The effects of high molecular weight- and low molecular weight-heparins on superoxide ion production and degranulation by human polymorphonuclear leukocytes

Ex vivo observation of granulocyte activity during thrombus formation

Background

The process of thrombus formation is thought to involve interactions between platelets and leukocytes. Leukocyte incorporation into growing thrombi has been well established in vivo, and a number of properties of platelet-leukocyte interactions critical for thrombus formation have been characterized in vitro in thromboinflammatory settings and have clinical relevance. Leukocyte activity can be impaired in distinct hereditary and acquired disorders of immunological nature, among which is Wiskott-Aldrich Syndrome (WAS). However, a more quantitative characterization of leukocyte behavior in thromboinflammatory conditions has been hampered by lack of approaches for its study ex vivo. Here, we aimed to develop an ex vivo model of thromboinflammation, and compared granulocyte behavior of WAS patients and healthy donors.

Results

Thrombus formation in anticoagulated whole blood from healthy volunteers and patients was visualized by fluorescent microscopy in parallel-plate flow chambers with fibrillar collagen type I coverslips. Moving granulocytes were observed in hirudinated or sodium citrate-recalcified blood under low wall shear rate conditions (100 s⁻¹). These cells crawled around thrombi in a step-wise manner with an average velocity of 90–120 nm/s. Pre-incubation of blood with granulocyte priming agents lead to a significant decrease in mean-velocity of the cells and increase in the number of adherent cells. The leukocytes from patients with WAS demonstrated a 1.5-fold lower mean velocity, in line with their impaired actin polymerization. It is noteworthy that in an experimental setting where patients’ platelets were replaced with healthy donor’s platelets the granulocytes’ crawling velocity did not change, thus proving that WASP (WAS protein) deficiency causes disruption of granulocytes’ behavior. Thereby, the observed features of granulocytes crawling are consistent with the neutrophil chemotaxis phenomenon. As most of the crawling granulocytes carried procoagulant platelets teared from thrombi, we propose that the role of granulocytes in thrombus formation is that of platelet scavengers.

Conclusions

We have developed an ex vivo experimental model applicable for observation of granulocyte activity in thrombus formation. Using the proposed setting, we observed a reduction of motility of granulocytes of patients with WAS. We suggest that our ex vivo approach should be useful both for basic and for clinical research.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-022-01238-x.

Pleiotropic effects of heparins: does anticoagulant treatment increase survival in cancer patients?

The association between venous thromboembolism (VTE) and cancer has been recognized for more than 100 years. Numerous studies have been performed to investigate strategies to decrease VTE incidence and to establish whether treating VTE impacts cancer progression and overall survival. Accordingly, it is important to understand the role of the hemostatic system in tumorigenesis and progression, as there is abundant evidence associating it with cell survival and proliferation, tumor angiogenesis, invasion, and dissemination, and metastasis formation. In attempts to further the scientific evidence, several studies examine survival benefits in cancer patients treated with anticoagulant therapy, specifically treatment with vitamin K antagonists, unfractionated heparin, and low-molecular-weight heparin. Several studies and meta-analyses have been conducted with a special focus on brain tumors. However, no definitive conclusions have been obtained, and more well-designed clinical trials are needed.

[Exocytosis of myeloperoxidase from activated neutrophils in the presence of heparin]

Exocytosis of myeloperoxidase (MPO) from activated neutrophils in the presence of the anionic polysaccharide heparin was studied. It was determined that the optimal concentration of heparin (0.1 u/ml), at which there is no additional activation of cells (absence of amplification of exocytosis of lysozyme contained in specific and azurophilic granules). It was found that after preincubation of cells with heparin (0.1 u/ml) the exocytosis of MPO from neutrophils activated by various stimulants (fMLP, PMA, plant lectins CABA and PHA-L) increased compared to that under the action of activators alone. In addition, it was shown that heparin in the range of concentrations 0.1-50 u/ml did not affect on the peroxidase activity of the MPO isolated from leukocytes. Thus, the use of heparin at a concentration of 0.1 u/ml avoids the artifact caused by the "loss" of MPO in a result of its binding to neutrophils, and increases the accuracy of the method of registration the degranulation of azurophilic granules of neutrophils based on determination of the concentration or peroxidase activity of MPO in cell supernatants.

