Induction of heme oxygenase-1 and stimulation of cGMP production by hemin in aortic tissues from hypertensive rats

1-Aminocyclopropanecarboxylic acid, an antagonist of N-methyl-D-aspartate receptors, causes hypotensive and antioxidant effects with upregulation of heme oxygenase-1 in stroke-prone spontaneously hypertensive rats

1-Aminocyclopropanecarboxylic acid (ACPC) has been shown to protect neurons against glutamate-induced neurotoxicity by reducing N-methyl-D-aspartate (NMDA) receptor activation. Recent studies have demonstrated that several antagonists of NMDA receptors have important cardiovascular effects. In this study, we examined whether the cardiovascular effects of ACPC involve the role of heme oxygenase-1 (HO-1) and its antioxidant effect in stroke-prone spontaneously hypertensive rats (SHRSP). Male SHRSP were divided into two groups: a control group and an ACPC group administered ACPC at 50 mg/kg per day for 4 weeks by peritoneal injection. Systolic blood pressure (SBP) and mortality of stroke were significantly lower in the ACPC group than in the control group. Urinary Na(+) and Cl(-) excretion and plasma superoxide dismutase (SOD) activity were increased in the ACPC group. Western analysis detected proteins that were immunoreactive to anti-nitrotyrosine antibody and showed lower levels of expression in the cerebral cortex compared to that in the control group. Immunohistochemical analysis revealed that 8-hydroxy-2'-deoxyguanosine (8-OHdG) formation in the hippocampus and cerebral cortex was reduced in the ACPC group. Quantitative reverse-transcription-polymerase chain reaction (RT-PCR) showed that administration of ACPC also significantly decreased the expression of neuronal nitric oxide synthase (nNOS) mRNA in the hippocampus and endotherial nitric oxide synthase (eNOS) mRNA in the cerebral cortex, and drastically increased HO-1 mRNA in the cerebral cortex. Enhanced HO-1 staining on sections from the hippocampus and cerebral cortex was observed in the ACPC group. These data suggest that the normalization by ACPC of blood pressure elevation and mortality of stroke involves induction of the expression of HO-1, which exerts antioxidant and vascular relaxation effects, in SHRSP.

Heme-oxygenase upregulation ameliorates angiotensin II-induced tubulointerstitial injury and salt-sensitive hypertension

BACKGROUND

Heme oxygenase-1 (HO-1) has been implicated in the modulation of several diseases including hypertension (HTN) and renal injury. The tubulointerstitial (TI) injuries are supposed to be the main determinants for the development of salt-sensitive HTN. Therefore, this study examined the role of HO-1 in angiotensin II (AngII)-induced TI injury and salt-sensitive HTN.

METHODS

Sprague-Dawley rats on a high salt diet were treated by AngII infusion plus either hemin, an inducer of HO-1, or hemin + zinc protoporphyrin, a HO-1 inhibitor, for 2 weeks, and then followed for 6 weeks.

RESULTS

The AngII infusion resulted in acute HTN and proteinuria. Light microscopy revealed focal areas of tubular atrophy with mononuclear cell infiltration and interstitial expansion. The overexpression of osteopontin and TGF-beta(1) accompanied by diminished expression of rat endothelial cell antigen-1, the hallmarks of TI injury, were observed. At 2 weeks, all interventions were withdrawn and systolic blood pressure returned towards normal. After a brief normal salt diet, rats were again placed on high salt diet, resulting in progressive increase in systolic blood pressure in the HO-1-inhibited group.

CONCLUSION

The induction of HO-1 attenuated the development of HTN, suggesting that HO-1 plays a crucial role in significant attenuation of AngII-mediated TI injury and resultant salt-sensitive HTN.

