Impact of indoleamine 2,3-dioxygenase on the antioxidant system in the placentas of severely pre-eclamptic patients.

Indoleamine 2,3-dioxygenase (IDO) is the rate limiting enzyme of the kynurenine pathway that degrades L-tryptophan, but a wider range of functions have now been proposed for this enzyme, including antioxidant activity. Our previous study revealed that reduced IDO expression in the placenta induces defective feto-maternal immuno-tolerance leading to the onset of pre-eclampsia. In our present study, we assessed the effects of low placental IDO activity as an antioxidant. The placental levels of 8-hydroxy-2'-deoxy-guanosine (8-OHdG), a maker for oxidative damage to DNA, were significantly higher in pre-eclamptic than normotensive pregnancies (P<0.05). Immunohistochemical signals of 8-OHdG were detected mainly in syncytiotrophoblasts and vascular endothelial cells, and co-localized with those for IDO. Furthermore, a significant inverse correlation was found between the IDO activity and 8-OhdG levels. These results show that oxidative stress is associated with decreased IDO activity in the pre-eclamptic placenta and suggest an impact of low IDO activity other than immune modulation in promoting the onset of this disorder.

Polymorphisms in the annexin A5 gene promoter in Japanese women with recurrent pregnancy loss.

Recent findings have raised the possibility that polymorphisms within the annexin A5 gene (ANXA5) promoter contribute to the etiology of recurrent pregnancy loss (RPL). In our present study, 243 Japanese women who had suffered more than three fetal losses and a group of 119 fertile controls were genotyped for four ANXA5 gene promoter single-nucleotide polymorphisms (SNPs; SNP1-4: g.-467G >A, g.-448A>C, g.-422T>C, g.-373G>A) previously reported to be associated with this disorder. An additional two SNPs located within the 5'-untranslated region of the ANXA5 (SNP5 and 6: g.-302T>G, g.-1C>T) were also evaluated. Our case--control study revealed that the minor allele was significantly more frequent in the RPL group than controls for all six of these SNPs, among which SNP5 showed the highest significance (P= 0.002). As with the M2 haplotype for SNP1-4 (A-C-C-A) for a western population in previous reports, a haplotype comprising all of the minor alleles for SNP1-6 (A-C-C-A-G-T), the third major haplotype in the Japanese population, showed a significantly higher frequency in our current RPL subjects than in controls (P= 0.025). In addition, the second major haplotype (G-A-T-G-G-C) was found to confer a significant risk of RPL (P= 0.036), implicating SNP5 as a major risk determinant for this disease. Our present findings support the hypothesis that genomic variations within the ANXA5 gene upstream region impact upon the disease susceptibility to RPL. Our data indicate that SNP5 is a novel risk factor for this disease in the Japanese population.

Genetic variation in the indoleamine 2,3-dioxygenase gene in pre-eclampsia.

PROBLEM: To investigate the contribution of genomic variations in the indoleamine 2,3-dioxygenase (IDO) gene to the onset of pre-eclampsia. METHOD OF STUDY: We examined sequence variations in the IDO1 gene using placental genomic DNA from 35 pre-eclamptic patients and 32 normotensive pregnant women. RESULTS: A case-control study revealed that none of the common variants influences the risk of disease. Sequencing of each IDO1 exon in diseased subjects revealed rare variants. This variation, c.-147_150delGAAA, was located within the 5'-untranslated region of the IDO1 gene, and its homozygote was identified only in pre-eclamptic subjects. However, despite the low levels of IDO expression and enzyme activity in the c.-147_150delGAAA homozygote, reporter assays indicated that this variation does not affect gene expression. CONCLUSION: Our findings indicate that genetic alteration of fetal IDO gene does not appear to be a primary cause of pre-eclampsia.

CD9 gene variations are not associated with female infertility in humans.

BACKGROUND/AIMS: To determine whether genetic alterations in the CD9 gene are associated with female infertility in humans. METHODS: We sequenced the entire coding region of this gene in 86 Japanese women with unexplained infertility and further conducted a case-control study of six tagging single nucleotide polymorphisms (SNPs) in this gene using an additional 164 samples obtained from a fertile control group. RESULTS: No disease-causing mutation in the CD9 gene was evident in these samples and no significant association between the tagging SNPs and the studied cohort was identified. CONCLUSIONS: Our findings do not support the hypothesis that genetic alterations of the CD9 gene cause female infertility in humans.

