Effects of endomorphin-1 postconditioning on myocardial ischemia/reperfusion injury and myocardial cell apoptosis in a rat model

MicroRNA-specific therapeutic targets and biomarkers of apoptosis following myocardial ischemia-reperfusion injury

MicroRNAs are single-stranded non-coding RNAs that participate in post-transcriptional regulation of gene expression, it is involved in the regulation of apoptosis after myocardial ischemia-reperfusion injury. For example, the alteration of mitochondrial structure is facilitated by MicroRNA-1 through the regulation of apoptosis-related proteins, such as Bax and Bcl-2, thereby mitigating cardiomyocyte apoptosis. MicroRNA-21 not only modulates the expression of NF-κB to suppress inflammatory signals but also activates the PI3K/AKT pathway to mitigate ischemia-reperfusion injury. Overexpression of MicroRNA-133 attenuates reactive oxygen species (ROS) production and suppressed the oxidative stress response, thereby mitigating cellular apoptosis. MicroRNA-139 modulates the extrinsic death signal of Fas, while MicroRNA-145 regulates endoplasmic reticulum calcium overload, both of which exert regulatory effects on cardiomyocyte apoptosis. Therefore, the article categorizes the molecular mechanisms based on the three classical pathways and multiple signaling pathways of apoptosis. It summarizes the targets and pathways of MicroRNA therapy for ischemia-reperfusion injury and analyzes future research directions.

Cardioprotective effects of co-administration of thymoquinone and ischemic postconditioning in diabetic rats

OBJECTIVES

Ischemia/reperfusion (I/R) is a leading cause of myocardial infarction (MI) injury, contributing to excess injury to cardiac tissues involved in inflammation, apoptosis, and oxidative stress. The present study was conducted to examine the effects of combined thymoquinone (TQ) with ischemic postconditioning (IPostC) therapy on apoptosis and inflammation due to I/R injury in diabetic rat hearts.

MATERIALS AND METHODS

A single dose injection of streptozotocin (STZ; 60 mg/kg) was administered to thirty-two Wistar male rats to induce diabetes. Hearts were fixed on a Langendorff setting and exposed to a 30 min regional ischemia subsequently to 60 min reperfusion. IPostC was induced at the onset of reperfusion by 3 cycles of 30 sec R/I. ELISA, Western blotting assay, and TUNEL staining were applied to assess the cardioprotective effect of IPostC and TQ against I/R injury in diabetic and non-diabetic rats.

RESULTS

Administration of TQ alone in non-diabetic isolated hearts significantly diminished CK-MB, TNF-α, IL-1β, and apoptosis and enhanced p-GSK-3β and Bcl-2 (P<0.05). Following administration of TQ, the cardioprotective effects of IPostC by elevating p-GSK-3β and Bcl-2 and alleviating apoptosis and inflammation were reestablished compared with non-IPostC diabetic hearts.

CONCLUSION

These results provide substantial evidence that co-administration of TQ plus IPostC can exert cardioprotective effects on diabetic myocardium during I/R damage by attenuating the inflammatory response and apoptosis.

[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.

Neural stem cell-conditioned medium ameliorates Aβ25-35-induced damage in SH-SY5Y cells by protecting mitochondrial function

Inhibition of amyloid β (Aβ)-induced mitochondrial damage is considered crucial for reducing the pathological damage in Alzheimer’s disease (AD). We evaluated the effect of neural stem cell-conditioned medium (NSC-CDM) on Aβ_25–35-induced damage in SH-SY5Y cells. An in vitro model of AD was established by treating SH-SY5Y cells with 40 μM Aβ_25–35 for 24 h. SH-SY5Y cells were divided into control, Aβ_25–35 (40 μM), Aβ_25–35 (40 μM) + NSC-CDM, and Aβ_25–35 (40 μM) + neural stem cell-complete medium (NSC-CPM) groups. Cell viability was detected by CCK-8 assay. Apoptosis, reactive oxygen species (ROS) production, and mitochondrial membrane potential (MMP) were detected by flow cytometry. Malondialdehyde content was detected by ELISA assay. Western blot analysis was used to detect cytochrome c release and apoptosis-related proteins. Transmission electron microscopy was used to observe mitochondrial morphology. Cell viability significantly decreased and apoptosis significantly increased in SH-SY5Y cells treated with Aβ_25–35, and both effects were rescued by NSC-CDM. In addition, NSC-CDM reduced ROS production and significantly inhibited the reduction of MMP caused by Aβ_25–35. Furthermore, NSC-CDM ameliorated Aβ_25–35-induced reduction in Bcl-2 expression levels and increased the expression levels of cytochrome c, caspase-9, caspase-3, and Bax. Moreover, Aβ_25–35 induced the destruction of mitochondrial ultrastructure and this effect was reversed by NSC-CDM. Collectively, our findings demonstrated the protective effect of NCS-CDM against Aβ_25–35-induced SH-SY5Y cell damage and clarified the mechanism of action of Aβ_25–35 in terms of mitochondrial maintenance and mitochondria-associated apoptosis signaling pathways, thus providing a theoretical basis for the development of novel anti-AD treatments.

