Phototransformation of hematoporphyrin in aqueous solution: Anomalous behavior at low oxygen concentration

The photoactivation of a photosensitizer is the initial step in photodynamic therapy (PDT) where photochemical reactions result in the production of reactive oxygen species and eventually cell death. In addition to oxidizing biomolecules, some of these photochemical reactions lead to photosensitizer degradation at a rate dependent on the oxygen concentration among other factors. We investigated photodegradation of Photogem A (R) (28 mu M), a hematoporphyrin derivative, at different oxygen concentrations (9.4 to 625.0 mu M) in aqueous solution. The degradation was monitored by fluorescence spectroscopy. The degradation rate (M/s) increases as the oxygen concentration increases when the molar ratio of oxygen to PhotogemA (R) is greater than 1. At lower oxygen concentrations (< 25 mu M) an inversion of this behavior was observed. The data do not fit a simple kinetic model of first-order dependence on oxygen concentration. This inversion of the degradation rate at low oxygen concentration has not previously been demonstrated and highlights the relationship between photosensitizer and oxygen concentrations in determining the photobleaching mechanism(s). The findings demonstrate that current models for photobleaching are insufficient to explain completely the effects at low oxygen concentration.

Occupational airborne contamination in South Brazil: 2. Oxidative stress detected in the blood of workers of incineration of hospital residues

One of the most useful methods for elimination of solid residues of health services (SRHS) is incineration. However, it also provokes the emission of several hazardous air pollutants such as heavy metals, furans and dioxins, which produce reactive oxygen species and oxidative stress. The present study, which is parallel to an accompanied paper (Avila Jr. et al., this issue), investigated several enzymatic and non-enzymatic biomarkers of oxidative stress in the blood (contents of vitamin E, lipoperoxidation = TBARS, reduced glutathione = GSH, oxidized glutathione = GSSG, and activities of glutathione S-transferase = GST, glutathione reductase = GR, glutathione peroxidase = GPx, catalase = CAT and superoxide dismutase = SOD), in three different groups (n = 20 each) exposed to airborne contamination associated with incineration of SRHS: workers directly (ca. 100 m from the incinerator) and indirectly exposed (residents living ca. 5 km the incineration site), and controls (non-exposed subjects). TBARS and GSSG levels were increased whilst GSH, TG and alpha-tocopherol contents were decreased in workers and residents compared to controls. Increased GST and CAT activities and decreased GPx activities were detected in exposed subjects compared to controls, while GR did not show any difference among the groups. In conclusion, subjects directly or indirectly exposed to SRHS are facing an oxidative insult and health risk regarding fly ashes contamination from SRHS incineration.

Tryptophan oxidation by singlet molecular oxygen [O-2 ((1)Delta(g))]: Mechanistic studies using O-18-labeled hydroperoxides, mass spectrometry, and light emission measurements

Proteins have been considered important targets for reactive oxygen species. Indeed, tryptophan (W) has been shown to be a highly susceptible amino acid to many oxidizing agents, including singlet molecular oxygen [O-2 ((1)Delta(g))]. In this study, two cis- and trans-tryptophan hydroperoxide (WOOH) isomers were completely characterized by HPLC/mass spectrometry and NMR analyses as the major W-oxidation photoproducts. These photoproducts underwent thermal decay into the corresponding alcohols. Additionally, WOOHs were shown to decompose under heating or basification, leading to the formation of N-formylkynurenine (FMK). Using O-18-labeled hydroperoxides ((WOOH)-O-18-O-18), it was possible to confirm the formation of two oxygen-labeled FMK molecules derived from (WOOH)-O-18-O-18 decomposition. This result demonstrates that both oxygen atoms in FMK are derived from the hydroperoxide group. In addition, these reactions are chemiluminescent (CL), indicating a dioxetane cleavage pathway. This mechanism was confirmed since the CL spectrum of the WOOH decomposition matched the FMK fluorescence spectrum, unequivocally identifying FMK as the emitting species.

