Sigma-1 Receptor Activation Improves Oligodendrogenesis and Promotes White-Matter Integrity after Stroke in Mice with Diabetic Mellitus.

Diabetes mellitus (DM) is a major risk factor for stroke and exacerbates white-matter damage in focal cerebral ischemia. Our previous study showed that the sigma-1 receptor agonist PRE084 ameliorates bilateral common-carotid-artery occlusion-induced brain damage in mice. However, whether this protective effect can extend to white matter remains unclear. In this study, C57BL/6 mice were treated with high-fat diets (HFDs) combined with streptozotocin (STZ) injection to mimic type 2 diabetes mellitus (T2DM). Focal cerebral ischemia in T2DM mice was established via injection of the vasoconstrictor peptide endothelin-1 (ET-1) into the hippocampus. Three different treatment plans were used in this study. In one plan, 1 mg/kg of PRE084 (intraperitoneally) was administered for 7 d before ET-1 injection; the mice were sacrificed 24 h after ET-1 injection. In another plan, PRE084 treatment was initiated 24 h after ET-1 injection and lasted for 7 d. In the third plan, PRE084 treatment was initiated 24 h after ET-1 injection and lasted for 21 d. The Y-maze, novel object recognition, and passive avoidance tests were used to assess neurobehavioral outcomes. We found no cognitive dysfunction or white-matter damage 24 h after ET-1 injection. However, 7 and 21 d after ET-1 injection, the mice showed significant cognitive impairment and white-matter damage. Only PRE084 treatment for 21 d could improve this white-matter injury; increase axon and myelin density; decrease demyelination; and increase the expressions of myelin regulator 2'-3'-cyclic nucleotide 3'-phosphodiesterase (CNpase) and myelin oligodendrocyte protein (MOG) (which was expressed by mature oligodendrocytes), the number of nerve/glial-antigen 2 (NG2)-positive cells, and the expression of platelet-derived growth factor receptor-alpha (PDGFRα), all of which were expressed by oligodendrocyte progenitor cells in mice with diabetes and focal cerebral ischemia. These results indicate that maybe there was more severe white-matter damage in the focal cerebral ischemia of the diabetic mice than in the mice with normal blood glucose levels. Long-term sigma-1 receptor activation may promote oligodendrogenesis and white-matter functional recovery in patients with stroke and with diabetes.

PINK1 overexpression prevents forskolin-induced tau hyperphosphorylation and oxidative stress in a rat model of Alzheimer's disease.

PTEN-induced putative kinase 1 (PINK1)/parkin pathway mediates mitophagy, which is a specialized form of autophagy. Evidence shows that PINK1 can exert protective effects against stress-induced neuronal cell death. In the present study we investigated the effects of PINK1 overexpression on tau hyperphosphorylation, mitochondrial dysfunction and oxidative stress in a specific rat model of tau hyperphosphorylation. We showed that intracerebroventricular (ICV) microinjection of forskolin (FSK, 80 µmol) induced tau hyperphosphorylation in the rat brain and resulted in significant spatial working memory impairments in Y-maze test, accompanied by synaptic dysfunction (reduced expression of synaptic proteins synaptophysin and postsynaptic density protein 95), and neuronal loss in the hippocampus. Adeno-associated virus (AAV)-mediated overexpression of PINK1 prevented ICV-FSK-induced cognition defect and pathological alterations in the hippocampus, whereas PINK1-knockout significantly exacerbated ICV-FSK-induced deteriorated effects. Furthermore, we revealed that AAV-PINK1-mediated overexpression of PINK1 alleviated ICV-FSK-induced tau hyperphosphorylation by restoring the activity of PI3K/Akt/GSK3ß signaling. PINK1 overexpression reversed the abnormal changes in mitochondrial dynamics, defective mitophagy, and decreased ATP levels in the hippocampus. Moreover, PINK1 overexpression activated Nrf2 signaling, thereby increasing the expression of antioxidant proteins and reducing oxidative damage. These results suggest that PINK1 deficiency exacerbates FSK-induced tau pathology, synaptic damage, mitochondrial dysfunction, and antioxidant system defects, which were reversed by PINK1 overexpression. Our data support a critical role of PINK1-mediated mitophagy in controlling mitochondrial quality, tau hyperphosphorylation, and oxidative stress in a rat model of Alzheimer's disease.

