Pindolol is a potent scavenger of reactive nitrogen species

Defense Mechanism of Phosphorothioated DNA under Peroxynitrite-Mediated Oxidative Stress

DNA phosphorothioation (PT) exists in many pathogenic bacteria; however, the mechanism of PT-DNA resistance to the immune response is unclear. In this work, we meticulously investigated the peroxynitrite (PN) tolerance using PT-bioengineered E. coli strains. The in vivo experiment confirms that the S⁺ strain survives better than the S^- strain under moderately oxidative stress. The LCMS, IC, and GCMS experiments demonstrated that phosphorothioate partially converted to phosphate, and the byproduct included sulfate and elemental sulfur. When O,O-diethyl thiophosphate ester (DETP) was used, the reaction rate k₁ was determined to be 4.3 ± 0.5 M^-1 s^-1 in the first-order for both phosphorothioate and peroxynitrite at 35 °C and pH of 8.0. The IC₅₀ values of phosphorothioate dinucleotides are dramatically increased by 400-700-fold compared to DETP. The SH/OH Yin-Yang mechanism rationalizes the in situ DNA self-defense against PN-mediated oxidative stress at the extra bioenergetic cost of DNA modification.

β-Carotene and its physiological metabolites: Effects on oxidative status regulation and genotoxicity in in vitro models

Carotenoids are ubiquitously distributed in nature, β-carotene being the most frequently found carotenoid in the human diet. In the human body, β-carotene is absorbed, distributed and metabolized by enzymatic and/or non-enzymatic oxidant cleavage into several metabolites. Despite the broadly accepted biological value of β-carotene, it has also been considered a double-edged sword, mainly due to its potential antioxidant versus pro-oxidant behaviour. In this sense, the aim of this work was to scrutinize the antioxidant or pro-oxidant potential of β-carotene and its metabolites, namely trans-β-apo-8'-carotenal and β-ionone. Several parameters were evaluated in this study, viz. their effects on reactive species production, both in human whole blood and neutrophils; their effects on lipid peroxidation, in the absence and presence of peroxynitrite anion (ONOO^-) or hydrogen peroxide (H₂O₂), using a synaptosomal model; and finally, their putative genotoxic effects in the human hepatic HepG2 cell line. In general, depending on the cellular model and conditions tested, β-carotene and its metabolites revealed antioxidant effects to varying degrees without significant pro-oxidant or genotoxic effects.

Solanum diploconos fruits: profile of bioactive compounds and in vitro antioxidant capacity of different parts of the fruit

Solanum diploconos is an unexploited Brazilian native fruit that belongs to the same genus of important food crops, such as tomato (Solanum lycorpersicum) and potato (Solanum tuberosum). In this study, we determined, for the first time, the profile of bioactive compounds (phenolic compounds, carotenoids, ascorbic acid and tocopherols) of the freeze-dried pulp and peel of Solanum diploconos fruits, as well as of an extract obtained from the whole fruit. Additionally, the antioxidant potential of the whole fruit extract was evaluated in vitro, against reactive oxygen species (ROS) and reactive nitrogen species (RNS). Eighteen phenolic compounds were identified in the peel and pulp and 6 compounds were found in the whole fruit extract. Coumaric, ferulic and caffeic acid derivatives were revealed to be the major phenolic constituents. All-trans-β-carotene was the major carotenoid (17-38 μg g(-1), dry basis), but all-trans-lutein and 9-cis-β-carotene were also identified. The peel and pulp presented <2 μg per mL of tocopherols, and ascorbic acid was not detected. The whole fruit extract exhibited scavenging capacity against all tested ROS and RNS (IC50 = 14-461 μg mL(-1)) with high antioxidant efficiency against HOCl. Thus, Solanum diploconos fruits may be seen as a promising source of bioactive compounds with high antioxidant potential against the most physiologically relevant ROS and RNS.

