Ischemia/Reperfusion Injury following Acute Myocardial Infarction: A Critical Issue for Clinicians and Forensic Pathologists

MicroRNA‑221‑3p contributes to cardiomyocyte injury in H2O2‑treated H9c2 cells and a rat model of myocardial ischemia‑reperfusion by targeting p57

Myocardial ischemia‑reperfusion (I/R) injury is a major cause of cardiovascular disease worldwide, and microRNAs have been implicated in the regulation of pathological and physiological processes in myocardial I/R injury. The present study aimed to investigate the role of microRNA (miR)‑221‑3p in myocardial I/R injury. Cell death and lactate dehydrogenase (LDH) activity were increased in hydrogen peroxide (H2O2)‑treated H9c2 cells, as measured by flow cytometry and an LDH detection kit. The expression of miR‑221‑3p was elevated in H2O2‑incubated cells and in remote areas of the rat I/R model, examined using reverse transcription‑quantitative polymerase chain reaction analysis. The overexpression of miR‑221‑3p enhanced the number of propidium iodide (PI)+ cells and the activity of LDH in H2O2‑treated cells. In I/R‑induced rats, the overexpression of miR‑221‑3p promoted the number of myosin+ cells and inhibited the fractional shortening of left ventricular diameter (FSLVD%). The results showed that the expression of p57 at the gene and protein levels was decreased in H9c2 cells incubated with H2O2 and in rats subjected to I/R surgery; the expression of p57 decreased following the overexpression of miR‑221‑3p. Subsequently, the hypothesis that p57 was the direct target of miR‑221‑3p was confirmed by performing a dual‑luciferase reporter assay. Finally, to examine the function of p57 in myocardial impairment, p57 was transfected into H9c2 cells and administered to the rats prior to undergoing H2O2 treatment and I/R surgery, respectively. The results indicated that p57 attenuated the number of PI+ cells and the activity of LDH in H2O2‑treated cells, whereas p57 downregulated the number of myosin+ cells and upregulated FSLVD% in the I/R‑treated rats. Therefore, these findings suggested that miR‑221‑3p exacerbated the H2O2‑induced myocardial damage in H9c2 cells and myocardial I/R injury in the rat model by modulating p57.

Improvement of a Closed Chest Porcine Myocardial Infarction Model by Standardization of Tissue and Blood Sampling Procedures

Myocardial ischemia reperfusion (I/R) injury contributes to almost half of the necrotic area after myocardial infarction. To date there is no approved drug to prevent or reduce myocardial I/R injury. The study and understanding of the pathophysiological mechanisms of myocardial I/R injury is essential to develop successful treatments. Large animal experiments are an important step in translational methods. The porcine model of acute myocardial infarction has been established and described by ourselves and others. We aimed to further improve the value of the model by focusing in detail on the sampling techniques for use in future experiments. Furthermore, we emphasize small but important steps that can affect the quality of the final results. To mimic the clinical situation of myocardial I/R injury, a percutaneous coronary intervention (PCI) catheter was inserted into the left anterior descending coronary artery (LAD) of an anesthetized pig. °°°This model mimics acute myocardial infarction and PCI treatment in humans with the possibility of accurately determining the area at risk as well as the necrotic- and viable ischemic tissue. Here the model was used to investigate the effect of a bicyclic peptide inhibitor of FXIIa. The model can also be modified to allow longer reperfusion times to study later effects of myocardial infarction.

Intermittent hypoxia, cardiovascular disease and obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is a common disorder and is associated with cardiovascular disease. Continuous positive airway pressure (CPAP), whilst reducing blood pressure, has not been shown to reduce cardiovascular events when used as a treatment solely for this purpose in patients with previous cardiovascular disease. Developing a better understanding of the mechanisms underlying cardiovascular disease in OSA is important to develop new treatments. Potential causative mechanisms for cardiovascular disease in OSA include arousal induced sympathetic activation, large intrathoracic pressure swings leading to shear stress on the heart and great vessels, and intermittent hypoxia (IH). This review discusses the role of IH, as a major physiological consequence of OSA, in the development of cardiovascular disease.

