Heme oxygenase-1 genotype is a vascular anti-inflammatory factor following balloon angioplasty

The clinical relevance of heme detoxification by the macrophage heme oxygenase system

Heme degradation by the heme oxygenase (HMOX) family of enzymes is critical for maintaining homeostasis and limiting heme-induced tissue damage. Macrophages express HMOX1 and 2 and are critical sites of heme degradation in healthy and diseased states. Here we review the functions of the macrophage heme oxygenase system and its clinical relevance in discrete groups of pathologies where heme has been demonstrated to play a driving role. HMOX1 function in macrophages is essential for limiting oxidative tissue damage in both acute and chronic hemolytic disorders. By degrading pro-inflammatory heme and releasing anti-inflammatory molecules such as carbon monoxide, HMOX1 fine-tunes the acute inflammatory response with consequences for disorders of hyperinflammation such as sepsis. We then discuss divergent beneficial and pathological roles for HMOX1 in disorders such as atherosclerosis and metabolic syndrome, where activation of the HMOX system sits at the crossroads of chronic low-grade inflammation and oxidative stress. Finally, we highlight the emerging role for HMOX1 in regulating macrophage cell death via the iron- and oxidation-dependent form of cell death, ferroptosis. In summary, the importance of heme clearance by macrophages is an active area of investigation with relevance for therapeutic intervention in a diverse array of human diseases.

Heme oxygenase‑1 improves the survival of ischemic skin flaps (Review)

Heat shock protein 32 (Hsp32), also known as heme oxygenase‑1 (HO‑1), is an enzyme that exists in microsomes. HO‑1 can be induced by a variety of stimuli, including heavy metals, heat shock, inflammatory stimuli, heme and its derivatives, stress, hypoxia, and biological hormones. HO‑1 is the rate‑limiting enzyme of heme catabolism, which splits heme into biliverdin, carbon monoxide (CO) and iron. The metabolites of HO‑1 have anti‑inflammatory and anti‑oxidant effects, and provide protection to the cardiovascular system and transplanted organs. This review summarizes the biological characteristics of HO‑1 and the functional significance of its products, and specifically elaborates on its protective effect on skin flaps. HO‑1 improves the survival rate of ischemic skin flaps through anti‑inflammatory, anti‑oxidant and vasodilatory effects of enzymatic reaction products. In particular, this review focuses on the role of carbon monoxide (CO), one of the primary metabolites of HO‑1, in flap survival and discusses the feasibility and existing challenges of HO‑1 in flap surgery.

Therapeutic Potential of Heme Oxygenase-1 in Aneurysmal Diseases

Abdominal aortic aneurysm (AAA) and intracranial aneurysm (IA) are serious arterial diseases in the aorta and brain, respectively. AAA and IA are associated with old age in males and females, respectively, and if rupture occurs, they carry high morbidity and mortality. Aneurysmal subarachnoid hemorrhage (SAH) due to IA rupture has a high rate of complication and fatality. Despite these severe clinical outcomes, preventing or treating these devastating diseases remains an unmet medical need. Inflammation and oxidative stress are shared pathologies of these vascular diseases. Therefore, therapeutic strategies have focused on reducing inflammation and reactive oxygen species levels. Interestingly, in response to cellular stress, the inducible heme oxygenase-1 (HO-1) is highly upregulated and protects against tissue injury. HO-1 degrades the prooxidant heme and generates molecules with antioxidative and anti-inflammatory properties, resulting in decreased oxidative stress and inflammation. Therefore, increasing HO-1 activity is an attractive option for therapy. Several HO-1 inducers have been identified and tested in animal models for preventing or alleviating AAA, IA, and SAH. However, clinical trials have shown conflicting results. Further research and the development of highly selective HO-1 regulators may be needed to prevent the initiation and progression of AAA, IA, or SAH.

