Association between Y-Maze Acquisition Learning and Major Histocompatibility Complex Class II Polymorphisms in Mice

Evidence of alterations in the learning and memory in offspring of stress-induced male rats

OBJECTIVES

There is extensive data pointing to offspring outcomes related to maternal life incidents, but there is less research concerning the association between paternal life events and progeny brain development and behaviour. As male gametogenesis is a continuous process, the incidences happening in life can modify the epigenetic regulation, altering the offspring's development and behaviour. The present study evaluates the effects of paternal stress during different life periods on their offspring's learning ability, memory, morphological and biochemical changes in the prefrontal cortex and hippocampus in the rat model.

METHODS

Four weeks' old male rats were subjected to five variable stressors at the rate of one per day. Stress received male rats were bred with naive female rats for 1 to 3 nights. The offspring's learning and memory were assessed by the Morris water maze test and automated Y maze. Following behavioural studies, offspring were euthanized to examine global DNA methylation, neurotransmitter levels, namely acetylcholine, glutamate in the hippocampus and frontal cortex.

RESULTS

The offspring of stress-induced animals exhibited a delay in acquiring learning and defect in memory and altered global DNA methylation in the hippocampus (p=0.000124). There was significant reduction of acetylcholine and glutamate levels in hippocampus (p=0.000018, p=0.00001, respectively) and in prefrontal cortex (p=0.00001, p=0.00001, respectively). HPA axis of offspring was altered considerably (p=0.00001). The histomorphometry of the prefrontal cortex and different hippocampal regions revealed a statistically significant (p<0.05) reduction in neuronal numbers in the offspring of stressed animals compared to that of control. These impacts were markedly high in the offspring of fathers who received stress during both pubertal and adult periods.

CONCLUSIONS

The findings of this study demonstrate that paternal stress can impact offspring learning and memory.

Synthetic Mono-Carbonyl Curcumin Analogues Attenuate Oxidative Stress in Mouse Models

Alzheimer’s disease is the commonest form of dementia associated with short-term memory loss and impaired cognition and, worldwide, it is a growing health issue. A number of therapeutic strategies have been studied to design and develop an effective anti-Alzheimer drug. Curcumin has a wide spectrum of biological properties. In this regard, the antioxidant potentials of mono-carbonyl curcumin analogues (h1−h5) were investigated using in vitro antioxidant assays and hippocampal-based in vivo mouse models such as light−dark box, hole board, and Y-maze tests. In the in vitro assay, mono-carbonyl curcumin analogues h2 and h3 with methoxy and chloro-substituents, respectively, showed promising 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2, 2′-azinobis-3-ethylbenzothiazo-line-6-sulfonate (ABTS) free radical scavenging activities. In the in vivo studies, scopolamine administration significantly (p < 0.001) induced oxidative stress and memory impairment in mice, in comparison to the normal control group. The pretreatment with mono-carbonyl curcumin analogues, specifically h2 and h3, significantly decreased (123.71 ± 15.23 s (p < 0.001), n = 8; 156.53 ± 14.13 s (p < 0.001), n = 8) the duration of time spent in the light chamber and significantly enhanced (253.95 ± 19.05 s (p < 0.001), n = 8, and 239.57 ± 9.98 s (p < 0.001), n = 8) the time spent in the dark compartment in the light−dark box arena. The numbers of hole pokings were significantly (p < 0.001, n = 8) enhanced in the hole board test and substantially increased the percent spontaneous alternation performance (SAP %) in the Y-maze mouse models in comparison to the stress control group. In the biomarker analysis, the significant reduction in the lipid peroxidation (MDA) level and enhanced catalase (CAT), superoxide dismutase (SOD), and glutathione (GSH) activities in the brain hippocampus reveal their antioxidant and memory enhancing potentials. However, further research is needed to find out the appropriate mechanism of reducing oxidative stress in pathological models.

