Retrovirus-mediated human heme oxygenase-1 (HO-1) gene transfer into rat endothelial cells: the effect of HO-1 inducers on the expression of cytokines

Low concentration of exogenous carbon monoxide protects mammalian cells against proliferation induced by radiation-induced bystander effect

Radiation-induced bystander effect (RIBE) has been proposed to have tight relationship with the irradiation-caused secondary cancers beyond the irradiation-treated area after radiotherapy. Our previous studies demonstrated a protective effect of low concentration carbon monoxide (CO) on the genotoxicity of RIBE after α-particle irradiation. In the present work, a significant inhibitory effect of low-dose exogenous CO, generated by tricarbonyldichlororuthenium (II) dimer [CO-releasing molecule (CORM-2)], on both RIBE-induced proliferation and chromosome aberration was observed. Further studies on the mechanism revealed that the transforming growth factor β1/nitric oxide (NO) signaling pathway, which mediated RIBE signaling transduction, could be modulated by CO involved in the protective effects. Considering the potential of exogenous CO in clinical applications and its protective effect on RIBE, the present work aims to provide a foundation for potential application of CO in radiotherapy.

A functional link between heme oxygenase-1 and tristetraprolin in the anti-inflammatory effects of nicotine

Nicotine stimulates the cholinergic anti-inflammatory pathway and prevents excessive inflammation by inhibiting the release of inflammatory cytokines from macrophages. We have previously reported that heme oxygenase-1 (HO-1) and tristetraprolin (TTP) are induced by nicotine and mediate the anti-inflammatory function of nicotine in macrophages. However, it was not clear whether the two molecules are functionally linked. In this study, we sought to determine whether HO-1 associates with TTP to mediate the anti-inflammatory effects of nicotine. Inhibition of HO-1 activity or HO-1 expression attenuated the effects of nicotine on STAT3 activation, TTP induction, and TNF-α production in LPS-treated macrophages. Induction of HO-1 expression increased the level of TTP in the absence of nicotine. In an LPS-induced endotoxemia model, HO-1 deficiency blocked the effects of nicotine on the STAT3 phosphorylation, TTP induction, and LPS-induced TNF-α production in the liver. Downregulation of STAT3 by siRNA attenuated the effect of nicotine on TTP expression and TNF-α production but did not affect the nicotine-mediated induction of HO-1. In TTP knockout mice, nicotine treatment enhanced HO-1 expression and STAT3 activation but failed to inhibit LPS-induced TNF-α production. Our results suggest that HO-1 and TTP are functionally linked in mediating the anti-inflammatory effects of nicotine; HO-1 is necessary for the induction of TTP by nicotine. This novel nicotine-HO-1-TTP signaling pathway provides new possibilities for the treatment of inflammatory diseases.

Proteomic screening of human targets of viral microRNAs reveals functions associated with immune evasion and angiogenesis

Kaposi's sarcoma (KS) is caused by infection with Kaposi's sarcoma-associated herpesvirus (KSHV). The virus expresses unique microRNAs (miRNAs), but the targets and functions of these miRNAs are not completely understood. In order to identify human targets of viral miRNAs, we measured protein expression changes caused by multiple KSHV miRNAs using pulsed stable labeling with amino acids in cell culture (pSILAC) in primary endothelial cells. This led to the identification of multiple human genes that are repressed at the protein level, but not at the miRNA level. Further analysis also identified that KSHV miRNAs can modulate activity or expression of upstream regulatory factors, resulting in suppressed activation of a protein involved in leukocyte recruitment (ICAM1) following lysophosphatidic acid treatment, as well as up-regulation of a pro-angiogenic protein (HIF1α), and up-regulation of a protein involved in stimulating angiogenesis (HMOX1). This study aids in our understanding of miRNA mechanisms of repression and miRNA contributions to viral pathogenesis.

