Aprotinin inhibits leukocyte-endothelial cell interactions after hemorrhage and reperfusion

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.

Hemorrhagic Shock and the Microvasculature

The microvasculature plays a central role in the pathophysiology of hemorrhagic shock and is also involved in arguably all therapeutic attempts to reverse or minimize the adverse consequences of shock. Microvascular studies specific to hemorrhagic shock were reviewed and broadly grouped depending on whether data were obtained on animal or human subjects. Dedicated sections were assigned to microcirculatory changes in specific organs, and major categories of pathophysiological alterations and mechanisms such as oxygen distribution, ischemia, inflammation, glycocalyx changes, vasomotion, endothelial dysfunction, and coagulopathy as well as biomarkers and some therapeutic strategies. Innovative experimental methods were also reviewed for quantitative microcirculatory assessment as it pertains to changes during hemorrhagic shock. The text and figures include representative quantitative microvascular data obtained in various organs and tissues such as skin, muscle, lung, liver, brain, heart, kidney, pancreas, intestines, and mesentery from various species including mice, rats, hamsters, sheep, swine, bats, and humans. Based on reviewed findings, a new integrative conceptual model is presented that includes about 100 systemic and local factors linked to microvessels in hemorrhagic shock. The combination of systemic measures with the understanding of these processes at the microvascular level is fundamental to further develop targeted and personalized interventions that will reduce tissue injury, organ dysfunction, and ultimately mortality due to hemorrhagic shock. Published 2018. Compr Physiol 8:61-101, 2018.

Microcirculatory perfusion shows wide inter-individual variation and is important in determining shock reversal during resuscitation in a porcine experimental model of complex traumatic hemorrhagic shock

Background

Traumatic hemorrhagic shock (THS) is a leading cause of preventable death following severe traumatic injury. Resuscitation of THS is typically targeted at blood pressure, but the effects of such a strategy on systemic and microcirculatory flow remains unclear. Failure to restore microcirculatory perfusion has been shown to lead to poor outcomes in experimental and clinical studies. Systemic and microcirculatory variables were examined in a porcine model of complex THS, in order to investigate inter-individual variations in flow and the effect of microcirculatory perfusion on reversal of the shock state.

Methods

Baseline standard microcirculatory variables were obtained for 22 large white pigs using sublingual incident dark field (IDF) video-microscopy. All animals were subjected to a standardised hind-limb injury followed by a controlled haemorrhage of approximately 35 % of blood volume (shock phase). This was followed by 60 min of fluid resuscitation with either 0.9 % saline or component blood products and a target SBP of 80 mmHg (early resuscitation phase). All animals were then given blood products to a target SBP of 110 mmHg for 120 min (mid-resuscitation phase), and a further 100 min (late resuscitation phase). IDF readings were obtained at the midpoint of each of these phases. Cardiac output was measured using a pulmonary artery catheter. Animals were divided into above average (A) and below average (B) perfused vessel density (PVD) groups based on the lowest recorded PVD measurement taken during the shock and early resuscitation phases.

Results

There was minimal inter-individual variation in blood pressure but wide variation of both systemic and microcirculatory flow variables during resuscitation. During shock and early resuscitation, group A (n = 10) had a mean PVD of 10.5 (SD ± 2.5) mm/mm² and group B (n = 12) 5.5 (SD ± 4.1) mm/mm². During the later resuscitation phases, group A maintained a significantly higher PVD than group B. Group A initially had a higher cardiac output, but the difference between the groups narrowed as resuscitation progressed. At the end of resuscitation, group A had significantly lower plasma lactate, higher lactate clearance, lower standard base deficit and smaller mixed venous-arterial CO₂ gradient. There was no significant difference in blood pressure between the two groups at any stage.

Conclusion

There was a wide variation in both macro- and microcirculatory flow variables in this pressure-targeted experimental model of THS resuscitation. Early changes in microvascular perfusion appear to be key determinants in the reversal of the shock state during resuscitation. Microcirculatory flow parameters may be more reliable markers of physiological insult than pressure-based parameters and are potential targets for goal-directed resuscitation.

Electronic supplementary material

The online version of this article (doi:10.1186/s40635-016-0088-z) contains supplementary material, which is available to authorized users.

