Involvement of reactive oxygen species in cardiac preconditioning in rats

To date, the involvement of reactive oxygen species in ischemic preconditioning in vivo in rats is not clearly demonstrated. The aim of the present study was to determine whether N-(2-mercaptopropionyl)glycine (MPG), a cell-diffusible hydroxyl radical scavenger, and carnosine, a potent singlet oxygen quencher, could block protection afforded by a single cycle of ischemic preconditioning in vivo in the rat. An ESR study was first performed to validate in vitro the specific antioxidant properties of carnosine and MPG. In a second set of experiments, open-chest rats were subjected to 30 min of left coronary occlusion followed by 60 min of reperfusion. Preconditioning was elicited by 5 min of ischemia and 5 min of reperfusion. Neither MPG (1-h infusion, 20 mg/kg) nor carnosine injection (bolus, 25 micro mol/rat) affected infarct size. The infarct size-limiting effect of preconditioning was completely blunted by MPG, whereas carnosine did not alter the cardioprotection. It is concluded that free radicals and especially hydroxyl radicals could be involved in the adaptive mechanisms induced by a single cycle of preconditioning in vivo in rats.     

Role of reactive oxygen species and protein kinase C in ischemic tolerance in the brain

It is now understood that the mechanisms leading to neuronal cell death after cerebral ischemia are highly complex. A well established fact in this field is that neurons continue to die over days and months after ischemia, and that reperfusion following cerebral ischemia contributes substantially to ischemic injury. It is now well accepted that central to ischemic/reperfusion-induced injury is what occurs to mitochondria hours to days following the ischemic insult. For many years, it has been established that reactive oxygen species (ROS) and reactive nitrogen species (RNS) promote lipid, protein, and DNA oxidation that affects normal cell physiology and eventually leads to neuronal demise. In addition to oxidation of neuronal molecules by ROS and RNS, a novel pathway for molecular modifications has risen from the concept that ROS can activate specific signal transduction pathways that, depending on the insult degree, can lead to either normal plasticity or pathology. Two examples of these pathways could explain why lethal ischemic insults lead to the translocation of protein kinase Cdelta (deltaPKC), which plays a role in apoptosis after cerebral ischemia, or why sublethal ischemic insults, such as in ischemic preconditioning, lead to the translocation of epsilonPKC, which plays a pivotal role in neuroprotection. A better understanding of the mechanisms by which ROS and/or RNS modulate key protein kinases that are involved in signaling pathways that lead to cell death and survival after cerebral ischemia will help devise novel therapeutic strategies.     

活性氧在大鼠心肌细胞低氧预适应中的作用

目的 探讨活性氧在心肌细胞低氧预适应过程中的作用机制。方法 建立SD乳鼠心肌细胞的低氧预适应模型;检测不同阶段超氧阴离子和H2O2含量以及T-SOD、Cu,Zn-SOD和Mn-SOD活性变化,分析活性氧在低氧预适应不同窗口期的作用。结果 （1）超氧阴离子和过氧化氢均能明显提高心肌细胞在第一窗口期低氧1h后的存活率（P〈0．05）;（2）超氧阴离子可明显升高心肌细胞第二窗口期低氧1h后的存活率（P〈0．05）,而过氧化氢作用不明显;（3）低氧预适应可使超氧阴离子和过氧化氢含量明显升高,同时伴有第一窗口期Cu、Zn-SOD活性及第二窗口期Mn-SOD活性显著升高（P〈0．05）。结论 说明低氧预适应可提高大鼠心肌细胞在不同窗口期对长时间缺氧的耐受性,其作用机制可能与活性氧及SOD有密切关系。     

活性氧在宫颈癌形成中的作用

活性氧是需氧细胞在代谢过程中产生的,当活性氧累积过多时会对细胞造成伤害,产生氧化应激。机体有自身的一套抗氧化应激系统,保护细胞免受损伤。随着活性氧研究的不断深入,它在肿瘤发生发展过程中的重要作用已被证实,体内活性氧与抗氧化应激系统的失衡是肿瘤形成的关键因素。宫颈癌作为一种妇科常见的恶性肿瘤,其形成机制尚不明了。近年来,活性氧在宫颈癌形成中的临床研究和体外研究成为国内外学者探讨的热点。      