Heme oxygenase-1 as a target for TGF-β in kidney disease

Transforming growth factor-β (TGF-β) is a multifunctional regulatory cytokine that is implicated in a variety of kidney diseases, including diabetic nephropathy and chronic transplant rejection, where it promotes stimulation of the extracellular matrix deposition, cell proliferation, and migration. TGF-β exerts its biological functions largely via its downstream complex signaling molecules, Smad proteins. Paradoxically, TGF-β also is essential for normal homeostasis and suppression of inflammation through mechanisms that are yet to be fully elucidated. One feasible mechanism by which TGF-β may exert its beneficial properties is through induction of heme oxygenase-1 (HO-1). Induction of this redox-sensitive enzyme is known to be cytoprotective through its potent antioxidant, anti-inflammatory, and anti-apoptotic properties in different conditions including several kidney diseases. In this overview, recent advances in our understanding of the role of TGF-β in kidney disease, its molecular regulation of HO-1 expression, and the potential role of HO-1 induction as a therapeutic modality in TGF-β-mediated kidney diseases are highlighted.

The effect of curcumin on insulin release in rat-isolated pancreatic islets

Curcumin exerts a hypoglycemic action and induces heme-oxygenase-1 (HO-1). We evaluated the effect of curcumin on isolated islets of Langerhans and studied whether its action on insulin secretion is mediated by inducible HO-1. Islets were isolated from rats and divided into control islets, islets incubated in different curcumin concentrations, islets incubated in hemin, islets incubated in curcumin and HO inhibitor, stannous mesoporphyrin (SnMP), islets incubated in hemin and SnMP, islets incubated in SnMP only, and islets incubated in 16.7 mmol/L glucose. Heme-oxygenase activity, HO-1 expression, and insulin estimation was assessed. Insulin secretion, HO-1 gene expression and HO activity were significantly increased in islets incubated in curcumin, hemin, and glucose compared with controls. This increase in insulin secretion was significantly decreased by incubation of islets in SnMP. The action of curcumin on insulin secretion from the isolated islets may be, in part, mediated through increased HO-1 gene expression.

Hemoxygenase-1 in cardiovascular disease

Hemoxygenase (HO)-1 is an inducible isoform of the first and rate-controlling enzyme of the degradation of heme into iron, carbon monoxide, and biliverdin, the latter being subsequently converted into bilirubin. Several positive biological effects exerted by this enzyme have gained attention, as anti-inflammatory, antiapoptotic, angiogenic, and cytoprotective functions are attributable to carbon monoxide and/or bilirubin. Thus, the physiological induction of HO-1 may be an adaptive and beneficial response to several possibly noxious stimuli, including heme itself, suggesting a potentially autoprotective and autodefensive role in several pathophysiological states including acute coronary syndromes and stroke. This review article provides a comprehensive overview of the biochemistry, physiology, and pathophysiology of HO-1 in relation to cardiovascular disease (CVD). Furthermore, we present some of the emerging evidence in support of the view that the induction of the HO-1 gene may be a new opportunity to target the pathophysiology of CVD, with therapeutic implications for management.

Heme oxygenase-1 deficiency promotes epithelial-mesenchymal transition and renal fibrosis

Induction of heme oxygenase-1 (HO-1) is associated with potential antifibrogenic effects. The effects of HO-1 expression on epithelial-mesenchymal transition (EMT), which plays a critical role in the development of renal fibrosis, are unknown. In this study, HO-1(-/-) mice demonstrated significantly more fibrosis after 7 d of unilateral ureteral obstruction compared with wild-type mice, despite similar degrees of hydronephrosis. The obstructed kidneys of HO-1(-/-) mice also had greater macrophage infiltration and renal tubular TGF-beta1 expression than wild-type mice. In addition, the degree of EMT was more extensive in obstructed HO-1(-/-) kidneys, as assessed by alpha-smooth muscle actin and expression of S100A4 in proximal tubular epithelial cells. In vitro studies using proximal tubular cells isolated from HO-1(-/-) and wild-type kidneys confirmed these observations. In conclusion, HO-1 deficiency is associated with increased fibrosis, tubular TGF-beta1 expression, inflammation, and enhanced EMT in obstructive kidney disease. Modulation of the HO-1 pathway may provide a new therapeutic approach to progressive renal diseases.

