S-Nitrosylation of Tissue Transglutaminase in Modulating Glycolysis, Oxidative Stress, and Inflammatory Responses in Normal and Indoxyl-Sulfate-Induced Endothelial Cells

Circulating uremic toxin indoxyl sulfate (IS), endothelial cell (EC) dysfunction, and decreased nitric oxide (NO) bioavailability are found in chronic kidney disease patients. NO nitrosylates/denitrosylates a specific protein's cysteine residue(s), forming S-nitrosothios (SNOs), and the decreased NO bioavailability could interfere with NO-mediated signaling events. We were interested in investigating the underlying mechanism(s) of the reduced NO and how it would regulate the S-nitrosylation of tissue transglutaminase (TG2) and its substrates on glycolytic, redox and inflammatory responses in normal and IS-induced EC injury. TG2, a therapeutic target for fibrosis, has a Ca²⁺-dependent transamidase (TGase) that is modulated by S-nitrosylation. We found IS increased oxidative stress, reduced NADPH and GSH levels, and uncoupled eNOS to generate NO. Immunoblot analysis demonstrated the upregulation of an angiotensin-converting enzyme (ACE) and significant downregulation of the beneficial ACE2 isoform that could contribute to oxidative stress in IS-induced injury. An in situ TGase assay demonstrated IS-activated TG2/TGase aminylated eNOS, NFkB, IkBα, PKM2, G6PD, GAPDH, and fibronectin (FN), leading to caspases activation. Except for FN, TGase substrates were all differentially S-nitrosylated either with or without IS but were denitrosylated in the presence of a specific, irreversible TG2/TGase inhibitor ZDON, suggesting ZDON-bound TG2 was not effectively transnitrosylating to TG2/TGase substrates. The data suggest novel roles of TG2 in the aminylation of its substrates and could also potentially function as a Cys-to-Cys S-nitrosylase to exert NO's bioactivity to its substrates and modulate glycolysis, redox, and inflammation in normal and IS-induced EC injury.

Association of Sickle Cell Trait With Incidence of Coronary Heart Disease Among African American Individuals

IMPORTANCE

The incidence of and mortality from coronary heart disease (CHD) are substantially higher among African American individuals compared with non-Hispanic White individuals, even after adjusting for traditional factors associated with CHD. The unexplained excess risk might be due to genetic factors related to African ancestry that are associated with a higher risk of CHD, such as the heterozygous state for the sickle cell variant or sickle cell trait (SCT).

OBJECTIVE

To evaluate whether there is an association between SCT and the incidence of myocardial infarction (MI) or composite CHD outcomes in African American individuals.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study included 5 large, prospective, population-based cohorts of African American individuals in the Women's Health Initiative (WHI) study, the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, the Multi-Ethnic Study of Atherosclerosis (MESA), the Jackson Heart Study (JHS), and the Atherosclerosis Risk in Communities (ARIC) study. The follow-up periods included in this study were 1993 and 1998 to 2014 for the WHI study, 2003 to 2014 for the REGARDS study, 2002 to 2016 for the MESA, 2002 to 2015 for the JHS, and 1987 to 2016 for the ARIC study. Data analysis began in October 2013 and was completed in October 2020.

EXPOSURES

Sickle cell trait status was evaluated by either direct genotyping or high-quality imputation of rs334 (the sickle cell variant). Participants with sickle cell disease and those with a history of CHD were excluded from the analyses.

MAIN OUTCOMES AND MEASURES

Incident MI, defined as adjudicated nonfatal or fatal MI, and incident CHD, defined as adjudicated nonfatal MI, fatal MI, coronary revascularization procedures, or death due to CHD. Cox proportional hazards regression models were used to estimate the hazard ratio for incident MI or CHD comparing SCT carriers with noncarriers. Models were adjusted for age, sex (except for the WHI study), study site or region of residence, hypertension status or systolic blood pressure, type 1 or 2 diabetes, serum high-density lipoprotein level, total cholesterol level, and global ancestry (estimated from principal components analysis).

RESULTS

A total of 23 197 African American men (29.8%) and women (70.2%) were included in the combined sample, of whom 1781 had SCT (7.7% prevalence). Mean (SD) ages at baseline were 61.2 (6.9) years in the WHI study (n = 5904), 64.0 (9.3) years in the REGARDS study (n = 10 714), 62.0 (10.0) years in the MESA (n = 1556), 50.3 (12.0) years in the JHS (n = 2175), and 53.2 (5.8) years in the ARIC study (n = 2848). There were no significant differences in the distribution of traditional factors associated with cardiovascular disease by SCT status within cohorts. A combined total of 1034 participants (76 with SCT) had incident MI, and 1714 (137 with SCT) had the composite CHD outcome. The meta-analyzed crude incidence rate of MI did not differ by SCT status and was 3.8 per 1000 person-years (95% CI, 3.3-4.5 per 1000 person-years) among those with SCT and 3.6 per 1000 person-years (95% CI, 2.7-5.1 per 1000 person-years) among those without SCT. For the composite CHD outcome, these rates were 7.3 per 1000 person-years (95% CI, 5.5-9.7 per 1000 person-years) among those with SCT and 6.0 per 1000 person-years (95% CI, 4.9-7.4 per 1000 person-years) among those without SCT. Meta-analysis of the 5 study results showed that SCT status was not significantly associated with MI (hazard ratio, 1.03; 95% CI, 0.81-1.32) or the composite CHD outcome (hazard ratio, 1.16; 95% CI, 0.92-1.47).

CONCLUSIONS AND RELEVANCE

In this cohort study, there was not an association between SCT and increased risk of MI or CHD in African American individuals. These disorders may not be associated with sickle cell trait-related sudden death in this population.

Impact of Benign Hematology Didactic Lectures on In-service Exam in a Hematology-Oncology Fellowship Program: a Cross-sectional Longitudinal Study

It remains unclear on whether the traditional formal didactic lecture sessions improve knowledge acquisition with conflicting data in the literature. This study evaluates the impact of an additional benign hematology didactic curriculum on the American Society of Hematology In-Service Exam (ASHISE). During the first 5 years of the study (2012-2016), formal didactic lectures consisted of medical oncology and malignant hematology topics only. Formal benign hematology didactic lectures were added during the last 2 years of the study (2017-2018). All fellows are required to take the ASHISE annually. All fellows' ASHISE scores from 2012 to 2018 were collected. The mean total and Coagulation scale score were calculated by year of fellowship training. Pre-intervention (2012-2016) and post-intervention (2017-2018) scores were analyzed using a Student's t test. Over a 7-year period, 34 hematology-oncology fellows took the ASHISE. There was no statistical difference in the mean total and Coagulation scale score for the ASHISE in the pre-intervention and post-intervention group. The addition of a benign hematology curriculum did not improve fellows' performance on the ASHISE.

AGA Clinical Practice Update: Coagulation in Cirrhosis

DESCRIPTION

This expert review was commissioned and approved by the AGA Institute Clinical Practice Updates Committee and the AGA Governing Board to provide timely guidance on a topic of high clinical importance to the AGA membership. The intent is to evaluate the current data on mechanism of altered coagulation in patients with cirrhosis, provide guidance on the use of currently available testing of the coagulation cascade, and help practitioners use anticoagulation and pro-coagulants appropriately in patients with cirrhosis.

