Novel aspects of blood coagulation factor XIII. I. Structure, distribution, activation, and function

"Long haul" flight and deep vein thrombosis: a model to help investigate the benefit of aspirin and below-knee compression stockings

OBJECTIVE

to develop a model simulating factors of "long haul" flight to investigate the relationship with DVT.

MATERIALS AND METHODS

volunteers (19 males: 20 females) sat for 6 h in a warm (>25 degrees C), dry environment, limited in movement, consuming alcohol (40 ml of 40% alcohol/hour) and salted foods (300 g). Half of the subjects received 150 mg aspirin and wore especially designed below-knee, compression stockings (Class 1 profile). Changes in full blood counts were recorded, and as an indication of DVT formation, plasma was analysed for D-dimer. Limb swelling was assessed from leg measurements.

RESULTS

after 6 h, in controls, there were significant rises in platelet packing (Pct p<0.04), total platelet numbers (p<0.003) and total numbers of white blood cells (WBC's p<0.001). With aspirin plus stockings, there were similar significant rises in total platelet numbers (p<0.002) and total WBC's (p<0.001). In both groups, significant rises were seen in all WBC types (except basophils). Wearing compression stockings prevented calf swelling seen in controls after 6 h (p<0.002). No subject developed a DVT, or a change in levels of D-dimer.

CONCLUSION

changes in the cellular components of blood, particularly WBC's, combined with vaso-compression and reduced flow could predispose towards DVT. Aspirin, combined with compression stockings, may provide prophylaxis.

A transglutaminase involved in the coagulation system of the freshwater crayfish, Pacifastacus leniusculus. Tissue localisation and cDNA cloning

The crayfish haemolymph can form stable and insoluble clots by a transglutaminase (TGase)-catalysed crosslinking reaction between the soluble clotting protein molecules from the plasma. The crayfish haemocytes, both semigranular and granular cells, as well as the muscle tissue, contain TGase activity, whereas the hepatopancreas and plasma have no TGase activity. A 3199 bp cDNA encoding a TGase was isolated from a crayfish haemocyte cDNA library. The deduced protein comprises 766 amino acid residues and has a calculated molecular mass of between 85,930 and 86,034 kDa due to four amino acid variations. This gene is expressed as a single 4.9 kb transcript exclusively in the haemocytes and at very low levels in muscle and the hepatopancreas. Sequence comparison shows that this TGase has significant similarities to other TGases from invertebrates and mammals.

Cell surface tissue transglutaminase is involved in adhesion and migration of monocytic cells on fibronectin

Expression of tissue transglutaminase (transglutaminase II, tTG) was shown to increase drastically during monocyte differentiation into macrophages; however, its role in monocytic cells remains largely unknown. This study describes a novel function of cell surface tTG as an adhesion and migration receptor for fibronectin (Fn). Two structurally related transglutaminases, tTG and the A subunit of factor XIII (FXIIIA), are expressed on the surface of monocytic cells, whereas only surface tTG is associated with multiple integrins of the beta1 and beta3 subfamilies. Both surface levels of tTG and the amounts of integrin-bound tTG are sharply up-regulated during the conversion of monocytes into macrophages. In contrast, a reduction in biosynthesis and surface expression of FXIIIA accompanies monocyte differentiation. Cell surface tTG is colocalized with beta1- and beta3-integrins in podosomelike adhesive structures of macrophages adherent on Fn. Down-regulation of surface tTG by expression of antisense tTG construct or its inhibition by function-blocking antibodies significantly decreases adhesion and spreading of monocytic cells on Fn and, in particular, on the gelatin-binding fragment of Fn consisting of modules I6II1,2I7-9. Likewise, interfering with the adhesive function of surface tTG markedly reduces migration of myeloid cells on Fn and its gelatin-binding fragment. These data demonstrate that cell surface tTG serves as an integrin-associated adhesion receptor that might be involved in extravasation and migration of monocytic cells into tissues containing Fn matrices during inflammation.

New anticoagulant drugs

Arterial and venous thrombosis are major causes of morbidity and mortality. Arterial thrombosis is the most common cause of myocardial infarction, stroke, and limb gangrene. Venous thrombosis leads to potentially fatal pulmonary embolism and to post-phlebitic syndrome. Because arterial thrombi consist of platelet aggregates held together by small amounts of fibrin, strategies to inhibit arterial thrombogenesis focus mainly on blocking platelet function, but often include anticoagulants to prevent fibrin deposition. Anticoagulants are used for the prevention and treatment of venous thrombosis because venous thrombi consist mainly of fibrin and red blood cells. This paper (1) reviews arterial and venous thrombogenesis, (2) outlines new anticoagulant strategies, and (3) provides clinical perspectives on these new strategies.

Effects of profound hemodilution on small-intestinal wound healing in rabbits

BACKGROUND

Wound healing is influenced by tissue oxygen tension and blood perfusion, but not by moderate anemia or hemodilution. The effect of perioperative profound hemodilution on small-intestinal wound healing remains unclear.

