Cytoprotective role of heme oxygenase-1 and heme degradation derived end products in liver injury

The activation of heme oxygenase-1 (HO-1) appears to be an endogenous defensive mechanism used by cells to reduce inflammation and tissue damage in a number of injury models. HO-1, a stress-responsive enzyme that catabolizes heme into carbon monoxide (CO), biliverdin and iron, has previously been shown to protect grafts from ischemia/reperfusion and rejection. In addition, the products of the HO-catalyzed reaction, particularly CO and biliverdin/bilirubin, have been shown to exert protective effects in the liver against a number of stimuli, as in chronic hepatitis C and in transplanted liver grafts. Furthermore, the induction of HO-1 expression can protect the liver against damage caused by a number of chemical compounds. More specifically, the CO derived from HO-1-mediated heme catabolism has been shown to be involved in the regulation of inflammation; furthermore, administration of low concentrations of exogenous CO has a protective effect against inflammation. Both murine and human HO-1 deficiencies have systemic manifestations associated with iron metabolism, such as hepatic overload (with signs of a chronic hepatitis) and iron deficiency anemia (with paradoxical increased levels of ferritin). Hypoxia induces HO-1 expression in multiple rodent, bovine and monkey cell lines, but interestingly, hypoxia represses expression of the human HO-1 gene in a variety of human cell types (endothelial cells, epithelial cells, T cells). These data suggest that HO-1 and CO are promising novel therapeutic molecules for patients with inflammatory diseases. In this review, we present what is currently known regarding the role of HO-1 in liver injuries and in particular, we focus on the implications of targeted induction of HO-1 as a potential therapeutic strategy to protect the liver against chemically induced injury.     

The role of heme oxygenase-1 in systemic-onset juvenile idiopathic arthritis

Abstract

We have determined the serum levels of heme oxygenase-1 (HO-1) in 56 patients with systemic-onset juvenile idiopathic arthritis (s-JIA) and compared these with serum HO-1 levels in healthy controls and patients with other pediatric rheumatic diseases. Serum HO-1 levels were measured by the sandwich enzyme-linked immunosorbent assay. The mean serum HO-1 level in s-JIA patients during the active phase was 123.6 ± 13.83 ng/ml, which was significantly higher than that in patients with polyarticular juvenile idiopathic arthritis (p-JIA), Kawasaki disease, systemic lupus erythematosus or mixed connective tissue disease (P < 0.0005). The serum levels of HO-1, cytokines and cytokine receptors in patients with s-JIA were also assessed at both the active and inactive phases. The serum HO-1 level in patients with s-JIA in the active phase was found to be significantly greater than that in patients with the disease in the inactive phase (P < 0.0001). An assessment of the relationships between serum HO-1 levels and other laboratory parameters or cytokines in patients with s-JIA did not reveal any strong correlations. These results suggest that the serum level of HO-1 may be a useful marker for the differential diagnosis of s-JIA. Further study will be necessary to elucidate the mechanism of HO-1 production and to clarify the role of HO-1 in the disease process.     

The role of heme oxygenase-1 in systemic-onset juvenile idiopathic arthritis

We have determined the serum levels of heme oxygenase-1 (HO-1) in 56 patients with systemic-onset juvenile idiopathic arthritis (s-JIA) and compared these with serum HO-1 levels in healthy controls and patients with other pediatric rheumatic diseases. Serum HO-1 levels were measured by the sandwich enzyme-linked immunosorbent assay. The mean serum HO-1 level in s-JIA patients during the active phase was 123.6 ± 13.83 ng/ml, which was significantly higher than that in patients with polyarticular juvenile idiopathic arthritis (p-JIA), Kawasaki disease, systemic lupus erythematosus or mixed connective tissue disease (P < 0.0005). The serum levels of HO-1, cytokines and cytokine receptors in patients with s-JIA were also assessed at both the active and inactive phases. The serum HO-1 level in patients with s-JIA in the active phase was found to be significantly greater than that in patients with the disease in the inactive phase (P < 0.0001). An assessment of the relationships between serum HO-1 levels and other laboratory parameters or cytokines in patients with s-JIA did not reveal any strong correlations. These results suggest that the serum level of HO-1 may be a useful marker for the differential diagnosis of s-JIA. Further study will be necessary to elucidate the mechanism of HO-1 production and to clarify the role of HO-1 in the disease process.     

