Heme oxygenase (HO)-1 is an inducible enzyme that catalyzes the first and rate-limiting step in the oxidative degradation of free heme into ferrous iron, carbon monoxide (CO), and biliverdin (BV), the latter being subsequently converted into bilirubin (BR). HO-1, once expressed during inflammation, forms high concentrations of its enzymatic by-products that can influence various biological events, and this expression is proven to be associated with the resolution of inflammation. The degradation of heme by HO-1 itself, the signaling actions of CO, the antioxidant properties of BV/BR, and the sequestration of ferrous iron by ferritin all concertedly contribute to the anti-inflammatory effects of HO-1. This review focuses on the anti-inflammatory mechanisms of HO-1 actions and its roles in inflammatory diseases.
Bilirubin ; Biliverdine ; Carbon Monoxide ; Ferritins ; Heme ; Heme Oxygenase (Decyclizing) ; Heme Oxygenase-1 ; Inflammation ; Iron

Heme oxygenase (HO)-1 is an inducible enzyme that catalyzes the first and rate-limiting step in the oxidative degradation of free heme into ferrous iron, carbon monoxide (CO), and biliverdin (BV), the latter being subsequently converted into bilirubin (BR). HO-1, once expressed during inflammation, forms high concentrations of its enzymatic by-products that can influence various biological events, and this expression is proven to be associated with the resolution of inflammation. The degradation of heme by HO-1 itself, the signaling actions of CO, the antioxidant properties of BV/BR, and the sequestration of ferrous iron by ferritin all concertedly contribute to the anti-inflammatory effects of HO-1. This review focuses on the anti-inflammatory mechanisms of HO-1 actions and its roles in inflammatory diseases.
Bilirubin ; Biliverdine ; Carbon Monoxide ; Ferritins ; Heme ; Heme Oxygenase (Decyclizing) ; Heme Oxygenase-1 ; Inflammation ; Iron

BACKGROUND: Heme oxygenase-1 (HO-1) is an inducible enzyme that catalyzes the oxidative degradation of heme to form biliverdin, carbon monoxide (CO), and free iron. The current evidence has indicated a critical role of HO-1 in cytoprotection and also in other, more diverse biological functions. It is known that the high expression of HO-1 occurs in various tumors, and that HO-1 has an important role in rapid tumor growth because of its antioxidative and antiapoptotic effects. Therefore, the role of HO-1 was analyzed in human lung cancer cell lines, and especially in the A549 cell line. MATERIAL AND METHODS: Human lung cancer cell lines, i.e., A549, NCI-H23, NCI-H157 and NCI-H460, were used for this study. The expression of HO-1 in the untreated state was defined by Western blotting. ZnPP, which is the specific HO inhibitor we used, and the viability of cells were tested for by conducting MTT assaysy. The HO enzymatic activity, as determined via the bilirubin level, was also indirectly measured. Moreover, the generation of intracellular hydrogen peroxide (H2O2) was monitored fluorimetrically with using a scopoletin-horse radish peroxidase (HRP) assay and 2',7'-dichlorofluorescein diacetate (DCFH-DA). We have also transfected small HO-1 interfering RNA (siRNA) into A549 cells, and the apoptotic effects were evaluated by flow cytometric analysis and Western blotting. RESULTS: The A549 cells had a greater expression of HO-1 than the other cell lines, whereas ZnPP significantly decreased the viability of the A549 cells more than the viability of the other lung cancer cells in a dose-dependant fashion. Consistent with the viability, the HO enzymatic activity also was decreased. Moreover, intracellular H2O2 generation via ZnPP was induced in a dose-dependent manner. Apoptotic events were, then induced in the HO-1 siRNA transfected A549 cells. CONCLUSION: HO-1 provides new important insights into the possible molecular mechanism of the antitumor therapy in lung cancer.
Bilirubin ; Biliverdine ; Blotting, Western ; Carbon Monoxide ; Cell Line ; Cytoprotection ; Heme Oxygenase-1* ; Heme* ; Humans ; Hydrogen Peroxide ; Iron ; Lung Neoplasms* ; Lung* ; Peroxidase ; Raphanus ; RNA ; RNA, Small Interfering

