Mode of Action of Pyrazinamide in Tubercle Bacillus

描述（由申请人提供）：吡嗪酰胺（Pyrazinamide， PZA）是一种重要的一线结核病（TB）药物，参与缩短结核病治疗。PZA是一种非传统的自相矛盾的药物。尽管PZA在体内具有强大的灭菌活性，在实现短期治疗方面具有重要意义，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下具有活性，并且PZA比活性生长的杆菌更有效地杀死非生长的杆菌。最近对开发可以缩短治疗时间的结核病新药的兴趣突出了了解PZA作用模式的重要性。尽管PZA自1952年（与INH同一年）就开始用于结核病的临床治疗，但由于PZA自相矛盾的性质，它的作用方式是所有结核病药物中最不为人所知的。在本申请的支持下，该实验室的工作已经产生了许多关于PZA作用模式的重要发现。基于这些观察结果，我们推测PZA的活性形式吡嗪酸（POA）以膜为靶点并干扰膜能量学。在本申请中，我们提出以下具体目标，以进一步了解这一重要的结核病药物：(1)研究影响膜能量代谢的因素对PZA/POA抗M. tuberculosis活性的影响。这些因素包括：低氧、弱酸、饥饿、呼吸链酶和乌头酶。(2)研究PZA活性增强剂对进一步提高小鼠体内PZA对结核分枝杆菌的杀菌活性的影响。(3)通过比较pncA无突变的耐药菌株和敏感菌株对PZA的基因表达谱，探讨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，并对设计新的抗结核药物以缩短结核病治疗具有指导意义。

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.