Role of heme oxygenase-1 in human endothelial cells: lesson from the promoter allelic variants.

OBJECTIVE: Heme oxygenase-1 (HO-1) is an antioxidative, antiinflammatory, and cytoprotective enzyme that is induced in response to cellular stress. The HO-1 promoter contains a (GT)n microsatellite DNA, and the number of GT repeats can influence the occurrence of cardiovascular diseases. We elucidated the effect of this polymorphism on endothelial cells isolated from newborns of different genotypes. METHODS AND RESULTS: On the basis of HO-1 expression, we classified the HO-1 promoter alleles into 3 groups: short (S) (most active, GT < or = 23), medium (moderately active, GT=24 to 28), and long (least active, GT > or = 29). The presence of the S allele led to higher basal HO-1 expression and stronger induction in response to cobalt protoporphyrin, prostaglandin-J(2), hydrogen peroxide, and lipopolysaccharide. Cells carrying the S allele survived better under oxidative stress, a fact associated with the lower concentration of oxidized glutathione and more favorable oxidative status, as determined by measurement of the ratio of glutathione to oxidized glutathione. Moreover, they proliferated more efficiently in response to vascular endothelial growth factor A, although the vascular endothelial growth factor-induced migration and sprouting of capillaries were not influenced. Finally, the presence of the S allele was associated with lower production of some proinflammatory mediators, such as interleukin-1beta, interleukin-6, and soluble intercellular adhesion molecule-1. CONCLUSIONS: The (GT)n promoter polymorphism significantly modulates a cytoprotective, proangiogenic, and antiinflammatory function of HO-1 in human endothelium.

Haptoglobin phenotype and gestational diabetes.

OBJECTIVE: Haptoglobin (Hp), an Hb-binding plasma protein, exists in two major allelic variants. Hp1 has higher Hb binding and antioxidant capacity compared with Hp2. Individuals with Hp1 exhibit a lower incidence of angiopathies. Gestational diabetes mellitus (GDM) is an early manifestation of type 2 diabetes in pregnant women. It is usually confined to the time of gestation, but carries an increased risk to develop type 2 diabetes later in life. RESEARCH DESIGN AND METHODS: From consecutive Caucasian pregnant women (n = 250) referred for oral glucose tolerance testing, the Hp phenotype was determined. Significance of distribution and odds ratios (ORs) associated with Hp phenotype were calculated for women with GDM (n = 110) and women with normal glucose tolerance (n = 140). RESULTS: -Frequency of GDM in Hp phenotype classes increased with the number of Hp2 alleles (P < 0.001). ORs for GDM in women heterozygous and homozygous for Hp2 were 2.7 (95% CI 1.06-6.84) and 4.2 (1.67-10.55), respectively. CONCLUSIONS: Hp phenotype is an apparent risk factor for the development of GDM in our study population. This might be due to the low antioxidative potential of Hp2 compared with Hp1.

Sensor-operated faucets: a possible source of nosocomial infection?

Recently, contamination of sensor-operated faucets (SOFs) with Pseudomonas aeruginosa was observed. To evaluate odds ratios, we conducted a case-control study in which handle-operated faucets served as controls. No statistically significant difference in P. aeruginosa counts was observed between SOFs and regular faucets in our study (odds ratio, 0.0; 95% confidence interval, 0.0 to 39.0; two-sided P exact = .99).

Nosocomial outbreak of Serratia marcescens in a neonatal intensive care unit.