Protein kinase C is involved in the neuroprotective effect of berberine against intrastriatal injection of quinolinic acid-induced biochemical alteration in mice.

Protein kinase C (PKC) shows a neuronal protection effect in neurodegenerative diseases. In this study, we test whether berberine has a positive effect on the activity of PKC in quinolinic acid (QA)-induced neuronal cell death. We used intrastriatal injections of QA mice model to test the effect of berberine on motor and cognitive deficits, and the PKC signalling pathway. Treatment with 50 mg/kg b.w of berberine for 2 weeks significantly prevented QA-induced motor and cognitive impairment and related pathologic changes in the brain. QA inhibited the phosphorylation of PKC and its downstream molecules, GSK-3ß, ERK and CREB, enhanced the glutamate level and release of neuroinflammatory cytokines; these effects were attenuated by berberine. We used in vivo infusion of Go6983, a PKC inhibitor to disturb PKC activity in mice brain, and found that the effect of berberine to reverse motor and cognitive deficits was significantly reduced. Moreover, inhibition of PKC also blocked the anti-excitotoxicity effect of berberine, which is induced by glutamate in PC12 cells and BV2 cells, as well as anti-neuroinflammatory effect in LPS-stimulated BV2 cells. Above all, berberine showed neuroprotective effect against QA-induced acute neurotoxicity by activating PKC and its downstream molecules.

Sigma-1 receptor protects against endoplasmic reticulum stress-mediated apoptosis in mice with cerebral ischemia/reperfusion injury.

Reports have showed that Sigma-1 receptor (Sig-1R) activation can protect neurons against cerebral ischemia/reperfusion (I/R) injury in mice and alleviate endoplasmic reticulum (ER) stress in cultured cells, but little known is about the protective role of Sig-1R on ER stress induced by cerebral I/R. The purpose of this study was to determine whether Sig-1R exerts a protective effect against ER stress-mediated apoptosis in cerebral I/R using a 15-min bilateral common carotid artery occlusion (BCCAO) mouse model. At 72 h after reperfusion in BCCAO mice, we found that Sig-1R knockout (Sig-1R KO) significantly increased terminal dUTP nick-end labeling (TUNEL)-positive cells and nuclear structural damage in cortical neurons. Treatment with the Sig-1R agonist PRE084 once daily for three consecutive days reduced the number of TUNEL-positive cells and improved the ultrastructural damage of neurons in the cerebral cortex. These protective effects could be blocked by the Sig-1R antagonist BD1047. Then, we used BCCAO mice at 24 h after reperfusion to detect the expression of ER stress-mediated apoptotic pathway proteins. We found that expression of the pro-apoptotic proteins p-PERK, p-eIF2α, ATF, CHOP, p-IRE, p-JNK, Bim, PUMA, cleaved-caspase-12 and cleaved-caspase-3 was significantly increased and that expression of the anti-apoptotic protein Bcl-2 was significantly decreased in Sig-1R KO-BCCAO mice compared with BCCAO mice. Meanwhile, we found that treatment with PRE084 twice a day decreased pro-apoptotic protein expression and increased anti-apoptotic protein expression. The effects of PRE084 were blocked by the Sig-1R antagonist BD1047. These results suggest that Sig-1R activation inhibits ER stress-mediated apoptosis in BCCAO mice, indicating that Sig-1R may be a therapeutic target for neuroprotection particularly relevant to ER stress-induced apoptosis after cerebral I/R injury.

Tolfenamic Acid Attenuates 3-Nitropropionic Acid-Induced Biochemical Alteration in Mice.

