Protecting the Myocardial Cell During Coronary Revascularization

Atrial nitroso-redox balance and refractoriness following on-pump cardiac surgery: a randomized trial of atorvastatin

AIMS

Systemic inflammation and increased activity of atrial NOX2-containing NADPH oxidases have been associated with the new onset of atrial fibrillation (AF) after cardiac surgery. In addition to lowering LDL-cholesterol, statins exert rapid anti-inflammatory and antioxidant effects, the clinical significance of which remains controversial.

METHODS AND RESULTS

We first assessed the impact of cardiac surgery and cardiopulmonary bypass (CPB) on atrial nitroso-redox balance by measuring NO synthase (NOS) and GTP cyclohydrolase-1 (GCH-1) activity, biopterin content, and superoxide production in paired samples of the right atrial appendage obtained before (PRE) and after CPB and reperfusion (POST) in 116 patients. The effect of perioperative treatment with atorvastatin (80 mg once daily) on these parameters, blood biomarkers, and the post-operative atrial effective refractory period (AERP) was then evaluated in a randomized, double-blind, placebo-controlled study in 80 patients undergoing cardiac surgery on CPB. CPB and reperfusion led to a significant increase in atrial superoxide production (74% CI 71-76%, n = 46 paired samples, P < 0.0001) and a reduction in atrial tetrahydrobiopterin (BH4) (34% CI 33-35%, n = 36 paired samples, P < 0.01), and in GCH-1 (56% CI 55-58%, n = 26 paired samples, P < 0.001) and NOS activity (58% CI 52-67%, n = 20 paired samples, P < 0.001). Perioperative atorvastatin treatment prevented the effect of CPB and reperfusion on all parameters but had no significant effect on the postoperative right AERP, troponin release, or NT-proBNP after cardiac surgery.

CONCLUSION

Perioperative statin therapy prevents post-reperfusion atrial nitroso-redox imbalance in patients undergoing on-pump cardiac surgery but has no significant impact on postoperative atrial refractoriness, perioperative myocardial injury, or markers of postoperative LV function.

CLINICAL TRIAL REGISTRATION

https://clinicaltrials.gov/ct2/show/NCT01780740.

RP105 plays a cardioprotective role in myocardial ischemia reperfusion injury by regulating the Toll‑like receptor 2/4 signaling pathways

The revascularization of blood vessels after myocardial infarction can lead to serious myocardial damage. Previous studies showed that radioprotective 105 kDa protein (RP105) is a specific negative regulator of myocardial ischemia reperfusion injury (MIRI). RP105 can modulate the Toll-like receptor (TLR)2/TLR4 signaling pathways. However, the synergistic effect of TLR2/4 regulated by RP105 during MIRI requires further investigation. To determine this effect, a MIRI model was established in rats in the present study. The expression of RP105 was depleted by transfecting RP105-siRNA and then detected using western blotting. Furthermore, the myocardium tissue was stained with the hematoxylin and eosin staining. Knockdown of RP105 promoted the activity of serum myocardial enzymes during MIRI and increased myocardial infarction. The present results indicated that knockdown of RP105 activated the TLR2/4 signaling pathway by modulating the myeloid differentiation primary response 88 and NF-κB signaling pathways. Furthermore, decreased expression of RP105 promoted myocardial cell apoptosis, which induced the damage of myocardial ischemic reperfusion. The present results suggested both TLR2 and TLR4 as key targets of RP105, thus RP105 may be a promising candidate to facilitate the development of novel therapeutic strategies for MIRI.

Astragaloside IV attenuates myocardial ischemia/reperfusion injury in rats via inhibition of calcium-sensing receptor-mediated apoptotic signaling pathways