Activation of Nrf2/HO-1 Pathway and Human Atherosclerotic Plaque Vulnerability:an In Vitro and In Vivo Study

Reactive oxygen species (ROS) induce nuclear factor erythroid 2-related factor 2 (Nrf2) activation as an adaptive defense mechanism, determining the synthesis of antioxidant molecules, including heme-oxygenase-1 (HO-1). HO-1 protects cells against oxidative injury, degrading free heme and inhibiting ROS production. HO-1 is highly expressed in macrophages during plaque growth. Macrophages are morpho-functionally heterogeneous, and the prevalence of a specific phenotype may influence the plaque fate. This heterogeneity has also been observed in monocyte-derived macrophages (MDMs), a model of macrophages infiltrating tissue. The study aims to assess oxidative stress status and Nrf2/HO-1 axis in MDM morphotypes obtained from healthy subjects and coronary artery disease (CAD) patients, in relation to coronary plaque features evaluated in vivo by optical coherence tomography (OCT). We found that MDMs of healthy subjects exhibited a lower oxidative stress status, lower Nrf2 and HO-1 levels as compared to CAD patients. High HO-1 levels in MDMs were associated with the presence of a higher macrophage content, a thinner fibrous cap, and a ruptured plaque with thrombus formation, detected by OCT analysis. These findings suggest the presence of a relationship between in vivo plaque characteristics and in vitro MDM profile, and may help to identify patients with rupture-prone coronary plaque.

The Number of GT(n) Repeats in the Hemeoxygenase-1 Gene Promoter is Increased in Pediatric Heart Failure but is Unrelated to Renal, Antioxidant and Anti-inflammatory Markers

Products of hemeoxygenase (HO)-1 have anti-inflammatory and antioxidant functions. The HO-1 promoter has a variable number of GT(n) repeats: A low number (n < 23) is associated with high transcriptional activity in response to oxidative stress. We hypothesized that the frequency of GT(n) repeats in pediatric heart failure (HF) reflects plasma biomarkers of different disease processes: the soluble receptor for advance glycation end products (sRAGE, marking cellular activation), oxLDL (oxidative stress), NGAL (impaired renal function), HIF-1α (hypoxia) and hsCRP (inflammation). Sixty HF children [aged 4-14 years, 30 with HF due to idiopathic dilated cardiomyopathy (IDCM), 30 due to chronic renal failure (CRF)] were compared to 20 healthy controls (HC). Leukocyte HO-1 GT(n) repeats were determined by PCR, plasma markers by ELISA or nephelometry. The number of GT(n) repeats in the HF patients was higher than the number of repeats in the controls, with no difference between the patient groups (p < 0.001). sRAGE, oxLDL, HIF-1α, NGAL and hsCRP were higher in both HF groups compared to HC (all p < 0.01). IDCM had higher sRAGEs and HIF-1α compared to CRF patients (p < 0.01). NGAL was higher in CRF compared to IDCM (p < 0.01). None of the plasma/serum markers correlated with the number of GT(n) repeats in any group. The number of HO-1 promoter GT(n) polymorphism is increased in both IDCM and CRF children with HF, but is unrelated to plasma markers of different pathological processes. This casts doubts on the clinical value of the number of GT(n) repeats in pediatric HF.

Heme Oxygenase-1 Promoter Polymorphism Protects Liver Allograft

Heme oxygenase-1 has been identified to protect allograft from ischemia/reperfusion and immunologic rejection. Activity of heme oxygenase-1 is regulated by a guanine-thymine dinucleotide length polymorphism in the heme oxygenase-1 gene promoter. In this study, we aimed to explore the impact of the heme oxygenase-1 gene promoter polymorphism of donors and recipients on the orthotopic liver graft function after transplantation. Sixty recipients and their accompanying donors of orthotopic liver allografts were included retrospectively in this study. Heme oxygenase-1 gene promoter polymorphism was assessed using genomic DNA isolated from cryopreserved splenocytes or peripheral blood mononuclear cells and analyzed by genetic analyzer. Small allele of the donor heme oxygenase-1 gene polymorphism significantly prolonged the graft survival (p = 0.017). Recipients of allografts from a class of small-allele carrier had significantly lower serum total bilirubin compared with recipients of a nonclass small-allele donor liver (p < 0.01). Additionally, in recipients of small-carrier allografts, cold ischemia time (<10 h or ≥10 h) did not affect the total bilirubin significantly. Our study suggested a protective function of donor-derived heme oxygenase-1 gene promoter polymorphism on orthotopic liver allograft function after transplantation.

