L-arginine reduces endothelial inflammation and myocardial stunning during ischemia/reperfusion

BACKGROUND

This study evaluated whether the nitric oxide precursor L-arginine could reduce ischemia/reperfusion injury by preventing leukocyte-endothelial interactions.

METHODS

Normothermic regional ischemia was induced in the open-chest working pig heart for 30 minutes followed by 90 minutes of reperfusion. A preischemic 10-minute intravenous infusion of 4 mg.kg-1.min-1 of L-arginine (n = 12) was compared with 12 control pigs. Nitric oxide release was measured from the coronary sinus using an amperometric probe. Left ventricular function, malonaldehyde, creatine kinase, myocardial oxygen extraction, and the soluble adhesion molecules (intracellular adhesion molecule-1, endothelial leukocyte adhesion molecule-1, and vascular cell adhesion molecule-1) were measured.

RESULTS

Nitric oxide release was significantly reduced from baseline throughout ischemia/reperfusion only in the control group. Systolic and diastolic function, and myocardial oxygen extraction were also significantly decreased during early reperfusion in the control compared with the L-arginine group. Peak creatine kinase release was not significantly different between groups. The incidence of ventricular fibrillation, malonaldehyde release, and soluble intracellular adhesion molecule-1, endothelial leukocyte adhesion molecule-1, and vascular cell adhesion molecule-1 were each significantly decreased during reperfusion in the L-arginine group.

CONCLUSIONS

L-Arginine reduced lipid peroxidation, plasma levels of soluble adhesion molecules, myocardial stunning, and arrhythmias. These results support an excessive endothelial injury/inflammatory response after regional ischemia/reperfusion that can be ameliorated through augmented nitric oxide.

Improved 4- and 6-hour myocardial preservation by hypoxic preconditioning

BACKGROUND

A brief hypoxic episode can precondition myocardium against a subsequent ischemic-reperfusion injury. The present study sought to determine whether intracellular ionic alterations, induced expression of heat-shock proteins (hsps), and/or catalase are involved in the cellular mechanisms by which hypoxic preconditioning can preserve postischemic function in a model of prolonged hypothermic storage.

METHODS AND RESULTS

Two groups of isolated working rat hearts were studied: control (CON) and hypoxically preconditioned (HP) hearts. Hearts were arrested at 4 degrees C with St Thomas' cardioplegic solution and immersion-stored for either a 4- or 6-hour period. Myocardial function (ie, heart rate, aortic flow, coronary flow, developed pressure, and its first derivative dP/dtmax) was determined at baseline, after preconditioning, and during reperfusion. At similar time points, myocardial [Na+]i, [K+]i, [Mg2+]i, and [Ca2+]i were measured using an atomic absorption spectrophotometer, and the induction of hsp 70 and catalase mRNAs was assayed using Northern blot analysis. After 4 and 6 hours of hypothermic storage, aortic flow, dP/dtmax, and [K+]i were increased, whereas [Na+]i and [Ca2+]i were decreased significantly in the HP group compared with the CON group. Steady state mRNA levels of catalase and hsp 70 were increased from baseline levels only in the HP group, with a peak (2.8- and 2.4-fold versus baseline) after 4 hours of storage.

CONCLUSIONS

Our results indicate that intracellular ionic alterations and upregulation of catalase and hsp 70 gene expression may contribute to the mechanisms underlying hypoxic preconditioning, leading to improved postischemic function during prolonged hypothermic storage of hearts.

Drug-induced heat-shock preconditioning improves postischemic ventricular recovery after cardiopulmonary bypass

BACKGROUND

Heat-stress preconditioning of mammalian heart has been found to confer protection against ischemic reperfusion injury. Heat shock is generally provided by warming the animal by mechanical means, which is often impractical in a clinical setting. Amphetamine, a sympathomimetic drug, can elevate the body temperature as a result of enhanced endogenous lipolysis. In this study, we examined the effects of heat shock induced by amphetamine on postischemic myocardial recovery in a setting of coronary revascularization for acute myocardial infarction.

