Potential candidates for ischemic preconditioning-associated vascular growth pathways revealed by antibody array

Our understanding of the phenomenon of myocardial vascular growth is very limited even though various studies have been conducted in several different models, because the focus in each has been on a select very few number of proteins as the possible growth factors. In the present study, we used the ischemic preconditioning (IP) model in the form of four in vivo repetitive cycles of coronary artery occlusion, each followed by reperfusion as the model to stimulate vascular growth, and performed the protein profiling using high-throughput antibody array technology. Rats were divided into two groups: control + left anterior descending coronary artery (LAD) occlusion (CMI), and IP+ LAD occlusion (IPMI). The antibody array experiment performed to compare the expression of 512 proteins between the IPMI and CMI samples revealed significant upregulation of growth proteins like TGF-beta, BMX, granulocyte-monocyte colony-stimulating factor, signal transducer and activator of transcription 3, alpha- and beta-catenins, ubiquitin-conjugating enzyme UbcH6, nexilin, and PKC-epsilon and -lambda. JNK1 and c-Src tyrosine kinase were expectedly found to be downregulated. Western blot experiments validated the changes in expression of these proteins. Therefore, this study puts forward the above-mentioned proteins as valid participants in the vascular growth signals that are known to be triggered by ischemic preconditioning of heart.

Antibody-array technique reveals overexpression of important DNA-repair proteins during cardiac ischemic preconditioning

It is well known that repetitive ischemia followed by reperfusion (four cycles of 5 min of ischemia and 10 min of reperfusion) demonstrates protective effect against subsequent severe ischemic insult, known as ischemic preconditioning (PC). This phenomenon causes reduction in oxidative DNA damage, infarct size, and the extent of apoptotic cell death, leading to adaptation on functional recovery. The involvement of DNA-repair mechanisms in PC has not been well studied. We utilized the antibody-array technique to identify DNA-repair proteins that were upregulated by ischemic PC in the permanent left anterior coronary artery occlusion myocardial infarction (MI) model. The antibody-array system enabled us to identify three double-strand-break-repair proteins--Rad50, DNA topoisomerase I, Ku80--that were upregulated and might be involved in cell-survival processes during adaptation. With Western blot analysis, we found no significant difference in Ku80 protein expression between preconditioned and control groups after MI. Therefore, this report focuses on the overexpression of Rad50 and DNA topoisomerase and proposes that the DNA-repair mechanism in the permanent left anterior descending coronary artery (LAD) occlusion model involves these two proteins.

MK2-/- gene knockout mouse hearts carry anti-apoptotic signal and are resistant to ischemia reperfusion injury

Stress-induced mitogen-activated protein (MAP) kinases have been implicated in various forms of cardiovascular diseases. Ischemia/reperfusion potentiates activation of p38 MAP kinase (p38MAPK) leading to the activation of its downstream target MAPKAP kinase 2 (MK2). While p38MAPK has been shown to induce pro-apoptotic signal, whether MK2 also generates death signal is not known. To determine if MK2 triggers death signal, the hearts of MK2-/- knockout mice and genetically matched wild-type mice were subjected to 30 min ischemia followed by 2 h of reperfusion via Langendorff mode. The results indicated that the hearts of MK2-/- mice were resistant to myocardial ischemic reperfusion injury as evidenced by enhance recovery of post-ischemic ventricular performance, reduced myocardial infarct size and diminished number of apoptotic cardiomyocytes. We conclude that MK2, similar to p38MAPK, is involved in transmitting the death signal to the ischemic myocardium.

Angiogenic signal triggered by ischemic stress induces myocardial repair in rat during chronic infarction