METHODS

We performed jejunectomy followed by end-to-end anastomosis in rabbits subjected to a variety of perioperative hemodilutions: HD((HES)), hemodiluted with hydroxyethylstarch; HD((P+HES)), hemodiluted with autologous plasma and hydroxyethylstarch; HD((HES))/R, hemodiluted with hydroxyethylstarch and retransfused afterward. Intraoperative hemoglobin levels were 5 g 100 ml(-1). On Postoperative Day 5, the tensile strength (TS) of the anastomosis was measured and histological specimen was obtained. The time courses of hemoglobin, serum albumin (Alb), plasma fibrinogen (Fbg), and plasma activity of factor XIII (F XIII) were measured.

RESULTS

TS in HD((HES))/R (236.0 +/- 52.2 gf) was similar to that in control (266.5 +/- 41.6 gf); however, TS in HD((HES)) (179.8 +/- 17.9 gf) and HD((P+HES)) (165.5 +/- 14.7 gf) decreased significantly. The histological findings in HD((HES))/R were similar to those of control, whereas they demonstrated a delayed healing process in HD((HES)) and HD((P+HES)). Hemoglobin levels were still lower on Postoperative Day 5 in HD((HES)) and HD((P+HES)), but increased to 10.0 g 100 ml(-1) after retransfusion in HD((HES))/R. Hemodilution caused significant decreases in Alb, Fbg, and F XIII, but the values after retransfusion in HD((HES))/R were similar to postoperative values in HD((P+HES)).

CONCLUSION

Intraoperative profound hemodilution does not interfere with small-intestinal wound healing as long as postoperative hemoglobin levels were maintained above 10 g 100 ml(-1). Postoperative levels of other plasma constituents may not influence wound healing.

Coagulation and cancer: implications for diagnosis and management

Coagulation disorders are a common problem in neoplastic patients and many factors contribute to increase the risk of thromboembolic events in these patients. An hypercoagulable state is induced by malignant cells interacting directly with hemostatic system and activating the coagulation cascade. More sensitive tests to assess an hypercoagulable state in cancer patients have been developed; even though these tests are always altered in cancer patients, none of them possess a clinical significance in terms of predictive value for the occurence of thromboembolism and disease prognosis in the individual patient. The most frequent thromboembolic complications in cancer patients are deep vein thrombosis of the lower extremities and pulmonary embolism; therefore, disseminated intravascular coagulation, thrombotic thrombocytopenic purpura or haemolytic uremic syndrome are special manifestations of neoplastic disease. Diagnosis of idiopathic deep vein thrombosis, in the absence of other risk factors, could indicate the presence of occult malignant disease; however, the need for an extensive work-up to detect malignancy is still controversial. Neoplastic patients showing a thromboembolic event should be treated with unfractioned heparin or, alternatively, with low molecular weight heparins. In order to prevent recurrence, the administration of heparin should be associated and followed by an oral anticoagulant drug. In recent years new approaches in anti-aggregation therapy have been studied, such as COX-inhibitors, cicaprost and ReoPro; further studies are needed to determine the usefulness of these molecules in treatment of malignancies.

Evaluation of a sensitive colorimetric FXIII incorporation assay. Effects of FXIII Val34Leu, plasma fibrinogen concentration and congenital FXIII deficiency

There is an increasing interest in the role of coagulation factor XIII (FXIII) in cardio- and cerebrovascular diseases. It has recently been reported that a common G-->T point mutation in the A-subunit gene of FXIII, which codes for a valine (val) to leucine (leu) change (FXIIIVal34Leu), is protective against thrombotic diseases but seems to increase the risk of intracerebral bleeding. We developed a colorimetric incorporation assay for detection of FXIII activity based on incorporation of 5-(biotinamido) pentylamine (BAPA) into fibrin or fibrinogen. With this new assay, we studied the effects of FXIIIVal34Leu mutation, plasma fibrinogen concentration and congenital FXIII deficiency on FXIII activity. There are no data available about the ability of different FXIII assays to detect altered activity in FXIIIVal34Leu genotypes. We therefore compared our results determined by the incorporation method with a commonly used photometric method based on ammonia release after cross-linking of glycine-ethylester to a specific glutamine containing peptide substrate. We also determined FXIII A-subunit antigen (Ag) levels using enzyme-linked immunosorbent assay (ELISA) technique. The FXIIIVal34Leu genotype could not be detected either by the photometric method nor by the FXIII A-subunit ELISA. The incorporation assay showed an increased specific FXIII activity in subjects possessing the leu allele. The photometric assay and ELISA gave similar results independent from genotype. In patients with congenital FXIII deficiency before and after substitution, however, ELISA and the incorporation assay gave similar results, whereas the photometric assay showed consistently higher values. Our results show that the incorporation assay, not the photometric assay based on ammonia release, can be used for detection of elevated activity in subjects with FXIIIVal34Leu. Because of specificity and over a wide range sensitivity, the assay can also be used for determination of FXIII deficiency and monitoring of FXIII substitution therapy.

