Nafamostat Mesilate, a Broad Spectrum Protease Inhibitor, Modulates Platelet, Neutrophil and Contact Activation in Simulated Extracorporeal Circulation

Anticoagulants in adult extracorporeal membrane oxygenation: alternatives to standardized anticoagulation with unfractionated heparin

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is a vital technique for severe respiratory or heart failure patients. Bleeding and thrombotic events are common during ECMO and negatively impact patient outcomes. Unfractionated heparin is the primary anticoagulant, but its adverse effects limit its use, necessitating alternative anticoagulants.

OBJECTIVE

Review available alternative anticoagulants for adult ECMO patients. Explore potential novel anticoagulants for future ECMO use. Aim to reduce complications (bleeding and thrombosis) and improve safety and efficacy for critically ill ECMO patients.

METHODS

Comprehensive literature review of existing and emerging anticoagulants for ECMO.

RESULTS

Identified a range of alternative anticoagulants beyond unfractionated heparin. Evaluated their potential utility in mitigating ECMO-related complications.

CONCLUSION

Diverse anticoagulant options are available and under investigation for ECMO. These alternatives may enhance patient safety and outcomes during ECMO support. Further research and clinical studies are warranted to determine their effectiveness and safety profiles.

Nafamostat mesilate prevented caerulein-induced pancreatic injury by targeting HDAC6-mediated NLRP3 inflammasome activation

OBJECTIVE

Nafamostat mesilate (NM), a synthetic broad-spectrum serine protease inhibitor, has been commonly used for treating acute pancreatitis (AP) and other inflammatory-associated diseases in some East Asia countries. Although the potent inhibitory activity against inflammation-related proteases (such as thrombin, trypsin, kallikrein, plasmin, coagulation factors, and complement factors) is generally believed to be responsible for the anti-inflammatory effects of NM, the precise target and molecular mechanism underlying its anti-inflammatory activity in AP treatment remain largely unknown.

METHODS

The protection of NM against pancreatic injury and inhibitory effect on the NOD-like receptor protein 3 (NLRP3) inflammasome activation were investigated in an experimental mouse model of AP. To decipher the molecular mechanism of NM, the effects of NM on nuclear factor kappa B (NF-κB) activity and NF-κB mediated NLRP3 inflammasome priming were examined in lipopolysaccharide (LPS)-primed THP-1 cells. Additionally, the potential of NM to block the activity of histone deacetylase 6 (HDAC6) and disrupt the association between HDAC6 and NLRP3 was also evaluated.

RESULTS

NM significantly suppressed NLRP3 inflammasome activation in the pancreas, leading to a reduction in pancreatic inflammation and prevention of pancreatic injury during AP. NM was found to interact with HDAC6 and effectively inhibit its function. This property allowed NM to influence HDAC6-dependent NF-κB transcriptional activity, thereby blocking NF-κB-driven transcriptional priming of the NLRP3 inflammasome. Furthermore, NM exhibited the potential to interfere the association between HDAC6 and NLRP3, impeding HDAC6-mediated intracellular transport of NLRP3 and ultimately preventing NLRP3 inflammasome activation.

CONCLUSIONS

Our current work has provided valuable insight into the molecular mechanism underlying the immunomodulatory effect of NM in the treatment of AP, highlighting its promising application in the prevention of NLRP3 inflammasome-associated inflammatory pathological damage.

Use of nafamostat mesilate for anticoagulation during extracorporeal membrane oxygenation: A systematic review

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) represents an advanced option for supporting refractory respiratory and/or cardiac failure. Systemic anticoagulation with unfractionated heparin (UFH) is routinely used. However, patients with bleeding risk and/or heparin-related side effects may necessitate alternative strategies: among these, nafamostat mesilate (NM) has been reported.

METHODS

We conducted a systematic literature search (PubMed and EMBASE, updated 12/08/2021), including all studies reporting NM anticoagulation for ECMO. We focused on reasons for starting NM, its dose and the anticoagulation monitoring approach, the incidence of bleeding/thrombosis complications, the NM-related side effects, ECMO weaning, and mortality.

RESULTS

The search revealed 11 relevant findings, all with retrospective design. Of these, three large studies reported a control group receiving UFH, the other were case series (n = 3) or case reports (n = 5). The main reason reported for NM use was an ongoing or high risk of bleeding. The NM dose varied largely as did the anticoagulation monitoring approach. The average NM dose ranged from 0.46 to 0.67 mg/kg/h, but two groups of authors reported larger doses when monitoring anticoagulation with ACT. Conflicting findings were found on bleeding and thrombosis. The only NM-related side effect was hyperkalemia (n = 2 studies) with an incidence of 15%-18% in patients anticoagulated with NM. Weaning and survival varied across studies.

CONCLUSION

Anticoagulation with NM in ECMO has not been prospectively studied. While several centers have experience with this approach in high-risk patients, prospective studies are warranted to establish the optimal space of this approach in ECMO.

Physiologically-based pharmacokinetic modeling of nafamostat to support dose selection for treatment of pediatric patients with COVID-19

Pediatric patients with coronavirus disease 2019 (COVID-19) are increasing, and severe cases such as multisystem inflammatory syndrome are being reported. Nafamostat, a repurposing drug, is currently being explored for the treatment of COVID-19 in adults. However, the data supporting its exposure in pediatrics remains scarce. Physiologically-based pharmacokinetic (PBPK) modeling enables the prediction of drug exposure in pediatrics based on ontogeny of metabolic enzymes and age dependent anatomical and physiological changes. The study aimed to establish a PBPK model of nafamostat in adults, then scale the adult PBPK model to children for predicting pediatric exposures of nafamostat and an optimal weight-based nafamostat dose in pediatric population. The developed model adequately described adult exposure data in healthy volunteers following i.v. administration with three doses (10, 20, and 40 mg). Scaling adult PBPK models to five pediatric groups predicted that as age advances from neonate to adult, the exposure of nafamostat slightly increased from neonate to infant, steadily decreased from infant to child, and then increased from child to adult after the administration of 0.2 mg/kg/h for 14 days, a dosing regimen being conducted in a clinical trial for COVID-19. Based on the fold change of predicted area under the curve for the respective pediatric group over those of adults, weight-based dosages for each pediatric group may be suggested. The novel PBPK model described in this study may be useful to investigate nafamostat pharmacokinetics in a pediatric subgroup further.

Nafamostat-Interferon-α Combination Suppresses SARS-CoV-2 Infection In Vitro and In Vivo by Cooperatively Targeting Host TMPRSS2

SARS-CoV-2 and its vaccine/immune-escaping variants continue to pose a serious threat to public health due to a paucity of effective, rapidly deployable, and widely available treatments. Here, we address these challenges by combining Pegasys (IFNα) and nafamostat to effectively suppress SARS-CoV-2 infection in cell culture and hamsters. Our results indicate that Serpin E1 is an important mediator of the antiviral activity of IFNα and that both Serpin E1 and nafamostat can target the same cellular factor TMPRSS2, which plays a critical role in viral replication. The low doses of the drugs in combination may have several clinical advantages, including fewer adverse events and improved patient outcome. Thus, our study may provide a proactive solution for the ongoing pandemic and potential future coronavirus outbreaks, which is still urgently required in many parts of the world.

