Transcriptome analysis identifies the role of Class I histone deacetylase in Alzheimer's disease

Epigenetics modification is a process that does not change the sequence of deoxyribonucleic acid (DNA) in disease progression but can alter the genetic expression of the brain in Alzheimer's disease (AD). In this study, we deployed the weighted gene co-expression network analysis (WGCNA) to explore the role of Class I histone deacetylases (HDACs) in AD, which included HDAC1, HDAC2, HDAC3, and HDAC8. The aim of the study was to find how Class I HDACs affected AD pathology by analyzing the Gene Expression Omnibus (GEO) microarray datasets GSE33000. We found that HDAC1 and HDAC8 were more highly expressed in the cortex of AD patients than in Controls, while HDAC2 and HDAC3 were lower expressed. By WGCNA analysis, we found the blue module was associated with HDAC1 and HDAC8, and the turquoise module was related to HDAC2 and HDAC3. Functional enrichment analysis revealed that the Wnt signaling pathway and synaptic plasticity played an important role in the modification of HDAC1 and HDAC8 while gap junction and cell-cell junction were involved in the regulation of HDAC2 and HDAC3 in the disease progression of AD. By Receiver Operating Characteristics (ROC) analysis, we concluded that HDAC1 might be the most probable diagnostic biomarker of Class I HDACs for AD. Our study provided a comprehensive understanding of Class I HDACs and provided new insight into the function of HDAC1 in AD disease progression.

Intestinal dysbiosis mediates cognitive impairment via the intestine and brain NLRP3 inflammasome activation in chronic sleep deprivation

Growing evidence suggests the involvement of the microbiota-gut-brain axis in cognitive impairment induced by sleep deprivation (SD), however how the microbiota-gut-brain axis work remains elusive. Here, we discovered that chronic SD induced intestinal dysbiosis, activated NLRP3 inflammasome in the colon and brain, destructed intestinal/blood-brain barrier, and impaired cognitive function in mice. Transplantation of "SD microbiota" could almost mimic the pathological and behavioral changes caused by chronic SD. Furthermore, all the behavioral and pathological abnormalities were practically reversed in chronic sleep-deprived NLRP3^-/- mice. Regional knockdown NLRP3 expression in the gut and hippocampus, respectively. We observed that down-regulation of NLRP3 in the hippocampus inhibited neuroinflammation, and ameliorated synaptic dysfunction and cognitive impairment induced by chronic SD. More intriguingly, the down-regulation of NLRP3 in the gut protected the intestinal barrier, attenuated the levels of peripheral inflammatory factors, down-regulated the expression of NLRP3 in the brain, and improved cognitive function in chronic SD mice. Our results identified gut microbiota as a driver in chronic SD and highlighted the NLRP3 inflammasome as a key regulator within the microbiota-gut-brain axis.

Submucosal esophageal abscess evolving into intramural submucosal dissection: A case report

BACKGROUND

Here we report a rare case of submucosal esophageal abscess evolving into intramural submucosal dissection.

CASE SUMMARY

An 80-year-old woman was admitted to our emergency department with a chief complaint of dysphagia and fever. Laboratory tests showed mild leukocytosis and elevated C-reactive protein level. Computed tomography showed thickening of the esophageal wall. Upper endoscopy showed a laceration of the esophageal mucosa and a submucosal mass. Spontaneous drainage occurred, and we could see purulent exudate from the crevasse. We closed the laceration with endoscopic clips. The patient did not remember swallowing a foreign body; however, she ate crabs before the symptoms occurred. We prescribed the patient with antibiotic, and the symptoms were gradually relieved. Two months later, upper endoscopy showed that the laceration was healed, and the submucosal abscess disappeared. However, intramural esophageal dissection was formed. We performed endoscopic incision of the septum using dual-knife effectively.

CONCLUSION

In conclusion, we are the first to report the case of esophageal submucosal abscess evolving into intramural esophageal dissection. The significance of this case lies in clear presentation of the evolution process between two disorders. In addition, we recommend that endoscopic incision be considered as one of the routine therapeutic modalities of intramural esophageal dissection.

