Plasminogen Activator Inhibitor Activity in Bacterial Infection

Hepatocyte growth factor mediates a novel form of hepatic stem/progenitor cell-induced tolerance in a rat xenogeneic liver rejection model

We have previously identified novel neural/glial antigen 2-expressing hepatic stem/progenitor cells (NG2+ HSPs) that are beneficial for tissue repair by inhibiting the immune cell response. In this in vivo study, we investigated the use of hepatocyte growth factor (HGF)-secreting NG2+ HSPs as a tolerogen in the well-established Syrian golden hamster (SGH) to Lewis (LEW) xenogeneic rat acute liver rejection (ARJ) model. Liver and blood cells were collected for histology and functional analyses using immunofluorescence staining, western blot, ELISA, and TUNEL assays. All recipient rats were randomly divided into 5 groups (n = 14 rats/group) and treated with: (1) ARJ + PBS: (2) ARJ + NG2: tail vein injection of NG2+ HSPs; (3) ARJ + tacrolimus (FK506, oral administration); (4) ARJ + an anti-cMet functional blocking antibody (a-cMet-Ab, I.V) 24 h before the injection of NG2+ HSPs; (5) ARJ + cHGF (clinically used HGF). LEW to LEW syngeneic rats were considered "normal" (n = 14, namely Syn). Significantly prolonged mean survival times (MSTs) and improved graft functions were observed after NG2+ HSP transplantation. An anti-cMet Ab significantly blocked the effect of NG2+ HSPs, suggesting that the effects were likely associated with HGF secreted from NG2+ HSPs. Notably, when intravenously injected into the xenogeneic rat model, the injected cHGF not only prolonged the MST of recipient rats but also increased the number of TUNEL-expressing xenoreactive cytotoxic T lymphocytes (CD8+ T cells). Based on these results, HGF-secreting NG2+ HSPs may specifically target recipient CD8+ T cells by inducing their apoptosis.

The 4G/4G Genotype of PAI-1 Polymorphism Is Associated with Higher Plasma PAI-1 Concentrations and Mortality in Patients with Severe Sepsis

Objective

Two studies have reported that patients with the 4G/4G genotype of the plasminogen activator inhibitor-1 (PAI-1) genetic polymorphism had higher plasma PAI-1 concentrations and higher risk of death than those with the 4G/5G or 5G/5G genotypes; one study involved 175 children with meningococcal disease, and the other included 88 adult patients with septic shock. Thus, the objective of this study was to determine whether there is an association between carriage of the 4G/4G genotype, plasma PAI-1 concentrations and mortality in a large series of adult septic patients.

Methods

An observational, prospective, multicenter study was carried out in six Spanish Intensive Care Units including severe septic patients. We determined the PAI-1 4G/5G polymorphism and plasma PAI-1 concentrations in all patients. The end-points of the study were 30-day and 6-month mortality.

Results

We included a total of 260 patients, 82 (31.5%) with 4G/4G, 126 (48.5%) with 4G/5G and 52 (20.0%) with 5G/5G genotype. Multivariate logistic regression analysis showed that the 4G/4G genotype was associated with higher mortality at 30 days (Odds Ratio = 1.95; 95% CI = 1.063–3.561; p = 0.03) and at 6 months (Odds Ratio = 2.19; 95% CI = 1.221–3.934; p = 0.01), and that higher plasma PAI-1 concentrations were associated with higher mortality at 30 days (Odds Ratio = 1.01; 95% CI = 1.002–1.022; p = 0.02) at 6 months (Odds Ratio = 1.01; 95% CI = 1.003–1.023; p = 0.01). Multivariate linear regression analysis showed that increased plasma PAI-1 concentrations were associated with the PAI-1 4G/4G genotype (regression coefficient = 4.82; 95% CI = 3.227 to 6.406; p<0.001).

Conclusions

The major findings of our study, to our knowledge the largest series reporting data about 4G/5G polymorphism of the PAI-1 gene, plasma PAI-1 concentrations and mortality in septic patients, were that septic patients with the 4G/4G genotype had higher plasma PAI-1 concentrations and higher risk of death than those with 4G/5G or 5G/5G genotypes.