Antiarrhythmic activity in occlusion-reperfusion model of 1-(1H-indol-4-yloxy)-3-{[2-(2-methoxyphenoxy)ethyl]amino} propan-2-ol and its enantiomers

Acute myocardial infarction (AMI) is a leading cause of mortality and morbidity worldwide, especially in developed countries. The most serious problem after myocardial infarction is reperfusion injury that manifests as functional impairment, arrhythmia, and accelerated progression of cell death in certain critically injured myocytes. Subsequently the infarcted myocardium develops features of necrosis and reactive inflammation. To reduce lethal reperfusion injury in patient with AMI antioxidants, anti-inflammatory agents, adenosine, opioids, metabolic modulators (glucose, insulin, and potassium, nicorandil and agents which reduce intracellular Ca(2+) overload and inhibit Na(+)-H(+) exchange) are used. In this study a novel compound (compound 9) 1-(1 h-indol-4-yloxy)-3-{[2-(2-methoxyphenoxy) ethyl]amino}propan-2-ol and its enantiomers are examined in arrhythmia associated with coronary artery occlusion and reperfusion in a rat model. Antioxidant properties are also determined for test compounds using the malondialdehyde (MDA) lipid peroxidation and ferric reducing antioxidant power (FRAP) tests. In summary, the tested compounds, especially the S enantiomer has a strong antiarrhythmic activity in a model of occlusion and reperfusion of the left coronary artery which is probably related to their adrenolytic action. In contrast to carvedilol, none of the test compound reduced the lipid peroxidation but increased ferric reducing antioxidant power. In the antioxidant effect, there was no difference between the optical forms of compound 9.

The seed of the Amazonian fruit Couepia bracteosa exhibits higher scavenging capacity against ROS and RNS than its shell and pulp extracts

Couepia bracteosa is an interesting source of bioactive compounds which may be investigated for protecting human health against oxidative damage.

Mechanism of protection of bystander cells by exogenous carbon monoxide: impaired response to damage signal of radiation-induced bystander effect

A protective effect of exogenous carbon monoxide (CO), generated by CO releasing molecule ticarbonyldichlororuthenium (II) dimer (CORM-2), on the bystander cells from the toxicity of radiation-induced bystander effect (RIBE) was revealed in our previous study. In the present work, a possible mechanism of this CO effect was investigated. The results from medium transfer experiments showed that α-particle irradiated Chinese hamster ovary (CHO) cells would release nitric oxide (NO), which was detected with specific NO fluorescence probe, to induce p53 binding protein 1 (BP1) formation in the cell population receiving the medium, and the release peak was found to be at 1h post irradiation. Treating the irradiated or bystander cells separately with CO (CORM-2) demonstrated that CO was effective in the bystander cells but not the irradiated cells. Measurements of NO production and release with a specific NO fluorescence probe also showed that CO treatment did not affect the production and release of NO by irradiated cells. Protection of CO on cells to peroxynitrite, an oxidizing free radical from NO, suggested that CO might protect bystander cells via impaired response of bystander cells to NO, a RIBE signal in our research system.

Antioxidant activity of unexplored indole derivatives: synthesis and screening

The present study envisaged the development of novel antioxidant candidates using the indole scaffold. Several tryptophan and tryptamine derivatives were synthesized, in particular prenylated indole compounds, and their scavenging activity for reactive oxygen species (ROS) and reactive nitrogen species (RNS) was investigated. The library substitution pattern included several alkyl chains at positions N-1, C-2 of the indole nucleus, including prenyl and isopentyl chain, as well as different groups at the side chain (C-3) that allowed the investigation of a possible radical stabilization. The results obtained showed that tryptophan (8), tryptamine (9), N-phthaloyl tryptamine (5) and N-prenyl tryptophan (13) were the most active against peroxyl radical (ROO(•)) with activities higher than Trolox, which was used as control. The scavenging of hypochlorous acid (HOCl) was also evaluated and tryptophan (8) and tryptamine (9) showed IC(50) of 3.50 ± 0.4 and 6.00 ± 0.60 μM, respectively. Significant activity was also found for the N-prenyl tryptophan (13) with an IC(50) of 4.13 ± 0.17 μM and C-2 prenylated derivative (14), with 4.56 ± 0.48 μM. The studies were extended to RNS and best results were obtained against peroxynitrite anion (ONOO(-)) in the presence of NaHCO(3). N-alkylated tryptophan (18) showed a high activity with an IC(50) of 14.0 ± 6.8 μM. The results show that the tested compounds are effective scavengers of ROS and RNS, and suggest that the radical stabilization is strongly dependent on the type of substituents on the indolic moiety and on their relative positions. In addition, the radical dissipation inside the indolic system is mandatory for the observed antioxidant activity.

