphates (r = 0.89, p < 0.01). Furthermore, we demonstrated that glibenclamide, a potent inhibitor of the ATP-sensitive K+ channel, attenuated the initial depression of developed pressure. On the other hand, the delayed elevation of end-diastolic pressure correlated well with the total ATP depletion (r = 0.96, p < 0.01). However, ATP loss was supposed to be a mere result from the increased ATP consumption corresponding to a rise in intracellular free Ca2+ (from the control value of 315+/-23 nmol/L to 708+/-104 after the administration of hydrogen peroxide, p < 0.01), which also paralleled the elevation of end-diastolic pressure. Thus glycolytic inhibition and intracellular Ca2+ overload are independently responsible for the biphasic contractile dysfunction induced by hydrogen peroxide.

Caffeic acid phenethyl ester prevents intestinal reperfusion injury in rats

BACKGROUND/PURPOSE

Ischemia-reperfusion injury is encountered frequently in conditions that diminish intestinal blood flow. Caffeic acid phenethyl ester (CAPE), which is a specific component of the honeybee hive product propolis, exhibits potential antioxidant properties. This experimental study was designed to determine the effect of CAPE on ischemia-reperfusion injury in rat intestine.

METHODS

Fifty rats were divided into 5 groups; sham (SH), saline ischemia (SI), saline reperfusion (SR), CAPE ischemia (CI), and CAPE reperfusion (CR). Either CAPE, 10 micromol/kg, or saline was administered intraperitoneally 30 minutes before ischemia. Intestinal ischemia for 30 minutes and reperfusion for 60 minutes were applied. Ileum specimens were obtained to determine the tissue levels of malondialdehyde, superoxide dismutase, catalase, and histological changes.

RESULTS

Malondialdehyde levels in the CR group did not increase after reperfusion when compared with the CI group. However, statistically significant differences were observed between the SR and SI groups. Additional mucosal injury in the CR group when compared with the CI group was not observed. Whereas, there was a statistically significant increase in mucosal injury in the SR group. Reperfusion did not cause further injuries through both biochemical and histological parameters in the CR group.

CONCLUSIONS

Results of this study showed that prophylactic administration of CAPE in ischemic condition prevents reperfusion injuries by eliminating oxygen radicals and inhibiting polymorphonuclear leukocyte infiltration. CAPE may be useful in combating the diseases of oxidative stress.

A single cell model of myocardial reperfusion injury: changes in intracellular Na+ and Ca2+ concentrations in guinea pig ventricular myocytes

To investigate the contribution of the changes in intracellular Na+ and Ca2+ concentrations ([Na+]i and [Ca2+]i) to myocardial reperfusion injury, we made an ischemia/reperfusion model in intact guinea pig myocytes. Myocardial ischemia was simulated by the perfusion of metabolic inhibitors (3.3 mM amobarbital and 5 microM carbonyl cyanide m-chlorophenylhydrazone) with pH 6.6 and reperfusion was achieved by the washout of them with pH 7.4. [Na+]i increased from 7.9 +/- 2.0 to 14.0 +/- 3.4 mM (means +/- S.E., p < 0.01 ) during 7.5 min of simulated ischemia (SI) and increased further to 18.8 +/- 3.0 mM at 7.5 min after reperfusion. [Ca2+]i, expressed as the ratio of fluo 3 fluorescence intensity, increased to 133 +/- 8% (p < 0.01) during SI and gradually returned to the control level after reperfusion. Intracellular pH decreased from 7.53 +/- 0.04 to 6.31 +/- 0.04 (p < 0.01) and recovered quickly after reperfusion. Reperfusion with the acidic solution or the continuous perfusion of hexamethylene amiloride (2 microM) prevented the reperfusion-induced increase in [Na+]i. When the duration of SI was prolonged to 15 min, the cell response after reperfusion varied, 16 of 37 cells kept quiescent, 21 cells showed spontaneous Ca2+ waves, and 4 cells out of these 21 cells became hypercontracted. In quiescent cells, both [Na+]i and [Ca2+]i decreased immediately after reperfusion. In cells with Ca2+ waves, [Na+]i transiently increased further at the early phase of reperfusion, while [Ca2+]i declined. In hypercontracted cells, [Na+]i increased as much as in 'Ca2+ wave' cells, but [Ca2+]i increased extensively and both ion concentrations continued to increase. Reperfusion with the Ca2+-free solution prevented both the [Ca2+]i increase and morphological change. In the presence of ryanodine (10 microM), the increase in [Ca2+]i after reperfusion was augmented and some cells became hypercontracted. We concluded that (1) Na+/H+ exchange is active both during SI and reperfusion, resulting in the additional [Na+]i elevation on reperfusion, (2) the [Na+]i level after reperfusion and the following Ca2+ influx via Na+/Ca2+ exchange are crucial for reperfusion cell injury, and (3) the Ca2+ buffering capacity of sarcoplasmic reticulum would also contribute to the Ca2+ regulation and cell injury after reperfusion.

