Time-Course Changes in Oxidative Stress and Inflammation in the Retinas of rds Mice: A Retinitis Pigmentosa Model.

(1) Background: Retinitis pigmentosa (RP) is characterized by progressive photoreceptor death. A Prph2Rd2 or an rds mouse is an RP model that closely reflects human RP. The objective of this study was to investigate the relationship of rod and cone death with oxidative stress and inflammation in rds mice. (2) Methods: The retinas of control and rds mice on postnatal days (PN) 11, 17, 21, 28, 35, and 42 were used. Oxidative damage to macromolecules, glutathione (GSH and GSSG), GSH synthesis enzymes, glial fibrillar acidic protein (GFAP), ionized calcium-binding adapter molecule 1 (Iba1), and cluster of differentiation 68 (CD68) was studied. (3) Results: The time sequence of oxidative stress and inflammation changes in rds mice occurs as follows: (i) At PN11, there is a small increase in photoreceptor death and in the microglial cells; (ii) at PN17, damage to the macromolecules is observed; (iii) at PN21, the maximum photoreceptor death rate is detected and there is an increase in GSH-GSSG and GFAP; (iv) at PN21, the microglial cells are activated; and(v) at PN28, there is a decrease in GSH synthesis enzymes. (4) Conclusions: These findings contribute to the understanding of RP physiopathology and help us to understand whether oxidative stress and inflammation are therapeutic targets. These findings contribute to our understanding that, in RP, oxidative stress and inflammation evolution and their relationship are time-dependent. In this sense, it is important to highlight that both processes are potential therapeutic targets in this disease.

Role of hippocampal NF-κB and GluN2B in the memory acquisition impairment of experiences gathered prior to cocaine administration in rats.

Cocaine can induce severe neurobehavioral changes, among others, the ones involved in learning and memory processes. It is known that during drug consumption, cocaine-associated memory and learning processes take place. However, much less is known about the effects of this drug upon the mechanisms involved in forgetting.The present report focuses on the mechanisms by which cocaine affects memory consolidation of experiences acquired prior to drug administration. We also study the involvement of hippocampus in these processes, with special interest on the role of Nuclear factor kappa B (NF-κB), N-methyl-D-aspartate glutamate receptor 2B (GluN2B), and their relationship with other proteins, such as cyclic AMP response element binding protein (CREB). For this purpose, we developed a rat experimental model of chronic cocaine administration in which spatial memory and the expression or activity of several proteins in the hippocampus were assessed after 36 days of drug administration. We report an impairment in memory acquisition of experiences gathered prior to cocaine administration, associated to an increase in GluN2B expression in the hippocampus. We also demonstrate a decrease in NF-κB activity, as well as in the expression of the active form of CREB, confirming the role of these transcription factors in the cocaine-induced memory impairment.

Flexible use of allocentric and egocentric spatial memories activates differential neural networks in mice.

Goal-directed navigation can be based on world-centered (allocentric) or body-centered (egocentric) representations of the environment, mediated by a wide network of interconnected brain regions, including hippocampus, striatum and prefrontal cortex. The relative contribution of these regions to navigation from novel or familiar routes, that demand a different degree of flexibility in the use of the stored spatial representations, has not been completely explored. To address this issue, we trained mice to find a reward relying on allocentric or egocentric information, in a modified version of the cross-maze task. Then we used Zif268 expression to map brain activation when well-trained mice were required to find the goal from a novel or familiar location. Successful navigation was correlated with the activation of CA1, posterior-dorsomedial striatum, nucleus accumbens core and infralimbic cortex when allocentric-trained mice needed to use a novel route. Allocentric navigation from a familiar route activated dorsomedial striatum, nucleus accumbens, prelimbic and infralimbic cortex. None of the structures analyzed was significantly activated in egocentric-trained mice, irrespective of the starting position. These data suggest that a flexible use of stored allocentric information, that allows goal finding even from a location never explored during training, induces a shift from fronto-striatal to hippocampal circuits.

Progesterone, Lipoic Acid, and Sulforaphane as Promising Antioxidants for Retinal Diseases: A Review.