Sustained high plasma plasminogen activator inhibitor-1 levels are associated with severity and mortality in septic patients

BACKGROUND

Higher plasma plasminogen activator inhibitor-1 (PAI-1) levels have been reported in septic patients. However, some questions remain unanswered, such as whether there is an association between plasma PAI-1 levels and sepsis severity and mortality, and inflammation state during the first week.

METHODS

Multicenter, observational and prospective study carried out in six Spanish Intensive Care Units of 260 patients with severe sepsis. Circulating levels of PAI-1 and tumour necrosis factor (TNF)-α were measured at day 1, 4 and 8. End-point was 30-day mortality.

RESULTS

Nonsurviving septic patients (n=89) presented higher PAI-1 levels than surviving (n=171) at day 1 (58.4 (33.3-83.8) vs 36.5 (21.1-62.5) ng/mL; p<0.001), 4 (34.0 (14.7-53.3) vs 16.2 (10.2-27.4) ng/mL; p<0.001) and 8 (30.6 (16.2-47.8) vs 18.9 (10.4-29.5) ng/mL; p=0.004). We found a positive correlation of PAI-1 levels with SOFA, lactic acid, aPTT, INR and TNF-α, and negative with platelet count at day 1, 4 and 8. Logistic regression analyses showed that PAI-1 levels at day 1 (p<0.001), 4 (p<0.001) and 8 (p=0.001) were associated with 30-day mortality. On ROC curve analysis to predict 30- day survival, the area under the curve of PAI-1 levels at day 1, 4 and 8 were 0.65 (95% CI=0.58-0.72; p<0.001), 0.69 (95% CI=0.60-0.78; p<0.001) and 0.65 (95% CI=0.54-0.75; p=0.005) respectively.

CONCLUSIONS

The most interesting findings of our study, to our knowledge the largest series reporting PAI-1 levels during follow-up in septic patients, were that plasma PAI-1 levels during the first week were associated with inflammation, severity and mortality.

Therapeutic intervention and targets for sepsis

Sepsis syndrome, a systemic response to infection, can beget devastating outcomes even in previously normal individuals. Recent research in septic patients has led to the discovery that early goal-directed resuscitation guided by continuous monitoring of mixed venous hemoglobin saturation, along with moderate doses of corticosteroids, can reduce mortality. An improved understanding of the complex interaction between the inflammatory and coagulant systems in sepsis pathophysiology has resulted in novel treatments, such as recombinant human activated protein C, which improves survival in patients with severe sepsis and a high risk of death. However, despite an increased understanding of the complex pathophysiology of this syndrome and the discovery of new, effective treatments, severe sepsis still results in significant morbidity and mortality. Consequently, investigations continue into additional therapeutic agents directed against novel targets. Following a review of recent advances in sepsis treatment, we briefly discuss a few of the new, promising therapeutic strategies currently being investigated.

Selective inducible nitric oxide synthase inhibition attenuates organ dysfunction and elevated endothelin levels in LPS-induced DIC model rats

We examined the role of nitric oxide (NO) produced by an inducible isoform of NO synthase (iNOS) using N[6]-(iminoethyl)-lysine (L-NIL), a selective iNOS inhibitor, in the rat model of lipopolysaccharide (LPS)-induced disseminated intravascular coagulation (DIC) and investigated changes in organ function, plasma levels of NOX (metabolites of NO) and endothelin. We induced experimental DIC by the sustained infusion of 30 mg kg(-1) LPS for 4 h via the tail vein. We then investigated the effect of L-NIL (6 mg kg(-1), from - 0.5 to 4 h) on LPS-induced DIC. Blood was withdrawn at 4 and 8 h, and all four groups (LPS with or without L-NIL at 4 and 8 h) consisted of eight rats. Three of the animals in the 8-h LPS group died, and we examined blood samples from five rats in this group. None of the other rats died. The LPS-induced elevation of creatinine, alanine aminotransferase, glomerular fibrin deposition and plasminogen activator inhibitor was significantly suppressed by L-NIL coadministration, although L-NIL did not affect the platelet count, fibrinogen concentration or the level of thrombin-antithrombin complex. Moreover, plasma levels of the D-dimer that reflect the lysis of cross-linked fibrin were significantly increased by L-NIL coadministration in the LPS-induced DIC model. Plasma levels of NOX and endothelin were obviously increased by LPS infusion. However, both levels were significantly suppressed in the LPS + L-NIL group, when compared with the LPS group. Although mean arterial pressure (MAP) was significantly decreased between 2 and 8 h compared with the control in the LPS group, this depression was significantly attenuated in the LPS + L-NIL group. Our results suggest that NO induced by iNOS contributes to hypotension (depressed MAP), the progression of hepatic and renal dysfunction, microthrombus deposition and elevated endothelin levels in the rat model of LPS-induced DIC.

