T3D-959: A Multi-Faceted Disease Remedial Drug Candidate for the Treatment of Alzheimer's Disease

BACKGROUND

T3D-959, a dual PPAR-δ/PPAR γ nuclear receptor agonist and former diabetes drug candidate, has been repositioned as an Alzheimer's disease (AD)-modifying therapy.

OBJECTIVE

This study examines the effectiveness and mechanisms of T3D-959's therapeutic effects using in vivo and ex vivo rat models of sporadic AD.

METHODS

A sporadic AD model was generated by intracerebral (i.c.) administration of streptozotocin (STZ). Control and i.c. STZ treated rats were gavaged with saline or T3D-959 (0.3 to 3.0 mg/kg/day) for 28 days. Spatial learning and memory were evaluated using the Morris water maze test. Frontal lobe slice cultures generated 24 hours after i.c. STZ or vehicle were used to study early effects of T3D-959 (0.5-1.0 μM) on viability and molecular markers of AD.

RESULTS

T3D-959 significantly improved spatial learning and memory in i.c STZ-treated rats. Mechanistically, T3D-959 significantly improved culture viability and brain morphology, reduced levels of oxidative stress and Aβ, and normalized expression of phospho-tau, choline acetyltransferase, and myelin-associated glycoprotein. Protective effects occurred even at the lowest tested dose of T3D-959.

CONCLUSIONS

Pre-clinical proof of concept has been demonstrated that T3D-959 can improve multiple pathologies of AD resulting in significant improvements in cognitive function and molecular and biochemical indices of neurodegeneration. These results support the theses that (1) effective disease modification in AD can be achieved by targeting relevant nuclear receptors, and (2) treating AD as a metabolic disease has the potential to be disease remedial. A Phase 2a trial of T3D-959 in mild-to-moderate AD patients has been initiated (ClinicalTrials.gov identifier NCT02560753).

A novel antibody targeting sequence 31-35 in amyloid β protein attenuates Alzheimer's disease-related neuronal damage

Amyloid β protein (Aβ) plays a critical role in pathogenesis of Alzheimer's disease (AD). Our previous studies indicated that the sequence 31-35 in Aβ molecule is an effective active center responsible for Aβ neurotoxicity in vivo and in vitro. In the present study, we prepared a novel antibody specifically targeting the sequence 31-35 of amyloid β protein, and investigated the neuroprotection of the anti-Aβ_31-35 antibody against Aβ_1-42 -induced impairments in neuronal viability, spatial memory, and hippocampal synaptic plasticity in rats. The results showed that the anti-Aβ_31-35 antibody almost equally bound to both Aβ_31-35 and Aβ_1-42 , and pretreatment with the antibody dose-dependently prevented Aβ_1-42 -induced cytotoxicity on cultured primary cortical neurons. In behavioral study, intracerebroventricular (i.c.v.) injection of anti-Aβ_31-35 antibody efficiently attenuated Aβ_1-42 -induced impairments in spatial learning and memory of rats. In vivo electrophysiological experiments further indicated that Aβ_1-42 -induced suppression of hippocampal synaptic plasticity was effectively reversed by the antibody. These results demonstrated that the sequence 31-35 of Aβ may be a new therapeutic target, and the anti-Aβ_31-35 antibody could be a novel immunotheraputic approach for the treatment of AD. © 2016 Wiley Periodicals, Inc.

[Dual co-agonist CI-1206 antagonizes Aβ1-42-induced impairments in spatial learning and memory in mice]

OBJECTIVE

To study the neuroprotective effects of a novel GIP/GLP-1 receptor dual agonist CI-1206 against Aβ1-42-induced impairments in spatial working memory and long term memory in mice.

METHODS

C57 mice, after receiving intracerebralventricular (i.c.v.) injection of Aβ1-42 and intraperitoneal injection of CI-1206, were divided into the following groups:saline+D-PBS, Aβ1-42+saline, CI-1206+D-PBS and Aβ1-42+CI-1206 group (n=12). Y maze spontaneous alternation of mice was tested to assess short term working memory, and Morris water maze task was used to assess long term reference memory.