The roles of myeloperoxidase in coronary artery disease and its potential implication in plaque rupture

Atherosclerosis is the main pathophysiological process underlying coronary artery disease (CAD). Acute complications of atherosclerosis, such as myocardial infarction, are caused by the rupture of vulnerable atherosclerotic plaques, which are characterized by thin, highly inflamed, and collagen-poor fibrous caps. Several lines of evidence mechanistically link the heme peroxidase myeloperoxidase (MPO), inflammation as well as acute and chronic manifestations of atherosclerosis. MPO and MPO-derived oxidants have been shown to contribute to the formation of foam cells, endothelial dysfunction and apoptosis, the activation of latent matrix metalloproteinases, and the expression of tissue factor that can promote the development of vulnerable plaque. As such, detection, quantification and imaging of MPO mass and activity have become useful in cardiac risk stratification, both for disease assessment and in the identification of patients at risk of plaque rupture. This review summarizes the current knowledge about the role of MPO in CAD with a focus on its possible roles in plaque rupture and recent advances to quantify and image MPO in plasma and atherosclerotic plaques.

Reactive Oxygen Species: A Key Hallmark of Cardiovascular Disease

Cardiovascular diseases (CVDs) have been the prime cause of mortality worldwide for decades. However, the underlying mechanism of their pathogenesis is not fully clear yet. It has been already established that reactive oxygen species (ROS) play a vital role in the progression of CVDs. ROS are chemically unstable reactive free radicals containing oxygen, normally produced by xanthine oxidase, nicotinamide adenine dinucleotide phosphate oxidase, lipoxygenases, or mitochondria or due to the uncoupling of nitric oxide synthase in vascular cells. When the equilibrium between production of free radicals and antioxidant capacity of human physiology gets altered due to several pathophysiological conditions, oxidative stress is induced, which in turn leads to tissue injury. This review focuses on pathways behind the production of ROS, its involvement in various intracellular signaling cascades leading to several cardiovascular disorders (endothelial dysfunction, ischemia-reperfusion, and atherosclerosis), methods for its detection, and therapeutic strategies for treatment of CVDs targeting the sources of ROS. The information generated by this review aims to provide updated insights into the understanding of the mechanisms behind cardiovascular complications mediated by ROS.

Heparin Interaction with the Primed Polymorphonuclear Leukocyte CD11b Induces Apoptosis and Prevents Cell Activation

Heparin is known to have anti-inflammatory effects, yet the mechanisms are not completely understood. In this study, we tested the hypothesis that heparin has a direct effect on activated polymorphonuclear leukocytes (PMNLs), changing their activation state, and can explain its anti-inflammatory effect. To test our hypothesis, we designed both in vitro and ex vivo studies to elucidate the mechanism by which heparin modulates PMNL functions and therefore the inflammatory response. We specifically tested the hypothesis that priming of PMNLs renders them more susceptible to heparin. Amplified levels of CD11b and increased rate of superoxide release manifested PMNL priming. Increase in cell priming resulted in a dose-dependent increase in heparin binding to PMNLs followed by augmented apoptosis. Blocking antibodies to CD11b inhibited heparin binding and abolished the apoptotic response. Moreover, heparin caused a significant dose-dependent decrease in the rate of superoxide release from PMNLs, which was blunted by blocking antibodies to CD11b. Altogether, this study shows that the interaction of heparin with the PMNL CD11b results in cell apoptosis and explains heparin's anti-inflammatory effects.

Citrate confers less filter-induced complement activation and neutrophil degranulation than heparin when used for anticoagulation during continuous venovenous haemofiltration in critically ill patients

Background

During continuous venovenous haemofiltration (CVVH), regional anticoagulation with citrate may be superior to heparin in terms of biocompatibility, since heparin as opposed to citrate may activate complement (reflected by circulating C5a) and induce neutrophil degranulation in the filter and myeloperoxidase (MPO) release from endothelium.

