Enrique Pinzón

Titanium dioxide nanoparticles impair lung mitochondrial function

Titanium dioxide nanoparticles (TiO(2) NPs) are used in an increasing number of human products such as cosmetics, sunscreen, toothpaste and paints. However, there is clear evidence about effects associated to TiO(2) NPs exposure, which include lung inflammation and tumor formation and these effects are related to reactive oxygen species (ROS) formation. The ROS generation could be attributed to a mitochondrial dysfunction. Even though, it has been shown that TiO(2) NPs exposure can induce some alterations in mitochondria including cytochrome c release to cytosol, change in mitochondrial permeability and decrease of mitochondrial membrane potential (ΔΨ(m)), there is no information about the changes in mitochondrial function induced by TiO(2) NPs. We hypothesized that TiO(2) NPs effects are associated with mitochondrial dysfunction and redox unbalance. To test our hypothesis we isolated mitochondria from lung tissue of rats and exposed them to 10(g TiO(2) NPs (particle size<25nm)/mg protein for 1h. Our results showed that TiO(2) NPs decreases NADH levels and impairs ΔΨ(m) and mitochondrial function accompanied by ROS generation during mitochondrial respiration.

On the antioxidant properties of kynurenic acid: Free radical scavenging activity and inhibition of oxidative stress

Kynurenic acid (KYNA) is an endogenous metabolite of the kynurenine pathway for tryptophan degradation and an antagonist of both N-methyl-D-aspartate (NMDA) and alpha-7 nicotinic acetylcholine (α7nACh) receptors. KYNA has also been shown to scavenge hydroxyl radicals (OH) under controlled conditions of free radical production. In this work we evaluated the ability of KYNA to scavenge superoxide anion (O(2)(-)) and peroxynitrite (ONOO(-)). The scavenging ability of KYNA (expressed as IC(50) values) was as follows: OH=O(2)(-)>ONOO(-). In parallel, the antiperoxidative and scavenging capacities of KYNA (0-150 μM) were tested in cerebellum and forebrain homogenates exposed to 5 μM FeSO(4) and 2.5 mM 3-nitropropionic acid (3-NPA). Both FeSO(4) and 3-NPA increased lipid peroxidation (LP) and ROS formation in a significant manner in these preparations, whereas KYNA significantly reduced these markers. Reactive oxygen species (ROS) formation were determined in the presence of FeSO(4) and/or KYNA (0-100 μM), both at intra and extracellular levels. An increase in ROS formation was induced by FeSO(4) in forebrain and cerebellum in a time-dependent manner, and KYNA reduced this effect in a concentration-dependent manner. To further know whether the effect of KYNA on oxidative stress is independent of NMDA and nicotinic receptors, we also tested KYNA (0-100 μM) in a biological preparation free of these receptors - defolliculated Xenopus laevis oocytes - incubated with FeSO(4) for 1 h. A 3-fold increase in LP and a 2-fold increase in ROS formation were seen after exposure to FeSO(4), whereas KYNA attenuated these effects in a concentration-dependent manner. In addition, the in vivo formation of OH evoked by an acute infusion of FeSO(4) (100 μM) in the rat striatum was estimated by microdialysis and challenged by a topic infusion of KYNA (1 μM). FeSO(4) increased the striatal OH production, while KYNA mitigated this effect. Altogether, these data strongly suggest that KYNA, in addition to be a well-known antagonist acting on nicotinic and NMDA receptors, can be considered as a potential endogenous antioxidant.