Astragaloside IV (AsIV) is an active saponin extracted from Astragalus membranaceus, which has shown cardioprotective effects in a number of experimental animals. In this study we investigated the molecular mechanisms by which AsIV attenuated the myocardial ischemia reperfusion (MI/R)-induced injury in vitro and in vivo by focusing on calcium-sensing receptor (CaSR) and extracellular signal-regulated kinase 1/2 (ERK1/2). Rat neonatal cardiac myocytes were subjected to a hypoxia/reoxygenation (H/R) procedure in vitro, which significantly decreased the cell viability, increased lactate dehydrogenase (LDH) release, induced cardiomyocyte apoptosis, and increased [Ca²⁺]_i. H/R also increased the expression of CaSR and decreased ERK1/2 phosphorylation levels in H/R-exposed myocytes. Pretreatment with AsIV (60 μmol/L) significantly improved the cell viability and decreased LDH release, attenuated myocyte apoptosis, decreased [Ca²⁺]_i and CaSR expression, and increased the ERK1/2 phosphorylation levels. The protective effects of AsIV against H/R injury were partially inhibited by co-treatment with a CaSR agonist, gadolinium chloride (GdCl₃) or with a specific ERK1/2 inhibitor U0126. For in vivo studies, a rat MI/R model was established. Pre-administration of AsIV (80 mg/kg every day, ig) significantly decreased the myocardium infarct size, creatine kinase-MB (CK-MB) production, serum cardiac troponin (cTnI) levels, and cardiomyocyte apoptosis in the rats with MI/R injury. The therapeutic effects of AsIV were associated with the downregulation of CaSR expression and upregulation of ERK1/2 phosphorylation in myocardial tissues. In summary, astragaloside IV attenuates myocardial I/R injury via inhibition of CaSR/ERK1/2 and the related apoptotic signaling pathways.

Salidroside mitigates hypoxia/reoxygenation injury by alleviating endoplasmic reticulum stress‑induced apoptosis in H9c2 cardiomyocytes

Endoplasmic reticulum (ER) stress-induced apoptosis serves a crucial role in the development of myocardial ischemia/reperfusion (I/R) injury. Salidroside is a phenylpropanoid glycoside isolated from Rhodiola rosea L., which is a plant often used in traditional Chinese medicine. It possesses multiple pharmacological actions and protects against myocardial I/R injury in vitro and in vivo. However, it is not yet clear whether ER stress or ER stress-induced apoptosis contributes to the cardioprotective effects of salidroside against myocardial I/R injury. Hence, hypoxia/reoxygenation (H/R)-treated H9c2 cardiomyocytes were used in the current study to mimic myocardium I/R injury in vivo. It was hypothesized that salidroside alleviates ER stress and ER stress-induced apoptosis, thereby reducing H/R injury in H9c2 cells. The results demonstrated that salidroside attenuated H/R-induced H9c2 cardiomyocyte injury, as cell viability was increased, lactate dehydrogenase release was decreased, morphological changes in apoptotic cells were ameliorated and the apoptosis ratio was reduced compared with the H/R group. ER stress was reversed, indicated by the downregulation of glucose regulated protein 78 and C/EBP homologous protein following pretreatment with salidroside. In addition, salidroside attenuated ER stress-induced apoptosis, as the expression of cleaved caspase-12 and pro-apoptotic protein Bcl-2 associated X protein and activity of caspase-3 was decreased, while the expression of anti-apoptotic protein Bcl-2 was increased following pretreatment with salidroside. Furthermore, the results indicated that salidroside decreases the activation of the ER stress-associated signaling pathway, as the expression of phosphorylated protein kinase RNA (PKR)-like ER kinase (p-PERK) and phosphorylated inositol-requiring enzyme-1α (p-IRE1α) proteins were decreased following pretreatment with salidroside. These results demonstrate that salidroside protects against H/R injury via regulation of the PERK and IRE1α pathways, resulting in alleviation of ER stress or ER stress-induced apoptosis in H9c2 cardiomyocytes.

Protective effect of N-acetylcysteine activated carbon release microcapsule on myocardial ischemia-reperfusion injury in rats

