3162

HMOX1

HMOX1D|HO-1|HSP32|bK286B10;heme oxygenase (decycling) 1;HMOX1;heme oxygenase (decycling) 1

heat shock protein, 32-kD|heme oxygenase 1

22q13.1

protein-coding

Count: Hmox1; 24451

AIM: To investigate the expression of heme oxygenase-1 gene and production of endogenous carbon monoxide in the rat lung tissue at different time points of chronic hypoxic pulmonary hypertension and the effect of hemin, an inducer of heme oxygenase, on the expression of HO-1 gene and production of endogenous carbon monoxide and pulmonary hypertension. METHODS: We recreated a rat model of hypoxic pulmonary hypertension by intermittent normal pressure hypoxia (10% O2). The following assays were carried out: Reverse transcriptase polymerase chain reaction (RT-PCR) were performed to determine the level of HO-1 mRNA in rat lung tissue, double wave length spectrophotometry was used to evaluate the quantity of COHb in arterial blood, cardiac catheterization was used to measure the right ventricular systolic pressure (RVSP) and HE staining was performed in dissected lung tissue to observe the pathologic changes of the intra-acinar pulmonary arteries(IAPA). RESULTS: (DT here was low level of HO-1 mRNA in normal rat lung tissue, but the level of HO-1 mRNA increased by 2-4 times in the lung tissue of hypoxic rats (P < 0.01). The quantity of COHb was 2-3 times as those of control group (P < 0.01 or P < 0.05). These were accompanied by the increase of RVSP and the thickness of IAPA. (2) Hemin could maintain the HO-1 mRNA and COHb in the hypoxic rat lung tissue at a high level, and partially suppressed the increase of rat RVSP, ameliorated the pathologic changes of IAPA. CONCLUSION: The upregulation of the expression of HO-1 gene and production of CO in the rat lung of hypoxic pulmonary hypertension plays a role of inhibition in the development of hypoxic pulmonary hypertension. Hemin has a therapeutic effect on hypoxic pulmonary hypertension.

BACKGROUND: Lung inflammation precedes the development of hypoxia-induced pulmonary hypertension (HPH); however, its role in the pathogenesis of HPH is poorly understood. We sought to characterize the hypoxic inflammatory response and to elucidate its role in the development of HPH. We also aimed to investigate the mechanisms by which heme oxygenase-1, an anti-inflammatory enzyme, is protective in HPH. METHODS AND RESULTS: We generated bitransgenic mice that overexpress human heme oxygenase-1 under doxycycline control in an inducible, lung-specific manner. Hypoxic exposure of mice in the absence of doxycycline resulted in early transient accumulation of monocytes/macrophages in the bronchoalveolar lavage. Alveolar macrophages acquired an alternatively activated phenotype (M2) in response to hypoxia, characterized by the expression of found in inflammatory zone-1, arginase-1, and chitinase-3-like-3. A brief 2-day pulse of doxycycline delayed, but did not prevent, the peak of hypoxic inflammation, and could not protect against HPH. In contrast, a 7-day doxycycline treatment sustained high heme oxygenase-1 levels during the entire period of hypoxic inflammation, inhibited macrophage accumulation and activation, induced macrophage interleukin-10 expression, and prevented the development of HPH. Supernatants from hypoxic M2 macrophages promoted the proliferation of pulmonary artery smooth muscle cells, whereas treatment with carbon monoxide, a heme oxygenase-1 enzymatic product, abrogated this effect. CONCLUSIONS: Early recruitment and alternative activation of macrophages in hypoxic lungs are critical for the later development of HPH. Heme oxygenase-1 may confer protection from HPH by effectively modifying the macrophage activation state in hypoxia.