Effect of flavonoids on 2 `-deoxyguanosine and DNA oxidation caused by singlet molecular oxygen

Antioxidant potential is generally investigated by assaying the ability of a compound to protect biological systems from free radicals. However, non-radical reactive oxygen species can also be harmful. Singlet molecular oxygen ((1)O(2)) is generated by energy transfer to molecular oxygen. The resulting (1)O(2) is able to oxidize the nucleoside 2`-deoxyguanosine (dGuo), which leads to the formation of 8-oxo-7,8-dihydro-2`-deoxyguanosine (8-oxodGuo) and spiroiminodihydantoin 2`-deoxyribonucleoside diastereomers (dSp) in an aqueous solution. The main objective of the present study was to verify whether the presence of flavonoids (flavone, apigenin, quercetin, morin and catechin) at different concentrations could protect dGuo from (1)O(2) damage. Of the tested flavonoids, flavone possessed antioxidant activity, as determined by a decrease in the formation of both products. Apigenin, morin, quercetin and catechin all increased the formation of 8-oxodGuo at a concentration of 100 mu M. The quantification of plasmid strand breaks after treatment with formamidopyrimidine-DNA glycosylase showed that flavone protected and quercetin and catechin enhanced DNA oxidation. Our results show that compounds, such as flavonoids, may affect the product distribution of (1)O(2)-mediated oxidation of dGuo, and, in particular, high concentrations of flavonoids with hydroxyl groups in their structure lead to an increase in the formation of the mutagenic lesion 8-oxodGuo. (C) 2010 Elsevier Ltd. All rights reserved.

Occupational airborne contamination in south Brazil: 1. Oxidative stress detected in the blood of coal miners

Reactive oxygen species and nitrogen species have been implicated in the pathogenesis of coal dust-induced toxicity. The present study investigated several oxidative stress biomarkers (Contents of lipoperoxidation = TBARS, reduced = GSH, oxidized = GSSG and total glutathione = TG, alpha-tocopherol, and the activities of glutathione S-transferase = GST, glutathione reductase = GR, glutathione peroxidase = GPx, catalase = CAT and superoxide dismutase = SOD), in the blood of three different groups (n = 20 each) exposed to airborne contamination associated with coal mining activities: underground workers directly exposed, surface workers indirectly exposed, residents indirectly exposed (subjects living near the mines), and controls (non-exposed subjects). Plasma TBARS were increased and whole blood TG and GSH levels were decreased in all groups compared to controls. Plasma alpha-tocopherol contents showed approximately half the values in underground workers compared to controls. GST activity was induced in workers and also in residents at the vicinity of the mining plant, whilst CAT activity was induced only in mine workers. SOD activity was decreased in all groups examined, while GPx activity showed decreased values only in underground miners, and GR did not show any differences among the groups. The results showed that subjects directly and indirectly exposed to coal dusts face an oxidative stress condition. They also indicate that people living in the vicinity of the mine plant are in health risk regarding coal mining-related diseases.

Coordenação entre as respostas da catalase e da ascorbato peroxidade em folhas de feijão caupi submetidas a diferentes fontes de peróxido de hidrogênio

