Heme Oxygenase-1 Gene (GT)n Polymorphism Linked to Deep White Matter Hyperintensities, Not Periventricular Hyperintensities

BACKGROUND

Oxidative stress plays a principal role in the pathogenesis of white matter hyperintensities (WMHs). The induction of heme oxygenase-1 (HO-1) gene in the brain represents 1 of the pivotal mechanisms to counteract the noxious effects of reactive oxygen species, and the transcriptional modulation of HO-1 induction depends on the length of a GT-repeat (GT)n in the promoter region. We investigated whether the HO-1 gene (GT)n polymorphism is associated with the risk of WMHs.

METHODS AND RESULTS

A total of 849 subjects from the memory clinic were consecutively enrolled, and the HO-1 (GT)n genotype was determined. WMHs were assessed with the Fazekas scale and further divided into periventricular WMHs and deep WMHs (DWMHs). Allelic HO-1 (GT)n polymorphisms were classified as short (≤24 (GT)n), median (25≤[GT]n<31), or long (31≤[GT]n). Multivariate logistic regression analysis was used to evaluate the effect of the HO-1 (GT)n variants on WMHs. The number of repetitions of the HO-1 gene (GT)n ranged from 15 to 39 with a bimodal distribution at lengths 23 and 30. The proportion of S/S genotypes was higher for moderate/severe DWMHs than none/mild DWMHs (22.22% versus 12.44%; P=0.001), but the association for periventricular WMHs was not statistically significant. Logistic regression suggested that the S/S genotype was significantly associated with moderate/severe DWMHs (S/S versus non-S/S: odds ratio, 2.001 [95% CI, 1.323-3.027]; P<0.001). The HO-1 gene (GT)n S/S genotype and aging synergistically contributed to the progression of DWMHs (relative excess risk attributable to interaction, 6.032 [95% CI, 0.149-11.915]).

CONCLUSIONS

Short (GT)n variants in the HO-1 gene may confer susceptibility to rather than protection from DWMHs, but not periventricular WMHs.

REGISTRATION

URL: https://www.chictr.org.cn; Unique identifier: ChiCTR2100045869.

Towards Personalized Treatment in Haemophilia: The Role of Genetic Factors in Iron and Heme Control to Identify Patients at Risk for Haemophilic Arthropathy

The treatment landscape for haemophilia is changing rapidly, creating opportunities for personalized treatment. As major morbidity is still caused by haemophilic arthropathy, understanding the factors affecting joint damage and joint damage progression might lead to more individualized treatment regimens. We investigated the association of HFE mutations or HMOX1 polymorphisms affecting iron/heme handling with radiographic joint damage in 252 haemophilia patients (severe and moderate). Although iron levels and transferrin saturation were significantly increased in the 95 patients with an HFE mutation, neither carrying this mutation nor the HMOX1 polymorphism was associated with radiographic joint damage, and the same was true after adjustment for well-known factors associated with arthropathy. In conclusion, this study does not support the hypothesis that HFE mutations or HMOX1 polymorphisms can be used to predict the development of haemophilic arthropathy.

Prevalence and Impact of HMOX1 Polymorphism (rs2071746: A > T) in Indian Sickle Cell Disease Patients

Introduction  Fetal hemoglobin (HbF) levels play significant role in lowering down the morbidity and mortality in sickle cell disease (SCD) patients. Coinheritance of heme oxygenase-1 (HMOX1) rs2071746:A > T polymorphism may contribute to variable HbF levels in Indian SCD patients. Objective  This study was aimed to evaluate the role of HMOX1 polymorphism and its impact on HbF level in Indian SCD patients. Materials and Methods  One-hundred twenty confirmed cases of SCD and 50 healthy controls were recruited. Their mean age was 11.5 ± 8.6 years (range: 3-23 years). Quantification of Hb, HbA2, HbF, and HbS was done by capillary zone electrophoresis. Allele-specific polymerase chain reaction was used to genotype HMOX1 (rs2071746:A > T) gene polymorphism. Results  Out of the 120 cases of SCD, 65 were hemoglobin sickle-shaped (HbSS) and 55 were sickle-beta thalassemia (Sβ). Out of 65 HbSS patients, 29 (44.6%) were heterozygous (AT), 20 (30.76%) were homozygous (TT), and 16 (24.61%) were found wild-type (AA) genotype. Out of 55 Sβ, 22 (40%) were heterozygous, 18 (32%) were homozygous and 15 (28%) were wild-type. Patients carrying HMOX1 (rs2071746:A > T), AT, and TT genotypes had less anemia, painful crisis, splenomegaly, hepatomegaly, jaundice, and blood transfusion. HbF level was found higher in TT genotype (in HbSS the HbF levels was 25.1 ± 4.4; in sickle-beta thalassemia the HbF levels was 36.1 ± 4.7) than wild-type(AA) and was statistically significant ( p -value <0.001). Conclusion  The TT genotype of the rs2071746:A > T polymorphism was associated with increased levels of Hb F ( p  < 0.001). It can serve as a HbF modifier in Indian sickle cell diseases patients.

The different facets of heme-oxygenase 1 in innate and adaptive immunity

Heme oxygenase (HO) enzymes are responsible for the main oxidative step in heme degradation, generating equimolar amounts of free iron, biliverdin and carbon monoxide. HO-1 is induced as a crucial stress response protein, playing protective roles in physiologic and pathological conditions, due to its antioxidant, anti-apoptotic and anti-inflammatory effects. The mechanisms behind HO-1-mediated protection are being explored by different studies, affecting cell fate through multiple ways, such as reduction in intracellular levels of heme and ROS, transcriptional regulation, and through its byproducts generation. In this review we focus on the interplay between HO-1 and immune-related signaling pathways, which culminate in the activation of transcription factors important in immune responses and inflammation. We also discuss the dual interaction of HO-1 and inflammatory mediators that govern resolution and tissue damage. We highlight the dichotomy of HO-1 in innate and adaptive immune cells development and activation in different disease contexts. Finally, we address different known anti-inflammatory pharmaceuticals that are now being described to modulate HO-1, and the possible contribution of HO-1 in their anti-inflammatory effects.

Association between HO‑1 gene promoter polymorphisms and diseases (Review)

Heme oxygenase‑1 (HO‑1) is an inducible cytoprotective enzyme that degrades heme into free iron, carbon monoxide and biliverdin, which is then rapidly converted into bilirubin. These degradation products serve an important role in the regulation of inflammation, oxidative stress and apoptosis. While the expression level of HO‑1 is typically low in most cells, it may be highly expressed when induced by a variety of stimulating factors, a process that contributes to the regulation of cell homeostasis. In the 5'‑non‑coding region of the HO‑1 gene, there are two polymorphic sites, namely the (GT)n dinucleotide and T(‑413)A single nucleotide polymorphism sites, which regulate the transcriptional activity of HO‑1. These polymorphisms have been shown to be closely associated with the occurrence and progression of numerous diseases, including cardiovascular, pulmonary, liver and kidney, various types of cancer and viral diseases. The present article reviews the progress that has been made in research on the association between the two types of polymorphisms and these diseases, which is expected to provide novel strategies for the diagnosis, treatment and prognosis of various diseases.

Regulation of inflammation by the antioxidant haem oxygenase 1

Haem oxygenase 1 (HO-1), an inducible enzyme responsible for the breakdown of haem, is primarily considered an antioxidant, and has long been overlooked by immunologists. However, research over the past two decades in particular has demonstrated that HO-1 also exhibits numerous anti-inflammatory properties. These emerging immunomodulatory functions have made HO-1 an appealing target for treatment of diseases characterized by high levels of chronic inflammation. In this Review, we present an introduction to HO-1 for immunologists, including an overview of its roles in iron metabolism and antioxidant defence, and the factors which regulate its expression. We discuss the impact of HO-1 induction in specific immune cell populations and provide new insights into the immunomodulation that accompanies haem catabolism, including its relationship to immunometabolism. Furthermore, we highlight the therapeutic potential of HO-1 induction to treat chronic inflammatory and autoimmune diseases, and the issues faced when trying to translate such therapies to the clinic. Finally, we examine a number of alternative, safer strategies that are under investigation to harness the therapeutic potential of HO-1, including the use of phytochemicals, novel HO-1 inducers and carbon monoxide-based therapies.

