STZ-induced Cognitive Impairment Research Articles

GW9508 ameliorates cognitive dysfunction via autophagy pathway in streptozotocin-induced mouse model of Alzheimer's disease.

G protein-coupled receptor 40 (GPR40) is a potential drug target for Alzheimer's disease (AD), and its agonist GW9508 ameliorates cognitive impairment by intravenous administration. The present study was conducted to investigate the efficacy of GW9508 administered peripherally on cognitive dysfunction in streptozotocin (STZ)-induced AD mice. Seventy male ICR mice were randomly divided into seven groups: vehicle sham group, model, Donepezil, GW9508-L, GW9508-M, GW9508-H, and GW1100 + GW9508-H groups, and administered either vehicle (artificial cerebrospinal fluid [aCSF]) or STZ (3mg/kg in the vehicle) once a day (9:00 a.m.) by intracerebroventricular injection bilaterally on day 1 and day 3, respectively. After 2weeks of recovery, all mice were given drug treatment. Behavioral experiments were applied to test the recognition and spatial memory of mice, while molecular biology experiments such as Western blot, ELISA, and Nissl staining were used to detect the corresponding changes of signaling pathways. Intraperitoneal administration of GW9508 prevented STZ-induced cognitive impairment as well as decreased the level of p-tau and Aβ1-42 in plasma and brain. GW9508 upregulated the expression of gut-brain peptides like PYY, CCK, IGF-1, and GLP-1 both in blood circulation and brain and downregulated the expression level of autophagy-related proteins through activating Akt/mTOR signaling pathway. Meanwhile, the treatment effect of GW9508 was reversed by GPR40 antagonist GW1100 significantly. Peripheral administration of GW9508 exhibits neuroprotective effects, and it could be a promising therapy for AD. The neuroprotective mechanism of GW9508 was based on promoting gut-brain peptide secretion, activating Akt/mTOR signal pathway, and regulating neuronal autophagy.

MCC950 reduces autophagy and improves cognitive function by inhibiting NLRP3-dependent neuroinflammation in a rat model of Alzheimer's disease

Alzheimer's disease (AD) is the seventh most common cause of mortality and one of the major causes of disability and vulnerability in the elderly. AD is characterized by gradual cognitive deterioration, the buildup of misfolded amyloid beta (Aβ) peptide, and the generation of neurofibrillary tangles. Despite enormous scientific progress, there is no effective cure for AD. Thus, exploring new treatment options to stop AD or at least slow down its progress is important. In this study, we investigated the potential therapeutic effects of MCC950 on NLRP3-mediated inflammasome-driven inflammation and autophagy in AD. Rats treated with streptozotocin (STZ) exhibited simultaneous activation of the NLRP3 inflammasome and autophagy, as confirmed by Western blot, immunofluorescence, and co-immunoprecipitation analyses. MCC950, a specific NLRP3 inhibitor, was intraperitoneally administered (50 mg/kg body weight) to rats with AD-like symptoms induced by intracerebroventricular STZ injections (3 mg/kg body weight). MCC950 effectively suppressed STZ-induced cognitive impairment and anxiety by inhibiting NLRP3-dependent neuroinflammation. Moreover, our findings indicate that MCC950 exerts neuroprotective effects by attenuating autophagy in neuronal cells. The inhibiting effects of MCC950 on inflammasome activation and autophagy were reproduced in vitro, provding further mechansistic insights into MCC950 therapeutic action. Our findings suggest that MCC950 impedes the progression of AD and may also improve cognitive function through the mitigation of autophagy and NLRP3 inflammasome inhibition.