Tolfenamic acid (TA), a nonsteroidal anti-inflammatory drug, shows neuroprotective effects and alleviates cognitive deficits in transgenic mouse models of Alzheimer's disease. However, whether TA can prevent the biochemical alterations induced by intraperitoneal injection of 3-nitropropionic acid (3-NP) in mice is still unknown. In this study, the striatal lesion area was measured by 2,3,5-triphenyltetrazolium chloride staining. Glutamate, SDH and ATP levels were tested using colorimetric assay kits. The neuroinflammatory cytokine levels were tested by ELISA kits. The expression of synaptic proteins and the subtypes of the NMDA receptor were tested by western blotting. TA was orally administered 10 days before 3-NP injection (pretreatment) or on the same day as 3-NP injection (co-treatment). TA pretreatment showed the strongest neuroprotective effects: pretreatment significantly attenuated the 3-NP-induced muscular weakness in the forelimb and alterations in glutamate level, mitochondrial function, and pro-inflammatory cytokine release in the brains of mice. These results suggest that TA has preventive and protective effects on 3-NP-induced neurotoxicity.

Xanthoceraside inhibits pro-inflammatory cytokine expression in Aß25-35/IFN-γ-stimulated microglia through the TLR2 receptor, MyD88, nuclear factor-κB, and mitogen-activated protein kinase signaling pathways.

An accumulating body of evidence suggests that Alzheimer's disease (AD) is associated with microglia-mediated neuroinflammation and pro-inflammatory cytokine expression. Therefore, the suppression of neuroinflammation and pro-inflammatory cytokine might theoretically slow down the progression of AD. Xanthoceraside, a novel triterpenoid saponin extracted from the husks of Xanthoceras sorbifolia Bunge, has potent antiinflammatory and neuroprotective effects. However, the molecular mechanism underlying its anti-inflammatory action remains unclear. In the present study, we attempted to determine the effects of xanthoceraside on the production of pro-inflammatory mediators in amyloid ß25-35 (Aß25-35)/interferon-γ (IFN-γ)-stimulated microglia. Our results indicated that xanthoceraside (0.01 and 0.1 µM) significantly inhibited the release of nitric oxide (NO) and pro-inflammatory cytokines interleukin-1ß and tumor necrosis factor-α in a concentration-dependent manner. Reverse transcriptase-polymerase chain reaction and western blotting analyses showed that xanthoceraside decreased the Aß25-35/IFN-γ-induced production of cyclooxygenase-2 and inducible NO synthase. These effects were accompanied by inhibited activities of nuclear factor-κB and mitogen-activated protein kinase through Toll-like receptor 2 in a myeloid differentiation protein 88-dependent manner. Our results provide support for the therapeutic potential of xanthoceraside in AD.

Protective effect of xanthoceraside against ß-amyloid-induced neurotoxicity in neuroblastoma SH-SY5Y cells.

ß-Amyloid (Aß)-induced neurotoxicity is a major pathological mechanism of Alzheimer's disease (AD). Xanthoceraside, a triterpene extracted from the husk of Xanthoceras sorbifolia Bunge, has been shown to have therapeutic effects on learning and memory impairment induced by Aß intracerebroventricular infusion in mice. In this study, we investigated the effect of xanthoceraside on the neurotoxicity of Aß25-35 in SH-SY5Y cells. Cell viability was measured by MTT (3-(3,4-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide) assay. Cell apoptosis, reactive oxygen species (ROS) generation, and mitochondrion membrane potential (MMP) were measured using Annexin V/propidium iodide, 2,7-dichlorofluorescein diacetate, and rhodamine 123 with flow cytometry, respectively. Intracellular calcium level was determined with Fura-2/AM. Caspase-3 activity in cell lysates was measured using the spectrophotometric method. Results indicated that pretreatment with xanthoceraside (0.01 and 0.1 µM) obviously increased the viability of SH-SY5Y cells injured by Aß25-35 in a dose-dependent manner. Aß25-35-induced early apoptosis, ROS overproduction, MMP dissipation, intracellular calcium overload, and increase in caspase-3 activity were markedly reversed by xanthoceraside. These findings suggested that xanthoceraside might be useful in the prevention and treatment of AD.