Haeme oxygenase signalling pathway: implications for cardiovascular disease

Evidence now points to the haeme oxygenase (HO) pathway as a possible actor in modulating risk for cardiovascular disease (CVD). In particular, the HO pathway may represent a key endogenous modulator of oxidative, inflammatory, and cytotoxic stress while also exhibiting vasoregulatory properties. In this review, we summarize the accumulating experimental and emerging clinical data indicating how activity of the HO pathway and its products may play a role in mechanisms underlying the development of CVD. We also identify gaps in the literature to date and suggest future directions for investigation. Because HO pathway activity can be influenced not only by genetic traits and environmental stimuli but also by a variety of existing pharmacologic interventions, the pathway could serve as a prime target for reducing the overall burden of CVD. Further work is needed to determine the role of HO pathway products as possible prognostic markers of risk for clinical CVD events and the extent to which therapeutic augmentation or inhibition of HO pathway activity could serve to modify CVD risk.

Association of HO-1 (GT)n Promoter Polymorphism and Cardiovascular Disease: A Reanalysis of the Literature

BACKGROUND

Heme-oxygenase 1 (HO-1), an inducible heme-degrading enzyme, has antiatherogenic effects through its enzymatic end products. HO-1 gene expression is modulated by a guanidine thymidine dinucleotide ([GT]n) repeat polymorphism in the promoter region. Shorter repeats with (GT)n < 25 are associated with higher inducibility and activity of HO-1.

METHODS

We performed a systematic review of all literature from 1997 to 2013 on the association of the HO-1 (GT)n and cardiovascular disease (CVD). On the basis of predefined criteria (patient characteristics, genotype data format, allelic distribution, repeat length cutoff) 41 articles were selected. Patients were redistributed into 4 homogeneous subpopulations: patients with CVD (CVD group), patients without CVD (nonCVD), 'controls' with unknown cardiovascular status (unspecified) and children younger than 20 years of age (unselected). Genotype distributions (homozygous short [SS] or long [LL], and heterozygous) of the 4 patient categories were compared and odds ratios (ORs) for CVD were calculated using logistic regression analysis.

RESULTS

Overall, the proportion of the SS genotype was lower in CVD compared with nonCVD and unspecified. The ORs for CVD was highest in patients carrying the LL genotype (OR LL vs SS, 1.769 [95% confidence interval, 1.594-1.963]). Furthermore, genotype distribution differed between Caucasian and Asian individuals, the latter having a much higher proportion of the SS genotype (22% vs 11%).

CONCLUSIONS

This review of the available literature on the epidemiological association between the HO-1 (GT)n repeat polymorphism and CVD supports the presumed protective effects of HO-1. The second but probably even more relevant finding of our review is that racial disparities in HO-1 (GT)n repeat length distribution exist and might influence the associations of the genotype with CVD status.

HMOX1 gene promoter polymorphism is not associated with coronary artery disease in Koreans

Background

The heme oxygenase-1 gene (HMOX1) promoter polymorphisms modulate its transcription in response to oxidative stress. This study screened for HMOX1 polymorphisms and investigated the association between HMOX1 polymorphisms and coronary artery disease (CAD) in the Korean population.