With the development of science and technology, and development of artery bypass, methods such as cardiopulmonary cerebral resuscitation have been practiced in recent years. Despite this, some methods fail to promote or recover the function of tissues and organs, and in some cases, may aggravate dysfunction and structural damage to tissues. The latter is typical of ischemia-reperfusion (IR) injury. Lipid peroxidation mediated by free radicals is an important process of myocardial IR injury. Myocardial IR has been demonstrated to induce the formation of large numbers of free radicals in rats, which promotes the peroxidation of lipids within unsaturated fatty acids in the myocardial cell membrane. Markers of lipid peroxidation include malondialdehyde, superoxide dismutase and lactic dehydrogenase. Recent studies have demonstrated that N-acetylcysteine (NAC) is able to dilate blood vessels, prevent oxidative damage, improve immunity, inhibit apoptosis and the inflammatory response and promote glutathione synthesis in cells. NAC also improves the systolic function of myocardial cells and cardiac function, prevents myocardial apoptosis, protects ventricular remodeling and vascular remodeling, reduces opiomelanocortin levels in the serum and increases the content of nitric oxide in the serum, thus improving vascular endothelial function. Therefore, NAC has potent pharmacological activity; however, the relatively fast metabolism of NAC, along with its large clinical dose and low bioavailability, limit its applications. The present study combined NAC with medicinal activated carbons, and prepared N-acetylcysteine activated carbon sustained-release microcapsules (ACNACs) to overcome the limitations of NAC. It was demonstrated that ACNACs exerted greater effective protective effects than NAC alone on myocardial IR injury in rats.

Tissue conservation for transplantation

Pathophysiological changes that occur during ischemia and subsequent reperfusion cause damage to tissues procured for transplantation and also affect long-term allograft function and survival. The proper preservation of organs before transplantation is a must to limit these injuries as much as possible. For decades, static cold storage has been the gold standard for organ preservation, with mechanical perfusion developing as a promising alternative only recently. The current literature points to the need of developing dedicated preservation protocols for every organ, which in combination with other interventions such as ischemic preconditioning and therapeutic additives offer the possibility of improving organ preservation and extending it to multiple times its current duration. This review strives to present an overview of the current body of knowledge with regard to the preservation of organs and tissues destined for transplantation.

Cancer Rates in Adults After Cardiac Interventions: A Preliminary Observational Report

BACKGROUND

The postprocedural state after cardiac revascularization interventions is characterized by intense inflammation and activation of inflammatory cytokines due to myonecrosis and ischemia/reperfusion injury. Involvement of similar processes also participates in cellular malignant transformation. In this study, the association between cardiac interventions and subsequent cancer risk development was therefore evaluated.

METHODS

The 5-year cumulative incidence of cancer was examined in 2 cardiac care cohorts: all patients undergoing either open heart surgery or percutaneous coronary interventions (PCI) at hospitals in the commonwealth of Massachusetts. The observed cases of cancer were compared with the number of expected cases based on the state cancer rates, adjusting for sex and 5-year age groups. The standardized morbidity ratio (SMR) was used for this comparison.

RESULTS

Of 10,301 patients in the surgical cohort, 804 (7.8%) incident cancers developed over 5 years of follow-up, whereas 245.7 incident cancers were expected. This yielded an SMR of 3.27 (95% CI, 3.05-3.51; P<0.0001). In the PCI cohort comprising 13,001 patients, 1029 (7.9%) incident cancers developed over 5 years, resulting in an SMR of 3.53 (95% CI, 3.32-3.75; P<0.0001). Excluding respiratory cancers from the analysis (to limit smoking-related cancers) reduced risk estimates only slightly. For the surgical cohort: SMR=2.80; 95% CI, 2.59-3.01; P<0.0001. For the PCI cohort: SMR=2.97; 95% CI, 2.78-3.18; P<0.0001.

CONCLUSIONS

Undergoing heart revascularization procedures was associated with increased rate of cancer development as compared with the state general population. This cohort may warrant increased monitoring.

Inflammation Activation Contributes to Adipokine Imbalance in Patients with Acute Coronary Syndrome

