Khat a drug of abuse: roles of free radicals and antioxidants

Many articles have reviewed the health impact of Khat consumption; however the role of free radicals in the pathogenesis associated with short- and long-term consumption of Khat is absent in the literature. As free radicals and antioxidants converge across various mechanisms in normal physiological function and in disease, this review attempts to uncover the role of endogenous free radicals and the mechanism of cellular injury associated with Khat consumption.     

Risk management of free radicals involved in air travel syndromes by antioxidants

Frequent air travelers and airplane pilots may develop various types of illnesses. The environmental risk factors associated with air travel syndromes (ATS) or air travel–related adverse health outcomes raised concerns and need to be assessed in the context of risk management and public health. Accordingly, the aim of the present review was to determine ATS, risk factors, and mechanisms underlying ATS using scientific data and information obtained from Medline, Toxline, and regulatory agencies. Additional information was also extracted from websites of organizations, such as the International Air Transport Association (IATA), International Association for Medical Assistance to Travelers (IAMAT), and International Civil Aviation Organization (ICAO). Air travelers are known to be exposed to environmental risk factors, including circadian rhythm disruption, poor cabin air quality, mental stress, high altitude conditions, hormonal dysregulation, physical inactivity, fatigue, biological infections, and alcoholic beverage consumption. Consequences of ATS attributed to air travel include sleep disturbances (e.g., insomnia), mental/physical stress, gastrointestinal disorders, respiratory diseases, circulatory-related dysfunction, such as cardiac arrest and thrombosis and, at worst, mechanical and terrorism-related airplane crashes. Thus safety measures in the cabin before or after takeoff are undertaken to prevent illnesses or accidents related to flight. In addition, airport quarantine systems are strongly recommended to prepare for any ultimate adverse circumstances. Routine monitoring of environmental risk factors also needs to be considered. Frequently, the mechanisms underlying these adverse manifestations involve free radical generation. Therefore, antioxidant supplementation may help to reduce or prevent adverse outcomes by mitigating health risk factors associated with free radical generation.     

Free radicals and antioxidants in cardiovascular disease

Several lines of evidence suggest that free radical-mediated oxidative damage to lipoproteins may be an important factor predisposing them to uptake into the vascular wall. This has led to interest in the factors that determine the susceptibility of lipoproteins to oxidation and their relationship to the development of coronary heart disease. Of these factors, the lipoprotein content of natural antioxidant vitamins such as vitamin E, and beta-carotene have aroused particular interest. Studies in animal models of atherosclerosis suggest that natural and synthetic antioxidants can retard the development of atheroma. Epidemiological comparisons between populations and studies within populations also support the contention that high plasma levels or dietary intake of natural antioxidant vitamins may protect against the development of coronary disease in man. Prospective randomized controlled trials of antioxidants in high risk groups are underway to test whether the theoretical promise of a beneficial role for antioxidants in coronary heart disease prevention will be fufilled.     

Structural damage to proteins caused by free radicals: asessment, protection by antioxidants, and influence of protein binding

Oxidative damage to proteins results in biological dysfunctions such as perturbed activity in enzymes, transport proteins, and receptors. Here, we investigated structural damage to proteins induced by free radicals. Structural alterations to lysozyme, human serum albumin (HSA) and beta-lactoglobulin A were monitored by capillary zone electrophoresis. Four well-known antioxidants (quercetin, melatonin, Trolox, and chlorogenic acid) were examined for their ability to inhibit protein damage and to bind to these proteins. Melatonin and chlorogenic acid, which did not bind to any of the three proteins under study, showed scavenging and protective activities well correlated with the amount of free radicals generated. Trolox, which bound only to HSA, was a better protector of HSA than of the two other proteins, indicating that its antioxidant capacity is increased by a shielding effect. Finally, quercetin was a good antioxidant in protecting lysozyme and beta-lactoglobulin A, but its binding to HSA resulted in a pro-oxidant effect that accelerated HSA fragmentation. These results demonstrate that binding of an antioxidant to a protein may potentiate protection or damage depending on the properties of the antioxidant.     

Free radicals and oxidative stress: targeted ESR measurement of free radicals

The detection of free radicals generated within the body may contribute to clarifying the pathophysiological role of free radicals in disease processes. As an appropriate procedure to examine the generation of free radicals in a biological system, electron spin resonance (ESR) has emerged as a powerful tool for detection and identification. A method for determination of oxygen radical scavenging activity using ESR and the spin trapping technique was developed. Oxygen radicals were trapped by 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) or alpha-phenyl-N-t-butylnitrone (PBN), and the DMPO or PBN spin adduct signal was measured quantitatively by an ESR spectrometer. The spin trapping method using ESR has also been reported for not only in vitro and ex vivo measurements but also in vivo measurements. In in vivo ESR, nitroxyl radical is being used as a spin trap well. ESR signal intensities of nitroxyl radical are measured after administration to animals and the signal decay rates of nitroxyl radical have reported to be influenced by various types of oxidative stress. With this method, it is possible to specify the type of radical or the location at which the free radicals are produced. The spin trapping method by in vivo ESR is an effective procedure for giving non-invasive measurements in animals. ESR imaging in the organs of live animals can also be obtained after injection of nitroxyl radicals as an imaging agent using ESR-computed tomography. In vivo ESR imaging has been established as a powerful technique for determining the spatial distribution of free radicals in living organs and tissues.     