Oxidative stress has been documented to be a key factor in the cause and progression of different retinal diseases. Oxidative cellular unbalance triggers a sequence of reactions which prompt cell degeneration and retinal dysfunction, both hallmarks of several retinal pathologies. There is no effective treatment, yet, for many retinal diseases. Antioxidant treatment have been pointed out to be an encouraging palliative treatment; the beneficial effects documented involve slowing the progression of the disease, a reduction of cell degeneration, and improvement of retinal functions. There is a vast information corpus on antioxidant candidates. In this review, we expose three of the main antioxidant treatments, selected for their promising results that has been reported to date. Recently, the sulforaphane, an isothiocyanate molecule, has been unveiled as a neuroprotective candidate, by its antioxidant properties. Progesterone, a neurosteroid has been proposed to be a solid and effective neuroprotective agent. Finally, the lipoic acid, an organosulfur compound, is a well-recognized antioxidant. All of them, have been tested and studied on different retinal disease models. In this review, we summarized the published results of these works, to offer a general view of the current antioxidant treatment advances, including the main effects and mechanisms described.

Modulation of salivary cytokines in response to alcohol, tobacco and caffeine consumption: a pilot study.

It has been shown that long-term stimulant consumption alters the biological and microbiological status of the oral cavity. We present a pilot study describing stimulant-specific oral immunomodulation in the oral cavity. Changes in salivary cytokine levels in response to long-term alcohol, tobacco and caffeine were identified. Volunteers were recruited from amongst the patients visiting University Dental Clinic of CEU Cardenal Herrera University (Alfara del Patriarca, Spain). Participants were grouped according to their self-reported levels of consumption of either caffeine, alcohol or tobacco (control group volunteers were non-consumers of all three). Informed consent was provided and stimulated saliva samples were obtained and assayed for interleukin-1α IL-1α), Tumor Necrosis Factor α (TNF-α) and Interferon γ IFN-γ). Long-term, high-level consumers of alcohol or tobacco exhibited elevated salivary concentrations of the three inflammatory cytokines with respect to control values. Specifically, IL-1α was found to be elevated in alcohol users whilst IFN-γ concentration higher in tobacco users versus controls. Long-term caffeine consumers displayed elevated levels of IFN-γ and TNF-α, whereas IL-1α levels were reduced with respect to control volunteers. This pilot study demonstrates that salivary cytokines can be modulated in response to quantity and duration of alcohol, caffeine or tobacco consumption.

Lipoic Acid and Progesterone Alone or in Combination Ameliorate Retinal Degeneration in an Experimental Model of Hereditary Retinal Degeneration.

Retinitis pigmentosa (RP) is a group of inherited retinopathies characterized by photoreceptors death. Our group has shown the positive progesterone (P4) actions on cell death progression in an experimental model of RP. In an effort to enhance the beneficial effects of P4, the aim of this study was to combine P4 treatment with an antioxidant [lipoic acid (LA)] in the rd1 mice. rd1 and control mice were treated with 100 mg/kg body weight of P4, LA, or a combination of both on postnatal day 7 (PN7), 9, and 11, and were sacrificed at PN11. The administration of LA and/or P4 diminishes cell death in rd1 retinas. The effect obtained after the combined administration of LA and P4 is higher than the one obtained with LA or P4 alone. The three treatments decreased GFAP staining, however, in the far peripheral retina, and the two treatments that offered better results were LA and LA plus P4. LA or LA plus P4 increased retinal glutathione (GSH) concentration in the rd1 mice. Although LA and P4 are able to protect photoreceptors from death in rd1 mice retinas, a better effectiveness is achieved when administering LA and P4 at the same time.

Alterations in glutamate cysteine ligase content in the retina of two retinitis pigmentosa animal models.

Retinitis Pigmentosa (RP) comprises a group of rare genetic retinal disorders in which one of several different mutations induces photoreceptor death. Oxidative stress and glutathione (GSH) alterations may be related to the pathogenesis of RP. GSH has been shown to be present in high concentrations in the retina. In addition, the retina has the capability to synthesize GSH. In this study, we tested whether the two subunits of glutamate cysteine ligase, the rate-limiting enzyme in GSH synthesis, and the concentrations of retinal GSH, oxidized glutathione (GSSG), cysteine (Cys) and glutamate are altered in the retina of two different RP mice models. Retinas from C3H and rd1 mice at different postnatal days (P7, P11, P15, P19, P21 and P28) and from C57BL/6 and rd10 mice at P21 were obtained. Western blot analysis was performed to determine the protein content of catalytic and modulatory subunits from glutamate cysteine ligase (GCLC and GCLM, respectively). In another set of experiments, control and rd1 mice were administered buthinine sulfoximine, a glutathione synthase inhibitor, or paraquat. GSH, GSSG, glutamate and Cys concentrations were determined, by HPLC. A decrease in retinal GCLC content was observed in C3H and rd1 mice with age, nevertheless, there was an increase in retinal GCLC in rd1 mice compared to control retinas at P19. No modifications in GCLM content with age and no difference between GCLM content in rd1 and control retinas were observed. The GSH concentration decreased in the rd1 retinas compared with control ones at P15, it increased at P19, and was again similar at P21 and P28. No changes in GSSG concentration in control retinas with age were observed; the GSSG levels in rd1 retinas were similar from P7 to P19 and then increased significantly at P21 and P28. Glutamate concentration was increased in the rd1 retinas compared to control mice from P7 to P15 and were comparable at P21 and P28. The Cys concentrations was measured in control and rd1 retinas, but no significant changes were observed between them. BSO administration decreases GSH retinal concentration in control and rd1 mice, while paraquat administration induced an increase in GSH retinal concentration in control mice and a decrease in GSH in rd1 mice retina. Retinal GCLC was significantly increased in rd10 mice at P21 as well as GSSG. Our results suggest alterations in retinal GCLC content and GSH and/or its precursors in these two RP animal models. Regulation of the enzymes related to GSH metabolism and the retinal concentration of glutamate may be a possible target to delay especially cone death in RP.

