Reduction of myocardial reperfusion injury by aprotinin after regional ischemia and cardioplegic arrest

Ischemic Tolerance—A Way to Reduce the Extent of Ischemia–Reperfusion Damage

Individual tissues have significantly different resistance to ischemia–reperfusion damage. There is still no adequate treatment for the consequences of ischemia–reperfusion damage. By utilizing ischemic tolerance, it is possible to achieve a significant reduction in the extent of the cell damage due to ischemia–reperfusion injury. Since ischemia–reperfusion damage usually occurs unexpectedly, the use of preconditioning is extremely limited. In contrast, postconditioning has wider possibilities for use in practice. In both cases, the activation of ischemic tolerance can also be achieved by the application of sublethal stress on a remote organ. Despite very encouraging and successful results in animal experiments, the clinical results have been disappointing so far. To avoid the factors that prevent the activation of ischemic tolerance, the solution has been to use blood plasma containing tolerance effectors. This plasma is taken from healthy donors in which, after exposure to two sublethal stresses within 48 h, effectors of ischemic tolerance occur in the plasma. Application of this activated plasma to recipient animals after the end of lethal ischemia prevents cell death and significantly reduces the consequences of ischemia–reperfusion damage. Until there is a clear chemical identification of the end products of ischemic tolerance, the simplest way of enhancing ischemic tolerance will be the preparation of activated plasma from young healthy donors with the possibility of its immediate use in recipients during the initial treatment.

Relevance and Recommendations for the Application of Cardioplegic Solutions in Cardiopulmonary Bypass Surgery in Pigs

Cardioplegic solutions play a major role in cardiac surgery due to the fact that they create a silent operating field and protect the myocardium against ischemia and reperfusion injury. For studies on cardioplegic solutions, it is important to compare their effects and to have a valid platform for preclinical testing of new cardioplegic solutions and their additives. Due to the strong anatomical and physiological cardiovascular similarities between pigs and humans, porcine models are suitable for investigating the effects of cardioplegic solutions. This review provides an overview of the results of the application of cardioplegic solutions in adult or pediatric pig models over the past 25 years. The advantages, disadvantages, limitations, and refinement strategies of these models are discussed.

Microvascular dysfunction in patients with diabetes after cardioplegic arrest and cardiopulmonary bypass

PURPOSE OF REVIEW

The purpose of the current review is to describe the changes of microvascular function in patients with diabetes after cardioplegic arrest and cardiopulmonary bypass (CPB) and cardiac surgery.

RECENT FINDINGS

Cardiac surgery, especially that involving cardioplegia and CPB, is associated with significant changes in vascular reactivity of coronary/peripheral microcirculation, vascular permeability, gene/protein expression, and programmed cell death, as well as with increased morbidity and mortality after surgical procedures. In particular, these changes are more profound in patients with poorly controlled diabetes.

SUMMARY

Because alterations in vasomotor regulation are critical aspects of mortality and morbidity of cardioplegia/CPB, a better understanding of diabetic regulation of microvascular function may lead to improved postoperative outcomes of patients with diabetes after cardioplegia/CPB and cardiac surgery.

Immunosuppressive nano-therapeutic micelles downregulate endothelial cell inflammation and immunogenicity

In this study, we developed a stable, nontoxic novel micelle nanoparticle to attenuate responses of endothelial cell (EC) inflammation when subjected to oxidative stress, such as observed in organ transplantation. Targeted Rapamycin Micelles (TRaM) were synthesized using PEG-PE-amine and N-palmitoyl homocysteine (PHC) with further tailoring of the micelle using targeting peptides (cRGD) and labeling with far-red fluorescent dye for tracking during cellular uptake studies. Our results revealed that the TRaM was approximately 10 nm in diameter and underwent successful internalization in Human Umbilical Vein EC (HUVEC) lines. Uptake efficiency of TRaM nanoparticles was improved with the addition of a targeting moiety. In addition, our TRaM therapy was able to downregulate both mouse cardiac endothelial cell (MCEC) and HUVEC production and release of the pro-inflammatory cytokines, IL-6 and IL-8 in normal oxygen tension and hypoxic conditions. We were also able to demonstrate a dose-dependent uptake of TRaM therapy into biologic tissues ex vivo. Taken together, these data demonstrate the feasibility of targeted drug delivery in transplantation, which has the potential for conferring local immunosuppressive effects without systemic consequences while also dampening endothelial cell injury responses.

