Influence of nitric oxide synthase gene polymorphisms on the risk of cardiovascular events in rheumatoid arthritis

Complex interactions between environmental and genetic determinants in both the host immune system and the vasculature may operate modifying the vascular risk in rheumatoid arthritis (RA). An increased incidence of cardiovascular (CV) events in RA patients carrying HLA-DRB1 shared epitope alleles, in particular HLA-DRB1*0404, has recently been found. In the present study we have assessed the potential contribution of inducible and endothelial nitric oxide synthase (NOS2A and NOS3) gene polymorphisms to CV events in a cohort of patients with rheumatoid arthritis (RA). Also, interactions between NOS2A or NOS3 gene polymorphisms and HLA-DRB1 alleles for the risk of developing CV events were assessed.

One hundred and eighty-two consecutive patients fulfilling the 1987 American College of Rheumatology classification criteria for RA seen at the Rheumatology outpatient clinic of Hospital Xeral Calde, Lugo, Northwest Spain, between March and September 1996 were included. Patients were genotyped by PCR based techniques for a multiallelic (CCTTT)n repeat in the promoter region of the NOS2A gene and for a T/C polymorphism at position -786 in the promoter region and a polymorphism in exon 7 (298Glu/Asp or 5557G/T) of the NOS3 gene. They were prospectively followed and clinical records were examined until patient's death or September 1, 2005. At the end of the study 39 (21%) patients had experienced CV events.

No significant differences in allele or genotype frequencies for the NOS2A promoter CCTTT repeat microsatellite and NOS3 gene polymorphisms between RA patients with or without CV events were found. However, an increased frequency of CV events was observed in RA patients who carried the HLA-DRB1*0404 allele and were homozygous for the NOS3 (-786) TT genotype (OR: 9.06 [95% CI: 1.29-63.37]; p= 0.03) or for the presence of long NOS2A alleles (OR: 11.7 [95% CI: 1.53-88.4]); p= 0.02).

Our results show that NOS2A or NOS3 gene polymorphisms do not infer a direct risk for CV events in RA. However, some interactions between NOS gene polymorphisms and HLA-DRB1 alleles confer and increased risk of developing CV events in patients with RA.