METHODS

This review is framed around the best practice points, which were derived from the most impactful publications in the area of coagulation in cirrhosis and agreed to by all authors. BEST PRACTICE ADVICE 1: Global tests of clot formation, such as rotational thromboelastometry, thromboelastography, sonorheometry, and thrombin generation, may eventually have a role in the evaluation of clotting in patients with cirrhosis, but currently lack validated target levels. BEST PRACTICE ADVICE 2: In general, clinicians should not routinely correct thrombocytopenia and coagulopathy before low-risk therapeutic paracentesis, thoracentesis, and routine upper endoscopy for variceal ligation in patients with hepatic synthetic dysfunction-induced coagulation abnormalities. BEST PRACTICE ADVICE 3: Blood products should be used sparingly because they increase portal pressure and carry a risk of transfusion-associated circulatory overload, transfusion-related acute lung injury, infection transmission, alloimmunization, and/or transfusion reactions. BEST PRACTICE ADVICE 4: The following transfusion thresholds for management of active bleeding or high-risk procedures may optimize clot formation in advanced liver disease: hematocrit ≥25%, platelet count >50,000, and fibrinogen >120 mg/dL. Commonly utilized thresholds for international normalized ratio correction are not supported by evidence. BEST PRACTICE ADVICE 5: Thrombopoietin agonists are a good alternative to platelet transfusion, but require time (about 10 days) to elevate platelet levels. BEST PRACTICE ADVICE 6: The large volume of fresh frozen plasma required to reach an arbitrary international normalized ratio target, limitations of the usual target, minimal effect on thrombin generation, and adverse effects on portal pressure limit the utility of this agent significantly. BEST PRACTICE ADVICE 7: The 4-factor prothrombin complex concentrate contains both pro- and anticoagulant factors that offer an attractive low-volume therapeutic to rebalance a disturbed hemostatic system. However, dosage is, in part, based on international normalized ratio, which is problematic in cirrhosis, and published experience in liver disease is limited. BEST PRACTICE ADVICE 8: Anti-fibrinolytic therapy may be considered in patients with persistent bleeding from mucosal oozing or puncture wound bleeding consistent with impaired clot integrity. Both ε-aminocaproic acid and tranexamic acid inhibit clot dissolution. Neither is believed to generate a hypercoagulable state, although both may exacerbate pre-existing thrombi. BEST PRACTICE ADVICE 9: Desmopressin releases von Willebrand factor as its primary hemostatic mechanism. As this factor is usually elevated in cirrhosis, the agent lacks a sound evidence-based foundation, but may be useful in patients with concomitant renal failure. BEST PRACTICE ADVICE 10: Systemic heparin infusion is recommended for symptomatic deep vein thrombosis and portal and mesenteric vein thrombosis, but there are unresolved issues regarding monitoring with both the anti-Xa assay and the partial thromboplastin time due to cirrhosis-related antithrombin deficiency (heparin cofactor). BEST PRACTICE ADVICE 11: Treatment of incidental portal and mesenteric vein thrombosis depends on estimated impact on transplantation surgical complexity vs risks of bleeding and falls. Therapy with low-molecular-weight heparin, vitamin K antagonists, and direct-acting anticoagulants improve portal vein repermeation vs observation alone. BEST PRACTICE ADVICE 12: Direct-acting anticoagulants, such as the factor Xa and thrombin inhibitors, are relatively safe and effective in stable cirrhotic patients, but are in need of further study in patients with more advanced liver disease.

Successful Management of Thrombotic Thrombocytopenic Purpura in a Jehovah's Witness: An Individualized Approach With Joint Decision-Making

The management of thrombotic thrombocytopenic purpura (TTP) presents a unique challenge in individuals who are unable to accept plasma due to religious beliefs, given that therapeutic plasma exchange (TPE) is the standard of care. A 61-year-old Jehovah’s Witness woman presented to our hospital with neurological symptoms and laboratory findings suggestive of TTP. On admission, she refused transfusion of blood products, specifically red blood cells, platelets, and plasma but accepted albumin and intravenous immunoglobulin (IVIG); fractions of plasma. She was started on steroids, IVIG, and TPE with albumin as replacement therapy with minimal improvement. After a detailed discussion with the patient and family, they agreed to accept cryosupernatant. The patient started TPE with cryosupernatant for replacement therapy, which resulted in clinical improvement. This case highlights the importance of an individualized approach with joint decision-making given the significant heterogeneity that exists in Jehovah’s Witnesses’ attitude toward the receipt of blood products.

Analyzing the impact of systems-based hematologist in the healthcare system at an academic medical center

Over the next decade, there is a predicted shortage of nonmalignant hematologist to maintain the workforce in the United States. To address this, the American Society of Hematology described the creation of the healthcare systems-based hematologist (SBH). The role of SBH has the potential to provide high-value, cost-conscious care to the healthcare system. In 2011, an Anticoagulation and Bleeding Management Medical Directorship position for a SBH was created at our healthcare system. We described our 6-year experience as SBH at a 750-bed tertiary academic medical center to improve clinical outcomes while reducing costs. Via four different initiatives, we were able to provide high-value, cost-conscious care as SBH by reducing cost of heparin-induced thrombocytopenia management, optimizing blood product utilization using goal-directed algorithms, reducing inappropriate thrombophilia testing and improving inferior vena cava filter retrieval rates. To ensure continuing success as a SBH, business plans need to include education, enforcement, monitoring, feedback, validation of safety and outcomes and a shared vision among leadership.

Practice Patterns of Inferior Vena Cava Filter Placement and Factors That Predict Retrieval Rates: A Single-Center Institution and Review of the Literature

Background

There is a wide variability in practice patterns on the use of inferior vena cava filters (IVCFs) among institutions, which is likely due to contrasting indication guidelines published by different professional societies. The aim of the present study is to report our healthcare system use of IVCF to: 1) determine practice patterns, 2) determine factors that may predict IVCF retrieval and 3) identify areas for improvement.

Methods

A retrospective review of 180 consecutive IVCF placement performed between July 2014 and December 2015 was conducted.

Results

One hundred nine (60.6%) IVCFs were placed for absolute indications, 27 (15.0%) for relative indications, 26 (14.4%) prophylactically and 18 (10.0%) for unknown indications. Average age was 59.3 years. Ninety-five had active cancer. Surgical and medical services requested filter placement in 112 (62.2%) and 68 (37.8%) patients, respectively. Thirteen (7.2%) patients had a hematology consult prior to IVCF placement. Documentation of the presence of an IVCF was present in 118/127 (92.9%) discharge summaries, and outlined instructions for filter retrieval post-discharge were present in 20/124 (16.1%) cases. Only 33 (25.0%) IVCF were retrieved at a median interval of 162 days (range: 4 - 1,053 days). None of the factors of interest was found to be significantly associated with IVCF retrieval.

Conclusion

A root cause analysis identified that the lack of a structured system for IVCF tracking resulted in poor IVCF retrieval rates. This study resulted in the development of a hospital-initiated multidisciplinary team to address these issues.

Limited Proteolysis of Vitronectin by Plasmin Destroys Heparin Binding Activity

Vitronectin (VN) stabilizes plasminogen activator inhibitor type 1 (PAI-1) activity and prevents the fibrin(ogen)-induced acceleration of plasminogen activation by t-PA. These antifibrinolytic activities as well as other functions are mediated by the glycosaminoglycan (GAG) binding domain of VN. Since the GAG binding region is rich in arginyl and lysyl residues, it is a potential target for enzymes such as plasmin. In this paper, the dose and time-dependent proteolysis of VN by plasmin is demonstrated. The addition of urokinase or streptokinase (200 units/ml) to plasma also produced proteolysis of VN. With minimal proteolysis, the 75 kDa band was degraded to a 62-65 kDa form of VN. This minimal proteolysis destroyed the binding of [3H]-heparin to VN and reversed the neutralization of heparin by VN.

Thus, the plasmin-mediated proteolysis of the GAG binding activity of VN could destroy the antifibrinolytic activity of VN during physiologic conditions and during thrombolytic therapy. Furthermore, other functions of VN in complement and coagulation systems that are mediated by the GAG binding domain may be destroyed by plasmin proteolysis.

Parenteral Anticoagulation with the Heparinoid Lomoparan (Org 10172) in Patients with Heparin Induced Thrombocytopenia and Thrombosis

Progressive thrombocytopenia may develop in as many as 5% of patients receiving heparin anticoagulation. In these patients, the risk of thromboembolic complications as well as continued thrombocytopenia necessitates discontinuation of heparin and initiation of an alternative anticoagulant when indicated. The heparinoid Lomoparan (Org 10172) is a mixture of several nonheparin low molecular weight glycosaminoglycans with proven anticoagulant efficacy that is generally non-reactive with platelets in the presence of plasma from patients with heparin induced thrombocytopenia, whereas standard heparin will induce platelet aggregation. We evaluated the role of heparinoid as a potential alternative anticoagulant in patients with heparin induced thrombocytopenia. During a 6 month period, we identified six patients with heparin induced thrombocytopenia who required an alternative parenteral anticoagulant, four as primary treatment for specific medical problem, and two as anticoagulation during a necessary surgical procedure. Heparinoid was used successfully in both medical and surgical patients requiring parenteral anticoagulation. In no case was there an exacerbation of the thrombocytopenia nor thromboembolic complications while on heparinoid therapy. Three of our patients sustained hemorrhagic complications, predominantly in the post-surgical setting in association with elevated anti-factor Xa levels and additional anticoagulant agents. We feel that these results confirm the utility of heparinoid anticoagulation in a select subset of patients with heparin induced thrombocytopenia who require continued parenteral anticoagulation.