Inflammation can be activated as a defensive response by the attack of acute coronary syndrome (ACS) for ischemic tissue injury. The aim of the present study was to investigate the impact of ACS-activated inflammation on adipokine imbalance and the effects of statins on the crosstalk between inflammation and adipokine imbalance during ACS. In this study, 586 subjects were categorized into: (1) control group; (2) SA (stable angina) group; and (3) ACS group. Circulating levels of hs-CRP, adiponectin and resistin were measured by ELISA. Furthermore, forty C57BL/6 mice were randomized into: sham, AMI, low-statin (atorvastatin, 2 mg/kg/day) and high-statin (atorvastatin, 20 mg/kg/day) group. After 3 weeks, AMI models were established by surgical coronary artery ligation. Circulating levels and adipose expressions of adiponectin and resistin were assessed in animals. Besides, we investigate the effects of atorvastatin on ox-LDL-induced adipokine imbalance in vitro. As a result, we found that ACS patients had higher hs-CRP and resistin levels and lower adiponectin levels. Our correlation analysis demonstrated hs-CRP concentrations were positively correlated with resistin but negatively with adiponectin levels in humans. Our animal findings indicated higher circulating hs-CRP and resistin levels and lower adiponectin levels in AMI mice. Atorvastatin pre-treatment dose-dependently decreased hs-CRP and resistin levels but increased adiponectin levels in mice. The consistent findings were observed about the adipose expressions of resistin and adiponectin in mice. In study in vitro, ox-LDL increased cellular resistin expressions and otherwise for adiponectin expressions, which dose-dependently reversed by the addition of atorvastatin. Therefore, our study indicates that the ACS attack activates inflammation leading to adipokine imbalance that can be ameliorated by anti-inflammation of atorvastatin.

"TRP inflammation" relationship in cardiovascular system

Despite considerable advances in the research and treatment, the precise relationship between inflammation and cardiovascular (CV) disease remains incompletely understood. Therefore, understanding the immunoinflammatory processes underlying the initiation, progression, and exacerbation of many cardiovascular diseases is of prime importance. The innate immune system has an ancient origin and is well conserved across species. Its activation occurs in response to pathogens or tissue injury. Recent studies suggest that altered ionic balance, and production of noxious gaseous mediators link to immune and inflammatory responses with altered ion channel expression and function. Among plausible candidates for this are transient receptor potential (TRP) channels that function as polymodal sensors and scaffolding proteins involved in many physiological and pathological processes. In this review, we will first focus on the relevance of TRP channel to both exogenous and endogenous factors related to innate immune response and transcription factors related to sustained inflammatory status. The emerging role of inflammasome to regulate innate immunity and its possible connection to TRP channels will also be discussed. Secondly, we will discuss about the linkage of TRP channels to inflammatory CV diseases, from a viewpoint of inflammation in a general sense which is not restricted to the innate immunity. These knowledge may serve to provide new insights into the pathogenesis of various inflammatory CV diseases and their novel therapeutic strategies.

Platelet density per monocyte predicts adverse events in patients after percutaneous coronary intervention

Monocyte recruitment to damaged endothelium is enhanced by platelet binding to monocytes and contributes to vascular repair. Therefore, we studied whether the number of platelets per monocyte affects the recurrence of adverse events in patients after percutaneous coronary intervention (PCI). Platelet-monocytes complexes with high and low median fluorescence intensities (MFI) of the platelet marker CD42b were isolated using cell sorting. Microscopic analysis revealed that a high platelet marker MFI on monocytes corresponded with a high platelet density per monocyte while a low platelet marker MFI corresponded with a low platelet density per monocyte (3.4 ± 0.7 vs 1.4 ± 0.1 platelets per monocyte, P=0.01). Using real-time video microscopy, we observed increased recruitment of high platelet density monocytes to endothelial cells as compared with low platelet density monocytes (P=0.01). Next, we classified PCI scheduled patients (N=263) into groups with high, medium and low platelet densities per monocyte and assessed the recurrence of adverse events. After multivariate adjustment for potential confounders, we observed a 2.5-fold reduction in the recurrence of adverse events in patients with a high platelet density per monocyte as compared with a low platelet density per monocyte [hazard ratio=0.4 (95% confidence interval, 0.2-0.8), P=0.01]. We show that a high platelet density per monocyte increases monocyte recruitment to endothelial cells and predicts a reduction in the recurrence of adverse events in patients after PCI. These findings may imply that a high platelet density per monocyte protects against recurrence of adverse events.

