Long-term toxicity can be predicted from studies with early life-stages, a good reason why using zebrafish larvae in toxicology screening.
ZeClinics will initiate every molecule safety study by testing its Acute Toxicity. This assay will allow the assessing of its possible lethality and teratogenicity. On the other hand, by testing a range of 5 logarithmic concentrations, it will provide values of LC50, EC50, and NOEC. Zebrafish embryos from these treatments can be used to test ADME (Bioavailability) of any given molecule (Service available upon request).
To warrant the safety of any given molecule, and once the NOEC value is established, ZeClinics can proceed to test the putative toxic effects on specific tissues known to be affected by novel drugs – i.e.: Liver (Hepatotoxicity), Heart (Cardiotoxicity) or CNS (Neurotoxicity).
Fact: Short term drug toxicity can be predicted from studies performed with animal models at early life-stages.
Aim: Analysis of severe short-term effects and the ADME of a new drug.
Method: Incubation of zebrafish embryos in 5 different logarithmic concentrations of the molecule of interest. Determination of the following parameters at different time-points (24, 48, and 96 hpf) of development: EC50, LC50, NOEC (No observed effect concentration), LOEC (Lowest observed effect concentration). Therefore, several parameters of embryopathy and teratogenic endpoints are analyzed.
Fact: Long term drug toxicity can be predicted from studies performed with animal models at early life-stages.
Aim: Analysis of severe long-term effects of a new drug.
Method: The early-life stage toxicity assay started with zebrafish larvae aged six days postfertilization (dpf), at the onset of exogenous feeding, and lasted 23 days, broadly corresponding to the end of the larval period. The assay was run in static conditions with daily renewal of the medium. Every morning, larvae were transferred to clean experimental units filled with freshly prepared test solutions at the same temperature and returned to the system.
Fact: Toxic compounds can affect fertility and hatching rate.
Aim: Analyze the effects of a compound on offspring production and sexual maturation signaling.
Method: Several adult zebrafish males and females will be fed three times per day during four weeks with medical fodder containing the molecule of interest. Every seven days, zebrafish will be crossed to evaluate the fecundity of the individuals, and we will analyze different parameters related to reproduction (Adapted for zebrafish from OECD test 421).
After the Acute toxicity treatment, entire embryos and water, in which the embryos have been treated, can be isolated for testing compound presence (bioavailability). Depending on the molecule synthesis origin, the samples will be analyzed with NMR or Mass spectrometry. A concentration curve of the molecule can be measured in tissues and water, and also the presence of possible metabolites.
Fact: Cardiac dysfunctions represent one of the most important types of drug toxicity; the majority of drugs that result in clinical problems interfere with the human Ether-`a-go-go Related Gene (hERG) channel, blocking the rapid component delayed rectifier potassium current.
Aim: Analysis of cardiac effect of the drug in zebrafish larvae.
Method: Larvae of 120 hours post fertilization (hpf) of transgenic GFP heart fishes are incubated with the NOEC concentration of the molecule of interest during 4h and video recorded for heart physiology. Videos are analyzed with ZeCardio software for the presence of the several cardiac dysfunctions
Fact: Drug-induced neurological effects are remarkably common and are among the most frequent reasons for poor drug compliance.
Aim: Analysis of neurotoxic effects of drugs in zebrafish larvae.
Method: Larvae of transgenic zebrafish expressing GFP in a sub-population of neurons will be exposed to the NOEC concentration of the molecule of interest from 3 dfp to 4 dpf. Larvae are fixed, and GFP neurons of defined region in the rosencephalon are counted. Simultaneusly, basal locomotor activity is also measured with more alive treated larvae.
Fact: New chemicals often cause hepatotoxicity in the process of drug-discovery.
Aim: Analysis of the effects on the liver of drugs in zebrafish larvae.
Method: Embryos of transgenic RFP liver from 5 days post fertilization (dpf) to 7 dpf are incubated with the NOEC concentration of the molecule of interest. Larvae are fixed and analyzed for the several outputs indicative of hepatotoxicity.
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