Histoplasma capsulatum synthesizes melanin-like pigments in vitro and during mammalian infection
Histoplasma capsulatum synthesizes melanin-like pigments in vitro and during mammalian infection
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DOI：
10.1128/iai.70.9.5124-5131.2002
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发表时间：
2002-09-01
影响因子：
3.1
通讯作者：
Hamilton, AJ
中科院分区：
文献类型：
--
作者：
Nosanchuk, JD;Gómez, BL;Hamilton, AJ
黑色素是由几种重要的病原真菌产生的，并且与许多真菌感染的发病机制有关。本研究调查了热二态性真菌病原体荚膜组织胞浆菌（Histoplasma capsulatum var. var. var. var. var. var. var. var. var. var. var. var. var. var. var。荚膜杆菌在体外和感染期间产生黑色素或黑色素样化合物。荚膜梭菌菌丝体在化学成分确定的基本培养基中生长，产生有色分生孢子。荚膜梭菌酵母在含有 L-3,4-二苯丙氨酸 (DOPA) 或 (-)-肾上腺素的化学成分确定的基本培养基中生长，产生色素细胞。用蛋白水解酶、变性剂和热浓酸处理色素细胞产生黑色颗粒，其大小和形状与其各自的繁殖体相似。黑色素结合单克隆抗体 (MAb) 标记有色素的分生孢子、酵母和通过免疫荧光显微镜测定的分离颗粒。电子自旋共振光谱显示，色素酵母细胞和源自色素细胞的颗粒是稳定的自由基，与其黑色素的鉴定一致。感染荚膜梭菌的小鼠组织和组织胞浆菌病患者的活检标本中含有被黑色素结合单克隆抗体标记的真菌细胞。消化受感染的小鼠组织会产生深色颗粒，该颗粒与黑色素结合单克隆抗体发生反应，其外观与荚膜梭菌酵母细胞相似。此外，受感染小鼠的血清含有结合黑色素颗粒的抗体。在酵母细胞的细胞质提取物中检测到能够从左旋多巴合成黑色素的酚氧化酶活性。这些发现表明，荚膜梭菌分生孢子和酵母可以在体外产生黑色素或黑色素样化合物，并且酵母细胞可以在体内合成色素。由于黑色素是其他病原真菌的重要毒力因子，因此这种色素可能在组织胞浆菌病的发病机制中发挥类似的作用。
Melanin is made by several important pathogenic fungi and has been implicated in the pathogenesis of a number of fungal infections. This study investigated whether the thermally dimorphic fungal pathogen Histoplasma capsulatum var. capsulatum produced melanin or melanin-like compounds in viitro and during infection. Growth of H. capsulatum mycelia in chemically defined minimal medium produced pigmented conidia. Growth of H. capsulatum yeast in chemically defined minimal medium with L-3,4-diltydroxyphenylalanine (DOPA) or (-)-epinephrine produced pigmented cells. Treatment of the pigmented cells with proteolytic enzymes, denaturant, and hot concentrated acid yielded dark particles that were similar in size and shape to their respective propagules. Melanin-binding monoclonal antibodies (MAb) labeled pigmented conidia, yeast, and the isolated particles as determined by immunofluorescence microscopy. Electron spin resonance spectroscopy revealed that pigmented yeast cells and particles derived from pigmented cells were stable free radicals consistent with their identification as melanins. Tissues from mice infected with H. capsulatum and from biopsy specimens from a patient with histoplasmosis contained fungal cells that were labeled by melanin-binding MAb. Digestion of infected mouse tissues yielded dark particles that reacted with the melanin-binding MAb and were similar in appearance to H. capsulatum yeast cells. Additionally, sera from infected mice contained antibodies that bound melanin particles. Phenoloxidase activity capable of synthesizing melanin from L-DOPA was detected in cytoplasmic yeast cell extracts. These findings indicate that H. capsulatum conidia and yeast can produce melanin or melanin-like compounds in vitro and that yeast cells can synthesize pigment in vivo. Since melanin is an important virulence factor in other pathogenic fungi, this pigment may have a similar role to play in the pathogenesis of histoplasmosis.