DI-3-n-butylphthalide mitigates stress-induced cognitive deficits in mice through inhibition of NLRP3-Mediated neuroinflammation

Our previous study has demonstrated that chronic stress could cause cognitive deficits and tau pathology. However, the underlying mechanism and whether/how DI-3-n-Butylphthalide (NBP) ameliorates these effects are still unclear. Here, Wild-type mice were subjected to chronic unpredictable and mild stress (CUMS) for 8 weeks. Following the initial 4 weeks, the stressed animals were separated into susceptible (depressive) and unsusceptible (resilient) groups based on behavioral tests. Then, NBP (30 mg/kg i.g) was administered for 4 weeks. Morris water maze (MWM), Western-blot, Golgi staining, immunofluorescence staining and ELISA were used to examine behavioral, biochemical, and pathological changes. The results showed that both depressive and resilient mice displayed spatial memory deficits and an accumulation of tau in the hippocampus. Activated microglia and NLRP3 inflammasome were found after 8-week chronic stress. We also found a decreased level of postsynaptic density (PSD) related proteins (PSD93 and PSD95) and decreased the number of dendritic spines in the hippocampus. Interestingly, almost all the pathological changes in depressive and resilient mice previously mentioned could be reversed by NBP treatment. To further investigate the role of NLRP3 inflammasome in chronic stress-induced cognitive deficits, NLRP3 KO mice were also exposed to chronic stress. And these changes induced by chronic stress could not be found in NLRP3 KO mice. These results show an important role for the NLRP3/caspase-1/IL-1β axis in chronic stress-induced cognitive deficits and NBP meliorates cognitive impairments and selectively attenuates phosphorylated tau accumulation in stressed mice through regulation of NLRP3 inflammatory signaling pathway.

Escitalopram Alleviates Alzheimer's Disease-Type Tau Pathologies in the Aged P301L Tau Transgenic Mice

BACKGROUND

The inhibition of tau hyperphosphorylation is one of the most promising therapeutic targets for the development of Alzheimer's disease (AD) modifying drugs. Escitalopram, a kind of selective serotonin reuptake inhibitor antidepressant, has been previously reported to ameliorate tau hyperphosphorylation in vitro.

OBJECTIVE

In this study, we determined whether escitalopram alleviates tau pathologies in the aged P301L mouse.

METHODS

Mice were intraperitoneal injected with either escitalopram or saline for 4 weeks, and a battery of behavioral tests were conducted before tissue collection and biochemical analyses of brain tissue with western blot and immunohistochemistry.

RESULTS

Wild-type (Wt) mice statistically outperformed the aged pR5 mice in the Morris water maze, while escitalopram treatment did not significantly rescue learning and memory deficits of aged pR5 mice. Tau phosphorylation at different phosphorylation sites were enhanced in the hippocampus of aged pR5 mice, while escitalopram treatment significantly decreased tau phosphorylation. The levels of phosphorylated GSK-3β and phosphorylated Akt were significantly decreased in the hippocampus of aged pR5 mice, while escitalopram administration markedly increased the expression level. The aged pR5 mice showed significant decreases in PSD95 and PSD93, while the administration of escitalopram significantly increased PSD95 and PSD93 to levels comparable with the Wt mice.

CONCLUSION

The protective effects of escitalopram exposure during advanced AD are mainly associated with significant decrease in tau hyperphosphorylation, increased numbers of neurons, and increased synaptic protein levels, which may via activation of the Akt/GSK-3β signaling pathway.

Spatial Training Ameliorates Long-Term Alzheimer's Disease-Like Pathological Deficits by Reducing NLRP3 Inflammasomes in PR5 Mice