Oxidative damage of cardiomyocytes is limited by extracellular regulated kinases 1/2-mediated induction of cyclooxygenase-2

Oxidative stress causes cardiac damage following ischemia/reperfusion and in response to anthracyclines. Extracellular signal-regulated kinases (ERK) 1/2 are activated by oxidative stress in cardiac myocytes and protect cardiac myocytes from apoptosis. Prostaglandins (PG) also protect cells from injury in a number of tissues, including the cardiomyocyte. Cyclooxygenase (COX) the rate-limiting enzyme in PG biosynthesis has two isoforms, the constitutive COX-1 and an inducible COX-2. Here, we examined the effects of two oxidative stresses, hydrogen peroxide (H2O2) and the anthracycline doxorubicin on the activity of ERK1/2 and the expression of COX isoforms and PG formation in neonatal rat primary cardiomyocytes. These cells expressed COX-1 at rest and both COX isoforms on treatment with phorbol 12-myristate 13-acetate. Exposure to 50 microM H2O2 for 10 min or doxorubicin at 10 and 100 micrograms/ml caused expression of COX-2 that was prevented by free radical scavengers. COX-2 induction was associated with activation of ERK1/2 and the specific ERK-inhibitor PD098059 abolished COX-2 expression. Treatment of cells with decoy oligonucleotides corresponding to COX-2 promoter elements implicated the AP-1 and NF-kappaB-2 but not the NF-kappaB-1 in the transcription of COX-2. Induction of COX-2 mRNA and protein was accompanied by increased prostacyclin formation, which was abolished by the selective COX-2 inhibitor, NS-398, and PD098059. H2O2 and doxorubicin enhanced the release of lactate dehydrogenase and free radical scavengers prevented this. NS-398 enhanced the release of lactate dehydrogenase in response to H2O2 and doxorubicin, whereas the injury was prevented by iloprost, a stable prostacyclin analogue. In cardiomyocytes cell injury by H2O2 and doxorubicin is limited by an increase in prostacyclin formation that reflects induction of COX-2 mediated by ERK1/2 activation.

Antioxidant function of the mitochondrial protein SP-22 in the cardiovascular system

The mitochondrial protein SP-22 has recently been reported to be a member of the thioredoxin-dependent peroxide reductase family, suggesting that it may be one of the antioxidant systems in mitochondria, which are the major site of reactive oxygen intermediate generation. The aim of this study was to examine whether SP-22 is involved in mitochondrial antioxidant mechanisms and whether its expression is induced by oxidative stresses, particularly those in mitochondria. The expression of SP-22 protein was enhanced by about 1.5-4.6-fold when bovine aortic endothelial cells (BAEC) were exposed to various oxidative stresses, including mitochondrial respiratory inhibitors which increased the superoxide generation in BAEC mitochondria. The expression of SP-22 mRNA increased 2.0-3.5-fold with a peak at 3-6 h after exposure to Fe2+/dithiothreitol or a respiratory inhibitor, antimycin A. BAEC with an increased level of SP-22 protein caused by pretreatment with mild oxidative stress became tolerant to subsequent intense oxidative stress. On the other hand, BAEC that had been depleted of SP-22 with an antisense oligodeoxynucleotide against SP-22 mRNA became more labile to oxidative stress than control BAEC. The induction of SP-22 protein by oxidative stress in vivo was demonstrated in an experimental model of myocardial infarction in rat heart. These findings indicate that SP-22 functions as an antioxidant in mitochondria of the cardiovascular system.