The bexarotene derivative OAB-14 ameliorates cognitive decline in APP/PS1 transgenic mice by suppressing microglia-mediated neuroinflammation through the PPAR-γ pathway.

Neuroinflammation is believed to be a critical process involved in the pathophysiology of Alzheimer's disease (AD). In this study, we investigated the pharmacological ability of OAB-14, a small molecule compound derived from bexarotene, to reduce neuroinflammation and improve cognitive decline in an AD mouse model (in vivo) and its ability to regulate signaling pathways implicated in neuroinflammation in vitro. It was found that OAB-14 significantly improved the cognitive function of 11-month-old AD mice (APP/PS1 transgenic mice) in a dose-dependent manner. Simultaneously, OAB-14 dramatically inhibited the activation of microglia in the cerebral cortex and hippocampus of AD mice and dose-dependently downregulated the expression of nuclear factor kappa B (NF-κB) and NOD-like receptor protein 3 (NLRP3) in the cerebral cortex. At the cellular level, OAB-14 reversed the downregulation of M2 phenotypic markers, including mannose receptor C-type 1 (MRC1) and arginase 1 (ARG1), in lipopolysaccharide (LPS)- or amyloid-ß protein oligomer (oAß1-42)-activated BV2 microglial cells and partially restored their ability to clear Aß. However, these effects were suppressed when peroxisome proliferator-activated receptor-γ (PPAR-γ) was specifically inhibited by GW9662, a selective PPAR-γ antagonist. These results suggested that OAB-14 could regulate microglial polarization by regulating PPAR-γ signaling, thereby mitigating neuroinflammation and improving cognitive function in AD mice.

PINK1 regulates mitochondrial fission/fusion and neuroinflammation in ß-amyloid-induced Alzheimer's disease models.

Disrupted mitochondrial fission/fusion balance is consistently involved in neurodegenerative diseases, including Alzheimer's disease. PTEN-induced putative kinase 1 (PINK1), a mitochondrial kinase, has been reported to prevent mitochondrial injury, oxidative stress, apoptosis, and inflammation. However, to the best of our knowledge, the contribution of PINK1 to Aß-induced mitochondrial fission/fusion has not been reported. In the present study, we showed that PINK1 deficiency promoted mitochondrial fission and fusion, aggravated mitochondrial dysfunction, and promoted neuroinflammatory cytokine factor production induced by intracerebroventricular (ICV) injection of Aß25-35 in rats. In vitro experiments have also showed that Aß25-35 caused more severe cell injury in PINK1-knockdown PC12 cells. These cells suffered more extensive death when exposed to proinflammatory cytokines. Lastly, we found that PINK1 overexpression significantly inhibited mitochondrial fusion, improved mitochondrial dysfunction, and reduced neuroinflammatory cytokine production induced by Aß25-35. The current study suggests the involvement of PINK1 in Aß25-35-mediated mitochondrial dynamics and that PINK1 may be a potential target for therapies aimed at enhancing neuroprotection to ameliorate Aß25-35-induced insults.

Sigma-1 receptor activation alleviates blood-brain barrier disruption post cerebral ischemia stroke by stimulating the GDNF-GFRα1-RET pathway.

