Inhibition of various immunological reactions in vivo by a new synthetic complement inhibitor

Classical Complement Pathway Inhibition in a "Human-On-A-Chip" Model of Autoimmune Demyelinating Neuropathies

Chronic autoimmune demyelinating neuropathies are a group of rare neuromuscular disorders with complex, poorly characterized etiology. Here we describe a phenotypic, human-on-a-chip (HoaC) electrical conduction model of two rare autoimmune demyelinating neuropathies, chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN), and explore the efficacy of TNT005, a monoclonal antibody inhibitor of the classical complement pathway. Patient sera was shown to contain anti-GM1 IgM and IgG antibodies capable of binding to human primary Schwann cells and induced pluripotent stem cell derived motoneurons. Patient autoantibody binding was sufficient to activate the classical complement pathway resulting in detection of C3b and C5b-9 deposits. A HoaC model, using a microelectrode array with directed axonal outgrowth over the electrodes treated with patient sera, exhibited reductions in motoneuron action potential frequency and conduction velocity. TNT005 rescued the serum-induced complement deposition and functional deficits while treatment with an isotype control antibody had no rescue effect. These data indicate that complement activation by CIDP and MMN patient serum is sufficient to mimic neurophysiological features of each disease and that complement inhibition with TNT005 was sufficient to rescue these pathological effects and provide efficacy data included in an investigational new drug application, demonstrating the model's translational potential.

Therapeutically Targeting Platelet-Derived Growth Factor-Mediated Signaling Underlying the Pathogenesis of Subarachnoid Hemorrhage-Related Vasospasm

INTRODUCTION

Vasospasm accounts for a large fraction of the morbidity and mortality burden in patients sustaining subarachnoid hemorrhage (SAH). Platelet-derived growth factor (PDGF)-β levels rise following SAH and correlate with incidence and severity of vasospasm.

METHODS

The literature was reviewed for studies investigating the role of PDGF in the pathogenesis of SAH-related vasospasm and efficacy of pharmacological interventions targeting the PDGF pathway in ameliorating the same and improving clinical outcomes.

RESULTS

Release of blood under high pressure into the subarachnoid space activates the complement cascade, which results in release of PDGF. Abluminal contact of blood with cerebral vessels increases their contractile response to PDGF-β and thrombin, with the latter upregulating PDGF-β receptors and augmenting effects of PDGF-β. PDGF-β figures prominently in the early and late phases of post-SAH vasospasm. PDGF-β binding to the PDGF receptor-β results in receptor tyrosine kinase domain activation and consequent stimulation of intracellular signaling pathways, including p38 mitogen-activated protein kinase, phosphatidylinositol-3-kinase, Rho-associated protein kinase, and extracellular regulated kinase 1 and 2. Consequent increases in intracellular calcium and increased expression of genes mediating cellular growth and proliferation mediate PDGF-induced augmentation of vascular smooth muscle cell contractility, hypertrophy, and proliferation.

CONCLUSION

Treatments with statins, serine protease inhibitors, and small molecular pathway inhibitors have demonstrated varying degrees of efficacy in prevention of cerebral vasospasm, which is improved with earlier institution.

Anticomplement therapy

The complement system is an important part of innate immunity; however, as with other parts of the immune system, the complement system can become pathologically activated and create or worsen disease. Anticomplement reagents have been studied for several years, but only recently have they emerged as a viable therapeutic tool. Here, we describe the role of the complement system in a wide array of diseases, as well as the use of anticomplement therapy as treatment for these diseases in animal models and in human clinical trials. Specifically, we will discuss the role of anticomplement therapy in paroxysmal nocturnal hemoglobinuria, glomerulonephritis, and heart disease, including coronary artery disease, myocardial infarction, and coronary revascularization procedures such as percutaneous coronary angioplasty and coronary artery bypass graft surgery.

Nafamostat Attenuated the Impairment of Fibrinolysis in Animal Sepsis Model by Suppressing the Increase of Plasminogen Activator Inhibitor Type 1

BACKGROUND

In endotoxemia, plasminogen activator inhibitor-1 (PAI-1) increases and develops clinical symptoms by suppressing fibrinolysis. We analyzed therapeutic advantage of nafamostat, a broad-range protease inhibitor, on fibrinolysis in an animal sepsis model.

METHODS

Male Wister rats infused with lipopolysaccharide (LPS) (50 mg/kg) alone or together with nafamostat (0.1 mg/kg/hr) for 4 hours were analyzed.

RESULTS

Plasma PAI-1 (4.2: 4.0-5.0 ng/mL, median and interquartile range) increased after LPS infusion (3700: 3400-4000), which was attenuated by nafamostat (2300: 2100-2600, p < 0.05). Fibrin(ogen) degradation products after LPS injection (173: 152-182 microg/mL) were further elevated by nafamostat (205: 205-228, p < 0.05), Nafamostat attenuated polymorphonuclear neutrophils infiltration in the liver, and tended to suppress plasma tumor necrosis factor-alpha levels. Nafamostat did not affect thrombin generation, platelet count, markers of liver and kidney function, and overall mortality.