Cardioprotection of pharmacological postconditioning on myocardial ischemia/reperfusion injury

Acute myocardial infarction is associated with high rates of morbidity and mortality and can cause irreversible myocardial damage. Timely reperfusion is critical to limit infarct size and salvage the ischemic myocardium. However, reperfusion may exacerbate lethal tissue injury, a phenomenon known as myocardial ischemia/reperfusion (I/R) injury. Pharmacological postconditioning (PPC), a strategy involving medication administration before or during the early minutes of reperfusion, is more efficient and flexible than preconditioning or ischemic conditioning. Previous studies have shown that various mechanisms are involved in the effects of PPC. In this review, we summarize the relative effects and potential underlying mechanisms of PPC to provide a foundation for future research attempting to develop novel treatments against myocardial I/R injury.

Protective Effect of Paeoniflorin on Acute Cerebral Infarction in Rats

OBJECTIVE

The purpose of this paper was to study the protective effect of paeoniflorin on acute cerebral ischemia. The animal model of cerebral infarction induced by Middle Cerebral Artery Occlusion (MCAO) was blocked by the suture method. Sixty SD rats were randomly divided into the shame group, MCAO group, paeoniflorin (60, 120, 240 mg/kg, respectively) and Nimodipine (NMDP) group (n = 10 per group).

METHODS

The rats were intragastrically administered immediately after the operation. After 7 days of gavage, the brains were decapitated at 24 h. Hematoxylin and Eosin (HE) staining was used to observe the degree of cell damage in the cerebral cortex of rats. Immunohistochemistry was used to detect silver plating and to observe changes in nerve cells. Rats in the model group showed obvious symptoms of neurological deficits, such as the ischemic morphological changed, the Malondialdehyde (MDA), Lactate Dehydrogenase (LD) content and lactate dehydrogenase (LDH) activity were significantly increased in the ischemic brain tissue, while the Superoxide Dismutase (SOD) activity was decreased.

RESULTS

The decrease in Na+-K+-ATPase activity was significantly lower than that in the sham group. The neurological symptoms and signs of MCAO in the different doses of paeoniflorin group were improved, and the neuronal edema in the cortical area was alleviated. The activities of SOD, LDH and Na+-K+-ATPase were significantly increased, and the contents of MDA and LD were decreased.

CONCLUSION

Therefore, paeoniflorin could alleviate the degree of tissue damage in rats with acute cerebral infarction, inhabit the formation of free radicals in the brain tissue after ischemia, and reduce the degree of lipid peroxidation. Thus, the degree of cell damage was reduced greatly and a protective effect was showed on cerebral ischemia.

miR-346 Inhibited Apoptosis Against Myocardial Ischemia-Reperfusion Injury via Targeting Bax in Rats

Purpose

Myocardial ischemia-reperfusion injury (MIRI) is a common pathophysiological process after occlusion of the blood vessels to restore blood supply. Apoptosis is one of the ways of myocardial cell death in this process. MicroRNAs (miRNAs), a class of short and noncoding RNAs, are involved in multiple biological processes by post-transcriptionally targeting their downstream effectors. To date, whether miRNAs exert biological effects in myocardial ischemia-reperfusion (I/R) injury remains to be further studied.

Methods

In this study, we induced MIRI model by ligating rat left anterior descending artery (LAD) for 30 mins and reperfusion for 2 hrs. The differential expression profile of miRNAs in rat models of MIRI was analyzed by miRNAs sequencing.