Heme oxygenase-1 and carbon monoxide in vascular pathobiology: focus on angiogenesis

Angiogenesis involves the formation of new blood vessels and is critical for fundamental events such as development and repair after injury. Perturbances in angiogenesis contribute to the pathogenesis of diverse clinical conditions including cancer, complications of diabetes mellitus, ischemia/reperfusion injury of the heart and other organs, and preeclampsia, as well as a number of inflammatory disorders. Recent work has identified heme oxygenase-1 and its gaseous product, carbon monoxide, to possess potent proangiogenic properties in addition to well-recognized antiinflammatory, antioxidant, and antiapoptotic effects. Angiogenic factors, such as vascular endothelial growth factor and stromal cell-derived factor-1, mediate their proangiogenic effects through induction of heme oxygenase-1, making it an attractive target for therapeutic intervention. This review will provide an overview of the role of heme oxygenase-1 and carbon monoxide in angiogenesis.

Growth factors and heme oxygenase-1: perspectives in physiology and pathophysiology

Growth factors are mediators of both normal homeostasis and pathophysiology through their effects on various cellular processes. Similarly, heme oxygenase-1 (HO-1) has a role in maintaining physiologic equilibrium, by which it can either alleviate or exacerbate disease, depending on several considerations, including amount, timing, and location of expression, as well as the disease setting. Thus, the synthesis and activities of growth factors and HO-1 are intricately regulated. Interestingly, several growth factors induce HO-1, and, conversely, HO-1 can regulate the expression of some growth factors. This review focuses on the influence of growth factors and HO-1 and potential physiologic effects of the growth factor(s)-HO-1 interaction.

Heme oxygenase-1 improves the survival of discordant cardiac xenograft through its anti-inflammatory and anti-apoptotic effects

HO-1 is a rate-limiting enzyme in hemoglobin metabolism, and exerts anti-inflammatory as well as anti-apoptotic effects. Previous studies have shown that expression of HO-1 can prolong the survival of concordant transplanted organs. However, little is known about the precise effect and mechanism of HO-1 in discordant xenotransplantation. In this study, we investigated the role of HO-1 in discordant cardiac xenotransplantation. First, HUVECs were used to assess the effect of HO-1 on TNF-alpha-induced apoptosis. Results showed that TNF-alpha induced apoptosis of HUVECs in a dose-dependent manner. Moreover, induction of HO-1 by hemin suppressed TNF-alpha-induced apoptosis. However, the anti-apoptotic action of HO-1 was reversed by SnPP. The up-regulation of HO-1 by hemin treatment significantly prolonged the survival time of discordant cardiac xenograft, greatly reduced the swelling and apoptosis of myocardial cells, interstitial edema, lymphocyte infiltration, and thrombus formation in small vessels. Furthermore, HO-1 overexpression significantly attenuated the serum level of xenoantibody IgM, tissue deposition of IgM and complement 3 (C(3)) in endangium. Finally, HO-1 mitigated CD40L transcription in the xenograft and recipient spleen. These results indicate that the up-regulation of HO-1 can improve the survival of discordant cardiac xenograft by inhibiting apoptosis and alleviating inflammation and thrombosis.