OBJECTIVES: To investigate and describe an outbreak of Serratia marcescens in a neonatal intensive care unit (NICU) and to report the interventions leading to cessation of the outbreak. SETTING: A 2,168-bed, tertiary-care, university teaching hospital in Vienna, Austria, with an 8-bed NICU. DESIGN: We conducted a case-control study to identify risk factors for colonization and infection with S. marcescens. A case-patient was defined as any neonate in the NICU with a positive culture for S. marcescens between October 1, 2000, and February 28, 2001. Polymerase chain reaction was applied to type isolates. METHODS: During unannounced observations, the NICU was examined and existing policies were reviewed. Staff were reinstructed in hand antisepsis and gloving policies. Admissions were halted on December 27. During previously planned technical maintenance of the ward, the NICU was closed for 10 days and thorough aldehyde-based disinfection of the NICU was performed. RESULTS: Ten neonates met the case definition: 6 with infections (among them 3 with cerebral abscesses) and 4 with asymptomatic colonization. Previous antibiotic treatment of the mothers with cefuroxime was the single significant risk factor for colonization or infection (P = .028; odds ratio, 17; 95% confidence interval, 1.3 to 489.5). CONCLUSIONS: S. marcescens can cause rapidly spreading outbreaks associated with fatal infections in NICUs. With aggressive infection control measures, such outbreaks can be stopped at an early stage. Affected neonates themselves may well be the source of cross-infection to other patients on the ward. Antibiotic treatment of mothers should be reevaluated to avoid unnecessary exposure to antibiotics with the potential of over-growth of resistant organisms.

Performance of a new chromogenic oxacillin resistance screen medium (Oxoid) in the detection and presumptive identification of methicillin-resistant Staphylococcus aureus.

A new chromogenic Oxacillin Resistance Screen Agar (ORSA; Oxoid) for the presumptive detection of methicillin-resistant Staphylococcus aureus (MRSA) was compared to a phenyl-mannitol-salt-oxacillin medium (MS-Oxa), blood agar and brain heart-infusion (BHI) on 579 clinical specimens. After 24 h [48h] sensitivity and specificity for ORSA vs. MS-Oxa were 50.8% [68.2%] vs. 53.8% [65.7%] and 95.6% [94.5%] vs. 92.7% [91.8], respectively. Within 24 h, ORSA and MS-Oxa identified 51% and 54% MRSA. It is not feasible to omit BHI in MRSA-screening protocols since 33% MRSA grew in BHI only.

The effect of a promoter polymorphism in the heme oxygenase-1 gene on the risk of ischaemic cerebrovascular events: the influence of other vascular risk factors.

Heme oxygenase-1 (HO-1) has been demonstrated to exert potent anti-oxidant and anti-inflammatory effects in the context of atherosclerotic vascular disease, and therefore was referred to as a potential vascular protective factor. A (GT)n dinucleotide repeat polymorphism in the HO-1 promoter has been shown to modulate HO-1 gene expression. Short (<25) GT repeats were associated with HO-1 up-regulation, and therefore may influence susceptibility to ischaemic vascular events. We investigated the association of HO-1 repeat length with the risk of cerebrovascular events in a case control study and assessed possible interrelations with vascular risk factors. We determined the number of GT repeats in the HO-1 promoter in 399 patients with ischaemic cerebrovascular events and 398 healthy controls and compared the frequencies of short (<25) repeat (class S) and long (> or =25) repeat (class L) alleles after adjustment for potentially confounding factors. Genotype distributions of S/S, S/L and L/L in patients were 9.8% (n=39), 45.1% (n=180) and 45.1% (n=180), which was similar to the distribution in controls with 11.5% (n=46), 44.5% (n=177) and 44.0% (n=175). In the presence of vascular risk factors, the HO-1 genotype became functionally relevant: in patients without hyperlipidemia the S/S genotype exerted a protective effect on the development of ischaemic cerebrovascular events (OR 0.2; 95% CI 0.1-0.6), while this effect was no longer present in hyperlipidemic patients. Short (<25 GT) repeats in the HO-1 gene promoter confer a reduced risk for cerebrovascular events in individuals with normal plasma lipid levels. This may explain controversial findings in different populations.

Transforming growth factor beta 2 and heme oxygenase 1 genes are risk factors for the cerebral malaria syndrome in Angolan children.

