Loxosceles spider venom induces the production of alpha and beta chemokines: Implications for the pathogenesis of dermonecrotic arachnidism

Bites from the brown recluse spider and other Loxosceles arachnids result i n dermonecrotic skin lesions. Neutrophils (PMN) are essential to the develo pment of Loxosceles-induced skin lesions, but paradoxically, in vitro PMN a ctivation is inhibited by direct exposure to Loxosceles venom. Neutrophil a ctivation occurs in response to a myriad of soluble mediators that include members of both the alpha and beta chemokine families. Because arachnid env enomation results in the exposure of several different cell types to venom, we investigated venom-induced expression of alpha and beta chemokines in b oth endothelial cells (human umbilical vein; HUVEC) and epithelial cells (A 549 pneumocytes). Chemokine-specific capture enzyme immunoassays (EIA) were used to measure Loxosceles deserta venom-induced alpha chemokines: interle ukin-8 (IL-8), growth-related oncogene-alpha (GRO-alpha), and beta chemokin es: monocyte chemoattractant protein-1 (MCP-1), and regulated on activation , normal T cell expressed and secreted (RANTES) in cell-free conditioned me dia from HUVEC and A549 cell monolayers. Exposure of HUVECs (8 h) to Loxosc eles venom resulted in the production of IL-8 (5.2 +/-1.30 ng/ml), MCP-1 (1 .44 +/- 0.11 ng/ml) and GRO-alpha (1.97 /-+ 0.15 ng/ml) in a dose and time- dependent manner. Exposure of A549 cell monolayers to venom resulted in IL- 8 (7.74 +/- 0.30 ng/ml), and MCP-1 (2.61 +/- 0.31 ng/ml), but neither GRO-a lpha nor RANTES accumulated during an 8-hour incubation period. Chemokines accumulated in a venom dose and time-dependent manner. Neither cell type se creted RANTES in response to Loxosceles venom. These data indicate that Lox osceles spider venom is a potent inducer of alpha and beta chemokines in bo th endothelial and epithelial cell types. Based on the established roles of IL-8, MCP-1, and GRO-alpha, in inflammation, these observations have relev ance to the pathophysiology of Loxosceles-Induced dermonecrosis.