Jordi Mallol

Melatonin reduces oxidative stress and increases gene expression in the cerebral cortex and cerebellum of aluminum-exposed rats.

Abstract:  The pro‐oxidant activity of aluminum (Al), the protective role of exogenous melatonin, as well as the mRNA levels of some antioxidant enzymes, were determined in cortex and cerebellum of rats following exposure to Al and/or melatonin. Two groups of male rats received intraperitoneal injections of Al lactate or melatonin at doses of 7 mg Al/kg/day and 10 mg/kg/day, respectively, for 11 wk. A third group of animals received concurrently Al lactate (7 mg Al/kg/day) plus melatonin (10 mg/kg/day) during the same period. A fourth group of rats was used as control. At the end of the treatment, the cerebral cortex and cerebellum were removed and processed to examine the following oxidative stress markers: glutathione transferase (GST), reduced glutathione (GSH), oxidized glutathione (GSSG), superoxide dismutase (SOD), glutathione reductase, glutathione peroxidase (GPx), catalase (CAT), thiobarbituric acid reactive substances (TBARS), as well as protein content. Moreover, gene expression of Cu‐ZnSOD, MnSOD, GPx and CAT was evaluated by real‐time RT‐PCR. On the other hand, Al, Fe, Mn, Cu and Zn concentrations were determined in cortex and cerebellum of rats. Oxidative stress was promoted in both neural regions following Al administration, resulting from the pro‐oxidant activity related with an increase in tissue Al concentrations. In contrast, melatonin exerted an antioxidant action which was related with an increase in the mRNA levels of the antioxidant enzymes evaluated. The results of the present investigation emphasize the potential use of melatonin as a supplement in the therapy of neurological disorders in which oxidative stress is involved.

Aluminum-induced pro-oxidant effects in rats: protective role of exogenous melatonin

Abstract: In recent years, it has been suggested that oxidative stress is a feature of Alzheimers disease in which aluminum (Al) could exacerbate oxidative events. The goal of the present study was to assess in rats the pro‐oxidant effects induced by Al exposure, as well as the protective role of exogenous melatonin. Two groups of male rats were intraperitoneally injected with Al only or melatonin only, at doses of 5 and 10 mg/kg/day, respectively for 8 wk. During this period, a third group of animals received Al (5 mg/kg/day) and melatonin (10 mg/kg/day). At the end of the treatment period, rats were anesthesized and arterial blood was obtained. Thereafter, animals were killed and liver and brain (cortex, hippocampus and cerebellum) were removed. These tissues were processed to examine oxidative stress markers: glutathione transferase (GST), reduced glutathione (GSH), oxidized glutathione (GSSG), superoxide dismutase (SOD), glutathione reductase (GR), glutathione peroxidase (GPx), catalase (CAT), thiobarbituric acid reactive substances (TBARS), as well as protein content. Samples of these tissues were also used to determine Al, Fe, Mn, Cu and Zn concentrations. The results show that Al exposure promotes oxidative stress in different neural areas, including those in which Al concentrations were not significantly increased. The biochemical changes observed in neural tissues show that Al acts as pro‐oxidant, while melatonin exerts an antioxidant action in Al‐treated animals. The protective effects of melatonin against cellular damage caused by Al‐induced oxidative stress, together with its low toxicity, make melatonin worthy of investigation as a potential supplement to be included in the treatment of neurological disorders in which the oxidative effects must be minimized.

Changes in oxidative stress parameters and neurodegeneration markers in the brain of the senescence-accelerated mice SAMP-8

The senescence-accelerated strains of mice (SAMP) are well-characterized animal models of senescence. Senescence may be related to enhanced production or defective control of reactive oxygen species, which lead to neuronal damage. Therefore, the activity of various oxidative-stress related enzymes was determined in the cortex of 5 months-old senescence-accelerated mice prone-8 (SAMP-8) of both sexes and compared with senescence-accelerated mice-resistant-1 (SAMR-1). Glutathione reductase and peroxidase activities in SAMP-8 male mice were lower than in male SAMR-1, and a decreased catalase activity was found in both male and female SAMP-8 mice, which correlates with the lower catalase expression found by Western blotting. Nissl staining showed marked loss of neuronal cells in the cerebral cortex of five month-old SAMP-8 mice. SAMP-8 mice also had marked astrogliosis and microgliosis. We also found an increase in caspase-3 and calpain activity in the cortex. In addition, we observed morphological changes in the immunostaining of tau protein in SAMP-8, indicative of a loss of their structural function. Altogether, these results show that, at as early as 5 months of age, SAMP-8 mice have cytological and molecular alterations indicative of neurodegeneration in the cerebral cortex and suggestive of altered control of the production of oxidative species and hyper-activation of calcium-dependent enzymes.