Aprotinin in cardiac surgery

Aprotinin is a naturally occurring serine protease inhibitor that is being used with increasing frequency in cardiac surgery and beyond to reduce blood loss and the need for perioperative blood transfusion. Through inhibition of serine proteases such as plasmin, aprotinin significantly reduces fibrinolysis, thereby aiding hemostasis during surgical procedures. In addition, aprotinin interacts with other factors in the coagulation and fibrinolytic cascade, creating a hemostatic balance, without increasing the risk of thrombosis. These proven benefits are supplemented by the anti-inflammatory properties of aprotinin, which may help curb some of the deleterious effects of cardiopulmonary bypass. This article will review the discovery of aprotinin, its mechanism of action, dosing and adverse effects, and highlight the major recent trials demonstrating its efficacy.

Effects of aprotinin on short-term and long-term outcomes after coronary artery bypass grafting surgery

BACKGROUND

Recent studies demonstrated that aprotinin use would increase the short-term and long-term mortality and complications after coronary artery bypass grafting (CABG). This study was to investigate effects of aprotinin during isolated primary CABG on short-term and long-term outcomes in Chinese patients.

METHODS

We studied 5,103 consecutive Chinese patients who underwent isolated primary CABG from 1999 to 2005. Of all the patients, 4,122 received aprotinin during operation (aprotinin group) and 981 received no aprotinin or other antifibrinolytic therapy (control group). Short-term and long-term mortality and major complications were analyzed with multivariate regression analysis. Propensity adjustment method was used to minimize the selection bias between the two groups, and propensity matching method was used to yield two well-matched groups for further comparison.

RESULTS

Blood loss after operation was significantly reduced in the aprotinin group compared with the control group (p < 0.001). Aprotinin use was neither associated with the perioperative mortality (p = 0.45, relative risk, 1.34) or major complications, nor was it associated with long-term mortality (p = 0.21, relative risk, 1.26) and major adverse cardiac and cerebrovascular events (p = 0.82, relative risk, 0.98). After propensity adjustment for the baseline characteristics, we obtained similar results. In addition, comparison between the two well-matched groups showed no significant difference either in baseline characteristics or in short-term and long-term outcomes.

CONCLUSIONS

Aprotinin use during isolated primary CABG reduced blood loss significantly, but was not associated with short-term or long-term mortality and complications. Aprotinin use in relatively low-risk CABG patients was effective and safe in a Chinese (Asian) population.

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.

Aprotinin attenuates genomic expression variability following cardiac surgery

BACKGROUND

Aprotinin was the subject of recent controversy regarding adverse clinical outcomes following cardiac surgery. We compared the role of Aprotinin and epsilon-aminocaproic acid on clinical outcomes and the attenuation of the postcardiopulmonary bypass (CPB) response at the genomic expression and cytokine (protein) level.

METHODS

Thirty-nine low-risk patients undergoing coronary revascularization (CABG) and/or valve procedures using cardiopulmonary CPB were enrolled into a prospective cohort study. Aprotinin or epsilon-aminocaproic acid was administered to patients. Gene expression was assessed from whole blood mRNA samples collected preoperatively (PRE) and 6 hours (6H) postoperatively. Validation of gene expression was performed with SYBR Green real-time polymerase chain reaction. Cytokine values were quantified from serum preoperatively and postoperatively at 6 H and 4 days and analyzed in a blinded fashion.

RESULTS

No difference was detected in baseline characteristics. Inflammatory markers measured did not reveal significant difference between patients receiving Aprotinin (APR) and those receiving epsilon-aminocaproic acid (Amicar). Intraoperative parameters and postoperative outcomes were not significantly different. Compared with PRE samples, 6H samples had 264 upregulated and 548 downregulated genes uniquely in the APR group compared to 4826 upregulated and 1114 downregulated genes uniquely in the Amicar group (p < 0.001). Compared to patients in the Amicar group, APR patients had significantly different gene expression pathways involving NF-kappabeta regulation, programmed cell death and cell-cell adhesion. None of the patients developed postoperative stroke, myocardial infarction, or systemic infections.

