The Pathophysiology of The Antiphospholipid Syndrome: A Perspective From The Blood Coagulation System.

The antiphospholipid syndrome (APS), a systemic autoimmune disease characterized by a hypercoagulability associated to vascular thrombosis and/or obstetric morbidity, is caused by the presence of antiphospholipid antibodies such as lupus anticoagulant, anti-ß-2-glycoprotein 1, and/or anticardiolipin antibodies. In the obstetrical APS, antiphospholipid antibodies induce the production of proinflammatory cytokines and tissue factor by placental tissues and recruited neutrophils. Moreover, antiphospholipid antibodies activate the complement system which, in turn, induces a positive feedback leading to recruitment of neutrophils as well as activation of the placenta. Activation of these cells triggers myometrial contractions and cervical ripening provoking the induction of labor. In thrombotic and obstetrical APS, antiphospholipid antibodies activate endothelial cells, platelets, and neutrophils and they may alter the multimeric pattern and concentration of von Willebrand factor, increase the concentration of thrombospondin 1, reduce the inactivation of factor XI by antithrombin, increase the activation of factor XII, and reduce the activity of tissue plasminogen activator with the subsequent production of plasmin. All these effects result in less permeable clots, denser, thinner, and with more branched fibrin fibers which are more difficult to lysate. As a consequence, thrombosis, the defining clinical criterion of APS, complicates the clinical course of the patient.

Identification of genetic risk factors associated with ischaemic stroke in young Mexican patients.

BACKGROUND: Numerous polymorphisms in candidate genes coding for haemostatic system proteins have been proposed as risk factors for thrombosis. METHODS: We performed a case-control study of consecutive ischaemic stroke survivors aged ≤45 years, treated at our neurology department from 2006 to 2014. Polymerase chain reaction-restriction fragment length polymorphism identified the following polymorphisms: Thr325Ile and Ala147Thr in TAFI, 4G/5G in PAI-1, PLA1/A2 in platelet glycoprotein IIb/IIIa, Glu298Asp in eNOS, and C677T in 5,10-MTHFR. A multivariate logistic regression analysis was performed to evaluate the independent risk of stroke. RESULTS: 204 cases and 204 age- and sex-matched controls were included in the study. Clinical and genetic variables associated with ischaemic stroke were hypertension (P=.03), tobacco use (P=.02), and the polymorphisms Glu298Asp (genotype: P=.001, allele frequency: P=.001) and C677T (genotype: P=.01); the Ala147Thr, Thr325IIe, 4G/5G, and PLA1/A2 mutations were not associated with ischaemic stroke. The 298Asp (P=.03) and T (P=.01) alleles, hypertension (P=.03), tobacco use (P=.01) and family history of stroke (P=.04) were identified as independent risk factors. CONCLUSION: The polymorphisms Glu298Asp and C677T, affecting the eNOS and 5,10-MTHFR enzymes, respectively, and smoking, hypertension, and family history of stroke were associated with ischaemic stroke in young Mexican patients; this was not the case for the Thr325Ile, Ala147Thr, 4G/5G, and PLA1/A2 polymorphisms of the genes coding for fibrinolytic proteins and platelet receptors.

Interethnic variation of the MMP-9 microsatellite in Amerindian and Mexican Mestizo populations: considerations for genetic association studies.