Oxidative Stress-Related Markers and Langerhans Cells in a Hairless Rat Model Exposed to UV Radiation

Biomarkers related to the oxidative stress in blood and epidermis and the number of Langerhans cells were determined in hairless rats after acute irradiation with 1.54, 1.93, or 2.41 J/cm2 of ultraviolet (UV) light and chronic exposure to 13 suberythemal UV doses of 1.1 J/cm2 for 2 mo. After acute UV irradiation, in epidermis, the thiobarbituric acid-reactive substances (TBARS) content increased at the highest UV dose, whereas the activities of glutathione S-transferase and catalase rose and the oxidized glutathione (GSSG) content diminished at all UV doses. In erythrocytes, glutathione S-transferase activity increased at the two lowest UV doses, glutathione peroxidase activity rose at all UV doses, and catalase activity increased after the highest UV dose. In plasma, the TBARS content and the reduced glutathione (GSH)/GSSG ratio increased at the highest UV dose; the number of Langerhans cells decreased at all UV doses. Linear Pearson correlation analysis revealed many relationships between different biomarkers, and multiple linear regression analysis indicated that the number of Langerhans cells was predicted by epidermal GSSG and catalase (R 2 = .64) and by erythrocytic glutathione peroxidase and GSSG (R 2 = .72). After suberythemal UV radiation, in epidermis, the GST activity and the content of GSH and GSSG increased; in erythrocytes, the GST activity decreased and the GSH/GSSG ratio increased. Thus, the hairless rat appears to be a useful model for studying the oxidative stress-related mechanisms after UV radiation, which are involved in the loss of the immune capacity mediated by Langerhans cells, even at suberythemal doses. This study was conducted at the School of Medicine, Rovira i Virgili University, Reus, Spain. This work was supported by a Research and Development grant (SAF-99-0048) from the Spanish Ministry of Health and Social Security and cosponsored by Novartis CH (Spain). We thank Prof. J. Fernández of the School of Medicine (Reus) for his help with the statistical analyses.

Melatonin reduces oxidative stress in erythrocytes and plasma of senescence‐accelerated mice

Abstract:  It has been suggested that oxidative stress is a feature of aging. The goal of the present study was to assess the oxidant effects related to aging and the protective role of exogenous melatonin in senescence‐accelerated mice (SAMP8). Two groups of SAMP8 mice (males and females) were compared with their respective control groups of SAMR1 mice (senescence‐resistant inbred strain) to determine their oxidative status without melatonin treatment. Four other groups of the same characteristics were treated with melatonin (10 mg/kg/day) in their drinking water. The melatonin concentration in the feeding bottles was titrated according to water consumption and body weight (i.e. 0.06 mg/mL for 30 g of body weight and 5 mL/day of water consumption). The treatment began when animals were 1‐month old and continued for 9 months. When mice were 10‐month old, they were anesthetized and blood was obtained. Plasma and erythrocytes were processed to examine oxidative stress markers: reduced glutathione (GSH), oxidized glutathione (GSSG), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR), glutathione S‐transferase (GST), thiobarbituric acid reactive substances (TBARS), and hemolysis. The results showed greater oxidative stress in SAMP8 than in SAMR1, largely because of a decrease in GSH levels and to an increase in GSSG and TBARS with the subsequent induction of the antioxidant enzymes GPX and GR. Melatonin, as an antioxidant molecule, improved the glutathione‐related parameters, prevented the induction of GPX in senescent groups, and promoted a decrease in SOD and TBARS in almost all the groups.

Polypodium leucotomos extract inhibits glutathione oxidation and prevents Langerhans cell depletion induced by UVB/UVA radiation in a hairless rat model.

Abstract:  In this report, we have addressed the effect of oral administration of a hydrophilic extract of the fern Polypodium leucotomos (PL) on the deleterious effects of ultraviolet radiation (UVR) on the levels of epidermal and plasmatic antioxidants in hairless rats. We have found that pretreatment with PL effectively reduced glutathione oxidation in both blood and epidermis, suggesting a potent systemic antioxidant effect. In addition, PL inhibited UVR‐mediated Langerhans cell (LC) depletion. Our results demonstrate the efficacy of PL as an oral antioxidant and photoimmunoprotective agent and support its employment as a complement to topical sunscreens.

