Effect of caspase inhibitors on myocardial infarct size and myocyte DNA fragmentation in the ischemia-reperfused rat heart

Natural antioxidants enhance the power of physical and mental activities versus risk factors inducing progression of Alzheimer's disease in rats

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disease that is exacerbated by social isolation (SI) and protein malnutrition (PM). Antioxidants, physical and mental activities (Ph&M) can maintain cognitive functions and protect against dementia.

OBJECTIVE

To investigate the impact of Epigallocatechin-3-gallate (EGCG), Vitamin E (VE), Vitamin C (VC), and Selenium (Se), in enhancing the potential effect of Ph&M versus SI&PM as risk factors in the progression of AD in rats.

METHODS

Aluminum chloride (70 mg/kg, I.P for 5 weeks) was used to induce AD in rats that either normally fed or socially isolated and protein malnourished (SI&PM). Simultaneously, rats were weekly exposed to Ph&M either alone or in combination with EGCG (10 mg/kg, I.P), VC (400 mg/kg, P.O), VE (100 mg/kg, P.O), and Se (1 mg/kg, P.O).

RESULTS

The combination protocol of EGCG, VE, VC, and Se together with Ph&M significantly increased brain monoamines, superoxide dismutase (SOD), total antioxidant capacity (TAC) and brain-derived neurotrophic factor (BDNF) in AD, SI&PM and SI&PM/AD groups. Additionally, this regimen significantly mitigated brain acetylcholine esterase (ACHE), β-amyloid (Aβ), Tau protein, β-secretase, malondialdehyde (MDA), tumor necrosis factor-alpha (TNF-α), and Interleukin 1β (IL-1β) as well as DNA fragmentation. These biochemical findings were supported by the histopathological examinations of brain tissue.

CONCLUSION

The combination protocol of antioxidants with Ph&M activities mitigated SI&PM-induced progressive risk of AD.

Does cardiac development provide heart research with novel therapeutic approaches?

Embryonic heart progenitors arise at specific spatiotemporal periods that contribute to the formation of distinct cardiac structures. In mammals, the embryonic and fetal heart is hypoxic by comparison to the adult heart. In parallel, the cellular metabolism of the cardiac tissue, including progenitors, undergoes a glycolytic to oxidative switch that contributes to cardiac maturation. While oxidative metabolism is energy efficient, the glycolytic-hypoxic state may serve to maintain cardiac progenitor potential. Consistent with this proposal, the adult epicardium has been shown to contain a reservoir of quiescent cardiac progenitors that are activated in response to heart injury and are hypoxic by comparison to adjacent cardiac tissues. In this review, we discuss the development and potential of the adult epicardium and how this knowledge may provide future therapeutic approaches for cardiac repair.

Blueberry extract attenuates γ-radiation-induced hepatocyte damage by modulating oxidative stress and suppressing NF-κB in male rats

Radiation exposure is known to produce many harmful effects in biological systems, and these effects are often mediated by oxygen free radicals. Because blueberries are rich in antioxidant compounds such as anthocyanins and phenolic acids, we divided forty adult rats into four treatment groups of 10 (G1-4) as follows: G1 rats were used as a control, G2 rats were irradiated with 8 Gy at 2 Gy/week at a dose rate of 0.5 Gy/min, G3 rats were administered blueberry extract (200 mg/kg) and G4 rats were administered blueberry extract during the same irradiation period. In subsequent determinations, γ-irradiated rats had increased levels of cholesterol, triglyceride, high density lipoprotein (HDL) and low density lipoprotein (LDL), and significantly elevated liver enzyme activities, including alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP), and total bilirubin. In contrast, significant reductions in albumin, total protein and globulin were observed, whereas gamma irradiation decreased activities of the antioxidant enzymes glutathione (GSH), catalase (CAT), xanthine dehydrogenase (XDH) and superoxide dismutase (SOD). We also observed incremental increases in DNA fragmentation percentages and histopathological changes in liver tissues. Serum pro-inflammatory cytokine levels (IL-6, IL-10 and TNF-α) were significantly elevated and hepatic NF-кB was upregulated. In G4 rats, treatments with blueberry extract restored liver pro-oxidant status, reduced cytokine levels, ameliorated histopathological parameters and reduced DNA damage. In conclusion, γ-radiation exerts toxic effects in the rat livers, and blueberry extract is protective against these.

Does p53 Inhibition Suppress Myocardial Ischemia-Reperfusion Injury?

p53 is well known as a regulator of apoptosis and autophagy. In addition, a recent study showed that p53 is a modulator of the opening of the mitochondrial permeability transition pore (mPTP), a trigger event of necrosis, but the role of p53 in necrosis induced by myocardial ischemia-reperfusion (I/R) remains unclear. The aim of this study was to determine the role of p53 in acute myocardial I/R injury in perfused mouse hearts. In male C57BL6 mice between 12 and 15 weeks of age, 2 types of p53 inhibitors were used to suppress p53 function during I/R: pifithrin-α, an inhibitor of transcriptional functions of p53, and pifithrin-μ, an inhibitor of p53 translocation from the cytosol to mitochondria. Neither infusion of these inhibitors before ischemia nor infusion for the first 30-minute period of reperfusion reduced infarct size after 20-minute ischemia/120-minute reperfusion. Infarct sizes were similar in p53 heterozygous knockout mice (p53^+/-) and wild-type mice (WT), but recovery of rate pressure product (RRP) 120 minutes after reperfusion was higher in p53^+/- than in WT. The protein expression of p53 in WT was negligible under baseline conditions, during ischemia, and at 10 minutes after the start of reperfusion, but it became detectable at 120 minutes after reperfusion. In conclusion, upregulation of p53 during the late phase of reperfusion plays a significant role in contractile dysfunction after reperfusion, although p53 is not involved in cardiomyocyte necrosis during ischemia or in the early phase of reperfusion.

Hypercholesterolemia Abrogates Remote Ischemic Preconditioning-Induced Cardioprotection: Role of Reperfusion Injury Salvage Kinase Signals

Remote ischemic preconditioning (RIPC) is one of the most powerful intrinsic cardioprotective strategies discovered so far and experimental data indicate that comorbidity may interfere with the protection by RIPC. Therefore, we investigate whether RIPC-induced cardioprotection was intact in hypercholesterolemic rat hearts exposed to ischemia reperfusion in vivo. Normal or hypercholesterolemic rat hearts were exposed to 30 min of ischemia and 2 h of reperfusion, with or without RIPC, PI3K inhibitor wortmannin, MEK-ERK1/2 inhibitor PD98059, GSK3β inhibitor SB216763. Infarct size, apoptosis, MG53, PI3K-p85, p-Akt, p-ERK1/2, p-GSK3β, and cleaved Caspase-3 were determined. RIPC reduced infarct size, limited cardiomyocyte apoptosis following IR that was blocked by wortmannin but not PD98059. RIPC triggered unique cardioprotective signaling including MG53, phosphorylation of Akt, and glycogen synthase kinase-3ß (GSK3β) in concert with reduced proapoptotic active caspase-3. In contrast, RIPC failed to reduce myocardial necrosis and apoptosis as well as to increase the phosphorylated Akt and GSK3β in hypercholestorolemic myocardium. Importantly, we found that inhibition of GSK with SB216763 reduced myocardial infarct size in healthy and hypercholesterolemic hearts, but no additional cardioprotective effect was achieved when combined with RIPC. Our results suggest that acute GSK3β inhibition may provide a novel therapeutic strategy for hypercholesterolemic patients during acute myocardial infarction, whereas RIPC is less effective due to signaling events that adversely affect GSK3β.