Beneficial effect of low-molecular-weight heparin against lipopolysaccharide-induced disseminated intravascular coagulation in rats is abolished by coadministration of tranexamic acid

OBJECTIVE

We examined the role of coagulation and fibrinolysis in lipopolysaccharide (LPS) induced disseminated intravascular coagulation (DIC) in rats, studying their contribution to fibrin deposition and organ failure in rats with LPS-induced DIC by concurrent administration of low molecular weight heparin (LMWH) with or without tranexamic acid (TA).

METHODS

DIC was induced in male Wistar rats by a 4-h infusion of LPS (30 mg/kg) via the tail vein (LPS group). In the LPS+LMWH group LMWH (200 u/kg) was administered to rats from 30 min before the infusion of LPS for 4.5 h. In the LPS+LMWH+TA group LMWH (200 microg/kg) and TA (50 mg/kg) were administered to rats from 30 min before the infusion of LPS for 4.5 h.

RESULTS

In the LPS+LMWH group lower plasma levels of TAT, D dimer, creatinine, and alanine aminotransferase were observed, along with less glomerular fibrin deposition and improved survival over rats administered LPS alone. However, these effects of LMWH were completely eliminated and damage beyond that observed in rats administered LPS alone resulted from combined administration of TA (LPS+LMWH+TA group), except that TAT and D dimer levels remained lower than in the group administered LPS alone.

CONCLUSIONS

Suppression of fibrinolysis by TA (despite coadministration of LMWH) resulted in increased organ damage in this study, suggesting that depressed fibrinolysis plays a large role in organ failure resulting from LPS-induced DIC, even though hemostatic activation is moderately suppressed by LMWH.

Pathophysiology of disseminated intravascular coagulation (DIC) progresses at a different rate in tissue factor-induced and lipopolysaccharide-induced DIC models in rats

Tissue factor (TF) and lipopolysaccharide (LPS) are frequently used to induce disseminated intravascular coagulation (DIC) in experimental animal models. Although the pathophysiology of DIC may differ depending on which agent is used for induction, previous studies on models of DIC have not distinguished which DIC-inducing agent was used. In the present paper, we evaluate the characteristics of TF-induced and LPS-induced DIC using two types of DIC models, with special reference to selected hemostatic parameters and pathological findings within the kidney. Male Wistar rats were administered TF (3.75 U/kg; sustained infusion for 4 h) or LPS (30 mg/kg; sustained infusion for 4 h) via the tail vein, and blood sampling was performed at 0, 1, 3, 4, 5, 7, 9, 11, and 28 h. Judging from changes in the levels of thrombin-antithrombin complex, fibrinogen levels, and platelet counts, it is reasonable to conclude that the severity of both types of experimental DIC is similar with regard to hemostatic activation and consumption coagulopathy. A marked elevation in the level of D-dimer was noted without any organ dysfunction or much fibrin deposition in the kidney upon administration of TF. However, a markedly prolonged period of elevation in plasminogen activator inhibitor activity, a prolonged depression in antithrombin III activity, severe organ failure, and a markedly prolonged period of fibrin deposition in the kidney was observed following LPS administration. A modest number of the rats from the TF-induced DIC model died during the experimental period, whereas a large number of rats died during LPS-induced DIC, especially after 9 h. Since the time course of the pathophysiology differed remarkably among the TF-induced and LPS-induced DIC models in rats, we recommend that TF-induced and LPS-induced DIC be approached as distinct models in order to determine the implications of their experimental and clinical use.