CONCLUSIONS

Aprotinin leads to significantly less genomic expression variability following CPB compared to Amicar and has a differential effect on specific genomic pathways.

Aprotinin exerts differential and dose-dependent effects on myocardial contractility, oxidative stress, and cytokine release after ischemia-reperfusion

BACKGROUND

Cardiac surgery can result in left ventricular ischemia and reperfusion (I/R), the release of cytokines such as tumor necrosis factor, and oxidative stress with release of myeloperoxidase. Although aprotinin has been used in cardiac surgery, the likely multiple effects of this serine protease inhibitor limit clinical utility. This study tested the hypothesis that different aprotinin doses cause divergent effects on left ventricular contractility, cytokine release, and oxidative stress in the context of I/R.

METHODS

Left ventricular I/R (30 minutes I, 60 minutes R) was induced in mice, and left ventricular contractility (maximal end-systolic elastance) determined. Mice were randomly allocated to 2 x 10(4) kallikrein inhibitory units (KIU)/kg aprotinin (n = 11), 4 x 10(4) KIU/kg aprotinin (n = 10), and vehicle (saline, n = 10). Based upon a fluorogenic assay, aprotinin doses of 2 and 4 x 10(4) KIU/kg resulted in plasma concentrations similar to those of the half and full Hammersmith doses, respectively.

RESULTS

After I/R, maximal end-systolic elastance fell by more than 40% from baseline (p < 0.05), and this effect was attenuated by 2 x 10(4) KIU/kg but not 4 x 10(4) KIU/kg aprotinin. Tumor necrosis factor increased by more than 60% from control (p < 0.05) with I/R, but was reduced with 4 x 10(4) KIU/kg aprotinin. Myeloperoxidase increased with I/R, and was reduced to the greatest degree by 2 x 10(4) KIU/kg aprotinin.

CONCLUSIONS

Aprotinin influences left ventricular contractility, cytokine release, and oxidative stress, which are dose dependent. These results provide mechanistic evidence that multiple pathways are differentially affected by aprotinin in a context relevant to cardiac surgery.

Anti-inflammatory actions of aprotinin provide dose-dependent cardioprotection from reperfusion injury

BACKGROUND AND PURPOSE

Myocardial injury following ischaemia and reperfusion has been attributed to activation and transmigration of polymorphonuclear leukocytes (PMNs) with release of mediators including oxygen-derived radicals and proteases causing damage.

EXPERIMENTAL APPROACH

We studied the serine protease inhibitor aprotinin in an in vivo rabbit model of 1 h of myocardial ischaemia followed by 3 h of reperfusion (MI+R). Aprotinin (10,000 Ukg(-1)) or its vehicle were injected 5 min prior to the start of reperfusion.

KEY RESULTS

Myocardial injury was significantly reduced with aprotinin treatment as indicated by a reduced necrotic area (11+/-2.7% necrosis as percentage of area at risk after aprotinin; 24+/-3.1% after vehicle; P<0.05) and plasma creatine kinase activity (12.2+/-1.5 and 17.3+/-2.3 IU g(-1) protein in aprotinin and vehicle groups, respectively, P<0.05). PMN infiltration (assessed by myeloperoxidase activity) was significantly decreased in aprotinin-treated animals compared to vehicle (P<0.01). Histological analysis also revealed a substantial increase in PMN infiltration following MI+R and this was significantly reduced by aprotinin therapy (44+/-15 vs 102+/-2 PMN mm2 in aprotinin vs vehicle-treated animals, P<0.05). In parallel in vitro experiments, aprotinin inhibited neutrophil-endothelium interaction by reducing PMN adhesion on isolated, activated aortic endothelium. Finally, immunohistochemical analysis illustrated aprotinin significantly reduced myocardial apoptosis following MI+R.