Benzolamide perpetuates acidic conditions during reperfusion and reduces myocardial ischemia-reperfusion injury

During ischemia, increased anaerobic glycolysis results in intracellular acidosis. Activation of alkalinizing transport mechanisms associated with carbonic anhydrases (CAs) leads to myocardial intracellular Ca²⁺ increase. We characterize the effects of inhibition of CA with benzolamide (BZ) during cardiac ischemia-reperfusion (I/R). Langendorff-perfused isolated rat hearts were subjected to 30 min of global ischemia and 60 min of reperfusion. Other hearts were treated with BZ (5 μM) during the initial 10 min of reperfusion or perfused with acid solution (AR, pH 6.4) during the first 3 min of reperfusion. p38MAPK, a kinase linked to membrane transporters and involved in cardioprotection, was examined in hearts treated with BZ in presence of the p38MAPK inhibitor SB202190 (10 μM). Infarct size (IZ) and myocardial function were assessed, and phosphorylated forms of p38MAPK, Akt, and PKCε were evaluated by immunoblotting. We determined the rate of intracellular pH (pH_i) normalization after transient acid loading in the absence and presence of BZ or BZ + SB202190 in heart papillary muscles (HPMs). Mitochondrial membrane potential (ΔΨ_m), Ca²⁺ retention capacity and Ca²⁺-mediated swelling after I/R were also measured. BZ, similarly to AR, reduced IZ, improved postischemic recovery of myocardial contractility, increased phosphorylation of Akt, PKCε, and p38MAPK, and normalized ΔΨ_m and Ca²⁺ homeostasis, effects abolished after p38MAPK inhibition. In HPMs, BZ slowed pH_i recovery, an effect that was restored after p38MAPK inhibition. We conclude that prolongation of acidic conditions during reperfusion by BZ could be responsible for the cardioprotective benefits of reduced infarction and better myocontractile function, through p38MAPK-dependent pathways. NEW & NOTEWORTHY Carbonic anhydrase inhibition by benzolamide (BZ) maintains acidity, decreases infarct size, and improves postischemic myocardial dysfunction in ischemia-reperfusion (I/R) hearts. Protection afforded by BZ mimicked the beneficial effects elicited by an acidic solution (AR). Increased phosphorylation of p38MAPK occurs in I/R hearts reperfused with BZ or with AR. Mitochondria from I/R hearts possess abnormal Ca²⁺ handling and a more depolarized membrane potential compared with control hearts, and these changes were restored by treatment with BZ or AR.

N-Methyl-D-Aspartate Receptor-Driven Calcium Influx Potentiates the Adverse Effects of Myocardial Ischemia-Reperfusion Injury Ex Vivo

BACKGROUND

Despite the adverse effects of N-methyl-D-aspartate receptor (NMDAR) activity in cardiomyocytes, no study has yet examined the effects of NMDAR activity under ex vivo ischemic-reperfusion (I/R) conditions. Therefore, our aim was to comprehensively evaluate the effects of NMDAR activity through an ex vivo myocardial I/R rat model.

METHODS

Isolated rat hearts were randomly segregated into 6 groups (n = 20 in each group): (1) an untreated control group; (2) a NMDA-treated control group; (3) an untreated I/R group; (4) an I/R+NMDA group treated with NMDA; (5) an I/R+NMDA+MK-801 group treated with NMDA and the NMDAR inhibitor MK-801; and (6) an I/R+NMDA+[Ca]-free group treated with NMDA and [Ca]-free buffer. The 4 I/R groups underwent 30 minutes of ischemia followed by 50 minutes of reperfusion. Left ventricular pressure signals were analyzed to assess cardiac performance. Myocardial intracellular calcium levels ([Ca]i) were assessed in isolated ventricular cardiomyocytes. Creatine kinase, creatine kinase isoenzyme MB, lactate dehydrogenase, cardiac troponin I, and cardiac troponin T were assayed from coronary effluents. TTC and TUNEL staining were used to measure generalized myocardial necrosis and apoptosis levels, respectively. Western blotting was applied to assess the phosphorylation of PKC-δ, PKC-ε, Akt, and extracellular signal-regulated kinase.

RESULTS

Enhanced NMDAR activity under control conditions had no significant effects on the foregoing variables. In contrast, enhanced NMDAR activity under I/R conditions produced significant increases in [Ca]i levels (∼1.2% increase), significant losses in left ventricular function (∼5.4% decrease), significant multi-fold increases in creatine kinase, creatine kinase isoenzyme MB, lactate dehydrogenase, cardiac troponin I, and cardiac troponin T, significant increases in generalized myocardial necrosis (∼36% increase) and apoptosis (∼150% increase), and significant multi-fold increases in PKC-δ, PKC-ε, Akt, and extracellular signal-regulated kinase phosphorylation (all P < 0.05). These adverse effects were rescued by the NMDAR inhibitor MK-801 or [Ca]-free buffer (all P < 0.05).

CONCLUSIONS

NMDAR-driven calcium influx potentiates the adverse effects of myocardial I/R injury ex vivo.

Visualization and Inhibition of Mitochondria-Nuclear Translocation of Apoptosis Inducing Factor by a Graphene Oxide-DNA Nanosensor

High concentrations of oxidized low density lipoprotein (oxLDL) induce aberrant apoptosis of vascular smooth muscle cells (VSMCs) in atherosclerotic plaques. This apoptosis cannot be blocked completely by the inhibition of caspase, and it eventually potentiates plaque disruption and risk for cardiovascular disease. Given the important role of apoptosis inducing factor (AIF) in caspase-independent apoptosis, here we develop an AIF-targeting nanosensor by the assembly of graphene oxide (GO) nanosheets and dye-labeled DNA hybrid structures. This nanosensor selectively localizes in the cytosol of VSMCs, where it exhibits a "turn-off" fluorescence signal. Under oxLDL stimuli, the release of AIF from mitochondria into cytosol liberates the DNA hybrid structures from the surface of GO and results in a "turn-on" fluorescence signal. This nanosensor is shown to possess rapid response, high sensitivity, and selectivity for AIF that enables real-time imaging of AIF translocation in VSMCs. Using this novel nanosensor, a better assessment of the apoptotic level of VSMCs and a more accurate evaluation of the extent of atherosclerotic lesions can be obtained. More importantly, the abundant binding between DNA hybrid structures and AIF inhibits the translocation of AIF into the nucleus and subsequent apoptosis in VSMCs. This inhibition may help stabilize plaque and reduce the risk of heart attack and stroke.

Modulatory effects of new curcumin analogues on gamma-irradiation - Induced nephrotoxicity in rats

In the present study, a new series of 2-amino-pyran-3-carbonitrile derivatives of curcumin 2-7 have been synthesized via one-pot simple and efficient protocol, involving the reaction of curcumin 1 with substituted-benzylidene-malononitrile to modify the 1,3-diketone moiety. The structures of the synthesized compounds 2-7 were elucidated by microanalytical and spectral data, which were found consistent with the assigned structures. The nephroprotective mechanism of these new curcumin analogues was evaluated on the post-gamma-irradiation (7 Gy) - induced nephrotoxicity in rats. Activation of Nrf2 by these curcumin analogues is responsible for the amendment of the antioxidant status, impairment of NF-κB signal, thus attenuate the nephrotoxicity induced post-γ-irradiation exposure. 4-Chloro-phenyl curcumin analogue 7 showed the most potent activity. In conclusion, the results of the present study demonstrate a promising role of these new curcumin analogues to attenuate the early symptoms of nephrotoxicity induced by γ-irradiation in rats via activation of Nrf2 gene expression. These new curcumin analogues need further toxicological investigations to assess their therapeutic index.

Hepatoprotective effect of grape seed oil against carbon tetrachloride induced oxidative stress in liver of γ-irradiated rat

Carbon tetrachloride (CCl4) and ionizing radiation are well known environmental pollutants that generate free radicals and induce oxidative stress. The liver is the primary and major target organ responsible for the metabolism of drugs, toxic chemicals and affected by irradiation. This study investigated the effect of grape seed oil (GSO) on acute liver injury induced by carbon tetrachloride (CCl4) in γ-irradiated rats (7Gy). CCl4-intoxicated rats exhibited an elevation of ALT, AST activities, IL-6 and TNF-α level in the serum. Further, the levels of MDA, NO, NF-κB and the gene expression of CYP2E1, iNOS and Caspase-3 were increased, and SOD, CAT, GSH-Px, GST activities and GSH content were decreased. Furthermore, silent information regulator protein 1 (SIRT1) gene expression was markedly down-regulated. Additionally, alterations of the trace elements; copper, manganese, zinc and DNA fragmentation was observed in the hepatic tissues of the intoxicated group. These effects were augmented in CCl4-intoxicated-γ-irradiated rats. However, the administration of GSO ameliorated these parameters. GSO exhibit protective effects on CCl4 induced acute liver injury in γ-irradiated rats that could be attributed to its potent antioxidant, anti-inflammatory and anti-apoptotic activities. The induction of the antioxidant enzymes activities, down-regulation of the CYP2E1, iNOS, Caspase-3 and NF-κB expression, up-regulation of the trace elements concentration levels and activation of SIRT1 gene expression are responsible for the improvement of the antioxidant and anti-inflammatory status in the hepatic tissues and could be claimed to be the hepatoprotective mechanism of GSO.