Successful conservative treatment for massive uterine bleeding with non-septic disseminated intravascular coagulation after termination of early pregnancy in a woman with huge adenomyosis: case report

BACKGROUND

Adenomyosis is a benign gynecological condition in which endometrial tissue or endometrial-like tissue develops within the uterine myometrium. Few cases of disseminated intravascular coagulation has been reported in the patients with adenomyosis. Although hysterectomy is indicated for refractory massive uterine bleeding in the patients with advanced uterine adenomyosis, conservative treatment is often desired in women in the late reproductive age. Recently such cases are increasing due to the social trend of late marriage.

CASE PRESENTATION

A 37-year-old woman with huge adenomyosis, gravida 2 para 0, was referred to our hospital to terminate her pregnancy. Acute, non-septic, disseminated intravascular coagulation (DIC) developed after early pregnancy was terminated in a woman with huge adenomyosis. Massive bleeding and DIC occurred 3 days after the dilatation and curettage. There was no evidence of infection as the cause of the DIC, because neither bacteria nor endotoxin could be detected in her blood, and antithrombin 3 (AT3), which would be expected to decrease in septic patients, was not decreased. Hemorrhage in the adenomyotic tissue after the termination presumably developed inflammation, with numerous microthrombi and necrosis in the adenomyotic tissue, which subsequently promoted coagulation and fibrinolysis, leading to the onset of massive uterine bleeding and DIC. Although severe hyperfibrinolysis is observed in peripheral blood, the fibrinolysis state in the uterine myometrium is considered to be even more severe. The newly formed clots for hemostasis under the uterine mucosa could be removed due to the excessive activation of fibrinolytic system happened in the adjacent myometrium, leading to the onset of massive uterine bleeding. Massive bleeding and DIC resolved quickly after the patient was treated with nafamostat mesilate, which is effective for both excessive coagulation and fibrinolysis.

CONCLUSIONS

Adenomyosis could cause massive bleeding and DIC when pregnancy is terminated. Massive bleeding was considered to occur because the excessive fibrinolysis system inside adenomyosis affected the adjacent endometrium. Before considering hysterectomy to control refractory uterine bleeding, nafamostat mesilate should be considered as one option, thinking the pathophysiology of the massive bleeding due to uterine adenomyosis.

Recent progress on inhibitors of the type II transmembrane serine proteases, hepsin, matriptase and matriptase-2

Members of the type II transmembrane serine proteases (TTSP) family play a vital role in cell growth and development but many are also implicated in disease. Two of the well-studied TTSPs, matriptase and hepsin proteolytically process multiple protein substrates such as the inactive single-chain zymogens pro-HGF and pro-macrophage stimulating protein into the active heterodimeric forms, HGF and macrophage stimulating protein. These two proteases also have many other substrates which are associated with cancer and tumor progression. Another related TTSP, matriptase-2 is expressed in the liver and functions by regulating iron homoeostasis through the cleavage of hemojuvelin and thus is implicated in iron overload diseases. In the present review, we will discuss inhibitor design strategy and Structure activity relationships of TTSP inhibitors, which have been reported in the literature.

Antifibrinolytic Therapy and Perioperative Considerations

Fibrinolysis is a physiologic component of hemostasis that functions to limit clot formation. However, after trauma or surgery, excessive fibrinolysis may contribute to coagulopathy, bleeding, and inflammatory responses. Antifibrinolytic agents are increasingly used to reduce bleeding, allogeneic blood administration, and adverse clinical outcomes. Tranexamic acid is the agent most extensively studied and used in most countries. This review will explore the role of fibrinolysis as a pathologic mechanism, review the different pharmacologic agents used to inhibit fibrinolysis, and focus on the role of tranexamic acid as a therapeutic agent to reduce bleeding in patients after surgery and trauma.

Serine protease inhibitor nafamostat given before reperfusion reduces inflammatory myocardial injury by complement and neutrophil inhibition

Animal data strongly support a role for inflammation in myocardial ischemia reperfusion injury. Attempts at cardioprotection by immunomodulation (such as with the specific C5 antibody pexelizumab) in humans have been disappointing. We hypothesized that a broader spectrum antiinflammatory agent might yield successful cardioprotection. The serine protease inhibitor nafamostat (FUT-175), which is already in clinical use, is a potent antiinflammatory synthetic serine protease inhibitor with anticomplement activity that we tested in a well-established rabbit model of 1 hour of myocardial ischemia followed by 3 hours of reperfusion. Compared to vehicle-treated animals, nafamostat (1 mg/kg of body weight) administered 5 minutes before reperfusion significantly reduced myocardial injury assessed by plasma creatine kinase activity (38.1 +/- 6.0 versus 57.9 +/- 3.7I U/g protein; P < 0.05) and myocardial necrosis (23.6 +/- 3.1% versus 35.7 +/- 1.0%; P < 0.05) as well as myocardial leukocyte accumulation (P < 0.05). In parallel in vitro studies, Nafamostat was a significantly more potent broad spectrum complement suppressor than C1 inhibitor. Nafamostat appears to have capability as an inhibitor of both complement pathways and as a broad-spectrum antiinflammatory agent by virtue of its serine protease inhibition. Administration of nafamostat before myocardial reperfusion after ischemia produced significant, dose-dependent cardioprotection. Reduced leukocyte accumulation and complement activity seem involved in the mechanism of this cardioprotective effect.

Nafamostat preserves neutrophil deformability and reduces microaggregate formation during simulated extracorporeal circulation

BACKGROUND

Initial sequestration of activated neutrophils and platelet microaggregates in capillaries are responsible for the inflammatory response associated with cardiopulmonary bypass. The study assesses the inhibitory effects of nafamostat mesilate on neutrophil and platelet activation, and on the neutrophil deformability change and microaggregate formation during simulated extracorporeal circulation.

METHODS

Fresh heparinized human blood was recirculated for 120 minutes in a membrane oxygenator and a roller pump with and without nafamostat (1.0 mg bolus plus 8.0 mg/h infusion; n = 10 for each group). Neutrophil and platelet counts and platelet aggregation were measured. CD11b, L-selectin, and cytoplasmic F-actin of neutrophils were measured by flow cytometry. The microchannel transit time of whole blood was measured as a marker of neutrophil deformability and microaggregate formation. Neutrophil elastase and complement C4d were measured using enzyme immunoassay.

RESULTS

Nafamostat preserved platelet counts and inhibited platelet aggregation. Nafamostat significantly reduced neutrophil elastase release at 120 minutes of recirculation, and F-actin expression at 30 and 60 minutes. The drug did not modulate the changes of CD11b, L-selectin, or C4d. Whole blood filterability was significantly preserved by nafamostat at 30 and 120 minutes.

