EFFECT OF SULFUR DIOXIDE ON ACTIVE AND PASSIVE AVOIDANCE IN EXPERIMENTAL DIABETES MELLITUS: RELATION TO OXIDANT STRESS AND ANTIOXIDANT ENZYMES

Hippocampal acetylcholine receptor activation-dependent long-term depression in streptozotocin-induced diabetic rats

Cholinergic innervation of the hippocampus correlates with memory formation. In a well-established animal model of type 1 diabetes mellitus, obtained by injecting young adult rats with streptozotocin (STZ), reductions have been reported in the expression of acetylcholine receptors and choline acetyltransferase. In this study, we showed that long-term synaptic depression (LTD) induced by carbachol (CCh), a nonselective cholinergic receptor agonist, at Schaffer collateral-CA1 synapses in hippocampal slices was significantly weaker in streptozotocin-induced diabetic rats (STZ rats) than in age-matched control rats. No significant change was observed in the paired-pulse ratio between before and 80 min after the application of CCh in control and STZ rats. Moreover, CCh-induced LTD in control and STZ rats was not affected by an NMDA receptor antagonist. Although the application of CCh down-regulated the surface expression of GluA2 in the hippocampus of control rats, but not STZ rats. Therefore, the present results suggest that acetylcholine receptor-mediated LTD in STZ rats requires the internalization of AMPA receptors on the postsynaptic surface and their intracellular effects in the hippocampus.

The interactive effects of verapamil and CB1 cannabinoid receptor antagonist/inverse agonist, AM251 on passive avoidance learning and memory in rat

There are reports regarding the effects of intracellular Ca2+ and synthesis and release of endocannabinoids. The secretion of endocannabinoids depends on the L-type calcium channel. The present study evaluated the involvement of the cannabinoid CB1 receptors in the effect of L-type calcium channel blocker verapamil on passive avoidance learning (PAL) in adult male rats. In this study, we examined the effects of an acute administration of the cannabinoid CB1 receptors antagonist/inverse agonist AM251 following a chronic administration of the Ca2+ channel blocker verapamil on PAL. Male Wistar rats were administered verapamil (10, 25 and 50 mg/kg) or saline intraperitoneally (i.p) daily for 13 days (n = 10/group). After this treatment period, a learning test (acquisition) was performed, and a retrieval test was performed the following day. The results indicated that chronic systemic administration of verapamil (in a dose-dependent manner) impaired memory acquisition and retrieval. Pre-training acute administration of a selective CB1 antagonist/inverse agonist, AM251 (5 mg/kg, i.p.) did not change memory acquisition and retrieval. Co-administration of the verapamil and AM251 significantly reversed verapamil-induced amnesia, suggesting a functional interaction between AM251 and verapamil. The results indicated the interactive effects of cannabinoid CB1 receptors and L-type calcium channel in passive avoidance learning and AM251 can counter the effects of verapamil on memory.

Sulfur dioxide derivatives attenuates consolidation of contextual fear memory in mice

Post-traumatic stress disorder (PTSD) is characterized by an enhancement of traumatic memory. Intervention strategies based on the different stages of memory have been shown to be effective in the prevention and control of PTSD. The endogenous gaseous molecule, sulfur dioxide (SO₂), has been reported to significantly exert neuromodulatory effects; however, its regulation of learning and memory remains unestablished. This study aimed to investigate the effects of exogenous SO₂ derivatives administration on the formation, consolidation, reconsolidation, retention, and expression of contextual fear memory. Behavioral results showed that both intraperitoneal injection (50 mg/kg, ip) and hippocampal infusion (5 μg/side) of SO₂ derivatives (a mixture of sodium sulfite and sodium bisulfite, Na₂SO₃/NaHSO₃, 3:1 M/M) significantly impaired consolidation but had no effect on reconsolidation and retention of contextual fear memory. These findings suggest that the attenuating effects of SO₂ on the consolidation of fear memory involves, at least partially, the region of the hippocampus. The findings of this study provide direct evidence for the development of new strategies for PTSD prevention and treatment involving the use of gaseous SO₂.

Effect of sulfur dioxide exposure on histopathology and morphometry of pancreatic islet cells and glycemic indices in Wistar rats

Sulfur dioxide (SO₂) is a ubiquitous air pollutant. Recent studies suggest that SO₂ is a momentous risk factor for diabetes mellitus (DM). The present investigation aimed to evaluate the effects of SO₂ exposure on histopathology and morphometry of pancreatic islet cells and serum glycemic indices in rats. Sixteen male Wistar rats were divided equally into SO₂ and control groups. SO₂ group was exposed to 10 parts per million (ppm) SO₂ for 5 weeks (6 days a week, 3 h/day) and control group to filtered air for the same time as SO₂ group. Blood serums were collected and pancreatic tissue isolated. Glycemic indices were measured. Pathological and morphometric changes were studied in the pancreatic tissues. Exposure to SO₂ caused a significant increase in blood glucose but did not significantly change insulin and HbA1c serum levels and HOMA-IR. There were significant differences in vascular congestion (p= 0.02) and insulitis (p= 0.04) between the groups. SO₂ inhalation significantly reduced beta cell number and beta-alpha cell ratio compared with the control group (p=0.03 and p<0.0001, respectively). These findings suggest that SO₂ exposure damages pancreatic tissue which subsequently influences either the incidence of DM or the trend of diabetic complications.

