Induction and Assessment of Ischemia-reperfusion Injury in Langendorff-perfused Rat Hearts

Long-term inorganic nitrate administration protects against myocardial ischemia-reperfusion injury in female rats

BACKGROUND

The favorable effects of nitrate against myocardial ischemia-reperfusion injury (MIRI) have primarily focused on male rats and in short term. Here we determine the impact of long-term nitrate intervention on baseline cardiac function and the resistance to MIRI in female rats.

METHODS

Female Wistar rats were randomly divided into untreated and nitrate-treated (100 mg/L sodium nitrate in drinking water for 9 months) groups (n = 14/group). At intervention end, levels of serum progesterone, nitric oxide metabolites (NOx), heart NOx concentration, and mRNA expressions of NO synthase isoforms (NOS), i.e., endothelial (eNOS), neuronal (nNOS), and inducible (iNOS), were measured. Isolated hearts were exposed to ischemia, and cardiac function indices (CFI) recorded. When the ischemia-reperfusion (IR) period ended, infarct size, NO metabolites, eNOS, nNOS, and iNOS expression were measured.

RESULTS

Nitrate-treated rats had higher serum progesterone (29.8%, P = 0.013), NOx (31.6%, P = 0.035), and higher heart NOx (60.2%, P = 0.067), nitrite (131%, P = 0.018), and eNOS expression (200%, P = 0.005). Nitrate had no significant effects on baseline CFI but it increased recovery of left ventricular developed pressure (LVDP, 19%, P = 0.020), peak rate of positive (+ dp/dt, 16%, P = 0.006) and negative (-dp/dt, 14%, P = 0.014) changes in left ventricular pressure and decreased left ventricular end-diastolic pressure (LVEDP, 17%, P < 0.001) and infarct size (34%, P < 0.001). After the IR, the two groups had significantly different heart nitrite, nitrate, NOx, and eNOS and iNOS mRNA expressions.

CONCLUSIONS

Long-term nitrate intervention increased the resistance to MIRI in female rats; this was associated with increased heart eNOS expression and circulating progesterone before ischemia and blunting ischemia-induced increased iNOS and decreased eNOS after MIRI.

Long-term Ovariectomy Reduces Tolerance of Rats to Myocardial Ischemia-reperfusion Injury

Background

The harmful impact of ovariectomy on myocardial ischemia-reperfusion (M/IR) injury has been established in the short term.

Objectives

In this study, we aimed to investigate the long-term effects of ovariectomy on M/IR injury.

Methods

Two methods involving dorsolateral skin incisions were used to induce the ovariectomized (OVX) rat model. The rats were divided into 2 groups: Control and OVX (n = 6). At the end of the study, the hearts were isolated and subjected to global ischemia using the Langendorff apparatus. Cardiac function indices (CFIs) were recorded, including left ventricular end-diastolic pressure (LVEDP), peak rates of positive (+dp/dt) and negative (-dp/dt) changes in LV pressure, and LV-developed pressure (LVDP). At the end of the reperfusion period, the hearts were used to measure the size of the infarct, levels of nitric oxide metabolites (NOx), and mRNA expression of NO synthase (NOS) enzymes, including endothelial (eNOS), neuronal (nNOS), and inducible (iNOS).

Results

Compared to controls, OVX rats had larger infarct size by 51%, higher LVEDP by 29%, and lower recovery of +dp/dt, -dp/dt, and LVDP by 29%, 22%, and 35%, respectively. Furthermore, in heart tissue, rats that underwent OVX had significantly higher concentrations of nitrate, nitrite, and NOx by 79%, 82%, and 83%, respectively. Additionally, these rats had lower mRNA levels of eNOS by 38% and higher mRNA levels of iNOS by 71%.

Conclusions

The long-term deficiency of estrogen increased the expression of iNOS and decreased the expression of eNOS in the heart tissue of OVX rats. Imbalanced NOS expressions were associated with exacerbated responses to M/IR injury in OVX rats.

Intra-ischemic hypothermia cardioprotection involves modulation of PTEN/Akt/ERK signaling and fatty acid oxidation

Therapeutic hypothermia (TH) provides cardioprotection from ischemia/reperfusion (I/R) injury. However, it remains unknown how TH regulates metabolic recovery. We tested the hypothesis that TH modulates PTEN, Akt, and ERK1/2, and improves metabolic recovery through mitigation of fatty acid oxidation and taurine release. Left ventricular function was monitored continuously in isolated rat hearts subjected to 20 min of global, no-flow ischemia. Moderate cooling (30°C) was applied at the start of ischemia and hearts were rewarmed after 10 min of reperfusion. The effect of TH on protein phosphorylation and expression at 0 and 30 min of reperfusion was investigated by western blot analysis. Post-ischemic cardiac metabolism was investigated by 13 C-NMR. TH enhanced recovery of cardiac function, reduced taurine release, and enhanced PTEN phosphorylation and expression. Phosphorylation of Akt and ERK1/2 was increased at the end of ischemia but decreased at the end of reperfusion. On NMR analysis, TH-treated hearts displayed decreased fatty acid oxidation. Direct cardioprotection by moderate intra-ischemic TH is associated with decreased fatty acid oxidation, reduced taurine release, enhanced PTEN phosphorylation and expression, and enhanced activation of both Akt and ERK1/2 prior to reperfusion.