CONCLUSIONS

Nafamostat preserves blood filterability during recirculation, possibly by suppression of F-actin expression and platelet activation. Nafamostat may reduce neutrophil sequestration and microaggregate formation in the microcirculation during cardiopulmonary bypass.

Effects of nafamostat mesilate on ADP-induced platelet aggregation and disaggregation in hemodialysis patients

Nafamostat mesilate (NM), a synthetic protease inhibitor, is the most commonly used anticoagulant in the setting of extracorporeal circulation (ECC) in patients with bleeding tendency. It inhibits both platelet aggregation and activation of coagulation factors. Although it has been reported that NM disaggregates aggregated platelets, little is known about such an effect in the setting of hemodialysis therapy (HD). We examined the effects of NM on adenosine 5'-diphosphate (ADP)-induced platelet aggregation and disaggregation using platelet-rich plasma obtained from 6 HD patients. The platelet aggregation was stimulated by 3 microM ADP and change of aggregation was monitored by an aggregometer. NM adjusted to the final concentrations of 0.1 (1.9 x 10(-7)), 1.0 (1.9 x 10(-6)), 10, (1.9 x 10(-5)), and 100 (1.9 x 10(-4)) microg/ml (M) or veronal-buffered saline (VBS) as control was added before or after to the stimulation of ADP. NM not only inhibited platelet aggregation, but also disaggregated already aggregated platelets at concentrations of 1.0 microg/mln or higher. Moreover, NM almost completely disaggregated at 100 microg/ml. This NM concentration of 1.0 microg/ml was lower than the therapeutic concentration in ECC of HD (i.e., 10 M(-5)). Both inhibitory and disaggregatory effects of NM expressed a dose-related dependency. Our results suggest that NM can exert both aggregation inhibitory and disaggregatory effects on platelets of HD patients within the therapeutic concentration.

Atrial Fibrillation After Cardiac Surgery/Cardiopulmonary Bypass Is Associated with Monocyte Activation

Atrial fibrillation (AF) contributes significantly to morbidity and mortality in as many as one-third of patients after cardiac surgery that requires cardiopulmonary bypass (CPB). Recent data suggest that inflammatory infiltration of the myocardium may predispose to AF. We conducted an exploratory pilot study to determine if there was an association between the perioperative leukocyte inflammatory response to cardiac surgery/CPB and postoperative AF. We enrolled 72 patients undergoing cardiac surgery with CPB; all patients were in sinus rhythm before surgery. Leukocyte activation (CD11b upregulation) was perioperatively measured in monocytes and neutrophils (PMN). Preoperative C-reactive protein (CRP) and perioperative neutrophil myeloperoxidase (MPO) were also monitored for inflammation, and troponin I was assayed for perioperative cardiac muscle damage. All markers were evaluated for differences between the subset of patients who developed AF versus those who remained in normal sinus rhythm after surgery. All 72 patients completed the study. Postoperative AF developed in 26 (36%) patients. Perioperative monocyte CD11b upregulation was significantly increased in patients who developed AF (P = 0.01), but increases in PMN CD11b were not significantly associated with AF (P = 0.057). The increase in both monocyte and PMN counts after aortic cross-clamp release was significantly associated with postoperative AF (P = 0.007 and P = 0.005, respectively). By contrast, preoperative CRP and perioperative MPO did not differ between AF and normal rhythm patients. Similarly, the peak value of troponin I did not differ between groups. In this pilot study of cardiac surgery/CPB patients, perioperative upregulation of the monocyte adhesion receptor, CD11b, and higher circulating monocyte and PMN numbers were associated with postoperative AF, suggesting that the induction of cellular inflammation during cardiac surgery/CPB may contribute to this pathophysiology.

Biomaterial-associated thrombosis: roles of coagulation factors, complement, platelets and leukocytes

Our failure to produce truly non-thrombogenic materials may reflect a failure to fully understand the mechanisms of biomaterial-associated thrombosis. The community has focused on minimizing coagulation or minimizing platelet adhesion and activation. We have infrequently considered the interactions between the two although we are generally familiar with these interactions. However, we have rarely considered in the context of biomaterial-associated thrombosis the other major players in blood: complement and leukocytes. Biomaterials are known agonists of complement and leukocyte activation, but this is frequently studied only in the context of inflammation. For us, thrombosis is a special case of inflammation. Here we summarize current perspectives on all four of these components in thrombosis and with biomaterials and cardiovascular devices. We also briefly highlight a few features of biomaterial-associated thrombosis that are not often considered in the biomaterials literature: The importance of tissue factor and the extrinsic coagulation system. Complement activation as a prelude to platelet activation and its role in thrombosis. The role of leukocytes in thrombin formation. The differing time scales of these contributions.

Effects of anti-inflammatory cytokine agent (FR167653) and serine protease inhibitor on warm ischemia-reperfusion injury of the liver graft

BACKGROUND

The shortage of donors has become a serious problem. Some institutes have tried to use grafts retrieved from non-heart-beating donors (NHBDs), but the results have not been satisfactory. This study clarifies the effects of nafamostat mesilate (NM), a strong serine protease inhibitor, and FR167653, a suppressant of both tumor necrosis factor-alpha and interleukin-1beta release, on warm ischemia-reperfusion injury and establishes the procurement of the grafts for a successful liver transplant using uncontrolled NHBDs.

METHODS

Male Wistar rats were divided into five groups as follows (n = 5): (1) heart-beating (HB) group, in which livers were retrieved from heart-beating donors; (2) non-heart-beating (NHB) group, in which livers were retrieved from NHBDs; (3) NM group, in which livers were retrieved from NHBDs pretreated with NM (0.2 mg/kg/hr, for 30 min); (4) FR group, in which livers were retrieved from NHBDs pretreated with FR167653 (2 mg/kg); and (5) FR+NM group, in which livers were retrieved from NHBDs pretreated with FR167653 and NM. The livers were perfused for 60 min with Krebs-Henseleit bicarbonate buffer after cold preservation 6 hr.

RESULTS

In the NHB group, the values of interleukin-1beta, tumor necrosis factor-alpha, thromboxane B2, and leukotriene B4, and the expressions of nuclear factor-kappaB, activating protein 1, and cyclooxygenase-2 were significantly higher than those in the HB group. In the FR+NM group, those values were low, the structure of the sinusoids was preserved, and the sinusoidal lumen was maintained (the same as observed in the HB group).

CONCLUSIONS

FR167653 and NM inhibited the induction of inflammatory cytokines and arachidonic acid cascade mediators. This combined therapy was effective in preserving sinusoidal microcirculation in the liver grafts from NHBDs.

Effects of nafamostat mesilate and minimal-dose aprotinin on blood-foreign surface interactions in cardiopulmonary bypass

BACKGROUND

The pharmacological inhibition of blood-foreign surface interactions is an attractive strategy for reducing the morbidity associated with cardiopulmonary bypass. We compared the inhibitory effects of nafamostat mesilate (a broad-spectrum synthetic protease inhibitor) and minimal-dose aprotinin on blood-surface interactions in clinical cardiopulmonary bypass.