Pyruvate dehydrogenase kinase 1 protects against neuronal injury and memory loss in mouse models of diabetes

Hyperglycemia-induced aberrant glucose metabolism is a causative factor of neurodegeneration and cognitive impairment in diabetes mellitus (DM) patients. The pyruvate dehydrogenase kinase (PDK)–lactic acid axis is regarded as a critical link between metabolic reprogramming and the pathogenic process of neurological disorders. However, its role in diabetic neuropathy remains unclear. Here, we found that PDK1 and phosphorylation of pyruvate dehydrogenase (PDH) were obviously increased in high glucose (HG)-stimulated primary neurons and Neuro-2a cell line. Acetyl-coA, a central metabolic intermediate, might enhance PDK1 expression via histone H3K9 acetylation modification in HG condition. The epigenetic regulation of PDK1 expression provided an available negative feedback pattern in response to HG environment-triggered mitochondrial metabolic overload. However, neuronal PDK1 was decreased in the hippocampus of streptozotocin (STZ)-induced diabetic mice. Our data showed that the expression of PDK1 also depended on the hypoxia-inducible factor-1 (HIF-1) transcriptional activation under the HG condition. However, HIF-1 was significantly reduced in the hippocampus of diabetic mice, which might explain the opposite expression of PDK1 in vivo. Importantly, overexpression of PDK1 reduced HG-induced reactive oxygen species (ROS) generation and neuronal apoptosis. Enhancing PDK1 expression in the hippocampus ameliorated STZ-induced cognitive impairment and neuronal degeneration in mice. Together, our study demonstrated that both acetyl-coA-induced histone acetylation and HIF-1 are necessary to direct PDK1 expression, and enhancing PDK1 may have a protective effect on cognitive recovery in diabetic mice.Schematic representation of the protective effect of PDK1 on hyperglycemia-induced neuronal injury and memory loss. High glucose enhanced the expression of PDK1 in an acetyl-coA-dependent histone acetylation modification to avoid mitochondrial metabolic overload and ROS release. However, the decrease of HIF-1 may impair the upregulation of PDK1 under hyperglycemia condition. Overexpression of PDK1 prevented hyperglycemia-induced hippocampal neuronal injury and memory loss in diabetic mice.

FGF-18 alleviates memory impairments and neuropathological changes in a rat model of Alzheimer's disease

Alzheimer's disease (AD) is a multifactorial pathology marked by amyloid beta (Aβ) accumulation, tau hyperphosphorylation, and progressive cognitive decline. Previous studies show that fibroblast growth factor 18 (FGF18) exerts a neuroprotective effect in experimental models of neurodegeneration; however, how it affects AD pathology remains unknown. This study aimed to ascertain the impact of FGF18 on the behavioral and neuropathological changes in the rat model of sporadic AD induced by intracerebroventricular (ICV) injection of streptozotocin (STZ). The rats were treated with FGF18 (0.94 and 1.88 pmol, ICV) on the 15th day after STZ injection. Their cognitive function was assessed in the Morris water maze and passive avoidance tests for 5 days from the 16th to the 21st days. Aβ levels and histological signs of neurotoxicity were detected using the enzyme-linked immunosorbent assay (ELISA) assay and histopathological analysis of the brain, respectively. FGF18 mildly ameliorated the STZ-induced cognitive impairment; the Aβ accumulation was reduced; and the neuronal damage including pyknosis and apoptosis was alleviated in the rat brain. This study highlights the promising therapeutic potential for FGF18 in managing AD.

“Plurol will not miss the boat”: A new manifesto of galantamine conveyance

Liquid crystalline nanoparticles (LCNPs) are lipid self-assembled nanostructures that meet plenty of advantageous features. The commonly used substrates for LCNPs preparation are glyceryl monooleate. The impact of other LCNPs forming substrates like Plurol® has not been extensively explored. Galantamine (GAL) is used as a typical therapy to control the symptoms of Alzheimer's disease (AD). The existing study intends to study Plurol® as an emerging cart for the conveyance of GAL to the brain after nasal application. Different stabilizers; Poloxamer 407, Myri 53 and Myrj 59 have been studied along with different water content in order to select the best formula that can permeate both the nasal mucosa and the BBB. In vitro and in vivo examinations had been performed to test for the applicability of the fabricated formulae. Results revealed the successful encapsulation of GAL into the developed Plurol-based cubosomes. The optimized formula had a particle size of 205 ± 4.38 nm, PDI of 0.356 ± 0.016, zeta potential of 2.44 ± 0.947 and entrapment efficiency of 60.8%. Y-maze task results showed that GAL LCNPs treated resulted in 39% boost in percentage alternation relative to the Streptozotocin (STZ) group. In addition, results of Morris water maze task showed that mice received GAL cubosomal gel settled longer in the target quadrant (time increased by 34.67 s relative to that recorded for the STZ group). The ex vivo and in vivo results point to the better performance of the cubic gel in terms of enhanced permeation through nasal mucosa and reversed STZ-induced cognitive impairment compared to the cubosomal dispersion.

