The effects of subchronic agmatine on passive avoidance memory, anxiety-like behavior and hippocampal Akt/GSK-3ß in mice.

Agmatine, a polyamine derived from l-arginine, has been suggested to modulate memory. However, the available evidence regarding the effect of agmatine on the memory of intact animals is contradictory. This study aimed to assess the dose-response effect of subchronic agmatine on passive avoidance memory and anxiety-like parameters of elevated plus maze in adult intact mice. Furthermore, considering the roles of Akt/GSK-3ß signaling pathway in memory and Alzheimer's disease, the hippocampal contents of phosphorylated and total forms of Akt and GSK-3ß proteins were determined using the western blot technique. Agmatine was administered intraperitoneally at the doses of 10, 20, 30, 40 and 80 mg/kg/daily to adult male NMRI mice for 10 days after which the behavioral assessments were performed. Upon completion of the passive avoidance test, the hippocampi were removed for western blot analysis to detect the phosphorylated and total levels of Akt and GSK-3ß proteins. Results showed the biphasic effect of agmatine on passive avoidance memory; in lower doses (10, 20 and 30 mg/kg), agmatine impaired memory whereas in higher ones (40 and 80 mg/kg) improved it. Though, agmatine in none of the doses affected animals' anxiety-like parameters in an elevated plus maze. Moreover, the memory-improving doses of agmatine augmented Akt/GSK-3ß pathway. This study showed the biphasic effect of agmatine on passive avoidance memory and an augmentation of hippocampal Akt/GSK-3ß signaling pathway following the memory-improving doses of this polyamine.

Effects of sub-chronic caffeine ingestion on memory and the hippocampal Akt, GSK-3ß and ERK signaling in mice.

Caffeine, one of the most widely consumed psychoactive substance in the world, has been shown to affect mood, memory, alertness, and cognitive performance. This study aimed to assess the effect of sub-chronic oral gavage of caffeine on memory and the phosphorylation levels of hippocampal Akt (protein kinase B), GSK-3ß (Glycogen Synthase Kinase-3beta) and ERK (extracellular signal-regulated kinase) in mice. Adult male NMRI mice were administered with caffeine at the doses of 0.25, 0.5, 0.75 and 1.5 mg/kg/oral gavage for 10 days before behavioral assessments. Upon completion of the behavioral tasks, the hippocampi were isolated for western blot analysis to detect the phosphorylated and total levels of Akt, GSK-3ß and ERK proteins. The results showed that sub-chronic caffeine ingestion at the dose of 0.5 mg/kg improves memory in mice both in passive avoidance and novel object recognition tasks. Furthermore, this memory enhancing dose of caffeine elevated the ratios of phosphorylated to total contents of hippocampal Akt, GSK-3ß and ERK. This study suggests that sub-chronic low dose of caffeine improves memory and increases the phosphorylation of hippocampal Akt, GSK-3ß and ERK proteins.

Sub-chronic oral cinnamaldehyde treatment prevents scopolamine-induced memory retrieval deficit and hippocampal Akt and MAPK dysregulation in male mice.

Objectives: Cholinergic system dysfunction was found to play a key role in Alzheimer's disease (AD) pathogenesis. Therefore, the animal model of scopolamine-induced amnesia has been widely used in AD researches. Cinnamon, as a spice commonly used in cuisine, has been shown to exert some therapeutic effects. The most abundant compound in cinnamon is cinnamaldehyde which recently was shown to exert several neuroprotective effects in animal models. Therefore, this study aimed to assess whether cinnamaldehyde has the potency to prevent memory retrieval impairment and hippocampal protein kinase B (Akt) and MAPK (extracellular signal-regulated kinase (ERK)) alterations induced by scopolamine in mice.Methods: Adult male mice were pretreated with cinnamaldehyde (12.5, 25, 40 and 100 mg/kg/oral gavage) 10 days before training. The training of passive avoidance task was performed on the 10th day and a memory retention test was done 24 h later. Scopolamine (1 mg/kg) was injected intraperitoneally, 30 min before the retention test to induce memory retrieval deficit. At the complement of the behavioral experiments, the hippocampi were isolated for western blot analysis to assess the phosphorylated and total levels of hippocampal MAPK and Akt proteins.Results: The results showed that cinnamaldehyde pretreatment at the dose of 100 mg/kg significantly prevented the amnesic effect of scopolamine. Furthermore, cinnamaldehyde prevented scopolamine induced dysregulations of hippocampal MAPK and Akt.Discussion: The results of the present study revealed that oral sub-chronic cinnamaldehyde administration has the capability to prevent memory retrieval deficit induced by cholinergic blockade and restores hippocampal MAPK and Akt dysregulations.

