Multigenerational consequences of early-life cannabinoid exposure in zebrafish

Phytocannabinoids in neuromodulation: From omics to epigenetics

BACKGROUND

Recent developments in metabolomics, transcriptomic and epigenetics open up new horizons regarding the pharmacological understanding of phytocannabinoids as neuromodulators in treating anxiety, depression, epilepsy, Alzheimer's, Parkinson's disease and autism.

METHODS

The present review is an extensive search in public databases, such as Google Scholar, Scopus, the Web of Science, and PubMed, to collect all the literature about the neurobiological roles of cannabis extract, cannabidiol, 9-tetrahydrocannabinol specially focused on metabolomics, transcriptomic, epigenetic, mechanism of action, in different cell lines, induced animal models and clinical trials. We used bioinformatics, network pharmacology and enrichment analysis to understand the effect of phytocannabinoids in neuromodulation.

RESULTS

Cannabidomics studies show wide variability of metabolites across different strains and varieties, which determine their medicinal and abusive usage, which is very important for its quality control and regulation. CB receptors interact with other compounds besides cannabidiol and Δ9-tetrahydrocannabinol, like cannabinol and Δ8-tetrahydrocannabinol. Phytocannabinoids interact with cannabinoid and non-cannabinoid receptors (GPCR, ion channels, and PPAR) to improve various neurodegenerative diseases. However, its abuse because of THC is also a problem found across different epigenetic and transcriptomic studies. Network enrichment analysis shows CNR1 expression in the brain and its interacting genes involve different pathways such as Rap1 signalling, dopaminergic synapse, and relaxin signalling. CBD protects against diseases like epilepsy, depression, and Parkinson's by modifying DNA and mitochondrial DNA in the hippocampus. Network pharmacology analysis of 8 phytocannabinoids revealed an interaction with 10 (out of 60) targets related to neurodegenerative diseases, with enrichment of ErbB and PI3K-Akt signalling pathways which helps in ameliorating neuro-inflammation in various neurodegenerative diseases. The effects of phytocannabinoids vary across sex, disease state, and age which suggests the importance of a personalized medicine approach for better success.

CONCLUSIONS

Phytocannabinoids present a range of promising neuromodulatory effects. It holds promise if utilized in a strategic way towards personalized neuropsychiatric treatment. However, just like any drug irrational usage may lead to unforeseen negative effects. Exploring neuro-epigenetics and systems pharmacology of major and minor phytocannabinoid combinations can lead to success.

A latest progress in the study of fish behavior: cross-generational effects of behavior under pollution pressure and new technologies for behavior monitoring

With the development of agriculture and industry, an increasing number of pollutants are being discharged into the aquatic environment. These pollutants can harm aquatic life. The behavioral characteristics of animals are an external manifestation of their internal mechanisms. Changes in behavior reflect damage and changes in the internal mechanisms. Environmental pollution may lead to behavioral changes not only in the parental generation but also in the offspring that has not been exposed to the pollutants. That is, the intrinsic mechanism that leads to behavioral changes is inheritable. Fish are representative species of aquatic organisms and are commonly used in various research studies. The behavior of fish has also received extensive attention, and the monitoring technology for fish behavior has developed rapidly. This article summarizes the development process of behavior monitoring technology and introduces some of the latest technologies for studying fish behavior. This article also summarizes the intergenerational effects of pollutants on fish behavior, as well as the potential intrinsic and genetic mechanisms that may lead to behavioral changes. This article provides a reference for future relevant neurobehavioral studies.