Recent studies have suggested that cognitive training could delay memory loss in Alzheimer's disease (AD). However, whether and how cognitive training produces long-term benefits remains unclear. Here, 10-month-old PR5 mice were spatially trained in a water maze for 4 consecutive weeks. The novel object recognition test (NORT), Western blots, Golgi staining, and ELISA were used to examine behavioral, biochemical, and pathological measures immediately after training and 3 months later. Immediately after training, we found that spatial training significantly improved cognitive performance; reduced tau neuropathology; increased the expression level of synaptophysin, PSD93, and PSD95 in the hippocampus; and increased the number of dendritic spines in PR5 mice. The expression levels of NLRP3, caspase-1, and interleukin (IL)-1β, which were significantly elevated in PR5 mice, were reversed by spatial training. Interestingly, these effects persisted 3 months later. To further detect the role of NLRP3 in spatial training, PR5/NLRP3-/- mice and PR5/NLRP3+/- mice were also used in our study. PR5/NLRP3-/- mice showed better cognitive performance than PR5 mice. After 1 week of spatial training, these changes (including those in expression levels of synaptophysin, PSD93, and PSD95; the number of dendritic spines; and caspase-1 and IL-1β content in PR5 mice) could be totally reversed in PR5/NLRP3-/- and PR5/NLRP3+/- mice. In addition, there was a positive correlation between NLRP3 content and the expression levels of caspase-1 and IL-1β. These results show an important role for the NLRP3/caspase-1/IL-1β axis in ameliorating the effect of spatial training on cognitive impairment in PR5 mice.

Spatial learning and memory impairments are associated with increased neuronal activity in 5XFAD mouse as measured by manganese-enhanced magnetic resonance imaging

Dysfunction of neuronal activity is a major and early contributor to cognitive impairment in Alzheimer's disease (AD). To investigate neuronal activity alterations at early stage of AD, we encompassed behavioral testing and in vivo manganese-enhanced magnetic resonance imaging (MEMRI) in 5XFAD mice at early ages (1-, 2-, 3- and 5-month). The 5XFAD model over-express human amyloid precursor protein (APP) and presenilin 1 (PS1) harboring five familial AD mutations, which have a high APP expression correlating with a high burden and an accelerated accumulation of the 42 amino acid species of amyloid-β. In the Morris water maze, 5XFAD mice showed longer escape latency and poorer memory retention. In the MEMRI, 5XFAD mice showed increased signal intensity in the brain regions involved in spatial cognition, including the entorhinal cortex, the hippocampus, the retrosplenial cortex and the caudate putamen. Of note, the observed alterations in spatial cognition were associated with increased MEMRI signal intensity. These findings indicate that aberrant increased basal neuronal activity may contribute to the spatial cognitive function impairment at early stage of AD, and may further suggest the potential use of MEMRI to predict cognitive impairments. Early intervention that targets aberrant neuronal activity may be crucial to prevent cognitive impairment.

LINGO-1 antibody ameliorates myelin impairment and spatial memory deficits in the early stage of 5XFAD mice

AIMS

Multiple evidence has indicated that myelin injury is common in Alzheimer's disease (AD). However, whether myelin injury is an early event in AD and the relationship between it and cognitive function is still elusive.

METHODS

Spatial memory of 5XFAD mice was determined by Morris water maze at 1 and 3 months old. Meanwhile, the deposition of Aβ, the expression of myelin basic protein (MBP), LINGO-1, NgR, and myelin ultrastructure in many memory-associated brain regions were detected in one-month-old and three-month-old mice (before and after LINGO-1 antibody administration) using immunostaining, Western blot (WB), and transmission electron microscopy (TEM), respectively.

RESULTS

No abnormal Aβ deposition was found in one-month-old 5XFAD mice. However, spatial memory deficits were proved in accordance with an obvious demyelination in memory-associated brain regions in one-month-old mice and both deteriorated with age. Administration of LINGO-1 antibody could obviously restore the myelin impairments in CA1 and DG region and partially ameliorate spatial memory deficits.

CONCLUSIONS

Our results demonstrated that myelin injury was an early event in 5XFAD mice even prior to emergence of deposition of Aβ. Intervention with the LINGO-1 antibody could attenuate impaired spatial memory deficits by remyelination, which suggested that myelin injury was involved in spatial memory deficits and remyelination may be a potential therapeutic strategy in early stage of AD or mild cognitive impairments.