Stabilization of neurites in cerebellar granule cells by transglutaminase activity: identification of midkine and galectin-3 as substrates

The formation of covalent isopeptide cross-links between cell surface protein molecules by the enzyme transglutaminase C influences cell adhesion and morphology. Retinoid-inducible cross-linking activity associated with this enzyme is present in the developing rat cerebellar cortex [Perry M. J. M. et al. (1995) Neuroscience 65, 1063-1076]. A monoclonal antibody was used to localize transglutaminase C to granule neurons in the developing cerebellar cortex. The enzyme was inducible by retinoic acid both in granule neurons cultured from postnatal rat cerebellar cortex and in cells of the embryonic dorsal rhombic lip, which contain granule neuron precursors. A possible biological function for transglutaminase activity was investigated in living granule neurons, cultured on a biomatrix substratum, studied by time-lapse cinematographic analysis using the transglutaminase inactivator RS-48373-007. Inhibition of cross-linking activity did not influence the number of neurites formed by granule neurons, but caused the destabilization of neurites during the initial outgrowth period, seen as an increase in the number of growth cone retractions and the onset of premature axon collateral formation (bifurcation). Inactivation of cross-linking activity prevented the formation of fascicles between neurites only when cells were cultured on a biomatrix surface. Two glial proteins involved in cell-extracellular matrix interactions, midkine and galectin-3, were identified as putative substrates for granule neuron transglutaminase. The results suggest that covalent cross-link formation by transglutaminase C or a related enzyme generates multimeric molecular forms of glial-derived proteins, and plays a role in stabilizing newly formed neurites. A possible non-pathological role for transglutaminase in the control of axon collateral branching by developing granule neurons in the cerebellar cortex is discussed.

A simple assay and histochemical localization of transglutaminase activity using a derivative of green fluorescent protein as substrate

Histidine-tagged green fluorescent protein (His(6)-Xpress-GFP), a widely used fluorescent probe, was found to be a good substrate for transglutaminase, an enzyme that catalyzes covalent crosslinking of proteins. GFP alone did not serve as a substrate but its derivative His(6)-Xpress-GFP was readily crosslinked through the Gln and Lys residues present in the short N-terminal extension (His(6)-Xpress). His(6)-Xpress-GFP was sensitive enough to detect the transglutaminase activity in guinea pig liver homogenates. The fluorescent substrate could also be used for activity staining of transglutaminase on histological tissue sections, and such applications revealed a surprisingly wide distribution of transglutaminase in the body, especially in the extracellular matrices of various tissues, suggesting an important role for transglutaminase in maintaining the integrity of the extracellular matrix and connective tissues by crosslinking its constituent proteins.(J Histochem Cytochem 49:247-258, 2001)

A Modified, Optimized Kinetic Photometric Assay for the Determination of Blood Coagulation Factor XIII Activity in Plasma

Background: Blood coagulation factor XIII (FXIII) is a zymogen that is transformed into an active transglutaminase by thrombin and Ca2+. FXIII plays an essential role in fibrin stabilization and in the protection of fibrin from proteolytic degradation. No convenient method has been available for the measurement of FXIII activity in plasma. The aim of the present study was to improve and optimize a kinetic photometric FXIII assay originally developed in our laboratory.

Methods: In the assay, FXIII was activated by thrombin and Ca2+. Fibrin polymerization was prevented by an inhibitory tetrapeptide. Glycine-ethyl ester and a glutamine residue of a synthetic dodecapeptide served as acyl acceptor and acyl donor transglutaminase substrates, respectively. The amount of ammonia released during the reaction was monitored using glutamate dehydrogenase and NADPH.

Results: The use of a new glutamine substrate and optimization of activator and substrate concentrations increased sensitivity. Substitution of NADPH for NADH and introduction of an appropriate blank eliminated systemic overestimation of FXIII activity. The recovery of FXIII was 96%, the assay was linear up to 470 U/L, the detection limit was 1 U/L, and the imprecision (CV) was &lt;8% even at very low FXIII activities. A reference interval of 108–224 U/L (69–143%) was established. The results correlated well with results obtained by an immunoassay specific for plasma FXIII.

Conclusions: The optimized FXIII assay is a simple, rapid method for the diagnosis of inherited or acquired FXIII deficiencies and increased FXIII concentrations. It can be easily adapted to clinical chemistry analyzers.

