SEARCH · Search PubMed

Results for “FIBRINOGEN”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 505 records · Page 28Linked to original sources

PubMed2007

The fibrinogen antigenic turbidimetric assay (FIATA): the X2x test--the corrected chi-square comparison against the control-mean.

Vancomycin precipitates fibrinogen. The turbidity induced by this vancomycin-fibrinogen interaction is used to establish a simple standardized antigenic assay for plasmatic fibrinogen, the FIATA. 1 mM vancomycin or 2 mM chloramine-T inactivates 50% of fibrinogen in human plasma. In contrast to chloramine-T, vancomycin does not react in NaJ-based photometric assay for chloramines,vancomycin does not inactivate the singlet oxygen-sensible antithrombin III, and the vancomycin action against fibrinogen is not changed in spite of the presence of the 1O2 quenchers methionine or ascorbic acid. The FIATA is performed as follows: to 25 microL plasma 50 microL PBS are added and the absorbance (A) at 405 nm is read. Then 50 microL FIATA-reagent, consisting of 4.4 mM vancomycin in PBS, are added. After 2 minutes (RT) DeltaA is determined and standardized against a plasma pool of 100% of norm (2.8 g/L) fibrinogen. The FIATA is nearly linear up to a fibrinogen concentration of about 150% of norm (4.2 g/L), resulting in a DeltaA of about 600 mA. The lower detection limit is 4% of norm (0.1 g/L). The intra-assay and interessay CV values are < 4%. The normal range of FIATA is 100% +/-20% (x- +/- 1 SD). In = 321 or 344 unselected patient plasmas the FIATA (x- = 130%; SD = 52% or 43%) correlated with the functional fibrinogen assays a) modified Clauss-Method (x- = 4.1 g/L; SD =1.7 g/L) with r = 0.755 and b) FIFTA (x- = 124%; SD = 40%) with r = 0.813. The vancomycin/fibrinogen interaction (binding of about 16 molecules of vancomycin/molecule of fibrinogen) can be used to purify fibrinogen out of plasma. Vancomycin also clouds dysfunctional fibrinogen (fibrinogen in presence of EDTA or chloramine-T)or soluble fibrin. Vancomycin-reacted fibrinogen stimulates tissue type plasminogen activator (t-PA) up to about 20-fold. The experimental data are analyzed by a new significance test: the two foldYates-corrected chi-square comparison against the mean value ofthe control-collective, called the Chi2x - Test. The P < .05 significance barrier calculated with the Chi2x - Test is equivalent to that calculated with the Fisher's Exact Test. The FIATA might be considered an interesting screening test for inactive fibrinogen forms or soluble fibrin, as eg in disseminated intravascular coagulation. Fibrinogen precipitation by vancomycin within the blood vessel might explain why vancomycin has to be infused slowly (< 10 mg/min) to prevent nephrotoxicity. The FIATA is of such a simplicity that the determination of fibrinogen antigen in plasma can be performed anywhere--even outside a hospital--within seconds. Thus, the presented FIATA might contribute to extra hospital testing of patients for assessing their risk for myocardial or cerebral ischemia/infarction.

Antigens↗

PubMed1991

Endogenous platelet fibrinogen surface expression on activated platelets.

Intracellular platelet fibrinogen surface expression was studied in arabinogalactan-purified, resting, and thrombin-stimulated platelets. Platelet fibrinogen is derived from endocytosis of plasma fibrinogen by megakaryocytes. Like a variety of other adhesive proteins, it is stored in the platelet alpha-granule. Platelet fibrinogen surface expression was studied by using the antigen-binding fragments of a murine monoclonal antibody to platelet fibrinogen, F26, and an immunopurified polyclonal antifibrinogen antibody. Studies correlating platelet fibrinogen surface expression with the presence of the glycoprotein IIb-IIIa (GPIIb-IIIa) complex showed that in the presence of ethylene glycol tetraacetic acid (EGTA) at 37 degrees C, neither the GPIIb-IIIa complex nor platelet fibrinogen was expressed on the surface of thrombin-activated platelets. Similar experiments performed in the presence of EGTA and calcium showed proportional expression of the GPIIb-IIIa complex and platelet fibrinogen. The addition of Arg-Gly-Asp-Ser-containing peptides, the pentadecapeptide of the fibrinogen gamma-chain carboxy terminus, or the monoclonal antibody 10E5, when directed against the GPIIb-IIIa complex before thrombin activation, inhibited 65% to 94% of the platelet fibrinogen expression, as determined with the polyclonal and monoclonal antigen-binding fragments. When these same inhibitory agents were added immediately after or 5 minutes after thrombin, the amount of inhibition decreased significantly. Similar studies with a washed platelet system revealed that when the inhibitors of platelet fibrinogen expression were added before thrombin stimulation, the degree of inhibition observed was only 24% to 38%. This suggests that the major portion of platelet fibrinogen expression involves the release of platelet fibrinogen and its subsequent binding to GPIIb-IIIa. This binding may occur within the open canalicular system or on the platelet surface; in either case, wherever the site of released platelet fibrinogen binding occurs, it can be markedly inhibited by the RGD-containing peptides and the gamma-chain fibrinogen peptides. Approximately 10% to 30% of platelet fibrinogen may be expressed prebound to a platelet receptor, or else it is released and binds to a platelet receptor other than the GPIIb-IIIa complex.

