Effect of aprotinin on endothelial cell activation

Aprotinin does not Impair Vascular Function in Patients Undergoing Coronary Artery Bypass Graft Surgery

Bleeding is a major complication in coronary artery bypass graft surgery. Antifibrinolytic agents like serine protease inhibitor aprotinin can decrease postoperative bleeding and complications of cardiac surgery. However, the effects of aprotinin on vascular function are not completely elucidated. We compared the ex vivo vascular function of left internal mammary arteries from patients undergoing coronary artery bypass graft surgery with and without intraoperative application of aprotinin using a Mulvany Myograph. Human internal mammary arteries were treated with aprotinin ex vivo and tested for changes in vascular function. We analyzed the impact of aprotinin on vascular function in rat aortic rings. Finally, impact of aprotinin on expression and activity of endothelial nitric oxide synthase was tested in human endothelial cells. Intraoperative application of aprotinin did not impair ex vivo vascular function of internal mammary arteries of patients undergoing coronary artery bypass graft surgery. Endothelium-dependent and -independent relaxations were not different in patients with or without aprotinin after nitric oxide synthase blockade. A maximum vasorelaxation of 94.5%±11.4vs. 96.1%±5.5% indicated a similar vascular smooth muscle function in both patient groups (n=13 each). Long-term application of aprotinin under physiological condition preserved vascular function of the rat aorta. In vitro application of increasing concentrations of aprotinin on human endothelial cells resulted in a similar expression and activity of endothelial nitric oxide synthase. In conclusion, intraoperative and ex vivo application of aprotinin does not impair the endothelial function in human internal mammary arteries and experimental models.

Preservation of renal endothelial integrity and reduction of renal edema by aprotinin does not preserve renal perfusion and function following experimental cardiopulmonary bypass

BACKGROUND

Acute kidney injury is a severe complication following cardiopulmonary bypass (CPB) and is associated with capillary leakage and microcirculatory perfusion disturbances. CPB-induced thrombin release results in capillary hyperpermeability via activation of protease-activated receptor 1 (PAR1). We investigated whether aprotinin, which is thought to prevent thrombin from activating PAR1, preserves renal endothelial structure, reduces renal edema and preserves renal perfusion and reduces renal injury following CPB.

METHODS

Rats were subjected to CPB after treatment with 33.000 KIU/kg aprotinin (n = 15) or PBS (n = 15) as control. A secondary dose of 33.000 KIU/kg aprotinin was given 60 min after initiation of CPB. Cremaster and renal microcirculatory perfusion were assessed using intravital microscopy and contrast echography before CPB and 10 and 60 min after weaning from CPB. Renal edema was determined by wet/dry weight ratio and renal endothelial structure by electron microscopy. Renal PAR1 gene and protein expression and markers of renal injury were determined.

RESULTS

CPB reduced cremaster microcirculatory perfusion by 2.5-fold (15 (10-16) to 6 (2-10) perfused microvessels, p < 0.0001) and renal perfusion by 1.6-fold (202 (67-599) to 129 (31-292) au/sec, p = 0.03) in control animals. Both did not restore 60 min post-CPB. This was paralleled by increased plasma creatinine (p < 0.01), neutrophil gelatinase-associated lipocalin (NGAL; p = 0.003) and kidney injury molecule-1 (KIM-1; p < 0.01). Aprotinin treatment preserved cremaster microcirculatory perfusion following CPB (12 (7-15) vs. 6 (2-10) perfused microvessels, p = 0.002), but not renal perfusion (96 (35-313) vs. 129 (31-292) au/s, p > 0.9) compared to untreated rats. Aprotinin treatment reduced endothelial gap formation (0.5 ± 0.5 vs. 3.1 ± 1.4 gaps, p < 0.0001), kidney wet/dry weight ratio (4.6 ± 0.2 vs. 4.4 ± 0.2, p = 0.046), and fluid requirements (3.9 ± 3.3 vs. 7.5 ± 3.0 ml, p = 0.006) compared to untreated rats. In addition, aprotinin treatment reduced tubulointerstitial neutrophil influx by 1.7-fold compared to untreated rats (30.7 ± 22.1 vs. 53.2 ± 17.2 neutrophil influx/section, p = 0.009). No differences were observed in renal PAR1 expression and plasma creatinine, NGAL or KIM-1 between groups.

CONCLUSIONS

Aprotinin did not improve renal perfusion nor reduce renal injury during the first hour following experimental CPB despite preservation of renal endothelial integrity and reduction of renal edema.

Synergistic Effect of β-alanine and Aprotinin on Mesenteric Ischemia

BACKGROUND

Acute mesenteric ischemia arises through sudden interruption of mesenteric blood flow, mostly due to an occlusion of the superior mesenteric artery and is associated with a high mortality of approximately 50% to 90%. In previous studies, the single application of β-alanine or aprotinin caused an ameliorated intestinal damage but without any systemic effects.

METHODS

To analyze the combined effect of β-alanine and aprotinin on acute ischemia and reperfusion of the small intestine, a model with anesthetized rats was used. Ischemia and reperfusion were initiated by occluding and reopening the superior mesenteric artery. After 120 min of ischemia and 180 min of reperfusion, the intestine was analyzed for tissue damage, the activity of the saccharase, and accumulation of granulocytes. In addition, systemic and metabolic as well as inflammatory parameters were measured in blood at certain points in time.