Zebrafish as an Animal Model in Cannabinoid Research

Cannabinoids are active substances present in plants of the Cannabis genus. Both the Food and Drug Administration (FDA) and European Medicines Agency (EMA) have approved several medicinal products containing natural cannabinoids or their synthetic derivatives for the treatment of drug-resistant epilepsy, nausea and vomiting associated with cancer chemotherapy, anorexia in AIDS patients, and the alleviation of symptoms in patients with multiple sclerosis. In fact, cannabinoids constitute a broad group of molecules with a possible therapeutic potential that could be used in the management of much more diseases than mentioned above; therefore, multiple preclinical and clinical studies on cannabinoids have been carried out in recent years. Danio rerio (zebrafish) is an animal model that has gained more attention lately due to its numerous advantages, including easy and fast reproduction, the significant similarity of the zebrafish genome to the human one, simplicity of genetic modifications, and body transparency during the early stages of development. A number of studies have confirmed the usefulness of this model in toxicological research, experiments related to the impact of early life exposure to xenobiotics, modeling various diseases, and screening tests to detect active substances with promising biological activity. The present paper focuses on the current knowledge of the endocannabinoid system in the zebrafish model, and it summarizes the results and observations from studies investigating the pharmacological effects of natural and synthetic cannabinoids that were carried out in Danio rerio. The presented data support the notion that the zebrafish model is a suitable animal model for use in cannabinoid research.

Review of the oral toxicity of cannabidiol (CBD)

Information in the published literature indicates that consumption of CBD can result in developmental and reproductive toxicity and hepatotoxicity outcomes in animal models. The trend of CBD-induced male reproductive toxicity has been observed in phylogenetically disparate organisms, from invertebrates to non-human primates. CBD has also been shown to inhibit various cytochrome P450 enzymes and certain efflux transporters, resulting in the potential for drug-drug interactions and cellular accumulation of xenobiotics that are normally transported out of the cell. The mechanisms of CBD-mediated toxicity are not fully understood, but they may involve disruption of critical metabolic pathways and liver enzyme functions, receptor-specific binding activity, disruption of testosterone steroidogenesis, inhibition of reuptake and degradation of endocannabinoids, and the triggering of oxidative stress. The toxicological profile of CBD raises safety concerns, especially for long term consumption by the general population.

Fluoxetine and Curcumin Prevent the Alterations in Locomotor and Exploratory Activities and Social Interaction Elicited by Immunoinflammatory Activation in Zebrafish: Involvement of BDNF and Proinflammatory Cytokines

The increase in proinflammatory cytokine expression causes behavioral changes consistent with sickness behavior, and this led to the suggestion that depression might be a psychoneuroimmunological phenomenon. Here, we evaluated the effects of the pretreatment with fluoxetine (10 mg/kg, i.p.) and curcumin (0.5 mg/kg, i.p.) on the immune response elicited by the inoculation of an Aeromonas hydrophila bacterin in zebrafish. Non-pretreated but A. hydrophila-inoculated and sham-inoculated groups of fish served as controls. The social preference, locomotor, exploratory activities, and cerebral expression of il1b, il6, tnfa, and bdnf mRNA were compared among the groups. Behavioral changes characteristic of sickness behavior and a significant increase in the expression of il1b and il6 cytokines were found in fish from the immunostimulated group. The behavioral alterations caused by the inflammatory process were different between males and females, which was coincident with the increased expression of cerebral BDNF. Fluoxetine and curcumin prevented the sickness behavior induced by A. hydrophila and the increased expression of proinflammatory cytokines. Our results point to the potential of zebrafish as a translational model in studies related to neuroinflammation and demonstrate for the first time the effects of fluoxetine and curcumin on zebrafish sickness behavior.

Cannabinoid receptor 2 (Cb2r) mediates cannabinol (CBN) induced developmental defects in zebrafish

Of the three primary cannabinoids in cannabis: Δ⁹-Tetrahydrocannabinol (Δ⁹-THC), cannabidiol (CBD) and cannabinol (CBN), very little is known about the actions of CBN, the primary oxidative metabolite of THC. Our goal was to determine if CBN exposure during gastrulation alters embryonic development, and if so, does it act via the canonical cannabinoid receptors. Zebrafish embryos were exposed to CBN during gastrulation and exhibited dose-dependent malformations, increased mortality, decreased locomotion and a reduction in motor neuron branching. Moreover, larva showed a significant reduction in the response to sound stimuli. CBN exposure altered the development of hair cells associated with otic vesicles and the lateral line. Pharmacological block of Cb2rs with AM 630 or JTE 907 prevented many of the CBN-induced developmental defects, while block of Cb1rs with AM 251 or CP 945598 had little or no effect. Altogether we show that embryonic exposure to CBN results in alterations in embryonic growth, neuronal and hair cell development, physiology and behavior via Cb2r-mediated mechanisms.

