Geldanamycin Reduces Aβ-Associated Anxiety and Depression, Concurrent with Autophagy Provocation

Protective effects of L-carnitine against Beta-amyloid-induced memory impairment and anxiety-like behavior in a rat model of Alzheimer's disease

Alzheimer's disease (AD), the most common cause of dementia, leads to neurodegeneration and cognitive decline. We investigated the therapeutic effects of L-carnitine on cognitive performance and anxiety-like behavior in a rat model of AD induced by unilateral intracerebroventricular injection of β-amyloid1-42 (Aβ1-42). L-carnitine (100 mg/kg/day) was administered intraperitoneally for 28 consecutive days. Following this, the open-field test, novel object recognition test, elevated plus-maze test, Barnes maze test, and passive avoidance learning test were used to assess locomotor activity, recognition memory, anxiety-like behavior, spatial memory, and passive avoidance memory, respectively. Plasma and hippocampal oxidative stress markers, including total oxidant status (TOS) and total antioxidant capacity (TAC), were examined. In addition, histological investigations were performed in the dentate gyrus of the hippocampus using Congo red staining and hematoxylin and eosin staining. The injection of Aβ1-42 resulted in cognitive deficits and increased anxiety-like behavior. These changes were associated with an imbalance of oxidants and antioxidants in plasma and the hippocampus. Also, neuronal death and Aβ plaque accumulation were increased in the hippocampal dentate gyrus region. However, injection of L-carnitine improved recognition memory, spatial memory, and passive avoidance memory in AD rats. These findings provide evidence that L-carnitine may alleviate anxiety-like behavior and cognitive deficits induced by Aβ1-42 through modulating oxidative-antioxidant status and preventing Aβ plaque accumulation and neuronal death.

The Role of HSP90 Molecular Chaperones in Depression: Potential Mechanisms

Major depressive disorder (MDD) is characterized by high rates of disability and death and has become a public health problem that threatens human life and health worldwide. HPA axis disorder and neuroinflammation are two common biological abnormalities in MDD patients. Hsp90 is an important molecular chaperone that is widely distributed in the organism. Hsp90 binds to the co-chaperone and goes through a molecular chaperone cycle to complete its regulation of the client protein. Numerous studies have demonstrated that Hsp90 regulates how the HPA axis reacts to stress and how GR, the HPA axis' responsive substrate, matures. In addition, Hsp90 exhibits pro-inflammatory effects that are closely related to neuroinflammation in MDD. Currently, Hsp90 inhibitors have made some progress in the treatment of a variety of human diseases, but they still need to be improved. Further insight into the role of Hsp90 in MDD provides new ideas for the development of new antidepressant drugs targeting Hsp90.

Protective effects of selegiline against amyloid beta-induced anxiety-like behavior and memory impairment

BACKGROUND

Alzheimer's disease (AD) is a complex and common neurodegenerative disorder. The present study aimed to investigate the potential effects of selegiline (SEL) on various aspects of memory performance, anxiety, and oxidative stress in an AD rat model induced by intracerebroventricular injection of amyloid beta1-42 (Aβ1-42).

METHODS

Oral administration of SEL at a dose of 0.5 mg/kg/day was performed for 30 consecutive days. Following the 30 days, several tests, including the open-field, elevated plus-maze, novel object recognition, Morris water maze, and passive avoidance learning were conducted to assess locomotor activity, anxiety-like behavior, recognition memory, spatial memory, and passive avoidance memory, respectively.

RESULTS

The results indicate that the induction of AD in rats led to recognition memory, spatial memory, and passive avoidance memory impairments, as well as increased anxiety. Additionally, the AD rats exhibited a decrease in total antioxidant capacity and an increase in total oxidant status levels, suggesting an imbalance in oxidative-antioxidant status. However, the administration of SEL improved memory performance, reduced anxiety, and modulated oxidative-antioxidant status in AD rats.

CONCLUSIONS

These findings provide evidence that SEL may alleviate anxiety-like behavior and cognitive deficits induced by Aβ through modulation of oxidative-antioxidant status.