Baicalin protects H9c2 cardiomyocytes against hypoxia/reoxygenation-induced apoptosis and oxidative stress through activation of mitochondrial aldehyde dehydrogenase 2

Baicalin, a flavonoid glycoside separated from Scutellaria baicalensis, has cardioprotection against ischaemia/reperfusion (I/R) injury. Mitochondrial aldehyde dehydrogenase 2 (ALDH2) is considered as an endogenous protective mechanism against I/R injury depending on its anti-oxidant and anti-apoptotic characteristics. The present study demonstrates whether ALDH2 contributes to the cardioprotection of baicalin against hypoxia/reoxygenation (H/R)-inudced H9c2 cardiomyocytes injury. Our results observed that H/R treatment resulted in a significant decrease in cells viability and obvious increases in caspase-3 activity and apoptosis rate in H9c2 cells, while these alterations were evidently reversed by baicalin pretreatment. Simultaneously, baicalin mitigated H/R-induced the decreases in the levels of ALDH2 mRNA and protein as well as the activity of ALDH2 in H9c2 cells. However, we found that daidzin, an ALDH2 antagonist, remarkably attenuated baicalin-elicited inhibitory action on H/R-induced the downregulation of cells viability and Bcl-2 protein expression, and the upregulations of caspase-3 activity, apoptosis rate, cytochrome c and Bax proteins expressions in H9c2 cells. In addition, baicalin reversed H/R-induced oxidative stress as evidenced by the downregulation of malondialdehyde (MAD) and 4-hydroxy aldehydes (4-HNE) levels, the inhibition of endogenous reactive oxygen species (ROS) generation, and the downregulation of superoxide dismutase (SOD) activity induced by H/R treatment, while these effects were also blocked by daidzin. Furthermore, we found that Alda-1, an ALDH2 agonist, also abolished H/R-induced cytotoxicity, apoptosis, and oxidative stress, indicating that ALDH2 mediated H/R-induced H9c2 cell injury. Overall, these results suggested that baicalin prevents H/R-induced apoptosis and oxidative stress through enhancing ALDH activity and expression in H9c2 cardiomyocytes.

Cardioprotection of CAPE-oNO2 against myocardial ischemia/reperfusion induced ROS generation via regulating the SIRT1/eNOS/NF-κB pathway in vivo and in vitro

Caffeic acid phenethyl ester (CAPE) could ameliorate myocardial ischemia/reperfusion injury (MIRI) by various mechanisms, but there hadn’t been any reports on that CAPE could regulate silent information regulator 1 (SIRT1) and endothelial nitric oxide synthase (eNOS) to exert cardioprotective effect. The present study aimed to investigate the cardioprotective potential of caffeic acid o-nitro phenethyl ester (CAPE-oNO₂) on MIRI and the possible mechanism based on the positive control of CAPE. The SD rats were subjected to left coronary artery ischemia /reperfusion (IR) and the H9c2 cell cultured in hypoxia/reoxygenation (HR) to induce the MIRI model. Prior to the procedure, vehicle, CAPE or CAPE-oNO₂ were treated in the absence or presence of a SIRT1 inhibitor nicotinamide (NAM) and an eNOS inhibitor Nω-nitro-L-arginine methyl ester (L-NAME). In vivo, CAPE and CAPE-oNO₂ conferred a cardioprotective effect as shown by reduced myocardial infarct size, cardiac marker enzymes and structural abnormalities. From immunohistochemical and sirius red staining, above two compounds ameliorated the TNF-α release and collagen deposition of IR rat hearts. They could agitate SIRT1 and eNOS expression, and consequently enhance NO release and suppress NF-κB signaling, to reduce the malondialdehyde content and cell necrosis. In vitro, they could inhibit HR-induced H9c2 cell apoptosis and ROS generation by activating SIRT1/eNOS pathway and inhabiting NF-κB expression. Emphatically, CAPE-oNO₂ presented the stronger cardioprotection than CAPE both in vivo and in vitro. However, NAM and L-NAME eliminated the CAPE-oNO₂-mediated cardioprotection by restraining SIRT1 and eNOS expression, respectively. It suggested that CAPE-oNO₂ ameliorated MIRI by suppressing the oxidative stress, inflammatory response, fibrosis and necrocytosis via the SIRT1/eNOS/NF-κB pathway.

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CAPE-oNO₂ exerting cardioprotective potential was firstly synthesized.

