Inhaled nitric oxide for the treatment of preterm infants with respiratory distress syndrome

Genetic Contributions to the Development of Complications in Preterm Newborns

Aim

We aimed to identify specific polymorphisms of genes encoding for vascular endothelial growth factor A (VEGFA), endothelial nitric oxide synthase (eNOS), renin-angiotensin system (angiotensinogen gene [AGT], angiotensinogen type 1 receptor [AGTR1], angiotensin-converting enzyme [ACE]), and heme oxygenase-1 (HMOX-1) in a cohort of preterm infants and correlate their presence with the development of respiratory distress syndrome (RDS) requiring mechanical ventilation (MV), bronchopulmonary dysplasia (BPD), intraventricular hemorrhage (IVH) and retinopathy of prematurity (ROP).

Study Design

We carried out a retrospective study to evaluate the allele frequency and genotype distribution of polymorphisms of VEGFA, eNOS, AGT, AGTR1, ACE, and HMOX-1 in a population of preterm neonates (n=342) with a gestational age ≤28 weeks according to the presence or absence of RDS requiring MV, BPD, IVH, or ROP. Moreover, we evaluated through the haplotype reconstruction analysis whether combinations of the selected polymorphisms are related to the occurrence of RDS, BPD, IVH and ROP.

Results

In our population 157 infants developed RDS requiring MV, 71 BPD, 70 IVH, and 43 ROP. We found that TC+CC rs2070744 eNOS (41.7 vs. 25.4%, p=0.01) and GT+TT rs1799983 eNOS (51.8 vs. 35.2%, p=0.01) polymorphisms are independent risk factors for BPD. Haplotype reconstruction showed that haplotypes in VEGF and eNOS are significantly associated with different effects on RDS, BPD, IVH, and ROP in our population.

Conclusions

We found that TC+CC rs2070744 eNOS and GT+TT rs1799983 eNOS polymorphisms are independent predictors of an increased risk of developing BPD. Haplotypes of VEGFA and eNOS may be independent protective or risk markers for prematurity complications.

Association of NOS3 tag polymorphisms with hypoxic-ischemic encephalopathy

Aim

To test the association of NOS3 gene with hypoxic-ischemic encephalopathy (HIE).

Methods

The study included 110 unrelated term or preterm born children (69 boys and 41 girls) with HIE and 128 term and preterm born children (60 boys and 68 girls) without any neurological problems after the second year of life. Children with perinatal HIE fulfilled the diagnostic criteria for perinatal asphyxia. All children were admitted to the Clinical Hospital Split between 1992 and 2008. We analyzed 6 tagging single nucleotide polymorphisms (SNP) within NOS3 gene (rs3918186, rs3918188, rs1800783, rs1808593, rs3918227, rs1799983), in addition to previously confirmed NOS3-associated SNP rs1800779. Genotyping was conducted using real-time polymerase chain reaction (PCR). Association analyses were performed according to allelic and genotypic distribution.

Results

Allelic test did not show any SNP association with HIE. SNP rs1808593 showed genotype association (P = 0.008) and rs1800783-rs1800779 TG haplotype showed an association with HIE (P < 0.001). The study had 80% statistical power to detect (α = 0.05) an effect with odds ratio (OR) = 2.07 for rs3918186, OR = 1.69 for rs3918188, OR = 1.70 for rs1800783, OR = 1.80 for rs1808593, OR = 2.10 for rs3918227, OR = 1.68 for rs1800779, and OR = 1.76 for rs1799983, assuming an additive model.

Conclusion

Despite the limited number of HIE patients, we observed genotypic and haplotype associations of NOS3 polymorphisms with HIE.

Is an endothelial nitric oxide synthase gene mutation a risk factor in the origin of intraventricular hemorrhage?

OBJECT

Studies have shown decreased levels of nitric oxide (NO), the product of endothelial NO synthase (eNOS) gene activity, in infants with respiratory conditions and intraventricular hemorrhage (IVH). The authors evaluated the association of the eNOS gene promoter polymorphism T-786C with the cause of these conditions (respiratory conditions and IVH) in premature infants.

METHODS

Blood samples from 124 African American premature infants were studied. The DNA was isolated and microplate polymerase chain reaction-restriction fragment length polymorphism assay was performed. Genotypes were scored as: TT homozygotes with 140 bp and 40 bp; CC homozygotes with 90 bp, 50 bp, and 40 bp; and TC heterozygotes with 140 bp, 90 bp, 50 bp, and 40 bp. Genotypes were stratified according to ethnicity, preterm status, and prematurity conditions.

RESULTS

The mutant allele -786C was present in 15.3% of premature infants with respiratory distress syndrome, bronchopulmonary dysplasia, and IVH, compared with 7.25% in those premature infants without these conditions. A significant 2-fold increase of the mutant allele in patients compared with controls (p = 0.04, OR 2.3) reveals that the eNOS -786C allele could be a significant risk factor in the origin of respiratory conditions and IVH in premature infants.

CONCLUSIONS

These results suggest that the mutant eNOS -786C allele is a significant risk factor in the origin of respiratory and IVH diseases, probably mediating an insufficient supply of endogenous NO in premature infants.

Pitfalls, problems, and progress in bronchopulmonary dysplasia

Bronchopulmonary dysplasia is a chronic lung disease associated with premature birth and characterized by early lung injury. In this review we discuss some pitfalls, problems, and progress in this condition over the last decade, focusing mainly on the last 5 years, limited to studies in human neonates. Changes in the definition, pathogenesis, genetic susceptibility, and recent biomarkers associated with bronchopulmonary dysplasia will be discussed. Progress in current management strategies, along with novel approaches/therapies, will be critically appraised. Finally, recent data on long-term pulmonary and neurodevelopmental outcomes of infants with bronchopulmonary dysplasia will be summarized.