In the present study, we examined a novel method of stimulating myocardial angiogenesis through ischemic preconditioning (IP) in the form of in vivo four repetitive cycles of coronary artery occlusion each followed by reperfusion. Rats divided into 4 groups: Control+Sham surgery (CS), Control+ Left anterior descending coronary artery (LAD) occlusion (CMI), IP+ Sham surgery (IPS) and IP+LAD occlusion (IPMI). For cardiac function, rats were subjected to stress testing with dobutamine after 2, 4, 7, 14 and 21 operative days. Capillary density (CD) and arteriolar density (AD) were evaluated by immunohistochemistry. Western blot was performed to examine the expression pattern for VEGF and anti-death candidates, Bcl-2 and survivin. Blood flow and the extent of endothelial and cardiomyocyte cell death were examined. The protein/DNA array was performed to determine the status of various transcription factor related to stress signal. Left ventricular functional reserve was better preserved in IPMI compared to the CMI group. The infarct size and apoptotic cell death were reduced in IPMI group significantly. Left ventricular regional blood flow, perfused capillary density and AD increased significantly in the IPMI group. VEGF, Bcl-2 and survivin expression were increased in IPMI compared to CMI. VEGF mediated vascular permeability was controlled in the IPMI due to suppression of c-Src in the infarcted myocardium. Our study documented first time the ability of IP to induce angiogenesis in the infarcted myocardium along with the activation of several transcription factors such as Stat3, Pax-5, NF kappa B, TFIID, SP1 and reduction of VEGF mediated vascular permeability by inhibition of c-Src in IPMI group thereby reducing ischemic injury in rat MI model.

Pharmacological preconditioning with resveratrol: role of CREB-dependent Bcl-2 signaling via adenosine A3 receptor activation

Recent studies demonstrated that resveratrol, a grape-derived polyphenolic phytoalexin, provides pharmacological preconditioning (PC) of the heart through a NO-dependent mechanism. Because adenosine receptors play a role in PC, we examined whether they play any role in resveratrol PC. Rats were randomly assigned to groups perfused for 15 min with 1) Krebs-Henseleit bicarbonate buffer (KHB) only; 2) KHB containing 10 microM resveratrol; 3) 10 microM resveratrol + 1 microM 8-cyclopentyl-1,3-dimethylxanthine (CPT; adenosine A(1) receptor blocker); 4) 10 microM resveratrol + 1 microM 8-(3-chlorostyryl)caffeine (CSC; adenosine A(2a) receptor blocker); 5) 10 microM resveratrol + 1 microM 3-ethyl-5-benzyl-2-methyl-4-phenylethynyl-6-phenyl-1,4-(+/-)-dihydropyridine-3,5-dicarboxylate (MRS-1191; adenosine A(3) receptor blocker); or 6) 10 microM resveratrol + 3 microM 2-(4-morpholinyl)-8-phenyl-1(4H)-benzopyran-4-one hydrochloride [LY-294002, phosphatidylinositol (PI)3-kinase inhibitor], and groups perfused with adenosine receptor blockers alone. Hearts were then subjected to 30-min ischemia followed by 2-h reperfusion. The results demonstrated significant cardioprotection with resveratrol evidenced by improved ventricular recovery and reduced infarct size and cardiomyocyte apoptosis. CPT and MRS 1191, but not CSC, abrogated the cardioprotective abilities of resveratrol, suggesting a role of adenosine A(1) and A(3) receptors in resveratrol PC. Resveratrol induced expression of Bcl-2 and caused its phosphorylation along with phosphorylation of cAMP response element-binding protein (CREB), Akt, and Bad. CPT blocked phosphorylation of Akt and Bad without affecting CREB, whereas MRS 1191 blocked phosphorylation of all compounds, including CREB. LY-294002 partially blocked the cardioprotective abilities of resveratrol. The results indicate that resveratrol preconditions the heart through activation of adenosine A(1) and A(3) receptors, the former transmitting a survival signal through PI3-kinase-Akt-Bcl-2 signaling pathway and the latter protecting the heart through a CREB-dependent Bcl-2 pathway in addition to an Akt-Bcl-2 pathway.

Redox regulation of angiotensin II signaling in the heart

A large number of studies have demonstrated the role of angiotensin II in cardiac preconditioning against ischemic reperfusion injury. Generally, angiotensin II is a detrimental factor for the heart, and its inhibition with an ACE inhibitor provides cardioprotection. This review provides an explanation for such paradoxical behavior of angiotensin II. Angiotensin II can potentiate the induction of the expression of a variety of redox-sensitive factors including p38 MAPK, JNK and Akt, IGF-IR, EGF-R, and HO-1 as well as redox-regulated genes and transcription factors such as NFkappaB. It becomes increasingly apparent that during the earlier phase, the heart attempts to adapt itself against the detrimental effects of angiotensin II by upregulating several cardioprotective genes and proteins. These genes and proteins are redox-regulated and the antioxidants or ROS scavengers block their expressions. Interestingly, an identical pattern of cardioprotective proteins and genes are expressed in the preconditioned heart, which are also inhibited with ROS scavengers. It is tempting to speculate that the induction of the expression of the redox-sensitive cardioprotective proteins is the results of adaptation of the heart against the oxidative stress resulting from angiotensin II; and preconditioning is the net result of harnessing its own protection during ischemic and/or oxidative stress through its ability to trigger redox signaling.