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IR-induced ROS increase aggravates inflammation, fibrosis and necrocytosis.

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The SIRT1/eNOS/NF-κB pathway is contributed to MIRI both in vivo and in vitro.

Reperfusion therapy-What's with the obstructed, leaky and broken capillaries?

Microvascular dysfunction is well established as an early and rate-determining factor in the injury response of tissues to ischemia and reperfusion (I/R). Severe endothelial cell dysfunction, which can develop without obvious morphological cell injury, is a major underlying cause of the microvascular abnormalities that accompany I/R. While I/R-induced microvascular dysfunction is manifested in different ways, two responses that have received much attention in both the experimental and clinical setting are impaired capillary perfusion (no-reflow) and endothelial barrier failure with a transition to hemorrhage. These responses are emerging as potentially important determinants of the severity of the tissue injury response, and there is growing clinical evidence that they are predictive of clinical outcome following reperfusion therapy. This review provides a summary of animal studies that have focused on the mechanisms that may underlie the genesis of no-reflow and hemorrhage following reperfusion of ischemic tissues, and addresses the clinical evidence that implicates these vascular events in the responses of the ischemic brain (stroke) and heart (myocardial infarction) to reperfusion therapy. Inasmuch as reactive oxygen species (ROS) and matrix metalloproteinases (MMP) are frequently invoked as triggers of the microvascular dysfunction elicited by I/R, the potential roles and sources of these mediators are also discussed. The available evidence in the literature justifies the increased interest in the development of no-reflow and hemorrhage in heart and brain following reperfusion therapy, and suggests that these vascular events may be predictive of poor clinical outcome and warrant the development of targeted treatment strategies.

Remote myocardial injury: the protective role of fluoxetine

Aortic cross-clamping-induced ischemia-reperfusion (IR) is an important factor in the development of postoperative acute cardiac injury following abdominal aortic surgery. We investigated the possible anti-oxidant/anti-inflammatory effects of fluoxetine (FLX), which is used widely as a preoperative anxiolytic on cardiac injury induced by IR of the infrarenal abdominal aorta. FLX was administered to IR-performed (60 min of ischemia and 120 min of reperfusion) rats for 3 days, once daily at 20 mg/kg i.p. dosage. Results were compared to control and non-FLX-treated IR-performed rats. Serum creatine kinase (CK) and CK-MB levels, lipid hydroperoxide, thiobarbituric acid reactive substances, and pro-oxidant/anti-oxidant balance levels in the IR group were significantly higher whereas superoxide dismutase activity, glutathione, and ferric reducing/anti-oxidant power levels were lower than for the control. IR also increased myeloperoxidase activity, tumor necrosis factor-α, interleukin-1β, and interleukin-6 and decreased interleukin-10 levels. FLX decreased CK, CK-MB, lipid hydroperoxide, thiobarbituric acid reactive substances, and pro-oxidant/anti-oxidant balance levels while increasing superoxide dismutase activity, glutathione, and ferric reducing/anti-oxidant power levels. FLX also decreased myeloperoxidase activity, tumor necrosis factor-α, interleukin-1β, and interleukin-6 levels and increased interleukin-10 levels compared to IR. FLX attenuated the morphological changes associated with cardiac injury. Our study clearly demonstrates that FLX confers protection against aortic IR-induced cardiac injury, tissue leucocyte infiltration, and cellular integrity via its anti-oxidant/anti-inflammatory effects.

[Effect of endomorphin-1 postconditioning against myocardial ischemia-reperfusion injury in rats and the role of Erk1/2 signaling pathway]

OBJECTIVE

To investigate the effect of postischemic treatment with endomorphin-1 (EM-1) against myocardial ischemia/reperfusion (IR) injury in rats and on extracellular signal regulated kinase 1/2 (Erk1/2)-dependent signaling pathway.

METHODS

Sprague-Dawley rats were randomly divided into 5 groups, namely the sham-operated group, IR group, EM-1 post-treatment group (EM50 group), EM-1 post-treatment group with PD98059 treatment (EM50+PD group), and PD98059 post-treatment group (PD group). The hemodynamic indexes of the rats were recorded. After reperfusion, CK-MB, LDH, CTnI, MDA, IL-6, TNF-α, and SOD activities or contents were measured, the infarct size was determined, and the expression levels of Erk1/2, P-Erk1/2 and cleaved caspase-3 were detected using Western blotting.