METHODS AND RESULTS

Adult Yorkshire swine were injected with amphetamine (3 mg/kg IM) (n = 12), and body temperature was continuously monitored. For control studies, the pigs were injected with saline (n = 12). Five swine in each group were killed after 3 hours to obtain biopsies of vital organs to measure heat-shock protein (HSP) mRNAs. After 40 hours, the remaining 7 pigs in each group were placed on cardiopulmonary bypass, and the isolated, in situ heart preparations were subjected to 1 hour of occlusion of the left anterior descending coronary artery followed by 1 hour of global hypothermic cardioplegic arrest and 1 hour of reperfusion. Postischemic myocardial performance was monitored by measuring left ventricular (LV) pressure, its dP/dt, myocardial segment shortening, and coronary blood flow. Cellular injury was examined by measurement of creatine kinase release. The antioxidant enzymes superoxide dismutase and catalase were also assayed. Amphetamine treatment was associated with the induction of mRNAs for HSP 27, HSP 70, and HSP 89 in all the vital organs, including heart, lung, liver, kidney, and brain. Amphetamine also enhanced superoxide dismutase and catalase activities in the heart. Significantly greater recovery of LV contractile functions was noticed, as demonstrated by improved recovery of LV developed pressure (61% versus 52%), LV dP/dtmax (52% versus 44%), and segment shortening (46.2% versus 10%) and reduced creatine kinase release in the amphetamine group.

CONCLUSIONS

The results demonstrate that amphetamine can induce whole-body heat shock that can precondition the heart, enhancing cellular tolerance to ischemia-reperfusion injury. Amphetamine is a sympathomimetic drug that may be used for preconditioning.

Nitric oxide signaling in ischemic heart

OBJECTIVE

Several recent studies have implicated a role of endogenous nitric oxide (NO) in the pathophysiology of myocardial ischemic/reperfusion injury. However, the mechanism by which NO exerts its beneficial/detrimental effects remains unknown. This study examined the intracellular signaling of NO by studying the role of the NO-cGMP signaling pathway on the phospho-diesteratic breakdown and turnover of phosphoinositides during myocardial ischemia and reperfusion.

METHODS

Isolated working rat hearts were made ischemic for 30 min followed by 30 min of reperfusion. A separate group of hearts were pre-perfused with 3 mM L-arginine for 10 min prior to ischemia. The release of NO was monitored using an on-line amperometric sensor. The aortic flow and developed pressure were examined to determine the effects of L-arginine on ischemic/reperfusion injury. For signal transduction experiments, sarcolemmal membranes were radiolabeled by perfusing the isolated hearts with [3H]myoinositol and [14C]arachidonic acid. Hearts were then perfused for 10 min in the presence or absence of L-arginine via the Langendorff mode. Ischemia was induced for 30 min followed by 30 min of reperfusion. Experiments were terminated before L-arginine and after L-arginine treatment, after ischemia, and during reperfusion. Biopsies were processed to determine the isotopic incorporation into various phosphoinositols as well as phosphatidic acid and diacylglycerol. cGMP was assayed by radioimmunoassay and SOD content was determined by enzymatic analysis.

RESULTS

The release of NO was diminished following ischemia and reperfusion and was augmented by L-arginine. L-Arginine reduced ischemic/reperfusion injury as evidenced by the enhanced myocardial functional recovery. cGMP, which remained unaffected by ischemia and reperfusion, was stimulated significantly after L-arginine treatment. The cGMP level persisted up to 10 min of reperfusion and then dropped slightly. Reperfusion of ischemic myocardium resulted in significant accumulation of radiolabeled inositol phosphate, inositol bisphosphate, and inositol triphosphate. Isotopic incorporation of [3H]inositol into phosphatidylinositol, phosphatidylinositol-4-phosphate, and phosphatidylinositol-4,5-bisphosphate was increased significantly during reperfusion. Reperfusion of the ischemic heart prelabeled with [14C]-arachidonic acid resulted in modest increases in [14C]diacylglycerol and [14C]phosphatidic acid. Pretreatment of the heart with L-arginine significantly reversed this enhanced phosphodiesteratic breakdown during ischemia and early reperfusion. However, at the end of the reperfusion the inhibitory effect of L-arginine on the phosphodiesterases seems to be reduced. In L-arginine-treated hearts, SOD activity was progressively decreased with the duration of reperfusion time.

CONCLUSIONS

The results suggest for the first time that NO plays a significant role in transmembrane signaling in the ischemic myocardium. The signaling seems to be transmitted via cGMP and opposes the effects of phosphodiesterases by inhibiting the ischemia/reperfusion-induced phosphodiesteratic breakdown. This signaling effect appears to be reduced as reperfusion progresses. These results, when viewed in the light of free radical chemistry of NO, suggest that such on- and off-signaling of NO may be linked to its interaction with the superoxide radical generated during the reperfusion of ischemic myocardium.