Cardioprotective action of aprepitant in a rat model of ischemia-reperfusioninduced myocardial injury: role of PI3K-AkT-GSK-3β-HIF-1α signaling pathway

PURPOSE

The present study explored the role and mechanism involved in aprepitant-induced cardioprotective effects in rat model of ischemia-reperfusion injury.

METHODS

The isolated hearts of Wistar male albino rats were subjected to ischemia-reperfusion injury on Langendorff apparatus. The extent of myocardial injury was assessed by measuring lactate dehydrogenase 1 and CK-MB release in the coronary effluent. The rats were treated with aprepitant (5, 10 and 20 mg/kg) before isolating hearts. After injury, the levels of HIF-1α, p-AkT, p-GSK-3β/GSK-3β were measured in heart homogenates. LY294002 was employed as PI3K inhibitor.

RESULTS

Ischemia-reperfusion led to significant myocardial injury and decreased the levels of HIF-1α, p-AkT and ratio of p-GSK-3β/GSK-3β. Aprepitant attenuated myocardial injury and restored the biochemical changes in a dose-dependent manner. Pre-treatment with LY294002 (10 and 20 mg/kg) abolished aprepitant-mediated cardioprotective effects and restored the biochemical parameters in the heart homogenate.

CONCLUSIONS

Aprepitant may be effective in preventing ischemia-reperfusion-induced myocardial injury, which may be due to activation of PI3K-AkT-GSK-3β and HIF-1α signaling pathway.

Cardiac phospholipidome is altered during ischemia and reperfusion in an ex vivo rat model

Acute myocardial infarction (AMI) is the leading cause of death, morbidity, and health costs worldwide. In AMI, a sudden blockage of blood flow causes myocardial ischemia and cell death. Reperfusion after ischemia has paradoxical effects and may exacerbate the myocardial injury, a process known as ischemic reperfusion injury. In this work we evaluated the lipidome of isolated rat hearts, maintained in controlled perfusion (CT), undergoing global ischemia (ISC) or ischemia followed by reperfusion (IR). 153 polar lipid levels were significantly different between conditions. 48 features had q < 0.001 and included 8 phosphatidylcholines and 4 lysophospholipids, which were lower in ISC compared to CT, and even lower in the IR group, suggesting that IR induces more profound changes than ISC. We observed that the levels of 16 alkyl acyl phospholipids were significantly altered during ISC and IR. Overall, these data indicate that myocardial lipid remodelling and possibly damage occurs to a greater extent during reperfusion. The adaptation of cardiac lipidome during ISC and IR described is consistent with the presence of oxidative damage and may reflect the impact of AMI on the lipidome at the cellular level and provide new insights into the role of lipids in the pathophysiology of acute myocardial ischemia/reperfusion injury.

miRNA-27a Transcription Activated by c-Fos Regulates Myocardial Ischemia-Reperfusion Injury by Targeting ATAD3a

MicroRNA-27a (miR-27a) has been implicated in myocardial ischemia-reperfusion injury (MIRI), but the underlying mechanism is not well understood. This study is aimed at determining the role of miR-27a in MIRI and at investigating upstream molecules that regulate miR-27a expression and its downstream target genes. miR-27a expression was significantly upregulated in myocardia exposed to ischemia/reperfusion (I/R) and cardiomyocytes exposed to hypoxia/reoxygenation (H/R). c-Fos could regulate miR-27a expression by binding to its promoter region. Moreover, overexpression of miR-27a led to a decrease in cell viability, an increase in LDH and CK-MB secretion, and an increase in apoptosis rates. In contrast, suppression of miR-27a expression resulted in the opposite effects. ATPase family AAA-domain-containing protein 3A (ATAD3a) was identified as a target of miR-27a. miR-27a regulated the translocation of apoptosis-inducing factor (AIF) from the mitochondria to the nucleus and H/R-induced apoptosis via the regulation of ATAD3a. It was found that inhibiting miR-27a in vivo by injecting a miR-27a sponge could ameliorate MIRI in an isolated rat heart model. In conclusion, our study demonstrated that c-Fos functions as an upstream regulator of miR-27a and that miR-27a regulates the translocation of AIF from the mitochondria to the nucleus by targeting ATAD3a, thereby contributing to MIRI. These findings provide new insight into the role of the c-Fos/miR-27a/ATAD3a axis in MIRI.

