International Journal of Toxicology

To support clinical development of S-nitrosoglutathione (GSNO) as a therapeutic agent, 28-day toxicology studies in rats and dogs were conducted. Rats (21-25/sex) and dogs (3-5/sex) were exposed for 4 hours or 1 hour, respectively, to inhaled GSNO (0, 3, 9.3, 19, and 28 mg/kg per d in rats and 0, 4.6, 9.0, and 16.2 mg/kg per d in dogs) or vehicle daily via a nebulizer. Animals were monitored throughout the 28-day dosing period and during a postexposure recovery period. Complete necropsy and tissue examinations were performed. Experimental end points included clinical pathology, toxicokinetics, and immunotoxicology. No biologically significant adverse findings were noted in either species, and the no observed adverse effect levels (NOAELs) under these conditions were the highest achieved doses (28 and 16.2 mg/kg per d in rats and dogs, respectively). These data demonstrate that GSNO is well tolerated in rodents and dogs and predict a favorable toxicity profile in humans, thus supporting future clinical development of GSNO or closely related compounds.

Three doses of (+)-usnic acid (100, 200, and 240 mg/kg per d) were administered orally to Wistar rats for 8 days, and metabonomic characterization of (+)-usnic acid-induced liver injury based on gas chromatography–mass spectrometry metabolic profiles was evaluated. Serum biochemical analysis and histopathological examinations were simultaneously performed. The liver/body weight ratio was significantly increased in (+)-usnic acid-treated groups, whereas serum alanine aminotransferase and total bilirubin were significantly elevated. In liver sections of 200 and 240 mg/kg dosage groups, widespread hydropic degeneration of hepatocytes was observed. Clusters in partial least squares discriminant analysis score plots showed control and (+)-usnic acid-treated groups had an obvious separation. (+)-Usnic acid exposure can lead to disturbances in energy metabolism, amino acid metabolism, lipid metabolism, and nucleotide metabolism, which may be attributable to (+)-usnic acid toxicological effects on the liver through oxidative stress. The significant changes in 22 metabolites in liver might be adopted as potential biomarkers.

A paving asphalt and a vacuum residuum (derived from crude oil by atmospheric and subsequent vacuum distillation and used as a blend stock for asphalt) were tested in skin carcinogenesis assays in mice and in optimized Ames assays for mutagenic activity. In the skin cancer tests, each substance was applied twice weekly for 104 weeks to the clipped backs of groups of 50 male C3H mice. Neither the paving asphalt nor the vacuum residuum (30% weight/volume and 75% weight/weight in US Pharmacopeia mineral oil, respectively) produced any tumors. The positive control benzo[a]pyrene (0.05% w/v in toluene) induced tumors in 46 of 50 mice, demonstrating the effectiveness of the test method. Salmonella typhimurium tester strain TA98 was used in the optimized Ames assay to evaluate mutagenic potential. Dimethylsulfoxide (DMSO) extractions of the substances were not mutagenic when tested up to toxic limits. Thus, under the conditions of these studies, neither the paving asphalt nor the vacuum residuum was carcinogenic or mutagenic.

We developed a new end point of the mouse stem cell test (EST) for developmental neurotoxicity. We tested 2 developmental neurotoxicants, namely, lead (II) acetate and Aroclor 1254, using this EST. Our results showed that lead (II) acetate is nonembryotoxic, and Aroclor 1254 is weakly embryotoxic. To identify a new end point for developmental neurotoxicity, we used the default method of neuronal differentiation for D3 mouse embryonic stem cells with basic fibroblast growth factor (bFGF) and ascorbic acid. Flow cytometry and real-time polymerase chain reaction were used to quantify the inhibition of neuronal differentiation. Our results showed that both lead (II) acetate and Aroclor 1254 reduced the percentage of microtubule-associated protein 2 (MAP-2)-positive cells and the messenger RNA (mRNA) expression level of MAP-2 in a dose-dependent manner. These results suggested that these methods can be used to develop an additional end point of the EST for developmental neurotoxicity using default differentiation of mouse embryonic stem cells.