The Nephroprotective Role of Carnosine Against Ifosfamide-Induced Renal Injury and Electrolytes Imbalance is Mediated Via the Regulation of Mitochondrial Function and Alleviation of Oxidative Stress.

BACKGROUND: Ifosfamide (IFO) is an alkylating agent administered against different types of malignancies. Several cases of renal injury and serum electrolytes disturbances have been reported in IFO-treated patients. Oxidative stress and mitochondrial dysfunction are suspected of being involved in the mechanism of IFO nephrotoxicity. Carnosine is a dipeptide which its antioxidant and mitochondria protecting properties have been mentioned in different experimental models. The current study aimed to evaluate the nephroprotective properties of carnosine against IFO-induced renal injury. METHODS: Rats were treated with IFO (50 mg/kg, i.p) alone or in combination with carnosine. Serum and urine biomarkers of renal injury in addition to kidney markers of oxidative stress were evaluated. Moreover, kidney mitochondria were isolated, and some mitochondrial indices were assessed. RESULTS: Elevated serum creatinine and BUN, hypokalemia, and hypophosphatemia, in addition, to an increase in urine glucose, protein, γ-GT, and alkaline phosphatase (ALP), were evident in IFO-treated animals. IFO also caused an increase in kidney reactive oxygen species (ROS) and lipid peroxidation (LPO). Renal GSH levels and antioxidant capacity were also depleted with IFO therapy. Mitochondrial dehydrogenase activity, GSH level, membrane potential, and ATP content were decreased while mitochondrial LPO and permeabilization were increased in IFO group. Carnosine (250 and 500 mg/kg, i.p) mitigated IFO-induced oxidative stress and mitochondrial impairment in renal tissue. CONCLUSION: Our data suggest mitochondrial dysfunction and oxidative stress as fundamental mechanisms of renal injury induced by IFO. On the other hand, carnosine supplementation protected kidneys against IFO-induced injury through regulating mitochondrial function and mitigating oxidative stress.

The effect of cinnamaldehyde on passive avoidance memory and hippocampal Akt, ERK and GSK-3ß in mice.

Cinnamon, a spice widely used in cuisine, has been reported to exert therapeutic effects. Recently, cinnamon was shown to improve memory in some animal models of memory impairment and in poor learning mice. This study aimed to investigate the effect of cinnamaldehyde, the major compound in cinnamon on passive avoidance memory and activation of hippocampal Akt (protein kinase B), ERK (extracellular signal-regulated kinase) and GSK-3ß (Glycogen Synthase Kinase-3beta) in mice. In the present study, oral cinnamaldehyde at doses of 12.5, 25, 30, 40, 45, 50 and 100 mg/kg/daily was administered to adult male NMRI mice, initiated 10 days before training and continued during training and retention days. Training of passive avoidance task was performed on day 10 and a retention trial was done 24 h after. Upon completion of the retention test, hippocampi were removed for Western blot analysis to detect the phosphorylated and total levels of Akt, ERK and GSK-3ß proteins. Results showed that cinnamaldehyde exerts a biphasic effect on passive avoidance memory by impairing memory at lower doses while improving at higher doses. Moreover, at memory improving doses, cinnamaldehyde increased the phosphorylated forms of hippocampal Akt, ERK and GSK-3ß while these proteins did not change at impairing doses of cinnamaldehyde. For the first time, this study revealed a biphasic effect of cinnamaldehyde on memory as well as indicating that the memory improving effect of higher doses of this substance is accompanied with hippocampal Akt, ERK and GSK-3ß signaling alterations in adult mice.