Facilitated wound healing by activation of the Transglutaminase 1 gene

Transglutaminase 1 (TGase 1) is a Ca(2+)-dependent enzyme which catalyzes epsilon-(gamma-glutamyl)lysine cross-linking of substrate proteins such as involucrin and loricrin to generate the cornified envelope at the cell periphery of the stratum corneum. We have shown that disruption of the TGase 1 gene in mice results in neonatal lethality, absence of the cornified envelope, and impaired skin barrier function. Based on the importance of TGase 1 in epidermal morphogenesis, we have now assessed its role in wound healing. In neonatal mouse skin, TGase 1 mRNA as well as keratin 6alpha was induced in the epidermis at the wound edges as early as 2 hours after injury and that expression continued in the migrating epidermis until completion of re-epithelialization. The TGase 1 enzyme co-localized on the plasma membrane of migrating keratinocytes with involucrin, but not with loricrin, which suggests the premature assembly of the cornified envelope. Similar injuries to TGase 1 knockout mouse skins grafted on athymic nude mice showed substantial delays in wound healing concomitant with sustained K6alpha mRNA induction. From these results, we suggest that activation of the TGase 1gene is essential for facilitated repair of skin injury.

Interaction of the factor XIII activation peptide with alpha -thrombin. Crystal structure of its enzyme-substrate analog complex

The serine protease thrombin proteolytically activates blood coagulation factor XIII by cleavage at residue Arg(37); factor XIII in turn cross-links fibrin molecules and gives mechanical stability to the blood clot. The 2.0-A resolution x-ray crystal structure of human alpha-thrombin bound to the factor XIII-(28-37) decapeptide has been determined. This structure reveals the detailed atomic level interactions between the factor XIII activation peptide and thrombin and provides the first high resolution view of this functionally important part of the factor XIII molecule. A comparison of this structure with the crystal structure of fibrinopeptide A complexed with thrombin highlights several important determinants of thrombin substrate interaction. First, the P1 and P2 residues must be compatible with the geometry and chemistry of the S1 and S2 specificity sites in thrombin. Second, a glycine in the P5 position is necessary for the conserved substrate conformation seen in both factor XIII-(28-37) and fibrinopeptide A. Finally, the hydrophobic residues, which occupy the aryl binding site of thrombin determine the substrate conformation further away from the catalytic residues. In the case of factor XIII-(28-37), the aryl binding site is shared by hydrophobic residues P4 (Val(34)) and P9 (Val(29)). A bulkier residue in either of these sites may alter the substrate peptide conformation.

Chicken coagulation factor XIIIA is produced by the theca externa and stabilizes the ovarian follicular wall

Development of the follicle in egg-laying species such as the chicken is regulated by systemic factors as well as by the highly orchestrated interplay of differentially expressed genes within this organ. Differential mRNA display analysis of defined phases of follicle development resulted in the characterization of coagulation factor XIIIA. It is expressed and produced by cells of the theca externa in a highly regulated manner during distinct growth phases of the follicle. Transcripts for factor XIIIA are already detectable at the beginning of follicle development and peak at the end of phase 2. Protein levels, however, still increase during phase 3, peak shortly after ovulation, and persist until the postovulatory tissue is completely resorbed. Factor XIIIA is secreted as a monomer into the extracellular matrix of the theca externa and is not associated with factor XIIIB as is the case in plasma. Our data suggest that, due to its transglutaminase activity, factor XIIIA stabilizes the follicular wall by cross-linking matrix components. Thus, coagulation factor XIIIA might play a key role in coping with the massive mechanical stress exerted by the large amount of yolk accumulating during the rapid growth phase of the oocyte.

Catalytic life of activated factor XIII in thrombi. Implications for fibrinolytic resistance and thrombus aging

BACKGROUND

Because the increased fibrinolytic resistance of older thrombi may be caused by the continuous cross-linking action of fibrin-bound activated factor XIII (FXIIIa), we examined the persistence of FXIIIa catalytic activity in clots of various ages.

METHODS AND RESULTS

The time-related changes in FXIIIa activity in clots was measured with (1) alpha(2)-antiplasmin (alpha(2)AP), a physiological glutamine substrate; (2) alpha(2)AP(13-24), a peptide; and (3) pentylamine, a nonspecific lysine substrate. The cross-linking of alpha(2)AP, alpha(2)AP(13-24), and pentylamine into fibrin by clot-bound FXIIIa declined rapidly with half-lives of 19, 21, and 26 minutes, respectively. Mutational studies showed that glutamine 14 (but not glutamine 3 or 16) and valine 17 of alpha(2)AP(13-24) were required for efficient cross-linking to fibrin. The loss of activity was not due primarily to FXIIIa proteolysis and was partially restored by reducing agents, suggesting that oxidation contributes to the loss of the enzyme's activity in clots. In vivo, the ability of thrombus-bound FXIIIa to cross-link an infused alpha(2)AP(13-24) peptide into existing pulmonary emboli also declined significantly over time.

CONCLUSIONS

FXIIIa cross-links alpha(2)AP and an alpha(2)AP peptide, in a sequence-specific manner, into formed clots with a catalytic half-life of approximately 20 minutes. This indicates that FXIIIa activity is a hallmark of new thrombi and that the antifibrinolytic cross-linking effects of FXIIIa are achieved more rapidly in thrombi than previously believed.