Lycopene Protects against Hypoxia/Reoxygenation Injury by Alleviating ER Stress Induced Apoptosis in Neonatal Mouse Cardiomyocytes

Endoplasmic reticulum (ER) stress induced apoptosis plays a pivotal role in myocardial ischemia/reperfusion (I/R)-injury. Inhibiting ER stress is a major therapeutic target/strategy in treating cardiovascular diseases. Our previous studies revealed that lycopene exhibits great pharmacological potential in protecting against the I/R-injury in vitro and vivo, but whether attenuation of ER stress (and) or ER stress-induced apoptosis contributes to the effects remains unclear. In the present study, using neonatal mouse cardiomyocytes to establish an in vitro model of hypoxia/reoxygenation (H/R) to mimic myocardium I/R in vivo, we aimed to explore the hypothesis that lycopene could alleviate the ER stress and ER stress-induced apoptosis in H/R-injury. We observed that lycopene alleviated the H/R injury as revealed by improving cell viability and reducing apoptosis, suppressed reactive oxygen species (ROS) generation and improved the phosphorylated AMPK expression, attenuated ER stress as evidenced by decreasing the expression of GRP78, ATF6 mRNA, sXbp-1 mRNA, eIF2α mRNA and eIF2α phosphorylation, alleviated ER stress-induced apoptosis as manifested by reducing CHOP/GADD153 expression, the ratio of Bax/Bcl-2, caspase-12 and caspase-3 activity in H/R-treated cardiomyocytes. Thapsigargin (TG) is a potent ER stress inducer and used to elicit ER stress of cardiomyocytes. Our results showed that lycopene was able to prevent TG-induced ER stress as reflected by attenuating the protein expression of GRP78 and CHOP/GADD153 compared to TG group, significantly improve TG-caused a loss of cell viability and decrease apoptosis in TG-treated cardiomyocytes. These results suggest that the protective effects of lycopene on H/R-injury are, at least in part, through alleviating ER stress and ER stress-induced apoptosis in neonatal mouse cardiomyocytes.

BKCa channel activation increases cardiac contractile recovery following hypothermic ischemia/reperfusion

Mitochondrial Ca(2+)-activated large-conductance K(+) (BKCa) channels are thought to provide protection during ischemic insults in the heart. Rottlerin (mallotoxin) has been implicated as a potent BKCa activator. The purpose of this study was twofold: 1) to investigate the efficacy of BKCa channel activation as a cardioprotective strategy during ischemic cardioplegic arrest and reperfusion (CP/R) and 2) to assess the specificity of rottlerin for BKCa channels. Wild-type (WT) and BKCa knockout (KO) mice were subjected to an isolated heart model of ischemic CP/R. A mechanism of rottlerin-induced cardioprotection was also investigated using H9c2 cells subjected to in vitro CP/reoxygenation and assessed for mitochondrial membrane potential and reactive oxygen species (ROS) production. CP/R decreased left ventricular developed pressure, positive and negative first derivatives of left ventricular pressure, and coronary flow (CF) in WT mice. Rottlerin dose dependently increased the recovery of left ventricular function and CF to near baseline levels. BKCa KO hearts treated with or without 500 nM rottlerin were similar to WT CP hearts. H9c2 cells subjected to in vitro CP/R displayed reduced mitochondrial membrane potential and increased ROS generation, both of which were significantly normalized by rottlerin. We conclude that activation of BKCa channels rescues ischemic damage associated with CP/R, likely via effects on improved mitochondrial membrane potential and reduced ROS generation.

Effects of gallic Acid and cyclosporine a on antioxidant capacity and cardiac markers of rat isolated heart after ischemia/reperfusion

BACKGROUND

Myocardial infarction is one of the important causes of death during old ages. Gallic acid as an antioxidant or cyclosporine A (CsA) as inhibitor of mitochondrial permeability transition pore (mPTP) alone could prevent these complications to some extent, but their combination effect has not been investigated.

OBJECTIVES

The aim of this study was to determine the combined effect of gallic acid and CsA on antioxidant capacity of isolated heart tissues during ischemia reperfusion.

MATERIALS AND METHODS

EIGHTY MALE WISTAR RATS WERE RANDOMLY ASSIGNED TO DIFFERENT GROUPS: sham, control (Ca, received saline, 1 mL/kg); 3 groups were pretreated with gallic acid (G1a: 7.5, G2a: 15, G3a: 30 mg/kg) for 10 days, and the other 3 groups were pretreated with gallic acid and received CsA (0.2 µM) for 10 minutes before induction of ischemia and during the first 10 minutes of reperfusion (G1b, G2b and G3b) and the last group received CsA alone (Cb). After 10 days of pretreatment, the heart was isolated and transferred to the Langendorff apparatus and exposed to 30 minutes ischemia followed by 60 minutes of reperfusion. After that cardiac markers and antioxidant enzymes were assessed in cardiac tissues.