Curcumin ameliorates scopolamine-induced mice memory retrieval deficit and restores hippocampal p-Akt and p-GSK-3ß.

The loss of cholinergic neurons has been a major issue in researches on Alzheimer's disease (AD) for about 40 years. Therefore, the scopolamine model of amnesia has been widely used in AD researches. Recently, it was reported that the early stage amnesia of AD is related to memory retrieval deficit. Curcumin, as the main ingredient of turmeric, has been suggested to decrease the prevalence of AD in human population. This study was conducted to assess if curcumin prevents retrieval deficit induced by scopolamine in passive avoidance task. Moreover, according to the proposed link between cholinergic system and Akt/GSK-3ß (Glycogen synthase kinase 3 beta) signaling, the hippocampal contents of these proteins were determined. Male NMRI mice (20-25 g body weight) were treated with 50 or 100 mg/kg/po curcumin or its vehicle for 10 days. On day 10, the animals were trained in passive avoidance apparatus. The retention trial was performed 24 h later. Scopolamine (1 mg/kg/i.p.) or its vehicle was administered 30 min before retention test. At the completion of behavioral studies, the hippocampi were removed and western blot analysis was performed to determine hippocampal phosphorylated and total Akt and GSK-3ß and beta actin contents. The results showed that curcumin treatment at 50 and 100 mg/kg doses prevented scopolamine-induced memory retrieval deficit and restored Akt and GSK dephosphorylation caused by scopolamine. Overall, these findings showed that pre-test scopolamine administration disrupts memory retrieval along with the diminished Akt and GSK-3ß phosphorylation in hippocampus while curcumin administration prevented those changes.

Aripiprazole prevents renal ischemia/reperfusion injury in rats, probably through nitric oxide involvement.

Renal ischemia/reperfusion (I/R) injury is strongly related to morbidity and mortality. Oxidative stress, inflammation, and apoptosis play key roles in renal dysfunction following renal I/R. Aripiprazole is an atypical antipsychotic which used for the treatment of schizophrenia and bipolar disorder. Recent studies have reported aripiprazole as displaying certain anti-inflammatory effects. Regarding the underlying mechanisms of renal ischemia-reperfusion, therefore, nephroprotective effects might be predicted to be seen with aripiprazole. I/R injury was induced by bilateral clamping of the renal pedicles (45min) followed by reperfusion (24h). The mechanism of aripiprazole-mediated nephroprotection was explored by a combined use of aripiprazole and L-NAME (non-selective nitric oxide synthase inhibitor). Animals were given aripiprazole (2.5, 5, 10 and 20mg/kg) intraperitoneally, 30min before ischemia. L-NAME was administered before the aripiprazole injection. Serum creatinine and blood urea nitrogen were assessed after 24h of reperfusion. Serum levels of malondialdehyde (MDA), TNF-α and IL-1ß were measured for rats treated with aripiprazole. The extent of necrosis was measured by the stereology method. Ischemia/reperfusion caused significant renal dysfunction and marked renal injury. Aripiprazole reduced creatinine and blood urea nitrogen. Serum levels of MDA, IL-1ß and TNF-α were significantly lower in the aripiprazole group. Aripiprazole treatment also decreased the volume of kidney necrosis. The administration of L-NAME reversed the renoprotective effect of aripiprazole on BUN and creatinine, but enhanced the anti-necrotic effect of aripiprazole. The results show that a single dose of aripiprazole significantly improved renal function following ischemia/reperfusion injury - probably through the involvement of nitric oxide.

The role of alpha-2 adrenoceptors in the anticonvulsant effects of adenosine on pentylenetetrazole-induced seizure threshold in mice.