Methods

The study population consisted of patients with CAD with obstructive lesions (n=110), CAD with minimal or no lesions (n=40), and controls (n=107). Thirty-nine patients with CAD with obstructive lesions underwent follow-up coronary angiography after six months for the presence of restenosis. The 5'-flanking region containing (GT)n repeats of the HMOX1 gene was analyzed by PCR.

Results

The numbers of (GT)n repeats in the HMOX1 promoter showed a bimodal distribution. The alleles were divided into two subclasses, S25 and L25, depending on whether there were less than or equal to and more than 25 (GT)n repeats, respectively. The allele and genotype frequencies among groups were statistically not different. More subjects in the S25-carrier group had the low risk levels of high sensitivity C-reactive protein (hsCRP) for the CAD than those in the non-S25 carrier group (P=0.034). Multivariate logistic regression analysis revealed that the genotypes of (GT)n repeats were not related to CAD status. The restenosis group in the coronary angiography follow-up did not show any significant difference in HMOX1 genotype frequency.

Conclusions

The HMOX1 genotypes were not found to be associated with CAD, but the short allele carrier group contained more individuals with hsCRP values reflecting low risk of cardiovascular disease in the Korean population.

New insights into intracellular locations and functions of heme oxygenase-1

SIGNIFICANCE

Heme oxygenase-1 (HMOX1) plays a critical role in the protection of cells, and the inducible enzyme is implicated in a spectrum of human diseases. The increasing prevalence of cardiovascular and metabolic morbidities, for which current treatment approaches are not optimal, emphasizes the necessity to better understand key players such as HMOX1 that may be therapeutic targets.

RECENT ADVANCES

HMOX1 is a dynamic protein that can undergo post-translational and structural modifications which modulate HMOX1 function. Moreover, trafficking from the endoplasmic reticulum to other cellular compartments, including the nucleus, highlights that HMOX1 may play roles other than the catabolism of heme.

CRITICAL ISSUES

The ability of HMOX1 to be induced by a variety of stressors, in an equally wide variety of tissues and cell types, represents an obstacle for the therapeutic exploitation of the enzyme. Any capacity to modulate HMOX1 in cardiovascular and metabolic diseases should be tempered with an appreciation that HMOX1 may have an impact on cancer. Moreover, the potential for heme catabolism end products, such as carbon monoxide, to amplify the HMOX1 stress response should be considered.

FUTURE DIRECTIONS

A more complete understanding of HMOX1 modifications and the properties that they impart is necessary. Delineating these parameters will provide a clearer picture of the opportunities to modulate HMOX1 in human disease.

The association between heme oxygenase-1 gene promoter polymorphism and the outcomes of catheter ablation of atrial fibrillation

A length polymorphism of GT repeats in the promoter region of the human heme oxygenase-1 (HO-1) gene modulates its gene transcription to protect against myocardial injury. The present study investigated the association between HO-1 promoter polymorphisms and the outcomes of catheter ablation of atrial fibrillation (AF). The allelic frequencies of GT repeats in the HO-1 gene promoter were screened in 205 random individuals who underwent catheter ablation for drug refractory AF.In the patients who received catheter ablation, those with AF recurrence had fewer GT repeats (53.4±7.1 vs. 56.1±6.5, p = 0.004), a lower incidence of hyperlipidemia, more non-paroxysmal AF, and a larger left atrial diameter. After conducting a multivariate logistic analysis, the number of GT repeats (Odds ratio: 0.94, 95% CI 0.90–0.99, p = 0.01) and the diameter of the left atrium (Odds ratio: 1.08, 95% CI 1.02–1.15, p = 0.01) remained independent predictors. The carriers of GT repeats, which were <29 in both alleles, were associated with a lower sinus maintenance rate after catheter ablation (38.5% vs. 60.1%, p = 0.003). The patients were divided into paroxysmal and non-paroxysmal AF groups; the number of GT repeats was associated with AF recurrence only in the patients with paroxysmal AF. The number of GT repeats, combined with LAD, was significant for predicting AF recurrence after catheter ablation (p = 0.01). The number of GT repeats was not found to be associated with differences in the left atrial diameter, the biatrial voltage, or the levels of bilirubin, ferritin, iron, C-reactive protein, or von-Willibrand factor. In conclusions, HO-1 gene promoter polymorphisms were associated with AF recurrence after catheter ablation.

