Platelet depletion enhances lethal, hemorrhagic and myotoxic activities of Bothrops asper snake venom in a murine model.

Platelets play key roles in hemostasis, inflammation, immune response, and tissue repair. Although it is known that viperid snake venoms induce thrombocytopenia and platelet hypoaggregation, the roles of these effects in the overall outcome of envenoming are poorly known. This study aimed to assess the effect of platelet depletion on several toxic activities induced by the venom of the Central American viperid snake Bothrops asper in a mouse model. A profound thrombocytopenia was induced in mice by the administration of aspercetin, a C-type lectin-like protein that induces platelet agglutination and drop in platelet counts, while a control group was treated with saline solution instead. Upon envenoming, animals rendered thrombocytopenic developed a higher extent of local and systemic hemorrhage and local myonecrosis, as compared to control envenomed mice. In addition, the median lethal dose (LD50), determined by the intraperitoneal route, was significantly lower in thrombocytopenic mice, underscoring a higher toxicity of venom in these conditions. No difference in the value of LD50 between the two groups was observed when using the intravenous route of injection, and no difference was observed in the magnitude and time-course of footpad edema. Skeletal muscle regeneration was assessed 14 days after venom injection in muscle. Both experimental groups showed a similarly poor regeneration, suggesting that platelets do not play a key role in the regenerative process in these experimental conditions. Results indicate that depletion of platelets increases hemorrhagic and myotoxic effects, as well as overall toxicity, of B. asper venom, implying that platelets play a protective hemostatic role in this model of envenoming.

Hemostatic and toxinological diversities in venom of Micrurus tener tener, Micrurus fulvius fulvius and Micrurus isozonus coral snakes.

The coral snake Micrurus tener tener (Mtt) from the Elapidae family inhabits the southwestern United States and produces severe cases of envenomations. Although the majority of Mtt venom components are neurotoxins and phospholipase A2s, this study demonstrated, by SDS-PAGE and molecular exclusion chromatography (MEC), that these venoms also contain high-molecular-weight proteins between 50 and 150 kDa that target the hemostatic system. The biological aspects of other Micrurus venoms were also studied, such as the LD50s of Micrurus isozonus (from 0.52 to 0.61 mg/kg). A pool from these venoms presented a LD50 of 0.57 mg/kg, Micrurus f. fulvius (Mff) and Mtt had LD50s of 0.32 and 0.78 mg/kg, respectively. These venoms contained fibrino(geno)lytic activity, they inhibited platelet aggregation, as well as factor Xa and/or plasmin-like activities. M. isozonus venoms from different Venezuelan geographical regions inhibited ADP-induced platelet aggregation (from 50 to 68%). Micrurus tener tener venom from the United States was the most active with a 95.2% inhibitory effect. This venom showed thrombin-like activity on fibrinogen and human plasma. Fractions of Mtt showed fibrino(geno)lytic activity and inhibition on plasmin amidolytic activity. Several fractions degraded the fibrinogen Aα chains, and fractions F2 and F7 completely degraded both fibrinogen Aα and Bß chains. To our knowledge, this is the first report on thrombin-like and fibrino(geno)lytic activity and plasmin or factor Xa inhibitors described in Micrurus venoms. Further purification and characterization of these Micrurus venom components could be of therapeutic use in the treatment of hemostatic disorders.

The influence of haemostatic agents on healing of healthy human dental pulp tissue capped with calcium hydroxide.

AIM: To investigate the hypothesis that different haemostatic agents could impair the histological response of human pulps capped with calcium hydroxide. METHODOLOGY: Forty-five third molars scheduled for extraction were selected. Class I cavities with pulp exposures were prepared. Three agents were used to control bleeding: 0.9% saline solution (control, n = 14), 5.25% sodium hypochlorite (n = 16) and 2% chlorhexidine digluconate (n = 15). The pulps were dressed with hard-setting calcium hydroxide cement. After 7, 30 or 90 days, teeth were extracted, formalin-fixed and prepared for histochemical techniques. The biological response was categorized using the following criteria: inflammatory response, soft tissue organization, reactionary dentine and reparative dentine. Data were submitted to statistical analysis, using nonparametric Kruskal-Wallis one-way analysis of variance on ranks. Differences amongst groups were detected using Dunn's method. RESULTS: The statistical analysis disclosed that whilst inflammatory response decreased over time, reactionary dentine deposition and reparative dentine formation increased in the latter periods of evaluation (P < 0.05). The three agents had similar performances for all criteria evaluated. The conventional pulp response to calcium hydroxide was observed over time, and complete pulp healing was observed in 88% of the specimens after 90 days. CONCLUSION: The three haemostatic agents did not impair the healing process following pulp exposure and capping with calcium hydroxide at different time intervals investigated.