The Protective Effects of Syringic Acid on Bisphenol A-Induced Neurotoxicity Possibly Through AMPK/PGC-1α/Fndc5 and CREB/BDNF Signaling Pathways

Bisphenol A (BPA), an endocrine disruptor, is commonly used to produce epoxy resins and polycarbonate plastics. Continuous exposure to BPA may contribute to the development of diseases in humans and seriously affect their health. Previous research suggests a significant relationship between the increased incidence of neurological diseases and the level of BPA in the living environment. Syringic acid (SA), a natural derivative of gallic acid, has recently considered much attention due to neuromodulator activity and its anti-oxidant, anti-apoptotic, and anti-inflammatory effects. Therefore, in this study, we aimed to investigate the effects of SA on oxidative stress, apoptosis, memory and locomotor disorders, and mitochondrial function, and to identify the mechanisms related to Alzheimer's disease (AD) in the brain of rats receiving high doses of BPA. For this purpose, male Wistar rats received BPA (50, 100, and 200 mg/kg) and SA (50 mg/kg) for 21 days. The results showed that BPA exposure significantly altered the rats' neurobehavioral responses. Additionally, BPA, by increasing the level of ROS, and MDA level, increased the level of oxidative stress while reducing the level of antioxidant enzymes, such as SOD, CAT, GPx, and mitochondrial GSH. The administration of BPA at 200 mg/kg significantly decreased the expression of ERRα, TFAM, irisin, PGC-1α, Bcl-2, and FNDC5, while it increased the expression of TrkB, cytochrome C, caspase 3, and Bax. Moreover, the Western blotting results showed that BPA increased the levels of P-AMPK, GSK3b, p-tau, and Aβ, while it decreased the levels of PKA, P-PKA, Akt, BDNF, CREB, P-CREB, and PI3K. Meanwhile, SA at 50 mg/kg reversed the behavioral, biochemical, and molecular changes induced by high doses of BPA. Overall, BPA could lead to the development of AD by affecting the mitochondria-dependent apoptosis pathway, as well as AMPK/PGC-1α/FNDC5 and CREB/BDNF/TrkB signaling pathways, and finally, by increasing the expression of tau and Aβ proteins. In conclusion, SA, as an antioxidant, significantly reduced the toxicity of BPA.

Protein Misfolding and Aggregation in the Brain: Common Pathogenetic Pathways in Neurodegenerative and Mental Disorders

Mental disorders represent common brain diseases characterized by substantial impairments of social and cognitive functions. The neurobiological causes and mechanisms of psychopathologies still have not been definitively determined. Various forms of brain proteinopathies, which include a disruption of protein conformations and the formation of protein aggregates in brain tissues, may be a possible cause behind the development of psychiatric disorders. Proteinopathies are known to be the main cause of neurodegeneration, but much less attention is given to the role of protein impairments in psychiatric disorders' pathogenesis, such as depression and schizophrenia. For this reason, the aim of this review was to discuss the potential contribution of protein illnesses in the development of psychopathologies. The first part of the review describes the possible mechanisms of disruption to protein folding and aggregation in the cell: endoplasmic reticulum stress, dysfunction of chaperone proteins, altered mitochondrial function, and impaired autophagy processes. The second part of the review addresses the known proteins whose aggregation in brain tissue has been observed in psychiatric disorders (amyloid, tau protein, α-synuclein, DISC-1, disbindin-1, CRMP1, SNAP25, TRIOBP, NPAS3, GluA1, FABP, and ankyrin-G).