Sustained normalization of high blood pressure in spontaneously hypertensive rats by implanted hemin pump

Treatment of established hypertension, especially for prolonged control of this pathogenic process, represents a great challenge. To upregulate the expression of heme oxygenase (HO) to lower blood pressure (BP) of spontaneously hypertensive rats (SHRs), we administered hemin to 12-week-old adult SHRs through subcutaneously implanted osmotic minipumps for 3 consecutive weeks (the hemin protocol). Systolic BP of SHRs was normalized 123+/-2 mm Hg (n=20; P<0.001) and this normalization maintained for 9 months after the removal of hemin pumps. At the end of the hemin protocol, HO-1 expression, HO activity, soluble guanylyl cyclase expression, and cGMP content were all increased, but phosphodiesterase-5 expression was downregulated in the mesenteric arteries. The hemin protocol also reversed SHR-featured arterial eutrophic inward remodeling and decreased expression levels of vascular endothelial growth factor. These changes lasted 9 months after the hemin protocol. Our study, thus, formulates a novel hemin protocol that will not only normalize BP in SHRs with established hypertension but, more importantly, will also provide long-lasting antihypertension protection. Sustained upregulation of HO-1-linked signaling pathways and reversal of vascular remodeling in peripheral blood vessels mediate likely the antihypertensive effect of the hemin protocol.

Possible mediators involved in decreasing peripheral vascular resistance with blackcurrant concentrate (BC) in hind-limb perfusion model of the rat

We analyzed mechanisms decreasing hind-limb perfusion pressure (PP) with blackcurrant concentrate (BC) in the rat. The decrease in PP with BC was abolished by endothelial removal, nitroarginine plus tetraethylammonium, nitroarginine plus catalase or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one as an inhibitor of guanylyl cyclase and potassium channel(s), and accompanied by the increased cyclic GMP level. Partial but significant inhibition caused by KCl was observed during contraction. Authentic H2O2 decreased the PP in a sensitive manner to catalase and tetraethylammonium. The decrease in PP with BC in the presence of nitroarginine was significantly attenuated by diverse potassium channel blockers. Two delphinidins of 4 anthocyanins purified from BC definitely decreased the PP through similar mechanisms to BC. These results suggest that the decreased PP with BC is possibly mediated by endothelial NO and H2O2, and partially through the activation of diverse potassium channels, and that 2 delphinidins play a major role as active components of BC.

Phototherapy and malignancy: Possible enhancement by iron administration and hyperbaric oxygen

Photodynamic therapy (PDT) is a new therapeutic approach for the treatment of malignant tumors. Hyperbaric oxygen (HBO(2)) shows beneficial effects in various modalities of cancer interventions. Tumor cells tend to accumulate large amount of iron. There is interaction between tissue content of oxygen, iron, free radical production and tissue damage. Accumulation of intracellular iron is necessary for the production of oxygen radicals. HBO(2) increases tissue oxygen and hydrogen peroxide production in the cells. Malignant cells require iron, and exhibit more transferrin receptors. The photodynamic sensitization of human leukemic cells is achieved with accumulation of porphyrins stimulated by 5-aminolaevulanic acid (ALA) plus hemin. Further, a significant improvement in tumor response is obtained when PDT is delivered during hyperoxygenation. When PDT is combined with hyperoxygenation, the hypoxic condition is improved and the cell killing rate at various time points after PDT is significantly enhanced. Photosensitization with use of porphyrins is used with HBO(2) and PDT for treatment of certain tumors. PDT with ALA is used for treatment of actinic keratosis (AK). The combination of iron administration (by injection or oral rout), hemin, or transferrin, as a source for iron, HBO(2) as a source of oxygen under pressure and PDT as a source of generating free-radical tissue damage may be useful in the treatment of tumors. The possibility of combining HBO(2), iron, light and local photosensitizers to overcome skin tumors deserve extensive laboratory and clinical research work. Conclusively, iron, HBO(2), and PDT may have synergistic effect to hamper tumor cells.

Gender-related differences in advanced glycation endproducts, oxidative stress markers and nitric oxide synthases in rats

An age- and blood pressure-associated increase in methylglyoxal (MG) and MG-induced advanced glycation endproducts (AGEs), including N(epsilon)-carboxyethyl-lysine (CEL) and N(epsilon)-carboxymethyl-lysine (CML), in the kidney of spontaneously hypertensive rats (SHR) has been shown. In the present study, gender-related changes in AGEs and nitric oxide synthase were investigated in Sprague-Dawley (SD) and stroke-prone SHR (SHRsp) rats. Immunohistochemical analyses were conducted on kidneys from 24-week-old male and female SD rats as well as SHRsp. The systolic blood pressure of SHRsp was significantly higher than that of SD rats. Male SD rats had more intense kidney staining for CEL than female SD rats. Both male and female SHRsp had more marked CEL and CML staining localized to kidney tubules, as opposed to SD rats. Female rats showed more staining in glomerular vessels than male rats in both SD and SHRsp. Nuclei containing nuclear factor-kappaB (NF-kappaB) p65 and activated macrophages were seen in the kidney from SHRsp, not so much in SD rats, localized to renal tubules in male and glomerular vessels in female SHRsp. A higher protein level of NF-kappaB p65 was found in SHRsp than in SD rats. SD rats had more intense kidney neuronal nitric oxide synthase staining than SHRsp. The intensity of inducible nitric oxide synthase staining was significantly higher in SHRsp than in SD rats, with no gender differences in either strain. SHRsp and male rats exhibited higher AGEs and oxidative stress than SD and female rats, respectively. These differences might partly account for the development of hypertension in SHRsp and the higher vulnerability of male animals to renal pathology.