We studied the interethnic variation of the MMP-9 microsatellite in the Mestizo and Amerindian populations using blood samples collected from 435 healthy unrelated individuals from the Central Valley of Mexico. DNA samples were genotyped using the -90 (CA)12-27 repeat near the MMP transcriptional start site using capillary electrophoresis. Our data were compared with those from African, Asian, and European populations (N = 729). Both Mestizo and Amerindian populations were in Hardy-Weinberg equilibrium (P ≥ 0.05). However, strong genetic heterogeneity was found within the Mestizo population (94%, P ≤ 0.0001), which exhibited the highest frequency of Amerindian, African, and European alleles. Likewise, Amerindians showed 6.7% variation among populations (P ≤ 0.0001), suggesting a genetic substructure potentially associated with linguistic affiliations. These findings were corroborated with principal component and population differentiation analyses, which showed relative proximity among the Mestizos and their historical parental populations: Asian (FST ≥ 0.05), European (FST ≥ 0.09), and African (FST ≥ 0.02). Nevertheless, important differences were found between Mestizo and Nahuas (P ≤ 0.0001), and between Mestizo and Me'Phaas (P ≤ 0.0001). These findings highlight the importance of determining local-specific patterns to establish the population variability of MMP-9 and other polymorphic markers. Validation of candidate markers is critical to identifying risk factors; however, this depends on knowledge of population genetic variation, which increases the possibility of finding true causative variants. We also show that dissimilar ethnic backgrounds might lead to spurious associations. Our study provides useful considerations for greater accuracy and robustness in future genetic association studies.

Impact of obesity severity and duration on pancreatic ß- and α-cell dynamics in normoglycemic non-human primates.

OBJECTIVE: Obesity is associated with high insulin and glucagon plasma levels. Enhanced ß-cell function and ß-cell expansion are responsible for insulin hypersecretion. It is unknown whether hyperglucagonemia is due to α-cell hypersecretion or to an increase in α-cell mass. In this study, we investigated the dynamics of the ß-cell and α-cell function and mass in pancreas of obese normoglycemic baboons. METHODS: Pancreatic ß- and α-cell volumes were measured in 51 normoglycemic baboons divided into six groups according to overweight severity or duration. Islets morphometric parameters were correlated to overweight and to diverse metabolic and laboratory parameters. RESULTS: Relative α-cell volume (RαV) and relative islet α-cell volume (RIαV) increased significantly with both overweight duration and severity. Conversely, in spite of the induction of insulin resistance, overweight produced only modest effects on relative ß-cell volume (RßV) and relative islet ß-cell volume (RIßV). Of note, RIßV did not increase neither with overweight duration nor with overweight severity, supposedly because of the concomitant, greater increase in RIαV. Baboons' body weights correlated with serum levels of interleukin-6 and tumor necrosis factor-α soluble receptors, demonstrating that overweight induces abnormal activation of the signaling of two cytokines known to impact differently ß- and α-cell viability and replication. CONCLUSION: In conclusion, overweight and insulin resistance induce in baboons a significant increase in α-cell volumes (RαV, RIαV), whereas have minimal effects on the ß cells. This study suggests that an increase in the α-cell mass may precede the loss of ß cells and the transition to overt hyperglycemia and diabetes.

von Willebrand's disease in Mexico: a pilot study.

von Willebrand's disease (VWD) is the most commonly inherited bleeding disorder. For a long time, it has been said that VWD was absent in some countries due to ethnical differences. Information about the prevalence of VWD in Mexico remains unclear, owing largely to poor awareness and diagnosis of the disease. The aim of this study was to objectively diagnose VWD in a cohort of highly selected Mexican patients with a chronic history of bleeding. Mexican Mestizos were recruited between July 2010 and August 2011. Included were 133 adult and paediatric patients with a high suspicion of VWD. Fifty-three were diagnosed with VWD: 47 (88.7%) with type 1 VWD, four (7.5%) with type 2a VWD and two (3.8%) with type 3 VWD. Mean age for female patients was 19.5 years (range 3-44 years) and 18.5 years (range 4-63 years) for male patients. Mean age at start of bleeding symptoms was 8.8 years (range 1-61). The most frequent clinical symptoms were epistaxis (84.9%), ecchymosis (79.2%), haematomas (71.7%), gum bleeds (62.3%) and petechia (50.9%). Severe transoperative or postoperative bleeding was found in 17 patients (32.1%). Twenty-six women at childbearing age had a history of abnormal gynaecological bleeding. Our results clearly demonstrate the presence of VWD in Mexican and underscore the importance of a more detailed description of VWD. Efforts to increase the awareness and diagnosis of VWD could help in better identification of patients with bleeding disorders and lead to early, appropriate management with safe and efficacious therapies such as desmopressin and plasma concentrates.

