In vivo gene delivery of XIAP protects against myocardial apoptosis and infarction following ischemia/reperfusion in conscious rabbits

MicroRNA-320a-3p Signatures as a Satisfactory Predictor of Acute Coronary Syndrome and Attenuates Inflammation by Targeting X-Linked Inhibitor of Apoptosis Protein

Acute coronary syndrome (ACS) is a heart disease with a high mortality rate. Recently, more and more evidence illustrated that microRNAs (miRNA) participated in regulating the occurrence of heart disease. This study aimed to detect the level of serum miR-320a-3p in patients with ACS, predict its possibility as a candidate gene for diagnosis, and explore its potential mechanism in the regulation of ACS. 139 ACS patients and 126 controls were recruited in this study. The expression level of miR-320a-3p was determined by qRT-PCR. The predictive value in ACS was assessed by receiver operating characteristic (ROC) curve. Enzyme-linked immunosorbent assay (ELISA) was used to measure the protein expression levels of inflammatory factors. The downstream targets of miR-320a-3p were verified by luciferase reporter gene assay. In ACS patients and rat models, the expression level of serum miR-320a-3p was significantly increased. ROC curve revealed that abnormal expression of miR-320a-3p was of diagnostic value for ACS. In an in vivo rat model, down-regulation of miR-320a-3p inhibited the production of von Willebrand factor (vWF), Heart fatty acid-binding protein (H-FABP), interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α). In other words, down-regulation of miR-320a-3p reduced rat vascular endothelial injury and inflammation. X-linked inhibitor of apoptosis protein (XIAP) was determined to be a direct target of miR-320a-3p. miR-320a-3p is useful for the diagnosis of ACS. Animal experiments confirmed that up-regulated miR-320a-3p promoted vascular endothelial injury and inflammatory response by targeting XIAP, thus promoting the development of ACS. MiR-320a-3p may be a new breakthrough in the diagnosis and treatment of ACS.

MiR-96 promotes myocardial infarction-induced apoptosis by targeting XIAP

Acute myocardial infarction (AMI) has becoming a common leading cause of sudden death worldwide. MiR-96 has been identified that can target anti-apoptotic related genes in various human diseases. However, its role in AMI remains unclear. In this study, we found that miR-96 was significantly upregulated in the ischemic heart of MI mice (mice with myocardial infarction) and also in the H₂O₂-treated neonatal rat ventricular cardiomyocytes (CMs). In response H₂O₂, miR-96 inhibitor could significantly promote cell viability and reduce cell apoptosis of CMs, and inhibit the expression of Cleaved caspase-3 and Bax, while promote Bcl-2 expression. In addition, downregulation of miR-96 remarkedly reduced the infarct size and the percentages of apoptotic cells in the heart tissues of MI mice, and then protected against the damaged cardiac function. Moreover, we identified that XIAP (X-linked inhibitor of apoptosis) acted as a direct target gene of miR-96, meanwhile si-XIAP could obviously reverse miR-96 inhibitor induced protective effect in H₂O₂-treated CMs Taken together, our study demonstrated that miR-96 promoted AMI progression by directly targeting XIAP, and inhibiting the anti-apoptotic function of XIAP (Graphical abstract), which provided a novel therapeutic target for AMI treatment.

SET8 mitigates hepatic ischemia/reperfusion injury in mice by suppressing MARK4/NLRP3 inflammasome pathway

AIMS

Hepatic ischemia/reperfusion (I/R) injury is a critical factor affecting the prognosis of liver surgery. The aim of this study is to explore the effects of SET8 on hepatic I/R injury and the putative mechanisms.

MAIN METHODS

The expression of SET8 and MARK4 in I/R group and sham group were detected both in vivo and in vitro. In addition, mouse and RAW 264.7 cells were transfected with MARK4 siRNA and SET8 siRNA knockdown of MARK4 and SET8, respectively. The expression of SET8, MARK4 and NLRP3-associated proteins were detected after different treatments. The pathology of liver and the serologic detection were detected after different treatments.

