The Anthelmintic Quassinoids Ailanthone and Bruceine a Induce Infertility in the Model Organism Caenorhabditis elegans by an Apoptosis-like Mechanism Induced in Gonadal and Spermathecal Tissues

Abstract

In continuation of the search for new anthelmintic natural products, the study at hand investigated the nematicidal effects of the two naturally occurring quassinoids ailanthone and bruceine A against the reproductive system of the model nematode Caenorhabditis elegans to pinpoint their anthelmintic mode of action by the application of various microscopic techniques. Differential Interference Contrast (DIC) and the epifluorescence microscopy experiments used in the presented study indicated the genotoxic effects of the tested quassinoids (c ailanthone = 50 µM, c bruceine A = 100 µM) against the nuclei of the investigated gonadal and spermathecal tissues, leaving other morphological key features such as enterocytes or body wall muscle cells unimpaired. In order to gain nanoscopic insight into the morphology of the gonads as well as the considerably smaller spermathecae of C. elegans, an innovative protocol of polyethylene glycol embedding, ultra-sectioning, acridine orange staining, tissue identification by epifluorescence, and subsequent AFM-based ultrastructural data acquisition was applied. This sequence allowed the facile and fast assessment of the impact of quassinoid treatment not only on the gonadal but also on the considerably smaller spermathecal tissues of C. elegans. These first-time ultrastructural investigations on C. elegans gonads and spermathecae by AFM led to the identification of specific quassinoid-induced alterations to the nuclei of the reproductive tissues (e.g., highly condensed chromatin, impaired nuclear membrane morphology, as well as altered nucleolus morphology), altogether implying an apoptosis-like effect of ailanthone and bruceine A on the reproductive tissues of C. elegans.

Natural Products for Drug Discovery in the 21st Century: Innovations for Novel Therapeutics

“…Overall, the many exciting findings newly described [6][7][8][9][10][11][12][13] and reviewed [14][15][16][17] in this Special Issue can confidently lead us to a simple conclusion: natural products have a very bright future in the drug research of the 21st century!…”

“…The contributions to this Special Issue demonstrate the huge potential that NPs continue to possess as hits and leads for developing prospective new drugs. Besides a strong focus on the identification and characterization of many new and very promising biologically active NPs against cancer [6][7][8][9][10], infective/parasitic diseases, including their vectors [9,12,13], and diabetic kidney disease [11], it is worth emphasizing that new approaches and methodologies for NP-related drug research are an important focus of this SI. Thus, new methods to identify new bioactive entities in the complex matrices of extracts using hyphenated analytical techniques in combination with computer-aided data analysis tools (e.g., multivariate statistics, molecular networking) are the focus of several articles [6,7,12] utilizing them successfully to identify new bioactive hits.…”

“…Such techniques provide a holistic evaluation of the active principle(s) in a candidate organism/extract under study in a short time and with little financial effort, so that they are now becoming increasingly important. A new approach to investigating the mechanism of action of bioactive NPs using atomic force microscopy described in the article by Knetzger et al also deserves special mention due to its high development potential [13]. The reviews within this SI [14][15][16][17], finally, provide a comprehensive source of current knowledge on particularly interesting types of NPs and their bioactivity.…”

“…Ailanthone and bruceine A, two degraded triterpenoids of the quassinoid-type known for their anthelminthic activity, were investigated by Knetzger et al [13] for their effects on the reproductive tissues of Caenorhabditis elegans, a model nematode, using a variety of microscopic techniques, including atomic force microscopy. The investigators showed that the quassinoids affected the development of proximal gonads and meiotic germ cells and caused defects in the nematode's spermathecae.…”

Natural products as anthelmintics: safeguarding animal health

“…70 It was also recently reported that 3.31 had an apoptosis-like effect on the reproductive tissues of C. elegans . 71 Such an expansive polypharmacology does not bode well for development of 3.31 as a commercial anthelmintic.…”