Awareness regarding venous thromboembolism among internal medicine practitioners in Mexico: a national cross-sectional study.

BACKGROUND: Venous thromboembolism (VTE) affects millions of patients worldwide and is responsible for thousands of hospitalisations annually. AIMS: To evaluate the awareness regarding VTE among Mexican internists. METHODS: We designed a cross-sectional survey using a questionnaire applied to Mexican internists mainly during academic meetings. RESULTS: We collected 1220 questionnaires. VTE was considered a potential complication for medical inpatients by 85% of the respondents, whereas 69% and 63%, respectively, considered pulmonary embolism to be a complication of deep vein thrombosis (DVT) and a cause of death. Awareness of some VTE risk factors was adequate, and 85% of those physicians surveyed routinely observed patients for these risk factors, although only 58% performed global risk stratification. Only 12% of the respondents considered length of hospital stay as a risk factor, and 58% assumed that the risk decreases after hospital discharge; 64% and 49% responded that the risk is higher, and VTE risk factors are more frequent in surgical versus medical inpatients respectively. VTE diagnosis was reported as easy or very easy for 59% of the respondents, but only 41% regarded phlebography as the gold standard for diagnosing DVT, although 85% of the respondents reported that d-dimer + Doppler ultrasound was an alternative. Pulmonary arteriography or helical computed tomography CT scan was the gold standard for diagnosing pulmonary embolism for 60% of the physicians, but 55% responded that electrocardiogram, arterial gasometry and chest X-ray are also useful. CONCLUSIONS: Awareness regarding VTE risk factors and the degree of diagnostic skills among Mexican internal medicine specialists are low.

[Joint position statement of the Mexican College of Orthopedics and Traumatology: prophylaxis for venous thromboembolic disease in high-risk orthopedic surgery]. / Declaración de posición conjunta del Colegio Mexicano de Ortopedia y Traumatología: profilaxis de la enfermedad tromboembólica venosa en cirugía ortopédica de alto riesgo.

Venous thromboembolic disease (VTED) is a public health problem worldwide. In the United States it causes 2 million annual cases. Its annual incidence is 1-2 cases per 1,000 individuals in the general population. It is a disease frequently associated with life threatening complications and its mortality rate is 1-5% of cases. Due to its high complication rate, its slow recovery, and the need for prolonged disability, it is considered as a high-cost disease. VTED may occur in both surgical and medical patients; the known associated risk factors include prolonged rest, active cancer, congestive heart failure, atrial fibrillation, and stroke, among the major medical conditions. Orthopedic surgery represents the main surgical risk factor for VTED, including mainly hip and knee replacements, as well as polytraumatized patients with severe spinal lesions, and major fractures. VTED may be prevented with the appropriate use of antithrombotics. The participants in this consensus defined thromboprophylaxis as the strategy and actions undertaken to reduce the risk of VTED in patients undergoing high risk orthopedic surgery. The position of the Mexican College of Orthopedics and Traumatology regarding the prevention of VTED in orthopedic surgery is described herein.

Multiple myeloma-associated amyloidosis is an independent high-risk prognostic factor.

Several prognostic factors have been recognized in patients with multiple myeloma (MM). Among the most important are: the serum levels of beta2-microglobulin, albumin, and LDH; the labeling index; and an abnormal karyotype. Patients with amyloidosis (AL) have poor prognosis; however, little is known concerning the prognostic significance of AL associated to MM. In 201 consecutive patients with de novo MM, we performed a fat-pad biopsy needle aspiration (FPBNA) that was stained with Congo red. Sixty eight (34%) patients had AL and a poorer prognosis disease: lower performance status, presence of B symptoms, higher LDH and calcium values, and worse response to chemotherapy. Cox regression model for overall survival detected three variables having independent prognostic significance: the presence of AL (RR = 3.4, P < 0.004), serum albumin levels <3.5 g/dl (RR 3.2, p < 0.005), and patients not achieving complete remission or very good partial remission (RR 2.9, p < 0.02). In 28% of patients with de novo MM, FPBNA was useful to detect incidental amyloidosis. During follow-up, 69% of these patients had symptoms of AL. Excluding 16 patients with obvious symptoms of AL at diagnosis, overall survival was worse in patients who developed later symptoms of AL. MM-associated AL represents a poorer prognosis disease even in the absence of symptoms at diagnosis, and this specific association may be considered as an independent high-risk prognostic factor. The routine study of periumbilical fat-pad tissue should be mandatory in all patients with MM.