Myocardial adaptation to ischemia by oxidative stress induced by endotoxin

In this study, we examined the effects of oxidative stress adaptation on myocardial ischemic reperfusion injury. Oxidative stress was induced by injecting endotoxin (0.5 mg/kg) into the rat. After 24 h, rats were killed, hearts were isolated, and the effects of ischemia-reperfusion were studied using an isolated working heart preparation. The development of oxidative stress was examined by assessing malonaldehyde production in the heart. The antioxidant defense system was studied by estimating antioxidant enzyme activities and ascorbate- as well as thiol-dependent antioxidant reserve. The results of our study indicated that endotoxin induced oxidative stress within 1 h of treatment; the stress was reduced progressively and steadily up to 24 h. The antioxidant enzymes superoxide dismutase, catalase, glutathione (GSH) peroxidase, and GSH reductase were lowered up to 2 h and then increased. Both thiol- and ascorbate-dependent antioxidant reserve were enhanced, but the enhancement of the former was only transitory. After 24 h, endotoxin provided adequate protection to the heart from the ischemic-reperfusion injury, as evidenced by improved left ventricular function and aortic flow. Our results suggest that the induction of oxidative stress by endotoxin-induced adaptive modification of the antioxidant defense in the heart, thereby reducing ischemic-reperfusion injury.

Detection of oxidative stress in heart by estimating the dinitrophenylhydrazine derivative of malonaldehyde

Accurate estimation of the oxidative stress in heart is necessary because the pathogenesis of many heart diseases are believed to be mediated at least in part from the development of oxidative stress resulting from the generation of oxygen free radicals and reduced antioxidant defense system. The most widely used method for this purpose has been the estimation of malonaldehyde (MDA), a lipid peroxidation product, by the thiobarbituric acid (TBA) reaction method. However, because of the nonspecificity of this method, the results are often erroneous. The present report describes a method using high-performance liquid chromatography (HPLC) to estimate MDA. To develop the oxidative stress, two different models were used: ischaemic-reperfused heart and perfusing the heart with a hydroxyl radical (OH+) generating system. The coronary effluents obtained from the isolated rat heart before ischaemia and during the reperfusion of ischaemic heart, as well as during the perfusion of the heart with the OH+ generating system were collected, derivatized with 2,4-dinitrophenylhydrazine (DNPH) and extracted with pentane. Aliquots of 25 microliters in acetonitrile were injected onto a Beckman Ultrasphere C18 (3 microns) column. The products were eluted isocratically with a mobile phase containing acetonitrile-water-acetic acid (40:60:0.1, v/v/v), measured at 307 nm using a Waters M-490 multichannel UV detector and collected for gas chromatography-mass spectrometry (GC-MS). The peaks were identified by co-chromatography with DNPH derivatives of authentic standards, peak addition, and by GC-MS. The retention time for MDA-DNPH was 5.3 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Oxidative stress adaptation improves postischemic ventricular recovery

Adaptation to various forms of stress has been found to be associated with increased cellular tolerance to myocardial ischemia. In this study, the effects of myocardial adaptation to oxidative stress was examined by injecting rats with endotoxin (0.5 mg/kg) and its non-toxic derivative, lipid A (0.5 mg/kg). Both compounds exerted oxidative stress within 1 h of treatment as evidenced by enhanced malonaldehyde formation. The oxidative stress disappeared steadily and progressively with time in concert with the appearance of the induction of glutathione and antioxidative enzymes that included superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase. After 24 h of endotoxin or lipid A treatment, the amount of oxidative stress and antioxidant enzyme levels were significantly lower and higher, respectively, compared to those at the baseline levels. Corroborating these results, both endotoxin and lipid A provided protection against myocardial ischemia and reperfusion injury as evidenced by a significantly improved postischemic recovery of left ventricular functions. The data presented here demonstrates that a controlled amount of oxidative stress induces the expression of intracellular antioxidants that can result in enhanced myocardial tolerance to ischemia. This suggests that myocardial adaptation to oxidative stress may be a potential tool for reduction of ischemic/reperfusion injury.