CONCLUSIONS

Nafamostat appeared to improve impaired fibrinolysis by suppressing the increase of PAI-1 in plasma, though it did not largely improve clinical parameters.

Potent pruritogenic action of tryptase mediated by PAR-2 receptor and its involvement in anti-pruritic effect of nafamostat mesilate in mice

The pruritogenic potency of tryptase and its involvement in anti-pruritic effect of intravenous nafamostat mesilate (NFM) were studied in mice. An intradermal injection of tryptase (0.05-1 ng/site) elicited scratching in ICR mice, while chymase was without effects at doses of 0.05-50 ng/site. The dose-response curve of tryptase action was bell-shaped and the effect peaked at 0.1 ng/site (approximately 0.7 fmol/site). NFM (10 mg/kg) inhibited scratching induced by tryptase but not by histamine and serotonin. NFM (1-10 mg/kg) produced the dose-dependent inhibition of scratching induced by intradermal compound 48/80 (10 microg/site). The inhibition by NFM (10 mg/kg) was abolished in mast cell-deficient (WBB6F1 W/W(V)) mice, but not in wild-type (WBB6F1 +/+) mice. NFM (10 mg/kg) suppressed tryptase activity in the mouse skin. Proteinase-activated receptor-2 (PAR-2) neutralizing antibody (0.1 and 1 microg/site) and the PAR-2 antagonist FSLLRY (10 and 100 microg/site) inhibited scratching induced by tryptase (0.1 ng/site) and compound 48/80 (10 microg/site). These results suggest that mast cell tryptase elicits itch through PAR-2 receptor and that NFM inhibits itch-associated responses mainly through the inhibition of mast cell tryptase.

Prevention of complement-mediated immune hemolysis by a small molecule compound

Complement sensitization of red blood cells (RBCs) can result in transfusion reactions and hemolytic anemias. We hypothesized that manipulating the complement system using small organic molecules might prevent RBC destruction, thereby prolonging RBC survival in patients. Using a simple, rapid, large-scale hemolytic assay, we screened a 10,000 compound library, enriched in anti-inflammatory compounds at a final concentration of 25 microM, and identified a 549Da compound (C(34)H(24)N(6)O(2)) with a symmetrical structure containing two benzimidazole rings that, as compared to a known anti-complement molecule FUT-175, was more effective in reducing hemolysis by the classical pathway and had comparable anti-hemolytic activity against the alternative pathway. Furthermore, in a xenotransfusion mouse model, treatment of mice with 1.2mg/kg of the compound significantly prolonged the survival of transfused RBCs, reducing C3 deposition, but not the deposition of control IgG or IgM, for the first hour post-transfusion. These data suggest that further studies are warranted to determine if this compound has usefulness in a transfusion setting.

Excellent long-term outcome of ABO-incompatible living donor kidney transplantation in Japan

Owing to the severe shortage of cadaveric grafts in Japan, we have performed ABO-incompatible living donor kidney transplantation since 1989. This study assessed short- and long-term outcomes in 441 patients who received ABO-incompatible living donor kidney transplants between January 1989 and December 2001. We compared our results with historical data from 1055 recipients of living kidney transplantation. Overall patient survival rates 1, 3, 5, 7, and 9 years after ABO-incompatible transplantation were 93%, 89%, 87%, 85%, and 84%, respectively. Corresponding overall graft survival rates were 84%, 80%, 71%, 65%, and 59%. After ABO-incompatible transplantation, graft survival rates were significantly higher in patients 29 years or younger than in those 30 years or older and in patients who received anticoagulation therapy than in those who did not receive such therapy. There were no significant differences between A-incompatible and B-incompatible recipients with respect to clinical outcomes. The graft survival rate at 1 year in the historical controls was slightly but not significantly higher than that in our recipients of ABO-incompatible transplants. We conclude that long-term outcome in recipients of ABO-incompatible living kidneys is excellent. Transplantation of ABO-incompatible kidneys from living donors is a radical, but effective treatment for end-stage renal disease.