Haem oxygenase-1: non-canonical roles in physiology and pathology

HO-1 (haem oxygenase-1) is a ubiquitously expressed inducible enzyme degrading haem to CO, biliverdin and Fe2+. Its activation reduces oxidative stress in cells and inhibits inflammation, both due to removal of haem and because of the biological activity of HO-1 products. CO may act similarly to NO, activating soluble guanylate cyclase and elevating cGMP production. It inhibits platelet aggregation, reduces leucocyte adhesion, decreases apoptosis and lowers the production of some pro-inflammatory cytokines. Biliverdin is converted into bilirubin by biliverdin reductase, and both compounds are potent antioxidants, free radical scavengers and inhibitors of the complement cascade. Iron ions can be potentially toxic, increasing the generation of hydroxyl radicals, but simultaneous induction of ferritin and activation of the Fe-ATPase iron transporter protects cells from oxidative stress. Importantly, basal and induced expression of HO-1 is very variable in the human population because of the highly polymorphic (GT)n fragment in the promoter, which may have clinical relevance. The recognized roles of HO-1 are far beyond cytoprotection. The enzyme is important in the regulation of cell proliferation, differentiation and apoptosis. Its activity improves neovascularization, attenuates inflammation and modulates the immune response, thereby influencing carcinogenesis, wound healing, transplant survival and the progression of cardiovascular diseases. Recent results indicate that HO-1 may also act through the regulation of microRNAs, which suggests a much broader involvement of HO-1 in the modulation of cell functions and offers a potential explanation for some well-known activities whose mechanism has hitherto been unclear.

Serum bilirubin and genes controlling bilirubin concentrations as biomarkers for cardiovascular disease

BACKGROUND

Serum bilirubin has been consistently shown to be inversely related to cardiovascular disease (CVD). Recent studies showed serum bilirubin to be associated with CVD-related factors such as diabetes, metabolic syndrome, and body mass index. Although the association of serum bilirubin with CVD has been found in both retrospective and prospective studies, less information is available on the role of genes that control bilirubin concentrations and their association with CVD.

CONTENT

In this review, we provide detailed information on the identity of the major genes that control bilirubin concentrations and their association with serum bilirubin concentrations and CVD risk. We also update the results of the major studies that have been performed on the association between serum bilirubin, CVD, and CVD-related diseases such as diabetes or metabolic syndrome. Studies consistently indicate that bilirubin concentrations are inversely associated with different types of CVD and CVD-related diseases. A conditional linkage study indicates that UGT1A1 is the major gene controlling serum bilirubin concentrations, and this finding has been confirmed in recent genomewide association studies. Studies also indicate that individuals homozygous for UGT1A1*28 have a significantly lower risk of developing CVD than carriers of the wild-type alleles.

SUMMARY

Serum bilirubin has a protective effect on CVD and CVD-related diseases, and UGT1A1 is the major gene controlling serum bilirubin concentrations. Pharmacologic, nonpharmacologic, or genetic interventions that increase serum bilirubin concentrations could provide more direct evidence on the role of bilirubin in CVD prevention.