Gene expression in acute myocardial stress. Induction by hypoxia, ischemia, reperfusion, hyperthermia and oxidative stress

It is apparent from the above discussion that acute stress, such as ischemia and reperfusion, hypoxia and reoxygenation, hyperthermia and oxidative stress, can rapidly potentiate the induction of genes for certain members of the HSP families and for antioxidants/antioxidant enzymes. Whether the stress response and induction of these genes have a direct role in myocardial protection is not known, but the induction of the expression of these genes are mostly associated with the preservation of myocardial cells from subsequent injury resulting from ischemia, hypoxia and reperfusion. The ubiquitous presence of some of these stress genes, such as for HSP 70 and catalase, in normal unstressed myocardium further suggests a role of these genes in many basic and essential biochemical and metabolic pathways. It is reasonable to speculate that the cells respond to the stress as a consequence of perturbations of one or more of the metabolic pathways by stimulating the induction of the stress genes of that particular pathway in which they participate. Thus, these genes are likely to be involved both in the protection and recovery/repair mechanisms. The precise mechanism by which myocardial cell recognizes and responds to a particular stress agent such as ischemia, hypoxia, hyperthermia or oxidative stress is not clear. While it is tempting to speculate that a generalized mechanism exists, applying to all different modes of stress response and gene induction, whether these agents induce the response via independent pathways or converge within a single point is entirely unclear. However, from the striking resemblance between the pattern of gene expression, especially with regard to HSP and antioxidant genes, it is reasonable to hypothesize the existence of a common and essential pathway of molecular signaling that leads to the expression of these stress genes (Fig. 2). The identification and characterization of the transcription factors that regulate the expression of the genes induced by these forms of stress should greatly facilitate our future understanding of the mechanism of stress response.

Hypoxic preconditioning preserves antioxidant reserve in the working rat heart

OBJECTIVE

The aim was to examine whether intracellular antioxidants play a role in myocardial preservation following hypoxic preconditioning.

METHODS

Isolated working rat hearts were subjected to 30 min ischaemia and 30 min reperfusion. Control hearts were compared to hearts preconditioned with 10 min hypoxia. Left ventricular function and lactate dehydrogenase (LDH) release were measured in each group. Ascorbate dependent (ADAR) and thiol dependent (TDAR) components of the endogenous myocardial antioxidant reserve were assessed using electron spin resonance spectroscopy.

RESULTS

a Hypoxic preconditioning had no effect on left ventricular function after 10 min reoxygenation. During reperfusion, the hypoxically preconditioned hearts had a significantly increased survival rate, aortic flow, developed pressure, and dP/dtmax, and a reduced lactate dehydrogenase release, compared to non-preconditioned controls (P < 0.05). Preconditioned hearts also had significantly higher preservation of baseline ADAR (79%) and TDAR (96%) compared with control hearts, (70%) and (77%), respectively (P < 0.05).

CONCLUSIONS

Hypoxic preconditioning enhances functional recovery and reduces cell necrosis following global ischaemia in the working rat heart. This phenomenon may, in part, be mediated through enhanced ascorbate and thiol components of the antioxidant reserve.

Myocardial salvage by 1-O-hexadecyl-Sn-glycerol: possible role of peroxisomal dysfunction in ischemia reperfusion injury

A recent study demonstrated biochemical and structural alterations of peroxisomes in rat kidney after ischemia/reperfusion. We examined whether peroxisomes play any role in the pathophysiology of myocardial ischemia/reperfusion injury. Isolated perfused rat heart was made ischemic for 30 min by terminating coronary flow (CF), followed by 30-min reperfusion. Experiments were divided into two groups; the experimental group received 1-O-hexadecyl-Sn-glycerol (chimyl alcohol) (25, 50, and 100 microM) before ischemia, and the control group received an equivalent amount of saline. Two of the experimental groups (50 and 100 microM) demonstrated improved postischemic myocardial performance, as demonstrated by accelerated recovery in left ventricular developed pressure (LVDP) and CF, as well as reduction in the incidence of ventricular fibrillation (VF). However, because the heart rate (HR) was significantly reduced in the 100-microM chimyl alcohol group, subsequent studies were performed with 50 microM chimyl alcohol as the optimal dose. Chimyl alcohol (50 microM) also reduced cellular injury, as evidenced by reduced creatine kinase (CK) release, and decreased development of oxidative stress, as evidenced by reduced formation of malonaldehyde (MDA). Peroxisomal catalase activity was decreased in the control group after ischemia/reperfusion, and chimyl alcohol treatment restored the activity of the enzyme. Our results indicate that chimyl alcohol, a precursor of ether-linked phosphoglyceride biosynthesis, can reduce myocardial ischemia/reperfusion injury, possibly by restoring catalase activity and reducing oxidative stress through synthesis of ether lipids, suggesting a possible role of peroxisomal disorder in ischemia/reperfusion injury.