The plants are often exposed to variations in environmental conditions that may trigger metabolic disturbances leading to a consequent loss in productivity of crops. These stressful conditions usually induce an accumulation of reactive oxygen species (ROS) in the cell, a condition known how oxidative stress. Among these species, hydrogen peroxide (H2O2) is an important molecule involved in numerous signaling mechanisms. The present study aimed to understand the relationship between the different enzymatic mechanisms of elimination of H2O2 by catalase (CAT) and ascorbate peroxidase (APX) in leaf tissues of seedlings of the species Vigna unguiculata L. Walp, under conditions of oxidative stress induced by application of CAT inhibitor, 3-amino-1,2,4-triazole (3-AT), and H2O2 itself on the roots. Three experiments were conducted. The first experiment was performed applying the compound 3-AT (5 mM) during the time (hours). In the second experiment, seedlings were exposed to different concentrations of H2O2 (2.5, 5.0, 7.5, 10 mM) for 48 h. The third strategy included the pre-treatment with H2O2 (2.5 mM) for 24 h, followed by subsequent treatment with the inhibitor 3-AT and recovery control condition. Treatment with 3-AT causes a strong inhibition of CAT activity in leaf tissues accompanied by an increase of activity of APX. However a decrease in oxidative damage to lipids is not observed as indicated by TBARS. It was observed that activity of APX is directly linked to the content of peroxide. Inductions in the activities of CAT and APX were observed mainly in the seedlings treated with 2.5 mM H2O2. This can be associated with a decrease in oxidative damage to lipids. In contrast, one same tendency was not observed in treatments with higher concentrations of this ROS. These results suggest that the concentration of 2.5 mM H2O2 can induce responses antioxidants later in seedling cowpea. This concentration when applied as pre-treatment for 24 h promoted an induction systems removers CAT and APX, both in activity and in terms of gene expression. However this increment was not observed in the recovered plants and the plants subsequently subjected to 3-AT. Additionally, the pretreatment was not sufficient to attenuate the inhibition of CAT activity and oxidative damage to lipids caused by the subsequent application of this inhibitor. The results showed that the application of 3-AT and H2O2 in the root systems of seedlings of cowpea promote changes in the parameters analyzed in leaf tissues that indicate a direct response to the presence of these factors or systemic signaling mecanisms. H2O2 appears to activate the responses of two antioxidant systems in this study thar does not promote greater protection in case of additional treatment with 3-AT. This demonstrates the importance of the CAT system. In this work, complete results indicate that there is a difference between the signaling and the effects caused by exposure to H2O2 and by treatment with 3-AT

The malate synthase of Paracoccidioides brasiliensis is a linked surface protein that behaves as an anchorless adhesin

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Intermediate reactive oxygen and nitrogen from macrophages induced by Brazilian lichens

The activity of ten compounds isolated from Brazilian lichen over the release of hydrogen peroxide and nitric oxide was evaluated in the culture of peritoneal macrophage cells from mice. Salazinic, secalonic A and fumarprotocetraric acids were the compounds that induced the greatest release of H2O2, whereas 12R-usnic and diffractaic acids induced the release of NO. These results indicate that lichen products have potential immunological modulating activities. (C) 2004 Elsevier B.V. All rights reserved.

Effects of pancreas transplantation on oxidative stress in pulmonary tissue from alloxan-induced diabetic rats

Purpose. There is considerable evidence that cellular oxidative stress caused by hyperglycemia plays an important role in the genesis and evolution of chronic diabetic lesions. In this study, we determined the effectiveness of pancreas transplantation (PT) in preventing the imbalance caused by excessive production of reactive oxygen species over antioxidant defenses in lungs of rats rendered diabetic by alloxan injection.Methods. Sixty inbred male Lewis rats, weighing 250-280 g, were randomly assigned to 3 experimental groups: NC, 20 nondiabetic control rats; DC, 20 untreated diabetic control rats; and PT, 20 diabetic rats that received syngeneic PT from normal donor Lewis rats. Each group was further divided into 2 subgroups of 10 rats each which were killed after 4 and 12 weeks of follow-up. Plasma glucose, glycosylated hemoglobin, and insulin levels were determined in all rats. Lipid hydroperoxide (LPO) concentrations and enzyme activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) were measured in the pulmonary tissue of all rats.Results. The DC rats showed elevated blood glucose and glycosylated hemoglobin levels, with insulin blood levels significantly lower than the NC rats (P < .001). They also showed significantly increased LPO concentrations in the lungs (P < .01) after 4 and 12 weeks of follow-up. In contrast, SOD, CAT, and GSH-Px antioxidant activities were significantly reduced in these periods (P < .01) 12 weeks after diabetes induction. Successful PT corrected all clinical and metabolic changes in the diabetic rats, with sustained normoglycemia throughout the study. Excessive lung LPO production and low SOD, CAT, and GSH-Px antioxidant activities were already back to normal 4 weeks after PT.Conclusion. PT can control oxidative stress in pulmonary tissue of diabetic rats. It may be the basis for preventing chronic diabetic lesions in lungs.

