血红素加氧酶-1在肺早期缺血再灌注损伤中的表达及意义

目的研究血红素加氧酶-1（HO-1）与供肺缺血再灌注损伤之间的关系。方法采用改进的套管吻合技术，建立同系大鼠左肺原位再灌注损伤的动物模型。采用HO-1的诱导剂钴原卟啉（CoPP）和抑制剂锌原卟啉（ZnPP）分别进行干预处理后，运用免疫组织化学技术和RT-PCR技术分别检测HO-1蛋白在供肺组织中的表达以及供肺中HO-1mRNA的表达；运用TUNEL技术检测供肺组织中细胞凋亡。结果肺组织发生缺血再灌注时可诱导HO-1蛋白的表达，且随着再灌注时间的延长，表达逐步增多，再灌注8 h后达到高峰；再灌注前使用CoPP进行预处理，可以诱导HO-1蛋白的表达上调。HO-1蛋白表达上调可以降低肺缺血再灌注后细胞凋亡的发生率。结论肺缺血再灌注损伤可诱导HO-1表达上调，CoPP诱导的HO-1过表达可以抑制肺缺血再灌注损伤诱导的肺细胞凋亡，从而减轻供肺的再灌注损伤。     

Biliverdin IX is an endogenous inhibitor of soluble guanylyl cyclase

Heme oxygenase (HO) converts heme to carbon monoxide (CO) and biliverdin IX. CO is a weak activator of soluble guanylyl cyclase (SGC), the enzyme that catalyzes the conversion of GTP to the second messenger cGMP. HO overexpression has recently been shown to inhibit production of cGMP by SGC in vivo. The aim of the present study was to investigate a possible influence of biliverdin IX on SGC activity. Using recombinant alpha(1)/beta(1) isoform of SGC, we show an inhibitory effect of biliverdin IX in the micromolar range both on basal and NO stimulated guanylyl cyclase activity. Bilirubin IX which differs from biliverdin IX in two hydrogen atoms had no effect. Biliverdin IX reduced maximal guanylyl cyclase activity (V(max) values) while it had no effect on the K(M) values indicating unchanged affinity towards the substrate GTP. Concentration response experiments using the NO donor, 2,2-diethyl-1-nitroso-oxyhydrazine (DEA/NO), showed that enzyme activities at maximal DEA/NO concentration were reduced by biliverdin IX. The affinity of the NO-donor, DEA/NO, towards SGC was significantly reduced in the presence of biliverdin IX. Biliverdin IX lowered enzyme activity at maximal activator concentrations of YC-1 and protoporphyrin IX (PPIX) while it had no significant effect on the EC(50) values of these two NO independent activators. The inhibitory effect of biliverdin IX on PPIX activated enzyme activity is not shared by ODQ, which indicates that the inhibitory mechanism of biliverdin IX is different from ODQ.     

Inhibitors of nitric oxide synthase block carbon monoxide-induced increases in cGMP in retina

We investigated the changes in glutamate release from the ipsi- and contra-lesional medial vestibular nucleus (MVN) following unilateral labyrinthectomy (UL) by in vivo microdialysis study. The concentration of glutamate in the ipsi-lesional MVN was decreased until 4 h. Twelve hours after UL, the concentration of glutamate was restored back to the basal level, after which the release did not show any change between 24 and 48 h post-UL. In contrast, the concentration of glutamate in the contra-lesional MVN, which increased immediately after UL, decreased gradually to the basal level until 3-4 h post-UL, followed by no further change. The difference in the glutamate concentration between ipsi- and contra-lesional MVN increased immediately after UL and gradually decreased accompanied by a reduction in the frequency of nystagmus, although spontaneous nystagmus had not disappeared by the time the imbalance of glutamate release diminished. These results suggest that the imbalance of glutamate release between bilateral nuclei induced the nystagmus, and the change in release is concerned with the rapid development of vestibular compensation.     

Myelin basic protein induces heme oxygenase-1 in human astroglial cells.

Heme oxygenase-1 (HO-1), also known as heat-shock protein 32 (HSP-32), is induced in many cells by a large variety of stimuli. Its induction in nervous system cells following toxic and oxidative stress was suggested to play a protective role. Its presence was recently detected by immunohistochemical studies at the level of inflammatory lesions of rat experimental autoimmune encephalomyelitis. In the present study, we demonstrate that myelin basic protein (MBP) induces HO-1 in human astroglial cells, as shown by Western blots and RT-PCR. Proteolytic fragments derived from the whole MBP show a different behavior in the HO-1 induction: MBP152-167 was able to produce a light but still significant increase in HO-1 mRNA and protein levels, whereas MBP68-84 was not. The increase in HO-1 production seems to be mediated by a Ca(2+)-dependent mechanism, since MBP addition to astrocytoma cultures induced a strong and immediate increment of [Ca(2+)](i) increase; MBP152-167 elicited a delayed and less pronounced [Ca(2+)](i) increase; no [Ca(2+)](i) changes were induced following cell treatment with MBP68-84. NO pathway involvement in the induction of HO-1 by MBP was ruled out since the expression of the inducible isoform of nitric oxide synthase was not upregulated in treated cells, neither nitrite levels were modified, as demonstrated by Greiss reaction. The possible significance of HO-1 induction following MBP stimulation is discussed.     