Results

We found that miRNAs sequencing analysis showed the expressions of 15 types of miRNAs, including miR-346, were downregulated and 29 types of miRNAs were elevated in the MIRI rat model. We observed the key regulator of apoptosis Bax was a predicted downstream target of miR-346 using online software TargetScan. And luciferase reporter assay was utilized to certify this prediction. Over-expression of miR-346 can attenuate myocardial injury and narrow infarct area by inhibiting myocardial cell apoptosis in rat models.

Conclusion

This study revealed a novel pathway, miR-346/Bax axis, in the regulation of apoptosis in MIRI and which might be a new molecular mechanism and therapeutic target.

Remote ischemic post-conditioning protects against myocardial ischemia/reperfusion injury by inhibiting the Rho-kinase signaling pathway

The aim of the present study was to observe the effect of Rho-kinase on remote ischemic post-conditioning (RIPostC) and explore the underlying mechanisms. Male Sprague Dawley rats (n=32) were randomly distributed into four groups: Sham group, ischemia/reperfusion (I/R) group, RIPostC group and I/R with fasudil group (I/R+Fas). Infarction size was detected by triphenyltetrazolium chloride staining. The levels of creatine kinase (CK), lactate dehydrogenase (LDH), superoxide dismutase (SOD), malondialdehyde (MDA) and cardiac troponin I (cTnI) were measured using an ultraviolet spectrophotometer. The mRNA expression levels of Rho-associated coiled-coil containing protein kinase (ROCK)-1 and ROCK2, B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (Bax) were detected via reverse transcription-PCR. The protein expression levels of phosphorylated-myosin phosphatase target subunit (p-MYPT1) and phosphorylated-myosin light chain (p-MLC) were assessed by western blotting. The results demonstrated that RIPostC could decrease the infarct size, the levels of CK, LDH, cTnI and MDA and increase the activity of SOD compared with the I/R group. In addition, the mRNA expression of ROCK1 and ROCK2 was downregulated, the protein expression of p-MYPT1 and p-MLC was decreased, and the ratio of Bcl-2/Bax was elevated in the RIPostC groups compared with the I/R group. Notably, the aforementioned index in I/R with Fas group was similar to the RIPostC group and no significant difference was observed between RIPostC and I/R+Fas. These results revealed that RIPostC could attenuate I/R injury and the underlying mechanisms might be associated with a reduction in myocardial apoptosis and the suppression of the Rho-kinase signaling pathway.

Effect of Chronic Continuous Normobaric Hypoxia on Functional State of Cardiac Mitochondria and Tolerance of Isolated Rat Heart to Ischemia and Reperfusion: Role of µ and δ2 Opioid Receptors

Chronic continuous normobaric hypoxia (CNH) increases cardiac tolerance to ischemia/reperfusion injury in vivo and this effect is mediated via µ and δ2 opioid receptors (ORs) activation. CNH has also been shown to be cardioprotective in isolated rat heart. In this study, we hypothesize that this cardioprotective effect of CNH is mediated by activation of µ and δ2 ORs and preservation of mitochondrial function. Hearts from rats adapted to CNH (12 % oxygen) for 3 weeks were extracted, perfused in the Langendorff mode and subjected to 45 min of global ischemia and 30 min of reperfusion. Intervention groups were pretreated for 10 min with antagonists for different OR types: naloxone (300 nmol/l), the selective δ OR antagonist TIPP(ψ) (30 nmol/l), the selective δ1 OR antagonist BNTX (1 nmol/l), the selective δ2 OR antagonist naltriben (1 nmol/l), the selective peptide μ OR antagonist CTAP (100 nmol/l) and the selective κ OR antagonist nor-binaltorphimine (3 nmol/l). Creatine kinase activity in coronary effluent and cardiac contractile function were monitored to assess cardiac injury and functional impairment. Additionally, cardiac tissue was collected to measure ATP and to isolate mitochondria to measure respiration rate and calcium retention capacity. Adaptation to CNH decreased myocardial creatine kinase release during reperfusion and improved the postischemic recovery of contractile function. Additionally, CNH improved mitochondrial state 3 and uncoupled respiration rates, ADP/O, mitochondrial transmembrane potential and calcium retention capacity and myocardial ATP level during reperfusion compared to the normoxic group. These protective effects were completely abolished by naloxone, TIPP(ψ), naltriben, CTAP but not BNTX or nor-binaltorphimine. These results suggest that cardioprotection associated with adaptation to CNH is mediated by µ and δ2 opioid receptors activation and preservation of mitochondrial function.