Elevated kallikrein activity in plasma from stable liver transplant recipients

Extensive in vitro conversion of complement components C3 and C4 has been observed in EDTA plasma obtained from a number of stable orthotopic liver transplant recipients (LTR) [Clin. Chem. 45 (1999) 1190]. Consequently, we designed a chromogenic substrate (Ac-Ala-Gly-Leu-Thr-Arg-p-nitroanilide, AGLTR-pNA), based on the C1s cleavage site in complement component C4, in an attempt to identify the plasma proteinase(s) that cleaves C4 in vitro. Average peptidase activity in EDTA plasma obtained from stable LTR (n = 16) was significantly higher (P<0.01) than that in plasma from healthy non-transplant donors (n = 16). This peptidase activity was also detected using commercial substrates designed for specific coagulation proteinases. The plasma proteinase was not inhibited by hirudin, a thrombin inhibitor, but was inhibited by the plasma kallikrein inhibitor D-Phe-Phe-Arg-chloromethylketone, which fails to inhibit C1s. We concluded that the peptidase detected inLTR plasma, using chromogenic substrates including AGLTR-pNA, was plasma kallikrein. Western blot analysis confirmed the presence of kallikrein-alpha-2-macroglobulin complexes (alpha2M) in LTR plasmas. We also demonstrated that kallikrein was not the proteinase responsible for the in vitro cleavage of C4. Elevation of the plasma peptidase activity correlated significantly with recurrent hepatitis C virus (HCV) infection in these liver recipients with a P value <0.02. Significant correlation was not observed between complement activation (i.e. the C4a levels) and recurrent HCV infection (P>0.15); however, C4a levels did correlate with rejection (P<0.02). These results suggest that elevation in plasma peptidase activity and activation of complement do signal different pathological events in LTR, events that appear related to HCV-induced infection and immune tissue injury, respectively.

Broad-spectrum and selective serine protease inhibitors prevent expression of platelet-derived growth factor-BB and cerebral vasospasm after subarachnoid hemorrhage: vasospasm caused by cisternal injection of recombinant platelet-derived growth factor-BB

BACKGROUND AND PURPOSE

Plasma serine protease cascade, including the complement system and thrombin, is activated in the subarachnoid space during the acute phase after subarachnoid hemorrhage (SAH). To examine the effect of protease cascade-based inflammation and subsequent vascular repair in the development of cerebral vasospasm, we examined the effect of 2 synthetic serine protease inhibitors-FUT-175, an inhibitor of thrombin and the complement system, and argatroban, a selective inhibitor of thrombin-on the development of cerebral vasospasm in a rabbit SAH model.

METHODS

One hundred Japanese White male rabbits were used in the study. The SAH was simulated by a single injection of autologous arterial blood into the cisterna magna. To evaluate the development of cerebral vasospasm, the caliber of the basilar artery was measured on x-ray film before and at 2 days after SAH. Nine groups of rabbits (n=6 each) were treated with continuous intravenous injection of FUT-175 (2.5, 5, 10, or 20 mg/d), argatroban (1.25, 2.5, or 5 mg/d), or the same amount of saline (vehicle) for 48 hours, starting 40 minutes after SAH. Two days after SAH, the expression of homodimer of platelet-derived growth factor-BB (PDGF-BB) in the basilar artery was examined with immunohistochemical techniques. In 20 normal rabbits, 5 microg of recombinant PDGF-BB or vehicle was injected into the cisterna magna, and the basilar arteries were examined on angiograms for 48 hours.

RESULTS

Significant differences were observed in the caliber of the basilar arteries between the vehicle group and the groups with the 3 larger doses of FUT-175 (vehicle, 52+/-5.0%; 5 mg, 79+/-5.7%; 10 mg, 80+/-2.5%; 20 mg, 80+/-3.7%) and between the vehicle group and the groups with the 2 larger doses of argatroban (vehicle, 52+/-6.4%; 2.5 mg, 81+/-9.0%; 5 mg, 85+/-4.1%) (P<0.05). In the histological examination, administration of effective doses of FUT-175 or argatroban suppressed the expression of PDGF-BB in the endothelial and medial smooth muscle cell layers. Exogenous PDGF-BB caused delayed and prolonged vasoconstriction on normal basilar arteries.

CONCLUSIONS

Activation of the serine protease cascade and/or thrombin after SAH was demonstrated to play an essential role in the development of cerebral vasospasm. The expression of PDGF-BB-like protein in the arterial walls correlated with the development of cerebral vasospasm. Elevated PDGF-BB level in the subarachnoid space was found to induce delayed and chronic vasoconstriction.

The Arthus reaction in rodents: species-specific requirement of complement

We induced reverse passive Arthus (RPA) reactions in the skin of rodents and found that the contribution of complement to immune complex-mediated inflammation is species specific. Complement was found to be necessary in rats and guinea pigs but not in C57BL/6J mice. In rats, within 4 h after initiation of an RPA reaction, serum alternative pathway hemolytic titers decreased significantly below basal levels, whereas classical pathway titers were unchanged. Thus the dermal reaction proceeds coincident with systemic activation of complement. The serine protease inhibitor BCX 1470, which blocks the esterolytic and hemolytic activities of the complement enzymes Cls and factor D in vitro, also blocked development of RPA-induced edema in the rat. These data support the proposal that complement-mediated processes are of major importance in the Arthus reaction in rats and guinea pigs, and suggest that BCX 1470 will be useful as an anti-inflammatory agent in diseases where complement activation is known to be detrimental.