Catecholamine-induced oligodendrocyte cell death in culture is developmentally regulated and involves free radical generation and differential activation of caspase-3

Oligodendrocyte cultures were used to study the toxic effects of catecholamines. Our results showed that catecholamine-induced toxicity was dependent on the dose of dopamine or norepinephrine used and on the developmental stage of the cultures, with oligodendrocyte progenitors being more vulnerable. A role for oxidative stress and apoptosis on the mechanism of action of catecholamines on oligodendrocyte cell death was next assessed. Catecholamines caused a reduction in intracellular glutathione levels, an accumulation in reactive oxygen species and in heme oxygenase-1, the 32 kDa stress-induced protein. All these changes were prevented by N-acetyl-L-cysteine, a thiocompound with antioxidant activity and a precursor of glutathione, and were more pronounced in progenitors than mature cells, which could contribute to their higher susceptibility. Apoptotic cell death, as assessed by activation of caspase-9 and -3 and cleavage of poly(ADP-ribose) polymerase (a substrate of caspase-3), was only observed in oligodendrocyte progenitors. Pretreatment with zVAD, a general caspase inhibitor, prevented activation of caspase-9 and -3, DNA fragmentation, and decreased progenitors cell death. Furthermore, the expression levels of procaspase-3 and the ratio of the proapoptotic protein bax to antiapoptotic protein bcl-xl were several folds higher in immature than mature oligodendrocytes. Taken together, these results strongly suggest that the catecholamine-induced cytotoxicity in oligodendrocytes is developmentally regulated, mediated by oxidative stress, and have characteristics of apoptosis in progenitor cells.     

Heme oxygenase‐1: a new drug target in oxidative tissue injuries in critically ill conditions

Oxidative stresses associated with ischemia/reperfusion, neutrophil activation, and anesthesia with certain volatile agents, etc., are thought to play an important role in the development of acute organ failure in critical illnesses, such as acute lung injury, acute coronary artery insufficiency, acute liver failure, acute renal failure, and multiple organ dysfunction syndrome. Such oxidative stressors provoke a set of cellular responses, particularly those that participate in the defense against tissue injuries. Free heme, which can be rapidly released from hemeproteins, may constitute a major threat in the oxidant stress because it catalyzes the formation of reactive oxygen species. To counteract such insults, cells respond by inducing the 33‐kDa heat shock protein, heme oxygenase (HO)‐1, the rate‐limiting enzyme in heme degradation. Induced HO‐1 as such removes free heme by an enzymatic process. In addition, HO‐1 induction itself confers protection to tissues from further oxidative injuries. In contrast, the abrogation of HO‐1 induction, or chemical ablation of HO activity abolishes the beneficial effect of HO‐1, and results in the aggravation of tissue injuries. In this article, we review recent advances in the essential role of HO‐1 in tissue protection in various models of experimental oxidative tissue injuries as well as in human disorders, which is related to critically ill conditions, with special emphasis on the role of its induction in tissue defense and its potential therapeutic implications. Drug Dev. Res. 67:130–153, 2006. © 2006 Wiley‐Liss, Inc.     

血红素氧合酶-CO-cGMP通路在体外培养人眼小梁细胞中的表达

目的 探讨体外培养人眼小梁细胞是否存在血红素氧合酶（HO）-一氧化碳（CO）-环磷酸鸟苷（cGMP）通路以及氯化血红素（hemin）对其的诱导作崩。方法 应用RT-PCR和免疫组织化学方法检测体外培养人眼小梁细胞中HO-1和HO-2 mRNA及蛋白的表达。向细胞培养液中加入氯化血红素，RT-PCR检测小梁细胞HO-1 mRNA，分光光度法检测培养上清液中碳氧血红蛋白（HbCO）浓度，并用放射免疫法检测细胞中cGMP浓度。结果 体外培养人眼小梁细胞存在HO-1和HO-2 mRNA及蛋白。氯化IffL红素对小梁细胞HO-1 mRNA、HbCO和cGMP浓度的诱导呈浓度依赖性。结论 人眼小梁细胞存在HO-CO-cGMP通路，并受氯化血红素诱导。药理诱导这一通路，可能为青光眼的治疗提供一个有效的新方法。     

2型糖尿病患者外周血单核细胞中血红素氧化酶-1表达及其与颈动脉内膜早期粥样斑块厚度的关系

[论文特点介绍]本研究用RT-PCR技术探讨2型糖尿病（T2DM）患者外周血单核细胞中血红素氧化酶（HO）-1的表达情况，同时评价HO-1表达与颈动脉内膜中层厚度（IMT）的相关性，从临床角度评价氧化应激在糖尿病及其并发症中的作用。