Visualizing Compound Distribution during Zebrafish Embryo Development: The Effects of Lipophilicity and DMSO

Abstract

The predictability of the zebrafish embryo model is highly influenced by internal exposure of the embryo/larva. As compound uptake is likely to be influenced by factors such as lipophilicity, solvent use, and chorion presence, this article focuses on investigating their effects on compound distribution within the zebrafish embryo. To visualize compound uptake and distribution, zebrafish embryos were exposed for 96 hr, starting at 4 hr postfertilization, to water-soluble dyes: Schiff's reagent (logP -4.63), Giemsa stain (logP -0.77), Van Gierson stain (logP 1.64), Cresyl fast violet (logP 3.5), Eosine Y (logP 4.8), Sudan III (logP 7.5), and Oil red O (logP 9.81), with and without 1% dimethyl-sulfoxide (DMSO). Three additional compounds were used to analytically determine the uptake and distribution: Acyclovir (logP -1.56), Zidovudine (logP 0.05), and Metoprolol Tartrate Salt (logP 1.8). Examinations were performed every 24 hr. Both methods (visualization and specific analysis) showed that exposure to higher logP values results in higher compound uptake. Specific analysis showed that for lipophilic compounds >90% of compound is taken up by the embryo. For hydrophilic compounds, >90% of compound within the complete egg could not be associated to embryo or chorion and is probably distributed into the perivitelline space. Overall, internal exposure analyses on at least two occasions (i.e., before and after hatching) is crucial for interpretation of zebrafish embryotoxicity data, especially for compounds with extreme logP values. DMSO did not affect exposure when examined with the visualization method, however, this method might be not sensitive enough to draw hard conclusions.

Behavioral screening of the LOPAC1280 library in zebrafish embryos

“…On the other hand, the vast majority of Tier-I hits (98%) had LogP values favoring water-to-embryo partitioning (LogP>0) and Tier-II hits clustered within a narrower range of LogP values relative to Tier-I hits, suggesting that a short (2-h) exposure biased hits to hydrophobic compounds within an optimal LogP range (LogP = ~2–5). Therefore, these results are consistent with other studies showing that compound bioactivity is not associated with compound size (for compounds ≤3000 g/mol) but, rather, tends to be dependent on compound hydrophobicity (LogP>0) and partitioning from water into zebrafish embryos (whether chorionated or not) over a specific exposure duration (de Koning et al, 2015; Gustafson et al, 2012; Pelka et al, 2017; Sachidanandan et al, 2008). Finally, the lack of structural similarity suggests that, similar to LogPs and molecular weights, 2D chemical structures do not have the potential to predict hits within our assay; however, it is important to note that this lack of predictability may be driven by the inherent chemical diversity of the LOPAC 1280 library.…”

Detection and Prioritization of Developmentally Neurotoxic and/or Neurotoxic Compounds Using Zebrafish

“…Some chemicals were not detected in the embryos while others highly accumulated (ie, pyrene was found almost 1000 times more concentrated in the embryos than the concentration at which they were treated). Several physicochemical properties of chemicals have been described to influence the uptake such as size, molecular weight, or lipophilicity, as well as the presence of active transport into and within embryos (de Koning et al, 2015) and the dissolved organic matter in the media . Chemicals exceeding 3 kDa or 3000 g/mol show a restricted uptake due to the chorion presence in zebrafish embryos until 48-72 hpf (de Koning et al, 2015).…”

Block copolymer composition drives function of self‐assembled nanoparticles for delivery of small‐molecule cargo

“…We investigated model cargo encapsulation using Oil Red O (ORO) (log P = 9.81) as a model hydrophobic cargo. PEG–PVL NPs had the highest encapsulation efficiencies.…”