Methods

No anticoagulation (n = 13), unfractionated heparin (n = 8) and trisodium citrate (n = 17) regimens during CVVH were compared. Blood samples were collected pre- and postfilter; C5a, elastase and MPO were determined by ELISA. Additionally, C5a was also measured in the ultrafiltrate.

Results

In the heparin group, there was C5a production across the filter which most decreased over time as compared to other groups (P = 0.007). There was also net production of elastase and MPO across the filter during heparin anticoagulation (P = 0.049 or lower), while production was minimal and absent in the no anticoagulation and citrate group, respectively. During heparin anticoagulation, plasma concentrations of MPO at the inlet increased in the first 10 minutes of CVVH (P = 0.024).

Conclusion

Citrate confers less filter-induced, potentially harmful complement activation and neutrophil degranulation and less endothelial activation than heparin when used for anticoagulation during continuous venovenous haemofiltration in critically ill patients.

Myeloperoxidase production by macrophage and risk of atherosclerosis

Myeloperoxidase (MPO), a member of the heme peroxidase superfamily, is a leukocyte-derived enzyme that generates reactive intermediates, leading to oxidative damage of host lipids and proteins. It has been shown that MPO is present within atherosclerotic plaque in human arteries and contributes to atherogenesis by catalyzing oxidative reactions in the vascular wall. This review provides an overview of the analytical and pathophysiologic characteristics of MPO and summarizes the possible clinical applicability of MPO as a marker for diagnosis of acute coronary syndrome and a marker for prediction of cardiovascular disease.

Reactive oxygen species in cardiovascular disease

Based on the "free radical theory" of disease, researchers have been trying to elucidate the role of oxidative stress from free radicals in cardiovascular disease. Considerable data indicate that reactive oxygen species and oxidative stress are important features of cardiovascular diseases including atherosclerosis, hypertension, and congestive heart failure. However, blanket strategies with antioxidants to ameliorate cardiovascular disease have not generally yielded favorable results. However, our understanding of reactive oxygen species has evolved to the point at which we now realize these species have important roles in physiology as well as pathophysiology. Thus, it is overly simplistic to assume a general antioxidant strategy will yield specific effects on cardiovascular disease. Indeed, there are several sources of reactive oxygen species that are known to be active in the cardiovascular system. This review addresses our understanding of reactive oxygen species sources in cardiovascular disease and both animal and human data defining how reactive oxygen species contribute to physiology and pathology.

Myeloperoxidase: a useful biomarker for cardiovascular disease risk stratification?

BACKGROUND

Inflammation and oxidative stress are associated with atherosclerosis. Myeloperoxidase (MPO) is linked to both inflammation and oxidative stress by its location in leukocytes and its role in catalyzing the formation of oxidizing agents. Recent evidence suggests that MPO activity precipitates atherogenesis. Measurement of MPO in plasma may therefore contribute to cardiovascular disease (CVD) risk stratification.

CONTENT

Cross-sectional studies, case-control studies, and prospective-cohort studies investigating the relation between MPO and CVD have been evaluated. Differences in study populations, sample materials, sample handling, and assays were ascertained. Potential causal mechanisms linking MPO to accelerated atherosclerosis are discussed here. A majority of studies indicate that measurement of MPO in plasma was associated with improved CVD risk stratification above and beyond risk stratification results obtained with markers used in routine clinical practice. However, comparison of these epidemiological studies with regard to MPO and outcome is hampered because the reported MPO concentration depends on the assay method, sampling material, and preanalytical and analytical procedures. The link between MPO and CVD can, at least partly, be explained by MPO-dependent oxidation of LDL and HDL, subsequently leading to cholesterol accumulation in the arterial wall. Furthermore, MPO may reduce the bioavailability of nitric oxide, resulting in endothelial dysfunction. Finally, MPO destabilizes atherosclerotic plaques.

SUMMARY

Increasing evidence suggests that MPO is causally linked to atherosclerosis and its measurement may improve CVD risk estimation. Before MPO can be used in routine clinical practice, however, standardization of sampling and laboratory procedures is needed.