Antioxidant role of heme oxygenase-1 in prehepatic portal hypertensive rats

AIM: To study the effect of bilirubin on the oxidative liver status and the activity and expression of heme oxy-genase-1 (HO-1) in rat liver injury induced by prehepatic portal hypertension. METHODS: Wistar male rats, weighing 200-250 g, were divided at random into two groups: one group with prehepatic portal hypertension (PH) induced by regulated prehepatic portal vein ligation (PPVL) and the other group corresponded to sham operated rats. Portal pressure, oxidative stress parameters, antioxidant enzymes, HO-1 activity and expression and hepatic sinusoidal va-sodilatation were measured. RESULTS: In PPVL rats oxidative stress was evidenced by a marked increase in thiobarbituric acid reactive substances (TBARS) content and a decrease in reduced glutathione (GSH) levels. The activities of liver antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) were also diminished while activity and expression of HO-1 were enhanced. Administration of bilirubin (5μmol/kg body weight) 24 h before the end of the experiment entirely prevented all these effects. Pretreatment with Sn-pro-toporphyrin IX (Sn-PPIX) (100μg/kg body weight, i.p.), a potent inhibitor of HO, completely abolished the oxidative stress and provoked a slight decrease in liver GSH levels as well as an increase in lipid peroxidation. Besides, carbon monoxide, another heme catabolic product, induced a significant increase in sinusoidal hepatic areas in PPVL group. Pretreatment of PPVL rats with Sn-PPIX totally prevented this effect. CONCLUSION: These results suggest a beneficial role of HO-1 overexpression in prehepatic portal hypertensive rats.     

Dr H C Bastian, scientific Jekyll and Hyde

The neurological library of S A Kinnier Wilson, now in the Royal College of Physicians of Edinburgh, contains two books by Henry Charlton Bastian. Various forms of hysterical or functional paralysis (1893) is inscribed "To Dr Wilson by the Author, July 1906". Wilson was Bastian's house-physician at the time. The second book, given to Wilson's son by Bastian's daughter in 1940, is a lavishly illustrated tome, Studies in heterogenesis (1903). The two books testify to a scientific Jekyll and Hyde--one of the founders of neurology and a wildly unorthodox biologist.     

血红素氧合酶-1在脂肪性肝病中的作用及其机制的研究进展

血红素氧合酶-1(HO-1)是一种可诱导的抗氧化酶,在多种慢性肝病的发病过程中表达增强而发挥抗氧化应激、抗凋亡、抗炎、抗纤维化等保护肝细胞的作用。但有关HO-1与脂肪性肝病发病过程关系的研究相对较少。此文总结近年文献报道的HO-1与非酒精性脂肪性肝病及酒精性肝病发病和进展关系的研究,探讨HO-1阻止脂肪性肝病发生及进展的作用机制,为化学药物干预或腺病毒基因导入等方法靶向性激活HO-1基因治疗脂肪性肝病的研究提供理论依据。     

EGb761诱导血红素加氧酶-1在肺缺血再灌注损伤中的抗凋亡作用

目的 探讨银杏叶提取物EGb761诱导血红素加氧酶-1(HO-1)在肺缺血再灌注损伤中的抗凋亡作用.方法 40只健康SD大鼠随机分为4组:对照组(Sham组,不阻断右肺门)、缺血/再灌注组(I/R组,阻断右肺门30 min再灌注2 h),EGb761组(术前给予EGb761腹腔注射)、锌原卟啉组(Znppix组,术前给予EGb761及术中给予HO-1抑制剂Znppix干预).采用蛋白免疫印迹法(Western blot)检测肺组织HO-1蛋白、磷酸化JNK蛋白及Bcl-2蛋白表达;DNA原位末端标记(TUNEL)法测定肺组织细胞凋亡指数.结果 EGb761组HO-1表达灰度比值较I/R组与Sham组均升高(3.257±0.432 vs 1.329±0.310、0.187±0.101,P<0.05).磷酸化JNK1、磷酸化JNK2、Bcl-2蛋白表达灰度比值与细胞凋亡指数在I/R组、EGb761组、Znppix组分别为1.897±0.354、1.674±0.273、0.420±0.093与(14.91±0.49)%,0.681±0.131、0.715±0.116、1.384±0.190与(7.48±0.72)%,1.031±0.201、0.965±0.167、0.621±0.114与(9.01 =0.65)%.与I/R组比较,EGb761组磷酸化JNK蛋白表达下降,Bcl-2蛋白表达增加,细胞凋亡指数下降(P值均<0.05).与EGb761组比较,Znppix组磷酸化JNK蛋白表达增高,Bcl-2蛋白表达下降,细胞凋亡指数增高(P值均<0.05).结论 银杏叶提取物EGb761可诱导HO-1表达,进一步通过抑制JNK蛋白激酶活性及促进Bcl-2表达而在肺缺血再灌注损伤中发挥抗凋亡作用.     