Role of reactive oxygen species in skin carcinogenesis

Reactive oxygen species (ROS) are associated not only with initiation, but also with promotion and progression in the multistage carcinogenesis model. In the present review, we will focus on the involvement of ROS in skin carcinogenesis, especially that induced by ultraviolet (UV) radiation. UV-specific DNA damage has been well studied thus far. However, recent reports have revealed the previously unknown participation of oxidative stress in UV-induced skin carcinogenesis. Indeed, in addition to transition-type mutations at dipyrimidine sites, G:C to T:A transversions, which may be induced by the presence of 8-oxoguanine during DNA replication, are frequently observed in the ras oncogene and p53 tumor suppressor gene in human skin cancers of sun-exposed areas and in UV-induced mouse skin cancers. Recent studies have shown that not only UV-B, but also UV-A is involved in UV-induced carcinogenesis. A wide variety of biological phenomena other than direct influence by UV, such as inflammatory and immunological responses and oxidative modifications of DNA and proteins, appear to play roles in UV-induced skin carcinogenesis. Furthermore, it has become clear that genetic diseases such as xeroderma pigmentosum show deficient repair of oxidatively modified DNA lesions. The involvement of ROS in skin carcinogeneisis caused by arsenic and chemical carcinogens will also be discussed.     

活性氧在脊髓损伤中的作用

脊髓损伤(spinal cord injury，SCI)治疗的实验性研究在18世纪就已经开始，研究者发现兴奋性毒性、Ca2+超载、神经元凋亡与氧化应激参与了神经损伤病理过程。近期研究中活性氧学说在脊髓损伤中的作用越来越受到研究者的重视，并有研究表明线粒体呼吸链、炎症反应中的呼吸爆发等多种途径参与了SCI后活性氧生成。本文在阐述活性氧生物学作用的同时，并结合近年来以活性氧为靶点的SCI治疗策略做一小结。     

血红素氧化酶-1在离体大鼠心肌缺血预处理中的作用

目的：观察缺血预处理对离体大鼠心肌缺血再灌注后心功能、乳酸脱氢酶（LDH）活性和丙二醛（MDA）含量及血红素氧化酶-1活性的影响。方法：应用Langendorff离体大鼠等容收缩灌流模型行离体大鼠心脏灌流。缺血预处理方案为停灌5 min后再灌5 min反复3次,持续缺血再灌方案为停灌40 min后再灌20 min,监测正常对照组、缺血再灌组（IR）和缺血预处理组（IPC）心功能指标的同时,测定冠脉流出液LDH活性、心肌MDA含量和HO-1活性变化。结果：IPC组再灌20 min时的心功能恢复率显著高于IR组（P<0.01）,心肌血红素氧化酶-1活性也明显高于IR组（P<0.05）,而LDH活性及MDA含量显著少于IR组（均为P<0.01）。结论：血红素氧化酶-1活性增高可能与缺血预处理对大鼠缺血再灌心肌的保护作用有关。     

Role of insulin-induced reactive oxygen species in the insulin signaling pathway

Oxidants, including hydrogen peroxide (H2O2), have been recognized for years to mimic insulin action on glucose transport in adipose cells. Early studies also demonstrated the complementary finding that H2O2 was elaborated during treatment of cells with insulin, suggesting that cellular H2O2 generation was integral to insulin signaling. Recently, reactive oxygen species elicited by various hormones and growth factors have been shown to affect signal transduction pathways in various cell types. We recently reported that insulin-stimulated H2O2 modulates proximal and distal insulin signaling, at least in part through the oxidative inhibition of protein tyrosine phosphatases (PTPases) that negatively regulate the insulin action pathway. Nox4, a homologue in the family of NADPH oxidase catalytic subunits, was found to be prominently expressed in insulin-sensitive cells. By various molecular approaches, Nox4 was shown to mediate insulin-stimulated H2O2 generation and impact the insulin signaling cascade. Overexpression of Nox4 also significantly reversed the inhibition of insulin-stimulated receptor tyrosine phosphorylation by PTP1B, a widely expressed PTPase implicated in the negative regulation of insulin signaling, by inhibiting its catalytic activity. These recent studies have provided insight into Nox4 as a novel molecular link between insulin-stimulated reactive oxygen species and mechanisms involved in their modulation of insulin signal transduction.     