Lamivudine-induced pure red cell aplasia.

The aim of this report is to describe five patients with lamivudine-induced pure red cell aplasia, an association not previously described. We describe patients with unresponsive anemia in whom a complete study including blood cell counts, reticulocyte counts, hemolysis tests, and bone marrow aspiration was performed. Pure red cell aplasia was considered when anemia was associated with normal leukocyte and platelet counts with a corrected reticulocyte count below 1% and less than 5% bone marrow erythroid progenitors in the absence of positive hemolysis tests. Complete remission was considered when bone marrow erythroid progenitors were at least 16%. Five male patients had pure red cell aplasia with a median age of 32 years (range 29 to 37 years). Before lamivudine, they had hemoglobin >11.8 g/dl without transfusion requirements. After receiving the drug, hemoglobin dropped to 5.2 g/dl (4.3 to 6.1 g/dl) with high transfusion requirements and mean bone marrow erythroid progenitors of 1.84% (0 to 4%). Withdrawal of lamivudine was attempted to confirm the diagnosis. Seven weeks after stopping lamivudine, hemoglobin rose up to 12.8 g/dl (11 .3 to 13.8 g/dl) and bone marrow erythroid progenitors increased up to 25.6% (21 to 40%) without transfusion requirements. Lamivudine-induced pure red cell aplasia may be a cause of anemia unresponsive to conventional treatment in AIDS. Since lamivudine use in Mexico has been relatively short, we expect more cases to appear in the future.

Residues F16-G33 and A784-N823 within platelet thrombospondin-1 play a major role in binding human neutrophils: evaluation by two novel binding assays.

The thrombospondin-1 (TSP1) structural requirements within its heparin-binding domain (HBD)(30 kd) or within the other domains of the molecule (450 kd) that interact with neutrophils (PMNs) have not been delineated. Synthetic peptides based on the HBD, a TSP1 proteolytic fragment lacking the HBD, a large C-terminal domain of TSP1 (210 kd), a TSP1 recombinant fragment (rTSP1(784-932)), and a monoclonal antibody directed against the TSP1 type 3 repeats (mAb D4.6) were utilized to map such structural requirements on TSP1. Synthetic peptides containing a heparin-binding motif and encompassing residues F16-G33 or A74-S95 of TSP1 competed quantitatively with iodine 125-labeled TSP1 for binding to heparinagarose beads. However, only F16-G33 was a competitor of TSP1 binding to PMNs, suggesting that the sequence F16-G33 within the HBD plays a role in PMN binding. The interaction site within the 450-kd fragment was further narrowed. A TSP1 -derived proteolytic fragment (210 kd), a recombinant TSP1 fragment (rTSP1(784-932)), and a type 3 repeat anti-TSP1 monoclonal antibody (mAb D4.6) competed for the binding of 125I-labeled TSP1 to PMNs. The N-terminal of rTSP1(784-932) and C-terminal sequence analysis of TSP1-210 kd delineated the structural requirements for the second binding region for PMNs-namely, residues A784-N823.

Serum erythropoietin levels in kidney donors after renal transplantation.