Protective effect of sulforaphane pretreatment against cisplatin-induced liver and mitochondrial oxidant damage in rats

In the present work was analyzed whether sulforaphane (SFN) may protect against cisplatin (CIS)-induced hepatic damage, oxidant stress and mitochondrial dysfunction. Four groups of male Wistar rats were studied: control, CIS, CIS+SFN and SFN. SFN was given i.p. (500 μg/kg/d × 3 days) before CIS administration (single i.p. injection, 10mg/kg). Rats were sacrificed 3 days after CIS injection to evaluate hepatic damage (histological analysis, liver/body weight ratio and serum activity of aspartate aminotransferase and alanine aminotransferase), oxidant stress (lipid peroxidation and protein carbonyl and glutathione content), antioxidant enzymes (catalase, glutathione reductase, glutathione peroxidase, glutathione-S-transferase and superoxide dismutase) in liver homogenates and isolated mitochondria and mitochondrial function (oxygen consumption using either malate/glutamate or succinate as substrates and the activity of mitochondrial complex I, II, II-III, IV and V). Furthermore it was evaluated if SFN is able to scavenge some reactive oxygen species in vitro. It was found that SFN prevents CIS-induced (a) hepatic damage, (b) oxidant stress and decreased activity of antioxidant enzymes in liver and mitochondria and (c) mitochondrial alterations in oxygen consumption and decreased activity of mitochondrial complex I. It was also found that the scavenging ability of SFN for peroxynitrite anion, superoxide anion, singlet oxygen, peroxyl radicals, hydrogen peroxide and hydroxyl radicals was very low or negligible. The hepatoprotective effect of SFN was associated to the preservation of mitochondrial function, antioxidant enzymes and prevention of liver and mitochondrial oxidant stress.

Deferoxamine pretreatment prevents Cr(VI)-induced nephrotoxicity and oxidant stress: Role of Cr(VI) chelation

Deferoxamine (DFO) is a recognized iron chelator which has been shown to exert nephroprotection in models of toxic nephropathies. In the present work the potential protective effects of DFO against Cr(VI)-induced nephrotoxicity and oxidant stress were evaluated. Rats were injected with a single injection (15mg/kg, s.c.) of potassium dichromate (K(2)Cr(2)O(7)). DFO was given as a single i.p. injection 30min before K(2)Cr(2)O(7) administration at three different doses (100, 200 and 400mg/kg). It was found that DFO pretreatment attenuated, in a dose-dependent way, K(2)Cr(2)O(7)-induced renal dysfunction and structural alterations evaluated by serum creatinine, blood urea nitrogen, creatinine clearance, proteinuria, plasma glutathione peroxidase activity, urinary excretion of N-acetyl-β-d-glucosaminidase and histological analyses. Furthermore, DFO prevented the K(2)Cr(2)O(7)-induced renal oxidant stress and the decrease in the activity of the antioxidant enzymes superoxide dismutase, glutathione reductase, glutathione peroxidase, glutathione-S-transferase and catalase. Finally it was found that DFO, at 400mg/kg, decreases renal Cr(VI) content which prompted us to evaluate the potential Cr(VI) chelating properties of this compound. Indeed was found in an in vitro assay that DFO was an effective Cr(VI) chelator with an IC(50) of 800μg. In additional groups of rats was found that DFO posttreatment was ineffective to attenuate K(2)Cr(2)O(7)-induced nephrotoxicity and renal oxidant stress. Furthermore, DFO was unable to modify urinary excretion of total chromium. The nephroprotective effect of DFO against Cr(VI)-induced nephrotoxicity and oxidant stress may be explained, at least partially, by the ability of DFO to chelate Cr(VI) and to attenuate renal Cr(VI) content. However, it cannot be excluded that the ability of DFO to chelate iron may also be involved in the protection observed in our study.

Cannabinoid receptor agonists reduce the short-term mitochondrial dysfunction and oxidative stress linked to excitotoxicity in the rat brain.

