Loxosceles Sphingomyelinase Induces Complement-Dependent Dermonecrosis, Neutrophil Infiltration, and Endogenous Gelatinase Expression

Abstract

Envenomation by the spider Loxosceles can result in dermonecrosis and severe ulceration. Our aim was to investigate the role of the complement system and of the endogenous metalloproteinases in the initiation of the pathology of dermonecrosis. Histological analysis of skin of rabbits injected with Loxosceles intermedia venom and purified or recombinant sphingomyelinases showed a large influx of neutrophils, concomitant with dissociation of the collagenous fibers in the dermis. Decomplementation, using cobra venom factor, largely prevented the influx of neutrophils, while influx of neutrophils was also reduced in genetically C6-deficient rabbits, suggesting roles for both C5a and the membrane attack complex in the induction of dermonecrosis. However, C-depletion and C6 deficiency did not prevent the haemorrhage and the collagen injury. Zymography analysis of skin extracts showed the induction of expression of the endogenous gelatinase MMP-9 in the skin of envenomated animals. Rabbit neutrophils contained high levels of MMP-9, expression of which was further increased after incubation with venom, suggesting that these cells may be a source of the MMP-9 found in the skin of envenomated animals. Furthermore, skin fibroblasts also secreted MMP-9 and MMP-2 upon incubation with venom, suggesting that locally produced MMPs can also contribute to proteolytic tissue destruction.

Histopathological characterization of experimentally induced cutaneous loxoscelism in rabbits inoculated with Loxosceles similis venom

“…According to our data, the inflammation increases progressively from two hours and then becomes severe eight hours post L. similis crude venom injection corroborating the already existing studies with L. laeta and L. intermedia venom (15,17,32). Morphometrical parameters showed here can be used to monitor the process dynamics, and also any treatment and sera effectiveness studies (22,31,33,34). In the present study, the heterophils/neutrophils were the predominant cells observed as mentioned by others for loxoscelism.…”

Neurotoxic activity and ultrastructural changes in muscles caused by the brown widow spider Latrodectus geometricus venom

“…In other spiders, such as those from the genus Loxosceles, the injection of their venom suggested that tissue injury is aggravated by leukocyte infiltration (including eosinophils) and deposition of complement component C3. Reduction of complement by cobra venom factor was able to postpone, but not restrain, the Loxosceles venom-induced tissue damage in the work of TAMBOURGI et al (2005) 27 . These findings not only imply essential functions for leukocytes and complement in the tissue pathogenesis of loxoscelism, but also prove that other causes are involved.…”

Pattern of inflammatory response to Loxosceles intermedia venom in distinct mouse strains: A key element to understand skin lesions and dermonecrosis by poisoning

“…L. intermedia venom causes an intense inflammatory response with infiltration of neutrophils and complement activation, hemolysis, renal failure and toxicity to various types of cell culture or animal lethality (Abdulkader et al, 2008;Appel et al, 2008;Tambourgi et al, 2010Tambourgi et al, , 2005. Locally, endogenous mechanisms are activated after envenomation, including activation of the complement system, cellular mobilization, platelet aggregation, releases of proteolytic enzymes by neutrophils and inflammatory cytokines that provided a significant disturbance of blood flow, edema and ischemic induction.…”

“…Locally, endogenous mechanisms are activated after envenomation, including activation of the complement system, cellular mobilization, platelet aggregation, releases of proteolytic enzymes by neutrophils and inflammatory cytokines that provided a significant disturbance of blood flow, edema and ischemic induction. These events lead to cell degeneration and local tissue damages (Futrell, 1992;Tambourgi et al, 1998Tambourgi et al, , 2005.…”