Analysis of nitric oxide metabolism as a placental or maternal factor underlying the etiology of pre-eclampsia.

BACKGROUND: Defective nitric oxide (NO)-mediated vasodilation is widely regarded as an underlying cause of hypertension in pre-eclampsia, although there are also arguments against this hypothesis. METHODS: We examined both the mRNA levels and the presence of a Glu298Asp substitution in the NO synthase (NOS) gene, as well as the NO metabolite concentration, in placentas and maternal sera from women with pre-eclampsia and in normotensive pregnant controls (25-40 vs. 24-41 weeks of gestation). RESULTS: Pre-eclamptic and control placentas did not show any significant differences in their NO metabolite levels or their NOS expression levels as measured by quantitative RT-PCR. In addition, we did not find any association between pre-eclampsia and the occurrence of the Glu298Asp amino acid substitution in the NOS gene. In contrast, high maternal circulating NO metabolites were evident in severe pre-eclampsia (p < 0.0001). Although a positive correlation between circulating NO metabolites and blood pressure was not observed, uterine artery resistance measured by ultrasound was found to positively correlate with the maternal NO levels. CONCLUSIONS: Our current data suggest that an altered placental NOS pathway is unlikely to be the primary cause of pre-eclampsia and that the activation of this pathway is possibly in response to maternal symptoms.

Mutations of the SYCP3 gene in women with recurrent pregnancy loss.

Aneuploidy, a chromosomal numerical abnormality in the conceptus or fetus, occurs in at least 5% of all pregnancies and is the leading cause of early pregnancy loss in humans. Accumulating evidence now suggests that the correct segregation of chromosomes is affected by events occurring in prophase during meiosis I. These events include homologous chromosome pairing, sister-chromatid cohesion, and meiotic recombination. In our current study, we show that mutations in SYCP3, a gene encoding an essential component of the synaptonemal complex that is central to the interaction of homologous chromosomes, are associated with recurrent pregnancy loss. Two out of 26 women with recurrent pregnancy loss of unknown cause were found to carry independent heterozygous nucleotide alterations in this gene, neither of which was present among a group of 150 fertile women. Analysis of transcripts from minigenes harboring each of these two mutations revealed that both affected normal splicing, possibly resulting in the production of C-terminally mutated proteins. The mutant proteins were found to interact with their wild-type counterpart in vitro and inhibit the normal fiber formation of the SYCP3 protein when coexpressed in a heterologous system. These data suggest that these mutations are likely to generate an aberrant synaptonemal complex in a dominant-negative manner and contribute to abnormal chromosomal behavior that might lead to recurrent miscarriage. Combined with the fact that similar mutations have been previously identified in two males with azoospermia, our current data suggest that sexual dimorphism in response to meiotic disruption occurs even in humans.

Increased levels of pregnancy-associated plasma protein-A2 in the serum of pre-eclamptic patients.

Pregnancy-associated plasma protein-A and -A2 (PAPP-A and -A2) are proteases that cleave insulin-like growth factor-binding proteins (IGFBPs), resulting in local activation of IGF signaling pathways. Here, we examined PAPP-A and -A2 mRNA and protein levels in placenta and maternal sera from women with pre-eclampsia and compared them with samples from uncomplicated pregnancy. PAPP-A2 but not PAPP-A mRNA and protein were elevated in pre-eclamptic placenta (P < 0.01). PAPP-A2 is normally produced in placental syncytiotrophoblast cells and maternal decidua. PAPP-A2 in syncytiotrophoblast cells was dramatically increased in pre-eclampsia. Maternal serum concentrations of PAPP-A2 but not PAPP-A were also significantly elevated in pre-eclampsia as compared with uncomplicated pregnancy. mRNA levels of IGFBP5, a specific substrate for PAPP-A2 protease activity, were also significantly increased, suggesting a potential role for IGFBP5 in fetal and placental growth suppression during pre-eclampsia. However, IGFBP5 protein levels were not increased in placenta from pre-eclampsia, possibly due to cleavage by up-regulated PAPP-A2. These data might imply that PAPP-A2 may be up-regulated in pre-eclamptic pregnancy to compensate for IGFBP5-mediated suppression of the IGF pathway, although final birthweights are still low in pre-eclamptic pregnancy.