Cisplatin (Cisp) is one of the most widely used chemotherapeutic agents for the treatment of several human malignancies. The efficacy of Cisp is dose dependent and at higher doses serious kidney injury may occur. Recombinant human erythropoietin (rhEPO) has recently been shown to exert an important cytoprotective effect in experimental brain injury and ischemic acute renal failure. The aim of the present study was to explore whether rhEPO administration is protective against Cisp-induced oxidative damage and renal injury. Our results showed that Cisp induced a marked oxidative stress and renal failure. Administration of rhEPO (pre-, co- or postadministration with regard to Cisp) decreased oxidative damage induced by Cisp. Recombinant human EPO reduced malondialdehyde and protein carbonyl levels. Recombinant human EPO also prevented glutathione depletion and ameliorated the increased catalase activity induced by Cisp treatment. Furthermore, rhEPO restored creatinine and blood urea nitrogen levels increased by Cisp. We concluded that rhEPO administration especially in pretreatment condition protected rats against Cisp-induced renal oxidative stress and nephrotoxicity.

The aim of study was to evaluate the effect of commonly used lisinopril, rosuvastatin and their combined action on site-specific nephrotoxicity in rats using clusterin and microalbumin nephrotoxic biomarkers and other related parameters using oral gavage. Rosuvastatin at 2 different doses showed increase in urinary microalbumin levels whereas lisinopril and its combination with rosuvastatin at 2 different doses did not show urinary microalbumin excretion indicating beneficial effects of lisinopril in terms of reducing microalbumin. Urinary clusterin levels significantly increased in high-dose treated animals of lisinopril and rosuvastatin. The use of lisinopril plus rosuvastatin at low dose also led to worsened renal function by raising urinary clusterin levels (217±4.6 ng/ml) when compared with the control (143±3.3 ng/ml). Renal histopathology showed multifocal regeneration of tubules indicating proximal tubule damaged. These results indicate that lisinopril (50 mg/kg), rosuvastatin (100 mg/kg), lisinopril+rosuvastatin (20+40 mg/kg) and lisinopril+rosuvastatin (50+100 mg/kg) showed toxicity only on proximal tubules.

This study evaluated the antiasthmatic effects of Gleditsia sinensis ethanolic extract (GSEE) and its underlying mechanisms, using an in vivo murine model of asthma. Female BALB/c mice were sensitized, challenged with ovalbumin, and then examined for asthmatic reactions. The results showed that GSEE exerted profound inhibitory effects on the accumulation of eosinophils in the airways and reduced the levels of interleukin (IL)-4 and IL-5 in bronchoalveolar lavage fluid (BALF) and immunoglobulin E (IgE) in BALF and plasma. Gleditsia sinensis ethanolic extract also suppressed the production of reactive oxygen species in BALF and inflammatory infiltration, in a dose-dependent manner, and it inhibited goblet-cell hyperplasia in lung tissue. Thus, GSEE shows antiasthmatic effects in a murine model of allergic asthma, which appeared to be mediated partially by the reduction of oxidative stress and airway inflammation. These results indicate that GSEE could be an effective novel therapeutic agent for the treatment of allergic asthma.

The toxicity of 3 chemical forms of beryllium (Be) was compared in this study. A total of 160 mice equally divided into 4 groups were exposed by inhalation (nose only) for 3 consecutive weeks, 5 d/week, 6 h/d. One group was used as control, while the 3 others were exposed to fine particles of Be metal, Be oxide (BeO), or Be aluminum (BeAl). Except for the controls, the target level of exposure was 250 μg/m³. In all, 35 mice/group were sacrificed 1 week postexposure and another 5 mice 3 weeks postexposure. The BeO group showed the highest lung Be concentration with higher interleukin 12 (IL-12) and interferon-γ (IFN-γ) levels, while the Be group produced the most severe lung inflammation and higher tumor necrosis factor-α (TNF-α) and CD4+ T cells levels. Data suggested that Be and BeO apparently produced more pulmonary toxicity than BeAl. However, this conclusion is not definitive, because of different confounding factors such as particle sizes, specific surface area, and solubility.

In the process of drug design, it is important to consider potential structural alerts that may lead to toxicosis. This work illustrates how using trifluoroethane as a part of a novel chemical entity led to cytochrome P450 – mediated N-dealkylation and the formation of trifluoroacetaldehyde, a known testicular toxicant, in exploratory safety studies in rats. Testicular toxicosis was noted microscopically in a dose-dependent manner as measured by testicular spermatocytic degeneration and necrosis and excessive intratubular cellular debris in the epididymis. This apparent toxic effect correlated well with the dose-dependent formation of trifluoroacetaldehyde, identified from in vitro rat liver microsome metabolism studies. A similar safety study performed with an N-tetrazole substitution in place of the N-trifluoroethane showed no evidence of testicular injury, implicating further the role of trifluoroacetaldehyde in the testicular lesion observed. These results highlight the relevance of early metabolic and safety testing in assessing potential structural alerts in drug design.