METHODS

Eighteen patients undergoing coronary surgery were divided into three groups: (1) the control group (heparin, 4 mg/kg; n = 6), (2) the nafamostat mesilate group (heparin plus nafamostat, 0.2 mg/kg bolus followed by 2.0 mg/kg/h during cardiopulmonary bypass; n = 6), and (3) the aprotinin group (heparin plus aprotinin, 2.0 x 10(4) KIU/kg; n = 6). Platelet count, platelet aggregation, beta-thromboglobulin, prothrombin fragment F1.2, thrombin-antithrombin complex, plasminogen activator inhibitor-1, alpha2-plasmin inhibitor-plasmin complex, D-dimer, neutrophil elastase, and interleukin-6 were measured before, during, and after bypass. Bleeding times and blood loss were recorded.

RESULTS

There were no significant differences between groups in platelet count, beta-thromboglobulin, plasminogen activator inhibitor-1, interleukin-6, bleeding times, or blood loss. Platelet aggregation was better preserved at 12 hours after surgery in the nafamostat and aprotinin groups than in the control group. Prothrombin fragment F1.2, thrombin-antithrombin complex and neutrophil elastase levels were significantly reduced by aprotinin, but not by nafamostat as compared with the control group. The alpha2-plasmin inhibitor-plasmin complex and D-dimer were significantly lower with either of the drugs. Aprotinin showed better control of D-dimer than did nafamostat.

CONCLUSIONS

Nafamostat mesilate fails to reduce thrombin formation and neutrophil elastase release, whereas minimal-dose aprotinin inhibits both. Neither nafamostat nor aprotinin inhibits platelet activation. Nafamostat reduces fibrinolysis during cardiopulmonary bypass, although its effect is not as potent as aprotinin.

ONO-6818, a novel, potent neutrophil elastase inhibitor, reduces inflammatory mediators during simulated extracorporeal circulation

BACKGROUND

Among the serine proteases, neutrophil elastase is a powerful cytotoxic enzyme and plays a pivotal role in the inflammatory response associated with cardiopulmonary bypass. This study assesses the effects of the specific inhibition of neutrophil elastase by a novel, potent, low-molecular-weight neutrophil elastase inhibitor, ONO-6818. We hypothesized that ONO-6818 reduces inflammatory mediators and modulates adhesion molecules and the deformability of neutrophils during simulated extracorporeal circulation.

METHODS

Simulated extracorporeal circulation was established by recirculating fresh heparinized (3.75 U/mL) human blood for 120 minutes in a membrane oxygenator and a roller pump with and without 1.0 micromol/L of ONO-6818 (n = 9 for control group, n = 7 for ONO-6818 group). The neutrophil adhesion molecules, CD11b and L-selectin, and the cytoplasmic F-actin of neutrophils were measured by flow cytometry. Neutrophil deformability was evaluated using simulated silicon microcapillaries. Neutrophil elastase, interleukin 8, and C5b-9 were measured using enzyme immunoassay.

RESULTS

Neutrophil elastase levels were significantly lower in the ONO-6818 group. ONO-6818 significantly reduced interleukin 8 and C5b-9 production. ONO-6818 did not modulate changes of CD11b and L-selectin during recirculation. Cytoplasmic F-actin content and changes of neutrophil deformability did not significantly differ between the groups.

CONCLUSIONS

Inhibition of neutrophil elastase activity with ONO-6818 reduces further interleukin 8 production and the formation of the complement membrane attack complex, and this results in a reduction of neutrophil elastase levels during simulated extracorporeal circulation. This study suggests that specific neutrophil elastase inhibition with ONO-6818 is a feasible therapeutic option to attenuate the exaggerated inflammatory response associated with cardiopulmonary bypass.

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.

Influence of heparin dosage on hemostasis under combined use of Nafamostat mesilate during deep hypothermic circulatory arrest

OBJECTIVE

Nafamostat mesilate (NM) is a guanidine acid derivative which is synthesized in Japan as an antifibrinolytic drug. It has been successfully used to decrease blood loss and blood product requirement in cardiac operations. As there have been some reports that insufficient heparinization might induce the coagulopathic state in aprotinin-treated patients undergoing deep hypothermia and circulatory arrest (DHCA), we have reviewed 16 consecutive patients who underwent total aortic arch replacement using DHCA and the associated use of NM.

METHODS

The patients were divided into two groups; a Normal-dosage Group (n = 8) who received 3 mg/kg of heparin, and a Low-dosage Group (n = 8) who received 1.5 mg/kg of heparin. The Celite-activating clotting time was maintained at longer than 1,000 seconds in both groups. Blood loss, transfusion requirements and the volume of postoperative mediastinal tube drainage were compared between the two groups.

RESULTS

We observed no adverse effects of NM and no significant difference in transfusion requirements between both groups. There was a significant difference in blood loss during the operation between the two groups (p < 0.05) (Low-dosage Group 1,973 +/- 959 ml vs Normal-dosage Group 1,059 +/- 704 ml).

CONCLUSIONS

NM was a safe antifibrinolytic drug. Adequate heparinization was necessary to reduce hemorrhage in patients undergoing aortic arch replacement using DHCA and the associated use of NM.

Neutrophil CD11b upregulation during cardiopulmonary bypass is associated with postoperative renal injury

BACKGROUND

Renal injury remains a persistent complication of cardiopulmonary bypass (CPB) that, when sufficient to require dialysis, increases mortality eight-fold. The high prevalence of renal failure in sepsis and adult respiratory distress syndrome has been linked to the systemic inflammatory response associated with those disorders. We hypothesized that components of the inflammatory response to CPB may similarly contribute to post-CPB acute renal injury.

METHODS

Markers of leukocyte and platelet activation peri-CPB were measured in 75 patients undergoing cardiac operation with CPB and were correlated with acute renal injury, defined as an increase (> or = 50%) in peak serum creatinine post-CPB.

RESULTS

Eleven patients sustained post-CPB acute renal injury. This subset of patients demonstrated significantly greater increases in neutrophil CD11b density (p = 0.01), as well as higher total neutrophil counts (p = 0.045), compared with patients with preserved renal function. Hemodynamic instability sufficient to require postoperative hemodynamic support also predicted an increased risk of acute renal injury. However, neutrophil CD11b upregulation did not correlate with this or any other clinical variables associated with renal risk, suggesting that this marker of the neutrophil inflammatory response may independently predict renal injury. By contrast other inflammatory markers, neutrophil myeloperoxidase levels, monocyte CD11b, base line C-reactive protein, and platelet CD62P expression did not differ between the two patient groups.

CONCLUSIONS

Upregulation of the neutrophil adhesion receptor CD11b and high circulating neutrophil numbers are associated with acute renal injury after CPB, suggesting a contribution by activated neutrophils to the pathophysiology of this complication.