To test the hypothesis that hypoxia inducible factor-1 alpha (HIF-1alpha) up-regulated the expression of heme oxygenase-1 (HO-1) gene in pulmonary arteries of rats with hypoxia-induced pulmonary hypertension, 8 male Wistar rats in each of 5 groups were exposed to hypoxia for 0, 3, 7, 14 or 21 d, respectively. Mean pulmonary arterial pressure (mPAP), vessel morphometry and right ventricle hypertrophy index were measured. Lungs were inflation fixed for immunohistochemistry, in situ hybridization; frozen for later measurement of HO-1 enzyme activity. mPAP increased significantly after 7 d of hypoxia [(18.4 +/- 0.4) mmHg, P<0.05], reaching its peak after 14 d of hypoxia, then remained stable. Pulmonary artery remodeling became to develop significantly after 14 d of hypoxia. HIF-1alpha protein in control was poorly positive (0.05 +/- 0.01), but was up-regulated in pulmonary arterial tunica intima of all hypoxic rats. In pulmonary arterial tunica media, the levels of HIF-1alpha protein were markedly up-regulated after 3 d and 7 d of hypoxia (0.20 +/- 0.02; 0.22 +/- 0.02, P<0.05), then declined after 14 d and 21 d of hypoxia. HIF-1alpha mRNA staining was poorly positive in control, hypoxia for 3 and 7 d, but enhanced significantly after 14 d of hypoxia (0.20 +/- 0.02, P<0.05), then remained stable. HO-1 protein increased after 7 d of hypoxia (0.10 +/- 0.01, P<0.05), reaching its peak after 14 d of hypoxia (0.21 +/- 0.02, P<0.05), then remained stable. HO-1 mRNA increased after 3 d of hypoxia, reaching its peak after 7 d of hypoxia (0.17 +/- 0.01, P<0.05), then declined. Linear correlation analysis showed that HIF-1alpha mRNA, HO-1 protein and mPAP were associated with pulmonary remodeling. HIF-1alpha protein (tunica intima) was conversely correlated with HIF-1alpha mRNA (r=0.921,P<0.01), HO-1 protein was conversely correlated with HIF-1alpha protein (tunica intima) (r=0.821, P<0.01). HIF-1alpha and HO-1 were both involved in the pathogenesis of hypoxia-induced pulmonary hypertension in rat. hypoxia inducible factor-1 alpha correlated the expression of heme oxygenase 1 gene in pulmonary arteries of rat with hypoxia-induced pulmonary hypertension.

Prolonged hypoxia leads to the development of pulmonary hypertension. Recent reports have suggested enhancement of heme oxygenase (HO), the major source of intracellular carbon monoxide (CO), prevents hypoxia-induced pulmonary hypertension and vascular remodeling in rats. Therefore, we hypothesized that inhibition of HO activity by tin protoporphyrin (SnPP) would exacerbate the development of pulmonary hypertension. Rats were injected weekly with either saline or SnPP (50 micromol/kg) and exposed to hypobaric hypoxia or room air for 5 wk. Pulmonary and carotid arteries were catheterized, and animals were allowed to recover for 48 h. Pulmonary and systemic pressures, along with cardiac output, were recorded during room air and acute 10% O2 breathing in conscious rats. No difference was detected in pulmonary artery pressure between saline- and SnPP-treated animals in either normoxic or hypoxic groups. However, blockade of HO activity altered both systemic and pulmonary vasoreactivity to acute hypoxic challenge. Despite no change in baseline pulmonary artery pressure, all rats treated with SnPP had decreased ratio of right ventricular (RV) weight to left ventricular (LV) plus septal (S) weight (RV/LV + S) compared with saline-treated animals. Echocardiograms suggested dilatation of the RV and decreased RV function in hypoxic SnPP-treated rats. Together these data suggest that inhibition of HO activity and CO production does not exacerbate pulmonary hypertension, but rather that HO and CO may be involved in mediating pulmonary and systemic vasoreactivity to acute hypoxia and hypoxia-induced RV function.