Amino Acid Sequence↗

PubMed1989

Association of fibrinogen with human platelets pretreated with chymotrypsin or aggregated with ADP or thrombin: an immunocytochemical study.

Although platelets can be induced to aggregate in the absence of external fibrinogen, the response is greatly potentiated by fibrinogen and fibrinogen becomes associated with the surface of stimulated platelets. We compared the aggregation response and association of fibrinogen with the surface of platelets aggregated by ADP or thrombin, and of chymotrypsin-treated platelets aggregated by fibrinogen. The association of fibrinogen with the surface of the platelets was visualized using an electron microscope immunocytochemical method. The aggregation response and the pattern of fibrinogen association was different with each of the three agonists studied. ADP-induced aggregation was associated with pseudopod formation and fibrinogen binding; granule contents were not released and aggregation and fibrinogen binding were reversible. Thrombin-induced aggregation was associated with extensive pseudopod formation and the release of granule contents, but platelet-to-platelet adherence did not appear to involve fibrinogen binding at sites remote from regions of granule discharge; disaggregation did not occur, and visible fibrin did not form rapidly in the absence of added fibrinogen. Fibrinogen-induced aggregation/agglutination of chymotrypsin-treated platelets was similar to ADP-induced aggregation in that fibrinogen binding was required and granule contents were not released; it differed from ADP-induced aggregation in that pseudopod formation did not occur and the aggregates were irreversible. Fibrinogen-induced aggregation of chymotrypsin-treated platelets differed from thrombin-induced aggregation of untreated platelets in every respect except irreversibility. Thus neither pseudopod formation, fibrinogen binding nor the release of granule contents is essential for platelet-to-platelet adherence, although one or other or all may occur in association with it. If platelets are not stimulated to release their granule contents, fibrinogen binding appears to be necessary for extensive platelet aggregation.

Adenosine Diphosphate↗

PubMed1977

Some factors influencing metabolism and distribution of fibrinogen in man and rabbits.

To shed some light on the homeostatic regulation of plasma fibrinogen, metabolic studies were made in healthy females, and in normal, thyroidectomized, and thyroxine-treated rabbits. In females, compared with normal males, plasma fibrinogen concentration, plasma and interstitial fibrinogen decreased consequent to an increased fractional catabolic rate and a normal fibrinogen synthesis rate. The interstitial/plasma fibrinogen ratio remained unchanged. In normal rabbits, with increasing body weight fractional catabolic rate and catabolic rate decreased, while fibrinogen concentration and plasma fibrinogen remained constant owing to a simultaneous decrease in fibrinogen synthesis. In addition, fractional transcapillary transfer rate and transcapillary flux also decreased resulting in a shrinkage of interstitial fibrinogen. Thyroidectomy and thyroxine-injection markedly altered fibrinogen metabolism: thyroid hormone accelerated fibrinogen catabolism but also stimulated synthesis. The net result was an increase in plasma fibrinogen and fibrinogen concentration. The interstitial/plasma fibrinogen ratio decreased in thyroxine-treated, and increased in thyroidectomized animals. This study defines the variations of the fibrinogen system parameters in these physiologic and pathologic conditions, and illustrates some patterns of alterations in fibrinogen metabolism.

Adult↗

PubMed1994

Localization of fibrinogen during aggregation of avian thrombocytes.