CONCLUSIONS AND IMPLICATIONS

Inhibition of serine proteases by aprotinin inhibits an inflammatory cascade initiated by MI+R. The cardioprotective effect appears to be at least partly due to reduced PMN adhesion and infiltration with subsequently reduced myocardial necrosis and apoptosis.

Aprotinin in Cardiac Surgery: A Review of Conventional and Novel Mechanisms of Action

Induction of the coagulation and inflammatory cascades can cause multiorgan dysfunction after cardiopulmonary bypass (CPB). In light of these observations, strategies that can stabilize the coagulation process as well as attenuate the inflammatory response during and after cardiac surgery are important. Aprotinin has effects on hemostasis. In addition, aprotinin may exert multiple biologically relevant effects in the context of cardiac surgery and CPB. For example, it decreases neutrophil and macrophage activation and chemotaxis, attenuates release and activation of proinflammatory cytokines, and reduces oxidative stress. Despite these perceived benefits, the routine use of aprotinin in cardiac surgery with CPB has been called into question. In this review, we examined this controversial drug by discussing the classical and novel pathways in which aprotinin may be operative in the context of cardiac surgery.

Effects of Aprotinin on Gene Expression and Protein Synthesis After Ischemia and Reperfusion in Rats

Background— Reperfusion injury of ischemic myocardium has been attributed to neutrophil infiltration, inflammatory activation and cardiac necrosis/apoptosis. Serine protease inhibition with aprotinin is cardioprotective, but the mechanism is unknown.

Methods and Results— We studied aprotinin in a rat model of myocardial ischemia for 20 minutes and reperfusion for 20 minutes, 8 hours or 24 hours. Aprotinin (20 000 IU/kg) given 5 minutes before reperfusion significantly reduced leukocyte accumulation ( P <0.01), myocardial injury (determined by CK depletion, P <0.01) and myocyte apoptosis ( P <0.05) compared with vehicle treated rats. Differential gene expression analysis showed myocardial ischemia plus reperfusion increased expression of proinflammatory genes like P-selectin, E-selectin, intercellular adhesion molecule, tumor necrosis factor-α, tumor necrosis factor-α receptor, interleukin-6, monocyte chemoattractant protein-1, p53, and Fas (CD59). Aprotinin before reperfusion suppressed expression of these inflammatory genes. Finally, differential protein expression analysis demonstrated increased intercellular adhesion molecule-1, tumor necrosis factor-α, and p53 after myocardial ischemia plus reperfusion, and this effect was diminished by aprotinin.

Conclusions— We demonstrated myocardial ischemia plus reperfusion induced leukocyte accumulation, inflammation, gene expression, protein expression and finally tissue injury and showed aprotinin limiting reperfusion injury through each of these stages, even after 24 hours of reperfusion. This effect seems partly attributable to suppression of proinflammatory genes and leukocyte accumulation. This work casts further light on the complex signaling of ischemia and reperfusion.

Effect of recombinant aprotinin on postoperative blood loss and coronary vascular function in a canine model of cardiopulmonary bypass

OBJECTIVE

Aprotinin is a widely used serine protease inhibitor during cardiopulmonary bypass to reduce blood loss and preserve platelet function. However, the bovine-derived aprotinin can induce hypersensitivity reaction with fatal complications. Furthermore, vascular effects of aprotinin are not completely elucidated. The current study is designed to investigate the effects of recently developed recombinant aprotinin on blood loss and coronary vascular function in a clinically relevant canine model of cardiopulmonary bypass without aortic cross-clamping and cardioplegia.

METHODS

Twenty-four dogs underwent cardiopulmonary bypass without aortic cross-clamping and cardioplegia. Dogs were divided into three groups in a blinded fashion: control animals (n=8) received placebo, aprotinin treatment groups received bovine (n=8) or recombinant aprotinin (n=8) according to the Hammersmith method. The doses of bovine and recombinant aprotinin were the same. Coagulation parameters and blood loss were measured regularly at different time points. Endothelium-dependent and -independent vasorelaxation were investigated in isolated left anterior descendent coronary arterial rings by using acetylcholine and bradykinin or sodium nitroprusside and adenosine, respectively.