Protein crosslinking in assembly and remodelling of extracellular matrices: the role of transglutaminases

Transglutaminases form a family of proteins that have evolved for specialized functions such as protein crosslinking in haemostasis, semen coagulation, or keratinocyte cornified envelope formation. In contrast to the other members of this protein family, tissue transglutaminase is a multifunctional enzyme apparently involved in very disparate biological processes. By virtue of its reciprocal Ca2+-dependent crosslinking activity or GTP-dependent signal transducing activity, tissue transglutaminase exhibits true multifunctionality at the molecular level. The crosslinking activity can subserve disparate biological phenomena depending on the location of the target proteins. Intracellular activation of tissue transglutaminase can give rise to crosslinked protein envelopes in apoptotic cells, whereas extracellular activation contributes to stabilization of the extracellular matrix and promotes cell-substrate interaction. While tissue transglutaminase synthesis and activation is normally part of a protective cellular response contributing to tissue homeostasis, the enzyme has also been implicated in a number of pathological conditions including fibrosis, atherosclerosis, neurodegenerative diseases, celiac disease, and cancer metastasis. This review discusses the role of transglutaminases in extracellular matrix crosslinking with a focus on the multifunctional enzyme tissue transglutaminase.

α-Fibrinogen Thr312Ala polymorphism and venous thromboembolism

The A-fibrinogen Thr312Ala polymorphism, which occurs in a region involved in factor XIII (FXIII)-dependent cross-linking processes, is associated with poststroke mortality in subjects with atrial fibrillation, suggesting an influence either on intraatrial clot formation or embolization. We have determined the association of Thr312Ala with deep vein thrombosis (DVT) and pulmonary embolism (PE) and have assessed the interaction of Thr312Ala with the FXIII Val34Leu polymorphism in 122 patients with DVT, 99 patients with PE, and 254 healthy control subjects. The genotype distribution of patients with PE (TT = 49%, TA = 36%, AA = 15%), but not DVT (TT = 50%, TA = 42%, AA = 8%), differed significantly from healthy control subjects (TT = 60%, TA = 34%, AA = 6%, P = .02). A significant interaction of Thr312Ala and Val34Leu was also identified (P = .01), indicating an inverse association between Leu34 and Ala312. These results support the hypothesis that Thr312Ala alters FXIII-dependent cross-linking, making formed fibrin clot more susceptible to embolization.

α-Fibrinogen Thr312Ala polymorphism and venous thromboembolism

The A-fibrinogen Thr312Ala polymorphism, which occurs in a region involved in factor XIII (FXIII)-dependent cross-linking processes, is associated with poststroke mortality in subjects with atrial fibrillation, suggesting an influence either on intraatrial clot formation or embolization. We have determined the association of Thr312Ala with deep vein thrombosis (DVT) and pulmonary embolism (PE) and have assessed the interaction of Thr312Ala with the FXIII Val34Leu polymorphism in 122 patients with DVT, 99 patients with PE, and 254 healthy control subjects. The genotype distribution of patients with PE (TT = 49%, TA = 36%, AA = 15%), but not DVT (TT = 50%, TA = 42%, AA = 8%), differed significantly from healthy control subjects (TT = 60%, TA = 34%, AA = 6%, P = .02). A significant interaction of Thr312Ala and Val34Leu was also identified (P = .01), indicating an inverse association between Leu34 and Ala312. These results support the hypothesis that Thr312Ala alters FXIII-dependent cross-linking, making formed fibrin clot more susceptible to embolization.

Human prostate-specific transglutaminase gene: promoter cloning, tissue-specific expression, and down-regulation in metastatic prostate cancer

OBJECTIVES

To investigate the tissue-specific and differential expression of the human prostate-specific transglutaminase (pTGase) gene in metastatic prostate cancer (CaP) and to study how this gene is regulated in the prostate.

METHODS

Northern blot hybridization and polymerase chain reaction (PCR) were performed using RNA from a variety of organs to confirm prostate-specific expression of the gene. Relative quantitative reverse transcriptase-PCR (RT-PCR) was performed to investigate the differential expression of the gene among normal prostates and prostates with CaP and metastatic CaP. The pTGase gene promoter was cloned using genomic library screening and sequencing. Transfection experiments and chloramphenicol acetyltransferase (CAT) assays were performed to study the regulation of the gene.

RESULTS

Northern hybridization and RT-PCR confirmed that the gene is only expressed in the prostate. Relative quantitative RT-PCR demonstrated a loss of expression of the pTGase gene among men with CaP and higher Gleason grades. In metastatic CaP tissue from various sites, 86% of the samples lost expression of the gene. We cloned and sequenced a 1.4-kilobase promoter region of the pTGase gene. Transfection and CAT assay results supported the theory that certain elements in the -1 to -520 region are sufficient to direct prostate-specific expression of the gene. Additional elements in the -520 to -1400 region may also contribute to its prostate-specific expression.

