Padwal Priyanka, Bandyopadhyaya Rajdip, Mehra Sarika
Department of Chemical Engineering, Indian Institute of Technology Bombay , Powai, Mumbai 400076, India.
Langmuir. 2014 Dec 23;30(50):15266-76. doi: 10.1021/la503808d. Epub 2014 Dec 8.
The emergence of drug resistance is a major problem faced in current tuberculosis (TB) therapy, representing a global health concern. Mycobacterium is naturally resistant to most drugs due to export of the latter outside bacterial cells by active efflux pumps, resulting in a low intracellular drug concentration. Thus, development of agents that can enhance the effectiveness of drugs used in TB treatment and bypass the efflux mechanism is crucial. In this study, we present a new nanoparticle-based strategy for enhancing the efficacy of existing drugs. To that end, we have developed poly(acrylic acid) (PAA)-coated iron oxide (magnetite) nanoparticles (PAA-MNPs) as efflux inhibitors and used it together with rifampicin (a first line anti-TB drug) on Mycobacterium smegmatis. PAA-MNPs of mean diameter 9 nm interact with bacterial cells via surface attachment and are then internalized by cells. Although PAA-MNP alone does not inhibit cell growth, treatment of cells with a combination of PAA-MNP and rifampicin exhibits a synergistic 4-fold-higher growth inhibition compared to rifampicin alone. This is because the combination of PAA-MNP and rifampicin results in up to a 3-fold-increased accumulation of rifampicin inside the cells. This enhanced intracellular drug concentration has been explained by real-time transport studies on a common efflux pump substrate, ethidium bromide (EtBr). It is seen that PAA-MNP increases the accumulation of EtBr significantly and also minimizes the EtBr efflux in direct proportion to the PAA-MNP concentration. Our results thus illustrate that the addition of PAA-MNP with rifampicin may bypass the innate drug resistance mechanism of M. smegmatis. This generic strategy is also found to be successful for other anti-TB drugs, such as isoniazid and fluoroquinolones (e.g., norfloxacin), only when stabilized, coated nanoparticles (such as PAA-MNP) are used, not PAA or MNP alone. We hence establish coated nanoparticles as a new class of efflux inhibitors for potential therapeutic use.
耐药性的出现是当前结核病治疗面临的一个主要问题，是一个全球卫生问题。由于大多数药物会被主动外排泵排出细菌细胞外，导致细胞内药物浓度较低，分枝杆菌对大多数药物天然耐药。因此，开发能够提高结核病治疗药物有效性并绕过外排机制的药物至关重要。在本研究中，我们提出了一种基于纳米颗粒的新策略来提高现有药物的疗效。为此，我们开发了聚（丙烯酸）（PAA）包被的氧化铁（磁铁矿）纳米颗粒（PAA-MNPs）作为外排抑制剂，并将其与利福平（一种一线抗结核药物）一起用于耻垢分枝杆菌。平均直径为9nm的PAA-MNPs通过表面附着与细菌细胞相互作用，然后被细胞内化。虽然单独的PAA-MNP不抑制细胞生长，但与单独使用利福平相比，用PAA-MNP和利福平联合处理细胞表现出协同的4倍更高的生长抑制。这是因为PAA-MNP和利福平的组合导致细胞内利福平的积累增加了3倍。通过对一种常见的外排泵底物溴化乙锭（EtBr）的实时转运研究解释了这种细胞内药物浓度的增加。可以看出，PAA-MNP显著增加了EtBr的积累，并且还与PAA-MNP浓度成正比地最小化了EtBr的外排。因此，我们的结果表明，将PAA-MNP与利福平一起添加可能绕过耻垢分枝杆菌的固有耐药机制。只有当使用稳定的包被纳米颗粒（如PAA-MNP）时，而不是单独使用PAA或MNP时，这种通用策略对于其他抗结核药物，如异烟肼和氟喹诺酮类（如诺氟沙星）也被发现是成功的。因此，我们将包被纳米颗粒确立为一类新的潜在治疗用途的外排抑制剂。
