Maternal and developmental toxicity of low doses of cytosine arabinoside in mice

Exposure to cytarabine causes side effects on adult development and physiology and induces intestinal damage via apoptosis in Drosophila

Cytarabine (Ara-C) is a widely used drug in acute myeloid leukemia (AML). However, it faces serious challenges in clinical application due to serious side effects such as gastrointestinal disorders and neurologic toxicities. Until now, the mechanism of Ara-C-induced damage is not clear. Here, we used Drosophila melanogaster (fruit fly) as the in vivo model to explore the side effects and mechanism of Ara-C. Our results showed that Ara-C supplementation delayed larval development, reduced lifespan, impaired locomotor capacity, and increased susceptibility to stress response in adult flies. In addition, Ara-C led to the intestinal morphological damage and ROS accumulation in the guts. Moreover, administration of Ara-C promoted gene expressions of Toll pathway, IMD pathway, and apoptotic pathway in the guts. These findings raise the prospects of using Drosophila as in vivo model to rapidly assess chemotherapy-mediated toxicity and efficiently screen the protective drugs.

Alpha-lipoic acid ameliorates cytarabine-induced developmental anomalies in rat fetus

Cytarabine (Ara-C) is a nucleoside analogue used in the treatment of cancers and viral infections. It has teratogenic potential and causes a variety of birth defects in fetuses. Alpha-lipoic acid (ALA) is a natural antioxidant offers protection against the developmental toxicity induced by drug- or toxicant-exposure or pathological conditions. This study was aimed at evaluating the protective effect of ALA against Ara-C induced developmental toxicity in rat fetus. Pregnant rats divided into five groups and received normal saline, ALA200 mg/kg, Ara-C12.5 mg/kg, Ara-C25 mg/kg and, Ara-C25 mg/kg plus ALA200 mg/kg respectively from gestational day (GD) 8 to GD14 and sacrificed on GD21. Ara-C treatment led to a significant and dose-dependent decrease in food intake, weight gain, placental weight, and an increase in oxidative stress in pregnant rats. Further, the in-utero exposure to Ara-C led to an increase in fetal mortality, resorptions, oxidative stress, external morphological anomalies and limb abnormalities, and impaired ossification. Co-administration of ALA resulted in amelioration of the footprints of Ara-C induced toxicity in pregnant rats as well as the fetus. These findings indicate that the ALA supplementation offers protection against developmental toxicity caused by Ara-C prenatal exposure in rats.

Characterizing cleft palate toxicants using ToxCast data, chemical structure, and the biomedical literature

Cleft palate has been linked to both genetic and environmental factors that perturb key events during palatal morphogenesis. As a developmental outcome, it presents a challenging, mechanistically complex endpoint for predictive modeling. A data set of 500 chemicals evaluated for their ability to induce cleft palate in animal prenatal developmental studies was compiled from Toxicity Reference Database and the biomedical literature, which included 63 cleft palate active and 437 inactive chemicals. To characterize the potential molecular targets for chemical-induced cleft palate, we mined the ToxCast high-throughput screening database for patterns and linkages in bioactivity profiles and chemical structural descriptors. ToxCast assay results were filtered for cytotoxicity and grouped by target gene activity to produce a "gene score." Following unsuccessful attempts to derive a global prediction model using structural and gene score descriptors, hierarchical clustering was applied to the set of 63 cleft palate positives to extract local structure-bioactivity clusters for follow-up study. Patterns of enrichment were confirmed on the complete data set, that is, including cleft palate inactives, and putative molecular initiating events identified. The clusters corresponded to ToxCast assays for cytochrome P450s, G-protein coupled receptors, retinoic acid receptors, the glucocorticoid receptor, and tyrosine kinases/phosphatases. These patterns and linkages were organized into preliminary decision trees and the resulting inferences were mapped to a putative adverse outcome pathway framework for cleft palate supported by literature evidence of current mechanistic understanding. This general data-driven approach offers a promising avenue for mining chemical-bioassay drivers of complex developmental endpoints where data are often limited.

Assessment of Developmental Toxicants using Human Embryonic Stem Cells

Embryonic stem (ES) cells have potential for use in evaluation of developmental toxicity because they are generated in large numbers and differentiate into three germ layers following formation of embryoid bodies (EBs). In earlier study, embryonic stem cell test (EST) was established for assessment of the embryotoxic potential of compounds. Using EBs indicating the onset of differentiation of mouse ES cells, many toxicologists have refined the developmental toxicity of a variety of compounds. However, due to some limitation of the EST method resulting from species-specific differences between humans and mouse, it is an incomplete approach. In this regard, we examined the effects of several developmental toxic chemicals on formation of EBs using human ES cells. Although human ES cells are fastidious in culture and differentiation, we concluded that the relevancy of our experimental method is more accurate than that of EST using mouse ES cells. These types of studies could extend our understanding of how human ES cells could be used for monitoring developmental toxicity and its relevance in relation to its differentiation progress. In addition, this concept will be used as a model system for screening for developmental toxicity of various chemicals. This article might update new information about the usage of embryonic stem cells in the context of their possible ability in the toxicological fields.