Carbon Monoxide: Endogenous Production, Physiological Functions, and Pharmacological Applications

Over the last decade, studies have unraveled many aspects of endogenous production and physiological functions of carbon monoxide (CO). The majority of endogenous CO is produced in a reaction catalyzed by the enzyme heme oxygenase (HO). Inducible HO (HO-1) and constitutive HO (HO-2) are mostly recognized for their roles in the oxidation of heme and production of CO and biliverdin, whereas the biological function of the third HO isoform, HO-3, is still unclear. The tissue type-specific distribution of these HO isoforms is largely linked to the specific biological actions of CO on different systems. CO functions as a signaling molecule in the neuronal system, involving the regulation of neurotransmitters and neuropeptide release, learning and memory, and odor response adaptation and many other neuronal activities. The vasorelaxant property and cardiac protection effect of CO have been documented. A plethora of studies have also shown the importance of the roles of CO in the immune, respiratory, reproductive, gastrointestinal, kidney, and liver systems. Our understanding of the cellular and molecular mechanisms that regulate the production and mediate the physiological actions of CO has greatly advanced. Many diseases, including neurodegenerations, hypertension, heart failure, and inflammation, have been linked to the abnormality in CO metabolism and function. Enhancement of endogenous CO production and direct delivery of exogenous CO have found their applications in many health research fields and clinical settings. Future studies will further clarify the gasotransmitter role of CO, provide insight into the pathogenic mechanisms of many CO abnormality-related diseases, and pave the way for innovative preventive and therapeutic strategies based on the physiologic effects of CO.

Apigenin decreases hemin-mediated heme oxygenase-1 induction

Hemin is a strong inducer of heme oxygenase-1 (HO-1) expression in vitro and in vivo. Whereas moderate overexpression of HO-1 is protective against oxidative stress, uncontrolled levels of HO-1 can be detrimental. Therefore, we evaluated the effects of apigenin (APG), a flavonoid involved in a number of phosphorylation pathways and also known to inhibit inducible genes, such as iNOS and COX-2, on HO-1 expression. Incubation of mouse embryonic fibroblasts with APG (5--40 microM) decreased hemin-induced HO-1 protein and mRNA expression. APG also reduced the induction of HO-1 promoter activity, as assessed by bioluminescence imaging, in NIH3T3 cells transfected with the 15-kb HO-1 promoter fused with the reporter gene luciferase (HO-1-luc). Furthermore, through the use of specific inhibitors, APG's effect was found to be unrelated to its PKC, CK 2, PI 3 K, p38, or ERK inhibitory activities. Quercetin (10--40 microM), also a flavonoid, also inhibited hemin-induced HO-1 expression. Additionally, in vivo studies using HO-1-luc transgenic mice showed that APG (50 mg/kg) decreased hemin-induced HO activity and HO-1 protein expression in the liver. These results suggest that hemin-induced HO-1 expression can be attenuated by flavonoids, such as APG.

Vascular methylglyoxal metabolism and the development of hypertension

OBJECTIVES

The pathogenic process of diabetes mellitus is associated with increased methylglyoxal (MG). MG causes non-enzymic glycation of proteins to form irreversible advanced glycation endproducts (AGEs). However, the correlation between MG and essential hypertension is unknown. The aim of the present study was to investigate whether MG, MG-induced AGEs, and oxidative stress were increased in the aorta of spontaneously hypertensive rats (SHR) and whether an increased formation of MG and related AGEs was correlated with the development of high blood pressure in these rats.

