RESUMEN
Envenomation by Loxosceles spider is characterized by the development of dermonecrosis. In previous studies, we have demonstrated that increased expression/secretion of matrix metalloproteinases 2 and 9, induced by Loxosceles intermedia venom Class 2 SMases D (the main toxin in the spider venom), contribute to the development of cutaneous loxoscelism. In the present study we show that the more potent venom containing the Class 1 SMase D from Loxosceles laeta, in addition to increasing the expression/secretion of MMP2 and MMP9, also stimulates the expression of MMP7 (Matrilysin-1), which was associated with keratinocyte cell death. Tetracycline, a matrix metalloproteinase inhibitor, prevented cell death and reduced MMPs expression. Considering that L. laeta venom is more potent at inducing dermonecrosis than L. intermedia venom, our results suggest that MMP7 may play an important role in the severity of dermonecrosis induced by L. laeta spider venom SMase D. In addition, the inhibition of MMPs by e.g. tetracyclines may be considered for the treatment of the cutaneous loxoscelism.
Asunto(s)
Proteínas de Artrópodos/farmacología , Queratinocitos/efectos de los fármacos , Hidrolasas Diéster Fosfóricas/farmacología , Venenos de Araña/farmacología , Arañas/enzimología , Animales , Antibacterianos/farmacología , Apoptosis/efectos de los fármacos , Western Blotting , Línea Celular , Supervivencia Celular/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Humanos , Queratinocitos/metabolismo , Metaloproteinasa 2 de la Matriz/metabolismo , Metaloproteinasa 7 de la Matriz/metabolismo , Metaloproteinasa 9 de la Matriz/metabolismo , Necrosis/prevención & control , Conejos , Piel/efectos de los fármacos , Piel/patología , Venenos de Araña/enzimología , Tetraciclina/farmacología , Factores de TiempoRESUMEN
Neutrophils are involved in numerous pathologies and are considered to be major contributors to the establishment of cutaneous loxoscelism after envenomation by the Loxosceles spider. Neutrophils are attracted to the site of envenomation by locally generated C5a and contribute to the tissue destruction. We have investigated the effects of this spider venom on the receptor for C5a: C5aR/CD88, a seven transmembrane G-protein coupled receptor. We show here that the Loxosceles venom induces the cleavage of the C5aR at two sites, resulting in the release of the extracellular N-terminus, while retaining part of the transmembrane regions. Using specific inhibitors, it was shown that the cleavage was induced by activation of an endogenous metalloprotease of the adamalysin (ADAM) family, which was activated by the sphingomyelinase D in the venom. Although it resulted in the near complete loss of the N-terminus, C5a was still able to induce a small increase in intracellular calcium and increase secretion of IL-8. The cleavage of the C5aR may well be a protective response after envenomation, rather than contributing to the pathology of Loxosceles envenomation and may represent a general mechanism for how the body protects itself against excess C5a generation in pathological circumstances such as sepsis.