Biliverdin (BV) has long been thought to be a cytotoxic metabolic waste product. It has also been demonstrated to have important cytoprotective functions during oxidative stress. The present study aimed to examine the cytoprotective effect of BV on NRK-52E cells, a proximal tubular cell line derived from rat kidney. Cells were treated with 50 µmol/L cisplatin for 24 h (cisplatin group) or pre-treated with BV for 30 min, then with 50 µmol/L cisplatin for 24 h (cisplatin+BV group). Those given no treatment served as a control. Cell apoptosis was evaluated by flow cytometry and cell viability by Cell Counting Kit-8 (CCK-8). The protein expressions of cleaved caspase3, Bax and Bcl-2 were assessed by Western blotting. Reactive oxygen species (ROS) levels were measured using carboxydichlorodihydrofluorescein diacetate (H2DCF). The results showed that cisplatin induced the apoptosis of NRK-52E cells, decreased cell viability, and increased the formation of ROS by upregulating the expression of cleaved caspase3 and Bax and decreasing Bcl-2 protein expression. These effects could be significantly reversed by pretreatment with BV. It was concluded that BV can protect against cisplatin-induced cell apoptosis through the anti-oxidative effects.
Animals ; Antioxidants ; pharmacology ; Apoptosis ; Biliverdine ; pharmacology ; Cell Line ; Cisplatin ; toxicity ; Epithelial Cells ; drug effects ; metabolism ; Kidney Tubules ; cytology ; Rats ; Reactive Oxygen Species ; metabolism

BACKGROUND: Reperfusion in ischemia is believed to generate cytotoxic oxidative stress, which mediates reperfusion injury. These stress conditions can initiate lipid peroxidation and damage to proteins, as well as promote DNA strand breaks. As biliverdin and bilirubin produced by heme oxygenase isoform 1 (HO-1) have antioxidant properties, the production of both antioxidants by HO-1 may help increase the resistance of the ischemic brain to oxidative stress. In the present study, the survival effect of HO-1 was confirmed using hemin. METHODS: To confirm the roles of HO-1, carbon monoxide, and cyclic guanosine monophosphate further in the antioxidant effect of HO-1 and bilirubin, cells were treated with cycloheximide, desferoxamine, and zinc deuteroporphyrin IX 2,4 bis glycol, respectively. RESULTS: HO-1 itself acted as an antioxidant. Furthermore, iron, rather than carbon monoxide, was involved in the HO-1-mediated survival effect. HO-1 activity was also important in providing bilirubin as an antioxidant. CONCLUSION: Our results suggested that HO-1 helped to increase the resistance of the ischemic brain to oxidative stress.
Animals ; Antioxidants ; Bilirubin ; Biliverdine ; Brain* ; Carbon Monoxide ; Cycloheximide ; DNA ; Guanosine Monophosphate ; Heme ; Heme Oxygenase (Decyclizing) ; Hemin ; Iron ; Ischemia ; Lipid Peroxidation ; Microvessels* ; Oxidative Stress ; Oxygen* ; Oxygenases ; Rats* ; Reperfusion ; Reperfusion Injury ; Zinc

Oxidative stress has been paid increasing attention to as an important causative factor for diabetic vascular complications. Among possible various sources, accumulating evidence has indicated that NAD(P)H oxidase may be the most important source for reactive oxygen species production in diabetic vascular tissues. The mechanisms underlying activation and up-regulation of NAD(P)H oxidase has been supposed to be mediated by high glucose-induced protein kinase C (PKC) activation. In this review article, activation of local renin-angiotensin II system induced by chymase activation is also shown to amplify such a PKC-dependent activation of NAD(P)H oxidase. Additionally, human evidence showing the beneficial effect of antioxidants on diabetic vascular complications. Bilirubin has been recognized as a strong endogenous antioxidant. Here markedly lower prevalence of vascular complications is shown in diabetic patients with Gilbert syndrome, a congenital hyperbilirubinemia, as well as reduced markers of oxidative stress and inflammation. Lastly, statin, angiotensin II receptor blocker, chymase inhibitor, bilirubin and biliverdin, PKC beta isoform inhibitor, and glucagon-like peptide-1 analog, are shown to serve as antioxidants and have some beneficial effect on diabetic vascular complications, via inhibiting PKC-NAD(P)H oxidase activation, supporting the notion that this mechanism may be an effective therapeutic target for preventing diabetic vascular complications.
Angiotensin II ; Antioxidants ; Bilirubin ; Biliverdine ; Chymases ; Diabetic Angiopathies ; Gilbert Disease ; Glucagon-Like Peptide 1 ; Humans ; Hydroxymethylglutaryl-CoA Reductase Inhibitors ; Hyperbilirubinemia ; Inflammation ; NADPH Oxidase ; Oxidative Stress ; Oxidoreductases ; Prevalence ; Protein Kinase C ; Reactive Oxygen Species ; Receptors, Angiotensin ; Up-Regulation