Simvastatin inhibits apoptosis of endothelial cells induced by sepsis through upregulating the expression of Bcl-2 and downregulating Bax

BACKGROUND

Many studies have showed that apoptosis of endothelial cells plays a curial role in the progress of sepsis. But the role of simvastatin in apoptosis of endothelial cells induced by sepsis is not clear. The present study aimed to investigate the role of simvastatin in apoptosis of endothelial cells induced by sepsis and its mechanism.

METHODS

Human umbilical vein endothelial cells (HUVECs) were randomly divided into three groups: control group, sepsis serum intervention group (sepsis group) and simvastatin+sepsis serum intervention group (simvastatin group). After 24-hour incubation with corresponding culture medium, the relative growth rate of HUVECS in different groups was detected by MTT assay; the apoptosis of HUVECs was detected by Hoechst33258 assay and flow cytometry; and the expression of the Bcl-2 and Bax genes of HUVECs was detected by PCR.

RESULTS

Compared with the sepsis group, HUVECs in the simvastatin group had a higher relative growth rate. Apoptotic HUVECs decreased significantly in the simvastatin group in comparison with the sepsis group. Expression of the Bcl-2 gene in HUVECs decreased obviously, but the expression of the Bax gene increased obviously after 24-hour incubation with sepsis serum; however, the expression of the Bcl-2 and Bax genes was just the opposite in the simvastatin group.

CONCLUSIONS

Our study suggests that simvastatin can inhibit apoptosis of endothelial cells induced by sepsis through upregulating the expression of Bcl-2 and downregulating Bax. It may be one of the mechanisms for simvastatin to treat sepsis.

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.

Antifibrinolytics attenuate inflammatory gene expression after cardiac surgery

OBJECTIVES

Anti-inflammatory effects of tranexamic acid and aprotinin, used to abate perioperative blood loss, are reported and might be of substantial clinical relevance. The study of messenger ribonucleic acid synthesis provides a valuable asset in evaluating the inflammatory pathways involved.

METHODS

Whole-blood messenger ribonucleic acid expression of 114 inflammatory genes was compared pre- and postoperatively in 35 patients randomized to receive either placebo, tranexamic acid, or aprotinin. These results were further confirmed by reverse transcription-polymerase chain reaction.

RESULTS

Of the 23 genes exhibiting independently altered postoperative gene expression levels, 8 were restricted to the aprotinin group only (growth differentiation factor 3, interleukin 19, interleukin 1 family member 7, transforming growth factor α, tumor necrosis factor superfamily 10, tumor necrosis factor superfamily 12, tumor necrosis factor superfamily 13B, vascular endothelial growth factor α), whereas both aprotinin and tranexamic acid altered gene expression of 3 genes as compared with placebo (FMS-related tyrosine kinase 3 ligand, growth differentiation factor 5, interferon-α8). In general, less upregulation of pro-inflammatory, and more upregulation of anti-inflammatory, genes was observed for patients treated with antifibrinolytics. Gene expression affected by aprotinin coded mostly for proteins that function through serine proteases.

CONCLUSIONS

This study demonstrates that the use of tranexamic acid and aprotinin results in altered inflammatory pathways on the genomic expression level. We further demonstrate that the use of aprotinin leads to significant attenuation of the immune response, with several inhibitory effects restricted to the use of aprotinin only. The results aid in a better understanding of the targets of these drugs, and add to the discussion on which antifibrinolytic can best be used in the cardiac surgical patient.

A comparative study of the immune modulating properties of antifibrinolytics in cardiac surgery

PURPOSE

Antifibrinolytics, used in cardiac surgery to abate postoperative blood loss, share anti-inflammatory properties by suppression of pro-inflammatory D-dimer and plasmin levels. Additional drug specific immune modulating qualities are often mentioned in the discussion on which antifibrinolytic can best be used. To determine the extent and relevance of these effects, we investigated cytokine and growth factor plasma levels in cardiac surgery patients randomized to receive either tranexamic acid, aprotinin, or placebo. Corticosteroid-treated patients served to put the effects in perspective.

METHODS

Using a biochip immunoassay, plasma of 36 cardiac surgery patients was quantified for 12 cytokines and growth factors, assessed preoperatively and 6, 12, 24, and 48 h after the start of cardiopulmonary bypass. Eight patients were treated with tranexamic acid, nine with aprotinin, and nine received placebo. Ten placebo-treated patients received corticosteroids.

