Induction of heme oxygenase 1 in radiation nephropathy: role of angiotensin II

Fluid shear stress regulates placental growth factor expression via heme oxygenase 1 and iron

Increased fluid shear stress (FSS) is a key initiating stimulus for arteriogenesis, the outward remodeling of collateral arterioles in response to upstream occlusion. Placental growth factor (PLGF) is an important arteriogenic mediator. We previously showed that elevated FSS increases PLGF in a reactive oxygen species (ROS)-dependent fashion both in vitro and ex vivo. Heme oxygenase 1 (HO-1) is a cytoprotective enzyme that is upregulated by stress and has arteriogenic effects. In the current study, we used isolated murine mesentery arterioles and co-cultures of human coronary artery endothelial cells (EC) and smooth muscle cells (SMC) to test the hypothesis that HO-1 mediates the effects of FSS on PLGF. HO-1 mRNA was increased by conditions of increased flow and shear stress in both co-cultures and vessels. Both inhibition of HO-1 with zinc protoporphyrin and HO-1 knockdown abolished the effect of FSS on PLGF. Conversely, induction of HO-1 activity increased PLGF. To determine which HO-1 product upregulates PLGF, co-cultures were treated with a CO donor (CORM-A1), biliverdin, ferric ammonium citrate (FAC), or iron-nitrilotriacetic acid (iron-NTA). Of these FAC and iron-NTA induced an increase PLGF expression. This study demonstrates that FSS acts through iron to induce pro-arteriogenic PLGF, suggesting iron supplementation as a novel potential treatment for revascularization.

Targets for protection and mitigation of radiation injury

Protection of normal tissues against toxic effects of ionizing radiation is a critical issue in clinical and environmental radiobiology. Investigations in recent decades have suggested potential targets that are involved in the protection against radiation-induced damages to normal tissues and can be proposed for mitigation of radiation injury. Emerging evidences have been shown to be in contrast to an old dogma in radiation biology; a major amount of reactive oxygen species (ROS) production and cell toxicity occur during some hours to years after exposure to ionizing radiation. This can be attributed to upregulation of inflammatory and fibrosis mediators, epigenetic changes and disruption of the normal metabolism of oxygen. In the current review, we explain the cellular and molecular changes following exposure of normal tissues to ionizing radiation. Furthermore, we review potential targets that can be proposed for protection and mitigation of radiation toxicity.

Dose-Dependent Increase of Nrf2 Target Gene Expression in Mice Exposed to Ionizing Radiation

Nuclear factor-erythroid-2-related factor 2 transcription factor (Nrf2) is activated by reactive oxygen species (ROS) and binds to antioxidant response elements in the promoter regions of its target genes involved in redox regulation and antioxidative functions. In this study, we elucidated the relationship between radiation dose and the expression response of Nrf2 target genes involved in oxidative stress, such as heme oxygenase 1, ferritin heavy polypeptide 1 ( Fth1), NADPH dehydrogenase quinone 1, glutamate-cysteine ligase catalytic subunit, glutamate-cysteine ligase modifier subunit, glutathione reductase ( Gsr) and thioredoxin reductase 1 genes, in peripheral blood from X-ray irradiated mice. Whole-body radiation doses ranged from 0.5 to 3 Gy, and gene expressions were analyzed using reverse transcription quantitative polymerase chain reaction. A significant relationship was observed only for one gene: a statistically significant positive correlation between radiation dose and Fth1 mRNA expression was detected. However, Fth1 did not show any correlations with the biological damages induced by radiation tested in this study. Furthermore, while Gsr expression was significantly associated with spleen weight loss, splenic cell number reduction and bone marrow cell death apoptosis, no significant correlation was observed between Gsr expression and radiation dose. Together these results indicate that Nrf2 target gene expression is closely related to radiation dose and its level may reflect biological damages induced by ionizing radiation. These findings suggest the possibility for application of these target genes as a bio-dosimeter and/or damage marker in individuals exposed to ionizing radiation.