BACKGROUND: Cerebral malaria (CM) represents a severe outcome of the Plasmodium falciparum infection. Recent genetic studies have correlated human genes with severe malaria susceptibility, but there is little data on genetic variants that increase the risk of developing specific malaria clinical complications. Nevertheless, susceptibility to experimental CM in the mouse has been linked to host genes including Transforming Growth Factor Beta 2 (TGFB2) and Heme oxygenase-1 (HMOX1). Here, we tested whether those genes were governing the risk of progressing to CM in patients with severe malaria syndromes. METHODOLOGY/PRINCIPAL FINDINGS: We report that the clinical outcome of P. falciparum infection in a cohort of Angolan children (n = 430) correlated with nine TGFB2 SNPs that modify the risk of progression to CM as compared to other severe forms of malaria. This genetic effect was explained by two haplotypes harboring the CM-associated SNPs (Pcorrec. = 0.035 and 0.036). In addition, one HMOX1 haplotype composed of five CM-associated SNPs increased the risk of developing the CM syndrome (Pcorrec. = 0.002) and was under-transmitted to children with uncomplicated malaria (P = 0.036). Notably, the HMOX1-associated haplotype conferred increased HMOX1 mRNA expression in peripheral blood cells of CM patients (P = 0.012). CONCLUSIONS/SIGNIFICANCE: These results represent the first report on CM genetic risk factors in Angolan children and suggest the novel hypothesis that genetic variants of the TGFB2 and HMOX1 genes may contribute to confer a specific risk of developing the CM syndrome in patients with severe P. falciparum malaria. This work may provide motivation for future studies aiming to replicate our findings in larger populations and to confirm a role for these genes in determining the clinical course of malaria.

Genetic variation in heme oxygenase 1 (HMOX1) and the risk of recurrent venous thromboembolism.

BACKGROUND/OBJECTIVE: Products of heme oxygenase 1 (HO1) possess antithrombotic properties, and impairment of HO1 activity may contribute to thrombus formation. Transcriptional activity of long GT-repeat alleles in HO1 gene (HMOX1) is lower as compared with short alleles. We hypothesize that these long alleles are associated with decreased HO1 anticoagulant activity and, thus, an increased risk of thrombosis.. DESIGN/METHODS: In a prospective cohort study, we followed 860 patients with a first VTE, and investigated the impact of a promoter GT-dinucleotid length polymorphism in HOMX1 on the risk of recurrent venous thromboembolism (VTE). RESULTS: Allele groups short (S), medium (M) and long (L) of the promoter GT-dinucleotide length polymorphism were distinguished. L-alleles, but not M- or S-alleles, were found to be more frequent among patients with recurrence. Heterozygous carriers of L-alleles had a two-fold higher relative risk of recurrence [(RR 2.2 (95% CI: 1.4-3.4)] as compared to wild type, which was independent of other thrombotic risk factors. At five years, the cumulative probability of recurrence was 18% (95% CI: 15%-22%) in patients without an L-allele compared to 32% (95% CI: 19%-46%) in patients heterozygous for the L-allele (P = .001). CONCLUSION: Patients with first VTE and long GT-repeat alleles in HMOX1 have an increased risk of recurrence. Genetically determined alterations in HO1 function may represent a new pathomechanism in VTE.

A microsatellite polymorphism in the heme oxygenase-1 gene promoter is associated with risk for melanoma.

Heme oxygenase-1 (HO-1) has been demonstrated to play an important role in the regulation of signaling systems, which are involved in the control of cell cycle progression and apoptosis. Recently, a (GT)n dinucleotide repeat polymorphism in the HO-1 promoter was shown to modulate HO-1 gene expression. Short (<25 GT) repeats are associated with an increased HO-1 upregulation after stimulation than are longer repeats. Malignant melanoma (MM) is the most serious cutaneous malignancy with high tendency to aggressive growth and resistance to apoptosis. Therefore, we sought to study the influence of this polymorphism on the progression of MM. We determined the HO-1 promoter genotype in 152 patients with MM and 398 healthy controls and studied their association in regard to susceptibility to MM, Breslow thickness and disease-free survival. In our study, the homozygous short allele with <25 (GT)n repeats (S/S) was found more frequently in the melanoma group compared to the healthy control population (21 and 12%, respectively). The calculated risk for acquiring primary MM in S/S carriers was 2-fold higher compared to those with L-allele types (95% confidence interval: 1.2-2.4, p = 0.03). Additionally, the S/S genotype was significantly associated with primary tumors with deeper Breslow thickness compared to L-allele (>25 repeats) carriers (mean Breslow thickness: 4.0 +/- 2.9 mm versus 3.1 +/- 1.7 mm, p = 0.03). These data suggest that HO-1 might render a higher risk for MM in S/S genotype individuals and could represent an important candidate gene in the pathogenesis and growth of malignant melanoma.

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.