Dexamethasone-treated Animals Research Articles

Immune Response After Cochlear Implantation.

A cochlear implant (CI) is an electronic device that enables hearing recovery in patients with severe to profound hearing loss. Although CIs are a successful treatment for profound hearing impairment, their effectivity may be improved by reducing damages associated with insertion of electrodes in the cochlea, thus preserving residual hearing ability. Inner ear trauma leads to inflammatory reactions altering cochlear homeostasis and reducing post-operative audiological performances and electroacoustic stimulation. Strategies to preserve residual hearing ability led to the development of medicated devices to minimize CI-induced cochlear injury. Dexamethasone-eluting electrodes recently showed positive outcomes. In previous studies by our research group, intratympanic release of dexamethasone for 14 days was able to preserve residual hearing from CI insertion trauma in a Guinea pig model. Long-term effects of dexamethasone-eluting electrodes were therefore evaluated in the same animal model. Seven Guinea pigs were bilaterally implanted with medicated rods and four were implanted with non-eluting ones. Hearing threshold audiograms were acquired prior to implantation and up to 60 days by recording compound action potentials. For each sample, we examined the amount of bone and fibrous connective tissue grown within the scala tympani in the basal turn of the cochlea, the cochleostomy healing, the neuronal density, and the correlation between electrophysiological parameters and histological results. Detection of tumor necrosis factor alpha, interleukin-6, and foreign body giant cells showed that long-term electrode implantation was not associated with an ongoing inflammation. Growth of bone and fibrous connective tissue around rods induced by CI was reduced in the scala tympani by dexamethasone release. For cochleostomy sealing, dexamethasone-treated animals showed less bone tissue growth than negative. Dexamethasone did not affect cell density in the spiral ganglion. Overall, these results support the use of dexamethasone as anti-inflammatory additive for eluting electrodes able to protect the cochlea from CI insertion trauma.

Dexamethasone and prednisolone treatment in beef cattle: influence on glycogen deposition and gene expression in the liver

The illegal administration of glucocorticoids in livestock is problematic and identification of pathways in which these hormones are involved is critically important, and new direct or indirect biomarkers should be identified. In this work, glucocorticoid transcriptional effects on some genes involved in the glucose metabolism were studied in the bovine liver. This study was conducted on adult Charolais male cattle treated with long-term low dose dexamethasone or prednisolone. Gene expression analysis was conducted in the liver by qPCR, and the geNorm algorithm was applied to select optimal reference genes. In line with the literature, a significant overexpression of genes involved in the gluconeogenic pathway and glycogen synthesis was detected in the liver of dexamethasone-treated animals, but histological and biochemical examination showed hepatocyte glycogen depletion particularly in dexamethasone-treated animals. It possible to hypothesize that glucocorticoids or adrenal insufficiency due to glucocorticoids withdrawal inhibit the enzymatic activity of glycogen synthase and/or induce glycogen autophagy in bovine liver. In fact, markers of glycophagy as starch-binding domain-containing protein 1 and γ-aminobutyric acid receptor-associated protein-like 1 mRNAs were upregulated in the liver by glucocorticoids treatment. Furthermore, glycogen synthase kinase-3 beta gene was significantly overexpressed in dexamethasone-treated animals, and this protein is also implicated in liver autophagy modulation and glycogen synthesis inhibition. These results showed that glucocorticoids likley have dual roles in hepatic glycogen metabolism of cattle, and investigation of these pathways could help find treatment biomarkers.