Infusion of Hypertonic Saline (7.5%) Does Not Change Neutrophil Oxidative Burst or Expression of Endothelial Adhesion Molecules After Abdominal Hysterectomy

BACKGROUND

Previous studies found hypertonicity to affect neutrophils in intact laboratory animals and in human blood cell cultures. We investigated whether infusion of hypertonic saline in a clinical relevant dose before hysterectomy affected peripheral blood neutrophils and their response to surgery.

METHODS

Fifteen women scheduled for open abdominal hysterectomy were randomized double-blindly to infusion of 4 mL/kg 7.5% NaCl, 4 mL/kg 0.9% NaCl, or 32 mL/kg 0.9% NaCl over 20 minutes. Blood was collected at baseline, after infusion, 1, 4, and 24 hours postoperatively for the determination of leukocyte and differential count, neutrophil membrane expression of endothelial adhesion molecules by flow cytometry, and O2- -generation by superoxide dismutase-inhibitable reduction of cytochrome C.

RESULTS

Surgery induced well-known changes in the number and distribution of white blood cells, reduced the expression of adhesion molecules, and halved the superoxide production unrelated to the tonicity or volume of the infused fluids.

CONCLUSION

Infusion of a clinically relevant dose of hypertonic saline has no detectable effect on the membrane expression of endothelial adhesion molecules or O2- -generation in circulating neutrophils after elective abdominal hysterectomy.

Myeloperoxidase as a marker of hemodialysis biocompatibility and oxidative stress: the underestimated modifying effects of heparin

Myeloperoxidase (MPO) is a microbicidal and reactive species-generating enzyme. It traditionally is considered to be stored mostly within polymorphonuclear leukocytes and is strongly implicated in the pathogenesis of numerous diseases. MPO also has been studied for at least 20 years as a marker of hemodialysis procedure biocompatibility and oxidative stress generation; research yielded discordant and inconclusive results. In this review, a novel and growing body of evidence indicating that MPO also is a potent blood vessel-bound enzyme that can be mobilized rapidly and extensively into circulating blood by exogenous heparin is discussed. Beneficial consequences of such evoked arterial wall MPO depletion that may be counterbalanced in part by the harmful effects of circulating MPO on polymorphonuclear leukocyte activation and thus atherosclerosis propagation also are presented. Potential clinical implications of these undervalued phenomena in commonly atherosclerotic maintenance hemodialysis patients regularly administered large doses of heparin for temporary blood anticoagulation (frequently over years) are stressed, including the challenging issue of morbidity and mortality. In view of the plausible clinical importance of the novel MPO-oxidative stress-heparin interaction in this population, the need for additional studies assessing different dialyzer membranes, various heparin types (unfractionated heparin versus low-molecular-weight heparins versus pentasaccharides), as well as different anticoagulation regimens, is emphasized.

Low-molecular-weight heparins and angiogenesis

The involvement of the vascular system in malignancy encompasses not only angiogenesis, but also systemic hypercoagulability and a pro-thrombotic state, and there is increasing evidence that pathways of blood coagulation and angiogenesis are reciprocally linked. In fact, cancer atients often display hypercoagulability resulting in markedly increased thromboembolism, which requires anti-coagulant treatment using heparins, for example. Clinical trials reveal that treatment with various low-molecular-weight heparins (LMWHs) improves the survival time in cancer patients receiving chemotherapy compared with those receiving unfractionated standard heparin (UFH) or no heparin treatment, as well as in cancer patients receiving LMWH as thrombosis prophylaxis during primary surgery. This anti-tumor effect of the heparins appears to be unrelated to their anti-coagulant activity, but the mechanisms involved are not fully understood. Tumor growth and spread are dependent on angiogenesis and it is noteworthy that the most potent endogenous pro- and anti-angiogenic factors are heparin-binding proteins that may be affected by systemic treatment with heparins. Heparin and other glycosaminoglycans play a role in vascular endothelial cell function, as they are able to modulate the activities of angiogenic growth factors by facilitating the interaction with their receptor and promoting receptor activation. To date, preclinical studies have demonstrated that only LMWH fragments produced by the heparinase digestion of UFH, i.e. tinzaparin, exert anti-angiogenic effects in any type of tissue in vivo. These effects are fragment-mass-specific and angiogenesis-type-specific. Data on the effect of various LMWHs and UFH on endothelial cell capillary tube formation and proliferation in vitro are also presented. We hope that this paper will stimulate and facilitate future research designed to elucidate whether the anti-angiogenic or anti-tumor effects of commercial LMWHs in their own right are agent specific and whether anti-angiogenic properties increase the anti-tumor properties of the LMWHs in the clinic.