Role of HMOX1 Promoter Genetic Variants in Chemoresistance and Chemotherapy Induced Neutropenia in Children with Acute Lymphoblastic Leukemia

Whilst the survival rates of childhood acute lymphoblastic leukemia (ALL) have increased remarkably over the last decades, the therapy resistance and toxicity are still the major causes of treatment failure. It was shown that overexpression of heme oxygenase-1 (HO-1) promotes proliferation and chemoresistance of cancer cells. In humans, the HO-1 gene (HMOX1) expression is modulated by two polymorphisms in the promoter region: (GT)n-length polymorphism and single-nucleotide polymorphism (SNP) A(−413)T, with short GT repeat sequences and 413-A variants linked to an increased HO-1 inducibility. We found that the short alleles are significantly more frequent in ALL patients in comparison to the control group, and that their presence may be associated with a higher risk of treatment failure, reflecting the role of HO-1 in chemoresistance. We also observed that the presence of short alleles may predispose to develop chemotherapy-induced neutropenia. In case of SNP, the 413-T variant co-segregated with short or long alleles, while 413-A almost selectively co-segregated with long alleles, hence it is not possible to determine if SNPs are actually of phenotypic significance. Our results suggest that HO-1 can be a potential target to overcome the treatment failure in ALL patients.

Donor-Derived Myeloid Heme Oxygenase-1 Controls the Development of Graft-Versus-Host Disease

Graft-versus-host disease (GVHD) remains a major clinical drawback of allogeneic hematopoietic stem cell transplantation (HSCT). Here, we investigated how the stress responsive heme catabolizing enzyme heme oxygenase-1 (HO-1, encoded by HMOX1) regulates GVHD in response to allogeneic hematopoietic stem cell transplantation in mice and humans. We found that deletion of the Hmox1 allele, specifically in the myeloid compartment of mouse donor bone marrow, promotes the development of aggressive GVHD after allogeneic transplantation. The mechanism driving GVHD in mice transplanted with allogeneic bone marrow lacking HO-1 expression in the myeloid compartment involves enhanced T cell alloreactivity. The clinical relevance of these observations was validated in two independent cohorts of HSCT patients. Individuals transplanted with hematopoietic stem cells from donors carrying a long homozygous (GT)n repeat polymorphism (L/L) in the HMOX1 promoter, which is associated with lower HO-1 expression, were at higher risk of developing severe acute GVHD as compared to donors carrying a short (GT)n repeat (S/L or S/S) polymorphism associated with higher HO-1 expression. In this study, we showed the unique importance of donor-derived myeloid HO-1 in the prevention of lethal experimental GVHD and we corroborated this observation by demonstrating the association between human HMOX1 (GT)n microsatellite polymorphisms and the incidence of severe acute GVHD in two independent HSCT patient cohorts. Donor-derived myeloid HO-1 constitutes a potential therapeutic target for HSCT patients and large-scale prospective studies in HSCT patients are necessary to validate the HO-1 L/L genotype as an independent risk factor for developing severe acute GVHD.

Heme oxygenase-1 modulation: A potential therapeutic target for COVID-19 and associated complications

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to infect hundred thousands of people every day worldwide. Since it is a novel virus, research continues to update the possible therapeutic targets when new evidence regarding COVID-19 are gathered. This article presents an evidence-based hypothesis that activating the heme oxygenase-1 (HO-1) pathway is a potential target for COVID-19. Interferons (IFNs) have broad-spectrum antiviral activity including against SARS-CoV-2. Induction of HO-1 and increase in the heme catabolism end-product confer antiviral activity. IFN activation results in inhibition of viral replication in various viral infections. COVID-19 induced inflammation as well as acute respiratory distress syndrome (ARDS), and coagulopathies are now known major causes of mortality. A protective role of HO-1 induction in inflammation, inflammation-induced coagulation, and ARDS has been reported. Based on an association of HO-1 promoter polymorphisms and disease severity, we propose an evaluation of the status of these polymorphisms in COVID-19 patients who become severely ill. If an association is established, it might be helpful in identifying patients at high risk. Hence, we hypothesize that HO-1 pathway activation could be a therapeutic strategy against COVID-19 and associated complications.

Neuroinflammation associates with antioxidant heme oxygenase-1 response throughout the brain in persons living with HIV

Previous studies showed that persons living with HIV (PLWH) demonstrate higher brain prefrontal cortex neuroinflammation and immunoproteasome expression compared to HIV-negative individuals; these associate positively with HIV levels. Lower expression of the antioxidant enzyme heme oxygenase 1 (HO-1) was observed in PLWH with HIV-associated neurocognitive impairment (HIV-NCI) compared to neurocognitively normal PLWH. We hypothesized that similar expression patterns occur throughout cortical, subcortical, and brainstem regions in PLWH, and that neuroinflammation and immunoproteasome expression associate with lower expression of neuronal markers. We analyzed autopsied brains (15 regions) from 9 PLWH without HIV-NCI and 7 matched HIV-negative individuals. Using Western blot and RT-qPCR, we quantified synaptic, inflammatory, immunoproteasome, endothelial, and antioxidant biomarkers, including HO-1 and its isoform heme oxygenase 2 (HO-2). In these PLWH without HIV-NCI, we observed higher expression of neuroinflammatory, endothelial, and immunoproteasome markers in multiple cortical and subcortical regions compared to HIV-negative individuals, suggesting a global brain inflammatory response to HIV. Several regions, including posterior cingulate cortex, globus pallidus, and cerebellum, showed a distinct pattern of higher type I interferon (IFN)-stimulated gene and immunoproteasome expression. PLWH without HIV-NCI also had (i) stable or higher HO-1 expression and positive associations between (ii) HO-1 and HIV levels (CSF, plasma) and (iii) HO-1 expression and neuroinflammation, in multiple cortical, subcortical, and brainstem regions. We observed no differences in synaptic marker expression, suggesting little, if any, associated neuronal injury. We speculate that this may reflect a neuroprotective effect of a concurrent HO-1 antioxidant response despite global neuroinflammation, which will require further investigation.

Relevance of Nrf2 and heme oxygenase-1 in articular diseases

Joint conditions pose an important public health problem as they are a leading cause of pain, functional limitation and physical disability. Oxidative stress is related to the pathogenesis of many chronic diseases affecting the joints such as rheumatoid arthritis and osteoarthritis. Cells have developed adaptive protection mechanisms to maintain homeostasis such as nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2) which regulates the transcription of many genes involved in redox balance, detoxification, metabolism and inflammation. Activation of Nrf2 results in the synthesis of heme oxygenase-1 (HO-1) leading to the formation of a number of bioactive metabolites, mainly CO, biliverdin and bilirubin. Ample evidence supports the notion that Nrf2 and HO-1 can confer protection against oxidative stress and inflammatory and immune responses in joint tissues. As a consequence, this pathway may control the activation and metabolism of articular cells to play a regulatory role in joint destruction thus offering new opportunities for better treatments. Further studies are necessary to identify improved strategies to regulate Nrf2 and HO-1 activation in order to enable the development of drugs with therapeutic applications in joint diseases.

Naturally Derived Heme-Oxygenase 1 Inducers and Their Therapeutic Application to Immune-Mediated Diseases

Heme oxygenase (HO) is the primary antioxidant enzyme involved in heme group degradation. A variety of stimuli triggers the expression of the inducible HO-1 isoform, which is modulated by its substrate and cellular stressors. A major anti-inflammatory role has been assigned to the HO-1 activity. Therefore, in recent years HO-1 induction has been employed as an approach to treating several disorders displaying some immune alterations components, such as exacerbated inflammation or self-reactivity. Many natural compounds have shown to be effective inductors of HO-1 without cytotoxic effects; among them, most are chemicals present in plants used as food, flavoring, and medicine. Here we discuss some naturally derived compounds involved in HO-1 induction, their impact in the immune response modulation, and the beneficial effect in diverse autoimmune disorders. We conclude that the use of some compounds from natural sources able to induce HO-1 is an attractive lifestyle toward promoting human health. This review opens a new outlook on the investigation of naturally derived HO-1 inducers, mainly concerning autoimmunity.

Icariin Prevents Extracellular Matrix Accumulation and Ameliorates Experimental Diabetic Kidney Disease by Inhibiting Oxidative Stress via GPER Mediated p62-Dependent Keap1 Degradation and Nrf2 Activation

The present study aimed to determine whether icariin could attenuate type 1 diabetic nephropathy (T1DN) induced by streptozotocin (STZ) after 4 weeks or not. Therefore, its therapeutic effect on diabetic kidney disease was investigated in view of reactive oxygen (ROS) and extracellular matrix (ECM) generation in human glomerular mesangial cells under high glucose. To establish the participation and the key role of GPER and Nrf2 in ECM deposition, a combination of G15 (antagonist of GPER) or siGPER and siNrf2 were performed, respectively. The results showed that T1DN can be significantly inhibited by oral icariin, evidenced by improvement of 24 h urinary volume, 24 h proteinuria, microalbuminuria, and histopathological changes of kidney. Icariin decreased the levels of intracellular superoxide anion, impeded the generation of fibronectin and increased the expression and activity of antioxidant enzymes in the human glomerular mesangial cells treated with high glucose. It acted as a GPER activator, increased dissociation of Nrf2/Keap1 complexes, combination of Keap1/p62 complexes, Nrf2 translocation to nuclear, Nrf2/ARE DNA binding activity, and ARE luciferase reporter gene activity in glomerular mesangial cells. The Nrf2 inhibitor ML385 or siNrf2 obviously abolished extracellular matrix (ECM) generation inhibited by icariin. Furthermore, icariin-induced Nrf2 activation was mainly dependent on p62-mediated Keap1 degradation, which functions as an adaptor protein during autophagy. The GPER antagonist G15 and siGPER obviously abolished the above effects by icariin. Taken together, the present study demonstrated that the therapeutic effects of icariin on type 1 diabetic nephropathy in rats via GPER mediated p62-dependent Keap1 degradation and Nrf2 activation.