Cytofluorometric Identification of Plasmin-Sensitive Factor XIIIa Binding to Platelets

We have investigated the binding of blood coagulation factor XIIIa to thrombin-stimulated platelets using cytofluorometric analysis. Washed thrombin-stimulated platelets bound exoge-nously added factor XIIIa in a calcium-dependent reaction. The expression of endogenous platelet factor XIII was also detected on the surface of thrombin-stimulated platelets. When fluorescence analysis was performed based on particle size, factor XIIIa bound to the surface of greater than 95% of particles which contained more than one platelet, but only 50% of single platelets. The binding of factor XIIIa to thrombin-stimulated platelets was inhibited by plasmin. Plasmin also inhibited thrombin-dependent expression of the factor XIIIa binding site on platelets. Experiments in which thrombin-stimulated platelets were incubated with factor XIIIa in the presence of 125I-dimethyl-casein or 3H-putrescine demonstrated that platelets bear both glutamyl and lysyl substrates for factor XIIIa. Thrombin increased the expression of factor XIIIa substrates by platelets. Plasmin inhibited both the expression of factor XIIIa substrates and degraded them. The binding of factor XIIIa to thrombin-stimulated platelets and the availability of factor XIIIa substrates on the platelet surface could provide a mechanism by which factor XIIIa stabilizes the hemostatic plug by promoting crosslinking reactions between platelet membrane proteins and adhesive glycoproteins. In contrast, plasmin inhibition of factor XIIIa binding and crosslinking could disrupt hemostasis.

Initial and long term impact of a multi-disciplinary task force in the diagnosis and management of heparin-induced thrombocytopenia

Many medical centers are faced with a major challenge in making an accurate diagnosis of heparin-induced thrombocytopenia (HIT) and ensuring appropriate changes in management strategy in line with guideline recommendations. We report the initial and long-term impact and challenges of institution-wide changes in the diagnosis and management of HIT in the inpatient setting at an academic medical center. We established a HIT Task Force, consisting of a multidisciplinary team of non-malignant hematologists, nursing, pharmacist, pathology, blood bank and clinical lab informatics. Changes were implemented from 2011 to 2012. In 2013, testing for PF4 and SRA decreased by 37.5 and 85%, respectively. 100% of positive PF4 received an automatic hematology consult to guide management, leading to a 78% reduction in the use of direct thrombin inhibitors. Annual audits in the subsequent years demonstrated increasing testing for HIT due to changes in the electronic ordering system. Through continuous monitoring, these shortfalls were detected and intervene early on with continued success. The implementation of a centralized hospital-wide protocol via a multidisciplinary task force that coordinates testing and treatment of patients suspected of having HIT led to a substantial reduction in PF4 and SRA testing, as well as use of DTIs, resulting in a safe and cost-effective approach for the diagnosis and treatment of HIT. Our study highlights the important of continuous monitoring to maintain the improvements made. Despite our initial success, annual re-auditing allowed for early detection of challenges, which then allowed appropriate early intervention.

Role of tissue transglutaminase-2 (TG2)-mediated aminylation in biological processes

Post-translational modification (PTM) is an important mechanism in modulating a protein's structure and can lead to substantial diversity in biological function. Compared to other forms of PTMs such as phosphorylation, acetylation and glycosylation, the physiological significance of aminylation is limited. Aminylation refers to the covalent incorporation of biogenic/polyamines into target protein by calcium-dependent transglutaminases (TGs). The development of novel and more sensitive techniques has led to more proteins identified as tissue transglutaminase (TG2) substrates and potential targets for aminylation. Many of these substrate proteins play a role in cell signaling, cytoskeleton organization, muscle contraction, and inflammation. TG2 is well studied and widely expressed in a variety of tissues and will be the primary focus of this review on recent advance in transglutaminase-mediated aminylation.

Effect of Chronic Blood Transfusion on Biomarkers of Coagulation Activation and Thrombin Generation in Sickle Cell Patients at Risk for Stroke

Hypercoagulability in sickle cell disease (SCD) is associated with multiple SCD phenotypes, association with stroke risk has not been well described. We hypothesized that serum levels of biomarkers of coagulation activation correlate with high transcranial Doppler ultrasound velocity and decreases with blood transfusion therapy in SCD patients. Stored serum samples from subjects in the Stroke Prevention in Sickle Cell Anemia (STOP) trial were analyzed using ELISA and protein multiplexing techniques. 40 subjects from each treatment arm (Standard Care [SC] and Transfusion [Tx]) at three time points—baseline, study exit and one year post-trial and 10 each of age matched children with SCD but normal TCD (SNTCD) and with normal hemoglobin (HbAA) were analyzed. At baseline, median vWF, TAT and D-dimer levels were significantly higher among STOP subjects than either HbAA or SNTCD. At study exit, median hemoglobin level was significantly higher while median TCD velocity was significantly lower in Tx compared to SC subjects. Median vWF (409.6 vs. 542.9 μg/ml), TAT (24.8 vs. 40.0 ng/ml) and D-dimer (9.2 vs. 19.1 μg/ml) levels were also significantly lower in the Tx compared to the SC group at study exit. Blood levels of biomarkers coagulation activation/thrombin generation correlated positively with TCD velocity and negatively with number of blood transfusions. Biomarkers of coagulation activation/thrombin generation were significantly elevated in children with SCD, at high risk for stroke. Reduction in levels of these biomarkers correlated with reduction in stroke risk (lower TCD velocity), indicating a possible role for hypercoagulation in SCD associated stroke.

Abstract 5192: TGM-2 mediated downregulation of fibronectin during TGFb-induced epithelial-mesenchymal transition in lung cancer NCI-H358 cells

The epithelial to mesenchymal transition (EMT), which converts epithelial cells into an elongated, motile, and invasive phenotype, is considered to be a critical step in the dissemination of tumor cells. During EMT, the loss of E-cadherin (ECad) and upregulation of N-cadherin (NCad) or fibronectin (FN) have been most frequently described. FN binds integrin Alpha5 and is known for its upregulation in aggressive tumor cells. In addition, FN binds tissue transglutaminase (TGM-2) with high affinity (∼in nM) and plays a role in TGM-2 secretion. TGM-2, a multifunctional enzyme with transamidation or crosslinking, and GTP/ATP binding activities, is up-regulated in various malignant diseases, including lung cancer. In breast, cervical and ovarian cancers, TGM-2 has been shown to play a role in chemotherapy resistance and tumor metastasis during induction of EMT. TGM-2 overexpression results in the loss of epithelial features, up-regulation of mesenchymal markers, increased migration and invasion, and up-regulation of transcriptional repressors (e.g., ZEB1/2, Snail) known to mediate the EMT process. However, most of these studies were performed in aggressive tumor cells. In this study, we investigated the role of TGM-2 in TGFbeta-induced EMT process using NSCLC H358 cells. H358 cells express high levels of epithelial genes and are relatively resistant to TGFbeta induced EMT when compared to A549 cells. Particularly, H358 expresses barely detectable TGM-2 and FN. To investigate the role of TGM-2 during TGFbeta induced EMT, we constructed three isogenic cell lines with doxycycline (Dox)-inducible TGM-2 or C277A (an inactive mutant of TGM-2 with no transamidating activity) using InVitrogen's Flp-in TRex system. We found continuing treatment of 10 ng/ml TGFbeta for 6 days inducing H358 flp-in (vector control) cells to mescenchymal phenotype as demonstrated by the disappearance of Ecad, and the increased expression of NCad and FN. Under the same condition, Dox inducible TGM-2 and C277A facilitate the disappearance of Ecad, and Occludin and the appearance of Ncad. However, the expression of FN was undetectable in H358/TGM-2 and H358/C277A cells. As a result, H358/TGM-2 and H358/C277A remained localized and failed to migrate as demonstrated by a scratch wound healing assay. Seahorse mitochondria stress assay also demonstrated H358/TGM-2 and H358/C277A utilize more oxidative phosphorylation pathway than glycolytic pathway when compared with H358/flp-in, an indication of shifting cells to more normal phenotype. In summary, overexpression of TGM-2 (or inactive C277A mutant) inhibited the expression of FN and resulted in a less migratory H358 cells. Our results demonstrated that the role of TGM-2 during EMT in less aggressive epithelial cells such as H358 is different from its role in promoting EMT in other aggressive tumor cell; the suppression of FN might be a critical factor.

Note: This abstract was not presented at the meeting.

