Gang Dai

Shear-sensitive microRNA-34a modulates flow-dependent regulation of endothelial inflammation

ABSTRACT Although many studies have described the roles of microRNAs (miRNAs) in the modulation of the endothelial response to shear stress, the mechanisms remain incompletely understood. Here, we demonstrate that miR-34a expression in endothelial cells was downregulated by atheroprotective physiological high shear stress (HSS), whereas it was upregulated by atheroprone oscillatory shear stress (OSS). Blockade of endogenous miR-34a dramatically decreased basal vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) protein expression levels. Conversely, miR-34a overexpression increased the protein levels of VCAM-1 and ICAM-1, consequently promoting monocyte adhesion to endothelial cells. Furthermore, miR-34a overexpression attenuated HSS-mediated suppression of VCAM-1 protein expression on endothelial cells, but promoted HSS-induced ICAM-1 expression. In addition, the OSS induction of endothelial cell VCAM-1 and ICAM-1 was suppressed by using an miR-34a inhibitor, which led to a reduction of monocyte adhesion to endothelial cells. Mechanistically, sirtuin 1 overexpression partially prevented miR-34a-induced VCAM-1 and ICAM-1 expression. Subsequent investigation demonstrated that miR-34a increased nuclear factor &kgr;B (NF-&kgr;B) p65 subunit (also known as RelA) acetylation (on residue Lys310), and silencing NF-&kgr;B signaling reduced miR-34a-induced VCAM-1 and ICAM-1 protein expression. These results demonstrate that miR-34a is involved in the flow-dependent regulation of endothelial inflammation.

Model of cardiac arrest in rats by transcutaneous electrical epicardium stimulation

OBJECTIVEnTo establish a new model of cardiac arrest (CA) in rats by transcutaneous electrical epicardium stimulation.nnnMETHODSnTwo acupuncture needles connected to the anode and cathode of a stimulator were transcutaneously inserted into the epicardium as electrodes. The stimulating current was steered to the epicardium and the stimulation was maintained for 3 min to induce CA. Cardiopulmonary resuscitation (CPR) was performed at 6 min after a period of nonintervention.nnnRESULTSnCA was successfully induced in a total of 20 rats. The success rate of induction was 12/20 at the current intensity of 1 mA; and reached 20/20 when the current intensity was increased to 2 mA. After the electrical stimulation, the femoral blood pressure quickly dropped below 25 mmHg and the arterial pulse waveform disappeared. The average time from the electrical stimulation to CA induction was 5.10 (+/-2.81) s. When the electrical stimulation stopped, 18/20 rats had ventricular fibrillation and 2/20 rats had pulseless electrical activity. CPR was performed for averagely 207.4 (+/-148.8) s. The restoration of spontaneous circulation (ROSC) was 20/20. The death rate within 4h after ROSC was 5/20, and the 72-h survival rate was 10/20. There were only two cases of complications, a minor muscle contraction and a minor lung lobe injury.nnnCONCLUSIONnThe model of CA in rats induced by transcutaneous electrical epicardium stimulation is a stable model that requires low-intensity current and has fewer complications. This model may provide another option for experimental research of CA induced by malignant arrhythmia (especially VF).

Ulinastatin attenuates oxidation, inflammation and neural apoptosis in the cerebral cortex of adult rats with ventricular fibrillation after cardiopulmonary resuscitation

OBJECTIVE: The role of Ulinastatin in neuronal injury after cardiopulmonary resuscitation has not been elucidated. We aim to evaluate the effects of Ulinastatin on inflammation, oxidation, and neuronal injury in the cerebral cortex after cardiopulmonary resuscitation. METHODS: Ventricular fibrillation was induced in 76 adult male Wistar rats for 6 min, after which cardiopulmonary resuscitation was initiated. After spontaneous circulation returned, the rats were split into two groups: the Ulinastatin 100,000 unit/kg group or the PBS-treated control group. Blood and cerebral cortex samples were obtained and compared at 2, 4, and 8 h after return of spontaneous circulation. The protein levels of tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6) were assayed using an enzyme-linked immunosorbent assay, and mRNA levels were quantified via real-time polymerase chain reaction. Myeloperoxidase and Malondialdehyde were measured by spectrophotometry. The translocation of nuclear factor-κB p65 was assayed by Western blot. The viable and apoptotic neurons were detected by Nissl and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL). RESULTS: Ulinastatin treatment decreased plasma levels of TNF-α and IL-6, expression of mRNA, and Myeloperoxidase and Malondialdehyde in the cerebral cortex. In addition, Ulinastatin attenuated the translocation of nuclear factor-κB p65 at 2, 4, and 8 hours after the return of spontaneous circulation. Ulinastatin increased the number of living neurons and decreased TUNEL-positive neuron numbers in the cortex at 72 h after the return of spontaneous circulation. CONCLUSIONS: Ulinastatin preserved neuronal survival and inhibited neuron apoptosis after the return of spontaneous circulation in Wistar rats via attenuation of the oxidative stress response and translocation of nuclear factor-κB p65 in the cortex. In addition, Ulinastatin decreased the production of TNF-α, IL-6, Myeloperoxidase, and Malondialdehyde.