Hemostatic disturbances in patients with systemic inflammatory response syndrome (SIRS) and associated acute renal failure (ARF)

Endothelial damage plays a central role in the development of an SIRS-related Multiple Organ Dysfunction Syndrome (MODS) as a consequence of the establishment of a hemostatic imbalance between coagulation and fibrinolysis systems. Until now, sepsis is the SIRS model that has been most studied. The aim of this study was to assess the endothelial damage and the hemostatic imbalance in early stages of an SIRS of different origins, and to study if there are any differences in these disturbances between infectious and noninfectious SIRS. The endothelial damage and hemostatic changes were studied in 40 patients with SIRS (with less than 12 h of evolution) and an acute renal failure. Infectious SIRS was diagnosed in 19 cases and noninfectious SIRS in the remaining 21 patients. Patients with SIRS presented significantly higher values (p<0.001) for factors related to endothelial damage [von Willebrand factor (vWF), thrombomodulin, tissue plasminogen activator (t-PA), and plasminogen activator inhibitor type 1 (PAI-1) antigen], hypercoagulability [prothrombin fragment 1+2 (F1+2) and thrombin-antithrombin complexes (TAT)], and fibrinolysis (D-dimer and PAI activity) with respect to the control group. However, although the group with infectious SIRS presented higher values for all the factors except for the t-PA and D-dimer with respect to SIRS of other origins, none of these differences reached statistical significance (p>0.05). Our data show that patients with SIRS and associated acute renal failure, irrespective of the origin (infectious or noninfectious), show signs of intense endothelial damage and hypercoagulability throughout the process.

Disseminated intravascular coagulation and purpura fulminans secondary to infection

Infection is one of the commonest causes of disseminated intravascular coagulation (DIC). DIC is a complex disorder that results from an imbalance of the pro- and anticoagulant regulatory pathways. This chapter will explain the cellular and molecular basis of the disorder and consider the rationale behind current and experimental treatment strategies.

Endotoxin-induced disseminated intravascular coagulation in rabbits: effect of recombinant hirudin on hemostatic parameters, fibrin deposits, and mortality

We evaluated the effect of r-hirudin on an experimental model of disseminated intravascular coagulation (DIC) in rabbits, through the continuous infusion of 100 microg/kg/hr of Escherichia coli endotoxin for a period of 6 hours. r-Hirudin (0.05, 0.3, and 0.6 mg/kg/hr) as treatment, or saline solution as placebo, were administered simultaneously with endotoxin. Severe DIC in the endotoxin control group was shown by impairment in hemostatic parameters, kidney fibrin deposition, and a high mortality rate. Medium and high doses of r-hirudin led to an improvement in such DIC-related parameters as platelet numbers and fibrinogen and protein C concentrations. High-dose r-hirudin also reduced consumption of antithrombin III (ATIII). All doses of r-hirudin prevented decreases in tissue plasminogen activator (t-PA) and reduced the increase in plasminogen activator inhibitor-1 (PAI-1) activity observed at 2 hours after endotoxin administration. A significant reduction in kidney fibrin deposition was seen in medium- and high-dose r-hirudin groups. Additionally, the mortality rate in rabbits receiving medium- and high-dose r-hirudin was 10%, and that in rabbits receiving low-dose r-hirudin was 20%, as compared with a mortality rate of 70% in the control group. Protein C activity was significantly lower (p < 0.001) in nonsurviving rabbits. Moreover, there was a strong positive correlation (r = 0.68, p < 0.001) between protein C consumption and kidney fibrin deposition. We conclude that r-hirudin can be a useful drug in the clinical treatment of DIC.

Notoginsenoside R1 counteracts endotoxin-induced activation of endothelial cells in vitro and endotoxin-induced lethality in mice in vivo