Albiflorin alleviates cognitive dysfunction in STZ-induced rats

BACKGROUND

To explore the effect of albiflorin (AL) on streptozotocin (STZ)-induced Alzheimer's disease (AD) in rats.

METHODS

A mouse model of diabetic encephalopathy was established by intraperitoneal injection of 1%STZ. Step down test and water maze test were used to test the cognitive function of rats. Congo Red Staining was used to detect the distribution of Aβ plaques in the hippocampus of rats. Cytokine levels in serum and hippocampus were measured using ELISA. Serum insulin, oral glucose tolerance (OGTT), serum superoxide dismutase (SOD) activity and malondialdehyde (MDA) content were measured by commercial kits. And the content of Nrf-2/HO-1/HMGB1/NF-kB in the hippocampus of diabetic rats were detected by western blot.

RESULTS AND CONCLUSION

Compared with the STZ model group, the average escape latency of rats in the AL group in the Morris water maze test was significantly shortened, and the average number of platform crossings and the ratio of distance/total swimming distance in the target quadrant were increased significantly. Staining of tissue sections and ELISA showed a decrease in Aβ plaque density in the hippocampus of rats in the AL group. And serum insulin levels of rats in the ALgroup were significantly reduced and OGTT was improved. In addition, AL could also regulate the Nrf-2/HO-1/HMGB1/NF-kB signal pathway in the hippocampus. Therefore, AL may ameliorate STZ-induced cognitive impairment in rats by regulating oxidative stress and inflammation in the brain.

Effects of Regular Exercise on Diabetes-Induced Memory Deficits and Biochemical Parameters in Male Rats

The main objective of current work was to determine the effects of treadmill-running and swimming exercise on passive avoidance learning (PAL) and blood biochemical parameters in rats with streptozotocin (STZ)-induced diabetes. Male Wistar rats were divided into the following 6 groups (N = 6-8 per group): CON, healthy rats without exercise (N = 8); STZ, diabetic rats without exercise (N = 8); CON-SE, healthy rats subjected to swimming exercise (2 months; N = 6); STZ-SE, diabetic rats subjected to swimming exercise (2 months; N = 7); CON-TE, healthy rats subjected to treadmill exercise (2 months; N = 8); STZ-TE, diabetic rats subjected to treadmill exercise (2 months; N = 8). Diabetes was induced by a single intraperitoneal injection of 50 mg/kg STZ. Our results showed that STZ decreased the step-through latency in the retention test (STLr) and increased the time spent in the dark compartment (TDC) when compared with the CON group. However, treadmill-running and swimming exercise in STZ-treated rats increased the STLr and decreased the TDC when compared with STZ-treated rats without exercise in PAL. Blood low-density lipoprotein (LDL) and triglyceride (TG) levels in the STZ group were significantly higher than those in the CON group, whereas plasma total antioxidant capacity (TAC) and levels of catalase (CAT) and glutathione peroxidase (GPx) were lower in the STZ group compared with the CON group. The levels of LDL and TG decreased and the levels of TAC, CAT, and GPx increased in the exercise groups in comparison with the STZ group. The present results indicate that regular exercise enhances learning and memory in diabetic rats and that these effects may occur through activation of the antioxidant system.

Chronic copper exposure leads to hippocampus oxidative stress and impaired learning and memory in male and female rats

Environmental and occupational exposures to copper (Cu) play a pivotal role in the etiology of some neurological diseases and reduced cognitive functions. However, the precise mechanisms of its effects on cognitive function have not been yet thoroughly established. In our study, we aimed to investigate the behavior and neurochemical alterations in hippocampus of male and female rats, chronically exposed to copper chloride (CuCl2) and the possible involvement of oxidative stress. Twenty-four rats, for each gender, were divided into control and three test groups (n = 6), and were injected intraperitoneally with saline (0.9% NaCl) or CuCl2 (0.25 mg/kg, 0.5 mg/kg and 1 mg/kg) for 8 weeks. After the treatment period, Y-maze test was used for the evaluation of spatial working memory and the Morris Water Maze (MWM) to test the spatial learning and memory. Biochemical determination of oxidative stress levels in hippocampus was performed. The main results of the present work are working memory impairment in spatial Y-maze which induced by higher Cu intake (1 mg/kg) in male and female rats. Also, In the MWM test, the spatial learning and memory were significantly impaired in rats treated with Cu at dose of 1 mg/kg. Additionally, markers of oxidative stress such as catalase, superoxide dismutase, lipid peroxidation products and nitric oxide levels were significantly altered following Cu treatments. These data propose that compromised behavior following Cu exposure is associated with increase in oxidative stress.

The Effects of Ripe Pistachio Hulls Hydroalcoholic Extract and Aerobic Training on Learning and Memory in Streptozotocin-induced Diabetic Male Rats

Introduction:

Diabetes mellitus has harmful effects on body functions, such as learning and memory. According to the role of exercise and medicinal plants on body health, the purpose of this study was to survey the effect of combined aerobic training and the use of Ripe Pistachio Hulls (RPH) hydro-alcoholic extract on learning and memory in streptozotocin-induced diabetic male rats.

Methods:

In this experimental study, 42 male Wistar rats weighing 250–280 g were used in 6 groups with an equal number of 7 rats in each one. Streptozotocin (STZ) (50 mg / kg)was used to induce diabetes, and the test protocol was applied for 8 weeks. Passive avoidance memory was assessed using a step-through passive avoidance apparatus (shuttle box). SPSS software was used to analyze the data and P<0.05 was significant.