Heme oxygenase-1 promoter (GT) n polymorphism associates with HIV neurocognitive impairment

Objective

To determine whether regulatory variations in the heme oxygenase-1 (HO-1) promoter (GT)_n dinucleotide repeat length could identify unique population genetic risks for neurocognitive impairment (NCI) in persons living with HIV (PLWH), we genotyped 528 neurocognitively assessed PLWH of European American and African American descent and linked genotypes to cognitive status.

Methods

In this cross-sectional study of PLWH (the CNS HIV Antiretroviral Therapy Effect Research cohort), we determined HO-1 (GT)_n repeat lengths in 276 African Americans and 252 European Americans. Using validated criteria for HIV-associated NCI (HIV NCI), we found associations between allele length genotypes and HIV NCI and between genotypes and plasma markers of monocyte activation and inflammation. For comparison of HO-1 (GT)_n allele frequencies with another population of African ancestry, we determined HO-1 (GT)_n allele lengths in African PLWH from Botswana (n = 428).

Results

PLWH with short HO-1 (GT)_n alleles had a lower risk for HIV NCI (OR = 0.63, 95% CI: 0.42–0.94). People of African ancestry had a lower prevalence of short alleles and higher prevalence of long alleles compared with European Americans, and in subgroup analyses, the protective effect of the short allele was observed in African Americans and not in European Americans.

Conclusions

Our study identified the short HO-1 (GT)_n allele as partially protective against developing HIV NCI. It further suggests that this clinical protective effect is particularly relevant in persons of African ancestry, where the lower prevalence of short HO-1 (GT)_n alleles may limit induction of HO-1 expression in response to inflammation and oxidative stress. Therapeutic strategies that enhance HO-1 expression may decrease HIV-associated neuroinflammation and limit HIV NCI.

Sex-specific effects of a microsatellite polymorphism on human growth hormone receptor gene expression

Growth hormone (GH) binds to its specific receptor (GHR) at the surface of target cells activating multiple signaling pathways implicated in growth and metabolism. Dysregulation of GHRs leads to pathophysiological states that most commonly affect stature. We previously showed the association of a polymorphic (n = 15-37) GT microsatellite in the human GHR gene promoter with short stature in a sex-specific manner. In the present study we evaluated the functional relevance of this polymorphism in regulating GHR expression. Using luciferase reporter assays, we found that the GT repeat had a significant cis regulatory effect in response to HIF1α and a potential repressor role following C/EBPβ stimulation. Using a digital PCR application to measure allelic imbalance (AI), we showed a high prevalence of AI (∼76%) at the GHR locus in lymphoblastoid cell lines (LCLs), with a significantly higher degree of imbalance in LCLs derived from males. Examination of expression of GHR as well as other members of the GH-IGF1 axis in the LCLs revealed significant associations of GHR, IGF1 and BCL2 expression with GT genotype in a sex-specific manner. Our results suggest that this GT microsatellite exerts both cis and trans effects in a sex-specific context, revealing a new mechanism by which GHR gene expression is regulated.

Association of Human FOS Promoter Variants with the Occurrence of Knee-Osteoarthritis in a Case Control Association Study

Our aim was to analyse (i) the presence of single nucleotide polymorphisms (SNPs) in the JUN and FOS core promoters in patients with rheumatoid arthritis (RA), knee-osteoarthritis (OA), and normal controls (NC); (ii) their functional influence on JUN/FOS transcription levels; and (iii) their associations with the occurrence of RA or knee-OA. JUN and FOS promoter SNPs were identified in an initial screening population using the Non-Isotopic RNase Cleavage Assay (NIRCA); their functional influence was analysed using reporter gene assays. Genotyping was done in RA (n = 298), knee-OA (n = 277), and NC (n = 484) samples. For replication, significant associations were validated in a Finnish cohort (OA: n = 72, NC: n = 548). Initially, two SNPs were detected in the JUN promoter and two additional SNPs in the FOS promoter in perfect linkage disequilibrium (LD). JUN promoter SNP rs4647009 caused significant downregulation of reporter gene expression, whereas reporter gene expression was significantly upregulated in the presence of the FOS promoter SNPs. The homozygous genotype of FOS promoter SNPs showed an association with the susceptibility for knee-OA (odds ratio (OR) 2.12, 95% confidence interval (CI) 1.2–3.7, p = 0.0086). This association was successfully replicated in the Finnish Health 2000 study cohort (allelic OR 1.72, 95% CI 1.2–2.5, p = 0.006). FOS Promoter variants may represent relevant susceptibility markers for knee-OA.

DC32, a Dihydroartemisinin Derivative, Ameliorates Collagen-Induced Arthritis Through an Nrf2-p62-Keap1 Feedback Loop

Artemisinins have been reported to have diverse functions, such as antimalaria, anticancer, anti-inflammation, and immunoregulation activities. DC32 [(9α,12α-dihydroartemisinyl) bis(2′-chlorocinnmate)], a dihydroartemisinin derivative possessing potent immunosuppressive properties, was synthesized in our previous study. Collagen-induced arthritis (CIA) in DBA/1 mice and inflammatory model in NIH-3T3 cells were established to evaluate the effect of DC32 on RA and discover the underlying mechanisms. The results showed that DC32 could markedly alleviate footpad inflammation, reduce cartilage degradation, activate the Nrf2/HO-1 signaling pathway, and increase the transcription of p62 in DBA/1 mice with CIA. Further mechanistic exploration with NIH-3T3 cells indicated that DC32 could increase the transcription, expression, and nuclear translocation of Nrf2. In addition, DC32 promoted degradation of Keap1 protein and upregulated HO-1 and p62 expression. Furthermore, the effect of DC32 on Keap1 degradation could be prevented by p62 knockdown using siRNA. Administration of DC32 could inhibit the activation of Akt/mTOR and ERK, and pretreatment of NIH-3T3 cells with the autophagy inhibitor 3-methyladenine (3-MA) attenuated the degradation of Keap1 induced by DC32. These results suggest that DC32 inhibits the degradation of Nrf2 by promoting p62-mediated selective autophagy and that p62 upregulation contributed to a positive feedback loop for persistent activation of Nrf2. In summary, our present study demonstrated that DC32 significantly suppressed rheumatoid arthritis (RA) via the Nrf2-p62-Keap1 feedback loop by increasing the mRNA and protein levels of Nrf2 and inducing p62 expression. These findings provide new mechanisms for artemisinins in RA treatment and a potential strategy for discovering antirheumatic drugs.

Study of the influence of heme oxygenase 1 gene single nucleotide polymorphism (rs2071746) on esophageal varices among patients with cirrhosis

INTRODUCTION

Cirrhosis as a pathological term has some criteria known to be common in all cases of liver cirrhosis. Esophageal varices are portosystemic collaterals arising in the submucosa of the lower esophagus because of portal hypertension. Portal hypertension is defined as hepatic venous pressure gradient greater than 5 mmHg that arises often as a sequelae of mesenchymal dysfunction in a cirrhotic liver. This study was carried out on 120 personnel divided into three groups: group A included 50 cases of liver cirrhosis with esophageal varices, group B consisted of 50 cases of cirrhosis without esophageal varices, and group C had 20 healthy volunteers a control group.

PATIENTS AND METHODS

DNA was extracted from the peripheral blood of the study participants. Genotyping of the HO1 413A>T promoter SNP (rs2071746) was performed using TaqMan SNP genotyping assay according to the manufacturer's protocol by RQ-PCR.

RESULTS

Patients carrying T allele of HO1 promoter were found to have 5.46-fold increased risk of esophageal varices development than patients with cirrhosis carrying A allele. T allele was significantly higher in cirrhotics with esophageal varices compared with those without esophageal varices (P<0.001). Rates of esophageal varices development in patients with cirrhotic liver were 52, 40, and 8% for genotypes TT, AT, and AA, respectively.

CONCLUSION

The T allele of heme oxygenase 1 gene SNP polymorphism (rs2071746) is a risk factor for esophageal varices development in cirrhotics.