Role of reactive oxygen species in vascular remodeling associated with pulmonary hypertension

Several manifestations of neonatal pulmonary hypertension are associated with vascular remodeling, resulting in increased muscularity of the small pulmonary arteries. Abnormal structural development of the pulmonary vasculature has been implicated in persistent pulmonary hypertension of the newborn (PPHN). Increased plasma levels of the vasoconstrictor endothelin-1 (ET-1) have been demonstrated in patients with PPHN, which is likely to contribute to hypertension. In addition, several studies have identified a role for ET-1 in the proliferation of vascular smooth muscle cells (SMCs), suggesting that ET-1 may also be involved in the vascular remodeling characteristic of this disease. However, the mechanisms of ET-1-induced SMC proliferation are unclear and appear to differ between cells from different origins within the vasculature. In SMCs isolated from fetal pulmonary arterial cells, ET-1 stimulated proliferation via an induction of reactive species (ROS). Furthermore, other lines of evidence have demonstrated the involvement of ROS in ET-1-stimulated SMC growth, suggesting that ROS may be a common factor in the mechanisms involved. This review discusses the potential roles for ROS in the abnormal pulmonary vascular development characteristic of PPHN, and the treatment strategies arising from our increasing knowledge of the molecular mechanisms involved.     

Role of neutrophil-derived reactive oxygen species for host defense and inflammation

Neutrophil accumulation is a critical event in the pathogenesis of inflammation. The generation of hypochlorous acid by myeloperoxidase (MPO) in neutrophils is crucial to the host defense response. MPO-deficient (MPO-KO) mice showed severely reduced cytotoxicity to Candida albicans, Aspergillus fumigatus, Cryptococcus neoformans and other microorganisms, demonstrating that an MPO-dependent oxidative system is important for in vivo host defense against fungi. On the other hand, impaired reactive oxygen species (ROS) production by neutrophils has previously been shown to cause an abnormal inflammatory response. In the present study, we have found that MPO-KO mice exhibit more severe pulmonary inflammation than wild-type mice when challenged with an intranasal administration of zymosan. In addition to measuring the kinetics of neutrophil accumulation, we also measured the production of macrophage inflammatory protein-2 (MIP-2) in the lung, and we correlate the degree of neutrophil accumulation with the production of this mediator. Our results demonstrate that MPO regulates the production of MIP-2, which may modulate neutrophil accumulation during lung inflammation.     

Remote vs. local ischaemic preconditioning in the rat heart: infarct limitation,suppression of ischaemic arrhythmia and the role of reactive oxygen species

The unmet clinical need for myocardial salvage during ischaemia–reperfusion injury requires the development of new techniques for myocardial protection. In this study the protective effect of different local ischaemic preconditioning (LIPC) and remote ischaemic preconditioning (RIPC) protocols was compared in the rat model of myocardial ischaemia–reperfusion, using infarct size and ischaemic tachyarrhythmias as end‐points. In addition, the hypothesis that there is involvement of reactive oxygen species (ROS) in the protective signalling by RIPC was tested, again in comparison with LIPC. The animals were subjected to 30‐min coronary occlusion and 90‐min reperfusion. RIPC protocol included either transient infrarenal aortic occlusion (for 5, 15 and 30 min followed by 15‐min reperfusion) or 15‐min mesenteric artery occlusion with 15‐min reperfusion. Ventricular tachyarrhythmias during test ischaemia were quantified according to Lambeth Conventions. It was found that the infarct‐limiting effect of RIPC critically depends on the duration of a single episode of remote ischaemia, which fails to protect the heart from infarction when it is too short or, instead, too prolonged. It was also shown that RIPC is ineffective in reducing the incidence and severity of ischaemia‐induced ventricular tachyarrhythmias. According to our data, the infarct‐limiting effect of LIPC could be partially eliminated by the administration of ROS scavenger N‐2‐mercaptopropionylglycine (90 mg/kg), whereas the same effect of RIPC seems to be independent of ROS signalling.     

Role of reactive oxygen species in contraction-mediated glucose transport in mouse skeletal muscle

Studies from our laboratory and others show that oestrogen reduces angiotensin II (Ang II)-induced water intake by ovariectomized rats. Elimination of endogenous oestrogen by ovariectomy causes weight gain that can be reversed or prevented by oestrogen replacement. Changes in body weight modify cardiovascular responses to Ang II but whether such changes have similar effects on central and behavioural responses to Ang II is unknown. The goal of this study was to evaluate the contributions of oestrogen and weight loss to isoproterenol (isoprenaline; Iso)-induced Fos immunoreactivity (IR) and to angiotensin type 1 (AT1) receptor mRNA in forebrain regions implicated in the control of fluid balance. Isoproterenol significantly increased Fos IR in the hypothalamic paraventricular and supraoptic nuclei, the subfornical organ (SFO), and the organum vasculosum of the lamina terminalis, but had no effect on AT1 mRNA expression. However, both Iso-induced Fos IR and the AT1 mRNA were attenuated in the SFO of the oestrogen and weight loss groups compared with that of the control group. Consequently, we examined the effect of weight loss on Iso-induced water intake and plasma renin activity (PRA) and found that weight loss decreased water intake after Iso, but had no effect on PRA. Thus, we propose that weight loss decreases Ang II-elicited water intake in the female rat by down-regulating the expression of the AT1 receptor.     