Results:

The results showed that step-through latency in the acquisition trial (STLa) was not significantly different among groups. Step-through latency in retrieval (STLr 24) test significantly reduced and time spent in The Dark Compartment (TDC) decreased in treated groups compared with the diabetic control groups (P<0.001). Also, there was no significant difference between the STZ and saline diabetic groups.

Conclusion:

The findings of this study revealed that the RPH hydro-alcoholic extract and aerobic exercise could improve passive avoidance memory in streptozotocin diabetic rats. Meanwhile, they might be an adjuvant therapy combined with other traditional medicine.

The effects of aqueous extract of Origanum vulgare on learning and memory in male rats

Introduction: The effectiveness of antioxidants on learning and memory improvement has been shown, previously. Due to the high level of antioxidants, available in Origanum vulgare, the present experiment aimed to examine the effect of aqueous extract of O. vulgare on passive avoidance learning (PAL) in male Wistar rats. Methods: This study was performed on 30 male Wistar rats weighing 250 to 290 g. The rats were randomly assigned into five groups (n=6), as follows: the control, sham (saline), and three groups treated with different doses of O. vulgare extract (150, 250, and 350 mg/kg). The saline or extract was administered via daily oral gavage for 14 days. The groups were then subjected to the passive avoidance task, and their behaviors were recorded. The rats’ locomotor activity was also measured using the open field test. Results: The number of trials to acquisition was significantly lower in the "O. vulgare (350 mg/ kg)" group than the control group. The step-through latency and the time spent in the dark compartment in the retention test, was significantly higher and lower in the "O. vulgare (250 and 350 mg/kg)" groups than the control group, respectively. No significant differences were found in the distances traveled among the experimental groups in the open field test. Conclusion: Aqueous extract of O. vulgare can enhance learning and memory. The high levels of antioxidants in O. vulgare extract may be responsible for its effectiveness in learning and memory.

Coenzyme Q10 supplementation reverses diabetes-related impairments in long-term potentiation induction in hippocampal dentate gyrus granular cells: An in vivo study

Diabetes mellitus (DM) is associated with impaired hippocampal synaptic plasticity. Coenzyme Q10 (CoQ10) acts as an antioxidant and exerts neuroprotective effects. Accordingly, this study aimed at evaluating the effects of CoQ10 on hippocampal long-term potentiation (LTP) and paired-pulse facilitation (PPF) in streptozotocin (STZ)-induced diabetic rats. Male Wistar rats were randomly divided into six groups (n = 8 per group) as follows and treated for 90 days: the control, control + low dose of CoQ10 (100 mg/kg), control + high dose of CoQ10 (600 mg/kg), diabetic, diabetic + low dose of CoQ10, and diabetic + high dose of CoQ10 groups. Diabetes was induced by a single intraperitoneal injection of 50 mg/kg STZ. The population spike (PS) amplitude and slope of excitatory post synaptic potentials (EPSPs) were measured in dentate gyrus (DG) area in response to the stimulation applied to the perforant path (PP). The results showed that the STZ-induced diabetes impaired LTP induction in the PP-DG synapses. This finding is supported by the decreased EPSP slope and PS amplitude of LTP (P < 0.05). Both low- and high-dose CoQ10 supplementation in the control and diabetic animals enhanced EPSP slope and PS amplitude of LTP in the granular cells of DG (P < 0.05). PPF was affected by LTP induction in diabetic animals receiving the high dose of CoQ10 (P < 0.05). It is suggested that CoQ10 administration could attenuate deteriorative effect of STZ-induced diabetes on in vivo LTP in the DG. The enhanced transmitter release can be partly one of the possible underlying mechanism(s) responsible for the LTP induction in the diabetic animals treated with CoQ10.

Effect of coenzyme Q10 supplementation on diabetes induced memory deficits in rats

The main objective of current work was to determine the effects of low and high dose supplementation with coenzyme Q10 (CoQ10) on spatial learning and memory in rats with streptozotocin (STZ)-induced diabetes. Male Wistar rats (weighing 220 ± 10) were randomly divided into six groups: (i) Control (Con, n = 8); (ii) Control+ Low dose of CoQ10 (100 mg/kg) (CLD, n = 10); (iii) Control+ high dose of CoQ10 (600 mg/kg) (CHD, n = 10); (iv) Diabetic (D, n = 10); (v) Diabetic + Low dose of CoQ10 (100 mg/kg) (DLD, n = 10); (vi) Diabetic + high dose of CoQ10 (600 mg/kg) (DHD, n = 10). Diabetes was induced by a single intraperitoneal injection of 50 mg/kg STZ. CoQ10 was administered intragastrically by gavage once a day for 90 days. After 90 days, Morris water maze (MWM) task was used to evaluate the spatial learning and memory in rats. Diabetic animals showed a slower rate of acquisition with respect to the control animals [F (1, 51) = 92.81, P < 0.0001, two-way ANOVA]. High dose (but no low dose) supplementation with CoQ10 could attenuate deteriorative effect of diabetes on memory acquisition. Diabetic animals which received CoQ10 (600 mg/kg) show a considerable decrease in escape latency and traveled distance compared to diabetic animals (p < 0.05, two-way ANOVA,). The present study has shown that low dose supplementation with CoQ10 in diabetic rats failed to improve deficits in cognitive function but high dose supplementation with CoQ10 reversed diabetes-related declines in spatial learning.