RESULTS

①The percentage of right alternation of mice in Aβ1-42+saline group was significantly decreased, while the percentage in Aβ1-42+CI-1206 group was significantly larger than that in Aβ1-42 alone group (P<0.05). ②In Morris water maze test, the escape latency of mice in Aβ1-42+saline group showed a significant increase, with a significant decline in swimming time in target quadrant. Treatment with CI-1206 significantly antagonized these detrimental effects induced by Aβ1-42. ③Aβ1-42 and CI-1206 did not affect the motor ability and vision of mice.

CONCLUSIONS

I.C.V. administration of Aβ1-42 impaired the short term and long term spatial memory of mice, while CI-1206 could effectively antagonize the detrimental effects.

Effects of melatonin on cognitive impairment and hippocampal neuronal damage in a rat model of chronic cerebral hypoperfusion

Chronic cerebral hypoperfusion (CCH), which induces oxidative stress and inflammation in the brain, has previously been associated with cognitive impairment and neuronal cell damage. Melatonin is a well-known free radical scavenger and antioxidant; therefore, the present study investigated the protective effects of melatonin against CCH-induced cognitive impairment and neuronal cell death in a CCH rat model, which was generated via permanent bilateral common carotid artery occlusion (2VO). The rats in the 2VO group exhibited markedly increased escape latencies in a Morris water maze test, as compared with the rats in the sham group. In addition, increased neuronal cell damage was detected in the hippocampal CA1 region of the 2VO rats, as compared with the rats in the sham group. Treatment of the 2VO rats with melatonin significantly reduced the escape latency and neuronal cell damage, and was associated with reduced levels of malondialdehyde, microglial activation, and tumor necrosis factor-α and interleukin-1β in the ischemic hippocampus. The results of the present study suggest that melatonin may attenuate CCH-induced cognitive impairment and hippocampal neuronal cell damage by decreasing oxidative stress, microglial activation and the production of pro-inflammatory cytokines in the ischemic hippocampus.

Bangle (Zingiber purpureum) Improves Spatial Learning, Reduces Deficits in Memory, and Promotes Neurogenesis in the Dentate Gyrus of Senescence-Accelerated Mouse P8

Bangle (Zingiber purpureum) is a tropical ginger that is used as a spice in Southeast Asia. Phenylbutenoid dimers isolated from Bangle have exhibited neurotrophic effects in primary cultured rat cortical neurons and PC12 cells. Furthermore, chronic treatment with phenylbutenoid dimers enhances hippocampal neurogenesis in olfactory bulbectomized mice. In this study, we investigated the effects of Bangle extract on behavior and hippocampal neurogenesis in vivo. SAMP8 mice, which are an established model for accelerated aging, with age-related learning and memory impairments, were given a Bangle-containing diet for 1 month, and subsequent behavioral tests and immunohistochemistry for Ki67, a proliferating cell marker, were performed. We found that the Bangle-containing diet improved spatial learning and memory deficits in the Morris water maze and significantly increased the numbers of Ki67-positive cells in the dentate gyrus of the SAMP8 mice. In addition, the Bangle extract exhibited a neurotrophin-like activity as indicated by the induction of neurite sprouting in PC12 cells. Our results suggest that Bangle is beneficial for the prevention of age-related progression of cognitive impairment.

Nxf7 deficiency impairs social exploration and spatio-cognitive abilities as well as hippocampal synaptic plasticity in mice