FIsetin Preserves Interfibrillar Mitochondria to Protect Against Myocardial Ischemia-Reperfusion Injury

According to our previous study, fisetin (3,3',4',7-tetrahydroxyflavone), a bioactive phytochemical (flavonol), reportedly showed cardioprotection against ischemia-reperfusion injury (IRI) by reducing oxidative stress and inhibiting glycogen synthase kinase 3β (GSK3β) [1]. GSK3β is said to exert a non-mitochondrial mediated cardioprotection; therefore, distinct mechanisms of GSK3β on the regulatory effect of mitochondria need to be addressed. The two distinct mitochondrial subpopulations in the heart, namely interfibrillar mitochondria (IFM) and subsarcolemmal mitochondria (SSM), respond differently to disease states. The current study aimed to understand the effect of fisetin on the subpopulation-specific preservation of IFM and SSM while rendering cardioprotection against ischemia reperfusion (I/R). Rats were pre-treated with fisetin (20 mg/kg) intraperitoneally, and IRI was induced using Langendorff isolated heart perfusion technique. Hemodynamic parameters were recorded, and the cardiac injury was assessed using infarct size (IS), lactate dehydrogenase (LDH), and creatine kinase (CK) levels. Subpopulation-specific mitochondrial preservation was evaluated by electron transport chain (ETC), catalase, superoxide dismutase (SOD), and glutathione (GSH) activities. The bioavailability of fisetin in IFM and SSM was measured using the fluorescence method. The ability of fisetin to bind directly to the mitochondrial complex-1 and activating it through donating electrons to FMN was studied using molecular docking studies and further validated by in vitro rotenone sensitivity assay. Cardioprotective effects exhibited by fisetin were mainly mediated through IFM preservation. Mitochondrial bioavailability of fisetin is more in IFM than SSM in both ex vivo and in vitro conditions. Fisetin increased mitochondrial ATP production in I/R insult hearts by activating ETC complex 1. Inhibition of complex 1 prevents the ATP-producing capacity of fisetin. Our results provide evidence that fisetin plays a protective role in myocardial IRI, possibly by preserving the functional activities of IFM.

Cannabidiol-mediated RISK PI3K/AKT and MAPK/ERK pathways decreasing reperfusion myocardial damage

Myocardial ischemia continues to be the first cause of morbimortality in the world; the definitive treatment is reperfusion; however, this action causes additional damage to ischemic myocardial tissue; this forces to seek therapies of cardioprotection to reduce this additional damage. There are many cardioprotective agents; within these, cannabinoids have shown to have beneficial effects, mainly cannabidiol (CBD). CBD is a non psychoactive cannabinoid. To evaluate the effect in experimental models of CBD in myocardial ischemia reperfusion in rats, twelve-week-old male rats have been used. The animals were divides in 3 groups: control(C), ischemia reperfusion (IR) and CBD pretreatment (1/day/5mg/kg /10days). Langendorff organ isolate studies were performed, and the area of infarction was assessed with triphenyl tetrazolium, in addition to molecular analysis of AT1 and AT2 receptors and Akt and Erk proteins and their phosphorylated forms related to RISK pathways. It was observed that there is an improvement with the use of CBD increasing inotropism and cardiac lusitropism, improving considerably the cardiovascular functionality. These could be related to the reduction of the area of infarction and activation of the AT2 receptor and the RISK pathway with absence of activation of the AT2 receptor (these could relate the reduction of the infarct area and the restoration of cardiovascular function with the activation of the AT2 receptor and the RISK pathway with the absence of activation of the AT2 receptor). The use of cannabinoids was shown to have beneficial effects when used as a treatment for myocardial reperfusion damage.

Sweroside Protects Against Myocardial Ischemia-Reperfusion Injury by Inhibiting Oxidative Stress and Pyroptosis Partially via Modulation of the Keap1/Nrf2 Axis

Aims: Sweroside, a secoiridoid glucoside extracted from Swertia pseudochinensis Hara, is reported to possess antioxidant and anti-inflammatory activities. However, whether sweroside has a protective effect on myocardial ischemia-reperfusion (IR) injury is yet to be elucidated. The present study aimed to confirm the cardioprotective effect of sweroside and to identify its underlying mechanism. Methods and Results: H9c2 cells were pretreated with sweroside and then underwent hypoxia-reoxygenation. Cell Counting Kit-8, creatine kinase-myocardial band (CK-MB) and lactate dehydrogenase (LDH) assays were conducted to detect cell viability and myocardial injury, respectively. The Langendorff method was used to induce myocardial IR injury ex vivo. Triphenyltetrazolium chloride staining was performed to detect myocardial infarct size, while protein expression was analyzed using western blotting. Overall, the results indicated that sweroside pretreatment dose-dependently led to a significant enhancement in cell viability, a decrease in release of CK-MB and LDH, a reduction in infarct size, and an improvement in cardiac function. Additionally, sweroside pretreatment caused a marked suppression of oxidative stress, as evidenced by the fact that sweroside decreased the accumulation of reactive oxygen species and malondialdehyde, while enhancing the activities of superoxide dismutase and glutathione peroxidase. Moreover, sweroside was found to notably repress pyroptosis, as sweroside blocked pore formation in the cell membrane, inhibited caspase-1 and interleukin (IL)-1β activity, and decreased the expression levels of NLR family pyrin domain containing 3 (NLRP3), apoptosis-associated speck-like protein containing a CARD, cleaved caspase-1, and IL-1β. Mechanistically, it was found that sweroside inhibited Kelch-like ECH-associated protein 1 (Keap1) and induced nuclear factor E2-associated factor 2 (Nrf2) nuclear translocation. Furthermore, the inhibition of oxidative stress and pyroptosis by sweroside could be abrogated via the inhibition of Nrf2 expression, which suggested that the protective effect induced by sweroside was Nrf2-dependent. Conclusions: The present study demonstrated that sweroside pretreatment could protect against myocardial IR injury by inhibiting of oxidative stress and NLRP3 inflammasome-mediated pyroptosis partially via modulation of the Keap1/Nrf2 axis.