The endocannabinoid system (ECS) is involved in a considerable number of physiological processes in the Central Nervous System. Recently, a modulatory role of cannabinoid receptors (CBr) and CBr agonists on the reduction of the N-methyl-d-aspartate receptor (NMDAr) activation has been demonstrated. Quinolinic acid (QUIN), an endogenous analog of glutamate and excitotoxic metabolite produced in the kynurenine pathway (KP), selectively activates NMDAr and has been shown to participate in different neurodegenerative disorders. Since the early pattern of toxicity exerted by this metabolite is relevant to explain the extent of damage that it can produce in the brain, in this work we investigated the effects of the synthetic CBr agonist WIN 55,212-2 (WIN) and other agonists (anandamide or AEA, and CP 55,940 or CP) on early markers of QUIN-induced toxicity in rat striatal cultured cells and rat brain synaptosomes. WIN, AEA and CP exerted protective effects on the QUIN-induced loss of cell viability. WIN also preserved the immunofluorescent signals for neurons and CBr labeling that were decreased by QUIN. The QUIN-induced early mitochondrial dysfunction, lipid peroxidation and reactive oxygen species (ROS) formation were also partially or completely prevented by WIN pretreatment, but not when this CBr agonist was added simultaneously with QUIN to brain synaptosomes. These findings support a neuroprotective and modulatory role of cannabinoids in the early toxic events elicited by agents inducing excitotoxic processes.

Nordihydroguaiaretic acid induces Nrf2 nuclear translocation in vivo and attenuates renal damage and apoptosis in the ischemia and reperfusion model

It has been shown that the pretreatment with nordihydroguaiaretic acid (NDGA), a lignan with direct and indirect antioxidant properties, protects against the ischemia-reperfusion (I/R)-induced renal oxidant damage. Although it has been shown that NDGA induces Nrf2 nuclear translocation in renal epithelial LLC-PK1 cells in culture, it is unknown if NDGA may induce Nrf2 translocation in vivo. In this work was explored if NDGA is able to induce in vivo Nrf2 nuclear translocation in kidneys of rats submitted to uni-nephrectomy (U-NX) or I/R injury. Four groups of male Wistar rats were used: U-NX, NDGA, I/R, and I/R+NDGA. NDGA was injected i.p. (10mg/kg/day) starting 48 h before I/R. Kidney samples were obtained at 3 h of reperfusion after to measure Nrf2 translocation. Additional groups of rats were studied at 24 h of reperfusion to measure histological damage and apoptosis. NDGA was able to induce Nrf2 translocation in vivo in kidneys of rats submitted to both U-NX and I/R injury and to protect against renal histological damage and apoptosis. It is concluded that the pretreatment of NDGA is able to induce in vivo nuclear Nrf2 translocation in kidney of rats suggesting that this may be involved in the renoprotection against I/R.

Antioxidant properties of xanthones from Calophyllum brasiliense: prevention of oxidative damage induced by FeSO4

BackgroundReactive oxygen species (ROS) are important mediators in a number of degenerative diseases. Oxidative stress refers to the imbalance between the production of ROS and the ability to scavenge these species through endogenous antioxidant systems. Since antioxidants can inhibit oxidative processes, it becomes relevant to describe natural compounds with antioxidant properties which may be designed as therapies to decrease oxidative damage and stimulate endogenous cytoprotective systems. The present study tested the protective effect of two xanthones isolated from the heartwood of Calophyllum brasilienses against FeSO4-induced toxicity.MethodsThrough combinatory chemistry assays, we evaluated the superoxide (O2●—), hydroxyl radical (OH●), hydrogen peroxide (H2O2) and peroxynitrite (ONOO—) scavenging capacity of jacareubin (xanthone III) and 2-(3,3-dimethylallyl)-1,3,5,6-tetrahydroxyxanthone (xanthone V). The effect of these xanthones on murine DNA and bovine serum albumin degradation induced by an OH• generator system was also evaluated. Additionally, we investigated the effect of these xanthones on ROS production, lipid peroxidation and glutathione reductase (GR) activity in FeSO4-exposed brain, liver and lung rat homogenates.ResultsXanthone V exhibited a better scavenging capacity for O2●—, ONOO- and OH● than xanthone III, although both xanthones were unable to trap H2O2. Additionally, xanthones III and V prevented the albumin and DNA degradation induced by the OH● generator system. Lipid peroxidation and ROS production evoked by FeSO4 were decreased by both xanthones in all tissues tested. Xanthones III and V also prevented the GR activity depletion induced by pro-oxidant activity only in the brain.ConclusionsAltogether, the collected evidence suggests that xanthones can play a role as potential agents to attenuate the oxidative damage produced by different pro-oxidants.