Clinical features and treatment strategies of Epstein-Barr virus-associated hemophagocytic lymphohistiocytosis

Epstein-Barr virus (EBV) is the major triggering factor producing hemophagocytic syndrome or hemophagocytic lymphohistiocytosis (HLH). In this review, diagnostic problems, clinical and histopathological features, and treatment strategies of EBV-HLH have been described. In patients with EBV-HLH, the EBV-infected T cells or natural killer (NK) cells are mostly mono- or oligo-clonally proliferating, where hypercytokinemia plays a major role and causes hemophagocytosis, cellular damage and dysfunction of various organs. Although the majority of EBV-HLH cases develop in apparently immunocompetent children and adolescents, it also occurs in association with infectious mononucleosis, chronic active EBV infection, familial HLH, X-linked lymphoproliferative disease, lymphoproliferative disease like peripheral T-cell lymphoma and NK cell leukemia. In terms of treatment, special therapeutic measures are required to control the cytokine storm generated by EBV and to suppress proliferating EBV-genome-containing cells, because the clinical courses are often fulminant and result in a poor outcome.

Specific therapy of digoxin intoxication in dogs by hybrid kidney overexpressing multidrug resistance protein

BACKGROUND

We have recently developed a unique hybrid artificial kidney, where the proximal tubular cell line, over-expressing multidrug resistance protein, MDR-1 (PCTL-MDR), was cultured on hollow fibers. While this module efficiently removed digoxin in vitro, its efficacy in vivo remained to be determined.

METHODS

The system was scaled up by connecting 10 similar modules in parallel, with the MDR-1 (PCTL-MDR) overexpressed proximal tubular cell line cultured as in our previous study. The system was connected to dogs intoxicated with digoxin, a representative substrate of MDR-1. Blood was circulated for 90 minutes through the system. Arterial and venous blood concentrations of digoxin and inulin were monitored. Complete blood cell count and granulocyte elastase were measured before and at the end of the study.

RESULTS

By using the system with PCTL-MDR, the arterial digoxin concentration was dramatically decreased from 2.89 +/- 0.10 to 0.92 +/- 0.11 ng/mL, but not by the system with PCTL alone. The clearance was 22.4 +/- 2.1 and 1.5 +/- 0.2 mL/min for the PCTL-MDR and PCTL equipment, respectively. Inulin was not transported in either system. White blood cell and platelet counts were slightly reduced by the treatment while hematocrit was unchanged; the granulocyte elastase concentration was slightly increased.

CONCLUSION

These data suggest that our new type of hybrid kidney can selectively remove digoxin sufficiently to reduce its systemic blood concentration in dogs with digoxin intoxication. Taking previous studies into consideration, this system may be a more powerful tool for the treatment of intoxication.

Two-dimensional analysis of myocardial protein expression following myocardial ischemia and reperfusion in rabbits

Myocardial ischemia and reperfusion injury (MI/R) can be related to leukocyte activation with subsequent release of cytokines and oxygen derived free radicals. Activation of the complement system has been implicated in the pathogenesis of myocardial ischemia and reperfusion injury. Inflammatory injury will subsequently result in cellular activation and protein synthesis. In the present study we analyzed the myocardial protein expression and its pattern following myocardial ischemia and reperfusion, with and without complement inhibition with the synthetic serine protease inhibitor Futhan/nafamstat mesilate (FUT-175) known to inhibit classical and alternative complement pathway in a rabbit model of myocardial ischemia and reperfusion (60 min I+180 min R). FUT-175 significantly reduced myocardial necrosis, i.e. creatine kinase release which were analyzed for the three groups (p<0.05). Similarly, histological analysis demonstrated preservation of myocardial tissue injury and reduced leukocyte accumulation following FUT-175 treatment. Further, the myocardial protein expression was analyzed by two-dimensional gel electrophoresis following MI/R in the different groups. The protein patterns were evaluated by means of MELANIE III, a computer assisted gel analysis system. The biochemical identification of the proteins of interest was, achieved using nanohigh-performance liquid chromatography/electrospray ionization-tandem mass spectrometry. On average, 509 +/- 25 protein spots were found on the gels. A pattern of 480 spots with identical positions was found on every gel of five animals of each group. We analyzed ten spots which were significantly altered (i.e., in eight spots we observed decreased protein expression and in two spots we observed increased expression, vehicle vs. sham), by using mass spectrometry. Superoxide dismutase precursor and alphaB-crystallin were identified. We compared sham group vs. vehicle group and vehicle group vs. FUT-175 treated animals. Expression of the two identified proteins decreased by half the amount in the vehicle group when compared to sham treated animals. Treatment with FUT-175 preserved significantly superoxide dismutase precursor and alphaB-crystallin protein expression when compared to vehicle animals. The results present marked differences in myocardial protein expression after ischemia and reperfusion and following treatment with the complement inhibitor FUT-175. Our results illustrate the application of proteomics to discover possible new therapeutic targets or to detect unexpected effects of pharmacological inhibitors.

Role of the complement system in ischaemic heart disease: potential for pharmacological intervention

The complement system is an innate, cytotoxic host defence system that normally functions to eliminate foreign pathogens. However, considerable evidence suggests that complement plays a key role in the pathophysiology of ischaemic heart disease (IHD). Experimental models of acute myocardial infarction (MI) and autopsy specimens taken from acute MI patients demonstrate that complement is selectively deposited in areas of infarction. Furthermore, inhibition of complement activation or depletion of complement components prior to myocardial reperfusion has been shown to reduce complement-mediated tissue injury in numerous animal models. IHD remains a leading cause of patient morbidity and mortality. Considerable effort in recent years has therefore been directed by biotechnology and pharmaceutical industries towards the development of novel, human complement inhibitors. Proposed anticomplement therapeutic strategies include the administration of naturally occurring or recombinant complement regulators, anticomplement monoclonal antibodies, and anticomplement receptor antagonists. Although data regarding the effectiveness of anticomplement therapy in humans is limited at present, a number of novel anticomplement therapeutic strategies are currently in clinical trials. The role of complement in IHD and potential for pharmacological intervention is reviewed.

Hemostatic Abnormalities in Cardiopulmonary Bypass: Pathophysiologic and Transfusion Considerations

Cardiac surgical procedures typically use cardiopulmo nary bypass (CPB), a technique that diverts blood from the heart and lungs, where it is oxygenated and pumped back into the circulation. CPB is associated with significant pathophysiologic changes leading to an increased bleeding risk. Bleeding during CPB occurs for multiple reasons; the primary reason is the expo sure of blood to the material components of the CPB system, with intense systemic coagulation and platelet, fibrinolytic, and endothelial activation. To counteract the coagulation activation, extremely high levels of heparin anticoagulation are required to prevent sys temic thrombosis. Thrombin generation through tissue factor pathway activation is now thought to be the predominant mechanism of coagulation activation in CPB. The stimulus for tissue factor exposure to blood is thought to be a systemic activation of tissue factor on monocytes and endothelial cells caused by comple ment activation by the CPB materials and circulating inflammatory mediators. Despite improvements in the CPB system, surgical techniques, and blood conserva tion methods, the demand for blood in such procedures remains sustantial. Optimal blood use can be achieved by combining blood conservation measures with the transfusion of blood components according to strict guidelines. Blood is a limited resource and must be used wisely and cautiously. The risks and costs associ ated with transfusion are compelling reasons to mini mize unnecessary exposure to blood. However, the bene fits of transfusion are well established, and the risks are reasonably low. New developments in the surfaces of the CPB system, use of established and new protease inhibitors, and new blood conservation measures offer promise in decreasing the bleeding risk associated with CPB.