Role of Akt Signaling in Mitochondrial Survival Pathway Triggered by Hypoxic Preconditioning

Background— The signaling pathways that control ischemia/reperfusion-induced cardiomyocyte apoptosis in heart have not been fully defined. In this study, we investigated whether Akt signaling has a role in the antiapoptotic pathways of preconditioning against hypoxia/reoxygenation (H/R).

Methods and Results— Primary cultures of adult rat ventricular myocytes (ARVMs) were subjected to preconditioning (PC) by exposing the cells to 10 minutes of hypoxia followed by 30 minutes of reoxygenation. Non-PC and PC myocytes were subjected to 90 minutes of hypoxia followed by 120 minutes of reoxygenation. Hypoxic-PC protected the myocytes from subsequent H/R injury, as evidenced by decreased apoptosis and LDH release and increased cell viability. H/R-induced cytochrome c release and activation of caspase-3 and -9 were blocked by PC. This protective effect was inhibited by treating the cells with LY294002 (50 μmol/L), a PI3 kinase inhibitor, for 10 minutes before and during PC. PC also induced phosphorylation of Akt and BAD. Protein levels of Bcl-2 in mitochondria were maintained in PC. ARVMs were infected with either a control adenovirus (Adeno lac-Z), an adenovirus expressing dominant-negative Akt, or an adenovirus expressing constitutively active Akt. Ectopic overexpression of constitutively active Akt protected ARVMs from apoptosis induced by hypoxia/reoxygenation compared with Adeno lac-Z. In contrast, dominant negative Akt overexpression abolished the antiapoptotic effect of PC.

Conclusions— Our data demonstrated that in adult cardiomyocytes, the antiapoptotic effect of PC against H/R requires Akt signaling leading to phosphorylation of BAD, inhibition of cytochrome c release, and prevention of caspase activation.

Role of ceramide in ischemic preconditioning

BACKGROUND

A recent study showed increased myocardial content of ceramide and sphingosine during preconditioning (PC). Because sphingosine-1-phosphate, a metabolite of ceramide, may function as an antiapoptotic factor, we hypothesized the increased ceramide during PC may be heart's effort to harness its own protection.

STUDY DESIGN

The isolated hearts were divided into five groups: 1) perfused for 3 hours 45 minutes with KHB buffer (control); 2) perfused with buffer for 45 minutes followed by 30 minutes of ischemia and 2 hours of reperfusion; 3) perfused for 15 minutes with desipramine followed by 30 minutes of perfusion with buffer, 30 minutes of ischemia, and 2 hours of reperfusion; 4) preconditioned followed by 30 minutes of ischemia and 2 hours of reperfusion; and 5) the same as 4), but preperfused for 15 minutes with desipramine. Myocardial preservation was assessed by examining left ventricular function, infarct size, and cardiomyocyte apoptosis.

RESULTS

Ischemia/reperfusion-mediated cardiac dysfunction was partially restored with desipramine. PC improved postischemic ventricular recovery and reduced myocardial infarct size and cardiomyocyte apoptosis. The cardioprotective abilities of PC were abolished with desipramine, which also downregulated a PC-mediated increase in antiapoptotic protein Bcl-2. The apparent paradoxical results of desipramine can be explained by the increase in proapoptotic ceramide content in the ischemic reperfused heart that was blocked with desipramine and an increase in antiapoptotic sphingosine-1-p content in the preconditioned heart that was inhibited with desipramine.

CONCLUSIONS

The results suggested for the first time that sphingolipid can induce the expression of Bcl-2 warranting its clinical use as a pharmacologic PC agent.

Ischemic preconditioning mediated angiogenic response in the heart

Angiogenesis represents a major focus for novel therapeutic approaches to the prevention and treatment of multiple diseases, most notably ischemic cardiovascular disease and cancer. Therapeutic angiogenesis achieved either through the use of discreet angiogenic proteins or by gene therapy is fast emerging as a highly attractive treatment modality for ischemic heart disease. The purpose of this review is to address this important clinical issue through the identification of potential signaling mechanisms by which a short episode of sublethal ischemia known as ischemic preconditioning causes angiogenesis and subsequently improves myocardial salvage following coronary artery occlusion.