Protective effect of dimethyl fumarate on oxidative damage and signaling in cardiomyocytes

Myocardial ischemia/reperfusion (I/R) injury contributes to the pathogenesis of numerous diseases. Based on its antioxidant and anti‑inflammatory effects, dimethyl fumarate (DMF) has been reported to exert protective effects against I/R. However, to the best of our knowledge, its potential role as a myocardial protective agent in heart disease has received little attention. Previous studies have suggested that DMF may exert its protective effects by activating nuclear factor erythroid 2‑related factor 2 (Nrf2); however, the exact underlying mechanisms remain to be elucidated. The aim of the present study was to investigate the protective role of DMF in myocardial I/R injury, and to determine the role of Nrf2 in mediating the activity of DMF. H9c2 cells were incubated with DMF (20 µM) for 24 h before establishing the I/R model, and were then subjected to myocardial ischemia for 6 h, followed by reperfusion. Cell viability, lactate dehydrogenase levels, anti‑oxidant enzyme expression levels and anti‑apoptotic effects were evaluated, and AKT/Nrf2 pathway‑associated mechanisms were investigated. The results of the present study indicated that DMF may reduce myocardial I/R injury in a Nrf2‑dependent manner. DMF significantly improved cellular viability, suppressed the expression of apoptotic markers, decreased the production of reactive oxygen species and increased the expression of Nrf2‑regulated antioxidative genes. Notably, these beneficial DMF‑mediated effects were not observed in the control or I/R groups. In conclusion, the results of the present study suggested that DMF may exert protective effects against a myocardial I/R model, and further validated Nrf2 modulation as a primary mode of action. Thus suggesting that DMF may be a potential therapeutic agent for AKT/Nrf2 pathway activation in myocardial, and potentially systemic, diseases.

The role of aldosterone inhibitors in cardiac ischemia-reperfusion injury

Myocardial ischaemia-reperfusion (I/R) injury is a well-known term for exacerbation of cellular destruction and dysfunction after the restoration of blood flow to a previously ischaemic heart. A vast number of studies that have demonstrated that the role of mineralocorticoids in cardiovascular diseases is based on the use of pharmacological mineralocorticoid receptor (MR) antagonists. This review paper aimed to summarize current knowledge on the effects of MR antagonists on myocardial I/R injury as well as postinfarction remodeling. Animal models, predominantly the Langendorff technique and left anterior descending coronary artery occlusion, have confirmed the potency of MR antagonists as preconditioning and postconditioning agents in limiting infarct size and postinfarction remodeling. Several preclinical studies in rodents have established and proved possible mechanisms of cardioprotection by MR antagonists, such as reduction of oxidative stress, reduction of inflammation, and apoptosis, therefore limiting the infarct zone. However, the results of some clinical trials are inconsistent, since they reported no benefit of MR antagonists in acute myocardial infarction. Due to this, further studies and the results of ongoing clinical trials regarding MR antagonist administration in patients with acute myocardial infarction are being awaited with great interest.

Curculigoside attenuates myocardial ischemia‑reperfusion injury by inhibiting the opening of the mitochondrial permeability transition pore

The aim of the present study was to determine whether curculigoside protects against myocardial ischemia-reperfusion injury (MIRI) and to investigate the underlying mechanisms. An in vitro model of hypoxia/reoxygenation (H/R) was established by culturing H9c2 cells under hypoxic conditions for 12 h, followed by reoxygenation for 1 h. Cell Counting kit-8 and lactate dehydrogenase (LDH) assays were subsequently used to examine cell viability and the degree of cell injury. In addition, isolated rat hearts were subjected to 30 min of ischemia followed by 1 h of reperfusion to establish a MIRI model. Triphenyltetrazolium chloride (TTC) staining was performed to measure the infarct size. Furthermore, TUNEL staining and flow cytometry were employed to evaluate cell apoptosis. The opening of the mitochondrial permeability transition pore (MPTP) and changes in the mitochondrial membrane potential (ΔΨm) were assessed. Reverse transcription-quantitative PCR and western blot analysis were performed to investigate the expression levels of mitochondrial apoptosis-related proteins. Curculigoside pre-treatment significantly improved cell viability, decreased cell apoptosis and LDH activity, and reduced the infarct size and myocardial apoptosis in vitro and ex vivo, respectively. Moreover, curculigoside markedly inhibited MPTP opening and preserved the ΔΨm. In addition, curculigoside significantly decreased the expression of cytochrome c, apoptotic protease activating factor-1, cleaved caspase-9 and cleaved caspase-3. Notably, atractyloside, a known MPTP opener, abrogated the protective effects of curculigoside. On the whole, the present study demonstrated that curculigoside protected against MIRI, potentially by decreasing the levels of mitochondria-mediated apoptosis via the inhibition of MPTP opening. Therefore, the results obtained in the present study may provide the theoretical basis for the future clinical application of curculigoside.