Activation of TGR5 Ameliorates Streptozotocin-Induced Cognitive Impairment by Modulating Apoptosis, Neurogenesis, and Neuronal Firing.

Takeda G protein-coupled receptor 5 (TGR5) is the first known G protein-coupled receptor specific for bile acids and is recognized as a new and critical target for type 2 diabetes and metabolic syndrome. It is expressed in many brain regions associated with memory such as the hippocampus and frontal cortex. Here, we hypothesize that activation of TGR5 may ameliorate streptozotocin- (STZ-) induced cognitive impairment. The mouse model of cognitive impairment was established by a single intracerebroventricular (ICV) injection of STZ (3.0 mg/kg), and we found that TGR5 activation by its agonist INT-777 (1.5 or 3.0 μg/mouse, ICV injection) ameliorated spatial memory impairment in the Morris water maze and Y-maze tests. Importantly, INT-777 reversed STZ-induced downregulation of TGR5 and glucose usage deficits. Our results further showed that INT-777 suppressed neuronal apoptosis and improved neurogenesis which were involved in tau phosphorylation and CREB-BDNF signaling. Moreover, INT-777 increased action potential firing of excitatory pyramidal neurons in the hippocampal CA3 and medial prefrontal cortex of ICV-STZ groups. Taken together, these findings reveal that activation of TGR5 has a neuroprotective effect against STZ-induced cognitive impairment by modulating apoptosis, neurogenesis, and neuronal firing in the brain and TGR5 might be a novel and potential target for Alzheimer's disease.

Metformin improves cognitive impairment in diabetic mice induced by a combination of streptozotocin and isoflurane anesthesia

ABSTRACT To investigate the protective effects of metformin on the diabetic mice with cognitive impairment induced by the combination of streptozotocin (STZ) and isoflurane anesthesia. The isoflurane-anesthetized cognitive impairment model mice were established and then observed via behavioral tests and histopathological examination. Then these model mice were randomly assigned to three groups, which received the PBS, low and high doses of metformin, respectively. The body weight, food and water consumption of model mice were measured every other day. The mechanisms of metformin on ameliorating the cognitive dysfunction were further investigated by histomorphological, biochemical and Western blot analysis. After 14-days treatment of metformin, the diabetic symptoms in STZ-induced diabetic mice were significantly alleviated. Metformin could restore the isoflurane- and STZ-induced hippocampal tissue damage, cognitive and memory impairment in exposed space via improving the oxidative stress, upregulating the contents of glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) in the hippocampus tissues of diabetic mice. Furthermore, chronic treatment of metformin significantly down-regulated the expression of AGEs, RAGE, pNF-κB, iNOS, and COX-2. In conclusion, metformin can improve the isoflurane- and STZ-induced cognitive impairment in diabetic mice via improving oxidative stress and inhibiting the AGEs/RAGE/NF-κB signaling pathway.

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.

Isoflurane-induced expression of miR-140-5p aggravates neurotoxicity in diabetic rats by targeting SNX12.

MicroRNAs (miRNAs) are widely known as critical regulators in isoflurane-induced neurotoxicity during the development of brain. Moreover, isoflurane could aggravate cognitive impairment in diabetic rats. The present study was designed to investigate the role and mechanism of miR-140-5p on isoflurane-induced neurotoxicity in diabetic rats. Firstly, a diabetic rat model was established by injection of streptozotocin (STZ) and identified by Morris water maze test. The result indicated that isoflurane treatment exacerbated STZ-induced cognitive impairment, as demonstrated by increase of the latency to the platform and decrease of the proportion of time spent in the target quadrant. Secondly, miR-140-5p was up-regulated in diabetic rats treated with isoflurane. Functional assays revealed that knockdown of miR-140-5p attenuated neurotoxicity in diabetic rats, which was shown by a decrease of the latency to the platform and an increase of the proportion of time spent in the target quadrant. Mechanistically, we demonstrated that miR-140-5p directly bonded to SNX12 (sorting nexin 12). At last, the neuroprotective effect of miR-140-5p knockdown against isoflurane-aggravated neurotoxicity in diabetic rats was dependent on up-regulation of SNX12 and inhibition of cell apoptosis. In summary, these meaningful results demonstrated the mitigation of miR-140-5p knockdown against isoflurane-aggravated neurotoxicity in diabetic rats via SNX12, suggesting a novel target for neuroprotection in diabetes under isoflurane treatment.

