Some properties of rat platelet aggregation and effects of butylated hydroxytoluene, warfarin and aspirin

Urbanization and anticoagulant poisons promote immune dysfunction in bobcats

Understanding how human activities influence immune response to environmental stressors can support biodiversity conservation across increasingly urbanizing landscapes. We studied a bobcat (Lynx rufus) population in urban southern California that experienced a rapid population decline from 2002-2005 due to notoedric mange. Because anticoagulant rodenticide (AR) exposure was an underlying complication in mange deaths, we aimed to understand sublethal contributions of urbanization and ARs on 65 biochemical markers of immune and organ function. Variance in immunological variables was primarily associated with AR exposure and secondarily with urbanization. Use of urban habitat and AR exposure has pervasive, complex and predictable effects on biochemical markers of immune and organ function in free-ranging bobcats that include impacts on neutrophil, lymphocyte and cytokine populations, total bilirubin and phosphorus. We find evidence of both inflammatory response and immune suppression associated with urban land use and rat poison exposure that could influence susceptibility to opportunistic infections. Consequently, AR exposure may influence mortality and has population-level effects, as previous work in the focal population has revealed substantial mortality caused by mange infection. The secondary effects of anticoagulant exposure may be a worldwide, largely unrecognized problem affecting a variety of vertebrate species in human-dominated environments.

Characterization of the aggregation responses of camel platelets

BACKGROUND

Despite evidence of active hemostasis, camel platelets barely respond to common aggregating agents at standard doses used for human platelet aggregation.

OBJECTIVES

The purpose of the study was to find out whether camel platelets can be activated by high doses or combinations of aggregation agonists, and to characterize the receptor that mediates the aggregation response to adenosine diphosphate (ADP), the most potent agonist for camel platelets known so far.

METHODS

Aggregation studies were performed with platelet-rich plasma (PRP) in response to multiple doses or combinations of ADP, epinephrine (EPN), collagen, and arachidonic acid (AA). Aggregation responses to ADP were performed before and after the addition of the ADP receptor (P2Y12) antagonist Clopidogrel.

RESULTS

Camel platelets responded to ADP at doses higher than the standard dose for human platelets, and to combinations of EPN and other agonists, while no aggregation was elicited with EPN or AA alone. Clopidogrel blocked the ADP-induced aggregation responses in a dose-dependent fashion in vitro.

CONCLUSIONS

Camel platelet aggregation can be activated by increasing the dose of some agonists such as ADP, but not AA or EPN. Irreversible aggregation of camel platelets could also be triggered by a combination of EPN and ADP, and collagen and AA. Inhibition with clopidogrel suggests that camel platelets express the ADP receptor, P2Y12. Understanding platelet function in camels will add to the understanding of platelet function in health and disease.

Effects of subacute oral warfarin administration on peripheral blood granulocytes in rats

Warfarin affects mainly vitamin K dependent (VKD) processes, but the effects on some non-VKD-related activities such as tumor growth inhibition and mononuclear cell-mediated immune reactions were shown as well. In this study, the effect of subchronic (30 days) oral warfarin (0.35 mg/l and 3.5mg/l) intake on peripheral blood granulocytes in rats was investigated. Increase in prothrombin and partial thromboplastin time at high warfarin dose reflected its basic activity. Priming effect for respiratory burst was noted at both warfarin doses, while only high warfarin dose resulted in priming for adhesion, the rise in intracellular myeloperoxidase content/release and stimulation of nitric oxide production. Differential effects of high warfarin dose were noted on granulocyte cytokines IL-6 (lack of the effect), TNF-α (decreased release and mRNA expression) and IL-12 (increase in mRNA for IL-12 subunits p35 and p40). Changes in granulocytes seems not to rely on mitogen activated kinases p38 and ERK. Warfarin intake was associated with an increase in circulating IL-6, fibrinogen and haptoglobin and with changes in the activity of erythrocyte antioxidant enzymes superoxide dismutase and catalase. The effects of oral warfarin intake on peripheral blood granulocytes demonstrated in this study might be relevant for oral anticoagulant therapy strategies in humans.