HO-1 polymorphism as a genetic determinant behind the malaria resistance afforded by haemolytic disorders

Malaria affects thousands of people around the world representing a critical issue regarding health policies in tropical countries. Similarly, also haemolytic diseases such as sickle cell disease and thalassemias are a concern in different parts of the globe. It is well established that haemolytic diseases, such as sickle cell disease (SCD) and thalassemias, represent a resistance factor to malaria, which explains the high frequencies of such genetic variants in malaria endemic areas. In this context, it has been shown that the rate limiting enzyme heme oxygenase I (HO-1), responsible for the catabolism of the free heme in the body, is an important resistance factor in malaria and is also important in the physiopathology of haemolytic diseases. Here, we suggest that allelic variants of HO-1, which display significant differences in terms of protein expression, have been selected in endemic malaria areas since the HO-1 enzyme can enhance the protection against malaria conferred by haemolytic diseases This protection apply mainly in what concerns protection against severe malaria forms. Therefore, HO-1 genotyping would be fundamental to determine resistance of a given individual to lethal forms of malaria as well as to common clinical complications typical to haemolytic diseases and would be helpful in the establishment of public health politics.

Prognostic factors influencing the patency of hemodialysis vascular access: literature review and novel therapeutic modality by far infrared therapy

In Taiwan, more than 85% of patients with end-stage renal disease undergo maintenance hemodialysis (HD). The native arteriovenous fistula (AVF) accounts for a prevalence of more than 80% of the vascular access in our patients. Some mechanical factors may affect the patency of hemodialysis vascular access, such as surgical skill, puncture technique and shear stress on the vascular endothelium. Several medical factors have also been identified to be associated with vascular access prognosis in HD patients, including stasis, hypercoagulability, endothelial cell injury, medications, red cell mass and genotype polymorphisms of transforming growth factor-beta1 and methylene tetrahydrofolate reductase. According to our previous study, AVF failure was associated with a longer dinucleotide (GT)n repeat (n > or = 30) in the promoter of the heme oxygenase-1 (HO-1) gene. Our recent study also demonstrated that far-infrared therapy, a noninvasive and convenient therapeutic modality, can improve access flow, inflammatory status and survival of the AVF in HD patients through both its thermal and non-thermal (endothelial-improving, anti-inflammatory, antiproliferative, antioxidative) effects by upregulating NF-E2-related factor-2-dependent HO-1 expression, leading to the inhibition of expression of E-selectin, vascular cell adhesion molecule-1, and intercellular adhesion molecule-1.

Genetic variability in iron-related oxidative stress pathways (Nrf2, NQ01, NOS3, and HO-1), iron intake, and risk of postmenopausal breast cancer

Oxidative stress resulting from excess reactive oxygen species and/or deficiencies in antioxidant capabilities may play a role in breast cancer etiology. In a nested case-control study of postmenopausal women (505 cases and 502 controls) from the American Cancer Society Prevention II Nutrition Cohort, we examined relationships between breast cancer risk and genetic polymorphisms of enzymes involved in the generation and removal of iron-mediated reactive oxygen species. Using unconditional logistic regression, genetic variations in Nrf2 (11108C>T), NQO1 (609C>T), NOS3 (894G>T), and HO-1 [(GT)(n) dinucleotide length polymorphism] were not associated with breast cancer risk in a multivariate model. A significant dose trend (P trend = 0.04), however, was observed for total number of putative "at-risk" alleles (Nrf T, NQO1 T, NOS T, and HO-1 LL and LM genotypes), with those carrying three or more at-risk alleles having an odds ratio (OR) of 1.56 [95% confidence interval (95% CI), 0.97-2.51] compared with those having none. When examined in relation to iron, carriage of three or more high-risk alleles in the highest tertile of iron intake (OR, 2.27; 95% CI, 0.97-5.29; P trend = 0.02; P interaction = 0.30) or among users of supplemental iron (OR, 2.39; 95% CI, 1.09-5.26; P trend = 0.02; P interaction = 0.11) resulted in a greater than 2-fold increased risk compared with women with no high-risk alleles. Increased risk was also observed among supplement users with the HO-1 LL or LM genotypes (OR, 1.56; 95% CI, 1.01-2.41; P interaction = 0.32) compared with S allele carriers and MM genotypes combined. These results indicate that women with genotypes resulting in potentially higher levels of iron-generated oxidative stress may be at increased risk of breast cancer and that this association may be most relevant among women with high iron intake.