Urinary trypsin inhibitor reduces C-X-C chemokine production in rat liver ischemia/reperfusion

BACKGROUND AND AIM

Protease inhibitors attenuate ischemia/reperfusion injury. However, the underlying mechanisms by which protease inhibitors prevent reperfusion injury remain obscure. Neutrophils play an important role in reperfusion injury. We studied the effects of urinary trypsin inhibitor (UTI) on production of the C-X-C chemokine, cytokine-induced neutrophil chemoattractant (CINC), by Kupffer cells during ischemia/reperfusion of the liver.

METHODS

Liver ischemia was induced in rats by occlusion of the portal vein for 30 min. UTI (50,000 U/kg) was injected intravenously 5 min before vascular clamping. Serum CINC concentrations were measured by enzyme-linked immunosorbent assay. Levels of CINC mRNA in the liver were determined by Northern blot analysis. We also examined the inhibitory effects of UTI on in vitro CINC production by peritoneal macrophages in response to neutrophil elastase (NE).

RESULTS

Serum CINC concentrations increased and peaked 6 h after reperfusion. However, pretreatment of animals with UTI blunted this increase in CINC and significantly reduced CINC mRNA levels in the liver after ischemia/reperfusion. UTI also decreased neutrophil accumulation in the liver 24 h after reperfusion. In vitro CINC production by Kupffer cells from rats pretreated with UTI 3 h after ischemia/reperfusion was significantly decreased compared to those from untreated animals. UTI reduced NE activity in vitro in a dose-dependent manner, and UTI significantly reduced in vitro CINC production by peritoneal macrophages stimulated with NE.

CONCLUSION

UTI reduces the production of CINC by Kupffer cells stimulated with NE, attenuating ischemia/reperfusion injury of the liver.

Nafamostat mesilate treatment during open heart operation in immune thrombocytopenic purpura

A 58-year old woman with idiopathic thrombocytopenic purpura underwent mitral and aortic valve replacements and tricuspid annuloplasty. Preoperative therapeutic interventions including prednisone and immunoglobulin were successful in elevating the platelet count to 93,000/ mm2. Furthermore, we used nafamostat mesilate for coagulopathy prophylaxis during cardiopulmonary bypass. Postoperative bleeding was average and clinical course was uneventful. The perioperative management for patients with idiopathic thrombocytopenic purpura requiring cardiac operation is reviewed.

Therapeutic efficacy of continuous arterial infusion of an antibiotic and a protease inhibitor via the superior mesenteric artery for acute pancreatitis in an animal model

The major cause of death in acute pancreatitis is severe infection owing to bacterial translocation. As a new strategy, we investigated the effects of continuous intra-arterial infusion of an antibiotic (imipenem) or protease inhibitor (nafamostat mesylate) via the superior mesenteric artery (SMA) on bacterial translocation in acute pancreatitis. Infusion of saline (group I), nafamostat mesylate (group II), or imipenem (group III) was started 6 hours after inducing acute pancreatitis in dogs by infusing autologous gallbladder bile into the main pancreatic duct. The survival rate in group III was significantly improved compared to group I(100 vs. 30% at 24 hours), and bacterial infection of the peritoneal fluid, mesenteric lymph nodes, and pancreas was completely prevented in group III. Intestinal damage assessed by light and scanning electron microscopy and by biochemical parameters (mucosal protein content and myeloperoxidase activity) was also significantly mitigated in group III, which showed milder pancreatic necrosis as well. There was little beneficial effect in preventing bacterial translocation in group II, although the survival rate at 24 hours (70%) was improved. Continuous arterial infusion of an antibiotic via the SMA is effective in mitigating intestinal mucosal damage and preventing bacterial translocation in acute pancreatitis, thereby improving survival.

Leukocyte-depleted blood cardioplegia reduces cardiac troponin T release in patients undergoing coronary artery bypass grafting

OBJECTIVE

Activated neutrophils have been implicated in reperfusion injury of the myocardium. Leukocyte depletion at reperfusion may contribute to better myocardial protection during cardiac surgery. We tested the efficacy of leukocyte-depleted blood cardioplegia in reducing myocardial injury during coronary artery bypass grafting.

METHODS

Subjects were 27 patients undergoing elective coronary artery bypass grafting divided into controls (perfused with nonfiltered blood cardioplegia, n = 12) and those undergoing leukocyte-depleted blood cardioplegia (n = 15). Oxygenated blood mixed with a potassium crystalloid cardioplegic solution was delivered through the aortic root at every 30 minutes during cardiac arrest and terminal warm blood was administered before aortic declamping in both groups. In leukocyte depletion, blood was filtered prior to the mixture with crystalloid solution in the cardioplegic reservoir.

RESULTS

Patient profiles did not differ significantly between groups, nor did systemic leukocyte count during or after surgery despite more than 81% removal of leukocytes in cardioplegic delivery. No consistent differences between groups in creatine kinase or creatine kinase-MB were seen up to 18 hours after surgery. Peak troponin T levels were significantly lower in the leukocyte-depleted blood cardioplegia group (0.52 +/- 0.13 ng/ml), however, than in controls (3.85 +/- 0.85 ng/ml).

CONCLUSION

We concluded that leukocyte-depleted blood cardioplegia reduces the release of cardiac troponin T in patients undergoing elective coronary artery bypass grafting and may produce better myocardial protection in patients with impaired cardiac function or a damaged myocardium.

Treatment strategies for Epstein-Barr virus-associated hemophagocytic lymphohistiocytosis (EBV-HLH)

In Epstein-Barr virus (EBV) infection, the virus immortalizes B lymphocytes and cytotoxic T lymphocytes (CTLs) are directed toward both latent and lytic viral antigens expressed on EBV-infected B-cells. Various EBV-associated diseases occur as a result of this disruption of immune surveillance. In the majority of EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH) cases, the major cell types containing EBV DNA are not B-cells, but clonally proliferating T-cells or NK-cells. Proliferation of these cells produces severe immune reactions in the host, and the clinical features related to massive cytokine production at the onset of disease are unique and distinct from other EBV-associated diseases. In the treatment of EBV-HLH, therapeutic infusion of EBV-specific CTLs appears to be ineffective, and eradication of EBV-containing cells is useful but not sufficient to save lives, because of high incidence of acute mortality due to cytokine-induced multiple organ failure and neutropenia-associated opportunistic infections. The optimal treatment strategy for this disease consists of three steps: (1) control of cytokine storm including coagulopathy and multiple organ failure, (2) control of opportunistic infections, and (3) eradication of clonally proliferating EBV-containing T- or NK- cells by immunochemotherapy and, if necessary, hemopoietic stem cell/bone marrow transplantation (SCT/BMT).