The thrombocyte is the avian equivalent of the mammalian blood platelet and is involved in hemostasis through a fibrinogen-mediated process. Although fibrinogen has been implicated as a molecular bridge between activated cells during aggregation, the location of this molecule and its receptor on thrombocytes has not been characterized. Pigeon fibrinogen, isolated from plasma by precipitation with PEG-1000 and purified over Sepharose 4B, was used to study receptor-ligand interaction. Separation of pigeon fibrinogen on SDS-PAGE resulted in three peptides of molecular mass 62, 55, and 47 kDa, which were comparable to those of human fibrinogen. The role of fibrinogen and its receptor in thrombocyte function was established by turbidimetric aggregation using thrombin as an agonist under conditions requiring Ca2+ and fibrinogen. Maximum response occurred using 3 mM Ca2+ and 100 micrograms/ml fibrinogen. Fibrinogen-dependent aggregation was inhibited by an anti-GPIIb antibody, verifying a role for fibrinogen receptors in thrombocyte function. Fibrinogen-gold conjugates were used to describe receptor and ligand localization on aggregated cells. Computer reconstruction was used to verify relocalization of fibrinogen receptors following activation. Fibrinogen distribution changed from a dispersed state in preactivated cells to focal localization at points of cell contact and along pseudopods following activation. This selective positioning of fibrinogen suggests that a functional relocalization of the receptor occurs upon thrombocyte activation, and this relocation facilitates the role of fibrinogen as a molecular bridge. These studies establish similarities between the avian and the human systems and document the conserved nature of the hemostatic process.

Animals↗

PubMed1982

Some chemical aspects of labeling human fibrinogen with 99m-technetium.

Human fibrinogen was labeled with 99m-Technetium. Tin(II)-chloride in citric acid served as reducing agent for the pertechnetate-ion, eluted from a Mo-Tc-generator. Before adding the fibrinogen, the citric acid was always neutralized with sodium hydrogen carbonate. The influences on the quantity of fibrinogen bound 99m-Tc of the relative concentrations of Sn(II), fibrinogen and sodium hydrogen carbonate, of the reaction time and temperature were tested by thin-layer chromatography. The reaction temperature of 28 degrees C showed an optimum of fibrinogen bound 99m-Tc for the reaction time from 1 and 2 hours. With a reaction time of 30 minutes not enough 99m-Tc was bound to fibrinogen, the doubling of the reaction time from 1 to 2 hours showed only an increase of binding of less than 4%. The concentration of Sn(II) with respect to the fibrinogen concentration showed no influence on the quantity of fibrinogen bound 99m-Tc at low Sn(II)-concentrations. At values higher than 34 times of the fibrinogen concentration a decrease of the quantity of bound 99m-Tc was observed. The concentrations of sodium hydrogen carbonate showed no influence on the quantity of fibrinogen bound 99m-Tc but on the clottability of fibrinogen, the pH of the solution must be approximately 7.5. In 3 parallel and independent experiments under optimized conditions (1 hour at 28 degrees C, molar ratio of Sn(II) : fibrinogen = 8.5, pH = 7.5) 89.97 +/- 0.92 % of 99 m-Tc were bound to fibrinogen. Controls of these results by column chromatography showed a binding of 81.08 +/- 1.47 % of 99m-Tc to fibrinogen. The clottability of fibrinogen tested by the method of Clauss (1) was entirely preserved.

Bicarbonates↗

PubMed1992

Update on fibrinogen as a cardiovascular risk factor.

Mounting data support a causal connection between high-normal fibrinogen levels and atherosclerotic cardiovascular disease. There is clearly a thrombogenic component to atherosclerosis and the onset of clinical manifestations. This offers the possibility to better identify high-risk candidates and also to protect them by reducing blood fibrinogen concentration or blocking its action. The relationship of antecedent fibrinogen to the subsequent development of cardiovascular disease is examined, based on 18 years of surveillance of a cohort of 1274 men and women aged 47 to 79 years who participated in the Framingham Study. The association with the development of peripheral arterial disease and cardiac failure is now examined in addition to previously studied relationships to coronary heart disease and stroke. In men and women, there is a significant age-adjusted relationship of fibrinogen level to coronary heart disease and to cardiovascular disease in general. In women, a significant relationship to cardiac failure and peripheral arterial disease, but not to stroke, was also found. These data on women are unique as they are not available elsewhere. Age-adjusted cardiovascular, all-cause, and coronary heart disease mortality were all related to fibrinogen in both sexes. In men, fibrinogen impact was the greatest for stroke and the least for peripheral arterial disease. For women, the impact on coronary heart disease was greatest. The absolute risk for an elevated fibrinogen level was greatest for coronary heart disease in both sexes. Average fibrinogen values are higher in women and in persons with other risk factors, including hypertension, cigarette smoking, diabetes, obesity, and elevated hematocrit. However, there is an independent contribution of fibrinogen to cardiovascular disease in general and coronary disease in particular, on adjustment for coexistent risk factors. Fibrinogen enhances the risk of cardiovascular disease in hypertensives, diabetics, and cigarette smokers. About half the cardiovascular risk of cigarette smoking appears due to the higher fibrinogen values. Now, five prospective studies document the excess incidence of cardiovascular events in persons with elevated fibrinogen levels within the "normal range." Each standard deviation increase in fibrinogen is associated with a 30% increment of coronary heart disease in men and a 40% increase in women. Fibrinogen should be added to the list of major cardiovascular risk factors. Trials of intervention to lower fibrinogen in high-risk coronary candidates are needed.