Ghrelin as an anti-inflammatory and protective agent in ischemia/reperfusion injury

Ischemia/reperfusion (I/R) continue to be the most frequent cause of damaged tissues. Injured tissues resulted from the first ischemic insult, which is determined by the interruption in the blood supply, followed by subsequent impairment induced by reperfusion. In addition, ischemia-reperfusion injury is mediated by tumor necrosis factor (TNF) and other cytokines that activate complements and proteases responsible for free radical production. However, earlier studies have reported the protective roles of bioactive peptides during ischemia reperfusion injury. In fact, ghrelin is a peptide hormone discovered since 1999 as GH secretagogue and its production was identified in gastric X/A-like endocrine cells in rats and P/D1 type cells in humans. To date, this peptide receives growing attention due to its pleiotropic action in the organism and its role in maintaining energy homeostasis. Ghrelin is also involved in stress responses, assuming a modulatory action on immune pathways. Previous studies have identified many other functions related to an anti-inflammatory role in ischemia reperfusion injury. Under these challenging conditions, studies described acylated and unacylated ghrelin in activation and/or inhibition processes related to ischemia-reperfusion injury. The aim of this article is to provide a minireview about ghrelin mechanisms involved in the proinflammatory response of I/R injury. However, the regulatory processes of ghrelin in this pathologic event are still very limited and warrant further investigation.

Changes in nitric oxide synthase levels are associated with impaired cardiac function and tolerance to ischemia-reperfusion injury in male rats with transient congenital hypothyroidism

Transient congenital hypothyroidism (TCH) has long-lasting consequences on the cardiovascular system during adulthood. The aim of this study was to determine whether nitric oxide (NO) and NO-producing enzymes are involved in impaired cardiac function as well as decreased tolerance to ischemia-reperfusion (IR) injury in adult male rats with TCH. Pregnant rats were divided into control and hypothyroid groups. Male offspring rats were categorized in control and hypothyroid (TCH) groups at week 16. Levels of NOx (nitrate+nitrite) and neuronal NOS (nNOS), inducible NOS (iNOS), and endothelial NOS (eNOS) were measured in hearts of rats and isolated perfused hearts from both groups were subjected to IR. Levels of NOx and NOSs were also measured in both groups after ischemia. Compared with controls, heart NOx levels were higher at baseline (48.0 ± 4.9 vs. 35.0 ± 2.6 μmol/L; P = 0.034) and following IR (103.6 ± 4.2 vs. 70.2 ± 2.7 μmol/L; P < 0.001) in rat with TCH. At baseline, compared with controls, heart iNOS and nNOS levels were significantly higher in rats with TCH (6.12 ± 0.34 vs. 4.78 ± 0.27 ng/mg protein; P = 0.008 for iNOS and 4.87 ± 0.28 vs. 3.55 ± 0.23 ng/mg protein; P = 0.003 for nNOS). Following IR, in rats with TCH, heart iNOS levels increased (11.75 ± 2.02 vs. 6.12 ± 0.34, ng/mg protein; P = 0.015) whereas nNOS level decreased (4.10 ± 0.25 vs. 4.87 ± 0.28 ng/mg protein; P = 0.063). Adverse effects of TCH on cardiac function are associated with increased ratio of iNOS/eNOS; in addition, increased heart nNOS levels are involved in impaired cardiac function while its decrease is associated with decreased tolerance to IR injury.

Sappanone A Protects Against Myocardial Ischemia Reperfusion Injury by Modulation of Nrf2

Background

Oxidative stress is a major contributor to the onset and development of myocardial ischemia reperfusion injury (MIRI). Sappanone A (SA), a homoisoflavanone extracted from the heartwood of Caesalpinia sappan L., has been demonstrated to possess powerful antioxidant activity. Therefore, this study aimed to determine the protective effect of SA on MIRI and investigate its underlying mechanism.

Methods

The rat hearts were isolated and underwent 30-min ischemia, followed by 120-min reperfusion to establish the MIRI model, using the Langendorff method. SA was administrated intraperitoneally into rats 1 h prior to heart isolation. The myocardial infarct size and apoptosis were measured by TTC and terminal deoxynucleotidyl transferase dUTP nick end labeling staining. Myocardial enzyme activity, MDA content and the activities of SOD and GSH-Px were detected by colorimetric spectrophotometric method. Reactive oxygen species (ROS) level was detected by DCFH-DA probe. The change in Keap1/Nrf2 signaling pathway was evaluated by Western blotting.

