Mutagenicity of methylvinyl ketone in Salmonella typhimurium TA100--indication for epoxidation as an activation mechanism

Acmella oleracea (L) R. K. Jansen Reproductive Toxicity in Zebrafish: An In Vivo and In Silico Assessment

The plant species Acmella oleracea L. is used in the north of Brazil for the treatment of a range of illnesses, such as tuberculosis, flu, cough, and rheumatism and as an anti-inflammatory agent; besides, hydroethanolic formulations with this species are popularly used as a female aphrodisiac agent. However, currently, there are no studies performed evaluating its effect on embryonic development. Hence, this research aimed to evaluate the effects of the hydroethanolic extract of A. oleracea (EHFAo) on the reproductive performance (parental) and embryonic development (F1 generation) of zebrafish, at concentrations of 50, 100, and 200 μg/L. Histopathology of parental gonads after 21 days of exposure to EHFAo reveals few alterations in the ovaries and testes, not impairing the reproduction; an increase of eggs deposition was observed in animals treated with EHFAo at the highest concentrations. Nevertheless, concerning the embryonic development of F1, teratogenic effects were observed including tail deformation, cardiac and yolk edema, scoliosis, and growth retardation; these alterations were more prominent in the groups born from progenitors exposed to the highest concentrations (100 and 200 μg/L.); but only the occurrence of yolk and cardiac edema had a statistically significant difference when compared to the control group. The chromatographic analysis shows that spilanthol (affinin) was the primary compound found in the EHFAo. Hence, in silico assessment was performed to evaluate the pharmacokinetic and toxicological properties of this molecule and 37 metabolites derived from it. Overall, our data show that the treatment caused no detrimental changes in progenitors regarding their gonads or fertility but caused some potentially teratogenic activity in embryos, which may be due to the action of spilanthol's metabolites M3, M6, M7, M8, M16, M28, and M31.

Liver-Targeted Drug Delivery Using HepDirect Prodrugs

Targeting drugs to specific organs, tissues, or cells is an attractive strategy for enhancing drug efficacy and reducing side effects. Drug carriers such as antibodies, natural and manmade polymers, and labeled liposomes are capable of targeting drugs to blood vessels of individual tissues but often fail to deliver drugs to extravascular sites. An alternative strategy is to use low molecular weight prodrugs that distribute throughout the body but cleave intracellularly to the active drug by an organ-specific enzyme. Here we show that a series of phosphate and phosphonate prodrugs, called HepDirect prodrugs, results in liver-targeted drug delivery following a cytochrome P450-catalyzed oxidative cleavage reaction inside hepatocytes. Liver targeting was demonstrated in rodents for MB06866 [(2R,4S)-9-[2-[4-(3-chlorophenyl)-2-oxo-1,3,2-dioxaphosphorinan-2-yl]methoxyethyl]adenine (remofovir)], a Hep-Direct prodrug of the nucleotide analog adefovir (PMEA), and MB07133 [(2R,4S)-4-amino-1-[5-O-[2-oxo-4-(4-pyridyl)-1,3,2-dioxaphosphorinan-2-yl]-beta-d-arabinofuranosyl]-2(1H)-pyrimidinone], a HepDirect prodrug of cytarabine (araC) 5'-monophosphate. Liver targeting led to higher levels of the biologically active form of PMEA and araC in the liver and to lower levels in the most toxicologically sensitive organs. Liver targeting also confined production of the prodrug byproduct, an aryl vinyl ketone, to hepatocytes. Glutathione within the hepatocytes rapidly reacted with the byproduct to form a glutathione conjugate. No byproduct-related toxicity was observed in hepatocytes or animals treated with HepDirect prodrugs. A 5-day safety study in mice demonstrated the toxicological benefits of liver targeting. These findings suggest that HepDirect prodrugs represent a potential strategy for targeting drugs to the liver and achieving more effective therapies against chronic liver diseases such as hepatitis B, hepatitis C, and hepatocellular carcinoma.

The role of alcohols as solvents in the genotoxicity testing of alpha,beta-unsaturated ketones in the SOS chromotest

alpha,beta-Unsaturated ketones are bifunctional compounds which form promutagenic 1,N(2)-propanodeoxyguanosine adducts like carcinogenic alpha,beta-unsaturated aldehydes and are mutagenic and genotoxic like these aldehydes. They are important industrial chemicals, are found in our environment and are widespread in our food. We investigated the SOS repair inducing activities of five ketones in the SOS chromotest and compared these results with that of the Ames test. Alkyl substitution at the beta-position of the alpha, beta-unsaturated carbonyl moiety leads to a decrease or loss in genotoxicity. Genotoxicity is higher if using ethanol as solvent instead of dimethylsulfoxide (DMSO). An increasing effect is also observed with methanol and n-propanol. Addition of the alcohol dehydrogenase inhibitor 4-methylpyrazole does not significantly influence the genotoxicity indicating that it is unlikely that the solvent effect depends on competitive inhibition of alcohol dehydrogenase by the alcohols used as solvents. Since other possible explanations e.g. ketal formation or solubility effects are also unlikely, the mechanism of this solvent effect observed with three different E. coli PQ-strains remains unresolved. No significant difference in genotoxicity of ethyl vinyl ketone was found between the strains PQ 37 and PQ 243 indicating that base excision repair does not play a role in the repair of 1,N(2)-propanodeoxyguanosine adducts, the main adducts of the alpha,beta-unsaturated ketones.

Collaborative study of mutagenicity with Salmonella typhimurium TA102

Thirty compounds of various chemical classes were investigated for mutagenicity in a collaborative study (3 laboratories) using Salmonella typhimurium TA102. With 5 compounds, namely hydrazine sulfate, phenylhydrazine, hydralazine, glutardialdehyde and glyoxal, mutagenicity was detected by all laboratories. Formaldehyde was assessed as weakly mutagenic in only 1 of 3 laboratories. The remaining 24 agents were uniformly described as non-genotoxic in TA102. In spite of the overall good qualitative agreement in the mutagenicity results between the 3 laboratories some quantitative discrepancies occurred in the dose response of the mutagenic compounds. Varying inter- and intra-laboratory differences in the spontaneous rate of revertants were obtained. The usefulness of the tester strain TA102 in routine mutagenicity testing is discussed.