Effects of ionizing radiation on biological molecules--mechanisms of damage and emerging methods of detection

SIGNIFICANCE

The detrimental effects of ionizing radiation (IR) involve a highly orchestrated series of events that are amplified by endogenous signaling and culminating in oxidative damage to DNA, lipids, proteins, and many metabolites. Despite the global impact of IR, the molecular mechanisms underlying tissue damage reveal that many biomolecules are chemoselectively modified by IR.

RECENT ADVANCES

The development of high-throughput "omics" technologies for mapping DNA and protein modifications have revolutionized the study of IR effects on biological systems. Studies in cells, tissues, and biological fluids are used to identify molecular features or biomarkers of IR exposure and response and the molecular mechanisms that regulate their expression or synthesis.

CRITICAL ISSUES

In this review, chemical mechanisms are described for IR-induced modifications of biomolecules along with methods for their detection. Included with the detection methods are crucial experimental considerations and caveats for their use. Additional factors critical to the cellular response to radiation, including alterations in protein expression, metabolomics, and epigenetic factors, are also discussed.

FUTURE DIRECTIONS

Throughout the review, the synergy of combined "omics" technologies such as genomics and epigenomics, proteomics, and metabolomics is highlighted. These are anticipated to lead to new hypotheses to understand IR effects on biological systems and improve IR-based therapies.

Renal Inhibition of Heme Oxygenase-1 Increases Blood Pressure in Angiotensin II-Dependent Hypertension

The goal of this study was to test the hypothesis that renal medullary heme oxygenase (HO) acts as a buffer against Ang-II dependent hypertension. To test this hypothesis, renal medullary HO activity was blocked using QC-13, an imidazole-dioxolane HO-1 inhibitor, or SnMP, a classical porphyrin based HO inhibitor. HO inhibitors were infused via IRMI catheters throughout the study starting 3 days prior to implantation of an osmotic minipump which delivered Ang II or saline vehicle. MAP was increased by Ang II infusion and further increased by IRMI infusion of QC-13 or SnMP. MAP averaged 113 ± 3, 120 ± 7, 141 ± 2, 153 ± 2, and 154 ± 3 mmHg in vehicle, vehicle + IRMI QC-13, Ang II, Ang II + IRMI QC-13, and Ang II + IRMI SnMP treated mice, respectively (n = 6). Inhibition of renal medullary HO activity with QC-13 in Ang II infused mice was also associated with a significant increase in superoxide production as well as significant decreases in antioxidant enzymes catalase and MnSOD. These results demonstrate that renal inhibition of HO exacerbates Ang II dependent hypertension through a mechanism which is associated with increases in superoxide production and decreases in antioxidant enzymes.

Radiation treatment of acute inflammation in mice

PURPOSE

Low-dose radiotherapy (RT) has often been used effectively for the treatment of a variety of benign diseases, particularly those with acute inflammatory features. Here we report findings on radiation treatment of acute inflammation using a murine carrageenin air pouch model.

MATERIALS AND METHODS

Air pouches raised on the dorsal surface of mice were injected with lambda carrageenin and were irradiated 6 h later with doses ranging from 0-5 Gy. Treatment success was evaluated at various times thereafter by volume of exudate and number of inflammatory cells, and levels of inflammation-related cytokines tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1beta) and transforming growth factor beta-1 (TGFbeta-1), and expression of inducible nitric oxide synthase (iNOS), heme oxygenase-1 (HO-1), cyclooxygenase-2 (COX-2) and inducible heat shock protein 70 (HSP70) as determined by enzyme-linked immunosorbent assay (ELISA) and Western blotting, respectively.

RESULTS

Crude inflammatory parameters such as the amount of exudates and number of inflammatory cells remained largely unaffected by radiation or were even a slightly and transiently increased. However, the expression of iNOS was attenuated by radiation concomitant with an increase in the levels of HO-1 and HSP70. Cytokine levels varied with the radiation dose and the time point.