RESULTS

The combination of β-alanine and aprotinin resulted in a clearly stabilized mean arterial blood pressure and blood glucose level during the reperfusion period. Furthermore, the combined administration resulted in significantly reduced tissue damage parameters, cytokine and cell-free hemoglobin concentrations in blood plasma. In addition, the damage to the small intestine was significantly attenuated, so that the animals ultimately survived the entire test period because of the administration of both substances.

CONCLUSIONS

Overall, the simultaneous application of both substances leads to a synergistic protection without the occurrence of undesirable side effects. The combined usage of β-alanine and aprotinin can be seen as a promising approach to inhibit the onset of acute mesenteric ischemia.

Pulmonary vascular resistance index during coronary artery bypass surgery with aprotinin

Low pulmonary vascular resistance index (PVRI) reflects favorable redundant pulmonary circulation following coronary artery bypass grafting with cardiopulmonary bypass surgery (CPB). This randomized study investigated whether aprotinin given in different modalities impacts PVRI after coronary artery bypass grafting. A total of 40 patients undergoing coronary artery bypass grafting were randomized to four groups according to aprotinin dose: (1) high dose, (2) early low dose, (3) late low dose, and (4) without aprotinin. Oxygenation index, pulmonary shunt, alveolar-arterial oxygen gradient and PVRI were determined. PVRI was calculated as the transpulmonary pressure gradient divided by cardiac index multiplied by 80. The results showed that PVRI remained relative low in all patients provided aprotinin regardless of treatment dosage; PVRI increased at 4 h after restarting ventilation after CPB in patients without aprotinin as compared with aprotinin (266 ± 137, 266 ± 115, 244 ± 86 vs. 386 ± 121, dynes-s-cm^-5, respectively, p = .047). Elevated postoperative PVRI was predictive for patients without aprotinin (AUC 0.668; SE 0.40; p < .0001; CI 0.590-0.746). There were no statistical differences in oxygenation index, pulmonary shunt or alveolar-arterial oxygen gradient between the groups. In conclusion, aprotinin maintains a low PVRI in elective patients with healthy lungs during CPB. We suggest that aprotinin maintains pulmonary arterial endothelial integrity.

The serine protease inhibitor camostat inhibits influenza virus replication and cytokine production in primary cultures of human tracheal epithelial cells

BACKGROUND

Serine proteases act through the proteolytic cleavage of the hemagglutinin (HA) of influenza viruses for the entry of influenza virus into cells, resulting in infection. However, the inhibitory effects of serine protease inhibitors on influenza virus infection of human airway epithelial cells, and on their production of inflammatory cytokines are unclear.

METHODS

Primary cultures of human tracheal epithelial cells were treated with four types of serine protease inhibitors, including camostat, and infected with A/Sendai-H/108/2009/(H1N1) pdm09 or A/New York/55/2004(H3N2).

RESULTS

Camostat reduced the amounts of influenza viruses in the supernatants and viral RNA in the cells. It reduced the cleavage of an influenza virus precursor protein, HA0, into the subunit HA1. Camostat also reduced the concentrations of the cytokines interleukin (IL)-6 and tumor necrosis factor (TNF)-α in the supernatants. Gabexate and aprotinin reduced the viral titers and RNA levels in the cells, and aprotinin reduced the concentrations of TNF-α in the supernatants. The proteases transmembrane protease serine S1 member (TMPRSS) 2 and HAT (human trypsin-like protease: TMPRSS11D), which are known to cleave HA0 and to activate the virus, were detected at the cell membrane and in the cytoplasm. mRNA encoding TMPRSS2, TMPRSS4 and TMPRSS11D was detectable in the cells, and the expression levels were not affected by camostat.

CONCLUSIONS

These findings suggest that human airway epithelial cells express these serine proteases and that serine protease inhibitors, especially camostat, may reduce influenza viral replication and the resultant production of inflammatory cytokines possibly through inhibition of activities of these proteases.

Proangiogenic microtemplated fibrin scaffolds containing aprotinin promote improved wound healing responses

Survival of tissue engineered constructs after implantation depends heavily on induction of a vascular response in host tissue, promoting a quick anastomosis of the cellular graft. Additionally, implanted constructs typically induce fibrous capsule formation, effectively preventing graft integration with host tissue. Previously we described the development of a high density microtemplated fibrin scaffold for cardiac tissue engineering applications with tunable degradation and mechanical properties which promoted seeded cell survival and organization in vitro (Thomson et al., Tissue Eng Part A, 2013). Scaffold degradation in vitro was controllable by addition of the serine protease inhibitor aprotinin and/or the fibrin cross-linker Factor XIII (FXIII). The goal of this study was to assess host tissue responses to these fibrin scaffold formulations by determining effects on scaffold degradation, angiogenic responses, and fibrous capsule formation in a subcutaneous implant model. Aprotinin significantly decreased scaffold degradation over 2 weeks of implantation. A significant increase in capillary infiltration of aprotinin implants was found after 1 and 2 weeks, with a significantly greater amount of capillaries reaching the interior of aprotinin scaffolds. Interestingly, after 2 weeks the aprotinin scaffolds had a significantly thinner, yet apparently more cellular fibrous capsule than unmodified scaffolds. These results indicate aprotinin not only inhibits fibrin scaffold degradation, but also induces significant responses in the host tissue. These included an angiogenic response resulting in increased vascularization of the scaffold material over a relatively short period of time. In addition, aprotinin release from scaffolds may reduce fibrous capsule formation, which could help promote improved integration of cell-seeded scaffolds with host tissue.