Effects of resveratrol postconditioning on cerebral ischemia in mice: role of the sirtuin-1 pathway

Evidence has demonstrated that resveratrol preconditioning exhibits neuroprotection against cerebral ischemia-reperfusion (IR) injury. The current investigation aimed to explore whether pharmacological postconditioning, by administering resveratrol, after a sustained ischemia and prior to prolonged reperfusion abrogates cerebral IR injury. Cerebral IR-induced injury mice model was employed in this study to evaluate the neuroprotective effects of pharmacological postconditioning with resveratrol (30 mg/kg; i.p.) administered 5 min before reperfusion. We administered sirtinol, a SIRT1/2 selective inhibitor (10 mg/kg; i.p.) 10 min before ischemia (17 min) and reperfusion (24 h), to elucidate whether the neuroprotection with resveratrol postconditioning depends on SIRT1 activation. Various biochemical and behavioural parameters and histopathological changes were assessed to examine the effect of pharmacological postconditioning. Infarct size is estimated using TTC staining. It was established that resveratrol postconditioning abrogated the deleterious effects of IR injury expressed with regard to biochemical parameters of oxidative stress (TBARS, SOD, GSH), acetylcholinesterase activity, behavioural parameters (memory, motor coordination), infarct size, and histopathological changes. Sirtinol significantly reversed the effect of resveratrol postconditioning. We conclude that induced neuroprotective benefits of resveratrol postconditioning may be the consequence of SIRT1 activation and resveratrol can be considered, for further studies, as potential agent inducing pharmacological postconditioning in clinical situations.

Gene expression profiling analysis to investigate the role of remote ischemic postconditioning in ischemia-reperfusion injury in rats

Background

Blood flow restoration is a definitive therapy for salvaging the myocardium following ischemic injury. Nevertheless, the sudden restoration of blood flow to the ischemic myocardium can induce ischemia-reperfusion injury (IRI).

Results

Herein, we investigated the cardioprotective effect of remote ischemic postconditioning (RPostC) through our in vivo rat model of myocardial IRI. The study included three groups: the control group, the IRI group, and the IRI + RPostC group. Ischemia-reperfusion treatment led to an increase in the myocardial infarction area, which was inhibited by RPostC. In contrast to that in the control group, the myocardial apoptosis level was enhanced in the IRI group, whereas RPostC treatment decreased IRI-induced cellular apoptosis. Affymetrix Rat Gene 2.0 ST chip data identified a total of 265 upregulated genes and 267 downregulated genes between the IRI and IRI + RPostC groups. A group of differentially expressed noncoding RNAs (ncRNAs), such as MTA_TC0600002772.mm, MTA_TC1300002394.mm, U7 small nuclear RNA (Rnu7) and RGD7543256_1, were identified. Gene Ontology (GO) enrichment analysis indicated that the positive regulation of some molecular functions, such as GTPase activity, GTP binding, cyclic-nucleotide phosphodiesterase activity and cytokine activity, may contribute to the cardioprotective role of RPostC. Moreover, pathway enrichment analysis using the Kyoto Encyclopedia of Genes and Genomes (KEGG) suggested the potential implication of the TNF signaling pathway and Toll-like receptor signaling pathway. Global signal transduction network analysis, co-expression network analysis and quantitative real-time polymerase chain reaction analysis further identified several core genes, including Pdgfra, Stat1, Lifr and Stfa3.

Conclusion

Remote ischemic postconditioning treatment can decrease IRI-mediated myocardial apoptosis by regulating multiple processes and pathways, such as GTPase activity, cytokine activity, and the TNF and Toll-like receptor signaling pathways. The potential role of the above ncRNAs and core genes in IRI-induced cardiac damage merits further study as well.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5743-9) contains supplementary material, which is available to authorized users.

