Response of anticoagulant pathways in disseminated intravascular coagulation.

This article describes the microvascular endothelium as both a target and a regulator of events after hemostatic and inflammatory stress. The first section describes the four-quadrant hemostatic system as consisting of the two coagulant and anticoagulant domains that control clot formation and the two fibrinolytic and antifibrinolytic domains that control clot removal. This section concentrates on the anticoagulant domain that operates from the microvascular endothelium and protects it from the effects of hemostatic and inflammatory stress. The next two sections present examples of pure hemostatic and inflammatory stress and illustrate how the four functional domains of the hemostatic systems respond as a unit to these stresses. The following section correlates the response of molecular markers that reflect the activity of the hemostatic system with markers of microvascular endothelial injury to increasing sublethal concentrations of Escherichia coli in the baboon model of E. coli sepsis. The final section correlates the response of these same markers to endotoxin in the human model of endotoxemia. Both sections emphasize that the hemostatic and inflammatory stress and injury to the microvascular endothelium occur at surprisingly low concentrations of E. coli and endotoxin, long before there is evidence of fibrinogen consumption and before the other standard criteria for disseminated intravascular coagulation (DIC) are met. We conclude that this represents a compensated response to stress that can be measured and can be designated as nonovert DIC. We further conclude that as bedside assays of these molecular markers become available they should be helpful in diagnosing and staging early nonovert DIC.

Response to Shiga toxin-1, with and without lipopolysaccharide, in a primate model of hemolytic uremic syndrome.

Shiga toxin (Stx) and lipopolysaccharide (LPS) both participate in the pathogenesis of post-diarrheal hemolytic uremic syndrome (HUS), yet little is known about the factors that modulate the host response to these toxins. We have previously shown that the baboon develops HUS if 100 ng/kg of purified Stx-1 is administered rapidly as a single bolus, but not if it is given as four 25-ng/kg doses every 12 h. We therefore used this baboon model to study the response to small intravenous doses of Stx-1, with and without the co-administration of LPS. The co-administration of two 1-mg/kg doses of LPS (given at 0 and 24 h) and four 25-ng/kg doses of Stx-1 (given at 0, 12, 24, and 36 h) resulted in HUS, but the administration of either toxin separately did not. The development of HUS was associated with a rise in urinary, but not plasma concentrations of TNF, and a rise in both urinary and plasma concentrations of IL-6 and IL-8. We speculate that LPS is not required for disease expression in the human, but that it can augment the response to otherwise subtoxic amounts of Stx and this augmentation may be mediated by LPS-induced cytokine release.

Recombinant tissue factor pathway inhibitor enhances the binding of factor Xa to human monocytes.

Tissue factor pathway inhibitor (TFPI) is a kunitz-type inhibitor of activated factor X (Xa). TFPI was reported to mediate Xa binding to a few of carcinoma cell lines. In this study it was observed that the Xa activity associated with human peripheral blood mononuclear cells (PBMC) incubated with Xa in the presence of recombinant TFPI (rTFPI) was much higher than with Xa alone. Xa activity on PBMC was also observed after whole blood was incubated with pre-formed Xa/TFPI complex. Further studies with flow cytometric analysis demonstrate that rTFPI enhances the binding of Xa to human monocytes. Western blot analysis showed that rTFPI was cleaved into a few of fragments after its incubation with monocytes either in the presence or absence of Xa. Based on these results and the observations reported by others, we speculate that Xa/TFPI complex may bind to human monocytes by a yet unidentified mechanism. The recovery of Xa activity from Xa/TFPI complex on PBMC may be related to the cleavage of rTFPI by Xa and/or monocyte proteases. This observation suggests a new mechanism by which monocytes become procoagulant in some pathological conditions in addition of the well known tissue factor expression on proinflammatic monocytes.

Comparing guanfacine and dextroamphetamine for the treatment of adult attention-deficit/hyperactivity disorder.

The objective of this study was to compare the efficacy of the alpha-2a agonist guanfacine with that of dextroamphetamine for the treatment of adult attention-deficit/hyperactivity disorder (ADHD). Seventeen adult outpatients who met DSM-IV criteria for ADHD participated in a double-blind, placebo-controlled, crossover study comparing drug effects on ADHD symptoms. Measures of change included the DSM-IV ADHD Behavior Checklist for Adults and the Copeland Symptom Checklist for Adult Attention Deficit Disorders. Cognitive measures of attention included the Stroop and Controlled Oral Word Association Test using the letters "C," "F," and "L" (COWAT, CFL version). For each trial, the drug was administered daily and titered up to optimal doses of maximum efficacy but with a minimum of side effects, and then data were collected. Both drugs significantly reduced ADHD symptoms on the DSM-IV Adult Behavior Checklist for Adults over placebo (p < 0.05). The Stroop Color subscale showed significant improvement for both drugs (p < 0.05), but the Color-Word measures showed significant improvement for guanfacine only (p < 0.01). The average dose of guanfacine was 1.10 (SD = 0.60), and the most common side effect of guanfacine was fatigue. No subjects discontinued drug trials. This preliminary study indicates that guanfacine may be a well-tolerated treatment option for adult ADHD.