Changes in cardiac electrophysiology, morphology, tissue biochemistry and vascular reactions in glutathione depleted animals

The effects of acute and chronic glutathione depletion (single i.p. injection of 3 mmol/kg L-buthionine-S,R-sulphoximine and 2 mmol/kg for 4 days) on heart action potential (AP) characteristics, electronmicroscopy, cytochemistry and biochemistry and vascular contractility and nitric oxide-mediated relaxation were studied in rats and guinea pigs. In guinea pig cardiac preparations both acute and chronic glutathione depletion caused a significant decrease of maximum rate of rise of depolarization phase and duration of action potential AP(APD) at 25, 50, and 90% of repolarization but did not modify the other AP parameters. The contractile responses of helically cut aortic strips to norepinephrine were not altered by chronic glutathione depletion but the relaxing responses of precontracted preparations to acetylcholine were significantly reduced both in rats and guinea pigs. Morphologically there were indications of permeability changes, intracellular and interstitial edema and myofilament damage in the myocardium. There was also a decrease in cytochromoxydase and succinyl dehydrogenase activities both in rats and guinea pigs. The present data suggest that glutathione depletion may influence the Na+ and K+ channel activities, causes morphological and biochemical changes in cardiac preparations and may interfere with nitric oxide generation or its action in aortic strips.

The Influence of Ischemia-Reperfusion Injury on Plasma Malondialdehyde in Children Undergoing Cardiopulmonary Bypass

Toxic oxygen free radicals (OFRs) are produced after ischemia-reperfusion injury, which can be observed during cardiopulmonary bypass (CPB). In a pilot study conducted in a tertiary care pediatric intensive care unit, we sought to determine plasma malondialdehyde (MDA) levels, a marker of OFR production, in children undergoing CPB, and to relate the findings to gastric intramucosal pH and PCO2 (pHi, PiCO2) and serum lactate. Thirteen nonconsecutive children (age: 56 ± 58 months) were included in the study. After induction of general anesthesia and endotracheal intubation, a tonometer nasogastric tube was positioned in the stomach; gastric pHi and PiCO2, arterial PCO2 (PaCO2), MDA, and lactate were measured 1 hour later (time 0) and 1 to 48 hours after initiation of CPB (times 1, 4, 8, 12, 16, 20, 24, 32, 40, and 48). Data for each variable were compared with baseline values for statistical significance. Free MDA levels increased by more than 50% in 11 patients (85%) and a statistically significant difference was found between the highest and the baseline free MDA concentrations (p < .0025). Low gastric pHi after the first 8 hours post-CPB was significantly associated with a late rise in MDA levels. A stepwise multivariate regression analysis showed that the highest PiCO2:PaCO2 ratio was correlated to the highest MDA level (p < .0001). A low gastric pHi later than 8 hours after CPB or a high PiCO2: PaCO2 ratio, as observed in this study, may indicate secondary splanchnic hypoperfusion with increased OFR production.

Impaired antioxidant defence in guinea pig heart tissues treated with halothane

PURPOSE

To investigate the effects of halothane and halothane plus vitamin E treatment on myocardial free radical metabolism in guinea pigs.

METHODS

Four groups of seven animals were studied: control, halothane, halothane plus vitamin E and vitamin E groups. In the halothane group, halothane 1.5% in oxygen was given for 90 min over three days. In the halothane plus vitamin E group, 300 mg.kg-1.day-1 vitamin E im was started three days before the first halothane treatment and continued for three days. Following sacrifice, the hearts were assayed for superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) and malondialdehyde (MDA) level was determined. Electron spin resonance (ESR) analysis and electron microscopy (EM) were also performed.