Monocrotaline (MCT), a pyrrolizidine alkaloid plant toxin, is known to cause pulmonary hypertension (PH) in rats. Recent findings suggest that pulmonary inflammation may play a significant role in the pathogenesis in MCT-induced PH. Heme oxygenase-1 (HO-1), the rate-limiting enzyme in heme catabolism, is known to be induced by various oxidative stresses, including inflammation and free heme, and its induction is thought essential in the protection against oxidative tissue injuries. In this study, we examined expression of HO-1 as well as non-specific delta-aminolevulinate synthase (ALAS1), the rate-limiting enzyme in heme catabolism and biosynthesis, respectively, in a rat model of PH produced by subcutaneous injection of MCT (60 mg/kg). MCT treatment caused infiltration of inflammatory cells, fibrosis of the interstitium, and pulmonary arterial wall thickening with marked elevation of right ventricular (RV) pressure, which are characteristics of MCT-induced PH. Gene expression of tumor necrosis factor-alpha (TNF-alpha) as well as DNA binding activity of nuclear factor-kappaB (NF-kappaB) increased at 1 week after MCT treatment, reached a maximum at 2 weeks, and then decreased to the pretreatment level at 3 weeks. HO-1 expression was markedly increased at 1 week, and continued to increase by 3 weeks following MCT treatment, both at transcriptional and protein levels in the mononuclear cells in the lung. ALAS1 mRNA levels in the lung also significantly increased at 2 weeks after MCT treatment. These findings suggest that pulmonary HO-1 expression was presumably induced by proinflammatory cytokine(s) in MCT-treated rats, resulting in the derepression of heme-repressible ALAS1 expression, and that HO-1 induction plays a significant role as an inflammatory factor in this condition.

BACKGROUND: Simvastatin has been shown to ameliorate pulmonary hypertension by several mechanisms in experimental animal models. In this study, we hypothesized that the major benefits of simvastatin in pulmonary hypertension occur via the heme oxygenase-1 pathway. METHODS: Simvastatin (10 mg/kgw/day) was tested in two rat models of pulmonary hypertension (PH): monocrotaline administration and chronic hypoxia. The hemodynamic changes, right heart hypertrophy, HO-1 protein expression, and heme oxygenase (HO) activity in lungs were measured in both models with and without simvastatin treatment. Tin-protoporphyrin (SnPP, 20 micromol/kg w/day), a potent inhibitor of HO activity, was used to confirm the role of HO-1. RESULTS: Simvastatin significantly ameliorated pulmonary arterial hypertension from 38.0 +/- 2.2 mm Hg to 22.1 +/- 1.9 mm Hg in monocrotaline-induced PH (MCT-PH) and from 33.3 +/- 0.8 mm Hg to 17.5 +/- 2.9 mm Hg in chronic hypoxia-induced PH (CH-PH) rats. The severity of right ventricular hypertrophy was significantly reduced by simvastatin in MCT-PH and CH-PH rats. Co-administration with SnPP abolished the benefits of simvastatin. Simvastatin significantly increased HO-1 protein expression and HO activity in the lungs of rats with PH; however co-administration of SnPP reduced HO-1 activity only. These observations indicate that the simvastatin-induced amelioration of pulmonary hypertension was directly related to the activity of HO-1, rather than its expression. CONCLUSION: This study demonstrated that simvastatin treatment ameliorates established pulmonary hypertension primarily through an HO-1-dependent pathway.

BACKGROUND: Acute pulmonary embolism (PE) causes pulmonary hypertension (PH) via several mechanisms including pulmonary vasospasm. We hypothesize that PE with associated PH leads to alterations in plasma protein concentrations indicative of disease severity and prognosis. OBJECTIVE: To identify plasma proteins altered in abundance by PE in rats. METHODS: Plasma samples were obtained from rats at 2, 6 and 18 h after experimental PE produced with intrajugular injection of polystyrene beads at three different levels of severity (mild, moderate and severe). Total plasma protein was separated using two-dimensional sodium dodecylsulfate-polyacrylamide gel electrophoresis (2D SDS-PAGE) and candidate protein spots altered in expression by PE were identified by mass spectroscopy. Haptoglobin identity and amount was verified by western blot analysis. RESULTS: The PE model produced a dose-dependent increase in right ventricular systolic pressure (RVSP) (mmHg) at 2 h: mild 39+/-1.7, moderate 40+/-1.8 and severe 51+/-1.3 mmHg, coincident with significant increases in free plasma (hemoglobin). Combined 2D SDS-PAGE and Western blot analysis indicated time- and dose-dependant loss of plasma haptoglobin levels in response to acute PE. Haptoglobin (HP) was essentially absent from plasma within 2 h of severe PE. Clearance of HP from plasma was accompanied by increased expression of heme oxygenase-1 (hmox1) in peripheral blood leukocytes and in HMOX1 enzyme activity in the liver. CONCLUSIONS: PE that causes pulmonary hypertension is associated with haptoglobin depletion and up-regulation of HMOX1 enzyme.