Hippocampal Subcellular Organelle Proteomic Alteration of Copper-Treated Mice

Copper neurotoxicity has been implicated in multiple neurological diseases. However, there is a lack of deep understanding on copper neurotoxicity, especially for low-dose copper exposure. In this study, we investigated the effects of chronic, low-dose copper treatment (0.13 ppm copper chloride in drinking water) on hippocampal mitochondrial and nuclear proteome in mice by 2-dimensional fluorescence difference gel electrophoresis coupled with MALDI-TOF-MS/MS. Behavioral tests revealed that low-dose copper caused spatial memory impairment, DNA oxidative damage as well as loss of synaptic proteins. Proteomic analysis revealed modulation of 31 hippocampal mitochondrial proteins (15 increased and 16 decreased), and 46 hippocampal nuclear proteins (18 increased and 28 decreased) in copper-treated versus untreated mice. Bioinformatic analysis indicated that these differentially expressed proteins are mainly involved energy metabolism (NDUV1, COX5B, IDH3A, and PGAM1), synapses (complexin-2, synapsin-2), DNA damage (PDIA3), apoptosis (GRP75), and oxidative stress (SODC, PRDX3). Among these differentially expressed proteins, synapsin-2, a synaptic-related protein, was found to be significantly decreased as confirmed by Western-blot analysis. In addition, we found that superoxide dismutase [Cu-Zn] (SODC), a copper ion target protein, was identified to be decreased in copper-treated mice versus untreated mice. We also found that stathmin (STMN1), a microtubule-destabilizing neuroprotein, was significantly decreased in hippocampal nuclei of copper-treated mice versus untreated mice. Taken together, we conclude that low-dose copper exposure causes spatial memory impairment and perturbs multiple biological/pathogenic processes by dysregulating the mitochondrial and nuclear proteome, particularly the proteins related to respiratory chain, synaptic vesicle fusion, axonal/neurtic integrity, and oxidative stress. The change of STMN1 and SODC may represent early novel biomarkers of copper neurotoxicity.

Influence of Chronic Coenzyme Q10 Supplementation on Cognitive Function, Learning, and Memory in Healthy and Diabetic Middle-Aged Rats

Diabetes mellitus can induce impairment in learning and memory. Cognitive and memory deficits are common in older adults and especially in those with diabetes. This is mainly because of hyperglycemia, oxidative stress, and vascular abnormalities. Coenzyme Q10 (CoQ10) can decrease oxidative stress, hyperglycemia, and inflammatory markers, and improve vascular function. Therefore, the aim of the present study was to investigate the possible effects of CoQ10 on cognitive function, learning, and memory in middle-aged healthy and diabetic rats. Adult middle-aged male Wistar rats (390-460 g, 12-13 months old) were divided into 6 experimental groups. Diabetes was induced by a single i.p. injection of streptozotocin (60 mg/kg). CoQ10 (20 or 120 mg/kg, orally by gavage) was administered for 45 days. The cognitive function and learning memory of rats were evaluated using novel object recognition (NOR) and passive avoidance tests. The discrimination index of the NOR test in the diabetic groups receiving CoQ10 (20 or 120 mg/kg) and the healthy group receiving CoQ10 (120 mg/kg) was significantly higher than that in the control group. In addition, the step through latency was significantly longer and the time spent in the dark compartment was significantly shorter in the diabetic groups receiving CoQ10 than in the control group. CoQ10 supplementation can improve learning and memory deficits induced by diabetes in older subjects. In addition, CoQ10 at higher doses can improve cognitive performance in older healthy subjects.

Resistance training and hawthorn extract ameliorate cognitive deficits in streptozotocin-induced diabetic rats

It has been shown that diabetic rats display cognitive impairment. The aim of this study was to investigate the effects of resistance training and natural antioxidants on learning and memory in type 1 diabetic rats. For this purpose, fifty male Wistar rats were randomly divided into five groups: (i) Control (Con, n=10), (ii) Diabetic (D, n=10), (iii) Diabetic+Resistance training (DRT, n=10), (iv) Diabetic+natural antioxidants (DHE, n=10), and (v) Diabetic+Resistance training+ natural antioxidants (DRH, n=10). Climbing the ladder for a period of 5days/week for 10 consecutive weeks was considered as the resistance training model in our study. Natural antioxidants (100mg/kg per day) were administered to natural antioxidant groups for a period of 10 weeks. Moreover, spatial and passive avoidance learning and memory function were evaluated by Morris Water Maze (MWM) and shuttle box tests. The results showed that, mean of total escape latency decreased 25% (P<0.0001) in the DRH group compared with the D group in MWM. The percentage of time spent in the target quadrant identically decreased (34%) in the D and DHE groups compared with the Con group (p=0.001). In this regard, time spent in the dark Compartment (TDC) respectively rose 86% and 95% in the D and DHE groups compared with the Con group (p<0.05), and decreased 88% in the DRT and DRH groups compared with the D group in the shuttle box test (p<0.05). Furthermore, we noticed that total antioxidant capacity increase and lipid peroxidation decrease in response to the treatments in the diabetic rats as well. Therefore, the current study indicated that exercise training and natural antioxidants synergistically ameliorated learning and memory deficits in type 1 diabetic rats via reducing oxidative stress. Hence, it may propose a potential role of resistance training and natural antioxidants as an adjuvant therapy for the prevention and treatment of diabetic complications.