KEY FINDINGS

Our present study identified SET domain-containing protein 8 (SET8) as an efficient protein, which can negatively regulate hepatic I/R-mediated inflammatory response and ameliorate hepatic I/R injury by suppressing microtubule affinity-regulating kinase 4 (MARK4)/ NLR family pyrin domain containing 3 (NLRP3) inflammasome pathway. The data showed that MARK4 deficiency inhibited hypoxia/reoxygenation (H/R)-induced NLRP3 inflammasome activation, while SET8 deficiency showed the opposite effect. We further demonstrated that SET8 restrained NLRP3 inflammasome activation by inhibiting MARK4. Moreover, we verified SET8 made protective effect on hepatic I/R injury.

SIGNIFICANCE

SET8 plays an essential role in hepatic ischemia/reperfusion injury in mice by suppressing MARK4/NLRP3 inflammasome pathway. Our results may offer a new strategy to mitigate hepatic I/R injury.

miR-146a-5p Mediates Intermittent Hypoxia-Induced Injury in H9c2 Cells by Targeting XIAP

MicroRNAs (miRNAs) have emerged as key modulators in the pathophysiologic processes of cardiovascular diseases. However, its function in cardiac injury induced by obstructive sleep apnea (OSA) remains unknown. The aim of the current study was to identify the effect and potential molecular mechanism of miR-146a-5p in intermittent hypoxia(IH)- induced myocardial damage. We exposed H9c2 cells to IH condition; the expression levels of miR-146a-5p were detected by RT-qPCR. Cell viability, cell apoptosis, and the expressions of apoptosis-associated proteins were assessed via Cell Counting Kit-8 (CCK-8), flow cytometry, and western blotting, respectively. Target genes of miR-146a-5p were confirmed by dual-luciferase reporter assay. IH remarkably lowered viability but enhanced cell apoptosis. Concomitantly, the miR-146a-5p expression level was increased in H9c2 cells after IH. Subsequent experiments showed that IH-induced injury was alleviated through miR-146a-5p silence. X-linked inhibitor of apoptosis protein (XIAP) was predicted by bioinformatics analysis and further confirmed as a direct target gene of miR-146a-5p. Surprisingly, the effect of miR-146a-5p inhibition under IH may be reversed by downregulating XIAP expression. In conclusion, our results demonstrated that miR-146a-5p could attenuate viability and promote the apoptosis of H9c2 by targeting XIAP, thus aggravating the H9c2 cell injury induced by IH, which could enhance our understanding of the mechanisms for OSA-associated cardiac injury.

Effects of miR-181a targeting XIAP gene on apoptosis of cardiomyocytes induced by hypoxia/reoxygenation and its mechanism

To investigate the effect of miR-181a targeting XIAP gene on the apoptosis of cardiomyocytes induced by hypoxia/reoxygenation (H/R) and its mechanism. The primary cultured cardiomyocytes were treated with hypoxia for 3 hours and reoxygenation for 4 hours to construct H/R cell model. The expression of miR-181a and XIAP messenger RNA in cardiomyocytes was detected by reverse-transcription polymerase chain reaction, and the expression of XIAP protein in cardiomyocytes was detected by Western blot analysis. H/R cardiomyocytes with low expression of miR-181a and overexpression of XIAP were constructed, and the effects of low expression of miR-181a and upregulation of XIAP on cardiomyocyte apoptosis were detected by flow cytometry. A dual luciferase reporter assay was used to detect the target relationship between miR-181a and XIAP. Further, H/R myocardial cells with low XIAP expression were constructed to observe the effect of downregulation of XIAP expression on apoptosis of myocardial cells with low expression of microarray-181a. The expression of apoptosis-related proteins Bax and Bcl-2 in myocardial cells was detected by Western blot analysis. After H/R treatment, the expression of microRNAs-181a was high but that of XIAP was low. The apoptosis of cardiomyocytes could be inhibited by both the low expression of miR-181a and the upregulation of XIAP. The results of dual luciferase reporter gene showed that XIAP was a potential target gene for miR-181a. The inhibitory effect of low expression of miR-181a on myocardial apoptosis could be reversed and the inhibitory effect of low expression of miR-181a on Bax protein expression and the promotion of Bcl-2 protein expression could be reversed by the downregulation of XIAP. MiR-181a can inhibit the apoptosis of hypoxic-reoxygenated cardiomyocytes by targeting XIAP to downregulate Bax and upregulate Bcl expression.