Therapeutic Effects of High-Intensity Interval Training Exercise Alone and Its Combination with Ecdysterone Against Amyloid Beta-Induced Rat Model of Alzheimer's Disease: A Behavioral, Biochemical, and Histological Study

Hippocampal oxidative stress has a vital role in the pathophysiology of Alzheimer's disease (AD)-associated behavioral deficits. Ecdysterone (Ecdy), a natural product and primary steroid hormone, exhibits anti-oxidative and neuroprotective effects. High-intensity interval training (HIIT) has emerged as an effective method for improving physiological brain functions. The present study was designed to investigate the comparative effects of separate and combined HIIT and Ecdy treatment on behavioral functions, hippocampal oxidative status, histological changes in an amyloid-beta (Aβ)-induced rat model of AD. Adult male rats were treated simultaneously with HIIT exercise and Ecdy (10 mg/kg/day; P.O.), starting ten days after Aβ-injection, and they continued for eight consecutive weeks. At the end of the treatment course, the behavioral functions of the rats were assessed by commonly-used behavioral paradigms. Subsequently, brain samples were collected for histological analysis and hippocampus samples were collected for biochemical analysis. Results illustrated that Aβ injection impaired learning and memory performances in both novel object recognition and Barnes maze tests, reduced exploratory/locomotor activities in open field test, enhanced anxiety-like behavior in elevated plus-maze (P < 0.05). These behavioral deficits accompanied hippocampal oxidative stress (decreased total antioxidant capacity content and glutathione peroxidase enzyme activity, increased total oxidant status and malondialdehyde level) and neuronal loss in the cerebral cortex and hippocampus in H&E staining (P < 0.05). HIIT and Ecdy improved anxiety-like behavior, attenuated total oxidant status and malondialdehyde, and prevented the neuronal loss (P < 0.05). However, their combination resulted in a more complete and powerful improvement in all the above-mentioned Aβ-related deficits (P < 0.05). Overall, these data provide evidence that a combination of HIIT and Ecdy treatment improves Aβ-induced behavioral deficits, possibly through ameliorating hippocampal oxidative status and preventing neuronal loss.

TRAP1 in Oxidative Stress and Neurodegeneration

Tumor necrosis factor receptor-associated protein 1 (TRAP1), also known as heat shock protein 75 (HSP75), is a member of the heat shock protein 90 (HSP90) chaperone family that resides mainly in the mitochondria. As a mitochondrial molecular chaperone, TRAP1 supports protein folding and contributes to the maintenance of mitochondrial integrity even under cellular stress. TRAP1 is a cellular regulator of mitochondrial bioenergetics, redox homeostasis, oxidative stress-induced cell death, apoptosis, and unfolded protein response (UPR) in the endoplasmic reticulum (ER). TRAP1 has attracted increasing interest as a therapeutical target, with a special focus on the design of TRAP1 specific inhibitors. Although TRAP1 was extensively studied in the oncology field, its role in central nervous system cells, under physiological and pathological conditions, remains largely unknown. In this review, we will start by summarizing the biology of TRAP1, including its structure and related pathways. Thereafter, we will continue by debating the role of TRAP1 in the maintenance of redox homeostasis and protection against oxidative stress and apoptosis. The role of TRAP1 in neurodegenerative disorders will also be discussed. Finally, we will review the potential of TRAP1 inhibitors as neuroprotective drugs.

In vitro model of perimenopausal depression implicates steroid metabolic and proinflammatory genes

The estimated 20-30% of women who develop perimenopausal depression (PMD) are at an increased risk of cardiovascular and all-cause mortality. The therapeutic benefits of estradiol (E2) and symptom-provoking effects of E2-withdrawal (E2-WD) suggest that a greater sensitivity to changes in E2 at the cellular level contribute to PMD. We developed an in vitro model of PMD with lymphoblastoid cell lines (LCLs) derived from participants of a prior E2-WD clinical study. LCLs from women with past PMD (n = 8) or control women (n = 9) were cultured in three experimental conditions: at vehicle baseline, during E2 treatment, and following E2-WD. Transcriptome analysis revealed significant differences in transcript expression in PMD in all experimental conditions, and significant overlap in genes that were changed in PMD regardless of experimental condition. Of these, chemokine CXCL10, previously linked to cardiovascular disease, was upregulated in women with PMD, but most so after E2-WD (p < 1.55 × 10-5). CYP7B1, an enzyme intrinsic to DHEA metabolism, was upregulated in PMD across experimental conditions (F(1,45) = 19.93, p < 0.0001). These transcripts were further validated via qRT-PCR. Gene networks dysregulated in PMD included inflammatory response, early/late E2-response, and cholesterol homeostasis. Our results provide evidence that differential behavioral responsivity to E2-WD in PMD reflects intrinsic differences in cellular gene expression. Genes such as CXCL10, CYP7B1, and corresponding proinflammatory and steroid biosynthetic gene networks, may represent biomarkers and molecular targets for intervention in PMD. Finally, this in vitro model allows for future investigations into the mechanisms of genes and gene networks involved in the vulnerability to, and consequences of, PMD.