Transcriptome Response to Heavy Metals in Sinorhizobium meliloti CCNWSX0020 Reveals New Metal Resistance Determinants That Also Promote Bioremediation by Medicago lupulina in Metal-Contaminated Soil

The symbiosis of the highly metal-resistant Sinorhizobium meliloti CCNWSX0020 and Medicago lupulina has been considered an efficient tool for bioremediation of heavy metal-polluted soils. However, the metal resistance mechanisms of S. meliloti CCNWSX00200 have not been elucidated in detail. Here we employed a comparative transcriptome approach to analyze the defense mechanisms of S. meliloti CCNWSX00200 against Cu or Zn exposure. Six highly upregulated transcripts involved in Cu and Zn resistance were identified through deletion mutagenesis, including genes encoding a multicopper oxidase (CueO), an outer membrane protein (Omp), sulfite oxidoreductases (YedYZ), and three hypothetical proteins (a CusA-like protein, a FixH-like protein, and an unknown protein), and the corresponding mutant strains showed various degrees of sensitivity to multiple metals. The Cu-sensitive mutant (ΔcueO) and three mutants that were both Cu and Zn sensitive (ΔyedYZ, ΔcusA-like, and ΔfixH-like) were selected for further study of the effects of these metal resistance determinants on bioremediation. The results showed that inoculation with the ΔcueO mutant severely inhibited infection establishment and nodulation of M. lupulina under Cu stress, while inoculation with the ΔyedYZ and ΔfixH-like mutants decreased just the early infection frequency and nodulation under Cu and Zn stresses. In contrast, inoculation with the ΔcusA-like mutant almost led to loss of the symbiotic capacity of M. lupulina to even grow in uncontaminated soil. Moreover, the antioxidant enzyme activity and metal accumulation in roots of M. lupulina inoculated with all mutants were lower than those with the wild-type strain. These results suggest that heavy metal resistance determinants may promote bioremediation by directly or indirectly influencing formation of the rhizobium-legume symbiosis.IMPORTANCE Rhizobium-legume symbiosis has been promoted as an appropriate tool for bioremediation of heavy metal-contaminated soils. Considering the plant-growth-promoting traits and survival advantage of metal-resistant rhizobia in contaminated environments, more heavy metal-resistant rhizobia and genetically manipulated strains were investigated. In view of the genetic diversity of metal resistance determinants in rhizobia, their effects on phytoremediation by the rhizobium-legume symbiosis must be different and depend on their specific assigned functions. Our work provides a better understanding of the mechanism of heavy metal resistance determinants involved in the rhizobium-legume symbiosis, and in further studies, genetically modified rhizobia harboring effective heavy metal resistance determinants may be engineered for the practical application of rhizobium-legume symbiosis for bioremediation in metal-contaminated soils.

Crocin improves spatial learning and memory deficits in the Morris water maze via attenuating cortical oxidative damage in diabetic rats

The purpose of the current study was to examine the influence of crocin on improving spatial memory deficits and cerebral oxidative damage in streptozotocin-induced diabetic rats. Crocin was administered intraperitoneally daily at doses of 15, 30 and 60mg/kg for 6 weeks. Spatial memory performance was measured in rats by the Morris water maze paradigm. Lipid peroxidation and total thiol levels as parameters of oxidative stress were assessed in the cerebral cortex at the end of week 6. Diabetic rats showed spatial learning and memory deficits in the Morris water maze which was accompanied by increased lipid peroxidation levels in the cerebral cortex. By contrast, chronic treatment with crocin (15, 30 and 60mg/kg, ip, 6 weeks) improved cognitive performance and lowered hyperglycaemia and oxidative stress in diabetic rats. In conclusion, the results suggest that beneficial effects of crocin on streptozotocin-induced memory dysfunction may be attributed to its antidiabetic and antioxidant activity, which could find clinical use in treating cognitive dysfunction in diabetics.

Protective effect of betulin on cognitive decline in streptozotocin (STZ)-induced diabetic rats

Betulin is extracted from birch tree bark and exerts diverse pharmacological activities. The present study was designed to investigate the protective effect of betulin (BE) on cognitive decline in streptozotocin (STZ)-induced diabetic rats. The diabetic model was built by streptozotocin (STZ) (30mg/kg, ip). After 4 weeks, the diabetic rats were treated with vehicle or BE (20mg/kg, 40mg/kg) for 4 weeks. The oral glucose tolerance (OGTT) and serum insulin were detected. Three days later, Morris water maze (MWM) test was used to evaluate memory function. Superoxide dismutase (SOD) activity and malondialdehyde (MDA) content in hippocampus were examined. Inflammatory cytokines including interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α) in serum and hippocampus were measured. The protein expressions of nuclear factor-erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1) and NF-κB pathways-related molecules in hippocampus were examined. As a results, BE could improve glucose intolerance and modify basal learning performance. Treatment with BE significantly restored SOD activity and decreased MDA content in hippocampus. BE also markedly reduced the contents of inflammatory cytokines in serum and hippocampus. Furthermore, administration of BE effectively upregulated the expressions of Nrf2, HO-1 and blocked the phosphorylations of IκB, NF-κB. In summary, BE might exhibit protective effect on cognitive decline in STZ-induced diabetic rats through HO-1/Nrf-2/NF-κB pathway.

