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

OBJECTIVETo investigate the location of heme oxygenase (HO) enzyme in the human testis, and explore the correlation of the expression of HO enzyme with azoospermia by analyzing its different expression levels in the testes of nonobstructive azoospermia, obstructive azoospermia and normal men.

METHODSWe detected the location of the cells expressing HO enzyme in the human testis tissue using immunohistochemistry, determined the mRNA and protein expression levels of HO-1 and HO-2 in the testes of azoospermia patients and normal healthy men by RT-fluorescence quantitative PCR (RT-FQ-PCR) and Western blot, and explored the correlation of HO expressions with the pathogenesis of azoospermia.

RESULTSHO-1 enzyme was expressed mainly in the Sertoli cells and HO-2 enzyme chiefly in the germ cells of the testis tissue. RT-FQ-PCR showed that the expression of HO-1 in the testis tissue was significantly lower in the nonobstructive azoospermia than in the normal and obstructive azoospermia groups (P < 0.05), with no significant difference between the latter two. Western blot revealed no obvious difference between the expression level of HO-1 protein and that of HO-1 mRNA. There were no differences in the expression level of HO-2 protein among the three groups.

CONCLUSIONThe expression level of HO enzyme is significantly decreased in the testis tissue of nonobstructive azoospermia patients, and the expression of HO-1 protein is consistent with that of HO-1 mRNA. As HO-1 protects the testis tissue against various stress injuries through its antioxidant, anti-inflammatory and anti-apoptotic effects, its decreased expression level may be correlated with spermatogenic dysfunction, and therefore considered as a possible mechanism of nonobstructive azoospermia.

Azoospermia ; enzymology ; metabolism ; Case-Control Studies ; Heme Oxygenase (Decyclizing) ; metabolism ; Heme Oxygenase-1 ; metabolism ; Humans ; Male ; Spermatogenesis ; Testis ; enzymology ; metabolism

PURPOSE: The inducible isoform of heme oxygenase(HO), HO-1, responds to hypoxia. HO-1 regulates vascular smooth muscle tone through carbon monoxide production. To investigate the possible role of HO-1 in low-flow priapism, we examined the expression and activity of HO-1 in artificially induced veno-occlusive priapism in rat. MATERIALS AND METHODS: Fourteen male Sprague Dawley rats were divided into 2 groups with 7 rats each. In the first group, low-flow priapism was induced using a vacuum-constriction device and a constriction rubber band; in the second group, low-flow priapism was induced using papaverine. We measured the expression level and activity of HO-1 in penile tissues after time periods of 0(control), 2, 3, 4, 8, 12, 24, and 48 hours. At the same time, the expression levels of i-NOS, e-NOS, and beta-actin(control) in penile tissues were also measured. RESULTS: In both groups, expression of HO-1 and HO-1 enzyme activities in penile tissue significantly increased in a time dependent fashion(p<0.01). However, there was no difference in the expression of i-NOS and e-NOS in both groups at any time period. CONCLUSIONS: HO-1 was induced over time in rats with artificially induced veno-occlusive priapism. Induction of HO-1 may play a protective role against hypoxic injury, but may also play an important role in the vicious cycle observed for low flow priapism. Increasing induction of HO-1 against hypoxic injury in a prolonged erectile state promotes sustained dilatation of corporal smooth muscle, and this may aggravate low-flow priapism.
Animals ; Anoxia ; Carbon Monoxide ; Constriction ; Dilatation ; Heme Oxygenase (Decyclizing) ; Heme Oxygenase-1* ; Heme* ; Humans ; Male ; Muscle, Smooth ; Muscle, Smooth, Vascular ; Papaverine ; Priapism* ; Rats* ; Rats, Sprague-Dawley ; Rubber

To investigate the expression of the HO-1 gene in PC12 cells in hypoxic environment and gain further insight to the role of HO-1 in cerebral ischemia, PC12 cells were exposed to hypoxia environment (95% N2, 5% CO2) for 0.5 h, 1 h, 4 h, 8 h, 12 h, 24 h respectively. The level of HO-1 mRNA was examined by reverse transcriptase polymerase chain reaction (RT-PCR); the volume of COHb in the media were measured spectrophotometrically and the cGMP concentration of PC12 cell extracts was determined by radioimmunoassay. We found that after exposure to hypoxia for 1 h, 4 h, 8 h, 12 h, 24 h, HO-1 mRNA increased by 3%, 4%, 17%, 31% 36% as compared with that in control group respectively (P < 0.01 or P < 0.05); the COHb increased by 12%, 29%, 59%, 88%, 94% as compared with that in control group respectively (P < 0.01 or P < 0.05), and the cGMP concentration were 2.2, 3.4, 5.2, 8.1, 10.9-fold as that of the control group (P < 0.01). We are led to conclude that hypoxia induced the expression of HO-1 gene, the production of endogenous CO, and the concentration of cGMP was elevated as well.
Carbon Monoxide/metabolism ; Cell Hypoxia ; Cyclic GMP/metabolism ; Heme Oxygenase (Decyclizing)/biosynthesis ; Heme Oxygenase (Decyclizing)/*genetics ; Heme Oxygenase-1 ; PC12 Cells ; RNA, Messenger/biosynthesis ; RNA, Messenger/genetics ; Up-Regulation

