Polymorphisms in the endothelial nitric oxide synthase gene in thalidomide embryopathy

Thalidomide is one of the most potent teratogens known to humans. It is currently used for many clinical situations such as treatment of leprosy reactions and multiple myeloma. However, the teratogenic mechanisms by which it produces morphological defects still remain unclear. One of the hypotheses is the blockage of angiogenesis by reduction of nitric oxide (NO). In this study, we evaluated two functional polymorphisms of the endothelial nitric oxide synthase (eNOS) gene which is a constitutively expressed enzyme responsible for production of NO. The promoter -786T>C exon 7 (896G>T) polymorphisms were genotyped using real-time PCR for 28 individuals with thalidomide embryopathy (TE), 27 first-degree relatives of these individuals, and 68 individuals from the general population. Their allele, genotypic, and haplotypic frequencies were compared. A significant difference was observed in the -786T>C polymorphism genotypes (p=0.03) between the groups affected by TE and those unaffected (non-relatives). The TT genotype of the 896G>T polymorphism was observed in 10.7% of those affected and 2.9% of those unaffected, but the difference was not statistically significant (p=0.09). The haplotypic analysis indicated that the wild haplotype -786T/896G was distributed differently in the affected and unaffected groups (p=0.004). These results indicate that the individuals with TE have a higher frequency of alleles associated with lower expression of eNOS, indicating that this may be a genotype susceptible to TE.