Hypercholesterolemia abrogates the protective effect of ischemic postconditioning by induction of apoptosis and impairment of activation of reperfusion injury salvage kinase pathway

The mechanism and targeted intervention of the HIF-1 pathway in improving atherosclerotic heart's sensitivity to ischemic postconditioning

BACKGROUND

IPoC possesses a preventive effect against IR injury in healthy myocardium, but IPoC's protective effect on atherosclerotic myocardium is controversial. The current investigation aims to determine whether IPoC remains protective in atherosclerotic myocardium subjected to ischemia-reperfusion (IR) injury; to explore the specific mechanisms by which IPoC exerts cardioprotection; to explore whether HIF-1 upregulation combined with IPoC could further the provide cardioprotection; and to gaze at the specific mechanism whereby combined treatment expert the cardioprotection.

METHODS

ApoE-/- mice fed with a high-fat diet (HFD) were used to develop a model of atherosclerosis. The myocardial IR model was induced by occlusion of the left anterior descending (LAD) artery for 45 min, followed by reperfusion for 120 min. The protection of IPoC in both healthy and atherosclerotic myocardium was evaluated by measuring oxidative stress, apoptosis, infarct size, pathology, mitochondrial dysfunction and morphology of myocardium. The specific mechanism by which IPoC exerts cardioprotection in healthy and atherosclerotic myocardium was observed by measuring the expression of proteins involved in HIF-1, APMK and RISK pathways. The effect of HIF-1α overexpression on the cardioprotection by IPoC was observed by intravenous AAV9 -HIF-1α injection.

RESULTS

In healthy ischemic myocardium, IPoC exerted myocardial protective effects (antioxidant, anti-apoptosis, and improved mitochondrial function) through the activation of HIF-1, AMPK and RISK pathways. In atherosclerotic ischemic myocardium, IPoC exerted cardioprotection only through the activation of HIF-1 pathway; however, HIF-1 overexpression combined IPoC restored the activation of AMPK and RISK pathways, thereby further alleviating the myocardial IR injury.

CONCLUSIONS

In the atherosclerotic state, the HIF-1 pathway is the intrinsic mechanism by which IPoC exerts cardioprotective effects. The combination of HIF-1 upregulation and IPoC has a significant effect in reducing myocardial injury, which is worth being promoted and advocated. In addition, HIF-1-AMPK and HIF-1-RISK may be two endogenous cardioprotective signalling pathways with great value, which deserve to be thoroughly investigated in the future.

[PI3K/Akt signaling pathway mediates the protective effect of endomorphin-1 postconditioning against myocardial ischemia-reperfusion injury in rats]

OBJECTIVE

To investigate the role of PI3K/Akt signaling pathway in mediating the protective effect of endomorphin-1 against myocardial ischemia-reperfusion (IR) injury.

OBJECTIVE

Fifty SD male rats were randomly divided into sham operation group, myocardial IR group, endomorphin-1 post-treatment group (EM50 group), endomorphin-1+wortmannin (a PI3K/Akt signaling pathway inhibitor) treatment group (EM50+Wort group), and wortmannin treatment group (Wort group). Rat models of myocardial IR injury were established by ligation of the left anterior descending coronary artery for 30 min followed by reperfusion for 120 min. The heart rate and mean arterial pressure were monitored during the experiment. Plasma levels of LDH, CK-MB, cTnI, IL-6, TNF-α, SOD and MDA were measured after reperfusion. The mRNA expression of Bax and Bcl-2 was detected using RT-PCR, and the expression of apoptosis-related protein cleaved caspase-3, phosphorylated Akt protein and total Akt protein in myocardial tissue was detected using Western blotting.