Blood-brain barrier (BBB) disruption is one of the most important pathological manifestations of ischemic stroke. Reducing BBB collapse is effective in alleviating brain parenchymal injury and cognitive dysfunction. Our previous study reported that Sigma-1 receptor (Sig-1R) activation in cerebral microvascular endothelial cells (CMECs) ameliorated BBB impairment, but the detailed mechanism remains unclear. In this study, we investigated Sig-1R activation as a BBB integrity promoter via many post ischemic stroke pathways. Sig-1R activation in BBB-associated astrocytes can increase glia-derived neurotrophic factor (GDNF) secretion in bilateral common carotid artery occlusion (BCCAO) mice. Upregulated GDNF activates its receptors in CMECs to promote BBB integrity, and activated Sig-1R in CMECs facilitates this process. In vitro experiments have found that Sig-1R activation in CMECs promotes the interaction between the GDNF α1 receptor and transduction rearrangement gene, increasing PI3K-AKT-junction protein signaling pathway expression. Sig-1R activation could be an effective therapeutic method for preventing BBB damage in ischemic stroke and other neurological conditions.

OAB-14 Effectively Ameliorates the Dysfunction of the Endosomal-Autophagic-Lysosomal Pathway in APP/PS1 Transgenic Mice.

In Alzheimer's disease (AD), damaged Aß clearance contributes to elevated levels of Aß that cause a series of cytotoxic cascade reactions. Thus, targeting Aß clearance has now been considered a valid therapeutic approach for AD. Cellular uptake and degradation are important mechanisms for Aß clearance, which are mainly performed by the endosomal-autophagic-lysosomal (EAL) pathway. Our previous study showed that OAB-14, a novel small molecule designed with bexarotene as the lead compound, treatment for 3 months significantly alleviated cognitive disorders and remarkably reduced the deposition of Aß without affecting its production in APP/PS1 transgenic mice. Here, we further revealed that enhancement of the EAL activity is one of the mechanisms that increases Aß clearance after OAB-14 administration for 3 months. OAB-14 facilitates receptor-mediated endocytosis and restores autophagy flux via the AMPK/mTOR pathway. Meanwhile, OAB-14 enhances the lysosomal activity, and reduced Aß accumulation in lysosomes was observed in OAB-14-treated AD mice. These results suggest that OAB-14 may promote Aß clearance in lysosomes by alleviating the EAL dysfunction in AD mice.

Tolfenamic acid inhibits GSK-3ß and PP2A mediated tau hyperphosphorylation in Alzheimer's disease models.

Tolfenamic acid, a nonsteroidal anti-inflammatory drug, alleviated learning and memory deficits and decreased the expression of specificity protein 1 (SP1)-mediated cyclin-dependent kinase-5 (CDK5), a major protein kinase that regulates hyperphosphorylated tau, in Alzheimer's disease (AD) transgenic mice. However, whether tolfenamic acid can regulate the major tau protein kinase, glycogen synthase kinase-3ß (GSK-3ß), or tau protein phosphatase, protein phosphatase 2A (PP2A), further inhibiting hyperphosphorylation of tau, remains unknown. To this end, tolfenamic acid was administered i.p. in a GSK-3ß overactivation postnatal rat model and orally in mice after intracerebroventricular (ICV) injection of okadaic acid (OA) to develop a PP2A inhibition model. We used four behavioural experiments to evaluate memory function in ICV-OA mice. In this study, tolfenamic acid attenuated memory dysfunction. Tolfenamic acid decreased the expression of hyperphosphorylated tau in the brain by inhibiting GSK-3ß activity, decreasing phosphorylated PP2A (Tyr307), and enhancing PP2A activity. Tolfenamic acid also increased wortmannin (WT) and GF-109203X (GFX) induced phosphorylation of GSK-3ß (Ser9) and prevented OA-induced downregulation of PP2A activity in PC12 cells. Altogether, these results show that tolfenamic acid not only decreased SP1/CDK5-mediated tau phosphorylation, but also inhibited GSK-3ß and PP2A-mediated tau hyperphosphorylation in AD models.

WJ-39, an Aldose Reductase Inhibitor, Ameliorates Renal Lesions in Diabetic Nephropathy by Activating Nrf2 Signaling.