RESULTS

IL-1ß, IL-6, IL-8, IL-10, IFN-γ, TNF-α, VEGF, MCP-1, and EGF plasma concentrations significantly changed over time across all patients. Aprotinin-treated patients showed decreased pro-inflammatory TNF-α and peak MCP-1 plasma levels when compared with placebo. However, corticosteroids attenuated the inflammatory response to a much larger extent, lowering postoperative IL-6, IL-10, IFN-γ, and VEGF concentrations also.

CONCLUSIONS

Aprotinin attenuates postoperative pro-inflammatory levels TNF-α and MCP-1 whereas tranexamic acid does not. The majority of plasma proteins studied, however, were not affected by the use of antifibrinolytics when compared with placebo. A clinically relevant common anti-inflammatory effect through inhibition of fibrinolysis seems therefore unlikely.

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.

Factor Xa induces tissue factor expression in endothelial cells by P44/42 MAPK and NF-κB-dependent pathways

BACKGROUND

Tissue factor (TF) is an initiator of coagulation. The serine protease factor Xa (FXa) is the convergence point of the extrinsic and intrinsic components of the coagulation cascade. In addition to its hemostatic function, FXa elicits inflammatory responses in endothelial cells that may be important in surgical procedures in which inflammation is triggered. This study tested the hypothesis that FXa can up-regulate TF on vascular endothelial cells by a mitogen-activated protein kinase (MAPK)- and NF-κB-dependent pathway.

METHODS AND RESULTS

Incubation of cultured human umbilical vein endothelial cells (HUVECs) with FXa increased TF protein expression and activity in a dose-dependent manner. Pre-incubation of HUVECs with the serine protease inhibitor antithrombin, which targets not only thrombin but also FXa and FIXa, inhibited FXa-induced TF expression, but the selective thrombin inhibitor hirudin did not inhibit FXa-induced TF expression, ruling out a thrombin-mediated pathway. After 10 min incubation with HUVECs, FXa rapidly induced P44/42 MAPK activation (immunoblotting of phosphorylated P44/42 MAPK) with a peak at 30 min. The MEK 1/2 inhibitor PD98059 partially reduced FXa-induced TF expression and activity (3.82 ± 0.11 vs 6.54 ± 0.08 fmol/min/cm(2), P < 0.05). NF-κB was activated by FXa, confirmed by cytoplasmic IkBα degradation and increased NF-κB P65 nuclear translocation. Interruption of the NF-κB pathway by the IkBα phosphorylation inhibitor Bay 11-7802 abrogated FXa-induced TF protein expression and activity (1.93 ± 0.02 versus 6.54 ± 0.08 fmol/min/cm(2), P < 0.05). However, inhibition of PI3 kinase by LY 294002 did not attenuate FXa-induced TF protein expression and activity.

CONCLUSIONS

(1) FXa up-regulates TF protein expression and activity in HUVECs, (2) FXa-induced up-regulation of TF is independent of the thrombin-PAR1 pathway, and (3) the MAPK and NF-κB pathways, but not PI3 kinase pathway, are involved in FXa-induced TF expression on human umbilical endothelial cells. FXa may be a feed-forward alternative mechanism of activating TF expression and activity, thereby increasing a procoagulant state or inflammation. This mechanism may be important in the pro-inflammatory state initiated by cardiac surgical procedures.

Redefining the Systemic Inflammatory Response

From the first description of the “systemic inflammatory response” in the early 1990s, it has been recognized that this is a multifaceted response of the body to the combined insult of cardiothoracic surgery with bypass, involving causation by “activation of complement, coagulation, fibrinolytic, and kallikrein cascades, activation of neutrophils with degranulation and protease enzyme release, oxygen radical production, and the synthesis of various cytokines from mononuclear cells.” Yet the intervening 15 years have seen a narrowing of research into individual systems and interventions naively targeted at single pathways without achieving clinically meaningful benefits. The time has come to redefine the systemic inflammatory response so that research can be more productively focused on objectively measuring and interdicting this multisystem disorder. A key concept of this new understanding is that translation into a hard adverse event occurs when the systemic imbalance is combined with a localized trigger. Triggers might be inadvertently provided by transient episodes of ischemia/malperfusion to vulnerable organs or handling trauma to major vessels. Future research should be directed at suppressing systemic activation with combinations of drugs and improved circuit coating, whereas changes in clinical practice and continuous monitoring of perfusion parameters can help eliminate localized triggering events.