Preconditioning potentiates redox signaling and converts death signal into survival signal

Reactive oxygen species (ROS) play a crucial role in the pathophysiology of ischemic heart disease by causing cardiac dysfunction and cell death. Several redox-sensitive anti- and pro-apoptotic transcription factors including NFkappaB and AP-1 progressively and steadily increase in the heart as a function of the duration of ischemia and reperfusion. When the heart is preconditioned to ischemic stress by repeated short-term ischemia and reperfusion, NFkappaB remains high while AP-1 is lowered to almost baseline value. The anti-apoptotic gene Bcl-2 is downregulated in the ischemic/reperfused heart, while it is upregulated in the adapted myocardium. Cardioprotective abilities of the preconditioning are abolished when heart is pre-perfused with N-acetyl cysteine, a scavenger for ROS, suggesting the role of ROS in redox signaling. Mammalian heart is protected by several defense systems which include among others, redox-regulated protein, thioredoxin. Reperfusion of ischemic myocardium results in the downregulation of thioredoxin 1 (Trx 1) expression, which was upregulated in the preconditioned myocardium. The increased expression of Trx 1 is completely blocked with an inhibitor of Trx 1, CDDP, which also abolished cardioprotection afforded by ischemic adaptation. The cardioprotective role of Trx 1 is confirmed further with transgenic mouse hearts overexpressing Trx 1. The Trx 1 mouse hearts displayed significantly improved post-ischemic ventricular recovery and reduced myocardial infarct size and apoptosis as compared to the corresponding wild-type mouse hearts. Taken together, preconditioning appears to potentiate redox signaling, which converts the "death signal" into "survival signal."

Conversion of Death Signal into Survival Signal by Redox Signaling

Reperfusion of ischemic myocardium produces reactive oxygen species (ROS) and results in apoptotic cell death and DNA fragmentation. Several redox-sensitive anti- and pro- apoptotic transcription factors including nuclear factor kappaB (NF-kappaB) and heterodimeric transcription factor AP-1 progressively and steadily increase in the heart as a function of the duration of ischemia and reperfusion. When the heart is adapted to ischemic stress by repeated short-term ischemia and reperfusion, NF-kappaB remains high, while AP-1 is lowered to almost baseline value. The anti-apoptotic gene Bcl-2 is downregulated in the ischemic/reperfused heart, while it is upregulated in the adapted myocardium. Cardioprotective abilities of the adapted myocardium are abolished when heart is pre-perfused with N-acetyl cysteine to scavenge ROS, suggesting a role of redox signaling. Mammalian heart is protected by several defense systems, which include, among others, the redox-regulated protein thioredoxin. Reperfusion of ischemic myocardium results in the downregulation of thioredoxin 1 (Trx 1) expression, which was upregulated in the adapted myocardium. The increased expression of Trx 1 is completely blocked with an inhibitor of Trx 1, cis-diammine-dichloroplatinum, which also abolished cardioprotection afforded by ischemic adaptation. The cardioprotective role of Trx 1 is further confirmed with transgenic mouse hearts overexpressing Trx 1. The Trx 1 mouse hearts displayed significantly improved post-ischemic ventricular recovery and reduced myocardial infarct size and apoptosis compared to the corresponding wild-type mouse hearts. The results of this study implicate a crucial role of redox signaling in transmitting anti-death signal.

Cardioprotection with sildenafil, a selective inhibitor of cyclic 3',5'-monophosphate-specific phosphodiesterase 5

The effects of sildenafil (Viagra), a specific inhibitor of phosphodiesterase 5, on ischemic myocardium was examined using an isolated rat heart model. Rats were pretreated with sildenafil at doses ranging from 0.001 mg to 0.5 mg/kg body weight. After 60 min, isolated hearts were subjected to ischemia for 30 min followed by 2 h of reperfusion. The results demonstrated that at 0.05 mg/kg (and to some extent at 0.01 mg/kg), sildenafil provided significant cardioprotection as evidenced by improved ventricular recovery, a reduced incidence of ventricular fibrillation and decreased myocardial infarction. At higher doses, it caused a significant increase in the incidence of ventricular fibrillation while at very low doses it had no effect on cardiac function. As expected, sildenafil increased cyclic 3',5'-monophosphate (cGMP) content in the heart. The results demonstrate for the first time that within a narrow dose range, sildenafil can protect the heart from ischemia/reperfusion injury, probably through a cGMP-signaling pathway.