CONCLUSIONS

Ionizing radiation, even at low doses, functionally modulates inflammatory cells. Our findings indicate possible mechanisms as to how low-dose radiation may exert anti-inflammatory effects and provide the first evidence that heat shock proteins may be involved in this response.

Chronic oxidative stress as a mechanism for radiation nephropathy

Suppression of the renin-angiotensin system has proven efficacy for mitigation and treatment of radiation nephropathy, and it has been hypothesized that this efficacy is due to suppression of radiation-induced chronic oxidative stress. It is known that radiation exposure leads to acute oxidative stress, but direct evidence for radiation-induced chronic renal oxidative stress is sparse. We looked for evidence of oxidative stress after total-body irradiation in a rat model, focusing on the period before there is physiologically significant renal damage. No statistically significant increase in urinary 8-isoprostane (a marker of lipid peroxidation) or carbonylated proteins (a marker of protein oxidation) was found over the first 42 days after irradiation, while a small but statistically significant increase in urinary 8-hydroxydeoxy-guanosine (a marker of DNA oxidation) was detected at 35-55 days. When we examined renal tissue from these animals, we found no significant increase in either DNA or protein oxidation products over the first 89 days after irradiation. Using five different standard methods for detecting oxidative stress in vivo, we found no definitive evidence for radiation-induced renal chronic oxidative stress. If chronic oxidative stress is part of the pathogenesis of radiation nephropathy, it does not leave widespread or easily detectable evidence behind.

Heme oxygenase-1 and the vascular bed: from molecular mechanisms to therapeutic opportunities

Heme oxygenase-1, an enzyme degrading heme to carbon monoxide, iron, and biliverdin, has been recognized as playing a crucial role in cellular defense against stressful conditions, not only related to heme release. HO-1 protects endothelial cells from apoptosis, is involved in blood-vessel relaxation regulating vascular tone, attenuates inflammatory response in the vessel wall, and participates in blood-vessel formation by means of angiogenesis and vasculogenesis. The latter functions link HO-1 not only to cardiovascular ischemia but also to many other conditions that, like development, wound healing, or cancer, are dependent on neovascularization. The aim of this comprehensive review is to address the mechanisms of HO-1 regulation and function in cardiovascular physiology and pathology and to demonstrate some possible applications of the vast knowledge generated so far. Recent data provide powerful evidence for the involvement of HO-1 in the therapeutic effect of drugs used in cardiovascular diseases. Novel studies open the possibilities of application of HO-1 for gene and cell therapy. Therefore, research in forthcoming years should help to elucidate both the real role of HO-1 in the effect of drugs and the clinical feasibility of HO-1-based cell and gene therapy, creating the effective therapeutic avenues for this refined antioxidant system.

Pharmacological and clinical aspects of heme oxygenase

This review is intended to stimulate interest in the effect of increased expression of heme oxygenase-1 (HO-1) protein and increased levels of HO activity on normal and pathological states. The HO system includes the heme catabolic pathway, comprising HO and biliverdin reductase, and the products of heme degradation, carbon monoxide (CO), iron, and biliverdin/bilirubin. The role of the HO system in diabetes, inflammation, heart disease, hypertension, neurological disorders, transplantation, endotoxemia and other pathologies is a burgeoning area of research. This review focuses on the clinical potential of increased levels of HO-1 protein and HO activity to ameliorate tissue injury. The use of pharmacological and genetic probes to manipulate HO, leading to new insights into the complex relationship of the HO system with biological and pathological phenomena under investigation, is reviewed. This information is critical in both drug development and the implementation of clinical approaches to moderate and to alleviate the numerous chronic disorders in humans affected by perturbations in the HO system.