The protective effect of Geniposide on diabetic cognitive impairment through BTK/TLR4/NF-κB pathway.

The purpose of the present study was to elucidate the pharmacological effects of Geniposide (GEN) on high diet fed and streptozotocin (STZ)-caused diabetic cognitive impairment. The mice were fed with high fat diet (HFD) for 4 weeks and intraperitoneally injected with 60 mg/kg STZ for three times within 72 h. The mice with glucose level over 15 mmol/l were regarded as diabetic and selected for further studies. The animals were intragastrically treated with metformin or GEN once daily for 4 weeks. Afterwards, the animals were applied for Y maze, novel object recognition (NOR) test, step-through passive avoidance test, and Morris water maze (MWM) test. The blood glucose and body weight were examined. The SH-SY5Y cells were treated with GEN in the presence or absence of ibrutinib and stimulated with high-glucose culture medium. The tumor necrosis factor-a (TNF-α) and interleukin (IL)-6 in serum, hippocampus, and supernatant were measured using ELISA method. The protein expressions of Bruton's tyrosine kinase (BTK), Toll-like receptor 4 (TLR4), myeloid differentiating factor 88 (MyD88), nuclear factor kappa-B (NF-κB), p-NF-κB, brain-derived neurotrophic factor (BDNF), cAMP-response element binding protein (CREB), p-CREB, and glucagon-like peptide-1 receptor (GLP-1R) were detected by western blot analyses. As a result, the GEN treatment notably attenuated the body weight, blood glucose, and cognitive decline. GEN also inhibited the generations of inflammatory cytokines. Furthermore, the administrations of GEN ameliorated the alterations of BTK, TLR4, MyD88, NF-κB, and BDNF in HFD + STZ-induced mice. With the application of ibrutinib, the selective inhibitor of BTK, it was also found that BTK/TLR4/NF-κB pathway was associated with the GEN treatment in high glucose-induced SH-SY5Y cells. In summary, the results suggested that GEN exerted the protective effect on STZ-induced cognitive impairment possibly through the modulation of BTK/TLR4/NF-κB signaling.

Sinapic acid mitigates intracerebroventricular streptozotocin induced oxidative stress and neuro-inflammatory changes in rats

Oxidative stress and inflammatory cytokines play an important role in progression of Alzheimer’s disease (AD). Sinapic acid, a natural phenolic compound has shown neuro-protection by amelioration of oxidative stress and neuro-inflammation. Here, we evaluated the effect of sinapic acid on oxidative stress and inflammatory cytokines in intracerebroventricular streptozotocin (ICV-STZ) sporadic model of AD in rats. Male Wistar rats (260 ± 20g), were administered ICV-STZ (3 mg/kg) and sinapic acid (10 and 20 mg/kg, orally) was administered for 21 days. Morris water maze and passive avoidance paradigm test was carried out on 0 and 21st days. On 21st day rats were sacrificed, levels of MDA, GSH, TNF-α and IL-1β were estimated in cortex and hippocampus. The expression of choline acetyltransferase (ChAT) was also assessed by western blot. On day 21, STZ produced memory impairment as evidenced by increased escape latency (p < 0.001), decreased time spent in target zone in Morris water maze. Sinapic acid attenuated the increased escape latency and improved the time spent in target quadrant at 20 mg/kg on 21st day (p < 0.05). STZ induced decreased transfer latency in passive avoidance paradigm was also significantly increased. STZ induced changes in levels of GSH and MDA were significantly normalised by sinapic acid. STZ induced levels of TNF-α and IL-1β were significantly (p < 0.05) attenuated by sinapic acid 20 mg/kg. Moreover, sinapic acid ameliorated the STZ induced decreased expression of ChAT in hippocampus. The results suggest that sinapic acid improves STZ-induced cognitive impairment by ameliorating oxidative stress and neuro inflammation in cortex and hippocampus.