Effects of cytosine arabinoside on rat and rabbit embryos cultured in vitro

The technique of rabbit whole embryo culture for 48 or 24 hr from day 9, 10 or 11 of gestation has been improved for elucidation of species differences. The effects of 1-beta-d-arabinofuranosylcytosine (ara-C) and its metabolite 1-beta-d-arabinofuranosyluracil (ara-U) on cultured rat and rabbit embryos were examined. Slc:SD rats on day 10.5 of gestation were explanted and cultured in rat serum containing ara-C (5-10 mug/ml) for 48 hr. Rabbit embryos of the Japanese White strain on day 9 or day 10 of gestation were explanted and cultured in rabbit serum containing ara-C (0.03-1.0 or 3-30 mug/ml) or ara-U (1.0 or 30 mug/ml) for 48 or 24 hr. Cultured rat embryos exposed to ara-C showed abnormalities of the head (malformations of the telencephalon, mesencephalon and rhombencephalon), mandible and limb bud, and short tail. Growth parameters, such as crown-rump length, head length, protein content and somite number, were reduced with increasing concentrations of ara-C. In the rabbit, embryos cultured from day 9 of gestation for 48 hr showed abnormalities of the head (telencephalon, rhombencephalon), mandible and limb bud with ara-C at 0.1 mug/ml and higher concentrations. Concentration-dependent decreases in crown-rump length, head length and protein content were observed. The findings in embryos cultured from day 10 of gestation were similar to those in embryos cultured from day 9. Ara-U produced no detectable abnormalities in embryos cultured for 48 hr from day 9 of gestation, or for 24 hr from day 10. These results indicate that ara-C has teratogenicity in vitro that is similar in both rat and rabbit embryos.

Demonstration of congenital anomalies in the joints of the forelimbs and hindlimbs caused by several pharmacological agents

In this study, fetal joint abnormalities caused by cytosine arabinoside, caffeine, sodium salicylate, and retinyl acetate administration during pregnancy, were investigated. In the cytosine-arabinoside-administered group, complete disappearance of joint spaces in the forelimbs, and narrowing or complete disappearance of joint spaces in the hindlimbs was highly noticeable. In the caffeine group, in all forelimb joints starting from art, humeri, there were abnormal fusions in bones, together with occasional disappearance of the joint space. In hindlimbs, similar findings were observed. In the sodium salicylate group, the complete disappearance of joint space and surfaces among humerus-radius and ulna was striking, and occasional fusions in tarsometatarsal joints were also present. Severe narrowing of the same joint space in the retinyl acetate group was striking. Total disappearance of the articulation manus and carpometacarpal joints was observed, together with hindlimb joint and bone findings.

Developmental toxicity of gemcitabine, an antimetabolite oncolytic, administered during gestation to CD-1 mice

Gemcitabine was given intravenously to female mice on gestation days (GD) 6-15 at doses of 0, 0.05, 0.25, or 1.5 mg/kg/day (0, 0.15, 0.75, or 4.5 mg/m2/day, respectively). Animals assigned to the teratology segment (25/group) were killed on GD 18 for examination of maternal hematologic parameters and organ weights, as well as fetal viability, weights, and morphology. The postnatal segment females (20/group) were allowed to deliver, and offspring physical, behavioral, and reproductive parameters were monitored. After offspring weaning, these dams were killed for hematologic and organ weight evaluations. At necropsy, 3 days after the final dose, the teratology segment dams showed dose-related increases in spleen and thymus weights. These changes were accompanied by a dose-related decrease in leukocytes and modest increases in mean corpuscular volume (MCV) and hemoglobin (MCH) at the two higher doses. On postpartum day (PPD) 21, the dams in the postnatal segment showed no treatment-related effects on these organ weights or hematologic parameters, indicating recovery of these maternal parameters within 3.5 weeks following termination of treatment. The decreases in maternal body weight and food consumption observed during gestation, and in liver and uterine weights at term in the 1.5 mg/kg/day group, were considered to be secondary to a high rate of prenatal mortality, evidenced by increased resorptions in the teratology segment and decreased live litter size in both segments of the study. Additional indications of developmental toxicity in this dose group were an increased incidence of malformations, primarily cleft palate, decreased fetal weights in the teratology segment, and decreased neonatal survival in the postnatal segment.(ABSTRACT TRUNCATED AT 250 WORDS)