DEHP and its active metabolites: leaching from different tubing types, impact on proinflammatory cytokines and adhesion molecule expression. Is there a subsumable context?

Introduction: Di(2-ethylhexyl)phthalate (DEHP) is suspected to be toxic for several reasons. During contact with a lipophilic medium, DEHP leaks from polyvinylchloride (PVC), but its influence on inflammatory reactions remains unknown. We examined specific DEHP leaching out of different tubing types, the possibly modulated liberation of proinflammatory cytokines and the induction of adhesion molecule expression in primary endothelial cells.

Materials and Methods: Blood samples were circulated in traditional PVC, nodioctyl phthalate (DOP) PVC and heparin-coated PVC tubing within a Chandler loop model. The blood was tested for the concentration of DEHP and its active metabolites as well as the liberation of the proinflammatory cytokines TNFα and IL1ß. Furthermore, we exposed human endothelial cells to circulated blood and analysed them for the expression of the adhesion molecules ICAM-1, VCAM-1 and E-selectin.

Results: In contrast to the other tubing, PVC tubing showed significantly elevated DEHP levels, but no alteration was observed concerning a potential up-regulation of the cytokines or activation of the endothelial adhesion molecule receptors.

Conclusions: Our data conclude that there is no correlation between DEHP leaching and the inflammatory response after ECC support, but this study showed that even DEHP-free material is leaching DEHP and its toxic metabolites.

Aprotinin and similar protease inhibitors as drugs against influenza

Efforts to develop new antiviral chemotherapeutic approaches are focusing on compounds that target either influenza virus replication itself or host factor(s) that are critical to influenza replication. Host protease mediated influenza hemagglutinin (HA) cleavage is critical for activation of virus infectivity and as such is a chemotherapeutic target. Influenza pathogenesis involves a "vicious cycle" in which host proteases activate progeny virus which in turn amplifies replication and stimulates further protease activities which may be detrimental to the infected host. Aprotinin, a 58 amino acid polypeptide purified from bovine lung that is one of a family of host-targeted antivirals that inhibit serine proteases responsible for influenza virus activation. This drug and similar agents, such as leupeptin and camostat, suppress virus HA cleavage and limit reproduction of human and avian influenza viruses with a single arginine in the HA cleavage site. Site-directed structural modifications of aprotinin are possible to increase its intracellular targeting of cleavage of highly virulent H5 and H7 hemagglutinins possessing multi-arginine/lysine cleavage site. An additional mechanism of action for serine protease inhibitors is to target a number of host mediators of inflammation and down regulate their levels in virus-infected hosts. Aprotinin is a generic drug approved for intravenous use in humans to treat pancreatitis and limit post-operative bleeding. As an antiinfluenzal compound, aprotinin might be delivered by two routes: (i) a small-particle aerosol has been approved in Russia for local respiratory application in mild-to-moderate influenza and (ii) a proposed intravenous administration for severe influenza to provide both an antiviral effect and a decrease in systemic pathology and inflammation.

Treatment of the brain-dead lung donor with aprotinin and nitric oxide

BACKGROUND

It has been previously shown that donor treatment with aprotinin or inhaled nitric oxide reduces reperfusion injury after lung transplantation in animals. These studies used living donors with normal lungs. However, the main source of lungs for transplantation is brain-dead donors. Brain death causes systemic inflammatory response and lung injury, rendering the organ susceptible to reperfusion injury after transplantation. We hypothesized that treatment with aprotinin or inhaled nitric oxide after brain death would improve the donor inflammatory response and reduce lung reperfusion injury after transplantation.

METHODS

Brain death was induced in 24 rats by intracranial balloon inflation. Subsequently, the animals received intravenous aprotinin (n = 8), inhaled nitric oxide (n = 7), or no treatment (n = 9) for 5 hours. The lungs were retrieved and reperfused for 2 hours using recipient rats.

RESULTS

After brain death, oxygenation deteriorated earlier and significantly more in rats that received treatment, especially with nitric oxide. Treatment did not reduce the donor systemic inflammatory response as assessed by serum levels of proinflammatory cytokines. Oxygenation, airway pressure, pulmonary vascular resistance, lung water index and bronchoalveolar lavage cytokine levels were similar after reperfusion of grafts from all three groups of donors.

CONCLUSIONS

Donor treatment with aprotinin or inhaled nitric oxide does not improve lungs that have been injured by brain death.

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.

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.

The inflammatory effect of cardiopulmonary bypass on leukocyte extravasation in vivo

OBJECTIVE

Extravascular trafficking of leukocytes into organs is thought to play a major role in the pathophysiologic mechanisms of the inflammatory response to cardiopulmonary bypass, yet leukocyte extravasation is difficult to study clinically. Here we have tested the hypothesis that leukocyte emigration into skin blisters can provide a way to monitor the inflammatory effect of cardiopulmonary bypass that allows testing of anti-inflammatory interventions (exemplified by aprotinin).

METHODS

Patients undergoing primary elective coronary artery bypass grafting (n = 14) were randomized into 2 equal groups to receive saline infusion during cardiopulmonary bypass (control group) or high-dose aprotinin. Experimental skin blisters (in duplicate) were induced on the forearm by means of topical application of the vesicant cantharidin, and blister fluid was sampled at 5 hours postoperatively. Inflammatory leukocyte subsets in blister fluid were analyzed by means of flow cytometry by using expression of CD11b and CD62L as a phenotypic marker of activation.