To investigate the expression of the HO-1 gene in PC12 cells in hypoxic environment and gain further insight to the role of HO-1 in cerebral ischemia, PC12 cells were exposed to hypoxia environment (95% N2, 5% CO2) for 0.5 h, 1 h, 4 h, 8 h, 12 h, 24 h respectively. The level of HO-1 mRNA was examined by reverse transcriptase polymerase chain reaction (RT-PCR); the volume of COHb in the media were measured spectrophotometrically and the cGMP concentration of PC12 cell extracts was determined by radioimmunoassay. We found that after exposure to hypoxia for 1 h, 4 h, 8 h, 12 h, 24 h, HO-1 mRNA increased by 3%, 4%, 17%, 31% 36% as compared with that in control group respectively (P < 0.01 or P < 0.05); the COHb increased by 12%, 29%, 59%, 88%, 94% as compared with that in control group respectively (P < 0.01 or P < 0.05), and the cGMP concentration were 2.2, 3.4, 5.2, 8.1, 10.9-fold as that of the control group (P < 0.01). We are led to conclude that hypoxia induced the expression of HO-1 gene, the production of endogenous CO, and the concentration of cGMP was elevated as well.
Animals ; Carbon Monoxide ; metabolism ; Cell Hypoxia ; Cyclic GMP ; metabolism ; Heme Oxygenase (Decyclizing) ; biosynthesis ; genetics ; Heme Oxygenase-1 ; PC12 Cells ; RNA, Messenger ; biosynthesis ; genetics ; Rats ; Up-Regulation

OBJECTIVESTo observe the function of heme oxygenase (HO) in the lung damage in hepatic cirrhosis rats.

METHODSLiver cirrhosis model rats were made by CCl4. Lung samples taken from normal and cirrhotic rats were examined for HO-1 and HO-2 protein and expression distribution with immunohistochemical staining and western blot.

RESULTSLiver cirrhosis model rats were successfully constructed. There was a notable increase of HO-1 staining (0.062+/-0.021 vs 0.185+/-0.044, t=11.24, P<0.01) and protein expression (0 vs 5294.92+/-46.02, t=11.45, P<0.01) in both vascular and bronchial smooth muscle cells and endothelium in cirrhotic rats, however, no statistical difference of HO-2 between cirrhotic and normal rats was observed.

CONCLUSIONThe HO-CO pathway is probably involved in the pathogenesis of lung damage in hepatic cirrhosis rats.

Animals ; Carbon Tetrachloride Poisoning ; Heme Oxygenase (Decyclizing) ; analysis ; biosynthesis ; Heme Oxygenase-1 ; Liver Cirrhosis, Experimental ; enzymology ; Lung ; enzymology ; Male ; Nitric Oxide ; metabolism ; Rats ; Rats, Sprague-Dawley

PURPOSE: Carbon monoxide (CO), a product of heme catalysis by heme oxygenase (HO-1, HO-2, HO-3), induces cytoprotection against ischemia/reperfusion (I/R) injury in a variety of organs such as the heart, lungs, kidneys, and liver. I examined whether CO would prevent chronic allograft nephropathy (CAN) associated with renal transplantation in rats. METHODS: Kidneys from male Fisher rats were perfused and harvested for transplantation. Lewis rats were used as recipients. After reperfusion of the implanted kidney, the recipient's remaining kidney was removed promptly. Recipients were then immediately treated with the indicated regimen of CO in a Plexiglas exposure chamber. At 90 days after transplantation, the animals were sacrificed for graft histopathology, serum creatinine, and blood urea nitrogen (BUN) as markers of kidney function. RESULTS: CAN in rats was achieved using a model of Fisher-to-Lewis transplants and evaluating kidney function over the 90 days following transplantation. CO administered at 100 ppm for 1 hr/day for 7 days prevented CAN at 90 days post-transplant. CO also decreased histopathological alterations, including leukocyte infiltration and cell death. CONCLUSION: These data expand our understanding of the protective effects of low-dose CO inhalation in preventing the development of chronic fibro-inflammatory changes associated with chronic allograft nephropathy and allow us to devise methods for improving long-term renal allograft function.
Animals ; Blood Urea Nitrogen ; Carbon ; Carbon Monoxide ; Catalysis ; Creatinine ; Cytoprotection ; Heart ; Heme ; Heme Oxygenase (Decyclizing) ; Heme Oxygenase-1 ; Humans ; Inhalation ; Kidney ; Kidney Transplantation ; Leukocytes ; Liver ; Lung ; Male ; Polymethyl Methacrylate ; Rats ; Reperfusion ; Transplantation, Homologous ; Transplants

