MicroRNA Expression Profile Changes after Cardiopulmonary Bypass and Ischemia/Reperfusion-Injury in a Porcine Model of Cardioplegic Arrest

The role and regulatory mechanism of HIF-1α in myocardial injury in rats undergoing cardiopulmonary bypass

BACKGROUND

Hypoxia-inducible factor-1alpha (HIF-1α) is a transcription factor implicated in physiological and pathological responses to hypoxia. The present study aims to investigate the effect and mechanism of HIF-1α on cardiopulmonary bypass (CPB)-related myocardial injury, thereby conferring a theoretical basis for the clinical treatment of myocardial injury in CPB.

METHODS

An experimental model of CPB was established in rats by surgery. Adenovirus-packaged overexpression vectors and antiagomiRNA were used to overexpress HIF-1α and NR4A1 or inhibit miR-124-3p expression in rat myocardial tissues, respectively. qRT-PCR and Western blot detected HIF-1α, miR-124-3p, and NR4A1 expression in myocardial tissues. The rat cardiac function was monitored through an echocardiogram. The rat plasma at different stages of CPB was collected, followed by the detection of IL-6, cTnT, CK-MB, and IL-1β. TUNEL staining measured apoptosis in myocardial tissues. ChIP assay analysed the enrichment of HIF-1α on the miR-124-3p promoter. The binding relationships between HIF-1α and miR-124-3p promoter sequence and between miR-124-3p and NR4A1 3'UTR sequence were confirmed by dual-luciferase reporter assay.

RESULTS

HIF-1α expression had no significant change after CPB modelling. Overexpression of HIF-1α improved the cardiac function of CPB rats, decreased plasma IL-6, cTnT, CK-MB, and IL-1β levels, and reduced TUNEL-positive myocardial cells. HIF-1α was enriched on the miR-124-3p promoter and promoted miR-124-3p expression. miR-124-3p bound to NR4A1 3'UTR sequence and targeted NR4A1 expression. Inhibition of miR-124-3p or overexpression of NR4A1 partially reversed the ameliorative effect of HIF-1α overexpression on myocardial injury in CPB rats.

CONCLUSION

Overexpression of HIF-1α can improve myocardial injury in CPB rats via the miR-124-3p/NR4A1 axis.

A novel survival rat model of hyperkalemia and landiolol induced cardioplegic arrest and resuscitation via cardiopulmonary bypass

OBJECTIVE

A small animal model would be an effective tool for research on the pathophysiology of cardiopulmonary bypass (CPB). However, numerous CPB models do not involve myocardial arrest and resuscitation. The aim of this research is to establish an easily achievable myocardial arrest and resuscitation CPB model through hyperkalemia and landiolol, simulating clinical cardiac surgery.

MATERIALS AND METHODS

Ten Sprague-Dawley rats were chosen for CPB. Rats underwent sevoflurane inhalation induction anesthesia and were sustained in an anesthesia state by intubation and intraperitoneal injection's of esketamine and propofol. The entire CPB circuit include a reservoir, a membrane oxygenator and a roller pump, which were connected into a complete loop via silicon tubes and infusion tube.After CPB was established through the tail artery and internal jugular vein, cardioplegic arrest was induced and maintained for 5 min at a rectum temperature of 28.5 ± 0.5°C with hyperkalemia and landiolol. Calcium chloride, epinephrine and insulin were then used for resuscitation.

RESULT

All rats successfully finished cardioplegic arrest, resuscitation procedure and survived 2 h postoperatively. Mean hematocrit during CPB was significantly lower than physiologic values of the baseline. The mean time of arrest-resuscitation and CPB was 5.4 ± 0.8 min and 98.5 ± 5.0 min. The blood gas at each detection point were in range with the normal standard requirement of CPB.

CONCLUSION

The establishment of cardioplegic arrest and resuscitation procedure via hyperkalemia and landiolol during CPB of WD rat could be achieved successfully. This animal model could be an alternative organ injury research on organ injury of patients undergoing cardiac surgery.

microRNA Expression Levels Change in Neonatal Patients During and After Exposure to Cardiopulmonary Bypass

Background The systemic inflammation that occurs after exposure to cardiopulmonary bypass (CPB), which is especially severe in neonatal patients, is associated with poorer outcomes and is not well understood. In order to gain deeper insight into how exposure to bypass activates inflammatory responses in circulating leukocytes, we studied changes in microRNA (miRNA) expression during and after exposure to bypass. miRNAs are small noncoding RNAs that have important roles in modulating protein levels and function of cells. Methods and Results We performed miRNA-sequencing on leukocytes isolated from neonatal patients with CPB (n=5) at 7 time points during the process of CPB, including before the initiation of bypass, during bypass, and at 3 time points during the first 24 hours after weaning from bypass. We identified significant differentially expressed miRNAs using generalized linear regression models, and miRNAs were defined as statistically significant using a false discovery rate-adjusted P<0.05. We identified gene targets of these miRNAs using the TargetScan database and identified significantly enriched biological pathways for these gene targets. We identified 54 miRNAs with differential expression during and after CPB. These miRNAs clustered into 3 groups, including miRNAs that were increased during and after CPB (3 miRNAs), miRNAs that decreased during and after CPB (10 miRNAs), and miRNAs that decreased during CPB but then increased 8 to 24 hours after CPB. A total of 38.9% of the target genes of these miRNAs were significantly differentially expressed in our previous study. miRNAs with altered expression levels are predicted to significantly modulate pathways related to inflammation and signal transduction. Conclusions The unbiased profiling of the miRNA changes that occur in the circulating leukocytes of patients with bypass provides deeper insight into the mechanisms that underpin the systemic inflammatory response that occurs in patients after exposure to CPB. These data will help the development of novel treatments and biomarkers for bypass-associated inflammation.