Age Factors↗

PubMed2003

Increased high molecular weight fibrinogen in pre-eclampsia.

INTRODUCTION: The major coagulation protein fibrinogen (Fg) is a heterogeneous protein with three main fractions: high molecular weight fibrinogen (HMW-Fg), low molecular weight fibrinogen (LMW-Fg) and low molecular weight' fibrinogen. The clottability of high molecular weight fibrinogen is highest as compared to the other fractions. Pre-eclampsia is associated with a state of hypercoagulability, and with an increase of fibrinogen concentration. The aim of the present study was to examine if the increased total fibrinogen plasma concentration in patients with pre-eclampsia is associated with a change in distribution of the main fibrinogen fractions. MATERIAL AND METHODS: Plasma was collected from 14 patients with pre-eclampsia and from 14 healthy pregnant matched controls. Total fibrinogen concentrations were determined according to Clauss. The percentage high molecular weight fibrinogen was assessed by SDS-electrophoresis and densitometry after isolation of fibrinogen by precipitation. The study groups were compared by the Mann-Whitney U-test. RESULTS: The median (range) total fibrinogen concentration in the pre-eclampsia group was 5.04 (3.25-6.51) g/l and in the control group 4.19 (3.61-5.38) g/l (p<0.05). The median (range) percentage high molecular weight fibrinogen was 76.5 (69.6-84.0)% and 73.0 (69.0-78.9)% in the pre-eclampsia and control group, respectively (p<0.05). CONCLUSIONS: In pre-eclampsia, the concentration of total fibrinogen is increased and the percentage high molecular weight fibrinogen is also slightly higher than in normal pregnancy. These results may be a reflection of the exaggerated inflammatory response, and subsequent endothelial activation, which are currently believed to be the key pathophysiological mechanisms in pre-eclampsia.

Adult↗

PubMed1996

Plasma factor XIII binds specifically to fibrinogen molecules containing gamma chains.

The difference between peak 1 and peak 2 fibrinogen lies in their gamma chains. Peak 1 molecules contain 2 gamma A chains; peak 2 molecules contain 1 gamma A and 1 gamma chain, the latter of which contains a 20 amino acid extension (gamma 408-427) replacing the carboxyl-terminal 4 amino acids of the gamma A chain (gamma A 408-411). While the existence of gamma chains in plasma fibrinogen molecules has been known for many years, their function remains unknown. When fibrinogen is purified from plasma, the factor XIII zymogen (A2B2) copurifies with it and is found only in the peak 2 fibrinogen when this fraction is separated from peak 1 fibrinogen by ion-exchange chromatography on DEAE-cellulose. Factor XIII alone applied to the same DEAE column elutes at a position between peak 1 and peak 2. When mixtures of peak 1 fibrinogen plus factor XIII or peak 2 fibrinogen plus factor XIII are applied to DEAE columns, the peak 1/factor XIII mixture elutes in two peaks, whereas the peak 2/factor XIII mixture elutes in the peak 2 fibrinogen position. Gel sieving on Superose 6 of peak 1/factor XIII mixtures results in two protein peaks, the first of which contains the fibrinogen. Most factor XIII activity elutes in the second peak with a small amount of activity emerging with the trailing end of the fibrinogen peak. Gel sieving of mixtures of peak 2 and factor XIII results in a single protein peak with all factor XIII activity emerging with the leading edge of the fibrinogen peak. The interaction between peak 2 fibrinogen and plasma factor XIII appears to be through binding to the B subunit of factor XIII since placental or platelet factor XIII (A2), which does not contain B subunits, elutes independently from peak 2 fibrinogen on DEAE-cellulose chromatography. The results indicate that peak 2 fibrinogen gamma chains have a physiologically significant affinity for the B subunits of plasma factor XIII and that through this interaction fibrinogen serves as a carrier for the plasma zymogen in circulating blood.

Binding Sites↗

PubMed2003

Associations of plasma fibrinogen assays, C-reactive protein and interleukin-6 with previous myocardial infarction.