RESULTS

Postoperative blood loss was significantly reduced in the aprotinin-treated groups in comparison to control and there was no significant difference between the two aprotinin-treated groups. Endothelium-dependent relaxation of coronary arteries to acetylcholine and bradykinin was unaffected in the aprotinin treatment groups. Both types of aprotinin significantly increased vasorelaxation to adenosine when compared with controls, but did not affect that to sodium nitroprusside.

CONCLUSIONS

The effectiveness of recombinant aprotinin on blood loss was equivalent to bovine-derived aprotinin. Neither types of aprotinin impaired endothelium-dependent relaxation in a canine model of cardiopulmonary bypass.

The effect of L-arginine and aprotinin on intestinal ischemia-reperfusion injury

BACKGROUND

Intestinal ischemia/reperfusion (I/R) results in local mucosal injury, systemic injuries, and organ dysfunction. These injuries are characterized by altered microvascular and epithelial permeability and villous damage. Activation of neutrophils, platelets, and endothelial factors are known to be involved in this process. Cytokines such as TNF-alpha, IL-1, IL-6, and oxygen-derived free radicals are believed to be important pathogenic mediators. Capillary no-reflow is also known to play a role in I/R. The aim of our study was to examine the role of L-arginine, a known nitric oxide (NO) donor, and aprotinin, a protease inhibitor with multiple effects, on intestinal I/R.

METHODS

Pigs weighing 20-25 kg were used. Ischemia was established by clamping the superior mesenteric artery (SMA) at its origin and was sustained for 2 hours. Duration of reperfusion was 2 hours. The animals were divided into four groups: group A, the control group, which was submitted to I/R injury only; group B, in which L-arginine was administered at a rate of 5 mg/kg/min during ischemia and continuing throughout reperfusion; group C, in which aprotinin was administered with an initial bolus dose of 20,000 U/kg during ischemia followed by a continuous dose at 50 U/hour throughout reperfusion; and group D in which both substances were administered. In all groups TNF-alpha, IL-1, and IL-6 levels were measured using ELISA at baseline, 2 hours of ischemia, and 1 hour and 2 hours of reperfusion. SMA blood flow was measured with a Doppler probe at baseline, 10 min, 1 hour, and 2 hours of reperfusion. Histological changes of the intestinal mucosa were examined and graded on a five-point scale in all groups.

RESULTS

In the control group, levels of TNF-alpha, IL-1, and IL-6 were significantly increased during reperfusion (p < 0.05) compared to baseline. Administration of L-arginine and aprotinin led to suppression of the release of TNF-alpha, IL-1, and IL-6 during reperfusion in a statistically significant manner (all p < 0.05). A synergistic or additive effect of L-arginine and aprotinin was not observed. SMA blood flow in the control group was decreased (p > 0.05) during reperfusion compared to baseline. In animals treated with L-arginine and aprotinin, SMA blood flow during reperfusion was significantly increased (p < 0.05) compared to the control group. Histologic examination of the intestinal mucosa was characterized by flattening of the villi and necrosis in the control group. In the treated animals, less severe histological changes were noted.

CONCLUSIONS

Administration of L: -arginine and aprotinin may lead to amelioration of intestinal I/R injury. We did not note a synergistic or additive effect of these two substances. These findings warrant further studies in clinical settings for future treatment efforts.

Anti-inflammatory Strategies and Hemostatic Agents: Old Drugs, New Ideas

Hemostatic abnormalities occur following injury associated with both cardiac and noncardiac surgery. These changes are part of inflammatory pathways with signaling mechanisms that link these diverse pathways. The inflammatory response to surgery is exacerbated by allogeneic blood transfusion by enhancing intrinsic inflammatory activity and directly increasing plasma levels of inflammatory mediators. Surgical patients can be preventively treated with pharmacologic agents to modulate inflammatory responses. Multiple studies have reported preventive pharmacologic therapies to reduce bleeding and the need for allogeneic transfusions in surgery. Strategies for cardiac surgical patients during cardiopulmonary bypass include administration of either lysine analogs, such as epsilon aminocaproic acid and tranexamic acid, or the serine protease inhibitor aprotinin.

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.