Possible Mechanism for in Vitro Complement Activation in Blood and Plasma Samples: Futhan/EDTA Controls in Vitro Complement Activation

Background: Ongoing in vitro complement (C) activation in citrate or EDTA plasma has prevented an accurate analysis of C-activation products generated in vivo. The aim of this study was to characterize handling and storage conditions required to prevent in vitro C activation in blood and plasma samples collected with Futhan/EDTA.

Methods: BiotrakTM RIAs were used to quantitatively measure C3a and C4a in blood and/or plasma samples from healthy individuals (controls) and from liver transplant patients. Blood samples were routinely drawn into either EDTA (1 g/L) tubes or into tubes containing both EDTA (1 g/L) and Futhan (0.1 g/L) and immediately centrifuged at 2000g for 15 min at 4 °C.

Results: In controls, C4a, but not C3a, in fresh samples (time 0) was higher in EDTA plasma than in Futhan/EDTA plasma (n = 20; P = 0.002). Futhan/EDTA prevented C3a and C4a generation in blood and plasma samples held at room temperature (22–23 °C) for 1 h and in plasma held for 24 h at 4 °C or −70 °C. The mean C3a concentration (1.76 mg/L; n = 19) at time 0 in EDTA plasma samples from liver transplant patients was significantly higher than for controls (0.34 mg/L; n = 11). In these patients, the mean C3a in EDTA samples increased to 13.8 mg/L after 60 min at room temperature, but there was no change in the C3a concentration of an EDTA plasma from a control. In the patients, C3a concentrations were lower in Futhan/EDTA plasma than in EDTA at time 0 and after 60 min at room temperature (1.40 and 2.02 mg/L, respectively). The mean patient C4a was 4.02 mg/L in EDTA plasma at time 0 vs 0.24 mg/L for controls; it increased to 16.9 mg/L after 60 min at room temperature compared with 0.76 mg/L for controls. The mean patient C4a was 0.83 mg/L in Futhan/EDTA plasma at time 0 vs 0.1 mg/L for controls. Neither patient nor control C4a concentrations increased vs time in Futhan/EDTA.

Conclusion: The combination of Futhan (0.1 g/L) and EDTA (1 g/L) eliminates in vitro C activation.

Prevention of neointimal formation by a serine protease inhibitor, FUT-175, after carotid balloon injury in rats

BACKGROUND AND PURPOSE

In vivo and vitro studies revealed the activation of thrombin and the complement system in vascular lesion formation during the process of atherosclerosis, along with pathological proliferation of smooth muscle cells. We examined the effect of the synthetic serine protease inhibitor FUT-175 (developed as a potent inhibitor of thrombin and the complement system) on vascular lesions using balloon dilatation-induced neointimal formation in the carotid artery of rats.

METHODS

Sprague-Dawley (SD) rats underwent balloon dilatation injury of the left carotid artery to induce neointimal formation. Three groups of these rats (n=8, each) were treated with daily intraperitoneal injections of 1 of the following doses of FUT-175: 0.5, 1.0, or 2.0 mg/d in 1 mL of saline for 7 consecutive days. The control group (n=8) was similarly treated with 1 mL of saline for 7 days. The injections were started immediately after balloon injury. Two weeks after the injury, the left carotid arteries were perfusion-fixed, and the areas of the neointimal and medial layer were analyzed under a microscope.

RESULTS

A morphometric analysis revealed that there were significant differences in the intima-media ratio between the 4 groups treated with vehicle (saline) or a low, medium, or high dose of FUT-175 (1.45+/-0.11, 1.08+/-0.06, 0.71+/-0.04, or 0.32+/-0.04, respectively). This suppression was achieved in a dose-dependent manner by the administration of FUT-175 after balloon injury. In the histological study, it was demonstrated that FUT-175 suppresses the production of platelet-derived growth factor (PDGF)-BB in the neointima and the medial smooth muscle cell layer.

CONCLUSIONS

After balloon injury activated proteases that were inhibited by FUT-175 were demonstrated to have an essential role in the development of the pathological thickening of the arterial wall.

A blockade of complement activation prevents rapid intestinal ischaemia-reperfusion injury by modulating mucosal mast cell degranulation in rats

We attempted to define the putative role of complement activation in association with mucosal mast cell (MMC) degranulation in the pathogenesis of rapid intestinal ischaemia-reperfusion (I/R) injury. We prepared complement activity-depleted rats by the administration of the anti-complement agent K-76COOH and the serine-protease inhibitor FUT-175. Autoperfused segments of the jejunum were exposed to 60 min of ischaemia, followed by reperfusion for various time periods, and the epithelial permeability was assessed by the 51Cr-EDTA clearance rate. The number of MMC was immunohistochemically assessed. In control rats, the maximal increase in mucosal permeability was achieved by 30-45 min of reperfusion. This increase was significantly attenuated by the administration of either K-76COONa alone or in combination with FUT-175. In contrast, the administration of carboxypeptidase inhibitor (CPI), which prevents the inactivation of complement-derived anaphylatoxins such as C5a, significantly enhanced the increase in I/R-induced mucosal permeability. These findings were confirmed morphologically by light microscopy and scanning electron microscopy. In addition, the I/R-induced mucosal injury was accompanied by a marked decrease in the number of MMC, and administration of K-76COOH significantly inhibited this change. These results indicate that complement activation and the generation of complement-derived anaphylatoxins are key events in I/R-induced mucosal injury. It is likely that intestinal I/R-induced mucosal injury may be partially mediated by MMC activation associated with the complement activation.

