Free radical biology and medicine: it's a gas, man!
Pryor WA,
Houk KN,
Foote CS,
Fukuto JM,
Ignarro LJ,
Squadrito GL,
Davies KJ.
Source
Biodynamics Institute, Louisiana State University, Baton Rouge, LA 70803, USA.
wpryor@LSU.edu
Abstract
We review gases that can affect oxidative stress and that themselves may be radicals. We discuss O(2) toxicity, invoking superoxide, hydrogen peroxide, and the hydroxyl radical. We also discuss superoxide dismutase (SOD) and both ground-state, triplet oxygen ((3)O(2)), and the more energetic, reactive singlet oxygen ((1)O(2)). Nitric oxide ((*)NO) is a free radical with cell signaling functions. Besides its role as a vasorelaxant, (*)NO and related species have other functions. Other endogenously produced gases include carbon monoxide (CO), carbon dioxide (CO(2)), and hydrogen sulfide (H(2)S). Like (*)NO, these species impact free radical biochemistry. The coordinated regulation of these species suggests that they all are used in cell signaling. Nitric oxide, nitrogen dioxide, and the carbonate radical (CO(3)(*-)) react selectively at moderate rates with nonradicals, but react fast with a second radical. These reactions establish "cross talk" between reactive oxygen (ROS) and reactive nitrogen species (RNS). Some of these species can react to produce nitrated proteins and nitrolipids. It has been suggested that ozone is formed in vivo. However, the biomarkers that were used to probe for ozone reactions may be formed by non-ozone-dependent reactions. We discuss this fascinating problem in the section on ozone. Very low levels of ROS or RNS may be mitogenic, but very high levels cause an oxidative stress that can result in growth arrest (transient or permanent), apoptosis, or necrosis. Between these extremes, many of the gasses discussed in this review will induce transient adaptive responses in gene expression that enable cells and tissues to survive. Such adaptive mechanisms are thought to be of evolutionary importance.
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A new gaseous signaling molecule emerges: cardioprotective role of hydrogen sulfide.
http://www.ncbi.nlm.nih.gov/pubmed/17991773?dopt=Citation
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[h=1]Garlic elicits a nitric oxide-dependent relaxation and inhibits hypoxic pulmonary vasoconstriction in rats.[/h]
Kim-Park S,
Ku DD.
[h=3]Source[/h]Department of Pharmacology and Toxicology, University of Alabama at Birmingham, 35294, USA. SKIMPARK@UAB.EDU
[h=3]Abstract[/h]1. The aims of the present study were to determine the characteristics of garlic extract-induced relaxation in rat isolated pulmonary arteries, its susceptibility to changes in oxygen tension and its protective effect against hypoxic pulmonary vasoconstriction. 2. In normoxia, garlic extract (3-500 microg/mL) produced a dose- and nitric oxide (NO)-dependent relaxation. Following 60 min hypoxia, maximum garlic relaxation was reduced compared with control (mean (-SEM) -86 +/- 3 vs-69 +/- 2% of phenylephrine (PE) precontraction, respectively), but recovered after 60 min reoxygenation (-85 +/- 3% PE precontraction). 3. Acetylcholine (0.1 micromol/L)-induced NO-dependent relaxation was reduced from a control value of -76 +/- 1% to -46 +/- 4% during hypoxia and was further reduced to -35 +/- 2 % after reoxygenation. 4. In endothelium-intact arteries, hypoxic exposure resulted in a triphasic response: early transient contraction (+24 +/- 4%), followed by transient relaxation (-37 +/- 7%) and then sustained contraction (+62 +/- 5%). 5. Pretreatment with NG-nitro-L-arginine methyl ester abolished the early transient contraction, moderately attenuated the sustained contraction and had no effect on the transient relaxation. Mechanical endothelial disruption inhibited all hypoxia-induced vascular changes. 6. Garlic pretreatment had no effect on the early transient contraction (+25 +/- 4%), but inhibited the transient relaxation (-5 +/- 3%; P<0.05) and the sustained contraction (+26 +/- 5%; 7. Garlic also significantly inhibited endothelin-l-induced contractions in a dose-dependent manner. 8. These findings show that garlic extract modulates the production and function of both endothelium-derived relaxing and constricting factors and this may contribute to its protective effect against hypoxic pulmonary vasoconstriction.
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[h=1]Garlic prevents hypoxic pulmonary hypertension in rats.[/h]
Fallon MB,
Abrams GA,
Abdel-Razek TT,
Dai J,
Chen SJ,
Chen YF,
Luo B,
Oparil S,
Ku DD.
[h=3]Source[/h]Liver Center, University of Alabama at Birmingham, Birmingham, Alabama 35294-0007, USA.
[h=3]Abstract[/h]Hypoxic pulmonary vasoconstriction underlies the development of high-altitude pulmonary edema. Anecdotal observations suggest a beneficial effect of garlic in preventing high-altitude symptoms. To determine whether garlic influences pulmonary vasoconstriction, we assessed the effect of garlic on pulmonary pressures in rats subjected to alveolar hypoxia and on vasoconstriction in isolated pulmonary arterial rings. Garlic gavage (100 mg/kg body wt) for 5 days resulted in complete inhibition of acute hypoxic pulmonary vasoconstriction compared with the control group. No difference in mean arterial pressure or heart rate response to hypoxia was seen between the groups. Garlic solution resulted in a significant dose-dependent vasorelaxation in both endothelium-intact and mechanically endothelium-disrupted pulmonary arterial rings. The administration of NG-nitro-L-arginine methyl ester (a nitric oxide synthase inhibitor) inhibited the vasodilatory effect of garlic by 80%. These studies document that garlic blocks hypoxic pulmonary hypertension in vivo and demonstrate a combination of endothelium-dependent and -independent mechanisms for the effect in pulmonary arterial rings.