Pindolol augmentation of serotonin reuptake inhibitors for the treatment of depressive disorder: a systematic review

Adding pindolol to serotonergic antidepressant treatment offers a potential strategy for producing a more rapid onset of action and an enhanced antidepressant effect. This review investigated whether pindolol enhances the efficacy of serotonergic antidepressant treatment in adult patients with depressive disorders at sequential time points up to 6 weeks.

SEARCH STRATEGY

Cochrane Collaboration Depression, Anxiety and Neurosis-Controlled Trials Register plus unpublished trial data.

STUDY SELECTION

Randomised trials including depressed patients, comparing serotonergic antidepressants + pindolol with serotonergic antidepressants + placebo and using depressive symptom clinical outcomes scales.

DATA EXTRACTION

Clinical response at time points up to 6 weeks as defined by >50% depression scale score reduction was extracted for each trial as possible. Eleven studies were identified including unpublished data. The pooled odds ratios for dichotomous response to treatment at time points from 1 to 6 weeks were 2.39 (95% CI 1.40-4.06), 2.39 (1.74-3.29), 1.94 (1.46-2.58), 1.59 (1.16-2.18), 1.42 (0.87-2.31) and 1.28 (0.91-1.81). Time-to-event analysis showed a greater response with pindolol augmentation versus placebo (P = 0.04). There was significant heterogeneity between studies at some time points. Dropout rates did not significantly differ between treatment arms. This review suggests an overall beneficial clinical effect of pindolol augmentation, most clearly up to 4 weeks of treatment.

Evaluation of Salicornia herbacea as a potential antioxidant and anti-inflammatory agent

In this study, the antioxidant and anti-inflammatory activities of Salicornia herbacea were evaluated. The crude CH(2)Cl(2)/methanol extract of S. herbacea showed 52% and 86% scavenging activities of the authentic ONOO(-) and ONOO(-) from 3-morpholinosydnomimine (SIN-1) at a concentration of 50 microg/mL, respectively, and was subjected to a further fractionation with n-hexane, 85% aqueous methanol, n-butanol, and water. Additional purification of the n-butanol fraction revealed that the most potent scavenging activity led to the isolation of isorhamnetin 3-O-beta-d-glucopyranoside as the active principle. The structure of isorhamnetin 3-O-beta-d-glucopyranoside was elucidated by extensive two-dimensional nuclear magnetic resonance experiments such as (1)H correlation spectroscopy nuclear Overhauser effect spectroscopy, heteronuclear single quantum correlation, and heteronuclear multiple-bond correlation as well as by comparison with the published spectral data. Isorhamnetin 3-O-beta-d-glucopyranoside exhibited dose-dependent scavenging activities of the authentic ONOO(-) and ONOO(-) from SIN-1. The electron spin resonance spin-trap techniques confirmed that reactive oxygen species, including the hydroxyl, superoxide, carbon-centered, and 1,1-diphenyl-2-picrylhydrazyl radicals, were actively quenched by addition of isorhamnetin 3-O-beta-d-glucopyranoside. In addition, isorhamnetin 3-O-beta-d-glucopyranoside suppressed the lipopolysaccharide-induced nitric oxide production and the expression of cytokines such as inducible nitric oxide synthase, tumor necrosis factor-alpha, and interleukin-1beta in Raw 264.7 cells. Findings from this study should underscore the nutraceutical value of S. herbacea-derived isorhamnetin 3-O-beta-d-glucopyranoside as a potent antioxidative and anti-inflammatory agent via alleviation of radical-induced toxicities and pro-inflammatory responses.