Citation Format: Thung S. Lai, Pin-Tsen Lin, Charles S. Greenberg, Harry A. Drabkin, Robert Gemmill. TGM-2 mediated downregulation of fibronectin during TGFb-induced epithelial-mesenchymal transition in lung cancer NCI-H358 cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5192. doi:10.1158/1538-7445.AM2015-5192

Histaminylation of fibrinogen by tissue transglutaminase-2 (TGM-2): potential role in modulating inflammation

Plasma fibrinogen plays an important role in hemostasis and inflammation. Fibrinogen is converted to fibrin to impede blood loss and serves as the provisional matrix that aids wound healing. Fibrinogen also binds to cytokine activated endothelial cells and promotes the binding and migration of leukocytes into tissues during inflammation. Tissue transglutaminase (TGM-2) released from injured cells could cross-link fibrinogen to form multivalent complexes that could promote adhesion of platelets and vascular cells to endothelium. Histamine released by mast cells is a potent biogenic amine that promotes inflammation. The covalent attachment of histamine to proteins (histaminylation) by TGM-2 could modify local inflammatory reactions. We investigated TGM-2 crosslinking of several biogenic amines (serotonin, histamine, dopamine and noradrenaline) to fibrinogen. We identified histaminylation of fibrinogen by TGM-2 as a preferred reaction in solid and solution phase transglutaminase assays. Histamine caused a concentration-dependent inhibition of fibrinogen cross-linking by TGM-2. Fibrinogen that was not TGM-2 crosslinked bound to unactivated endothelial cells with low affinity. However, the binding was increased by sevenfold when fibrinogen was cross-linked by TGM-2. Histaminylation of fibrinogen also inhibited TGM-2 crosslinking of fibrinogen and the binding to un-activated HUVEC cells by 75–90 %. In summary, the histaminylation of fibrinogen by TGM-2 could play a role in modifying inflammation by sequestering free histamine and by inhibiting TGM-2 crosslinking of fibrinogen.

TGM2 and implications for human disease: role of alternative splicing

Alternative splicing is an important mechanism for modulating gene function that accounts for a considerable proportion of proteomic complexity in higher eukaryotes. Alternative splicing is often tightly regulated in a cell-type- or developmental-stage- specific manner and can cause a single gene to have multiple functions. Human Tissue transglutaminase (TGM2) is a multifunctional enzyme with transglutaminase crosslinking (TGase), G protein signaling and kinase activities that are postulated to play a role in many disease states. TGM2 mRNA is regulated by alternative splicing, producing C-terminal truncated forms of TGM2 that are predicted to have distinct biochemical properties and biological functions. In this review, we will discuss how alternatively spliced forms of TGM2 could modulate its roles in cancer, neurodegeneration, inflammation and wound healing.

The Use of Activated Recombinant Factor VII in a Patient with Fulminant Hepatic Failure Requiring Placement of an Intracranial Pressure Monitor

Objective:

To evaluate the use of recombinant activated factor VII (rFVIIa) in a patient with fulminant hepatic failure (FHF) requiring placement of an intracranial pressure monitor.

Case Summary:

A 21-year-old female with no significant medical history was admitted to an outside hospital with elevated results of liver function tests. Subsequently, the patient was diagnosed with autoimmune hepatitis. Systemic corticosteroids were started, but her condition continued to decompensate. She was transferred to our tertiary care facility 5 days after initial presentation. The liver function test results remained elevated (eg, total bilirubin 27 mg/dL), and international normalized ratio (INR) was 3.57. The medical team decided to place an intracranial pressure monitor, with the neurosurgery team's goal being an INR less than 1.5 before placement of the monitor. After multiple units of fresh frozen plasma (FFP) failed to lower the patient's INR, rFVIIa 40 μg/kg was administered. A rapid decrease of the INR allowed the neurosurgery team to perform the procedure without complications.

Discussion:

The use of rFVIIa allowed for decrease of this patient's INR after multiple units of FFP had failed to correct it. The utility of INR as a marker of coagulopathy in fulminant hepatic failure has been debated, but it is currently used as the standard laboratory test prior to invasive procedures, as in the case presented here.

Conclusions:

The use of rFVIta for rapid decrease of INR in a patient with FHF prior to an invasive procedure was safe and efficacious. When considering the use of rFVIIa, clinicians should be aware of the risk of thrombosis. In our experience, and in the limited literature on the matter, rFVIIa 40 μg/kg appears to be an appropriate dose for decrease of the INR. Further studies are needed to confirm this finding.

Clinical Usefulness of Recombinant Activated Factor VII in Patients with Liver Failure Undergoing Invasive Procedures

Objective:

To evaluate the use of recombinant activated factor VII (rFVIIa) in patients with liver failure undergoing invasive procedures.

Methods:

An OVID/MEDUNE and PubMed search (1997-June 2011) was performed to identify literature on the use of rFVIIa to reduce bleeding risk in patients with liver failure undergoing invasive procedures.

Study Selection and Data Extraction:

English-language data evaluating the efficacy of rFVIIa to reverse coagulopathies prior to invasive procedures in patients with liver disease were included.

Data Synthesis:

Following administration of rFVIIa, prothrombin time (PT) and international normalized ratio (INR) response is within 30 minutes. Doses ranging from 20 to 120 μg/kg have been studied, with a reduction in PT seen in a dose-dependent manner. One study in patients with no bleeding administered 5, 20, and 80 μg/kg sequentially during a 24-day period. All doses provided reversal of prolonged PT within 10 minutes, and the duration was dose-dependent. In a study of 15 patients with fulminant liver failure, requiring intracranial pressure monitor placement, a rFVIIa dose of 40 μg/kg was compared to fresh frozen plasma. In patients who received rFVIIa, the PT and INR normalized, compared to none of the patients in the fresh frozen plasma group.

Conclusions:

Retrospective and prospective data demonstrate that rFVIIa effectively reverses elevated PT and INR, reducing the risk of bleeding and safely facilitating invasive procedures. Based on available data, a dose of 20-40 μg/kg 30 minutes prior to an invasive procedure should be considered in patients with acute or chronic liver failure at risk for bleeding complications. A major limitation of rFVIIa use is the high cost of therapy. A prospective, randomized trial could help determine the appropriate dose of rFVIIa, timing of dose in relationship to procedure, and usefulness of subsequent doses.

Wound healing monitoring using near infrared fluorescent fibrinogen

We demonstrate a method for imaging the wound healing process with near infrared fluorescent fibrinogen. Wound healing studies were performed on a rat punch biopsy model. Fibrinogen was conjugated with a near infrared fluorescent dye and injected into the tail vein. Fibrinogen is a useful protein for tracking wound healing because it is involved in fibrin clot formation and formation of new provisional matrix through transglutaminase's crosslinking activity. Strong fluorescence specific to the wound was observed and persisted for several days, indicating that the fibrinogen is converted to crosslinked fibrin. Administration of contrast agent simultaneously with wound creation led to primary labeling of the fibrin clot, indicating that the wound was in its early phase of healing. Administration on the following day showed labeling on the wound periphery, indicating location of formation of a new provisional matrix. This method may prove to be useful as a diagnostic for basic studies of the wound healing process, in drug development, or in clinical assessment of chronic wounds.

Human tissue transglutaminase is inhibited by pharmacologic and chemical acetylation

Human tissue transglutaminase (TGM2) is implicated in the pathogenesis of several neurodegenerative disorders including Alzheimer's, Parkinson's and expanded polyglutamine (polyQ) diseases. TGM2 promotes formation of soluble and insoluble high molecular weight aggregates by catalyzing a covalent linkage between peptide-bound Q residues in polyQ proteins and a peptide-bound Lys residue. Therapeutic approaches to modulate the activity of TGM2 are needed to proceed with studies to test the efficacy of TGM2 inhibition in disease processes. We investigated whether acetylation of Lys-residues by sulfosuccinimidyl acetate (SNA) or aspirin (ASA) would alter the crosslinking activity of TGM2. Acetylation by either SNA and/or ASA resulted in a loss of >90% of crosslinking activity. The Lys residues that were critical for inhibition were identified by mass spectrometry as Lys(444), Lys(468), and Lys(663). Hence, acetylation of Lys-residues may modulate the enzymatic function of TGM2 in vivo and offer a novel approach to treatment of TGM2 mediated disorders.