Fatty acid amide hydrolase inhibitor URB597 prevented tolerance and cognitive deficits induced by chronic morphine administration in rats

Inhibitors of the endocannabinoid metabolic enzyme fatty acid amide hydrolase exert therapeutic effects, but might also be associated with some of the adverse effects of cannabis. However, at least one fatty acid amide hydrolase inhibitor, URB597, has beneficial effects without signs of abuse or dependence. Although previous investigations have evaluated URB597-morphine interactions, the effects of URB597 on morphine tolerance and cognition deficits have not been studied previously. Rats were rendered tolerant to or dependent on morphine by an injection of morphine (10 mg/kg, subcutaneous) twice daily, respectively, for 7 or 10 days. URB597 (1 mg/kg, intraperitoneal) was administered before morphine. The tail-flick and passive avoidance learning tests were used to evaluate tolerance and cognition. Chronic morphine injection led to significant tolerance to the antinociceptive effect on days 5 and 7. URB597 completely prevented the development of morphine tolerance. URB597 also enhanced memory acquisition in the passive avoidance learning test, and although morphine impaired memory, URB597 alleviated this effect. These data show that URB597 protects against tolerance and memory deficits in chronic usage of morphine and suggests URB597 as a promising candidate for the treatment of adverse effects of opioids.

Preventive effects of Salvia officinalis L. against learning and memory deficit induced by diabetes in rats: Possible hypoglycaemic and antioxidant mechanisms

Learning and memory impairment occurs in diabetes. Salvia officinalis L. (SO) has been used in Iranian traditional medicine as a remedy against diabetes. We hypothesized that chronic administration of SO (400, 600 and 800mg/kg, p.o.) and its principal constituent, rosmarinic acid, would affect on passive avoidance learning (PAL) and memory in streptozocin-induced diabetic and non-diabetic rats. We also explored hypoglycemic and antioxidant activities of SO as the possible mechanisms. Treatments were begun at the onset of hyperglycemia. PAL was assessed 30days later. Retention test was done 24h after training. At the end, animals were weighed and blood samples were drawn for further analyzing of glucose and oxidant/antioxidant markers. Diabetes induced deficits in acquisition and retrieval processes. SO (600 and 800mg/kg) and rosmarinic acid reversed learning and memory deficits induced by diabetes and improved cognition of healthy rats. While the dose of 400mg/kg had no effect, the higher doses and rosmarinic acid inhibited hyperglycemia and lipid peroxidation as well as enhanced the activity of antioxidant enzymes superoxide dismutase and catalase. SO prevented diabetes-induced acquisition and memory deficits through inhibiting hyperglycemia, lipid peroxidation as well as enhancing antioxidant defense systems. Therefore, SO and its principal constituent rosmarinic acid represent a potential therapeutic option against diabetic memory impairment which deserves consideration and further examination.

Investigation of the effects of a sulfite molecule on human neuroblastoma cells via a novel oncogene URG4/URGCP

AIM

The aim of this study is to determine the anticancer effect of sulfite on SH-SY5Y neuroblastoma cells in vitro conditions and elucidate underlying molecular mechanism of sulfite and explore its therapeutic activity.

MAIN METHODS

In this study, cytotoxic effects of sulfite in SH-SY5Y cels were detected over time in a dose dependent manner with the IC50 doses ranging from 0.5 to 10 mM. Genotoxic effect of sulfite was shown by comet assay. IC50 doses in the SH-SY5Y cells were detected as 5 mM. Expression profiles of the target genes related to apoptosis and cell cycle control were determined by quantitative RT-PCR. Protein changes were determined by western blot analysis.

KEY FINDINGS

URG4/URGCP, CCND1, CCND2, CDK4, CDK6, E2F4 and BCL-2 gene expression levels were significantly reduced and RB1, TP53, BAX, BID, CASP2, CASP3, CASP9 and DIABLO gene expressions were significantly increased in dose group cells. The mechanism of this result may be related to sulfite dependent inhibition of cell cycle at the G1 phase by down-regulating URG4/URGCP or CCND1, CDK4, CDK6 gene expression and stimulating apoptosis via the intrinsic pathway. Sulfite suppressed invasion and colony formation in SH-SY5Y cell line using matrigel invasion chamber and colony formation assay, respectively.

SIGNIFICANCE

It is thought that sulfite demonstrates anticarcinogenesis activity by affecting cell cycle arrest, apoptosis s, invasion, and colony formation on SH-SY5Y cells. Sulfite may be an effective agent for treatment of neuroblastoma as a single agent or in combination with other agents.

Ameliorative effect of rosmarinic acid on scopolamine-induced memory impairment in rats

Rosmarinic acid (RA) is a natural phenol that exerts different biological activities, such as antioxidant activity and neuroprotective effects. In this study, we hypothesized that administration of RA (8, 16, and 32 mg/kg, p.o.) for 7 days would effect on scopolamine-induced cognitive dysfunction as an extensively used model of cognitive impairment. The rats were divided into 10 groups. The acquisition trial was done 1h after the last administration of RA. Animals were divided into control, RA (8, 16, and 32 mg/kg) and donepezil (2 mg/kg) treated controls, scopolamine, RA (8, 16, and 32 mg/kg), and donepezil (2 mg/kg) treated scopolamine groups. Memory impairment was induced by scopolamine treatment (1 mg/kg, i.p.) 30 min after the administration of RA, donepezil, or saline. Scopolamine administration caused cognition deficits in the PAL and memory paradigm. While orally RA administration (16 and 32 mg/kg) improved learning and memory in control rats, it reversed learning and memory deficits of scopolamine received groups. Administration of RA at the dose of 8 mg/kg did not alter cognitive function in control and scopolamine treated groups. The combination of anticholinesterase, neuroprotective, and antioxidant properties of RA may all be responsible for the observed effects. These results indicate the beneficial effects of subchronic RA administration in passive avoidance learning and memory in control rats as well as in a pharmacological model of cholinergic deficit which continue to expand the knowledge base in creating new treatment strategies for cognition deficits and dementia. Of course, further studies are warranted for clinical use of RA in the management of demented subjects.