BACKGROUND: Renal transplantation is the treatment of choice for many patients with end-stage renal disease. In the donor, renal excretory function is not affected after nephrectomy; however, little is known about other functions such as erythropoietin production. We studied the erythropoietin production in renal donors after nephrectomy. METHODS: We included healthy individuals fulfilling the criteria for kidney donation. Blood samples were collected before and monthly from 1 to 6 months after nephrectomy. Complete blood cell counts and erythropoietin were assayed. RESULTS: Eight kidney donors were studied. A significant increase in erythropoietin levels was observed during the first 3 months, but no difference was observed by the 4th month as compared with basal values. CONCLUSIONS: Erythropoietin production rose during the first 3 months after nephrectomy. However, erythropoietin was normal by the 4th month. Unchanged hemoglobin levels may suggest that the compensatory production of erythropoietin could participate in the preservation of an adequate physiological status of the donor after nephrectomy.

[Thrombophilia, thromboembolism and the use of the unfractionated and low-molecular-weight heparins]. / Trombofilia, tromboembolia y el uso de las heparinas no fraccionadas y de bajo peso molecular.

An overview of the key concepts about detection of thrombophilic states, establishment of risk factors for thrombosis, the current strategies on diagnosis of thrombophilia, as well as an analysis of the current experience with the use of fractionated and unfractionated heparins, is presented. It is well known that thrombotic disease is multifactorial and that its treatment must be interdisciplinary and multidisciplinary in order to perform an opportune diagnosis and to establish an adequate prophylaxis and anti-thrombotic therapy. Even though several advantages are observed when low molecular weight heparins are used, unfractionated heparins still have some specific indications. Furthermore, under specific conditions, they can work synergistically to achieve a maximal effect on the thromboembolic states. We propose that every medical unit should establish its own criteria and diagnostic and therapeutic algorithms that allow to detect, to diagnose, and to treat the thrombotic events in the best way thus diminishing the morbidity and mortality associated with these thrombotic events.

External quality control program of four blood cell counters.

OBJECTIVE: To evaluate an internal-external quality control program of four automated counters. METHODS: Every one or two weeks during 14 months, six direct cell parameters were measured in three fresh blood samples in four Coulter counters. The median per parameter of the working day was used to detect inaccuracies and if the participants' internal control program confirmed it, a recalibration of the parameter was performed. RESULTS: In 21 of 22 instances, the internal program confirmed an inaccuracy and a recalibration was done (4 leukocyte and 5 erythrocyte counts, 5 hemoglobins, 7 red-cell volumes). In these four parameters there were no large differences between the lowest and highest counter upon analyzing all results whereas all counters differed from one another in the parameters that cannot be recalibrated by the user (platelet volume, red-cell distribution width). CONCLUSIONS: 1. The program contributed to good accuracy and precision within-counters and good concordancy between-counters in the parameters that can be recalibrated. 2. The counter differences in red-cell distribution width were sufficiently large (up to 9%) to affect clinical interpretation. This poses the need of width distribution reference ranges for each counter.

Refractory anemia with excess of blasts: increased survival when treated with cyclophosphamide, methotrexate and 6-mercaptopurine.

Owing to the lack of efficacious treatments for refractory anemia with an excess of blasts (RAEB), evaluation of other therapeutic strategies is necessary, especially in elderly patients. We report herein our experience with an oral triple drug regimen with cyclophosphamide 200 mg/m2 and methotrexate 20 mg/m2 once a week, and 6-mercaptopurine 50 mg/m2 daily for the treatment of RAEB. Eighteen patients with a median age of 62 yr (range 17-80) received a triple drug regimen (TDR), and they were compared with 6 patients who received oxymetholone (2 mg/m2/d) and 9 who received supportive therapy only. Partial response was achieved in 45% of patients receiving TDR. In 77% of patients treated with TDR the number of bone marrow blasts decreased to <5%; however, they persisted with trilineage dyspoietic morphologic changes. Median survival for TDR was 23 months (range 1-96), which was longer than that for the other groups. A slight rise in liver enzymes was the only side effect of TDR. TDR seems to be a useful alternative in patients with RAEB, a finding to be confirmed in further prospective studies.