Final report on the safety assessment of BHT(1)

BHT is the recognized name in the cosmetics industry for butylated hydroxytoluene. BHT is used in a wide range of cosmetic formulations as an antioxidant at concentrations from 0.0002% to 0.5%. BHT does penetrate the skin, but the relatively low amount absorbed remains primarily in the skin. Oral studies demonstrate that BHT is metabolized. The major metabolites appear as the carboxylic acid of BHT and its glucuronide in urine. At acute doses of 0.5 to 1.0 g/kg, some renal and hepatic damage was seen in male rats. Short-term repeated exposure to comparable doses produced hepatic toxic effects in male and female rats. Subchronic feeding and intraperitoneal studies in rats with BHT at lower doses produced increased liver weight, and decreased activity of several hepatic enzymes. In addition to liver and kidney effects, BHT applied to the skin was associated with toxic effects in lung tissue. BHT was not a reproductive or developmental toxin in animals. BHT has been found to enhance and to inhibit the humoral immune response in animals. BHT itself was not generally considered genotoxic, although it did modify the genotoxicity of other agents. BHT has been associated with hepatocellular and pulmonary adenomas in animals, but was not considered carcinogenic and actually was associated with a decreased incidence of neoplasms. BHT has been shown to have tumor promotion effects, to be anticarcinogenic, and to have no effect on other carcinogenic agents, depending on the target organ, exposure parameters, the carcinogen, and the animal tested. Various mechanism studies suggested that BHT toxicity is related to an electrophillic metabolite. In a predictive clinical test, 100% BHT was a mild irritant and a moderate sensitizer. In provocative skin tests, BHT (in the 1% to 2% concentration range) produced positive reactions in a small number of patients. Clinical testing did not find any depigmentation associated with dermal exposure to BHT, although a few case reports of depigmentation were found. The Cosmetic Ingredient Review Expert Panel recognized that oral exposure to BHT was associated with toxic effects in some studies and was negative in others. BHT applied to the skin, however, appears to remain in the skin or pass through only slowly and does not produce systemic exposures to BHT or its metabolites seen with oral exposures. Although there were only limited studies that evaluated the effect of BHT on the skin, the available studies, along with the case literature, demonstrate no significant irritation, sensitization, or photosensitization. Recognizing the low concentration at which this ingredient is currently used in cosmetic formulations, it was concluded that BHT is safe as used in cosmetic formulations.

Characteristics of rat platelets and relative contributions of platelets and blood coagulation to haemostasis

In order to understand some of the haemostatic mechanisms in rats for the interpretation of toxicological data, basic haemostatic parameters with a special emphasis on platelet functions were first measured in vitro. The results of reactions of rat platelets to many aggregating agents suggest that only ADP may be a consistently significant aggregator. The search for physiologic aggregators revealed ADP to be available from erythrocytes. Adhesion reaction also required ADP. Collagen was not considered to be essential for either reaction. Aggregation and adhesion were probably both reversible in flowing blood, while irreversible thrombi were formed in blood at rest ex vivo. Blood coagulation parameters determined revealed that the intrinsic pathway may be more important than the extrinsic one. The rate of intrinsic coagulation reaction was rapid, and plasma coagulation appeared to be of primary importance while the influence of platelet aggregation was minor. A simple model of rat haemostatic mechanism is proposed based on these results. Additionally, to define the relative contribution of platelets versus other cellular and plasma coagulation in vivo, rats were administered antiplatelet drugs (ticlopidine, suprofen and clopidogrel) and an anticoagulant (warfarin) intraperitoneally. Bleeding times (BTs) were significantly increased in all treated groups. ADP-induced platelet aggregations were significantly depressed by the administration of the three antiplatelet drugs, while kaolon-activated partial thromboplastin time and prothrombin time were greatly increased in the warfarin-treated rats. The increase in BT may be due to the inhibition of platelet activity or blood coagulation defect in rats given antiplatelet drugs or warfarin, respectively. These results suggest that platelets play a key role in haemostasis in the rat. Two possible explanations of the disparity between in vitro and in vivo results may be that functional tests used here are not adequate to cover the properties of rat platelets or that mechanisms leading to the formation of platelet thrombi in rats are ADP-dependent adhesion and ADP-induced aggregation.

Defective blood coagulation is not causative of hepatic haemorrhage induced by microcystin-LR

Male rats were intraperitoneally administered a lethal dose of microcystin-LR (a toxin of cyanobacteria). Prior to haemorrhage in the liver, blood coagulation and platelet aggregation activities were measured. The number of cellular components, white blood cells, red blood cells and, especially, platelets, decreased 1-1.5 hr after the injection. Plasma kaolin-activated partial thromboplastin time was prolonged and fibrinogen concentration was reduced, but antithrombin III activity and fibrin degradation product concentration were not significantly changed. Platelet aggregation was not affected for up to 0.5-1.0 hr after administration. Sequential analyses of those parameters and hepatotoxic markers indicate that those hematologic changes as well as the hepatic injury occur suddenly after the massive bleeding. These results suggest that microcystin-LR does not directly act on the haemostatic system to cause a disseminated intravascular coagulation-like state. The decrease in blood coagulation activity and platelet particle concentration may be the results of secondary consumptive effects following the hepatic haemorrhage.