Identification of chemical inhibitors to human tissue transglutaminase by screening existing drug libraries

Human tissue transglutaminase (TGM2) is a calcium-dependent crosslinking enzyme involved in the posttranslational modification of intra- and extracellular proteins and implicated in several neurodegenerative diseases. To find specific inhibitors to TGM2, two structurally diverse chemical libraries (LOPAC and Prestwick) were screened. We found that ZM39923, a Janus kinase inhibitor, and its metabolite ZM449829 were the most potent inhibitors with IC(50) of 10 and 5 nM, respectively. In addition, two other inhibitors, including tyrphostin 47 and vitamin K(3), were found to have an IC(50) in the micromolar range. These agents used in part a thiol-dependent mechanism to inhibit TGM2, consistent with the activation of TGM2 by reduction of an intramolecular disulfide bond. These inhibitors were tested in a polyglutamine-expressing Drosophila model of neurodegeneration and found to improve survival. The TGM2 inhibitors we discovered may serve as valuable lead compounds for the development of orally active TGM2 inhibitors to treat human diseases.

Transglutaminases: the missing link in nephrogenic systemic fibrosis

Nephrogenic systemic fibrosis (NSF), also known as nephrogenic fibrosing dermopathy (NFD), occurs in renal failure patients after gadolinium contrast exposure. The fibrosis of the dermis and subcutaneous septae accompanies fibrosis of other organs, including the heart, liver, lungs, and muscle. The fibrotic skin demonstrates increased dermal collagen, fibroblasts, and mucin. The mechanism by which gadolinium is associated with fibrosis is not known. We tested the hypothesis that upregulation of transglutaminases contributes to the fibrosis seen in the organs, including skin, of renal failure patients exposed to gadolinium contrast. We performed immunohistochemical studies using antibodies to transglutaminase-2, factor XIIIa, transglutaminase isopeptide, and the histiocyte marker CD68 on five archived skin biopsies of NSF. The results indicate that the dermal fibroblasts and histiocytes of NSF express transglutaminase-2, CD68, factor XIIIa, and transglutaminase isopeptide, indicating increased expression and/or activation of transglutaminases in NSF. We recommend further research into the use of transglutaminase inhibitors in the treatment and prevention of NSF.

Identification of two GTP-independent alternatively spliced forms of tissue transglutaminase in human leukocytes, vascular smooth muscle, and endothelial cells

Tissue transglutaminase (tTG) is a multifunctional enzyme with transglutaminase crosslinking (TGase), GTP binding, and hydrolysis activities that play a role in many different disorders. We identified, characterized, and investigated the function and stability of two alternatively spliced forms of tTG using biochemical, cellular, and molecular biological approaches. Using a human aortic vascular smooth muscle cells (VSMC) cDNA library, we identified two cDNAs encoding C-terminal truncated forms, tTG(V1) and tTG(V2). tTG(V1,2) mRNAs were synthesized by a rare splicing event using alternate splice sites within exons 12 and 13 of the tTG gene, respectively. Quantitative PCR and immunoblotting demonstrated that there was unique expression and localization of tTG(V1,2) compared with tTG in human umbilical vein endothelial cells (HUVECs), VSMC, and leukocytes. The loss of C-terminal 52 amino acid residues (AAs) in tTG(V1,2) altered GTP binding, enhanced GTP hydrolysis, rendered the variants insensitive to GTP inhibition, and resulted in <10% residual Ca(+2)-dependent TGase activity. Transfection in HEK293 demonstrated a 28- and 5-fold reduction in the expression of tTG(V1) and tTG(V2), respectively, demonstrating that the C-terminal GTP-binding domain is important in stabilizing and promoting the half-life of tTG. The altered affinity for GTP allowed tTG(V1,2) to exhibit enhanced TGase activity when there is a transient increase in Ca(+2) levels. The abundance of tTG(V1,2) and its distinct intracellular expression patterns in human vascular cells and leukocytes indicate these isoforms likely have unique physiological functions.

Arterial vimentin is a transglutaminase substrate: a link between vasomotor activity and remodeling?

BACKGROUND/AIMS

The transglutaminases (TG2 and factor XIIIa) may contribute to the stability of arteries by cross-linking a variety of substrates, including extracellular matrix proteins and protease inhibitors. The preferred substrates have never been determined, however.

METHODS

We used an amine donor, 5-biotinamidopentylamine, that is covalently linked to acceptor glutamine residues, to determine transglutaminase substrates in carotid endarterectomy tissue.

RESULTS

The incorporation of 5-biotinamidopentylamine was calcium dependent, resulting in the labeling of several proteins that were detected by streptavidin-peroxidase and purified over a monomeric avidin affinity column. A major band of 42 kDa that was eluted from the column was sequenced along with 2 additional bands (80 and 65 kDa), revealing an internal fragment of vimentin, transferrin and albumin, respectively. Vimentin dimers were detected in 5 out of 5 carotid plaque homogenates.

CONCLUSIONS

Vimentin is a major arterial substrate for transglutaminases. It has previously been shown that TG2 activity and vimentin contribute to vasomotor activity of arteries. Furthermore, transglutaminases (both TG2 and factor XIIIa), as well as vimentin, regulate structural alterations (inward remodeling) that occur in response to low flow states. Transglutaminase-mediated vimentin dimerization produces a novel unifying pathway by which vasodilatory and remodeling responses may be regulated.

Roles of transglutaminases in cardiac and vascular diseases

All transglutaminases share the common enzymatic activity of transamidation, or the cross-linking of glutamine and lysine residues to form N epsilon (gamma-glutamyl) lysyl isopeptide bonds. The plasma proenzyme factor XIII is responsible for stabilizing the fibrin clot against physical and fibrinolytic disruption. Another member of the transglutaminase family, tissue transglutaminase or TG2 is abundantly expressed in cardiomyocytes, vascular cells and macrophages. The transglutaminases have a variety of functions independent of their transamidating activity. For example, TG2 binds and hydrolyzes GTP, thereby fostering signal transduction by several G protein coupled receptors. Accumulating evidence points to novel roles for factor XIII and TG2 in cardiovascular biology including: (a) modulating platelet activity, (b) regulating glucose control, (c) contributing to the development of hypertension, (d) influencing the progression of atherosclerosis, (e) regulating vascular permeability and angiogenesis (f) and contributing to myocardial signaling, contractile activity and ischemia/reperfusion injury. In this review, we summarize the cardiovascular biology of two members of the family of transglutaminases, Factor XIII and TG2.

Preoperative anti-PF4/heparin antibody level predicts adverse outcome after cardiac surgery

OBJECTIVE

Preexisting serum antibodies to heparin/platelet factor 4 complexes may predispose adult cardiac surgical patients to increased perioperative morbidity and mortality. We sought to determine the association between preoperative serum antibodies directed against platelet factor 4/heparin complexes and major complications (in-hospital death or length of stay >10 days) in adult cardiac surgical patients.

METHODS

In a prospective observational study of 466 patients undergoing elective coronary artery bypass grafting, valvular heart surgery, or both, preoperative serum was assayed for anti-platelet factor 4/heparin antibody by using a commercially available enzyme-linked immunosorbent assay (Asserachrom HPIA). Known preoperative risk factors were assessed, and patients were assigned a risk score by using the validated method of Parsonnet and colleagues.

RESULTS

Major complications (death or postoperative hospitalization >10 days) occurred in 108 patients (23%). Overall, 59 (13%) patients had a positive preoperative anti-platelet factor 4/heparin antibody screen (upper limit of normal is 0.5 optical density units). A positive assay result independently predicted an increased risk of major complications (P = .0284; odds ratio, 1.98; 95% confidence interval, 1.06-3.62) over and above the effect of the Parsonnet risk score (P < .001; odds ratio, 1.07; 95% confidence interval, 1.05-1.10). The level of preoperative anti-platelet factor 4/heparin antibody was also significantly associated with major complications (P = .036; odds ratio, 1.31; 95% confidence interval, 1.02-1.68) independently of the Parsonnet risk score. No association (P > .75) existed between the Parsonnet risk score and preoperative anti-platelet factor 4/heparin antibody level.

CONCLUSIONS

Serum antibodies directed against platelet factor 4/heparin complexes are prevalent in the adult patient population undergoing cardiac surgery. The presence of these antibodies before surgery is an independent predictor for death or prolonged hospitalization after adult cardiac surgery.

Development of magnetic resonance imaging contrast material for in vivo mapping of tissue transglutaminase activity

Transglutaminases are a family of enzymes that play an important role in tissue remodeling by catalyzing covalent cross-links between proteins of the extracellular matrix. Elevated activity of transglutaminase was shown at the boundaries of invading tumors, in association with angiogenesis, in stabilization of atherosclerotic plaques, and in generation of blood clots. The aim of this work was to develop a low molecular weight substrate of transglutaminase that could serve for noninvasive magnetic resonance and optical mapping of transglutaminase-mediated cross-linking activity. A 2 kDa contrast material was generated which showed cross-linking by either tissue transglutaminase or factor XIII in the context of multicellular tumor spheroids or fibrin clots, respectively. Successful detection by nuclear magnetic resonance microscopy of transglutaminase-mediated cross-linking of the contrast material to MCF7 multicellular spheroids provides hope that this approach could potentially be developed for clinical demarcation of sites of transglutaminase activity.