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.

The protective effect of aprotinin and alpha-tocopherol on ischemia-reperfusion injury of the rat liver

BACKGROUND

Liver injury caused by ischemia-reperfusion (I/R) processes is a complication of hepatic resection surgery and transplantation, particularly using grafts from marginal donors. Despite improvements in organ preservation and advances in surgical techniques, I/R injury remains a significant clinical problem. In this study, we investigated whether aprotinin provided protection against the adverse effects of I/R injury in liver tissue.

METHODS

Forty rats were randomized into four groups (n = 10): group I: (control group) I/R + no medication; group II: sham-operated group + no medication or I/R; group III: I/R + aprotinin; group IV: I/R + alpha-tocopherol. Malondialdehyde (MDA) was measured in the liver tissue and superoxide dismutase (SOD), catalase (CAT), aspartate aminotransferase (AST), alanine aminotransferase (ALT), as well as lactate dehydrogenase (LDH) in rat serum.

RESULTS

Administration of aprotinin and alpha-tocopherol before I/R resulted in significant reductions of MDA levels compared to the I/R alone group (group I; P = .01 and P < .01, respectively). Administration of aprotinin or alpha-tocopherol prior to I/R resulted in significant increases in SOD and CAT levels compared with the I/R group (P < .05 each). Compared to the I/R group, significant decreases in plasma AST, ALT, and LDH levels were observed both in the aprotinin and in the alpha-tocopherol group (P < .05). Histological evaluation revealed the injury grade to be relatively lower among groups III and IV compared to group I.

DISCUSSION

In conclusion, rat hepatic structures in aprotinin and alpha-tocopherol administered groups were well protected. Therefore, aprotinin may provide protection against the adverse effects of I/R injury in liver transplantation.

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.

The Effect of Aprotinin on Brain Ischemic-Reperfusion Injury After Hemorrhagic Shock in Rats: An Experimental Study

BACKGROUND

We aimed to demonstrate the positive effects of the serine protease inhibitor aprotinin on neural ischemia-reperfusion injury and apoptosis in a rat model.

METHODS

There were 18 rats divided into 3 groups: group A (sham, n = 6), group B (ischemia-reperfusion, n = 6), and group C (ischemia-reperfusion + aprotinin, n = 6). The systolic blood pressure of the group B and C rats was decreased to 40% to 50% of the normal level by taking blood from the femoral vein to develop hemorrhagic shock. The blood was retained and given to the remaining group B and C rats for reperfusion 20 minutes after the procedure. In group B, isotonic solution and, in group C, aprotinin was administered to the rats 5 minutes before reperfusion. After the rats were killed, the brain tissue samples were fixed for histopathologic examination. Brain tissue superoxide dismutase, malondialdehyde, and tissue myeloperoxidase level and apoptotic cell analyses were performed in all groups.

RESULTS

Superoxide dismutase level decreased from group A to group B and increased from group B to group C (p < 0.05). Malondialdehyde and myeloperoxidase levels and apoptotic cells increased from group A to group B and decreased from group B to group C (p < 0.05).

CONCLUSION

The results suggest that the systemic use of aprotinin in ischemic neural tissue prevents reperfusion injury and also protects the morphologic, functional, and biochemical integrity of the neural tissue.

Inflammation, proinflammatory mediators and myocardial ischemia-reperfusion Injury

Ischemic myocardium must be reperfused to terminate the ischemic event; otherwise the entire myocardium involved in the area at risk will not survive. However, there is a cost to reperfusion that may offset the intended clinical benefits of minimizing infarct size, postischemic endothelial and microvascular damage, blood flow defects, and contractile dysfunction. There are many contributors to this reperfusion injury. Targeting only one factor in the complex web of reperfusion injury is not effective because the untargeted mechanisms induce injury. An integrated strategy of reducing reperfusion injury in the catheterization laboratory involves controlling both the conditions and the composition of the reperfusate. Mechanical interventions such as gradually restoring blood flow or applying postconditioning may be used independently in or conjunction with various cardioprotective pharmaceuticals in an integrated strategy of reperfusion therapeutics to reduce postischemic injury.