In this study we investigated a possible counteracting activity notoginsenoside R1 (NG-R1) on lipopolysaccharide (LPS)-induced effects in vitro and in vivo. The upregulation of plasminogen activator inhibitor-1 (PAI-1) antigen due to LPS (1 microgram/mL for 12 hours) in human umbilical vein endothelial cells (HUVECs) was prevented when the cells were incubated simultaneously with 100 micrograms/mL NG-R1 (PAI-1 antigen: LPS-treated cells, 969 +/- 54 ng/10(5) cells; control cells, 370 +/- 15 ng/10(5) cells; LPS + NG-R1-treated cells, 469 +/- 29 ng/10(5) cells; n = 6). The 2.5- and 3.4-fold (2.2- and 3.2-kb) increases in PAI-1 mRNA levels induced by LPS (1 microgram/mL for 6 hours) were reduced to 1.4- and 2.6-fold increases in the presence of both LPS and 100 micrograms/mL NG-R1. LPS-induced tissue factor (TF) activity in HUVECs was also counteracted when the cells were coincubated with both LPS and 100 micrograms/mL NG-R1 for 6 hours (TF activity: LPS-treated cells, 88.6 +/- 6.5 mU/10(6) cells; control cells, 0.7 +/- 0.01 mU/10(6) cells; LPS + NG-R1-treated cells, 56.0 +/- 1.9 mU/10(6) cells). The 26-fold increase in TF mRNA levels induced by LPS (1 microgram/mL for 2 hours) was reduced to a 13-fold increase in the presence of both LPS and 100 micrograms/mL NG-R1. PAI activity levels in the plasma of mice 4 hours after injection of LPS (10 ng/g body wt) increased 2.3-fold compared with a control group. In contrast, PAI activity from LPS + NG-R1 (1 microgram/g body wt NG-R1)-treated animals was at control level (PAI-1 activity: LPS-treated group, 11.3 +/- 3.1 U/mL; control group, 4.9 +/- 0.3 U/mL; LPS + NG-R1-treated group, 4.3 +/- 1.0 U/mL; n = 5 to 8). The production of TNF-alpha induced by 1 microgram/mL LPS by cultured human whole-blood cells was inhibited by 46% when the cells were incubated together with 100 micrograms/mL NG-R1. NG-R1 protected mice from the lethal effects of LPS. The 78% lethality induced by LPS/galactosamine was reduced to 23% when NG-R1 was administered simultaneously (P < .01 by chi 2 test). To extend this study to inflammatory cells, the effect of NG-R1 on LPS stimulation of the monocytic cell line THP-1 was investigated. NG-R1 inhibited the LPS-induced degradation of I kappa B-alpha and superinduced LPS-induced I kappa B-alpha mRNA, indicating that the effect of NG-R1 is not restricted to endothelial cells and is at least in part mediated by interference with the NF-kappa B/I kappa B-alpha pathway.

Influence of white blood cells on the fibrinolytic response to sepsis: studies of septic patients with or without severe leucopenia

In septic patients capable of normal white cell responses, high plasma levels of PAI-I, t-PA antigen and t-PA-PAI-I complex were observed. The ratios of t-PA and PAI-I were such that free PA activity was almost never observed. In patients severely leucopenic prior to becoming septic the changes were significantly less marked, so presence of leucocytes enhances the fibrinolytic inhibition occurring in sepsis. The non-leucopenic septic group showed greater evidence of thrombin generation in that FPA levels were higher but fibrinogen levels were only slightly less and antithrombin levels not different from those in the leucopenic group. A greater tendency to fibrin deposition and the striking fibrinolytic inhibition noted in patients with normal white cell responses may contribute to the development of some of the complications of sepsis in which fibrin deposition participates and may explain their relative rarity in leucopenic patients. When shock supervened, levels of PAI-I were high in both leucopenic and non-leucopenic groups, indicating that a source of PAI-I outwith the leucocytes themselves contributes to the phenomena observed.

Haemostatic and fibrinolytic parameters in septic patients with leukopenia or leukocytosis

Induction of leukocytopenia by cytotoxic drugs protects against the generalized Shwartzman reaction induced by endotoxin. To elucidate the relationship between leukocyte number and in haemostatic and fibrinolytic disturbances in human sepsis, we studied 32 septic patients with abnormal leukocyte counts. Twenty patients had sepsis in the setting of leukopenia after chemotherapy for haematological malignancies. Twelve patients with leukocytosis developed sepsis associated with benign disorders. Concentrations of thrombin-antithrombin III complex (TAT), plasminogen activator inhibitor-1 (PAI-1) and plasma thrombomodulin (TM) in the leukocytosis group of (12.0 +/- 11.0, 40.2 +/- 27.0 and 5.5 +/- 2.3 ng/ml, respectively) were significantly elevated compared to the leukopenia group of (3.8 +/- 2.3, 18.0 +/- 15.0 and 3.1 +/- 1.0 ng/ml, respectively) and controls (3.3 +/- 0.4, 10.5 +/- 5.3, 3.0 +/- 0.5 ng/ml, respectively). On the other hand, there were no significant differences in these values between leukopenia group and controls. Thus leucocytes may play important roles in thrombin generation, PAI-1 release and injury to endothelial cells.