BACKGROUND: The association of plasma fibrinogen with myocardial infarction (MI) may (like that of C-reactive protein, CRP) be a marker of subclinical inflammation, mediated by cytokines such as interleukin-6 (IL-6). There are well-recognized discrepancies between commonly performed fibrinogen assays. Increased ratio of clottable fibrinogen to intact fibrinogen (measured by a recently developed immunoassay) has been proposed as a measure of hyperfunctional fibrinogen, and is elevated in acute MI. OBJECTIVE: To compare the associations of intact fibrinogen and four routine fibrinogen assays (two von Clauss assays; one prothrombin-time derived; and one immunonephelometric) in a case-control study of previous MI. PATIENTS/METHODS: Cases (n=399) were recruited 3-9 months after their event; 413 controls were age- and sex- matched from the case-control study local population. Intact fibrinogen was measured in 50% of subjects. RESULTS: All routine fibrinogen assays showed high intercorrelations (r=0.82-0.93) and significant (P<0.0001) increased mean levels in cases vs. controls. These four routine assays correlated only moderately with intact fibrinogen (r=0.45-0.62), while intact fibrinogen showed only a small, nonsignificant increase in cases vs. controls. Consequently, the ratio of each of the four routine assays to the intact fibrinogen assay was significantly higher (P<0.0003) in cases vs. controls. Each fibrinogen assay correlated with plasma levels of CRP and IL-6 (which were also elevated in cases vs. controls). Each routine fibrinogen assay remained significantly elevated in cases vs. controls after further adjustment for C-reactive protein and interleukin-6. CONCLUSIONS: These data provide evidence for acquired, increased hyperfunctional plasma fibrinogen in MI survivors, which is not associated with markers of inflammatory reactions. The causes and significance of these results remain to be established in prospective studies.

Biomarkers↗

PubMed1997

Characterization of the interaction between the Staphylococcus aureus clumping factor (ClfA) and fibrinogen.

The ability of Staphylococcus aureus to adhere to adsorbed fibrinogen and fibrin is believed to be an important step in the initiation of biomaterial and wound-associated infections. In this study, we show that the binding site in fibrinogen for the recently identified S. aureus fibrinogen-binding protein clumping factor (ClfA) is within the C-terminus of the fibrinogen gamma chain. S. aureus Newman cells expressing ClfA adhered to microtitre wells coated with recombinant fibrinogen purified from BHK cells, but did not adhere to wells coated with a purified recombinant fibrinogen variant where the 4 C-terminal residues of the gamma chain were replaced by 20 unrelated residues. In addition, a synthetic peptide corresponding to the 17 C-terminal amino acids of the fibrinogen gamma chain effectively inhibited adherence of ClfA-expressing cells to fibrinogen. In western ligand blots, a recombinant truncated ClfA protein called Clf33 (residues 221-550) recognized intact recombinant fibrinogen gamma chains, but failed to recognize recombinant fibrinogen gamma chains where the 4 C-terminal amino acids were altered by deletion or substitution. Previous studies have shown that the C-terminal domain of fibrinogen gamma chains contains a binding site for the integrin alphaIIb beta3 (glycoprotein gpIIb/IIIa) receptor on platelets [Kloczewiak, M., Timmons, S., Bednarek, M. A., Sakon, M. & Hawiger, J. (1989) Biochemistry 28, 2915-1919; Farrell, D. H., Thiagarajan, P., Chung, D. W. & Davie, E. W. (1992) Proc. Natl. Acad. Sci. USA 89, 10729-10732; Hettasch, J. M., Bolyard, M. G. & Lord, S. T. (1992) Thromb. Haemostasis 68, 701-706]. We now show that Clf33 inhibits ADP-induced, fibrinogen-dependent platelet aggregation in a concentration-dependent manner and inhibits adhesion of platelets to immobilized fibrinogen under fluid shear stress, indicating that the binding sites for the platelet integrin and the staphylococcal adhesin overlap. The interaction between Clf33 and fibrinogen was further characterized using the BIAcore biosensor. When soluble Clf33 was allowed to bind to immobilized fibrinogen, a Kd of 0.51 +/- 0.19 microM was experimentally determined using equilibrium binding data. It was also shown that the synthetic C-terminal gamma-chain peptide effectively inhibited this interaction.

Adenosine Diphosphate↗

PubMed2002

Effect of Helicobacter pylori infection on fibrinogen level in elderly patients with ischaemic heart disease.