Aprotinin does not diminish blood loss in elective operations for infrarenal abdominal aneurysms: a randomized double-blind controlled trial

Surgery for abdominal aneurysm is associated with substantial blood loss. In cardiac surgery, aprotinin, a fibrinolysis inhibitor, has shown to reduce blood loss significantly. Our aim was to assess the effect of aprotinin, when administered during elective surgery of infrarenal abdominal aneurysm, on coagulation, blood loss, and morbidity. A double-blind randomized trial was performed on 35 consecutive patients. They were randomized to either an aprotinin or a placebo group. The aprotinin group received 2,000,000 kallikrein inhibiting units (KIU) of aprotinin (500,000 KIU in 50 mL NaCl 0.9%) as a starting dose, followed by 500,000 KIU per hour during the operation. The placebo group received equal amounts of only NaCl 0.9%. During the operation and 24 hr thereafter, blood samples were taken to assess coagulation factors. Blood loss was measured in suction devices and swabs. All patients were followed until their discharge from the hospital. Statistical analysis was performed by independent t-test or Mann-Whitney U-test and chi-squared test. There was no significant difference in the amount of blood loss or the amount of blood products administered between the two groups. Morbidity and mortality were also comparable. In both groups, consumption of clotting factors could be detected, indicating activation of the coagulation cascade. However, in the aprotinin group, the alpha2-antiplasmin level was raised during surgery, indicating inhibition of fibrinolysis. Administration of aprotinin during elective operations for infrarenal aortic aneurysm induces inhibition of fibrinolysis. However, it does not significantly reduce blood loss or the need for blood products.

Aprotinin decreases ischemic damage during coronary revascularization

BACKGROUND AND AIM

This study sought to determine whether the favorable anti-inflammatory effects of aprotinin might limit ischemic damage during the revascularization of ischemic myocardium.

METHODS

Twenty pigs underwent 90 minutes of coronary occlusion followed by 45 minutes of blood cardioplegic arrest and 180 minutes of reperfusion. Ten animals received a loading dose of aprotinin (40,000 kallikrein inhibiting units/kg) during the start of coronary occlusion followed by an infusion of 20,000 kallikrein inhibiting units/kg/hour. Ten other animals received no aprotinin. Summary statistics are expressed as the mean +/- standard error.

RESULTS

The aprotinin-treated animals required less cardioversions for ventricular arrhythmias (1.0 +/- 0.7 vs. 3.6 +/- 0.6; p < 0.001), accumulated less lung water (1.0 +/- 0.2% change vs. 6.2 +/- 0.9% change; p = 0.038), had more complete coronary relaxation to bradykinin (34.1 +/- 5.9% change vs. 9.2 +/- 3.5% change; p = 0.01), and had reduced infarct size (area necrosis/area risk = 20 +/- 1.1% vs. 39 +/- 1.2%; p = 0.003).

CONCLUSIONS

Aprotinin limits ischemic injury during acute coronary revascularization by decreasing ventricular arrhythmias and lung edema, preserving endothelial function, and minimizing myocardial necrosis.

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.

Profiling biochemical and hemodynamic markers using chronically instrumented, conscious and unrestrained rats undergoing severe, acute controlled hemorrhagic hypovolemic shock as an integrated in-vivo model system to assess new blood substitutes

