Inhibition of Fatty Acid Amide Hydrolase by PF-3845 Alleviates the Nitrergic and Proinflammatory Response in Rat Hippocampus Following Acute Stress.

BACKGROUND: Long-term exposure to stress has been demonstrated to cause neuroinflammation through a sustained overproduction of free radicals, including nitric oxide, via an increased inducible nitric oxide synthase activity. We previously demonstrated that inducible nitric oxide synthase activity and mRNA are significantly upregulated in the rat hippocampus following just 4 hours of restraint stress. Similar to nitric oxide, endocannabinoids are synthesized on demand, with preclinical observations suggesting that cannabinoid receptor agonists and endocannabinoid enhancers inhibit nitrergic activity. Specifically, previous work has shown that enhancement of endocannabinoids via inhibition of fatty acid amide hydrolase with PF-3845 reduced inducible nitric oxide synthase-expressing microglia following traumatic brain injury. However, this describes cannabinoid modulation following physical injury, and therefore the present study aimed to examine the effects of PF-3845 in the modulation of nitrergic and inflammatory-related genes within the hippocampus after acute stress exposure. METHODS: Following vehicle or PF-3845 injections (5 mg/kg; i.p.), male Wistar rats were exposed to 0 (control), 60, 240, or 360 minutes of restraint stress after which plasma and dorsal hippocampus were isolated for further biochemical and gene expression analysis. RESULTS: The results demonstrate that pretreatment with PF-3845 rapidly ameliorates plasma corticosterone release at 60 minutes of stress. An increase in endocannabinoid signalling also induces an overall attenuation in inducible nitric oxide synthase, tumor necrosis factor-alpha convertase, interleukin-6, cyclooxygenase-2, peroxisome proliferator-activated receptor gamma mRNA, and the transactivation potential of nuclear factor kappa-light-chain-enhancer of activated B cells in the hippocampus. CONCLUSIONS: These results suggest that enhanced endocannabinoid levels in the dorsal hippocampus have an overall antinitrosative and antiinflammatory effect following acute stress exposure.

Adrenocortical function in cane toads from different environments.

The adrenocortical function of cane toads (Rhinella marina) exposed to different experimental procedures, as well as captured from different environments, was assessed by challenging the hypothalamic-pituitary-adrenal (HPA) axis. It was found that restriction stress as well as cannulation increased plasma corticosterone (B) levels for up to 12h. A single dose of dexamethasone (DEX 2mg/kg) significantly reduced B levels demonstrating its potential for use in the evaluation of the HPA axis in amphibia. We also demonstrate that 0.05 IU/g BW (im) of synthetic adrenocorticotropic hormone (ACTH) significantly increased plasma B levels in cane toads. Changes in size area of the cortical cells were positively associated with total levels of B after ACTH administration. We also found differences in adrenal activity between populations. This was assessed by a DEX-ACTH test. The animals captured from the field and maintained in captivity for one year at the animal house (AH) present the highest levels of total and free B after ACTH administration. We also found that animals from the front line of dispersion in Western Australia (WA) present the weakest adrenal response to a DEX-ACTH test. The animals categorized as long established in Queensland Australia (QL), and native in Mexico (MX), do not shown a marked difference in the HPA activity. Finally we found that in response to ACTH administration, females reach significantly higher levels of plasma B than males. For the first time the adrenocortical response in cane toads exposed to different experimental procedures, as well as from different populations was assessed systematically.

A combination of plant-derived odors reduces corticosterone and oxidative indicators of stress.