Paroxetine with pindolol augmentation: a double-blind, randomized, placebo-controlled study in depressed in-patients

Pindolol, a 5-HT1A autoreceptor antagonist, given in combination with selective serotonin reuptake inhibitors (SSRIs), may enhance and/or accelerate the therapeutic efficacy of SSRIs. Fifty patients, meeting ICD-10 criteria for major depressive disorder or bipolar depression, were enrolled in our randomized, placebo-controlled, double-blind trial. One group received paroxetine plus pindolol (2.5 mg t.i.d.), and the other group received paroxetine plus placebo. The proportion of patients with sustained response (>or=50% reduction of baseline HAM-D 17 score maintained until the endpoint; p=0.252) and the proportion of patients with remission (HAM-D 17 <or=8 at last visit; p=0.769) did not differ significantly between the two treatment groups. However, a significantly greater proportion of patients who were not previously treated with antidepressants (n=15; p=0.041) and of patients with bipolar depression (n=11; p=0.015) had a sustained response in the paroxetine plus pindolol group compared to the paroxetine plus placebo group; furthermore there was a trend for first episode depressed patients to have a greater response in the paroxetine plus pindolol group (n=12; p=0.071). Summarizing, the entire study population showed no antidepressive benefit from pindolol augmentation. Nevertheless patients with bipolar depression irrespective of previous treatments and duration of illness, and unipolar patients not previously treated demonstrated a significant benefit from pindolol augmentation.

Peroxynitrite: biochemistry, pathophysiology and development of therapeutics

Peroxynitrite--the product of the diffusion-controlled reaction of nitric oxide with superoxide radical--is a short-lived oxidant species that is a potent inducer of cell death. Conditions in which the reaction products of peroxynitrite have been detected and in which pharmacological inhibition of its formation or its decomposition have been shown to be of benefit include vascular diseases, ischaemia-reperfusion injury, circulatory shock, inflammation, pain and neurodegeneration. In this Review, we first discuss the biochemistry and pathophysiology of peroxynitrite and then focus on pharmacological strategies to attenuate the toxic effects of peroxynitrite. These include its catalytic reduction to nitrite and its isomerization to nitrate by metalloporphyrins, which have led to potential candidates for drug development for cardiovascular, inflammatory and neurodegenerative diseases.

2-Styrylchromones: novel strong scavengers of reactive oxygen and nitrogen species

2-Styrylchromones are a small group of naturally occurring chromones, vinylogues of flavones (2-phenylchromones). Natural and synthetic 2-styrylchromones have been tested in different biological systems, showing activities with potential therapeutic applications. In particular, the potential and hitherto understudied antioxidant behavior of these compounds has been raised as a matter of interest. Thus the present work consisted in the study of the in vitro scavenging activities for reactive oxygen species (ROS) and reactive nitrogen species (RNS) of various 2-styrylchromone derivatives and structurally similar flavonoids. Some of the studied 2-styrylchromones proved to be extremely efficient scavengers of the different ROS and RNS, showing, in some cases, IC(50)s under 1 microM. The hydroxylation pattern of 2-styrylchromones, especially in the B-ring but also in the A ring, modulates the activity of these compounds, the catecholic derivatives being the most effective scavengers. The styryl pattern also contributes to their observed outstanding antioxidant activity. In conclusion, the scavenging activities for ROS/RNS of 2-styrylchromone derivatives, here shown for the first time, provide novel and most promising compounds to be applied as antioxidants.

Constitutive nitric oxide acting as a possible intercellular signaling molecule in the initiation of radiation-induced DNA double strand breaks in non-irradiated bystander cells