TIGAR Attenuates High Glucose-Induced Neuronal Apoptosis via an Autophagy Pathway.

Hyperglycemia-induced neuronal apoptosis is one of the important reasons for diabetic neuropathy. Long-time exposure to high glucose accelerates many aberrant glucose metabolic pathways and eventually leads to neuronal injury. However, the underlying mechanisms of metabolic alterations remain unknown. TP53-inducible glycolysis and apoptosis regulator (TIGAR) is an endogenous inhibitor of glycolysis and increases the flux of pentose phosphate pathway (PPP) by regulating glucose 6-phosphate dehydrogenase (G6PD). TIGAR is highly expressed in neurons, but its role in hyperglycemia-induced neuronal injury is still unclear. In this study, we observed that TIGAR and G6PD are decreased in the hippocampus of streptozotocin (STZ)-induced diabetic mice. Correspondingly, in cultured primary neurons and Neuro-2a cell line, stimulation with high glucose induced significant neuronal apoptosis and down-regulation of TIGAR expression. Overexpression of TIGAR reduced the number of TUNEL-positive neurons and prevented the activation of Caspase-3 in cultured neurons. Furthermore, enhancing the expression of TIGAR rescued high glucose-induced autophagy impairment and the decrease of G6PD. Nitric oxide synthase 1 (NOS1), a negative regulator of autophagy, is also inhibited by overexpression of TIGAR. Inhibition of autophagy abolished the protective effect of TIGAR in neuronal apoptosis in Neuro-2a. Importantly, overexpression of TIGAR in the hippocampus ameliorated STZ-induced cognitive impairment in mice. Therefore, our data demonstrated that TIGAR may have an anti-apoptosis effect via up-regulation of autophagy in diabetic neuropathy.

A long noncoding RNA LOC103690121 promotes hippocampus neuronal apoptosis in streptozotocin-induced type 1 diabetes

Diabetes related cognitive impairment is a severe complication. The diabetes-induced cognitive impairment is associated with insulin resistance and glucose-induced neuron apoptosis in the brain. We intended to investigate the association of long non-coding RNAs with diabetes-induced cognitive impairment in rats. Here, Type 1diabetes (T1D) rat model was induced using streptozotocin (STZ). The diabetic rats showed significant cognitive dysfunction, with increased latency period to find the hidden platform during morris water maze test. The brain injury and reduced neuronsin STZ-induced diabetic rats was determined using hematoxylin and eosin staining and Nissl’s staining. We performed the LncRNA microarray analysis and identified 101 differentially expressed lncRNAs in streptozotocin (STZ)-induced type 1 diabetes (T1D) comparing with control. Among these lncRNA, LOC103690121 was upregulated. in vitro glucose treatment in hippocampal neurons showed LOC103690121 and neuron apoptosis was increased by glucose treatment. Transfection experiments showed LOC103690121 overexpression promoted neuron apoptosis, and its inhibition suppressed glucose-induced apoptosis. Western blot analysis showed that the expression profiles of apoptosis related proteins (cleaved-caspase-3, -8, -9, and Bax) were in line with LOC103690121 expression, while the profiles of Bcl-2 and PI3K/Akt signaling pathway was contrast to LOC103690121 expression. In conclusion, the results of our study confirmed lncRNA LOC103690121 promoted STZ-induced cognitive impairment in diabetic rats by promoting neuron apoptosis through PI3K/Akt signaling pathway.

The protective effect of formononetin on cognitive impairment in streptozotocin (STZ)-induced diabetic mice