Attenuation of Scopolamine-Induced Amnesia via Cholinergic Modulation in Mice by Synthetic Curcumin Analogs

Alzheimer’s disease is an emerging health disorder associated with cognitive decline and memory loss. In this study, six curcumin analogs (1a−1f) were synthesized and screened for in vitro cholinesterase inhibitory potential. On the basis of promising results, they were further investigated for in vivo analysis using elevated plus maze (EPM), Y-maze, and novel object recognition (NOR) behavioral models. The binding mode of the synthesized compounds with the active sites of cholinesterases, and the involvement of the cholinergic system in brain hippocampus was determined. The synthesized curcumin analog 1d (p < 0.001, n = 6), and 1c (p < 0.01, n = 6) showed promising results by decreasing retention time in EPM, significantly increasing % SAP in Y-maze, while significantly (p < 0.001) enhancing the % discrimination index (DI) and the time exploring the novel objects in NORT mice behavioral models. A molecular docking study using MOE software was used for validation of the inhibition of cholinesterase(s). It has been indicated from the current research work that the synthesized curcumin analogs enhanced memory functions in mice models and could be used as valuable therapeutic molecules against neurodegenerative disorders. To determine their exact mechanism of action, further studies are suggested.

Protective Effects of Dapsone on Scopolamine-Induced Memory Impairment in Mice: Involvement of Nitric Oxide Pathway

Introduction

The leading cause of memory impairment is dementia-related disorders. Since current treatments for memory impairment target the neuroinflammatory pathways, we selected dapsone, an anti-inflammatory agent, to evaluate its effects on scopolamine-induced memory impairment in mice and the underlying role of nitric oxide (NO).

Methods

Scopolamine (1 mg/kg, intraperitoneal [i.p.]) was used for induction of memory impairment. The animals received various doses of dapsone (0.1, 0.3, 1, 5, and 10 mg/kg, i.p.). Duration and number of arms visits in the Y-maze and step-through latency in the passive-avoidance were documented. To evaluate the underlying signaling pathway, N(ω)-nitro-L-arginine methyl ester (a nonspecific NO synthase [NOS] inhibitor), aminoguanidine (a specific inducible NOS inhibitor), and 7-nitroindazole (a specific neuronal NOS inhibitor) were administered 30 min after dapsone administration.

Results

Dapsone (5 mg/kg) substantially improved memory acquisition in scopolamine-induced memory impairment. Additionally, NOS inhibitors considerably reversed the observed neuroprotective effects of dapsone, accompanied by the elevation of NO levels.

Conclusion

Dapsone revealed a neuroprotective effect against scopolamine-induced memory impairment in mice, possibly through the nitrergic pathway.

3-O-Acetyl-11-keto-β-boswellic acid ameliorates acquired, consolidated and recognitive memory deficits through the regulation of hippocampal PPAR γ, MMP9 and MMP2 genes in dementia model

Pentacyclic Phytomolecule 3-O-Acetyl-11-keto-β-boswellic acid (AKBA) from Frankincense family has proven for the neuroprotection and recognized as an orphan drug for the treatment of cerebral edema. Nonetheless, AKBA have promising indications with Peroxisome proliferator activated receptor gamma (PPARγ) associated to cognitive function not deliberated so far. In order to substantiate the potential role of AKBA on memory function, we examine the contribution of PPARγ activation and its downstream process. Modified method of scopolamine induced dementia rats were treated with AKBA (5, 10&15 mg/kg,i.p) and Donepezil (2.5 mg/kg,i.p). Scopolamine induced short term spatial, working memory and recognition memory impairment was reversed significantly after AKBA treatment. AKBA administration diminished the Acetylcholine esterase (AchE) activity and preserved brain GABA and glutamate mediated neuronal excitability. Further, gene expression study reveals AKBA ameliorates the memory impairment via activating PPARγ and its downstream regulators, matrix metalloproteinase 2 (MMP2) and matrix metalloproteinase 9 (MMP9) genes in hippocampus. This study concludes that the treatment with AKBA can be a novel Phyto-molecule of interest for treating dementia via up-regulating hippocampus genes mediated cholinergic activation.

