International Journal of Toxicology

Toxicokinetic investigations are an essential component of nonclinical toxicology studies and generally rely on bioanalysis of plasma samples, which requires relatively large volumes of blood and, often, additional numbers of animals. Dried blood spot (DBS) analysis can substantially reduce the volume of blood needed and, therefore, presents a particular opportunity for reducing animal use in studies involving small animals; an approach consistent with industry objectives to reduce animal use and refine methods that are minimally invasive and improve animal welfare. Investigations using mice and juvenile rats indicate that implementation of DBS technology can reduce the number of animals used, and data are as good as those derived from whole blood in terms of AUC, drug-concentration-over-time curves, quantitation, accuracy, variability, and precision. These factors, and the improved data quality arising from less reliance on composite data, suggest that DBS analysis should be considered from the early stages of nonclinical development.

Cationic amphiphilic drugs and aminoglycoside antibiotics can induce phospholipidosis (PLD), an abnormal accumulation of phospholipids in lysosome-derived vesicles, in preclinical studies. The incidence of PLD in patients and its clinical relevance are difficult to assess without noninvasive biomarkers. Di-docosahexaenoyl bis(monoacylglycerol)phosphate (di-22:6-BMP) is a phospholipid that is enriched in lysosomal membranes and a proposed urinary biomarker of drug-induced PLD. The specificity of di-22:6-BMP for PLD was compared to other phospholipid species that can increase in urine with nephrotoxicity. Using liquid chromatography coupled to mass spectrometry, 12 phospholipids were assayed in the urine of rats treated with drugs that induced PLD or caused renal or skeletal muscle injury. In receiver operating curve analyses, urinary di-22:6-BMP was a significantly better predictor of PLD and the least predictive of tissue injury of the phospholipids assayed. The data provide evidence supporting the use of di-22:6-BMP as a urinary biomarker of PLD in rats.

The correlation between 52 physicochemical parameters and mean residence time (MRT) for 27 drugs used in human and dog were investigated. The physicochemical parameter values calculated provided a basis for deriving a series of arithmetic expressions, which were used to build a mathematical model describing the relationship between them and the MRT values. From the entire set of analyzed parameters, a subset of 14 was identified that contributed to the derivation of an arithmetic expression:

L o g ( P S A − W P S A + A C I D ) × [ X L o g P − ( L o g K p − E A × L n ( C a c o 2 + A M I N E + S A F ) ) ) ] + + ( A M I D E + I P − F G ) − L n ( M W + P I S A )

the value of which is highly correlated with the MRT value in dogs (P < .001) and allowed prediction of the MRT predicted (MRT_(pred)). In humans, no correlation was found that allowed the calculation of MRT_(pred). These results indicate that predicting the pharmacokinetics of any specific drug for humans based on pharmacokinetic data obtained in the dog should be undertaken with knowledge of the inherent limitations.

A safety evaluation was performed for EpiCor, a product produced by a proprietary fermentation process using Saccharomyces cerevisiae. Studies included the following assays: bacterial reverse mutation, mouse lymphoma cell mutagenicity, mitogenicity assay in human peripheral lymphocytes, and a cytochrome P450 ([CYP] CYP1A2 and CYP3A4) induction assessment as well as 14-day acute, 90-day subchronic, and 1-year chronic oral toxicity studies in rats. No evidence of genotoxicity or mitogenicity was seen in any of the in vitro or in vivo studies. The CYP assessment showed no interactions or inductions. No toxic clinical symptoms or histopathological lesions were observed in the acute, subchronic, or chronic oral toxicity studies in the rat. Results of the studies performed indicate that EpiCor does not possess genotoxic activity and has a low order of toxicity that is well tolerated when administered orally. The no observable adverse effect level (NOAEL) was 1500 mg/kg body weight (bw)/d for the 90-day study and 800 mg/kg bw/d for the 1 year study, for the highest doses tested.