The present study was aimed to elucidate the pharmacological effect of Formononetin (FMN) treatment on STZ-induced diabetic cognitive dysfunction. The diabetic model was induced by an intraperitoneally injection of 180 mg/kg STZ. The animals were randomly divided into five groups: control group, streptozocin (STZ, 180 mg/kg) group, STZ + metformin (Met, 200 mg/kg) group, STZ + FMN (25 mg/kg) group, STZ + FMN (50 mg/kg) group. The mice were intragastrically administrated with metformin (Met, 200 mg/kg) or FMN (25, 50 mg/kg) once daily for 6 weeks. The blood glucose content and body weight were examined. Morris water maze test and Y maze test were used to evaluate the learning and memory abilities. The cognitive decline was reversed by regulating superoxide dismutase (SOD), malondialdehyde (MDA), tumor necrosis factor-a (TNF-α), interleukin(IL)-1β, IL-6 in serum and hippocampus. The protein expressions of high mobility group box-1 protein (HMGB1), toll like receptor 4 (TLR4), myeloid differentiating factor 88 (MyD88), inhibitor of NF-κB (IκBα), p-IκBα, nuclear factor kappa-B(NF-κB), p-NF-κB, NOD-like receptor 3(NLRP3), apoptosis-associated speck-like protein containing CARD(ASC) and caspase-1 were detected. Furthermore, the SH-SY5Y cells were exposed to high glucose stimulation, FMN (2.5, 5 and 10 μM) treatment, and glycyrrhizin, the selective inhibitor of HMGB1. After an incubation for 22 h, the SH-SY5Y cells were harvested for detection. As a result, FMN treatment effectively attenuated the body weight, learning and memory abilities, as well as the levels of blood glucose, SOD, MDA, TNF-α, IL-1β, IL-6. FMN administration also downregulated the protein expressions of HMGB1, TLR4, MyD88, p-IκB, p-NF-κB, NLRP3, ASC and caspase-1. The inhibition of HMGB1 by glycyrrhizin also confirmed the involvement of HMGB1/TLR4/NF-κB/NLRP3 pathway in high glucose-induced SH-SY5Y cells. In summary, the results suggested that FMN exhibited the protective effect on STZ-induced cognitive impairment possibly via the mediation of HMGB1/TLR4/NF-κB signaling and NLRP3 inflammasome.

Attenuation of dementia by AS605240‐PI3K inhibitor in ICV‐STZ induced sporadic Alzheimer's disease rat model

Sporadic Alzheimer's disease is an age allied neurological and psychiatric disorder branded by impaired energy metabolism. Oxidative stress and neuro‐inflammation are associated in pathophysiology of sporadic type of dementia. The quest for chemical entities able to kerb the action of the PI3K/AKT/mTOR pathway is evolving as a potential therapeutic stratagem for its treatment and/or prevention.The Intra‐cerebroventricular (ICV) administration of streptozotocin prompts behavioural and biochemical changes resembling those in sporadic type of Alzheimer's patients. The current study was intended to investigate the effects of chronic pre‐treatment with Phosphoinositide 3‐kinase(PI3K)inhibitor AS605240 on cognitive dysfunction and oxidative stress markers in intracerebroventricular (ICV) streptozotocin‐treated albino rats.Treatment with AS605240 orally was done on a daily basis for a period of 21 days, 1 hr prior to ICV‐STZ injection using stereotaxy and evaluated for cognitive function tests and biochemical parameters.AS605240 when given orally on a daily basis for a period of 21 days significantly improved STZ‐induced cognitive impairment. Besides, improving cognitive dysfunction, AS605240, reduced elevated nitrite levels, and restored reduced glutathione and superoxide dismutase levels, Lipid peroxidation and total Protein content.Taken together, these results demonstrate that PI3K inhibitor AS605240 can be helpful in treatment of sporadic Alzheimer's Disease.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Ethyl acetate fraction from Hibiscus sabdariffa L. attenuates diabetes-associated cognitive impairment in mice

