Department of Oral Microbiology, Division of Oral Infection Health Sciences, Asahi University School of Dentistry, Mizuho, Gifu, Japan.
PLoS One. 2022 Aug 30;17(8):e0273663. doi: 10.1371/journal.pone.0273663. eCollection 2022.
Candidalysin, a peptide toxin produced specifically from hyphae of Candida albicans, plays a crucial role in C. albicans pathogenesis in the oral cavity and vagina. Synthetic peptides have been widely used in previous studies to investigate the bioactivity of candidalysin. Although the solubility of the peptide, which is expected to have a hydrophobic property, has not been well characterized, candidalysin solutions are usually prepared in water. In this study, we prepared the synthetic peptide candidalysin in water (CLw) or in dimethyl sulfoxide (CLd) and compared their cytotoxicity and interleukin (IL)-1β-producing activity to determine whether the activity of the peptide would be affected. In addition, we evaluated whether the NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome pathway or other pathways were involved in their activities. Unexpectedly, we found that CLw was not completely solubilized and contained abundant insoluble microparticles. CLw was active at comparably high concentrations (≥ 10 μM). In contrast, CLd is completely solubilized and sufficiently active at low concentrations, that is, 1 μM or less. CLw showed weak cytotoxicity and NLRP3-dependent and cathepsin B-dependent IL-1β-producing activity, whereas CLd showed strong cytotoxicity and cathepsin B-dependent IL-1β-producing activity. Fractionation of CLw revealed that NLRP3-dependent activity was caused by insoluble microparticles. Furthermore, nanoparticle tracking of CLd revealed that the peptide was present as nanoparticles with a size of 96 nm. CLw contained a small amount of such nanoparticles. Thus, the bioactivities of the synthetic peptide candidalysin, especially the IL-1β-producing activity, are affected by the solubility of the peptide depending on the solvent employed. The NLRP3-dependent activity of the synthetic peptide is caused by insoluble microparticles and may not be the intrinsic activity of candidalysin.
白色念珠菌甘露聚糖酶是一种由白色念珠菌菌丝体特异性产生的肽毒素，在口腔和阴道白色念珠菌病发病机制中发挥关键作用。合成肽在以前的研究中被广泛用于研究甘露聚糖酶的生物活性。尽管预计具有疏水性的肽的溶解度尚未得到很好的描述，但甘露聚糖酶溶液通常在水中制备。在这项研究中，我们在水中（CLw）或二甲基亚砜（CLd）中制备了合成肽甘露聚糖酶，并比较了它们的细胞毒性和白细胞介素（IL）-1β产生活性，以确定肽的活性是否会受到影响。此外，我们评估了 NOD 样受体家族 pyrin 结构域包含 3（NLRP3）炎性小体途径或其他途径是否参与其活性。出乎意料的是，我们发现 CLw 未完全溶解，并且含有丰富的不溶性微粒。CLw 在比较高的浓度（≥10 μM）下具有活性。相比之下，CLd 完全溶解并且在低浓度（即 1 μM 或更低）下具有足够的活性。CLw 显示出弱的细胞毒性和 NLRP3 依赖性和组织蛋白酶 B 依赖性 IL-1β产生活性，而 CLd 显示出强的细胞毒性和组织蛋白酶 B 依赖性 IL-1β产生活性。CLw 的分级分离表明 NLRP3 依赖性活性是由不溶性微粒引起的。此外，CLd 的纳米颗粒跟踪显示该肽以 96nm 大小的纳米颗粒存在。CLw 含有少量此类纳米颗粒。因此，合成肽甘露聚糖酶的生物活性，特别是 IL-1β产生活性，取决于所使用的溶剂的肽的溶解度而受到影响。合成肽的 NLRP3 依赖性活性是由不溶性微粒引起的，可能不是甘露聚糖酶的固有活性。