Evaluation of oxidative stress biomarkers in patients with chronic renal failure: a case control study

BackgroundOxidative stress is related to several diseases, including chronic renal insufficiency. The disequilibrium in the oxidant-antioxidant balance is the result of several metabolic changes. The majority of studies to-date have evaluated the grade of oxidative stress with a single biomarker, or a very limited number of them.FindingsThe present study used several important biomarkers to establish a score relating to oxidative stress status (glutathione S-transferase, superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, reduced and oxidized glutathione, thiobarbituric acid reactive substances and hemolysis test). The score of oxidative stress (SOS) was then applied to a group of patients with renal insufficiency not on hemodialysis, and compared to healthy control individuals.The score for patients with chronic renal insufficiency was significantly different from that of the healthy control group (0.62 ± 1.41 vs. -0.05 ± 0.94; p < 0.001). The comparison between patients with chronic renal insufficiency and control individuals showed significant differences with respect to changes in the enzymatic antioxidant systems (glutathione S-transferase, glutathione reductase), non-enzymatic antioxidant system (oxidized glutathione) and oxidizability (hemolysis test) indicating significant oxidative stress associated with chronic renal insufficiency.ConclusionsPatients with chronic renal insufficiency not on hemodialysis are susceptible to oxidative stress. The mechanisms that underlie this status are the consequence of changes in glutathione and related enzymes. The SOS scoring system is a useful biochemical parameter to evaluate the influence of oxidative stress on the clinical status of these patients.

Synthesis and pharmacological evaluation of (2-oxaadamant-1-yl)amines

Abstract The synthesis of several (2-oxaadamant-1-yl)amines is reported. They were evaluated as NMDA receptor antagonists and several of them were more active than amantadine, but none was more potent than memantine. None of the tested compounds displayed antiviral activity. Two of the derivatives showed a significant level of trypanocidal activity.

Polypodium leucotomos decreases UV‐induced epidermal cell proliferation and enhances p53 expression and plasma antioxidant capacity in hairless mice

A single dose of ultraviolet radiation (UVR) induces significant changes in blood and skin of hairless mice. Oral administration of a hydrophilic extract of the fern Polypodium leucotomos (PL, 300 mg/kg during 5 days before UVR and for two additional days after irradiation) modulates some of the effects of UVR. Most significantly, PL administration reduced the number of proliferating cells by 13%, increased the number of p53+ cells by 63%, enhanced the antioxidant plasma capacity (ORAC) by 30% and reinforced the network of dermal elastic fibres. Western blot analysis of skin antioxidant‐related enzymes failed to demonstrate significant changes caused by PL. Thus, the beneficial effect of PL likely owes to its antioxidant and anti‐ROS properties rather than its modulation of the expression of endogenous antioxidant systems. These data provide mechanistic clues for its efficacy as a systemic photoprotective agent with antioxidant and anti‐photo‐ageing properties.

Oral administration of Polypodium leucotomos delays skin tumor development and increases epidermal p53 expression and the anti‐oxidant status of UV‐irradiated hairless mice

Chronic exposure to ultraviolet radiation (UVR) induces skin tumors in hairless mice. Daily oral administration of a Polypodium leucotomos (PL) extract significantly delayed tumor development in PL‐treated versus non‐PL‐treated mice. UVR and/or PL treatment modified several oxidative stress markers. In all irradiated mice, erythrocytic glutathione S‐transferase (GST) activity and glutathione disulphide (GSSG) content increased and in all PL‐treated mice GSSG content decreased, specially in non‐irradiated animals, and total plasma anti‐oxidant capacity (ORAC) increased. In dorsolateral non‐tumoral skin of all irradiated mice, glutathione reductase (GR) and glutathione peroxidase (GPx) activities increased and GSSG decreased in non‐irradiated PL‐treated animals. UVR induced a steep increase of p53 expression in epidermal cells. In non‐tumoral skin, this increase was significantly higher in PL‐treated animals than in non‐treated mice and can contribute in delaying tumor development, either by repairing the damaged DNA or by increasing apoptosis. These results reinforce the usefulness of PL as systemic photoprotective agent, especially in patients highly sensitive to UVR.