Cocaine promotes oxidative stress and microglial-macrophage activation in rat cerebellum.

Different mechanisms have been suggested for cocaine neurotoxicity, including oxidative stress alterations. Nuclear factor kappa B (NF-κB), considered a sensor of oxidative stress and inflammation, is involved in drug toxicity and addiction. NF-κB is a key mediator for immune responses that induces microglial/macrophage activation under inflammatory processes and neuronal injury/degeneration. Although cerebellum is commonly associated to motor control, muscular tone, and balance. Its relation with addiction is getting relevance, being associated to compulsive and perseverative behaviors. Some reports indicate that cerebellar microglial activation induced by cannabis or ethanol, promote cerebellar alterations and these alterations could be associated to addictive-related behaviors. After considering the effects of some drugs on cerebellum, the aim of the present work analyzes pro-inflammatory changes after cocaine exposure. Rats received daily 15 mg/kg cocaine i.p., for 18 days. Reduced and oxidized forms of glutathione (GSH) and oxidized glutathione (GSSG), glutathione peroxidase (GPx) activity and glutamate were determined in cerebellar homogenates. NF-κB activity, CD68, and GFAP expression were determined. Cerebellar GPx activity and GSH/GSSG ratio are significantly decreased after cocaine exposure. A significant increase of glutamate concentration is also observed. Interestingly, increased NF-κB activity is also accompanied by an increased expression of the lysosomal mononuclear phagocytic marker ED1 without GFAP alterations. Current trends in addiction biology are focusing on the role of cerebellum on addictive behaviors. Cocaine-induced cerebellar changes described herein fit with previosus data showing cerebellar alterations on addict subjects and support the proposed role of cerebelum in addiction.

Chronic cocaine effects in retinal metabolism and electrophysiology: treatment with topiramate.

PURPOSE: Cocaine abuse is a major public health problem with multiple-related complications. Indeed, cocaine can affect almost every organ of the human body, but little is known about its effects on the visual system. The main purpose of this work was to study if topiramate was able to reverse changes in retinal metabolism and retinal function induced by chronic cocaine exposure in adult rats. MATERIALS AND METHODS: Sixteen Wistar rats were treated with a daily oral dose of cocaine during 36 days. Sixteen rats receiving NaCl 0.9% served as controls. Eight control and eight cocaine animals were administered topiramate from day 18 to day 36 of the experiment. Malondialdehyde (MDA), glutathione (GSH) and glutamate content, as well as glutathione peroxidase (GPx) activity in retina tissue homogenates were determined. Retinal function was assessed by electroretinogram (ERG). RESULTS: Glutamate concentration was increased in the retinas of cocaine-treated rats. No changes in oxidative stress parameters were observed in the retinas of cocaine-treated rats when compared with the control ones. Cocaine induced a decrease in the a-wave and b-wave ERG amplitude. The administration of topiramate reversed cocaine-induced increase in glutamate concentration and had little effect on a-wave and b-wave ERG amplitude. Topiramate, a drug used during the last decade for the treatment of epileptic seizures, is able to reverse the cocaine-induced alterations observed in retinal glutamate concentration. CONCLUSIONS: We can conclude that retinal glutamate metabolism and function may be affected by exposure to cocaine. We confirm that topiramate, a treatment recently proposed for cocaine dependence, is also able to recover partially cocaine-induced changes in the retina.

Naltrexone reverses ethanol-induced rat hippocampal and serum oxidative damage.