BACKGROUND: Fibrinogen is an important risk factor for ischaemic heart disease (IHD) (1) and an elevated fibrinogen level has been reported in younger patients infected with Helicobacter pylori (H pylori) infection (2, 3). However, the effect of Helicobacter pylori infection on fibrinogen level in elderly population with IHD is not known. Also in particular the effect on fibrinogen with eradication of Helicobacter pylori has not been previously reported. The aim of this study was to investigate the influence of H pylori on fibrinogen levels in elderly patients with IHD and to assess the effect of eradication therapy on fibrinogen levels. PATIENTS AND METHODS: Forty patients over the age of 65 years presenting with symptomatic IHD and an age-matched control group of 21 patients were studied. The 14-C urea breath test was used for detecting H pylori infection. Patients found to be H pylori positive were treated with omeprazole 40 mg daily and amoxicillin 500 mg three times daily for 14 days. Fibrinogen concentration was measured at the beginning of treatment and repeated at 4 weeks after completion of treatment along with the urea breath test in those tested positive for H pylori and fibrinogen level was repeated at 6 weeks in the H pylori negative patients. RESULTS: The prevalence of H pylori infection was 19/40 (47.5%) in the IHD group and 9/21 (42.8%) in the control group. The median serum fibrinogen level was 4.34 g/l (3.73-6.04 i.q. range) in H Pylori positive patients and 4.86 g/l (3.58-6.11 i.q. range) in H Pylori negative patients in both the IHD and age-matched control group, with no significant difference between the two groups, p = 0.78 (Mann-Whitney test). In the IHD group 27/40 (67.5%) had a fibrinogen level >4.0 g/l compared to 11/21 (52.3%) in the control group. The median fibrinogen level decreased significantly from 5.75g/l (i.q. range 4.39-6.71) to 4.41 g/l (i.q. range 3.80-6.06) after eradication treatment of H pylori in patients with raised fibrinogen levels (p < 0.01). CONCLUSION: The presence of H Pylori infection did not correlate with the presence of IHD, and the fibrinogen level was not raised in the IHD group. However, in elderly patients with H pylori infection, eradication therapy lowered fibrinogen levels in those with elevated (>4.0 g/l) fibrinogen level.

Aged↗

PubMed1999

Fibrates suppress fibrinogen gene expression in rodents via activation of the peroxisome proliferator-activated receptor-alpha.

Plasma fibrinogen levels have been identified as an important risk factor for cardiovascular diseases. Among the few compounds known to lower circulating fibrinogen levels in humans are certain fibrates. We have studied the regulation of fibrinogen gene expression by fibrates in rodents. Treatment of adult male rats with fenofibrate (0.5% [wt/wt] in the diet) for 7 days decreased hepatic Aalpha-, Bbeta-, and gamma-chain mRNA levels to 52% +/- 7%, 46% +/- 8%, and 81% +/- 19% of control values, respectively. In parallel, plasma fibrinogen concentrations were decreased to 63% +/- 7% of controls. The suppression of fibrinogen expression was dose-dependent and was already evident after 1 day at the highest dose of fenofibrate tested (0.5% [wt/wt]). Nuclear run-on experiments showed that the decrease in fibrinogen expression after fenofibrate occurred at the transcriptional level, as exemplified for the gene for the Aalpha-chain. Other fibrates tested showed similar effects on fibrinogen expression and transcription. The effect of fibrates is specific for peroxisome proliferator-activated receptor-alpha (PPARalpha) because a high-affinity ligand for PPARgamma, the thiazolidinedione BRL 49653, lowered triglyceride levels, but was unable to suppress fibrinogen expression. Direct evidence for the involvement of PPARalpha in the suppression of fibrinogen by fibrates was obtained using PPARalpha-null (-/-) mice. Compared with (+/+) mice, plasma fibrinogen levels in (-/-) mice were significantly higher (3.20 +/- 0.48 v 2.67 +/- 0.42 g/L). Also, hepatic fibrinogen Aalpha-chain mRNA levels were 25% +/- 11% higher in the (-/-) mice. On treatment with 0.2% (wt/wt) fenofibrate, a significant decrease in plasma fibrinogen to 77% +/- 10% of control levels and in hepatic fibrinogen Aalpha-chain mRNA levels to 65% +/- 12% of control levels was seen in (+/+) mice, but not in (-/-) mice. These studies show that PPARalpha regulates basal levels of plasma fibrinogen and establish that fibrate-suppressed expression of fibrinogen in rodents is mediated through PPARalpha.

Animals↗

PubMed1975

[Chemical properties of plasma fibrinogens and fibrins from normal and cobalt-treated rabbits].