Cardioprotection of tilianin ameliorates myocardial ischemia-reperfusion injury: Role of the apoptotic signaling pathway

Our previous research demonstrated that tilianin protects the myocardium in a myocardial ischemia reperfusion injury (MIRI) rat model and has prominent pharmacological potential as a cardiovascular drug. Our study aimed to investigate the molecular signaling implicated in the improvement of myocardial survival induced by tilianin, a flavonoid antioxidant. Tilianin (2.5, 5, and 10 mg/kg/d) or saline was orally administered to rats for 14 days. On the 15th day, ischemia was induced by ligating the left anterior descending artery for 45 min, followed by 4 h of reperfusion. The levels of MIRI-induced serum myocardial enzymes and cardiomyocyte apoptosis as well as infarct size were examined to assess the cardioprotective effects. Cardiac tissues were collected for western blot analyses to determine the protein expression of anti-apoptotic signaling molecules. In MIRI-treated rats, our results revealed that pre-administration of high dose-tilianin the reduced release of LDH, MDA, and CK-MB and increased the plasma SOD level, and significantly attenuated the infarct size. Western blot analysis showed that a remarkable rise in expression of Bcl-2 and XIAP, and decline in expression of Bax, Smac/Diablo, HtrA2/Omi, cleaved caspase-3, caspase-7 and caspase-9 was observed in the myocardium. The apoptosis index of cardiomyocytes further supports the cardioprotective effect of tilianin. Additionally, compared with the MIRI model group, pretreatment with high dose-tilianin group upregulated phosphorylated Akt and PI3K. In contrast, using the PI3K inhibitor LY294002 to block Akt activation effectively inhibited the protective effects of tilianin against MIRI. Tilianin pretreatment was beneficial for activating the PI3K/Akt signaling pathway and inhibiting myocardial apoptosis.

The expression of microRNA-23a regulates acute myocardial infarction in patients and in vitro through targeting PTEN

Cardiovascular disease is responsible for one of the highest rates of fatality worldwide. The present study investigated the presence and influence of microRNA (miRNA)-23a in the regulation of acute myocardial infarction (AMI). A total of 6 patients with AMI and 6 normal volunteers without myocardial disease were included, and blood samples were taken to analyze the expression of miRNA‑23a by reverse transcription‑quantitative polymerase chain reaction. miRNA‑23a expression in patients with AMI was downregulated compared with the normal group. In H9C2 cells treated with H2O2, upregulation of miRNA‑23a expression increased the superoxide dismutase, glutathione and catalase activity levels, and suppressed the malonaldehyde activity level, as determined by ELISA. Western blot analysis and a caspase‑3 substrate assay demonstrated that upregulation of miRNA‑23a expression suppressed the Bcl‑2‑associated X (Bax)/Bcl‑2 protein expression ratio, caspase‑3 activity level and tumor suppressor p53 (p53) protein expression in H2O2‑induced H9C2 cells. Furthermore, downregulation of phosphatase and tensin homolog (PTEN), by the PTEN inhibitor bpV(HOpic), increased miRNA‑23a expression and suppressed the Bax/Bcl‑2 protein expression ratio, caspase‑3 activity level and p53 protein expression in H2O2‑induced H9C2 cells. Therefore, the results of the present study indicate that the expression of miRNA‑23a may regulate AMI through targeting PTEN in patients and in vitro, and PTEN/miRNA‑23a may therefore be potential targets for the clinical treatment of AMI.