Studies on the role of apoptosis after transient myocardial ischemia: genetic deletion of the executioner caspases-3 and -7 does not limit infarct size and ventricular remodeling

Although it is widely accepted that apoptosis may contribute to cell death in myocardial infarction, experimental evidence suggests that adult cardiomyocytes repress the expression of the caspase-dependent apoptotic pathway. The aim of this study was to analyze the contribution of caspase-mediated apoptosis to myocardial ischemia-reperfusion injury. Cardiac-specific caspase-3 deficient/full caspase-7-deficient mice (Casp3/7DKO) and wild type control mice (WT) were subjected to in situ ischemia by left anterior coronary artery ligation for 45 min followed by 24 h or 28 days of reperfusion. Heart function was assessed using M-mode echocardiography. Deletion of caspases did not modify neither infarct size determined by triphenyltetrazolium staining after 24 h of reperfusion (40.0 ± 5.1 % in WT vs. 36.2 ± 3.6 % in Casp3/7DKO), nor the scar area measured by pricosirius red staining after 28 days of reperfusion (41.1 ± 5.4 % in WT vs. 44.6 ± 8.7 % in Casp3/7DKO). Morphometric and echocardiographic studies performed 28 days after the ischemic insult revealed left ventricular dilation and severe cardiac dysfunction without statistically significant differences between WT and Casp3/7DKO groups. These data demonstrate that the executioner caspases-3 and -7 do not significantly contribute to cardiomyocyte death induced by transient coronary occlusion and provide the first evidence obtained in an in vivo model that argues against a relevant role of apoptosis through the canonical caspase pathway in this context.

Gastroprotective effect of kefir on ulcer induced in irradiated rats

The current study was designed to investigate the protective effect of kefir milk on ethanol-induced gastric ulcers in γ-irradiated rats. The results of the present study revealed that treatment with γ-irradiation and/or ethanol showed a significant increase in ulcers number, total acidity, peptic, H(+)K(+)ATPase, MMP-2 and MMP-9 activities and MDA level, which were accompanied by a significant decrease in the mucus content, the stomach GSH level, the GSH-Px activity and DNA damage. Pre-treatment with kefir milk exert significant improvement in all the tested parameters. Kefir milk exerts comparable effect to that of the antiulcer drug ranitidine. In conclusion, the present study revealed that oral administration of kefir milk prevents ethanol-induced gastric ulcer in γ-irradiated rats that could attribute to its antioxidant, anti-apoptotic and radio-protective activities.

Upregulation of genes involved in cardiac metabolism enhances myocardial resistance to ischemia/reperfusion in the rat heart

Genes encoding enzymes involved in fatty acids (FA) and glucose oxidation are transcriptionally regulated by peroxisome proliferator-activated receptors (PPAR), members of the nuclear receptor superfamily. Under conditions associated with O(2) deficiency, PPAR-alpha modulates substrate switch (between FA and glucose) aimed at the adequate energy production to maintain basic cardiac function. Both, positive and negative effects of PPAR-alpha activation on myocardial ischemia/reperfusion (I/R) injury have been reported. Moreover, the role of PPAR-mediated metabolic shifts in cardioprotective mechanisms of preconditioning (PC) is relatively less investigated. We explored the effects of PPAR-alpha upregulation mimicking a delayed "second window" of PC on I/R injury in the rat heart and potential downstream mechanisms involved. Pretreatment of rats with PPAR-alpha agonist WY-14643 (WY, 1 mg/kg, i.p.) 24 h prior to I/R reduced post-ischemic stunning, arrhythmias and the extent of lethal injury (infarct size) and apoptosis (caspase-3 expression) in isolated hearts exposed to 30-min global ischemia and 2-h reperfusion. Protection was associated with remarkably increased expression of PPAR-alpha target genes promoting FA utilization (medium-chain acyl-CoA dehydrogenase, pyruvate dehydrogenase kinase-4 and carnitine palmitoyltransferase I) and reduced expression of glucose transporter GLUT-4 responsible for glucose transport and metabolism. In addition, enhanced Akt phosphorylation and protein levels of eNOS, in conjunction with blunting of cardioprotection by NOS inhibitor L-NAME, were observed in the WY-treated hearts.

CONCLUSIONS

upregulation of PPAR-alpha target metabolic genes involved in FA oxidation may underlie a delayed phase PC-like protection in the rat heart. Potential non-genomic effects of PPAR-alpha-mediated cardioprotection may involve activation of prosurvival PI3K/Akt pathway and its downstream targets such as eNOS and subsequently reduced apoptosis.

SPRC protects hypoxia and re-oxygenation injury by improving rat cardiac contractile function and intracellular calcium handling

S-Propargyl-L-cysteine (SPRC, also named as ZYZ-802) is a new compound synthesized in our lab. We investigated whether SPRC has exerted protective effects against cardiac hypoxia/re-oxygenation (H/R) and also explored its mechanisms. In our study, isolated ventricular myocytes were subject to a simulated hypoxia solution for 30 min to induce cell injury. Intracellular concentration of Ca(2+) ([Ca(2+)]i) was measured using specific dyes and detected by digital imaging apparatus. Apoptotic cells were evaluated by TUNEL assay. Intervention with SPRC (10 μM) 30 min before hypoxia, can significantly attenuate the apoptosis of isolated papillary muscles resulting from the H/R injury and protect morphology of the muscles. In isolated ventricular myocytes, SPRC considerably improved left ventricular functional recovery. SPRC also suppressed the increase of ([Ca(2+)]i) during hypoxia stage. By measuring the calcium transient of the cell we concluded that SPRC can preserve the RyR and SERCA activities and improve Ca(2+) handling during the H/R. Furthermore, the protective effect of SPRC can be partly blocked by CSE inhibitor PAG.

Hypercholesterolemia blocked sevoflurane-induced cardioprotection against ischemia-reperfusion injury by alteration of the MG53/RISK/GSK3β signaling

BACKGROUND

Recent studies have demonstrated that volatile anesthetic preconditioning confers myocardial protection against ischemia-reperfusion (IR) injury through activation of the reperfusion injury salvage kinase (RISK) pathway. As RISK has been shown to be impaired in hypercholesterolemia, we investigate whether anesthetic-induced cardiac protection was maintained in hypercholesterolemic rats.

METHODS

Normocholesteolemic or hypercholesterolemic rat hearts were subjected to 30 min of ischemia and 2 h of reperfusion. Animals received 2.4% sevoflurane during three 5 min periods with and without PI3K antagonist wortmannin (10 μg/kg, Wort) or the ERK inhibitor PD 98059 (1 mg/kg, PD). The infarct size, apoptosis, p-Akt, p-ERK1/2, p-GSK3β were determined.

RESULTS

Two hundred and six rats were analyzed in the study. In the healthy rats, sevoflurane significantly reduced infarct size by 42%, a phenomenon completely reversed by wortmannin and PD98059 and increased the phosphorylation of Akt, ERK1/2 and their downstream target of GSK3β. In the hypercholesterolemic rats, sevoflurane failed to reduce infarct size and increase the phosphorylated Akt, ERK1/2 and GSK3β. In contrast, GSK inhibitor SB216763 conferred cardioprotection against IR injury in healthy and hypercholesterolemic hearts.

CONCLUSIONS

Hyperchoesterolemia abrogated sevoflurane-induced cardioprotection against IR injury by alteration of upstream signaling of GSK3β and acute GSK inhibition may provide a novel therapeutic strategy to protect hypercholesterolemic hearts against IR injury.

Hypercholesterolemic myocardium is vulnerable to ischemia-reperfusion injury and refractory to sevoflurane-induced protection

Recent studies have demonstrated that volatile anesthetic postconditioning confers myocardial protection against ischemia-reperfusion (IR) injury through activation of the reperfusion injury salvage kinase (RISK) pathway. As RISK has been shown to be impaired in hypercholesterolemia. Therefore, we investigate whether anesthetic-induced cardiac protection was maintained in hypercholesterolemic rats. In the present study, normocholesteolemic or hypercholesterolemic rat hearts were subjected to 30 min of ischemia and 2 h of reperfusion. Animals received 2.4% sevoflurane for 5 min or 3 cycles of 10-s ischemia/10-s reperfusion. The hemodynamic parameters, including left ventricular developed pressure, left ventricular end-diastolic pressure and heart rate, were continuously monitored. The infarct size, apoptosis, p-Akt, p-ERK1/2, p-GSK3β were determined. We found that both sevoflurane and ischemic postconditioning significantly improved heart pump function, reduced infarct size and increased the phosphorylation of Akt, ERK1/2 and their downstream target of GSK3β in the healthy rats. In the hypercholesterolemic rats, neither sevoflurane nor ischemic postconditioning improved left ventricular hemodynamics, reduced infarct size and increased the phosphorylated Akt, ERK1/2 and GSK3β. In contrast, GSK inhibitor SB216763 conferred cardioprotection against IR injury in healthy and hypercholesterolemic hearts. In conclusions, hyperchoesterolemia abrogated sevoflurane-induced cardioprotection against IR injury by alteration of upstream signaling of GSK3β and acute GSK inhibition may provide a novel therapeutic strategy to protect hypercholesterolemic hearts against IR injury.

