The Amino acid Derivative Reactivity Assay (ADRA) is an in chemico alternative to animal testing for the prediction of skin sensitization potential. Although co-elution of test chemicals and nucleophilic reagents during HPLC analysis is sometimes problematic when using the Direct Peptide Reactivity Assay (DPRA), it rarely occurs when using ADRA. Nevertheless, the application of either of these tests to multi-constituent substances requires nucleophilic reagents capable of selective detection. With this issue in mind, the authors developed an ADRA fluorescence detection method (ADRA-FL), which utilizes the natural fluorescence of ADRA nucleophilic reagents. In this study, we demonstrate the efficacy of ADRA-FL by testing 82 test chemicals used in the development of both DPRA and the conventional ADRA (ADRA-UV) as well as establish a threshold value for distinguishing sensitizers and non-sensitizers. Our results show that not only are depletion values obtained using ADRA-FL virtually identical to those obtained using ADRA-UV, the threshold value for either test is 4.9%. Additionally, in order to demonstrate the applicability of ADRA-FL to multi-constituent substances, we prepared test samples that consisted of a set of 10 non-sensitizers combined with one of 10 different sensitizers and tested each using ADRA-FL. The test results were concordant with those obtained using ADRA-UV. Also, because ADRA-FL chromatograms showed a significant decrease in multiple peaks as well as extremely stable baselines, we conclude that ADRA-FL is a highly selective and highly accurate mans of quantifying nucleophilic reagents that is applicable to a wide variety of chemical substances.
Drug-induced liver injury is not readily detectable using conventional animal studies during pre-clinical drug development. To address this problem, other researchers have proposed the use of co-administration of lipopolysaccharide (LPS), an endotoxin produced by gram-negative bacteria, and a drug. Using this approach, liver injury that is otherwise not detected following drug administration alone can be successfully identified. Previous studies have demonstrated that such injury is suppressed by heparin; therefore, the mechanism may involve coagulation-dependent ischemia. However, it has not been established how LPS-induced ischemia might sensitize hepatocytes to a potentially hepatotoxic drug. In the present study, we aimed to determine the effect of LPS-induced ischemia on liver mitochondrial function and downstream toxicologic responses. Consistent with previous findings, plasma alanine transaminase (ALT) activity was higher in rats co-administered with LPS (1 mg/kg) and diclofenac (100 mg/kg), but reduced by heparin. Liver mRNA expression of Hmox1, encoding heme oxygenase-1, an oxidative stress indicator, was three times higher at 2 hr after LPS administration. Furthermore, respiratory activity via mitochondrial complex II, lipid peroxidation in mitochondria, and the susceptibility to mitochondrial permeability transition pore opening in response to diclofenac administration were significantly increased by LPS administration. The increase in plasma ALT activity and the sensitization to mitochondrial permeability transition pore opening were reduced by the co-administration of heparin. In conclusion, LPS-induced transient ischemia disrupts respiratory chain complex activities, enhances reactive oxygen species production, especially in mitochondria, and sensitizes mitochondria to permeability transition pore opening when testing a potentially hepatotoxic drug in vivo.
As the field of utilization of organic-inorganic hybrid molecules expands, the toxicology of these compounds is becoming more important. We have shown previously that there is a strong correlation between cytotoxicity and intracellular accumulation detected as metal content, which is modulated by the substituents, of organic-inorganic hybrid molecules. In this study, we investigated the cytotoxicity of pentavalent organoantimony compounds with three phenyl groups on cultured vascular endothelial cells. The results indicated that the cytotoxicity of pentavalent organoantimony compounds was not correlated with the hydrophobicity and intracellular accumulation of these compounds. Therefore, we suggest that hydrophobicity and intracellular accumulation are not necessarily predictive of cytotoxicity in organic-inorganic hybrid molecules.
