Investigation of anthrax lethal and edema toxins pulmonary effects in an isolated perfused lung model

炭疽芽孢杆菌（B.炭疽或炭疽）仍然是发达国家的健康威胁。致死毒素和水肿毒素（分别为LT和ET）参与炭疽感染时器官损伤和致死的发病机制。了解毒素致病作用的机制对于改善这种致命感染的结果将是重要的。体外实验结果确实表明，每种毒素都能造成内皮损伤、血管完整性丧失和通透性增加。虽然从未在肺中测试过，但毒素增加的内皮通透性可能导致液体外溢，氧转移和肺顺应性降低，肺血管阻力增加。为了研究这些可能性，本研究将采用离体灌注大鼠肺模型来检查LT或ET是否会引起肺内皮损伤和肺血管通透性增加。这种离体模型可以直接测量肺重量随时间的变化，这是计算肺渗透系数所必需的。确定这两种毒素是否会改变肺通透性将提高我们对炭疽相关肺损伤的发病机制和临床治疗的理解。

Bacillus anthracis (B. anthracis or anthrax) remains a health threat for the developed world. Both lethal and edema toxin (LT and ET respectively) contribute to the pathogenesis of organ injury and lethality during anthrax infection. Understanding the mechanisms underlying the toxins pathogenic effects will be important for improving the outcome with this lethal infection. In vitro findings do suggest that each toxin can produce endothelial injury and loss of vascular integrity and increased permeability. Although never tested in the lung, increased endothelial permeability with the toxins could result in extravasation of fluid, reductions in oxygen transfer and lung compliance, and increased pulmonary vascular resistance. To investigate these possibilities, the present study will employ an isolated perfused rat lung model to examine whether LT or ET does cause pulmonary endothelial injury and increased pulmonary vascular permeability. This ex vivo model will allow a direct measure of changing lung weight over time, which is required to calculate a lung permeability coefficient. Determining whether either toxin alters lung permeability will improve our understanding of the pathogenesis and management of anthrax associated lung injury clinically. This study will be done in two parts. In the first part (Part 1), an isolated perfused rat lung model will be developed and the models ability to measure changes in endothelial permeability, oxygenation, compliance and vascular resistance tested with lungs isolated from healthy rats. As a positive control, Part 1 will include experiments in lungs challenged with thromboxane A2, a mediator known to increase lung endothelial permeability. In the second part (Part 2), lungs will be challenged with LT or ET introduced into the isolated lungs perfusion circuit and lung function will be measured. Some experiments in this part of the study will also include the use of Raxibacumab, a monoclonal antibody that inhibits host cell uptake of LT and ET, and adefovir, an intracellular inhibitor of ET, to further explore mechanisms underlying these toxins pathogenic effects. The functional parameters tested in Part 2 will include permeability, oxygenation, compliance and vascular resistance. Some lungs from Part 2 will be sent for histology and examination by electron microscopy.