Endothelial cell protein C receptor plays an important role in protein C activation in vivo.

Endothelial cell protein C receptor (EPCR) augments protein C activation by the thrombin-thrombomodulin complex about 5-fold in vitro. Augmentation is EPCR concentration dependent even when the EPCR concentration is in excess of the thrombomodulin. EPCR is expressed preferentially on large blood vessel endothelium, raising questions about the importance of protein C-EPCR interaction for augmenting systemic protein C activation. In these studies, this question was addressed directly by infusing thrombin into baboons in the presence or absence of a monoclonal antibody to EPCR that blocks protein C binding. Activated protein C levels were then measured directly by capturing the enzyme on a monoclonal antibody and assaying with chromogenic substrate. Blocking protein C-EPCR interaction resulted in about an 88% decrease in circulating activated protein C levels generated in response to thrombin infusion. Leukocyte changes, fibrinogen consumption, fibrin degradation products, and vital signs were similar between the animals infused with thrombin alone and those infused with thrombin and the anti-EPCR antibody. The results indicate that EPCR plays a major role in protein C activation and suggest that defects in the EPCR gene might contribute to increased risk of thrombosis.

Comparison of the responses of global tests of coagulation with molecular markers of neutrophil, endothelial, and hemostatic system perturbation in the baboon model of E. colisepsis--toward a distinction between uncompensated overt DIC and compensated non-overt DIC.

This study correlates changes in neutrophilic activity and endothelial injury with markers of hemostatic activity following the infusion of increasing concentrations of E. coli organisms. It focuses on the hemostatic response as a marker of microvascular injury and uses the response to increasing concentrations of E. coli to refine our definition of disseminated intravascular coagulation (DIC) and distinguish between a compensated (non-overt DIC) and uncompensated (overt DIC) response. We observed that the global coagulation tests reflected activation of the hemostatic system in a dose dependent manner (overt DIC) in the early phases (T+2 to 6 h) of the response to increasing concentrations of E. coli, but that they failed to do so in the late phases (T+ 24 to 48 h). We observed that molecular markers, soluble thrombomodulin and elastase, unlike thrombin/antithrombin and plasmin/antiplasmin complexes, remained elevated out to T+24 to 48 h indicating endothelial injury that persists beyond the initial inflammatory insult in compensated as well as uncompensated DIC.

Description of compensated and uncompensated disseminated intravascular coagulation (DIC) responses (non-overt and overt DIC) in baboon models of intravenous and intraperitoneal Escherichia coli sepsis and in the human model of endotoxemia: toward a better definition of DIC.