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[h=1]Effects of onion extract on endogenous vascular H2S and adrenomedulin in rat atherosclerosis.[/h]
Li W,
Tang C,
Jin H,
Du J.
[h=3]Source[/h]Department of Pediatrics, Peking University First Hospital, Beijing 100034, China.
[h=3]Abstract[/h][h=4]OBJECTIVE:[/h]This study aimed to explore the effect of onion extract on endogenous hydrogen sulfide (H2S) and adrenomedulin (ADM) and on atherosclerotic progression in rats with atherosclerosis (AS).
[h=4]METHODS AND RESULTS:[/h]Male Sprague-Dawley rats were randomly divided into control, AS and AS+onion groups. Ultrastructure of aorta and atherosclerotic lesions both in aorta and in coronary artery were detected. Plasma and aortic H2S were detected by using a sulfide- sensitive electrode. Plasma and aortic ADM was determined with radioimmunoassay. Cystathionine-γ-lyase (CSE), calcitonin receptor-like receptor (CRLR), receptor activity-modifying protein (RAMP1, RAMP2 and RAMP3) mRNA expressions were analysed. Glutathione peroxidase (GSH-PX), superoxide dismutase (SOD), malondialdehyde (MDA), nitric oxide (NO) and NO synthase (NOS) contents in plasma, SOD1, SOD2 and ICAM-1 expressions in aorta were detected. Rats in the AS group showed marked atherosclerotic lesions both in aorta and in coronary artery but decreased aortic H2S production. Decreased plasma and aortic ADM content, but increased levels of aortic CRLR, RAMP2 and RAMP3 mRNAs were observed. Plasma GSH-PX and SOD were reduced but MDA elevated. Plasma ICAM-1 and NO contents and iNOS activity were increased. Onion extract, however, lessened atherosclerotic lesions and increased endogenous aortic H2S production, but decreased plasma ADM content, aortic ADM content and aortic CRLR, RAMP2 and RAMP3 mRNAs. In addition, it increased plasma GSH-PX level and SOD activities but reduced MDA; it decreased inflammatory response but increased plasma eNOS activity and NO content.
[h=4]CONCLUSIONS:[/h]Onion extract exerted a marked antiatherogenic effect in association with the up-regulation of the endogenous CSE/H2S pathway but down-regulation of the ADM/CRLR family in atherosclerotic rats.
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[h=1]S-allylcysteine mediates cardioprotection in an acute myocardial infarction rat model via a hydrogen sulfide-mediated pathway.[/h]
Chuah SC,
Moore PK,
Zhu YZ.
[h=3]Source[/h]Cardiovascular Biology Research Group, Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, China.
[h=3]Abstract[/h]S-allylcysteine (SAC) is an organosulfur-containing compound derived from garlic. Studies have shown that garlic is beneficial in the treatment of cardiovascular diseases. This study aims to elucidate if SAC is responsible for this cardioprotection using acute myocardial infarction (AMI) rat models. In addition, we hypothesized that SAC may mediate cardioprotection via a hydrogen sulfide (H(2)S)-related pathway. Rats were pretreated with saline, SAC (50 mg x kg(-1) x day(-1)), SAC + propagylglycine (PAG; 50 mg + 10 mg x kg(-1) x day(-1)) or PAG (10 mg x kg(-1) x day(-1)) for 7 days before AMI induction and killed 48 h after. Our results showed that SAC significantly lowered mortality (12.5% vs. 33.3%, P < 0.05) and reduced infarct size. SAC + PAG- and PAG-treated rats had larger infarct sizes than controls (60.9 +/- 0.01 and 62.0 +/- 0.03%, respectively, vs. 50.0 +/- 0.03%; P < 0.05). Pretreatment with SAC did not affect BP, but BP was significantly elevated in SAC + PAG and PAG-treated groups (P < 0.05). In addition, plasma H(2)S levels and left ventricular cystathionine-gamma-lyase (CSE) activities were analyzed to investigate the involvement of H(2)S. CSE is the enzyme responsible for H(2)S production in the heart. SAC increased left ventricular CSE activity in AMI rats (2.75 +/- 0.34 vs. 1.23 +/- 0.16 micromol x g protein(-1) x h(-1); P < 0.01). SAC + PAG-treated rats had significantly lower CSE activity compared with the SAC-treated group (1.22 +/- 0.27 vs. 2.75 +/- 0.34 micromol x g protein(-1) x h(-1); P < 0.05). Similarly, SAC-treated rats had higher plasma H(2)S concentration compared with controls and the SAC + PAG-treated group. Protein expression studies revealed that SAC upregulated CSE expression (1.1-fold of control; P < 0.05), whereas SAC + PAG and PAG downregulated its expression (0.88-fold of control in both groups; P < 0.005). In conclusion, our study provides novel evidence that SAC is protective in myocardial infarction via an H(2)S-related pathway.