Aqueous polymer dispersions are important raw materials used in a variety of industrial processes. They may contain particles with diameters ranging from 10 to 1500 nm. Polymer exposure alone may cause pulmonary lesions after inhalation exposure. Polymer dispersions with increased proportions of nano-sized particles are being developed for improved material characteristics, and this may pose even increased pulmonary hazards upon potential inhalation exposure. In a 5-day screening study, male rats were nose-only exposed to aerosols generated from 2 dispersions of acrylic ester polymers with identical chemical composition but different nano-sized particle proportions at particle concentrations of 3 and 10 mg/m³. Immediately and 19 days after the end of inhalation, necropsies were conducted with major emphasis on respiratory tract histopathology. Three and 23 days after the end of inhalation, bronchoalveolar lavage was performed to screen for early pulmonary injury and inflammation. In contrast to the adverse effects known for other materials in short-term inhalation studies, none of the tested preparations of acrylic ester polymers elicited any adverse effect at the end of the inhalation or postinhalation periods. No shift in toxicity could be observed by the increased proportion of nano-sized polymer particles. Under the conditions of this study, the no observable adverse effect levels for both preparations were >10 mg/m³, that is 2- to 3-fold beyond current nuisance dust threshold limit values.

To support phase III testing of coenzyme Q10 (CoQ₁₀) in humans, we conducted pharmacokinetic and toxicology studies in beagle dogs. Following single gavage administration of CoQ₁₀ at 600, 1200, 1800, or 2400 mg/kg per d no obvious dose response was observed in maximum concentration (C _max) or area under the curve (AUC) versus time curve at the 3 highest dosages. In a repeated-dose study of CoQ₁₀ at 600, 1200, 1800, or 2400 mg/kg per d for 4 weeks, CoQ₁₀ reached steady state in plasma by 2 weeks at all dosages. Both C _max and AUC increased with increasing dosage of CoQ₁₀. The highest plasma levels were recorded at 1800 mg/kg per d. In a 39-week chronic toxicity study of CoQ₁₀ at 1200 and 1800 mg/kg per d or placebo, CoQ₁₀ reached steady state in plasma by 13 weeks. Behaviors, blood chemistries, and detailed histopathology were normal. No deaths occurred. These results support the use of a 2400 mg/d dosage of CoQ₁₀ in human clinical trials.

Sanguinarine is an alkaloid obtained from the bloodroot plant Sanguinaria canadensis and has beneficial effects on oxidative stress and inflammatory disorders. Previous reports have demonstrated that sanguinarine also exhibit anticancer properties. In the current study, we investigated the effects of sanguinarine on HT-29 human colon cancer cells. It was observed that sanguinarine treatment induces a dose-dependent increase in apoptosis of human colon cancer cells. We also investigated the effects of sanguinarine on the expression of apoptosis-associated proteins, and the results revealed that there was an increase in Bax and a decrease in B-cell lymphoma 2 (Bcl-2) protein levels. Moreover, sanguinarine treatment significantly increases the activation of caspases 3 and 9 that are the key executioners in apoptosis. Our results suggest that sanguinarine induces apoptosis of HT-29 human colon cancer cells and may have a potential therapeutic use in the treatment of human colon cancer.

Dimethoate (DM) is an organophosphate insecticide with numerous uses on field and agricultural crops and ornamentals. Data concerning DM-acute genotoxicity are controversial and knowledge on its delayed effect is limited. For this reason, we aimed to further explore DM genotoxicity resulting from subchronic intoxication of experimental mice. Thus, DM was administered to mice at doses ranging from 1 to 30 mg/kg body weight for a period of 30 consecutive days. There was a significant increase (P < .05) in the frequency of micronucleated bone marrow cells following DM administration. Furthermore, the chromosome aberration assay revealed a significant increase in the percentage of chromosome abnormalities in a dose-dependent manner. Dimethoate was also found to induce significant DNA damage in mouse bone marrow cells as assessed by the comet assay. Altogether, our results showed that, after a subchronic exposure, DM was a genotoxic compound in experimental mice.

Aflatoxin B1 (AFB1), one of the most common mycotoxins found in human foods and animal feed, is principally hepatotoxic and hepatocarcinogenic. The aim of the present study was to explore the effect of AFB1 on messenger RNA (mRNA) expression of pregnane X receptor (PXR), constitutive androstane receptor (CAR), and aryl hydrocarbon receptor (AhR) and some of their target cytochromes using primary cultures of human hepatocytes. Our results showed that AFB1, at noncytotoxic increasing concentrations, caused a significant upregulation of cytochrome P 2B6 (CYP2B6), CYP3A5, and to a lesser extent CYP3A4 and CYP2C9. Pregnane X receptor and CAR mRNA expression increased in the 3 treated livers. Aflatoxin B1 was found also to induce an overexpression of CYP1A1 and CYP1A2 genes accompanied by an increase in AhR mRNA expression. These findings suggest that AFB1 could activate PXR, CAR, and AhR; however, further investigations are needed to confirm nuclear receptor activation by AFB1.