Thymus vulgaris extract modulates dexamethasone induced liver injury and restores the hepatic antioxidant redox system

BackgroundThe liver is the largest important organ and the site for essential biochemical reactions and detoxifying toxic substances in the human body. Long-term, high-dose dexamethasone administration can cause severe alterations in liver function. Therefore, Thymus vulgaris leave extract possess a modulatory role on dexamethasone-induced hepatotoxicity by attenuating antioxidant defense system.By subcutaneous route, animals will receive three doses per week for 8 weeks of dexamethasone (0.1 mg/kg. b. wt.) concomitant with oral administration of thyme aqueous extract (500 mg/kg b.wt.).ResultsDXM treatment led to a marked increase in the liver function enzyme activities that are successfully ameliorated by thyme aqueous extract. Thyme natural antioxidants augmented the antioxidant defense system that overcomes oxidative stress caused by dexamethasone. Conversely, although dexamethasone-treated animals rose lipid peroxidation, thyme extract pretreatment did the reverse.ConclusionHepatotoxicity and oxidative stress caused by dexamethasone might improve by thyme natural antioxidants.

ANTI HYPERGLYCAEMIC AND ANTIOXIDANT ACTIVITY OF CATUNAREGAM SPINOSA (THUNB) AGAINST DEXAMETHASONE INDUCED DIABETES IN RATS

Objective: The study was aimed at evaluating the folkloric use of the Catunaregam spinosa (Thunb) bark for its hypoglycaemic and antioxidant activity against dexamethasone-induced diabetes in wistar rats.
 Methods: Diabetes was induced in wistar rats by dexamethasone administration 10 mg/kg, b. wt., s. c for 11 consecutive days to all group animals (except Group I). After confirmation of diabetes, the animals were divided into 5 groups (n=6). Group I: Vehicle control treated with normal saline only, Group II: Diabetic control treated with dexamethasone only, Group III: Standard control treated with dexamethasone plus glibenclamide (5 mg/kg, b. wt., p. o), Group IV and V: Test control received dexamethasone plus ethanolic extract of Catunaregam spinosa (EECS) at graded doses of 200 mg/kg, b. wt. and 400 mg/kg, b. wt., p. o for 21days respectively. On the last day of the experiment, the effect of Catunaregam spinosa bark was measured by estimating the biochemical and antioxidant parameters.
 Results: There was a significant alteration in the serum glucose, HbA1c, total proteins, serum lipid profile and tissue antioxidant parameters in dexamethasone-treated animals when compared to the normal control rats.
 In test groups treated with glibenclamide and EECS, it was significantly ameliorated the altered parameters such as serum glucose, HbA1c, total proteins, serum lipid profile and the antioxidant parameters like SOD, CAT, GSH and MDA when compared to dexamethasone-treated animals with evidence of histopathological studies of the pancreas.
 Conclusion: The results indicated that the ethanolic extract of Catunaregam Spinosa (Thunb) bark has shown the hypoglycemic and antioxidant property.

Rosmarinic acid affects immunological and inflammatory mediator levels and restores lung pathological features in asthmatic rats

BackgroundThe effects of rosmarinic acid (RA) on immunological and inflammatory mediator levels in bronchoalveolar lavage fluid (BALF) as well as lung pathological changes in asthmatic rats were investigated. MethodsThe levels of IFN-γ, IL-4, IFN-γ/IL-4 ratio, IgE, PLA2, and total protein (TP) in BALF and pathological changes in the lung were evaluated in control group (C), asthma group (sensitized to ovalbumin) (A), asthma groups treated with RA and dexamethasone. ResultsCompared to the control group, asthmatic rats showed increased levels of IL-4, IgE, PLA2, and TP as well as all pathological scores with decreased levels of IFN-γ and IFN-γ/IL-4 ratio (P<0.05 to P<0.001). The levels of IL-4, IgE, PLA2, and TP significantly reduced in groups treated with all concentrations of RA compared to asthma group (P<0.001 for all cases). IFN-γ was significantly decreased in groups treated with two lower concentrations of RA but IFN-γ/IL-4 ratio was increased in groups treated with two higher concentrations of RA compared to asthma group (P<0.05 to P<0.001). Treatment with all doses of RA led to significant improvement in pathological scores in asthmatic animals (P<0.05 to P<0.001). Most measured parameters were also significantly improved in dexamethasone-treated animals (P<0.01 to P<0.001) but IFN-γ/IL-4 ratio and the scores of interstitial fibrosis, bleeding and epithelial damage did not change in this group. ConclusionThe results indicated a preventive effect for RA on immunological and inflammatory mediators as well as lung pathological changes in asthmatic rats which were comparable or even more potent than that of dexamethasone.