Moderate and high amounts of tamoxifen in αMHC-MerCreMer mice induce a DNA damage response, leading to heart failure and death

Numerous mouse models have utilized Cre-loxP technology to modify gene expression. Adverse effects of Cre recombinase activity have been reported, including in the heart. However, the mechanisms associated with cardiac Cre toxicity are largely unknown. Here, we show that expression of Cre in cardiomyocytes induces a DNA damage response, resulting in cardiomyocyte apoptosis, cardiac fibrosis and cardiac dysfunction. In an effort to increase the recombination efficiency of a widely used tamoxifen-sensitive Cre transgene under control of the α-myosin-heavy-chain promoter (αMHC-MerCreMer), we observed myocardial dysfunction and decreased survival, which were dependent on the dose of tamoxifen injected. After excluding a Cre-independent contribution by tamoxifen, we found that Cre induced myocardial fibrosis, activation of pro-fibrotic genes and cardiomyocyte apoptosis. Examination of the molecular mechanisms showed activation of DNA damage response signaling and p53 stabilization in the absence of loxP sites, suggesting that Cre induced illegitimate DNA breaks. Cardiomyocyte apoptosis was also induced by expressing Cre using adenoviral transduction, indicating that the effect was not dependent on genomic integration of the transgene. Cre-mediated homologous recombination at loxP sites was dose-dependent and had a ceiling effect at ∼80% of cardiomyocytes showing recombination. By titrating the amount of tamoxifen to maximize recombination while minimizing animal lethality, we determined that 30 μg tamoxifen/g body weight/day injected on three consecutive days is the optimal condition for the αMHC-MerCreMer system to induce recombination in the Rosa26-lacZ strain. Our results further highlight the importance of experimental design, including the use of appropriate genetic controls for Cre expression.

Caspase-3 as a therapeutic target for heart failure

INTRODUCTION

Heart failure is a condition with significant morbidity and high mortality. It is likely to become unmanageable in the rapidly increasing aging population, due mainly to lack of effective treatment. Apoptosis is one of the major mechanisms causing cardiomyocyte loss in the failing hearts of both human patients and animal models. Thus, anti-apoptosis has been proposed as a provocative new concept for preventive and therapeutic strategies for heart failure.

AREAS COVERED

This review summarizes evidence that apoptotic cells in heart are not completely committed to death. They are likely to be targeted for reversing the cardiac dysfunction. Drugs that inhibit the progression of apoptosis help restore systolic function, reverse remodeling or even prevent heart failure. Inhibitors of caspase-3, the major executors of apoptosis, have been shown to hold great promises for apoptosis interruption in heart tissues.

EXPERT OPINION

Although the underlying cause and the pathophysiological role of apoptosis remain elusive, antiapoptotic therapy has emerged as an enigma for heart failure. Caspases promote the progressive loss of contractile function in heart failure by facilitating the degradation of myofibrillar proteins. Selective inhibition of the proteolytic functions of caspase-3 may represent an attractive approach to attenuate or reverse heart failure.

Apoptosis in Anthracycline Cardiomyopathy

Apoptosis is a tightly regulated physiologic process of programmed cell death that occurs in both normal and pathologic tissues. Numerous in vitro or in vivo studies have indicated that cardiomyocyte death through apoptosis and necrosis is a primary contributor to the progression of anthracycline-induced cardiomyopathy. There are now several pieces of evidence to suggest that activation of intrinsic and extrinsic apoptotic pathways contribute to anthracycline-induced apoptosis in the heart. Novel strategies were developed to address a wide variety of cardiotoxic mechanisms and apoptotic pathways by which anthracycline influences cardiac structure and function. Anthracycline-induced apoptosis provides a very valid representation of cardiotoxicity in the heart, an argument which has implications for the most appropriate animal models of damaged heart plus diverse pharmacological effects. In this review we describe various aspects of the current understanding of apoptotic cell death triggered by anthracycline. Differences in the sensitivity to anthracycline-induced apoptosis between young and adult hearts are also discussed.

Administration of pigment epithelium-derived factor inhibits left ventricular remodeling and improves cardiac function in rats with acute myocardial infarction

Oxidative stress and inflammation are involved in cardiac remodeling after acute myocardial infarction (AMI). We have found that pigment epithelium-derived factor (PEDF) inhibits vascular inflammation through its anti-oxidative properties. However, effects of PEDF on cardiac remodeling after AMI remain unknown. We investigated whether PEDF could inhibit left ventricular remodeling and improve cardiac function in rats with AMI. AMI was induced in 8-week-old Sprague-Dawley rats by ligation of the left ascending coronary artery. Rats were treated intravenously with vehicle or 10 μg PEDF/100 g b.wt. every day for up to 2 weeks after AMI. Each rat was followed until 16 weeks of age. PEDF levels in infarcted areas and serum were significantly decreased at 1 week after AMI and remained low during the observational periods. PEDF administration inhibited apoptotic cell death and oxidative stress generation around the infarcted areas at 2 and 8 weeks after AMI. Further, PEDF injection suppressed cardiac fibrosis by reducing transforming growth factor-β and type III collagen expression, improved left ventricular ejection fraction, ameliorated diastolic dysfunction, and inhibited the increase in left ventricular mass index at 8 weeks after AMI. The present study demonstrated that PEDF could inhibit tissue remodeling and improve cardiac function in AMI rats. Substitution of PEDF may be a novel therapeutic strategy for cardiac remodeling after AMI.

Mitochondria to nucleus translocation of AIF in mice lacking Hsp70 during ischemia/reperfusion

Heat shock protein 70 (Hsp70) has been shown to have an anti-apoptotic function, but its mechanism is not clear in heart. In this study, we examined the effect of Hsp70 deletion on AIF-induced apoptosis during ischemia/reperfusion (I/R) in vivo. Although Hsp70 KO and WT mice demonstrated similar amounts of AIF released from mitochondria after I/R surgery, Hsp70 KO mice showed a significantly greater increase in apoptosis, larger infarct size, and decreased cardiac output. There was also a significant fourfold increase in the nuclear accumulation of AIF in Hsp70 KO mice compared with WT mice. Treatment with 4-AN (4-amino-1,8-napthalimide, 3 mg/kg), a potent inhibitor of PARP-1, which is a critical regulator of AIF-induced apoptosis, significantly blocked the release of AIF from mitochondria and the translocation of AIF into the nuclei after I/R in both WT and Hsp70 KO mice. In addition, 4-AN treatment resulted in a significant inhibition of apoptosis, a reduction of infarct size, and attenuated cardiac dysfunction in both WT and Hsp70 KO mice after I/R. The anti-apoptotic function of Hsp70 occurs through the inhibition of AIF-induced apoptosis by blocking the mitochondria to nucleus translocation of AIF. PARP-1 inhibition improves cardiac function by blocking AIF-induced apoptosis.

Hypoxia and fetal heart development

Fetal hearts show a remarkable ability to develop under hypoxic conditions. The metabolic flexibility of fetal hearts allows sustained development under low oxygen conditions. In fact, hypoxia is critical for proper myocardial formation. Particularly, hypoxia inducible factor 1 (HIF-1) and vascular endothelial growth factor play central roles in hypoxia-dependent signaling in fetal heart formation, impacting embryonic outflow track remodeling and coronary vessel growth. Although HIF is not the only gene involved in adaptation to hypoxia, its role places it as a central figure in orchestrating events needed for adaptation to hypoxic stress. Although "normal" hypoxia (lower oxygen tension in the fetus as compared with the adult) is essential in heart formation, further abnormal hypoxia in utero adversely affects cardiogenesis. Prenatal hypoxia alters myocardial structure and causes a decline in cardiac performance. Not only are the effects of hypoxia apparent during the perinatal period, but prolonged hypoxia in utero also causes fetal programming of abnormality in the heart's development. The altered expression pattern of cardioprotective genes such as protein kinase c epsilon, heat shock protein 70, and endothelial nitric oxide synthase, likely predispose the developing heart to increased vulnerability to ischemia and reperfusion injury later in life. The events underlying the long-term changes in gene expression are not clear, but likely involve variation in epigenetic regulation.

