Activation of leukocyte rolling by the cysteine-rich domain and the hyper-variable region of HF3, a snake venom hemorrhagic metalloproteinase.

The functionality of the disintegrin-like/cysteine-rich domains of snake venom metalloproteinases (SVMPs) has been shown to reside in the cysteine-rich region, which can interact with VWA-containing proteins. Recently, the hyper-variable region (HVR) of the cysteine-rich domain was suggested to constitute a potential protein-protein adhesive interface. Here we show that recombinant proteins of HF3, a hemorrhagic P-III SVMP, containing the cysteine-rich domain (disintegrin-like/cysteine-rich and cysteine-rich proteins) but not the disintegrin-like protein were able to significantly increase leukocyte rolling in the microcirculation. Peptides from the HVR also promoted leukocyte rolling and this activity was inhibited by anti-alpha(M)/beta2 antibodies. These results show, for the first time, that the cysteine-rich domain and its HVR play a role in triggering pro-inflammatory effects mediated by integrins.

Delayed polymorphonuclear leukocyte infiltration is an important component of Thalassophryne maculosa venom pathogenesis.

Thalassophryne maculosa fish envenomation is characterized by severe pain, dizziness, fever, edema and necrosis. Here, the dynamic of cellular influx, activation status of phagocytic cells, and inflammatory modulator production in the acute inflammatory response to T. maculosa venom was studied using an experimental model. Leukocyte counting was performed (2 h to 21 days) after venom injection in BALB/c mice footpads. Our results showed an uncommon leukocyte migration kinetic after venom injection, with early mononuclear cell recruitment followed by elevated and delayed neutrophil influx. The pattern of chemokine expression is consistent with the delay in neutrophil recruitment to the footpad: T. maculosa venom stimulated an early production of IL-1beta, IL-6, and MCP-1, but was unable to induce an effective early TNF-alpha and KC release. Complementary to these observations, we detected a marked increase in soluble KC and TNF-alpha in footpad at 7 days post-venom injection when a prominent influx of neutrophils was also detected. In addition, we demonstrated that bone marrow-derived macrophages and dendritic cells were strongly stimulated by the venom, showing up-regulated ability to capture FITC-dextran. Thus, the reduced levels of KC and TNF-alpha in footpad of mice concomitant with a defective accumulation of neutrophils at earlier times provide an important clue to uncovering the mechanism by which T. maculosa venom regulates neutrophil movement.

Analysis of the intersexual variation in Thalassophryne maculosa fish venoms.

Gender related variation in the molecular composition of venoms and secretions have been described for some animal species, and there are some evidences that the difference in the toxin (s) profile among males and females may be related to different physiopathological effects caused by the envenomation by either gender. In order to investigate whether this same phenomenon occurs to the toadfish Thalassophryne maculosa, we have compared some biological and biochemical properties of female and male venoms. Twenty females and males were collected in deep waters of the La Restinga lagoon (Venezuela) and, after protein concentration assessed, the induction of toxic activities in mice and the biochemical properties were analyzed. Protein content is higher in males than in females, which may be associated to a higher size and weight of the male body. In vivo studies showed that mice injected with male venoms presented higher nociception when compared to those injected with female venoms, and both venoms induced migration of macrophages into the paw of mice. On the other hand, mice injected with female venoms had more paw edema and extravasation of Evans blue in peritoneal cavity than mice injected with male venoms. We observed that the female venoms had more capacity for necrosis induction when compared with male venoms. The female samples present a higher proteolytic activity then the male venom when gelatin, casein and FRETs were used as substrates. Evaluation of the venoms of females and males by SDS-PAGE and chromatographic profile showed that, at least three components (present in two peaks) are only present in males. Although the severity of the lesion, characterized by necrosis development, is related with the poisoning by female specimens, the presence of exclusive toxins in the male venoms could be associated with the largest capacity of nociception induction by this sample.

Characterization of a new bioactive peptide from Potamotrygon gr. orbignyi freshwater stingray venom.

Brazilian freshwater stingrays, Potamotrygon gr. orbigyni, are relatively common in the middle-western regions of Brazil, where they are considered an important public health threat. In order to identify some of their naturally occurring toxin peptides available in very low amounts, we combine analytical protocols such as reversed-phase high-performance liquid chromatography (RP-HPLC), followed by a biological microcirculatory screening and mass spectrometry analysis. Using this approach, one bioactive peptide was identified and characterized, and two analogues were synthesized. The natural peptide named Porflan has the primary structure ESIVRPPPVEAKVEETPE (MW 2006.09 Da) and has no similarity with any bioactive peptide or protein found in public data banks. Bioassay protocols characterized peptides as presenting potent activity in a microcirculatory environment. The primary sequences and bioassay results, including interactions with the membrane phospholipids, suggest that these toxins are a new class of fish toxins, directly involved in the inflammatory processes of a stingray sting.