Heme oxygenase-1 promoter region (GT)n polymorphism associates with increased neuroimmune activation and risk for encephalitis in HIV infection

BACKGROUND

Heme oxygenase-1 (HO-1) is a critical cytoprotective enzyme that limits oxidative stress, inflammation, and cellular injury within the central nervous system (CNS) and other tissues. We previously demonstrated that HO-1 protein expression is decreased within the brains of HIV+ subjects and that this HO-1 reduction correlates with CNS immune activation and neurocognitive dysfunction. To define a potential CNS protective role for HO-1 against HIV, we analyzed a well-characterized HIV autopsy cohort for two common HO-1 promoter region polymorphisms that are implicated in regulating HO-1 promoter transcriptional activity, a (GT)n dinucleotide repeat polymorphism and a single nucleotide polymorphism (A(-413)T). Shorter HO-1 (GT)n repeats and the 'A' SNP allele associate with higher HO-1 promoter activity.

METHODS

Brain dorsolateral prefrontal cortex tissue samples from an autopsy cohort of HIV-, HIV+, and HIV encephalitis (HIVE) subjects (n = 554) were analyzed as follows: HO-1 (GT)n polymorphism allele lengths were determined by PCR and capillary electrophoresis, A(-413)T SNP alleles were determined by PCR with allele specific probes, and RNA expression of selected neuroimmune markers was analyzed by quantitative PCR.

RESULTS

HIV+ subjects with shorter HO-1 (GT)n alleles had a significantly lower risk of HIVE; however, shorter HO-1 (GT)n alleles did not correlate with CNS or peripheral viral loads. In HIV+ subjects without HIVE, shorter HO-1 (GT)n alleles associated significantly with lower expression of brain type I interferon response markers (MX1, ISG15, and IRF1) and T-lymphocyte activation markers (CD38 and GZMB). No significant correlations were found between the HO-1 (GT)n repeat length and brain expression of macrophage markers (CD163, CD68), endothelial markers (PECAM1, VWF), the T-lymphocyte marker CD8A, or the B-lymphocyte maker CD19. Finally, we found no significant associations between the A(-413)T SNP and HIVE diagnosis, HIV viral loads, or any neuroimmune markers.

CONCLUSION

Our data suggest that an individual's HO-1 promoter region (GT)n polymorphism allele repeat length exerts unique modifying risk effects on HIV-induced CNS neuroinflammation and associated neuropathogenesis. Shorter HO-1 (GT)n alleles increase HO-1 promoter activity, which could provide neuroprotection through decreased neuroimmune activation. Therapeutic strategies that induce HO-1 expression could decrease HIV-associated CNS neuroinflammation and decrease the risk for development of HIV neurological disease.

Genetic variations at the human growth hormone receptor (GHR) gene locus are associated with idiopathic short stature

GH plays an essential role in the growing child by binding to the growth hormone receptor (GHR) on target cells and regulating multiple growth promoting and metabolic effects. Mutations in the GHR gene coding regions result in GH insensitivity (dwarfism) due to a dysfunctional receptor protein. However, children with idiopathic short stature (ISS) show growth impairment without GH or GHR defects. We hypothesized that decreased expression of the GHR gene may be involved. To test this, we investigated whether common genetic variants (microsatellites, SNPs) in regulatory regions of the GHR gene region were associated with the ISS phenotype. Genotyping of a GT‐repeat microsatellite in the GHR 5′UTR in a Montreal ISS cohort (n = 37 ISS, n = 105 controls) revealed that the incidence of the long/short (L/S) genotype was 3.3× higher in ISS children than controls (P = 0.04, OR = 3.85). In an Italian replication cohort (n = 143 ISS, n = 282 controls), the medium/short (M/S) genotype was 1.9× more frequent in the male ISS than controls (P = 0.017, OR = 2.26). In both ISS cohorts, logistic regression analysis of 27 SNPs showed an association of ISS with rs4292454, while haplotype analysis revealed specific risk haplotypes in the 3′ haploblocks. In contrast, there were no differences in GT genotype frequencies in a cohort of short stature (SS) adults versus controls (CARTaGENE: n = 168 SS, n = 207 controls) and the risk haplotype in the SS cohort was located in the most 5′ haploblock. These data suggest that the variants identified are potentially genetic markers specifically associated with the ISS phenotype.

Correlation between genetic polymorphisms within the MAPK1/HIF-1/HO-1 signaling pathway and risk or prognosis of perimenopausal coronary artery disease

BACKGROUND

Mitogen-activated protein kinase-1 (MAPK1), as well as its downstream factors of hypoxia-inducible factor-1 (HIF-1) and heme oxygenase-1 (HO-1), have been documented to be involved in modulating development of coronary artery disease (CAD).

HYPOTHESIS

Genetic mutations within the MAPK1/HIF-1/HO-1 signaling pathway could alter the risk of perimenopausal CAD in Chinese patients.

METHODS

Peripheral blood samples were gathered from 589 CAD patients and 860 healthy controls, and 12 potential single-nucleotide polymorphisms (SNPs) were obtained from HapMap database and previously published studies. Genotyping of SNPs was implemented with the TaqMan SNP Genotyping Assays. Odds ratios (OR) and 95% confidence intervals (CI) were utilized to evaluate the correlations between SNPs and CAD risk.

RESULTS

Regarding MAPK1 , rs6928 (OR: 1.71, 95% CI: 1.47-1.98, P < 0.05), rs9340 (OR: 0.85, 95% CI: 0.73-0.99, P < 0.05), and rs11913721 (OR: 0.70, 95% CI: 0.52-0.95, P < 0.05) were remarkably associated with susceptibility to perimenopausal CAD. Of these, rs9340 and rs11913721 were also regarded as protective factors for perimenopausal CAD patients. Moreover, results of HIF-1 indicated noticeable correlations between combined SNPs of rs1087314 and rs2057482 and risk of perimenopausal CAD (OR: 1.24, 95% CI: 1.01-1.53, P < 0.05; and OR: 0.71, 95% CI: 0.55-0.91, P < 0.05, respectively). Nonetheless, rs2071746 in HO-1 was found to be only associated with perimenopausal CAD risk (OR: 0.67, 95% CI: 0.58-0.78, P < 0.05).

CONCLUSIONS

The genetic mutations within MAPK1 (rs6928, rs9340, rs11913721), HIF-1 (rs1087314, rs2057482), and HO-1 (rs2071746) could alter susceptibility to perimenopausal CAD in this Chinese population.

The active metabolite of leflunomide, A77 1726, attenuates inflammatory arthritis in mice with spontaneous arthritis via induction of heme oxygenase-1

Background

Leflunomide is a low-molecular-weight compound that is widely used in the treatment of rheumatoid arthritis. Although leflunomide is thought to act through the inhibition of the de novo pyrimidine synthesis, the molecular mechanism of the drug remains largely unknown. We investigated the antiarthritis effects and mechanisms of action of the active metabolite of leflunomide, A77 1726, in interleukin-1 receptor antagonist-knockout (IL-1Ra-KO) mice.

Methods

14- to 15-week-old male IL-1Ra-KO mice were treated with 10 or 30 mg/kg A77 1726 via intraperitoneal injection three times per week for 6 weeks. The effects of A77 1726 on arthritis severities were assessed by clinical scoring and histological analysis. The serum concentrations of IL-1β, tumor necrosis factor-α (TNF-α), and malondialdehyde were measured by enzyme-linked immunosorbent assay. Histologic analysis of the joints was performed using Safranin O, and immunohistochemical staining. The frequencies of interleukin-17-producing CD4⁺ T (Th17) cells were analyzed by flow cytometry. Heme oxygenase-1 (HO-1) expression in splenic CD4⁺ T cells isolated from A77 1726-treated arthritis mice were assessed by western blotting.

Results

A77 1726 treatment induced heme oxygenase-1 (HO-1) in Jurkat cells and primary mouse T cells. Interestingly, A77 1726 inhibited Th17 cell differentiation. In vivo, A77 1726 reduced the clinical arthritis severity of histological inflammation and cartilage destruction. The joints isolated from A77 1726-treated mice showed decreased expression of inducible nitric oxide synthase, nitrotyrosine, TNF-α, and IL-1β. The serum levels of TNF-α, IL-1β, and malondialdehyde were also decreased in A77 1726-treated mice. Whereas the number of Th17 cells in spleens was decreased in A77 1726-treated arthritis mice, a significant increase in the number of Treg cells in spleens was observed. Interestingly, HO-1 expression was significantly higher in splenic CD4⁺ T cells isolated from A77 1726-treated mice compared with those from vehicle-treated mice, whereas HO-1 expression of splenic non-CD4⁺ T cells did not differ between groups.

Conclusion

The inhibitory effects of A77 1726 on joint inflammation and oxidative stress in autoimmune arthritis may be associated with HO-1 induction in CD4⁺ T cells.

