The octanol/water partition coefficient P (logP) is a hydrophobicity index and is one of the determining factors for the pharmacokinetics of orally administered substances because it influences membrane permeability. To illustrate the wide-ranging variety of compounds in the chemical space, a two-dimensional data plot consisting of 25 blocks was previously proposed based on a substance’s in silico chemical descriptors. The logP values of approximately 200 diverse chemicals (test plus reference compounds covering all 25 blocks of the chemical space) were estimated experimentally using retention times in reverse-phase liquid chromatography; these values were compared with those of authentic reference compounds with established logP values (available for 17 of 60 reference substances in the Organization for Economic Co-operation and Development Test Guideline 117). The logP values of 140 of 165 chemicals successfully estimated using four different mobile phase conditions (pH 2, 4, 7, and 10 for molecular forms) correlated significantly with those calculated using the in silico packages ChemDraw and ACD/Percepta (r > 0.72). Although substances that neighbored authentic compounds in the chemical space had precisely correlated logP values estimated experimentally and in silico, some compounds that were more distant from authentic substances showed lower logP values than those estimated in silico. These results indicate that additional authentic reference materials with wider ranging chemical diversity and their logP values from reverse-phase liquid chromatography should be included in the international test guidance to promote simple and reliable estimation of octanol/water partition coefficients, which are important determinant factors for the pharmacokinetics of general chemicals.

Busulfan is an anticancer drug known to cause serious damage to seminiferous tubules in the testes and deplete germ cells in human and animal models. The testicular artery is anastomosed with deferential and cremasteric arteries and is divided into capsular arteries, which give rise to the centripetal arteries and then recurrent arteries. The arterial blood in the testicular tissue is supplied by such a consequent system of arterial vessels, in order from the peripheral to the central area. As anticancer drugs are generally distributed throughout the whole body via the bloodstream and the running and distribution of arteries differ among the testicular areas, we hypothesized that the efficacy of busulfan differs in different testicular areas, particularly between the central and peripheral areas. In this study, busulfan was intraperitoneally injected at 40 mg/kg body weight into C57BL/6J male mice. After 28 days, in busulfan-treated mice, the diameters of seminiferous tubules were significantly higher in the central than in the peripheral area of the testes. The seminiferous tubular areas also significantly decreased in the peripheral areas compared with the central areas. The number of germ cells per seminiferous tubule was significantly higher in the central than in the peripheral area. Sertoli cell nuclei were detached into the lumen in the peripheral area. The number of Leydig cells was significantly lower in the peripheral areas. These data suggest that the effects of busulfan differ between the central and peripheral areas of the testis at 4 weeks after busulfan administration.

Alpha-glycosyl isoquercitrin (AGIQ) is composed of isoquercitrin and its glucosylated derivatives and has many biological activities, including anti-inflammatory, antioxidant, and anti-cancer properties. However, the effect of AGIQ administered orally on gut microbiota composition remains unclear. The objective of this study was to evaluate the effect of AGIQ on the gut microbiota of animals in different dose groups. Male rats and mice received different doses of AGIQ (1.5%, 3%, or 5% w/v) in diet for carcinogenic or chronic toxicity studies (rasH2 mice: 6 months; Sprague-Dawley rats: 12 months). Male minipigs received 100, 300, or 1000 mg/kg/day for 28 days. Fecal samples were collected from the different animal species and analyzed using 16S-rRNA gene sequencing. No significant changes were observed in alpha and beta diversity of the gut microbiota. Characteristic bacteria that responded to AGIQ were identified in each animal species, and, interestingly, Kineothrix alysoides, a butyrate-producing bacterium, was commonly detected in all three species, suggesting that it may be related to the biological activities of AGIQ. AGIQ selectively modulated the number of beneficial butyrate-producing commensal bacterium beneficial bacteria without changing the diversity of gut microbiota, which further supports the safe use of AGIQ in food products.

