Cryptococcus neoformans, a life-threatening human yeast pathogen, has the ability to produce melanin, which is one of the common virulence factors contributing to cryptococcal pathogenesis. This virulence factor is closely associated with the cryptococcal cell wall, specifically chitin and chitosan polysaccharides, a complex structure that is essential for maintaining cellular structure and integrity. In this study, we aim to investigate the effects of two stingless bee (SLB) propolis from Tetragonula laeviceps and Tetrigona melanoleuca against cell wall-associated melanin in C. neoformans, and its immune response in RAW 264.7 macrophage. The ethanolic extract of SLB propolis (EEP) has strongly exhibited anti-cryptococcal activity. Moreover, EEP from both sources reduced chitin/chitosan and melanin production against C. neoformans in a dose-dependent manner. Likewise, the mRNA expression level of CDA1, IPC1-PKC1 and LAC1 genes involved in the cryptococcal melanization pathway was significantly decreased at 2 mg/mL in EEP treatment. Additionally, pretreatment with EEP prior to yeast infection dramatically reduced intracellular replication of C. neoformans in RAW 264.7 macrophages in a dose-dependent manner. This study might be a new insight to use a natural powerful source, not only acting to target cell wall-associated molecules, but also being capable to explore a novel strategy by which dysregulation of these molecules leads to promote immunomodulatory activity.

中文翻译：

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通过减少与细胞壁相关的隐球菌黑色素和增强巨噬细胞的杀真菌活性，揭示泰国无刺蜂胶的特性。

新型隐球菌是 一种威胁生命的人类酵母菌，具有产生黑色素的能力，而黑色素是导致隐球菌发病的常见毒力因子之一。该毒力因子与隐球菌细胞壁密切相关，特别是几丁质和壳聚糖多糖，这是维持细胞结构和完整性必不可少的复杂结构。在这项研究中，我们旨在研究来自Tetragonula laeviceps和Tetrigona melanoleuca的两种无刺蜂（SLB）蜂胶对新孢子虫细胞壁相关黑色素的影响， 及其在RAW 264.7巨噬细胞中的免疫反应。SLB蜂胶（EEP）的乙醇提取物具有很强的抗隐球菌活性。此外，两种来源的EEP均以剂量依赖性方式降低了针对新孢子虫的几丁质/壳聚糖和黑色素生成。同样，在EEP治疗中，隐球菌黑色化途径中涉及的CDA1，IPC1-PKC1和LAC1基因的mRNA表达水平显着降低。此外，在酵母感染之前用EEP进行预处理可显着减少新孢梭菌的细胞内复制在RAW 264.7巨噬细胞中呈剂量依赖性。这项研究可能是使用天然强大来源的新见解，不仅可以作用于与细胞壁相关的分子，还可以探索一种新的策略，这些分子的失调可促进免疫调节活性。