Hydra, a candidate for an alternative model in environmental genomics

Application of organoid technology in the human health risk assessment of microplastics: A review of progresses and challenges

Microplastic (MP) pollution has become a global environmental issue, and increasing concern has been raised about its impact on human health. Current studies on the toxic effects and mechanisms of MPs have mostly been conducted in animal models or in vitro cell cultures, which have limitations regarding inter-species differences or stimulation of cellular functions. Organoid technology derived from human pluripotent or adult stem cells has broader prospects for predicting the potential health risks of MPs to humans. Herein, we reviewed the current application advancements and opportunities for different organoids, including brain, retinal, intestinal, liver, and lung organoids, to assess the human health risks of MPs. Organoid techniques accurately simulate the complex processes of MPs and reflect phenotypes related to diseases caused by MPs such as liver fibrosis, neurodegeneration, impaired intestinal barrier and cardiac hypertrophy. Future perspectives were also proposed for technological innovation in human risk assessment of MPs using organoids, including extending the lifespan of organoids to assess the chronic toxicity of MPs, and reconstructing multi-organ interactions to explore their potential in studying the microbiome-gut-brainaxis effect of MPs.

Sensitivity of Hydra vulgaris to Nanosilver for Environmental Applications

Nanosilver applications, including sensing and water treatment, have significantly increased in recent years, although safety for humans and the environment is still under debate. Here, we tested the environmental safety of a novel formulation of silver nanoparticles functionalized with citrate and L-cysteine (AgNPcitLcys) on freshwater cnidarian Hydra vulgaris as an emerging ecotoxicological model for the safety of engineered nanomaterials. AgNPcitLcys behavior was characterized by dynamic light scattering (DLS), while Ag release was measured by inductively coupled plasma mass spectrometry (ICP-MS). H. vulgaris (n = 12) subjects were evaluated for morphological aberration after 96 h of exposure and regeneration ability after 96 h and 7 days of exposure, after which the predatory ability was also assessed. The results show a low dissolution of AgNPcitLcys in Hydra medium (max 0.146% of nominal AgNPcitLcys concentration) and highlight a lack of ecotoxicological effects, both on morphology and regeneration, confirming the protective role of the double coating against AgNP biological effects. Predatory ability evaluation suggests a mild impairment of the entangling capacity or of the functionality of the tentacles, as the number of preys killed but not ingested was higher than the controls in all exposed animals. While their long-term sub-lethal effects still need to be further evaluated on H. vulgaris, AgNPcitLcys appears to be a promising tool for environmental applications, for instance, for water treatment and sensing.

A systematic review on toxicity assessment of persistent emerging pollutants (EPs) and associated microplastics (MPs) in the environment using the Hydra animal model

Emerging pollutants (EPs) are causative for teratogenic and reproductive effects. EPs are detected in all the environmental matrices at higher levels. A suitable model for aquatic toxicity assessment is Hydra, because of morphological, behavioral, reproductive (sexual and asexual), and biochemical changes. Many researchers have used Hydra for toxicity assessment of organic chemicals (BPA), heavy metals, pharmaceuticals, nanomaterials and microplastics. Various Hydra species were used for environmental toxicity studies; however H. magnipapillata was predominantly used due to the availability of its genome and proteome sequences. Teratogenic and reproductive changes in Hydra are species specific. Teratogenic effects were studied using sterozoom dissecting microscope, acridine orange (AO) and 4',6-diamidino-2-phenylindole (DPAI) staining. Reactive oxygen species (ROS) generation by EPs had been understood by the Dichlorodihydrofluorescein Diacetate (DCFDA) staining and comet assay. Multiple advanced techniques would aid to understand the effects at molecular level, such as real-time PCR, rapid amplification of cDNA end- PCR. EPs modulated the major antioxidant enzyme levels, therefore, defense mechanism was affected by the higher generation of reactive oxygen species. Genome sequencing helps to know the mode of action of pollutants, role of enzymes in detoxification, defense genes and stress responsive genes. Molecular techniques were used to obtain the information for evolutionary changes of genes and modulation of gene expression by EPs.