OBJECTIVE

Myocardial IR injury significantly decreased heart rate and blood pressure of the rats in comparison with the sham operation (P < 0.05). Compared with those in the IR group, the rats in EM50 group showed significantly increased heart rate and blood pressure (P < 0.05) with decreased plasma LDH, CK-MB, cTnI, IL-6, TNF-α and MDA levels (P < 0.05), increased SOD activity (P < 0.05), increased expression of p-Akt protein and Bcl-2 mRNA (P < 0.05), and decreased expression of Bax mRNA and cleaved caspase-3 protein (P < 0.05). In EM50+Wort group, the heart rate and blood pressure were significantly lowered (P < 0.05), plasma LDH, CK-MB, cTnI, IL-6, TNF-α and MDA levels increased (P < 0.05), SOD activity decreased (P < 0.05), the expression of p-Akt protein and Bcl-2 mRNA was reduced (P < 0.05), and the expression of Bax mRNA and cleaved caspase-3 protein increased (P < 0.05) as compared with those in EM50 group.

OBJECTIVE

EM-1 postconditioning can regulate cardiac myocyte apoptosis and reduce myocardial IR injury in rats. The PI3K/Akt signaling pathway may play a role in mediating the myocardial protective effects of EM-1 postconditioning.

The Rise of ST-Elevation Myocardial Infarction in Women of Northeast China

The women of China's Liaoning province display some morbidities in ways that defy medical explanation. Women have higher rates of hypertension, hypercholesterolemia, and metabolic syndrome than men, an anomaly for all three conditions. Most of these patients also suffer from Type 2 Diabetes Mellitus (T2DM) while there was a negative association between being female and T2DM for the rest of China. Each of these conditions can exist independently, but the increase in both their rates and congruence is a recent phenomenon. Stranger still is that Liaoning women are now presenting in hospital emergency departments with ST-Elevation Myocardial Infarction (STEMI), while diabetics predominantly suffer more benign Non-STEMI (NSTEMI) events. Confounding factors in any attempt to study this phenomenon include trace metals like manganese that have been shown to reduce systolic blood pressure in Asian men and raise it in Asian women. Some of the phenomenon may also be associated with the gene for Apolipoprotein 5, but its recent nature suggests other factors besides lipid profiles. Trace metals in the air, water, and diet of Liaoning province, or any urban environment, could play a role.

Reduced effect of ischemic preconditioning against endothelial ischemia-reperfusion injury with cardiovascular risk factors in humans

The extent that clustered CVD risk factors interfere with ischemic preconditioning (IPC) to protect against microvascular endothelial dysfunction with ischemia-reperfusion (I/R) injury in humans is unclear. We hypothesized that adults with a clustered burden of ≥3 CVD risk factors would demonstrate a reduced capacity of IPC to protect endothelial function with I/R injury. Twenty-two (age: 45 ± 14 year) adults [12 healthy controls; 10 raised risk (10-year FRS risk score ~3%)] were studied using a 2 × 2 randomized cross-over design. Pulse arterial tonometry was used to assess microvascular endothelium-dependent vasodilation during reactive hyperemia in response to endothelial I/R injury (20 min brachial artery occlusion/45 min reperfusion) that was preceded by remote IPC (3 × 5 min ischemia/reperfusion) or mock IPC. In both groups, microvascular reactive hyperemia was reduced ~20% (both P < 0.01) after endothelial I/R injury without remote IPC. However, in control subjects remote IPC prevented endothelial I/R injury (from baseline reactive hyperemic ratio: 2.1 ± 0.4 AU to post I/R injury: 2.5 ± 0.5 AU; P = 0.09). In contrast, the reactive hyperemia ratio in raised risk subjects was significantly reduced from 2.2 ± 0.6 AU to 1.9 ± 0.5 AU (P = 0.0087) despite attempts to induce protection by remote IPC, with the magnitude of reduction similar to their mock IPC trial. The magnitude of remote IPC-mediated endothelial protection against I/R injury was inversely related to the number of risk factors. CVD risk factors diminish the effect of IPC to protect the microvasculature from I/R injury in humans. Translating IPC to clinical practice for vasculoprotection will continue to be challenging in patients with increased CVD risk.