In this study, we measured typical stress markers in addition to oxidative status and reduced glutathione in erythrocytes, and plasma lipid peroxidation of restraint-stressed animals exposed to a combination of plant-derived odors (0.03% Z-3-hexen-1-ol, 0.03% E-2-hexenal, and 0.015% α-pinene in triethyl citrate). Male Wistar rats aged 6-7 weeks postnatal were exposed to vehicle (triethyl citrate, n = 12), plant-derived odors (n = 12), or 1% propionic acid odor (n = 12) under control or stress conditions, and blood samples were collected. Restraint stress increased plasma glucose and plasma corticosterone concentrations by approximately 10% (P < 0.01) and 125% (P < 0.001), respectively, in vehicle-exposed animals. Similar increases were observed in animals exposed to a 1% propionic acid odor, indicating the novelty of odor exposure does not alter stress responsiveness. There was also an increase of approximately 15% in both erythrocytic oxidative status (P < 0.001) and plasma lipid peroxidation (P < 0.05), and a decrease of approximately the same magnitude in reduced glutathione (P < 0.05) in restrained animals with vehicle exposure. There were no differences observed between control and stress treatment with plant-derived odor exposure in any of the measured parameters. It was concluded that exposure to plant-derived odors reduce corticosterone, glucose, and redox responses elicited by psychological stress.

Reactive nitrogen species contribute to the rapid onset of redox changes induced by acute immobilization stress in rats.

Acute stress leads to the rapid secretion of glucocorticoids, which accelerates cellular metabolism, resulting in increased reactive oxygen and nitrogen species generation. Although the nitrergic system has been implicated in numerous stress-related diseases, the time course and extent of nitrosative changes during acute stress have not been characterized. Outbred male Wistar rats were randomly allocated into control (n = 9) or 120 min acute immobilization stress (n = 9) groups. Serial blood samples were collected at 0 (baseline), 60, 90, and 120 min. Plasma corticosterone concentrations increased by approximately 350% at 60, 90, and 120 (p < 0.001) min of stress. The production of nitric oxide, measured as the benzotriazole form of 4-amino-5-methylamino-2',7'-difluorofluorescein, increased during stress exposure by approximately 5%, 10%, and 15% at 60 (p < 0.05), 90 (p < 0.01) and 120 (p < 0.001) min, respectively, compared to controls. Nitric oxide metabolism, measured as the stable metabolites nitrite and nitrate, showed a 40-60% increase at 60, 90, and 120 (p < 0.001) min of stress. The oxidative status of 2',7'-dichlorofluorescein in plasma was significantly elevated at 60 (p < 0.01), 90, and 120 (p < 0.001) min. A delayed decrease of approximately 25% in the glutathione redox ratio at 120 min (p < 0.001) also indicates stress-induced cellular oxidative stress. The peroxidation of plasma lipids increased by approximately 10% at 90 (p < 0.05) and 15% at 120 (p < 0.001) min, indicative of oxidative damage. It was concluded that a single episode of stress causes early and marked changes of both oxidative and nitrosative status sufficient to induce oxidative damage in peripheral tissues.

Ferulic acid improves cardiovascular and kidney structure and function in hypertensive rats.

Ferulic acid is a simple phenolic acid commonly present in cereals. In this study, changes in heart and kidney structure and function were measured in young N(ω)-nitro-L-arginine methyl ester (L-NAME)-treated Wistar rats and 10-month-old spontaneously hypertensive rats (SHR) alone and after chronic treatment with ferulic acid (FA; 50 mg·kg⁻¹·d⁻¹; n = 6-10; *P < 0.05). Systolic blood pressures were increased after L-NAME treatment (control 125 ± 2 mm Hg, L-NAME 205 ± 6* mm Hg after 8 weeks) and in SHR (250 ± 2 mm Hg; WKY 149 ± 4 mm Hg). Hypertensive rats developed left ventricular hypertrophy, increased ventricular diastolic stiffness (κ; Wistar, 21.4 ± 1.6; L-NAME, 30.1 ± 0.9*; WKYs, 24.1 ± 0.9; SHR 29.5 ± 0.7) and fibrosis of heart and kidneys. Treatment with ferulic acid reduced systolic blood pressure (L-NAME + FA, 157 ± 4*; SHR + FA 214 ± 8* mm Hg), reduced left ventricular diastolic stiffness (L-NAME + FA, 25.2 ± 0.5*; SHR + FA 26.3 ± 0.5*) and attenuated inflammatory cell infiltration, ferric iron accumulation, and collagen deposition in left ventricles and kidneys. Ferulic acid improved both endothelium-dependent relaxation in isolated thoracic aortic rings and antioxidant status by increasing superoxide dismutase and catalase activity in the heart and kidneys. FA decreased plasma liver enzyme activities and plasma creatinine concentrations. Thus, FA improved the structure and function of the heart, blood vessels, liver, and kidneys in hypertensive rats.