RESULTS

In the control group of patients, cardiopulmonary bypass surgery triggered a 381% increase in leukocyte extravasation into the skin compared with reference blisters carried out before surgical intervention, with neutrophil (P = .014), monocyte (P = .014), and eosinophil (P = .009) levels all statistically significantly increased. In the aprotinin group there was no statistically significant increase during cardiopulmonary bypass surgery in any inflammatory leukocyte subset. The activation phenotype of extravascular leukocytes was not significantly altered between surgical groups.

CONCLUSIONS

This study introduces the cantharidin blister technique as a powerful new research tool for analyzing the inflammatory effect of cardiopulmonary bypass in vivo. It has provided detailed molecular insight into the extravascular leukocyte population during cardiopulmonary bypass. Although aprotinin blocked cardiopulmonary bypass-dependent extravasation of leukocytes, there was no change in their CD11b/CD62L activation status. The cantharidin skin test thus represents a novel research tool for evaluating future anti-inflammatory interventions in cardiothoracic 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.

Aprotinin reduces cardiac troponin I release and inhibits apoptosis of polymorphonuclear cells during off-pump coronary artery bypass surgery

OBJECTIVES

In addition to blood-sparing effects, aprotinin may have cardioprotective and anti-inflammatory effects during cardiopulmonary bypass-assisted cardiac surgery. In this study, the authors examined whether aprotinin had cardioprotective and/or anti-inflammatory effects in patients undergoing off-pump coronary artery bypass grafting.

DESIGN

A prospective randomized clinical trial.

SETTING

University hospital.

PARTICIPANTS

Fifty patients were randomized to control (n = 25) or aprotinin treatment (n = 25) groups.

INTERVENTIONS

Aprotinin was given as a loading dose (2 x 10(6) KIU) followed by a continuous infusion at 5 x 10(5) KIU/h until skin closure.

MEASUREMENTS AND MAIN RESULTS

Blood samples for cardiac troponin I; interleukin-6, interleukin-8, and interleukin-10; tumor necrosis factor alpha; and elastase were taken after anesthesia induction, completion of revascularization, and 6 hours, 12 hours, and 24 hours after revascularization. Blood samples were taken to assess for apoptosis in polymorphonuclear cells. Baseline plasma levels for cardiac troponin I did not differ between groups but were significantly lower in aprotinin-treated patients at the time of revascularization (p = 0.03) and 6 hours (p = 0.004) and 24 hours (p = 0.03) later. Aprotinin significantly reduced apoptosis in polymorphonuclear cells compared with control-treated patients (p = 0.04). There were no differences in plasma cytokine or elastase levels between groups.

CONCLUSIONS

The authors conclude that aprotinin reduces perioperative cardiac troponin I release and attenuates apoptosis in polymorphonuclear cells but has no significant effects on plasma cytokine levels in patients undergoing off-pump coronary artery bypass graft surgery.

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

BACKGROUND

Aprotinin is a serine protease inhibitor used extensively in cardiac operations to reduce postoperative bleeding. It also has cardioprotective effects in ischemia/reperfusion injury. In this study, the effects of aprotinin on the release of cardiac markers were evaluated in patients who had good ventricular function and were undergoing coronary artery bypass grafting with cardiopulmonary bypass (CPB).

METHODS AND RESULTS

Eighty male patients with an ejection fraction >or=40%, were randomized into either an aprotinin (Group-I; n=40) or control (Group-II; n=40) group. Patients in the aprotinin group received the full Hammersmith doses of aprotinin (2 x 10(6) KIU pre-CPB, 2 x 10(6) KIU at pump prime, 500,000 KIU/h during CPB), whereas the patients in the control group received only saline solutions. Cardiac troponin-I (cTnI) levels were measured before surgery, immediately after surgery, and at postoperative 6(th), 12(th), 24(th) h and 5(th) day. Creatine kinase (CK)-MB measurements were performed at the same time except for the postoperative 5(th) day. Cardiac index (CI), mixed venous oxygen saturation and lactate dehydrogenase (LDH) measurements were also performed.

CONCLUSION

Although all patients were in reasonable condition, less myocardial enzyme leakage occurred on the aprotinin group, suggesting that aprotinin has a protective effect on the myocardium beyond that achieved with blood cardioplegia and systemic hypothermia. Because of aprotinin's effects on multiple targets of metabolism, its protective value might increase in more complicated cases.

Aprotinin and the protease-activated receptor 1 thrombin receptor: antithrombosis, inflammation, and stroke reduction

Cardiopulmonary bypass, although remaining an indispensable asset in cardiac surgery, especially in more complex and repeat operations, is associated with significant thrombin generation in the bypass circuit, leading to the activation of platelets, the coagulation system, an inflammatory response, and perioperative stroke. Recent clinical studies and meta-analyses of clinical trials in coronary artery bypass grafting surgery have confirmed that aprotinin not only reduces transfusion requirements in cardiac surgery but also confers significant protection against platelet dysfunction, activation of the systemic inflammatory response, and perioperative stroke when administered at the full (or "Hammersmith") dose. This article reviews research from several independent groups to propose a novel mechanism through which the antithrombotic, anti-inflammatory, and neuroprotective mechanism might be mediated, via protection of the high-affinity thrombin receptor protease-activated receptor 1 (PAR1).