Improved postischemic ventricular functional recovery by amphetamine is linked with its ability to induce heat shock

Heat shock has been shown to increase the cellular tolerances to ischemic injury. In this study, we examined the effects of heat shock induced by amphetamine on postischemic myocardial functional recovery in a setting of coronary revascularization for acute myocardial infarction. Intramuscular injection of amphetamine (3 mg/kg, i.m.) to pigs increased the body temperature to 42.5 degrees C within 1 h, and maintained this temperature for an additional 2 h. Fourty h after the amphetamine injection, the pigs were placed on by cardiopulmonary bypass and then isolated, in situ heart preparations were subjected to 1 h of global hypothermic cardioplegic arrest and 1 h of normothermic reperfusion. Postischemic myocardial performance was monitored by measuring left ventricular (LV) pressure, its dp/dt, myocardial segmental shortening (%SS), and coronary blood flow. Cellular injury was examined by measuring creatine kinase (CK) release. Biochemical measurements included quantification of plasma catecholamines and study of the induction of heat shock gene expression and antioxidative enzymes in the heart tissue. The results of this study indicated significantly greater recovery of LV contractile functions by amphetamine as demonstrated by improved recovery of LVDP (61% vs 52%), dp/dtmax (52% vs 44%), and segmental shortening (46.2% vs 10%). Myocardial CK release was significantly reduced in the amphetamine group. Furthermore, amphetamine pretreatment was associated with the induction of heat shock protein (HSP) 27 mRNA and stimulated Cu/Zn-superoxide dismutase and catalase levels, suggesting that amphetamine mediated improved postischemic ventricular recovery might be linked with its ability to induce heat shock and stimulate antioxidant enzymes.

Cytokines stimulate lipid membrane peroxidation of human sperm

Reactive oxygen species production has been demonstrated to impair sperm function. We have noted the potential for the cytokines IL-1 alpha, IL-1 beta, and TNF alpha to stimulate reactive oxygen species production by fertile donor sperm at levels that are consistent with the levels of IL-1 occurring in human seminal plasma. Reactive oxygen species-related sperm membrane peroxidation may be one mechanism by which cytokines can exert a detrimental effect on male fertility. This study suggests a new mechanism by which cell-mediated immunological male infertility may occur.

Myocardial salvage by chimyl alcohol: possible role of peroxisomal dysfunction in reperfusion injury

The results of this study suggest that reperfusion of ischemic myocardium may lead to the peroxisomal disorder both functionally and biochemically. An alkyl glycerol such as chimyl alcohol can protect the ischemic heart from the reperfusion injury probably by enhancing the plasmalogen synthesis.

High-performance liquid chromatographic method for the simultaneous detection of malonaldehyde, acetaldehyde, formaldehyde, acetone and propionaldehyde to monitor the oxidative stress in heart

Lipid peroxidation (LPO) is the oxidative deterioration of polyunsaturated fatty acids (PUFA) with the production of lipid hydroperoxides, cyclic peroxides, cyclic endoperoxides, and finally fragmentation to ketones and aldehydes (including malonaldehyde, MDA). Estimation of LPO through MDA formation measured by assaying thiobarbituric acid (TBA) reactive products remains the method of choice to study the development of oxidative stress in tissues. However, MDA estimation by TBA reactive products is non-specific and often gives erroneous results. In this report we describe a method using high-performance liquid chromatographic separation to estimate MDA, formaldehyde (FDA), acetaldehyde (ADA), acetone, and propionaldehyde (PDA), the degradation products of oxygen-derived free radicals (ODFR) and PUFA, as presumptive markers for LPO. Oxidative stress was induced in the tissue by perfusing an isolated rat heart with hydroxyl radical generating system (xanthine + xanthine oxidase + FeCl3 + EDTA). The coronary effluents were collected, derivatized with 2,4-dinitrophenylhydrazine (DNPH), and extracted with pentane. Aliquots of 25 microliters in acetonitrile were injected onto a Beckman Ultrasphere C18 (3 microns) column. The products were eluted isocratically with a mobile phase containing acetonitrile-water-acetic acid (40:60:0.1, v/v/v), measured at three different wavelengths (307, 325 and 356 nm) using a Waters M-490 multichannel UV detector and collected for gas chromatography-mass spectrometry (GC-MS) analysis. The peaks were identified by cochromatography with DNPH derivatives of authentic standards, peak addition, UV pattern of absorption at the three wavelengths, and by GC-MS. The retention items of MDA, FDA, ADA, acetone, and PDA were 5.3, 6.6, 10.3, 16.5, and 20.5 min, respectively. The results of our study indicated progressive increase of all five lipid metabolites as a function of the duration of ODFR perfusion. Hydroxyl radical scavengers, superoxide dismutase plus catalase, completely inhibited the formation of these lipid metabolites, demonstrating that the release of lipid metabolites from the isolated heart was indeed in response to oxidative stress. Since MDA, FDA, ADA, acetone, and PDA are the products of ODFR-PUFA interactions, this method allows proper estimation of LPO which monitors the oxidative stress developed during the reperfusion of ischemic myocardium.