The sulfitolysis products of fibrinogens from normal and cobalt-treated rabbits (5 mg Co2+/kg b.w.) were resolved by ion exchange chromatography on CM-cellulose columns. The elution patterns of both fibrinogens showed a distinct heterogeneity of gamma-chains. Furthermore, a gamma-chain derivative from cobalt fibrinogen could be distinguished electrophoretically from the corresponding one of normal fibrinogen because of its reduced electrophoretic mobility. Normal and cobalt fibrinogen did not differ from each other in their N-terminal (Val2 Ala2 Tyr2) and C-terminal (Pro1-2 Val4-5) amino acid compositions related to a subunit structure of A alpha 2 B beta 2 gamma 2, and their carbohydrate contents - neutral hexoses 1,21% (1,26%), N-acetyl hexosamines 1,16% (1,05%), N-acetyl neuraminic acid 1,19% (1, 13%), values for cobalt fibrinogen in parentheses. The main amounts of carbohydrates are bound to gamma- and B beta-chains, The BrCn cleavage products from cobalt fibrinogen and its gamma- and B beta-chains showed other electrophoretic properties than the corresponding derivatives from normal fibrinogen. But BrCN split products of A alpha-chains of both fibrinogens were electrophoretically very similar. Spectrographic investigations of the S-sulfoderivates demonstrated a diminution of the absorption maximum near 282mn of gamma and B beta derivatives of cobalt fibrinogen. A alpha-chains of both fibrinogens were not different from each other. Using autoradiography the highest 58Co binding could be found in the gamma-chain with a reduced electrophoretic migration velocity, whereas B beta-and gamma-chains with unchanged electrophoretic mobility bound only small amounts. A alpha-chains of cobalt fibrinogens were apparently not loaded with 58Co. gamma-chain and alpha-chain cross-links could be observed in normal fibrins stabilized by factor XII, however, in cobalt fibrins a gamma-dimer formation was demonstrable without participation of gamma-chains with reduced electrophoretic mobility. A distinct alpha-chain cross-link could not be demonstrated either. From these and other investigations on molecular weights of both fibrinogens it was assumed that earlier observed changes of physicochemical properties and biological behaviour of cobalt fibrinogen might result from a complex binding of cobalt ions on specific structures of the fibrinogen molecule.

Amino Acid Sequence↗

PubMed1992

Effect of stimulation on the stabilization of platelet-fibrinogen interactions.

The interaction between fibrinogen and stimulated platelets is a multiphasic process that culminates in the stabilization of ligand binding and reduced accessibility of bound fibrinogen to exogenous antibody. The present study was designed to further explore platelet-fibrinogen interactions by examining the effect of agonist on bound fibrinogen expression and interaction with stimulated platelets as a function of time after ligand binding. Two agents were identified, Zn2+ and phorbol myristate acetate (PMA), which support progressive decreases in bound fibrinogen expression on platelets, but fail to support the stabilization of fibrinogen binding. Sixty min after binding to platelets, approximately 80% of bound fibrinogen remained reversibly associated with Zn(2+)- or PMA-treated platelets and failed to associate with the Triton X-100 insoluble cytoskeleton. In contrast, polyclonal anti-fibrinogen antibody binding decreased by more than 66%. Over the same time course, fibrinogen binding to control platelets, stimulated with thrombin or ADP, was not only accompanied by a 70% decrease in antifibrinogen antibody binding, but also an inability of EDTA or excess exogenous fibrinogen to dissociate more than half of platelet-associated fibrinogen, as well as the progressive association of bound fibrinogen with the platelet cytoskeleton. Costimulation of platelets with ZnCl2 and thrombin or ZnCl2 and ADP enhanced overall fibrinogen binding but not the EDTA-resistant component, and prevented the recovery of irreversibly bound fibrinogen with the Triton X-100 insoluble cytoskeleton. Costimulation of PMA- or Zn(2+)-treated platelets with low doses of A23187, however, restored the stabilization of platelet-fibrinogen interactions.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Platelets↗

PubMed1986

Fibrinogen binding to human blood platelets: effect of gamma chain carboxyterminal structure and length.

Recent evidence suggests that fibrinogen binding to platelets is mediated by the 12 carboxyterminal amino acid residues of the gamma chain. Because human plasma fibrinogen gamma chains differ in mol wt and carboxyterminal amino acid sequence, we examined the effect of such gamma chain heterogeneity on platelet-fibrinogen interactions, using two fibrinogens of distinct composition, separated by ion exchange chromatography. One fibrinogen possessed only gamma chains of mol wt 50,000 (F gamma 50), the predominant gamma chain species found in plasma. The other fibrinogen possessed equal amounts of gamma chains with mol wt 50,000 and 57,500 (F gamma 50,57.5), with the longer gamma chain (gamma 57.5) possessing an amino acid extension at the carboxyterminal end. The latter fibrinogen was 50% less effective than F gamma 50 in supporting ADP-induced platelet aggregation at concentrations of .01 to 2 mg/mL. Scatchard analysis revealed no difference in the binding affinities of the two fibrinogens to ADP-treated platelets, but the amount of F gamma 50,57.5 that was bound to platelets at saturation was only 50% that of F gamma 50. Fibrinogen receptors that remained unoccupied in the presence of saturating concentrations of F gamma 50,57.5, however, could be occupied by fresh F gamma 50. Excess unlabeled F gamma 50 displaced both radiolabeled fibrinogens from activated platelets, and both fibrinogens bound to the same platelet receptor, as judged by the inhibition of binding to stimulated platelets by a monoclonal antibody directed against the glycoprotein (GP) IIb/IIIa complex. Furthermore, an intact GPIIb/IIIa complex was required for these reactions, since platelets incubated with EDTA at 37 degrees C at alkaline pH failed to aggregate and bound neither fibrinogen in response to ADP following recalcification. Approximately 50% of each fibrinogen bound irreversibly to platelets after one hour and failed to dissociate in the presence of 10 mmol/L of EDTA or excess unlabeled F gamma 50. The data demonstrate that heterodimeric F gamma 50,57.5 binds less well to platelets and supports platelet aggregation only half as well as homodimeric F gamma 50. These results support prior conclusions that the carboxyterminal portion of the gamma chain is important in platelet-fibrinogen interactions, and suggest that the 20 amino acid, hydrophobic gamma chain carboxyterminal extension of F gamma 50,57.5 may sterically hinder the interaction of this fibrinogen with platelet receptors.

