Mode of Action of Pyrazinamide in Tubercle Bacillus

描述(申请人提供)：吡津酰胺(PZA)是一种重要的一线结核病(TB)药物，涉及缩短结核病治疗。PZA是一种非常规的、矛盾的药物。尽管PZA在体内具有强大的杀菌活性，在实现短程治疗方面具有重要作用，但在正常培养条件下对结核分枝杆菌没有活性，但在酸性pH条件下具有活性，而且PZA比活跃生长的杆菌更有效地杀灭不生长的细菌。最近，人们对开发可以缩短治疗时间的新的结核病药物的兴趣突显了了解PZA的作用模式的重要性。尽管PZA自1952年以来一直用于结核病的临床治疗--与异烟肼同年--但由于PZA的矛盾性质，其作用方式是所有结核病药物中最不为人所知的。在这项申请的支持下，该实验室的工作已经导致了关于PZA作用模式的一些重要发现。基于这些观察结果，我们假设PZA的活性形式吡津酸(POA)以膜为靶标并干扰膜的能量学。在这一应用中，我们提出了以下具体目的，以加深我们对这一重要的结核病药物的理解：(1)探讨影响膜能量代谢的因素对PZA/POA抗结核活性的影响。这些因素包括：低氧、弱酸、饥饿、呼吸链酶和乌头酸酶；(2)评估PZA活性增强剂在进一步提高PZA在小鼠体内对结核分支杆菌的杀菌活性方面的效果；(3)通过比较无pncA突变的耐药株和敏感株对PZA的响应，确定PZA作用和耐药的新机制。这些研究将提高我们对PZA作用和耐药机制的理解，并将对设计能够缩短结核病治疗的新的抗结核药物具有一定的指导意义。

DESCRIPTION (provided by applicant): Pyrazinamide (PZA) is an important frontline tuberculosis (TB) drug that is involved in shortening the TB therapy. PZA is an unconventional and paradoxical drug. Despite its powerful sterilizing activity in vivo and its importance in achieving the short course therapy, PZA has no activity against M. tuberculosis under normal culture conditions but is active at acid pH, and PZA kills nongrowing bacilli more effectively than actively growing bacilli. The recent interest to develop new TB drugs that can shorten the therapy has highlighted the importance to understand the mode of action of PZA. Although PZA has been used in clinical treatment of TB since 1952 -the same year as INH, its mode of action is the least understood of all TB drugs because of the paradoxical nature of PZA. Work from this laboratory supported by this application has resulted in a number of significant findings about the mode of action of PZA. Based on these observations, we hypothesize that pyrazinoic acid (POA), the active form of PZA, targets the membrane and interferes with membrane energetics. In this application, we propose the following specific aims to further our understanding of this important TB drug: (1) To investigate the effect of factors that affect membrane energy metabolism on the activity of PZA/POA against M. tuberculosis. These factors include: low oxygen, weak acids, starvation, respiratory chain enzymes and aconitase (2) To assess the effect of enhancers of PZA activity on further improving the sterilizing activity of PZA against M. tuberculosis in vivo in mice, (3) To identify new mechanisms of PZA action and resistance by comparing the gene expression profiles of resistant strains without pncA mutations with sensitive strain in response to PZA. These studies will improve our understanding of mechanisms of PZA action and resistance and should have implications for the design of new antituberculosis drugs that can shorten the TB therapy.