The aim of the present study was to assess several biochemical and physiological endpoint parameters alongside controlled hemorrhagic and recovery phases of chronically instrumented, conscious and unrestrained healthy rats. Male Sprague-Dawley rats (12-14 weeks; 430+/-20 g; n=22-18) were instrumented with a saline-perfused femoral arterial catheter and placed individually in a metabolic cage for up to 20 days, allowing instant assessments of the hemodynamic profile and blood and urine sampling for hematological profile and biochemical measurements to assess hepatic, renal and metabolic functions. In addition, body weight, food and water intake, and diuresis were monitored daily. After a 7-day stabilization period, the rats underwent severe and acute hemorrhagic shock (HS) (removal of 50% of total circulating blood volume), kept in hypovolemic shock for an ischemic period of 50 min and then resuscitated over 10 min. Gr. 1 was re-infused with autologous shed blood (AB; n=10) whereas Gr. 2 was infused 1:1 with a solution of sterile saline-albumin (SA; 7% w/v) (n=8-12). Ischemic rats recovered much more rapidly following AB re-infusion than those receiving SA. Normal hemodynamic and biochemical profiles were re-established after 24 h. Depressed blood pressure lasted 4-5 days in SA rats. The hematological profile in the SA resuscitated rats was even more drastically affected. Circulating plasma concentrations of hemoglobin (-40%), hematocrit (-50%), RBC (-40%) and platelets (-41%) counts were still severely decreased 24 h after the acute ischemic event whereas WBC counts increased 2.2-fold by day 4. It took 5-9 days for these profiles to normalize after ischemia-reperfusion with SA. Diuresis increased in both groups (by 45+/-7% on day 1) but presented distinct electrolytic profiles. Hepatic and renal functions were normal in AB rats whereas altered in SA rats. The present set of experiments enabled us to validate a model of HS in conscious rats and the use of an integrated in vivo platform as a valuable tool to characterize HS-induced stress and to test new classes of blood substitutes in real time, post-event, over days.

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.

Aprotinin ameliorates ischemia/reperfusion injury in a rat hind limb model

The aim of the study was to investigate the protective effect of aprotinin in a rat hind limb ischemia/reperfusion (I/R) model. A well-known antioxidant, alpha-tocopherol, was also tested for comparison. Ischemia was induced for 4 h by vascular clamping of the iliac arteries of 24 Sprague-Dawley rats, followed by 1 h of reperfusion. Muscle injury was evaluated in three groups: a saline group, an alpha-tocopherol group and an aprotinin group. Blood pH, pO2, pCO2, HCO3, creatine kinase (CPK), lactate dehyrogenase (LDH) and thiobarbituric acid reactive substances (TBARS) as well as muscle TBARS were measured at the end of the reperfusion. Muscle tissue samples were taken for histological examination. alpha-Tocopherol and aprotinin groups showed a significant amelioration of plasma CPK (p=0.002, p=0.002), LDH (p=0.004, p=0.004) and muscle tissue TBARS (p=0.001, p=0.001) compared with the control. Plasma TBARS were significantly lower in the aprotinin group compared with the control (p=0.017). Also, tissue TBARS was significantly lower in the aprotinin group than the alpha-tocopherol group (p<0.001). Neutrophil infiltration was less prominent in the alpha-tocopherol and aprotinin groups compared to the control (p=0.006, p=0.001). These results suggest that aprotinin, a potent anti-inflammatory drug, is more useful than alpha-tocopherol, a powerful antioxidant, for attenuating muscle injury after I/R.

Aprotinin inhibits local platelet trapping and improves tissue destruction in hepatic cryosurgery

BACKGROUND

During the last decade, cryosurgery became an interesting alternative in the treatment of nonresectable liver neoplasms. The freeze-thaw procedure, however, may be associated with life-threatening thrombocytopenia due to local platelet trapping, and success of neoplasm ablation may be compromised by inadequate parenchymal cell destruction.

METHODS

Because aprotinin is capable of inhibiting the initiation of both coagulation and fibrinolysis, we studied-by whole body scintigraphy of Indium-111-labeled platelets and histomorphology in a porcine model of hepatic cryosurgery-whether this serine protease inhibitor is effective in attenuating platelet trapping and in improving tissue destruction.

RESULTS

Fifteen minutes of cryotherapy (-168 degrees C at the tip of the cryoprobe) induced a 30 +/- 4 cm(3) cryolesion, which presented with massive platelet trapping (14.0 +/- 1.7% cryolesion activity/whole body activity) and incomplete parenchymal cell destruction (0.9 +/- 0.3; score of hepatocyte nuclear destruction within the margin of the cryolesion). Aprotinin treatment with 500,000 IU initial bolus injection and additional 500,000 IU infusion over 3 hours did not affect the size of the cryolesion (29 +/- 3 cm(3)) but reduced local platelet activity (1.9 +/- 1.9%; P<.001) and induced hepatocyte nuclear destruction (3.0 +/- 0.0; P<.001).

CONCLUSIONS

Thus, our study indicates that aprotinin inhibits cryoablation-associated platelet trapping and improves tissue destruction. The serine protease inhibitor may represent a valuable adjunct in cryosurgery of hepatic neoplasms.