Adenosine Diphosphate↗

PubMed1995

Bound fibrinogen distribution on stimulated platelets. Examination by confocal scanning laser microscopy.

Previous studies have suggested that qualitative changes in platelet bound fibrinogen modulate platelet aggregation. The present study used confocal scanning laser microscopy to further evaluate post-ligand binding events over a 60-minute time course. When fluorescein isothiocyanate (FITC)-streptavidin was added to ADP-stimulated platelets 1 minute after biotinylated fibrinogen binding at 22 degrees C, bound fibrinogen was found in variously sized patches on the cell surface. When streptavidin was added 60 minutes later, bound fibrinogen had been cleared from the platelet surface and was observed in clusters penetrating into platelets to various extents. ADP-activated platelets did not stain with a monoclonal antibody against CD62 suggesting that platelets were not permeabilized during the experiment and had not released alpha-granules. Additional studies using either biotinylated fibrinogen that had been prelabeled with FITC-streptavidin or FITC-labeled fibrinogen revealed similar patterns of platelet-associated fibrinogen clearance and redistribution. Pretreatment of platelets with cytochalasin D prevented this redistribution. Dual labeling experiments using biotinylated fibrinogen and FITC-streptavidin as well as a monoclonal anti-GPIIIa antibody labeled with rhodamine-conjugated anti-mouse IgG demonstrated the co-localization of fibrinogen and GPIIIa. Similar observations were made with fibrinogen bound to thrombin-stimulated platelets. In contrast, fibronectin bound to thrombin-activated platelets retained a predominantly surface membrane distribution under identical experimental conditions. Since surface-cleared fibrinogen was accessible to exogenous FITC-streptavidin under conditions that did not lead to platelet permeabilization, the data suggest fibrinogen deposition in compartments that are accessible to the extracellular milieu. This is consistent with the ability of exogenous plasmin to completely remove cleared fibrinogen pools without detectable fibrinogen reexpression on the platelet surface or alpha-granule secretion. The data provide morphological evidence for the selective, GPIIb-IIIa mediated, actin-dependent clearance of bound fibrinogen from the activated platelet surface, suggesting a mechanism for preventing and limiting thrombus development.

Bacterial Proteins↗

PubMed1988

Fibrin(ogen) peptide B beta 15-42 inhibits platelet aggregation and fibrinogen binding to activated platelets.

The binding of fibrinogen to activated platelets leads to platelet aggregation. Fibrinogen has multiple binding sites to platelet membrane glycoprotein IIb-IIIa complex. At least two well-defined sequences in fibrinogen, Arg-Gly-Asp sequence of A alpha 95-97 and A alpha 572-574 and gamma 400-411, have been shown to interact with glycoprotein IIb-IIIa. A possible binding site on the amino-terminal end of fibrinogen to platelet glycoprotein IIb-IIIa has also been reported. In this paper the effect of synthetic peptides derived from the amino-terminal end of the B beta chain on platelet aggregation and fibrinogen binding has been examined. B beta 15-42 peptide inhibits platelet aggregation and 125I-fibrinogen binding to activated platelets in a dose-dependent manner. Since B beta 15-42 contains a previously identified fibrinogen binding site, B beta 15-18, exposed by thrombin cleavage of native fibrinogen, we also examined the effect of B beta 15-18, B beta 19-42, and B beta 1-14 (fibrinopeptide B) on platelet aggregation and fibrinogen binding. Synthetic fibrinopeptide B and B beta 15-18 had no effect on platelet aggregation and fibrinogen binding while B beta 19-42 retained the inhibitory effect. When fibrinogen is chromatographed on a column of agarose-bound B beta 15-42, a cation-dependent retention of fibrinogen on the peptide column was observed, and fibrinogen was eluted from the column by B beta 15-42 but not by B beta 1-14. Under the same conditions, platelet glycoprotein IIb-IIIa was not retained in the column. Thus, the observed inhibitory effect is due to its interaction with fibrinogen rather than to platelet glycoprotein IIb-IIIa.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