5公里越野训练氧自由基代谢及抗氧化剂的保护作用

目的探讨抗氧化剂对战士5km越野训练氧自由基和尿蛋白的影响。方法选择109名战士为研究对象,分三组。观察服用抗氧化剂维生素C和维生素E后训练,血清超氧化物歧化酶(SOD)活性、丙二醛(MDA)、VitC、VitE、尿蛋白(PRO)、尿微量白蛋白(mALb)水平。探讨这些指标的变化和氧化应激的关系。结果服用抗氧化剂组战士血清SOD、VitC、VE水平升高、MDA、PRO、mALb含量明显降低,与训练组比较有显著性差异(P<0.01)。训练组血清中SOD活性下降,MDA水平升高、PRO、mALb阳性率增高,与对照组比较有显著性差异(P<0.01)。结论补充抗氧化剂可以提高血清中抗氧化酶的活性,降低尿液PRO和mALb的水平,对提高机体抗氧化能力、防止训练后肾损伤,提高部队战斗力具有积极的意义。     

The influence of exogenous antioxidants and physical exercise on some parameters associated with production and removal of free radicals

Metabolic processes generate chemically active forms of oxygen, among which a prominent role is played by the superoxide ion. Cells are equipped with defence systems against the effects of superoxide radicals, superoxide dismutase is the most important one. The organism depends on the delivery of exogenous antioxidants, like selenium, vitamins E and C. Physical exercise triggers the production of superoxide radicals, which can at least partly be responsible for muscular damage. This work has studied the effect of Protection Zellaktiv (Smith Kline Beecham, Fink Naturarznei GmbH), a preparation containing selenium, vitamins C, E, B2, niacin and beta-carotene on the activities of superoxide dismutase and catalase, levels of glutathione malondialdehyde selenium, iron, zinc, triglicerides, total cholesterol, HDL- and LDL-cholesterol, before and after physical exercise. Muscle status was monitored by the activities of lactic dehydrogenase and creatine kinase. Protecton Zellaktiv was administered orally for one month, the measurements were repeated and the results before and after treatment were compared. It was found that treatment diminished the levels of malondialdehyde and zinc in serum, as well as cholesterol and triglicerides. Physical exercise before treatment decreased the levels of reduced glutatione, zinc and triglycerides. As expected, the levels of selenium were increased by the preparation. Protecton Zellaktiv suppressed the production of malondialdehyde during physical exercise. The preparation had a beneficial effect on lipid levels and it is inferred that lipid peroxidation was suppressed.     

Effects of oxygen free radicals on extracellular glutamate accumulation in cultured cells

Exogenously applied oxygen free radical generating agent, pyrogallol, highly elevated extracellular glutamate accumulation and augmented N-methyl-D-aspartate (NMDA)-induced glutamate accumulation in cerebellar granule neuronal cells, but did not in astrocytes. Superoxide dismutase remarkably decreased the pyrogallol-induced glutamate accumulation, but either NMDA or kainate antagonists did not. In addition, pyrogallol did not affect the NMDA-induced intracellular calcium elevation. Pyrogallol partially blocked glutamate uptake into astrocytes. These results suggest that oxygen free radicals elevate extracellular glutamate accumulation by stimulating the release of glutamate as well as blocking the glutamate uptake.     

Curative effect of Terminalia chebula extract on acetic acid-induced experimental colitis: role of antioxidants, free radicals and acute inflammatory marker

The present study has evaluated the healing effects of extract of dried fruit pulp of Terminalia chebula (TCE) on acetic acid (AA)-induced colitis in rats. TCE (600 mg/kg) showed healing effects against AA-induced colonic damage score and weight when administered orally daily for 14 days. TCE was further studied for its effects on various physical (mucus/blood in stool and stool frequency, food and water intake and body weight changes), histology, antibacterial activity and free radicals (NO and LPO), antioxidants (SOD, CAT and GSH) and myeloperoxidase in colonic tissue. Intra-colonic AA administration increased colonic mucosal damage and inflammation, mucus/bloody diarrhoea, stool frequency, but decreased body weight which were reversed by TCE and sulfasalazine (SS, positive control) treatments. TCE showed antibacterial activity and both TCE and SS enhanced the antioxidants, but decreased free radicals and myeloperoxidase activities affected in acetic acid-induced colitis. TCE indicated the presence of active principles with proven antioxidants, anti-inflammatory, immunomodulatory, and free radical scavenging and healing properties. Thus, TCE seemed to be safe and effective in healing experimental colitis.     