Modulation of Antiviral Immunity by Heme Oxygenase-1

Heme oxygenase-1 (HO-1) is a stress-inducible, anti-inflammatory, and cytoprotective enzyme expressed in most cell types in the organism. Under several stress stimuli, HO-1 expression and activity is up-regulated to catalyze the rate-limiting enzymatic step of heme degradation into carbon monoxide, free iron, and biliverdin. Besides its effects on cell metabolism, HO-1 is also capable of modulating host innate and adaptive immune responses in response to sepsis, transplantation, and autoimmunity, and preventing oxidative damage associated with inflammation. In addition, recent studies have reported that HO-1 can exert a significant antiviral activity against a wide variety of viruses, including HIV, hepatitis C virus, hepatitis B virus, enterovirus 71, influenza virus, respiratory syncytial virus, dengue virus, and Ebola virus, among others. Herein, we address the current understanding of the functional significance of HO-1 against a variety of viruses and its potential as a therapeutic strategy to prevent and control viral infections. Furthermore, we review the most important features of the immunoregulatory functions for this enzyme.

Heme Oxygenases in Cardiovascular Health and Disease

Heme oxygenases are composed of two isozymes, Hmox1 and Hmox2, that catalyze the degradation of heme to carbon monoxide (CO), ferrous iron, and biliverdin, the latter of which is subsequently converted to bilirubin. While initially considered to be waste products, CO and biliverdin/bilirubin have been shown over the last 20 years to modulate key cellular processes, such as inflammation, cell proliferation, and apoptosis, as well as antioxidant defense. This shift in paradigm has led to the importance of heme oxygenases and their products in cell physiology now being well accepted. The identification of the two human cases thus far of heme oxygenase deficiency and the generation of mice deficient in Hmox1 or Hmox2 have reiterated a role for these enzymes in both normal cell function and disease pathogenesis, especially in the context of cardiovascular disease. This review covers the current knowledge on the function of both Hmox1 and Hmox2 at both a cellular and tissue level in the cardiovascular system. Initially, the roles of heme oxygenases in vascular health and the regulation of processes central to vascular diseases are outlined, followed by an evaluation of the role(s) of Hmox1 and Hmox2 in various diseases such as atherosclerosis, intimal hyperplasia, myocardial infarction, and angiogenesis. Finally, the therapeutic potential of heme oxygenases and their products are examined in a cardiovascular disease context, with a focus on how the knowledge we have gained on these enzymes may be capitalized in future clinical studies.

Modulation of antigen processing by haem-oxygenase 1. Implications on inflammation and tolerance

Haem-oxygenase-1 (HO-1) is an enzyme responsible for the degradation of haem that can suppress inflammation, through the production of carbon monoxide (CO). It has been shown in several experimental models that genetic and pharmacological induction of HO-1, as well as non-toxic administration of CO, can reduce inflammatory diseases, such as endotoxic shock, type 1 diabetes and graft rejection. Recently, it was shown that the HO-1/CO system can alter the function of antigen-presenting cells (APCs) and reduce T-cell priming, which can be beneficial during immune-driven inflammatory diseases. The molecular mechanisms by which the HO-1 and CO reduce both APC- and T-cell-driven immunity are just beginning to be elucidated. In this article we discuss recent findings related to the immune regulatory capacity of HO-1 and CO at the level of recognition of pathogen-associated molecular patterns and T-cell priming by APCs. Finally, we propose a possible regulatory role for HO-1 and CO over the recently described mitochondria-dependent immunity. These concepts could contribute to the design of new therapeutic tools for inflammation-based diseases.

Targeting heme oxygenase-1 and carbon monoxide for therapeutic modulation of inflammation

The heme oxygenase-1 (HO-1) enzyme system remains an attractive therapeutic target for the treatment of inflammatory conditions. HO-1, a cellular stress protein, serves a vital metabolic function as the rate-limiting step in the degradation of heme to generate carbon monoxide (CO), iron, and biliverdin-IXα (BV), the latter which is converted to bilirubin-IXα (BR). HO-1 may function as a pleiotropic regulator of inflammatory signaling programs through the generation of its biologically active end products, namely CO, BV and BR. CO, when applied exogenously, can affect apoptotic, proliferative, and inflammatory cellular programs. Specifically, CO can modulate the production of proinflammatory or anti-inflammatory cytokines and mediators. HO-1 and CO may also have immunomodulatory effects with respect to regulating the functions of antigen-presenting cells, dendritic cells, and regulatory T cells. Therapeutic strategies to modulate HO-1 in disease include the application of natural-inducing compounds and gene therapy approaches for the targeted genetic overexpression or knockdown of HO-1. Several compounds have been used therapeutically to inhibit HO activity, including competitive inhibitors of the metalloporphyrin series or noncompetitive isoform-selective derivatives of imidazole-dioxolanes. The end products of HO activity, CO, BV and BR may be used therapeutically as pharmacologic treatments. CO may be applied by inhalation or through the use of CO-releasing molecules. This review will discuss HO-1 as a therapeutic target in diseases involving inflammation, including lung and vascular injury, sepsis, ischemia-reperfusion injury, and transplant rejection.

Association Between Heme Oxygenase-1 Promoter Polymorphisms and the Development of Albuminuria in Type 2 Diabetes: A Case-Control Study

Heme oxygenase (HO)-1 is a key enzyme in cytoprotective mechanisms against oxidative stress in the cardiovascular-renal system. The T(-413)A single nucleotide polymorphism (SNP) and (GT)n microsatellite polymorphism in the HO-1 gene promoter modulate the HO-1 gene transcriptional activity and these polymorphisms are associated with various human diseases.We investigated the association between HO-1 promoter polymorphisms and nephropathy in type 2 diabetes. We sequenced the T(-413)A SNP and (GT)n repeat segments of the HO-1 gene promoter in 536 patients with type 2 diabetes. (GT)n alleles were divided into 2 groups: short (S, ≤25 GT repeats) and long (L, >25 GT repeats) alleles. The presence of albuminuria was used as a marker of diabetic nephropathy.Patients with the TT genotype in the T(-413)A SNP were significantly more susceptible to albuminuria development than those carrying the A allele, with an odds ratio of 1.577 (95% confidence interval, 1.088 - 2.285; P = 0.016). Subgroup analysis showed that patients carrying the TT genotype with long duration of diabetes (≥20 years), poor glycemic control, male gender and without hypertension had higher odds ratios for the development of albuminuria. In vitro, promoter activity of the T(-413)A SNP was higher with A allele than T allele. Regarding to the (GT)n repeats, the LL genotype showed a higher odds ratio for the development of albuminuria only in patients with hypertension when compared to the S allele.In conclusion, the T(-413)A SNP in the HO-1 promoter is significantly associated with albuminuria development in type 2 diabetes patients, especially with longer duration and poor glycemic control.

Association of HMOX1 gene promoter polymorphisms with hyperbilirubinemia in the early neonatal period

BACKGROUND

Heme oxygenase (HO) is the rate-limiting enzyme in the heme degradation pathway that produces bilirubin. The promoter region of human heme oxygenase-1 (HMOX1) contains a polymorphic (GT)n repeat that can regulate gene expression. Here, we investigated the association of (GT)n repeat length in the HMOX1 promoter region with neonatal hyperbilirubinemia in a population of Japanese term neonates.

METHODS

Using polymerase chain reaction and fragment analysis, we determined the number of (GT)n repeats in 149 Japanese neonates. To omit the effects of the G71R mutation in uridine diphosphoglucuronosyltransferase on hyperbilirubinemia, we excluded 41 neonates with the G71R mutation. As a result, 25 neonates with hyperbilirubinemia and 83 non-hyperbilirubinemic controls were included in this prospective case-control study. Allele and genotype frequencies of (GT)n repeats in the HMOX1 gene were compared between hyperbilirubinemic and non-hyperbilirubinemic control neonates.

RESULTS

The prevalence of short alleles (< 22 (GT)n repeats) was significantly higher in hyperbilirubinemic than in control neonates (18% vs 7%, P = 0.015). Hyperbilirubinemia was more frequent in homozygous or heterozygous short allele carriers than control neonates (28% vs 11%, respectively, P = 0.03). Possession of short alleles was significantly associated with the development of neonatal hyperbilirubinemia (OR, 3.1; 95%CI: 1.03-9.53).

CONCLUSIONS

Infants carrying short alleles (< 22 (GT)n repeats) in the HMOX1 gene promoter region appear to be at a higher risk for developing neonatal hyperbilirubinemia.

