Assay for lipid peroxides in animal tissues by thiobarbituric acid reaction

A radical is any molecule that contains one or more unpaired electrons. Radicals are normally generated in many metabolic pathways. Some of these radicals can exist in a free form and subsequently interact with various tissue components resulting in dysfunction. The potential role of oxygen- or xenobiotic-derived free radicals in the pathology of several human diseases has stimulated extensive research linking the toxicity of numerous xenobiotics and disease processes to a free radical mechanism. However, because free radical-mediated changes are pervasive and often poorly understood, the question of whether such species are a major cause of tissue injury and human disease remains equivocal. This review discusses cellular sources of various radical species and their reactions with vital cellular constituents. Examples of purported free radical-mediated disorders are discussed in detail to provide insights into the controversy over whether free radicals are important mediators of tissue injury.

Free radicals as mediators of tissue injury and disease.

ObjectivesIn view of the critical role of intracellular Ca2+-overload in the genesis of myocyte dysfunction and the ability of reactive oxygen species (ROS) to induce the intracellular Ca2+-overload, this article is concerned with analysis of the existing literature with respect to the role of oxida

Role of oxidative stress in cardiovascular diseases.

Background—The predictive value of heart rate variability (HRV) in chronic heart failure (CHF) has never been tested in a comprehensive multivariate model using short-term laboratory recordings designed to avoid the confounding effects of respiration and behavioral factors. Methods and Results—A multivariate survival model for the identification of sudden (presumably arrhythmic) death was developed with data from 202 consecutive patients referred between 1991 and 1995 with moderate to severe CHF (age 529 years, left ventricular ejection fraction 247%, New York Heart Association class 2.30.7; the derivation sample). Time- and frequency-domain HRV parameters obtained from an 8 recording of ECG at baseline and during controlled breathing (12 to 15 breaths/min) were challenged against clinical and functional parameters. This model was then validated in 242 consecutive patients referred between 1996 and 2001 (validation sample). In the derivation sample, sudden death was independently predicted by a model that included low-frequency power (LFP) of HRV during controlled breathing 13 ms 2 and left ventricular end-diastolic diameter 77 mm (relative risk [RR] 3.7, 95% CI 1.5 to 9.3, and RR 2.6, 95% CI 1.0 to 6.3, respectively). The derivation model was also a significant predictor in the validation sample (P0.04). In the validation sample, LFP 11 ms 2 during controlled breathing and 83 ventricular premature contractions per hour on Holter monitoring were both independent predictors of sudden death (RR 3.0, 95% CI 1.2 to 7.6, and RR 3.7, 95% CI 1.5 to 9.0, respectively). Conclusions—Reduced short-term LFP during controlled breathing is a powerful predictor of sudden death in patients with CHF that is independent of many other variables. These results refine the identification of patients who may benefit from prophylactic implantation of a cardiac defibrillator. (Circulation. 2003;107:565-570.)

Short-term heart rate variability strongly predicts sudden cardiac death in chronic heart failure patients.

Background: Myocardial ischemia–reperfusion represents a clinically relevant problem associated with thrombolysis, angioplasty and coronary bypass surgery. Injury of myocardium due to ischemia–reperfusion includes cardiac contractile dysfunction, arrhythmias as well as irreversible myocyte damage. These changes are considered to be the consequence of imbalance between the formation of oxidants and the availability of endogenous antioxidants in the heart. Observations: An increase in the formation of reactive oxygen species during ischemia–reperfusion and the adverse effects of oxyradicals on myocardium have now been well established by both direct and indirect measurements. Although several experimental studies as well as clinical trials have demonstrated the cardioprotective effects of antioxidants, some studies have failed to substantiate the results. Nonetheless, it is becoming evident that some of the endogenous antioxidants such as glutathione peroxidase, superoxide dismutase, and catalase act as a primary defense mechanism whereas the others including vitamin E may play a secondary role for attenuating the ischemia–reperfusion injury. The importance of various endogenous antioxidants in suppressing oxidative stress is evident from the depression in their activities and the inhibition of cardiac alterations which they produce during ischemia–reperfusion injury. The effects of an antioxidant thiol containing compound, N -acetylcysteine, and ischemic preconditioning were shown to be similar in preventing changes in the ischemic-reperfused hearts. Conclusions: The available evidence support the role of oxidative stress in ischemia–reperfusion injury and emphasize the importance of antioxidant mechanisms in cardioprotection.

Status of myocardial antioxidants in ischemia–reperfusion injury

Peroxidation of membrane phospholipid polyunsaturated fatty acids is considered a major mechanism of the damage occurring on reperfusion of the myocardium after a prolonged period of ischemia. The evidence in support of this mechanism of damage is based on tissue malondialdehyde quantitation by the thiobarbituric acid test (TBA test). In an attempt to verify this topic, we have subjected isolated and Langendorff-perfused rabbit hearts to a period of 60 min of severe ischemia plus 30 min of reperfusion. At appropriate time points, malondialdehyde was determined in the tissue by means of TBA test and directly by reversed-phase, high-pressure liquid chromatography (HPLC). We have found no correlation between the two compared assays. During reperfusion, there was the formation of non-lipid-related, malondialdehyde-like, TBA-reactive substance that leads to overestimation of the extent of lipid peroxidation. On the contrary, by direct HPLC quantitation, there was a decrease of tissue malondialdehyde during ischemia and during the early phases of reperfusion. Our results demonstrate that TBA test is not a reliable index of lipid peroxidation in organ systems.