Adenosine has anticonvulsant effects in various models of seizures. Alpha-2 adrenoceptors have also demonstrated different effects in different models of epilepsy. In this study, the role of alpha-2 adrenoceptors in the anticonvulsant effects of adenosine in mice was determined according to the method of intravenous pentylenetetrazole-induced seizure. In this study, N(6)-cyclohexyladenosine (CHA) (a selective A1 receptor agonist), clonidine (an alpha-2 adrenoceptors agonist), yohimbine (an alpha-2 adrenoceptors antagonist) and 8-cyclopentyl-1,3-dimethylxanthine (8-CPT) (a selective A1 receptor antagonist) were used. CHA at doses of 0.5, 1 and 2mg/kg significantly increased seizure threshold with the maximum anticonvulsant effect at 2mg/kg. Yohimbine (0.1, 1 and 10mg/kg), clonidine (0.1, 0.5, 1 and 2mg/kg) and 8-CPT (0.5, 1, 2 and 4mg/kg) had no effect on seizure by itself. Combination of yohimbine (10mg/kg) and CHA (0.25mg/kg) increased clonic seizure latency showing that yohimbine and CHA have an additive effect. Increasing the seizure threshold created by combining ineffective doses of yohimbine (10mg/kg) and CHA (0.25mg/kg) was completely inhibited by 8-CPT (4mg/kg) or clonidine (1 and 2mg/kg). Clonidine (0.5, 1 and 2mg/kg) inhibited the anticonvulsant effects of CHA (2mg/kg). Combination of 8-CPT (1mg/kg) and clonidine (0.5mg/kg) which completely inhibited the anticonvulsant effect of CHA (2mg/kg) indicates that 8-CPT and clonidine have an additive effect. In conclusion, adenosine and yohimbine exhibit an additive effect on the enhancement of the pentylenetetrazole-induced seizure threshold in mice, indicating the interaction of alpha-2 adrenoceptors and A1 adenosine receptors.

The increased gastroprotective effect of pioglitazone in cholestatic rats: role of nitric oxide and tumour necrosis factor alpha.

The prevalence of gastric ulcers is high in cholestatic patients, but the exact mechanism of this increased frequency remains uncertain. It has been shown that pioglitazone accelerates the healing of pre-existing gastric ulcers. The present study was designed to investigate the effect of pioglitazone, on the gastric mucosal lesions in cholestatic rats. Cholestasis was induced by surgical ligation of common bile duct and sham-operated rats served as control. Different groups of sham and cholestatic animals received solvent or pioglitazone (5, 15, 30 mg/kg) for 7 days. On the day eight rats were killed after oral ethanol administration and the area of gastric lesions was measured. The serums of rats were also collected to determine serum levels of tumour necrosis factor alpha (TNF-α), IL-1ß and bilirubin. The ethanol-induced gastric mucosal damage was significantly more severe in cholestatic rats than sham-operated ones. Pretreatment with pioglitazone dose-dependently attenuated gastric lesions induced by ethanol in both sham and cholestatic rats, but this effect was more prominent in cholestatic ones. The effect of pioglitazone was associated with a significant fall in serum levels of TNF-α in cholestatic rats. L-NAME, a non-selective nitric oxide synthase (NOS) inhibitor, and decreased pioglitazone-induced gastroprotective effect in cholestatic rats, while aminoguanidine, a selective inducible NOS inhibitor, potentiated pioglitazone-induced gastroprotective effect in the cholestatic rats. Chronic treatment with pioglitazone exerts an enhanced gastroprotective effect on the stomach ulcers of cholestatic rats compared to sham rats probably due to constitutive NOS induction and/or inducible NOS inhibition and attenuating release of TNF-α.

Enhanced anti-ulcer effect of pioglitazone on gastric ulcers in cirrhotic rats: the role of nitric oxide and IL-1ß.