Hemeoxygenase-1 maintains bone mass via attenuating a redox imbalance in osteoclast

Heme oxygenase-1 (HO-1) has long been considered to be an endogenous antioxidant. However, the role of HO-1 is highly controversial in developing metabolic diseases. We hypothesized that HO-1 plays a role in maintaining bone mass by alleviating a redox imbalance. We investigated its role in bone remodeling. The absence of HO-1 in mice led to decreased bone mass with elevated activity and number of OCs, as well as higher serum levels of reactive oxygen species (ROS). HO-1, which is constitutively expressed at a high level in osteoclast (OC) precursors, was down-regulated during OC differentiation. HO-1 deficiency in bone marrow macrophages (BMM) in vitro resulted in increased numbers and activity of OCs due to enhanced receptor activator of nuclear factor-κB ligand (RANKL) signaling. This was associated with increased activation of nuclear factor-κB and of nuclear factor of activated T-cells, cytoplasmic 1 along with elevated levels of intracellular calcium and ROS. Decreased bone mass in the absence of HO-1 appears to be mainly due to increased osteoclastogenesis and bone resorption resulting from elevated RANKL signaling in OCs. Our data highlight the potential role of HO-1 in maintaining bone mass by negatively regulating OCs.

Therapeutic potential of HO-1 in autoimmune diseases

Heme oxygenase-1 (HO-1), the inducible isoform of heme oxygenase (HO), has raised a lot of concerns in recent years due to its multiple functions. HO-1 was found to be a pivotal cytoprotective, antioxidant, anti-apoptotic, immunosuppressive, as well as anti-inflammatory molecule. Recent studies have clarified its significant functions in many diseases with substantial findings. In autoimmune diseases, HO-1 may have promising therapeutic potential. Here, we briefly reviewed recent advances in this field, aiming at hopefully exploring the potential therapeutic roles of HO-1, and design HO-1-based strategies for the treatment of autoimmune diseases.

Association of HMOX1 and NQO1 Polymorphisms with Metabolic Syndrome Components

Metabolic syndrome (MetS) is among the most important public health problems worldwide, and is recognized as a major risk factor for various illnesses, including type 2 diabetes mellitus, obesity, and cardiovascular diseases. Recently, oxidative stress has been suggested as part of MetS aetiology. The heme oxygenase 1 (HMOX1) and NADH:quinone oxidoreductase 1 (NQO1) genes are crucial mediators of cellular defence against oxidative stress. In the present study, we analysed the associations of HMOX1 (GT)n and NQO1 C609T polymorphisms with MetS and its components. Our study population comprised 735 Mexican Mestizos unrelated volunteers recruited from different tertiary health institutions from Mexico City. In order to know the HMOX1 (GT)n and NQO1 C609T allele frequencies in Amerindians, we included a population of 241 Amerindian native speakers. Their clinical and demographic data were recorded. The HMOX1 (GT)n polymorphism was genotyped using PCR and fluorescence technology. NQO1 C609T polymorphism genotyping was performed using TaqMan probes. Short allele (<25 GT repeats) of the HMOX1 polymorphism was associated with high systolic and diastolic blood pressure, and the T allele of the NQO1 C609T polymorphism was associated with increased triglyceride levels and decreased HDL-c levels, but only in individuals with MetS. This is the first study to analyse the association between MetS and genes involved in oxidative stress among Mexican Mestizos. Our data suggest that polymorphisms of HMOX1 and NQO1 genes are associated with a high risk of metabolic disorders, including high systolic and diastolic blood pressure, hypertriglyceridemia, and low HDL-c levels in Mexican Mestizo individuals.

Protective role of hemeoxygenase-1 in gastrointestinal diseases

Disorders and diseases of the gastrointestinal system encompass a wide array of pathogenic mechanisms as a result of genetic, infectious, neoplastic, and inflammatory conditions. Inflammatory diseases in general are rising in incidence and are emerging clinical problems in gastroenterology and hepatology. Hemeoxygenase-1 (HO-1) is a stress-inducible enzyme that has been shown to confer protection in various organ-system models. Its downstream effectors, carbon monoxide and biliverdin have also been shown to offer these beneficial effects. Many studies suggest that induction of HO-1 expression in gastrointestinal tissues and cells plays a critical role in cytoprotection and resolving inflammation as well as tissue injury. In this review, we examine the protective role of HO-1 and its downstream effectors in modulating inflammatory diseases of the upper (esophagus and stomach) and lower (small and large intestine) gastrointestinal tract, the liver, and the pancreas. Cytoprotective, anti-inflammatory, anti-proliferative, antioxidant, and anti-apoptotic activities of HO-1 make it a promising if not ideal therapeutic target for inflammatory diseases of the gastrointestinal system.

Neonatal hemolysis and risk of bilirubin-induced neurologic dysfunction

The pathologic phenotype of severe hyperbilirubinemia in the newborn infant is primarily due to excessive bilirubin production and/or impaired conjugation, resulting in an increased bilirubin load. This may, in turn, increase an infant's risk for the development of bilirubin-induced neurologic dysfunction (BIND). The highest-risk infants are those with increased bilirubin production rates due to hemolysis. Several immune and non-immune conditions have been found to cause severe hemolysis, and these are often exacerbated in those infants with perinatal sepsis and genetic predispositions. Therefore, identification of these infants, with novel technologies, is paramount in reducing the incidence of BIND and the long-term neurologic sequelae for these at-risk infants.

Heme oxygenase-1 gene promoter polymorphism is associated with the development of necrotizing acute pancreatitis

OBJECTIVES

Acute pancreatitis is a severe and frequently life-threatening disease, which can lead to pancreatic necrosis, acute lung injury, systemic inflammatory response syndrome, and other complications. In this study, we hypothesized that the expression of heme oxygenase-1 determined by the number of guanidinium thiocyanate (GT) repeats can influence the occurrence of acute pancreatitis.

METHODS

Patients with acute pancreatitis (n = 131) and age- and sex-matched healthy controls (n = 108) were studied. The polymerase chain reaction products were analyzed by ABI 3130 genetic analyzer and the exact size of the polymerase chain reaction products was determined by GeneMapper software. A short allele was defined as containing 27 GT repeats or fewer, whereas a long allele was more than 27 repeats.

RESULTS

The subjects were categorized into 3 groups on the basis of the genotype results: 1 short and 1 long, 2 short, and 2 long alleles (L/L). Patients with necrotizing disease more frequently were carriers of LL genotype compared with those who had edematous acute pancreatitis. Furthermore, logistic regression analysis revealed that the presence of L/L allele type doubles the risk for developing pancreatic necrosis in patients with acute pancreatitis.

CONCLUSIONS

The polymorphism of the GT repeats in the heme oxygenase-1 promoter region may be a risk factor for developing severe and necrotizing acute pancreatitis.

Design of oral agents for the management of multiple sclerosis: benefit and risk assessment for dimethyl fumarate

Dimethyl fumarate (DMF) is the most recent oral disease-modifying therapy approved by the US Food and Drug Administration and is indicated for the treatment of relapsing forms of multiple sclerosis (MS). Prior to approval for use in MS, DMF and its active metabolite, monomethyl fumarate, had been used for decades as two of the fumaric acid esters in Fumaderm, a medication used in Europe for the treatment of psoriasis. The unique mechanism of action of DMF remains under evaluation; however, it has been shown to act through multiple pathways leading to shifts away from the Th1 proinflammatory response to the less inflammatory Th2 response. Preliminary data suggest that DMF may induce neuroprotective effects in central nervous system white matter, although further studies are needed to demonstrate these effects on inflammatory demyelination. The DMF Phase III clinical trials demonstrated its efficacy with regard to a reduction in the annualized relapse rate and reductions in new or enlarging T2 lesions and numbers of gadolinium-enhancing lesions on magnetic resonance imaging. DMF has a well-defined safety profile, given the experience with its use in the treatment of psoriasis, and more recently from the DMF clinical trials program and post-marketing era for treatment of MS. The safety profile and oral mode of administration of DMF place it as an attractive first-line therapy option for the treatment of relapsing forms of MS. Long-term observational studies will be needed to determine the effects of DMF on progression of disability in MS.

The multifunctional role and therapeutic potential of HO-1 in the vascular endothelium

SIGNIFICANCE

Heme oxygenases (HO-1 and HO-2) catalyze the degradation of the pro-oxidant heme into carbon monoxide (CO), iron, and biliverdin, which is subsequently converted to bilirubin. In the vasculature, particular interest has focused on antioxidant and anti-inflammatory properties of the inducible HO-1 isoform in the vascular endothelium. This review will present evidence that illustrates the potential therapeutic significance of HO-1 and its products, with special emphasis placed on their beneficial effects on the endothelium in vascular diseases.

RECENT ADVANCES

The understanding of the molecular basis for the regulation and functions of HO-1 has led to the identification of a variety of drugs that increase HO-1 activity in the vascular endothelium. Moreover, therapeutic delivery of HO-1 products CO, biliverdin, and bilirubin has been shown to have favorable effects, notably on endothelial cells and in animal models of vascular disease.

CRITICAL ISSUES

To date, mechanistic data identifying the downstream target genes utilized by HO-1 and its products to exert their actions remain relatively sparse. Likewise, studies in man to investigate the efficacy of therapeutics known to induce HO-1 or the consequences of the tissue-specific delivery of CO or biliverdin/bilirubin are rarely performed.