The ameliorating effects of the ethyl acetate fraction from Hibiscus sabdariffa L. (EFHS)22EFHS: ethyl acetate fraction from Hibiscus sabdariffa L. against diabetes mellitus (DM)33DM: diabetes mellitus. and DM-induced cognitive impairment were investigated on streptozotocin (STZ)44STZ: streptozotocin.-induced DM mice. The EFHS groups showed improved hyperglycemia and glucose tolerance compared to the STZ group. Furthermore, their liver and kidney function and lipid metabolic imbalance in the blood serum were effectively recovered. The EFHS groups significantly ameliorated STZ-induced cognitive impairment in Y-maze, passive avoidance, and Morris water maze (MWM)55MWM: Morris water maze. tests. The EFHS groups showed significant improvement in the antioxidant and cholinergic systems of the brain tissue. In addition, EFHS had an excellent ameliorating effect on protein expression levels from the tau hyperphosphorylation pathways, such as phospho-c-Jun N-terminal kinases (p-JNK),66p-JNK: phospho-c-Jun N-terminal kinases. phospho-tau (p-tau),77p-tau: phospho-tau. and cleaved poly (ADP-ribose) polymerase (c-PARP).88c-PARP: cleaved poly (ADP-ribose) polymerase. The main compounds of EFHS were identified as various phenolic compounds, including hibiscus acid, caffeoylquinic acid (CQA)99CQA: caffeoylquinic acid. isomers, and quercetin derivates. Therefore, EFHS containing various physiologically active materials can potentially be used for improving DM-induced cognitive impairment via its antioxidant activity, improvement of the cholinergic system, and hyperphosphorylation tau signaling.

Edaravone attenuates intracerebroventricular streptozotocin-induced cognitive impairment in rats.

Alzheimer's disease is a major cause of dementia worldwide. Edaravone, a potent free radical scavenger, is reported to be neuroprotective. The present study was designed to investigate the effect of chronic edaravone administration on intracerebroventricular-streptozotocin (ICV-STZ) induced cognitive impairment in male Wistar rats. Cognitive impairment was developed by single ICV-STZ (3mg/kg) injection bilaterally on day 1. Edaravone (1, 3 and 10mg/kg, orally, once daily) was administered for 28days. Morris water maze and passive avoidance tests were used to assess cognitive functions at baseline and on days 14 and 28. ICV-STZ caused cognitive impairment as evidenced by increased escape latency and decreased time spent in target quadrant in the Morris water maze test and reduced retention latency in the passive avoidance test. STZ caused increase in oxidative stress, cholinesterases, inflammatory cytokines and protein expression of ROCK-II and decrease in protein expression of ChAT. Edaravone ameliorated the STZ-induced cognitive impairment. STZ-induced increase in oxidative stress and increased levels of pro-inflammatory cytokines (TNF-α, IL-1β) were mitigated by edaravone. Edaravone also prevented STZ-induced increased protein expression of ROCK-II. Moreover, edaravone significantly prevented STZ-induced increased activity of cholinesterases in the cortex and hippocampus. The decreased expression of ChAT caused by STZ was brought towards normal by edaravone in the hippocampus. The results thus show that edaravone is protective against STZ-induced cognitive impairment, oxidative stress, cholinergic dysfunction and altered protein expressions. This study thus suggests the potential of edaravone as an adjuvant in the treatment of Alzheimer's disease.

Chronic treatment with taurine after intracerebroventricular streptozotocin injection improves cognitive dysfunction in rats by modulating oxidative stress, cholinergic functions and neuroinflammation

The present study investigated the neuroprotective effects of taurine, an essential amino acid for growth and development of central nervous system. Intracerebroventricular streptozotocin (ICV-STZ) model of cognitive impairment was used in male Wistar rats (270 ± 20 g). Morris water maze, elevated plus maze and passive avoidance paradigm were used to assess cognitive performance. Taurine (40, 60 and 120 mg/kg) was administered orally for 28 days following STZ administration on day 1. Oxidative stress parameters (malondialdehyde, glutathione, nitric oxide and superoxide dismutase) and cholinesterases (acetylcholinesterase and butyrylcholinesterase) activity were measured at end of the study in the cortex and hippocampus. Levels of TNF-α, IL-1β, expression of rho kinase-II (ROCK-II), glycogen synthase kinase-3β (GSK-3β) and choline acetyltransferase (ChAT) were studied in cortex and hippocampus. STZ caused significant cognitive impairment as compared to normal control. Chronic administration of taurine attenuated STZ-induced cognitive impairment. Increased oxidative stress and increased levels of TNF-α, IL-1β induced by STZ were also significantly attenuated by taurine. Taurine significantly (p < 0.05) decreased the STZ-induced increased expression of ROCK-II in cortex and hippocampus. Further, STZ-induced increased activity of cholinesterases was significantly (p < 0.001) mitigated by taurine. STZ decreased the expression of ChAT in hippocampus which was significantly (p < 0.05) reversed by taurine. However, GSK-3β expression was not altered by either STZ or taurine. The present study indicates that taurine exerts a neuroprotective role against STZ-induced cognitive impairment in rats. This effect is probably mediated by modulating oxidative stress, cholinesterases, inflammatory cytokines and expression of ROCK-II. Thus, this study suggests a potential of chronic taurine administration in cognitive impairment of Alzheimer's type.