STAT signaling in ischemic heart: a role of STAT5A in ischemic preconditioning

We recently demonstrated that ischemic preconditioning (PC) induced by cyclic episodes of short duration of ischemia and reperfusion potentiates a signal transduction cascade involving Janus kinase (JAK) 2 and signal transducer and activator of transcription 3 (STAT3). A rapid activation of JAK and several STATs, including STAT3, STAT5A, and STAT6 also occurred during myocardial ischemia and reperfusion. This study sought to examine whether STAT5A and STAT6 were also involved in PC. Two different animal models were used: isolated perfused working rat hearts and STAT5A and STAT6 knockout mouse hearts. The results of our study indicated phosphorylation of STAT 5A and STAT6 in the preconditioned myocardium. Tyrphostin AG490, a JAK2 inhibitor, or 4-amino-5-(4-methylphenyl)-7-(t-butyl)-pyrazolo-3,4-d-pyrimidine (PPI), a Src kinase blocker, blocked STAT5A phosphorylation, whereas STAT6 phosphorylation was blocked only with tyrphostin. As expected, significant cardioprotection was achieved in the preconditioned heart as evidenced by reduced myocardial infarct size and decreased number of apoptotic cardiomyocytes. PC-mediated cardioprotection was partially abolished when hearts were pretreated with tyrphostin, PPI, or LY-294002, a phosphatidylinositol (PI)-3 kinase inhibitor. Studies with STAT5A and STAT6 knockout mouse hearts revealed that STAT6 knockout mouse hearts, and not STAT5A knockout mouse hearts, were resistant to myocardial ischemia-reperfusion injury. The hearts from STAT5A knockout mice could not be preconditioned, whereas those from STAT6 knockout mice were easily preconditioned. The results of the present study demonstrate that STAT5A, and not STAT6, plays a role in ischemic PC. For the first time, the results also indicated a role of Src kinase pathway in STAT5A PC and PI-3 kinase-Akt pathways appear to be the downstream regulator for STAT5A-STAT6 signaling pathway.

HFE mutation and dietary iron content interact to increase ischemia/reperfusion injury of the heart in mice

Hereditary hemochromatosis is an inherited pathological condition characterized by iron overload in several vital organs including heart. To increase our understanding of the underlying pathogenic mechanisms of hereditary hemochromatosis, we used a HFE gene knockout mouse model that replicates hereditary hemochromatosis. A group of mice with no copies of HFE gene and corresponding wild-type mice were maintained either on low-iron (30 ppm) or high-iron (300 ppm) diet since birth. The results of our study revealed that HFE gene knockout mouse hearts were susceptible to ischemia-reperfusion injury as evidenced by increased postischemic ventricular dysfunction, increased myocardial infarct size and cardiomyocyte apoptosis compared with wild-type control hearts. The degree of injury increased in the hearts of the mice fed high-iron diet. The hearts of the HFE knockout mice showed increased iron deposition, increased content of reactive oxygen species (ROS) as evidenced by the increased formation of malondialdehyde, and reduced antioxidant enzymes including superoxide dismutase, catalase, and glutathione peroxidase. The results suggest that increased amount of ROS and reduced antioxidant reserve secondary to iron overloading may be instrumental for the susceptibility of the HFE gene knockout mice to cardiac injury.

Thioredoxin redox signaling in the ischemic heart: an insight with transgenic mice overexpressing Trx1

This study examined if thioredoxin, the major redox-regulator in the mammalian system, plays any role in the redox signaling of ischemic myocardium. Isolated working rat hearts were made globally ischemic for 30 min followed by 2 h of reperfusion. Another group of hearts was rendered tolerant to ischemia by four cyclic episodes of 5 min ischemia each followed by another 10 min of reperfusion. Reperfusion of ischemic myocardium resulted in the downregulation of thioredoxin 1 (Trx1) expression, which was upregulated in the adapted myocardium. The increased expression of Trx1 was completely blocked with cis-diammine-dichloroplatinum (CDDP), an inhibitor of Trx1. CDDP also abolished cardioprotection afforded by ischemic adaptation as evidenced by a reduction of post-ischemic ventricular recovery, increase in myocardial infarct size and cardiomyocyte apoptosis. The decreased amount of reactive oxygen species in the adapted heart was increased significantly, when Trx1 was blocked with CDDP. The cardioprotective role of Trx1 was further confirmed with transgenic mouse hearts overexpressing Trx1. The Trx1 mouse hearts displayed significantly improved post-ischemic ventricular recovery and reduced myocardial infarct size as compared to the corresponding wild-type mouse hearts. Taken together, the results of this study implicate a crucial role of Trx1 in redox signaling of the ischemic myocardium.