Future strategies for mitigation and treatment of chronic radiation-induced normal tissue injury

Until the mid-1990s, radiation-induced normal-tissue injury was generally assumed to be solely caused by the delayed mitotic death of parenchymal or vascular cells, and these injuries were held to be progressive and untreatable. From this assumption, it followed that postirradiation interventions would be unlikely to reduce either the incidence or the severity of radiation-induced normal tissue injury. It is now clear that parenchymal and vascular cells are active participants in the response to radiation injury, an observation that allows for the possibility of pharmacologic mitigation and/or treatment of these injuries. Mitigation or treatment of chronic radiation injuries has now been experimentally shown in multiple organ systems (eg, lung, kidney, and brain), with different pharmacologic agents (eg, angiotensin-converting enzyme inhibitors, pentoxifylline, and superoxide dismutase mimetics) and with seemingly different mechanisms (eg, suppression of the renin-angiotensin system and suppression of chronic oxidative stress). Unfortunately, the mechanistic basis for most of the experimental successes has not been established, and assessment of the utility of these agents for clinical use has been slow. Clinical development of pharmacologic approaches to mitigation or treatment of chronic radiation injuries could lead to significant improvement in survival and quality of life for radiotherapy patients and for victims of radiation accidents or nuclear terrorism.

Heme oxygenase-1: a provenance for cytoprotective pathways in the kidney and other tissues

Heme oxygenase (HO) is the rate-limiting enzyme in the degradation of heme, converting heme to biliverdin, during which iron is released and carbon monoxide (CO) is emitted; biliverdin is subsequently converted to bilirubin by biliverdin reductase. At least two isozymes possess HO activity: HO-1 represents the isozyme induced by diverse stressors, including ischemia, nephrotoxins, cytokines, endotoxin, oxidants, and vasoactive substances; HO-2 is the constitutive, glucocorticoid-inducible isozyme. HO-1 is upregulated in the kidney in assorted conditions and diseases. Interest in HO is driven by the capacity of this system to protect the kidney against injury, a capacity likely reflecting, at least in part, the cytoprotective properties of its products: in relatively low concentrations, CO exerts vasorelaxant, antiapoptotic, and anti-inflammatory effects while bile pigments are antioxidant and anti-inflammatory metabolites. This article reviews the HO system and the extent to which it influences the function of the healthy kidney; it summarizes conditions and stimuli that elicit HO-1 in the kidney; and it explores the significance of renal expression of HO-1 as induced by ischemia, nephrotoxins, nephritides, transplantation, angiotensin II, and experimental diabetes. This review also points out the tissue specificity of the HO system, and the capacity of HO-1 to induce renal injury in certain settings. Studies of HO in other tissues are discussed insofar as they aid in elucidating the physiologic and pathophysiologic significance of the HO system in the kidney.

The effect of heme oxygenase-1 induction by glutamine on radiation-induced intestinal damage: the effect of heme oxygenase-1 on radiation enteritis

BACKGROUND

Radiation enteritis is a significant clinical problem in patients receiving ionizing radiation directed at the abdomen or pelvis. The small intestine is the most radiosensitive gastrointestinal organ. Myeloperoxidase (MPO) activity and malondialdehyde (MDA) levels of the small intestine were measured to determine the oxidative damage caused by radiation. In addition, caspase-3 activity of the small intestine was measured to define the degree of apoptosis. The present study was undertaken to investigate the effect of glutamine administration on heme oxygenase-1 (HO-1) expression of the radiation enteritis model.

METHODS

Rats received 1 g/kg/d glutamine (HO-1-inducer) for 7 days before irradiation and continued for 3 days after irradiation. Zn-prothoporphyin (Zn-PP) 40 micromol/kg was delivered subcutaneously for 1 day before irradiation. Intestinal MPO activities and MDA levels are indicators of oxidative damage, whereas caspase-3 activities show the degree of apoptosis of the small intestine. At histopathologic examination, terminal ileum tissue was analyzed for morphologic changes. Also, the nuclear factor-kappa (NF-kappa) expression level of the terminal ileum was determined with immunohistochemistry methods to show the mucosal inflammatory process.

RESULTS

Irradiation significantly increased the intestinal MPO and caspase-3 activities, MDA levels, and HO-1 expression in comparison with the sham group. Glutamine treatment was associated with increased HO-1 expression, decreased MPO activity, caspase-3 activity, and MDA levels. Inhibition of HO-1 activity by Zn-PP completely eliminated the protective effects of glutamine. Histopathologic examination showed that the intestinal mucosal structure was preserved in the glutamine-treated group. In the irradiation group, NF-kappaB overexpression was detected. NF-kappaB positivity was strongest in the intestine of animals in the radiation alone group and the Zn-PP-treated irradiation group.

