天然鹤草酚类似物干扰结核杆菌菌内pH值抗结核研究

Tuberculosis (TB), caused by Mycobacterium tuberculosis(Mtb), is one of the longest and most widespread deadly infectious diseases on earth, which still seriously threaten human health in recent. Resistant TB and latent TB remain to be a major challenge to treat TB effectively that characterized problems including longer treatment duration, increasing pill burden and drug-drug interactions (such as AIDs and other chronic syndrome drugs). Many factors and Mtb unique cell wall characteristic significantly slow down the development of new anti-TB drugs in a long time. Mtb can survive under an acidic environment of phagosomes in its host macrophage with a ability to maintain intrabacterial pH (pHIB) near neutrality. Mtb can also replicate in a very slow rate and live in latent status. Nature product Agrimophol was identified as a disruptor of Mtb’s intrabacterial pH (pHIB) in acidic condition and therefore inhibit Mtb CFU formation. Mechanism study revealed that Agrimophol binds to BCG’s membrane protein Rv3852. This proposal aims to optimize diphenylmethane scaffold compounds that is a scaffold hopping structure of Agrimophol. An outline SARs will gained in final for finding out new anti-TB drug candidates. The goals of this proposal are to develop new and effective method to synthesis of diphenylmethane scaffold compounds; to discover the compounds that could effectively inhibit BCG and Mtb infected macrophage; and investigate new drug delivery systems with improved ability of lead compound transmembrane of Mtb host macrophage and phagolysosome.

结核病是由结核分枝杆菌（Mycobacterium Tuberculosis, Mtb）引起的致死传染性疾病，至今仍严重影响人类健康。结核的耐药性及潜伏性是有效治疗TB的难题，特点是用药周期长和种类多，抗结核药物与其他药物的合用等。受诸多因素影响以及Mtb特有细胞壁特征，开发新型抗TB药物长期处于缓慢状态。Mtb能够抵抗宿主巨噬细胞内的酸性环境，保持其pHIB稳态，进入非复制状态并持留。天然鹤草酚被发现具有在酸性环境下破坏其pHIB稳态的能力，并发现其作用于BCG膜蛋白Rv3852。本研究拟通过骨架跃迁的策略，合成天然鹤草酚类似物二苯甲基化合物，研究其构效关系，寻找新的抗结核药物候选物。研究拟解决天然鹤草酚骨架跃迁化合物的高效合成方法；优化得到显著抑制感染巨噬细胞的BCG及Mtb活性化合物；发展新的递送方式，有效递送新分子达到Mtb生存的巨噬细胞吞噬溶酶体内，抑制活动性及潜伏性Mtb。

项目执行期分离出天然agrimophol（1）并化学合成了1，证明其可干扰结核分枝杆菌菌内pH值稳态。新发现的二苯甲基类化合物可以模拟天然1的生物活性，降低结核分枝杆菌内（BCG，Mtb）的pH值。通过骨架跃迁策略、分子内氢键模拟以及细致的构效关系研究，发现了新化合物5a及5c，它们比天然1具有明显改进的生物活性（提高降低菌内pH值能力两个数量级以上）。研究结果显示，新分子的抑菌（包括杀菌）活性与化合物降低菌内pH值的能力相关，提示化合物5a的作用机制很可能与1相同，但5a展示出更好的体外代谢稳定性以及可以接受的治疗指数。在pH 4.5的酸性培养条件下，5a对wild-type Mtb（H37Rv）的杀菌活性较1提高了两个数量级；同时，也对临床分离得到的MDR- 及XDR-Mtb展示出较好的杀菌活性。研究结果提示，通过干扰菌内pH值稳态可能是发现抗结核分枝杆菌药物的新途径。