Role of Rac-GTPase and reactive oxygen species in cardiac differentiation of stem cells

In the life of a cell, there is a constant balance between generation of reactive oxygen species (ROS) and activity of antioxidant defense mechanisms. Besides the damaging effects of ROS on many biomolecules, ROS also play a significant role in signal transduction pathways of growth factors suggesting a role of oxidative species in cell differentiation. ROS have recently been involved in the process of cardiac differentiation of stem cells. Several molecular mechanisms, including ones mediated by the GTPase Rac that underlie the regulatory role of ROS in the process of stem cell differentiation toward a cardiac lineage, are reviewed.     

Targeting reactive oxygen species in hypertension

Oxidative stress plays an important role in the pathogenesis of hypertension. A number of sources of reactive oxygen species have been identified including NADPH oxidase, endothelial NO synthase, and xanthine oxidase. Inhibitors of these systems reduce blood pressure in experimental models. Targeted overexpression of antioxidant systems and interference with expression of oxidant systems has also been successfully used in animal models of hypertension. It is expected that these strategies will eventually be translated to human disease, but currently, the specificity and toxicity of such measures are not yet fulfilling quality criteria for treatment of humans. In the meantime, presumably nontoxic measures, such as administration of antioxidant vitamins, are the only available treatments for oxidative stress in humans. In this review, we discuss strategies to target oxidative stress both in experimental models and in humans. We also discuss how patients could be selected who particularly benefit from antioxidant treatment. In clinical practice, diagnostic procedures beyond measurement of blood pressure will be necessary to predict the response to antioxidants; these procedures will include measurement of antioxidant status and detailed assessment of vascular structure and function.     

Role of arachidonic acid metabolites and reactive oxygen species in glomerular immune-inflammatory process

Conclusions This short review of the various contributions of AA metabolites and ROS to renal injury in glomerulonephritis lets many uncertainties persist: (1) what are the respective roles of the resident glomerular cells and of the invading blood cells as sources of these mediators? (2) What is the specific role of each product, and is one of them particularly toxic? The response to the latter question will be facilitated by the use of new specific pharmacological tools, such as receptor antagonists, specific scavengers, or synthesis inhibitors apt to penetrate the cells.     

Characterization of reactive oxygen species in diaphragm

Reactive oxygen species (ROS) exist as natural mediators of metabolism to maintain cellular homeostasis. However, ROS production may significantly increase in response to environmental stressors, resulting in extensive cellular damage. Although several potential sources of increased ROS have been proposed, exact mechanisms of their generation have not been completely elucidated. This is particularly true for diaphragmatic skeletal muscle, the key muscle used for respiration. Several experimental models have focused on detection of ROS generation in rodent diaphragm tissue under stressful conditions, including hypoxia, exercise, and heat, as well as ROS formation in single myofibres. Identification methods include direct detection of ROS with confocal or fluorescent microscopy and indirect detection of ROS through end product analysis. This article explores implications of ROS generation and oxidative stress, and also evaluates potential mechanisms of cellular ROS formation in diaphragmatic skeletal muscle.     

Role of reactive oxygen species in neutrophil apoptosis following ingestion of heat-killed Staphylococcus aureus

Neutrophils, short-lived leucocytes that die by apoptosis, play an important role in the first stage of defense against bacterial infections. It has been reported that phagocytosis of intact bacteria or Candida albicans can accelerate neutrophil apoptosis. However, the mechanism of phagocytosis-mediated neutrophil apoptosis is not well characterized. In this study, we evaluated whether ingestion of heat-killed Staphylococcus aureus (S. aureus) enhances neutrophil apoptosis and whether this type of apoptosis is mediated by oxidative stress by using antioxidants and polymorphonuclear leucocytes (PMNs) from patients with chronic granulomatous disease (CGD). Co-culture of PMNs with varying doses of S. aureus resulted in accelerated PMN death in a dose- and time-dependent manner. Increased PMN apoptosis was observed by both Annexin V and PI staining. Similar results were observed in PMNs of CGD patients. Dimethyl sulphoxide (DMSO, an OH* scavenger) did not significantly inhibit either S. aureus-ingested PMN apoptosis or spontaneous PMN apoptosis. On the other hand glutathione (GSH, an H2O2 scavenger) significantly inhibited both types of apoptosis. Our findings suggest that oxygen-independent pathways may mainly operate in the process of phagocytosis-induced apoptosis.