Aprotinin inhibits proinflammatory activation of endothelial cells by thrombin through the protease-activated receptor 1

OBJECTIVE

Thrombin is generated in significant quantities during cardiopulmonary bypass and mediates adverse events, such as platelet aggregation and proinflammatory responses, through activation of the high-affinity thrombin receptor protease-activated receptor 1, which is expressed on platelets and endothelium. Thus antagonism of protease-activated receptor 1 might have broad therapeutic significance. Aprotinin, used clinically to reduce transfusion requirements and the inflammatory response to bypass, has been shown to inhibit protease-activated receptor 1 on platelets in vitro and in vivo. Here we have examined whether aprotinin inhibits endothelial protease-activated receptor 1 activation and resulting proinflammatory responses induced by thrombin.

METHODS

Protease-activated receptor 1 expression and function were examined in cultured human umbilical vein endothelial cells after treatment with alpha-thrombin at 0.02 to 0.15 U/mL in the presence or absence of aprotinin (200-1600 kallikrein inhibitory units/mL). Protease-activated receptor 1 activation was assessed by using an antibody, SPAN-12, which detects only the unactivated receptor, and thrombin-mediated calcium fluxes. Other thrombin-dependent inflammatory pathways investigated were phosphorylation of the p42/44 mitogen-activated protein kinase, upregulation of the early growth response 1 transcription factor, and production of the proinflammatory cytokine interleukin 6.

RESULTS

Pretreatment of cultured endothelial cells with aprotinin significantly spared protease-activated receptor 1 receptor cleavage (P < .0001) and abrogated calcium fluxes caused by thrombin. Aprotinin inhibited intracellular signaling through p42/44 mitogen-activated protein kinase (P < .05) and early growth response 1 transcription factor (P < .05), as well as interleukin 6 secretion caused by thrombin (P < .005).

CONCLUSIONS

This study demonstrates that endothelial cell activation by thrombin and downstream inflammatory responses can be inhibited by aprotinin in vitro through blockade of protease-activated receptor 1. Our results provide a new molecular basis to help explain the anti-inflammatory properties of aprotinin reported clinically.

Endothelial activation in the transplanted human heart from organ retrieval to 3 months after transplantation: an observational study

BACKGROUND

Endothelial activation in the donor heart has been described variably after brain death and transplantation. We aimed to characterize the time course of endothelial activation in right ventricle (RV) and left ventricle (LV) during the acute phase of clinical transplantation.

METHODS

We studied biopsy specimens from the RVs and the LVs of 40 donor hearts: at initial assessment of the donor, at end-ischemia, and after 10 minutes of reperfusion. We also included follow-up RV biopsy specimens at 1 week, 1 month, and 3 months after surgery. Six of the patients had cystic fibrosis and were domino donors.

RESULTS

P-selectin and vascular cell adhesion molecule 1 (VCAM-1), but not E-selectin were up-regulated in brain-dead and in domino donors vs controls. Unused donor hearts (n = 6) had significantly less up-regulation of P-selectin and of VCAM-1. We found no difference between the RV and the LV during surgery, but we did see important time-dependent variations. P-selectin was present in 85% of vessels throughout transplantation and decreased to approximately 60% after transplantation (p < 0.001). We initially detected VCAM-1 in 20% of vessels, which decreased to 5% during storage, then increased to 47% at reperfusion, and gradually decreased thereafter (p < 0.001). E-selectin expression increased progressively from 15% initially to 45% at reperfusion and then decreased after surgery (p = 0.001). Thrombomodulin expression was decreased at baseline, and the decrease was accentuated afterward (p = 0.02). Patients with donor organ failure did not have a specific pattern of endothelial activation.

CONCLUSION

Cardiac transplantation is associated with marked endothelial activation, with no difference between the two ventricles. The changes persist in the post-operative period, even in the absence of acute rejection.

Aprotinin decreases the incidence of cognitive deficit following CABG and cardiopulmonary bypass: a pilot randomized controlled study

PURPOSE

Cognitive deficit after coronary artery bypass surgery (CABG) has a high prevalence and is persistent. Meta-analysis of clinical trials demonstrates a decreased incidence of stroke after CABG when aprotinin is administrated perioperatively. We hypothesized that aprotinin administration would decrease the incidence of cognitive deficit after CABG.

METHODS

Thirty-six ASA III-IV patients undergoing elective CABG were included in a prospective, randomized, single-blinded pilot study. Eighteen patients received aprotinin 2 x 10(6) KIU (loading dose), 2 x 10(6) KIU (added to circuit prime) and a continuous infusion of 5 x 10(5) KIU.hr(-1). A battery of cognitive tests was administered to patients and spouses (n = 18) the day before surgery, four days and six weeks postoperatively.

RESULTS

Four days postoperatively new cognitive deficit (defined by a change in one or more cognitive domains using the Reliable Change Index method) was present in ten (58%) patients in the aprotinin group compared to 17 (94%) in the placebo group [95% confidence interval (CI) 0.10-0.62, P = 0.005); (P = 0.01)]. Six weeks postoperatively, four (23%) patients in the aprotinin group had cognitive deficit compared to ten (55%) in the placebo group (95% CI 0.80-0.16, P = 0.005); (P = 0.05).

CONCLUSION

In this prospective pilot study, the incidence of cognitive deficit after CABG and cardiopulmonary bypass is decreased by the administration of high-dose aprotinin.