Participation of opioid receptors in the cytoprotective effect of chronic normobaric hypoxia

We studied the role of the delta, micro, and kappa opioid receptor (OR) subtypes in the cardioprotective effect of chronic continuous normobaric hypoxia (CNH) in the model of acuteanoxia-reoxygenation of isolated cardiomyocytes. Adaptation of rats to CNH was performed by their exposure to atmosphere containing 12% of O(2) for 21 days. Anoxia-reoxygenation of cardiomyocytes isolated from normoxiccontrol rats caused the death of 51 % of cells and lactate dehydrogenase (LDH) release. Adaptation of rats to CNH resulted in the anoxia/reoxygenation-induced cardiomyocyte death of only 38 %, and reduced the LDH release by 25 %. Pre-incubation of the cells with either the non-selective OR (opioid receptor) blocker naloxone (300 nM/l), the delta OR antagonist TIPP(psi) (30 nM/l), the selective delta(2) OR antagonist naltriben (1 nM/l) or the micro OR antagonist CTAP (100 nM/l) for 25 minutes before anoxia abolished the reduction of cell death and LDH release afforded by CNH. The antagonist of delta(1) OR BNTX (1 nM/l) or the kappa OR antagonist nor-binaltorphimine (3 nM/l) did not influence the cytoprotective effects of CNH. Taken together, the cytoprotective effect of CNH is associated with the activation of the delta(2) and micro OR localized on cardiomyocytes.

Neuroprotective effect of pharmacological postconditioning on cerebral ischaemia-reperfusion-induced injury in mice

OBJECTIVES

To investigate the mechanism of neuroprotection rendered via pharmacological postconditioning in cerebral ischaemia-reperfusion-induced injury in mice.

METHODS

Pharmacological postconditioning is strategy which either involves hindering deleterious pathway or inducing modest stress level which triggers intracellular defence pathway to sustain more vigorous insult leading to conditioning. Hence, in current research we explored the potentiality of CGS21680 (0.5 mg/kg; i.p), an adenosine A₂ A receptor agonist and PTEN inhibitor, SF1670 (3 mg/kg; i.p.) to trigger postconditioning after inducing cerebral global ischaemia (17 min) and reperfusion (24 h)-induced injury via occlusion of both carotid arteries. Mice were also given treatment with LY294002 (1.5 mg/kg; i.p.), a PI3K inhibitor and adenosine A₂ A receptor antagonist, Istradefylline (2 mg/kg; i.p.), to establish the precise mechanism of postconditioning. Various biochemical and behavioural parameters were assessed to examine the effect of pharmacological postconditioning.

KEY FINDINGS

Pharmacological postconditioning induced with CGS21680 and SF1670 attenuated the infarction along with improved behavioural and biochemical parameters in comparison with ischaemia-reperfusion control group. The outcome of postconditioning with CGS21680 and SF1670 was significantly reversed by LY294002 and Istradefylline, respectively.

CONCLUSIONS

The neuroprotective effects of CGS21680 and SF1670 postconditioning on cerebral ischaemia-reperfusion injury may be due to PI3K/Akt pathway activation.

MiR-320 regulates cardiomyocyte apoptosis induced by ischemia-reperfusion injury by targeting AKIP1

Background

MicroRNAs play important roles in regulation of the cardiovascular system. The purpose of this study was to investigate microRNA-320 (miR-320) expression in myocardial ischemia-reperfusion (I/R) injury and the roles of miR-320 in cardiomyocyte apoptosis by targeting AKIP1 (A kinase interacting protein 1).

Methods

The level of miR-320 was detected using quantitative real-time polymerase chain reaction (qRT-PCR), and cardiomyocyte apoptosis was detected via terminal dUTP nick end-labeling assay. Cardiomyocyte apoptosis and the mitochondrial membrane potential were evaluated via flow cytometry. Bioinformatics tools were used to identify the target gene of miR-320. The expression levels of AKIP1 mRNA and protein were detected via qRT-PCR and Western blot, respectively.

Results

Both the level of miR-320 and the rate of cardiomyocyte apoptosis were substantially higher in the I/R group and H9c2 cells subjected to H/R than in the corresponding controls. Overexpression of miR-320 significantly promoted cardiomyocyte apoptosis and increased the loss of the mitochondrial membrane potential, whereas downregulation of miR-320 had an opposite effect. Luciferase reporter assay showed that miR-320 directly targets AKIP1. Moreover, knock down and overexpression of AKIP1 had similar effects on the H9c2 cells subjected to H/R.

Conclusions

miR-320 plays an important role in regulating cardiomyocyte apoptosis induced by I/R injury by targeting AKIP1 and inducing the mitochondrial apoptotic pathway.