IVF/ICSI outcomes after culture of human embryos at low oxygen tension: a meta-analysis

Background: Improved pregnancy, implantation, and birth rates have been reported after the use of reduced O2 concentration during embryo culture, mainly due to a reduction of the cumulative detrimental effects of reactive oxygen species. However, some studies have failed to report any positive effects. The objective of this meta-analysis was to evaluate the effect of a low-O2 environment on IVF/intracytoplasmic sperm injection (ICSI) outcomes.Methods: All available published and ongoing randomised trials that compared the effects of low (similar to 5%; OC similar to 5) and atmospheric (similar to 20%; OC similar to 20) oxygen concentrations on IVF/ICSI outcomes were included. Search strategies included online surveys of databases from 1980 to 2011. The outcomes measured were fertilisation rate, implantation rate and ongoing pregnancy rates. The fixed effects model was used to calculate the odds ratio.Results: Seven studies were included in this analysis. The pooled fertilisation rate did not differ significantly (P = 0.54) between the group of oocytes cultured at low O2 tension and the group at atmospheric O2 tension. Concerning all cycles, the implantation (P = 0.06) and ongoing pregnancy (P = 0.051) rates were not significantly different between the group receiving transferred sets containing only OC similar to 5 embryos and the group receiving transferred sets with only OC similar to 20 embryos. In a meta-analysis performed for only those trials in which embryos were transferred on day 2/3, implantation (P = 0.63) and ongoing pregnancy (P = 0.19) rates were not significantly different between the groups. In contrast, when a meta-analysis was performed using only trials in which embryos were transferred on days 5 and 6 (at the blastocyst stage), the group with transferred sets of only OC similar to 5 embryos showed a statistically significantly higher implantation rate (P = 0.006) than the group receiving transferred sets with only OC similar to 20 embryos, although the ongoing pregnancy (P = 0.19) rates were not significantly different between the groups.Conclusions: Despite some promising results, it seems too early to conclude that low O2 culture has an effect on IVF outcome. Additional randomised controlled trials are necessary before evidence-based recommendations can be provided. It should be emphasised that the present meta-analysis does not provide any evidence that low oxygen concentration is unnecessary.

Lipid peroxidation and generation of hydrogen peroxide in frozen-thawed ram semen cryopreserved in extenders with antioxidants

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Production of reactive oxygen (H2O2) and nitrogen (NO) intermediates and TNF-α in mice genetically selected for high (H) and low (L) antibody response and experimentally infected with Leptospira serovar pomona

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Nitric oxide in plants: a brief discussion on this multifunctional molecule

Diversos estudos vêm sendo realizados com a finalidade de aumentar o conhecimento sobre a ocorrência e a atividade do óxido nítrico (ON) nas plantas. Nesse sentido, a presente revisão objetivou abordar alguns aspectos referentes ao on nas plantas, tais como propriedades químicas, vias de síntese, efeitos fisiológicos, ação antioxidante, transdução do sinal, interação com hormônios vegetais e expressão gênica. Nos últimos anos, muitos avanços têm sido obtidos em relação à síntese de on e seus efeitos fisiológicos nas plantas. Porém, os mecanismos moleculares que fundamentam seus efeitos permanecem pouco compreendidos. É sinalizada uma investigação em detalhes sobre as estreitas interações entre ON, Ca2+, ADP-ribose cíclica (cADPR) e proteínas quinases. Além disso, ainda não foi possível identificar uma enzima vegetal que apresente atividade semelhante à da óxido nítrico sintase (NOS). A elucidação de tais aspectos representa um desafio para futuros trabalhos.

Interaction between Advanced Glycation End Products Formation and Vascular Responses in Femoral and Coronary Arteries from Exercised Diabetic Rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)