Effect of aprotinin on in vitro cerebral endothelial ICAM-1 expression induced by astrocyte-conditioned medium

BACKGROUND AND OBJECTIVE

Aprotinin administration may decrease the incidence of stroke associated with coronary artery bypass surgery by an unknown mechanism. Astrocytes exposed to hypoxia produce proinflammatory cytokines and upregulate intercellular adhesion molecule (ICAM)-1 on cerebral endothelium. This study investigated the effects of aprotinin on cerebral endothelial activation by hypoxic astrocytes in vitro.

METHODS

Mouse astrocytes were exposed to hypoxia in an anaerobic chamber for 4 h followed by reoxygenation for 24 h. Astrocyte-conditioned medium (ACM) collected from mouse astrocytes subjected to hypoxia/reoxygenation (HR) or normoxia were applied to mouse cerebral endothelial cell (MCEC) cultures for 4 and 24 h in normoxia. Endothelial cells were preincubated for 1 h with aprotinin (1600 KIU mL(-1)) prior to exposure to ACM. Flow cytometry was used to estimate endothelial ICAM-1 expression. Interleukin (IL)-1beta space concentrations in ACM were estimated with enzyme-linked immunosorbent assay (ELISA). Repeated comparisons were made using analysis of variance (ANOVA) and post hoc Tukey test as appropriate. P < 0.05 was considered significant. Data is presented as mean (standard deviation, SD).

RESULTS

MCEC ICAM-1 expression was greater after 24 h exposure to HR-ACM compared to normoxic-ACM (mean channel flouresence (MCF) 107.5 (4.5) vs. 74.3 (4.5), respectively, P < 0.001). ICAM-1 expression was decreased by aprotinin preincubation compared to control (MCF 91.0 (1.1) vs. 107.5 (2.1), P = 0.006). Supernatant IL-1beta concentrations in astrocytes exposed to HR were greater than those exposed to normoxia (7.1 (0.2) vs. 4.1 (0.2), P = 0.01).

CONCLUSIONS

This may be a neuroprotective mechanism associated with aprotinin administration.

Evidence for injurious effect of cocaethylene in human microvascular endothelial cells

BACKGROUND

Cocaethylene (CE) is a conjugate of cocaine and ethanol that may contribute to the pathogenesis of systemic vascular diseases. This study was conducted to investigate the effect of CE on human microvascular endothelial cells (HMEC-1) in culture.

METHODS

Proliferating and confluent monolayers of HMEC-1 were used for assessing growth kinetics, viability, cytotoxicity, and morphologic/barrier alterations after CE treatment (0-1 mmol/l) for up to 7 days. The Trypan blue exclusion, lactate dehydrogenase (LDH) release assay, manual cell counts, and silver nitrate staining technique were used.

RESULTS

The doubling times of 30.0 and 31.4 h for the 0.5 and 1.0 mmol/l CE-treated HMEC-1, respectively, were significantly longer than the 28.6 h for the control group (p < 0.05). The viabilities of 90.4 +/- 3.8% (control) and 93.1 +/- 1.9% (CE-treated) from the Trypan blue exclusion-staining experiments indicated non-lethality of CE. LDH activities of 173 +/- 33 U/l (control) and 157 +/- 43 U/l (CE-treated) confirmed the absence of CE cytotoxicity. Silver staining results indicated increased monolayer permeability as demonstrated by the formation of intercellular gaps after 1 h of exposure.

CONCLUSIONS

HMEC-1 exposure to CE induced cellular injury that could affect the permeability of small blood vessels. These cellular changes could in part be the pivotal point for studies to explain the edema and inflammation in surrounding tissues of individuals exposed to CE.

Neutrophils both reduce and increase permeability in a cell culture model of the blood-brain barrier

This study was carried out to determine the effects that human neutrophils have on permeability across a model of the blood-brain barrier (BBB) formed by primary cultures of bovine brain microvessel endothelial cells (BBMEC). Transendothelial electrical resistance (TEER) was used to measure changes in permeability across BBMEC monolayers in a dual compartment system, during neutrophil interactions. When neutrophils (5 x 10(6)/ml) were applied to monolayers, TEER increased (permeability decreased). Adenosine was implicated, since the TEER increase was blocked by adenosine deaminase (1 U/ml) and the adenosine A2 receptor antagonist ZM 241385 (at 10(-6) M but not 10(-8) M, implicating A2B receptors). Oxygen free radicals were implicated as the TEER increase was blocked by combined catalase (100 U/ml) and superoxide dismutase (60 U/ml). When a gradient of the bacterial chemoattractant peptide formyl methionyl leucine phenylalanine (fMLP, 10(-7) M) was applied to neutrophils, the TEER decreased (permeability increased), concurrent with migration. When fMLP (10(-7) M) was added to the neutrophils, without migration, no change occurred. The TEER decrease was blocked by loading endothelium with the calcium buffer BAPTA (10 microM) and partially blocked by the serine protease inhibitor aprotinin (20 microg/ml). Measures to block the potential extracellular triggers heparin binding protein, glutamate, oxygen free radicals and binding to intercellular cell adhesion molecule-1 (ICAM-1) were ineffective. These data indicate that neutrophils both reduce and increase permeability in a cell culture model of the BBB, correlated to their proximity and migration through the endothelium. They explore the role of neutrophils in BBB breakdown, and the formation or amelioration of vasogenic cerebral edema.