Fibrinolytic activity in plasma from horses with gastrointestinal diseases: changes associated with diagnosis, surgery, and outcome

Plasma fibrinolytic activity was evaluated over 5 consecutive days in 59 horses admitted to the Large Animal Teaching Hospital with acute gastrointestinal diseases. Only horses hospitalized for at least 5 days were included in the study. Tissue plasminogen activator (tPA) and plasminogen activator inhibitor type-1 (PAI-1) were quantitated using standard chromogenic activity assays. Statistical analyses were performed using analysis of variance; differences were considered significant when P < or = .05. Activity of PAI-1, the primary endogenous inhibitor of fibrinolysis, was significantly increased on hospital days 2, 4, and 5 in horses that died, when compared with those that were discharged from the hospital. Plasma PAI-1 activity was not different at admission, but was significantly increased on hospital days 2 and 3 in horses that underwent surgery, when compared with those that did not, suggesting an acute phase response to surgical intervention. Horses with strangulating intestinal lesions had significantly increased PAI-1 activity on day 3, while PAI-1 activity was significantly greater in horses with inflammatory conditions at the time of admission, when compared with horses with strangulating or nonstrangulating/noninflammatory lesions. Among all horses, PAI-1 activity was significantly higher and tPA activity was significantly lower on day 2 when compared with other hospital days. These results suggest that fibrinolysis is inhibited early in the course of inflammatory gastrointestinal diseases and in response to surgery. In addition, among all horses, the prognosis for survival was poor for those with persistently increased PAI-1 activity, reflecting treatment failure and the loss of hemostatic regulation.

Regulation of equine fibrinolysis in blood and peritoneal fluid based on a study of colic cases and induced endotoxaemia

Much of the pathophysiology associated with equine gastrointestinal diseases is attributed to the effects of endotoxin on haemostasis. Because little is known about the responses of the equine fibrinolytic system to endotoxin, regulation of the system was investigated. Tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor type-1 (PAI-1) were identified as the primary plasminogen activator and plasminogen activator inhibitor, respectively, in equine blood. Under experimental conditions, the equine fibrinolytic system responded to endotoxin in a manner similar to that reported in man, with an early, transient increase in t-PA activity followed by an overwhelming and prolonged increase in activity of PAI-1. To investigate the response of the equine fibrinolytic system to clinical endotoxaemia, endotoxin concentrations were measured in plasma and peritoneal fluid, and activities of t-PA and PAI-1 were compared between healthy horses (n = 38) and horses with naturally occurring gastrointestinal diseases (n = 150). It was observed that plasma PAI-1 and peritoneal t-PA were increased concurrently in abnormal horses; and that these increases were associated with the presence of endotoxin. The results of this study suggest that 1) fibrinolysis is regulated in horses in a manner similar to that in man; 2) regulation of fibrinolysis is altered in endotoxaemic horses with gastrointestinal diseases; 3) events occurring in the vascular system may not reflect those in the peritoneal cavity; and 4) t-PA activity is increased in the peritoneal fluid of endotoxaemic horses with gastrointestinal diseases.

Fibrinolytic activity in the abdominal cavity of rats with faecal peritonitis

Generalized peritonitis causes a reduction in abdominal fibrinolytic activity, resulting in persistence of intraabdominal fibrin with subsequent adhesion and abscess formation. The activities of tissue plasminogen activator (tPA) and plasminogen activator inhibitor (PAI) were measured in the peritoneal fluid of rats with faecal peritonitis and correlated with the extent of peritoneal damage to determine the cause of decreased fibrinolysis. Activity of tPA was low during the study period of 8 days, but higher in rats with peritonitis than in controls. The activity of PAI in rats with peritonitis was significantly increased compared with that of controls during the whole study period (P < 0.001). Histological signs of damage to the peritoneum were similar in rats with peritonitis and controls. There was no correlation between the extent of peritoneal damage and tPA or PAI activity. The increased activity of PAI in the peritoneal fluid of rats with faecal peritonitis may be the main cause of reduced fibrinolysis in the abdominal cavity. Activities of tPA and PAI may originate not only from the mesothelium but from other sources.