Diabetic nephropathy (DN) is a chronic diabetic microvascular complication. Hyperactivity of the polyol pathway is involved in the pathogenesis of DN. Aldose reductase (AR), the rate-limiting enzyme of the polyol pathway, is expected to be an effective target in the treatment of DN. WJ-39 is a novel inhibitor of AR. The present study aimed at exploring the effects of WJ-39 in DN. DN was induced in rats by injecting 30 mg/kg streptozotocin (STZ). After 14 weeks, WJ-39 (10, 20, and 40 mg/kg) was intragastrically administered to the rats for 12 weeks. Treatment with WJ-39 significantly inhibited AR activation and ameliorated renal dysfunction and fibrosis in DN rats. WJ-39 reduced oxidative stress in the kidneys of DN rats by activating the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. WJ-39 suppressed the activation of the nuclear factor-kappa B (NF-κB) pathway and the nucleotide-binding and oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome to reduce the secretion of inflammatory factors. Rat mesangial cells (RMCs) were cultured under hyperglycemic conditions. WJ-39 abrogated the high glucose- (HG-) induced, excessive production of reactive oxygen species (ROS) and inflammatory factors. However, transfection with Nrf2 small interfering RNA abolished the effects of WJ-39. WJ-39 also blocked the transforming growth factor-ß1/Smad pathway to reduce the production of glomerular extracellular matrix proteins, ultimately reducing fibrogenesis in DN. Our results show that WJ-39 ameliorated renal injury in DN rats, and its effects on oxidative stress and inflammation were associated with the activation of Nrf2 signaling. Thus, WJ-39 and its mechanism of amelioration of renal lesions in DN rats by reducing renal inflammation, oxidative stress, and fibrosis injury could be an effective strategy for the treatment of DN.

Interaction between hyperphosphorylated tau and pyroptosis in forskolin and streptozotocin induced AD models.

Amyloid-ß (Aß) activating the pyroptotic cell pathway has been reported to act as a component in the progression of Alzheimer's disease (AD). As another major pathophysiological protein process in AD, the abnormal hyperphosphorylation of tau proteins exerts neurotoxic effects through a variety of mechanisms. However, data describing the relationship between hyperphosphorylated tau proteins and pyroptosis are very scarce. In this study, we used two hyperphosphorylated tau models, intracerebroventricular (ICV) forskolin (FSK, a PKA activator) rat model and ICV-streptozotocin (STZ) rat model; also, FSK and STZ treated PC12 cells as in vitro models to test the relationship between hyperphosphorylated tau proteins and pyroptosis. We found that FSK and STZ significantly increased the hyperphosphorylated tau level, pyroptosis-related protein in PC12 cell and rats' brain, and inhibited the activity of caspase-1 by caspase-1 inhibitor, caspase-1 siRNA, or incubated with Interleukin(IL)-1ß/IL-18 neutralizing antibody could notably alleviate the FSK and STZ induced PC12 cells damage and improve the cognitive disorder in ICV-FSK and ICV-STZ rats. Suppressed the level of hyperphosphorylated tau by LiCl also significantly decreased caspase-1 activity and the content of inflammatory cytokines in FSK or STZ treated PC12 cells. In summary, our results demonstrated that inflammasomes mediated pyroptosis at least one underlying pathogenic mechanism for the neurotoxicity induced by hyperphosphorylated tau in PC12 cells and dementia rats. IL-1ß and IL-18, the downstream of caspase-1, in turn increased hyperphosphorylated tau while spreading neuroinflammation.

Protective effects of xanthoceraside on learning and memory impairment induced by Abeta(25-35) in mice.