Ulinastatin improved cardiac dysfunction after cardiac arrest in New Zealand rabbits

OBJECTIVEnThe present study was designed to evaluate the effects of ulinastatin (UTI) on cardiac dysfunction after cardiopulmonary resuscitation (CPR).nnnMETHODSnA total of 48 healthy adult male New Zealand rabbits were untreated for 8 minutes after the induction of ventricular fibrillation (VF) by an external transthoracic alternating current and then treated by CPR. These rabbits were then randomly divided into the control and UTI groups after the return of spontaneous circulation (ROSC) and were observed for 8 hours after the ROSC. Before CPR and after ROSC at 2, 4, and 8 hours, blood samples were collected to determine the levels of tumor necrosis factor α (TNF-α), interleukin-6 (IL-6), malondialdehyde (MDA), cardiac troponin I (cTnI), and N-terminal probrain natriuretic peptide (NT-proBNP), and the left ventricular ejection fraction (EF) was measured by echocardiography.nnnRESULTSnNineteen of 24 rabbits in the control group and 18 of 24 in the UTI group were successfully resuscitated. The plasma levels of TNF-α, IL-6, MDA, cTnI, and NT-proBNP were significantly increased, accompanying a deceased EF in the control group, but the cotreatment with UTI decreased the plasma levels of TNF-α, IL-6, MDA, cTnI, and NT-proBNP (P < .05), attenuating the myocardial injury and improving the EF in the UTI group. Only 9 of 19 animals in the control group but 14 of 18 animals in the UTI group survived longer than 8 hours (P = .011).nnnCONCLUSIONSnThe progression of proinflammatory responses, oxidative stress, and myocardial injury have been linked to the reduced EF after VF/CPR, and the administration of UTI at a cardioprotective dosage preserved the cardiac function after VF/CPR.

The changes of brain water diffusion and blood flow on diffusion-weighted and perfusion-weighted imaging in a canine model of cardiac arrest

OBJECTIVEnTo study the changes of brain water diffusion and cerebral haemodynamics of cortical areas using magnetic resonance imaging (MRI) in canine models of cardiac arrest (CA) and restoration of spontaneous circulation (ROSC). The secondary study objective was to evaluate whether MRI can be used to observe haemodynamic disorders in brain microcirculation.nnnMETHODSnCA was induced in six beagle dogs using electrical stimulation followed by resuscitation to spontaneous circulation 3 min later. The dogs were scanned using MRI for echo planar, diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) with injection of Gd-diethylene triamine pentaacetic acid (DTPA) prior to induction of CA and 3 days after ROSC. The arterial blood pressure, unilateral common carotid artery flow and intracranial microcirculation were recorded.nnnRESULTSnAll dogs successfully underwent electric-induced ventricular fibrillation which lasted 3 min and were resuscitated to maintain blood pressure stability. Serial MRI scans found that cerebral blood flow (RCBF) decreased in day 1 after ROSC and returned to baseline on day 3. Apparent diffusion coefficient (ADC), however, decreased on day 1 and remained lower than baseline on day 3, with 765.8±82.5×10(-6) mm(2) s(-1) on day 1 and 770.4±59.4×10(-6) mm(2) s(-1) on day 3 comparing to 855.8±43.4×10(-6) mm(2) s(-1) on baseline.nnnCONCLUSIONSnThese data provide the evidence that early MRI can be used to observe acute haemodynamic disorders in brain microcirculation in a canine model of cardiac arrest.