Delayed activation of caspase-independent apoptosis during heart failure in transgenic mice overexpressing caspase inhibitor CrmA

Although caspase activation is generally thought to be necessary to induce apoptosis, recent evidence suggests that apoptosis can be activated in the setting of caspase inhibition. In this study, we tested the hypothesis that caspase-independent apoptotic pathways contribute to the development of heart failure in the absence of caspase activation. Acute cardiomyopathy was induced using a single dose of doxorubicin (Dox, 20 mg/kg) injected into male wild-type (WT) and transgenic (Tg) mice with a cardiac-specific expression of cytokine response modifier A (CrmA), a known caspase inhibitor. Early (6 day) survival was significantly better in CrmA Tg (81%) than WT (38%) mice. Twelve days after Dox injection, however, the mortality benefit had dissipated, and increased cardiac apoptosis was observed in both groups. There was, however, a significantly greater release of apoptosis-inducing factor (AIF) from mitochondria to cytosol in CrmA Tg compared with WT mice, which suggests that an enhancement of activation in caspase-independent apoptotic pathways had occurred. The administration of a poly(ADP-ribose) polymerase-1 inhibitor, 4-amino-1,8-naphthalimide (4-AN), to Dox-treated mice resulted in significantly improved cardiac function, a significant blockade of AIF released from mitochondria, and decreased cardiac apoptosis. There were also significantly improved survival in WT (18% without 4-AN vs. 89% with 4-AN) and CrmA Tg (13% without 4-AN vs. 93% with 4-AN) mice 12 days after Dox injection. In conclusion, these findings suggest that apoptosis can be induced in the heart lacking caspase activation via caspase-independent pathways and that enabling the inhibition of AIF activation may provide a significant cardiac benefit.

Apoptosis in cardiovascular diseases: mechanism and clinical implications

Apoptosis is a tightly regulated, cell deletion process that plays an important role in various cardiovascular diseases, such as myocardial infarction, reperfusion injury, and heart failure. Since cardiomyocyte loss is the most important determinant of patient morbidity and mortality, fully understanding the regulatory mechanisms of apoptotic signaling is crucial. In fact, the inhibition of cardiac apoptosis holds promise as an effective therapeutic strategy for cardiovascular diseases. Caspase, a critical enzyme in the induction and execution of apoptosis, has been the main potential target for achieving anti-apoptotic therapy. Studies suggest, however, that a caspase-independent pathway may also play an important role in cardiac apoptosis, although the mechanism and potential significance of caspase-independent apoptosis in the heart remain poorly understood. Herein we discuss the role of apoptosis in various cardiovascular diseases, provide an update on current knowledge about the molecular mechanisms that govern apoptosis, and discuss the clinical implications of anti-apoptotic therapies.

Caspase inhibition modulates left ventricular remodeling following myocardial infarction through cellular and extracellular mechanisms

BACKGROUND

Myocyte death occurs by necrosis and caspase-mediated apoptosis in myocardial infarction (MI). In vitro studies suggest caspase activation causes myocardial contractile protein degradation without inducing apoptosis. Thus, caspase activation may evoke left ventricular (LV) remodeling through independent processes post-MI. The effects of caspase activation on LV geometry post-MI remain unclear. This project applied pharmacologic caspase inhibition (CASPI) to a porcine model of MI.

METHODS AND RESULTS

Pigs (34 kg) were instrumented to induce 60 minutes of coronary artery occlusion followed by reperfusion and a 7-day follow-up period. Upon reperfusion, the pigs were randomized to saline (n = 12) or CASPI (n = 10, IDN6734, 6 mg/kg i.v., then 6 mg/kg/h for 24 hours). Plasma troponin-I values were reduced with CASPI compared with saline at 24 hours post-MI (133 +/- 15 vs. 189 +/- 20 ng/mL, respectively, P < 0.05). LV end-diastolic area (echocardiography) and interregional length (sonomicrometry) increased from baseline in both groups but were attenuated with CASPI by 40% and 90%, respectively (P < 0.05). Myocyte length was reduced with CASPI compared with saline (128 +/- 3 vs. 141 +/- 4 microm, respectively, P < 0.05). Plasma-free pro-matrix metalloproteinase-2 values increased from baseline with CASPI (27% +/- 6%, P < 0.05) indicative of reduced conversion to active MMP-2. Separate in vitro studies demonstrated that activated caspase species cleaved pro-MMP-2 yielding active MMP-2 forms and that MMP activity was increased in the presence of activated caspase-3.

CONCLUSIONS

CASPI attenuated regional and global LV remodeling post-MI and altered viable myocyte geometry. Caspases increased MMP activity in vitro, whereas CASPI modified conversion of MMP-2 to the active form in vivo. Taken together, the results of the present study suggest that the elaboration of caspases post-MI likely contribute to LV remodeling through both cellular and extracellular mechanisms.

Effect of hydrogen sulfide on myocardial protection in the setting of cardioplegia and cardiopulmonary bypass

We investigated the impact of hydrogen sulfide (H(2)S) on myocardium in the setting of cold crystalloid cardioplegia and cardiopulmonary bypass (CP/CPB). Eighteen male Yorkshire pigs underwent 1 h CP/CPB followed by 2 h of reperfusion. Pigs received either: placebo (control, n=9), or H(2)S (as NaHS) as a bolus/infusion (bolus/infusion, n=6), or as an infusion (infusion, n=6). The expression pattern of various myocardial effector pathways was investigated. Coronary microvascular relaxation to endothelium-dependent and -independent agonists was assessed. No differences in cardiac function were observed among groups. Endothelium-dependent microvascular relaxation to adenosine diphosphate was improved in the H(2)S bolus/infusion group only (P<0.05). The expression of hemeoxygenase-1, phospho-heat shock proteins27 and phospho-p44/42 MAPK extracellular signal-regulated kinase were higher in H(2)S-treated groups (P<0.05). Phospho-endothelial nitric oxide synthase (P=0.08), phospho-B-cell lymphoma 2 (P=0.09), and phospho-Bad (P=0.06) all displayed a trend to be higher with H(2)S treatment. The expressions of apoptosis inducing factor and Bcl 2/adenovirus E1B 19 kDa-interacting protein were lower in H(2)S treated groups (P<0.05). The microtubule-associated protein 1 light chain 3 ratio was lower in the infusion group vs. control animals (P<0.05). There was a trend for lower phospho-mammalian target of rapamycin expression in the infusion group (P=0.07), whereas phosphorylation of p70S6K1 was higher with H(2)S-treatment (P=0.09). This study demonstrates that H(2)S-treatment may offer biochemical myocardial protection via attenuation of caspase-independent apoptosis and autophagy in the setting of CP/CPB.

Role of AIF in cardiac apoptosis in hypertrophic cardiomyocytes from Dahl salt-sensitive rats

AIMS

The caspases are thought to be central mediators of the apoptotic program, but recent data indicate that apoptosis may also be mediated by caspase-independent mechanisms such as apoptosis-inducing factor (AIF). The role of AIF-induced apoptosis in heart, however, is currently not well understood. The aim of this study was to investigate the presence of and conditions for AIF-induced cardiac apoptosis in vitro.

METHODS AND RESULTS

Hypertrophic cardiomyocyte (H-CM) cultures were prepared from the hearts of Dahl salt-sensitive rats fed a high salt diet. Apoptotic stimulation induced by hypoxia/reoxygenation or staurosporine (1 microM) enhanced AIF release in H-CMs compared with non-hypertrophic cardiomyocytes (N-CMs). Caspase inhibition using zVAD.fmk (25 microM) or overexpression of CrmA using recombinant adenovirus only partially protected N-CMs from apoptosis (63 +/- 0.93%) and provided no significant protection against apoptosis in hypertrophic cells (23 +/- 1.03%). On the other hand, poly-ADP-ribose polymerase inhibition using 4-AN (20 microM) during apoptotic stimulation blocked the release of AIF from mitochondria and significantly improved cell viability in hypertrophied cardiomyocytes (74 +/- 1.18%).

CONCLUSION

A caspase-dependent, apoptotic pathway is important for N-CM death, whereas a caspase-independent, AIF-mediated pathway plays a critical role in H-CMs.