Effects of Late Gestational Fetal Exposure to Dexamethasone Administration on the Postnatal Hypothalamus-Pituitary-Adrenal Axis Response to Hypoglycemia in Pigs

Background: Prenatal glucocorticoid administration alters the activity of the fetal hypothalamic-pituitary-adrenocortical axis (HPAA), and correspondingly the adenocorticotropic hormone (ACTH) and cortisol levels after birth. The dosages required for these effects are critically discussed. Activation of the HPAA is related to metabolic syndrome and diabetes mellitus. Hypoglycemia is the classic side effect of antidiabetic treatment. We hypothesized that a low dosage of dexamethasone in late pregnancy alters the HPAA response to hypoglycemia in pigs. Methods: 12 pregnant sows were randomly assigned to two groups which received either a low-dose intramuscular injection (99th and 100th day of gestation) of dexamethasone (0.06 μg/kg body weight) or vehicle. Three months after birth, 18 dexamethasone-treated anaesthetized offspring and 12 control offspring underwent a 75 min hypoglycemic clamp (blood glucose below 4 mmol/L) procedure. Heart rate (HR), blood pressure, ACTH and cortisol levels and body weight (at birth and after three months) were recorded. Results: Dexamethasone-treated animals exhibited significantly elevated ACTH (139.9 ± 12.7 pg/mL) and cortisol (483.1 ± 30.3 nmol/L) levels during hypoglycemia as compared to the control group (41.7 ± 6.5 pg/mL and 257.9 ± 26.7 nmol/L, respectively), as well as an elevated HR (205.5 ± 5.7 bpm) and blood pressure (systolic: 128.6 ± 1.5, diastolic: 85.7 ± 0.7 mmHg) response as compared to the control group (153.2 ± 4.5 bpm; systolic: 118.6 ± 1.6, diastolic: 79.5 ± 1.4 mmHg, respectively; p < 0.001). Conclusions: Low-dose prenatal administration of dexamethasone not only exerts effects on the HPAA (ACTH and cortisol concentration) and vital parameters (HR and diastolic blood pressure) under baseline conditions, but also on ACTH, HR and systolic blood pressure during hypoglycemia.

A single high dose of dexamethasone increases GAP-43 and synaptophysin in the hippocampus of aged rats

The administration of dexamethasone, a synthetic glucocorticoid receptor agonist, has been reported to modulate cognitive performance in both animals and humans. In the present study, we demonstrate the effects of a single high dose of dexamethasone on the expression and distribution of synaptic plasticity-related proteins, growth-associated protein-43 (GAP-43) and synaptophysin, in the hippocampus of 6-, 12-, 18- and 24-month-old rats. Acute dexamethasone treatment significantly altered the expression of GAP-43 at the posttranslational level by modulating the levels of phosphorylated GAP-43 and proteolytic GAP-43-3 fragment. The effect was the most pronounced in the hippocampi of the aged animals. The total GAP-43 protein was increased only in 24-month-old dexamethasone-treated animals, and was concomitant with a decrease in calpain-mediated proteolysis. Moreover, by introducing the gray level co-occurrence matrix method, a form of texture analysis, we were able to reveal the subtle differences in the expression pattern of both GAP-43 and synaptophysin in the hippocampal subfields that were not detected by Western blot analysis alone. Therefore, the current study demonstrates, through a novel combined approach, that dexamethasone treatment significantly affects both GAP-43 and synaptophysin protein expression in the hippocampus of aged rats.

Short-Term and Long-Term Effects of Dexamethasone on Cognitive Dysfunction Induced by Sevoflurane in Adult Rats.

