Liu Jin, Shi Lu, Tuo Xiaohong, Ma Xinxin, Hou Xinyao, Jiang Sijin, Lv Jia, Cheng Yue, Guo Dagang, Han Bei
School of Public Health, Health Science Center, Xi'an Jiaotong University, Xi'an, China.
School of Public Health, Health Science Center, Xi'an Jiaotong University, Xi'an, China; Key Laboratory for Disease Prevention and Control and Health Promotion of Shaanxi Province, Xi'an, China.
J Trace Elem Med Biol. 2022 Dec;74:127056. doi: 10.1016/j.jtemb.2022.127056. Epub 2022 Aug 4.
Elemental selenium, a new type of selenium supplement, can be biosynthesized via microorganisms. This study is to characterize a patent probiotic bacteria Enterococcus durans A8-1, capable of reducing selenite (Se or Se) to elemental selenium (Se) with the formation of Se nanoparticles (SeNPs).
The selenium nanoparticles synthesized from A8-1 were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and X-ray photoelectron energy (XPS). The Caco2 cells were used to investigate the effects of Se-enriched A8-1 on the viability, membrane integrity, and the regulation of cellular inflammation through MTT and ELISA assays. The selenium-enriched metabolic function of A8-1 was analyzed by transcriptome sequencing.
E. durans A8-1 has the ability to synthesize intracellular SeNPs that are incubated with 60 mg/L sodium selenite for 18 h at 37 °C with 7 % inoculum under aerobic conditions. The selenium-enriched transformation rate increased to 43.46 %. After selenium enrichment, there were no significant morphological changes in E. durans A8-1 cells. The cells also exhibited no cytotoxicity when incubated with Caco-2 cells, and increased cellular proliferation. Furthermore, Se-enriched A8-1 cells antagonize the adhesion of S. typhimurium ATCC14028 onto the surface of Caco-2 cells protecting cell membrane integrity and was assessed by measuring LDH and AKP activities (P <0.001, P <0.001). Moreover, Se-enriched A8-1 could protect Caco-2 cells from inflammation induced by lipopolysaccharide and help the cells alleviate the inflammation through the reduced expression of cytokine IL-8 (P = 0.0012, P <0.001) and TNF-α (P <0.001, P <0.001). Based on transcriptome sequencing in Se-enriched E. durans A8-1 cells, there were 485 up-regulated genes and 322 down-regulated genes (P < 0.05). There were 19 predicted up-regulated genes that are highly related to the potential selenium metabolism pathway, which focuses on the transportation of NaSeO by membrane proteins, and gradually reduces NaSeO to elemental selenium aggregates that are deposited onto the membrane surface via the intracellular redox response.
E. durans A8-1 could convert extracellular selenite into intracellular biological SeNPs via redox pathway with strong selenium-rich metabolism, and its biological SeNPs have anti-inflammatory properties, which have the potential for the development of composite selenium nanomaterials and can be further studied for the function of SeNPs with potential applications.
元素硒作为一种新型的硒补充剂，可通过微生物进行生物合成。本研究旨在鉴定一种专利益生菌耐久肠球菌A8 - 1，其能够将亚硒酸盐（Se或Se）还原为元素硒（Se）并形成硒纳米颗粒（SeNPs）。
利用扫描电子显微镜（SEM）、透射电子显微镜（TEM）、能量色散光谱（EDS）和X射线光电子能谱（XPS）对由A8 - 1合成的硒纳米颗粒进行表征。使用Caco2细胞通过MTT和ELISA检测法研究富硒A8 - 1对细胞活力、膜完整性以及细胞炎症调节的影响。通过转录组测序分析A8 - 1的富硒代谢功能。
耐久肠球菌A8 - 1具有在有氧条件下，以7%的接种量于37℃与60mg/L亚硒酸钠孵育18小时合成细胞内SeNPs的能力。富硒转化率提高到43.46%。富硒后，耐久肠球菌A8 - 1细胞的形态没有明显变化。与Caco - 2细胞孵育时，这些细胞也没有表现出细胞毒性，反而促进了细胞增殖。此外，富硒A8 - 1细胞可拮抗鼠伤寒沙门氏菌ATCC14028对Caco - 2细胞表面的黏附，保护细胞膜完整性，这通过测量乳酸脱氢酶（LDH）和碱性磷酸酶（AKP）活性进行评估（P < 0.001，P < 0.001）。而且，富硒A8 - 1可以保护Caco - 2细胞免受脂多糖诱导的炎症，并通过降低细胞因子白细胞介素 - 8（IL - 8）（P = 0.0012，P < 0.001）和肿瘤坏死因子 - α（TNF - α）（P < 0.001，P < 0.001）的表达帮助细胞减轻炎症。基于富硒耐久肠球菌A8 - 1细胞的转录组测序，有485个上调基因和322个下调基因（P < 0.05）。有19个预测的上调基因与潜在的硒代谢途径高度相关，该途径主要涉及膜蛋白对亚硒酸钠的转运，并通过细胞内氧化还原反应逐渐将亚硒酸钠还原为沉积在膜表面的元素硒聚集体。
耐久肠球菌A8 - 1可通过氧化还原途径将细胞外亚硒酸盐转化为细胞内生物SeNPs，具有强大的富硒代谢能力，其生物SeNPs具有抗炎特性，具有开发复合硒纳米材料的潜力，并且可以进一步研究SeNPs的功能以用于潜在应用。