Nuclear RNA export factors (NXF) are conserved in all metazoans and are deemed essential for shuttling RNA across the nuclear envelope and other post-transcriptional processes (such as mRNA metabolism, storage and stability). Disruption of human NXF5 has been implicated in intellectual and psychosocial disabilities. In the present report, we use recently described Nxf7 knockout (KO) mice as an experimental model to analyze in detail the behavioral consequences of clinical NXF5 deficiency. We examined male Nxf7 KO mice using an extended cognitive and behavioral test battery, and recorded extracellular field potentials in the hippocampal CA1 region. We observed various cognitive and behavioral changes including alterations in social exploration, impaired spatial learning and spatio-cognitive abilities. We also defined a new experimental paradigm to discriminate search strategies in Morris water maze and showed significant differences between Nxf7 KO and control animals. Furthermore, while we observed no difference in a nose poke suppression in an conditioned emotional response (CER) protocol, Nxf7 KO mice were impaired in discriminating between differentially reinforced cues in an auditory fear conditioning protocol. This distinct neurocognitive phenotype was accompanied by impaired hippocampal Long-term potentiation (LTP), while long-term depression (LTD) was not affected by Nxf7 deficiency. Our data demonstrate that disruption of murine Nxf7 leads to behavioral phenotypes that may relate to the intellectual and social deficits in patients with NXF5 deficiency.

The effects of chronic restraint on the morphology of ventral CA1 neurons in female Long Evans rats

Women are more likely than men to develop psychopathology as a result of stress, but there is little research regarding the effects of a stressful condition and its treatment in female non-human animals, perhaps because of inherent hormonal activity. Recent studies have demonstrated that there are structural and functional differences between the dorsal and ventral hippocampus, but the effects of stress on the morphology of CA1 and CA3 neurons have been studied primarily in the dorsal hippocampus. This study assessed the effects of stress induced by restricted movement on the morphology of ventral hippocampal CA1 neurons in male and female rats. Male and female Long Evans (LE) rats were subjected to restraint stress for 6 h every day for 25 days. One group of rats was used to study the dendritic morphology of CA1 ventral hippocampal neurons using the Golgi-Cox stain. A second group of rats was used to analyze learning and memory using the Morris water maze. Stressed female rats exhibited a decrease in the density of basilar dendritic spines, an increase in the number of apical dendritic intersections and deficits in spatial memory. There were no apparent effects of stress on male rats. Our data support previous findings of a dimorphic response to chronic stress and indicate that the ventral hippocampus is not particularly susceptible to the effects of stress.

CREB SUMOylation by the E3 ligase PIAS1 enhances spatial memory

cAMP-responsive element binding protein (CREB) phosphorylation and signaling plays an important role in long-term memory formation, but other posttranslational modifications of CREB are less known. Here, we found that CREB1Δ, the short isoform of CREB, could be sumoylated by the small ubiquitin-like modifier (SUMO) E3 ligase protein inhibitor of activated STAT1 (PIAS1) at Lys271 and Lys290 and PIAS1 SUMOylation of CREB1Δ increased the expression level of CREB1Δ. CREB1Δ could also be sumoylated by other PIAS family proteins, but not by the E3 ligases RanBP2 and Pc2 or by the E2 ligase Ubc9. Furthermore, water maze training increased the level of endogenous CREB SUMOylation in rat CA1 neurons determined by in vitro SUMOylation assay, but this effect was not observed in other brain areas. Moreover, transduction of Lenti-CREBWT to rat CA1 area facilitated, whereas transduction of Lenti-CREB double sumo-mutant (CREBK271RK290R) impaired, spatial learning and memory performance. Transduction of Lenti-CREBWT-SUMO1 fusion vector to rat CA1 area showed a more significant effect in enhancing spatial learning and memory and CREB SUMOylation. Lenti-CREBWT transduction increased, whereas Lenti-CREBK271RK290R transduction decreased, CREB DNA binding to the brain-derived neurotrophic factor (bdnf) promoter and decreased bdnf mRNA expression. Knock-down of PIAS1 expression in CA1 area by PIAS1 siRNA transfection impaired spatial learning and memory and decreased endogenous CREB SUMOylation. In addition, CREB SUMOylation was CREB phosphorylation dependent and lasted longer. Therefore, CREB phosphorylation may be responsible for signal transduction during the early phase of long-term memory formation, whereas CREB SUMOylation sustains long-term memory.