Reduced expression of heme oxygenase-1 in patients with coronary atherosclerosis

Heme oxigenase-1 (HO-1) is known to be an inducible cytoprotective enzyme that copes with oxidative stress. However, changes in HO-1 expression and their association with human diseases have not been studied. To test the hypothesis that the capacity to upregulate HO-1 in response to oxidative stress is an intrinsic marker for susceptibility to coronary atherosclerosis, we assessed stimulation-induced change in HO-1 expression in blood cells in 110 patients who underwent coronary angiography, comparing the results with the extent of coronary atherosclerosis and (GT)(n) repeat polymorphism in the HO-1 gene promoter region, which is believed to affect the gene expression level. The extent of coronary atherosclerosis was assessed by coronary score. Mononuclear cells were incubated with 10 micromol/l hemin or vehicle for 4 h to maximally stimulate HO-1 expression, then the HO-1 expression level was determined by real-time polymerase chain reaction (PCR). The difference between the HO-1 mRNA levels of hemin- and vehicle-treated cells (DeltaHO-1 mRNA) was taken as an index of the capacity to upregulate HO-1 mRNA. The coefficient of variance of DeltaHO-1 mRNA was 7.2%. Consistent with previous studies, DeltaHO-1 mRNA was significantly lower in patients carrying a long (GT)(n) repeat. DeltaHO-1 mRNA negatively and significantly correlated with the coronary score (r(2)=0.50, p<0.01). In conclusion, the capacity to upregulate HO-1 expression may be determined, at least in part, by genetics, and reduced ability to induce HO-1 may be involved in the mechanism of coronary atherosclerosis.

Restenosis after percutaneous angioplasty: the role of vascular inflammation

Restenosis after endovascular treatment of atherosclerotic lesions in the peripheral, cerebrovascular, and coronary circulation is the major drawback of this minimally invasive technique. Although certain advances have been made during recent years to improve patency rates after percutaneous angioplasty, restenosis remains a challenging clinical problem. Understanding factors that contribute to the pathophysiology of late lumen loss is an effective strategy to improving patients' postangioplasty outcome. Vascular inflammation after balloon angioplasty or stent implantation has been identified as a cornerstone of the restenotic process, and several markers of inflammation have been referred to as potential predictors of outcome. This article reviews recent findings on the issue of inflammation and restenosis after percutaneous angioplasty with special attention given to the role of inflammatory parameters as markers for the restenosis risk in the peripheral vessel area.

Clinical restenosis after coronary stent implantation is associated with the heme oxygenase-1 gene promoter polymorphism and the heme oxygenase-1 +99G/C variant

BACKGROUND

Vascular remodeling after percutaneous coronary stent implantation frequently leads to restenosis. Heme oxygenase 1 (HO-1) is involved in the generation of the endogenous antioxidant bilirubin and carbon monoxide, both of which exert antiinflammatory and antiproliferative effects. The aim of the present study was to evaluate the influence of genetic risk factors combined with the conventional risk factors on the development of coronary restenosis after percutaneous coronary intervention (PCI) with stent implantation.

METHODS

The HO-1 gene GT dinucleotide repeat promoter polymorphism and HO-1 +99G/C variant were evaluated in 199 patients with coronary artery disease after coronary stent implantation and control angiography at 6 months after the intervention. Coronary restenosis was confirmed by quantitative angiography.

RESULTS

Carriers of the long allele of the HO-1 gene promoter (>29 repeats) had a significantly higher risk of developing restenosis after PCI than noncarriers [odds ratio (OR)=1.9; 95% confidence interval (95% CI), 1.0-3.4; P=0.04]. Interestingly, the allele longer than 29 repeats conferred a significantly higher risk of developing restenosis (OR=3.4; 95% CI, 1.2-9.1; P=0.017) in nonsmokers than in smokers (OR=2.0; 95% CI, 0.7-5.2; P=0.18).