Protective role of intracoronary vasoactive intestinal peptide in ischemic and reperfused myocardium

Vasoactive intestinal peptide (VIP) has been shown to exert vasodilatory action and positive ionotropic effect on the heart and to possess free radical-scavenging ability. Because these properties are likely to make this peptide a suitable agent for myocardial preservation, we examined the role of VIP in myocardial ischemia and reperfusion. Isolated rat heart perfused by the Langendorff technique was subjected to 30 min of normothermic ischemia followed by 60 min of reperfusion. A significant amount of VIP was found to be released from the ischemic reperfused heart. The amount of VIP released from the heart increased progressively with the duration of reperfusion and paralleled the release of creative kinase from the heart. In another set of experiments, hearts were divided into two groups. The experimental group received three different doses of VIP (0.1 microM, 0.3 microM and 1 microM) before ischemia. After perfusing the isolated heart with VIP for 15 min, ischemia was induced for 30 min by terminating the coronary flow, which was followed by 60 min of reperfusion. The results of our study indicated a significant improvement of myocardial functions by VIP (0.3 and 1 microM), as evidenced by enhanced left ventricular functions and coronary flow, and reduction of tissue injury, as judged by the decrease in creatine kinase release (0.3 microM only). Intracellular Ca++ ([Ca++]i) transients increased during ischemia and further increased during reperfusion. The increase in [Ca++]i transients was significantly reduced in the VIP-treated hearts. A significant amount of hydroxyl radical was detected in the ischemic reperfused heart, but the quantity of the hydroxyl radical was much lower in the VIP-treated group.(ABSTRACT TRUNCATED AT 250 WORDS)

Antioxidant effectiveness in ischemia-reperfusion tissue injury

In summary, much evidence supports the formation of toxic oxygen metabolites in ischemic reperfused tissue. Tissues are equipped with both an intracellular and extracellular antioxidant defense system. The defense system can also be divided into enzymatic and nonenzymatic defenses. Important components of a nonenzymatic antioxidant include alpha-tocopherol, ascorbic acid, and beta-carotene as well as other compounds that can react with radicals to form less reactive products such as sulfur-containing amino acids. Extracellular fluid comprises a second line of defense against oxidant injury. These extracellular antioxidants include ceruloplasmin, albumin, transferrin, haptoglobin, and uric acid. The oxidant injury can potentially occur during ischemia and reperfusion due to (1) an excess production of oxygen free radicals, (2) a decrease in antioxidant defenses, or (3) both. Because antioxidants function by removing the toxic oxygen metabolites, they are generally highly effective in reducing ischemia-reperfusion injury.

Postischemic deterioration of sarcoplasmic reticulum: warm versus cold blood cardioplegia

Impaired cardiac sarcoplasmic reticulum (SR) function, as evidenced by reduced SR Ca2+ uptake rate and decreased SR Ca(2+)-adenosine triphosphatase activity, has been found in postischemic "stunned" myocardium and in hearts subjected to hypothermic arrest. In this study, we compared the effects of retrograde continuous coronary sinus warm blood cardioplegia (WBC) and retrograde intermittent cold blood cardioplegia (CBC) on cardiac SR function and postischemic ventricular functional recovery in pig hearts. Twelve in situ isolated pig hearts supported by cardiopulmonary bypass were subjected to 120 minutes of cardioplegic arrest with either WBC (37 degrees C) or CBC (6 degrees to 10 degrees C), followed by 60 minutes of 37 degrees C reperfusion. Left ventricular global contractile function and coronary blood flow were measured before arrest and during reperfusion. Cardiac SR was isolated from left ventricular biopsy specimens, and 45Ca2+ uptake by SR and SR Ca(2+)-adenosine triphosphatase activity were determined. The recovery of left ventricular global contractile function as indicated by the maximum of the first derivative of left ventricular pressure was significantly improved in the WBC group compared with that of the CBC group (70% versus 46%; p < 0.05). The SR Ca(2+)-adenosine triphosphatase activity was better preserved after 60 minutes reperfusion in WBC compared with CBC (0.31 +/- 0.02 versus 0.20 +/- 0.03 microM Pi/min/mg protein, p < 0.05), and the recovery of SR Ca2+ uptake was significantly improved by WBC compared with CBC (1.15 +/- 0.12 versus 0.83 +/- 0.04 microM Ca2+/min/mg protein; p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Interleukin-1 alpha preconditioning reduces myocardial ischemia reperfusion injury

BACKGROUND

Interleukin-1 (IL-1) has been shown to induce superoxide dismutase (SOD) activity and to express heat shock protein (HSP). Since the reperfusion of ischemic heart is associated with the reduction of antioxidative enzymes including SOD and expression of HSP, it was hypothesized that IL-1 could be beneficial against ischemic reperfusion injury.