Results

SA reduced myocardial infarct size and the release of CK-MB and LDH in a dose-dependent manner. Moreover, SA improved the recovery of cardiac function, inhibited MIRI-induced apoptosis, repressed the production of ROS and MDA, and enhanced the activities of SOD and GSH-Px. Mechanistically, SA downregulated Keap1, induced Nrf2 nuclear accumulation, and enhanced Nrf2 transcriptional activity, subsequently resulting in an increase in the expression of the Nrf2 target genes heme oxygenase-1 and NAD(P)H quinone dehydrogenase 1. Moreover, SA enhanced the phosphorylation of Nfr2, but the enhancement in Nfr2 phosphorylation was abrogated by PKC or PI3K inhibitor.

Conclusion

Collectively, it was demonstrated that SA prevents MIRI via coordinating the cellular antioxidant defenses and maintaining the redox balance, by modulation of Nrf2 via the PKC or PI3K pathway. Therefore, SA was a potential therapeutic drug for treating MIRI.

Rosuvastatin Attenuates Myocardial Ischemia-Reperfusion Injury via Upregulating miR-17-3p-Mediated Autophagy

Myocardial diseases usually appear ischemic. Reperfusion therapy is one of the effective methods that can improve clinical therapeutic efficacy. However, reperfusion results in myocardial injury named I/R injury. Rosuvastatin (RS) is HMG-CoA reductase inhibitor. We investigated the role of RS in the myocardial I/R injury in vitro and its active mechanism. Oxygen-glucose deprivation/reoxygenation (OGD/R) model was applied to investigate I/R in vitro. OGD/R decreased cell viability and increased levels of miR-17-3p and lactate dehydrogenase (LDH) leakage. Besides, RS decreased cleaved caspase-3 level and LDH leakage, promoted the levels of miR-17-3p and LC3II/LC3I, and increased cell viability when H9C2 cell was treated by OGD/R. miR-17-3p inhibitor reduced the H9C2 cell viability and LC3II/LC3I level, whereas miR-17-3p mimics increased H9C2 cell viability and LC3II/LC3I level. RS promoted cell viability and increased LC3II/LC3I level while it lowered LDH leakage, apoptosis rate, and the levels of cleaved caspase-3 and Cyto c. Our study suggested that RS reduced I/R injury in cardiocyte via cleaved caspase-3/Cyto c apoptosis signaling pathway and autophagy. Moreover, the autophagy happens to cardiocyte by upregulating the expression of miR-17-3p.

Investigating the physiology of normothermic ex vivo heart perfusion in an isolated slaughterhouse porcine model used for device testing and training

Background

The PhysioHeart™ is a mature acute platform, based isolated slaughterhouse hearts and able to validate cardiac devices and techniques in working mode. Despite perfusion, myocardial edema and time-dependent function degradation are reported. Therefore, monitoring several variables is necessary to identify which of these should be controlled to preserve the heart function. This study presents biochemical, electrophysiological and hemodynamic changes in the PhysioHeart™ to understand the pitfalls of ex vivo slaughterhouse heart hemoperfusion.

Methods

Seven porcine hearts were harvested, arrested and revived using the PhysioHeart™. Cardiac output, SaO2, glucose and pH were maintained at physiological levels. Blood analyses were performed hourly and unipolar epicardial electrograms (UEG), pressures and flows were recorded to assess the physiological performance.

Results

Normal cardiac performance was attained in terms of mean cardiac output (5.1 ± 1.7 l/min) and pressures but deteriorated over time. Across the experiments, homeostasis was maintained for 171.4 ± 54 min, osmolarity and blood electrolytes increased significantly between 10 and 80%, heart weight increased by 144 ± 41 g, free fatty acids (− 60%), glucose and lactate diminished, ammonia increased by 273 ± 76% and myocardial necrosis and UEG alterations appeared and aggravated. Progressively deteriorating electrophysiological and hemodynamic functions can be explained by reperfusion injury, waste product intoxication (i.e. hyperammonemia), lack of essential nutrients, ion imbalances and cardiac necrosis as a consequence of hepatological and nephrological plasma clearance absence.

Conclusions

The PhysioHeart™ is an acute model, suitable for cardiac device and therapy assessment, which can precede conventional animal studies. However, observations indicate that ex vivo slaughterhouse hearts resemble cardiac physiology of deteriorating hearts in a multi-organ failure situation and signalize the need for plasma clearance during perfusion to attenuate time-dependent function degradation. The presented study therefore provides an in-dept understanding of the sources and reasons causing the cardiac function loss, as a first step for future effort to prolong cardiac perfusion in the PhysioHeart™. These findings could be also of potential interest for other cardiac platforms.