RESULTS

Compared with the sham group, the IR group showed significantly decreased heart rate and mean arterial pressure (P<0.05), which were increased obviously by EM-1 post-treatment (P<0.05). EM-1 post-treatment also resulted in significantly decreased LDH, CK-MB, CTnI, MDA, IL-6, and TNF-α activities or contents (P<0.05), increased SOD activity (P<0.05), reduced the infarct size (P<0.05), and increased the expression level of P-Erk protein (P<0.05). Compared with EM50 group, EM50+PD group showed significantly decreased heart rate and mean arterial pressure (P<0.05), increased LDH, CK-MB, CTnI, MDA, IL-6, and TNF-α activities or contents (P<0.05), decreased SOD activity, increased infarct size (P<0.05), and lowered expression of P-Erk protein (P<0.05).

CONCLUSION

Postischemic treatment with EM-1 protects the heart against IR injury by improving the cardiac function, inhibiting inflammation, and inhibiting oxidative stress and myocardial apoptosis, and Erk1/2 signaling pathway may be involved in this process.

[Effect of endomorphin-1 postconditioning against myocardial ischemia-reperfusion injury in rats and the role of Erk1/2 signaling pathway]

OBJECTIVE

To investigate the effect of postischemic treatment with endomorphin-1 (EM-1) against myocardial ischemia/reperfusion (IR) injury in rats and on extracellular signal regulated kinase 1/2 (Erk1/2)-dependent signaling pathway.

METHODS

Sprague-Dawley rats were randomly divided into 5 groups, namely the sham-operated group, IR group, EM-1 post-treatment group (EM50 group), EM-1 post-treatment group with PD98059 treatment (EM50+PD group), and PD98059 post-treatment group (PD group). The hemodynamic indexes of the rats were recorded. After reperfusion, CK-MB, LDH, CTnI, MDA, IL-6, TNF-α, and SOD activities or contents were measured, the infarct size was determined, and the expression levels of Erk1/2, P-Erk1/2 and cleaved caspase-3 were detected using Western blotting.

RESULTS

Compared with the sham group, the IR group showed significantly decreased heart rate and mean arterial pressure (P<0.05), which were increased obviously by EM-1 post-treatment (P<0.05). EM-1 post-treatment also resulted in significantly decreased LDH, CK-MB, CTnI, MDA, IL-6, and TNF-α activities or contents (P<0.05), increased SOD activity (P<0.05), reduced the infarct size (P<0.05), and increased the expression level of P-Erk protein (P<0.05). Compared with EM50 group, EM50+PD group showed significantly decreased heart rate and mean arterial pressure (P<0.05), increased LDH, CK-MB, CTnI, MDA, IL-6, and TNF-α activities or contents (P<0.05), decreased SOD activity, increased infarct size (P<0.05), and lowered expression of P-Erk protein (P<0.05).

CONCLUSION

Postischemic treatment with EM-1 protects the heart against IR injury by improving the cardiac function, inhibiting inflammation, and inhibiting oxidative stress and myocardial apoptosis, and Erk1/2 signaling pathway may be involved in this process.

IRF-5 accelerates leukocyte adhesion to endothelial cells in ischemia-reperfusion injury through regulating the transcription of VCAM-1

Ischemia-reperfusion injury (IRI) has been implicated in many pathological conditions, including cardiovascular diseases. Adhesion of leukocytes to the surface of endothelial cells has been considered as one of the principle steps in the pathological cascade of inflammatory tissue damage during IRI. The role of the transcriptional factor interferon regulatory factor-5 (IRF-5) in endothelial physiology remains unknown. Here, we report that IRF-5 is expressed in human umbilical vein endothelial cells (HUVECs) and is rapidly upregulated in response to IRI, mediated by the JAK2/STAT3 pathway. Importantly, IRF-5 is involved in IRI-induced attachment of THP-1 leukocytes to HUVECs. Mechanistically, it was found that IRF-5 targeted the expression of vascular cell adhesion molecule 1 (VCAM-1) at the transcriptional level by binding to its promoter. In conclusion, we identify IRF-5 as a new regulator and thus a therapeutic target in IRI-driven cardiovascular pathologies.