Sugui Janyce A, Pardo Julian, Chang Yun C, Zarember Kol A, Nardone Glenn, Galvez Eva M, Müllbacher Arno, Gallin John I, Simon Markus M, Kwon-Chung Kyung J
Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD 20892, USA.
Eukaryot Cell. 2007 Sep;6(9):1562-9. doi: 10.1128/EC.00141-07. Epub 2007 Jun 29.
Gliotoxin is an immunosuppressive mycotoxin long suspected to be a potential virulence factor of Aspergillus fumigatus. Recent studies using mutants lacking gliotoxin production, however, suggested that the mycotoxin is not important for pathogenesis of A. fumigatus in neutropenic mice resulting from treatment with cyclophosphomide and hydrocortisone. In this study, we report on the pathobiological role of gliotoxin in two different mouse strains, 129/Sv and BALB/c, that were immunosuppressed by hydrocortisone alone to avoid neutropenia. These strains of mice were infected using the isogenic set of a wild type strain (B-5233) and its mutant strain (gliPDelta) and the the glip reconstituted strain (gliP(R)). The gliP gene encodes a nonribosomal peptide synthase that catalyzes the first step in gliotoxin biosynthesis. The gliPDelta strain was significantly less virulent than strain B-5233 or gliP(R) in both mouse models. In vitro assays with culture filtrates (CFs) of B-5233, gliPDelta, and gliP(R) strains showed the following: (i) deletion of gliP abrogated gliotoxin production, as determined by high-performance liquid chromatography analysis; (ii) unlike the CFs from strains B-5233 and gliP(R), gliPDelta CFs failed to induce proapoptotic processes in EL4 thymoma cells, as tested by Bak conformational change, mitochondrial-membrane potential disruption, superoxide production, caspase 3 activation, and phosphatidylserine translocation. Furthermore, superoxide production in human neutrophils was strongly inhibited by CFs from strain B-5233 and the gliP(R) strain, but not the gliPDelta strain. Our study confirms that gliotoxin is an important virulence determinant of A. fumigatus and that the type of immunosuppression regimen used is important to reveal the pathogenic potential of gliotoxin.
gliotoxin是一种免疫抑制性霉菌毒素，长期以来一直被怀疑是烟曲霉的潜在毒力因子。然而，最近使用缺乏gliotoxin产生的突变体的研究表明，这种霉菌毒素对于环磷酰胺和氢化可的松治疗导致的中性粒细胞减少小鼠中烟曲霉的发病机制并不重要。在本研究中，我们报告了gliotoxin在两种不同小鼠品系（129/Sv和BALB/c）中的病理生物学作用，这两种品系仅通过氢化可的松进行免疫抑制以避免中性粒细胞减少。使用野生型菌株（B-5233）及其突变菌株（gliPDelta）和gliP重组菌株（gliP(R)）的同基因组感染这些小鼠品系。gliP基因编码一种非核糖体肽合成酶，催化gliotoxin生物合成的第一步。在两种小鼠模型中，gliPDelta菌株的毒力均明显低于B-5233菌株或gliP(R)菌株。对B-5233、gliPDelta和gliP(R)菌株的培养滤液（CFs）进行的体外试验显示：（i）通过高效液相色谱分析确定，gliP的缺失消除了gliotoxin的产生；（ii）与来自B-5233菌株和gliP(R)菌株的CFs不同，gliPDelta CFs未能在EL4胸腺瘤细胞中诱导促凋亡过程，这通过Bak构象变化、线粒体膜电位破坏、超氧化物产生、半胱天冬酶3激活和磷脂酰丝氨酸易位进行测试。此外，B-5233菌株和gliP(R)菌株的CFs强烈抑制人中性粒细胞中的超氧化物产生，但gliPDelta菌株的CFs则无此作用。我们研究证实，gliotoxin是烟曲霉的重要毒力决定因素，并且所使用的免疫抑制方案类型对于揭示gliotoxin的致病潜力很重要。