Fluoxetine in the environment may interfere with the neurotransmission or endocrine systems of aquatic animals

Antidepressants are extensively used to treat the symptoms of depression in humans, and the environmentally discharged drugs potentially threaten aquatic organisms. In this study, the acute toxic effects of fluoxetine (FLX) were investigated in two aquatic organisms, the freshwater polyp (Hydra magnipapillata) and Javanese medaka (Oryzias javanicus). The median lethal concentration (LC₅₀) of FLX in H. magnipapillata was 3.678, 3.082, and 2.901 mg/L after 24, 48, and 72 h, respectively. Morphological observations of the FLX-exposed H. magnipapillata showed that 1.5 mg/L FLX induced the contraction of the tentacles and body column. The LC₅₀ of FLX in O. javanicus was 2.046, 1.936, 1.532, and 1.237 mg/L after 24, 48, 72, and 96 h, respectively. Observation of the behavior of the FLX-exposed fish showed that FLX reduced their swimming performance at a minimum concentration of 10 µg/L. The half-maximal effective concentration (EC₅₀) of FLX for swimming behavior in O. javanicus was 0.135, 0.108, and 0.011 mg/L after 12, 24, and 96 h, respectively. Transcriptomic analyses indicated that FLX affects various physiological and metabolic processes in both species. FLX exposure induced oxidative stress, reproductive deficiency, abnormal pattern formation, DNA damage, and neurotransmission disturbance in H. magnipapillata, whereas it adversely affected O. javanicus by inducing oxidative stress, DNA damage, endoplasmic reticulum stress, and mRNA instability. Neurotransmission-based behavioral changes and endocrine disruption were strongly suspected in the FLX-exposed fish. These results suggest that FLX affects the behavior and metabolic regulation of aquatic organisms.

Chronic exposure of Brown (Hydra oligactis) and green Hydra (Hydra viridissima) to environmentally relevant concentrations of pharmaceuticals

Low concentrations of pharmaceuticals in the environment (ng/L to μg/L) are an environmental concern. We used the invertebrates, Hydra oligactis and Hydra viridissima, as freshwater models for primary toxicity testing to study effects of chronic low concentrations of pharmaceuticals in the environment. H. oligactis were exposed to three concentrations (0.1, 1.0 and 10 μg/L) of either fluoxetine, carbamazepine, or triclosan; H. viridissima were exposed to three concentrations (0.1, 1.0 and 10 μg/L) of triclosan. Ecologically relevant endpoints including morphology, budding rate, feeding behaviour, and regenerative capacity were examined during the 14 days exposure period. The interstitial:epithelial stem cell ratios was also examined in H. oligactis. There were no significant effects on the morphology, budding rate and feeding behaviour of the H. oligactis across all concentrations of fluoxetine, carbamazepine, and triclosan. However, regenerative capacity significantly decreased in comparison to the controls when H. oligactis was exposed to 10 μg/L of triclosan and fluoxetine, although there was no significant difference when exposed to carbamazepine. Neither fluoxetine nor carbamazepine treatment altered stem cell ratios. Exposure to triclosan at any concentration did not impact H. viridissima morphology, budding rate, regeneration or feeding behaviour. These results show there are limited effects in Hydra after exposure to chronic, low concentrations of fluoxetine, carbamazepine, and triclosan, except for regeneration in H. oligactis. These endpoints can be used effectively (and cost effectively) to study the effects of environmentally relevant concentrations of pharmaceuticals in Hydra species.

Transcriptomic profiling of Hydra magnipapillata after exposure to naproxen

The extensive use in humans and animals of nonsteroidal anti-inflammatory drugs (NSAIDs) increases their possible impact on aquatic organisms. In the present study, we investigated acute toxicity, morphological responses, and potential physiological and metabolic impacts of naproxen exposure on Hydra magnipapillata. The median lethal concentrations (LC₅₀) of naproxen in H. magnipapillata were 51.999 mg/L, 44.935 mg/L, and 42.500 mg/L after exposure for 24, 48, and 72 h, respectively. Morphological observation of the exposed Hydra showed that 40 mg/L naproxen stimulated the contraction of body column and tentacles after 24 h. A KEGG pathway analysis of the genes differentially expressed in the Hydra after exposure to naproxen for 6, 24, or 48 h demonstrated various cellular and metabolic effects, including protein processing in the endoplasmic reticulum, Wnt signaling, and tryptophan metabolism. These results suggest that exposure to naproxen affects the genetic material, inflammatory processes, and metabolic processes of aquatic organisms.