Ice plant (Mesembryanthemum crystallinum) improves hyperglycaemia and memory impairments in a Wistar rat model of streptozotocin-induced diabetes

BACKGROUND

Ice plant (Mesembryanthemum crystallinum) has been used as an anti-diabetic agent in Japan because it contains d-pinitol. The efficacy of ice plant in the regulation of blood glucose is unclear at present. Recently, memory impairment and development of Alzheimer's disease found in diabetic patients are thought to be caused by high blood glucose. The mechanism by which ice plant protects against the impairment of memory and learning abilities caused by high blood glucose remains unclear. The aim of this study was to evaluate the protection of ice plant water extracts (IPE) and D-pinitol against memory impairments in a Wistar rat model of streptozotocin (STZ)-induced diabetes. We hypothesised that IPE and D-pinitol could suppress blood glucose and elevate insulin sensitivity in these rats.

RESULTS

For memory evaluation, IPE and D-pinitol also improved the passive avoidance task and the working memory task. In addition, inhibition of acetylcholinesterase activity in hippocampus and cortex was found in this rat model administered IPE or D-pinitol. IPE and D-pinitol also markedly elevated superoxide dismutase activity against oxidative stress and reduced malondialdehyde production in hippocampus and cortex of the rats.

CONCLUSION

These findings indicated that IPE and D-pinitol possess beneficial effects for neural protection and memory ability in a rat model of diabetes.

Effect of tempol on the passive avoidance and novel object recognition task in diabetic rats

Diabetes mellitus (DM) has several effects, including cognitive impairment. Oxidative stress is associated with complications from diabetes. It seems that antioxidants can reduce some complications of the diabetes induced by oxidative stress. The objective of this study was to evaluate the effect of synthetic antioxidant, tempol on the passive avoidance (PA) memory and novel object recognition (NOR) tests in the diabetic rats. Forty male Wistar rats randomly divided into the control, diabetic, diabetic receiving tempol and healthy receiving tempol groups. Diabetes was induced by injection of streptozotocin (STZ) (60 mg/kg, i.p.). Then, the rats received saline or tempol (30 mg/kg) orally by gavages for 60 days. After that, they were assessed using the PA memory and NOR tests. The results of NOR test showed that the discrimination index (DI) in the healthy receiving tempol group and diabetic control group was significantly lower than control group. Also the amount of this index in diabetic receiving tempol group was significantly higher than diabetic group. The results of PA test indicated that the number of trials to acquisition in the diabetic rats is significantly more than control and diabetic tempol treated groups. Also, the time spent in the dark compartment (TDC) in the control and diabetic receiving tempol groups was less than diabetic group. TDC in the healthy receiving tempol group was more than control group. It can be concluded that although use of tempol is restricted as a cognitive enhancer in non-diabetic subjects but long-term administration of synthetic antioxidant, tempol, is able to dramatically improve diabetes-induced learning and memory deficit in both PA and NOR tests.

Estrogen: a master regulator of bioenergetic systems in the brain and body

Estrogen is a fundamental regulator of the metabolic system of the female brain and body. Within the brain, estrogen regulates glucose transport, aerobic glycolysis, and mitochondrial function to generate ATP. In the body, estrogen protects against adiposity, insulin resistance, and type II diabetes, and regulates energy intake and expenditure. During menopause, decline in circulating estrogen is coincident with decline in brain bioenergetics and shift towards a metabolically compromised phenotype. Compensatory bioenergetic adaptations, or lack thereof, to estrogen loss could determine risk of late-onset Alzheimer's disease. Estrogen coordinates brain and body metabolism, such that peripheral metabolic state can indicate bioenergetic status of the brain. By generating biomarker profiles that encompass peripheral metabolic changes occurring with menopause, individual risk profiles for decreased brain bioenergetics and cognitive decline can be created. Biomarker profiles could identify women at risk while also serving as indicators of efficacy of hormone therapy or other preventative interventions.

The effect of sodium metabisulphite on active avoidance performance in hypercholesterolemic rats

The purpose of this study was to investigate the effects of hypercholesterolemia and sulphite on active avoidance learning. Male Wistar rats were divided into eight groups as follows: Control (C), Sulphite (S), Vitamin E (E), Sulphite + Vitamin E (SE), Hypercholesterolemia (H), Hypercholesterolemia + Sulphite (HS), Hypercholesterolemia + Vitamin E (HE), and Hypercholesterolemia + Sulphite + Vitamin E (HSE). At the end of the experimental period, the serum cholesterol level (mean ± SD) was significantly higher in H group (111.5 ± 11.11 mg dL(-1) ) as compared to C group (63.5 ± 4.9 mg dL(-1) ). Levels of thiobarbituric acid reactive substances (TBARS) were increased in HS group as compared to C, H, and S groups. Vitamin E reduced TBARS levels in HSE group compared with HS group. Active avoidance results indicated that hypercholesterolemia was associated with learning impairment. Our data clearly revealed that the combination of hypercholesterolemia and sulphite results in exaggerated impairment of active avoidance. Vitamin E improved active avoidance in HSE group compared with HS group. Therefore, the synergistic effect of hypercholesterolemia and sulphite may be associated with a considerable health risk.