CONCLUSIONS

The results of our study demonstrate that the human pTGase gene is only expressed in prostate tissue and that its expression is inhibited in most metastatic CaP. Prostate-specific expression of the gene is controlled by elements in the promoter region. The observed preferential loss of pTGase gene expression in metastatic CaP may be important to the pathogenesis and progression of this disease.

Factor XIIIa positive dendritic cells are a major accessory cell population in the elicitation phase of DNCB-induced contact hypersensitivity

The phenotypes and distribution of accessory cells in the ear skin of lambs during the elicitation phase of dinitrochlorobenzene (DNCB)-induced contact hypersensitivity (CHS) were examined using indirect immunoperoxidase histochemistry (ABC method), and a panel of antibodies. Thirty lambs, between 21 and 26 weeks of age, were divided into groups of 10. The shaved right ear of one group was treated with DNCB. Two weeks later this group was challenged with DNCB. One group was treated with the vehicle alone and the remaining group was left untreated. The lambs were slaughtered 48 h after challenge, and tissue specimens were collected from the ears of the three groups. Factor XIIIa+ (FXIIIa+) cells were prominent in the superficial dermis and showed predominantly a perivascular and subepidermal distribution. The other markers were less prominent, and whereas CD1+ cells and CD68+ cells showed a reaction pattern similar to the FXIIIa+ cells, CD14+ cells were found scattered predominantly in the deep dermis. There appeared to be an increase in FXIIIa+ cells, CD1+ cells, and CD68+ cells in the dermis of the DNCB-treated lambs 48 h after challenge. Only CD1+ cells were detected in epidermis of normal controls, and these cells appeared to be decreased in number in the two treated groups. Computer-assisted morphometric analysis was used to estimate the relative presence of the accessory cell subpopulations in the superficial and deep dermis and the entire dermis. A statistical analysis of the relative area of immunostaining showed a significantly increased presence of FXIIIa+ cells and CD68+ cells in the dermis of the DNCB-treated lambs 48 h after challenge. Interestingly, FXIIIa+ cells and CD68+ cells were also significantly increased in the vehicle treated group compared with untreated controls. We found no significant difference in the presence of CD1+ cells or CD14+ cells in the DNCB treated group compared with the controls. The study showed that FXIIIa+ DDC are the major accessory cell population in normal ear skin of lambs and the major responsive population during the elicitation phase of CHS. The lack of response in the CD1+ cell population suggests a less prominent role for the LC-related DC in the skin during the elicitation phase.

Genetic determinants of arterial thrombosis

This chapter describes examples of genetic variation involved in the function or regulation of a number of haemostatic proteins involved in the thrombotic process. In each case, the data suggest associations between genotype and disease and, particularly in the case of fibrinogen, PAI-1, Factor VII and Factor XIII, there is interaction between genotype and environment in determination of the relevant plasma level, providing a possible explanation for the differential response of individuals to their environment.

A superfamily of archaeal, bacterial, and eukaryotic proteins homologous to animal transglutaminases

Computer analysis using profiles generated by the PSI-BLAST program identified a superfamily of proteins homologous to eukaryotic transglutaminases. The members of the new protein superfamily are found in all archaea, show a sporadic distribution among bacteria, and were detected also in eukaryotes, such as two yeast species and the nematode Caenorhabditis elegans. Sequence conservation in this superfamily primarily involves three motifs that center around conserved cysteine, histidine, and aspartate residues that form the catalytic triad in the structurally characterized transglutaminase, the human blood clotting factor XIIIa'. On the basis of the experimentally demonstrated activity of the Methanobacterium phage pseudomurein endoisopeptidase, it is proposed that many, if not all, microbial homologs of the transglutaminases are proteases and that the eukaryotic transglutaminases have evolved from an ancestral protease.

Subunit antigen and activity levels of blood coagulation factor XIII in healthy individuals. Relation to sex, age, smoking, and hypertension