FUTURE DIRECTIONS

Based on the promising in vivo data from animal models, clinical trials to explore the safety and efficacy of the therapeutic induction of HO-1 and the delivery of its products should now be pursued further, targeting, for example, patients with severe atherosclerotic disease, ischemic limbs, restenosis injury, or at high risk of organ rejection.

Human pharmacokinetics of high dose oral curcumin and its effect on heme oxygenase-1 expression in healthy male subjects

Purpose. Heme oxygenase-1 (HO-1) has been proposed to exert pharmacological benefits by its antioxidative and anti-inflammatory effects. HO-1 expression may be affected by the GT length polymorphism in the promoter region of the HO-1 gene. We investigated the inducibility of HO-1 by orally administered curcumin in healthy male subjects and its correlation with the GT length polymorphism. Methods. In an open label uncontrolled phase-1 pilot study, ten male subjects received 12 g of oral curcumin. To investigate the effects of the GT length polymorphism on the inducibility of HO-1, five subjects with homozygous short and five with homozygous long GT genotypes were studied. Plasma concentrations of curcumin, bilirubin, HO-1 mRNA, and protein expression in peripheral blood mononuclear cells (PBMCs) were analyzed over 48 hours. Results. At a detection limit of 1 µg/mL curcumin could not be detected in plasma of any subject. Compared to baseline, HO-1 mRNA and protein levels were not induced in PBMCs at any time point up to 48 hours. There was no correlation between any of the parameters and GT length polymorphism. Conclusions. Oral curcumin administration has low bioavailability and does not induce HO-1 on mRNA or protein level in PBMCs.

Polymorphism in the HMOX1 gene is associated with high levels of fetal hemoglobin in Brazilian patients with sickle cell anemia

The aim of this study was to investigate the association between three polymorphisms involved in the oxidative stress pathway and fetal hemoglobin (Hb F) levels in patients with sickle cell anemia in a Brazilian population. One hundred and seven patients with sickle cell anemia were recruited for genomic DNA extraction. The levels of Hb F, sex and age were evaluated. Three polymorphisms, rs4673:T>C and rs9932581:G>A in the CYBA gene and rs2071746:A>T in the HMOX1 gene, were identified through direct sequencing. Hb F levels were not associated with sex, age, or the polymorphisms rs4673:T>C and rs9932581:G>A. However, the TT genotype of the rs2071746:A>T polymorphism was associated with increased levels of Hb F (p value = 0.0131). We observed an association between the TT genotype of the rs2071746:A>T polymorphism, present in the HMOX1 gene, and increased levels of Hb F, indicating the presence of a new marker related to Hb F levels in sickle cell anemia patients.

Development of inhibitory antibodies to therapeutic factor VIII in severe hemophilia A is associated with microsatellite polymorphisms in the HMOX1 promoter

Induction of heme oxygenase-1, a stress-inducible enzyme with anti-inflammatory activity, reduces the immunogenicity of therapeutic factor VIII in experimental hemophilia A. In humans, heme oxygenase-1 expression is modulated by polymorphisms in the promoter of the heme oxygenase-1-encoding gene (HMOX1). We investigated the relationship between polymorphisms in the HMOX1 promoter and factor VIII inhibitor development in severe hemophilia A. We performed a case-control study on 99 inhibitor-positive patients and 263 patients who did not develop inhibitors within the first 150 cumulative days of exposure to therapeutic factor VIII. Direct sequencing and DNA fragment analysis were used to study (GT)n polymorphism and single nucleotide polymorphisms located at -1135 and -413 in the promoter of HMOX1. We assessed associations between the individual allele frequencies or genotypes, and inhibitor development. Our results demonstrate that inhibitor-positive patients had a higher frequency of alleles with large (GT)n repeats (L: n≥30), which are associated with lesser heme oxygenase-1 expression (odds ratio 2.31; 95% confidence interval 1.46-3.66; P<0.001]. Six genotypes (L/L, L/M, L/S, M/M, M/S and S/S) of (GT)n repeats were identified (S: n<21; M: 21≤n<30). The genotype group including L alleles (L/L, L/M and L/S) was statistically more frequent among inhibitor-positive than inhibitor-negative patients, as compared to the other genotypes (33.3% versus 17.1%) (odds ratio 2.21, 95% confidence interval 1.30-3.76; P<0.01). To our knowledge, this is the first association identified between HMOX1 promoter polymorphism and development of anti-drug antibodies. Our study paves the way towards modulation of the endogenous anti-inflammatory machinery of hemophilia patients to reduce the risk of inhibitor development.

Gene polymorphisms in the heme degradation pathway and outcome of severe human sepsis

Heme and its breakdown products CO, Fe, and bilirubin are being recognized as signaling molecules or even therapeutic agents, but also exert adverse effects when released at high concentrations. Manipulating the pathway confers protection in rodent sepsis models via both control of free heme and formation of its first and higher-order products. Thus, regulatory elements present in human heme oxygenase 1 (HMOX1) and biliverdin reductases (BLVRA/B) genes might impact outcome. We tested whether a highly polymorphic (GT)n microsatellite and single-nucleotide polymorphisms in HMOX1 and BLVRA/B genes are associated with outcome of sepsis. Two cohorts (n = 430 and 398 patients) with severe sepsis were screened for single-nucleotide polymorphisms and/or the microsatellite by fragment length analysis and genotyping techniques. Heme oxygenase 1 plasma levels were determined in additional patients with severe sepsis (n = 92) by enzyme-linked immunosorbent assay. Based on mean Sepsis-related Organ Failure Assessment scores, patients homozygous for rs2071746 A allele or medium length (GT)n microsatellites of HMOX1 showed higher 28-day mortality (P = 0.047 and P = 0.033) in one cohort compared with other genotypes, whereas 90-day mortality rates showed no association. The T allele was less frequently observed in both cohorts than would be expected according to Hardy-Weinberg equilibrium. Heme oxygenase 1 plasma levels were elevated in septic patients, independent of the genotype. Single-nucleotide polymorphisms within BLVRA/B showed no association with outcome. Short (GT)n repeats that are in linkage disequilibrium with the T allele of rs2071746 in HMOX1 are associated with favorable outcome, whereas no association with gene variants of BLVRA/B, involved in the generation of higher-order metabolites, was noticed.

GT microsatellite repeats in the heme oxygenase-1 gene promoter associated with abdominal aortic aneurysm in Croatian patients

Abdominal aortic aneurysm (AAA) is a complex genetic disorder caused by the interplay of genetic and environmental risk factors. The number of (GT)(n) repeats in the heme oxygenase-1 (HO-1) gene promoter modulates transcription of this enzyme, which might have anti-inflammatory, antioxidant, antiapoptotic, and antiproliferative effect. The distribution of alleles and genotypes in Croatian individuals genotyped for the (GT)(n) HO-1 polymorphism was similar to that in other European populations. Frequency of the short (S) alleles (GT < 25) was higher in AAA patients (41.9%) than in non-AAA individuals (28.2%, p = 0.0026) because there were more SL heterozygotes among the AAA patients. The SL genotype appeared to increase the risk for AAA, but the increase was not statistically significant after adjustment for age, sex, smoking, hypertension, and hyperlipidemia (OR = 1.53, 95% CI 0.90-3.09, p = 0.062). These findings contradict those of the only other study performed so far on the association of (GT)(n) HO-1 polymorphism and AAA.

Heme oxygenase-1 regulates the progression of K/BxN serum transfer arthritis

Background

Heme oxygenase-1 (HO-1) is induced in many cell types as a defense mechanism against stress. We have investigated the possible role of endogenous HO-1 in the effector phase of arthritis using the K/BxN serum transfer model of arthritis in HO-1 heterozygous and homozygous knock-out mice.

Methodology/Principal Findings

Arthritis was induced in C57/Black-6 xFVB (HO-1^+/+, HO-1^+/− and HO-1^−/−) mice by intraperitoneal injection of 150 µl serum from arthritic K/BxN mice at days 0 and 2. Blood was collected and animals were sacrificed at day 10. Histological analysis was performed in ankle sections. The levels of inflammatory mediators were measured in serum and paw homogenates by enzyme-linked immunosorbent assay or Multiplex technology. The incidence of arthritis was higher in HO-1^+/− and HO-1^−/− groups compared with HO-1^+/+. The inflammatory response was aggravated in HO-1^+/− mice as shown by arthritic score and the migration of inflammatory cells that could be related to the enhancement of CXCL-1 production. In addition, the HO-1^+/− group showed proteoglycan depletion significantly higher than HO-1^+/+ mice. Serum levels of matrix metalloproteinase-3, monocyte chemotactic protein-1, plasminogen activator inhibitor-1, E-selectin and intercellular adhesion molecule-1 were increased in arthritic HO-1^−/− mice, whereas vascular endothelial growth factor and some cytokines such as interferon-γ showed a reduction compared to HO-1^+/+ or HO-1^+/− mice. In addition, down-regulated gene expression of ferritin, glutathione S-reductase A1 and superoxide dismutase-2 was observed in the livers of arthritic HO-1^+/− animals.