MiR-219a-2 relieves myocardial ischemia-reperfusion injury by reducing calcium overload and cell apoptosis through HIF1α/ NMDAR pathway

OBJECTIVE

During the process of myocardial ischemia-reperfusion injury (MIRI), the intracellular Ca²⁺ concentration ([Ca²⁺]_i) continues to increase, leads to the cardiomyocyte apoptosis and eventually causes myocardial damage, while the upstream regulation mechanism of calcium overload is still unknown. This study focuses on the role of miR-219a-2 in MIRI and aims to elaborate its regulatory mechanism on calcium overload that occurs during MIRI.

METHODS

The expression of miR-219a-2 was determined in the heart tissues of MIRI mice by qRT-PCR. The [Ca²⁺]_i was measured by fluo-3 using a fluorescence microplate reader. The expression of hypoxiainducible factor 1α (HIF1α) and NR1, the obligatory subunit of N-methyl-d-aspartate receptor 1 (NMDAR), were measured by qRT-PCR and western blot. The luciferase reporter assay was used to confirm the interplay between miR-219a-2 and HIF1α and the interplay between HIF1α and NR1. The cell apoptosis was measured by the expression level of B-cell lymphoma 2 interacting mediator of cell death (Bim) and the number of TUNEL-positive cells. The myocardial infarct size of mice was measured by TTC/Evans Blue staining.

RESULTS

MiR-219a-2 was down-regulated in the heart tissues of MIRI mice. miR-219a-2 overexpression decreased [Ca²⁺]_i and the expression of HIF1α and NR1 in hypoxia/reoxygenation (H/R)-treated HL-1 cells. Then, the luciferase reporter assay showed that miR-219a-2 inhibited the transcription of HIF1α and HIF1α promoted the transcription of NR1. Both HIF1α overexpression and NMDAR function enhancement removed the inhibitory effect of miR-219a-2 on calcium overload and cell apoptosis in H/R-treated HL-1 cells. Finally, the overexpression of miR-219a-2 decreased Ca²⁺ concentration, cell apoptosis, and myocardial infarction size in MIRI mice, while the NMDAR function enhancer reversed the therapeutic effect of miR-219a-2.

CONCLUSION

MiR-219a-2 reducing NMDAR-mediated calcium overload via HIF1α/NR1 axis, thus alleviating cell apoptosis in MIRI.

Lycopene protects against myocardial ischemia-reperfusion injury by inhibiting mitochondrial permeability transition pore opening

BACKGROUND

Mitochondria permeability transition pore (MPTP) is an important therapeutic target for myocardial ischemia-reperfusion injury (MIRI). Lycopene (LP) is a potent antioxidant extracted from the mature fruits of plants and has been reported to protect against MIRI; however, its mechanism of action has yet to be completely elucidated. The present study aimed to investigate the role of MPTP in the cardioprotection of LP.

METHODS

H9c2 cells were pretreated with LP for 12 hrs and were subjected to 12-hr hypoxia/1-hr re-oxygenation, and cell viability was measured by a Cell Counting Kit-8 (CCK-8) assay. Male rats were subsequently intraperitoneally injected with LP for 5 consecutive days. At 24 hrs following the final injection, the rat hearts were isolated and subjected to 30-min ischemia/120-min reperfusion using Langendorff apparatus. The myocardial infarct size was measured by a TTC stain. Opening of the MPTP was induced by CaCl2 and measured by colorimetry. The change in mitochondrial transmembrane potential (ΔΨm) was observed under a fluorescence microscope. Apoptosis was measured by flow cytometry and a TUNEL stain, and the expression of apoptosis-related proteins was detected by Western blotting.

RESULTS

LP pretreatment significantly increased cell viability, reduced myocardial infarct size and decreased the apoptosis rate. In addition, opening and the decrease of ΔΨm were attenuated by LP and the expressions of cytochrome c, APAF-1, cleaved caspase-9 and cleaved caspase-3 were also decreased by LP. However, these beneficial effects on MIRI were abrogated by the MPTP opener (atractyloside). Furthermore, LP treatment markedly increased Bcl-2 expression, decreased Bax expression and the Bax/Bcl-2 ratio.