Evaluation of phospholipid peroxidation as malondialdehyde during myocardial ischemia and reperfusion injury

Rats given monocrotaline develop severe right ventricular hypertrophy often accompanied by ascites and pleural effusions. In rats with right ventricular hypertrophy and no serous effusions (“hypertrophy” group), ventricular concentrations of noradrenaline were reduced but ventricular contents were unchanged. Atrial concentrations of noradrenaline were unaffected. Those with more severe right ventricular hypertrophy and serous effusions (“failure” group) had greatly reduced concentrations of noradrenaline in all four chambers, particularly on the right side; the right and left ventricular contents of noradrenaline were also diminished.

The distributions of ir-ANP, ir-bombesin and ir-neurotensin in the normal rat heart are presented. ANP concentration fell to 33% in the right atrium and 46% in the left atrium of “failure” animals and to 57% in the right atrium of “hypertrophy” animals. Right ventricular content of ANP, normally low, increased more than two-fold in both groups, the concentration remaining unchanged. Left ventricular content of ANP decreased in the “failure” group. Concentrations of bombesin and neurotensin fell in both ventricles of both groups. Ventricular contents of bombesin did not change, but ventricular contents of neurotensin decreased, especially on the right side.

Plasma ANP rose nearly six-fold while plasma bombesin and neurotensin fell in the “failure” group. Plasma peptide concentrations were unchanged in the “hypertrophy” group.

The studies show the utility of die monocrotaline model in distinguishing between the effects of hypertrophy and those associated specifically with the syndrome of congestive cardiac failure.

Noradrenaline, atrial natriuretic peptide, bombesin and neurotensin in myocardium and blood of rats in congestive cardiac failure

Metabolic changes during post-ischaemic reperfusion.

There is evidence that oxygen free radicals play a role in myocardial ischemic and reperfusion injury. We investigated the effect of ischemia and reperfusion on glutathione status. Reperfusion after prolonged ischemia (60 min) induced an important release of reduced (GSH) and oxidized (GSSG) glutathione, concomitant with an increase of tissue GSSG and no recovery of mechanical function, indicating that reperfusion results in oxidative stress. These alterations are associated with tissue and mitochondrial calcium accumulation, loss of mitochondrial function, and membrane damage. We also determined the arteriocoronary sinus difference for GSH and GSSG of 16 CAD patients undergoing coronary artery bypass. Patients were divided in two groups according to the length of clamping period: 25 +/- 2 min (group 1), and 55 +/- 6 min (group 2). In group 1, reperfusion resulted in a transient release of GSH, GSSG, CPK, and lactate, with return to preclamping values in 10 minutes. In group 2, reperfusion determined a sustained and pronounced release of GSH, GSSG, CPK, and lactate during declamping, suggesting the occurrence of an oxidative stress. Using an in vitro model, administration of alpha-tocopherol bound with albumin showed protection of mitochondrial function, improved recovery of contraction, and reduced oxidative stress during reperfusion.

Oxygen Free Radical‐Mediated Heart Injury in Animal Models and during Bypass Surgery in Humans Effects of α‐Tocopherola

We studied the acute and chronic effects of propionyl-L-carnitine (PLC) on mechanical function of isolated rabbit heart. Propionyl-L-carnitine was either directly delivered in the perfusate (10-9 to 10-3 M) or intraperitoneally injected (250 mg/kg) for 10 days to the animals. When added acutely, propionyl-L-carnitine had no effect on inotropism, heart rate, or coronary perfusion pressure. When added chronically, propionyl-L-carnitine induced a positive inotropic effect, with no changes in heart rate or in coronary perfusion pressure, and it ameliorated the pressure-volume relationship. This effect of propionyl-L-carnitine was independent of the calcium concentration of the perfusion medium, but it was correlated with an increase in the myocardial content of propionyl-L-carnitine. The effect was not apparent after 5 days of treatment, although the tissue content of propionyl-L-carnitine remained unchanged. These data suggest that propionyl-L-carnitine, when given chronically, exerts a positive inotropic effect.

E. Condorelli

Papers

Evaluation of phospholipid peroxidation as malondialdehyde during myocardial ischemia and reperfusion injury

Noradrenaline, atrial natriuretic peptide, bombesin and neurotensin in myocardium and blood of rats in congestive cardiac failure

Metabolic changes during post-ischaemic reperfusion.

Oxygen Free Radical‐Mediated Heart Injury in Animal Models and during Bypass Surgery in Humans Effects of α‐Tocopherola

Effect of Propionyl-L-Carnitine on Mechanical Function of Isolated Rabbit Heart