Effect of tissue transglutaminase on the solubility of proteins containing expanded polyglutamine repeats

The expansion of a polyglutamine (polyQ) domain in neuronal proteins is the molecular genetic cause of at least eight neurodegenerative diseases. Proteins with a polyQ domain that is greater than 40 Q (Q40) residues form insoluble intranuclear and cytoplasmic inclusions. Expanded polyQ proteins self-associate by non-covalent interactions and become insoluble. They can also be covalently cross-linked by tissue transglutaminase (TTG), a calcium-dependent enzyme present in cells throughout the nervous system. However, it remains unclear whether TTG cross-linking directly contributes to the insolubility of the expanded polyQ proteins. Using an in vitro solubility assay, we found TTG cross-linked Q62 monomers into high molecular weight soluble complexes in a calcium-dependent reaction. Inhibition of TTG cross-linking by primary amine substrates including putrescine and biotinylated pentylamine antagonized TTG's ability to form soluble complexes. In contrast, primary amines (histamine and lysine) that were less effective inhibitors of TTG cross-linking did not inhibit Q62 from becoming insoluble. In summary, TTG can increase the solubility of expanded polyQ proteins by catalyzing intermolecular cross-links. This demonstrates directly that TTG will reduce the ability of expanded polyQ proteins from becoming insoluble. Furthermore, the effectiveness of a primary amine substrate at inhibiting formation of insoluble inclusions may be related to their ability to inhibit intermolecular cross-linking by TTG.

Role of factor XIII in fibrin clot formation and effects of genetic polymorphisms

Factor XIII and fibrinogen are unusual among clotting factors in that neither is a serine protease. Fibrin is the main protein constituent of the blood clot, which is stabilized by factor XIIIa through an amide or isopeptide bond that ligates adjacent fibrin monomers. Many of the structural and functional features of factor XIII and fibrin(ogen) have been elucidated by protein and gene analysis, site-directed mutagenesis, and x-ray crystallography. However, some of the molecular aspects involved in the complex processes of insoluble fibrin formation in vivo and in vitro remain unresolved. The findings of a relationship between fibrinogen, factor XIII, and cardiovascular or other thrombotic disorders have focused much attention on these 2 proteins. Of particular interest are associations between common variations in the genes of factor XIII and altered risk profiles for thrombosis. Although there is much debate regarding these observations, the implications for our understanding of clot formation and therapeutic intervention may be of major importance. In this review, we have summarized recent findings on the structure and function of factor XIII. This is followed by a review of the effects of genetic polymorphisms on protein structure/function and their relationship to disease.

SU5416 delays wound healing through inhibition of TGF-beta 1 activation

Angiogenesis, development of new blood vessels, is essential for wound healing and tumor growth. A potentially important side effect of anti-angiogenic therapy can be delayed wound healing. In this study we address this issue by using a novel in vivo method utilizing fibrin containing dual porous plexiglass chambers (Fibrin Z-Chambers; F-ZC) to investigate wound healing in rats administered with SU5416 (inhibitor of Flk-1 and Flt-1, at 20 mg/kg i.p.). SU5416 treated F-ZCs developed 45% less granulation tissue (p = 0.0076) and showed a 10% reduction in microvessel density (p = 0.0009) than controls treated with drug carrier alone. The granulation tissue showed distinctly decreased collagen deposition (p = 0.0006) in SU5416 treated animals that was associated with 90% reduction in active TGF-beta 1 level. We found that tissue transglutaminase (TG), a cross-linking enzyme involved in TGF-beta 1 activation and matrix stabilization, was inhibited by SU5416. These results suggest that SU5416 delays wound healing by reducing matrix synthesis and stabilization through inhibition of TGF-beta 1 activation. This study was made feasible via the development of a unique method to study anti-angiogenic compounds that provides highly reproducible and quantitative results. Further studies are needed to evaluate in vivo whether anti-angiogenic agents alter wound healing.

Tissue transglutaminase localization and activity regulation in the extracellular matrix of articular cartilage

Tissue transglutaminase (tTG) catalyzes a Ca2+-dependent transglutaminase (TGase) activity which cross-links proteins and stabilizes many tissues [C.S. Greenberg et al. FASEB J. 5 (1991) 3071]. Because cartilage is subjected to great stress in vivo, an enzyme that strengthens and stabilizes tissue could play an integral role in maintaining cartilage integrity. The purpose of this study was to determine if active tTG is present in the extracellular matrix (ECM) of adult human osteoarthritic articular cartilage. Using a TGase activity assay along with immunolabeling for tTG of cartilage sections, TGase activity and tTG immunoreactivity were localized in the ECM in cartilage sections, predominantly in the superficial layer. Previous in vitro studies have demonstrated that the Mg-GTP complex inhibits the TGase activity of tTG [T.S. Lai et al. J. Biol. Chem. 273 (1998) 1776]. To investigate the in situ regulation of the TGase activity of tTG, a TGase activity assay was done with a dose response of GTP, measuring incorporation of fluorescein cadaverine. TGase activity was inhibited by GTP in a similar manner as in vitro. These results not only confirm tTG presence in the ECM. but also indicate tTG as the major TGase activity of the ECM. Secondly, the study provides a possible mechanism by which extracellular tTG is regulated in vivo.

Calcium regulates S-nitrosylation, denitrosylation, and activity of tissue transglutaminase

Nitric oxide (NO) and related molecules play important roles in vascular biology. NO modifies proteins through nitrosylation of free cysteine residues, and such modifications are important in mediating NO's biologic activity. Tissue transglutaminase (tTG) is a sulfhydryl rich protein that is expressed by endothelial cells and secreted into the extracellular matrix (ECM) where it is bound to fibronectin. Tissue TG exhibits a Ca(2+)-dependent transglutaminase activity (TGase) that cross-links proteins involved in wound healing, tissue remodeling, and ECM stabilization. Since tTG is in proximity to sites of NO production, has 18 free cysteine residues, and utilizes a cysteine for catalysis, we investigated the factors that regulated NO binding and tTG activity. We report that TGase activity is regulated by NO through a unique Ca(2+)-dependent mechanism. Tissue TG can be poly-S-nitrosylated by the NO carrier, S-nitrosocysteine (CysNO). In the absence of Ca(2+), up to eight cysteines were nitrosylated without modifying TGase activity. In the presence of Ca(2+), up to 15 cysteines were found to be nitrosylated and this modification resulted in an inhibition of TGase activity. The addition of Ca(2+) to nitrosylated tTG was able to trigger the release of NO groups (i.e. denitrosylation). tTG nitrosylated in the absence of Ca(2+) was 6-fold more susceptible to inhibition by Mg-GTP. When endothelial cells in culture were incubated with tTG and stimulated to produce NO, the exogenous tTG was S-nitrosylated. Furthermore, S-nitrosylated tTG inhibited platelet aggregation induced by ADP. In conclusion, we provide evidence that Ca(2+) regulates the S-nitrosylation and denitrosylation of tTG and thereby TGase activity. These data suggest a novel allosteric role for Ca(2+) in regulating the inhibition of tTG by NO and a novel function for tTG in dispensing NO bioactivity.

Reversible shear-mediated platelet dysfunction during cardiac surgery as assessed by the PFA-100 platelet function analyzer

We undertook this investigation to assess alterations in shear-mediated platelet function during cardiac surgery and to determine the potential for the PFA-100 to predict post-operative bleeding. Platelet aggregation and PFA-100 closure times were determined in 18 adult patients at five intervals during cardiac surgery. Associations between post-operative bleeding and closure times were examined in an additional 58 patients. Statistical analysis consisted of Student's t, Wilcoxon signed rank, and Spearman correlation tests. All results are reported as mean +/- SEM. Collagen/epinephrine closure times were prolonged prior to and throughout surgery. Collagen/adenosine-5'-diphosphate (ADP) closure times were significantly prolonged by heparin administration, 141 +/- 15 s versus 115 +/- 10 s (P = 0.01), and subsequent initiation of cardiopulmonary bypass (CPB), 203 +/- 12 s (P= 0.0001); however, 15 min after protamine administration, closure times returned to near pre-operative values, 138 +/- 12 s (P = not significant). In contrast, platelet aggregation in response to ADP remained impaired in 17 of 19 patients after CPB. Neither ex vivo correction of sample hematocrits nor supplementation with Humate P affected closure times. Positive and negative predictive values for post-CPB collagen/ADP closure times to predict bleeding were 18 and 96%, respectively. These results suggest that factors both intrinsic and extrinsic to the platelet contribute to reversible shear-mediated platelet dysfunction during CPB, and that the PFA-100 may prove useful after CPB to identify patients unlikely to benefit from platelet transfusions.