Effect of hypercholesterolemia on myocardial necrosis and apoptosis in the setting of ischemia-reperfusion

BACKGROUND

Hypercholesterolemia is prevalent in patients who experience myocardial ischemia-reperfusion injury (IR). We investigate the impact of dietary-induced hypercholesterolemia on the myocardium in the setting of acute IR.

METHODS AND RESULTS

In normocholesterolemic (NC, n=7) and hypercholesterolemic (HC, n=7) Yucatan male pigs, the left anterior descending coronary artery was occluded for 60 minutes, followed by reperfusion for 120 minutes. Hemodynamic values were recorded, and TTC staining was used to assess necrosis. Oxidative stress was measured. Specific cell death and survival signaling pathways were assessed by Western blot and TUNEL staining. Infarct size was 45% greater in HC versus NC (42% versus 61%, P<0.05), whereas the area at risk (AAR) was similar in both groups (P=0.61). Whereas global LV function (+dP/dt, P<0.05) was higher during entire period of IR in HC versus NC, regional function deteriorated more following reperfusion in HC (P<0.05). Ischemia increased indices of myocardial oxidative stress such as protein oxidation (P<0.05), lipid peroxidation (P<0.05), and nitrotyrosylation in HC versus NC, as well as the expression of phospho-eNOS (P<0.05). The expression of myeloperoxidase, p38 MAPK, and phospho-p38 MAPK was higher in HC versus NC (all P<05). Ischemia caused higher expression of the proapoptotic protein PARP (P<0.05), and lower expression of the prosurvival proteins Bcl2 (P<0.05), phospho-Akt, (P<0.05), and phospho-PKCepsilon (P<0.05) in the HC versus NC. TUNEL-positive cell count was 3.8-fold (P<0.05) higher in the AAR of HC versus NC.

CONCLUSIONS

This study demonstrates that experimental hypercholesterolemia is associated with increased myocardial oxidative stress and inflammation, attenuation of cell survival pathways, and induction of apoptosis in the ischemic territory, which together may account for the expansion of myocardial necrosis in the setting of acute IR.

Effect of hydrogen sulfide in a porcine model of myocardial ischemia-reperfusion: comparison of different administration regimens and characterization of the cellular mechanisms of protection

OBJECTIVE

We investigate the impact of different regimens of parenteral hydrogen sulfide (H2S) administration on myocardium during ischemia-reperfusion (IR) and the molecular pathways involved in its cytoprotective effects.

METHODS

Eighteen male Yorkshire pigs underwent 60 minutes of mid-left anterior descending coronary artery occlusion followed by 120 minutes of reperfusion. Pigs received either placebo (control, n = 6) or H2S as a bolus (bolus group, n = 6, 0.2 mg/kg over 10 seconds at the start of reperfusion) or as an infusion (infusion group, n = 6, 2 mg.kg.h initiated at the onset of ischemia and continued into the reperfusion period). Myocardial function was monitored throughout the experiment. The area at risk and myocardial necrosis was determined by Monastral blue/triphenyl tetrazolium chloride staining. Apoptosis and the expression pattern of various intracellular effector pathways were investigated in the ischemic territory. Coronary microvascular reactivity to endothelium-dependent and endothelium-independent factors was measured.

RESULTS

H2S infusion but not bolus administration markedly reduce myocardial infarct size (P < 0.05) and improve regional left ventricular function, as well as endothelium-dependent and endothelium-independent microvascular reactivity (P < 0.05). The expression of B-cell lymphoma 2 (P = 0.059), heat shock protein 27 and alphaB-crystallin (P < 0.05) were lower in H2S-treated groups. Infusion of H2S caused higher expression of phospho-glycogen synthase kinase-3 beta isoform(P < 0.05) and lower expression of mammalian target of rapamycin and apoptosis-inducing factor (P < 0.05). Bolus of H2S caused higher expression of phospho-p44/42 MAPK extracellular signal-regulated kinase and lower expression of Beclin-1 (P < 0.05). The expression of caspase 3 and cleaved caspase 3 were lower (P < 0.05), whereas the expression of phospho-Bad(Ser136) was higher in the bolus group versus control and infusion groups (P < 0.05). The terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cell count was lower in both H2S-treated groups compared with the control (P < 0.05).

CONCLUSIONS

This study demonstrates that infusion of H2S is superior to a bolus alone in reducing myocardial necrosis after IR injury, even though some markers of apoptosis and autophagy were affected in both H2S-treated groups. Thus, the current results indicate that infusion of H2S throughout IR may offer better myocardial protection from IR injury.

Effect of thrombin fragment (TP508) on myocardial ischemia-reperfusion injury in hypercholesterolemic pigs

Myocardial ischemia-reperfusion (IR) injury occurs frequently in the setting of hypercholesterolemia. We investigated the potential efficacy of a novel thrombin fragment (TP508) on IR injury in a hypercholesterolemic porcine model. Twenty-one hypercholesterolemic male Yucatan pigs underwent 60 min of mid-left anterior descending coronary artery occlusion followed by 120 min of reperfusion. Pigs received either placebo (control, n = 7) or TP508 in two doses (TP508 low dose, n = 7, as bolus of 0.5 mg/kg 50 min into ischemia and an infusion of 1.25 mg.kg(-1).h(-1) during reperfusion period or TP508 high dose, n = 7, a double dose of TP508 low-dose group). Myocardial function was monitored throughout the experiment. The area at risk and myocardial necrosis were determined by Monastryl blue/triphenyl tetrazolium chloride staining. Apoptosis in the ischemic territory was assessed. Coronary microvascular reactivity to endothelium-dependent and -independent factors was measured. Myocardial necrosis was lower in both TP508-treated groups vs. control (P < 0.05). Regional left ventricular function was improved only in the TP508 high-dose group (P < 0.05). Endothelium-dependent coronary microvascular reactivity was greater in both TP508-treated groups (P < 0.05) vs. control. The expression of proteins favoring cell survival, 90-kDa heat shock protein and phospho-Bad (Ser112) was higher in the TP508 high-dose group (P < 0.05). The expression of the cell death signaling proteins, cleaved caspase-3 (P < 0.05), apoptosis-inducing factor (P < 0.05), and poly-ADP ribose polymerase (P = 0.07) was lower in the TP508 low-dose group vs. TP508 high-dose and control. The terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling positive cell count was lower in both TP508 groups compared with the control (P < 0.05). This study demonstrates that, in hypercholesterolemic pigs, TP508 decreases myocardial necrosis and apoptosis after IR. Thus TP508 may offer a novel approach in protecting the myocardium from IR injury.

Thrombin fragment (TP508) decreases myocardial infarction and apoptosis after ischemia reperfusion injury

BACKGROUND

Myocardial ischemia-reperfusion injury may lead to cardiac dysfunction or death. This study investigates the potential efficacy of a novel thrombin fragment (TP508) on myocardial ischemia-reperfusion injury.

METHODS

Fourteen male Yucatan pigs underwent 60 minutes of mid-left anterior descending coronary artery occlusion followed by 120 minutes of reperfusion. Pigs received either saline vehicle (control, n = 7) or thrombin fragment TP508 (n = 7) as a bolus (0.5 mg/kg) 50 minutes into the ischemic period, followed by continuous intravenous infusion (1.25 mg x kg(-1) x h(-1)) during reperfusion. Myocardial function was monitored throughout the experiments. Monastryl blue/triphenyl tetrazolium chloride staining was utilized to measure the area at risk and infarcted tissue. Apoptosis was assessed by Western blotting and dUTP nick-end labeling (TUNEL) staining. Coronary microvascular reactivity to endothelium-dependent factors (adenosine diphosphate, substance P, A23187) and endothelium-independent factor (sodium nitroprusside) was examined.

RESULTS

Global and regional left ventricular function was not significantly different between groups. Endothelium-dependent coronary microvascular relaxation was greater in the TP508 group and associated with higher endothelial nitric oxide synthase phosphorylation. Both infarct size and TUNEL staining was significantly decreased in the TP508 group compared with the control group (p < 0.05). Expression of the cell survival proteins B-cell lymphoma 2 (2.2-fold, p < 0.05) and heat shock protein-73 (1.6-fold, p < 0.05) was higher in the TP508 group. Expression of the cell-death-signaling proteins poly adenosine diphosphate-ribose polymerase (1.6-fold, p < 0.05), cleaved poly adenosine diphosphate-ribose polymerase (6.4-fold, p < 0.05), and B-cell lymphoma 2/adenovirus E1B 19 kDa-interacting protein 3 (3.8-fold, p < 0.05) was significantly higher in the TP508 group in the ischemic territory.