Postoperative cognitive dysfunction (POCD) is common after anaesthesia in elderly patients. However, it may appear in patients of all ages. The main pathogenesis of cognitive dysfunction remains unclear, although there is some evidence that brain inflammation may alter cognitive abilities. In the present study, we aim to evaluate short-term and long-term effects of dexamethasone on cognitive dysfunction induced by sevoflurane anaesthesia in adult rats. Seven-month-old 30 male Wistar albino rats were randomised into three groups: sevoflurane group (exposure to sevoflurane), sevoflurane + dexamethasone group (exposure to sevoflurane and dexamethasone injection), and control group (exposure to 100% oxygen). Spatial learning and short-term (7 days after exposure) and long-term (30 days after exposure) memory were evaluated using Morris water maze test. Sevoflurane induced significant deficit in spatial learning and short-term and long-term memory in adult rats. Dexamethasone-treated animals exposed to sevoflurane had equivalent performance as control animals in training and probe trials. Sevoflurane may impair spatial learning and short-term and long-term memories in adult rats. The co-administration of dexamethasone and sevoflurane may ameliorate short-term and long-term cognitive dysfunctions induced by sevoflurane in adult rats.

Dexamethasone Attenuates the Enhanced Rewarding Effects of Cocaine Following Experimental Traumatic Brain Injury

Clinical studies have identified traumatic brain injury (TBI) as a risk factor for the development of cocaine dependence. This claim is supported by our recent preclinical studies showing enhancement of the rewarding effects of cocaine in mice sustaining moderate controlled cortical impact (CCI) injury during adolescence. Here we test the efficacy of dexamethasone, an anti-inflammatory corticosteroid, to attenuate augmentation of the behavioral response to cocaine observed in CCI-TBI animals using the conditioned place preference (CPP) assay. These studies were performed in order to determine whether proinflammatory activity in the nucleus accumbens (NAc), a key brain nucleus in the reward pathway, mediates enhanced cocaine-induced CPP in adolescent animals sustaining moderate CCI-TBI. Our data reveal robust glial activation in the NAc following CCI-TBI and a significant increase in the cocaine-induced CPP of untreated CCI-TBI mice. Furthermore, our results show that dexamethasone treatment following CCI-TBI can attenuate the cocaine place preference of injured animals without producing aversion in the CPP assay. Our studies also found that dexamethasone treatment significantly reduced the expression of select immune response genes including Monocyte chemoattractant protein-1 (MCP-1/CCL2) and intercellular adhesion molecule-1 (ICAM-1), returning their expression to control levels, which prompted an investigation of peripheral blood monocytes in dexamethasone-treated animals. Experimental findings showed that no craniectomy/dexamethasone mice had a significant increase, while CCI-TBI/dexamethasone animals had a significant decrease in the percentage of circulating nonclassical patrolling monocytes. These results suggest that a portion of these monocytes may migrate to the brain in response to CCI-TBI, potentially sparing the development of chronic neuroinflammation in regions associated with the reward circuitry such as the NAc. Overall, our findings indicate that anti-inflammatory agents, such as dexamethasone, may be effective in normalizing the rewarding effects of cocaine following CCI-TBI.

Prenatal glucocorticoid exposure in rats: programming effects on stress reactivity and cognition in adult offspring

Human epidemiological studies have provided compelling evidence that prenatal exposure to stress is associated with significantly increased risks of developing psychiatric disorders in adulthood. Exposure to excessive maternal glucocorticoids may underlie this fetal programming effect. In the current study, we assessed how prenatal dexamethasone administration during the last week of gestation affects stress reactivity and cognition in adult offspring. Stress reactivity was assessed by evaluating anxiety-like behavior on an elevated plus maze and in an open field. In addition, to characterize the long-term cognitive outcomes of prenatal exposure to glucocorticoids, animals were assessed on two cognitive tasks, a spatial reference memory task with reversal learning and a delayed matching to position (DMTP) task. Our results suggest that prenatal exposure to dexamethasone had no observable effect on anxiety-like behavior, but affected cognition in the adult offspring. Prenatally dexamethasone-exposed animals showed a transient deficit in the spatial reference memory task and a trend to faster acquisition during the reversal-learning phase. Furthermore, prenatally dexamethasone-treated animals also showed faster learning of new platform positions in the DMTP task. These results suggest that fetal overexposure to glucocorticoids programs a phenotype characterized by cognitive flexibility and adaptability to frequent changes in environmental circumstances. This can be viewed as an attempt to increase the fitness of survival in a potentially hazardous postnatal environment, as predicted by intrauterine adversity. Collectively, our data suggest that prenatal exposure to dexamethasone in rats could be used as an animal model for studying some cognitive components of related psychiatric disorders.

