Sun Liu-Liu, Li Hao, Yan Tian-Hua, Fang Ting, Wu Hao, Cao Yong-Bing, Lu Hui, Jiang Yuan-Ying, Yang Feng
Department of Pharmacology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China.
Department of Physiology and Pharmacology, School of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University, Nanjing, China.
Microbiol Spectr. 2023 Feb 28;11(2):e0301622. doi: 10.1128/spectrum.03016-22.
Candida albicans is a prevalent, opportunistic, human fungal pathogen. Antifungal drug resistance and tolerance are two distinct mechanisms of adaptation to drugs. Studies of mechanisms of drug resistance are limited to the applications of high doses of drugs. Few studies have investigated the effects of subinhibitory amounts of drugs on the development of drug resistance or tolerance. In this study, we found that growth in a subinhibitory amount of fluconazole (FLC), a widely used antifungal drug, for just a short time was sufficient to induce aneuploidy in C. albicans. Surprisingly, the aneuploids displayed fitness loss in the presence of subinhibitory FLC, but a subpopulation of cells could tolerate up to 128 μg/mL FLC. Particular aneuploidy (ChrR trisomy) caused tolerance, not resistance, to FLC. In the absence of FLC, the aneuploids were unstable. Depending on the karyotype, aneuploids might become completely euploid or maintain particular aneuploidy, and, accordingly, the tolerance would be lost or maintained. Mechanistically, subinhibitory FLC was sufficient to induce the expression of several genes and as well as the drug efflux gene . Aneuploids had a constitutive high-level expression of genes on and outside the aneuploid chromosomes, including most of the genes as well as the drug efflux genes and . Therefore, aneuploids were prepared for FLC challenges. In summary, aneuploidy provides a rapid and reversible strategy of adaptation when C. albicans is challenged with subinhibitory concentrations of FLC. Genome instability is a hallmark of C. albicans. Aneuploidy usually causes fitness loss in the absence of stress but confers better fitness under particular stress conditions. Therefore, aneuploidy is considered to be a double-edged sword. Here, we extend the understanding of aneuploidy. We found that aneuploidy arose under weak stress conditions but that it did not confer better fitness to the stress. Instead, it was less fit than its euploid counterparts. If the stress was withdrawn, aneuploidy spontaneously reverted to euploidy. If the stress became stronger, aneuploidy enabled subpopulation growth in a dose-independent manner of the stress. Therefore, we posit that aneuploidy enables the rapid and reversible development of drug tolerance in C. albicans. Further studies are required to investigate whether this is a general mechanism in human fungal pathogens.
白色念珠菌是一种常见的机会性人类真菌病原体。抗真菌药物耐药性和耐受性是两种不同的药物适应机制。耐药机制的研究仅限于高剂量药物的应用。很少有研究调查亚抑菌剂量的药物对耐药性或耐受性发展的影响。在本研究中，我们发现，在广泛使用的抗真菌药物氟康唑（FLC）的亚抑菌剂量下短暂生长就足以在白色念珠菌中诱导非整倍体。令人惊讶的是，在存在亚抑菌剂量的FLC时，非整倍体表现出适应性丧失，但一小部分细胞能够耐受高达128μg/mL的FLC。特定的非整倍体（ChrR三体）导致对FLC的耐受性，而非耐药性。在没有FLC的情况下，非整倍体不稳定。根据核型，非整倍体可能完全变成整倍体或维持特定的非整倍体，相应地，耐受性会丧失或维持。从机制上讲，亚抑菌剂量的FLC足以诱导几个基因以及药物外排基因的表达。非整倍体在非整倍体染色体上和之外的基因具有组成型高水平表达，包括大多数基因以及药物外排基因和。因此，非整倍体为应对FLC挑战做好了准备。总之，当白色念珠菌受到亚抑菌浓度的FLC挑战时，非整倍体提供了一种快速且可逆的适应策略。基因组不稳定是白色念珠菌的一个标志。非整倍体在没有压力的情况下通常会导致适应性丧失，但在特定压力条件下具有更好的适应性。因此，非整倍体被认为是一把双刃剑。在这里，我们扩展了对非整倍体的理解。我们发现非整倍体在弱应激条件下出现，但它并没有赋予对这种应激更好的适应性。相反，它比其整倍体对应物适应性更差。如果应激消除，非整倍体自发地恢复为整倍体。如果应激变得更强，非整倍体能够以与应激剂量无关的方式使亚群生长。因此，我们认为非整倍体能够使白色念珠菌快速且可逆地产生药物耐受性。需要进一步研究来调查这是否是人类真菌病原体中的一种普遍机制。