Antitumor and antimetastatic effect of warfarin and heparins

Experimental and clinical studies have shown an anticancer effect of anticoagulant drugs. The aim of this study is to review the mechanisms by which the common types of anticoagulants influence the primary tumor and metastatic processes of solid tumors. The review evaluates the interference of unfractionated heparin (UFH), low molecular weight heparin (LMWH) and warfarin on the growth of primary tumors and on the development of metastases. The first part of the review evaluates the effect on the growth and development of primary tumors. Attention is paid to the interference with proliferation of cancer cells, tumor angiogenesis and to the interference with the immune system. The second part of the review describes the metastatic process and the effect of anticoagulants on the cell motility and cancer cell adhesion. The third part refers to the outcomes of clinical studies with anticoagulant treatment in patients with cancer. The problem of thromboembolic disease in patients with advanced cancer is also mentioned. The anticoagulants are more effective in inhibition of stages of the metastatic cascade than in the influence on primary tumors. They can interfere with tumor angiogenesis, immunity system, cancer cell motility and adhesion. The first clinical trials showed an effect on the development of primary tumors and survival of patients namely with lung cancer.

Enoxaparin in experimental stroke: neuroprotection and therapeutic window of opportunity

BACKGROUND AND PURPOSE

Heparin and heparinoids have long been proposed for stroke treatment. This study investigates the effect of enoxaparin (Lovenox, Clexane), a low-molecular-weight heparin, on functional outcome (neuroscore) and lesion size in stroke models with reversible and irreversible cerebral ischemia using middle cerebral artery occlusion (MCAO) in the rat.

METHODS

Ischemia was induced in rats by transient occlusion for 2 hours or by permanent electrocoagulation of the left MCA. Forty-eight hours after ischemia, neurological deficit was evaluated by scoring sensorimotor functions and ischemic damage was quantified by histological evaluation of lesion volumes.

RESULTS

After transient MCAO, enoxaparin at 2x1.5 mg/kg IV (2 and 24 hours after insult) significantly reduced lesion size by 30% (P<0.05) and improved neuroscore (P<0.01). This significant effect on lesion size and neuroscore was still evident when treatment was started 5 hours after insult. Administered under the same protocol with a 5 hours delay post permanent MCAO, enoxaparin reduced lesion size by 49% (P<0.05) and improved neuroscore (P<0.01).

CONCLUSIONS

This study indicates that standard nonhemorrhagic doses of enoxaparin reduce ischemic damage with a wide therapeutic window. In addition to its anticoagulant properties, other properties of enoxaparin could act in synergy to explain its neuroprotective profile in ischemia. Thus clinical application of enoxaparin treatment in stroke warrants serious consideration.

Oxidative stress during hemodialysis: effect of heparin

BACKGROUND

Patients on chronic hemodialysis (HD) are exposed to oxidative stress. An HD session is used in this study as an in vivo model for studying the influence of heparin on oxidative stress caused partially by activated peripheral blood polymorphonuclear leukocytes (PMNLs) during a HD session.

METHODS

Each patient underwent HD once with and once without heparin. Oxidative stress was determined by evaluating both the rate of superoxide release from phorbol 12-myristate 13-acetate (PMA)-stimulated PMNLs and plasma levels of oxidized glutathione (GSSG), both measured before and after the dialysis session.