Pretreatment with low-dose gadolinium chloride attenuates myocardial ischemia/reperfusion injury in rats

AIM

We have shown that low-dose gadolinium chloride (GdCl3) abolishes arachidonic acid (AA)-induced increase of cytoplasmic Ca(2+), which is known to play a crucial role in myocardial ischemia/reperfusion (I/R) injury. The present study sought to determine whether low-dose GdCl3 pretreatment protected rat myocardium against I/R injury in vitro and in vivo.

METHODS

Cultured neonatal rat ventricular myocytes (NRVMs) were treated with GdCl3 or nifedipine, followed by exposure to anoxia/reoxygenation (A/R). Cell apoptosis was detected; the levels of related signaling molecules were assessed. SD rats were intravenously injected with GdCl3 or nifedipine. Thirty min after the administration the rats were subjected to LAD coronary artery ligation followed by reperfusion. Infarction size, the release of serum myocardial injury markers and AA were measured; cell apoptosis and related molecules were assessed.

RESULTS

In A/R-treated NRVMs, pretreatment with GdCl3 (2.5, 5, 10 μmol/L) dose-dependently inhibited caspase-3 activation, death receptor-related molecules DR5/Fas/FADD/caspase-8 expression, cytochrome c release, AA release and sustained cytoplasmic Ca(2+) increases induced by exogenous AA. In I/R-treated rats, pre-administration of GdCl3 (10 mg/kg) significantly reduced the infarct size, and the serum levels of CK-MB, cardiac troponin-I, LDH and AA. Pre-administration of GdCl3 also significantly decreased the number of apoptotic cells, caspase-3 activity, death receptor-related molecules (DR5/Fas/FADD) expression and cytochrome c release in heart tissues. The positive control drug nifedipine produced comparable cardioprotective effects in vitro and in vivo.

CONCLUSION

Pretreatment with low-dose GdCl3 significantly attenuates I/R-induced myocardial apoptosis in rats by suppressing activation of both death receptor and mitochondria-mediated pathways.

Diabetic cardiomyopathy: role of the E3 ubiquitin ligase

Diabetic cardiomyopathy (DCM) is the leading cause of mortality in diabetes. As the number of cases of diabetes continues to rise, it is urgent to develop new strategies to protect against DCM, which is characterized by cardiac hypertrophy, increased apoptosis, fibrosis, and altered insulin metabolism. The E3 ubiquitin ligases (E3s), one component of the ubiquitin-proteasome system, play vital roles in all of the features of DCM listed above. They also modulate the activity of several transcription factors involved in the pathogenesis of DCM. In addition, the E3s degrade both insulin receptor and insulin receptor substrates and also regulate insulin gene transcription, leading to insulin resistance and insulin deficiency. Therefore, the E3s may be a driving force for DCM. This review summarizes currently available studies to analyze the roles of the E3s in DCM, enriches our knowledge of how DCM develops, and provides a novel strategy to protect heart from diabetes.

Intramyocardial thrombin promotes angiogenesis and improves cardiac function in an experimental rabbit model of acute myocardial infarction

OBJECTIVE

Thrombin has been reported to play a pivotal role in the initiation of angiogenesis by indirectly regulating and organizing a network of angiogenic molecules. On the basis of these reports, we investigated the angiogenic action of thrombin in a rabbit model of acute myocardial infarction.

METHODS

A rabbit model of acute myocardial infarction was established by ligation of the left anterior descending coronary branch. Subjects were then divided into 2 groups and treated with intramyocardial administration of thrombin (2500 IU; n = 13) or an equal volume of normal saline (n = 13). Four weeks later, animals were euthanized and histopathologic analysis, immunohistochemical staining for endothelial markers CD31 and vascular endothelial growth factor-A, and electron microscopy examination were performed on excised hearts. Electrocardiography, cardiac enzymes, and assessment of cardiac function by measuring left ventricular end-diastolic pressure and ejection fraction were recorded before and after myocardial infarction, and both left ventricular end-diastolic pressure and ejection fraction were further measured on the day of euthanasia (n = 5-8 in each case).