METHODS

High-performance liquid chromatography (HPLC) was used to determine MG and reduced glutathione levels in plasma and aorta. MG-induced AGEs, N(epsilon)-carboxyethyl-lysine (CEL) and N(epsilon)-carboxymethyl-lysine (CML), in aorta were determined using immunohistochemistry. Hydrogen peroxide and superoxide levels in aorta and glutathione peroxidase and reductase activities were also determined.

RESULTS

Aortic and plasma MG levels were significantly elevated in SHR, but not in Wistar-Kyoto (WKY) rats, at 8, 13 and 20 weeks of age, in parallel with blood pressure increase. Immunohistochemistry revealed more intense staining for CML and CEL in aorta from SHR than those of WKY rats from 8 weeks onwards. Most of the staining was localized to endothelial cells. Superoxide and hydrogen peroxide levels were significantly elevated in aorta of SHR at 13 weeks, whereas reduced glutathione levels, glutathione peroxidase and glutathione reductase activities were significantly decreased compared to WKY rats.

CONCLUSIONS

Increased aortic MG, AGE formation and oxidative stress were associated with blood pressure increase in SHR, which may cause endothelial dysfunction and altered vascular reactivity.

Carbon monoxide and hypertension

The enzymatic action of heme oxygenase yields carbon monoxide, biliverdin and iron. Carbon monoxide is implicated in many physiological processes, including the regulation of vascular tissue contractility and apoptosis. By stimulating the soluble guanylyl cyclase (sGC)/cGMP pathway and activating K channels in vascular smooth muscle cells (SMCs), carbon monoxide relaxes vascular tissues under physiological conditions. Altered metabolism and functions of carbon monoxide have been linked to the pathogenesis and maintenance of hypertension. The expression and activity of heme oxygenase-1, sGC and cGMP in vascular SMCs are associated with different stages of development of hypertension in spontaneously hypertensive rats (SHRs). The importance of altered heme oxygenase-2 expression in vascular tissues in hypertension remains unclear. Increased vascular contractility, unbalanced cellular apoptosis and proliferation in the vascular wall, increased oxidative stress, and the altered interaction of carbon monoxide and nitric oxide are among the consequences of heme oxygenase/carbon monoxide system dysfunction in hypertension. Acute application of pharmacological inducers to upregulate the expression of heme oxygenase-1 or the use of gene delivery method to overexpress heme oxygenase-1 decreases blood pressure in young SHRs and other animal models of hypertension. These blood pressure-decreasing effects are annulled by metalloporphyrins. In adult SHRs, the heme oxygenase/carbon monoxide system appears to be normalized as a compensatory reaction. To date, acute manipulation of the expression of heme oxygenase-1 has not been successful in decreasing blood pressure in adult SHRs. In conclusion, abnormality of the heme oxygenase/carbon monoxide system has a critical role in the pathogenesis of hypertension, and novel therapeutic approaches should be pursued to achieve selective improvement in the function of this system in hypertension.

The pro-oxidant role of methylglyoxal in mesenteric artery smooth muscle cells

Methylglyoxal (MG), a highly reactive metabolite of glucose, causes non-enzymatic glycation of proteins to form irreversible advanced glycation endproducts (AGEs). The present study investigated whether methylglyoxal induced oxidative stress and activated nuclear factor kappa B (NF-κB) in freshly isolated and cultured smooth muscle cells (SMCs) from rat mesenteric artery. The treatment of cells with MG (50 or 100 µmol/L) induced a significant increase in AGE formation and oxidation of DCF. MG-enhanced generation of AGEs and the oxidation of DCF was markedly inhibited by antioxidant n-acetylcysteine (NAC, 600 µmol/L). MG at a concentration of 100 µmol/L increased the heme-oxygenase-1 expression in these cells. Moreover, MG activated NF-κB p65, indicated by an increased im muno cytochemistry stain for NF-κB p65 located in the nucleus after the treatment of mesenteric artery SMCs with MG. MG-induced activation of NF-κB p65 was inhibited by NAC. In summary, MG significantly increases oxidative stress and activates NF-κB p65 in mesenteric artery SMCs. The pro-oxidant role of methylglyoxal may contribute to various pathological changes of SMCs from resistance arteries.Key words: methylglyoxal, oxidative stress, NF-κB p65, vascular smooth muscle cells, mesenteric artery.