RESULTS

Lactate dehydrogenase (LDH), Superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) activity increased and malondialdehyde (MDA) decreased in animals pretreated with gallic acid significantly. However, pretreatment with gallic acid followed by CsA during reperfusion improved the antioxidant capacity and cardiac marker enzymes and restored the lipid peroxidation more effective than gallic acid or CsA alone. Nevertheless, CsA did not change the cardiac marker enzymes significantly.

CONCLUSIONS

Gallic acid and CsA combination improved antioxidant capacity and cell membrane integrity more than each one alone. Therefore, it can be a therapeutic approach to reduce the I/R injury.

Remote ischemic preconditioning in percutaneous coronary revascularization: a double-blind randomized controlled clinical trial

OBJECTIVE

To assess the impact of pre-procedural remote ischemic preconditioning on the incidence of myocardial complications following percutaneous coronary intervention.

BACKGROUND

Ischemic preconditioning of a remote vascular territory improves the subsequent ischemic tolerance of distant organs.

METHOD

The Myocardial Event Reduction with Ischemic Preconditioning Therapy (MERIT) trial recruited 80 consecutive patients undergoing elective angioplasty with drug-eluting stents to receive two 5-min lower limb tourniquet occlusions or an un-inflated tourniquet (controls) 1 h before the procedure. The primary outcome was troponin T level at 24 h. Secondary outcomes were intra-procedural chest pain and ST-segment deviation.

RESULTS

6 patients in the control group and 2 in the ischemic preconditioning group had pre-procedural raised troponin T (p = 0.23). This increased to 16 (40%) in the control group and 5 (12.5%) in the study group at 24 h (p = 0.01). Fewer patients in the study group experienced intra-procedural chest pain (1 vs. 7, p = 0.056). Mean ST-segment deviation time was 13 ± 35 s in the study group and 58 ± 118 s in the control group (p = 0.02). At a mean follow-up of 11 months, the major adverse cardiac event rate did not differ significantly between the groups.

CONCLUSION

These data suggest that ischemic preconditioning reduces the absolute risk of post-procedure cardiomyocyte necrosis by 27.5%, and reduces intra-procedural chest pain and ST-segment deviation in patients undergoing percutaneous coronary interventions. We suggest its routine use in percutaneous coronary intervention, although the long-term prognostic impact in this patient group warrants further investigation.

Cardiosphere-derived cells improve function in the infarcted rat heart for at least 16 weeks--an MRI study

Aims

Endogenous cardiac progenitor cells, expanded from explants via cardiosphere formation, present a promising cell source to prevent heart failure following myocardial infarction. Here we used cine-magnetic resonance imaging (MRI) to track administered cardiosphere-derived cells (CDCs) and to measure changes in cardiac function over four months in the infarcted rat heart.

Methods and Results

CDCs, cultured from neonatal rat heart, comprised a heterogeneous population including cells expressing the mesenchymal markers CD90 and CD105, the stem cell marker c-kit and the pluripotency markers Sox2, Oct3/4 and Klf-4. CDCs (2×10⁶) expressing green fluorescent protein (GFP+) were labelled with fluorescent micron-sized particles of iron oxide (MPIO). Labelled cells were administered to the infarcted rat hearts (n = 7) by intramyocardial injection immediately following reperfusion, then by systemic infusion (4×10⁶) 2 days later. A control group (n = 7) was administered cell medium. MR hypointensities caused by the MPIOs were detected at all times and GFP+ cells containing MPIO particles were identified in tissue slices at 16 weeks. At two days after infarction, cardiac function was similar between groups. By 6 weeks, ejection fractions in control hearts had significantly decreased (47±2%), but this was not evident in CDC-treated hearts (56±3%). The significantly higher ejection fractions in the CDC-treated group were maintained for a further 10 weeks. In addition, CDC-treated rat hearts had significantly increased capillary density in the peri-infarct region and lower infarct sizes. MPIO-labelled cells also expressed cardiac troponin I, von Willebrand factor and smooth muscle actin, suggesting their differentiation along the cardiomyocyte lineage and the formation of new blood vessels.

Conclusions

CDCs were retained in the infarcted rat heart for 16 weeks and improved cardiac function.