Heme oxygenage-1 (HO-1) is the rate-limiting enzyme in heme catabolism, which leads to the generation of carbon monoxide (CO), biliverdin, and free iron. HO-1 has been known to show strong immunosuppressive properties although its mechanisms are not completely understood. In this study, it was therefore investigated anti-inflammatory properties of HO-1 in HT-29 cell, human colonic epithelial cell line. CoPPIX, HO-1 inducer, induced HO-1 expression without NF-kappa B activation and significantly blocked the I kappa B-alpha degradation by TNF-alpha in HT-29. Inhibition of HO-1 activity by ZnPPIX reversed the suppressive effects of CoPPIX on I kappa B-alpha degradation by TNF-alpha. Calcium chelating agent BAPTA/AM and calcium channel blockers, Verapamil and Flunarizine suppressed I kappa B-alpha degradation by TNF-alpha in HT-29 cells like CoPPIX while calcium ionophore A23187 also dose-dependently reversed the suppressive effects of CoPPIX on I kappa B-alpha degradation by TNF-alpha like a ZnPPIX. Interestingly, treatment of ZnPPIX increased basal intracellular calcium in HT-29 cells. Collectively, these results suggest that HO-1 exerts anti-inflammatory effects by down-regulation of NF-kappa B activity via suppression of intracellular calcium during pathogenesis of colitis in colonic epithelium.
Biliverdine ; Calcimycin ; Calcium Channel Blockers ; Calcium* ; Carbon Monoxide ; Colitis ; Colon* ; Down-Regulation ; Epithelial Cells* ; Epithelium ; Flunarizine ; Heme ; HT29 Cells ; Humans* ; Iron ; Metabolism ; NF-kappa B* ; Tumor Necrosis Factor-alpha ; Verapamil

PURPOSE: Heme oxygenase-1 (HO-1), an inducible heat shock protein, catalyzes the heme to iron, biliverdin and carbon monoxide. It also has an inhibitory effect on necrosis and inflammation. Cobalt (III)-protoporphyrin IX (CoPP) is known to be a HO-1 inducer. Our intension was to find whether CoPP has an anti-inflammatory effect through the induction of HO-1 in rats with epididymitis. MATERIALS AND METHODS: Thirty two Sprague-Dawley male rats (age: 8-12 weeks, weight: 200-250gm) were selected for the experiments. Anesthesia was performed with an intraperitoneal injection of ketamine hydrochloride (140mg/kg). Four rats were taken and used as a control group. Epididymitis was induced in 28 rats by an injection of E. coli (1 x 10(5)/ml) to the epididymis. In the first step, groups of 4 rats were sacrificed serially after 4, 12, 48, and 72 hours for Hematoxylin & Eosin (H&E) staining and Western blot for inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2. In the second step, groups of 4 rats were injected with either dimethyl sulphoxide (DMSO) 7 microliter, DMSO 7 microliter with 50mg/ml CoPP or DMSO 7 microliter with 100mg/ml CoPP. They were then sacrificed 72 hours later for H&E staining and Western blot for iNOS and COX-2. RESULTS: In the first step, increased inflammation was evident H&E staining over time. Western blots, iNOS expression was detected after 48 hours and COX-2 was after 12 hours. In the second step, decreased inflammation was evident H&E staining, and the expressions of iNOS and COX-2 were suppressed in the CoPP treated group. CONCLUSIONS: CoPP can reduce the inflammation of epididymis in rats, and the mechanism may be related with HO-1.
Anesthesia ; Animals ; Biliverdine ; Blotting, Western ; Carbon Monoxide ; Cobalt ; Dimethyl Sulfoxide ; Eosine Yellowish-(YS) ; Epididymis ; Epididymitis* ; Escherichia coli Infections* ; Escherichia coli* ; Escherichia* ; Heat-Shock Proteins ; Hematoxylin ; Heme ; Heme Oxygenase (Decyclizing) ; Heme Oxygenase-1 ; Humans ; Inflammation ; Injections, Intraperitoneal ; Iron ; Ketamine ; Male ; Necrosis ; Nitric Oxide Synthase Type II ; Prostaglandin-Endoperoxide Synthases ; Rats* ; Rats, Sprague-Dawley