OBJECTIVE: Work toward a better definition of disseminated intravascular coagulation (DIC) by characterizing the difference between compensated and uncompensated responses of the hemostatic system to inflammatory stress in baboons and human subjects using global coagulation and molecular marker assays of hemostatic, inflammatory, and endothelial perturbation. DESIGN: We conducted prospective evaluation of the response of baboons to increasing concentrations of intravenous Escherichia coli, human subjects to intravenous endotoxin, and baboons to intraperitoneal E. coli. SETTING: Animal laboratory and medical intensive care facilities, University of Oklahoma Medical School laboratories. SUBJECTS: Cynocephalus baboons; normal healthy male human subjects (age, 24-37 yrs). MEASUREMENTS AND MAIN RESULTS: Global coagulation assays, white blood cell counts, and molecular marker assays (ELISA) of components of the inflammatory and hemostatic systems, neutrophil release products, and endothelial injury. A fall in both fibrinogen concentration and platelet counts indicated a decompensated hemostatic response to inflammatory stress (ie, overt DIC). These responses were observed 2-6 hrs after intravenous infusion of 10(9) and 10(10) colony-forming units (CFU)/g of E. coli and after implantation of 10(11) CFU/g of E. coli into the peritoneal cavity. However, 6 hrs after E. coli challenge, these tests were much less reliable as markers of overt DIC because the fibrinogen underwent an acute phase response and the platelet count fell and remained depressed for 48 hrs in the face of a coagulopathic response that was already beginning to resolve, as reflected by a rising fibrinogen concentration. This lack of reliability was particularly evident in the E. coli peritonitis studies, in which one third of the animals recovered, one third remained sick for up to 14 days, and one third died. In contrast, fibrin degradation products and the molecular markers thrombin/antithrombin, soluble fibrin monomer, protein C, and activated protein C/inhibitor complexes responded consistently in a dose-dependent manner regardless of the length of time after challenge. These variables exhibited this dose response to 106 and 108 CFU/g of E. coli in absence of a fall in fibrinogen concentration. This was defined as a compensated hemostatic response to inflammatory stress (ie, non-overt DIC). The values of these variables correlated closely with rising concentrations of markers of neutrophil activation (elastase/alpha 1 antitrypsin) and endothelial injury (soluble thrombomodulin). This was particularly evident in the human response to endotoxin, in which there was abundant evidence of hemostatic marker response in absence of a fall in platelet or fibrinogen concentration, both immediately after endotoxin infusion (first stage, 0-8 hrs after endotoxin) and later (second stage, 12-48 hrs after endotoxin). CONCLUSION: Global coagulation tests are most useful in detecting overt consumptive coagulopathy (overt DIC) near the time of challenge or injury (1 to 6 hrs). Molecular markers can detect and grade the degree of hemostatic stress of a non-overt consumptive coagulopathy (nonovert DIC). These markers correlate with degree of endothelial cell injury and reveal a reperfusion injury stage (second stage) in the human endotoxin model of compensated hemostatic stress after all clinical symptoms have subsided and the subjects have returned to work.

Peritonitis in the baboon: a primate model which stimulates human sepsis.

The physiological, hemostatic, and immunological responses of 12 chronically instrumented conscious baboons with sepsis due to Escherichia coli peritonitis were compared with that of similarly instrumented controls. Chronic indwelling cannulae were placed in the aorta and pulmonary artery to monitor pressure, cardiac output, and obtain blood samples. At t = 0 a sterile or E. coli-laden fibrin clot containing 1.9-6.7 x 10(11) CFU/kg was introduced into the peritoneal cavity. The control animals were group 1 (n = 3). The animals with peritonitis were divided into three groups depending on their clinical response. Group 2 animals (n = 3) were clinically well at the time of sacrifice (day 14), group 3 (n = 4) survived but were obviously sick on day 14, and group 4 (n = 5) died of sepsis. Implantation of a sterile fibrin clot was well tolerated with little hemodynamic change and a transient minimal inflammatory response in group 1. Implantation of an E. coli-containing clot elicited a hyperdynamic cardiovascular response and evoked a marked inflammatory reaction and a disseminated intravascular coagulopathy. Five of 12 (42%) E. coli animals died from sepsis. In general, the physiological, hemostatic, and immunological disturbances tended to be greatest in these animals. Autopsy revealed residual peritoneal inflammation and varying degrees of inflammation in the lungs, adrenal, spleen, liver, and kidneys in all the animals that received E. coli with the inflammatory infiltrate increasing in severity from group 2 through group 4. Tissue necrosis was observed only in the latter group. We conclude that the cardiovascular, hemostatic, and immunological responses of baboons with sepsis due to E. coli peritonitis exhibit a variable course that resembles the clinical manifestations of gram-negative sepsis in humans.

Recombinant human antithrombin III improves survival and attenuates inflammatory responses in baboons lethally challenged with Escherichia coli.

Plasma-derived antithrombin III (ATIII) prevents the lethal effects of Escherichia coli infusion in baboons, but the mechanisms behind this effect are not clear. In the present study, we evaluated the effects of recombinant human ATIII (rhATIII) on the clinical course and the inflammatory cytokine and coagulation responses in baboons challenged with lethal dose of E coli. Animals in the treatment group (n = 5) received high doses of rhATIII starting 1 hour before an E coli challenge. Those in the control group were administered saline. Survival was significantly improved in the treatment group (P =.002). Both groups had similar hemodynamic responses to E coli challenge but different coagulation and inflammatory responses. The rhATIII group had an accelerated increase of thrombin-ATIII complexes and significantly less fibrinogen consumption compared to controls. In addition, the rhATIII group had much less severe thrombotic pathology on autopsy and virtually no fibrinolytic response to E coli challenge. Furthermore, the rhATIII group had a significantly attenuated inflammatory response as evidenced by marked reduction of the release of various cytokines. We conclude that the early administration of high doses of rhATIII improves the outcome in baboons lethally challenged with E coli, probably due to the combined anticoagulation and anti-inflammatory effects of this therapy. (Blood. 2000;95:1117-1123)

The endothelial cell protein C receptor aids in host defense against Escherichia coli sepsis.