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.

Animal models for complement deficiencies

The complement system plays a key role in host defense and in the development of autoimmunity. Three types of animal models of complement-mediated disease have traditionally been used: they involve normal animals, animals with spontaneously arising genetic deficiency, and animals treated with complement-inactivating agents. All of these approaches have had partial success in our attempts to understand complement mechanisms. Most animal models of genetic deficiency have been studied relatively little, as the availability of such animals is limited. C4, C2, and partial C3 deficiency in the guinea pig are well characterized, although only C4 deficiency in the guinea pig has been exclusively studied. C3 deficiency in the dog and C6 deficiency in the rabbit are well described, although studies are limited in number. C6 deficiency in the rat has been described recently and C5 deficiency in inbred mice strains has been studied fairly extensively. Factor H deficiency in the Yorkshire pig has also been described. Relatively few agents that inhibit complement are in use. Most widely used in animal studies is cobra venom factor. This inactivates the alternative complement pathway in the fluid phase and thereby depletes complement protein levels. The antigenicity of this protein, purified from the venom of cobras, limits its duration of use in most animal models. Complement-inhibiting agents are rare and, as yet, not widely used. We recently described the use of intravenous immune globulin for inhibiting complement in animal studies and present data on its use in animals, including discordant xenograft rejection, and its potential use in human disease. New developments in molecular biology provide the potential for a vast new array of deficiency models. A limited number of laboratories are actively engaged in the production of animals with inactivated genes. For example, gene knockout mice with no C3, and with no factor B, have been generated. Several complement control proteins have been prepared by genetic molecular biological techniques. Most promising among these is CR1, which limits complement damage in several animal models. Transgenic animals, which complement regulatory proteins expressed on their cells, have been prepared. As complement control proteins tend to be more efficient at regulating complement of the same species type as the regulatory protein, these animals may be useful in such areas as xenograft transplantation. The various animal models are reviewed and their potential application to understanding of human disease is emphasized.

Effects of protease inhibitor and immunosuppressant on cerebral vasospasm after subarachnoid hemorrhage in rabbits

The possible role of the immune-defense system in the development of cerebral vasospasm after subarachnoid hemorrhage (SAH) was investigated in rabbits. We used a synthetic serine protease inhibitor, gabexate mesilate (GM), a glucocorticoid, betamethasone sodium phosphate (B-P), and an immunosuppressant, ciclosporin (Cyclosporin A, CYA), to prevent cerebral vasospasm. These agents were administered intra-venously every 12 hours for three injections, starting 20 minutes after SAH. In the group treated with GM, B-P, or CYA, there were no statistically significant differences in arterial calibers between treated and untreated controls on day 2. The synthetic serine protease inhibitor, FUT-175 has been reported to prevent cerebral vasospasm when the treatment is started 20 minutes after SAH in rabbits [38]. In rabbits treated with FUT-175 at different starting times from 3 to 6 hours, reductions in arterial caliber on day 2 were significantly prevented in each group. The contrasting effects of the two serine protease inhibitors, GM and FUT-175, are discussed.

Cerebral vasospasm caused by cisternal injection of polystyrene latex beads in rabbits is inhibited by a serine protease inhibitor

During subarachnoid hemorrhage (SAH), coagulated blood in the subarachnoid space may be regarded as foreign by the immune system. To investigate how cerebral arteries are affected by activation of the host immune system, foreign body, polystyrene latex beads were injected into the cerebrospinal fluid (CSF) space of rabbits, and the caliber changes of the basilar arteries were studied for 7 days by angiography. Prolonged arterial narrowing peaking on day 2 was observed after cisternal injection of the beads. The increase in peak narrowing correlated with an increase in the number of beads injected. The course of the change in vessel caliber over 7 days was similar to that seen in cerebral vasospasm caused by SAH. Also investigated was the preventive effect of the synthetic serine protease inhibitor, FUT-175 on the arterial narrowing caused by the cisternal injection of the latex beads. The administration of FUT-175 significantly prevented latex beads-induced vasospasm (p < 0.01). The possible role of a non-specific immune response is discussed, and also the role of the serine protease cascades in the development of cerebral vasospasm.

Therapeutic regulation of the complement system in acute injury states

The study of the intrinsic regulation of complement has uncovered a broad array of proteins with differing specificities and physicochemical properties. This will allow application of these proteins, native or modified, to the problem of controlling inflammation. The availability of sCR1, as the first such agent, has permitted further definition of those adverse clinical situations which are complement-dependent. The use of sCR1 as a drug might be anticipated in situations of thermal injury, ARDS, septic shock, and ischemia/reperfusion injury, such as myocardial infarction after thrombolytic therapy. sCR1 may also serve as the tool with which to unravel and possibly treat xenograft rejection. It can be anticipated that other such specific inhibitors will become available.