RESULTS

Increased levels of troponin, ST elevation, and histopathologically confirmed myocardial infarction were observed in all animals. A significant increase of microvessel density at the infarct border zone, as evaluated by CD31 immunohistochemistry, was observed in the thrombin-treated group compared with the control group (30.3 ± 12.8 vs 12.6 ± 4.8, P = .0065). A significantly higher number of vascular endothelial growth factor-A-positive vessels at the infarct border zone was observed in the thrombin-treated animals compared with the control group (21.8 ± 8.9 vs 5.6 ± 4.4; P = .0009). The thrombin-treated animals showed a statistically significant reduction in left ventricular end-diastolic pressure values (6.9 ± 1.8 mm Hg vs 12.7 ± 2.2 mm Hg, P = .0002) and significant improvement in left ventricular ejection fraction (59.8% ± 3.1% vs 42.2% ± 6.14%, P = .002) on the day of euthanasia compared with the post-infarct day, reflecting significantly improved cardiac function compared with control subjects that showed no significant change.

CONCLUSIONS

Intramyocardial administration of thrombin seems to promote angiogenesis and improve cardiac function of the ischemic myocardium, which may provide a new therapeutic approach in patients with myocardial ischemia.

Right ventricular pacing with mechanical dyssynchrony causes apoptosis interruptus and calcium mishandling

BACKGROUND

Mechanical dyssynchrony associated with rapid pacing induces cardiac cell stress and myocardial apoptotic pathway activation that has been implicated in the pathophysiology of left ventricular (LV) dysfunction. Effects of dyssynchrony per se are not fully understood. The objective of our study was to test whether ventricular dyssynchrony would elicit myocardial alterations in LV calcium handling regulation and cell survival or apoptosis signalling in right ventricular-paced swine.

METHODS

Implantation of pacemaker was performed under anaesthesia. Endocardial bipolar screw lead was inserted into the right jugular vein and positioned either in the right atrium or at the right ventricular (RV) apex. Swine were paced at 150 beats per minute for 3 weeks.

RESULTS

Compared with right atrial pacing, RV pacing led to abnormal LV sarcoplasmic reticulum calcium uptake (315 ± 65 vs 155 ± 55 nmol/min/mg, P < 0.05) and LV calcium-handling protein expression, ie, 35% reduction in ryanodine receptor 2, 25% decline in sarcoplasmic reticulum Ca(2+) ATPase, 70% increase in Na(+)/Ca(2+) exchanger, and 10% increase in phospholamban. RV pacing also elicited activation of LV apoptotic cascades without nuclear apoptosis. So-called interrupted apoptosis was the result of increased expression of X-linked inhibitor of apoptosis protein. Apoptosis and calcium mishandling were documented in absence of depressed heart function (ejection fraction 62 ± 8% vs 57 ± 12%, in right atrial- and RV-paced hearts, respectively, P > 0.05).

CONCLUSIONS

Slow rate RV pacing causes mechanical dyssynchrony and profound LV alterations in both apoptotic pathways and calcium handling in the early stages of pacing-induced cardiomyopathy.

Cell death signalling mechanisms in heart failure

Cardiac disease is a global epidemic that is on the rise, despite the recent advances in cardiovascular research. Once the myocardium is injured, it has a limited capacity to activate reparative mechanisms to restore proper cardiac function, leading to the development of systemic heart failure. Autophagy, under certain conditions, may result in cell death, further emphasizing the controversial issues regarding the autophagic process as an adaptive or maladaptive biological response. Although significant progress in understanding the signalling mechanisms of cell death in myocytes has been made, the role of apoptotic cell death and programmed necrosis during heart failure is not completely understood. Insight to how myocytes determine whether to activate apoptotic or programmed necrosis signalling machinery remains under current investigation because it is a major problem for both scientists and clinicians in treating heart failure patients. Herein, the different modes of cell death implicated in heart failure are highlighted, as well as the role of B-cell lymphoma-2 family members and how mitochondria act as central organelles in directing such cell death mechanisms.