Cardioprotective effect of aprotinin on myocardial ischemia/reperfusion injury during cardiopulmonary bypass

Pharmacological Cardioprotection against Ischemia Reperfusion Injury-The Search for a Clinical Effective Therapy

Pharmacological conditioning aims to protect the heart from myocardial ischemia-reperfusion injury (IRI). Despite extensive research in this area, today, a significant gap remains between experimental findings and clinical practice. This review provides an update on recent developments in pharmacological conditioning in the experimental setting and summarizes the clinical evidence of these cardioprotective strategies in the perioperative setting. We start describing the crucial cellular processes during ischemia and reperfusion that drive acute IRI through changes in critical compounds (∆G_ATP, Na⁺, Ca²⁺, pH, glycogen, succinate, glucose-6-phosphate, mitoHKII, acylcarnitines, BH₄, and NAD⁺). These compounds all precipitate common end-effector mechanisms of IRI, such as reactive oxygen species (ROS) generation, Ca²⁺ overload, and mitochondrial permeability transition pore opening (mPTP). We further discuss novel promising interventions targeting these processes, with emphasis on cardiomyocytes and the endothelium. The limited translatability from basic research to clinical practice is likely due to the lack of comorbidities, comedications, and peri-operative treatments in preclinical animal models, employing only monotherapy/monointervention, and the use of no-flow (always in preclinical models) versus low-flow ischemia (often in humans). Future research should focus on improved matching between preclinical models and clinical reality, and on aligning multitarget therapy with optimized dosing and timing towards the human condition.

Long noncoding RNA-MEG3 contributes to myocardial ischemia-reperfusion injury through suppression of miR-7-5p expression

Long noncoding RNA (lncRNA) maternally expressed gene 3 (MEG3) plays an important role in protection of ischemia–reperfusion (I/R) injury in brain and liver. However, role of MEG3 in myocardial I/R injury remains unclear. Here, the role of MEG3 in protection of myocardial I/R injury and its association with microRNA-7-5p (miR-7-5p) was investigated using rat cardiac I/R model and myocardial I/R cell model. Our results showed that MEG3 was significantly up-regulated and miR-7-5p was significantly down-regulated after I/R. Following I/R, the levels of intact PARP and intact caspase-3 were reduced, while the cleaved fragments of PARP and caspase-3 were increased. TUNEL assay showed an increase in cardiomyocyte apoptosis after I/R. The levels of I/R-induced creatine kinase (CK) and lactate dehydrogenase (LDH) were inhibited by knockdown of MEG3 (siMEG3). SiMEG3 increased cell proliferation and inhibited cell apoptosis after I/R. In contrast, overexpression of MEG3 increased the I/R-induced CK and LDH activities and cell apoptosis and decreased cell proliferation. The dual-luciferase reporter system showed a direct binding of MEG3 to miR-7-5p. The level of miR-7-5p was negatively associated with the change in levels of MEG3 in H9c2 cells. The levels of intact RARP1 and caspase-3 were significantly increased by knockdown of MEG3. Co-transfection of miR-7-5p inhibitor with siMEG3 activates CK and LDH, significantly decreased cell proliferation, increased cell apoptosis, and decreased intact poly(ADP-ribose) polymerase 1 (PARP1) and caspase-3. In summary, down-regulation of MEG3 protects myocardial cells against I/R-induced apoptosis through miR-7-5p/PARP1 pathway, which might provide a new therapeutic target for treatment of myocardial I/R injury.

Ischemic Postconditioning (IPostC) Protects Fibrotic and Cirrhotic Rat Livers after Warm Ischemia

BACKGROUND

Decreased organ function following liver resection is a major clinical issue. The practical method of ischemic postconditioning (IPostC) has been studied in heart diseases, but no data exist regarding fibrotic livers.

AIMS

We aimed to determine whether IPostC could protect healthy, fibrotic, and cirrhotic livers from ischemia reperfusion injury (IRI).