Activation of GSK-3 disrupts cholinergic homoeostasis in nucleus basalis of Meynert and frontal cortex of rats

The cholinergic impairment is an early marker in Alzheimer's disease (AD), while the mechanisms are not fully understood. We investigated here the effects of glycogen synthase kinse-3 (GSK-3) activation on the cholinergic homoeostasis in nucleus basalis of Meynert (NBM) and frontal cortex, the cholinergic enriched regions. We activated GSK-3 by lateral ventricular infusion of wortmannin (WT) and GF-109203X (GFX), the inhibitors of phosphoinositol-3 kinase (PI3-K) and protein kinase C (PKC), respectively, and significantly decreased the acetylcholine (ACh) level via inhibiting choline acetyl transferase (ChAT) rather than regulating acetylcholinesterase (AChE). Neuronal axonal transport was disrupted and ChAT accumulation occurred in NBM and frontal cortex accompanied with hyperphosphorylation of tau and neurofilaments. Moreover, ChAT expression decreased in NBM attributing to cleavage of nuclear factor-κB/p100 into p52 for translocation into nucleus to lower ChAT mRNA level. The cholinergic dysfunction could be mimicked by overexpression of GSK-3 and rescued by simultaneous administration of LiCl or SB216763, inhibitors of GSK-3. Our data reveal the molecular mechanism that may underlie the cholinergic impairments in AD patients.

LINGO-1 antibody ameliorates myelin impairment and spatial memory deficits in experimental autoimmune encephalomyelitis mice

More than 50% of multiple sclerosis patients develop cognitive impairment. However, the underlying mechanisms are still unclear, and there is no effective treatment. LINGO-1 (LRR and Ig domain containing NOGO receptor interacting protein 1) has been identified as an inhibitor of oligodendrocyte differentiation and myelination. Using the experimental autoimmune encephalomyelitis (EAE) mouse model, we assessed cognitive function at early and late stages of EAE, determined brain expression of myelin basic protein (MBP) and investigated whether the LINGO-1 antibody could restore deficits in learning and memory and ameliorate any loss of MBP. We found that deficits in learning and memory occurred in late EAE and identified decreased expression of MBP in the parahippocampal cortex (PHC) and fimbria-fornix. Moreover, the LINGO-1 antibody significantly improved learning and memory in EAE and partially restored MBP in PHC. Furthermore, the LINGO-1 antibody activated the AKT/mTOR signaling pathway regulating myelin growth. Our results suggest that demyelination in the PHC and fimbria-fornix might contribute to cognitive deficits and the LINGO-1 antibody could ameliorate these deficits by promoting myelin growth in the PHC. Our research demonstrates that LINGO-1 antagonism may be an effective approach to the treatment of the cognitive impairment of multiple sclerosis patients.

Phospho-Rb mediating cell cycle reentry induces early apoptosis following oxygen-glucose deprivation in rat cortical neurons

The aim of this study was to investigate the relationship between cell cycle reentry and apoptosis in cultured cortical neurons following oxygen-glucose deprivation (OGD). We found that the percentage of neurons with BrdU uptake, TUNEL staining, and colocalized BrdU uptake and TUNEL staining was increased relative to control 6, 12 and 24 h after 1 h of OGD. The number of neurons with colocalized BrdU and TUNEL staining was decreased relative to the number of TUNEL-positive neurons at 24 h. The expression of phosphorylated retinoblastoma protein (phospho-Rb) was significantly increased 6, 12 and 24 h after OGD, parallel with the changes in BrdU uptake. Phospho-Rb and TUNEL staining were colocalized in neurons 6 and 12 h after OGD. This colocalization was strikingly decreased 24 h after OGD. Treatment with the cyclin-dependent kinase inhibitor roscovitine (100 μM) decreased the expression of phospho-Rb and reduced neuronal apoptosis in vitro. These results demonstrated that attempted cell cycle reentry with phosphorylation of Rb induce early apoptosis in neurons after OGD and there must be other mechanisms involved in the later stages of neuronal apoptosis besides cell cycle reentry. Phosphoralated Rb may be an important factor which closely associates aberrant cell cycle reentry with the early stages of neuronal apoptosis following ischemia/hypoxia in vitro, and pharmacological interventions for neuroprotection may be useful directed at this keypoint.