Conclusion/Significance

Endogenous HO-1 regulates the production of systemic and local inflammatory mediators and plays a protective role in K/BxN serum transfer arthritis.

Microsatellite polymorphism in the heme oxygenase-1 gene promoter and the risk of psoriasis in Taiwanese

Psoriasis is a chronic disease characterized by inflammation of the skin. The expression of heme oxygenase-1 (HO-1), the rate-limiting enzyme involved in heme degradation, correlates well with the severity of psoriasis, and is a heritable trait. This study aimed to assess the role of (GT)(n) dinucleotide repeat polymorphisms in the promoter region of the HO-1 gene in Chinese-Taiwanese patients with psoriasis. In total, 288 patients with psoriasis and 542 control subjects were analyzed for the presence of the HO-1 microsatellite polymorphism by using polymerase chain reaction. The alleles were classified as the S and L alleles according to the number of (GT)(n) repeats, with the alleles with ≤26 repeats designated as S and alleles with ≥27 repeats designated as L alleles. The subjects were then classified as having S/S, S/L, or L/L genotypes according to each of their HO-1 alleles. No significant difference was observed in either the genotype or allele distribution between the patients and healthy controls. However, the average number of repeats of both alleles in psoriasis patients with late disease onset was lower than that of psoriasis patients with early disease onset (26.7 ± 3.2 vs. 27.5 ± 3.4; P = 0.043, adjusted for age and sex), but the difference was not significant after additional adjustment for body mass index, smoking, diabetes, and hypertension (P = 0.189). Our results suggest that the HO-1 microsatellite polymorphism may not contribute to the genetic background of psoriasis in Chinese-Taiwanese patients.

Haem oxygenase 1 expression is altered in monocytes from patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by multiple functional alterations affecting immune cells, such as B cells, T cells, dendritic cells (DCs) and monocytes. During SLE, the immunogenicity of monocytes and DCs is significantly up-regulated, promoting the activation of self-reactive T cells. Accordingly, it is important to understand the contribution of these cells to the pathogenesis of SLE and the mechanisms responsible for their altered functionality during disease. One of the key enzymes that control monocyte and DC function is haem oxygenase-1 (HO-1), which catalyses the degradation of the haem group into biliverdin, carbon monoxide and free iron. These products possess immunosuppressive and anti-inflammatory capacities. The main goal of this work was to determine HO-1 expression in monocytes and DCs from patients with SLE and healthy controls. Hence, peripheral blood mononuclear cells were obtained from 43 patients with SLE and 30 healthy controls. CD14(+) monocytes and CD4(+) T cells were sorted by FACS and HO-1 expression was measured by RT-PCR. In addition, HO-1 protein expression was determined by FACS. HO-1 levels in monocytes were significantly reduced in patients with SLE compared with healthy controls. These results were confirmed by flow cytometry. No differences were observed in other cell types, such as DCs or CD4(+) T cells, although decreased MHC-II levels were observed in DCs from patients with SLE. In conclusion, we found a significant decrease in HO-1 expression, specifically in monocytes from patients with SLE, suggesting that an imbalance of monocyte function could be partly the result of a decrease in HO-1 expression.

Bach1 regulates osteoclastogenesis in a mouse model via both heme oxygenase 1-dependent and heme oxygenase 1-independent pathways

OBJECTIVE

Reducing inflammation and osteoclastogenesis by heme oxygenase 1 (HO-1) induction could be beneficial in the treatment of rheumatoid arthritis (RA). However, the function of HO-1 in bone metabolism remains unclear. This study was undertaken to clarify the effects of HO-1 and its repressor Bach1 in osteoclastogenesis.

METHODS

In vitro osteoclastogenesis was compared in Bach1-deficient and wild-type mice. Osteoclasts (OCs) were generated from bone marrow-derived macrophages by stimulation with macrophage colony-stimulating factor and RANKL. Osteoclastogenesis was assessed by tartrate-resistant acid phosphatase staining and expression of OC-related genes. Intracellular signal pathways in OC precursors were also assessed. HO-1 short hairpin RNA (shRNA) was transduced into Bach1(-/-) mouse bone marrow-derived macrophages to examine the role of HO-1 in osteoclastogenesis. In vivo inflammatory bone loss was evaluated by local injection of tumor necrosis factor α (TNFα) into calvaria.

RESULTS

Transcription of HO-1 was down-regulated by stimulation with RANKL in the early stage of OC differentiation. Bach1(-/-) mouse bone marrow-derived macrophages were partially resistant to the RANKL-dependent HO-1 reduction and showed impaired osteoclastogenesis, which was associated with reduced expression of RANK and components of the downstream TNF receptor-associated factor 6/c-Fos/NF-ATc1 pathway as well as reduced expression of Blimp1. Treatment with HO-1 shRNA increased the number of OCs and expression of OC-related genes except for the Blimp1 gene during in vitro osteoclastogenesis from Bach1(-/-) mouse bone marrow-derived macrophages. TNFα-induced bone destruction was reduced in Bach1(-/-) mice in vivo.

CONCLUSION

The present findings demonstrate that Bach1 regulates osteoclastogenesis under inflammatory conditions, via both HO-1-dependent and HO-1-independent mechanisms. Bach1 may be worthy of consideration as a target for treatment of inflammatory bone loss in diseases including RA.

Short (GT) ( n ) repeats in heme oxygenase-1 gene promoter are associated with lower risk of coronary heart disease in subjects with high levels of oxidative stress

Although (GT) ( n ) repeats in heme oxygenase-1 (HO-1) promoter may modulate gene transcriptional activity, the association between (GT) ( n ) repeats polymorphism and risk of coronary heart disease (CHD) from different levels of oxidative stress (OS) is unknown. We determined the allelic frequencies of (GT) ( n ) repeats in the HO-1 gene promoter and plasma malonaldehyde (MDA) as biomarkers of OS in 2,298 pairs of CHD patients and controls in the Chinese population. Furthermore, we measured MDA in culture mediums and HO-1 expressions levels in cell lysates of endothelial cells carrying various (GT) ( n ) genotypes under different concentrations of H(2)O(2). Compared with L/L genotype (>25 repeats) carriers, the adjusted odd ratios for S/S genotype (≤25 repeats) in subjects with different levels of OS (MDA < 1.83, 1.83-2.91, >2.91 μmol/L) were 1.06 (95%CI, 0.75 to 1.49), 0.79 (95%CI, 0.55 to 1.12), and 0.60 (95%CI, 0.44 to 0.81), respectively (P (interaction) = 0.002). In biological experiments, compared with endothelial cells carrying L/L genotype, cells with S/S genotype did not have a significantly higher HO-1 expression under 0 μmol/L H(2)O(2), but displayed a significantly higher HO-1 expression under 50 μmol/L H(2)O(2) (P (interaction) = 0.003). S/S genotype in HO-1 gene promoter is associated with a lower risk of CHD in subjects with higher levels of OS, because under conditions of high OS, the S/S genotype has higher levels of HO-1, an antioxidant.

Association of serum bilirubin and promoter variations in HMOX1 and UGT1A1 genes with sporadic colorectal cancer

Heme oxygenase-1 (HMOX1) and bilirubin UDP-glucuronosyltransferase (UGT1A1) enzymes, both involved in bilirubin homeostasis, play an important role in the oxidative stress defense. The objective of our study was to assess the effect of promoter variations of HMOX1 and UGT1A1 genes and of serum bilirubin on the risk of sporadic colorectal cancer (CRC). This exploratory case-control study was based on 777 CRC patients and 986 controls from the Czech Republic. The (GT)(n) and (TA)(n) dinucleotide variations in HMOX1 and UGT1A1 gene promoters, respectively, were determined by fragment analysis. In addition, the A(-413)T variant in HMOX1 promoter was also analyzed using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Serum bilirubin levels were compared in a subset of 174 cases and 247 controls, for whom biochemical data were available. After adjustment for age, a significant association between CRC risk and UGT1A1*28 allele carrier status was detected [odds ratio (95% confidence intervals) = 0.80 (0.60-0.97), p = 0.022]. No association between CRC risk and individual HMOX1 gene variants was observed, although a diplotype analysis revealed an increased risk for a specific HMOX1 genotype combination. These effects were more pronounced in males. Substantially lower serum bilirubin levels were detected in CRC patients compared to the controls (p < 0.001); each 1 μmol/L decrease in serum bilirubin was associated with a 7% increase of CRC risk (p < 0.001). In conclusion, UGT1A1*28 allele carrier status might be a protective factor against the development of CRC in the male population, whereas low serum bilirubin levels are associated with an increased risk of CRC in both genders.