CONCLUSIONS

Glutamine appears to have protective effects against radiation-induced intestinal damage. This protective effect is mediated in part by the induction of HO-1 activity because inhibition of Zn-PP resulted in the complete abolishment of the protective effect of glutamine.

Curcumin blocks fibrosis in anti-Thy 1 glomerulonephritis through up-regulation of heme oxygenase 1

BACKGROUND

Induction of heme oxygenase 1 (HO-1) has been shown to be beneficial in a variety of pathologic settings. Curcumin, a polyphenolic compound, has antifibrotic effects in lung models of fibrosis, and is known to induce HO-1 in renal tubular cells. In this study, we determined whether curcumin has antifibrotic properties in glomerular fibrosis and if these effects are mediated by induction of HO-1.

METHODS

Curcumin effects on HO-1 expression in cultured mesangial cells and in glomeruli in vivo were analyzed by Northern and Western blotting. The dose-dependent effect of curcumin on glomerular fibrosis was tested in the anti-Thy 1 glomerulonephritis model. Curcumin was applied at doses of 10 to 200 mg/kg body weight by intraperitoneal injection from days 3 to 5 after induction of disease. On day 6, glomeruli were harvested and markers of fibrosis [plasminogen activator inhibitor-1 (PAI-1), transforming growth factor-beta (TGF-beta), fibronectin, periodic acid-Schiff (PAS) staining] were analyzed. The effect of HO-1 inhibition was tested in a second experiment were nephritic rats were treated with curcumin (100 mg/kg body weight) or the combination of curcumin and the HO-1 inhibitor zinc protoporphyrin (100 microg/kg).

RESULTS

Curcumin potently induced mesangial cell HO-1 expression in vitro and up-regulated glomerular HO-1 expression in nephritic animals in vivo. Curcumin treatment led to a significant, dose-dependent reduction of markers of fibrosis and proteinuria, with maximal inhibition at doses of 50 to 100 mg/kg. Beneficial effects of curcumin on markers of fibrosis and proteinuria were lost after HO-1 inhibition.

CONCLUSION

Curcumin has antifibrotic effects in glomerular disease, which are mediated through an induction of HO-1.

Differential regulation of the rat heme oxygenase-1 expression by Ets oncoproteins in glomerular mesangial cells

The Ets-1 oncoprotein and the heme-catabolizing enzyme heme oxygenase (HO)-1 have been implicated in the pathogenesis of renal disease. We investigated the role of the putative Ets-binding sites (EBSs) in the transactivation of the proximal promoter of rat heme oxygenase 1 (hmox1) gene by the Ets oncoproteins Fli-1, Erg-2, and Ets-1 in mesangial cells. We examined several rat hmox1-chloramphenicol acetytransferase (CAT) constructs and EBS mutant constructs in an effort to assess the effect of ETS oncoproteins on transactivation of the rat hmox1 proximal promoter in renal glomerular mesangial cells. CAT assays demonstrated that the proximal promoter region (-1387 to -40) contains positive and negative regulatory regions and that the EBS-2, 3, and 4 play a role in basal promoter activity. Overexpression of Fli-1 and Erg-2 proteins showed a significant increase in promoter activity, whereas Ets-1 showed no effect on promoter activity. The Fli-1-induced transcriptional activation was not altered by mutation of EBSs, either independently or in combination. However, mutation of EBS-4 independently or a combined mutation of sites 3 and 4 led to a 50% reduction in Erg-2-induced transcriptional activation. Furthermore, mutation of EBS-2 and 4 completely abolished Erg-2-mediated promoter activation. Our results support a role for Ets transcription factors in the regulation of rat hmox-1 gene expression in mesangial cells.