CONCLUSION

The results of the present study demonstrated that LP protects against MIRI by inhibiting MPTP opening, partly through the modulation of Bax and Bcl-2.

Lycopene restores the effect of ischemic postconditioning on myocardial ischemia‑reperfusion injury in hypercholesterolemic rats

Ischemic postconditioning (IPoC) has been demonstrated to prevent myocardial ischemia-reperfusion injury (MIRI), but its cardioprotective effect is abrogated by hypercholesterolemia. The aim of the present study was to determine whether lycopene (LP), a type of carotenoid, can restore the cardioprotective effect of IPoC in hypercholesterolemic rats. Male Wistar rats were fed a cholesterol-enriched diet for 12 weeks to establish a hypercholesterolemic model. The rat hearts were isolated and subjected to 30 min ischemia and 60 min reperfusion using a Langendorff apparatus. LP was administered to the rats intraperitoneally for 5 consecutive days prior to ischemia and reperfusion. Myocardial pathological changes, infarct size and cell apoptosis were measured by hematoxylin and eosin, triphenyltetrazolium chloride and TUNEL staining, respectively. The changes in endoplasmic reticulum (ER) stress markers, the reperfusion injury salvage kinase (RISK) pathway and mitochondrial apoptosis-related proteins were detected by western blotting. Overall, the results demonstrated that low-dose LP in combination with IPoC ameliorated myocardial histopathological changes, reduced the infarct size and release of cardiac enzymes, and decreased cardiomyocyte apoptosis in hypercholesterolemic rats, but no beneficial effects were achieved by the same dose of LP or IPoC treatment were used alone. Furthermore, the combination of LP and IPoC inhibited the expression of glucose-regulated protein 78 and C/EBP homologous protein, increased the phosphorylation levels of AKT, ERK1/2 and glycogen synthase kinase-3β, repressed mitochondrial permeability transition pore opening, and reduced the expression of cytochrome c, cleaved caspase-9 and cleaved caspase-3. Collectively, these findings demonstrated that LP can restore the cardioprotective effects of IPoC on MIRI in hypercholesterolemic rats, and this restoration by LP was mediated by inhibition of ER stress and reactivation of the RISK pathway in hypercholesterolemic rat myocardium.

Intra-coronary morphine versus placebo in the treatment of acute ST-segment elevation myocardial infarction: the MIAMI randomized controlled trial

BACKGROUND

Experimental studies suggest that morphine may protect the myocardium against ischemia-reperfusion injury by activating salvage kinase pathways. The objective of this two-center, randomized, double-blind, controlled trial was to assess potential cardioprotective effects of intra-coronary morphine in patients with ST-segment elevation myocardial infarction (STEMI) referred for primary percutaneous intervention.

METHODS

Ninety-one patients with STEMI were randomly assigned to intracoronary morphine (1 mg) or placebo at reperfusion of the culprit coronary artery. The primary endpoint was infarct size/left ventricular mass ratio assessed by magnetic resonance imaging on day 3-5. Secondary endpoints included the areas under the curve (AUC) for troponin T and creatine kinase over three days, left ventricular ejection fraction assessed by echocardiography on days 1 and 6, and clinical outcomes.

RESULTS

Infarct size/left ventricular mass ratio was not significantly reduced by intracoronary morphine compared to placebo (27.2% ± 15.0% vs. 30.5% ± 10.6%, respectively, p = 0.28). Troponin T and creatine kinase AUCs were similar in the two groups. Morphine did not improve left ventricular ejection fraction on day 1 (49.7 ± 10.3% vs. 49.3 ± 9.3% with placebo, p = 0.84) or day 6 (48.5 ± 10.2% vs. 49.0 ± 8.5% with placebo, p = 0.86). The number of major adverse cardiac events, including stent thrombosis, during the one-year follow-up was similar in the two groups.