METHODS

Fibrosis was induced in male SD rats using bile duct ligation (BDL, 4 weeks), and cirrhosis was induced using thioacetamide (TAA, 18 weeks). Fibrosis and cirrhosis were histologically confirmed using HE and EvG staining. For healthy, fibrotic, and cirrhotic livers, isolated liver perfusion with 90 min of warm ischemia was performed in three groups (each with n=8): control, IPostC 8x20 sec, and IPostC 4x60 sec. additionally, healthy livers were investigated during a follow-up study. Lactate dehydrogenase (LDH) and thromboxane B₂ (TXB₂) in the perfusate, as well as bile flow (healthy/TAA) and portal perfusion pressure, were measured.

RESULTS

LDH and TXB₂ were reduced, and bile flow was increased by IPostC, mainly in total and in the late phase of reperfusion. The follow-up study showed that the perfusate derived from a postconditioned group had much less damaging potential than perfusate derived from the nonpostconditioned group.

CONCLUSION

IPostC following warm ischemia protects healthy, fibrotic, and cirrhotic livers against IRI. Reduced efflux of TXB₂ is one possible mechanism for this effect of IPostC and increases sinusoidal microcirculation. These findings may help to improve organ function and recovery of patients after liver resection.

Ventricular assist devices and increased blood product utilization for cardiac transplantation

BACKGROUND AND AIM OF STUDY

The purpose of this study was to examine whether blood product utilization, one-year cell-mediated rejection rates, and mid-term survival significantly differ for ventricular assist device (VAD patients compared to non-VAD (NVAD) patients following cardiac transplantation.

METHODS

From July 2004 to August 2011, 79 patients underwent cardiac transplantation at a single institution. Following exclusion of patients bridged to transplantation with VADs other than the HeartMate II® LVAD (n = 10), patients were stratified by VAD presence at transplantation: VAD patients (n = 35, age: 54.0 [48.0-59.0] years) vs. NVAD patients (n = 34, age: 52.5 [42.8-59.3] years). The primary outcomes of interest were blood product transfusion requirements, one-year cell-mediated rejection rates, and mid-term survival post-transplantation.

RESULTS

Preoperative patient characteristics were similar for VAD and NVAD patients. NVAD patients presented with higher median preoperative creatinine levels compared to VAD patients (1.3 [1.1-1.6] vs. 1.1 [0.9-1.4], p = 0.004). VAD patients accrued higher intraoperative transfusion of all blood products (all p ≤ 0.001) compared to NVAD patients. The incidence of clinically significant cell-mediated rejection within the first posttransplant year was higher in VAD compared to NVAD patients (66.7% vs. 33.3%, p = 0.02). During a median follow-up period of 3.2 (2.0, 6.3) years, VAD patients demonstrated an increased postoperative mortality that did not reach statistical significance (20.0% vs. 8.8%, p = 0.20).

CONCLUSIONS

During the initial era as a bridge to transplantation, the HeartMate II® LVAD significantly increased blood product utilization and one-year cell-mediated rejection rates for cardiac transplantation. Further study is warranted to optimize anticoagulation strategies and to define causal relationships between these factors for the current era of cardiac transplantation.

Perioperative metabolic changes in patients undergoing cardiac surgery

Perioperative metabolic changes in cardiac surgical patients are not only induced by tissue injury and extracorporeal circulation per se: the systemic inflammatory response to surgical trauma and extracorporeal circulation, perioperative hypothermia, cardiovascular and neuroendocrine responses, and drugs and blood products used to maintain cardiovascular function and anesthesia contribute to varying degrees. The pathophysiologic changes include increased oxygen consumption and energy expenditure; increased secretion of adrenocorticotrophic hormone, cortisol, epinephrine, norepinephrine, insulin, and growth hormone; and decreased total tri-iodothyronine levels. Easily measurable metabolic consequences of these changes include hyperglycemia, hyperlactatemia, increased aspartate, glutamate and free fatty acid concentrations, hypokalemia, increased production of inflammatory cytokines, and increased consumption of complement and adhesion molecules. Nutritional risk before elective cardiac surgery-defined as preoperative unintended pathologic weight loss/low amount of food intake in the preceding week or low body mass index-is related to adverse postoperative outcome. Improvements in surgical techniques, anesthesia, and perioperative management have been designed to minimize the stressful stimulus to catabolism, thereby slowing the wasting process to the point where much less nutrition is required to meet metabolic requirements. Early nutrition in cardiac surgery is safe and well tolerated.