The influence of the endothelial protein C receptor (EPCR) on the host response to Escherichia coli was studied. Animals were treated with 4 separate protocols for survival studies and analysis of physiologic and biochemical parameters: (1) monoclonal antibody (mAb) that blocks protein C/activated protein C binding to EPCR plus sublethal numbers of E coli (SLEC) (n = 4); (2) mAb to EPCR that does not block binding plus SLEC (n = 3); (3) SLEC alone (n = 4); and (4) blocking mAB alone (n = 1). Those animals receiving blocking mAb to EPCR plus sublethal E coli died 7 to 54 hours after challenge, whereas all animals treated with the other protocols were permanent survivors. Histopathologic studies of tissues from animals receiving blocking mAb plus SLEC removed at postmortem were compared with those animals receiving SLEC alone killed at T+24 hours. The animals receiving the blocking mAb exhibited consumption of fibrinogen, microvascular thrombosis with hemorrhage of both the adrenal and renal cortex, and an intense influx of neutrophils into the adrenal, renal, and hepatic microvasculature, whereas the tissues from animals receiving only sublethal E coli exhibited none of these abnormal histopathologic changes. Compared with the control animals, the animals receiving the blocking mAb exhibited significantly elevated serum glutamic pyruvic transaminase, anion gap, thrombin-antithrombin complex, IL-6, IL-8, and soluble thrombomodulin. The levels of circulating activated protein C varied too widely to allow a clear determination of whether the extent of protein C activation was altered in vivo by blocking protein C binding to EPCR. We conclude that protein C/activated protein C binding to EPCR contributes to the negative regulation of the coagulopathic and inflammatory response to E coli and that EPCR provides an additional critical step in the host defense against E coli. (Blood. 2000;95:1680-1686)

Efficacy of modafinil compared to dextroamphetamine for the treatment of attention deficit hyperactivity disorder in adults.

Our objective was to compare the efficacy of the new wake-promoting drug modafinil to that of dextroamphetamine for the treatment of attention deficit hyperactivity disorder (ADHD) in adults. Twenty-two adults who met DSM-IV criteria for ADHD participated in a randomized, double-blind, placebo-controlled, three-phase crossover study comparing placebo, modafinil, and dextroamphetamine for the treatment of ADHD. The twice-daily study medications were titrated to doses of optimum efficacy over 4-7 days and then held constant during the rest of each 2-week treatment phase. Measures of improvement included the DSM-IV ADHD Behavior Checklist for Adults, the Controlled Oral Word Association Test (COWAT, using the letters C, F, and L version), Stroop, and Digit Span (Wechsler Adult Intelligence Scale version). For the 21 (96%) completers, the mean (+/- SD) optimum doses of modafinil and dextroamphetamine were 206.8 mg/day +/- 84.9 and 21.8 mg/day +/- 8.9, respectively. Scores on the DSM-IV ADHD Checklist (p < 0.001) were significantly improved over the placebo condition following treatment with both active medications. Performance on the COWAT (p < 0.05) reached trend levels of significance. Both medications were generally well tolerated. This preliminary study suggests that modafinil may be a viable alternative to conventional stimulants for the treatment of adults with ADHD.

Divergent inducible expression of P-selectin and E-selectin in mice and primates.

We used in vitro and in vivo approaches to examine whether tumor necrosis factor-alpha (TNF-alpha) and oncostatin M (OSM), cytokines that bind to distinct classes of receptors, differentially regulate expression of P- and E-selectin in murine and primate endothelial cells. In human umbilical vein endothelial cells, TNF-alpha rapidly increased mRNA for E-selectin but not P-selectin. OSM elicited little or no change in mRNA for E-selectin, but induced a delayed and prolonged increase in P-selectin mRNA. TNF-alpha and OSM did not cooperate to further enhance P- or E-selectin mRNA. Intravenous infusion of Escherichia coli, which markedly elevates plasma lipopolysaccharide and TNF-alpha, increased mRNA for E-selectin but not P-selectin in baboons. In murine bEnd.3 endothelioma cells, TNF-alpha and OSM individually and cooperatively increased mRNA and protein for both P- and E-selectin. Intravenous injection of these cytokines also individually and cooperatively increased mRNA for P- and E-selectin in mice. We conclude that the murine P- and E-selectin genes respond to both TNF-alpha and OSM, whereas the primate P- and E-selectin genes have much more specialized responses. Such differences should be considered when extrapolating the functions of P- and E-selectin in murine models of inflammation to humans.