The effect of three anaesthetic protocols on the stress response in cane toads (Rhinella marina).

OBJECTIVE: Three anaesthetics (MS222, clove oil and a mixture of ketamine/diazepam) were administered to cane toads to determine their effect on the hypothalamic-pituitary-adrenal (HPA) axis. Time to induction and recovery and any adverse events were also evaluated. STUDY DESIGN: Prospective randomized experimental trial. ANIMALS: Thirty adult male cane toads (Rhinella marina) with body mass ranging between 130 and 250 g were captured from the field. METHODS: Three groups of 10 toads were anaesthetized with ketamine (200 mg kg(-1) ) and diazepam (0.2 mg kg(-1) ) by intramuscular injection, MS222 (3 g L(-1) ) or clove-oil (0.3 mL L(-1) ) both by immersion. Blood samples were collected to determine plasma corticosterone concentrations. Induction and recovery time were recorded in each treatment. After full recovery animals were euthanized and a complete post-mortem examination was performed. RESULTS: Significant differences were found in the activation of the HPA axis and in the times of induction and recovery between treatments (p < 0.001). Animals anaesthetized with clove-oil had the highest levels of corticosterone in plasma (42.5 ± 21.6 ng mL(-1) ). No differences were found between ketamine/diazepam (15.0 ± 13.3 ng mL(-1) ) and MS222 (22.0 ± 13.6 ng mL(-1) ) groups. The mean ± SD induction (minutes) and recovery (hours) times respectively were; ketamine/diazepam 66.5 ± 11 and 8 ± 3, clove oil 39 ± 12 and 7.6 ± 3, and MS222 42.5 ± 11 and 1.5 ± 0.5. Clove oil exposure had 30% mortality. Death followed a period of respiratory distress with changes consistent with non-cardiogenic oedema observed at post-mortem examination. CONCLUSIONS AND CLINICAL RELEVANCE: Based on shorter induction and recovery times and minimal activation of HPA, MS222 is the anaesthetic of choice in cane toads. If it is not possible to use immersion methods of anaesthesia, ketamine/diazepam can be used but induction and recovery times are prolonged. Clove oil had unacceptable mortality in this study and should be used with extreme caution.

High-carbohydrate high-fat diet­induced metabolic syndrome and cardiovascular remodeling in rats.

The prevalence of metabolic syndrome including central obesity, insulin resistance, impaired glucose tolerance, hypertension, and dyslipidemia is increasing. Development of adequate therapy for metabolic syndrome requires an animal model that mimics the human disease state. Therefore, we have characterized the metabolic, cardiovascular, hepatic, renal, and pancreatic changes in male Wistar rats (8-9 weeks old) fed on a high-carbohydrate, high-fat diet including condensed milk (39.5%), beef tallow (20%), and fructose (17.5%) together with 25% fructose in drinking water; control rats were fed a cornstarch diet. During 16 weeks on this diet, rats showed progressive increases in body weight, energy intake, abdominal fat deposition, and abdominal circumference along with impaired glucose tolerance, dyslipidemia, hyperinsulinemia, and increased plasma leptin and malondialdehyde concentrations. Cardiovascular signs included increased systolic blood pressure and endothelial dysfunction together with inflammation, fibrosis, hypertrophy, increased stiffness, and delayed repolarization in the left ventricle of the heart. The liver showed increased wet weight, fat deposition, inflammation, and fibrosis with increased plasma activity of liver enzymes. The kidneys showed inflammation and fibrosis, whereas the pancreas showed increased islet size. In comparison with other models of diabetes and obesity, this diet-induced model more closely mimics the changes observed in human metabolic syndrome.

High-carbohydrate, high-fat diet-induced metabolic syndrome and cardiovascular remodeling in rats.