CONCLUSIONS

Intracoronary morphine at reperfusion did not significantly reduce infarct size or improve left ventricular systolic function in patients with STEMI. Presence of comorbidities in some patients may contribute to explain these results.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01186445 (date of registration: August 23, 2010).

Myocyte membrane and microdomain modifications in diabetes: determinants of ischemic tolerance and cardioprotection

Cardiovascular disease, predominantly ischemic heart disease (IHD), is the leading cause of death in diabetes mellitus (DM). In addition to eliciting cardiomyopathy, DM induces a ‘wicked triumvirate’: (i) increasing the risk and incidence of IHD and myocardial ischemia; (ii) decreasing myocardial tolerance to ischemia–reperfusion (I–R) injury; and (iii) inhibiting or eliminating responses to cardioprotective stimuli. Changes in ischemic tolerance and cardioprotective signaling may contribute to substantially higher mortality and morbidity following ischemic insult in DM patients. Among the diverse mechanisms implicated in diabetic impairment of ischemic tolerance and cardioprotection, changes in sarcolemmal makeup may play an overarching role and are considered in detail in the current review. Observations predominantly in animal models reveal DM-dependent changes in membrane lipid composition (cholesterol and triglyceride accumulation, fatty acid saturation vs. reduced desaturation, phospholipid remodeling) that contribute to modulation of caveolar domains, gap junctions and T-tubules. These modifications influence sarcolemmal biophysical properties, receptor and phospholipid signaling, ion channel and transporter functions, contributing to contractile and electrophysiological dysfunction, cardiomyopathy, ischemic intolerance and suppression of protective signaling. A better understanding of these sarcolemmal abnormalities in types I and II DM (T1DM, T2DM) can inform approaches to limiting cardiomyopathy, associated IHD and their consequences. Key knowledge gaps include details of sarcolemmal changes in models of T2DM, temporal patterns of lipid, microdomain and T-tubule changes during disease development, and the precise impacts of these diverse sarcolemmal modifications. Importantly, exercise, dietary, pharmacological and gene approaches have potential for improving sarcolemmal makeup, and thus myocyte function and stress-resistance in this ubiquitous metabolic disorder.

Acute atorvastatin treatment restores the cardioprotective effects of ischemic postconditioning in hyperlipidemic rats

BACKGROUND

Ischemic Postconditioning (IPC) reduces ischemia/reperfusion (I/R) injury under normal conditions. HMG-CoA reductase inhibitors (statins), which inhibit the synthesis of mevalonate, can interfere with the cardioprotective effect of IPC. However, the beneficial role of IPC in hyperlipidemic patients, post-acute administration of statins remains unknown. This study was to determine if acute administration of atorvastatin affect the infarct size-limiting effect of IPC in hyperlipidemic rats.

RESULTS

Compared to control group, infarct size decreased more significantly in atorvastatin+IPC and atorvastatin+IPC+wortmannin groups than IPC or atorvastatin+IPC+PD98059 groups. Phosphorylation of PI3K/Akt was attenuated in atorvastatin + IPC+ wortmannin group, phosphorylation of P42 MAPK/ERK was increased in atorvastatin+IPC and atorvastatin+IPC+wortmannin groups.

MATERIALS AND METHODS

Ninety four-weeks old male SD rats fed with cholesterol enriched diet for six weeks were randomized into nine groups (n = 10/group) - sham group, control group, IPC group, atorvastatin group, wortmannin group, PD98059 group, atorvastatin+IPC group, atorvastatin+IPC+wortmannin group and atorvastatin+IPC+PD98059 group. Atorvastatin was administered orally 12 hours before myocardial reperfusion.

CONCLUSIONS

Post-translational activation of P42 MAPK/ERK, rather than PI3K/Akt, participates in the net protective effect of IPC and atorvastatin in hyperlipidemia.