Spontaneous hypertensive rats (SHR) are an established model of genetic hypertension. Vascular smooth muscle cells (VSMC) from SHR proliferate faster than those of control rats (Wistar-Kyoto rats; WKY). We tested the hypothesis that induction of heme oxygenase (HO)-1 induced by aprotinin inhibits VSMC proliferation through cell cycle arrest in hypertensive rats. Aprotinin treatment inhibited VSMC proliferation in SHR more than in normotensive rats. These inhibitory effects were associated with cell cycle arrest in the G1 phase. Tin protoporphyrin IX (SnPPIX) reversed the anti-proliferative effect of aprotinin in VSMC from SHR. The level of cyclin D was higher in VSMC of SHR than those of WKY. Aprotinin treatment downregulated the cell cycle regulator, cyclin D, but upregulated the cyclin-dependent kinase inhibitor, p21, in VSMC of SHR. Aprotinin induced HO-1 in VSMC of SHR, but not in those of control rats. Furthermore, aprotinin-induced HO-1 inhibited VSMC proliferation of SHR. Consistently, VSMC proliferation in SHR was significantly inhibited by transfection with the HO-1 gene. These results indicate that induction of HO-1 by aprotinin inhibits VSMC proliferation through cell cycle arrest in hypertensive rats.
Animals ; Aprotinin ; Cell Cycle ; Cell Cycle Checkpoints ; Cell Proliferation ; Cyclin D ; G1 Phase ; Heme ; Heme Oxygenase (Decyclizing) ; Heme Oxygenase-1 ; Hypertension ; Metalloporphyrins ; Muscle, Smooth, Vascular ; Phosphotransferases ; Protoporphyrins ; Rats ; Tin ; Transfection

Chinese herb medicines have traditionally been used to treat or alleviate the symptom of various diseases. The rationale for use of certain herbs to certain disorder is now getting unveiled by modern technology. In the present study, we investigated whether herb mix extract (HMX), which is alleged to be useful for gastric ulcer, protects stomach from oxidative stress. Rats were allowed to normal diet with and without HMX (1, 5, 10 mg/kg) for 30 days. To induce gastric ulcer, ethanol (75%, 1.5 ml) or acidified aspirin (100 mg/kg in 0.2 N HCl) was administered by oral route in 24 h-fasted rats and examined the gastric ulceration (bleeding) by measuring the size 1 h after the treatment. Results indicated the area of gastric bleeding was significantly less in HMX fed rats than in normal diet fed ones, and it was dependent on the duration and amount of HMX. To investigate the underlying mechanism by which HMX protects stomach from oxidative stress, expression of enzymes like heme oxygenase (HO), cyclooxygenase (COX), and inducible nitric oxide (iNOS) were investigated in MKN-74 cells, where aspirin or H. pylori was introduced. The results were compared with RAW 264.7 cells to check if there's cell specificities exist. The expression of HO-1 but not COX-2, iNOS was significantly increased by HMX. Furthermore, HO-1 inhibitor, SnPP IX reduced the HO-1 activity and reversed the survival rate in HMX-treated MKN-74 cells. There's no difference between RAW 264.7 cells and MKN-74 cells. We, thus, concluded that HMX is beneficial for protection from oxidative injury, and induction of HO-1 by HMX in gastric cells is, at least, responsible for protection from oxidative stress such as ethanol, aspirin and possibly H. pylori infection.
Animals ; Asian Continental Ancestry Group ; Aspirin* ; Cell Survival* ; Diet ; Ethanol* ; Heme Oxygenase (Decyclizing) ; Heme Oxygenase-1* ; Heme* ; Hemorrhage* ; Humans ; Nitric Oxide ; Oxidative Stress ; Prostaglandin-Endoperoxide Synthases ; Rats* ; Reactive Oxygen Species ; Stomach Ulcer ; Stomach* ; Survival Rate