CONCLUSIONS

The long allele of the HO-1 gene promoter (>29 repeats) polymorphism, which leads to low HO-1 inducibility, may represent an independent prognostic marker for restenosis after PCI and stent implantation. The effect of the >29 repeat allele is attenuated in smokers, who have chronic exogenous CO exposure.

The hyperbilirubinemic Gunn rat is resistant to the pressor effects of angiotensin II

ANG II induces vasoconstriction, at least in part, by stimulating NADPH oxidase and generating reactive oxygen species. ANG II also induces heme oxygenase activity, and bilirubin, a product of such activity, possesses antioxidant properties. We hypothesized that bilirubin, because of its antioxidant properties, may reduce the pressor and prooxidant effects of ANG II. Our in vivo studies used the hyperbilirubinemic Gunn rat which is deficient in the enzyme uridine diphosphate glucuronosyl transferase, the latter enabling the excretion of bilirubin into bile. ANG II (0.5 mg x kg(-1) x day(-1)) or saline vehicle was administered by osmotic minipump to control and Gunn rats for 4 wk. The rise in systolic blood pressure induced by ANG II, as observed in control rats, was markedly reduced in Gunn rats, the latter approximately 50% less at 3 and 4 wk after the initiation of ANG II infusion. The chronic administration of ANG II also impaired endothelium-dependent relaxation responses in control rats but not in Gunn rats. As assessed by the tetrahydrobiopterin/dihydrobiopterin ratio, ANG II induced oxidative stress in the aorta in control rats but not in Gunn rats. Heightened generation of superoxide anion in aortic rings in ANG II-infused rats and by vascular smooth muscle cells exposed to ANG II was normalized by bilirubin in vitro. We conclude that the pressor and prooxidant effects of ANG II are attenuated in the hyperbilirubinemic Gunn rat, an effect which, we speculate, may reflect, at least in part, the scavenging of superoxide anion by bilirubin.

Heme oxygenase-1 gene promoter polymorphism is associated with abdominal aortic aneurysm

OBJECTIVE

Vascular inflammation is a hallmark in the development of abdominal aortic aneurysms (AAA). Heme oxygenase-1 (HO-1) is a novel vascular anti-inflammatory factor. A (GT)(n) dinucleotide repeat in the HO-1 gene promoter shows a length polymorphism that modulates the level of gene transcription. Short (< 25 GT) repeats are associated with an increased HO-1 upregulation in response to inflammatory stimuli than are longer repeats. We hypothesised that patients with AAA had less frequently short repeats in the HO-1 gene promoter compared to patients with coronary (CAD) or peripheral artery disease (PAD), or healthy controls.

METHODS

70 consecutive patients with atherosclerotic AAA, each 70 age- and sex-matched patients with CAD and PAD as well as 61 unmatched healthy atherosclerosis-free controls for a total of 271 individuals were studied. The frequency of carriers of short repeats in the HO-1 gene promoter was determined and compared between the groups.

RESULTS

In the AAA group, 29 patients (41%) were carriers of short (GT)(n) repeats compared to 47 patients (67%) in the CAD group, 44 patients (63%) in the PAD group and 35 healthy controls (59%). Patients with AAA were less frequently carriers of short repeats compared to age- and sex-matched patients with CAD (OR = 0.38, p = 0.006) and PAD (OR = 0.35, p = 0.01). Healthy controls exhibited short alleles more frequently than patients with AAA (p = 0.04), but comparable to CAD (p = 0.3) and PAD patients (p = 0.7).

CONCLUSION

Patients with AAA were less frequently carriers of short (< 25 GT) repeats in the HO-1 gene promoter than patients with atherosclerosis or healthy subjects. This suggests that short alleles, and thus, facilitated upregulation of HO-1, may be a protective anti-inflammatory factor against the development of AAA.