BACKGROUND: The frequency of gastrointestinal ulcerations is higher in cirrhotic patients than in the normal population. It has been shown that pioglitazone exhibits gastroprotective actions. This study was designed to investigate the effect of pioglitazone, on the gastric mucosal lesions in cirrhotic rats. METHODS: Different groups of bile duct-ligated and sham animals received solvent, or 5, 10 or 15 mg/kg pioglitazone, for 5 days in the last days of 28-day period of cirrhosis. On day 28, rats were killed 1 h after oral ethanol administration and the area of gastric lesions was measured. The serum of rats was also collected to evaluate serum concentrations of TNF-α and IL-1ß. Histopathologic examination of liver specimens was also done with hematoxylin-eosin to show possible toxicity of pioglitazone in cirrhosis. RESULTS: Pretreatment with pioglitazone dose dependently attenuated gastric lesions induced by ethanol in both sham and cirrhotic rats, but this effect was more prominent in cirrhotic ones. L-NAME, a non-selective inhibitor of nitric oxide synthase, decreased pioglitazone-induced gastric healing effect in cirrhotic rats, while aminoguanidine, a selective inducible nitric oxide synthase inhibitor, increased pioglitazone-induced gastric healing effect in the same group. The protective effect of pioglitazone was accompanied by a fall in serum IL-1ß level. CONCLUSIONS: Chronic treatment with pioglitazone exerts a more prominent gastroprotective effect on the stomach ulcers of cirrhotic rats compared to control group probably due to constitutive nitric oxide synthase induction or inducible nitric oxide synthase inhibition. Suppression of IL-1ß could be another mechanism in pioglitazone-induced healing effect of gastric ulcers in cirrhotic rats.

The interaction of adenosine and morphine on pentylenetetrazole-induced seizure threshold in mice.

Adenosine agonists or low doses of morphine exert anti-convulsant effects in different models of seizures. On the other hand, a tight interaction has been reported between morphine and adenosine in various paradigms. This study investigated the effect of the interaction of adenosine and morphine on seizure susceptibility in the intravenous mouse model of pentylenetetrazole (PTZ)-induced clonic seizures. The researchers used acute systemic administration of morphine, N(6)-cyclohexyladenosine (CHA) (a selective A1 receptor agonist), naltrexone (an opioid receptor antagonist) and 8-Cyclopentyl-1,3-dimethylxanthine (8-CPT) (a selective A1 receptor antagonist). Acute administration of morphine (0.25, 0.5 and 1 mg/kg) or CHA (0.25, 0.5, 1, 2 and 4 mg/kg) raised the threshold of seizures induced by PTZ. Non-effective dose of 8-CPT (2 mg/kg) inhibited the anticonvulsant effects of CHA (0.5 and 1 mg/kg). Combination of sub-effective doses of morphine (0.125 mg/kg) and CHA (0.125 mg/kg) increased clonic seizure latency showing the additive effect of morphine and CHA. The enhanced latency induced by combination of low doses of morphine and CHA completely reversed by 8-CPT (2 mg/kg) or naltrexone (1 mg/kg). Moreover, 8-CPT (2 mg/kg) inhibited anticonvulsant effects of morphine (0.25 and 0.5 mg/kg) and naltrexone (1 mg/kg) inhibited anticonvulsant effects of CHA (0.25, 0.5 and 1 mg/kg). Combination of low doses of 8-CPT (1 mg/kg) and naltrexone (0.5 mg/kg) inhibited the anticonvulsant effect of CHA (0.5 and 1 mg/kg). In conclusion, adenosine and morphine exhibit an additive effect on the enhancement of the pentylenetetrazole-induced seizure threshold in mice, probably through A1 or µ receptors.

Cholestasis induces apoptosis in mice cardiac cells: the possible role of nitric oxide and oxidative stress.