Hemophagocytic syndrome associated with hematological neoplasias.

Hemophagocytic syndrome (HPS) is a reactive process that complicates several diseases including hematological neoplasias (HN). It has been suggested that HPS may be a negative prognosis factor for neoplastic diseases. In this retrospective analysis, 13 cases with HPS associated to HN were compared with two age, sex, diagnosis, disease stage and treatment matched controls in order to determine the impact of this syndrome on the survival. Cases with HPS were adult patients with a male:female ratio of 1:1 and their clinical picture was characterized by fever, lymphadenopathy, hepatosplenomegaly, and pancytopenia. Median survival since HN diagnosis was 7 and 48 months for the HPS and control groups, respectively (P = 0.0001). In ten patients who died, median survival after HPS presentation was 1 month. These results suggest that the presence of HPS is a negative prognosis factor in patients with HN. Due to its high mortality rate, an individualized, early, and intensive chemotherapeutic regimen may be required for HN complicated with this syndrome.

Usefulness of a low-dose intravenous immunoglobulin regimen for the treatment of thrombocytopenia associated with AIDS.

Infection with the human immunodeficiency virus (HIV) frequently is complicated with thrombocytopenia (HIV-Thr) during all stages of the infection. The treatments for autoimmune thrombocytopenic purpura (ITP) are used in HIV-Thr; however, their effects upon the immune status of patients with acquired immunodeficiency syndrome (AIDS) are unknown. Intravenous immunoglobulin (IVIg) is used in patients with ITP and HIV-Thr; however, its usefulness in thrombocytopenic AIDS patients has not been directly addressed. We used a low-dose IVIg regimen (0.04 g/kg per week during five weeks) for the treatment of HIV-Thr complicating AIDS. Thirteen patients received IVIg. We observed a response to IVIg in 13 patients by the end of week one and in 10 patients by the end of week five. Long-term response, evaluated three months after stopping IVIg, was present in four cases. IVIg was well tolerated and no opportunistic infections were observed during the study period. Compared with previous reports, we used 10% of the previously proposed dosage with an important decrease in the cost of treatment. Our results suggest that this low-dose IVIg regimen is a highly effective, nonexpensive alternative in treating HIV-Thr in AIDS. If sustained responses can be obtained with a similar low-dose maintenance regimen, IVIg may be the first choice for the treatment of HIV-Thr in AIDS patients.

Cyclic AMP-specific phosphodiesterase inhibitor rolipram and RO-20-1724 promoted apoptosis in HL60 promyelocytic leukemic cells via cyclic AMP-independent mechanism.

Phosphodiesterases (PDEs) are responsible for the hydrolysis of cAMP and cGMP which act as intracellular second messengers in a variety of cellular functions. In this paper we report that PDE3 and PDE4 were two dominant classes of PDEs expressed in HL60 cells. The influence of specific PDE inhibitors on apoptosis in HL60 cells was studied. The non-specific inhibitor IBMX and PDE3 specific inhibitors (milrinone and trequinsin) did not promote apoptosis. They inhibited apoptosis induced by paclitaxel or thapsigargin. However, PDE4 specific inhibitors (rolipram and RO-20-1724) promoted apoptosis within 5 h. In HL60 cells, other cAMP-eliciting reagents (8-bromo-cAMP, Sp-cAMP and forskolin) also inhibited apoptosis, while cell-permeable cGMP analogs did not affect apoptosis. Therefore, IBMX and PDE3 specific inhibitors may prevent HL60 cells from apoptosis by increasing intracellular cAMP. However, apoptosis induced by PDE4 specific inhibitors is not likely due to increased cAMP level. These results suggest that rolipram and RO-20-1724 promoted apoptosis in HL60 cells through cAMP-independent mechanism.

Three noncontiguous peptides comprise binding sites on high-molecular-weight kininogen to neutrophils.