The prevalence of metabolic syndrome including central obesity, insulin resistance, impaired glucose tolerance, hypertension, and dyslipidemia is increasing. Development of adequate therapy for metabolic syndrome requires an animal model that mimics the human disease state. Therefore, we have characterized the metabolic, cardiovascular, hepatic, renal, and pancreatic changes in male Wistar rats (8-9 weeks old) fed on a high-carbohydrate, high-fat diet including condensed milk (39.5%), beef tallow (20%), and fructose (17.5%) together with 25% fructose in drinking water; control rats were fed a cornstarch diet. During 16 weeks on this diet, rats showed progressive increases in body weight, energy intake, abdominal fat deposition, and abdominal circumference along with impaired glucose tolerance, dyslipidemia, hyperinsulinemia, and increased plasma leptin and malondialdehyde concentrations. Cardiovascular signs included increased systolic blood pressure and endothelial dysfunction together with inflammation, fibrosis, hypertrophy, increased stiffness, and delayed repolarization in the left ventricle of the heart. The liver showed increased wet weight, fat deposition, inflammation, and fibrosis with increased plasma activity of liver enzymes. The kidneys showed inflammation and fibrosis, whereas the pancreas showed increased islet size. In comparison with other models of diabetes and obesity, this diet-induced model more closely mimics the changes observed in human metabolic syndrome.

Restraint Stress Alters Expression of Glucocorticoid Bioavailability Mediators, Suppresses Nrf2, and Promotes Oxidative Stress in Liver Tissue.

Hepatic glutathione synthesis and antioxidant protection are critically important for efficient detoxification processes in response to metabolic challenges. However, this biosynthetic pathway, regulated by nuclear factor (erythroid-derived 2)-like 2 (Nrf2), previously demonstrated paradoxical repression following exposure to glucocorticoid stress hormones in cultured hepatic cells. Therefore, the present study used an in vivo model of sub-acute psychological stress to investigate the relationship between hepatic corticosteroid regulation and antioxidant systems. Male Wistar rats were kept under control conditions or subjected to six hours of restraint stress applied for 1 or 3 days (n = 8 per group) after which the liver was isolated for assays of oxidative/nitrosative status and expression of corticosteroid regulatory and Nrf2-antioxidant response element pathway members. A single stress exposure produced a significant increase in the expression of corticosterone reactivator, 11-beta-hydroxysteroid dehydrogenase 1 (11ß-Hsd1), while the 11ß-Hsd2 isozyme and corticosteroid-binding globulin were down-regulated following stress, indicative of an elevated availability of active corticosterone. Exposure to restraint significantly decreased hepatic concentrations of total cysteine thiols and the antioxidant reduced glutathione on Day 1 and increased 3-nitrotyrosinated and carbonylated proteins on Day 3, suggestive of oxidative/nitrosative stress in the liver following stress exposure. Conversely, there was a sustained down-regulation of Nrf2 mRNA and protein in addition to significant reductions in downstream glutamate-cysteine ligase catalytic subunit (Gclc), the rate-limiting enzyme in glutathione synthesis, on Day 1 and 3 of stress treatment. Interestingly, other antioxidant genes including superoxide dismutase 1 and 2, and glutathione peroxidase 4 were significantly up-regulated following an episode of restraint stress. In conclusion, the results of the present study indicate that increased expression of 11ß-Hsd1, indicative of elevated tissue glucocorticoid concentrations, may impair the Nrf2-dependent antioxidant response.

Sub-acute restraint stress progressively increases oxidative/nitrosative stress and inflammatory markers while transiently upregulating antioxidant gene expression in the rat hippocampus.