Leukocyte-depleted reperfusion after long cardioplegic arrest attenuates ischemia-reperfusion injury of the coronary endothelium and myocardium in rabbit hearts

OBJECTIVE

Cardiopulmonary bypass activates leukocytes, which should injure the coronary endothelium and myocardium during reperfusion especially after long cardioplegic arrest with long cardiopulmonary bypass time. The present study was designed to determine the protective efficacy of leukocyte-depleted reperfusion in blood-perfused parabiotic isolated rabbit hearts as a surgically relevant model with long cardioplegic arrest.

METHODS

Each isolated rabbit heart, with a latex balloon inserted in the left ventricle, was parabiotically blood-perfused using a modified Langendorff column. The left ventricular developed pressure (DP), rate of pressure development (dP/dT), and coronary flow with a left ventricular end-diastolic pressure of 10 mmHg were measured before ischemia and after 15, 30, 45, and 60 min reperfusion after 4 h cardioplegic arrest kept at 20 degrees C (control, n=10). Leukocyte-depleted reperfusion was done in the test group (n=10). The endothelium of the coronary artery was observed by scanning electron microscopy (SEM) with percent injured area of endothelial cells measured to evaluate the extent of endothelial ischemia-reperfusion injury.

RESULTS

The control hearts showed 53.3, 54.3, 48.4, and 39.0% recovery of DP compared to the pre-ischemia baseline data at 15, 30, 45, and 60 min after reperfusion began respectively. Leukocyte-depleted reperfusion enhanced the recovery of DP at 45 min (81.3%, P=0.0021) and 60 min (85.8%, P=0.0005) after reperfusion compared with that in the control group. The control hearts revealed 58.8%, 59.8%, 52.6%, and 43.4% recovery of dP/dT compared to the pre-ischemia baseline data at 15, 30, 45, and 60 min after reperfusion began, respectively. Leukocyte-depleted reperfusion also enhanced the recovery of dP/dT at 45 min (93.2%, P=0.0071) and 60 min (98.8%, P=0.0011) after reperfusion compared with that in the control group. There was also improvement of the recovery of coronary flow by leukocyte-depleted reperfusion (97.2%) compared with that in the control group (58.3%) after 60 min reperfusion (P=0.0121). Scanning electron microscopy showed that 69. 7% of coronary endothelial cells were morphologically injured in the control group. In contrast, leukocyte-depleted reperfusion prevented the extent of coronary endothelial damage with less injured area (0. 5%, P=0.0002).

CONCLUSIONS

Leukocyte-depleted reperfusion improved functional recovery with reduced coronary endothelial injury after long cardioplegic arrest.

The kinetic and structural characterization of the reaction of nafamostat with bovine pancreatic trypsin

Nafamostat mesilate (FUT-175), a synthetic serine protease inhibitor, is active against a number of the serine proteases involved in coagulation. This has been proposed as the basis of its anticoagulant activity. We investigated the reaction of Nafamostat with bovine pancreatic trypsin as a model system. It was shown to act as a time-dependent competitive inhibitor, and the inhibition constants for the binding of Nafamostat to trypsin (i.e., Ki) and the overall inhibition constants (i.e., Ki*) were calculated to be 11.5 microM and 0.4+/-0.14 nM, respectively. The second-order rate constant for the reaction was 4.5+/-0.19x10(5) M(-1)s(-1), and the product released following the acylation step, 6-amidino2-naphthol, showed mixed-type inhibition. The competitive (Kic) and uncompetitive (Kiu) inhibition constants were 14.7 microM and 19.5 microM, respectively. Formation of the acyl-enzyme intermediate was dissected into at least two steps, with rates of 0.9 s(-1) and 195 s(-1). The deacylation step was relatively much slower (3.2+/-0.19x10(-5) s(-1), enabling the mass spectroscopic analysis of the acyl-enzyme intermediate, which confirmed the covalent attachment of 4-guanidinobenzoic acid to trypsin. The product of the deacylation step, 4-guanidinobenzoic acid, showed no inhibition up to a concentration of 200 microM. These data strongly suggest that while Nafamostat is a potent inhibitor of trypsin, it is actually an extremely poor substrate, and that apparent inhibition is due to the competitive formation of a very stable acyl-enzyme intermediate, analogous to some other active site titrants.

Role of C3 cleavage in monocyte activation during extracorporeal circulation

BACKGROUND

We previously demonstrated that inhibiting formation of terminal complement components (C5a and C5b-9) prevents platelet and neutrophil (PMN) but not monocyte activation during simulated extracorporeal circulation (SECC). This study examined whether earlier complement inhibition during SECC, blocking C3a formation, would additionally prevent monocyte activation.

METHODS AND RESULTS

SECC was established by recirculating heparinized whole blood from human volunteers on a membrane oxygenator. CAB-2, a chimeric protein constructed from genes encoding the complement regulatory proteins CD46 and CD55, inactivates the C3/C5 convertases and blocks in vitro generation of C3a, C5a, and C5b-9. CAB-2 was used in 4 experiments at a final concentration of 300 micrograms/mL and 4 experiments at 30 micrograms/mL; 4 control runs used vehicle alone. Samples were assayed for C3a and C5b-9, monocyte activation (CD11b upregulation), PMN activation (CD11b upregulation and elastase release), and platelet activation (P-selectin expression and monocyte-platelet conjugate formation). CAB-2 at both doses significantly inhibited formation of C3a and C5b-9 during SECC. High-dose CAB-2 significantly blocked monocyte and PMN CD11b upregulation and PMN elastase release. CAB-2 also inhibited formation of platelet activation-dependent monocyte-platelet conjugates.

CONCLUSIONS

Blockade of complement activation early in the common pathway inhibited monocyte CD11b upregulation during SECC, suggesting that early complement components contribute most to monocyte activation during SECC. As expected, PMN and platelet activation were blocked by terminal complement inhibition. This investigation further elucidates the relation between complement and blood cell activation during simulated cardiopulmonary bypass.

Inflammatory response to cardiopulmonary bypass

This article reviews the roles of the contact and complement systems and of neutrophils and monocytes in the inflammatory response to cardiopulmonary bypass and open heart operation. These blood proteins and cells, together with other blood elements, produce the vasoactive and cytotoxic substances and microemboli that cause the morbidity associated with cardiopulmonary bypass and open heart operation.