Naltrexone, an antagonist of µ-opioid receptors, is clinically used as adjuvant therapy of alcohol dishabituation. The aim of the present work was to test the effect of 1 mg/kg body weight of naltrexone to revert oxidative stress-related biochemical alterations, in the hippocampus and serum of chronic alcoholic adult rats. Malondialdehyde concentration was increased and glutathione peroxidase activity was decreased in hippocampus and serum of alcohol-treated rats. Naltrexone treatment restored these alterations. The in vitro antioxidant ability of Ntx could not justify these effects considering the doses used. Thus this apparent protective effect of Ntx can only be attributed to its pharmacological effects, as herein discussed.

Differential hippocampal response to chronic alcohol consumption of young adult and mature adult rats.

AIMS: Early ethanol consumption could be a risk factor for young brain integrity and its maturation, and also for the development of addictive behaviors in adulthood. Neuronal nitric oxide synthase (nNOS) expressing neurons are specifically located in the subgranular layer (SGL) of dentate gyrus and may be relevant for hippocampal neurogenesis. The focus of this work is aimed to determine local changes in the nNOS-like immunoreactive (nNOS-LIR) cell populations of the SGL after chronic ethanol exposure in young adult and mature adult rats. METHODS: We used the nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase (NADPH-d) reaction as a qualitative marker of nNOS enzyme activity. We also analyzed the nNOS-LIR cell density by the nNOS immunocytochemistry in order to compare these two methods of labeling. Dorsal striatum (CPu) was also analyzed in order to compare two neural areas with high nNOS-LIR cell density. RESULTS: The young adult group showed less hippocampal NADPH-d(+) cell density than the mature adult group. Interestingly, the NADPH-d(+) cell density was increased in the SGL of the young adult ethanol-treated group, whereas it decreased in the mature adult ethanol-treated group, when compared with their respective controls. No change was observed in any of the groups for the hippocampal nNOS-LIR cell density and no differences could be established in CPu for nNOS-LIR and NADPH-d(+) cell densities in any of the groups studied. CONCLUSION: The NADPH-d expression is affected by chronic ethanol exposure in opposite ways between both age groups studied. Further studies are needed to evaluate the relative importance of these findings, especially when considering human subjects.

Cocaine causes memory and learning impairments in rats: involvement of nuclear factor kappa B and oxidative stress, and prevention by topiramate.

Different mechanisms have been suggested for cocaine toxicity including an increase in oxidative stress but the association between oxidative status in the brain and cocaine induced-behaviour is poorly understood. Nuclear factor kappa B (NFkappaB) is a sensor of oxidative stress and participates in memory formation that could be involved in drug toxicity and addiction mechanisms. Therefore NFkappaB activity, oxidative stress, neuronal nitric oxide synthase (nNOS) activity, spatial learning and memory as well as the effect of topiramate, a previously proposed therapy for cocaine addiction, were evaluated in an experimental model of cocaine administration in rats. NFkappaB activity was decreased in the frontal cortex of cocaine treated rats, as well as GSH concentration and glutathione peroxidase activity in the hippocampus, whereas nNOS activity in the hippocampus was increased. Memory retrieval of experiences acquired prior to cocaine administration was impaired and negatively correlated with NFkappaB activity in the frontal cortex. In contrast, learning of new tasks was enhanced and correlated with the increase of nNOS activity and the decrease of glutathione peroxidase. These results provide evidence for a possible mechanistic role of oxidative and nitrosative stress and NFkappaB in the alterations induced by cocaine. Topiramate prevented all the alterations observed, showing novel neuroprotective properties.

Antioxidants rescue photoreceptors in rd1 mice: Relationship with thiol metabolism.

We have previously shown that the use of a combination of antioxidants delayed the degeneration process in rd1 mouse retina. In an effort to understand the mechanism of action of these substances (zeaxanthin, lutein, alpha-lipoic acid, glutathione, and Lycium barbarum extract) the changes in the levels of several proteins and oxidative stress markers in the rd1 retina have been studied. The treatment increased glutathione peroxidase activity and glutathione levels and decreased cystine concentrations in rd1 retinas. Considering all the results obtained from treated and untreated animals, a high correlation was present between glutathione concentration and glutathione peroxidase activity, and there was a negative correlation between glutathione retinal concentration and number of TUNEL-positive cells. No difference was observed between the numbers of nNOS- and NADPH-diaphorase-positive cells in treated and untreated rd1 mice. Thiol contents and thiol-dependent peroxide metabolism seem to be directly related to the survival of photoreceptors in rd1 mouse retina.