STAT1 negatively regulates spatial memory formation and mediates the memory-impairing effect of Aβ

Signal transducer and activator of transcription-1 (STAT1) has an important role in inflammation and the innate immune response, but its role in the central nervous system is less well understood. Here, we examined the role of STAT1 in spatial learning and memory, and assessed the involvement of STAT1 in mediating the memory-impairing effect of amyloid-beta (Aβ). We found that water maze training downregulated STAT1 expression in the rat hippocampal CA1 area, and spatial learning and memory function was enhanced in Stat1-knockout mice. Conversely, overexpression of STAT1 impaired water maze performance. STAT1 strongly upregulated the expression of the extracellular matrix protein laminin β1 (LB1), which also impaired water maze performance in rats. Furthermore, Aβ impaired spatial learning and memory in association with a dose-dependent increase in STAT1 and LB1 expression, but knockdown of STAT1 and LB1 both reversed this effect of Aβ. This Aβ-induced increase in STAT1 and LB1 expression was also associated with a decrease in the expression of the N-methyl-D-aspartate receptor (NMDAR) subunits, NR1, and NR2B. Overexpression of NR1 or NR2B or exogenous application of NMDA reversed Aβ-induced learning and memory deficits as well as Aβ-induced STAT1 and LB1 expression. Our results demonstrate that STAT1 negatively regulates spatial learning and memory through transcriptional regulation of LB1 expression. We also identified a novel mechanism for Aβ pathogenesis through STAT1 induction. Notably, impairment of spatial learning and memory by this STAT1-mediated mechanism is independent of cAMP responsive element-binding protein signaling.

Coffee, but not caffeine, has positive effects on cognition and psychomotor behavior in aging

The complex mixture of phytochemicals in fruits and vegetables provides protective health benefits, mainly through additive and/or synergistic effects. The presence of several bioactive compounds, such as polyphenols and caffeine, implicates coffee as a potential nutritional therapeutic in aging. Moderate (three to five cups a day) coffee consumption in humans is associated with a significant decrease in the risk of developing certain chronic diseases. However, the ability of coffee supplementation to improve cognitive function in aged individuals and the effect of the individual components in coffee, such as caffeine, have not been fully evaluated. We fed aged rats (19 months) one of five coffee-supplemented diets (0, 0.165, 0.275, 0.55, and 0.825% of the diet) for 8 weeks prior to motor and cognitive behavior assessment. Aged rats supplemented with a 0.55% coffee diet, equivalent to ten cups of coffee, performed better in psychomotor testing (rotarod) and in a working memory task (Morris water maze) compared to aged rats fed a control diet. A diet with 0.55% coffee appeared to be optimal. The 0.165% coffee-supplemented group (three cups) showed some improvement in reference memory performance in the Morris water maze. In a subsequent study, the effects of caffeine alone did not account for the performance improvements, showing that the neuroprotective benefits of coffee are not due to caffeine alone, but rather to other bioactive compounds in coffee. Therefore, coffee, in achievable amounts, may reduce both motor and cognitive deficits in aging.

Effect of repeated morphine withdrawal on spatial learning, memory and serum cortisol level in mice

BACKGROUND

One of the serious problems that opioid addicted people are facing is repeated withdrawal syndrome that is accompanying with a significant stress load for addicts. Therefore, the aim of this study was to evaluate the effects of repeated withdrawal on spatial learning, memory and serum cortisol levels in morphine-dependent mice.

MATERIALS AND METHODS

Male NMRI mice received morphine as daily increasing doses for 3 days. After that, the mice underwent one time or repeated spontaneous or pharmacologic (naloxone-precipitated) withdrawal. Then spatial learning and memory were investigated by morris water maze test, and at the end trunk blood samples were collected for measurement of serum cortisol levels.

RESULTS

The results showed that only repeated spontaneous withdrawal significantly increases escape latency (P < 0.05), and in other models of withdrawal, spatial learning and memory were intact. The results of probe trial were intact in all groups. Radioimmunoassay showed that serum cortisol levels were increased significantly in all models of withdrawal (P < 0.05 and P < 0.01) except the repeated spontaneous withdrawal.