Inflammation in the Pathogenesis of Lyme Neuroborreliosis

Lyme neuroborreliosis, caused by the spirochete Borrelia burgdorferi, affects both peripheral and central nervous systems. We assessed a causal role for inflammation in Lyme neuroborreliosis pathogenesis by evaluating the induced inflammatory changes in the central nervous system, spinal nerves, and dorsal root ganglia (DRG) of rhesus macaques that were inoculated intrathecally with live B. burgdorferi and either treated with dexamethasone or meloxicam (anti-inflammatory drugs) or left untreated. ELISA of cerebrospinal fluid showed significantly elevated levels of IL-6, IL-8, chemokine ligand 2, and CXCL13 and pleocytosis in all infected animals, except dexamethasone-treated animals. Cerebrospinal fluid and central nervous system tissues of infected animals were culture positive for B. burgdorferi regardless of treatment. B. burgdorferi antigen was detected in the DRG and dorsal roots by immunofluorescence staining and confocal microscopy. Histopathology revealed leptomeningitis, vasculitis, and focal inflammation in the central nervous system; necrotizing focal myelitis in the cervical spinal cord; radiculitis; neuritis and demyelination in the spinal roots; and inflammation with neurodegeneration in the DRG that was concomitant with significant neuronal and satellite glial cell apoptosis. These changes were absent in the dexamethasone-treated animals. Electromyography revealed persistent abnormalities in F-wave chronodispersion in nerve roots of a few infected animals; which were absent in dexamethasone-treated animals. These results suggest that inflammation has a causal role in the pathogenesis of acute Lyme neuroborreliosis.

Astroglial Plasticity Is Implicated in Hippocampal Remodelling in Adult Rats Exposed to Antenatal Dexamethasone.

The long-term effects of antenatal dexamethasone treatment on brain remodelling in 3-month-old male Sprague Dawley rats whose mothers had been treated with dexamethasone were investigated in the present study. Dorsal hippocampus, basolateral amygdala and nucleus accumbens volume, cell numbers, and GFAP-immunoreactive astroglial cell morphology were analysed using stereology. Total brain volume as assessed by micro-CT was not affected by the treatment. The relative volume of the dorsal hippocampus (% of total brain volume) showed a moderate, by 8%, but significant reduction in dexamethasone-treated versus control animals. Dexamethasone had no effect on the total and GFAP-positive cell numbers in the hippocampal subregions, basolateral amygdala, and nucleus accumbens. Morphological analysis indicated that numbers of astroglial primary processes were not affected in any of the hippocampal subregions analysed but significant reductions in the total primary process length were observed in CA1 by 32%, CA3 by 50%, and DG by 25%. Mean primary process length values were also significantly decreased in CA1 by 25%, CA3 by 45%, and DG by 25%. No significant astroglial morphological changes were found in basolateral amygdala and nucleus accumbens. We propose that the dexamethasone-dependent impoverishment of hippocampal astroglial morphology is the case of maladaptive glial plasticity induced prenatally.

Age- and gender-related changes in glucose homeostasis in glucocorticoid-treated rats.