The effect of nitric oxide synthase inhibition on the plasma fibrinolytic system in septic shock in rats

1. We have investigated the effect of pretreatment of rats with nitric oxide (NO) synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME) on the E. coli lipopolysaccharide (LPS)-induced changes in the plasma fibrinolytic system, platelet count, fibrinogen level, as well as in gross and microscopic pathophysiological changes indicative of disseminated intravascular coagulation (DIC) in rats. 2. E. coli LPS (6 mg kg-1, i.p.) produced a decrease in the levels of plasma fibrinogen and a drop in the blood platelet count 6 h after administration. The decrease in fibrinogen but not the drop in platelet count was reversed by pretreatment with L-NAME (30 mg kg-1, i.p., 24 h and 15 min before administration of LPS). 3. Pretreatment with L-NAME antagonized the LPS-induced activation of fibrinolysis as measured by changes in the euglobulin clot lysis time (ECLT) and enhanced the LPS-induced rise in the plasma level of plasminogen activator inhibitor (PAI). In animals pretreated with L-NAME there was also a marked reduction in the histological changes indicative of DIC. 4. We propose that L-NAME can act as a protective agent in LPS-induced DIC, and this protection is due to an increased generation of PAI following inhibition of NO synthase.

Increased vascular endothelial cell markers in patients with disseminated intravascular coagulation

We examined vascular endothelial cell markers, thrombomodulin (TM), plasminogen activator inhibitor-I (PAI-I), tissue plasminogen activator (t-PA), and von Willebrand factor, in 80 patients with disseminated intravascular coagulation (DIC). The levels of thrombin-antithrombin III complex (TAT), plasmin-alpha 2 plasmin inhibitor complex (PIC) and FDP-D-dimer were significantly increased both before and after the onset of DIC, but were not correlated with organ failure or prognosis. However, the PIC/TAT ratio was lower in patients with poor prognosis than in those with good prognosis, and it was also lower in those with organ failure than in those without. Plasma TM, PAI-I, and t-PA levels were increased in DIC patients with organ failure or poor outcome, but were not significantly increased before the onset of DIC. We consider that the prognosis of patients with DIC might be related to organ failure or endothelial cell damage and that plasma levels of TM, PAI-I, and t-PA might be useful in the detection of these disorders and in assessing prognosis. A hypofibrinolytic state might enhance organ failure in patients with DIC.

Elevated plasma levels of vascular endothelial cell markers in patients with hypercholesterolemia

Hypercholesterolemia is associated with an increased incidence of vascular complications. To assess the actual degree of activation of coagulation systems and vascular disorders in hypercholesterolemia, plasma levels of vascular endothelial cell markers, such as thrombomodulin (TM), tissue-type plasminogen activator, plasminogen activator inhibitor-I (PAI-I), and von Willebrand factor, were measured in 51 patients with hypercholesterolemia. We also investigated the effects of Pravastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, on plasma lipid, lipoprotein a, and hemostatic markers. The mean plasma levels of thrombin-antithrombin III complex (TAT), fibrinopeptide A (FPA), TM, and PAI-I were significantly elevated in hypercholesterolemia. Of the hemostatic markers, only TM was significantly increased in patients with ischemic heart diseases (IHD). The mean concentration of total cholesterol and levels of TAT, FPA, PAI-I, and TM were significantly reduced after the Pravastatin treatment. The PIC/TAT ratio was significantly increased in non-IHD patients after treatment, this was not the case in IHD patients. These findings suggested the presence of a thrombogenic state and vascular endothelial cell disorders in hypercholesterolemia; such a state might well be related to hypofibrinolysis.

