The insect, Galleria mellonella, is a compatible model for evaluating the toxicology of okadaic acid

Abstract

The polyether toxin, okadaic acid, causes diarrhetic shellfish poisoning in humans. Despite extensive research into its cellular targets using rodent models, we know little about its putative effect(s) on innate immunity. We inoculated larvae of the greater wax moth, Galleria mellonella, with physiologically relevant doses of okadaic acid by direct injection into the haemocoel (body cavity) and/or gavage (force-feeding). We monitored larval survival and employed a range of cellular and biochemical assays to assess the potential harmful effects of okadaic acid. Okadaic acid at concentrations ≥ 75 ng/larva (≥ 242 μg/kg) led to significant reductions in larval survival (> 65%) and circulating haemocyte (blood cell) numbers (> 50%) within 24 h post-inoculation. In the haemolymph, okadaic acid reduced haemocyte viability and increased phenoloxidase activities. In the midgut, okadaic acid induced oxidative damage as determined by increases in superoxide dismutase activity and levels of malondialdehyde (i.e. lipid peroxidation). Our observations of insect larvae correspond broadly to data published using rodent models of shellfish-poisoning toxidrome, including complementary LD 50 values: 206–242 μg/kg in mice, ~ 239 μg/kg in G . mellonella . These data support the use of this insect as a surrogate model for the investigation of marine toxins, which offers distinct ethical and financial incentives. Electronic supplementary material The online version of this article (10.1007/s10565-018-09448-2) contains supplementary material, which is available to authorized users.

Boric acid‐induced immunotoxicity and genotoxicity in model insectGalleria mellonellaL. (Lepidoptera: Pyralidae)

“…Arguably, the observed suppression of cell viability in our study is a viable explanation for the decrement in the circulating THC in G. mellonella larvae. Consistent with our findings, recent studies about the effects of several insecticides on the hemocyte numbers of G. mellonella larvae have reported similar findings (Coates et al, 2018;Er et al, 2017;Kurt & Kayis, 2015;Yücel & Kayis, 2018).…”

“…Arguably, the observed suppression of cell viability in our study is a viable explanation for the decrement in the circulating THC in G. mellonella larvae. Consistent with our findings, recent studies about the effects of several insecticides on the hemocyte numbers of G. mellonella larvae have reported similar findings (Coates et al, ; Er et al, ; Kurt & Kayis, ; Yücel & Kayis, 2018). Interestingly, despite the observed decrease in THC, no significant change in hemocyte mitotic indices were observed following BA administration in this study, although, studies in literature reported that boron inhibited cell proliferation by inhibition of mitosis (Fail et al, ; Ying et al, ).…”

“…Besides altering the DHC, BA elicited a drastic decrease in the THC and cell viability while increasing the ratio of apoptotic and necrotic cells in force‐fed G. mellonella larvae. It is well known that cell death pathways as apoptosis and necrosis post infection aids pathogen or xenobiotic elimination (Altuntaş et al, ; Coates et al, ; Lavine & Strand, ; Wu et al, ) and also helps in the elimination of immunocompetent cells (Cho & Kim, ). Post BA administration we observed that the number of dead cells increased with increasing BA concentrations with a 50% hemocyte mortality noted at LC 70 .…”

Indomethacin-induced gut damage in a surrogate insect model, Galleria mellonella

“…When screening common food preservatives (e.g., potassium nitrate), Maguire et al (2016) obtained comparable toxicology data (LD 50 ) between insect larvae, human cell lines (HEp-2) and rats. We recently provided evidence that larvae can also be used to assess the lethality and putative immune-toxicological effects of shellfish poisoning toxins (e.g., okadaic acid) at FDA-regulated levels in contaminated foods (Coates et al 2019). Okadaic acid that was force-fed to insects disrupted midgut homeostasis, leading to detrimental levels of lipid peroxidation (malondialdehyde accumulation) in a dose-dependent manner-resembling symptoms found often in the standardised mouse bioassay.…”

“…One such in vivo alternative is the larvae of the greater wax-moth, Galleria mellonella. These insects are now used widespread as 'mini-hosts' for the investigation of microbial pathogenicity (Mowlds et al 2010;Kloezen et al 2015;Lim et al 2018;Cools et al 2019), screening of xenobiotics/toxins (Allegra et al 2018;Coates et al 2019) and functional characterisation of virulence factors (Altincicek et al 2007;Champion et al 2016). Larvae of G. mellonella are designated a non-animal technology (Allegra et al 2018), which means there are fewer ethical restrictions and regulations compared to vertebrates.…”