We have previously demonstrated that acute stress decreases neuronal nitric oxide synthase (NOS) expression in the hippocampus despite increased concentrations of nitric oxide which may indicate feedback inhibition of neuronal NOS expression via inducible NOS-derived nitric oxide. Moreover, the hippocampus undergoes an initial oxidative/nitrosative insult that is rapidly followed by upregulation of protective antioxidants, including the zinc-binding metallothioneins, in order to counter this and restore redox balance following acute stress exposure. In the present study, we have utilized indicators of oxidative/nitrosative stress, members of the nuclear factor (erythroid-derived 2)-like 2 (Nrf2) pathway, antioxidant metallothioneins, and neuroinflammatory markers to observe the changes occurring in the hippocampus following short term repeated stress exposure. Male Wistar rats were subjected to control conditions or 6 h of restraint stress applied for 1, 2, or 3 days (n = 8 per group) after which the hippocampus was isolated for redox assays and relative gene expression. The hippocampus showed increased oxidative stress, transient dys-homeostasis of total zinc, and increased expression of the Nrf2 pathway members. Moreover, repeated stress increased nitrosative status, nitric oxide metabolites, and 3-nitrotyrosine, indicative of nitrosative stress in the hippocampus. However, levels of neuronal NOS decreased over all stress treatment groups, while increases were observed in inducible NOS and xanthine dehydrogenase. In addition to inducible NOS, mRNA expression of other inflammatory markers including interleukin-6 and interleukin-1ß also increased even in the presence of increased anti-inflammatory glucocorticoids. Together, these results demonstrate that despite increases in antioxidant expression, sub-acute stress causes an inflammatory phenotype in the hippocampus by inducing oxidative/nitrosative stress, zinc dys-homeostasis, and the accumulation of nitrotyrosinated proteins which is likely driven by increased inducible NOS signaling.

Changes in hippocampal inflammatory-related and redox enzyme genes in response to sub-acute restraint stress: Additional dataset.

This data article presents complementary results pertaining to the research article entitled "Sub-acute restraint stress progressively increases oxidative/nitrosative stress and inflammatory markers while transiently upregulating antioxidant gene expression in the rat hippocampus" (Chen et al., 2018). The present article provides additional gene expression data of selected neuroinflammatory markers and regulatory enzymes involved in oxidation-reduction reactions. Male Wistar rats aged 7-8 weeks were exposed to control, 1, 2, or 3 episodes of 6-h restraint stress in the light cycle after which the whole brain was quickly removed and the hippocampus excised for relative gene expression analysis. Specifically, mRNA levels of inflammatory regulators including allograft inflammatory factor 1, class II major histocompatibility complex, integrin alpha M, interferon gamma, and prostaglandin-endoperoxide synthase 2 were analyzed by real-time PCR. The gene expression of redox regulatory enzymes including glutathione peroxidase 1, glutathione peroxidase 4, superoxide dismutase 1, superoxide dismutase 2, myeloperoxidase, and NADPH oxidase subunit P47phox were also determined. These data provide useful insights in the molecular basis of inflammatory and redox regulation in the hippocampus following a short term to repeated psychological challenge in rats.

Acute restraint stress induces specific changes in nitric oxide production and inflammatory markers in the rat hippocampus and striatum.

Chronic mild stress has been shown to cause hippocampal neuronal nitric oxide synthase (NOS) overexpression and the resultant nitric oxide (NO) production has been implicated in the etiology of depression. However, the extent of nitrosative changes including NOS enzymatic activity and the overall output of NO production in regions of the brain like the hippocampus and striatum following acute stress has not been characterized. In this study, outbred male Wistar rats aged 6-7 weeks were randomly allocated into 0 (control), 60, 120, or 240 min stress groups and neural regions were cryodissected for measurement of constitutive and inducible NOS enzymatic activity, nitrosative status, and relative gene expression of neuronal and inducible NOS. Hippocampal constitutive NOS activity increased initially but was superseded by the inducible isoform as stress duration was prolonged. Interestingly, hippocampal neuronal NOS and interleukin-1ß mRNA expression was downregulated, while the inducible NOS isoform was upregulated in conjunction with other inflammatory markers. This pro-inflammatory phenotype within the hippocampus was further confirmed with an increase in the glucocorticoid-antagonizing macrophage migration inhibitory factor, Mif, and the glial surveillance marker, Ciita. This indicates that despite high levels of glucocorticoids, acute stress sensitizes a neuroinflammatory response within the hippocampus involving both pro-inflammatory cytokines and inducible NOS while concurrently modulating the immunophenotype of glia. Furthermore, there was a delayed increase in striatal inducible NOS expression while no change was found in other pro-inflammatory mediators. This suggests that short term stress induces a generalized increase in inducible NOS signaling that coincides with regionally specific increased markers of adaptive immunity and inflammation within the brain.