Protective effects of FUT-175 on acute massive hepatic necrosis induced in mice following endotoxin injection and immunization with liver proteins

Experimental autoimmune hepatitis was induced in C57BL/6 mice by immunization with syngeneic liver protein and adjuvant. Hepatitis was characterized by marked cellular infiltrates, but hepatic necrosis was mild to moderate. A small dose of endotoxin (25 micrograms/mouse) produced lethal hepatitis with elevation of serum transaminase levels in these mice. The endotoxin-induced reactions were completely inhibited by i.p. administration of FUT-175 (5 mg/kg), a synthetic protease inhibitor, 1 h before the endotoxin injection. In vitro experiments showed that two-thirds of the inflammatory infiltrates were monocyte/macrophages. Cytotoxicity against syngeneic hepatocytes was significantly increased by the addition of endotoxin (25 micrograms/ml), but the same dose of endotoxin alone had no effect on the viability of hepatocytes. The endotoxin-induced increase in cytotoxicity was prominent in the glass-dish adherent (monocyte/macrophage enriched) fraction and was also demonstrated after depletion of T-cells. However, elevated cytotoxicity did not occur when FUT-175 (> 1 x 10(-7) M) was present throughout the assay period. These results seem to indicate that the hepatotoxic effects of endotoxin are mediated, at least in part, by monocytes or macrophages infiltrating the liver following immunization of liver proteins. Our results also suggest that FUT-175 has protective effects against endotoxin-induced hepatotoxic reactions.

Preventive effect of synthetic serine protease inhibitor, FUT-175, on cerebral vasospasm in rabbits

The effect of the synthetic multiserine protease inhibitor FUT-175 on cerebral vasospasm after subarachnoid hemorrhage (SAH) was investigated in rabbits. The SAH in rabbits was simulated by a single injection of autologous arterial blood into the cisterna magna, and, for 7 days, the caliber of each basilar artery was examined several times via angiogram. In 10 SAH rabbits, the peak of the arterial narrowing was observed on Day 2. In this model, the effect of intravenous administrations of FUT-175 was examined. Twenty-seven SAH rabbits were randomly divided into three groups, and 3 doses of 1, 2, or 3 mg of FUT-175 were administered intravenously. Angiographic arterial narrowing on Day 2 in nontreated SAH rabbits (Control) was 35% compared with 21, 5, and 14% in rabbits treated with a total of 3 (Group A; n = 9), 6 (Group B; n = 13), and 9 mg (Group C; n = 5) of FUT-175, respectively. There were statistically significant differences in the arterial calibers between Group A and the Control on Days 1 and 2, between Group B and the Control from days 1 to 4, and between Group C and the Control from days 1 to 4. In three other rabbits, after vasospasm reached its maximum on Day 2, no vasodilatory effect was observed when a total of 6 mg of FUT-175 was administered intravenously. The results indicate that the inhibition of the plasma serine protease cascades at an early stage of SAH prevents the development of cerebral vasospasm.(ABSTRACT TRUNCATED AT 250 WORDS)

Therapeutic trial of cerebral vasospasm with the serine protease inhibitor, FUT-175, administered in the acute stage after subarachnoid hemorrhage

The therapeutic effect of the synthetic serine protease inhibitor, FUT-175, on cerebral vasospasm after subarachnoid hemorrhage (SAH) was investigated. Twenty-three patients with severe SAH who were admitted between February and July 1990 and who underwent surgery within 48 hours of the initial aneurysmal rupture were treated with an intravenous administration of FUT-175 soon after the operation. The patients were divided randomly into three groups, each receiving a different dose of FUT-175 (Group A, 20 mg every 12 hours for 4 days; Group B, 20 mg every 6 hours for 4 days, Group C, 40 mg every 6 hours for 4 days). The results were compared with another group of twenty-two patients with severe SAH who were admitted before February 1990 and received equivalent treatment, except they were not treated with FUT-175. In 64% of all the patients treated with FUT-175 (Groups A, B, C), and in 85% of those treated with higher doses of FUT-175 (Groups B and C), there was no spasm or only mild vasospasm on the angiogram. The incidence of a delayed ischemic neurological deficit significantly decreased from 55% in the control group to 13% in all patients treated with FUT-175 and to 7% in the patients treated with higher doses (P less than 0.05). The incidence of cerebral infarction resulting from vasospasm significantly decreased from 43% in the control group to 9% in patients treated with FUT-175. In the patients treated with higher doses of FUT-175 (Groups B and C), none developed cerebral infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of three novel thromboxane A2 receptor antagonists (S-1452, AA-2414 and ONO-3708) on the increase in pulmonary pressure caused by Forssman anaphylaxis in guinea-pigs