This study examined the effects of xanthoceraside (1) on learning and memory impairment induced in mice by intracerebroventricular injection of aggregated peptide beta-amyloid 25-35 (Abeta(25-35)). Learning and memory functions in mice were examined using step-through, Y-maze and water maze tests. Administration of 1 reduced the number of errors and prolonged latency in the step-through test in mice impaired by Abeta(25-35). Likewise, latency to find the terminal platform was decreased and the number of right reflects was increased in the water maze test, and the percentage of alternation behaviors in the Y-maze test was increased. Biochemical studies showed that decreased activities of superoxide dismutase, glutathione peroxidase, and acetylcholinesterase, and increased content of malondialdehyde in mice impaired by Abeta(25-35) were significantly ameliorated by administration of 1. The present results suggest that 1 may provide a potential treatment strategy for Alzheimer's disease.

Prevention of Huntington's Disease-Like Behavioral Deficits in R6/1 Mouse by Tolfenamic Acid Is Associated with Decreases in Mutant Huntingtin and Oxidative Stress.

Tolfenamic acid is a nonsteroidal anti-inflammatory drug with neuroprotective properties, and it alleviates learning and memory deficits in the APP transgenic mouse model of Alzheimer's disease. However, whether tolfenamic acid can prevent motor and memory dysfunction in transgenic animal models of Huntington's disease (HD) remains unclear. To this end, tolfenamic acid was orally administered to transgenic R6/1 mice from 10 to 20 weeks of age, followed by several behavioral tests to evaluate motor and memory function. Tolfenamic acid improved motor coordination in R6/1 mice as tested by rotarod, grip strength, and locomotor behavior tests and attenuated memory dysfunction as analyzed using the novel object recognition test and passive avoidance test. Tolfenamic acid decreased the expression of mutant huntingtin in the striatum of 20-week-old R6/1 mice by inhibiting specificity protein 1 expression and enhancing autophagic function. Furthermore, tolfenamic acid exhibited antioxidant effects in both R6/1 mice and PC12 cell models. Collectively, these results suggest that tolfenamic acid has a good therapeutic effect on R6/1 mice, and may be a potentially useful agent in the treatment of HD.

Xanthoceraside prevented synaptic loss and reversed learning-memory deficits in APP/PS1 transgenic mice.

Xanthoceraside, a novel triterpenoid saponin, has been found to attenuate learning and memory impairments in AD animal models. However, whether xanthoceraside has a positive effect on synaptic morphology remains unclear. Herein, we evaluated the effects of xanthoceraside on learning and memory impairments and the abnormalities of synaptic structure in APP/PS1 transgenic mice. The behavioral experiments demonstrated that xanthoceraside attenuated the imaginal memory and spatial learning impairments, and improved social interaction. Transmission electron microscopy and Golgi staining showed that xanthoceraside ameliorated synapse morphology abnormalities and dendritic spine density deficits, respectively. Western-blot analysis identified that xanthoceraside increased the expression of SYP and PSD95, activated BDNF/TrkB/MAPK/ERK and PI3K/Akt signaling pathways, meanwhile decreased the expression of RhoA, ROCK and Snk, increased the levels of SPAR, and activated the BDNF/TrkB/cofilin signaling pathway. Taken together, our study indicated that xanthoceraside improved cognitive function and protected both synaptic morphology and dendritic spine in APP/PS1 transgenic mice, which might be related in part to its activation in the BDNF/TrkB pathway.

OAB-14, a bexarotene derivative, improves Alzheimer's disease-related pathologies and cognitive impairments by increasing ß-amyloid clearance in APP/PS1 mice.

The pathogenesis of Alzheimer's disease (AD) is complex, though the clinical failures of anti-AD candidates targeting Aß production (such as ß- and γ-secretase inhibitors) make people suspect the Aß hypothesis, in which the neurotoxicity of Aß is undoubtedly involved. According to studies, >95% of AD patients with sporadic AD are primarily associated with abnormal Aß clearance. Therefore, drugs that increase Aß clearance are becoming new prospects for the treatment of AD. Here, the novel small molecule OAB-14, designed using bexarotene as the lead compound, significantly alleviated cognitive impairments in amyloid precursor protein (APP)/presenilin 1 (PS1) transgenic mice after administration for 15 days or 3 months. OAB-14 rapidly cleared 71% of Aß by promoting microglia phagocytosis and increasing IDE and NEP expression. This compound also attenuated the downstream pathological events of Aß accumulation, such as synaptic degeneration, neuronal loss, tau hyperphosphorylation and neuroinflammation in APP/PS1 mice. Moreover, OAB-14 had no significant effect on body weight or liver toxicity after acute and chronic treatment. OAB-14 was well tolerated and its maximum-tolerated dose in mice was >4.0 g/kg. Based on these findings, OAB-14 represents a promising new candidate for AD treatment.