The antithrombotic effect of the aminoestrogen prolame (N-(3-hydroxy-1,3,5(10)-estratrien-17B-YL)-3-hydroxypropylamine) is linked to an increase in nitric oxide production by platelets and endothelial cells

OBJECTIVE Women under hormone replacement therapy carry an increased risk of venous thromboembolism (VTE), mostly during the first year. Despite great efforts devoted to hormone therapy research, VTE remains a major drawback of estrogenic therapy, and the search for new compounds continues. We have synthesized and evaluated prolame, an aminoestrogen with anticoagulant properties. The aim of our work was to elucidate the anticoagulant mechanism of prolame. METHODS We studied the effects of prolame on nitric oxide (NO) synthesis in cultured endothelial cells and platelets using flow cytometry, on NO metabolites using a modified Griess method, on NO formation in vivo using electron paramagnetic resonance spectroscopy, on participation of nuclear estrogen receptors using flow cytometry, and on endothelial NO synthase (eNOS) mRNA expression using RT-PCR. We also studied the impact of prolame-treated endothelial cells (EC) on ADP-induced platelet aggregation, as well as the ability to prevent occlusive thrombi in an in vivo mice thrombosis model. RESULTS (a) Prolame induces NO production in ECs, platelets, and in a mouse model in vivo. (b) The NO-elevating effect of prolame can only be partially attributed to the nuclear estrogen receptors (ERs) since endothelial nitric oxide synthase (e-NOS) is slightly induced (37%) in ECs treated with prolame. (c) Platelets become 60% less responsive to aggregation induced by 10muM ADP when in suspension with prolame-treated ECs. (d) Prolame reduces the formation of thrombi in an in vivo thrombosis model. CONCLUSIONS Prolame could be a preferred alternative to other estrogens because of its reduced thromboembolic risk.

Curcumin prevents paracetamol-induced liver mitochondrial alterations

In the present study was evaluated if curcumin is able to attenuate paracetamol (PCM)‐induced mitochondrial alterations in liver of mice.

Acute restraint stress reduces hippocampal oxidative damage and behavior in rats: Effect of S-allyl cysteine.

AIMS This simple study was designed to investigate whether acute restraint stress can generate changes in behavioral tests and hippocampal endpoints of oxidative stress in rats, and if the antioxidant S-allyl cysteine (SAC) can prevent these alterations. MATERIALS AND METHODS We evaluated motor activity, forced swimming and anxiety behavior, as well as the hippocampal levels of lipid peroxidation and the activities of glutathione-related enzymes in animals submitted to mild immobilization. The effect of SAC (100 mg/kg, i.p.), given to rats every day 30 min before starting the immobilization session, was also investigated. Immobilization (restraint) stress was induced for a period of 6 h per day for five consecutive days. KEY FINDINGS Our results indicate that, under the tested conditions, acute restraint stimulates compensatory behavioral tasks (motor activity, anxiety and forced swimming) to counteract the stressing conditions prevailing, and selectively increased the levels of lipid peroxidation and the enzyme activities of glutathione-S-transferase (GST) and glutathione peroxidase (GPx) in the hippocampus also as adaptive responses. SAC exhibited preventive effects in the stressed group as it improved behavior, reduced lipid peroxidation and prevented the increase of GST and GPx activities, suggesting that this antioxidant blunted primary pro-oxidative stimuli induced by restraint stress. SIGNIFICANCE Findings of this work also confirm that the use of antioxidants such as SAC can provide effective protection against the acute oxidative damage associated with anxiety produced by stressing conditions.