Natural heme oxygenase-1 inducers in hepatobiliary function

Many physiological effects of natural antioxidants, their extracts or their major active components, have been reported in recent decades. Most of these compounds are characterized by a phenolic structure, similar to that of o-tocopherol, and present antioxidant properties that have been demonstrated both in vitro and in vivo. Polyphenors may increase the capacity of endogenous antioxidant defences and modulate the cellular redox state. Changes in the cellular redox state may have wide-ranging consequences for cellular growth and differentiation. The majority of in vitro and in vivo studies conducted so far have attributed the protective effect of bioactive polyphenols to their chemical reactivity toward free radicals and their capacity to prevent the oxidation of important intracellular components. However, in recent years a possible novel aspect inthe mode of action of these compounds has been suggested; that is, the ultimate stimulation of the heme oxygenase-1 （HO-1） pathway is likely to account for the established and powerful antioxidant/anti-inflammatory properties of these polyphenols. The products of the HO-catalyzed reaction, particularly carbon mon- oxide （CO） and biliverdin/bilirubin have been shown to exert protective effects in several organs against oxidative and other noxious stimuli. In this context, it is interesting to note that induction of HO-1 expression by means of natural compounds contributes to protection against liver damage in various experimental models. The focus of this review is on the significance of targeted induction of HO-1 as a potential therapeutic strategy to protect the liver against various stressors in several pathological conditions.     

Bifunctional role for VEGF-induced heme oxygenase-1 in vivo: induction of angiogenesis and inhibition of leukocytic infiltration

Heme-oxygenases (HOs) catalyze the conversion of heme into carbon monoxide and biliverdin. HO-1 is induced during hypoxia, ischemia/reperfusion, and inflammation, providing cytoprotection and inhibiting leukocyte migration to inflammatory sites. Although in vitro studies have suggested an additional role for HO-1 in angiogenesis, the relevance of this in vivo remains unknown. We investigated the involvement of HO-1 in angiogenesis in vitro and in vivo. Vascular endothelial growth factor (VEGF) induced prolonged HO-1 expression and activity in human endothelial cells and HO-1 inhibition abrogated VEGF-driven angiogenesis. Two murine models of angiogenesis were used: (1) angiogenesis initiated by addition of VEGF to Matrigel and (2) a lipopolysaccharide (LPS)-induced model of inflammatory angiogenesis in which angiogenesis is secondary to leukocyte invasion. Pharmacologic inhibition of HO-1 induced marked leukocytic infiltration that enhanced VEGF-induced angiogenesis. However, in the presence of an anti-CD18 monoclonal antibody (mAb) to block leukocyte migration, VEGF-induced angiogenesis was significantly inhibited by HO-1 antagonists. Furthermore, in the LPS-induced model of inflammatory angiogenesis, induction of HO-1 with cobalt protoporphyrin significantly inhibited leukocyte invasion into LPS-conditioned Matrigel and thus prevented the subsequent angiogenesis. We therefore propose that during chronic inflammation HO-1 has 2 roles: first, an anti-inflammatory action inhibiting leukocyte infiltration; and second, promotion of VEGF-driven noninflammatory angiogenesis that facilitates tissue repair.     

