Radiation-induced coagulopathy (RIC) is one of the major causes of death during acute radiation syndrome (ARS). The aim of this study was to characterize the responses of the hemostasis system to ARS of a moderate level on the 1st and 9th days after irradiation. We aimed to identify molecular markers of the blood coagulation system that are most affected by ARS and to estimate the enterosorption effect on the development of irradiation-induced changes. Platelet aggregation rate, activated partial thromboplastin time (APTT) and fibrinogen concentration were determined by standard methods. Level of protein C (PC) was measured using­ chromogenic substrate S2366 (p-Glu-Pro-Arg-pNa) and Agkistrodon halys halys snake venom activa­ting enzyme. Functionally inactive forms of prothrombin (FIFPs) were determined using two activators in parallel – thromboplastin or prothrombin activator from Echis multisqumatis venom. Rats of both irradia­ted groups had a higher risk of intravascular clotting in comparison to both control groups. Statistically significant shortening of clotting time in the APTT test (24 ± 4 s vs. 33 ± 5 s) and increased fibrinogen concentration (4.2 ± 0.6 mg/ml vs. 3.2 ± 0.3 mg/ml) were detected. Both parameters were normalized on the 9th day after irradiation. However the platelet count was decreased (0.3∙106 ± 0.05∙106 1/μl vs. 0.145∙106 ± 0.04∙106 1/μl) due to the impaired megakaryocytic function. The level of PC was decreased after X-ray irradiation (70 ± 10%) and partly restored on the 9th day after irradiation (87 ± 10%). Administration of activated carbon (AC) inhibited the drop in the PC concentration after X-ray irradiation (86 ± 15%) and accelerated its restoration on the 9th day (103 ± 14%). The statistically significant accumulation of FIFPs was detected in blood plasma of irradia­ted rats at the 1st and 9th days after irradiation. No FIFPs were found in any irradiated rat treated with AC. Characterization of the hemostasis system of rats that were exposed to a semilethal dose of X-rays allowed us to select parameters that can be used for monitoring of ARS development. Apart of from basic coagulation tests (APTT) and the measurement of platelet aggregation, fibrinogen and protein C level we can recommend the determination of FIFPs as a useful tool for estimation of the hemostasis response after irradiation with X-rays. This test indicates the intravascular thrombin generation and can help predict thrombotic complication or disseminated intravascular coagulation. Determination of FIFPs in blood plasma of irradia­ted rats allowed us to study the enterosorption effect on the development of irradiation-induced changes. It was shown that enterosorption with AC prevented accumulation of FIFPs which appears to be a newly discovered anti-thrombotic effect of therapy with AC. ARS influenced hemostasis by inducing thrombin generation (indicated by FIFPs generation), low-grade inflammation (indicated by PC concentration decrease) and thrombocytopenia. Enterosorption with AC minimizes inflammation and pro-coagulant processes caused by a moderate dose of X-ray irradiation. Accumulation of FIFPs can be assumed to be one of the most sensitive markers of the blood coagulation response to X-ray irradiation.
C-145 (octasodium salt of calixarene-tetra-methylenebisphosphonic acid) was previously considered as specific anti-сoagulant agent that affects fibrin polymerization and does not notably influence other parameters of coagulation system. C-145S (octasodium salt of thiacalixarene-tetra-methylenebisphosphonic acid) possessing wider hydrophobic hole was expected to be more effective antithrombotic agent than C-145. The aim of present work was to compare the action of both organic compounds on fibrin polymerization, fibrinolysis, platelets and endothelial cells. The change of turbidity during fibrin clot formation induced by APTT-reagent and digestion induced by tPA was estimated. Turbidity study was used for the estimation of polymeric fibrin hydrolysis by plasmin in the presence of thiacalixarene C-145S and calixarene C-145. Effects of thiacalixarene C-145S and calixarene C-145 on the activation of Glu-plasminogen by streptokinase were studied using chromogenic substrate S2251. Platelet aggregation study was performed using aggregometry. Stimulated Ca2+ efflux from endoplasmic reticulum and cytoplasm were determined using specific Ca2+-sensitive probes targeted to endoplasmic reticulum (Mag-Fluo-4) and cytoplasm (FURA-2) by spectrofluorimetry. Both C-145 and C-145S decreased the final turbidity of clot and prolonged clot lysis time in blood plasma in comparison to control value. C-145 was shown to be the more effective fibrinolysis inhibitor when studied in model system of polymerized fibrin desAB. C-145S but not C-145 induced concentration changes of Ca2+ in cytoplasm of resting platelets and significantly inhibited (up to 30%) Ca2+ efflux from endoplasmic reticulum of platelets activated by ADP. Both C-145 and C-145S stimulated the proliferation of endothelial cells of PAE cell line. The effect of C-145S was more prominent. In conclusion, calixarene C 145S proved to be the more potent inhibitor of fibrin polymerization in comparison to C-145, which suggested earlier as anticoagulant agent. C-145S proved to have much more outlined inhibitory action on Ca2+-signaling in platelets and stimulatory effect on endothelial cells proliferation. Thus C-145 remained the most prospective molecular platform for the development of antithrombotic agent.
Obesity is an important factor in pathogenesis of disorders caused by chronic inflammation. Diet-induced obesity leads to dyslipidemia and insulin resistance (IR) that in turn provoke the development of type 2 diabetes and cardiovascular diseases. Thus, the aim of this work was to investigate the possible pro-atherogenic effects in the blood coagulation system and aortic wall of rats with obesity-induced IR. The experimental model was induced by a 6-month high-fat diet (HFD) in white rats. Blood samples were collected from 7 control and 14 obese IR rats. Prothrombin time (PT) and partial activated thromboplastin time (APTT) were performed by standard methods using Coagulometer Solar СТ 2410. Fibrinogen concentration in the blood plasma was determined by the modified spectrophotometric method. Levels of protein C (PC), prothrombin and factor X were measured using specific chromogenic substrates and activa­ting enzymes from snake venoms. Platelet aggregation was measured and their count determined using Aggregometer Solar AP2110. The aorta samples were stained by hematoxylin and eosin according to Ehrlich. Aortic wall thickness was measured using morphometric program Image J. Statistical analysis was performed using Mann-Whitney U Test. The haemostasis system was characterized by estimation of the levels of individual coagulation factors, anticoagulant system involvement and platelet reactivity. PT and APTT demonstrated that blood coagulation time strongly tended to decrease in obese IR rats in comparison to the control group. It was also detec­ted that 30% of studied obese IR rats had decreased factor X level, 40% had decreased level of prothrombin whereas fibrinogen concentration was slightly increased up to 3 mg/ml in 37% of obese IR rats. A prominent decrease of anticoagulant PC in blood plasma of obese rats was detected. Obese IR rats also had increased platelet count and higher rate of platelet aggregation in comparison to control animals. Histological analysis identified the disruption of aorta endothelium and tendency for the thickening of the aorta wall in the group with obesity-induced IR compared to the group of control rats. Changes of individual coagulation factors were assumed as the evidence of imbalance in the blood coagulation system. Increase of fibrinogen level, drop in PC concentration and pathological platelet reactivity were taken to corroborate the development of low-grade inflammation in obese IR rats. Instant generation of small amounts of thrombin in their blood plasma is expected. Since the aorta morphology assay detected the trend of its wall to thicken and the emergence of disruptions, we assumed there were initial stages of atherosclerosis and the danger of developing atherothrombosis. We detected an increase of blood coagulability and changes in aorta morphology in rats with obesity-induced IR which we assume indicate early development of atherosclerosis.