Cannabidiol impairs neural tube closure in mouse whole embryo culture

BACKGROUND

Cannabidiol (CBD) is a nonpsychoactive constituent of cannabis widely available as a dietary supplement. Previous reports that it impairs the retinoid, sonic hedgehog, and folate metabolism pathways raise concern that it may impair closure of the embryonic neural tube (NT), producing NT defects including spina bifida and exencephaly.

METHODS

We undertook teratogenicity testing of CBD in mouse whole embryo culture.

RESULTS

At concentrations that do not diminish embryo viability, growth, or axial rotation, CBD dose-dependently impairs cranial NT closure, increasing the proportion of embryos that develop exencephaly. It concomitantly diminishes closure of the spinal NT, the posterior neuropore (PNP), producing longer neuropores at the end of culture which is a hallmark of spina bifida risk. Exposure to CBD does not disrupt the formation of long F-actin cables in surface ectoderm cells flanking the PNP or folding of the neuroepithelium at predictable hinge points. At the cellular level, CBD exposure does not alter proliferation or apoptosis of the spinal neuroepithelium.

DISCUSSION

Thus, CBD acts selectively as a neuroteratogen predisposing to spina bifida and exencephaly in mouse whole embryo culture at exposure levels not associated with overt toxicity. Large-scale testing of CBD's effects on NT closure, particularly in at-risk groups, is warranted to inform its marketing to women of childbearing age.

Cannabidiol improves Nile tilapia cichlid fish welfare

Cannabidiol (CBD) is a substance derived from Cannabis sativa, widely studied in medicine for controlling neural diseases in humans. Besides the positive effects on humans, it also presents anxiolytic proprieties and decreases aggressiveness and stress in mammals. Therefore, CBD has the potential to increase welfare in reared animals, as it seems to reduce negative states commonly experienced in artificial environments. Here, we tested the effect of different CBD doses (0, 1, 10 and 20 mg/kg) on aggressiveness, stress and reproductive development of the Nile tilapia (Oreochromis niloticus) a fish reared worldwide for farming and research purposes. CBD mixed with fish food was offered to isolated fish for 5 weeks. The 10 mg/kg dose decreased fish's aggressiveness over time, whereas 20 mg/kg attenuated non-social stress. Both doses decreased the baseline cortisol level of fish and increased the gonadosomatic index. However, CBD 1 and 10 mg/kg doses decreased the spermatozoa number. No CBD dose affected feeding ingestion and growth variables, showing that it is not harmful to meat production amount. Despite the effect on spermatozoa, CBD supplementation exhibits high potential to benefit animals' lives in artificial environments. Therefore, we showed for the first time that CBD could be used as a tool to increase non-mammal welfare, presenting a great potential to be explored in other husbandry and captivity species.

Single-shot Mueller-matrix imaging of zebrafish tissues: In vivo analysis of developmental and pathological features

Zebrafish is a well-established animal model for developmental and disease studies. Its optical transparency at early developmental stages allows in vivo tissues visualization. Interaction of polarized light with these tissues provides information on their structure and properties. This approach is effective for muscle tissue analysis due to its birefringence. To enable real-time Mueller-matrix characterization of unanesthetized fish, we assembled a microscope for single-shot Mueller-matrix imaging. First, we performed a continuous observation of 48 species within the period of 2 to 96 hpf and measured temporal dependencies of the polarization features in different tissues. These measurements show that hatching was accompanied by a sharp change in the angle and degree of linearly polarized light after interaction with muscles. Second, we analyzed nine species with skeletal disorders and demonstrated that the spatial distribution of light depolarization features clearly indicated them. Obtained results demonstrated that real-time Mueller-matrix imaging is a powerful tool for label-free monitoring zebrafish embryos.