CONCLUSIONS

This study demonstrates that TP508 decreases infarct size, improves endothelial microvascular function, and induces cell-survival signaling in the setting of ischemia-reperfusion injury. Thus, TP508 may be a useful agent to attenuate myocardial reperfusion injury.

Activation of caspase-3 may not contribute to postresuscitation myocardial dysfunction

We have previously reported that postresuscitation myocardial dysfunction is accompanied by the release of cytochrome c and caspase-3 activation. We now investigated the role of caspase-3 activation by examining whether such process prompts apoptotic DNA fragmentation, whether caspase-3 inhibition attenuates myocardial dysfunction, and whether myocardial protective effects of sodium-hydrogen exchanger isoform-1 (NHE-1) inhibition involve caspase-3 inhibition using a rat model of ventricular fibrillation (VF) of closed-chest resuscitation. Resuscitation after 4 or 8 min of untreated VF caused significant reductions in left ventricular stroke work index averaging 23% of sham control rats at 4 h postresuscitation. Left ventricular dysfunction was accompanied by increases in cytosolic cytochrome c, decreases in pro- and cleaved caspase-9 fragments, increases in 17-kDa caspase-3 fragments, and increases in caspase-3 activity indicating the activation of the mitochondrial apoptotic pathway but without evidence of apoptotic DNA fragmentation. In addition, levels of heat shock protein 70 were increased and levels of X-linked inhibitor of apoptosis protein and alphabeta-crystallin were preserved, all of which can exert antiapoptotic effects. In a separate series, the caspase-3 inhibitor z-Asp-Glu-Val-Asp chloromethyl ketone given before the induction of VF failed to prevent postresuscitation myocardial dysfunction despite reductions in caspase-3 activity (2.3 +/- 0.5 vs. 1.3 +/- 0.5 pmol fluorophore AFC released.mg protein(-1).min-1; P < 0.03). Treatment with the NHE-1 inhibitor cariporide had no effect on caspase-3 activity. Accordingly, in this rat model of VF and severe postresuscitation myocardial dysfunction, activation of caspase-3 did not lead to DNA fragmentation or contribute to myocardial dysfunction. Concomitant activation of intrinsic antiapoptotic mechanisms could play a protective role downstream to caspase-3 activation.

Caspase inhibitor zVAD.fmk reduces infarct size after myocardial ischaemia and reperfusion in rats but not in mice

OBJECTIVE

Apoptosis of cardiomyocytes has been suggested to contribute to outcome following myocardial ischaemia and reperfusion (MI/R). Caspase inhibitors were developed as potential therapeutics for MI/R. However, various reports using the broad-spectrum caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (zVAD.fmk) in the latter setting present conflicting results. Therefore, it is still unclear whether inhibition of apoptosis by caspase inhibitors promotes cardioprotection.

MATERIALS AND METHODS

This study evaluated whether zVAD.fmk or novel caspase inhibitor quinoline-Val-Asp(Ome)-CH2-O-phenoxy (Q-VD-OPh) reduce myocardial infarct size in mice. Secondly, we tested zVAD.fmk's potential infarct-sparing effects in rats and whether these are accompanied by improved left ventricular function.

RESULTS

In mice neither zVAD.fmk nor Q-VD-OPh reduced infarct size. In rats, however, zVAD.fmk reduced infarct size following ischaemia (25min) and reperfusion (7 days) by approximately 53%. This was, however, accompanied by an increase in left ventricular end-diastolic pressure.

CONCLUSION

This study provides further evidence that abrogation of apoptosis via caspase inhibition might not be sufficient to effectively limit infarct size following MI/R.

The rationale for cardiomyocyte resuscitation in myocardial salvage

Clinical heart failure results from the cumulative loss of functioning myocardium from any cause. At the cellular level, cardiac myocytes die from three causes, individually or in combination: Necrosis occurs when external conditions are not sufficient to sustain minimal cellular functions, as with ischemia, and there is a general and unorganized breakdown of cell organelles, engendering an inflammatory response that may have harmful collateral tissue effects. Apoptosis, or cell suicide, occurs when specific external or internal conditions provoke a highly structured sequence of events to shut down cellular functions and remove the cell, with minimal consequences to surrounding tissue. Autophagy is a normal response to cell starvation that is induced under conditions of chronic metabolic or other stress. Current therapeutics, such as early myocardial revascularization after myocardial infarction, are focused exclusively upon minimizing cardiac myocyte necrosis and may even contribute to secondary apoptosis and autophagy. This review explores possible approaches to bring cardiac myocytes that are destined to die, back to life, i.e., cellular resuscitation. Two pro-apoptotic proteins in particular, Bnip3 and Nix, are transcriptionally upregulated specifically in response to myocardial ischemia and pathological hypertrophy and have been examined as therapeutic targets. In Bnip3 and Nix genetic mouse models, prevention of cardiac myocyte apoptosis in ischemic and hemodynamically overloaded hearts salvaged myocardium, minimized late ventricular remodeling, and enhanced ventricular performance. Cardiomyocyte resuscitation by preventing programmed cell death shows promise as an additive approach to minimizing necrosis for long-term prevention of heart failure.

Caspases in myocardial infarction

The discovery of apoptosis sheds a new light on the role of cell death in myocardial infarction and other cardiovascular diseases. There is mounting evidence that apoptosis plays an important role at multiple points in the evolution of myocardial infarction, and comprises not only cardiomyocytes but also inflammatory cells, as well as cells of granulation tissue and fibrous tissue. It appears that apoptosis contributes to cardiomyocyte loss in the border zone and in remote myocardium in the early phase, as well as months after myocardial infarction, thus playing a role in remodeling and development of heart failure after myocardial infarction. Apoptosis, being a highly regulated process, is a potential target for therapeutic intervention. Caspases are the key effector molecules in apoptosis, and are therefore a particularly attractive target for pharmacological modulation of apoptosis. Although several potential therapeutic agents have been tested in animal models of ischemia/reperfusion heart injury with some success, nearly none of the specific antiapoptotic agents have reached the stage of clinical research.

Recombinant human-activated protein C inhibits cardiomyocyte apoptosis in a rat model of myocardial ischemia-reperfusion

OBJECTIVES

Myocardial apoptosis is recognized as a major mechanism of cell death during ischemia-reperfusion. In this study, we assessed the hypothesis that activated protein C may have a cardioprotective effect via preventing apoptosis in a rat model of myocardial ischemia-reperfusion.

METHODS

Thirty male Sprague-Dawley rats were anesthetized, instrumented for hemodynamic measurements and ventilated mechanically. Twenty rats were subjected to 20 min of left anterior descending coronary artery occlusion and 2 h of reperfusion. They were randomly assigned to receive intravenous Ringer lactate (vehicle) or activated protein C (2 mg/kg/h) 10 min after occlusion and during reperfusion. The other 10 rats were sham-operated. At the end of the reperfusion period, serum samples were obtained for evaluation of creatine kinase, C-reactive protein and tumor necrosis factor-alpha. Apoptosis was measured quantitatively by the terminal deoxynucleotide transferase-mediated dUTP nick-end labeling method.

RESULTS

Serum creatine kinase, C-reactive protein and tumor necrosis factor-alpha values and percentage of terminal deoxynucleotide transferase-mediated dUTP nick-end labeling- positive myocyte nuclei demonstrated negligible myocardial injury in sham-operated controls. During reperfusion, mean arterial pressures were significantly higher in activated protein C-treated rats than in the control group (68.2+/-10.3 vs. 55.4+/-11.6 mmHg, P=0.01). Number of apoptotic cells was significantly reduced from 47.7 to 24.8% with activated protein C administration (P=0.008). No difference was seen between activated protein C-treated and untreated animals with respect to creatine kinase, C-reactive protein and tumor necrosis factor-alpha levels.

CONCLUSIONS

Treatment with activated protein C significantly improved hemodynamics after ischemia-reperfusion and reduced ischemia-reperfusion-induced myocardial apoptosis in rats.

