Innovative and Future Applications for Ecdysteroids

Abstract

We review the current and potential importance and applications of ecdysteroids in the areas of agriculture, medicine and ecotoxicology. Since ecdysteroids are not only the steroid hormones of arthropods (and probably other invertbrate groups), but also have significant pharmaceutical effects on vertebrates, man's use of ecdysteroid agonists and antagonists (steroidal or non-steroidal) could potentially have considerable impact upon human health and the environment. The challenge is to maximise the benefits, while minimising the potential negative impacts. As agrochemicals, ecdysteroids themselves have little potential as exogenous pest control agents, but the many analogues are highly useful for determining the structural and spatial requirements for binding to nuclear and taste receptors and elevation of phytoecdysteroid levels in selected plant species could provide an environmentally benign approach to protect crop species against phytophagous predators (insects and nematodes). We briefly summarise the many attributed positive pharmaceutical effects of ecdysteroids in vertebrates (especially humans) and critically assess the reports associating ecdysteroids with cancer and embryotoxicity and the probable use of ecdysteroids as doping substances for athletes. We stress the need for much more extensive research into the metabolism and mode of action of ecdysteroids particularly in mammals. The presence of natural and, increasingly, man-made ecdysteroid agonists and antagonists may have considerable impact on the environment. On the one hand, non-steroidal (ant)agonists offer considerable promise as environmentally friendlier, more selective pesticides, but, on the other hand, could become endocrine disruptors of non-target species, especially in aquatic ecosystems. We consider in some depth the development of strategies for the identification and environmental monitoring of potential endocrine disruptors affecting ecdysteroid hormonal systems in invertebrates and emphasise the overwhelming need for basic research into the endocrinology of aquatic invertebrates which would be suitable as signal species.R. Lafont ( ) and L. Dinan

The Karlson Lecture. Phytoecdysteroids: What use are they?

“…The vast majority of insects appear to be susceptible to high doses of ecdysteroids and most succumb when exposed to low to moderate doses. However, the application of very low doses has proven beneficial to improve the synchrony of development and yield of certain commercially important arthropods (Dinan et al, 2008;Lafont and Dinan, 2009). The most extensively studied examples are silkmoths (especially Bombyx mori), where protocols have been developed for the preparation of ecdysteroidcontaining extracts from native plants and application to the food plant (Morus spp.)…”

Ecdysteroid hormone action

“…In addition, in two recent reviews, the impact of phytoecdysteroids on humans is summarised [120,121]. We therefore concentrate on recent developments.…”

Dietary Phytoecdysteroids

“…The two ecdysteroids did not have sex hormonal or, interestingly in the context of more recent studies, anti-inflammatory or anabolic effects in rats. El Mofty et al (1987 have claimed that E is carcinogenic to toads and mice, but the certainty of these findings has been questioned (Sláma and Lafont 1995;Lafont and Dinan 2009) on the basis of the low doses used, relative to the amounts of ecdysteroids expected in the animals' normal diets. Neves et al (2016) believe that 20-hydroxyecdyonse is genotoxic in a rat bone marrow micronuclei assay and an Allium cepa (onion) cell abnormality assay.…”

“…As indicated above, the toxicity and safety data for 20E and the few other ecdysteroid analogues which have been in any way assessed do not indicate that dietary or environmental contact would have negative impacts on mammals. However, significant releases of ecdysteroids into the environment, either as a by-product of the isolation of large amounts of 20E for pharmaceutical/nutraceutical purposes or as the consequence of excretion of 20E or its metabolites by those taking doses (probably 0.5-5 g/person/day) for medical, health, or aesthetic reasons, might have serious detrimental effects on arthropods and other invertebrates, with aquatic insects and crustaceans being particularly susceptible if waste water and sewage are not appropriately treated before it enters natural water courses (Lafont and Dinan 2009). It will be necessary to determine the extent to which ecdysteroids are subjected to microbial degradation in passing through a sewage works and whether they can be readily removed from purified water by adsorption onto charcoal or reverse-phase materials.…”