[Role of mitochondrial permeability transition pore in mediating the effect of endomorphin-1 postconditioning against myocardial ischemia-reperfusion injury in rats]

OBJECTIVE

To investigate the role of mitochondrial permeability transition pore (MPTP) opening in mediating the effect of endomorphine-1 postconditioning to alleviate myocardial ischemia-reperfusion (IR) injury in rats.

METHODS

Forty-five male SD rats were randomized equally for sham operation, myocardial IR injury, endomorphin-1 postconditioning, atractyloside (a MPTP opener) postconditioning, or endomorphin-1 + atractyloside postconditioning. The hemodynamic param-eters of the rats were monitored in real time via carotid artery cannulation to the left ventricle. After reperfusion, plasma samples were collected for biochemical analyses. The size of myocardial infarct area was detected using Evans blue and TTC double staining, and the myocardial expressions of apoptosis-related proteins Bax, Bcl-2 and cleaved caspase-3 were analyzed using Western blotting.

RESULTS

Myocardial IR injury resulted in significantly decreased heart rate and blood pressure in the rats (P<0.05). Compared with those in IR group, the rats with endomorphin-1 postconditioning showed significantly increased heart rate and blood pressure (P<0.05), lowered contents or activities of LDH, CK-MB, cTnI, IL-6, TNF-α, Cyt-C and MDA in the plasma (P<0.05), increased plasma SOD activity (P<0.05), reduced size of myocardial infarction, decreased myocardial expression of Bax and cleaved caspase-3 protein (P<0.05), and increased myocardial expression of Bcl-2 protein (P<0.05). All these changes induced by endomorphin-1 were obviously reversed by atractyloside postconditioning (P<0.05).

CONCLUSION

Endomorphin-1 postconditioning protects against myocardial IR injury in rats probably by inhibiting the opening of MPTP and reducing cardiac myocyte apoptosis via down-regulating cleaved caspase-3 expression.

ω-3 Polyunsaturated Fatty Acid Postconditioning Protects the Isolated Perfused Rat Heart from Ischemia-Reperfusion Injury

AIMS

This study aimed to evaluate the cardioprotective effects of ω-3 polyunsaturated fatty acids (PUFAs) postconditioning against ischemia-reperfusion (I/R) injury.

METHODS

Sixty Sprague-Dawley rats were randomly divided into 4 groups (n = 15 for each) and used to generate the Langendorff isolated perfused rat heart model. The sham group received a continuous perfusion of 150 min. The remaining three I/R-treated groups sequentially received a 30-min perfusion, a 30-min cardioplegia, and a 90-min reperfusion. The I/R-ischemic preconditioning (IP) group additionally received three cycles of 20-s reperfusion and 20-s coronary reocclusion preceded the 90 min of reperfusion. The I/R-ω group were perfused with ω-3 PUFAs for 15 min before the 90 min of reperfusion. The myocardial infarct size, the degree of mitochondrial damage, the antioxidant capacity of the myocardium, and the cardiac functions during reperfusion were compared among groups.

RESULTS

Compared with the I/R group, the I/R-ω group had significantly reduced myocardial infarct size, reduced levels of lactate dehydrogenase and malondialdehyde, elevated superoxide dismutase level, and elevated rising (+dp/dtmax) and descending (-dp/dtmax) rate of left ventricular pressure. The I/R-ω group had a significantly lower rate of mitochondrial damage in myocardial tissue compared with the I/R and I/R-IP groups.

CONCLUSION

ω-3 PUFA postconditioning possesses good cardioprotective effects and may be developed into a therapeutic strategy for myocardial I/R injury.

Effects of Dexmedetomidine Postconditioning on Myocardial Ischemia/Reperfusion Injury in Diabetic Rats: Role of the PI3K/Akt-Dependent Signaling Pathway

OBJECTIVE

The present study was designed to determine whether dexmedetomidine (DEX) exerts cardioprotection against myocardial I/R injury in diabetic hearts and the mechanisms involved.