Aprotinin use in thoracic aortic surgery: Safety and outcomes

OBJECTIVES

Previous studies of aprotinin use in thoracic aortic surgery, limited in size and design, reported minimal information regarding outcomes other than blood loss and transfusion. The evaluation of impact of aprotinin on surgical outcomes in a large sample is needed.

METHODS

Patients at Yale New Haven Hospital undergoing thoracic aortic surgery (aneurysm repair, dissections, penetrating ulcers, intramural hematomas) between 1995 and 2003 were considered for inclusion. Each patient receiving aprotinin was matched to a control per preoperative profile (age, gender, urgency of surgery, dissection/location of aortic disease). Data (surgical specifics, demographic variables, comorbidities, disease location-related variables, preoperative medications, intraoperative medications, surgical/operative data) were abstracted from the records of successfully matched aprotinin-treated patients and controls (n = 168). Comparison and determination of success of matching were performed using bivariate analyses. Outcome variables were compared using statistical tests for paired data. Supplementary unpaired and regression analyses were also performed.

RESULTS

Baseline demographics of groups were similar, although controls had reduced history of aortic disease, but greater intraoperative use of lysine analogs (P < .05). Aprotinin significantly reduced platelet transfusion (P < .05). Paired bivariate analyses showed a tendency toward reduced ventilation time, pulmonary complications, and permanent arrhythmias (P < .05) associated with aprotinin. Supplementary analyses were supportive only for pulmonary complications and permanent arrhythmias.

CONCLUSIONS

The current evaluation substantiates previous reports that aprotinin may be safe to use and likely to improve some outcomes of thoracic aortic surgery. However, further studies for rare safety and efficacy end points are warranted.

Trimetazidine reduces oxidative stress in cardiac surgery

BACKGROUND

Trimetazidine is an anti-ischemic agent that is used to treat angina and it has cardioprotective effects without inducing any significant hemodynamic changes. It inhibits the long-chain mitochondrial 3-ketoacyl coenzyme A thiolase enzyme in the myocyte and can improve cardiac mitochondrial metabolism, as well as scavenge free radicals. The aim of this double-blind prospective randomized study was to investigate the effect of preoperative use of trimetazidine on the reduction of oxidative stress during coronary artery bypass grafting (CABG) under cardiopulmonary bypass (CPB).

METHODS AND RESULTS

The study group (group T) and the control group (group C) each comprised 12 patients. Pretreatment began 2 weeks before CABG with trimetazidine (60 mg/day po); the control group did not receive any medication. Serial blood samples were collected before and after CPB for measurement of the serum concentrations of these major endogenous antioxidant enzyme systems, which are markers for oxidative degradation of the cellular membranes; postoperative levels were significantly different between the groups (p<0.05). There were no significant difference in hemodynamic values.

CONCLUSION

The findings suggest that pretreatment with trimetazidine alleviates malondialdehyde production and preserves endogenous antioxidant capacity during CABG with CPB and cardioplegic arrest.

Aprotinin preserves cellular junctions and reduces myocardial edema after regional ischemia and cardioplegic arrest

BACKGROUND

Cardiac surgery with cardiopulmonary bypass (CPB) and cardioplegic arrest has been associated with myocardial edema attributable to vascular permeability, which is regulated in part by thrombin-induced alterations in cellular junctions. Aprotinin has been demonstrated to prevent activation of the thrombin protease-activated receptor, and we hypothesized that aprotinin preserves myocardial cellular junctions and prevents myocardial edema in a porcine model of regional ischemia and cardioplegic arrest.