RESULTS

In vitro, heparin reduced the rate of superoxide release from separated PMA-stimulated PMNLs. In vivo, the rate of superoxide release from PMNLs was always increased after the dialysis session, regardless of the presence of heparin. However, in the presence of heparin, this increase was significantly smaller. The augmentation in the rate of superoxide release after the dialysis session without heparin was accompanied by a significant elevation of GSSG, reflecting a preceding oxidation of plasma glutathione.

CONCLUSIONS

The increase in both parameters, the rate of superoxide release, and the plasma GSSG concentration after HD treatment suggest that heparin in vivo alleviates the oxidative stress induced by the dialysis process. Based on our results, heparin should be the anticoagulant of choice because of its suppressant action on HD-induced oxidative stress.

Heparins and blood polymorphonuclear stimulation in haemodialysis: an expansion of the biocompatibility concept

BACKGROUND

At the concentrations used in haemodialysis and in a dose-dependent way, unfractionated heparin (UFH) and, to a lesser degree, a low-molecular-weight heparin (LMWH) stimulate polymorphonuclear cells (PMN) in vitro, and could act in synergy with the stimulatory effect of dialysis membranes in vivo. To examine this hypothesis, we studied the effects of different heparin types and regimens on blood PMNs during haemodialysis sessions.

METHODS

Ten haemodialysed patients were studied during regular dialysis sessions on a cellulose triacetate membrane (CT 110 G; 1.10 m(2); Baxter), with four different random heparin protocols: one high-UFH regimen (HHR) at 90 IU/kg body-weight (b.w.) and one low-UFH regimen (LHR) at 50 IU/kg b.w., and with a LMWH (nadroparin calcium) at 85 (HHR) or 45 (LHR) IU/kg b.w. Blood granulocytes, platelet counts, and plasma granulocyte degranulation products (elastase, lactoferrin) were measured serially during 4 h dialysis sessions.

RESULTS

After 10 min, the reduction in PMNs with UFH was 29.5% for HHR (P<0.01) and 28.5% for LHR (P<0.01), and only 16.8 and 18.6% with LMWH (NS), significantly higher for HHR with UFH than with LMWH (P<0.01). At 60 min, the elastase increase with HHR was greater, 61% with UFH (P<0.01) and 37.8% with LMWH (P<0.01), significantly higher than LHR for UFH (P<0.05) or LMWH (P<0.05). The overall decrease in platelets (with LMWH P<0.01) and the overall increase in lactoferrin (P<0.001) were not different between heparinization procedures.

CONCLUSION

Under a conventional heparin regimen, the PMN variation during the course of the dialysis session suggests a more biocompatible effect of LMWH over UFH. In addition, the variation of elastase favours the lower dose, whatever the type of heparin. Heparin type and dose should therefore be considered in studies addressing biocompatibility in haemodialysis: a low dose of LMWH may be viewed as a better biocompatible treatment with regard to leukocyte stimulation.

The prevention of lipopolysaccharide-induced pulmonary vascular injury by pretreatment with cepharanthine in rats

Cepharanthine, a biscoclaurine alkaloid, has been shown to inhibit leukocyte activation in vitro. To determine whether cepharanthine may be of use in the treatment of acute respiratory distress syndrome (ARDS), we investigated its effect on lipopolysaccharide (LPS)-induced pulmonary vascular injury in rats, in which activated leukocytes have been implicated. Intravenous administration of LPS (5 mg/kg) induced pulmonary vascular injury, as indicated by increases in both the pulmonary vascular permeability and the lung wet/dry weight ratio. LPS-induced pulmonary vascular injury was significantly less in animals given cepharanthine (10 mg/kg) intraperitoneally. Cepharanthine significantly inhibited the LPS-induced increases in plasma tumor necrosis factor-alpha (TNF-alpha) concentrations in vivo and significantly inhibited the production of TNF-alpha by LPS-stimulated monocytes in vitro. Cepharanthine also inhibited the functions of activated neutrophils in vitro such as neutrophil elastase release, oxygen radical generation, and neutrophil aggregation, probably by inhibiting a rise in the intracellular free calcium concentration. These findings suggest that cepharanthine prevents LPS-induced pulmonary vascular injury by inhibiting leukocyte activation.

