Wrońska Anna Katarzyna, Boguś Mieczysława Irena
1Witold Stefański Institute of Parasitology, Polish Academy of Sciences, Twarda 51/55, 00-818 Warsaw, Poland.
BIOMIBO, Ul. Strzygłowska 15, 04-872 Warsaw, Poland.
Cell Biosci. 2019 Mar 25;9:29. doi: 10.1186/s13578-019-0291-1. eCollection 2019.
Although the β-carboline alkaloids harman and norharman are considered as plant metabolites, they can also be secreted by fungi such as the entomopathogen . Norharman and harman are also known to be reversible competitive monamine oxidase inhibitors, which increase serotonin concentrations in tissues. In addition, these alkaloids are able to bind to serotonin receptors, an important immune regulatory molecule in both vertebrates and invertebrates. In insects, serotonin modulates hemocyte phagocytosis, nodule formation and the populations of hemocyte classes. The present study examines whether harman and norharman may influence the phagocytic activity of insect hemocytes by regulating serotonin levels.
Significantly greater serotonin levels and hemocyte phagocytic activity were observed after 24 h of exposure to food contaminated with harman and norharman. Similar responses were noticed 1 h after topical application or addition to in vitro hemocyte cultures. Observations and measurements performed 24 h later revealed decreased responses, suggesting decomposition and/or exertion of alkaloids and/or serotonin. Harman and norharman influenced the activity of plasmatocytes and the granulocyte cytoskeleton. Disturbances in hemocyte network formation, abnormal cell shape, naked nuclei, cell aggregates, fragments of disintegrated cells, interrupted cell membrane continuity and actin condensation in cells were observed.
Our findings may have a considerable impact on research concerning insect physiology, parasitology, immunology and biocontrol of pests. They confirm for the first time that harman and norharman (metabolites of the entomopathogenic fungus ) elevate serotonin levels in hemocytes, thus potentially stimulating their phagocytic activity. Our studies shed light on the mechanisms underlying the interaction between innate insect immune responses and entomopathogen metabolites.
尽管β-咔啉生物碱哈尔满和去甲哈尔满被认为是植物代谢产物，但它们也可由诸如昆虫病原体等真菌分泌。已知去甲哈尔满和哈尔满还是可逆性竞争性单胺氧化酶抑制剂，可增加组织中的血清素浓度。此外，这些生物碱能够与血清素受体结合，血清素是脊椎动物和无脊椎动物中一种重要的免疫调节分子。在昆虫中，血清素可调节血细胞吞噬作用、结节形成以及血细胞类群数量。本研究探讨哈尔满和去甲哈尔满是否可能通过调节血清素水平来影响昆虫血细胞的吞噬活性。
在接触被哈尔满和去甲哈尔满污染的食物24小时后，观察到血清素水平和血细胞吞噬活性显著升高。在局部应用或添加到体外血细胞培养物1小时后也观察到类似反应。24小时后进行的观察和测量显示反应减弱，表明生物碱和/或血清素发生了分解和/或消耗。哈尔满和去甲哈尔满影响了浆细胞的活性和粒细胞细胞骨架。观察到血细胞网络形成紊乱、细胞形状异常、裸核、细胞聚集、细胞解体碎片、细胞膜连续性中断以及细胞内肌动蛋白凝聚。
我们的发现可能对昆虫生理学、寄生虫学、免疫学和害虫生物防治方面的研究产生重大影响。它们首次证实哈尔满和去甲哈尔满（昆虫病原真菌的代谢产物）可提高血细胞中的血清素水平，从而可能刺激其吞噬活性。我们的研究揭示了昆虫先天免疫反应与昆虫病原代谢产物之间相互作用的潜在机制。