Bax ablation protects against myocardial ischemia-reperfusion injury in transgenic mice

The role of the proapototic Bax gene in ischemia-reperfusion (I/R) injury was studied in three groups of mice: homozygotic knockout mice lacking the Bax gene (Bax(-/-)), heterozygotic mice (Bax(+/-)), and wild-type mice (Bax(+/+)). Isolated hearts were subjected to ischemia (30 min, 37 degrees C) and then to 120 min of reperfusion. The left ventricular developed force of Bax-deficient vs. Bax(+/+) hearts at stabilization and at 120 min of reperfusion was 1,411 +/- 177 vs. 1,161 +/- 137 mg and 485 +/- 69 vs. 306 +/- 68 mg, respectively. Superior cardiac function of Bax(-/-) hearts after I/R was accompanied by a decrease in creatine kinase release, caspase 3 activity, irreversible ischemic injury, and the number of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive cardiomyocytes. Electron microscopic evaluation revealed reduced damage to mitochondria and the nuclear chromatin structure in Bax-deficient mice. In the Bax(+/-) hearts, the damage markers were moderate. The superior tolerance of Bax knockout hearts to I/R injury recommends this gene as a potential target for therapeutic intervention in patients with severe and intractable myocardial ischemia.

cAMP-mediated suppression of a Th1 clone associated with an alteration of the intracellular redox environment

We have shown previously that the elevation of intracellular cAMP in antigen or anti-CD3-activated murine Th1 clones in the absence of antigen inhibits antigen-induced proliferation and the production of IL-2 by H2O2-mediated oxidation of p56lck and inhibits antigen-induced production of interferon-gamma by the induction of intracellular nitric oxide. Moreover, activated Th1 clones are resistant to cAMP-induced suppression. These results suggest that the immunosuppression of Th1 cells mediated by elevated intracellular cAMP is associated with an alteration in the intracellular oxidation/reduction environment. Here we report that the culture of an antigen or anti-CD3-activated murine Th1 clone with the adenylcyclase agonist forskolin (FSK) in the absence of antigen reduces the activity of intracellular catalase, and diminishes levels of intracellular reduced glutathione (GSH). Resting cells resistant to cAMP-induced suppression have higher intracellular GSH levels than antigen-activated cells susceptible to cAMP-induced suppression. The results provide further evidence that cAMP-induced suppression of Th1 clones is mediated by profound alterations in the intracellular redox environment and may be used to selectively inactivate Th1 cells activated by antigen.

Cardioprotection with white wine

The cardioprotective effects of red wine have been attributed to several polyphenolic antioxidants including resveratrol and proanthocyanidins. The goal of the present study was to determine whether white wines could also provide cardioprotection. Three different white wines (white wine #1, #2 and #3) were chosen for this study. Ethanol-free extracts of the wines were prepared by vacuum evaporation. Rats weighing approximately 200 g were given either 50 mg/kg or 100 mg/kg of each wine extract for 3 weeks. The rats were anesthetized and sacrificed and their hearts were excised for the preparation of isolated working rat heart. All hearts were subjected to 30 min of global ischemia followed by 2 h of reperfusion. Cardiac function including heart rate, left ventricular developed pressure (LVDP), maximum first derivative of developed pressure (LVdp/dtmax), left ventricular systolic pressure (LVSP), left ventricular end diastolic pressure (LVEP), aortic flow (AF) and coronary flow (CF) were continuously monitored and myocardial infarct size was measured at the end of the experiments. The results of our study demonstrated that among the three different white wines, only white wine #2 conferred cardioprotection as evidenced by improved postischemic ventricular recovery compared with controls. The same white wine at a dose of 50 mg/kg also showed improvement in postischemic contractile recovery but the differences compared with controls were not significant. The amount of malondialdehyde production from these hearts was lower than that found in control hearts, indicating reduced formation of reactive oxygen species in white wine #2-treated rats. In vitro studies using a chemiluminescence technique revealed that white wine #2 scavenged both superoxide anions and hydroxyl radicals. The results of our study demonstrate that white wine #2 provided cardioprotection and the cardioprotective effect of the wine can be attributed, at least in part, to its ability to function as an in vivo antioxidant.

