Prognostic value of T786C and G894T eNOS polymorphisms in sickle cell disease

•eNOS T786C and G894T polymorphisms affect clinical phenotype of Sickle Cell Disease according to beta globin gene genotype.•786CC genotype predisposes Sickle Cell Disease patients with S/S and β0/S genotype to proliferative retinopathy.•894TT genotype is associated with higher hematocrit in Sickle Cell Disease patients of S/S and β0/S genotype.•Peripheral blood eNOS mRNA levels are not associated with beta globin gene genotype or eNOS T786C genotype.

Endothelial Nitric Oxide Synthase (eNOS) is crucial for vascular homeostasis. Polymorphisms T786C and G894T affect eNOS regulation and have been related to various diseases. Sickle Cell Disease (SCD), a clinically diverse chronic hemolytic anemia, implies impaired nitric oxide bioavailability. Our aim was to determine eNOS genotype for T786C and G894T polymorphisms in Greek patients with SCD and to elucidate its consequences and effects if any on clinical phenotype. Seventy nine steady state cases, mostly compound heterozygous for Sickle Cell anemia/beta thalassemia and 48 controls were measured. Peripheral blood DNA was extracted and genotyped with PCR-RFLPs and Sanger sequencing. Total RNA was extracted from 18 patients and 9 controls and eNOS mRNA levels were determined by real-time PCR. Genotypes, allele distribution and eNOS mRNA levels did not differ between patients and controls, or among patients with different beta globin gene mutations. The 786CC genotype was more common in S/S and β0/S patients with retinopathy. Moreover, 894TT S/S and β0/S patients tended to have a higher hematocrit than 894GG and GT ones. However, the T786C eNOS genotype does not seem to affect peripheral blood cell-derived eNOS mRNA levels, at least in steady state conditions. This work is the first one describing the effects of eNOS polymorphisms on different forms of SCD, the first enrolling SCD patients of Caucasian origin and the first determining eNOS mRNA levels in peripheral blood from steady-state SCD patients.