ABSTRACT
Leflunomide has inhibitory effects on dihydroorotate-dehydrogenase activity and protein tyrosine kinase activity. In the present study, a single dose of 50 mg/kg Leflunomide was administered to pregnant mice on one of gestation days (GD)6-11. Characteristic external malformations were craniofacial defects following dosing on GD7, cleft palate on GD9, cleft palate and limb and tail deformities on GD10, and limb deformities on GD11. Skeletal examination revealed cervical to caudal vertebral malformations after treatment on GD7, GD8, GD9 or GD10. In the viscera, cardiovascular deformities were observed in the GD7 and GD9 Leflunomide-treated groups. These results demonstrate that multiple malformations were seen in various organs and most of the malformations observed appeared to be developmental stage-specific responses to Leflunomide treatment.
Subject(s)
Abnormalities, Drug-Induced , Abnormalities, Multiple/pathology , Embryo, Mammalian/drug effects , Fetal Viability/drug effects , Immunosuppressive Agents/toxicity , Isoxazoles/toxicity , Adjuvants, Immunologic/toxicity , Animals , Critical Period, Psychological , Embryo Loss , Embryo, Mammalian/cytology , Female , Gestational Age , Leflunomide , Male , Mice , Mice, Inbred ICR , PregnancyABSTRACT
Leflunomide is an immunosuppressant drug displaying teratogenicity in mice, rats, and rabbits. Its immunosuppressive effect occurs via inhibition of dihydroorotate dehydrogenase (DHODH) and tyrosine kinases. In this study, we coadministered Leflunomide and uridine, a precursor substance of pyrimidine nucleotides, to pregnant CD-1 mice, and examined whether or not a decreased level of intracellular pyrimidine nucleotides with inhibition of DHODH is related to the teratogenicity of Leflunomide. Then we examined the alteration of the nucleotide level in fetal tissue by Leflunomide and the effect of coadministered uridine. We administered Leflunomide with or without uridine to pregnant mice on gestation day 10, and used the vehicle of Leflunomide as a control. Leflunomide caused multiple malformations in all fetuses, but coadministration with uridine inhibited most of its teratogenicity. Leflunomide decreased the concentration of pyrimidine nucleotides, not purine nucleotides, whereas uridine coadministered with Leflunomide partially restored the level of pyrimidine nucleotides. These results indicate that the inhibitory effect of DHODH activity is related to the teratogenicity of Leflunomide.
Subject(s)
Immunosuppressive Agents/antagonists & inhibitors , Immunosuppressive Agents/toxicity , Isoxazoles/antagonists & inhibitors , Isoxazoles/toxicity , Teratogens , Uridine/pharmacology , Abnormalities, Drug-Induced/pathology , Animals , Dihydroorotate Dehydrogenase , Embryonic Development/drug effects , Female , Fetal Viability/drug effects , Fetus/drug effects , Fetus/metabolism , Fetus/pathology , Leflunomide , Mice , Mice, Inbred ICR , Oxidoreductases Acting on CH-CH Group Donors/antagonists & inhibitors , Oxidoreductases Acting on CH-CH Group Donors/metabolism , Pregnancy , Pyrimidine Nucleotides/metabolismABSTRACT
Leflunomide is an immunosuppressive agent that inhibits de novo synthesis of pyrimidine nucleotides and the activity of protein tyrosine kinase. This study examined the teratogenicity of Leflunomide in mice. Pregnant mice were treated orally with Leflunomide at a dose of 10, 30 or 70 mg/kg/day from day 6 to 15 of pregnancy. At 70 mg/kg, all embryos were resorbed and no live fetuses were detected. At 30 mg/kg, Leflunomide reduced fetal viability, and increased the incidence of multiple external, skeletal and visceral malformations. Characteristic external malformations were neural tube defects, cleft palate and tail deformities. Limb malformations were observed in a small number of fetuses. Skeletal examinations revealed malformations of cervical to sacral vertebrae, ribs and sternebrae. In the viscerae, the main anomalies were membranous ventricular septum defect and persistent truncus arteriosus. The results of this study indicate that Leflunomide administered at 30 mg/kg on days 6 to 15 of pregnancy can induce craniofacial malformations and deformities of the axial skeleton, heart and great vessels in mice.