The effects were studied of three novel thromboxane A2 (TXA2) receptor antagonists (S-1452, AA-2414 and ONO-3708) on the increase in pulmonary pressure caused by Forssman anaphylaxis in guinea-pigs. Three TXA2 antagonists at doses of between 1 and 10 mg/kg administered orally 1 h before the challenge clearly inhibited the pulmonary pressure increase. At a dose of 10 mg/kg, all three antagonists inhibited the pulmonary pressure increase caused by leukotriene D4 (LTD4) and U-46619, but not that caused by histamine. The decrease in peripheral platelet counts caused by Forssman anaphylaxis was also clearly inhibited by the three TXA2 antagonists. However, the decreased peripheral leukocyte counts were unaffected by the three agents. The decrease in serum complement activity (CH50) was inhibited by S-1452 and AA-2414 at a dose of 10 mg/kg. In bronchoalveolar lavage fluid (BALF), significant increases in eosinophils and neutrophils were observed after Forssman anaphylaxis. Three TXA2 antagonists at a dose of 10 mg/kg (except for AA-2414 on eosinophils) did not affect the changes of leukocyte counts in BALF. Moreover, increases in the TXB2 and 6-keto-PGF1 alpha levels of the BALF brought about by Forssman anaphylaxis were unaffected by the three TXA2 receptor antagonists. Histamine and LTD4 were not changed in the BALF after Forssman anaphylaxis. These results indicate the efficacy of TXA2 receptor antagonists on the increase in pulmonary pressure caused by Forssman anaphylaxis in guinea-pigs by direct antagonism to released TXA2.

Deleterious effects of complement activation on the lungs during extracorporeal circulation and its inhibition by FUT-175

The purpose of this paper is to review the deleterious effects of complement activation during extracorporeal circulation on the lungs and to discuss the feasibility of FUT-175, a new synthetic protease inhibitor, as a complement activation inhibitor. Complement activation causes leukocyte aggregation and aggregated leukocytes behave as microemboli in the pulmonary vessels. Anaphylatoxins produced by complement activation have potent vasoactive properties and many chemical mediators are also released from leukocytes. FUT-175 might be effective to inhibit complement activation during cardiopulmonary bypass (CPB). Although deleterious effects of CPB on the lungs are multifactorial, we hypothesize that complement activation may play a major role in lung injury during CPB.

Role of thromboxane (Tx) A2 in guinea pig Forssman shock and the effect of OKY-046, Tx A2 synthetase inhibitor

To study the role of thromboxane (Tx) A2 in Forssman systemic shock (FSS) in guinea pig, the effect of (E)-3-[p-(1H-Imidazol-1-ylmethyl)phenyl]-2-propenoic acid hydrochloride (OKY-046), a specific Tx A2 synthetase inhibitor, was studied. OKY-046 administered intravenously clearly prolonged survival time and protected against fatal shock. In shocked animals, definite decreases in serum complement hemolytic activity (CH50), leucocyte counts and platelet counts and an increase in lactate dehydrogenase (LDH) activity were observed. In addition, a significant increase of Tx B2 and incoagulability of blood were observed after shock. Whereas OKY-046 had no effect on the decreases in CH50, platelet counts and leucocyte counts, it inhibited the increase of Tx B2 and increased the amount of 6-keto PG F1 alpha. When Forssman antibody (half a lethal dose) was injected, a diphasic increase in airway resistance was observed. OKY-046 inhibited this diphasic increase in airway resistance. These data suggest a pathophysiological role for Tx A2 in FSS. OKY-046 inhibited the Forssman antibody induced respiratory disorders probably due to the inhibition of Tx A2 synthesis after shock.

Effects of FUT-175, a novel synthetic protease inhibitor, on the development of adjuvant arthritis in rats and some biological reactions dependent on complement activation

1. The effects of FUT-175 on the development of adjuvant arthritis in rats were studied and compared with those of indomethacin. FUT-175 inhibited both primary and secondary paw lesions in the adjuvant arthritic rats when it was administered orally on a daily basis from the day before through 18th day after adjuvant injection. 2. In addition, FUT-175 inhibited the increase in hemolytic complement in adjuvant arthritic rats in a dose-dependent manner. 3. Indomethacin also showed an inhibitory effect on the development of arthritic lesion, but had no effect on the increase in hemolytic complement in the adjuvant arthritis in rats. 4. Furthermore, FUT-175 inhibited the activities of various proteases in vitro, and then strongly inhibited complement-mediated hemolysis via the classical and alternative pathways, while indomethacin had no effect on them. 5. These results suggest that the anti-inflammatory activity of FUT-175 may differ from indomethacin in the mechanisms of action and, at least in part, due to the anti-complement activity.