The initiation and propagation of the early processes of bystander signaling induced by low-dose alpha-particle irradiation are very important for understanding the underlying mechanism of the bystander process. Our previous investigation showed that the medium collected from cell culture exposed to low-dose alpha-particle rapidly induced phosphorylated form of H2AX protein foci formation among the non-irradiated medium receptor cells in a time-dependent manner. Using N(G)-methyl-L-arginine, 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate and N(omega)-nitro-L-arginine (L-NNA) treatment before exposure to 1 cGy alpha-particle, we showed in the present study that nitric oxide (NO(*)) produced in the irradiated cells was important and necessary for the DNA double strand break inducing activity (DIA) of conditioned medium and the generation of NO(*) in irradiated confluent AG1522 cells is in a time-dependent manner and that almost all NO(*) was generated within 15 min post-irradiation. Concurrently, the kinetics of NO(*) production in the medium of irradiated cells after irradiation was rapid and in a time-dependent manner as well, with a maximum yield observed at 10 min after irradiation with electron spin resonance analysis. Furthermore, our results that 7-Nitroindazole and L-NNA, but not aminoguanidine hemisulfate, treatment before exposure to 1 cGy alpha-particle significantly decrease the DIA of the conditioned medium suggested that constitutive NO(*) from the irradiated cells possibly acted as an intercellular signaling molecule to initiate and activate the early process (<or=30 min) of bystander response after low-dose irradiation.

Dipyrone and aminopyrine are effective scavengers of reactive nitrogen species

Reactive nitrogen species (RNS), namely nitric oxide (NO*) and peroxynitrite (ONOO-) are produced in the inflammatory sites and may contribute to the deleterious effects of inflammation. The aim of the present study was to evaluate the putative scavenging effect of a particular group of non-steroidal anti-inflammatory drugs (NSAIDs), the pyrazolone derivatives dipyrone, aminopyrine, isopropylantipyrine, and antipyrine against RNS, using in vitro non-cellular screening systems. The results obtained showed that dipyrone and aminopyrine were highly potent scavengers of NO* and ONOO- while antipyrine exerted little effect and isopropylantipyrine no effect whatsoever against these two RNS and that, in the presence of bicarbonate, the scavenging potencies of both dipyrone and aminopyrine were slightly decreased. It could thus be inferred that the observed scavenging effects may be of therapeutic benefit for patients under anti-inflammatory treatment with dipyrone and aminopyrine in the case of overproduction of RNS. On the other hand, the possible depletion of physiological NO* concentrations, namely at the gastrointestinal tract as well as the formation of reactive derivatives of aminopyrine and/or dipyrone, resulting from their reaction with RNS, may otherwise be harmful for these patients.

Reactions of indoles with nitrogen dioxide and nitrous acid in an aprotic solvent

The reaction of 2-phenyl- and 1-methyl-2-phenylindole with nitrogen dioxide or with nitrous acid (NaNO2-CH3COOH) in benzene leads mainly to the formation of the isonitroso and 3-nitroso indole derivatives, respectively. When reacted with nitrous acid, 1-methyl-2-phenylindole gives also the corresponding azo-bis-indole in good yields. The reaction of indole with nitrogen dioxide leads to 2-(indol-3-yl)-3H-indol-3-one as the main product together with small amounts of 2-(indol-3-yl)-3H-indol-3-oxime; whereas the major product obtained when the same indole is reacted with nitrous acid is represented by 2-(indol-3-yl)-3H-indol-3-oxime. The reaction of 3-alkyl substituted indoles with nitrogen dioxide is rather complex and results in the formation of different nitro indoles, whereas nitrosation is observed when nitrous acid is used. Crystal structures of 2-(indol-3-yl)-3H-indol-3-one and of 4-nitro-N-acetyltryptamine have been determined by X-ray analysis.

Antioxidant activity of β-blockers: An effect mediated by scavenging reactive oxygen and nitrogen species?

The therapeutic effects of beta-blockers are normally explained by their capacity to block the beta-adrenoceptors, however, some of the beneficial cardiovascular effects shown by this group of compounds have already been associated with the antioxidant properties that some of them seem to possess. The beta-blockers atenolol, labetalol, metoprolol, pindolol, propranolol, sotalol, timolol, and carvedilol were tested for their putative scavenging activity for ROS (O(2)(-), H(2)O(2), HO(.), HOCl, and ROO(.)) and RNS ((.)NO and ONOO(-)). Some of the studied compounds are effective ROS and/or RNS scavengers, these effects being possibly useful in preventing oxidative damage verified in hypertension as well as in other cardiovascular diseases that frequently emerge in association with oxidative stress.