METHODS AND RESULTS

Rats were injected with recombinant IL-1 alpha (30 micrograms/kg IP); after 48 hours, they were anesthetized and hearts were removed, isolated, and perfused by the Langendorff technique. Myocardial functions were studied by measuring left ventricular developed pressure (LVDP) and its maximum first derivative (LV dP/dt), and cellular injury was studied by estimating creatine kinase (CK) release. Induction of the expression of HSP27 mRNA and HSP27 protein was examined by Western blot analysis and Northern blot analysis, respectively. Antioxidant enzymes were assayed by enzymatic analysis. Our results indicated reduction of ischemic reperfusion injury by IL-1 alpha, as evidenced by better recovery in postischemic ventricular functions (LVDP [mm Hg]: control, 63 +/- 14; IL-1, 102 +/- 11; P < .05), increased coronary flow (mL/min) (control, 2.93 +/- 0.58; IL-1, 5.17 +/- 0.43; P < .03), and reduced creatine kinase release (IU/L) (control, 110 +/- 5.78; IL-1, 81.76 +/- 7.71; P < .01). IL-1 alpha induced the expression of HSP27 mRNA within 2 hours as examined by Northern blot analysis and the expression of HSP27 after 48 hours. In addition, hearts pretreated with IL-1 alpha for 48 hours and then subjected to 30-minute ischemia and 60-minute reperfusion enhanced the activities (nmol/min/mg protein) of Cu/Zn SOD (control, 1.55 +/- 0.22; IL-1 alpha, 2.92 +/- 0.04; P < .004), Mn-SOD (control, 4.54 +/- 0.19; IL-1 alpha, 6.33 +/- 0.09, P < .001), catalase (control, 15.53 +/- 0.37; IL-1 alpha, 21.67 +/- 0.72; P < .002), glutathione peroxidase (control, 17.49 +/- 0.35; IL-1 alpha, 25.87 +/- 0.58; P < .001), and glucose-6-phosphate dehydrogenase (control, 22.71 +/- 0.44; IL-1 alpha, 29.53 +/- 0.48; P < .001).

CONCLUSIONS

The results of this study indicate that low doses of IL-1 alpha can be used as a therapeutic agent to precondition a heart from ischemia reperfusion injury.

Identification and characterization of plasmalogen fatty acids in swine heart

Reperfusion of ischemic swine myocardium is associated with the loss of sarcolemmal phospholipids resulting in the accumulation of amphiphilic metabolites, lysophosphoglycerides and free fatty acids, especially arachidonic acid, causing electro-physiological dysfunction and cell death. Recently, phospholipids containing a vinyl ether bond at the Sn-1 position, commonly known as plasmalogens, have been identified as major constituents of heart, which contain a large amount of arachidonic acid in the Sn-2 position. Because of the potential importance of plasmalogens, the fatty acid composition of the choline and ethanolamine phosphoglycerides in swine heart was determined. Lipids were extracted from the left ventricular biopsies from swine heart, phosphoglycerides were separated from the neutral lipids by thin layer chromatography, converted into methyl derivatives and analysed by GC. The peaks for fatty acid methyl ester (FAME) and dimethylacetal (DMA) derivatives of choline and ethanolamine phosphoglycerides were confirmed using GC-MS. The results showed high amounts of 18:1 (17 mol%), 18:2 (24 mol %) FAME in choline phosphoglycerides in contrast to the occurrence of a high amount of 20:4 (28 mol%) FAME in ethanolamine phosphoglycerides, suggesting that plasmenylethanolamine, and not plasmenylcholine, may serve as the depot for arachidonic acid in swine heart.