The disruption to glucose homeostasis upon glucocorticoid (GC) treatment in adult male rats has not been fully characterized in older rats or in females. Thus, we evaluated the age- and gender-related changes in glucose homeostasis in GC-treated rats. We injected male and female rats at 3 months and 12 months of age with either dexamethasone (1.0 mg/kg body mass, intraperitoneally) or saline, daily for 5 days. All of the GC-treated rats had decreased body mass and food intake, and adrenal hypotrophy. Increased glycemia was observed in all of the GC-treated groups and only the 3-month-old female rats were not glucose intolerant. Dexamethasone treatment resulted in hyperinsulinemia and hypertriacylglyceridemia in all of the GC-treated rats. The glucose-stimulated insulin secretion (GSIS) was higher in all of the dexamethasone-treated animals, but it was less pronounced in the older animals. The β-cell mass was increased in the younger male rats treated with dexamethasone. We conclude that dexamethasone treatment induces glucose intolerance in both the 3- and 12-month-old male rats as well as hyperinsulinemia and augmented GSIS. Three-month-old female rats are protected from glucose intolerance caused by GC, whereas 12-month-old female rats developed the same complications that were present in 3- and 12-month-old male rats.

PET imaging of disease progression and treatment effects in the experimental autoimmune encephalomyelitis rat model.

The experimental autoimmune encephalomyelitis model is a model of multiple sclerosis that closely mimics the disease characteristics in humans. The main hallmarks of multiple sclerosis are neuroinflammation (microglia activation, monocyte invasion, and T-cell infiltration) and demyelination. PET imaging may be a useful noninvasive technique for monitoring disease progression and drug treatment efficacy in vivo. Experimental autoimmune encephalomyelitis was induced by myelin-oligodendrocyte glycoprotein immunization in female Dark Agouti rats. Experimental autoimmune encephalomyelitis rats were imaged at baseline and at days 6, 11, 15, and 19 after immunization to monitor monocyte and microglia activation ((11)C-PK11195) and demyelination ((11)C-MeDAS) during normal disease progression and during treatment with dexamethasone. (11)C-PK11195 PET detected activation of microglia and monocytes in the brain stem and spinal cord during disease progression. The uptake of (11)C-PK11195 was elevated in dexamethasone-treated animals that had shown mild clinical symptoms that had resolved at the time of imaging. Demyelination was not detected by (11)C-MeDAS PET, probably because of the small size of the lesions (average, 0.13 mm). PET imaging of neuroinflammation can be used to monitor disease progression and the consequences of treatment in the experimental autoimmune encephalomyelitis rat model. PET imaging was more sensitive than clinical symptoms for detecting inflammatory changes in the central nervous system.

Dexamethasone reduces energy expenditure and increases susceptibility to diet‐induced obesity in mice

ObjectiveTo investigate how long-term treatment with dexamethasone affects energy expenditure and adiposity in mice and whether this is influenced by feeding on a high fat diet (HFD).Design and MethodsMice were placed on a HFD for 2 weeks and started on dexamethasone at 5mg/kg every other day during the next 7 weeks.ResultsTreatment with dexamethasone increased body fat, an effect that was more pronounced in the animals kept on HFD; dexamethasone treatment also worsened liver steatosis caused by the HFD. At the same time, treatment with dexamethasone lowered the RQ in chow-fed animals and slowed nightly metabolic rate in the animals kept on HFD. In addition, the acute VO2 acceleration in response to β3 adrenergic-stimulation was significantly limited in the dexamethasone-treated animals, as a result of marked decrease in UCP-1 mRNA observed in the BAT of these animals.ConclusionsLong-term treatment with dexamethasone in a mouse model of diet-induced obesity decreases BAT thermogenesis and exaggerates adiposity and liver steatosis.