METHODS

A total of 30 diabetic rats induced by high-glucose-fat diet and streptozotocin (STZ) were randomly assigned to five groups: diabetic sham-operated group (DM-S), diabetic I/R group (DM-I/R), diabetic DEX group (DM-D), diabetic DEX + Wort group (DM-DW), and diabetic Wort group (DM-W). Another 12 age-matched male normal SD rats were randomly divided into two groups: sham-operated group (S) and I/R group (I/R). All rats were subjected to 30 min myocardial ischemia followed by 120 min reperfusion except sham groups. Plasmas were collected to measure the malondialdehyde (MDA), creatine kinase isoenzymes (CK-MB), and lactate dehydrogenase (LDH) levels and superoxide dismutase (SOD) activity at the end of reperfusion. Pathologic changes in myocardial tissues were observed by H-E staining. The total and phosphorylated form of Akt and GSK-3β protein expressions were measured by western blot. The ratio of Bcl-2/Bax at mRNA level was detected by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

DEX significantly reduced plasma CK-MB, MDA concentration, and LDH level and increased SOD activity caused by I/R. The phosphorylation of Akt and GSK-3β was increased, Bcl-2 mRNA and the Bcl-2/Bax ratio was increased, and Bax mRNA was decreased in the DEX group as compared to the I/R group, while posttreatment with Wort attenuated the effects induced by DEX.

CONCLUSION

The results of this study suggest that DEX postconditioning may increase the phosphorylation of GSK-3β by activating the PI3K/Akt signaling pathway and may inhibit apoptosis and oxidative stress of the myocardium, thus exerting protective effects in diabetic rat hearts suffering from I/R injury.

MicroRNA-206 Protects against Myocardial Ischaemia-Reperfusion Injury in Rats by Targeting Gadd45β

MicroRNAs are widely involved in the pathogenesis of cardiovascular diseases through regulating gene expression via translational inhibition or degradation of their target mRNAs. Recent studies have indicated a critical role of microRNA-206 in myocardial ischaemia-reperfusion (I/R) injury. However, the function of miR-206 in myocardial I/R injury is currently unclear. The present study was aimed to identify the specific role of miR-206 in myocardial I/R injury and explore the underlying molecular mechanism. Our results revealed that the expression level of miR-206 was significantly decreased both in rat I/R group and H9c2 cells subjected to hypoxia/reoxygenation (H/R) compared with the corresponding control. Overexpression of miR-206 observably decreased infarct size and inhibited the cardiomyocyte apoptosis induced by I/R injury. Furthermore, bioinformatics analysis, luciferase activity and western blot assay proved that Gadd45β (growth arrest DNA damage-inducible gene 45β) was a direct target gene of miR-206. In addition, the expression of pro-apoptotic-related genes, such as p53, Bax and cleaved caspase3, was decreased in association with the down-regulation of Gadd45β. In summary, this study demonstrates that miR-206 could protect against myocardial I/R injury by targeting Gadd45β.

3,3'‑Diindolylmethane attenuates cardiomyocyte hypoxia by modulating autophagy in H9c2 cells

Autophagy is activated in the ischemic heart and is a process that is essential for survival, differentiation, development and homeostasis. 3,3'‑Diindolylmethane (DIM) is a natural product of the acid‑catalyzed condensation of indole‑3‑carbinol in cruciferous vegetables. Numerous studies have suggested that DIM has various pharmacological effects, including antioxidant, antitumor, anti‑angiogenic and anti‑apoptotic properties. However, the function of DIM on hypoxia‑induced cardiac injury remains to be elucidated. In the present study, H9c2 cells were pretreated with DIM (1, 5 and 10 µM) for 12 h and exposed to hypoxia for 12 h. It was demonstrated that DIM markedly attenuated the increased transcription of interleukin (IL)‑1β, IL‑6 and tumor necrosis factor‑α induced by hypoxia. In addition, the transcription of autophagy associated genes increased in the DIM pretreated group, compared with the hypoxia group. DIM additionally attenuated the increased apoptosis, as determined by terminal deoxynucleotidyl transferase dUTP nick end labeling staining, and regulated the relative protein expression level of B cell lymphoma (Bcl) 2 associated X protein, Bcl‑xL and cleaved caspase 3. Furthermore, the phosphorylation of the 5' AMP‑activated protein kinase a (AMPKa) was activated and the phosphorylation of c‑Jun N‑terminal kinase (JNK) was inhibited. The effect of DIM on hypoxia‑induced apoptosis was abolished following pretreatment with JNK activator (anisomycin, 40 ng/ml). The effect of DIM on autophagy was reversed following pretreatment with AMPKa inhibitor (CpC, 20 µM) following stimulation with hypoxia. The results demonstrated that DIM prevented hypoxia‑induced inflammation and apoptosis and activated cardiomyocyte autophagy, which may be mediated by activation of AMPKa and inhibition of JNK pathways.