Increased methylglyoxal and advanced glycation end products in kidney from spontaneously hypertensive rats

BACKGROUND

Methylglyoxal (MG), a metabolite of glucose, causes nonenzymatic glycation of proteins to form irreversible advanced glycation end products (AGEs). The role of MG in the development of essential hypertension is unknown, although MG has been extensively studied in relation to diabetes.

METHODS

Blood pressure of spontaneously hypertensive rats (SHR) and paired Wistar Kyoto (WKY) rats was measured at 5, 8, 13, and 20 weeks of age. HPLC was used to determine the levels of plasma and kidney MG, as well as reduced or oxidized glutathione in the kidney. MG-induced AGEs, Nepsilon-carboxyethyl-lysine (CEL), and Nepsilon-carboxymethyl-lysine (CML) in the kidney were detected by immunohistochemistry. Glutathione peroxidase and reductase activities in the kidney were also determined.

RESULTS

Plasma MG levels were significantly elevated in SHR, but not in WKY rats, at 8, 13, and 20 weeks of age in parallel with blood pressure increase. Kidney MG levels in SHR were increased by 21% and 38% at 13 and 20 weeks, respectively, compared to age-matched WKY rats. There were no differences in blood pressure and MG levels in plasma and kidney between SHR and WKY rats at 5 weeks of age. Immunohistochemistry revealed more intense staining for CML and CEL in kidneys from SHR compared to WKY rats from 8 weeks onward. Most of the staining was localized to renal tubules with some staining in the glomerular vessels.

CONCLUSION

MG and AGEs formation was significantly elevated in kidney from SHR, which may cause local vascular and tubular damage, contributing to the development and complications of hypertension.

Induction of heme oxygenase-1 expression inhibits platelet-dependent thrombosis

Heme oxygenase-1 (HO-1) plays a key role in protecting tissue from oxidative stress. Although some studies implicate HO-1 in modulating thrombosis after vascular injury, the impact of HO-1 on the rate of clot formation in vivo is poorly defined. This study examined the potential function of HO-1 in regulating platelet-dependent arterial thrombosis. Platelet-rich thrombi were induced in C57BL/6J mice by applying 10% ferric chloride to the exposed carotid artery. Mean occlusion time of wild-type mice (n = 10) was 14.6 +/- 1.0 min versus 12.9 +/- 0.6 min for HO-1-/- mice (n = 11, p = 0.17). However, after challenge with hemin, mean occlusion time was significantly longer in wild-type mice (16.3 +/- 1.2 min, n = 15) than HO-1-/- mice (12.0 +/- 1.0 min, n = 9; p = 0.021). Hemin administration induced an approximately twofold increase in oxidative stress, measured as plasma thiobarbituric acid reactive substances. Immunohistochemical analysis revealed that hemin induced a robust increase in HO-1 expression within the carotid arterial wall. Ex vivo blood clotting within a collagen-coated perfusion chamber was studied to determine whether the accelerated thrombosis observed in HO-1-/- mice was contributed to by effects on the blood itself. Under basal conditions, mean clot formation during perfusion of blood over collagen did not differ between wild-type mice and HO-1-/- mice. However, after hemin challenge, mean clot formation was significantly increased in HO-1-/- mice compared with wild-type controls. These results suggest that, under basal conditions, HO-1 does not exert a significant effect on platelet-dependent clot formation in vivo. However, under conditions that stimulate HO-1 production, platelet-dependent thrombus formation is inhibited by HO-1. Enhanced HO-1 expression in response to oxidative stress may represent an adaptive response mechanism to down-regulate platelet activation under prothrombotic conditions.

Vascular CO counterbalances the sensitizing influence of 20-HETE on agonist-induced vasoconstriction