Factor (F) XIII covalently cross-links and stabilizes the fibrin-clot. Recent evidence suggests a role for FXIII in atherothrombotic diseases, but no information is available regarding the association of FXIII with common risk factors. The aim of this study was to investigate the relationship of FXIII with age, sex, smoking, and hypertension. Plasma levels of FXIII A-subunit antigen, FXIII B-subunit antigen, and FXIII cross-linking activity were measured in 612 healthy individuals (250 men and 362 women). FXIII A- and B-subunit levels were correlated significantly with age in both men (r=0.21, P=0.001, and r=0.17, P=0.008, respectively) and women (r=0.20, P<0.0005, and r=0.13, P=0.011, respectively). FXIII B-subunit levels and activity were correlated significantly with FXIII A-subunit levels (r=0.60, P<0.0005, and r=0.14, P<0.0005, respectively) and fibrinogen (r=0.26, P<0.0005, and r=0.14, P=0.001, respectively). Women had higher levels of FXIII A-subunit (111.8% versus 105.2%, P<0.01) and B-subunit (109.5% versus 103.8%, P<0.01) than did men. FXIII A-subunit was significantly increased in smokers (117.0% versus 104.6%, P<0.0005) and in subjects with hypertension (114.9% versus 107.8%, P<0.05). In a multiple regression model, FXIII A-subunit was significantly increased by female sex (+6.4%, P<0.007), smoking (+12.3%, P<0.0005), and increasing age (+3.7% per 10 years, P<0.0005). FXIII B-subunit was significantly related to female sex and fibrinogen, and FXIII activity was significantly related to fibrinogen levels. In conclusion, the FXIII A-subunit level increases significantly with female sex, age, and smoking, whereas FXIII B-subunit and FXIII activity are associated with FXIII A-subunit level and fibrinogen. Although evidence for a causal relationship between FXIII A-subunit and vascular disease is not available, these results might suggest a role for elevated FXIII A-subunit levels in the pathogenesis of vascular disease.

Association of the alpha-fibrinogen Thr312Ala polymorphism with poststroke mortality in subjects with atrial fibrillation

BACKGROUND

The alpha-fibrinogen Thr312Ala polymorphism occurs in close proximity to several sites important for factor XIIIa-dependent cross-linking, which raises the possibility that it affects fibrin clot stability.

METHODS AND RESULTS

We determined the association of this polymorphism with ischemic stroke, stroke subtype, and poststroke mortality. There was no significant difference in the genotype distributions of patients with acute ischemic stroke (n=519) and healthy control subjects (n=423), nor was there any association of this polymorphism with stroke subtype. In a Cox regression model, a significant interaction between Thr312Ala and atrial fibrillation was identified in relation to poststroke mortality (P=0.002). In subjects in sinus rhythm (n=418), there was no difference according to genotype in the proportion of subjects who survived (approximately 60% in each group), whereas in subjects with atrial fibrillation (n=101), there was decreased survival in those possessing the A allele (TT=42.1%, TA=18%, AA=0%).

CONCLUSIONS

The Thr312Ala polymorphism may give rise to an increased susceptibility for embolization of intra-atrial clot, and these findings could have important implications for identifying subjects most at risk of developing thromboembolic complications.

Effect of factor XIII on endothelial barrier function

The effect of factor XIII on endothelial barrier function was studied in a model of cultured monolayers of porcine aortic endothelial cells and saline-perfused rat hearts. The thrombin-activated plasma factor XIII (1 U/ml) reduced albumin permeability of endothelial monolayers within 20 min by 30 +/- 7% (basal value of 5.9 +/- 0.4 x 10(-6) cm/s), whereas the nonactivated plasma factor XIII had no effect. Reduction of permeability to the same extent, i.e., by 34 +/- 9% could be obtained with the thrombin-activated A subunit of factor XIII (1 U/ml), whereas the iodoacetamide-inactivated A subunit as well as the B subunit had no effect on permeability. Endothelial monolayers exposed to the activated factor XIII A exhibited immunoreactive deposition of itself at interfaces of adjacent cells; however, these were not found on exposure to nonactivated factor XIII A or factor XIII B. Hyperpermeability induced by metabolic inhibition (1 mM potassium cyanide plus 1 mM 2-deoxy-D-glucose) was prevented in the presence of the activated factor XIII A. Likewise, the increase in myocardial water content in ischemic-reperfused rat hearts was prevented in its presence. This study shows that activated factor XIII reduces endothelial permeability. It can prevent the loss of endothelial barrier function under conditions of energy depletion. Its effect seems related to a modification of the paracellular passageways in endothelial monolayers.

Effect on platelet FXIII and partial characterization of Lonomin V, a proteolytic enzyme from Lonomia achelous caterpillars

Contact with Lonomia achelous caterpillars venom induces a severe bleeding syndrome in humans. A constant finding in all reported cases is a marked decrease of blood coagulation factor XIII (FXIII), which has been attributed to the presence of a proteolytic enzyme, isolated and named Lonomin V, in the hemolymph and hair secretion. In this study, the effect of Lonomin V on transglutaminase activity from human plasma, rabbit plasma, and platelet FXIII was analyzed. The decrease of activity was more pronounced in platelet (A2) when compared with rabbit plasma (AB) and human plasma FXIII (A2B2). This finding might be explained by the differences in FXIII molecular structure. In addition, platelet FXIII molecule was degraded by Lonomin to several fragments of low molecular mass. Lonomin V was stable over a wide range of pH (6-8.5) and temperatures of -70 degrees C, -20 degrees C and between 4 to 24 degrees C, with a progressive decrease at 37 degrees C and total inactivation at 60 degrees C after 2 hours incubation. Diisopropyl fluoro-phosphate, phenylmethylsulfonyl fluoride, tosyl-l-lysine chloromethyl ketone, and iodoacetamide abolished the effect of Lonomin V on FXIII; in contrast dithiothreitol and EDTA-Na enhance the activity. We concluded that Lonomin V is a serine proteinase with a free Cys essential for the enzymatic activity. Due to its proteolytic activity on FXIII, with concomitant impairment of fibrin cross-linking, Lonomin V might be useful in association with thrombolytic drugs for preventing rethrombosis.