RESULTS

In the halothane group, SOD activities and MDA concentrations were increased compared with control and GSH-Px and CAT activities were decreased. In the halothane plus vitamin E group, there were no differences in enzyme activity compared with halothane alone but the MDA level was decreased. In the vitamin E group, enzyme activities were increased compared with control. Mainly the CF3CHCl radical was identified by ESR analysis in heart tissues exposed to halothane and the concentration of this radical was reduced by vitamin E. Electron microscopy showed cytoplasmic vacuolisation and dilation in sarcoplasmic reticulum in the heart tissues exposed to halothane: both were prevented by vitamin E.

CONCLUSION

Although halothane causes impairment in enzymatic antioxidant defence potential, due to lowered GSH-Px and CAT activity, and accelerates peroxidative reactions in the tissues affected, no subcellular damage occurred. Vitamin E may protect tissues against free radical attack by scavenging toxic free radicals formed in heart tissue during halothane anaesthesia.

Effect of prolonged hypothermic ischemia and reperfusion on oxygen consumption and total mechanical energy in rat myocardium: participation of mitochondrial oxidative phosphorylation

BACKGROUND

To reduce ischemia-reperfusion injury of hearts in open heart surgery and transplantation, it is important to know the critical period of ischemia in which donor hearts can sustain their function satisfactorily. Cardiac function has been deduced from oxygen consumption (VO2) and mechanical parameters such as pressure-volume area (PVA). Inhibited mitochondrial oxidative phosphorylation during ischemia indicates that ATP production is uncoupled from VO2. Therefore, both mitochondrial oxidative phosphorylation and total mechanical energy should be examined to evaluate cardiac function after ischemia and reperfusion.

METHODS

Isolated rat hearts were stored in Euro-Collins solution at 4 degrees C for 8, 12, and 24 hr and reperfused in a working mode with a modified Krebs-Henseleit bicarbonate solution. PVA and VO2 were examined in isovolumic contraction, and ventricular contractility and total mechanical energy were assessed, respectively, by the end-systolic elastance (Ees) and PVA. Mitochondrial oxidative phosphorylation in the presence of succinate and mitochondrial lipid peroxide levels were estimated in similarly treated rat hearts.

RESULTS

Ees was decreased by ischemia without significant difference. The VO2 to PVA ratio remained linear, although VO2 at null PVA and the VO2 to PVA ratio significantly increased after 12 hr of ischemia. Mitochondrial oxidative phosphorylation was decreased significantly by reperfusion after 12 hr of ischemia. Mitochondrial lipid peroxide levels were increased significantly after 12 hr of ischemia.

CONCLUSIONS

In isolated rat hearts, decreased efficiency for energy conversion from consumed oxygen to cardiac performance occurs between 8 and 12 hr of hypothermic ischemia, which was coincident with disturbed mitochondrial oxidative phosphorylation, to which lipid peroxidation may contribute.

Protective effect of the angiotensin-converting enzyme inhibitor captopril on postischemic myocardial damage in perfused rat heart

This study was undertaken to examine whether a sulfhydryl-containing angiotensin-converting enzyme (ACE) inhibitor, captopril, improves postischemic cardiac function and myocardial metabolism in the perfused working rat heart, and to elucidate the mechanism by which captopril protects the myocardium from postischemic damage. Isolated rat hearts were perfused by the working heart technique for 15 min. Ischemia was then induced for 30 min by lowering the afterload pressure and coronary flow to zero. After ischemia, hearts were reperfused for 30 min by returning afterload pressure to 60 mmHg. Captopril, a non-sulfhydryl-containing ACE inhibitor, enalapril, or a type 1 angiotensin II receptor antagonist, DuP 753, was added to the perfusate 5 min before ischemia, and the treatment was continued during the first 10-min period of reperfusion. In all groups there was no significant difference in pressure-rate product, coronary flow, tissue levels of ATP, total adenine nucleotides (TANs), energy charge potential (ECP), or creatine phosphate (CrP) before and during ischemia. During reperfusion following ischemia, captopril significantly improved the recovery of pressure-rate product, coronary flow, and tissue levels of ATP, TAN, ECP, and CrP, but neither enalapril nor DuP 753 had an effect. In conclusion, captopril improved postischemic cardiac function and myocardial metabolism in the perfused rate heart and its effect was independent of the blunting of angiotensin II formation.