Bax deficiency reduces infarct size and improves long-term function after myocardial infarction

We have previously found that, following myocardial ischemia/reperfusion injury, isolated hearts from bax gene knockout mice [Bax(-/-)] exhibited higher cardioprotection than the wild-type. We here explore the effect of Bax(-/-), following myocardial infarction (MI) in vivo. Homozygotic Bax(-/-) and matched wild-type were studied. Mice underwent surgical ligation of the left anterior descending coronary artery (LAD). The progressive increase in left-ventricular end diastolic diameter, end systolic diameter, in Bax(-/-) was significantly smaller than in Bax(+/+) at 28 d following MI (p < 0.03) as seen by echocardiography. Concomitantly, fractional shortening was higher (35 +/- 4.1% and 27 +/- 2.5%, p < 0.001) and infarct size was smaller in Bax(-/-) compared to the wild-type at 28 days following MI (24 +/- 3.7 % and 37 +/- 3.3%, p < 0.001). Creatine kinase and lactate dehydrogenase release in serum were lower in Bax(-/-) than in Bax(+/+) 24 h following MI. Caspase 3 activity was elevated at 2 h after MI only in the wild-type, but reduced to baseline values at 1 and 28 d post-MI. Bax knockout mice hearts demonstrated reduced infarct size and improved myocardial function following permanent coronary artery occlusion. The Bax gene appears to play a significant role in the post-MI response that should be further investigated.

Mechanisms of apoptosis after ischemia and reperfusion: role of the renin-angiotensin system

BACKGROUND

Apoptosis plays a key role in the pathogenesis of cardiac diseases. We examined the influence of the renin-angiotensin system (RAS) on different regulators of apoptosis using an isolated hemoperfused working porcine heart model of acute ischemia (2 h), followed by reperfusion (4 h).

METHODS AND RESULTS

23 porcine hearts were randomized to 5 groups: hemoperfused non-infarcted hearts (C), infarcted hearts (MI: R. circumflexus), infarcted hearts treated with quinaprilat (Q), infarcted hearts treated with angiotensin-I (Ang I), and infarcted hearts treated with angiotensin-I and quinaprilat (QA). Fas, Bax, bcl-2 and p53 proteins were increased in MI hearts and further elevated by Ang I. Quinaprilat reduced Bax and p53. Bcl-2 was elevated in Q and reduced in QA. An early upregulation of caspase-3 gene and protein expression was detected in MI and Ang I hearts compared to C. Q reduced caspase-3 gene expression, but had no effect on caspase-3 and Fas protein.

CONCLUSIONS

These data suggest that the RAS plays a pivotal role in cardiac apoptosis which is the early and predominant form of death in myocardial infarction. Ischemia/reperfusion induces programmed cell death via extrinsic and intrinsic pathways. Early treatment with quinaprilat attenuated cardiomyocyte apoptosis.

Morphological aspects of apoptosis in heart diseases

It has been suggested that apoptosis may be responsible for a significant amount of cardiomyocyte death during acute myocardial infarction as well as for a progressive loss of surviving cells in failing hearts. Typical apoptosis can indeed be induced in cardiomyocytes at the experimental conditions. In actual heart diseases, in contrast, there is very little direct morphological evidence of apoptosis in cardiomyocytes occurring at any stage of myocardial infarction and heart failure, despite the availability of much indirect evidence that includes detection of DNA fragmentation and apoptosis-related factors. For that reason, the potential efficacy of therapeutic intervention to prevent apoptosis remains controversial. This review will survey available data from both animals and humans to critically assess the role of cardiomyocyte apoptosis during myocardial infarction and its relevance to myocardial remodeling and during progression to heart failure. Also considered will be nonmyocyte interstitial cells, which have received less attention than myocytes despite definitive evidence of their apoptosis in the infarcted heart and recent studies suggesting that blockade of apoptosis among these cells mitigates postinfarction cardiac remodeling and heart failure. We conclude from our survey that there are many hurdles to surmount before regulation of apoptosis can be clinically applied in the treatment of myocardial infarction and heart failure.

Changes in cardiovascular function on treatment of inhibitors of apoptotic signal transduction pathways in left ventricular remodeling after myocardial infarction

INTRODUCTION

It has been suggested that apoptosis in cardiac remodeling after myocardial infarction (MI) occurs in cardiomyocytes and is critically involved in the process of postinfarct cardiac remodeling. We investigated the pathophysiological link between myocardial apoptosis and cardiovascular function by modulating apoptotic signal transduction pathways.

METHODS

Either a caspase-3 inhibitor (CasI) or a calpain inhibitor (CalI) was administered immediately after MI in a rat model of MI. Blood pressure (BP), heart rate (HR), and blood flow velocity (BFV) were measured, and pressure-rate product (PRP) was calculated to estimate the changes in cardiovascular function (n=6 for each group).

RESULTS

BFV showed no remarkable changes in any of the groups. Both systolic blood pressure (SBP) and HR changed significantly (P<.01) in the MI+CasI and MI+CalI groups at 1 day after MI and returned to control levels thereafter. In contrast, SBP and HR remained significantly (P<.01) altered in the MI group. PRP in the MI groups was significantly decreased (P<.05 in the MI and MI+CasI groups; P<.01 in the MI+CalI group) at 1 day after MI and returned to control levels at 4 days.

CONCLUSION

This study suggests that inhibition of apoptosis during left ventricular remodeling ameliorates cardiovascular function in remodeled hearts.

Myocyte apoptosis during acute myocardial infarction in rats is related to early sarcolemmal translocation of annexin A5 in border zone

Annexin A5 is a Ca2+-dependent phospholipid binding protein well known for its high phosphatidylserine affinity. In vitro, translocation to sarcolemma and externalization of endogenous annexin A5 in the cardiomyocyte has recently been demonstrated to exert a proapoptotic effect. To determine whether these in vitro findings occurred in vivo, we performed myocardial infarction (MI) and studied the time course of apoptosis and annexin A5 localization (0.5 to 8 h) in the border zone around the infarcted area. This zone that was defined as Evans blue unstained and triphenyltetrazolium chloride (TTC) stained, represented 42.3 ± 5.5% of the area at risk and showed apoptotic characteristics (significant increases in caspase 3 activity 2.3-fold at 0.5 h; P < 0.05), transferase-mediated dUTP nick-end labeling-positive cardiomyocytes (15.8 ± 0.8% at 8 h), and DNA ladder. When compared with sham-operated rats, we found that in this area, annexin A5 was translocated to the sarcolemma as early as 0.5 h after MI and that translocation increased with time. Moreover, the amount of annexin A5 was unchanged in the border zone and decreased in the infarcted area after 1 h (77.1 ± 4.8%; P < 0.01 vs. perfused area), suggesting a release in the latter but not in the former. In conclusion, we demonstrated that annexin A5 translocation is an early and rapid event of the whole border zone, likely due to Ca2+increase. Part of this translocation occurred in areas where apoptosis was later detected and suggests that in vivo as in vitro annexin A5 might be involved in the regulation of early apoptotic events during cardiac pathological situations.

Pleiotropic effects of the beta-adrenoceptor blocker carvedilol on calcium regulation during oxidative stress-induced apoptosis in cardiomyocytes

Carvedilol is a nonselective beta-adrenoceptor blocker with multiple pleiotropic actions. A recent clinical study suggested that carvedilol may be superior to other beta-adrenoceptor blockers in the treatment of heart failure. Despite numerous investigations, the underlying mechanisms of carvedilol on improving heart failure are yet to be fully established. The purpose of this study is to clarify the pleiotropic effect of carvedilol on cytosolic and mitochondrial calcium regulation during oxidative stress-induced apoptosis in cardiomyocytes. Carvedilol (10 microM), but not metoprolol (10 microM), reduced H2O2 (100 microM)-induced apoptosis in neonatal rat cardiomyocytes. During the process, changes in cytosolic calcium concentration ([Ca2+]i) and mitochondrial calcium concentration ([Ca2+]m) and mitochondrial membrane potential (DeltaPsim) were measured by fluorescent probes [Fluo-3/acetoxymethyl ester (AM), Rhod-2/AM, and tetramethylrhodamine ethyl ester, respectively] and imaged by laser confocal microscopy. The results showed that H2O2 caused [Ca2]m overload first, followed by [Ca2+]i overload, leading to DeltaPsim dissipation and the induction of apoptosis. Carvedilol (10 microM) significantly delayed these processes and reduced apoptosis. These effects were not observed with other beta-adrenoceptor blockers (metoprolol, atenolol, and propranolol) or with a combination of the alpha (phentolamine)- and the beta-adrenoceptor blocker. The antioxidant N-acetyl-L-cysteine (NAC, 5 mM) and the combination of NAC and propranolol (10 microM) showed an effect similar to that of carvedilol. Therefore, the effect of carvedilol on H2O2-induced changes in [Ca2+]m, [Ca2+]i, and DeltaPsi(m) is independent of alpha- and beta-adrenoceptors but is probably dependent on the antioxidant effect.