Preventive effect of Teucrium polium on learning and memory deficits in diabetic rats

Background

Cognitive impairment occurs in diabetes mellitus. Teucrium polium L. (Lamiaceae) has been used in folk medicine to improve mental performance. Here we hypothesized that chronic treatment with an aqueous extract of Teucrium polium (100, 200 and 400 mg/kg, p.o.) would have an effect on passive avoidance learning (PAL) and memory in control and streptozocin-induced diabetic rats.

Material/Methods

Treatments were begun at the onset of hyperglycemia, and PAL was assessed 30 days later. A retention test was performed 24 h (hours) after training. After PAL and memory assessment, animals were weighed and blood samples were drawn for plasma glucose measurement.

Results

Diabetes caused impairment in acquisition of PAL and retrieval of memory. Teucrium polium treatment (200 and 400 mg/kg) improved learning and memory in control rats and reversed learning and memory deficits in diabetic rats. The 100 mg/kg dose did not affect cognitive function. Teucrium polium treatment partially improved the reduced body weight and hyperglycemia of treated diabetic rats, although the differences were not significant compared to non-treated diabetic rats.

Conclusions

These results show that Teucrium polium prevented the deleterious effects of diabetes on PAL and memory. Antioxidant, anticholinesterase and hypoglycemic effects of Teucrium may be involved in the obtained effects. Therefore, Teucrium polium appears to be a promising candidate for memory improvement in diabetes, but this needs confirmation by future clinical studies.

Chronic cyanidin-3-glucoside administration improves short-term spatial recognition memory but not passive avoidance learning and memory in streptozotocin-diabetic rats

This research study was conducted to evaluate the efficacy of chronic cyanidin-3-glucoside (C3G) on alleviation of learning and memory deficits in diabetic rats as a result of the observed antidiabetic and antioxidant activity of C3G. Male Wistar rats were divided into control, diabetic, C3G-treated-control and -diabetic groups. The C3G was administered i.p. at a dose of 10 mg/kg on alternate days for eight weeks. For evaluation of learning and memory, initial latency (IL) and step-through latency (STL) were determined at the end of study using passive avoidance test. Meanwhile, spatial recognition memory was assessed as alternation in the Y-maze task. Oxidative stress markers in brain tissue were also measured. It was found that the alternation score of the diabetic rats was lower than that of control (p < 0.01) and C3G-treated diabetic rats showed a higher alternation score as compared to diabetic group (p < 0.05). Diabetic rats also developed a significant impairment in retention and recall in passive avoidance test (p < 0.01) and C3G treatment of diabetic rats did not produce any significant improvement. Meanwhile, increased level of malondialdehyde (MDA) in diabetic rats was significantly reduced following C3G treatment (p < 0.05). Taken together, chronic C3G could improve short-term spatial recognition memory disturbance in the Y-maze test but not retention and recall capability in passive avoidance test in STZ-diabetic rats.

Effects of combined treatment with vitamins C and E on passive avoidance learning and memory in diabetic rats

Learning and memory deficits occur in diabetes mellitus. Although the pathogenesis of cognitive impairment in diabetes has not been fully elucidated, factors such as metabolic impairments, vascular complications and oxidative stress are thought to play possible roles. Here we investigated the effect of chronic treatment with vitamin C (50mg/kg, p.o), vitamin E (100mg/kg, p.o) and both together on passive avoidance learning (PAL) and memory in male Wistar control and diabetic rats. Treatments were begun at the onset of hyperglycemia. Passive avoidance learning was assessed 30 days later. Retention was tested 24h after training. At the end, animals were weighed and blood samples were drawn for plasma glucose measurement. Diabetes caused impairment in acquisition and retrieval processes of PAL and memory. The combination of vitamin C and E improved learning and memory in controls and reversed learning and memory deficits in diabetic rats. Combined treatment also affected the body weight and plasma glucose level of diabetic treated animals compared to untreated diabetic animals. Hypoglycemic effects and antioxidant properties of the vitamins may be involved in the nootropic effect of such treatment. These results show that combined treatment with vitamins C and E improved PAL and memory of control rats. In addition, combined vitamins administration to rats for 30 days from onset of diabetes alleviated the negative influence of diabetes on learning and memory. Therefore, combined vitamins treatment may provide a new potential alternative for prevention of impaired cognitive functions associated with diabetes and may warrant further clinical study.

SO(2) inhalation induces protein oxidation, DNA-protein crosslinks and apoptosis in rat hippocampus

Previous studies provide evidence for the possible neurotoxicity of SO(2), but little information is available about its mechanisms. In the present study, SO(2) inhalation-induced effects on the protein oxidation, DNA-protein crosslinks and apoptosis in rat hippocampus were studied, by exposing Wistar rats to SO(2) at 14, 28 and 56mg/m(3). The results indicate that the protein carbonyl content, an indicator of protein oxidation, and DNA-protein crosslink coefficient were significantly augmented with concentration-dependent properties. In addition, SO(2) inhalation at all concentrations tested caused the increases of caspase-3 activity and number of TUNEL positive staining neuron and the statistical difference was observed after 28 and 56mg/m(3) exposure, suggesting the occurrence of apoptosis. The results imply that attacking protein, nucleic acids and lipids by free radicals, generated via SO(2) derivatives in vivo, is one of the main mechanisms for SO(2)-induced injuries in central neuronal system.