, 2004) seem to play essential roles in the edematogenic, hypotensive and nociceptive effects. Additionally, studies using molecular and biochemical approaches have reported the biological effect of the venom fractions on different cell types Autophagy signaling pathway inhibitors in vitro. Lopap and Losac, for example, besides their significant effects

on hemostasis, have been shown direct effects on endothelial cells, upregulating the expression of pró-inflammatory molecules as IL-8, ICAM-1 and E-selectin, inducing NO production ( Chudzinski-Tavassi et al., 2001). Most of studies using L. obliqua crude venom, in vivo or in vitro, have been done treating animals with doses that strongly affect the coagulation and fibrinolitic systems, causing MS-275 datasheet extensive hemorrhage. Under this situation, the mechanisms underlying the onset of inflammatory events, especially those related to alteration of endothelial

cells physiology and the involved intracellular signaling cascades could be masked. In our study, using intravital microscopy, we show that low (1–3 μg/ml), non-hemorrhagic doses of L. obliqua venom induced remarkable affects in the micro-vascular circulation of hamster’s cheek pouch. At those concentrations, although no significant vasodilatation was seen, occurred a marked slowing in blood flow, increasing in leukocyte rolling and adhesion on endothelial wall that were dose-dependent and more evident through time ( Supl. Fig. 7). The activation of vascular endothelial cells by inflammatory stimuli increases adhesion molecules expression and endothelial interactions with circulating blood leukocytes at post-capillary venules ( Granger and Kubes, 1994). Consistently, the analysis of those tissues of hamster cheek pouches by confocal find more microscopy showed that the venom activates the vascular endothelium, increasing the expression

of pro-inflammatory adhesion molecules E-selectin and VCAM-1 and inducing leukocyte adhesion and extravasation to neighboring inflamed tissue. This clear and typical inflammatory response occurred without the hemorrhage usually described for L. obliqua envenomation, although an intravascular effect on coagulation system cannot be discharge. For example, the potent pro-coagulant components of the venom may act triggering intravascular platelet aggregation and blood clotting ( Berger et al., 2010), and then contribute to slow down blood flow, to the activation of endothelial vascular cells and the overall inflammatory panel. Increase in vascular permeability requires cytoskeleton reorganization, a necessary prerequisite to inter-endothelial cell gap formation. The actin reorganization from its cortical distribution into stress fibers is an important component of the endothelial response to inflammation. We show, for the first time, that L. obliqua venom promoted a marked effect in the cytoskeleton reorganization in endothelial cells.