Down-regulation of GAS5 ameliorates myocardial ischaemia/reperfusion injury via the miR-335/ROCK1/AKT/GSK-3β axis

Growth arrest‐specific transcript 5 (GAS5), along non‐coding RNA (LncRNA), is highly expressed in hypoxia/reoxygenation (H/R)‐cardiomyocytes and promotes H/R‐induced apoptosis. In this study, we determined whether down‐regulation of GAS5 ameliorates myocardial ischaemia/reperfusion (I/R) injury and further explored its mechanism. GAS5 expression in cardiomyocytes and rats was knockdown by transfected or injected with GAS5‐specific small interfering RNA or adeno‐associated virus delivering small hairpin RNAs, respectively. The effects of GAS5 knockdown on myocardial I/R injury were detected by CCK‐8, myocardial enzyme test, flow cytometry, TTC and terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) staining. qRT‐PCR and luciferase reporter assay were carried out to analyse the relationship between GAS5 and miR‐335. The regulation of GAS5 on Rho‐associated protein kinase 1 (ROCK1) expression, the activation of PI3K/AKT/GSK‐3β pathway and mitochondrial permeability transition pore (mPTP) opening was further evaluated. The results indicated that GAS5 knockdown enhanced the viability, decreased apoptosis and reduced the levels of lactate dehydrogenase and creatine kinase‐MB in H/R‐treatment cardiomyocytes. Meanwhile, down‐regulation of GAS5 limited myocardial infarct size and reduced apoptosis in I/R‐heart. GAS5 was found to bind to miR‐335 and displayed a reciprocal inhibition between them. Furthermore, GAS5 knockdown repressed ROCK1 expression, activated PI3K/AKT, thereby leading to inhibition of GSK‐3β and mPTP opening. These suppressions were abrogated by miR‐335 inhibitor treatment. Taken together, our results demonstrated that down‐regulation of GAS5 ameliorates myocardial I/R injury via the miR‐335/ROCK1/AKT/GSK‐3β axis. Our findings suggested that GAS5 may be a new therapeutic target for the prevention of myocardial I/R injury.

Taxifolin protects rat against myocardial ischemia/reperfusion injury by modulating the mitochondrial apoptosis pathway

Background

Taxifolin (TAX), is an active flavonoid, that plays an underlying protective role on the cardiovascular system. This study aimed to evaluate its effect and potential mechanisms on myocardial ischemia/reperfusion (I/R) injury.

Methods

Healthy rat heart was subjected to I/R using the Langendorff apparatus. Hemodynamic parameters, including heart rate, left ventricular developed pressure (LVDP), maximum/minimum rate of the left ventricular pressure rise (+dp/dt_max and −dp/dt_min) and rate pressure product (RPP) were recorded during the perfusion. Histopathological examination of left ventricular was measured by hematoxylin-eosin (H&E) staining. Creatine kinase-MB (CK-MB) and lactate dehydrogenase (LDH) activities in the effluent perfusion, and the levels of malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GSH-PX) in the tissue were assayed. Apoptosis related proteins, such as B-cell lymphoma-2 (Bcl-2), Bcl2-associated X (Bax), and cytochrome c (Cyt-c) were also assayed by ELISA. Western blot was employed to determine apoptosis-executive proteins, including caspase 3 and 9. Transferase-mediated dUTP-X nick end labeling assay was performed to evaluate the effect TAX on myocardial apoptosis.

Results

Taxifolin significantly improved the ventricular functional recovery, as evident by the increase in LVDP, +dp/dt_max, −dp/dt_min and RPP, the levels of SOD, GSH-PX were also increased, but those of LDH, CK-MB, and MDA were decreased. Furthermore, TAX up-regulated the Bcl-2 protein level but down-regulated the levels of Bax, Cyt-c, caspase 3 and 9 protein, thereby inhibits the myocardial apoptosis.

Discussion

Taxifolin treatment remarkably improved the cardiac function, regulated oxidative stress and attenuated apoptosis. Hence, TAX has a cardioprotective effect against I/R injury by modulating mitochondrial apoptosis pathway.

The cardioprotective effects of secretory leukocyte protease inhibitor against myocardial ischemia/reperfusion injury

Protease enzymes generated from injured cells and leukocytes are the primary cause of myocardial cell damage following ischemia/reperfusion (I/R). The inhibition of protease enzyme activity via the administration of particular drugs may reduce injury and potentially save patients' lives. The aim of the current study was to investigate the cardioprotective effects of treatment with recombinant human secretory leukocyte protease inhibitor (rhSLPI) on in vitro and ex vivo models of myocardial I/R injury. rhSLPI was applied to isolated adult rat ventricular myocytes (ARVMs) subjected to simulated I/R and to ex vivo murine hearts prior to I/R injury. Cellular injury, cell viability, reactive oxygen species (ROS) levels, and levels of associated proteins were assessed. The results demonstrated that administration of rhSLPI prior to or during sI/R significantly reduced the death and injury of ARVMs and significantly reduced intracellular ROS levels in ARVMs during H₂O₂ stimulation. In addition, treatment of ARVMs with rhSLPI significantly attenuated p38 mitogen-activated protein kinase (MAPK) activation and increased the activation of Akt. Furthermore, pretreatment of ex vivo murine hearts with rhSLPI prior to I/R significantly decreased infarct size, attenuated p38 MAPK activation and increased Akt phosphorylation. The results of the current study demonstrated that treatment with rhSLPI induced a cardioprotective effect and reduced ARVM injury and death, intracellular ROS levels and infarct size. rhSLPI also attenuated p38 MAPK phosphorylation and activated Akt phosphorylation. These results suggest that rhSLPI may be developed as a novel therapeutic strategy of treating ischemic heart disease.