Montelukast ameliorates streptozotocin-induced cognitive impairment and neurotoxicity in mice

Extensive studies have demonstrated that neuroinflammation is associated with Alzheimer’s disease (AD) and cysteinyl leukotriene receptor 1 (CysLT1R) was involved in neuroinflammation. Montelukast, a highly selective CysLT1R antagonist, has been reported to attenuate learning and memory impairments in the amyloid-β-induced mouse model of AD. However, whether montelukast also exerts beneficial effects on streptozotocin (STZ)-induced memory deficits in mice is not well known. In the present study, we aimed to investigate the effects of montelukast on STZ-induced cognitive impairment, neuroinflammation and apoptosis in mice. Our data showed that intra-hippocampal microinfusion of STZ resulted in learning and memory impairments, including increased escape latency during acquisition trials and decreased exploratory activities in the probe trial in Morris watermaze (MWM) task, and decreased number of correct choices and increased latency to enter the shock-free compartment in Y-maze test, and caused neuroinflammatory and apoptotic responses, evidenced by increments of nuclear NF-κB p65, TNF-α, IL-1β, cleaved caspase-3, Bax as well as decreased expression of Bcl-2 in hippocampus. Interestingly, STZ treatment led to up-regulation of protein and mRNA of CysLT1R in hippocampus. Of note, consecutive oral administration of montelukast (1 or 2mg/kg, 3 weeks) remarkably attenuated these effects induced by STZ. However, montelukast had no effect on normal mice. These results suggest that montelukast improves memory impairment and inhibits neuroinflammation and apoptosis in mice exposed to STZ. Montelukast may provide a novel strategy for treating or preventing AD.

Tocilizumab's effect on cognitive deficits induced by intracerebroventricular administration of streptozotocin in Alzheimer's model.

Neuroinflammation plays pivotal roles in the pathogenesis of Alzheimer's disease (AD). IL-6 is pleiotropic cytokine which plays significant pathological role in inflammatory diseases and causes prolonged inflammation. Additionally, IL-6 activates microglia cells and enhances the accumulation of amyloid-β peptides. Moreover, IL-6 signal transduction is mediated by membrane-bound and soluble IL-6 receptors. Tocilizumab which is a humanized anti-human IL-6 receptor (IL-6R) monoclonal antibody binds to both of these receptors and inhibits IL-6 signaling by this route. The objective was to investigate tocilizumab's potential effects in the treatment of AD. Male Sprague-Dawley rats were divided into three groups: sham (control), streptozotocin (STZ), and tocilizumab-STZ. We used a single dose of intracerebroventricular (ICV) tocilizumab, beginning 1 h prior to injection of STZ for 3 weeks. The rats in STZ and tocilizumab-STZ groups were given ICV-STZ (3mg/kg). Behavioral parameters were evaluated on days 17-20 and the rats were sacrificed on day-21 to examine histopathological changes. STZ injection caused significant decrease in the mean escape latency in passive avoidance and also declined the performance improvement in Morris water maze tests. Tocilizumab-STZ group significantly improved learning and spatial memory functions by increasing RLT in the passive avoidance and by shortening escape latency in reaching the platform in the Morris water maze. Histopathological changes were examined using hematoxylin and eosin and immunohistochemical (IHC) stainings. IHC analysis revealed that while protein expressions of amyloid-ß (3.5±0.2) and IL-6 (2.9±0.4) showed intense immune-positivity in STZ group, amyloid-ß (1.3±0.1) and IL-6 (1.5±0.2) immunoreactivities were substantially decreased in tocilizumab treatment group. We conclude that tocilizumab treatment attenuated significantly STZ-induced cognitive impairment and histopathological changes. Further studies would be desirable to investigate clinically relevant protective effects of tocilizumab in AD.