Post-training glucocorticoid receptor activation during Pavlovian conditioning reduces Pavlovian-instrumental transfer in rats

Considerable evidence suggests that glucocorticoid receptor activation can enhance memory consolidation in Pavlovian learning tasks. For instance, post-training injections of the synthetic glucocorticoid receptor agonist dexamethasone increased conditioned responding to reward-predictive Pavlovian stimuli. Here we explored whether post-training dexamethasone injections can enhance appetitive Pavlovian learning and amplify the ability of Pavlovian stimuli to invigorate instrumental behaviour, a phenomenon termed Pavlovian-instrumental transfer (PIT). Animals were given 8 training days with two sessions per day, an instrumental training session in the morning and a Pavlovian training session in the afternoon. Dexamethasone or vehicle injections were administered daily immediately after Pavlovian training sessions. In a subsequent transfer test, we measured the general PIT effect, i.e. the enhancement of lever pressing for expected reward during presentation of an appetitive Pavlovian stimulus predictive for the same reward. Repeated high-dose (1.2mg/kg, i.p.) dexamethasone injections elicited pronounced body weight loss, markedly reduced instrumental performance and left Pavlovian learning unaltered, whereas repeated low-dose (3μg/kg, i.p.) dexamethasone injections inhibited body weight gain, slightly reduced instrumental performance and left Pavlovian learning unaltered during training. Importantly, in rats subjected to high- and low-dose dexamethasone injections, the overall response rates and the PIT effect were reduced in the transfer test. Thus, dexamethasone given after Pavlovian training was not able to amplify the invigorating effects of Pavlovian stimuli on instrumental action. Considerable evidence suggests that body weight changes after repeated low- and high-dose dexamethasone treatment as observed here are associated with muscle atrophy that could impair response capabilities. However, our data suggest that impaired response capabilities are not a major factor accounting for reduced PIT in dexamethasone-treated animals.

Investigation of the mechanisms contributing to the compensatory increase in insulin secretion during dexamethasone-induced insulin resistance in rhesus macaques

Dexamethasone has well-described effects to induce insulin resistance and increase insulin secretion. Herein, we examined potential contributors to the effect of dexamethasone to increase insulin secretion in rhesus macaques. Six male rhesus macaques received daily injections of either saline or dexamethasone (0.25 mg/kg i.m. for 7 days) in random order with 3 weeks between treatments. At the end of the treatment period, animals were fasted overnight and underwent a feeding study the next day, during which blood samples were taken before and for 60 min after a meal in order to assess islet hormone and incretin secretion. Dexamethasone induced marked increases in fasting plasma insulin, glucagon, leptin, and adiponectin concentrations (P<0.05). Surprisingly, the glycemic response after meal ingestion was decreased twofold during dexamethasone treatment (P<0.05). Dexamethasone-treated animals exhibited a significant increase in both insulin and glucose-dependent insulinotropic polypeptide (GIP) secretion during the feeding study (P<0.05). However, glucagon-like peptide-1 secretion was significantly lower in dexamethasone-treated animals compared with controls (P<0.01). Fasting and meal-stimulated pancreatic polypeptide concentrations (an index of the parasympathetic input to the islet) did not differ between saline and dexamethasone treatments. However, the proinsulin:insulin ratio was decreased throughout the feeding study with dexamethasone treatment suggesting an improvement of β-cell function (P<0.05). In conclusion, the maintenance of euglycemia and reduction of postprandial glycemia with short-term dexamethasone treatment appears to be due to the marked elevations of fasting and meal-stimulated insulin secretion. Furthermore, increases in postprandial GIP secretion with dexamethasone treatment appear to contribute to the effect of dexamethasone treatment to increase insulin secretion.