In the Swim of Cannabis: Developmental Toxicity and Metabolomic Pathway Alterations of Zebrafish Larvae Exposed to THC for the Assessment of Its Potential Environmental and Human Health Impact

As the pharmacological properties and therapeutic applications of Cannabis sativa L. pace with the upsurge of interest of the scientific community in harnessing its constituent phytocannabinoids, illicit use may raise serious health issues. Tetrahydrocannabinol (THC) is one of the most well-known phytoactive constituents of cannabis and continues to garner scientific and public attention not only because of its pharmacological value but also because over-the-counter products of THC and prescription medications are becoming increasingly available from pharmacies, dispensaries, Internet, local retail stores, or by illicit means. Hence, a multidimensional approach was employed to examine the impact of THC on zebrafish larvae. The acute toxicity, expressed as LC50, was 1.54 mg/L. Adverse effects were observed on the phenotype, such as tail bending, pericardial edema, etc., even at concentrations lower than LC50, and fundamental functions of larvae (e.g., heart rate and cardiac contractility, and rhythm) were significantly affected. Behavioral changes were noticed, which were reflected in locomotor activity and sensitivity to light/dark changes. Finally, an untargeted metabolomic study was carried out to shed light on the metabolic alterations that occurred, providing substantiating evidence of the observed phenotype alterations. Overall, the potentially detrimental effects of THC on a vertebrate model are depicted.

A Review on the Bioactivity of Cannabinoids on Zebrafish Models: Emphasis on Neurodevelopment

For centuries, the cannabis plant has been used as a source of food, fiber, and medicine. Recently, scientific interest in cannabis has increased considerably, as its bioactive compounds have shown promising potential in the treatment of numerous musculoskeletal and neurological diseases in humans. However, the mechanisms that underlie its possible effects on neurodevelopment and nervous-system functioning remain poorly understood and need to be further investigated. Although the bulk of research on cannabis and cannabinoids is based on in vitro or rodent models, the zebrafish has now emerged as a powerful in vivo model for drug-screening studies and translational research. We here review the available literature on the use of cannabis/cannabinoids in zebrafish, and particularly in zebrafish models of neurological disorders. A critical analysis suggests that zebrafish could serve as an experimental tool for testing the bioactivity of cannabinoids, and they could thus provide important insights into the safety and efficacy of different cannabis-extract-based products. The review showed that zebrafish exhibit similar behaviors to rodents following cannabinoid exposure. The authors stress the importance of analyzing the full spectrum of naturally occurring cannabinoids, rather than just the main ones, THC and CBD, and they offer some pointers on performing behavioral analysis in zebrafish.

A scoping review of the use of cannabidiol in psychiatric disorders

Cannabidiol (CBD) has become a fast-growing avenue for research in psychiatry, and clinicians are challenged with understanding the implications of CBD for treating mental health disorders. The goal of this review is to serve as a guide for mental health professionals by providing an overview of CBD and a synthesis the current evidence within major psychiatric disorders. PubMed and PsycINFO were searched for articles containing the terms "cannabidiol" in addition to major psychiatric disorders and symptoms, yielding 2952 articles. Only randomized controlled trials or within-subject studies investigating CBD as a treatment option for psychiatric disorders (N = 16) were included in the review. Studies were reviewed for psychotic disorders (n = 6), anxiety disorders (n = 3), substance use disorders (tobacco n = 3, cannabis n = 2, opioid n = 1), and insomnia (n = 1). There were no published studies that met inclusion criteria for alcohol or stimulant use disorder, PTSD, ADHD, autism spectrum disorder, or mood disorders. Synthesis of the CBD literature indicates it is generally safe and well tolerated. The most promising preliminary findings are related to the use of CBD in psychotic symptoms and anxiety. There is currently not enough high-quality evidence to suggest the clinical use of CBD for any psychiatric disorder.

Understanding early-life pain and its effects on adult human and animal emotionality: Translational lessons from rodent and zebrafish models

Critical for organismal survival, pain evokes strong physiological and behavioral responses in various sentient species. Clinical and preclinical (animal) studies markedly increase our understanding of biological consequences of developmental (early-life) adversity, as well as acute and chronic pain. However, the long-term effects of early-life pain exposure on human and animal emotional responses remain poorly understood. Here, we discuss experimental models of nociception in rodents and zebrafish, and summarize mounting evidence of the role of early-life pain in shaping emotional traits later in life. We also call for further development of animal models to probe the impact of early-life pain exposure on behavioral traits, brain disorders and novel therapeutic treatments.