Cardioprotection with grapes

Epidemiologic studies suggest that mild-to-moderate wine consumption is associated with a reduced incidence of mortality and morbidity from coronary heart disease. Because wines are produced from grapes, this study was done to determine whether the grapes were equally cardioprotective. Sprague-Dawley male rats were given (orally) standardized grape extract (SGE) (obtained from the California Table Grape Commission, Fresno, CA, U.S.A.) (50, 100, or 200 mg/kg body weight per day) for 3 weeks. Time-matched control experiments were performed by feeding the animals 45 microg/100 g of glucose plus 45 microg/100 g of fructose per day for 3 weeks. After 21 days, rats were killed and the hearts excised and perfused via working mode. Hearts were made ischemic for 30 min followed by 2 h of reperfusion. At 100 mg/kg and at 200 mg/kg, grapes provided significant cardioprotection as evidenced by improved postischemic ventricular recovery (aortic flow, developed pressure, the maximum first derivative of the developed pressure) and reduced amount of myocardial infarction. There were no differences in results between the two groups (100 mg/kg versus 200 mg/kg). No cardioprotection was apparent when rats were given grape samples at a dose of 50 mg/100 g/d. SGE reduced the malonaldehyde content of the heart, indicating reduction of oxidative stress during ischemia and reperfusion. In vitro studies demonstrated that the SGE could directly scavenge superoxide and hydroxyl radicals that are formed in the ischemic reperfused myocardium. The results demonstrate that the hearts of the rats fed SGE are resistant to myocardial ischemia reperfusion injury, suggesting a cardioprotective role of grapes.

Redox signaling in vascular angiogenesis

Angiogenesis is thought to be regulated by several growth factors (EGF, TGF-alpha, beta-FGF, VEGF). Induction of these angiogenic factors is triggered by various stresses. For instance, tissue hypoxia exerts its pro-angiogenic action through various angiogenic factors, the most notable being vascular endothelial growth factor, which has been mainly associated with initiating the process of angiogenesis through the recruitment and proliferation of endothelial cells. Recently, reactive oxygen species (ROS) have been found to stimulate angiogenic response in the ischemic reperfused hearts. Short exposure to hypoxia/reoxygenation, either directly or indirectly, produces ROS that induce oxidative stress which is associated with angiogenesis or neovascularization. ROS can cause tissue injury in one hand and promote tissue repair in another hand by promoting angiogenesis. It thus appears that after causing injury to the cells, ROS promptly initiate the tissue repair process by triggering angiogenic response.

Redox signaling of angiogenesis

Reactive oxygen species (ROS) play a crucial role in vascular angiogenesis. Both in vitro and in vivo studies indicate that angiogenic response in vascular tissue is triggered by ROS signaling in a highly coordinated manner. It appears that massive amounts of ROS produced during ischemia and reperfusion in the vascular tissue, especially in heart, cause significant injury to the cardiomyocyte and endothelial cells. However, during the reperfusion, the same ROS potentiates a repair process and triggers a signal transduction cascade leading to angiogenesis. Although several other factors are likely to be involved for such angiogenic response, ROS certainly plays a crucial role as evident from its direct role as mediator of angiogenesis and inhibition of angiogenesis with free radical scavengers and/or antioxidants. Angiogenesis is regulated by redox-sensing transcription factors such as nuclear factor-kappaB, and oxidants such as hydrogen peroxide and free radicals, such as nitric oxide may function as second messengers in this highly coordinated process. Furthermore, expression of many angiogenic genes including those for vascular endothelial growth factor, fibroblast growth factor, platelet-derived growth factor, and receptors such as Flt-1, Flk-1, Ang-1, and Ang-2 are likely to be regulated by redox signaling. It is tempting to speculate that the angiogenic response is under the autocrine and/or paracrine control of one or more cytokines, which in turn is redox-regulated. Through angiogenesis, ROS appear to pave the way of repairing the vascular tissues that have been damaged during ischemia and reperfusion.