Pig Skin Gelatin Hydrolysates Attenuate Acetylcholine Esterase Activity and Scopolamine-induced Impairment of Memory and Learning Ability of Mice

The protective effect of pig skin gelatin water extracts (PSW) and the low molecular weight hydrolysates of PSW generated via enzymatic hydrolysis with Flavourzyme® 1000L (LPSW) against scopolamine-induced impairment of cognitive function in mice was determined. Seventy male ICR mice weighing 20–25 g were randomly assigned to seven groups: Control (CON); scopolamine (SCO, 1 mg/kg B.W., intraperitoneally (i.p.); tetrahydroaminoacridine 10 [THA 10, tacrine; 10 mg/kg B.W. per oral (p.o.) with SCO (i.p.)]; PSW 10 (10 mg/kg B.W. (p.o.) with SCO (i.p.); PSW 40 (40 mg/kg B.W. (p.o.) with SCO (i.p.); LPSW 100 (100 mg/kg B.W. (p.o.) with SCO (i.p.); LPSW 400 (400 mg/kg B.W. (p.o.) with SCO (i.p.). All treatment groups, except CON, received scopolamine on the day of the experiment. The oxygen radical absorbance capacity of LPSW 400 at 1 mg/mL was 154.14 μM Trolox equivalent. Administration of PSW and LPSW for 15 weeks did not significantly affect on physical performance of mice. LPSW 400 significantly increased spontaneous alternation, reaching the level observed for THA and CON. The latency time of animals receiving LPSW 400 was higher than that of mice treated with SCO alone in the passive avoidance test, whereas it was shorter in the water maze test. LPSW 400 increased acetylcholine (ACh) content and decreased ACh esterase activity (p<0.05). LPSW 100 and LPSW 400 reduced monoamine oxidase-B activity. These results indicated that LPSW at 400 mg/kg B.W. is a potentially strong antioxidant and contains novel components for the functional food industry.

An Antisense Oligonucleotide Leads to Suppressed Transcription of Hdac2 and Long-Term Memory Enhancement

Knockout of the memory suppressor gene histone deacetylase 2 (Hdac2) in mice elicits cognitive enhancement, and drugs that block HDAC2 have potential as therapeutics for disorders affecting memory. Currently available HDAC2 catalytic activity inhibitors are not fully isoform specific and have short half-lives. Antisense oligonucleotides (ASOs) are drugs that elicit extremely long-lasting, specific inhibition through base pairing with RNA targets. We utilized an ASO to reduce Hdac2 messenger RNA (mRNA) in mice and determined its longevity, specificity, and mechanism of repression. A single injection of the Hdac2-targeted ASO in the central nervous system produced persistent reduction in HDAC2 protein and Hdac2 mRNA levels for 16 weeks. It enhanced object location memory for 8 weeks. RNA sequencing (RNA-seq) analysis of brain tissues revealed that the repression was specific to Hdac2 relative to related Hdac isoforms, and Hdac2 reduction caused alterations in the expression of genes involved in extracellular signal-regulated kinase (ERK) and memory-associated immune signaling pathways. Hdac2-targeted ASOs also suppress a nonpolyadenylated Hdac2 regulatory RNA and elicit direct transcriptional suppression of the Hdac2 gene through stalling RNA polymerase II. These findings identify transcriptional suppression of the target gene as a novel mechanism of action of ASOs.

Brain Amide Proton Transfer Imaging of Rat With Alzheimer's Disease Using Saturation With Frequency Alternating RF Irradiation Method

Amyloid-β (Aβ) deposits and some proteins play essential roles in the pathogenesis of Alzheimer's disease (AD). Amide proton transfer (APT) imaging, as an imaging modality to detect tissue protein, has shown promising features for the diagnosis of AD disease. In this study, we chose 10 AD model rats as the experimental group and 10 sham-operated rats as the control group. All the rats underwent a Y-maze test before APT image acquisition, using saturation with frequency alternating RF irradiation (APT_SAFARI) method on a 7.0 T animal MRI scanner. Compared with the control group, APT (3.5 ppm) values of brain were significantly reduced in AD models (p < 0.002). The APT_SAFARI imaging is more significant than APT imaging (p < 0.0001). AD model mice showed spatial learning and memory loss in the Y-maze experiment. In addition, there was significant neuronal loss in the hippocampal CA1 region and cortex compared with sham-operated rats. In conclusion, we demonstrated that APT imaging could potentially provide molecular biomarkers for the non-invasive diagnosis of AD. APT_SAFARI MRI could be used as an effective tool to improve the accuracy of diagnosis of AD compared with conventional APT imaging.