Passive exposure to cannabidiol oil does not cause microbiome dysbiosis in larval zebrafish

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We show that 200 µg/L cannabidiol oil has a limited effect on in zebrafish larvae microbiome.

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Cannabidiol oil decreases the abundance of Methylobacterium-methylorubrum sp.

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Cannabidiol oil decreases the abundance of staphylococcus sp.,.

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Cannabidiol oil increased the abundance of chryseobacterium sp., a commensal bacterium.

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Our results suggest that cannabidiol oil is unlikely to have a major impact on local fauna.

The use of cannabidiol oil derived products has dramatically increased in popularity and is predicted to grow steadily over the next decade. Given its relative stability, cannabidiol is likely to accumulate in the environment and affect aquatic animals and their host-associated microbiomes. Here, using zebrafish larvae, a model system in environmental toxicology, we show that passive exposure to a concentration as high as 200 µg/L cannabidiol oil did not affect larvae survival and had limited effects on their host-associated microbial communities. We found that the changes in community structure were limited to a decrease in two sequence variants identified as Methylobacterium-Methylorubrum sp. and one ASV identified as Staphylococcus sp., as well as the increase of one sequence variant identified as Chryseobacterium sp., a bacterium commensal to zebrafish. More importantly, we found that cannabidiol oil did not affect the overall richness and diversity of the exposed fish microbiomes. These results suggest that passive exposure to cannabidiol oil is unlikely to impact aquatic organisms in significant ways.

Assessing the bioactivity of cannabis extracts in larval zebrafish

Background

Whole-plant cannabis extracts are consumed by the public for medical and non-medical (“recreational”) purposes but are poorly researched compared to pure cannabinoids. There is emerging evidence that cannabis extracts comprising complex mixtures of cannabinoids may have different biological effects from that of pure cannabinoids. In the current study, we sought to assess the effect of whole-plant cannabis extracts produced from different chemotypes of cannabis on the normal behavior of zebrafish larvae.

Methods

Three cannabis plant chemotypes were used in this study that contained either high amounts of THC, high amounts of CBD, high but equal amounts of THC and CBD, or low but equal amounts of THC and CBD. Following solvent extraction, liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS) was performed for the detection and quantitation of target cannabinoids. Larval zebrafish behavioral models were subsequently used to assess the effect of the four different whole-plant cannabis extracts on the normal larval behavior using the DanioVision behavioral tracking systems and software. To compare, changes in the behavior activity levels for 30 min periods were compared to controls using 2-way ANOVA with multiple comparisons followed by a Bonferroni post hoc test.

Results

It was found that the whole-plant extracts that contained high levels of THC had similar effects on larval behavior, while the high CBD and low THC:CBD extracts produced distinct effects on normal larval behavior. Exposure of larvae to concentration-matched levels of THC and CBD found in the extracts revealed that a subset of the cannabis extracts tested had similar behavioral profiles to the pure cannabinoids while others did not.

Conclusions

To our knowledge, this is the first study to test and compare the bioactivity of different whole-plant cannabis extracts in larval zebrafish. This work will provide a framework for future studies of distinct cannabis extracts and will be useful for comparing the bioactivity of extracts from different cannabis chemotypes as well as extracts made through various heating processes. It will also act as the first stage of assessment before testing the extracts against zebrafish models of toxicity and disease.

Transcriptomic Changes and the Roles of Cannabinoid Receptors and PPARγ in Developmental Toxicities Following Exposure to Δ9-Tetrahydrocannabinol and Cannabidiol