Reduction of myocardial ischemic reperfusion injury by sialylated glycosphingolipids, gangliosides

Gangliosides, sialic acid-containing glycosphigolipids, are localized mostly to the outer leaflet of the lipid bilayer in the plasma membrane, particularly in brain. Gangliosides reduce edema formation, restore glucose metabolism, and increase cerebral blood flow after focal ischemia in the rat brain. We wished to determine whether gangliosides could also reduce myocardial ischemic and reperfusion injury. Isolated rat heart perfused by Langendorff technique was pretreated with gangliosides (1 microM) purified from the rat brain. After 15-min perfusion with gangliosides, hearts were made ischemic for 30 min by termination of coronary flow, followed by 60-min reperfusion. Ganglioside-treated heart exhibited better myocardial preservation, as evidenced by reduction in creatine kinase release and lipid peroxidation product formation enhanced coronary flow and contractile functions [left ventricular developed pressure (LVDP) and maximum first derivative of LVDP, LVdp/dtmax]. In addition, gangliosides reduced the hydroxyl radical formed during reperfusion of ischemic myocardium, as shown by high-performance liquid chromatography (HPLC)-electrochemical detection technique. In vitro studies demonstrated that these gangliosides were direct scavengers of superoxide anions (IC50 0.8 microM), and hydroxyl radicals (IC50 10 microM), as well hypohalite radicals (IC50 0.7 microM). Furthermore, ganglioside pretreatment was accompanied by reduced intracellular calcium overloading during ischemia and reperfusion as compared with untreated controls. The results of this study thus suggest that gangliosides can reduce ischemic reperfusion injury in isolated heart, probably by inhibiting intracellular calcium overloading and/or by directly scavenging the free radicals generated during reperfusion of ischemic myocardium.

Molecular adaptation of vascular endothelial cells to oxidative stress

Cellular organisms respond at the cellular and molecular level when confronted with sudden changes in environment, and molecular adaptation represents the ability of the cells to acclimate themselves to their new environment. In this study we examined the response of bovine vascular endothelial cells (VEC) to the oxidative stress by exposing the cultured cells to two different concentrations of H2O2, 0.04 or 0.08 mM, for 18-24 h. H2O2-exposed VEC displayed good viability (85-90% for 0.04 mM H2O2; 75-80% for 0.08 mM H2O2) and exhibited normal morphology. H2O2 treatment of the VEC was associated with the expression of a number of new proteins, as demonstrated by two-dimensional gel electrophoresis of total cell lysate. Cells exposed to 0.04 mM H2O2 expressed 25 new proteins, whereas 19 newly expressed proteins were detected when the cells were exposed to 0.08 mM H2O2. Western blot analysis of H2O2-treated VEC using specific antibodies to heat-shock proteins (HSP) identified one of these proteins as a member of the HSP 70 family. In addition, H2O2 induced an increase in antioxidative enzyme activities in the VEC, including superoxide dismutase, catalase, and glutathione peroxidase. Moreover, these changes were a truly adaptive phenomenon because challenging the VEC with brief exposure to toxic levels of H2O2 (1 mM for 30 min) showed increased viability (by Trypan blue exclusion test) and decreased injury (by lactate dehydrogenase supernatant-to-cellular ratio determination) in adapted cells (preexposed to 0.04 or 0.08 mM H2O2) compared with control cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Estimation of the extent of lipid peroxidation in the ischemic and reperfused heart by monitoring lipid metabolic products with the aid of high-performance liquid chromatography

Estimation of lipid peroxidation (LPO) through malonaldehyde (MDA) formation measured by assaying thiobarbituric acid reactive products remains the method of choice to study the development of oxidative stress to assess myocardial ischemic reperfusion injury. However, MDA estimation by this assay is non-specific and often gives erroneous results. In this report, we describe a method to estimate MDA, formaldehyde (FDA), acetaldehyde (ADA), and acetone, the degradation products of oxygen free radicals (OFR) and polyunsaturated fatty acids (PUFA), as presumptive markers for LPO. Isolated rat hearts were made ischemic for 30 min, followed by 60 min of reperfusion. The perfusates were collected, derivatized with 2,4-dinitrophenylhydrazine, and extracted with pentane. Aliquots of 25 microliters in acetonitrile were injected on a Beckman Ultrasphere C18 (3 microns) column. The products were eluted isocratically with a mobile phase containing acetonitrile-water-acetic acid (40:60:0.1, v/v/v). The peaks were identified by co-chromatography with the hydrazine derivatives of authentic standards. The retention times of MDA, FDA, ADA and acetone were 5.0, 6.3, 9.8 and 15.7 min, respectively. The results of our study indicated progressive increase in all four lipid metabolites with reperfusion time. Thus, our results demonstrate that the release of lipid metabolites from the isolated heart increased in response to oxidative stress. Since MDA, FDA, ADA, and acetone are the products of OFR-PUFA interactions, this method allows proper estimation of LPO to monitor the oxidative stress developed during the reperfusion of ischemic myocardium.