Interrelationship between cellular calcium homeostasis and free radical generation in myocardial reperfusion injury

This review describes the interrelationship between two important biological factors, intracellular calcium overloading and oxygen-derived free radicals, which play a crucial role in the pathogenesis of myocardial ischemic reperfusion injury. Free radicals are generated during the reperfusion of ischemic myocardium, and polyunsaturated fatty acids in the membrane phospholipids are the likely targets of the free radical attack. On the other hand, activation of phospholipases can provoke the breakdown of membrane phospholipids which results in the activation of arachidonate cascade leading to the generation of prostaglandins, and oxygen free radicals can be produced during the interconversion of the prostaglandins. In conclusion, it has been emphasized that the two seemingly different causative factors of reperfusion injury, intracellular calcium overloading and free radical generation are, in fact, highly interrelated.

Susceptibility of caffeine- and Ins(1,4,5)P3-induced contractions to oxidants in permeabilized vascular smooth muscle

Two principal pathways of Ca2+ release from the sarcoplasmic reticulum of excitable and non-excitable cells have been described: one pathway dependent on the second messenger D-myo-inositol 1,4,5-trisphosphate (Ins(1,4,5)P3), and a second pathway sensitive to Ca2+ and regulated by caffeine and ryanodine. It was found that the Ca(2+)-pump activity of vascular smooth muscle sarcoplasmic reticulum is inhibited by superoxide anion radicals (O2.-); however, the effects of reactive oxygen intermediates on sarcoplasmic reticulum Ca2+ release in vascular muscle cells are not well defined. The purpose of the present study was to evaluate the effects of reactive oxygen intermediates generated from the hypoxanthine/xanthine oxidase reaction system on contractions induced by caffeine, Ins(1,4,5)P3 and norepinephrine in staphylococcal alpha-toxin-permeabilized rabbit mesenteric arteries. This system generates O2.-, H2O2, and hydroxyl radicals. We wished to identify which class of reactive oxygen intermediates is responsible for the associated loss of vascular smooth muscle contractile function. Caffeine and Ins(1,4,5)P3 produced a transient contraction when the sarcoplasmic reticulum of the permeabilized, preparations was preloaded with pCa 7.0 solution for 5 min before washing with 0.5 mM EGTA solution; norepinephrine also produced a transient contraction. Exposure of the preparations to hypoxanthine/xanthine oxidase (for 30 min) attenuated caffeine-induced contraction, but was without effect on Ins(1,4,5)P3-induced contraction. The observed effect of hypoxanthine/xanthine oxidase exposure was superoxide dismutase-inhibitable, suggesting O2.- involvement. Hypoxanthine/xanthine oxidase also inhibited norepinephrine-induced contraction. The effect of hypoxanthine/xanthine oxidase on norepinephrine contraction was protected by catalase, but not by superoxide dismutase and dimethyl sulfoxide; exogenously added H2O2 mimicked the effect of hypoxanthine/xanthine oxidase exposure. H2O2, added exogenously, was without effect on Ins(1,4,5)P3-induced contraction. It is suggested that the pathway of Ca2+ release from the sarcoplasmic reticulum dependent on Ins(1,4,5)P3 is insensitive to O2.-. Instead, caffeine-induced Ca2+ release mechanisms may be susceptible to O2.- and H2O2, rather than O2.- and hydroxyl radicals, may be the active agent in the norepinephrine-induced contraction. Our results are also consistent with the view that the attenuation by H2O2 of the norepinephrine-induced contraction may be linked to the receptor-associated pathway of Ins(1,4,5)P3 formation, but not to degradation processes of Ins(1,4,5)P3.

