International University - VNU HCM, Applied Microbiology Laboratory, School of Biotechnology, Quarter 6, Linh Trung Ward, Thu Duc District, Ho Chi Minh City, Vietnam.
Vrije Universiteit Brussel (VUB), Department of Analytical Chemistry, Applied Chemometrics and Molecular Modelling, Laarbeeklaan 103, Brussels, 1090, Belgium.
BMC Biotechnol. 2024 Nov 11;24(1):89. doi: 10.1186/s12896-024-00918-6.
Microbial melanins possess a broad spectrum of biological activities. However, there is little understanding of their neuroprotective and neuronal cell differentiation properties. This study aimed to extract, purify, and modify melanins from two medicinal fungi (Daedaleopsis tricolor and Fomes fomentarius), and to evaluate their antioxidant activity, as well as their cell protective ability against neurotoxins. In addition, the study also investigated the feasibility of combining melanins or modified melanins with retinoic acid (RA) to induce neuronal differentiation.
Melanin was extracted and purified using alkaline acid-based methods. Antioxidant activities and neuroprotective effects were evaluated using the DPPH (1,1-diphenyl-2-picrylhydrazyl) and MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assays, respectively. In addition, morphological changes of SH-SY5Y cells were recorded by using a Pannoramic MIDI scanner.
All melanins and arginine-modified melanins displayed mild DPPH scavenging activities, which were statistically lower than that of ascorbic acid (p < 0.05). In terms of neuroprotection, both melanins and arginine-modified melanins exhibited significant cell protection against HO after 24 h exposure (p < 0.05). Notably, there is no significant difference between F. fomentarius melanin and its modified form as they both increased cell viability by about 20%. Contrarily, while D. tricolor melanin enhanced the cell viability with 16%, its modified form increased the cell viability with 21%. These activities, however, are significantly lower than the positive control (N-acetylcysteine, p < 0.05). Regarding MPTP, only the arginine-modified melanins of the two fungi significantly protected the cells after 24 h exposure to the toxin (p < 0.05). Specifically, F. fomentarius and D. tricolor modified melanins enhanced the cell viability with 10.2% and 11.1%, respectively, whereas that of the positive control was 13.2%. Interestingly, combining RA (10 µM) with 20 µg/mL of either F. fomentarius, or especially D. tricolor arginine-modified melanin, significantly promoted neuroblastoma cell differentiation into mature neuronal cells compared to using RA alone (p < 0.05).
The arginine-modified melanins of D. tricolor and F. fomentarius have potential for neuroprotection against Parkinsonian neurotoxins. In addition, the arginine-modified melanin of D. tricolor may serve as an excellent material for research in neuroblastoma treatment.
微生物黑色素具有广泛的生物活性。然而，人们对其神经保护和神经元细胞分化特性的了解甚少。本研究旨在从两种药用真菌（大秃马勃和硫色多孔菌）中提取、纯化和修饰黑色素，并评估其抗氧化活性以及对神经毒素的细胞保护能力。此外，该研究还探讨了将黑色素或修饰的黑色素与视黄酸（RA）结合诱导神经元分化的可行性。
使用碱性酸基方法提取和纯化黑色素。使用 DPPH（1,1-二苯基-2-苦基肼）和 MTT（3-[4,5-二甲基噻唑-2-基]-2,5-二苯基四唑溴化物）测定法分别评估抗氧化活性和神经保护作用。此外，使用 Panoramic MIDI 扫描仪记录 SH-SY5Y 细胞的形态变化。
所有黑色素和精氨酸修饰的黑色素均表现出轻微的 DPPH 清除活性，其活性明显低于抗坏血酸（p<0.05）。在神经保护方面，两种黑色素和精氨酸修饰的黑色素在暴露于 HO 24 小时后均对细胞具有显著的保护作用（p<0.05）。值得注意的是，F. fomentarius 黑色素与其修饰形式之间没有显著差异，因为它们都使细胞活力增加了约 20%。相反，虽然 D. tricolor 黑色素使细胞活力增加了 16%，但其修饰形式使细胞活力增加了 21%。然而，这些活性明显低于阳性对照（N-乙酰半胱氨酸，p<0.05）。关于 MPTP，只有两种真菌的精氨酸修饰黑色素在暴露于毒素 24 小时后显著保护细胞（p<0.05）。具体而言，F. fomentarius 和 D. tricolor 修饰的黑色素使细胞活力分别提高了 10.2%和 11.1%，而阳性对照的细胞活力提高了 13.2%。有趣的是，与单独使用 RA 相比，将 RA（10 μM）与 20 μg/mL 的 F. fomentarius 或特别是 D. tricolor 精氨酸修饰黑色素组合使用可显著促进神经母细胞瘤细胞分化为成熟神经元细胞（p<0.05）。
D. tricolor 和 F. fomentarius 的精氨酸修饰黑色素具有对抗帕金森神经毒素的神经保护潜力。此外，D. tricolor 的精氨酸修饰黑色素可能是研究神经母细胞瘤治疗的极好材料。
