Tityus discrepans scorpion venom activates platelets through GPVI and a novel Src-dependent signaling pathway

Novel phosphatidylethanolamine derivatives accumulate in circulation in hyperlipidemic ApoE-/- mice and activate platelets via TLR2

A prothrombotic state and increased platelet reactivity are common in dyslipidemia and oxidative stress. Lipid peroxidation, a major consequence of oxidative stress, generates highly reactive products, including hydroxy-ω-oxoalkenoic acids that modify autologous proteins generating biologically active derivatives. Phosphatidylethanolamine, the second most abundant eukaryotic phospholipid, can also be modified by hydroxy-ω-oxoalkenoic acids. However, the conditions leading to accumulation of such derivatives in circulation and their biological activities remain poorly understood. We now show that carboxyalkylpyrrole-phosphatidylethanolamine derivatives (CAP-PEs) are present in the plasma of hyperlipidemic ApoE(-/-) mice. CAP-PEs directly bind to TLR2 and induces platelet integrin αIIbβ3 activation and P-selectin expression in a Toll-like receptor 2 (TLR2)-dependent manner. Platelet activation by CAP-PEs includes assembly of TLR2/TLR1 receptor complex, induction of downstream signaling via MyD88/TIRAP, phosphorylation of IRAK4, and subsequent activation of tumor necrosis factor receptor-associated factor 6. This in turn activates the Src family kinases, spleen tyrosine kinase and PLCγ2, and platelet integrins. Murine intravital thrombosis studies demonstrated that CAP-PEs accelerate thrombosis in TLR2-dependent manner and that TLR2 contributes to accelerate thrombosis in mice in the settings of hyperlipidemia. Our study identified the novel end-products of lipid peroxidation, accumulating in circulation in hyperlipidemia and inducing platelet activation by promoting cross-talk between innate immunity and integrin activation signaling pathways.

Predictive Factors for Determining the Clinical Severity of Pediatric Scorpion Envenomation Cases in Southeastern Turkey

OBJECTIVE

The aim of this study was to define the epidemiological, clinical, and laboratory manifestations of scorpion envenomation and to identify factors that are predictive of severe cases.

METHODS

The medical files of 41 scorpion envenomation cases were reviewed retrospectively. The cases were classified as mild-moderate or severe. The epidemiological, clinical, and laboratory findings of patients were recorded.

RESULTS

There were 27 patients (65.9%) in the mild-moderate group and 14 patients (34.1%) in the severe group. The median age of all patients was 48 months. The most common systemic finding was cold extremities (41.5%). In all patients, the most commonly observed dysrhythmia was sinus tachycardia (34.1%). Two patients (4.9%) had pulseless ventricular tachycardia and died. Pulmonary edema and myocarditis were observed in 9 patients (22%). Median values of leukocyte and glucose levels were markedly increased in the severe group. Additionally, the mean thrombocyte level (540,857 ± 115,261 cells/mm(3)) in the severe group was significantly increased compared with the mild-moderate group (391,365 ± 150,017 cells/mm(3)). Thrombocyte levels exhibited a positive correlation with leukocyte and glucose values and a negative correlation with patient left ventricular ejection fraction. Multivariate analysis of laboratory parameters indicated that the most predictive factor for clinical severity is thrombocytosis (odds ratio 23.9; 95% CI: 1.6-353.5, P = .021).

CONCLUSIONS

Although our results share some similarities with those of other reports, thrombocytosis was markedly increased in the severe group and served as the most predictive laboratory factor of clinical severity.

Effect of clonidine in mice injected with Tityus discrepans scorpion venom

A study was conducted to assess the effect of clonidine (α(2)-adrenoceptor selective agonist) on glycemia, serum and urine α-amylase, blood urea nitrogen (BUN), serum creatinine, white blood cell count, kidney histology and zymogen granule content in pancreatic acini, in mice under the effect of Tityus discrepans (Td) scorpion venom. BALB/c male mice (20 ± 2 g, n = 7-11) were intraperitoneally (ip) injected with a sublethal dose (1 μg/g) of Td venom, and were treated (ip) with 0.1 μg/g of clonidine (Catapresan(®)) or 0.9% NaCl 30 min after the venom injection, and then every 2 h. Six hours later, mice were anesthetized with diethylether and urine and blood samples were withdrawn by cystocentesis and cardiocentesis, respectively. Tissue samples were obtained and fixed immediately in buffered formalin (2%, pH 7.4) and then processed for stain H&E. Td venom did not cause hyperglycemia by itself. However, clonidine induced hyperglycemia, which was synergized by Td venom. Although the venom did not produce hyperamylasemia, clonidine significantly diminished serum α-amylase activity in envenomed mice. Td venom did not significantly increase urinary α-amylase activity, which was unaffected by clonidine. Morphometric analysis using microphotographs of pancreata from mice injected with Td venom showed a reduced zymogen granule content as judged by the acidophilic bidimensional area of acini. This effect was significantly reduced by clonidine. Kidney samples showed histological changes which were partially affected by the drug. Clonidine reduced the increase in BUN and serum creatinine concentration in envenomed mice. Td venom produced neutrophilia and lymphopenia, which were clonidine-resistant at the assayed dose. These results suggest that α(2)-adrenoceptor selective agonists would be able to reduce some scorpion venom-induced renal and pancreatic disturbances, possibly through the inhibition of neurotransmitter release from presynaptic cholinergic and noradrenergic terminals, as well as from adrenal medulla.