We examined the influence of interactions between CO and 20-hydroxyeicosatetraenoic acid (20-HETE) on vascular reactivity to phenylephrine and vasopressin. Renal interlobar arteries incubated in Krebs buffer released CO at a rate that is decreased (from 125.0+/-15.2 to 46.3+/-8.8 pmol/mg protein per hour, P<0.05) by the heme oxygenase inhibitor chromium mesoporphyrin (CrMP; 30 micromol/L). The level of 20-HETE in vessels was not affected by CrMP (74.3+/-6.1 versus 72.5+/-16.2 pmol/mg protein), but was decreased (P<0.05) by CO (1 micromol/L; 33.2+/-7.9 pmol/mg protein) or the cytochrome P450-4A inhibitor N-methylsulfonyl-12,12-dibromododec-11-enamide (DDMS; 30 micromol/L; 11.4+/-3.3 pmol/mg protein). Phenylephrine elicited development of isometric tension in vascular rings mounted on a wire-myograph (EC(50), 0.29+/-0.02 micromol/L; R(max), 3.78+/-0.19 mN/mm). The sensitivity to phenylephrine was decreased (P<0.05) by CO (1 micromol/L; EC(50), 0.60+/-0.04 micromol/L) or DDMS (EC(50), 0.71+/-0.12 micromol/L) and increased (P<0.05) by 20-HETE (10 micromol/L; EC(50), 0.08+/-0.02 micromol/L) or CrMP (EC(50), 0.11+/-0.02 micromol/L). Notably, neither CO nor CrMP changed the sensitivity to phenylephrine in vessels treated with DDMS. Refractoriness to CO and CrMP in such a setting was eliminated by inclusion of 20-HETE (1 micromol/L) in the bathing buffer. The aforementioned interventions affected the vascular reactivity to vasopressin in a similar manner. These data indicate that the reactivity of renal arteries to phenylephrine and vasopressin is reciprocally influenced by CO and 20-HETE of vascular origin and that CO desensitizes the vascular smooth muscle to constrictor agonists by interfering with the sensitizing influence of 20-HETE.

The source of heme for vascular heme oxygenase I: heme uptake in rat aorta

During the last decade, heme oxygenase (HO) and carbon monoxide (CO) have garnered substantial research interest in terms of cell and organ regulation, especially as they bear on the central nervous system, organ transplantation, and the cardiovascular system. While the enzymatic mechanism, substrates, and products of HO are well known, it is not clear whether the cardiovascular system derives its supply of the heme substrate through de novo synthesis or uptake from the extracellular milieu. The objective of the present study was to test the latter possibility in rat aorta and to determine the influence of plasma proteins that bind heme in vivo, viz. hemopexin and albumin. Aortic tissue was exposed to [14C]heme in vitro, and the concentration and time dependence of heme uptake was assessed. The presence of hemopexin or albumin in the incubation medium dramatically decreased heme uptake by the aorta. Heme uptake by aortic tissue was not altered after induction of HO-1, which would be expected to increase tissue heme demand. In summary, the rat, isolated aorta was capable of obtaining heme from its external milieu, but this was obtunded in the presence of the plasma proteins hemopexin or albumin. For normal physiological situations, heme uptake may not be a usual source of substrate for vascular HO and hemoenzymes such as nitric oxide synthase, soluble guanylyl cyclase, and cyclooxygenase.Key words: heme uptake, vasculature, heme oxygenase, hemopexin.

Heme oxygenase expression in small intestine of experimental hepatic cirrhosis rats

AIM: To investigate the expression of heme oxygenase(HO) in the small intestine in cirrhotic rats and control rats.

METHODS: The expression of heme oxygenase isoenzyme 1 and 2 (HO-1, HO-2) proteins in the small intestine was assessed by immunohistochemistry. The change of expression of HO was studied by computer image system and quantitative analysis.

RESULTS: The portal venous pressure (PVP) of cirrhotic rats was significantly higher than that of controls (2.609±0.144 vs 0.916±0.034, t = 39.37, P < 0.01), whereas the mean arterial pressure (MAP) was significantly lower than that of controls (13.411±1.208 vs 17.423±1.472, t = 7.297, P < 0.05). It was found that HO-1 positive staining localized in submucosal small artery and small vein, the layer of muscle, serosa, even in submucosal gland of cirrhotic rats, but only poor positive staining in those of normal controls (0.4 813±0.1 223 vs 0.3 762± 0.0 689, t = 19.022, P < 0.01). In both groups, HO-2 was observed in submucosal blood vessel and gland, the layer of muscle, serosa. In cirrhotic rats, HO-2 staining did not display any notable changes compared with that of in control rats (0.4 834±0.0 997 vs 0.4 813±0.1 056, t = 0.595, P > 0.05). In addition, the expression levels of heme oxygenase were correlated positively with portal venous pression (r = 0.655, P < 0.05) and negatively with the mean arterial pressure (r = -0.852, P < 0.01).

CONCLUSION: The expression of HO-1 is elevated in the small intestine of cirrhotic rats. It may play an important role in the development of portal hypertension enteropathy.