The binding of high-molecular-weight kininogen (HK) to neutrophils (polymorphonuclear leukocytes, PMN) is required for the stimulation of aggregation and degranulation by human plasma kallikrein as well as the displacement of fibrinogen from this cell surface. The putative receptor for HK is the leukocyte integrin alphaMbeta2, and domains 3 (D3) and 5 (D5) of HK form its binding site. To further map the binding sites on HK for PMN, we used D3 recombinant exon products and designed peptides from D3 and D5. In D3, a heptapeptide, Leu271-Ala277, from exon 7 product, and a peptide, Cys333-Cys352, from exon 9 product can inhibit binding of kininogen to PMN. Two contiguous peptides from D5 in the histidine-glycine-rich region, Gly442-Lys458 and Phe459-Lys478, each inhibit the binding of HK to PMN. This study has thus delineated three noncontiguous surface-oriented sequences on HK, which together comprise all or most of the binding site for human PMN.

Recombinant tumor necrosis factor receptor p75 fusion protein (TNFR:Fc) alters endotoxin-induced activation of the kinin, fibrinolytic, and coagulation systems in normal humans.

The effects of inhibition of tumor necrosis factor (TNF) on cell and protease activation were evaluated in 18 normal volunteers given endotoxin (4 ng/kg, i.v.) after an infusion of low (10 mg/m2 i.v., n = 6) or high dose (60 mg/m2 i.v., n = 6) recombinant human dimeric TNF receptor protein (TNFR:Fc) or its vehicle (placebo n = 6). Activation of the coagulation system occurred by 2 h in the TNFR:Fc vehicle-placebo group manifested by decreased prekallikrein functional levels and increased levels of prothrombin F1+2 fragments (p < 0.0001). High or low dose TNFR:Fc delayed the fall in prekallikrein functional levels by 1 h and 4 h, respectively (p < 0.0002), but did not inhibit the increase in circulating levels of prothrombin F1+2 fragments. In contrast, endothelium activation, characterized by increased levels of tissue plasminogen activator, plasminogen activator inhibitor-1, and von Willebrand Factor antigen was blunted by both low and high dose TNFR:Fc (p < 0.001). While the endotoxin-associated decrease in platelet number was not altered, platelet-derived beta-thromboglobulin peak levels were blunted and delayed by TNFR:Fc (p < 0.02). Increased levels of neutrophil elastase were attenuated by low and high dose TNFR:Fc (p < 0.001). These results suggest that although TNF is functionally linked to the activation of endothelium, neutrophils, coagulation, and fibrinolysis, alternative pathways are present in vivo that result in activation of the kallikrein-kinin system after endotoxin-induced TNF release. These alternative pathways may limit some of the anti-inflammatory effects of TNFR:Fc.

Specific inhibition of plasma kallikrein modulates chronic granulomatous intestinal and systemic inflammation in genetically susceptible rats.

The kallikrein-kinin (K-K) (contact) system is activated during acute and chronic relapsing phases of enterocolitis induced in genetically susceptible Lewis rats by intramural injection of peptidoglycan-polysaccharide (PG-APS). Using the selective plasma kallikrein inhibitor P8720, we investigate whether activation of the K-K system plays a primary role in chronic granulomatous intestinal and systemic inflammation in this model. Group I (negative control) received human serum albumin intramurally. Group II (treatment) received PG-APS intramurally and P8720 orally. Group III (positive control) received PG-APS intramurally and albumin orally. P8720 attenuated the consumption of the contact proteins, high molecular weight kininogen (P<0.03), and factor XI (P<0.04) in group II vs. group III. P8720 decreased chronic intestinal inflammation measured by blinded gross (P<0.01) and histologic (P<0.0005) scores as well as systemic complications (arthritis, splenomegaly, hepatomegaly, leukocytosis, and acute-phase reaction) (P<0.01) in group II as compared with group III. We conclude that relapsing chronic enterocolitis and systemic complications are in part due to plasma K-K system activation, and that inhibition of this pathway is a potential therapeutic approach to human inflammatory bowel disease and associated extraintestinal manifestations.