Identification of the calcium binding site and a novel ytterbium site in blood coagulation factor XIII by x-ray crystallography

The presence or absence of calcium determines the activation, activity, oligomerization, and stability of blood coagulation factor XIII. To explore these observed effects, we have determined the x-ray crystal structure of recombinant factor XIII A2 in the presence of calcium, strontium, and ytterbium. The main calcium binding site within each monomer involves the main chain oxygen atom of Ala-457, and also the side chains from residues Asn-436, Asp-438, Glu-485, and Glu-490. Calcium and strontium bind in the same location, while ytterbium binds several angstroms removed. A novel ytterbium binding site is also found at the dimer two-fold axis, near residues Asp-270 and Glu-272, and this site may be related to the reported inhibition by lanthanide metals (Achyuthan, K. E., Mary, A., and Greenberg, C. S. (1989) Biochem. J. 257, 331-338). The overall structure of ion-bound factor XIII is very similar to the previously determined crystal structures of factor XIII zymogen, likely due to the constraints of this monoclinic crystal form. We have merged the three independent sets of water molecules in the structures to determine which water molecules are conserved and possibly structurally significant.

Factor XIIIa as a nerve-associated transglutaminase

Recent findings have led to changes in the traditional concept of nerve recovery, including the realization that injured nerves, like any other injured tissue, need the assistance of blood-derived cells and factors in order to heal. We show that factor XIIIa (FXIIIa, the potentially active a2subunit of factor XIII), an enzyme that participates in blood coagulation by stabilizing the fibrin clot, is also active in the nervous system where it may play a key role in the healing of injured tissue. We demonstrate that the plasma, macrophages and nerves of fish contain a 55 kDa form of transglutaminase that cross-reacts immunologically with the a-subunit of FXIII in mammals (80 kDa). The fish enzyme in the plasma, unlike its mammalian counterpart, is active, pointing to a difference in control of the coagulation pathway in the two species. Analysis of FXIIIa expression in mammalian neural tissues and their response to injury revealed high levels of the enzyme in media conditioned by peripheral nerves as compared with medium conditioned by nerves of the central nervous system. Furthermore, similarity was observed in the postinjury behavior of FXIIIa in regenerating nerve tissues (peripheral nervous system of mammals and the central nervous system of fish). We suggest that the postinjury level of factor XIIIa in the nervous system may be related to the tissue's regenerative capacity, and that FXIIIa may therefore be a link underlying a possible association between the processes of blood coagulation and nerve healing.

Factor XIIIa cross-links lipoprotein(a) with fibrinogen and is present in human atherosclerotic lesions

During the development of atherosclerotic lesions, lipoprotein(a) [Lp(a)], a highly atherogenic lipoprotein, accumulates within fibrin clots attached to blood vessel walls. As Lp(a) accumulates within the fibrin clot with time, fatty streaks are formed that develop into occlusive atherosclerotic plaques. It is not understood, however, which mechanisms are involved in the binding of Lp(a) to fibrin and, hence, the stable incorporation of Lp(a) into the fibrin clot. The results of the present study demonstrate that factor XIIIa, a transglutaminase that catalyzes the formation of amide bonds between endo-gamma-glutaminyl and endo-epsilon-lysyl residues of proteins, is capable of cross-linking Lp(a) to fibrinogen, the soluble precursor of fibrin. Biochemical assays were conducted to demonstrate that factor XIIIa cross-links Lp(a) with fibrinogen in a time- and concentration-dependent manner. Additionally, immunohistochemical studies revealed that factor XIII protein expression colocalizes with Lp(a) expression in human atherosclerotic plaques. It is proposed that factor XIIIa-mediated cross-linking of Lp(a) to fibrin effectively increases the local concentration of Lp(a) within a fibrin clot. The accumulation of Lp(a) within the blood vessel promotes an antifibrinolytic environment, foam cell formation, the generation of a fatty streak, and an increase in smooth muscle cell content, all of which may contribute to the pathogenesis of atherosclerosis.

Two non-proline cis peptide bonds may be important for factor XIII function

The structure of recombinant human cellular factor XIII zymogen was solved in its monoclinic crystal form and refined to an R-factor of 18.3% (Rfree = 23.6%) for all data between 40.0 and 2.1 A resolution. Two non-proline cis peptide bonds were detected. One is between Arg310 and Tyr311 close to the active site cysteine residue (Cys314) and the other is between Gln425 and Phe426 at the dimerization interface. The structure and the role of these cis peptides are discussed in the light of their possible importance for factor XIII function.