Compstatin Inhibits Complement and Cellular Activation in Whole Blood in Two Models of Extracorporeal Circulation

Recently, a C3-binding cyclic synthetic peptide (Compstatin) has been identified that binds to complement component C3 and inhibits complement activation. Here we have examined the influence of Compstatin on complement activation and its indirect effects on cellular responses in whole blood in two models for extracorporeal circulation. Compstatin effectively inhibited the generation of C3a and sC5b-9 and the binding of C3/ C3 fragments to the polymer surface. As a result of the inhibition of complement activation, the activation of polymorphonuclear leukocytes (PMNs; as assessed by the expression of CD11b) and the binding of these cells (CD16+) to the polymer surface were almost completely lost. In contrast, blood cell counts were not affected. Using surface plasmon resonance technology, we have confirmed that Compstatin exerts its inhibitory effect on complement activation by binding to native C3. These data show that complement activation, leading to activation and binding of PMNs to the biomaterial surface, can be abolished by the addition of Compstatin. The properties of Compstatin make Compstatin a promising drug for use in extracorporeal circuits to avoid bioincompatibility reactions, eg, during cardiopulmonary bypass, but also a favorable precursor peptide for the development of an anticomplement drug for oral use.

© 1998 by The American Society of Hematology.

Compstatin Inhibits Complement and Cellular Activation in Whole Blood in Two Models of Extracorporeal Circulation

Recently, a C3-binding cyclic synthetic peptide (Compstatin) has been identified that binds to complement component C3 and inhibits complement activation. Here we have examined the influence of Compstatin on complement activation and its indirect effects on cellular responses in whole blood in two models for extracorporeal circulation. Compstatin effectively inhibited the generation of C3a and sC5b-9 and the binding of C3/ C3 fragments to the polymer surface. As a result of the inhibition of complement activation, the activation of polymorphonuclear leukocytes (PMNs; as assessed by the expression of CD11b) and the binding of these cells (CD16+) to the polymer surface were almost completely lost. In contrast, blood cell counts were not affected. Using surface plasmon resonance technology, we have confirmed that Compstatin exerts its inhibitory effect on complement activation by binding to native C3. These data show that complement activation, leading to activation and binding of PMNs to the biomaterial surface, can be abolished by the addition of Compstatin. The properties of Compstatin make Compstatin a promising drug for use in extracorporeal circuits to avoid bioincompatibility reactions, eg, during cardiopulmonary bypass, but also a favorable precursor peptide for the development of an anticomplement drug for oral use.

© 1998 by The American Society of Hematology.

Heparinless cardiopulmonary bypass with active-site blocked factor IXa: a preliminary study on the dog

OBJECTIVE

Cardiopulmonary bypass is a potent stimulus for activation of procoagulant pathways. Heparin, the traditional antithrombotic agent, however, is often associated with increased perioperative blood loss because of its multiple sites of action in the coagulation cascade and its antiplatelet and profibrinolytic effects. Furthermore, heparin-mediated immunologic reactions (that is, heparin-induced thrombocytopenia) may contraindicate its use. Cardiopulmonary bypass with a selective factor IXa inhibitor was tested to see whether it could effectively limit bypass circuit/intravascular space thrombosis while decreasing extravascular bleeding, thereby providing an alternative anticoagulant strategy when heparin may not be safely administered.

METHODS

Active site-blocked factor IXa, a competitive inhibitor of the assembly of factor IXa into the factor X activation complex, was prepared by modification of the enzyme's active site by the use of dansyl glutamic acid-glycine-arginine-chlormethylketone. Twenty mongrel dogs (five were given standard heparin/protamine; 15 were given activated site-blocked factor IXa doses ranging from 300 to 600 microg/kg) underwent 1 hour of hypothermic cardiopulmonary bypass, and blood loss was monitored for 3 hours after the procedure.

RESULTS

Use of activated site-blocked factor IXa as an anticoagulant in cardiopulmonary bypass limited fibrin deposition within the extracorporeal circuit as assessed by scanning electron microscopy, comparable with the antithrombotic effect seen with heparin. In contrast to heparin, effective antithrombotic doses of activated site-blocked factor IXa significantly diminished blood loss in the thoracic cavity and in an abdominal incisional bleeding model.

CONCLUSION

These initial studies on the dog suggest that administration of activated site-blocked factor IXa may be an effective alternative anticoagulant strategy in cardiopulmonary bypass when heparin is contraindicated, affording inhibition of intravascular/extracorporeal circuit thrombosis with enhanced hemostasis in the surgical wound.

Hemostatic-endothelial interactions: a potential anticoagulant role of the endothelium in the pulmonary circulation during cardiac surgery

The use of extracorporeal circulation during cardiopulmonary bypass (CPB) procedures is associated with significant morbidity and mortality. Exposure of blood to the foreign surface of the extracorporeal circuit results in activation of complement, kinin, fibrinolytic and coagulation systems as well as cellular mediators of inflammation. Without the use of anticoagulants, the extracorporeal circuit would clot; high-dose heparin prevents coagulation, but activation of the coagulation system and consequent thrombin generation still occur. During CPB, the lungs are effectively removed from the circulation, and, hence, heparinized blood remains static within the pulmonary vasculature for this period. It was postulated that under these conditions, the hemostatic system may become activated and could contribute to pulmonary dysfunction in some patients after CPB. However, it appears that during CPB interactions among heparin, the hemostatic system, and the endothelium may exert a protective effect, at least against activation of the tissue factor coagulation pathway. In this article, the effect of CPB on the coagulation system, with particular reference to changes in coagulation proteins occurring in the pulmonary vasculature, are reviewed.

Nafamostat mesilate reduces blood-foreign surface reactions similar to biocompatible materials

BACKGROUND

Nafamostat mesilate (FUT-175) is a synthetic serine protease inhibitor that inactivates coagulation, fibrinolysis, and platelet aggregation. Nafamostat mesilate may suppress the blood-foreign surface reaction similar to biocompatible materials by blocking factor XIIa.

METHODS

We performed an in vitro study of cardiopulmonary bypass (CPB) with fresh human blood among the following three groups: standard CPB sets (C), biocompatible CPB sets (B), and standard CPB sets with FUT-175 (10 mg/L) (F). A clinical study using these same CPB groups also was performed in 45 patients undergoing aortocoronary bypass operations (15 patients each). We injected FUT-175 at 40 mg/h during CPB.

RESULTS

In the in vitro study, both groups B and F showed significantly lower levels of coagulation factors, thrombin-antithrombin III complex, fibrinopeptide A, beta-thromboglobulin, complement C3a, granulocyte elastase, and free hemoglobin than group C at the conclusion of the study. Thrombin-antithrombin III complex and free hemoglobin in group F also were lower than in group B. The platelet count remained at a higher level in group F than in the other groups. Separation of bradykinin was suppressed most significantly in group F. In the clinical study, group F also showed significantly lower levels of alpha 2-plasmin inhibitor plasmin complex and C3a than both groups C and B. There were minimal levels of free hemoglobin in group F.

CONCLUSIONS

Nafamostat mesilate may contribute major beneficial effects toward conservation of blood during CPB and prevention of coagulopathy after CPB.