Creating a Structurally Realistic Finite Element Geometric Model of a Cardiomyocyte to Study the Role of Cellular Architecture in Cardiomyocyte Systems Biology

With the advent of three-dimensional (3D) imaging technologies such as electron tomography, serial-block-face scanning electron microscopy and confocal microscopy, the scientific community has unprecedented access to large datasets at sub-micrometer resolution that characterize the architectural remodeling that accompanies changes in cardiomyocyte function in health and disease. However, these datasets have been under-utilized for investigating the role of cellular architecture remodeling in cardiomyocyte function. The purpose of this protocol is to outline how to create an accurate finite element model of a cardiomyocyte using high resolution electron microscopy and confocal microscopy images. A detailed and accurate model of cellular architecture has significant potential to provide new insights into cardiomyocyte biology, more than experiments alone can garner. The power of this method lies in its ability to computationally fuse information from two disparate imaging modalities of cardiomyocyte ultrastructure to develop one unified and detailed model of the cardiomyocyte. This protocol outlines steps to integrate electron tomography and confocal microscopy images of adult male Wistar (name for a specific breed of albino rat) rat cardiomyocytes to develop a half-sarcomere finite element model of the cardiomyocyte. The procedure generates a 3D finite element model that contains an accurate, high-resolution depiction (on the order of ~35 nm) of the distribution of mitochondria, myofibrils and ryanodine receptor clusters that release the necessary calcium for cardiomyocyte contraction from the sarcoplasmic reticular network (SR) into the myofibril and cytosolic compartment. The model generated here as an illustration does not incorporate details of the transverse-tubule architecture or the sarcoplasmic reticular network and is therefore a minimal model of the cardiomyocyte. Nevertheless, the model can already be applied in simulation-based investigations into the role of cell structure in calcium signaling and mitochondrial bioenergetics, which is illustrated and discussed using two case studies that are presented following the detailed protocol.

Baicalin Suppresses Hypoxia-Reoxygenation-Induced Arterial Endothelial Cell Apoptosis via Suppressing PKCδ/p53 Signaling

Background

This study was aimed to investigate the protective role of baicalin on vascular endothelium exposed to ischemia reperfusion injury and the involved molecular mechanisms.

Material/Methods

Cultured human arterial endothelial cells (HAECs) were exposed to hypoxia/deoxygenation (H/R). Cells were also treated with baicalin at serially diluted concentrations. Cells were also treated with PKC activator PEP005 or specific siRNA against protein kinase Cδ (PKCδ). MTT assay was used to evaluate the cell viabilities. Flow cytometry was used to detect cell apoptosis. The protein phosphorylation and expression levels were determined by Western blotting.

Results

PKCδ-siRNA transfection increased cell viabilities and reduced cell apoptosis in HAECs exposed to H/R. Baicalin treatment preserved cell viabilities and reduced apoptosis of H/R-exposed HAECs in a concentration-dependent manner. Baicalin treatment reduced phosphorylation levels of PKCδ and p53, as well as the expression levels of active caspase3 and bax in HAECs exposed to H/R. The treatment of PKC activator PEP005 impaired the protective effects of baicalin in increasing cell viabilities and reducing apoptosis in HAECs exposed to H/R.

Conclusions

Baicalin exerts vascular a protective effect on HAECs exposed to H/R by reducing cell apoptosis. The PKCδ/p53 apoptotic signaling pathway was the pharmacological target of baicalin.

The Inverted Heart Model for Interstitial Transudate Collection from the Isolated Rat Heart

The present protocol describes a unique approach that enables the collection of cardiac transudate (CT) from the isolated, saline-perfused rat heart. After isolation and retrograde perfusion of the heart according to the Langendorff technique, the heart is inverted into an upside-down position and is mechanically stabilized by a balloon catheter inserted into the left ventricle. Then, a thin latex cap - previously cast to match the average size of the rat heart - is placed over the epicardial surface. The outlet of the latex cap is connected to silicon tubing, with the distal opening 10 cm below the base level of the heart, creating slight suction. CT continuously produced on the epicardial surface is collected in ice-cooled vials for further analysis. The rate of CT formation ranged from 17 to 147 µL/min (n = 14) in control and infarcted hearts, which represents 0.1-1% of the coronary venous effluent perfusate. Proteomic analysis and high performance liquid chromatography (HPLC) revealed that the collected CT contains a wide spectrum of proteins and purinergic metabolites.