Neuronal and inducible nitric oxide synthase upregulation in the rat medial prefrontal cortex following acute restraint stress: A dataset.

This data article provides additional evidence on gene expression changes in the neuronal and inducible isoforms of nitric oxide synthase in the medial prefrontal cortex following acute stress. Male Wistar rats aged 6-8 weeks were exposed to control or restraint stress conditions for up to four hours in the dark cycle after which the brain was removed and the medial prefrontal cortex isolated by cryodissection. Following RNA extraction and cDNA synthesis, gene expression data were measured using quantitative real-time PCR. The mRNA levels of the neuronal and inducible nitric oxide synthase isoforms, and the inhibitory subunit of NF-κB, I kappa B alpha were determined using the ΔΔCT method relative to control animals. This data article presents complementary results related to the research article entitled 'Acute restraint stress induces specific changes in nitric oxide production and inflammatory markers in the rat hippocampus and striatum' [1].

Acute restraint stress induces rapid changes in central redox status and protective antioxidant genes in rats.

The stress-induced imbalance in reduction/oxidation (redox) state has been proposed to play a major role in the etiology of neurological disorders. However, the relationship between psychological stress, central redox state, and potential protective mechanisms within specific neural regions has not been well characterized. In this study, we have used an acute psychological stress to demonstrate the dynamic changes that occur in the redox system of hippocampal and striatal tissue. Outbred male Wistar rats were subject to 0 (control), 60, 120, or 240min of acute restraint stress and the hippocampus and striatum were cryodissected for redox assays and relative gene expression. Restraint stress significantly elevated oxidative status and lipid peroxidation, while decreasing glutathione ratios overall indicative of oxidative stress in both neural regions. These biochemical changes were prevented by prior administration of the glucocorticoid receptor antagonist, RU-486. The hippocampus also demonstrated increased glutathione peroxidase 1 and 4 antioxidant expression which was not observed in the striatum, while both regions displayed robust upregulation of the antioxidant, metallothionein 1a. This was observed with concurrent upregulation of 11ß-hydroxysteroid dehydrogenase 1, a local reactivator of corticosterone, in addition to decreased expression of the cytosolic regulatory subunit of superoxide-producing enzyme, NADPH-oxidase. Together, this study demonstrates distinctive regional redox profiles following acute stress exposure, in addition to identifying differential capabilities in managing oxidative challenges via altered antioxidant gene expression in the hippocampus and striatum.

Response of the nitrergic system to activation of the neuroendocrine stress axis.

Exposure to stressful stimuli causes activation of the hypothalamic-pituitary-adrenal axis which rapidly releases high concentrations of glucocorticoid stress hormones, resulting in increased cellular metabolism and spontaneous oxygen and nitrogen radical formation. High concentrations of nitrogen radicals, including nitric oxide, cause damage to cellular proteins in addition to inhibiting components of the mitochondrial transport chain, leading to cellular energy deficiency. During stress exposure, pharmacological inhibition of nitric oxide production reduces indicators of anxiety- and depressive-like behavior in animal models. Therefore, the purpose of this review is to present an overview of the current literature on stress-evoked changes in the nitrergic system, particularly within neural tissue.

Effect of atrazine and fenitrothion at no-observed-effect-levels (NOEL) on amphibian and mammalian corticosterone-binding-globulin (CBG).

This study determines the effect of atrazine and fenitrothion no-observed-effect-levels (NOEL) on the binding of corticosterone (B) to corticosterone-binding-globulin (CBG) in an amphibian and a mammal. Plasma from five cane toads and five Wistar rats was exposed to atrazine and fenitrothion at the NOEL approved for Australian fresh water residues and by the World Health Organization (WHO). The concentration required to displace 50% (IC50) of B binding to CBG was determined by a competitive microdialysis protein assay. Competition studies showed that both atrazine and fenitrothion at NOEL are able to compete with B for CBG binding sites in toad and rat plasma. The IC50 levels for atrazine in toads and rats were 0.004 nmol/l and 0.09 nmol/l respectively. In the case of fenitrothion the IC50 level found in toads was 0.007 nmol/l, and 0.025 nmol/l in rats. Plasma dilution curves showed parallelism with the curve of B, demonstrating that these agro-chemicals are competitively inhibiting binding to CBG. The displacement of B by atrazine and fenitrothion would affect the total:free ratio of B and consequently disrupt the normal stress response. This is the first time that the potential disruptive effect of atrazine and fenitrothion on B-CBG interaction at the NOELs has been demonstrated in amphibian and mammalian models.