Differential effect of gamma-radiation-induced heme oxygenase-1 activity in female and male C57BL/6 mice

Ionizing radiation produces reactive oxygen species, which exert diverse biological effects on cells and animals. We investigated alterations of heme oxygenase (HO) and non-protein thiols (NPSH), which are known as two major anti-oxidant enzymes, in female and male C57BL/6 mice in the lung, liver, and brain after whole-body gamma-irradiation with 10 Gy (1-7 days) as well as in the lung after whole-thorax gamma-irradiation (WTI) with 12.5 Gy (1-26 weeks). Most significant alteration of HO activity was observed in the liver, which elevated 250% in males. NPSH level in female liver was increased on the 5th-7th days but decreased in males on the 3rd day. In the lung, the elevation of HO activity in both sexes and the pattern of NPSH change were similar to that of the liver. On the other hand, the increase of HO activity on the 16th week and the decrease of NPSH level on the 2nd week were observed only in male lung after WTI. This study shows that the liver is the most sensitive tissue to gamma-irradiation-induced alterations of HO activity in both female and male mice. In addition, there exists significant differential effect of gamma-irradiation on anti-oxidant system in female and male mice.

Angiotensin II induces carbon monoxide production in the perfused kidney: relationship to protein kinase C activation

Heme oxygenase (HO)-derived carbon monoxide (CO) attenuates vascular reactivity to constrictor stimuli. ANG II produces vasoconstriction and induces HO-1 isoform expression. However, direct evidence that ANG II promotes HO product generation is lacking. Therefore, we examined the effects of ANG II on CO release and HO isoform expression in isolated rat kidneys. Kidneys were perfused with oxygenated Krebs buffer. ANG II (1 μmol/l) increased ( P < 0.05) perfusion pressure from 97 ± 9 to 150 ± 14 mmHg; it also increased ( P < 0.05) the concentration of CO in the venous effluent (from 27.1 ± 11.9 to 45.6 ± 11.7, 62.5 ± 16.7, 94.8 ± 20.7, and 101.9 ± 13.1 nmol/l after 30, 60, 90, and 120 min, respectively). The pressor effect of ANG II was blunted ( P < 0.05) in kidneys perfused with buffer containing losartan (10 μmol/l) or PKC inhibitors staurosporine (0.1 μmol/l) or calphostin C (1 μmol/l). Kidneys perfused with buffer containing ANG II for 120 min also displayed increased ( P < 0.05) HO-1 expression. Stannous mesoporphyrin (30 μmol/l) decreased CO release ( P < 0.05) in preparations perfused with and without ANG II; the HO inhibitor also increased ( P < 0.05) perfusion pressure, more so in kidneys perfused with that without ANG II. We conclude that ANG II stimulates CO production and release in isolated, perfused rat kidneys. This action of ANG II is linked to the activation of AT1receptors and involves PKC activation and upregulation of renal HO-1 but not of HO-2 protein expression. The study suggests upregulation of renal HO-1 and CO release are protagonic events in a counterregulatory mechanism that attenuates ANG II-induced renal vasoconstriction.

Heme oxygenase-1 gene expression modulates angiotensin II-induced increase in blood pressure