BACKGROUND/AIMS: Acute cholestasis is associated with cardiovascular complications. The purpose of the present study was to investigate the effect of cholestasis on heart apoptosis and the involvement of nitric oxide (NO) and oxidative stress in the possible altered apoptosis of cholestatic hearts. METHODS: Cholestasis was induced by bile duct-ligation, and sham-operated mice served as controls. Three days after the surgery, heart tissues were evaluated for apoptosis and the level of malondialdehyde (MDA), and the activities of catalase (CAT), glutathione peroxidase (GSHPx) and superoxide dismutase (SOD) have been studied in cardiac tissues. The role of treatment with l-NAME, a non-selective inhibitor of NO synthase, or with d-NAME, an inactive isomer of l-NAME, on cholestatic and sham cardiac apoptosis, level of MDA and CAT, SOD and GSHPx activities was also investigated. The content of NO in cardiac tissue was also determined. RESULTS: Cholestatic hearts showed structural abnormalities and increased apoptosis compared with sham hearts. Treatment with l-NAME, but not d-NAME, improved both structural abnormalities and enhanced apoptosis of cholestatic hearts. Cholestatic hearts also had an increased level of MDA and decreased activities of CAT and GSHPx, which were not modified by d-NAME treatment. By l-NAME treatment, the level of MDA decreased and activities of CAT, GSHPx and SOD increased in BDL mice. The content of NO was higher in cholestatic cardiac tissue, which was decreased by l-NAME treatment. CONCLUSION: In conclusion, apoptosis in cholestatic heart might have occurred because of NO overproduction, which could induce oxidative stress in the heart of cholestatic mice.

Nanoparticles of quaternized chitosan derivatives as a carrier for colon delivery of insulin: ex vivo and in vivo studies.

The aim of the present study was to develop insulin nanoparticulate systems by using chitosan (CS), triethylchitosan (TEC) and dimethyl-ethylchitosan (DMEC, a new quaternized derivative of chitosan) for colon delivery. The nanoparticles were prepared by the polyelectrolyte complexation (PEC) method. Particle size distribution, zeta potential and polydispersity index of the nanoparticles were determined using dynamic light scattering technique. Transmission electron microscopy (TEM) was also used to observe the morphology of the nanoparticles. It was found that the nanoparticles carried positive charges and showed a size distribution in the range of 170-270 nm with spherical morphology and smooth surface structure. The amount of insulin loaded into the nanoparticles was determined by measuring the association efficiency and also the content of insulin in the nanoparticles. Insulin loading was found to be more than 80% for all of the nanoparticles. In vitro release studies showed a small burst effect at the beginning and then a sustained release characteristic for 5h. Ex vivo investigations revealed better insulin transport across the colon membrane of rats for nanoparticles made with quaternized derivatives than those made of chitosan. In vivo studies in rats have showed enhanced colon absorption of insulin by using these nanoparticles compared to free insulin in diabetic rats. The insulin absorption from the rat's colon was evaluated by its hypoglycemic effect.

Involvement of nitrergic and opioidergic systems in the hypothermia induced by cholestasis in rats.

BACKGROUND AND AIM: Cholestatic animals display abnormal hypothalamic responses to pyrogenic stimuli and decreased febrile response to lipopolysaccharide. The present study was undertaken to determine if obstructive cholestasis was associated with abnormal thermoregulation under thermoneutral conditions. METHODS: Male Sprague-Dawley rats weighing 200-250g were randomly divided into 21 groups. Three sets of seven groups were unoperated control, sham-operated and bile duct-ligated rats. The groups of unoperated control, sham-operated and bile duct-ligated rats were treated with daily administration of isotonic saline solution, N(omega)-nitro-l-arginine methyl ester (l-NAME) (3, 10, or 20mg/kg), naltrexone (10 or 20mg/kg) or aminoguanidine (150mg/kg). Body temperatures were measured before and 1, 3, 5 and 7 days after the surgery. RESULTS: Bile duct-ligated rats had lower body temperature than sham-operated animals at 3 (P<0.001) and 5 (P<0.01) days after surgery. l-NAME, a non-selective inhibitor of nitric oxide synthase (NOS) (10, 20mg/kg, i.p.) or aminoguanidine, a selective iNOS inhibitor (150mg/kg, i.p.), completely reversed this hypothermia (P>0.05). Naltrexone, a non-selective opioid antagonist (20mg/kg, i.p.), also completely corrected this hypothermia (P>0.05). There was a drop in temperature in the first day after the surgery in sham and BDL groups compared to unoperated controls, which was significant in some groups demonstrating the effect of surgery and anesthetic drugs on the body temperature. CONCLUSIONS: Cholestatic rats show impaired thermoregulation suggesting the involvement of nitrergic and opioidergic systems.