Effect of curcumin on dexamethasone-induced testicular toxicity in mice

Context: Curcumin is a yellow-orange polyphenol derived from turmeric [Curcuma longa L. (Zingiberaceaerhizomes)]. Turmeric is a main ingredient of Indian, Persian, and Thai dishes. Extensive studies within the last half a century have demonstrated the protective action of curcumin in many disorders of the body.Objective: This study evaluated the protective effect of curcumin on dexamethasone-induced spermatogenesis defects in mice.Materials and methods: Thirty-two NMRI mice were randomly divided into 4 groups. The first (control) group received 1 mL/day of distilled water by intraperitoneal (i.p.) injection for 7 days. The second group received 200 mg/kg/day of curcumin (Cur) for 10 days. Third group received 7 mg/kg/day of dexamethasone (Dex) for 7 days. Forth group received 200 mg/kg of curcumin for 10 days after dexamethasone treatment. Testicular histopathology, morphometric analysis, head sperm counting, and immunohistochemistry assessments were performed for evaluation of the dexamethasone and curcumin effects.Results: Expression of Bcl-2 was significantly increased in the curcumin + dexamethasone group compared with dexamethasone-treated animals (p < 0.05). Dexamethasone induced spermatogenesis defects including epithelial vacuolizations, sloughing of germ cells, reduction of seminiferous tubule diameter, reduction in the number of sperm heads and significant maturation arrest (p < 0.001). Curcumin + dexamethasone treatment significantly prevented these changes (p < 0.05).Discussion and conclusion: The results of this study demonstrate that curcumin increases the expression of Bcl-2 protein, an important anti-apoptotic factor, and improves the spermatogenesis defects in dexamethasone treated mice. Curcumin has a potent protective effect against the testicular toxicity and might be clinically useful.

Stress Hormone Leads to Memory Deficits and Altered Tau Phosphorylation in a Model of Alzheimer's Disease

Several studies have linked stress with Alzheimer's disease (AD) vulnerability; however, the mechanism remains to be fully elucidated. In the current paper, we investigated the role of glucocortitcoids on the AD-like phenotype. We administered the glucocorticoid dexamethasone to Tg2576 mice for 4 weeks and then investigated its effect on memory, amyloid-β and tau levels, and metabolism. At the end of the treatment period, we observed that mice receiving dexamethasone had a significant impairment in the fear conditioning paradigm compared with controls. Dexamethasone-treated animals showed a significant increase in the amount of brain soluble Aβ40 levels, but no alteration in the steady state levels of its precursor protein, AβPP, or in the major protease enzymes involved in its metabolism (i.e., ADAM-10, BACE-1, or γ-secretase complex). While total tau protein levels were unaltered between the two groups, we found that dexamethasone significantly reduced tau phosphorylation at specific sites that were mediated by decreases in glycogen synthase kinase-3β protein level activity. Finally, we observed a direct correlation between memory impairments and tau phosphorylation levels. Our study highlights the significant role that glucocorticoids play in exacerbating AD-like cognitive impairments via alteration of tau protein phosphorylation state.

Topical Application of Fucoidan Improves Atopic Dermatitis Symptoms in NC/Nga Mice

Fucoidan is a sulphated polysaccharide extracted from brown seaweed and possesses a wide range of pharmacological properties including antiallergic and immunologic activities. The present study attempted to examine the effectiveness of fucoidan from Undaria pinnatifida in the treatment of atopic dermatitis (AD) in the NC/Nga mice model. Three per cent fucoidan or 0.1% dexamethasone was topically applied to the dorsal skin of AD-induced mice for 4 weeks. The dermatitis severity scores and scratch counts of fucoidan or dexamethasone-treated animals were significantly lower than the control group. Histological analysis showed that the number of mast cells infiltrating into skin lesions and the epidermis thickness were significantly decreased after the treatments. Levels of serum histamine and IgE were also decreased. There was no significant difference on improvement of AD-like symptoms between fucoidan and dexamethasone. To elucidate possible mechanism of action, effects of fucoidan on regulation of AD-associated chemokines, such as thymus- and activation-regulated chemokine (TARC), macrophage-derived chemokine (MDC) and regulated upon activation, normal T-cell expressed and secreted (RANTES) chemokine, were investigated in human epidermal keratinocytes. Fucoidan significantly inhibited mRNA expression of these chemokines in a dose-dependent manner. This is the first animal study to demonstrate that fucoidan has significant effects on improving AD-like conditions as effective as dexamethasone, a well-recognized corticosteroid remedy for the disease.