The PPAR-gamma agonist rosiglitazone facilitates Akt rephosphorylation and inhibits apoptosis in cardiomyocytes during hypoxia/reoxygenation

BACKGROUND AND AIM

Results on the cardiovascular effects of PPAR-gamma agonists are conflicting. On one hand, it was suggested that the PPAR-gamma agonist rosiglitazone may increase the risk of cardiovascular events. On the other hand, PPAR-gamma agonists reduce myocardial infarct size and improve myocardial function during ischemia/reperfusion in animal studies in vivo. However, the mechanism of this effect is unclear, and it is open if PPAR-gamma agonists have a direct effect on cardiac myocyte survival in ischemia/reperfusion. The aim of this study was to determine the effect of the PPAR-gamma agonist rosiglitazone on hypoxia/reoxygenation-induced apoptosis of isolated cardiomyocytes.

METHODS

Isolated rat cardiac myocytes were pretreated with rosiglitazone or vehicle for 30 min before they were subjected to hypoxia for 4 h followed by different times of reoxygenation (5 min to 12 h). Apoptosis was determined by in situ hybridization for DNA fragmentation (TUNEL) as well as detection of cytoplasmic accumulation of histone-associated DNA fragments by enzyme-linked immunosorbent assay (ELISA). Activation of apoptosis regulating intracellular signalling pathways was studied by immunoblotting using phosphospecific antibodies.

RESULTS

Rosiglitazone significantly reduced apoptosis of isolated cardiomyocytes subjected to hypoxia/reoxygenation, independently determined with two methods. After 4 h of hypoxia and 12 h of reoxygenation, 34 +/- 3.6% of the vehicle treated cardiac myocytes stained positive for DNA fragmentation in the TUNEL staining. Rosiglitazone treatment reduced this effect by 23% (p < 0.01). Even more pronounced, cytoplasmic accumulation of histone-associated DNA fragments detected by ELISA was reduced by 35% (p < 0.05) in the presence of rosiglitazone. This inhibition of hypoxia/reoxygenation-induced apoptosis was associated with an increased reoxygenation-induced rephosphorylation of the protein kinase Akt, a crucial mediator of cardiomyocyte survival in ischemia/reperfusion of the heart. This effect was reversed by GW-9662, an irreversible PPAR-gamma antagonist. However, rosiglitazone did not alter phosphorylation of the MAP kinases ERK1/2 and c-Jun N-terminal kinase (JNK).

CONCLUSION

It can be concluded that cardiac myocytes are direct targets of PPAR-gamma agonists promoting its survival in ischemia/reperfusion, at least in part by facilitating Akt rephosphorylation. This effect may be of clinical relevance inhibiting the reperfusion-induced injury in patients suffering from myocardial infarction or undergoing cardiac surgery.

Cardiac stunning in the clinic: the full picture

Cardiac stunning refers to different dysfunctional levels occurring after an episode of acute ischemia, despite blood flow is near normal or normal. The phenomenon was initially identified in animal models, where it has been very well characterized. After being established in the experimental setting, it remained unclear, whether a similar syndrome occurs in humans. In addition, it remained controversial, whether stunning was of any clinical relevance as it is spontaneously reversible. Hence, many studies continue to focus on the properties and mechanisms of stunning, although therapies seem more relevant for attenuating and treating myocardial ischemia/reperfusion (I/R) injury, i.e. to bridge until recovery. This article reviews the different facets of cardiac stunning, i.e. myocardial, vascular/microvascular/endothelial, metabolic, neural/neuronal, and electrical stunning. This review also displays where these facets exist and which clinical relevance they might have. Particular attention is directed to the different therapeutic interventions that the various facets of this I/R-induced cardiac injury might require. A final outlook considers possible alternatives to further reduce the detrimental consequences of brief episodes of ischemia and reperfusion.