Inhibitory effects of FUT-175, a new synthetic protease inhibitor, on intravascular hemolysis by human serum in mice

Effects of FUT-175, a new protease inhibitor, on intravascular hemolysis of mouse erythrocytes caused by intravenous injection of human serum was studied in mice. In in vitro experiments, unsensitized erythrocytes obtained from various species of animals were lysed with sera in EGTA-GVB-Mg++. After heat inactivation of sera at 50 degrees C for 30 min, hemolysis in EGTA-GVB-Mg++ was abolished, indicating loss of activity of the alternative complement pathway. FUT-175 inhibited the alternative complement pathway-mediated hemolysis with IC50 values of 1.3 X 10(-7) to 4.0 X 10(-7) M. Intravenous injection of human serum caused intravascular hemolysis of mouse erythrocytes in mice. No remarkable change was observed in the mice that were injected with heat-inactivated (56 degrees C, 30 min) human serum. Intravenous administration of FUT-175 at a dose of 3 or 10 mg/kg inhibited intravascular hemolysis of mouse erythrocytes regardless of whether it was administered before or after injection of human serum. These results indicated that FUT-175 prevents intravascular hemolysis of mouse erythrocytes through the inhibitory effect of both alternative and classical complement pathway.

The anaemia of chronic renal failure: a potentially treatable catabolic phenomenon?

It is proposed that the anaemia of chronic renal failure and the apparent lack of erythropoietin response is a result of increased proteolytic and lysosomal enzyme action on both the red cell and erythropoietin itself. Removal of the sialic acid from the red cell membrane is known to cause sequestration and a shortened cell survival. Similarly removal of sialic acid from the carbohydrate coat of erythropoietin both increases clearance by the liver and renders it susceptible to cleavage into inactive fragments by proteolytic attack. If the hypothesis is correct therapeutic intervention using enzyme inhibitors may offer hope for the amelioration of the anaemia.

Studies on the effects of primary therapy for DIC following circulatory arrest

Comparative studies in early treatment for DIC caused by circulatory arrest were carried out on three groups of dogs during 300 min from the recovery of circulatory arrest: a heparin group, a FOY (gabexate mesilate) group, and a FUT-175 (nafamostat mesilate) group. The parameters employed were platelet count, prothrombin time (PT), activated partial prothrombin time (APTT), fibrinogen, antithrombin-III (AT-III), and fibrin or fibrinogen degradation products (FDP). In the heparin group, there was less of a drop in the platelet count and the level of AT-III than in the control group, but the FDP levels were the same as in the control group. The PT and APTT remained within normal limits in the FOY group and no decrease was observed in either platelet count or AT-III levels. In addition, FDP levels were kept within normal limits. In the FUT-175 group, prolongation of APTT, no decline in the platelet count and AT-III levels, and normal levels of FDP were observed. The results of these experiments indicate the importance of early treatment for DIC. Judging from the parameters, better results were obtained in the FOY and FUT-175 group than in the heparin group.

Pharmacological studies of FUT-175, nafamstat mesilate. I. Inhibition of protease activity in in vitro and in vivo experiments

FUT-175, 6-amidino-2-naphthyl p-guanidinobenzoate dimethanesulfonate (nafamstat mesilate), a novel synthetic protease-inhibiting agent, was studied to determine its in vitro effects against various proteases and other enzymes, as well as to determine its in vivo protease inhibitory effects. FUT-175 was found to inhibit, in an intense, specific and reversible way, the enzyme activities of trypsin, C1r, C1s, thrombin, kallikrein and plasmin with IC50 values of the order of 10(-6)-10(-8) M. FUT-175 also inhibited complement-mediated hemolysis, including both classical and alternative pathways, sites of inhibition being on C1r and C1s as evidenced by the intermediate-cell technique. In animal model reactions in which the complement system is known to be involved as pathogenetic factors, e.g., Forssman shock, Forssman cutaneous vasculitis, zymosan-induced paw edema, endotoxin shock and local Shwartzman reaction, FUT-175 was highly effective in that, for example, intravenous dosing at 3 mg/kg could completely protect guinea pigs from the lethal Forssman shock. FUT-175 was also found to be effective in trypsin-induced shock in mice, in lethality due to thrombin-thrombosis in mice and in kinin formation in the inflammatory process in rats.

Endogenous inhibitors of factor B

proteins which were able to bind noncovalently with mouse factor B were found in cells that are nonsecretors of factor B such as mouse-established monocytic cells and L cells but not in peritoneal resident macrophages. These proteins were isolated from lysates of L cells and separated into four distinct proteins by preparative SDS-polyacrylamide gel electrophoresis, with molecular weights of 25K , 28K , 33K, and 35K . The individual proteins formed a complex with purified mouse factor B at a molecular ratio of 1: 1 and inhibited its hemolytic activity. Proteins 25K and 28K inhibited the hemolytic activity of an activated form of factor B combined with cobra venom factor as well as that of the native form. These inhibitors did not affect the hemolytic activity of the second component of complement in mouse serum. The inhibitory activity of the 25K protein was partially inhibited by antiserum raised against it in rabbits.