Heparin in inflammation: potential therapeutic applications beyond anticoagulation

In this chapter we have described anti-inflammatory functions of heparin distinct from its traditional anticoagulant activity. We have presented in vivo data showing heparin's beneficial effects in various preclinical models of inflammatory disease as well as discussed some clinical studies showing that the anti-inflammatory activities of heparin may translate into therapeutic uses. In vivo models that use low-anticoagulant heparins indicate that the anticoagulant activity can be distinguished from heparin's anti-inflammatory properties. In certain cases such as hypovolemic shock, the efficacy of a low-anticoagulant heparin derivative (GM1892) exceeds heparin. Data also suggest that nonconventional delivery of heparin, specifically via inhalation, has therapeutic potential in improving drug pharmacokinetics (as determined by measuring blood coagulation parameters) and in reducing the persistent concerns of systemic hemorrhagic complications. Results from larger clinical trials with heparin and LMW heparins are eagerly anticipated and will allow us to assess our predictions on the effectiveness of this drug class to treat a variety of human inflammatory diseases.

Gabexate mesilate, a synthetic protease inhibitor, attenuates endotoxin-induced pulmonary vascular injury by inhibiting tumor necrosis factor production by monocytes

OBJECTIVE

In order to determine whether gabexate mesilate, a synthetic protease inhibitor with anticoagulant properties, is useful for the treatment of adult respiratory distress syndrome, we examined its effect on endotoxin-induced pulmonary vascular injury in rats.

DESIGN

Prospective, randomized, controlled study.

SETTING

Research laboratory at a university medical center.

SUBJECTS

Male Wistar rats (180 to 220 g.)

INTERVENTIONS

Animals received intravenous infusions of endotoxin (5 mg/kg iv) or saline (control). Pulmonary vascular injury was assessed 6 hrs after administration of endotoxin in terms of the increase in vascular permeability. Rats received gabexate mesilate (10 mg/kg ip), heparin, antithrombin III, an inactive derivative of activated factor X (a selective inhibitor of thrombin generation), or N-[2-[4-(2,2-dimethyl-propionyloxy) phenylsulfonylamino] benzoyl] aminoacetic acid (ONO-5046) (a potent granulocyte elastase inhibitor) 30 mins before endotoxin administration. Leukocytopenia was induced by administration of methotrexate. The effects of the gabexate mesilate on the function of activated neutrophils and the production of tumor necrosis factor -alpha (TNF-alpha) by endotoxin-stimulated monocytes were examined in vitro using neutrophils and monocytes prepared from healthy human volunteers.

MEASUREMENTS AND MAIN RESULTS

Pulmonary vascular permeability was determined by measuring the vascular leakage of intravenously administered 125I-labeled bovine serum albumin. Intravenous administration of endotoxin significantly increased pulmonary vascular permeability. Gabexate mesilate significantly inhibited pulmonary vascular injury observed 6 hrs after the administration of endotoxin. Pulmonary vascular injury was not attenuated by the administration of heparin, heparin plus antithrombin III, or the inactive derivative of activated factor X, but pulmonary vascular injury was significantly attenuated in animals with methotrexate-induced leukocytopenia and in those animals treated with N-[2-[4-(2,2-dimethyl-propionyloxy) phenylsulfonylamino] benzoyl] aminoacetic acid. Gabexate mesilate in concentrations of 10(-4) to 10(-3) M inhibited the release of granulocyte elastase and leukocyte aggregation stimulated by N-formyl-methionyl-leucyl-phenylalanine and the opsonized zymosan-activated production of superoxide radical by neutrophils in vitro. Gabexate mesilate significantly inhibited the endotoxin-induced increase in the serum concentration of TNF-alpha in vivo and, at a concentration of 10(-8) M, the production of TNF-alpha by endotoxin-stimulated monocytes in vitro.

CONCLUSION

Our findings suggest that gabexate mesilate attenuated endotoxin-induced pulmonary vascular injury mainly by inhibiting TNF-alpha production by monocytes, which may play a central role in sepsis-related lung injury.