Hemostatic effects of antithrombin III supplementation during cardiac surgery: results of a prospective randomized investigation

Failure to suppress thrombin generation during cardiac surgery promotes fibrin generation, fibrinolysis, and a consumptive coagulopathy. Acquired deficiencies of antithrombin III may play a contributory role. We hypothesized that antithrombin III supplementation to normal physiologic concentrations would decrease thrombin generation and potentially reduce peri-operative bleeding. Twenty patients undergoing coronary artery bypass graft surgery were randomized for this prospective, double-blind, placebo-controlled study. Ten patients received antithrombin III supplementation (50 U/kg) by intravenous infusion prior to incision, and 10 patients received a placebo. Blood samples were obtained pre-operatively, at 1 and 2 h following initiation of cardiopulmonary bypass (CPB), and at 1, 3, and 24 h after completion of CPB. Samples were analyzed for antithrombin III, thrombin-antithrombin III (TAT) complex, and D-dimer concentrations. Cumulative blood loss was recorded at 6 and 12 h after CPB. No statistically significant differences in patient demographics or total heparin dose administered were observed between groups. As expected, plasma antithrombin III concentrations were maintained near pre-operative values in the treatment group, but not in the placebo group. Despite this difference, no statistically significant alterations in generation of TAT complex, D-dimer, or blood loss occurred between groups. Antithrombin III supplementation to maintain normal physiologic concentrations during CPB did not alter significantly thrombin generation, fibrinolytic activity, or blood loss in adults undergoing elective cardiac surgery.

Localization of tissue transglutaminase in human carotid and coronary artery atherosclerosis: implications for plaque stability and progression

Although atherosclerosis progresses in an indolent state for decades, the rupture of plaques creates acute ischemic syndromes that may culminate in myocardial infarction and stroke. Mechanical forces and matrix metalloproteinase activity initiate plaque rupture, whereas tissue inhibitors of metalloproteinases have an important (albeit indirect) role in plaque stabilization. In this paper, an enzyme that could directly stabilize the plaque is described. Tissue transglutaminase (TG) catalyzes the formation of epsilon(gamma-glutamyl)lysine isopeptide bonds that are resistant to enzymatic, mechanical, and chemical degradation. We performed immunohistochemistry for TG in atherosclerotic human coronary and carotid arteries. TG was most prominent along the luminal endothelium and in the medium of the vessels with a distribution mirroring that of smooth muscle cells. Variable, often prominent, immunoreactivity for TG was also seen in the intima, especially in regions with significant neovascularization. Additionally, TG was detected in fibrous caps and near the "shoulder regions" of some plaques. A monoclonal antibody to the transglutaminase product epsilon(gamma-glutamyl)lysine isopeptide demonstrated co-localization with TG antigen. Transglutaminase activity was found in 6 of 14 coronary artery atherectomy samples. Cross-linking of TG substrates such as fibrinogen, fibronectin, vitronectin, collagen type I, and protease inhibitors stabilized the plaque. Furthermore, the activation of transforming growth factor-beta-1 by TG might be an additional mechanism for the promotion of plaque stabilization and progression by increasing the synthesis of extracellular matrix components.

Tamoxifen inhibits angiogenesis in estrogen receptor-negative animal models

Inhibition of tumor angiogenesis is a therapeutic strategy that can inhibit tumor growth and metastases. The aim of this study was to determine whether the estrogen receptor (ER) ligand drug tamoxifen has antiangiogenic effects. We used three different models of angiogenesis, including measurement of microvessel densities in murine tumors, ex vivo aortic ring assays, and corneal pocket assays. ER-negative fibrosarcoma tumors in tamoxifen-treated ovariectomized rats had significantly less vessel formation compared with untreated animals (median microvessel density, 53.6 versus 94.3 counts/per x 200 field; P = 0.002). Rat aortic rings treated with tamoxifen at several different concentrations demonstrated significantly less vascular sprouting than control rings (P = 0.0001). Corneal pocket assays performed in tamoxifen-treated rats compared with control and estrogen-treated rats demonstrated decreased vascular length (0.88 mm versus 1.26 mm versus 1.47 mm; P = 0.022) and vessel area (21% versus 34% versus 47%; P = 0.018). These three animal models all showed significant inhibition of angiogenesis by tamoxifen and suggest a possible contributory mechanism of ER-independent manipulation by tamoxifen in the treatment and prevention of breast cancer. These studies raise the question as to whether or not newer ER ligand drugs might possess even more potent antiangiogenic effects, which in turn could lead to the broadening of the clinical usefulness of these compounds in a number of diseases. More importantly, these studies suggest that the antiangiogenic effects of tamoxifen are due, in part, to ER-independent mechanisms.

Assessment of primary hemostasis by PFA-100 analysis in a tertiary care center

We evaluated the utility of the PFA-100 platelet function analyzer in identifying disorders in platelet function and/or von Willebrand factor (vWF) in patients with various systemic disorders being followed at a tertiary care center. Closure times were determined with collagen/ ADP (CADP) and collagen/epinephrine (CEPI) cartridges for 305 patients, and abnormal results were further evaluated with platelet aggregometry and vWF analysis. Prolonged CADP and/or CEPI closure times were identified in 114 patients (37.3%), but most were isolated prolonged CEPI closure times predominantly due to aspirin therapy (79 patients). Prolonged CADP closure times were most frequently due to qualitative platelet defects and/or decreased vWF levels. Prolonged CADP closure times were encountered most frequently in patients with sickle cell disease and were associated with a decreased hematocrit. This study demonstrated that the PFA-100 analyzer can accurately assess vWF-dependent platelet function and detect other platelet defects under high shear stress in complex patient populations.

Pain assessment in infants and children

The science of pain assessment for infants and children has grown substantially in the past several decades to the point that valid and reliable methods for pain assessment are available for use in clinical settings. Accurate pain assessment requires consideration of children's developmental level, type of pain experienced, history and context of pain, family influences, and interaction with the health care team. Research is needed to improve the sensitivity, specificity, and generalizability of pain-assessment tools and to more fully incorporate contextual factors into the objective assessment process. Finally, the improvement of pain assessment in the clinical setting can be viewed as a patient care quality issue, and continuous quality improvement methods can be used effectively to incorporate pain assessment as an integral component of every infant's and child's health care.

Myocardial ischemia correlates with reduced fibrinolytic activity following peripheral vascular surgery

STUDY OBJECTIVES

To evaluate the relationship between perioperative ischemia and serial concentrations of D-dimer, which is a sensitive and specific marker of fibrinolytic activity. Myocardial ischemia and infarction are well-recognized complications of peripheral vascular surgery. We hypothesized that patients at increased risk of perioperative myocardial ischemia might be identified preoperatively by abnormal hemostatic indices.

DESIGN

Prospective clinical outcomes study.

SETTING

A 1,124-bed tertiary care medical center.

PATIENTS

42 ASA physical status II, III, and IV patients undergoing peripheral vascular surgery.

INTERVENTIONS

Serial D-dimer concentrations were measured preoperatively, and at 24 and 72 hours postoperatively. Continuous 12-lead ST-segment monitoring (Mortara Instrument, Inc., Milwaukee, WI) was performed with the acquisition of a 12-lead ECG every 20 seconds for 72 hours.

MEASUREMENTS AND MAIN RESULTS

D-dimer measurements were performed in duplicate using the Dimer Gold assay (American Diagnostica, Greenwich CT). Ischemic episodes, as defined by continuous 12-lead ST-segment monitoring, occurred in 49% of patients. There were no demographic differences between ischemic and nonischemic groups. Although baseline D-dimer concentrations were not statistically significantly different between groups, patients experiencing perioperative myocardial ischemia generated significantly less D-dimer during the perioperative period (p = 0. 014).

CONCLUSIONS

PATIENTS with an impaired fibrinolytic response, as defined by reduced generation of D-dimer, experienced an increased incidence of perioperative myocardial ischemia.