Xanthoceraside modulates NR2B-containing NMDA receptors at synapses and rescues learning-memory deficits in APP/PS1 transgenic mice.

RATIONALE: Alzheimer's disease (AD) is characterized by memory loss and synaptic damage. Previous studies suggested that xanthoceraside decreases glutamate-induced PC12 cell death, ameliorates memory deficits, and increases the number of dendritic spines in AD mice. These results indicated that xanthoceraside might have activities that protect synaptic plasticity. Herein, we detected the effect of xanthoceraside on synaptic function. MATERIALS AND METHODS: Three-month-old APP/PS1 transgenic mice were orally treated with xanthoceraside (0.02, 0.08, or 0.32 mg/kg) once daily for 4 months and then behavioral tests were performed. LTP and Fluo-4/AM were carried out in vivo and in vitro, respectively. CaMKII-GluR1 and NR2B-associated proteins on synapses were measured. RESULTS: Xanthoceraside administration alleviated learning-memory deficits and increased the LTP in APP/PS1 transgenic mice. Meanwhile, xanthoceraside increased the expression of pT286-CaMKII in synaptic and extrasynaptic pools and CaMKII, pS831-GluR1, and GluR1 in synaptic pools. In addition, xanthoceraside increased the total pY1472-NR2B and NR2B expression and increased the levels of pY1472-NR2B in synaptic and extrasynaptic pools and NR2B in synaptic pools. However, NR2B was decreased in extrasynaptic pools, which might be associated with decreased expression of STEP61 and pY531-Fyn. In vitro studies showed that xanthoceraside inhibited intracellular calcium overload and increased the number of and extended the length of dendrites in primary hippocampal neurons compared with the Aß25-35 group. CONCLUSIONS: The mechanism of xanthoceraside on ameliorating learning-memory deficits might be related to decrease intracellular calcium overload, increase CaMKII-GluR1 proteins, and up-regulate trafficking of pY1472-NR2B at synapse, thereby improving LTP in APP/PS1 transgenic mice.

Time-course investigation of blood-brain barrier permeability and tight junction protein changes in a rat model of permanent focal ischemia.

Permanent middle cerebral artery occlusion (pMCAO) is an animal model that is widely used to simulate human ischemic stroke. However, the timing of the changes in the expression of tight junction (TJ) proteins and synaptic proteins associated with pMCAO remain incompletely understood. Therefore, to further explore the characteristics and mechanisms of blood-brain barrier (BBB) damage during cerebral ischemic stroke, we used a pMCAO rat model to define dynamic changes in BBB permeability within 120 h after ischemia in order to examine the expression levels of the TJ proteins claudin-5 and occludin and the synaptic proteins synaptophysin (SYP) and postsynaptic density protein 95 (PSD95). In our study, Evans blue content began to increase at 4 h and was highest at 8 and 120 h after ischemia. TTC staining showed that cerebral infarction was observed at 4 h and that the percentage of infarct volume increased with time after ischemia. The expression levels of claudin-5 and occludin began to decline at 1 h and were lowest at 8 and 120 h after ischemia. The expression levels of SYP and PSD95 decreased from 12 to 120 h after ischemia. GFAP, an astrocyte marker, gradually increased in the cortex penumbra over time post-ischemia. Our study helps clarify the characteristics of pMCAO models and provides evidence supporting the translational potential of animal stroke models.