Oxygen free radicals and the penis

Penile erection is dependent upon vascular smooth muscle relaxation in erectile tissue and penile arteries, the principal mediator of relaxation being nitric oxide (NO). Evidence from basic scientific studies indicates that oxidative stress mediated through the superoxide radical (superoxide) and other reactive oxygen species (ROS) may be central to impaired cavernosal function in erectile dysfunction (ED). Increased inactivation of NO by superoxide results in impaired penile NO transmission and smooth muscle relaxation. Furthermore, propagation of endothelial dysfunction by ROS may result in chronic impairment of penile vascular function, a process analogous to early atherogenesis. Indeed, ED and atherosclerosis are closely linked through shared risk factors. Given our current understanding of ED pathophysiology, antioxidants may be of benefit in both the short- and long-term. Evidence supporting the paradigm of antioxidant therapy for the prevention or treatment of ED is presented herein.     

帕金森病与氧自由基

该文对近年来在帕金森病与氧自由基关系方面的研究工作做了回顾 ,许多事实表明 ,氧自由基在帕金森病的发病过程中起着重要作用 ,帕金森病患者机体处于氧应激状态 ,帕金森病病变部位的选择性决定了其氧自由基产生的特点 ,其它有关帕金森病的致病学说均与氧自由基有着密切关系。     

Life and death of free radicals

In 1900, the term as used for the first time by Moses Gomberg, a chemist working in Michigan University. He discovered the triphenylmethyl radical when he treated triphenylmethyl chloride by metals (Ag, Zn). The term "free radicals" has been used for 93 years to distinguish between radicals as distinct chemical species and the term radical used to describe a substitutive group. In 1993, JUPAC decided to call , "radicals" chemical species bearing an unpaired electron and "groups" the substituting groups.     

Oxygen free radicals and the penis

Penile erection is dependent upon vascular smooth muscle relaxation in erectile tissue and penile arteries, the principal mediator of relaxation being nitric oxide (NO). Evidence from basic scientific studies indicates that oxidative stress mediated through the superoxide radical (superoxide) and other reactive oxygen species (ROS) may be central to impaired cavernosal function in erectile dysfunction (ED). Increased inactivation of NO by superoxide results in impaired penile NO transmission and smooth muscle relaxation. Furthermore, propagation of endothelial dysfunction by ROS may result in chronic impairment of penile vascular function, a process analogous to early atherogenesis. Indeed, ED and atherosclerosis are closely linked through shared risk factors. Given our current understanding of ED pathophysiology, antioxidants may be of benefit in both the short- and long-term. Evidence supporting the paradigm of antioxidant therapy for the prevention or treatment of ED is presented herein.     

PLA2 mediated arachidonate free radicals: PLA2 inhibition and neutralization of free radicals by anti-oxidants--a new role as anti-inflammatory molecule

PLA2 enzyme catalyses the hydrolysis of cellular phospholipids at the sn-2 position to liberate arachidonic acid and lysophospholipid to generate a family of pro-inflammatory eicosanoids and platelet activating factor. The generation of pro-inflammatory eicosanoids involves a series of free radical intermediates with simultaneous release of reactive oxygen species (superoxide and hydroxyl radicals). Reactive oxygen species formed during arachidonic acid metabolism generates lipid peroxides and the cytotoxic products such as 4-hydroxy nonenal and acrolein, which induces cellular damage. Thus PLA2 catalyzes the rate-limiting step in the production of pro-inflammatory eicosanoids and free radicals. These peroxides and reactive oxygen species in turn activates PLA2 enzyme and further attenuates the inflammatory process. Therefore scavenging these free radicals and inhibition of PLA2 enzyme simultaneously by a single molecule such as antioxidants is of great therapeutic relevance for the development of anti-inflammatory molecules. PLA2 enzymes have been classified into calcium dependent cPLA2 and sPLA2 and calcium independent iPLA2 forms. In several inflammatory diseases sPLA2 group IIA is the most abundant isoform identified. This isoform is therefore targeted for the development of anti-inflammatory molecules. Many secondary metabolites from plants and marine sponges exhibit both anti-inflammatory and antioxidant properties. Some of them include flavonoids, terpenes and alkaloids. But in terms of PLA2 inhibition and antioxidant activity, the structural aspects of flavonoids are well studied rather than terpenes and alkaloids. In this line, molecules having both anti-oxidant and PLA2 inhibitions are reviewed. A single molecule with dual activities may prove to be a powerful anti-inflammatory drug.     

Interaction between carotenoids and free radicals in human skin

Environmental factors like air pollutants, radiation of the sun and stress factors such as illness, smoking, or alcohol abuse produce free radicals in the human tissue as well as in the skin. Free radicals serve as the main cause for premature skin aging. Additionally, they also contribute towards immunosuppression and the formation of skin diseases including cancer. The human organism has developed a protection system against the destructive action of free radicals by means of the antioxidant network. In the present study, the interaction of free radicals and carotenoid antioxidants in the human skin under in vivo conditions was investigated and summarized. The measurement of carotenoids in human skin was performed in vivo using resonance Raman spectroscopy.