Normothermic blood polarizing versus depolarizing cardioplegia in a porcine model of cardiopulmonary bypass

OBJECTIVES

We have previously demonstrated beneficial cardiac protection with hypothermic polarizing cardioplegia compared to a hyperkalemic depolarizing cardioplegia. In this study, a porcine model of cardiopulmonary bypass was used to compare the protective effects of normothermic blood-based polarizing and depolarizing cardioplegia during cardiac arrest.

METHODS

Thirteen pigs were randomized to receive either normothermic polarizing (n = 8) or depolarizing (n = 5) blood-based cardioplegia. After initiation of cardiopulmonary bypass, normothermic arrest (34°C, 60 min) was followed by 60 min of on-pump and 90 min of off-pump reperfusion. Primary outcome was myocardial injury measured as arterial myocardial creatine kinase concentration. Secondary outcome was haemodynamic function and the energy state of the hearts.

RESULTS

During reperfusion, release of myocardial creatine kinase was comparable between groups (P = 0.36). In addition, most haemodynamic parameters showed comparable results between groups, but stroke volume (P = 0.03) was significantly lower in the polarizing group. Adenosine triphosphate levels were significantly (18.41 ± 3.86 vs 22.97 ± 2.73 nmol/mg; P = 0.03) lower in polarizing hearts, and the requirement for noradrenaline administration (P = 0.002) and temporary pacing (6 vs 0; P = 0.02) during reperfusion were significantly higher in polarizing hearts.

CONCLUSIONS

Under normothermic conditions, polarizing blood cardioplegia was associated with similar myocardial injury to depolarizing blood cardioplegia. Reduced haemodynamic and metabolic outcome and a higher need for temporary pacing with polarized arrest may be associated with the blood-based dilution of this solution.

H2S Pretreatment Is Promigratory and Decreases Ischemia/Reperfusion Injury in Human Microvascular Endothelial Cells

Endothelial cell injury and vascular function strongly correlate with cardiac function following ischemia/reperfusion injury. Several studies indicate that endothelial cells are more sensitive to ischemia/reperfusion compared to cardiomyocytes and are critical mediators of cardiac ischemia/reperfusion injury. H₂S is involved in the regulation of cardiovascular system homeostasis and can act as a cytoprotectant during ischemia/reperfusion. Activation of ERK1/2 in endothelial cells after H₂S stimulation exerts an enhancement of angiogenesis while its inhibition significantly decreases H₂S cardioprotective effects. In this work, we investigated how H₂S pretreatment for 24 hours prevents the ischemia/reperfusion injury and promotes angiogenesis on microvascular endothelial cells following an ischemia/reperfusion protocol in vitro, using a hypoxic chamber and ischemic buffer to simulate the ischemic event. H₂S preconditioning positively affected cell viability and significantly increased endothelial cell migration when treated with 1 μM H₂S. Furthermore, mitochondrial function was preserved when cells were preconditioned. Since ERK1/2 phosphorylation was extremely enhanced in ischemia/reperfusion condition, we inhibited ERK both directly and indirectly to verify how H₂S triggers this pathway in endothelial cells. Taken together, our data suggest that H₂S treatment 24 hours before the ischemic insult protects endothelial cells from ischemia/reperfusion injury and eventually decreases myocardial injury.

miR-362-3p Targets Orosomucoid 1 to Promote Cell Proliferation, Restrain Cell Apoptosis and Thereby Mitigate Hypoxia/Reoxygenation-Induced Cardiomyocytes Injury

This study aimed to investigate the mechanism of how miR-362-3p/orosomucoid 1 (ORM1) involved in hypoxia/reoxygenation (H/R)-induced cardiomyocytes injury. Based on data obtained from Gene Expression Omnibus (GEO) database, we revealed that ORM1 was highly expressed and positively correlated with the expression of inflammatory factors (MAPK1, MAPK3, IL1B and CASP9). miR-362-3p was identified as an upstream regulatory miRNA of ORM1 and negatively modulated the mRNA and protein expression levels of ORM1 in H/R-injured cardiomyocytes. Moreover, we found that miR-362-3p was downregulated in cardiomyocytes injured by H/R. The promoting influence of miR-362-3p mimic on the proliferation and the inhibitory effect of miR-362-3p mimic on the apoptosis of H/R-stimulated cardiomyocytes were eliminated by overexpression of ORM1. Furthermore, miR-362-3p affected the expression of MAPK1, MAPK3, IL1B and CASP9 in H/R-injured cardiomyocytes through targeting ORM1. Our outcomes illustrated that miR-362-3p exhibited a protective influence on H/R-induced cardiomyocytes through targeting ORM1.

Non-coding RNAs participate in the ischemia-reperfusion injury

Ischemia, being defined as blood supply deficiency is involved in the pathogenesis of a number of life-threatening conditions such as myocardial infarction and cerebral stroke. Assessment of the molecular pathology of these conditions has led to identification of the role of reperfusion in induction and aggravation of tissue injury and necrosis. Thus, the term "ischemia/ reperfusion (I/R) injury" has been introduced. This process involves aberrant regulation of the mitochondrial function, apoptotic and autophagic pathways and signal transducers. More recently, non-coding RNAs including long non-coding RNAs (lncRNAs) ad microRNAs (miRNAs) have been shown to influence I/R injury. Animal studies and clinical investigations have shown up-/down-regulation of tens of lncRNAs and miRNAs in this process. In the current study, we summarize the role of these transcripts in the pathophysiology of I/R injury and their potential as biomarkers for detection of extent of tissue injury.