A natural sweetener, Momordica grosvenori, attenuates the imbalance of cellular immune functions in alloxan-induced diabetic mice

Momordica grosvenori (MG), a traditional medicinal herb in China used as a substitute sugar for obese and diabetic patients, exhibited an enhancement of immunity. Heme oxygenase-1 (HO-1) is among the acute phase proteins that play an important role in the inflammatory process and have antiinflammatory activities with their antioxidant properties. The hypothesis that MG could modulate an imbalance of the cellular immune system and prevent the progression of diabetes mellitus, via induction of HO-1 protein expression was investigated. Diabetes was induced in male Balb/c mice by intraperitoneal injection of alloxan (200 mg/kg). The mice were randomly assigned to non-diabetic and diabetic groups, and further subdivided according to their treatments: control (distilled water), low dose MG (150 mg/kg) and high dose MG (300 mg/kg), which were administered by gavage in 24 h cycles over a 30 day period. MG administration effectively regulated the immune imbalance in diabetic mice, principally by upregulating the CD4(+) T lymphocyte subsets, and remodeling the intracellular cytokine profiles (reducing the expression of pro-inflammatory Th1 cytokines towards a beneficial Th2 pattern), ascribed to its induction and upregulation of HO-1. In conclusion, MG exhibited antidiabetic effects and may be used as a new natural drug for the treatment of diabetes.

HO-1 and VGEF gene expression in human arteries with advanced atherosclerosis

OBJECTIVES

Both heme oxygenase-1 (HO-1) and vascular endothelial growth factor (VEGF) have been shown to be involved in the progression of atherosclerosis. The relationship between HO-1 and VEGF gene expression and their proteins in endothelial cells from human atherosclerotic arterial specimens was investigated.

DESIGN AND METHODS

The study included seventeen human arterial specimens with early and six specimens with advanced atherosclerotic lesions. Ten specimens were obtained from healthy young adults undergoing arterial reconstruction for trauma and were considered as non-atherosclerotic control. HO-1 and VEGF expressions as well as HO activity and VEGF protein content were measured in isolated endothelial cells (ECs).

RESULTS

HO-1 expression and activity (5.3+/-2.1 nmol bilirubin/mg protein/h) were only present in ECs from advanced atherosclerotic lesions. VEGF expression was more strongly expressed in ECs from advanced lesion compared with early lesions and was absent in healthy arteries. VEGF protein (1.35+/-0.69 ng/mg) was only detected in advanced lesions. A significant positive correlation (r=0.9, p<0.01) exists between HO activity and VEGF protein content in ECs of advanced lesions.

CONCLUSIONS

This study demonstrated that HO-1 expression and activity in ECs are present only in advanced atherosclerosis whereas, VEGF expression is present in early as well as in advanced atherosclerosis and the degree of its expression increases with severity of atherosclerosis. This study suggests an association between HO activity and VEGF protein in human ECs from advanced atherosclerotic lesions.

Functional genomics and the development of pathogenesis-targeted therapies for Kaposi's sarcoma

Kaposi's sarcoma (KS) is a multifocal angioproliferative disorder affecting the skin, mucosa and viscera of individuals infected with human herpesvirus-8 (HHV-8; also Kaposi's sarcoma-associated herpesvirus [KSHV]). KS is the most common neoplasm in AIDS patients; the clinical outcome of AIDS-KS is significantly improved by highly active antiretroviral therapy (HAART). However, in Africa, where the severest manifestations of KS occur, there is limited access to these and other effective but expensive drugs. Here we present a review of current efforts to identify novel therapeutic targets for the treatment of KS using functional genomics, with recommendations regarding the development of economically feasible treatments for use in Africa.

Effect of Doxazosin on Oxidative Stress-Related Proteins in Benign Prostatic Hyperplasia

BACKGROUND AND OBJECTIVES

Oxidative stress can induce cell mutations or proliferation which then can progress to carcinogenesis or remodeling. The same oxidative stress-mediated mechanism could participate in prostate cell proliferation and remodeling present in benign prostatic hyperplasia (BPH). Doxazosin induces prostate epithelial and stromal cell apoptosis through production of transforming growth factor-beta (TGF-beta), but cellular mechanisms are not completely clarified. In 10 prostate samples from BPH untreated patients who underwent TUR, we have assessed the gene and protein expression of: p22(phox) (subunit of NAD(P)H oxidase essential for O(2)(-) production); heme oxygenase-1 (HO-1) (induced by oxidative stress and antiapoptotic); TGF-beta (inhibitor of prostatic epithelial and stromal cell growth); the in vitro effect of doxazosin on expression of these markers.