Mas-related G-protein-coupled receptor X2 (MRGPRX2), expressed on mast cells, is associated with drug-induced pseudo-allergic reactions. Although it is well known that there are differences of sensitivity between species in the pseudo-allergic reactions, no platform for evaluating a human risk of the pseudo-allergic reactions observed in nonclinical studies has been established. Valemetostat tosylate, developed as an anti-cancer drug, induced histamine release in a nonclinical study with dogs. The purpose of the current study was to identify the mechanism and assess the human risk of valemetostat-tosylate-induced histamine release using dog and human MRGPRX2-expressing cells. In an experiment with human or dog MRGPRX2-expressing cells, valemetostat tosylate caused activation of human and dog MRGPRX2. Importantly, the EC₅₀ for dog MRGPRX2 was consistent with the C_max value at which histamine release was observed in dogs. Furthermore, the EC₅₀ for human MRGPRX2 was ca. 27-fold higher than that for dog MRGPRX2, indicating a species difference in histamine-releasing activity. In a clinical trial, histamine release was not observed in patients receiving valemetostat tosylate. In conclusion, an in vitro assay using human and animal MRGPRX2-expressing cells would be an effective platform to investigate the mechanism and predict the human risk of histamine release observed in nonclinical studies.

The Hippo pathway plays an important role in the growth, development, and regeneration of cells and organs. Transcriptional enhanced associate domain (TEAD), a transcription activator of the Hippo pathway, forms the complex with a transcriptional coactivator yes-associated protein (YAP) or a transcriptional coactivator PDZ-binding motif (TAZ). Their excessive activations are involved in carcinogenesis such as malignant pleural mesothelioma (MPM), and thus inhibition of the TEAD complex is expected to have potent anticancer activity against MPM. On the other hand, YAP or TAZ conditional knockout mice have been reported to show abnormal findings in various tissues, including the kidney, liver, and lung. In the present study, we evaluated the systemic toxicity of K-975, a novel TEAD inhibitor, in rats. When K-975 was administered orally to rats for 1 week, proteinuria suggestive of nephrotoxicity was observed. Electron microscopy revealed that K-975 at 300 mg/kg induced glomerular podocyte foot process effacement. After a 2-week recovery period, proteinuria with foot process effacement was recovered completely. Urinalysis and urinary biomarker evaluation suggested that the urinary albumin index (urinary albumin/urinary creatinine) was the most sensitive marker for detecting K-975-induced nephrotoxicity. After 3 cycles of 1-week administration followed by 2-week recovery periods, nephrotoxicity was reversible; however, incomplete reversibility was observed in rats with severe proteinuria. In conclusion, this study revealed that in rats, oral K-975 treatment induced severe proteinuria by podocyte foot process effacement, which was reversible and monitorable by the urinary albumin index, suggesting important information for developing K-975 as an anticancer drug.

Vascular endothelial cells serve as barriers between blood components and subendothelial tissue and regulate the blood coagulation-fibrinolytic system. Ionizing radiation is a common physical stimulant that induces a bystander effect whereby irradiated cells influence neighboring cells through signalings, including purinergic receptor signaling, activated by adenosine 5′-triphosphate (ATP), adenosine 5′-diphosphate (ADP), and adenosine as secondary soluble factors. Human vascular endothelial EA.hy926 cells were cultured and irradiated with γ-rays or treated with ATP, ADP, or adenosine under non-toxic conditions. RNA-seq, gene ontology, and hierarchical clustering analyses were performed. The transcriptome analysis of differentially expressed genes in vascular endothelial cells after γ-ray irradiations suggests that the change of gene expression by γ-irradiation is mediated by ATP and ADP. In addition, the expression and activity of the proteins related to blood coagulation and fibrinolysis systems appear to be secondarily regulated by ATP and ADP in vascular endothelial cells after exposure to γ-irradiation. Although it is unclear whether the changes of the gene expression related to blood coagulation and fibrinolysis systems by γ-irradiation affected the increased hemorrhagic tendency through the exposure to γ-irradiation or the negative feedback to the activated blood coagulation system, the present data indicate that toxicity associated with γ-irradiation involves the dysfunction of vascular endothelial cells related to the blood coagulation-fibrinolytic system, which is mediated by the signalings, including purinergic receptor signaling, activated by ATP and ADP.