Abuse of recreational drugs (i.e., synthetic chemicals with the structure or expected neurotropic effects, or both, similar to those of controlled substances) is a serious and continuous social harm. Designer drugs are often manufactured or synthesized in small-scale clandestine laboratories with impure starting materials, poor handling skills and inferior storage conditions. Therefore, in addition to the objective compound, diverse impurities may be present, for example, from the starting material, intermediates, catalytic metals formed during chemical synthesis, and materials from the environment. Impurity profiling of drug seizures is a useful scientific tool to obtain information on the clandestine manufacturers and drug trafficking networks. 1-Phenyl-2-(1-pyrrolidinyl)-1-pentanone (α-PVP), a novel psychoactive substance of the cathinone type that is banned in many countries, is still supplied and distributed within the illicit drug market. By using GC-MS and ICP-MS, we identified and estimated the relative contents of organic and inorganic impurities in the bulk powder of 15 batches of α-PVP. We then conducted multivariate data analyses to reveal characteristic patterns of the profiles. Hierarchical cluster analysis of both the organic and inorganic impurities revealed two groups that showed similar impurity profiles, which suggested that the batches in these groups were synthesized in similar routes under similar synthetic environments. The initial groups revealed by the organic impurities were further divided when combined with the data from the inorganic impurities. The present study, therefore, demonstrated the effectiveness of integrated analyses of organic and inorganic impurities for the accurate clustering of designer drugs, to provide precise information to drug investigation authorities.
We validated a motion field imaging (MFI) assay with human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs) as a model to assess multiple cardiac liabilities by comparing the guinea-pig Langendorff heart with hiPS-CMs using 4 reference compounds and 9 internal compounds. We investigated repolarization duration, beating rate (BR), conduction speed, contractility, and inhibitory profile of three cardiac ion channels: hERG, Cav1.2, and Nav1.5. For repolarization, the contraction-relaxation duration (CRDc) of hiPS-CMs was generally consistent with the QTc interval of Langendorff heart. However, 2 internal compounds shortened CRDc despite QTc prolongation in Langendorff heart. Cardiac ion channel profiling revealed that hiPS-CMs could not be used to detect QTc prolongation when the value of Cav1.2 IC50 / hERG IC50 for a compound was between 1 and 10, whereas hiPS-CMs showed responses largely consistent with Langendorff heart when Cav1.2 IC50 / hERG IC50 was below 1 or above 10. The accuracy of hiPS-CMs for the BR was not high, mainly because the BR of hiPS-CMs was increased by an inhibition of Cav1.2. The hiPS-CMs were highly sensitive to conduction speed and contractility, able to detect QRS widening caused by Nav1.5-inhibition, as well as decreased LVdP/dtmax caused by the inhibition of Cav1.2 and/or Nav1.5. In conclusion, the MFI assay with hiPS-CMs would be useful for evaluating multiple cardiac liabilities. The ion channel profile helps to interpret the results of MFI assay and correctly evaluate cardiac risks. Therefore, an integrated cardiac safety assessment with MFI and ion channel profiling is recommended.
Colibactin is a polyketide-peptide genotoxin produced by enteric bacteria such as E. coli, and is considered to contribute to the development of colorectal cancer. We previously isolated E. coli strains from Japanese colorectal cancer patients, and in the present study we investigated the genotoxic potency of the colibactin-producing (clb+) E. coli strains that carry the polyketide synthases “pks” gene cluster (pks+) and an isogenic clb- mutant in which the colibactin-producing ability is impaired. Measurement of phosphorylated histone H2AX indicated that DNA double strand breaks were induced in mammalian CHO AA8 cells infected with the clb+ E. coli strains. Induction of DNA damage response (SOS response) by crude extract of the clb+ strains was 1.7 times higher than that of the clb- E. coli in an umu assay with a Salmonella typhimurium TA1535/pSK1002 tester strain. Micronucleus test with CHO AA8 cells revealed that infection with the clb+ strains induced genotoxicity, i.e., the frequencies of micronucleated cells infected with clb+ strain were 4-6 times higher than with the clb- strain. Since the intestinal flora are affected by dietary habits that are strongly associated with ethnicity, these data may contribute to both risk evaluation and prevention of colorectal cancer in the Japanese population.