METHODS

RT-PCR and Western blot with specific primers and antibodies. p22(phox), HO-1 and TGF-beta were quantified by the ratio between their PCR and Western blot products and GAPDH.

RESULTS

Doxazosin significantly reduced p22(phox) gene and protein expression (0.61 +/- 0.04 vs. 0.36 +/- 0.04 d.u., p < 0.0002; 0.85 +/- 0.03 vs. 0.47 +/- 0.03, p < 0.0001, respectively). Doxazosin concentration dependently reduced HO-1 gene and protein expression (0.57 +/- 0.07 vs. 0.49 +/- 0.06 d.u. (1 microM) p < 0.04, vs. 0.22 +/- 0.08 (10 microM) p < 0.0001; 0.78 +/- 0.04 vs. 0.44 +/- 0.1 (10 microM) p < 0.003 respectively) and increased TGF-beta protein expression (0.58 +/- 0.05 vs. 0.74 +/- 0.16 (1 microM) n.s. vs. 0.81 +/- 0.07 (10 microM) p < 0.01).

CONCLUSIONS

Induction of oxidative stress-related proteins seems to be involved in the prostate cell proliferation and remodeling present in BPH. Doxazosin may reduce oxidative stress through reduction of p22(phox). Surprisingly, HO-1, which is induced and protected by oxidative stress, is also reduced by doxazosin. HO-1 is a potent antiapoptotic factor and downregulator of TGF-beta. From the results of this preliminary study it could be proposed that the proapoptotic effect of doxazosin could be mediated, at least in part, through the contemporary inhibition of HO-1.

A molecular cascade showing nitric oxide-heme oxygenase-1-vascular endothelial growth factor-interleukin-8 sequence in human endothelial cells

Heme oxygenase (HO)-1 has been shown to be an important biological target of nitric oxide (NO). NO can induce HO-1 expression and IL-8 production, particularly, in endothelial cells. Interestingly, HO-1 tends to induce the production of vascular endothelial growth factor (VEGF) that is involved in endothelial IL-8 syntheses. Whether HO-1 expression by NO may provide a link with IL-8 or VEGF synthesis was investigated in human umbilical vein endothelial cells (HUVECs). The NO donor S-nitroso-N-acetyl-penicillamine (SNAP) dose-dependently increased IL-8 and VEGF productions and HO-1 expression in HUVECs. Transfection with either HO-1 small interfering RNA or HO-1 antisense oligodeoxynucleotide abrogated the ability of SNAP to induce HO-1 expression and IL-8 and VEGF productions. Both pharmacological induction and gene transfer of HO-1 directly induced IL-8 and VEGF productions. Anti-VEGF neutralizing antibody blocked SNAP-mediated IL-8 production and VEGF itself induced IL-8 production, whereas anti-IL-8 neutralizing antibody had no effect on VEGF production in SNAP-treated HUVECs. Neither anti-VEGF nor anti-IL-8 antibodies influenced SNAP-induced HO-1 expression. Moreover, neither VEGF nor IL-8 showed an additive effect on SNAP-induced HO-1 expression. HO-1 transfection had no significant effect on productions of other CXC chemokines, such as growth-related oncogen-alpha and epithelial neutrophil activation peptide-78. Taken together, these results provide a molecular cascade showing NO-HO-1-VEGF-IL-8 sequence in human endothelial cells.