METHODS AND RESULTS

Fourteen pigs were subjected to 30 minutes of regional ischemia, followed by 60 minutes of CPB, with 45 minutes of crystalloid cardioplegia, then 90 minutes of post-CPB reperfusion. The treatment group (n=7) was administered aprotinin (40,000 kallikrein inhibitor units [KIU]/kg loading dose, 40,000 KIU/kg pump prime, and 10,000 KIU/kg per hour continuous infusion). Control animals (n=7) received normal saline. Myocardial vascular endothelial (VE)-cadherin, beta-catenin and gamma-catenin, and associated mitogen-activated protein kinase (MAPK) pathways were assessed by immunoblot and immunoprecipitation. Histologic analysis of the cellular junctions was done by immunofluorescence. Myocardial tissue water content was measured. VE-cadherin, beta-catenin, and gamma-catenin levels were significantly greater in the aprotinin group (all P<0.05). Immunfluorescence confirmed that aprotinin prevented loss of coronary endothelial adherens junction continuity. Aprotinin reduced tyrosine phosphorylation in myocardial tissue sections. Phospho-p38 activity was approximately 30% lower in the aprotinin group (P=0.007). The aprotinin group demonstrated decreased myocardial tissue water content (81.2+/-0.5% versus 83.5+/-0.3%; P=0.01) and reduced intravenous fluid requirements (2.9+/-0.2 L versus 4.0+/-0.4 L; P=0.03).

CONCLUSIONS

Aprotinin preserves adherens junctions after regional ischemia and cardioplegic arrest through a mechanism potentially involving the p38 MAPK pathway, resulting in preservation of the VE barrier and reduced myocardial tissue edema.

The effect of aprotinin in a model of uncontrolled hemorrhagic shock

BACKGROUND

Aprotinin has been shown to promote clot formation through its antifibrinolytic activity, by inhibiting the plasmin-induced complement activation and by protecting the platelets adhesive surface receptors. It has been successfully used in cardiac and liver transplantation surgery.

OBJECTIVE

To evaluate the effect of aprotinin in a model of uncontrolled intra-abdominal bleeding as a basis for its potential use in trauma patients.

METHODS

Twenty rats were randomly divided into 2 groups. All animals were operated on and bleeding was induced by transecting 1 lobe of the liver. In the treatment group a single dose of 30,000 U/kg of aprotinin was administered 5 minutes after the injury. The animals were monitored for hemodynamic parameters, blood loss volume, and mortality rates.

RESULTS

At 120 minutes from trauma induction a significant difference in mean blood pressure was observed: 67+/-22 mm Hg in the treatment group versus 53+/-28 mm Hg in the control group (P=.04). This difference remained consistent until the end of the experiment. Treatment with aprotinin also resulted in a tendency to an increased survival rate (P=.05) and increased mean survival time: 175+/-46 minutes as compared to 123+/-48 minutes in the controls (P=.027).

CONCLUSIONS

Early administration of aprotinin resulted in temporary hemodynamic stabilization and prolonged survival in a model of uncontrolled bleeding. Further studies are needed to establish the possible use of aprotinin in the treatment of trauma patients.

Gene expression analysis of ischemic and nonischemic cardiomyopathy: shared and distinct genes in the development of heart failure

Cardiomyopathy can be initiated by many factors, but the pathways from unique inciting mechanisms to the common end point of ventricular dilation and reduced cardiac output are unclear. We previously described a microarray-based prediction algorithm differentiating nonischemic (NICM) from ischemic cardiomyopathy (ICM) using nearest shrunken centroids. Accordingly, we tested the hypothesis that NICM and ICM would have both shared and distinct differentially expressed genes relative to normal hearts and compared gene expression of 21 NICM and 10 ICM samples with that of 6 nonfailing (NF) hearts using Affymetrix U133A GeneChips and significance analysis of microarrays. Compared with NF, 257 genes were differentially expressed in NICM and 72 genes in ICM. Only 41 genes were shared between the two comparisons, mainly involved in cell growth and signal transduction. Those uniquely expressed in NICM were frequently involved in metabolism, and those in ICM more often had catalytic activity. Novel genes included angiotensin-converting enzyme-2 (ACE2), which was upregulated in NICM but not ICM, suggesting that ACE2 may offer differential therapeutic efficacy in NICM and ICM. In addition, a tumor necrosis factor receptor was downregulated in both NICM and ICM, demonstrating the different signaling pathways involved in heart failure pathophysiology. These results offer novel insight into unique disease-specific gene expression that exists between end-stage cardiomyopathy of different etiologies. This analysis demonstrates that transcriptome analysis offers insight into pathogenesis-based therapies in heart failure management and complements studies using expression-based profiling to diagnose heart failure of different etiologies.