AT1 Receptor Modulator Attenuates the Hypercholesterolemia-Induced Impairment of the Myocardial Ischemic Post-Conditioning Benefits

Background and Objectives

Ischemic post-conditioning (PostC) has been demonstrated as a novel strategy to harness nature's protection against myocardial ischemia-reperfusion (I/R). Hypercholesterolemia (HC) has been reported to block the effect of PostC on the heart. Angiotensin II type-1 (AT1) modulators have shown benefits in myocardial ischemia. The present study investigates the effect of a novel inhibitor of AT1, azilsartan in PostC of the heart of normocholesterolemic (NC) and HC rats.

Materials and Methods

HC was induced by the administration of high-fat diet to the animals for eight weeks. Isolated Langendorff's perfused NC and HC rat hearts were exposed to global ischemia for 30 min and reperfusion for 120 min. I/R-injury had been assessed by cardiac hemodynamic parameters, myocardial infarct size, release of tumor necrosis factor-alpha troponin I, lactate dehydrogenase, creatine kinase, nitrite in coronary effluent, thiobarbituric acid reactive species, a reduced form of glutathione, superoxide anion, and left ventricle collagen content in normal and HC rat hearts.

Results

Azilsartan post-treatment and six episodes of PostC (10 sec each) afforded cardioprotection against I/R-injury in normal rat hearts. PostC protection against I/R-injury was abolished in HC rat hearts. Azilsartan prevented the HC-mediated impairment of the beneficial effects of PostC in I/R-induced myocardial injury, which was inhibited by L-N⁵-(1-Iminoethyl)ornithinehydrochloride, a potent inhibitor of endothelial nitric oxide synthase (eNOS).

Conclusion

Azilsartan treatment has attenuated the HC-induced impairment of beneficial effects of PostC in I/R-injury of rat hearts, by specifically modulating eNOS. Azilsartan may be explored further in I/R-myocardial injury, both in NC and HC conditions, with or without PostC.

Effect of hypercholesterolaemia on myocardial function, ischaemia-reperfusion injury and cardioprotection by preconditioning, postconditioning and remote conditioning

Hypercholesterolaemia is considered to be a principle risk factor for cardiovascular disease, having direct negative effects on the myocardium itself, in addition to the development of atherosclerosis. Since hypercholesterolaemia affects the global cardiac gene expression profile, among many other factors, it results in increased myocardial oxidative stress, mitochondrial dysfunction and inflammation triggered apoptosis, all of which may account for myocardial dysfunction and increased susceptibility of the myocardium to infarction. In addition, numerous experimental and clinical studies have revealed that hyperlcholesterolaemia may interfere with the cardioprotective potential of conditioning mechanisms. Although not fully elucidated, the underlying mechanisms for the lost cardioprotection in hypercholesterolaemic animals have been reported to involve dysregulation of the endothelial NOS-cGMP, reperfusion injury salvage kinase, peroxynitrite-MMP2 signalling pathways, modulation of ATP-sensitive potassium channels and apoptotic pathways. In this review article, we summarize the current knowledge on the effect of hypercholesterolaemia on the non-ischaemic and ischaemic heart as well as on the cardioprotection induced by drugs or ischaemic preconditioning, postconditioning and remote conditioning. Future perspectives concerning the mechanisms and the design of preclinical and clinical trials are highlighted.

LINKED ARTICLES

This article is part of a themed section on Redox Biology and Oxidative Stress in Health and Disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.12/issuetoc.

Acute and Chronic Pretreatment With Atenolol Attenuates Intestinal Ischemia and Reperfusion Injury in Hypercholesterolemic Rats

OBJECTIVE

To evaluate the protective effects of preinjury atenolol (acute v chronic) on apoptosis, contractility, oxidative stress, and inflammatory markers in hypercholesterolemic rats undergoing intestinal ischemia-reperfusion (I/R) injury.

DESIGN

Prospective, experimental animal study.

SETTING

University laboratory.