Early wound healing exhibits cytokine surge without evidence of hypoxia

OBJECTIVE

To ascertain the spatial and temporal relation of wound hypoxia to the cell types involved, expression of selected angiogenic cytokines, the proliferative status of cells in the wound site, and angiogenesis.

SUMMARY BACKGROUND DATA

Hypoxia is considered to drive the angiogenic response by upregulating angiogenic cytokines observed during wound healing. But this correlation has not been shown on a cell-to-cell basis in vivo because of limitations in measuring tissue PO2 at the cellular level.

METHODS

Using punch biopsy wounds in rats as a wound healing model, the distributions of vascular endothelial growth factor, transforming growth factor-beta, tumor necrosis factor-alpha, and pimonidazole adducts (as a hypoxia marker) were followed immunohistochemically during the healing process.

RESULTS

Hypoxia was absent on day 1 after wounding, even though angiogenesis and maximal expression of cytokines were observed in the wounds. Hypoxia peaked in the granulation tissue stage at day 4 and correlated with increased cellularity and cellular proliferation. Hypoxia started to decrease after day 4 and was limited to the remnant blood vessels and epithelial layer in the scar tissue.

CONCLUSIONS

Induction of angiogenic cytokines early during wound healing may be due to triggering mechanisms other than hypoxia. Alternatively, the unique pattern of development and decline of cellular hypoxia as wound cellularity and proliferation regress suggest its involvement in initiating vascular regression during the later stages of healing.

Tissue transglutaminase is expressed as a host response to tumor invasion and inhibits tumor growth

A stable extracellular matrix (ECM) constitutes an important part of host response mechanism against tumor growth and invasion. Tissue transglutaminase (TG), a calcium-dependent enzyme, can cross-link all major ECM proteins to form a stable ECM, because these cross-links are resistant to proteolytic and mechanical damage. TG can also enhance stability and strength of the ECM by its ability to facilitate the activation of transforming growth factor-beta. We hypothesized that TG ECM-promoting abilities form an important part of the host response mechanism against tumor growth. Increased expression of TG was observed in the ECM of the host tumor interface of subcutaneously implanted rat mammary adenocarcinoma R3230 Ac. TG expression was also detected in the endothelial cells and macrophages. We also detected the cross-link product at the host tumor interface and within the tumor tissue, showing that TG was active. Western blots showed TG was degraded into three fragments of 55-, 50-, and 20-kDa forms. When recombinant wild-type TG was applied to R3230 Ac implanted in rat dorsal skin flap window chamber, it caused significant growth delay at day 7 compared with recombinant inactive TG controls. Collagen was detected in increased amounts in TG treated tumors, suggesting augmentation of production and stability of the ECM. We conclude that TG forms a distinct part of host response system against and acts to inhibit tumor growth.

Tissue transglutaminase is expressed, active, and directly involved in rat dermal wound healing and angiogenesis

Tissue transglutaminase (TG) is an enzyme that stabilizes the structure of tissues by covalently ligating extracellular matrix molecules. Expression and localization of TG are not well established during wound healing. We performed punch biopsy wounds on anesthetized rats and monitored the wound healing process by histological and immunohistochemical methods. The TG antigen and activity are expressed at sites of neovascularization in the provisional fibrin matrix within 24 h of wounding. Endothelial cells, macrophages, and skeletal muscle cells expressed TG throughout the healing process. The TG antigen within the wound was active in vivo based on the detection of isopeptide bonds. The TG antigen increased four- to fivefold by day 3 postwounding and was proteolytically degraded. TG expression occurred in association with TGF-beta, TNF-alpha, IL-6, and VEGF production in the wound. Recombinant TG increased vessel length density (a measure of angiogenesis) when applied topically in rat dorsal skin flap window chambers. We have established that TG is an important tissue stabilizing enzyme that is active during wound healing and can function to promote angiogenesis.

Site-directed mutagenesis of the calcium-binding site of blood coagulation factor XIIIa

Blood coagulation factor XIIIa is a calcium-dependent enzyme that covalently ligates fibrin molecules during blood coagulation. X-ray crystallography studies identified a major calcium-binding site involving Asp(438), Ala(457), Glu(485), and Glu(490). We mutated two glutamic acid residues (Glu(485) and Glu(490)) and three aspartic acid residues (Asp(472), Asp(476), and Asp(479)) that are in close proximity. Alanine substitution mutants of these residues were constructed, expressed, and purified from Escherichia coli. The K(act) values for calcium ions increased by 3-, 8-, and 21-fold for E485A, E490A, and E485A,E490A, respectively. In addition, susceptibility to proteolysis was increased by 4-, 9-, and 10-fold for E485A, E490A, and E485A,E490A, respectively. Aspartic acids 472, 476, and 479 are not involved directly in calcium binding since the K(act) values were not changed by mutagenesis. However, Asp(476) and Asp(479) are involved in regulating the conformation for exposure of the secondary thrombin cleavage site. This study provides biochemical evidence that Glu(485) and Glu(490) are Ca(2+)-binding ligands that regulate catalysis. The binding of calcium ion to this site protects the molecule from proteolysis. Furthermore, Asp(476) and Asp(479) play a role in modulating calcium-dependent conformational changes that cause factor XIIIa to switch from a protease-sensitive to a protease-resistant molecule.

Regulation of human tissue transglutaminase function by magnesium-nucleotide complexes. Identification of distinct binding sites for Mg-GTP and Mg-ATP

Tissue transglutaminase (tTG) catalyzes a Ca(2+)-dependent transglutaminase (TGase) activity that stabilizes tissues and a GTP hydrolysis activity that regulates cell receptor signaling. The purpose of this study was to examine the true substrates for nucleotide hydrolysis and the effects of these substrates on modulating the dual enzymatic activities of tTG. We found that Mg-GTP and Mg-ATP are the true substrates of the hydrolysis reaction. tTG hydrolyzed Mg-GTP and Mg-ATP at similar rates and interacted with Mg-ATP (Km = 38 +/- 10 microM) at a 3-fold greater steady-state affinity than with Mg-GTP (Km = 130 +/- 35 microM). In addition, Mg-ATP inhibited GTP hydrolysis (IC50 = 24 microM), whereas 1 mM Mg-GTP reduced ATP hydrolysis by only 20%. Furthermore, the TGase activity of tTG was inhibited by Mg-GTP, Mg-GDP, and Mg-GMP, with IC50 values of 9, 9, and 400 microM, respectively, whereas the Mg-adenine nucleotides were ineffective. Kinetic analysis of the hydrolysis reaction demonstrates the presence of separate binding sites for Mg-GTP and Mg-ATP. Finally, we found that Mg-GTP protected tTG from proteolytic degradation by trypsin, whereas Mg-ATP was ineffective. In conclusion, we report that Mg-GTP and Mg-ATP can bind to distinct sites and serve as substrates for nucleotide hydrolysis. Furthermore, binding of Mg-GTP causes a conformational change and the inhibition of TGase activity, whereas Mg-ATP is ineffective. The implication of these findings in regulating the intracellular and extracellular function of tTG is discussed.

Standardization of prothrombin fragment 1.2 measurement: effects of preanalytical variables and calibrator selection

BACKGROUND

Immunoassays for prothrombin fragment 1.2 (F1.2) provide a specific measure of thrombin generation and offer potential value in detecting activation of the coagulation system and monitoring anticoagulant therapy. To standardize laboratory measurements of this analyte, it is important to define factors affecting interassay variability.

OBJECTIVE

To determine the potential for standardization of F1.2 measurement by examining the effects of preanalytical variables and calibrator selection on F1.2 measurement.

MATERIALS AND METHODS

Using three commercially available immunoassays, interassay and intra-assay correlations for F1.2 were determined using blood samples collected into heparin, citrate, and a solution of ethylenediaminetetraacetic acid, aprotinin, and D-phenylalanyl-L-prolyl-L-arginyl chloromethyl ketone. In a cohort of patients, interassay correlations for F1.2 were determined using blood collected from an arterial catheter. Dose-response curves were generated for each manufacturer-supplied calibrator set by substitution into each of the previously untested competing immunoassays.

RESULTS

F1.2 immunoassays with the same recommended specimen anticoagulant displayed stronger correlation than assays requiring different anticoagulants. Furthermore, a stronger interassay correlation was elicited by samples collected through an intra-arterial catheter as opposed to venipuncture. F1.2 calibrator sets differed quantitatively, with buffer-related matrix effects contributing to interassay variability.

CONCLUSION

Analytical standardization of F1.2 immunoassays is possible when a common anticoagulant, blood collection method, and calibrator set are used.