Enhanced external counterpulsation improves cerebral blood flow following cardiopulmonary resuscitation

BACKGROUNDnTo investigate the therapeutic value of enhanced external counterpulsation (EECP) on recovery of cerebral blood flow following cardiac arrest (CA) and successful resumption of spontaneous circulation (ROSC) by cardiopulmonary resuscitation.nnnMETHODSnCA models were conducted using beagle dogs induced by alternating current. After successful ROSC by cardiopulmonary resuscitation, 16 dogs were randomly divided into the EECP and control group (n = 8 per group). Dogs underwent dynamic contrast-enhanced and diffusion-weighted magnetic resonance imaging at baseline prior to CA and during the 3 days following ROSC. Mean blood pressure, right common carotid artery blood flow, intracranial microcirculation and blood lactate levels were measured. Neurological outcome was assessed by the neurologic deficit score. Hematoxylin-eosin staining and transmission electron microscopy were performed for morphology and microconstruction of the cerebral cortex.nnnRESULTSnThe EECP group exhibited a significant elevation in right common carotid artery blood flow, intracranial microcirculation and a substantial decrease in blood lactate levels relative to the control group. Relative cerebral blood flow and volume were higher in the EECP group during the 3 days. Apparent diffusion coefficients were significantly higher in the EECP group on the first and third days. After ROSC, the neurologic deficit score was significantly higher in the control group compared to those in the EECP group during the three days of experiment. The cell swelling of neurons and increase of mitochondrial mass were more pronounced in the control group.nnnCONCLUSIONnEECP is beneficial for recovery of cerebral blood flow and attenuation of ischemic cerebral edema following CA and successful ROSC.

Activation of autophagy improved the neurologic outcome after cardiopulmonary resuscitation in rats.

OBJECTIVEnRecent studies have shown the existence of autophagy in cerebral ischemia; however, there has been no research on the role of autophagy in cerebral injury after cardiopulmonary resuscitation (CPR). This study was conducted to determine the role of autophagy in an animal model of ventricular fibrillation (VF)/CPR.nnnMETHODSnExperiment 1: A total of 48 adult Wistar rats were untreated for 7 minutes after induction of VF using an external transthoracic alternating current, and subsequent CPR was performed to observe the existence of autophagy after the return of spontaneous circulation (ROSC). Experiment 2: A total of 72 rats were pretreated with intracerebroventricular injection of physiologic saline (control group), the autophagy inducer (rapamycin group), or the autophagy inhibitor 3-methyladenine (3-methyladenine group) before ROSC to evaluate the contribution of autophagy to neuronal injury after ROSC.nnnRESULTSnThe activation of autophagy was attenuated 2 to 4 hours after ROSC, which was related to the activity decrease of 5-adenosine monophosphate-activated protein kinase after ROSC. Rapamycin treatment significantly increased the expressions of LC3-II and Beclin-1 after ROSC, attenuated the activation of caspase-3, promoted neuronal survival and decreased neuronal apoptosis, and improved the neurologic deficit score after CPR.nnnCONCLUSIONSnThe activation of autophagy after ROSC offered a remarkable tolerance to VF/CPR ischemic insult and improved the neurologic outcomes.

Assessing the early changes of cerebral glucose metabolism via dynamic 18FDG-PET/CT during cardiac arrest

To study the changes of cerebral glucose metabolism (CGM) during the phase of return of spontaneous circulation (ROSC) after cardiac arrest (CA), we used 18-fluorodeoxyglucose-positron emission tomography/computed tomography (18FDG-PET/CT) to measure the CGM changes in six beagle canine models. After the baseline 18FDG-PET/CT was recorded, ventricular fibrillation (VF) was induced for 6xa0min, followed by close-chest cardiopulmonary resuscitation (CPR) in conjunction with intravenous (IV) administration of epinephrine and external defibrillator shocks until ROSC was achieved, within 30xa0min. The 18FDG was recorded prior to intravenous administration at 0xa0h (baseline), and at 4, 24, and 48xa0h after CA with ROSC. We evaluated the expression of two key control factors in canine CGM, hexokinase I (HXK I) and HXK II, by immunohistochemistry at the four above mentioned time points. Electrically induced VF of 6xa0min duration was successfully induced in the dogs. Resuscitation was then performed to maintain blood pressure stability. Serial 18FDG-PET/CT scans found that the CGM decreased at 4xa0h after ROSC and remained lower than the baseline even at 48xa0h. The expression of HXK I and II levels were consistent with the changes in CGM. These data from our present work showed that 18FDG-PET/CT imaging can be used to detect decreased CGM during CA and was consistent with the results of CMRgl. Furthermore, there were also concomitant changes in the expression of HXK I and HXK II. The decrease in CGM may be an early sign of hyperacute global cerebral ischemia.