Gómez Beatriz L, Nosanchuk Joshua D
Dermatology Department, St. Johns Institute of Dermatology, Guy's Hospital, Guy's, Kings, and St Thomas Medical School, London, UK.
Curr Opin Infect Dis. 2003 Apr;16(2):91-6. doi: 10.1097/00001432-200304000-00005.
Production of melanin has been associated with virulence in diverse microorganisms. Melanization of fungi has been noted for many years in predominantly subcutaneous infections such as chromoblastomycosis and more recently most extensively studied in a yeast causing systemic infection, Cryptococcus neoformans. Pigmented fungi are increasingly important human pathogens and currently available antifungals are often sub-optimal for serious infections. This review focuses on recent publications on melanin in fungi with particular reference to the role of melanin in virulence, protection against antifungal drugs, and promoting survival in the environment.
Inhibition of melanin production by C. neoformans can prolong survival of lethally infected mice. In contrast, melanin in C. neoformans and Histoplasma capsulatum yeast cells can bind amphotericin B and caspofungin, thereby reducing the fungicidal affects of these drugs. H. capsulatum and Paracoccidioides brasiliensis have only recently been shown to produce melanin in vitro and during infection. Additionally, melanin derived from melanized C. neoformans yeast and Aspergillus niger conidia can activate complement, which may modify immune responses to infection. Studies on C. neoformans laccase have revealed that the enzyme is located on the cell wall, which may allow for interactions with the host. Melanization reduces the susceptibility of C. neoformans to enzymatic degradation and toxicity from a heavy metal, which may afford protection to the fungus against similar insults in the environment.
Melanin has been referred to as 'fungal armor' due to the ability of the polymer to protect microorganisms against a broad range of toxic insults. Recent publications continue to reveal important contributions of melanin to survival of fungi in the environment and during infection.
黑色素的产生与多种微生物的毒力相关。真菌的黑化现象在主要的皮下感染（如着色芽生菌病）中已被关注多年，最近在引起全身感染的酵母——新型隐球菌中得到了最广泛的研究。色素沉着真菌作为人类病原体的重要性日益增加，而目前可用的抗真菌药物对于严重感染往往效果欠佳。本综述聚焦于近期有关真菌黑色素的出版物，特别提及黑色素在毒力、抗真菌药物抗性及促进环境中生存方面的作用。
抑制新型隐球菌黑色素的产生可延长致死性感染小鼠的存活时间。相反，新型隐球菌和荚膜组织胞浆菌酵母细胞中的黑色素可结合两性霉素B和卡泊芬净，从而降低这些药物的杀菌效果。荚膜组织胞浆菌和巴西副球孢子菌直到最近才被证明在体外及感染过程中可产生黑色素。此外，源自黑化的新型隐球菌酵母和黑曲霉分生孢子的黑色素可激活补体，这可能会改变对感染的免疫反应。对新型隐球菌漆酶的研究表明，该酶位于细胞壁上，这可能使其与宿主发生相互作用。黑化降低了新型隐球菌对酶降解和重金属毒性的敏感性，这可能为真菌在环境中抵御类似侵害提供保护。
由于黑色素聚合物能够保护微生物免受多种毒性侵害，它被称为“真菌铠甲”。近期的出版物不断揭示黑色素对真菌在环境中及感染期间生存的重要贡献。