PARTICIPANTS

Male Wistar rats (n = 32).

INTERVENTIONS

Rats were divided into the following 4 groups: 1 group was fed a normal diet (ND) (group ND+NoAT [no atenolol]), and the other 3 groups were fed a high-cholesterol diet (HCD)-group HCD+NoAT, group HCD+ChAT (chronic atenolol, 3 mg/kg/day for 8 weeks), and group HCD+AcAT (acute atenolol, 1.5 mg/kg, given 5 minutes before intestinal clamping). All rats underwent I/R injury. The superior mesenteric artery was clamped for 60 minutes, then opened for 120 minutes (reperfusion). Apoptotic cells and stimulated contractions of ileal segments were examined. Tissue markers of intestinal I/R injury were examined. Intestinal malondialdehyde, superoxide dismutase, and nitrate/nitrite levels were measured.

MEASUREMENTS AND MAIN RESULTS

The chronic atenolol group had fewer apoptotic cells and higher superoxide dismutase activity compared with the other groups. Intestinal contraction was higher in both atenolol pretreatment groups compared with the NoAT groups. Chronic and acute atenolol resulted in lower ileal levels of malondialdehyde and immunolabeling-positive cells (intestinal inducible nitric oxide synthase, endothelial nitric oxide synthase, interleukin-1, and interleukin-8) after I/R injury compared with the no atenolol groups.

CONCLUSIONS

Both chronic and acute pre-I/R injury treatment with atenolol attenuated I/R injury in this hypercholesterolemic rat model. These findings should encourage future studies of atenolol in hypercholesterolemic patients undergoing procedures with a high risk of intestinal ischemia.

Involvement of inducible nitric oxide synthase in the loss of cardioprotection by ischemic postconditioning in hypothyroid rats

Cardioprotection by ischemic postconditioning (IPost) is negated in hypothyroidism; the underlying mechanisms however are unknown. This study aimed at determining whether changes in Bax, Bcl-2, eNOS, and iNOS gene expressions are involved in the negating effects of IPost against ischemia-reperfusion (IR) injury in hypothyroidism. The hearts from control and hypothyroid rats were perfused in Langendorff apparatus and exposed to 30 min ischemia, followed by 120 min reperfusion and IPost. In a subgroup of hypothyroid rats, ischemia duration was extended to 40 min. Hemodynamic parameters, infarct size, and gene expressions were measured. Compared to controls, hypothyroid rats with 30 min ischemia had higher recovery of post-ischemic LVDP and ± dp/dt, confirmed by decreased CK and LDH levels (187 ± 16 vs. 485 ± 41 and 191 ± 9 vs. 702 ± 48 U/L, respectively; p<0.05), decreased infarct size (6.7 ± 1.1 vs. 46.1 ± 1.7%; p<0.05), and a reduced DNA laddering pattern. Recovery of post-ischemic LVDP and ± dp/dt decreased and infarct size increased following extension of ischemia period in hypothyroid rats. IPost increased eNOS and Bcl-2 expression by 3.2-fold and 3.7-fold and decreased Bax and iNOS expression by 79% and 38%, respectively; it also reduced IR-induced DNA laddering pattern in controls, whereas no change was observed in hypothyroid rats, regardless of the ischemia period. In conclusion, hearts from hypothyroid rats were resistant to IR injury, partly due to the lower expression of iNOS and subsequent reduction in apoptosis after IR. In hypothyroid rats, IPost was not associated with further reduction in iNOS expression and failed to provide additional cardioprotection against ischemia.

Ginsenoside Rb1 prevents hypoxia-reoxygenation-induced apoptosis in H9c2 cardiomyocytes via an estrogen receptor-dependent crosstalk among the Akt, JNK, and ERK 1/2 pathways using a label-free quantitative proteomics analysis

Rb1 prevents H/R-induced apoptosis of H9c2 cells via an estrogen receptor-dependent crosstalk among the Akt, JNK, and ERK 1/2 pathways.