Heme oxygenase 1 expression induced by IL-10 requires STAT-3 and phosphoinositol-3 kinase and is inhibited by lipopolysaccharide

Heme-oxygenase 1 (HO-1) is a stress-response protein with anti-inflammatory activity. This study has examined the regulation of HO-1 expression by the anti-inflammatory factor, interleukin (IL)-10 and whether HO-1 could account for the function of the cytokine. IL-10-induced expression of HO-1 required the activation of signal transducer and activator of transcription (STAT)-3 but not p38 mitogen-activated protein kinase. However, expression of HO-1 also required the activation of the phosphatidylinositol-3 kinase pathway, a signaling mechanism not required for the anti-inflammatory activity of IL-10. Moreover, induction of HO-1 expression was not restricted to IL-10, as IL-6, a cytokine known to activate STAT-3, could also induce the protein. In human macrophages, lipopolysaccharide inhibited HO-1 expression induced by IL-10. Also, inhibition of HO-1 activity by the specific inhibitor zinc-II-protoporphyrin-IX had no effect on the anti-inflammatory function of IL-10. In summary, although IL-10 does regulate HO-1 expression, it does not appear to play a significant role in the anti-inflammatory activity of the cytokine.

Kaposi sarcoma-associated herpesvirus (KSHV) induces heme oxygenase-1 expression and activity in KSHV-infected endothelial cells

Kaposi sarcoma (KS) is the most common AIDS-associated malignancy and is characterized by angiogenesis and the presence of spindle cells. Kaposi sarcoma-associated herpesvirus (KSHV) is consistently associated with all clinical forms of KS, and in vitro infection of dermal microvascular endothelial cells (DMVECs) with KSHV recapitulates many of the features of KS, including transformation, spindle cell proliferation, and angiogenesis. To study the molecular mechanisms of KSHV pathogenesis, we compared the protein expression profiles of KSHV-infected and uninfected DMVECs. This comparison revealed that heme oxygenase-1 (HO-1), the inducible enzyme responsible for the rate-limiting step in heme catabolism, was up-regulated in infected endothelial cells. Recent evidence suggests that the products of heme catabolism have important roles in endothelial cell biology, including apoptosis and angiogenesis. Here we show that HO-1 mRNA and protein are up-regulated in KSHV-infected cultures. Comparison of oral and cutaneous AIDS-KS tissues with normal tissues revealed that HO-1 mRNA and protein were also up-regulated in vivo. Increased HO-1 enzymatic activity in vitro enhanced proliferation of KSHV-infected DMVECs in the presence of free heme. Treatment with the HO-1 inhibitor chromium mesoporphyrin IX abolished heme-induced proliferation. These data suggest that HO-1 is a potential therapeutic target for KS that warrants further study.

Prolactin increases HO-1 expression and induces VEGF production in human macrophages

The pituitary hormone prolactin (PRL) is a multifunctional polypeptide which exerts a role on cell proliferation and may also contribute to cell differentiation. PRL is also produced by immune cells and is regarded as a key component of the neuroendocrine-immune loop and as a local regulator of macrophage response. The involvement of PRL in regulating monocyte/macrophage functions is suggested by the presence of PRL receptors in these cells. It has been shown that PRL possess both angiogenic and antiangiogenic effects. Recently, we revealed that augmentation of HO-1 activity enhances PRL-mediated angiogenesis in human endothelial cells. Since macrophages are key participants in angiogenesis our objective was to investigate the effect of PRL also in human macrophages. In vitro treatment of macrophages with PRL was found to increase both heme oxygenase-1 (HO-1) expression and protein synthesis in a time and dose dependent manner as quantified respectively by reverse-transcriptase real-time polymerase chain reaction and Western blot analysis. PRL-treated macrophages also showed an enhanced release of vascular endothelial growth factor (VEGF) as demonstrated by ELISA assay. Furthermore, to determine whether PRL-induced HO-1 activity was required for VEGF production by macrophages, the effect of PRL on the induction of VEGF was studied in the presence of an inducer stannic chloride (SnCl(2)) and of an inhibitor stannic mesoporphyrin (SnMP) of HO activity. Our observations suggest that PRL may regulate monocyte activation and influences not only immune function but also angiogenesis.