BACKGROUNDHeme-oxygenase 1 (HO-1) is a rate-limiting enzyme in the degradation of heme to bilirubin, ferritin and carbon monoxide (CO) and may have significant anti-inflammatory function. The HO-1 gene promoter region shows microsatellite polymorphism with different (GT)n repeats, reported to differently induce gene expression, with the short allele associated with higher gene expression. We measured the acute inflammatory response using coronary artery bypass surgery (CABG) as a well-characterized and uniform stimulus and examined the correlation between levels of IL-6, C-reactive protein (CRP) and fibrinogen and their relationship to HO-1 genotype.

METHODSTwo hundred and seventy-five consecutive patients undergoing CABG were genotyped for the HO-1 promoter polymorphism using PCR and automated DNA capillary sequencer. IL-6, CRP and fibrinogen were measured at baseline and 6, 24, 48, 72, 96 and 120 hours after CABG.

RESULTSComplete IL-6, CRP and fibrinogen measures were available in 220 patients. Before surgery IL-6 levels showed a strong correlation with CRP and fibrinogen (r = 0.48, P < 0.0001; r = 0.41, P < 0.0001 respectively), with a significant correlation between CRP and fibrinogen (r = 0.61, P < 0.0001). All three acute phase reactants showed a significant increase after CABG. After surgery, peak IL-6 was strongly correlated with peak CRP (r = 0.34, P = 0.0009) but not with peak fibrinogen (r = 0.15, P = 0.13), while peak CRP and peak fibrinogen were significantly correlated (r = 0.415, P < 0.0001). HO-1 allelic repeats ranged from 22-42, with (GT)25 and (GT)32 being the two most common alleles, and subsequently divided into three groups according to previous published work: <30 (GT)n were designated as S (short), 30-37 (GT)n as M (middle) and long repeats with >37 (GT)n as L (long); allele frequency 0.35, 0.58 and 0.07 respectively. Baseline CRP differed by genotype: those carrying at least one long allele having higher CRP than those with no long allele (3.76 +/- 0.79 vs. 2.07 +/- 0.17, P = 0.013). Conversely, those carrying at least one short allele had higher fibrinogen levels than those with no short allele (3.83 +/- 0.79 vs. 3.51 +/- 0.88, P = 0.006).

CONCLUSIONSThere is a strong correlation between the measured acute phase reactants both at baseline and after the inflammatory response to CABG in patients with coronary disease. There was an association between the HO-1 microsatellite polymorphism and CRP and fibrinogen levels at baseline but there was no similar association following CABG. This may indicate that HO-1 is associated with chronic atherosclerotic inflammatory processes rather than acute.

Adult ; Aged ; C-Reactive Protein ; analysis ; Coronary Artery Bypass ; Fibrinogen ; analysis ; Genotype ; Heme Oxygenase (Decyclizing) ; genetics ; Heme Oxygenase-1 ; Humans ; Inflammation ; etiology ; Interleukin-6 ; blood ; Membrane Proteins ; Microsatellite Repeats ; Middle Aged ; Polymorphism, Genetic

BACKGROUNDVascular smooth muscle cells (VSMCs) can express heme-oxygenase (HO), a rate-limiting enzyme in the degradation of heme to bilirubin, ferritin and carbon monoxide (CO). VSMC-derived CO can suppress VSMC proliferation and may serve as an antiproliferation factor. The promoter region of HO-1 shows a polymorphism with different (GT) n repeats that has been reported to differently induce gene expression. The objective of this study was to examine the effect of this variation on the occurrence of restenosis after in-stent treatment in patients with coronary artery disease.

METHODSCandidates who underwent coronary stent implantation were genotyped for the HO-1 promoter polymorphism using polymerase chain reaction (PCR) and automated DNA capillary sequencer. Serum levels of IL-6 and C-reactive protein (CRP) were obtained at baseline, 24 hours and 48 hours after stenting. The primary end point for the study was angiographic evidence of in-stent restenosis at 6 months. All parameters for evaluation of restenosis were analysed by quantitative computer-assisted angiographic analysis (QCA).

RESULTSOne hundred and eighty-seven patients who underwent coronary stent implantation were studied of whom 27.8% showed > or = 50% restenosis after 6 months. The distribution of (GT) n repeats of all patients in the promoter region of HO-1 genotype ranged from 22 to 42, with (GT) 25 and (GT) 32 being the two most common alleles. The allelic repeats were divided into the short class (S) with 29 (GT) n, the middle class (M) with 30-37 (GT) n and the long class (L) with 38 (GT) n. There was no significant difference in the restenosis between the genotype groups or between post operation levels of inflammation markers, but carriers of the S allele (n = 120) had 33.3% lower baseline IL-6 compared with non-S carriers (n = 67, P = 0.0008).

CONCLUSIONSAlthough no association was observed between the HO-1 promoter polymorphism and coronary in-stent restenosis following the stent procedure, the association with plasma IL-6 levels suggests that HO-1 S allele might protect from the atherosclerotic inflammatory process.

Adult ; Aged ; Angioplasty, Balloon, Coronary ; C-Reactive Protein ; analysis ; Coronary Restenosis ; blood ; enzymology ; genetics ; Female ; Genotype ; Heme Oxygenase (Decyclizing) ; genetics ; Heme Oxygenase-1 ; Humans ; Interleukin-6 ; blood ; Male ; Membrane Proteins ; Microsatellite Repeats ; Middle Aged ; Polymorphism, Genetic ; Promoter Regions, Genetic ; Stents