New Ops:Vasc Leakage Inhibition Protects Against Anthrax Pleural Effusions &Edema

1. 摘要

1. Abstract Human case studies have described pleural effusions and the presence of a widened mediastinum on chest x-rays as the most common clinical features of anthrax disease. Of the 11 people who developed acute anthrax disease in 2001, 6 survived due to the intensive care received at hospitals that included fluid drainage from the lung, and treatment with antibiotics. Increased vascular permeability has been strongly implicated in anthrax toxin induced tissue edema in a large number of mammalian models (non-human primates, rabbits, guinea pigs, rats, mice). The importance of blood vessels and endothelial cells in anthrax toxicity has been difficult to investigate due to the inability to observe progressive vascular changes without sacrificing the mammalian host. Therefore, we developed the transparent zebrafish embryo as a model to facilitate live imaging of anthrax lethal toxin action on intact blood vessels. We observed that lethal toxin induced increased vascular permeability as an early consequence leading to progressive defects in cardiovascular function. Since vascular permeability is regulated by the vascular endothelial growth factor, also called the vascular permeability factor (VEGFNPF), we employed chemical inhibitors to block this pathway to reduce toxin effects, achieving remarkable levels of attenuation. These data were confirmed using an established vascular permeability assay in adult mouse skin microvasculature termed the Miles Assay. Here, inhibition of the VEGFNPF pathway reduced lethal toxin induced vascular leakage as measured by a colorimetric dye. Since the Fischer 344 rat is an established anthrax toxin model where vascular defects have been observed, we are currently employing this model to test the hypothesis that blocking the VEGF pathway can yield protective effects against lethal toxin action as measured by increased survival time. This model is extremely sensitive to lethal toxin challenge, typically inducing death in about 45-60 minutes. In our experiments, we observe vascular defects in multiple organs and extensive pleural effusions at late stages during toxin challenge. Analysis of VEGFR phosphorylation levels in the lung demonstrated increased activation of this pathway post toxin injection, suggesting that inhibitors of the VEGF pathway could attenuate toxin effects. Since anti-VEGF therapies are already in clinical use for cancer therapy and for the treatment of age-related vascularized macula degeneration, further testing of their usefulness as an anti-anthrax therapeutic could be expedited. This approach may be combined with antibiotics or anti-toxins to increase the therapeutic window for the effective treatment of anthrax disease.