Reduction in Toxicity of Nano-Ag-Polyvinyl-pyrrolidone Using Hydra Proteins and Peptides during Zebrafish Embryogenesis

Hydra magnipapillata cells reduce the toxicity of silver nanomaterials to zebrafish (Danio rerio) embryos. In this study, we investigated whether Hydra protein (HP) and Hydra basal disc peptide (Hym176) materials reduce nano-Ag-polyvinylpyrrolidone (N-Ag-PVP) toxicity during embryogenesis of the nanosensitive organism zebrafish. Protein (HP) was extracted from Hydra, and peptide (Hym176) was extracted from the hydra basal disc, which is attractive to nanomaterials and related to the immune system. The experimental conditions were exposure to N-Ag-PVP, HP, N-Ag-PVP+HP, Hym176, or N-Ag-PVP+Hym176 during embryo development. N-Ag-PVP+HP group showed lower toxicity than N-Ag-PVP group. In addition, in the N-Ag-PVP+HP group formed aggregated nanomaterials (≥200 nm size) through electrostatic bonding. In the gene expression profile, HP group differed in gene expression profile compared the other experimental groups and it was no genetic toxicity. HP showed a tendency to reduce side effects and abnormal gene expression produced by N-Ag-PVP with no evidence of inherent toxicity. Considering the potential nanotoxicity effects of released nanomaterials on the ecosystem, the reduction of nanotoxicity observed with HP natural materials should be regarded with great interest in terms of the overall health of the ecosystem.

A simple and rapid method for toxicity evaluation of zinc oxide nanoparticle (ZnO NPs) in benthic animal Hydra magnipapillata

Toxicity evaluation is necessary to investigate the possible risk of chemical or pollutants newly produced such as nanoparticles in the environments. The assessment should apply a method that is effective to determine the toxic concentration and the exposure time of the pollutants in an animal model. This study described three main stages including determining the median lethal concentrations (LC50) with Probit program and detecting toxic effects of ZnO NPs in morphology and regeneration observed by the changes in morphology of Hydra magnipapillata (H. magnipapillata). We also provide a strategy for culturing hydra in laboratory condition to use the animal for the experiment. The exposure to ZnO NPs led to the abnormality in regeneration such as formation of extraordinary number of tentacles and bifurcated tips in tentacles and the toxic effects in morphology appeared the clubbing tentacle, slender body, and retracting body column and tentacles by the exposure time. The method described here is simple and useful to evaluate the toxic effects of ZnO NPs using morphological characters in H. magnipapillata and could suggest the concentration and the exposure time for further investigations on cellular and molecular responses of the animal after exposure to other nanoparticles. •A simple method to evaluate the toxic effects of ZnO NPs using morphological characters of H. magnipapillata and other hydra species.•A rapid method to evaluate the toxic effects of ZnO NPs and other nanoparticles in H. magnipapillata.

Acute toxic effects of zinc oxide nanoparticles on Hydra magnipapillata

Zinc oxide nanoparticles (ZnO NPs) are increasingly used in various products as coating and additive materials for household goods, personal-care products, and drug delivery systems. Because of their broad applications, the potential risks to nontarget organisms associated with their input into aquatic environments have generated much concern. We investigated the acute toxicity, morphological responses, and potential impact on physiology and metabolism in polyps exposed to spherical ZnO NPs of either 20 nm (ZnO NP₂₀) or 100 nm (ZnO NP₁₀₀). The median lethal concentrations (LC₅₀) of ZnO NP₂₀ were 55.3, 8.7, and 7.0 μg/mL after exposure for 48, 72, and 96 h, respectively; and those of ZnO NP₁₀₀ were 262.0, 14.9, and 9.9 μg/mL, respectively. The morphological responses of the hydra polyps to a range of ZnO NP concentrations suggest that ZnO NPs may negatively affect neurotransmission in Hydra. ZnO NPs may also induce abnormal regeneration in the polyps by affecting the expression of several genes related to the Wnt signaling pathway. The presence of ZnO NP₂₀ in the hydra tissue was confirmed with electron microscopy. A Gene Ontology analysis of the genes differentially expressed in hydra polyps after exposure to ZnO NP₂₀ for 12 or 24 h revealed changes in various processes, including cellular and metabolic process, stress response, developmental process, and signaling. A KEGG pathway analysis of hydra polyps after exposure of ZnO NP₂₀ or ZnO NP₁₀₀ for 12 or 24 h demonstrated various changes, including in the DNA replication and repair, endocytosis, lysosomes, Wnt signaling, and natural killer-cell-mediated cytotoxicity pathways, suggesting the mechanisms that maintain cellular homeostasis in response to ZnO NPs. Progesterone-mediated oocyte maturation was also affected by the ZnO NPs nanoparticles, suggesting that they are potential endocrine disruptors. This study should increase our concern regarding the dispersal of ZnO NPs in aquatic environments.