The heme-heme oxygenase (HO) system has been implicated in the regulation of vascular reactivity and blood pressure. This study examines the notion that overexpression of HO decreases pressor responsiveness to angiotensin II (Ang II). Five-day-old Sprague-Dawley rats received an intraleft ventricular injection of approximately 5x10(9) cfu/mL of retroviruses containing human HO-1 sense (LSN-HHO-1), rat HO-1 antisense (LSN-RHO-1-AS), or control retrovirus (LXSN). Three months later, rats were instrumented with femoral arterial and venous catheters for mean arterial pressure (MAP) determination and Ang II administration, respectively. Rats injected with LSN-HHO-1, but not with LXSN, expressed human HO-1 mRNA and protein in several tissues. BP increased with administration of Ang II in rats expressing and not expressing human HO-1. However, the Ang II-induced pressor response (mm Hg) in LSN-HHO-1 rats (16+/-3, 27+/-3, and 38+/-3 at 0.5, 2, and 10 ng) was surpassed (P<0.05) in LXSN rats (23+/-1, 37+/-2, and 52+/-2 at 0.5, 2, and 10 ng). Importantly, treating LSN-HHO-1 rats with the HO inhibitor tin mesoporphyrin (SnMP) enhanced (P<0.05) the Ang II-induced pressor response to a level not different from that observed in LXSN rats. Rats injected with LSN-RHO-1-AS showed a decrease in renal HO-1 protein expression and HO activity relative to control LXSN rats. Administration of Ang II (0.1 to 2 ng) caused small (4 to 5 mm Hg) but significant increases in MAP in rats injected with LSN-RHO-1-AS (P<0.05) compared with rats injected with LXSN. These data demonstrate that overexpression of HO-1 brings about a reduction in pressor responsiveness to Ang II, which is most likely due to increased generation of an HO-1 product, presumably CO, with the ability to inhibit vascular reactivity to constrictor stimuli.

Gene transfer-induced local heme oxygenase-1 overexpression protects rat kidney transplants from ischemia/reperfusion injury

Heme oxygenase-1 (HO-1) overexpression using gene transfer protects rat livers against ischemia/reperfusion (I/R) injury. This study evaluates the effects of Ad-HO-1 gene transfer in a rat renal isograft model. Donor LEW kidneys were perfused with Ad-HO-1, Ad-beta-gal, or PBS, stored at 4 degrees C for 24 h, and transplanted orthotopically into LEW recipients, followed by contralateral native nephrectomy. Serum creatinine, urine protein/creatinine ratios, severity of histologic changes, HO-1 mRNA/protein expression, and HO enzymatic activity were analyzed. Ad-HO-1 gene transfer conferred a survival advantage when compared with PBS- and Ad-beta-gal-treated controls, with median survival of 100, 7, and 7 d, respectively (P < 0.01). Serum creatinine levels were elevated at day 7 in all groups (range, 2.2 to 5.8 mg/dl) but recovered to 1.0 mg/dl by day 14 (P < 0.01) in Ad-HO-1 group, which was sustained thereafter. Urine protein/creatinine ratio at day 7 was elevated in both PBS and Ad-beta-gal, as compared with the Ad-HO-1 group (12.0 and 9.8 versus 5.0; P < 0.005); histologically, ATN and glomerulosclerosis was more severe in Ad-beta-gal group at all time points. Reverse transcriptase-PCR-based HO-1 gene expression was significantly increased before reperfusion (P < 0.001) and remained increased in the Ad-HO-1-treated group for 3 d after transplantation. Concomitantly, HO enzymatic activity was increased at transplantation and at 3 d posttransplant in the Ad-HO-1 group, compared with Ad-beta-gal controls (P < 0.05); tubular HO-1 expression was discernible early posttransplant in the Ad-HO-1 group alone. These findings are consistent with protective effects of HO-1 overexpression using a gene transfer approach against severe renal I/R injury, with reduced mortality and attenuation of tissue injury.

Whole-body X-irradiation induces acute and transient expression of heme oxygenase-1 in rat liver

Activation of the stress-inducible heme oxygenase-1 (HO-1) gene by X-irradiation was investigated in rat liver. When male Wistar MS strain rats (8 weeks) received whole-body irradiation of 17.0 Gy, 7 h later the activity of heme oxygenase in the liver was significantly enhanced (2.5 times). The level of HO-1 mRNA expression was increased by 2.3 and 4.0 times 2 and 4 h after radiation, and then declined at 7 and 10 h to the level of 2.0 and 1.6 times of the control. When the X-ray dose was varied from 4.0 to 21.7 Gy, the transcription of the gene was enhanced at all doses and the level of activation was dose-dependent. Finally, western blotting of irradiated liver demonstrated a significant increase in the level of HO-1 induced by X-rays, peaking at 4 h. Thus, X-rays were confirmed to be stressors that induce acute HO-1 expression transiently in the liver.