Microvascular Inflammatory Response in Cardiac Surgery

Cardiac surgical procedures, with or without cardiopulmonary bypass, elicit a systemic inflammatory response in patients that induces the elaboration of multiple cytokines, chemokines, adhesion molecules, and destructive enzymes. This inflammatory reaction involves multiple interdependent and redundant cell types and humoral cascades, which allows for amplification and positive feedback at numerous steps. This systemic inflammatory response ultimately results in a broad spectrum of clinical manifestations, with multiple organ failure being the most severe form. Investigative efforts have focused on understanding the mechanism of this systemic inflammatory response syndrome in order to develop potential therapeutic targets to inhibit it, thereby possibly decreasing postoperative morbidity and mortality. Multiple therapeutic methods have been investigated, including pharmacologic inhibitors and modifications of surgical technique and the cardiopulmonary bypass circuit. Although studies have demonstrated that the use of these therapies in experimental and clinical settings has attenuated the systemic inflammatory response, they have failed to conclusively show clinical benefit from these therapies. These therapies may be too specific to minimize the deleterious effects of a systemic inflammatory response that results from the activation of multiple, interdependent, and redundant inflammatory cascades and cell types. Hence, further studies that investigate the molecular and cellular events underlying the systemic inflammatory response syndrome and the resultant effects of anti-inflammatory therapies are warranted to ultimately achieve improvements in clinical outcome after cardiac surgical procedures.

Aortic atherosclerosis and postoperative neurological dysfunction in elderly coronary surgical patients

BACKGROUND

Arteriosclerosis of the ascending aorta is an important risk factor for cerebral embolism. However, the association between arteriosclerosis of the ascending aorta and neurologic dysfunction after coronary artery surgery has not been evaluated prospectively.

METHODS

We examined whether varying degrees of arteriosclerosis in the ascending aorta, assessed by epiaortic ultrasonography, increased the incidence of neuropsychologic dysfunction and stroke in 463 elderly patients (> or = 60 years old) after coronary artery surgery.

RESULTS

Patients with severe arteriosclerosis (n = 76) had higher rates of postoperative neuropsychologic dysfunction (26%) and intraoperative stroke (10.5%); the moderately atherosclerotic patients (n = 57) had rates of 7% and 1.8%, respectively; whereas control patients (almost normal or mild arteriosclerosis, n = 330) had rates of 8% and 1.2%, respectively (all p < 0.001). Univariate analysis indicated that multiple small infarctions or broad infarctions, cerebral arterial stenosis, circulatory arrest, maximal thickness of intima around the site of aortic manipulation, and deformities due to clamp or cannulation were associated significantly with intraoperative strokes in patients with severe arteriosclerosis.

CONCLUSIONS

Severe arteriosclerosis of the ascending aorta significantly increased the risk of postoperative neuropsychologic dysfunction and stroke after coronary artery bypass grafting. If a thick plaque is noted near the manipulation site, a nontouch method of the ascending aorta should be applied to reduce the incidence of neurologic dysfunction.

Inflammatory response to cardiopulmonary bypass

Inflammation in cardiac surgical patients is produced by complex humoral and cellular interactions with numerous pathways including activation, generation, or expression of thrombin, complement, cytokines, neutrophils, adhesion molecules, mast cells, and multiple inflammatory mediators. Because of the redundancy of the inflammatory cascades, profound amplification occurs to produce multiorgan system dysfunction that can manifest as coagulopathy, respiratory failure, myocardial dysfunction, renal insufficiency, and neurocognitive defects. Coagulation and inflammation are also closely linked through networks of both humoral and cellular components including proteases of the clotting and fibrinolytic cascades, including tissue factor. Vascular endothelial cells also mediate inflammation and the cross talk between coagulation and inflammation. Novel antiinflammatory agents inhibit these processes by several mechanisms such as preventing proteolysis of the protease-activated receptor (aprotinin), inhibiting complement-mediated injury (pexelizumab), or inhibiting contact activation (kallikrein inhibitors). Surgery alone also activates specific hemostatic responses, activation of immune mechanisms, and inflammatory response mediated by the release of various cytokines and chemokines. Novel agents are under investigation to further improve outcomes in cardiac surgical patients.

Soluble adhesion molecules in coronary surgery and cardiopulmonary bypass with pump prime aprotinin

OBJECTIVE

The purpose of the present study was to establish whether pump prime aprotinin could influence soluble adhesion molecules in patients undergoing elective coronary artery bypass surgery.

DESIGN

Thirty patients admitted for first-time elective coronary artery bypass surgery were randomized into control or aprotinin groups. Patients in the aprotinin group received 280 mg of aprotinin in the pump prime. Plasma levels of soluble adhesion molecules were analyzed perioperatively.

RESULTS

There were no significant changes in plasma sE-selectin after the operation in either group. Plasma sP-selectin increased significantly up to 20 h after reperfusion to the myocardium. Plasma sICAM-1 decreased in the early stage after cardiopulmonary bypass (CPB), then recovered at 4 h after reperfusion and a significant increase in sICAM-1 was observed 20 h later. There were no significant differences between the groups in postoperative changes in sP-selectin (p = 0.21) and sICAM-1 (p = 0.91).

CONCLUSION

Pump prime aprotinin did not influence plasma levels of E-selectin, P-selectin and ICAM-1 in the present patients. The present results do not support the concept of an anti-inflammatory effect of pump prime aprotinin.