The effects of gentamicin on the activities of glutathione peroxidase and superoxide dismutase enzymes and malondialdehyde levels in heart tissues of guinea pigs

In this study, superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities and malondialdehyde (MDA) levels were measured in heart tissues from guinea pigs treated with gentamicin and gentamicin plus vitamin E combination. Mean values were compared with those of the controls treated with only physiological saline solution. The activities of SOD and GSH-Px were found to be lower and the MDA level higher in the hearts from gentamicin-treated animals compared with those of the controls. In the gentamicin plus vitamin E group, however, tissue SOD activity was found to be increased and MDA level decreased significantly relative to the gentamicin group. GSH-Px activity was lowest in this group. Results suggest that gentamicin suppresses SOD and GSH-Px activities in heart tissue, thereby making the tissue more vulnerable to oxidative stress and peroxidative attacks, an important indicator of which is increased MDA level in the heart tissues from gentamicin-treated guinea pigs. This effect might be deleterious when gentamicin is used after cardiac surgery since a potential risk of free radical injury exists in the heart tissue during and/or after cardiac surgery owing to ischaemia and reperfusion processes, and, possibly, in the management of the patients with certain types of heart disease. Our results showed that vitamin E given concomitantly with gentamicin could protect the heart tissue against free radical injury.

Oxy free radical system in heart failure and therapeutic role of oral vitamin E

Twenty patients of heart failure and ten matched healthy controls were included in the trial. Out of these 20 patients of heart failure, 12 patients were also studied prospectively. Plasma levels of superoxide anion and malonyldialdehyde were increased while the levels of superoxide dismutase, catalase and glutathione reductase were decreased in patients of heart failure as compared to control subjects. The alteration in oxidative stress and antioxidant system did not correlate with the age and sex of patients or the etiology of heart failure. With the increasing severity of heart failure the malonyldialdehyde and superoxide anion increased significantly and catalase, glutathione reductase and superoxide dismutase levels decreased. The group of heart failure patients with ejection fraction < 40% (n = 7) exhibited significantly higher levels of malonyldialdehyde than those with an ejection fraction > 40% (n = 13). The superoxide anion and malonyldialdehyde levels were significantly higher in patients of heart failure in the pre-treatment state as compared to those in post-treatment state. Conversely catalase, glutathione reductase and superoxide dismutase were higher in the post-treatment period as compared to their values before treatment. The addition of vitamin E in doses of 400 mg once a day orally for 4 weeks significantly reduced the malonyldialdehyde and superoxide anion levels and produced an elevation of the antioxidant enzymes. Thus, there is an apparent normalisation of the indices of oxidative stress following treatment of heart failure and a markedly improved response on vitamin E supplementation which may be more beneficial.

Dietary fish oil decreases superoxide generation by human neutrophils: relation to cyclooxygenase pathway and lysosomal enzyme release

12 volunteers with slightly elevated serum triglyceride levels were given 30 ml fish oil (5.4 g eicosapentaenoic acid and 3.2 g docosahexaenoic acid) daily for 4 weeks. The percentage of eicosapentaenoic acid increased (P < 0.01) and the percentage of linoleic (P < 0.05) and arachidonic acid (P < 0.01) decreased in neutrophil phospholipids. Superoxide generation by neutrophils initiated by phorbol myristate acetate decreased significantly from 48.6 +/- 8.8 to 34.7 +/- 11.1 nmol/10 min/400,000 cells (means +/- SD, P < 0.01, n = 11). Treatment of the cells with the cyclooxygenase inhibitor indomethacin had no significant influence on the decrease in superoxide generation, indicating that cyclooxygenase products were not involved in this effect of fish oil. Neutrophil elastase release did not change significantly, suggesting that neutrophil lysosomal enzyme release and superoxide generation may be under separate control. In conclusion, dietary fish oil decreased superoxide generation by human neutrophils without involvement of the cyclooxygenase pathway and without altering neutrophil lysosomal enzyme release. Dietary fish oil could have beneficial effects in pathological conditions with activated neutrophils, such as ischaemic heart disease.