Human consumption of cannabinoid-containing products during early life or pregnancy is rising. However, information about the molecular mechanisms involved in early life stage Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) toxicities is critically lacking. Here, larval zebrafish (Danio rerio) were used to measure THC- and CBD-mediated changes on transcriptome and the roles of cannabinoid receptors (Cnr) 1 and 2 and peroxisome proliferator activator receptor γ (PPARγ) in developmental toxicities. Transcriptomic profiling of 96-h postfertilization (hpf) cnr+/+ embryos exposed (6 - 96 hpf) to 4 μM THC or 0.5 μM CBD showed differential expression of 904 and 1095 genes for THC and CBD, respectively, with 360 in common. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways enriched in the THC and CBD datasets included those related to drug, retinol, and steroid metabolism and PPAR signaling. The THC exposure caused increased mortality and deformities (pericardial and yolk sac edemas, reduction in length) in cnr1-/- and cnr2-/- fish compared with cnr+/+ suggesting Cnr receptors are involved in protective pathways. Conversely, the cnr1-/- larvae were more resistant to CBD-induced malformations, mortality, and behavioral alteration implicating Cnr1 in CBD-mediated toxicity. Behavior (decreased distance travelled) was the most sensitive endpoint to THC and CBD exposure. Coexposure to the PPARγ inhibitor GW9662 and CBD in cnr+/+ and cnr2-/- strains caused more adverse outcomes compared with CBD alone, but not in the cnr1-/- fish, suggesting that PPARγ plays a role in CBD metabolism downstream of Cnr1. Collectively, PPARγ, Cnr1, and Cnr2 play important roles in the developmental toxicity of cannabinoids with Cnr1 being the most critical.

Alternative model organisms for toxicological fingerprinting of relevant parameters in food and nutrition

In the field of (food) toxicology, there is a strong trend of replacing animal trials with alternative methods for the assessment of adverse health effects in humans. The replacement of animal trials is not only driven by ethical concerns but also by the number of potential testing substances (food additives, packaging material, contaminants, and toxicants), which is steadily increasing. In vitro 2D cell culture applications in combination with in silico modeling might provide an applicable first response. However, those systems lack accurate predictions of metabolic actions. Thus, alternative in vivo models could fill the gap between cell culture and animal trials. In this review, we highlight relevant studies in the field and spotlight the applicability of alternative models, including C. elegans, D. rerio, Drosophila, HET-CAM and Lab-on-a-chip.

Cannabis constituents reduce seizure behavior in chemically-induced and scn1a-mutant zebrafish

Current antiepileptic drugs (AEDs) are undesirable for many reasons including the inability to reduce seizures in certain types of epilepsy, such as Dravet syndrome (DS) where in one-third of patients does not respond to current AEDs, and severe adverse effects that are frequently experienced by patients. Epidiolex, a cannabidiol (CBD)-based drug, was recently approved for treatment of DS. While Epidiolex shows great promise in reducing seizures in patients with DS, it is used in conjunction with other AEDs and can cause liver toxicity. To investigate whether other cannabis-derived compounds could also reduce seizures, the antiepileptic effects of CBD, Δ9-tetrahydrocannabinol (THC), cannabidivarin (CBDV), cannabinol (CBN), and linalool (LN) were compared in both a chemically-induced (pentylenetetrazole, PTZ) and a DS (scn1Lab^-/-) seizure models. Zebrafish (Danio rerio) that were either wild-type (Tupfel longfin) or scn1Lab^-/- (DS) were exposed to CBD, THC, CBDV, CBN, or LN for 24 h from 5 to 6 days postfertilization. Following exposure, total distance traveled was measured in a ViewPoint Zebrabox to determine if these compounds reduced seizure-like activity. Cannabidiol (0.6 and 1 μM) and THC (1 and 4 μM) significantly reduced PTZ-induced total distance moved. At the highest THC concentration, the significant reduction in PTZ-induced behavior was likely the result of sedation as opposed to antiseizure activity. In the DS model, CBD (0.6 μM), THC (1 μM), CBN (0.6 and 1 μM), and LN (4 μM) significantly reduced total distance traveled. Cannabinol was the most effective at reducing total distance relative to controls. In addition to CBD, other cannabis-derived compounds showed promise in reducing seizure-like activity in zebrafish. Specifically, four of the five compounds were effective in the DS model, whereas in the PTZ model, only CBD and THC were, suggesting a divergence in the mode of action among the cannabis constituents.

