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.

Important biological activities induced by Thalassophryne maculosa fish venom.

The accidents caused by Thalassophryne maculosa fish venoms are frequent and represent a public health problem in some regions of Venezuela. Most accidents occur in the fishing communities and tourists. The clinical picture is characterized by severe pain, dizziness, fever, edema, and necrosis. Due to the lack of efficient therapy it may take weeks, or even months for complete recovery of the victims. The investigations presented here were undertaken to assess the eletrophoretical profile and principal biological properties of the T. maculosa venom. Venom obtained from fresh captured specimens of this fish was tested in vitro or in animal models for a better characterization of its toxic activities. In contrast to other fish venoms, T. maculosa venom showed relative low LD50. The injection of venom in the footpad of mice reproduced a local inflammatory lesion similar to that described in humans. Significant increase of the nociceptive and edematogenic responses was observed followed within 48 h by necrosis. Pronounced alterations on microvascular hemodynamics were visualized after venom application. These alterations were represented by fibrin depots and thrombus formation followed by complete venular stasis and transient arteriolar contraction. T. maculosa venom is devoid of phospholipase A2 activity, but the venom showed proteolytic and myotoxic activities. SDS-Page analysis of the crude venom showed important bands: one band located above 97 M(w), one band between 68 and 97 M(w), one major band between 29 and 43 M(w) and the last one located below 18.4 M(w) Then, the results presented here support that T. maculosa venom present a mixture of bioactive toxins involved in a local inflammatory lesion.