Aprotinin: Antithrombotic and Vasoactive Mechanisms of Action

Aprotinin is a serine protease inhibitor that has been in clinical use since the late 1980s to reduce blood loss in patients undergoing cardiopulmonary bypass surgery. Its hemostatic mechanism of action is mediated predominantly through inhibition of plasmin, thus exerting a net antifibrinolytic effect. Compared to other antifibrinolytics, however, aprotinin provides an additional patient benefit at the level of improved platelet function and diminished inflammatory response to bypass. Recent work on platelets has identified a cell-associated target for aprotinin: the thrombin-receptor, protease-activated receptor 1. Selective blockade of the protease-activated receptor 1 limits thrombin-induced activation and consequent “exhaustion” of platelets in the bypass circuit, while maintaining the hemostatic activity of platelets in the pericardial cavity in response to nonproteolytic agonists, such as collagen, adenosine diphosphate and epinephrine. While no specific cellular receptors have as yet been identified to explain the antiinflammatory and vasoactive properties of aprotinin, awareness is growing that serine protease-sensitive receptors belonging to the protease-activated receptor family (1-4) may represent important aprotinin targets, since these receptors are expressed by all major cells of the vasculature and act as sensors of the coagulation, inflammatory and vasoactive pathways activated by major surgery or trauma. The possibility is discussed that endothelial protease-activated receptor 2, whose natural ligands are trypsin, tryptase and the ternary tissue factor-Vlla-Xa complex, may be targeted by aprotinin.

The human immunodeficiency virus-1 Tat protein activates human umbilical vein endothelial cell E-selectin expression via an NF-kappa B-dependent mechanism

Human immunodeficiency virus infection is associated with inflammation and endothelial cell activation that cannot be ascribed to direct infection by the virus or to the presence of opportunistic infections. Factors related to the virus itself, to the host and/or to environmental exposures probably account for these observations. The HIV protein Tat, a viral regulator required for efficient transcription of the viral genome in host cells is secreted from infected cells and taken up by uninfected by-stander cells. Tat can also act as a general transcriptional activator of key inflammatory molecules. We have examined whether Tat contributes to this endothelial cell activation by activating NF-kappaB. Human endothelial cells exposed to Tat in the culture medium activated E-selectin expression with delayed kinetics compared with tumor necrosis factor (TNF). Tat-mediated E-selectin up-regulation required the basic domain of Tat and was inhibited by a Tat antibody. Transfection of human E-selectin promoter-luciferase reporter constructs into Tat-bearing cells or into endothelial cells co-transfected with a Tat expression vector resulted in induction of luciferase expression. Either Tat or TNF activated p65 translocation and binding to an oligonucleotide containing the E-selectin kappaB site 3 sequence. Tat-mediated p65 translocation was also delayed compared with TNF. Neither agent induced new synthesis of p65. A super-repressor adenovirus (AdIkappaBalphaSR) that constitutively sequesters IkappaB in the cytoplasm as well as cycloheximide or actinomycin D inhibited Tat- or TNF-mediated kappaB translocation and E-selectin up-regulation.

The antithrombotic and antiinflammatory mechanisms of action of aprotinin

Aprotinin (Trasylol) is generally regarded to be an effective hemostatic agent that prevents blood loss and preserves platelet function during cardiac surgery procedures requiring cardiopulmonary bypass (CBP). However, its clinical use has been limited by the concern that such a potent hemostatic agent might be prothrombotic, particularly in relation to coronary vein graft occlusion. In this review we present a mechanism of action that challenges such a viewpoint and explains how aprotinin can be simultaneously hemostatic and antithrombotic. Aprotinin achieves these two apparently disparate properties by selectively blocking the proteolytically activated thrombin receptor on platelets, the protease-activated receptor 1 (PAR1), while leaving other mechanisms of platelet aggregation unaffected. We also review recent research leading to the discovery of novel antiinflammatory targets for aprotinin. A better understanding of its mechanisms of action has led to the conclusion that aprotinin is a remarkable drug with the capacity to correct many of the imbalances that develop in the coagulation system and the inflammatory system after CPB. Nonetheless, it has been clinically underused for fear of causing thrombotic complications, a fear that in light of recent evidence may be unfounded.

New antiinflammatory and platelet-preserving effects of aprotinin

The clinical benefit of aprotinin with respect to improved hemostasis, platelet function, and inflammatory response to cardiopulmonary bypass (CPB) surgery has been well documented, but these benefits have been overshadowed by the concern that such a potently hemostatic agent might also be prothrombotic. In this article, we discuss recent advances in the understanding of the basic mechanism of aprotinin that have led to the identification of new antiinflammatory targets and the discovery that aprotinin is, in fact, antithrombotic with respect to platelets. Its antithrombotic action is mediated by the selective blocking of the major thrombin receptor, the protease-activated receptor 1 (PAR1), but not other receptors of platelet activation (ie, collagen, adenosine diphosphate [ADP], or epinephrine receptors). The selective targeting of PAR1 enables aprotinin to protect platelets from unwanted activation by thrombin generated during CPB surgery (consistent with a role in platelet-preservation), while permitting the participation of platelets in the formation of hemostatic plugs at wound and suture sites, where collagen, ADP, and epinephrine are most likely to be expressed. Aprotinin therefore exerts a subtle hemostatic yet antithrombotic mechanism of action, which, when allied with its multitiered antiinflammatory effect, makes this drug a valuable companion to cardiac surgery.