氟暴露对昆虫肠道微生态系统的损害影响

Disruptive effects of fluoride exposure on the insect gut microecosystem

摘要:

目的 探讨氟暴露对模式昆虫家蚕肠道微生态系统的影响，深入解析氟在不同条件下对昆虫宿主的毒害机制。方法 通过测定氟暴露后家蚕肠道组织中多种生理相关酶活性的变化，结合苏木精-伊红(hematoxylin-eosin, HE)染色观察肠道组织的病理学变化。同时，采用16S rRNA基因扩增子测序技术分析肠道菌群的动态变化，并利用实时定量聚合酶链式反应技术检测肠道组织中免疫相关基因的表达变化。结果 氟暴露显著增加了家蚕肠道组织中丙二醛(malondialdehyde, MDA)的含量，降低了还原型谷胱甘肽(glutathione, GSH)水平，并削弱了过氧化氢酶(catalase, CAT)、超氧化物歧化酶(superoxide dismutase, SOD)、乙酰胆碱酯酶(acetylcholinesterase, AChE)、羧酸酯酶(carboxylesterase, CarE)、碱性磷酸酶(alkaline phosphatase, AKP/ALP)和乳酸脱氢酶(lactate dehydrogenase, LDH)等的活性；此外，肠道上皮细胞碎裂，细胞与基底膜分离。Toll免疫调节途径受到抑制，导致抗菌肽蛋白基因(如attacin、cecropin、lebocin和lysozyme)的表达显著下降。肠道菌群分析显示，谷氨酸杆菌(Glutamicibacter)、葡萄球菌(Staphylococcus)、不动杆菌(Acinetobacter)和甲基杆菌(Methylobacterium)的相对丰度显著减少，且菌群结构发生显著异质性变化。菌群功能预测显示，其代谢途径(metabolic pathways)和次级代谢物生物合成(biosynthesis of secondary metabolites)功能明显增强。结论 氟暴露显著削弱昆虫宿主的抗氧化能力、基础代谢和免疫功能，损害肠道组织的结构完整性，并导致肠道菌群失衡。这种对肠道微生态系统稳态的破坏可能是引发昆虫物种多样性降低和生物量减少的重要原因。

Abstract:

Objective To investigate the effects of fluoride exposure on the gut microecosystem of the model insect Bombyx mori and elucidate the toxic mechanisms of fluoride under different conditions on insect hosts.Methods We measured physiological enzyme activity changes in the gut tissue of B. mori following fluoride exposure and observed histopathological changes by using hematoxylin and eosin (HE) staining. We also analyzed the dynamic changes in gut microbiota by using 16S rRNA amplicon sequencing and examined the expression changes of immune-related genes in gut tissue by qPCR.Results Fluoride exposure significantly increased the malondialdehyde (MDA) level and decreased the reduced glutathione (GSH) level in the gut tissue. Enzyme activities of catalase (CAT), superoxide dismutase (SOD), acetylcholinesterase (AChE), carboxylesterase (CarE), alkaline phosphatase (AKP/ALP), and lactate dehydrogenase (LDH) were also markedly suppressed. Additionally, we observed epithelial cell rupture and separation from the basement membrane. The Toll immune pathway was inhibited, which resulted in significantly reduced expression of antimicrobial peptide genes, such as attacin, cecropin, lebocin, and lysozyme. Gut microbiota analysis revealed significant declines in the relative abundances of Glutamicibacter, Staphylococcus, Acinetobacter, and Methylobacterium. The gut microbiota exhibited notable structural heterogeneity with strengthened functions related to metabolic pathways and biosynthesis of secondary metabolites.Conclusion Fluoride exposure significantly weakened the host insect’s antioxidant capacity, basal metabolism, and immune function, damaged the integrity of gut tissue, and caused gut microbiota dysbiosis. This disruption of the gut microecosystem might be a major factor contributing to reduced insect species diversity and biomass.