This study determined the metabolism of 3 drinking water disinfection by-products (halogenated acetic acids [HAAs]), bromodichloroacetic acid (BDCAA), chlorodibromoacetic acid (CDBAA), and tribromoacetic acid (TBAA), using rat, mouse, human liver microsomes, and recombinant P450. Metabolism proceeded by reductive debromination forming a di-HAA; the highest under nitrogen >>2% oxygen > atmospheric headspaces. V _max for the loss of tri-HAA was 4 to 5 times higher under nitrogen than atmospheric headspace. Intrinsic metabolic clearance was TBAA>CDBAA>>BDCAA. At the high substrate concentrations, tri-HAA consumption rate was 2 to 3 times higher than the formation of di-HAA. Liberation of Br⁻ from TBAA corresponded to the expected amount produced after DBAA formation, indicating retention of Br⁻ by additional metabolite/metabolites. Subsequent experiments with CDBAA detected negligible formation of chlorodibromomethane (CDBM) and failed to account for the missing tri-HAA. Carbon monoxide and especially diphenyleneiodonium ([DPI] P450 reductase inhibitor) blocked CDBAA metabolism. Other chemical inhibitors were only partially able to block CDBAA metabolism. Most effective were inhibitors of CYP 2E1 and CYP 3A4. Immunoinhibition studies using human liver microsomes and anti-human CYP 2E1 antibodies were successful in reducing CDBAA metabolism. However, CDBAA metabolism in wild-type (WT) and CYP 2E1 knockout (KO) mouse liver microsomes was similar, suggesting significant interspecies differences in CYP isoform in tri-HAA metabolism. Additional assessment of CYP isoform involvement was complicated by the finding that recombinantly expressed rat and human P450 reductase was able to metabolize CDBAA, which may be a contributing factor in interspecies differences in tri-HAA metabolism.

The ability of 2 combinations of oximes (HI-6 + trimedoxime and HI-6 + K203) to reactivate VX-inhibited acetylcholinesterase and reduce acute toxicity of VX was compared with the reactivating and therapeutic efficacy of antidotal treatment involving a single oxime (HI-6, trimedoxime, K203) in rats and mice. Our results showed that the reactivating efficacy of both combinations of oximes studied in rats is significantly higher than the reactivating efficacy of all individual oximes in diaphragm and roughly corresponds to the most effective individual oxime in blood and brain. Both combinations of oximes were found to be more effective in the reduction of acute lethal toxicity of VX in mice than the antidotal treatment involving the most efficacious individual oxime although the difference is not significant. Based on the obtained data, we can conclude that the antidotal treatment involving the chosen combinations of oximes brings benefit for the reactivation of VX-inhibited acetylcholinesterase in rats and for the antidotal treatment of VX-induced acute poisoning in mice.

Toxicologic pathologists contribute significantly to the development of new biopharmaceuticals, yet there is often a lack of awareness of this specialized role. As the members of multidisciplinary teams, toxicologic pathologists participate in all aspects of the drug development process. This review is part of an initiative by the Society of Toxicologic Pathology to educate scientists about toxicologic pathology and to attract junior scientists, veterinary students, and veterinarians into the field. We describe the role of toxicologic pathologists in identifying candidate agents, elucidating bioactive pathways, and evaluating efficacy and toxicity in preclinical animal models. Educational and specialized training requirements and the challenges of working in a global environment are discussed. The biopharmaceutical industry provides diverse, challenging, and rewarding career opportunities in toxicologic pathology. We hope that this review promotes understanding of the important role the toxicologic pathologist plays in drug development and encourages exploration of an important career option.

Selection of a pharmacologically responsive species can represent a major challenge in designing nonclinical safety assessment programs for many biopharmaceuticals (eg, monoclonal antibodies (mAbs)). Frequently, the only relevant species for nonclinical testing of mAbs is the non-human primate (NHP). This situation, coupled with a rapidly increasing number of mAb drugs in development, has resulted in a significant increase in the number of NHPs used in nonclinical safety assessment. Apart from ethical considerations related to responsible animal use, there is a clear need for more efficient and innovative approaches to drug discovery and development; these factors drive the need to investigate alternative approaches and strategies for the safety assessment. This review summarizes important scientific and regulatory perspectives derived from presentations and audience discussions in an educational forum at the 2010 annual American College of Toxicology meeting regarding opportunities for employing alternative approaches to minimize NHP use in mAb drug development.