Association of eNOS Glu298Asp Polymorphism With End-Stage Renal Disease

Abstract

Abstract-Nitric oxide (NO) derived from endothelial cells is profoundly related to the maintenance of physiological vascular tone. Impairment of endothelial NO generation brought about by gene polymorphism is considered the major deterioration factor for progressive renal disease, including diabetic nephropathy. The present study aimed to elucidate the Glu298Asp polymorphism of endothelial NO synthase (eNOS) in patients with end-stage renal disease (ESRD) and its role as a predisposing factor for cardiovascular complications. Glu298Asp in exon 7 of the eNOS gene was determined by polymerase chain reaction, followed by restriction fragment length polymorphism analysis, in ESRD patients (nϭ185) and compared with that of unrelated healthy individuals (nϭ304). Key Words: polymorphism Ⅲ polymerase chain reaction Ⅲ nitric oxide synthase Ⅲ diabetes mellitus T he endothelial isoform of nitric oxide (NO) synthase (eNOS, NOSIII) is a constitutively expressed 135 kDa protein predominantly associated with the particulated specific structures in the plasmalemmal membrane, caveolae, of vascular endothelial cells. 1,2 NO is produced from L-arginine and diffuses to vascular smooth muscle cells, where it increases the concentration of cGMP by stimulating soluble guanylate cyclase, leading to vascular relaxation. It also inhibits platelet and/or leukocyte adhesion to vascular endothelium. Therefore, the impairment of eNOS expression has been considered a primary factor for diseases such as hypertension, coronary artery disease, thromboembolic diseases, and atherosclerosis. Indeed, knocking out the gene encoding eNOS in mice resulted in significant hypertension, and aortic rings from these animals studied ex vivo displayed no relaxation in response to acetylcholine. 3 Patients with endstage renal disease (ESRD) derived from diabetes mellitus (DM) nephropathy have a higher prevalence of cardiovascular complications than those with non-DM ESRD, and this limits their 5-year survival rate to less than 50%. Therefore, polymorphism in eNOS is considered one of the major predisposing factors for endothelial dysfunction.The gene polymorphisms of eNOS have been detected at 4b/4a variable number of tandem repeats in intron 4, Glu298Asp in exon 7, CA repeat in intron 13, A27 to C (A to C nucleotide conversion) in intron 18, and G10 to T in intron 23. A part of candidate variations (4b/4a tandem repeats in intron 4) has been investigated in glomerulonephritis and/or ESRD patients, but no conclusive results have been obtained so far. Recently, the G/T polymorphism in exon 7 coding for Glu298Asp was detected and reported to have a remarkable association with coronary spasm, acute myocardial infarction, 4 and hypertension. 5 To date, this is the only known eNOS polymorphism associated with an altered protein sequence, though recent expression studies have demonstrated no functional difference between 298Glu and 298Asp despite the accumulating clinical evidence. 6,7

Genetic risk factors for diabetic nephropathy on chromosomes 6p and 7q identified by the set-association approach

“…One of the first indications that genes within chromosome 7q35 (including NOS3) could influence genetic susceptibility to DN came from the nonparametric linkage study in Pima Indians [16]. Several positive associations of some of the numerous NOS3 SNPs with renal disease were documented in type 1 [41] and type 2 diabetes [42], as well as in non-diabetic subjects [43,44], while other studies did not find an association [45]. The two 'set-associated' SNPs in our study-silent substitution 774C/T in exon 6 altering the third base of the codon (both encoding an Asp) and non-synonymous substitution 894G/ T alleles in exon 7 (probably not functional though since the resulting amino acid difference at position 298 Glu to Asp in the oxygenase domain is a conservative one)-are the most probably neutral genetic markers of a yet unidentified functional NOS3 or neighbouring gene polymorphism in a linkage disequilibrium with the two SNPs.…”

The Glu298Asp variant of the endothelial nitric oxide synthase gene is associated with an increased risk for abruptio placentae in pre-eclampsia

“…Failure of this adaptation is thought to result in increased blood pressure, proteinuria, and wide-spread endothelial dysfunction (classical pre-eclampsia), arteriolar contraction, ischaemia of the decidua basalis, necrosis and haemorrhage (classical placental abruption). Although reduced NO bio-availability has already been reported in eNOS Asp298 homozygous individuals, there remains controversy about the interpretation of these findings (Fairchild et al 2001;Noiri et al 2002;Serrano et al 2004).…”

Haplotype analysis of NAD(P)H oxidase p22 phox polymorphisms in end-stage renal disease

“…They found a significant association with diabetic nephropathy in type 2 diabetes when they examined the 242C/T polymorphism accompanied with the receptor for advanced glycation end products (RAGE) gene 1704G/T polymorphism. It is likely that other genetic factors in addition to RAGE polymorphisms, such as nitric oxide synthetase, methylenetetrahydrofolate reductase, peroxisome proliferator-activated receptor cÀ2, and aldose reductase gene polymorphisms may also contribute predisposing factors to diabetic nephropathy (Caramori et al 2003;Noiri et al 2000Noiri et al , 2002Zhao et al 2004b). Hodgkinson et al 2003) showed an association of the 242C/T polymorphism with diabetic nephropathy in type 1 diabetes.…”