Developmental exposure to Δ9-tetrahydrocannabinol (THC) causes biphasic effects on longevity, inflammation, and reproduction in aged zebrafish (Danio rerio)

Increased availability of cannabis and cannabinoid-containing products necessitates the need for an understanding of how these substances influence aging. In this study, zebrafish (Danio rerio) were exposed to different concentrations of THC (0.08, 0.4, 2 μM) during embryonic-larval development and the effects on aging were measured 30 months later and in the offspring of the exposed fish (F1 generation). Exposure to 0.08 μM THC resulted in increased male survival at 30 months of age. As the concentration of THC increased, this protective effect was lost. Treatment with the lowest concentration of THC also significantly increased egg production, while higher concentrations resulted in impaired fecundity. Treatment with the lowest dose of THC significantly reduced wet weight, the incidence of kyphosis, and the expression of several senescence and inflammatory markers (p16^ink4ab, tnfα, il-1β, il-6, pparα and pparγ) in the liver, but not at higher doses indicating a biphasic or hormetic effect. Exposure to THC did not affect the age-related reductions in locomotor behavior. Within the F1 generation, many of these changes were not observed. However, the reduction in fecundity due to THC exposure was worse in the F1 generation because offspring whose parents received high dose of THC were completely unable to reproduce. Together, our results demonstrate that a developmental exposure to THC can cause significant effects on longevity and healthspan of zebrafish in a biphasic manner.

Developmental exposure to cannabidiol (CBD) alters longevity and health span of zebrafish (Danio rerio)

Consumption of cannabinoid-containing products is on the rise, even during pregnancy. Unfortunately, the long-term, age-related consequences of developmental cannabidiol (CBD) exposure remain largely unknown. This is a critical gap given the established Developmental Origins of Health and Disease (DOHaD) paradigm which emphasizes that stressors, like drug exposure, early in life can instigate molecular and cellular changes that ultimately lead to adverse outcomes later in life. Thus, we exposed zebrafish (Danio rerio) to varying concentrations of CBD (0.02, 0.1, 0.5 μM) during larval development and assessed aging in both the F0 (exposed generation) and their F1 offspring 30 months later. F0 exposure to CBD significantly increased survival (~ 20%) and reduced size (wet weight and length) of female fish. While survival was increased, the age-related loss of locomotor function was unaffected and the effects on fecundity varied by sex and dose. Treatment with 0.5 μM CBD significantly reduced sperm concentration in males, but 0.1 μM increased egg production in females. Similar to other model systems, control aged zebrafish exhibited increased kyphosis as well as increased expression markers of senescence, and inflammation (p16^ink4ab, tnfα, il1b, il6, and pparγ) in the liver. Exposure to CBD significantly reduced the expression of several of these genes in a dose-dependent manner relative to the age-matched controls. The effects of CBD on size, gene expression, and reproduction were not reproduced in the F1 generation, suggesting the influence on aging was not cross-generational. Together, our results demonstrate that developmental exposure to CBD causes significant effects on the health and longevity of zebrafish.

Analysis of ZnO nanoparticle-induced changes in Oreochromis niloticus behavior as toxicity endpoint

The toxicity of zinc oxide nanoparticles (ZnO NPs) has been investigated in different animal models. However, concentrations tested in most studies are often much higher than the ones potentially identified in the environment. Therefore, such toxicity limits the application of these studies to evaluate ecotoxicological risks posed by these nanopollutants. Thus, the aim of the current study is to evaluate the impacts of ZnO NPs (at environmentally relevant concentrations - 760 μg/L and 76,000 μg/L, for 72 h) on the behavioral responses of Oreochromis niloticus (Nile tilapia) exposed to it. Results did not evidence harmful effects of NPs on animals' locomotor abilities (evaluated through open-field and light-dark transition tests), or anxiety-predictive behavior. On the other hand, Zn bioaccumulation in the body tissues of the analyzed tilapias was correlated to changes in eating behavior (motivated by ration pellets), as well as to deficits in antipredatory defensive behavior (under individual and collective conditions). Tilapia exposed to ZnO NPs recorded lower avoidance, flight and territorialist behavior rates when they were individually confronted with potential predators (Salminus brasiliensis). However, collectively exposed animals were unable to recognize their predators, as well as to differentiate them from artificial baits ("false predators"). The present study is the first to report biological impacts resulting from the short exposure of fish-group representatives to ZnO NPs. Thus, we believe that it may be relevant to improve the knowledge about ecotoxicological risks posed by these pollutants.