Department of Preventive Medicine and Biostatistics, Uniformed Services University, Bethesda, MD, USA.
Center for Global Health, University of New Mexico Health Sciences Center, Albuquerque, NM, USA.
Parasit Vectors. 2022 May 28;15(1):183. doi: 10.1186/s13071-022-05307-6.
Yeast-encapsulated orange oil (YEOO) is a novel, ingestible larvicide that combines the benefits of a low-cost essential oil with yeast, an attractive food source for mosquito larvae. In this work, we investigated the underlying mechanisms of action associated with YEOO ingestion by Aedes aegypti larvae.
Aedes aegypti third-stage larvae (L3) were treated with sublethal or lethal concentrations of YEOO. Genes associated with apoptosis, autophagy and innate immune responses were investigated by RT-qPCR in guts and carcasses dissected from treated and control larvae. Differential expression of cytochrome P450 genes in the CYP6 and CYP9 families were also investigated. Confocal and transmission electron microscopy were used to assess damage caused by YEOO throughout the larval alimentary canal. TUNEL was used to assess apoptosis via DNA fragmentation.
The apoptosis genes IAP1 and IAP2 in larvae displayed opposing effects following exposure to lethal doses of YEOO, with a 26-fold induction of IAP1 at 8 h post YEOO ingestion. The effector caspase CASPS8 displayed a 6.7-fold induction in the gut and concomitant 70-fold induction in the carcass at 8 h post YEOO ingestion. The midgut epithelia regenerator, Vein, had an 11-fold induction in the gut after 4 h and was repressed 7.6-fold in the carcass at 24 h. Sublethal concentrations (< LC) led to significant differential expression of CYP6 and CYP9 genes. Midgut epithelial damage was highlighted by the destruction of microvilli, vacuolization of midgut cells and damage to cell junctions and basal lamina as early as 30 min. Larval type 2 peritrophic matrix structural integrity and porosity remain unchanged.
Our results strongly suggest that the robust larvicidal activity of YEOO is due to a generalized broad-acting mechanism combining epithelial damage and apoptosis, with concomitant expression of multiple innate response genes involved in epithelial regeneration and detoxification. YEOO's amenability for use as part of an integrated vector management program makes this novel larvicide a practical approach for mosquito larval control in the future.
酵母包封的橙油（YEOO）是一种新型的可食用杀幼虫剂，它结合了低成本精油和酵母的优点，而酵母是蚊子幼虫的一种有吸引力的食物来源。在这项工作中，我们研究了 YEOO 被埃及伊蚊幼虫摄入的相关作用机制。
用亚致死或致死浓度的 YEOO 处理埃及伊蚊三龄幼虫（L3）。通过 RT-qPCR 研究与凋亡、自噬和先天免疫反应相关的基因，对处理和对照幼虫的肠道和尸体进行分析。还研究了 CYP6 和 CYP9 家族中细胞色素 P450 基因的差异表达。利用共聚焦和透射电子显微镜评估 YEOO 对整个幼虫消化道造成的损伤。通过 DNA 片段化的 TUNEL 评估凋亡。
在摄入致死剂量的 YEOO 后，幼虫中的凋亡基因 IAP1 和 IAP2 表现出相反的作用，IAP1 在 YEOO 摄入后 8 小时诱导了 26 倍。效应半胱天冬酶 CASPS8 在肠道中的诱导倍数为 6.7 倍，在尸体中的诱导倍数为 8 小时时为 70 倍。中肠上皮再生因子 Vein 在摄入 YEOO 后 4 小时在肠道中诱导了 11 倍，而在 24 小时时在尸体中抑制了 7.6 倍。亚致死浓度（<LC）导致 CYP6 和 CYP9 基因的显著差异表达。早在 30 分钟，微绒毛的破坏、中肠细胞的空泡化以及细胞连接和基底膜的损伤就突出了中肠上皮的损伤。幼虫型 2 型围食膜结构完整性和孔隙率保持不变。
我们的结果强烈表明，YEOO 强大的杀幼虫活性是由于一种广泛作用的机制，结合了上皮损伤和凋亡，同时表达了多个参与上皮再生和解毒的先天反应基因。YEOO 易于用作综合病媒管理计划的一部分，这使得这种新型杀幼虫剂成为未来蚊子幼虫控制的一种实用方法。