Ischaemia/reperfusion induced cardiac stem cell homing to the injured myocardium by stimulating stem cell factor expression via NF-kappaB pathway

Ischaemia/reperfusion (I/R) is a major cause of heart failure. Recently cardiac stem cells (CSCs) were proposed as the most appropriate cell type for heart disease therapy. However, it is still unclear whether I/R can stimulate the CSCs homing to the injured myocardium. Male Sprague-Dawley rats were subjected to a 30-min ischaemia followed by reperfusion of different intervals. RT-PCR, western blotting and immunohistochemistry were performed to detect stem cell factor (SCF) expression at mRNA and protein levels respectively. Activation of nuclear factor-kappaB (NF-kappaB) was determined by electrophoretic mobility shift assay. To assess the homing of CSCs in vivo, BrdU-labelled CSCs were injected into AV-groove before induction of ischaemia and examined by immunofluorescent staining in the injured myocardium after I/R. From day 3 to day 6 after reperfusion, the accumulation of CSCs was significantly elevated in the injured area, which was matched with the increased SCF expression during I/R. Pretreatment of rats with NF-kappaB inhibitor, N-acetyl-L-cysteine (NAC) not only suppressed NF-kappaB activation induced by I/R but also attenuated SCF expression. Further analysis revealed that I/R induced phosphorylation of IkappaBalpha after 15 min of reperfusion, and the raised phosphor-IkappaBalpha returned to the basal level at 2 h of reperfusion. In simulated I/R(SI/R) in vitro, it enhanced NF-kappaB activation and SCF expression in cultured neonatal rat cardiomyocytes, which was markedly inhibited by NF-kappaB decoy oligodeoxynucleotide or NAC. Taken together, our results demonstrated that I/R induced CSCs homing to the injured myocardium by stimulating myocardial SCF expression via activation of NF-kappaB.

Comparison of intra-coronary cell transplantation after myocardial infarction: Autologous skeletal myoblasts versus bone marrow mesenchymal stem cells

Cell transplantation promises restoration of cardiac function after myocardial infarction (MI). Comparison of intracoronary cell transplantation with skeletal myoblasts (SMs) versus bone marrow mesenchymal stem cells (BM-MSCs) was carried out in rabbits with MI induced by ligation of the left anterior descending artery. The infarction-affected artery was injected with SMs, BM-MSCs or cell-free medium (control) 24 h post-infarction (n = 15 per group). At baseline, there were no differences in cardiac parameters between the groups. At 4 weeks post-transplantation, left ventricular ejection fraction significantly improved and left ventricular end-diastolic diameter was significantly decreased in the cell-treated groups compared with pre-transplantation and the control group. Engrafted cells were found in all of the cell-treated rabbits. The cell-treated animals had significantly higher numbers of neovessels compared with the control. No significant difference was seen between the SM and BM-MSC groups. In conclusion, intra-coronary transplantation of SMs and BM-MSCs induced neoangiogenesis with comparable enhancements of cardiac performance and reduced cardiac remodelling in a rabbit MI model.

Astaxanthin: a novel potential treatment for oxidative stress and inflammation in cardiovascular disease

Oxidative stress and inflammation are implicated in several different manifestations of cardiovascular disease (CVD). They are generated, in part, from the overproduction of reactive oxygen species (ROS) and reactive nitrogen species (RNS) that activate transcriptional messengers, such as nuclear factor-kappaB, tangibly contributing to endothelial dysfunction, the initiation and progression of atherosclerosis, irreversible damage after ischemic reperfusion, and even arrhythmia, such as atrial fibrillation. Despite this connection between oxidative stress and CVD, there are currently no recognized therapeutic interventions to address this important unmet need. Antioxidants that provide a broad, "upstream" approach via ROS/RNS quenching or free radical chain breaking seem an appropriate therapeutic option based on epidemiologic, dietary, and in vivo animal model data. However, human clinical trials with several different well-known agents, such as vitamin E and beta-carotene, have been disappointing. Does this mean antioxidants as a class are ineffective, or rather that the "right" compound(s) have yet to be found, their mechanisms of action understood, and their appropriate targeting and dosages determined? A large class of potent naturally-occurring antioxidants exploited by nature-the oxygenated carotenoids (xanthophylls)-have demonstrated utility in their natural form but have eluded development as successful targeted therapeutic agents up to the present time. This article characterizes the mechanism by which this novel group of antioxidants function and reviews their preclinical development. Results from multiple species support the antioxidant/anti-inflammatory properties of the prototype compound, astaxanthin, establishing it as an appropriate candidate for development as a therapeutic agent for cardiovascular oxidative stress and inflammation.