CONCLUSION

The results showed that short periods of withdrawal syndrome can increase serum cortisol levels; however they do not affect spatial learning and memory. Nevertheless, repeated spontaneous withdrawal can make learning slow.

Effect of Royal Jelly on spatial learning and memory in rat model of streptozotocin-induced sporadic Alzheimer's disease

Background:

It has been recently demonstrated that Royal jelly (RJ) has a beneficial role on neural functions. Alzheimer's disease (AD) is associated with impairments of learning and memory. Therefore, the present study was designed to examine the effect of RJ on spatial learning and memory in rats after intracerebroventricular injection of streptozotocin (icv-STZ).

Materials and Methods:

Rats were infused bilaterally with an icv injection of STZ, while sham rats received vehicle only. The rats were feed with RJ-contained food (3% w/w) (lyophilized RJ mixed with powdered regular food) or regular food for 10 days. Then spatial learning and memory was tested in the rats by Morris water maze test.

Results:

Results showed that in icv-STZ group latency and path length were increased as compared to sham group, also icv-STZ rats less remembered the target quadrant that previously the platform was located; however, these were protected significantly in STZ group that received RJ-containing food.

Conclusions:

Our findings support the potential neuroprotective role of RJ and its helpful effects in AD.

NF-kappaB activity affects learning in aversive tasks: possible actions via modulation of the stress axis

The role of altered activity of nuclear factor kappaB (NF-kappaB) in specific aspects of motivated behavior and learning and memory was examined in mice lacking the p50 subunit of the NF-kappaB/rel transcription factor family. Nfkb1-deficient mice are unable to produce p50 and show specific susceptibilities to infections and inflammatory challenges, but the behavioral phenotype of such mice has been largely unexamined, owing in large part to the lack of understanding of the role of NF-kappaB in nervous system function. Here we show that Nfkb1 (p50) knockout mice more rapidly learned to find the hidden platform in the Morris water maze than did wildtype mice. The rise in plasma corticosterone levels after the maze test was greater in p50 knockout than in wildtype mice. In the less stressful Barnes maze, which tests similar kinds of spatial learning, the p50 knockout mice performed similarly to control mice. Adrenalectomy with corticosterone replacement eliminated the differences between p50 knockout and wildtype mice in the water maze. Knockout mice showed increased levels of basal anxiety in the open-field and light/dark box tests, suggesting that their enhanced escape latency in the water maze was due to activation of the stress (hypothalamic-pituitary-adrenal) axis leading to elevated corticosterone production by strongly but not mildly anxiogenic stimuli. The results suggest that, as in the immune system, p50 in the nervous system normally serves to dampen NF-kappaB-mediated intracellular activities, which are manifested physiologically through elevated stress responses to aversive stimuli and behaviorally in the facilitated escape performance in learning tasks.

Mitochondrial dihydrolipoyl succinyltransferase deficiency accelerates amyloid pathology and memory deficit in a transgenic mouse model of amyloid deposition

Mitochondrial dysfunction and oxidative stress are involved in Alzheimer disease (AD) pathogenesis. In human AD brains, the activity of the alpha-ketoglutarate dehydrogenase enzyme complex (alpha-KGDHC) is reduced. KGDHC is mostly involved in NADH production. It can also participate in oxidative stress and reactive oxygen species (ROS) production. The mitochondrial dihydrolipoyl succinyltransferase enzyme (DLST) is a key subunit specific to the alpha-KGDHC. In cultured cells, reduction of DLST increased H(2)O(2)-induced ROS generation and cell death. Thus, we asked whether partial genetic deletion of DLST could accelerate the onset of AD pathogenesis, using a transgenic mouse model of amyloid deposition crossed with DLST(+/-) mice. Tg19959 mice, which carry the human amyloid precursor protein with two mutations, develop amyloid deposits and progressive behavioral abnormalities. We compared Tg19959 mice to Tg19959-DLST(+/-) littermates at 2-3 months of age and studied the effects of DLST deficiency on amyloid deposition, spatial learning and memory, and oxidative stress. We found that alpha-KGDHC activity was reduced in DLST(+/-) mice. We also found that DLST deficiency increased amyloid plaque burden, Abeta oligomers, and nitrotyrosine levels and accelerated the occurrence of spatial learning and memory deficits in female Tg19959 mice. Our data suggest that alpha-KGDHC may be involved in AD pathogenesis through increased mitochondrial oxidative stress.