Characterization of proteasome inhibition on astrocytes cell cycle

Increasing evidence indicates that proteasome inhibition occurs in multiple central nervous system (CNS) disorders, including Alzheimer's disease (AD) and Parkinson's disease (PD). Compared with the extensive studies on neurons, little attention is paid on the proteasome inhibition in astrocytes. Here, we demonstrated that lactacystin inhibited proteasome dose-dependently in cultured astrocytes. Simultaneously, lactacystin suppressed the expression of cell cycle proteins in astrocytes and caused the proliferating astrocytes arrested at G1/S checkpoint. Western blots showed that proteasome inhibition led to a decrease in cdk-2, cdk-4, cyclin D1 expression accompanied with an increase in p21waf1/cip1 expression. The effect of chronic low-level proteasome inhibition on astrocytes was consistent with that in acute proteasome inhibition. Furthermore, increased levels of interleukin-6 (IL-6) secretion, STAT-3 and phospho-STAT-3 expression were found, suggesting that proteasome inhibition in astrocytes could stabilize signals of grow arrest through the JAK/STAT signaling cascade.

Effects of tau phosphorylation on proteasome activity

Dysfunction of proteasome contributes to the accumulation of the abnormally hyperphosphorylated tau in Alzheimer's disease. However, whether tau hyperphosphorylation and accumulation affect the activity of proteasome is elusive. Here we found that a moderate tau phosphorylation activated the trypsin-like activity of proteasome, whereas further phosphorylation of tau inhibited the activity of the protease in HEK293 cells stably expressing tau441. Furthermore, tau hyperphosphorylation could partially reverse lactacystin-induced inhibition of proteasome. These results suggest that phosphorylation of tau plays a dual role in modulating the activity of proteasome.

The involvement of glycogen synthase kinase-3 and protein phosphatase-2A in lactacystin-induced tau accumulation

Here, we demonstrated that lactacystin inhibited proteasome dose-dependently in HEK293 cells stably expressing tau. Simultaneously, it induces accumulation of both non-phosphorylated and hyperphosphorylated tau and decreases the binding of tau to the taxol-stabilized microtubules. Lactacystin activates glycogen synthase kinsase-3 (GSK-3) and decreases the phosphorylation of GSK-3 at serine-9. LiCl inhibits GSK-3 and thus reverses the lactacystin-induced accumulation of the phosphorylated tau. Lactacystin also inhibits protein phosphase-2A (PP-2A) and it significantly increases the level of inhibitor 1 of PP-2A. These results suggest that inhibition of proteasome by lactacystin induces tau accumulation and activation of GSK-3 and inhibition of PP-2A are involved.

Protoporphyrin IX production and its photodynamic effects on glioma cells, neuroblastoma cells and normal cerebellar granule cells in vitro with 5-aminolevulinic acid and its hexylester

5-Aminolevulinic acid (ALA) has shown promising in photodynamic detection and therapy of brain tumor. However, the knowledge on selective accumulation of ALA-induced protoporphyrin IX (PpIX) in brain tumor tissue is still fragment. In the present study, the rat C6 glioma cells, human SK-N-SH neuroblastoma cells, and rat normal cerebellar granule cells (RCG) were used to investigate the PpIX production and photocytotoxicity in vitro. The C6 cells and SK-N-SH cells showed a similar kinetics of PpIX accumulation after exposure to ALA or ALA hexyl ester (ALA-H), with an initial increase up to 6-8 h and then saturated. In the case of RCG cells, the PpIX accumulation slowly increased until 12 h studied. However the cellular PpIX content was more than 10 times higher in the C6 and SK-N-SH cells than that in the normal RCG cells. The intracellular localization of PpIX measured by cofocal laser scanning microscopy was in same pattern in the C6 glioma cells and RCG normal cells with a diffuse cytoplasm distribution. The sensitivity of the C6 cells and SK-N-SH cells to ALA or ALA-H PDT was similar. It appears that ALA-H could achieve similar or slightly better results than ALA with respect to PpIX production and photoinactivation of cells, although a 10 times lower concentration of ALA-H was used.