Increased levels of vascular endothelial cell markers in thrombotic thrombocytopenic purpura

We found that patients with thrombotic thrombocytopenic purpura (TTP) have significantly elevated plasma thrombin antithrombin III complex (TAT) and FDP-D-dimer levels, while the plasmin-alpha 2 plasmin inhibitor complex (PIC) level was only slightly increased. The tissue-type plasminogen activator (t-PA) level was increased, but it was well correlated with the plasminogen activator inhibitor-I (PAI-I) level. These findings suggest that hypercoagulable and hypofibrinolytic states coexist in these patients, in contrast to patients with disseminated intravascular coagulation, who exhibit coexisting hypercoagulable and hyperfibrinolytic states. Levels of vascular endothelial cell markers, such as PAI-I, thrombomodulin (TM), and t-PA, were increased at the onset of TTP, but the level of von Willebrand factor (vWF) antigen was not increased. The outcome in TTP patients was correlated with plasma t-PA and TM levels but not with TAT or PIC. These results suggest that vascular endothelial cell markers, such as TM and t-PA, are released from injured or stimulated endothelial cells, reflecting the degree of vascular endothelial damage, and that the main factor in the pathogenesis of TTP is vascular endothelial cell injury.

Time course of hemostatic abnormalities in sepsis and its relation to outcome

OBJECTIVES

To investigate the time course and the relation to prognosis of coagulation and fibrinolytic abnormalities in patients with septic shock.

PATIENTS AND METHODS

Forty-eight consecutive patients admitted to the medical ICU with the diagnosis of septic shock (diagnosed by defined criteria) were studied. Mortality was 25 of 48. Mean age was 57 +/- 7.3 years. Blood samples were obtained on days 1, 4, and 7 after hospital admission to measure tissue-type plasminogen activator antigen (t-PA), urokinase-type plasminogen activator (u-PA), plasminogen activator inhibitor antigen (PAI-1), plasminogen, alpha 2-antiplasmin, fibrinogen, antithrombin III, protein C, protein S, thrombin-antithrombin complexes (TAT), D-dimer, and von Willebrand factor-related antigen (vWF:Ag).

RESULTS

All patients showed marked abnormalities in both the coagulation and fibrinolytic systems. There were signs of coagulation activation and elevation of both activators and inhibitors of fibrinolysis. Nonsurvivors showed lower levels of protein C and antithrombin III and higher concentration of TAT than survivors. While both t-PA and PAI-1 concentrations were high in survivors and nonsurvivors, only survivors showed a progressive normalization of both parameters during the study period. Low plasminogen levels and plasminogen/alpha 2-antiplasmin ratio were found in both groups, presenting a trend toward normalization only in survivors. The differences reported were not apparent at the time of hospital admission.

CONCLUSIONS

Septic shock is characterized by coagulation activation and fibrinolysis activation and inhibition. Nonsurvivors present a particular hemostatic profile characterized by a more marked activation of coagulation and a more intense inhibition of fibrinolysis. None of the abnormalities studied was significantly different between survivors and nonsurvivors at the time of hospital admission. In the presence of fibrin formation, nonsurvivors present a maintained imbalance in the fibrinolytic response determined by higher PAI-1 plasma concentration, probably contributing to their poor outcome.

Thrombin vs. plasmin generation in disseminated intravascular coagulation associated with various underlying disorders

In order to assess the thrombin and plasmin generation in vivo in disseminated intravascular coagulation (DIC), plasma levels of thrombin-antithrombin III (ATIII) complex (TAT) and plasmin-alpha 2-antiplasmin (a2AP) complex (PAP) were measured together with standard coagulation and fibrinolytic parameters in 80 patients with DIC. Both TAT and PAP were markedly elevated in patients with DIC. When plotted by the underlying disease categories, differences in the magnitude of the elevations of these complexes were recognized among groups. Patients with acute promyelocytic leukemia (APL) had the highest PAP, the lowest TAT/PAP ratio, low a2AP, and low fibrinogen, indicating that the most excessive fibrinolysis can occur in APL. Similar profiles, although less marked, were observed in patients with other leukemias and vascular diseases. Patients with sepsis showed the highest TAT/PAP ratio and the lowest PAP with no decrease in a2AP or fibrinogen, demonstrating a relatively impaired fibrinolysis. Patients with cancer had a relatively high TAT and high TAT/PAP ratio. In addition, both TAT and PAP were markedly elevated in patients with shock. From these, it was suggested that, although laboratory manifestations in DIC are extremely variable from patient to patient, underlying disorders are, at least in part, responsible for the observed variations. Recognition of this variable activation of coagulation and fibrinolysis would be helpful for the proper management of patients with DIC.