Serine protease inhibitor aprotinin ameliorates renal injury in a rat model of ischemia-perfusion injury

BACKGROUND

Renal ischemia-reperfusion (I/R) injury may occur after renal transplantation, thoracoabdominal aortic surgery, and renal artery interventions.

OBJECTIVE

To investigate the therapeutic effects of aprotinin on tissue protection against I/R injury in a rat model. N-acetylcysteine (NAC), a potent antioxidant, was also tested to assess the experimental model.

MATERIALS AND METHODS

Twenty-four rats were categorized into 3 groups of 8 rats each: those receiving isotonic sodium chloride solution (control group); NAC, 150 mg/kg; and aprotinin, 40,000 KIU/kg. The animals underwent unilateral nephrectomy after 60 minutes of warm ischemia and 60 minutes of reperfusion of the kidney. Malondialdehyde, a lipid peroxidation marker, and antioxidant glutathione levels were measured in the kidney parenchyma. Tissue samples were obtained for histologic analysis.

RESULTS

Compared with the control group, the NAC group demonstrated significantly low levels of malondialdehyde (P = .04) and high levels of glutathione (P = .01). At histopathologic analysis, less acute tubular necrosis (ATN) and cellular swelling was noted in the NAC group (P = .002 and P = .005, respectively). In the aprotinin group, histopathologic analysis revealed less tissue damage in terms of ATN (P < .001, cellular swelling (P < .001), and vacuolysis (P = .002). Compared with the NAC group, ATN (P = .01), vacuolysis (P = .04), and congestion (P = .05) were significantly less in the aprotinin group.

CONCLUSIONS

Our results suggest that administration of aprotinin attenuates renal I/R injury. This observation has potential application for kidney preservation for transplantation, for aortic surgery, and for renal artery interventions by protecting cells from free radical damage.

Release of cardiac biochemical and inflammatory markers in patients on cardiopulmonary bypass undergoing coronary artery bypass grafting

BACKGROUND

Determination of cardiac markers can assess cardiac injury induced by cardiopulmonary bypass (CPB) during coronary artery bypass grafting (CABG). However, the markers and their release pattern are not well defined. This study was aimed at assessing the release and timing of cardiac biochemical and inflammatory markers in patients undergoing elective CABG with CPB.

METHODS

Forty patients undergoing elective CABG were included in this study. Blood samples were collected for biochemical measurements at the following time points: immediately prior to the induction of anesthesia, one, six, 12, and 24 hours after initiation of CPB.

RESULTS

Increased release of cardiac troponin I was observed one hour after initiation of CPB (p < 0.05) and reached the maximum at 12 hours after CPB (p < 0.01). Serum CK-MB enzyme activity and CK-MB mass both were highly elevated starting at one hour after initiation of CPB, peaked at six hours, and remained elevated until 24 hours after CPB. Both lactate and lactate dehydrogenase were highly elevated six hours after CPB and peaked at 12 hours after CPB (p < 0.01). Serum levels of interleukin-6 and tumor necrosis factor-alpha increased significantly one hour after initiation of CPB and peaked at six hours (p < 0.01), while serum high sensitivity C-reactive protein levels started to elevate 12 hours after CPB (p < 0.01).

CONCLUSION

Monitoring of these markers could help to determine implementation of protective interventions during CABG with CPB to prevent myocardial deterioration and to predict the risk and prognosis.

Is There Still a Role for Aprotinin in Cardiac Surgery?

Cardiac surgery is associated with a systemic inflammatory response and systemic coagulopathy, which can result in significant organ dysfunction and bleeding. Aprotinin, a serine protease inhibitor, can limit systemic inflammation, and has been associated with myocardial, pulmonary and cerebral protection in addition to its proven haemostatic efficacy. Data are currently conflicting regarding the haemostatic efficacy of aprotinin relative to alternative agents including tranexamic acid. Recent studies have demonstrated aprotinin usage is associated with increased rates of thrombotic and renal complications, but these findings are at odds with the majority of studies relating to aprotinin safety to date. The lack of adequately powered, randomised studies evaluating aprotinin and alternative agents limits drawing conclusions about the complete use or disuse of aprotinin presently and requires individualised patient selection based on bleeding risk and co-morbidities for its usage.