The multiple functions of heme oxygenase-1 in the liver

Heme oxygenases (HO) are essential enzymes which degrade heme into carbon monoxide (CO), biliverdin and free iron. Due to its anti-inflammatory, anti-apoptotic and, as recently described, anti-viral properties the inducible HO isoform HO-1 is an important molecule which could find its way into therapy of gastrointestinal diseases. Acute and chronic liver injuries including acute liver failure, alcoholic or viral hepatitis, chronic inflammation, fibrosis, cirrhosis, and hepatocellular carcinoma are life threatening diseases and as a consequence might result in the necessity of liver transplantation. HO-1 as well as its reaction products of heme degradation has been linked to cytoprotection. HO-1 induction in rodent models of acute and chronic hepatic inflammation resulted in improvement of liver damage and down-regulation of pro-inflammatory cytokine levels. Furthermore HO-1 induction interfered with fibrosis progression in mice and partially resolved existing fibrosis. Likewise, HO-1 induction interfered with replication of hepatitis viruses B and C, which frequently are the reason for chronic hepatitis and subsequent tumor growth. Liver transplantation is limited by ischemia/reperfusion (I/R) injury, which is characterized by hypoxia and nutrient deficiency resulting in oxidative stress, apoptosis and immune activation. Induction of HO-1 and application predominantly of CO have been shown to interfere with I/R liver injury and to improve recipient and graft survival. On the other hand HO-1 has been shown to be over-expressed in various tumors, including hepatocellular carcinoma (HCC). Due to its anti-apoptotic properties this bears the risk to promote tumor growth. Anti-apoptotic effects are predominantly mediated by CO. This review aims to summarize beneficial as well as detrimental effects of HO-1 and its products within the liver.     

类叶升麻苷在体内诱导血红素加氧酶-1的表达

目的探讨类叶升麻苷(AS)是否在体内诱导血红素加氧酶-1(HO-1)的表达。方法 AS 12.5 mg/kg和25 mg/kg以腹腔注射的方式给予SD大鼠,在特定时间处死大鼠,取大脑皮层和纹状体组织以及肾脏和肝脏组织。提取组织蛋白,Western印迹方法检测HO-1。结果与正常对照组相比,AS可在皮层和纹状体中剂量依赖性诱导HO-1的表达上调,在外周肾脏和肝脏组织中AS剂量依赖诱导HO-1的表达上调。结论 AS可在体内诱导HO-1的表达。     

Expression of heme oxygenase-1 in ischemic colitis]

BACKGROUND/AIMS: Ischemic colitis is a vascular condition of inadequate blood flow in the colon which leads to colonic inflammation and can cause significant morbidity and mortality. Oxidative stress is an early initiating event in ischemia and reperfusion injury. Heme oxygenase (HO) is considered to be an antioxidant enzyme that catabolizes heme to carbon monoxide, free iron and biliverdin. The aim of this study was to evaluate the expression patterns of HO-1, inducible form of HO, in ischemic colitis. METHODS: We analyzed the twelve cases of clinically and pathologically diagnosed ischemic colitis without surgical intervention compared with normal colon (n=10) and psedomembranous colitis (n=5). Immunohistochemical stainings for HO-1 were performed in paraffin-embedded tissues. RESULTS: The age of the patients ranged from 56 to 84 years (mean: 67 years) in ischemic colitis. Eight patients (66.7%) were female. The most common presenting symptom was bloody stool (66.7%) and rectosigmoid area (91.7%) of the large intestine was the most common ischemic site. Expression of HO-1 in ischemic colitis was high in contrast to normal colonic mucosa or psedomembranous colitis. CONCLUSIONS: Ischemic colitis usually involves the rectosigmoid area in elderly female patients with a history of bloody stool. High expression of HO-1 in ischemic colitis may be responsible for a protective mechanism to ischemia or heme injury.     

血红素氧合酶-1与心血管疾病研究

血红素氧合酶-1(HO-1)是血红素氧合酶的诱导型,能催化血红素分解生成CO、胆红素和铁.这三种代谢产物通过多种机制对心血管系统产生保护作用,包括抗氧化应激、抗炎症损伤、抗细胞增殖、抗凋亡、抑制血小板聚集、调节血管张力及参与细胞内信号传递等.HO-1在多种心血管疾病中均有适应性表达,并在防治这些心血管疾病方面发挥重要作用.