Circadian activity associated with spatial learning and memory in aging rhesus monkeys

In rodents, spatial learning and memory tests require navigation, whereas in nonhuman primates these tests generally do not involve a navigational component, thus assessing nonhomologous neural systems. To allow closer parallels between rodent and primate studies, we developed a navigational spatial learning and memory task for nonhuman primates and assessed the performance of elderly (19-25 years) female rhesus monkeys (Macaca mulatta). The animals were allowed to navigate in a room containing a series of food ports. After they learned to retrieve food from the ports, a single port was repeatedly baited and the animals were tested until they learned the correct location. The location of the baited port was then changed (shift position). We also determined whether test performance was associated with circadian activity measured with accelerometers. Performance measures included trials to criterion, search strategies, and several indices of circadian activity. Animals learned the task as reflected in their search strategies. Correlations were found between the number of initial or shift trials and circadian activity parameters including day activity, dark:light activity ratio, sleep latency, and wake bouts. Thus, disruptions in circadian rhythms in nonhuman primates are associated with poorer performance on this novel test. These data support the usefulness of this spatial navigational test to assess spatial learning and memory in rhesus monkeys and the importance of circadian activity in performance.

Androgens protect against apolipoprotein E4-induced cognitive deficits

Compared with apolipoprotein (apo) E2 and E3, apoE4 increases the risk of Alzheimer's disease (AD), but it remains unknown how apoE4 affects neuronal function. ApoE4 interacts with female gender, further increasing the risk of AD and decreasing treatment response. Female mice are also more susceptible to apoE4-induced impairments of spatial learning and memory than male mice. To assess the role of sex steroids in this process, we studied mice deficient in mouse apoE (Apoe(-/-)) and expressing human apoE4 or apoE3 in the brain at comparable levels. Even brief periods of androgen treatment improved the memory deficits of female apoE4 mice. Female apoE3 mice had no memory deficits and did not benefit from the treatment. ApoE4 male mice, which performed normally in a water-maze test at baseline, developed prominent deficits in spatial learning and memory after blockade of androgen receptors (ARs), whereas apoE3 male mice did not. Untreated apoE4 mice had significantly lower cytosolic AR levels in the neocortex than wild-type, Apoe(-/-), and apoE3 mice. Improved memory in androgen-treated female apoE4 mice was associated with increased cytosolic AR levels. Our findings suggest that apoE4 contributes to cognitive decline by reducing AR levels in the brain, and that stimulating AR-dependent pathways can reverse apoE4-induced cognitive deficits.

Phosphodiesterase 1B knock-out mice exhibit exaggerated locomotor hyperactivity and DARPP-32 phosphorylation in response to dopamine agonists and display impaired spatial learning

Using homologous recombination, we generated mice lacking phosphodiesterase-mediated (PDE1B) cyclic nucleotide-hydrolyzing activity. PDE1B(-/-) mice showed exaggerated hyperactivity after acute D-methamphetamine administration. Striatal slices from PDE1B(-/-) mice exhibited increased levels of phospho-Thr34 DARPP-32 and phospho-Ser845 GluR1 after dopamine D1 receptor agonist or forskolin stimulation. PDE1B(-/-) and PDE1B(+/-) mice demonstrated Morris maze spatial-learning deficits. These results indicate that enhancement of cyclic nucleotide signaling by inactivation of PDE1B-mediated cyclic nucleotide hydrolysis plays a significant role in dopaminergic function through the DARPP-32 and related transduction pathways.