Activation of the hypothalamic-pituitary-adrenal stress axis induces cellular oxidative stress.

Glucocorticoids released from the adrenal gland in response to stress-induced activation of the hypothalamic-pituitary-adrenal (HPA) axis induce activity in the cellular reduction-oxidation (redox) system. The redox system is a ubiquitous chemical mechanism allowing the transfer of electrons between donor/acceptors and target molecules during oxidative phosphorylation while simultaneously maintaining the overall cellular environment in a reduced state. The objective of this review is to present an overview of the current literature discussing the link between HPA axis-derived glucocorticoids and increased oxidative stress, particularly focussing on the redox changes observed in the hippocampus following glucocorticoid exposure.

Chronic l-arginine treatment improves metabolic, cardiovascular and liver complications in diet-induced obesity in rats.

l-Arginine is an important dietary amino acid in both health and disease, especially of the cardiovascular system. This study has determined whether dietary supplementation with l-arginine attenuates cardiovascular, metabolic, pancreatic and liver changes in a rat model of the human metabolic syndrome. Male Wistar rats (8-9 weeks old) were divided into four groups. Two groups of rats were fed a corn starch-rich diet (C) whereas the other two groups were given a high carbohydrate, high fat diet (H) with 25% fructose in the drinking water, for 16 weeks. One group fed each diet was supplemented with 5% l-arginine in the food for the final 8 weeks of this protocol. The corn starch diet (C) contained ∼68% carbohydrates mainly as polysaccharides, while the high-carbohydrate, high-fat diet contained ∼68% carbohydrates mainly as fructose and sucrose together with 24% fat mainly as saturated and monounsaturated fats from beef tallow. The high-carbohydrate, high-fat diet-fed rats showed the symptoms of metabolic syndrome including obesity and hypertension with heart and liver damage. Supplementation with l-arginine attenuated impairment in left ventricular and liver structure and function, glucose tolerance, and decreased blood pressure, abdominal fat pads, inflammatory cell infiltration, pancreatic cell hypertrophy and oxidative stress. This study indicates that oral supplementation with l-arginine attenuated or normalised obesity-related changes in the heart, liver and pancreas by reducing inflammation and oxidative stress associated with high carbohydrate, high fat feeding in rats.

Acute restraint stress induces rapid and prolonged changes in erythrocyte and hippocampal redox status.

The onset and consequential changes in reduction-oxidation (redox) status that take place in response to short-term stress have not been well defined. This study utilized erythrocytes and neural tissue from male Wistar rats to demonstrate the rapid redox alterations that occur following an acute restraining stress. Serial blood samples collected from catheterized animals were used to measure prolactin, corticosterone, glucose, general oxidative status, and glutathione/glutathione disulfide ratios. Restraint increased prolactin concentration by approximately 300% at 30 min and rapidly returned to baseline values by 120 min of stress. Baseline blood glucose and corticosterone increased during stress exposure by approximately 25% and 150% respectively. Over the experimental period, the erythrocytic oxidative status of restrained animals increased by approximately 10% per hour which persisted after stress exposure, while changes in the glutathione redox couple were not observed until 120 min following the onset of stress. Application of restraint stress increased hippocampal oxidative status by approximately 17% while no change was observed in the amygdala. It was concluded that while endocrine and metabolic markers of stress rapidly increase and habituate to stress exposure, redox status continues to change following stress in both peripheral and neural tissue. Studies with longer post-restraint times and the inclusion of several brain regions should further elucidate the consequential redox changes induced by acute restraint stress.