Role of BDNF-mTORC1 Signaling Pathway in Female Depression

Depression is a common psychological and mental disorder, characterized by low mood, slow thinking and low will, and even suicidal tendencies in severe cases. It imposes a huge mental and economic burden on patients and their families, and its prevention and treatment have become an urgent public health problem. It is worth noting that there is a significant gender difference in the incidence of depression. Studies have shown that females are far more likely to suffer from depression than males, confirming a close relationship between estrogen and the onset of depression. Moreover, recent studies suggest that the brain-derived neurotrophic factor- (BDNF-) mammalian target of rapamycin complex-1 (mTORC1) signaling pathway is a crucial target pathway for improving depression and mediates the rapid antidepressant-like effects of various antidepressants. However, it is not clear whether the BDNF-mTORC1 signaling pathway mediates the regulation of female depression and how to regulate female depression. Hence, we focused on the modulation of estrogen-BDNF-mTORC1 signaling in depression and its possible mechanisms in recent years.

Thymoquinone improves behavioral and biochemical deficits in hepatic encephalopathy induced by thioacetamide in rats

Hepatic encephalopathy (HE) is a cerebral function alteration in patients with liver dysfunction. The present study aimed to evaluate the therapeutic effects of thymoquinone (TQ) on behavioral deficits and its possible mechanism(s) in a thioacetamide (TAA)-induced HE model. HE was induced in male Wistar rats by intraperitoneal (i.p.) injection of TAA (200 mg/kg) for once every 48 h for 14 consecutive days. Thymoquinone (5, 10, and 20 mg/kg) was administered for seven consecutive days (i.p.) after HE induction. Anxiety and depression-like behaviors assessed by standard paradigms respectively. Finally, their brain hippocampus sections prepared to evaluate the oxidative stress changes in rats. Data showed treatment HE rats with TQ ameliorated anxiety and depression-like behaviors. TQ administration also reduced oxidative stress due to its potential to enhance the levels of glutathione-peroxidase (GPx), catalase (CAT), and total thiol content in the hippocampus. These findings suggest that TQ has notable effects against acute hepatic failure and HE complications through modulation of oxidative stress.

Stress and signaling pathways regulating autophagy: From behavioral models to psychiatric disorders

Autophagy is a process of degradation and recycling of cytoplasmatic components by the lysosomes. In the central nervous system (CNS), autophagy is involved in cell surveillance, neuroinflammation, and neuroplasticity. Neuropsychiatric conditions are associated with functional disturbances at molecular and cellular levels, causing significant impairments in cell homeostasis. Additionally, emerging evidence supports that dysfunctions in autophagy contribute to the pathophysiology of neurological diseases. However, the studies on autophagy in psychiatric disorders are highly heterogeneous and have several limitations, mainly to assess causality and determine the autophagy flux in animals and human samples. Besides, the role of this mechanism in non-neuronal cells in the CNS is only recently being explored. Thus, this review summarizes and discusses the changes in the autophagy pathway in animal models of psychiatric disorders and the limitations underlying the significant findings. Moreover, we compared these findings with clinical studies. Understanding the involvement of autophagy in psychiatric conditions, and the limitation of our current models may contribute to the development of more effective research approaches and possibly pharmacological therapies.

PNU282987 alleviates Aβ-induced anxiety and depressive-like behaviors through upregulation of α7nAChR by ERK-serotonin receptors pathway

Patients with Alzheimer's disease often undergo anxiety and depression. Our previous studies have shown that α7nAChR protects against Aβ-induced neurotoxicity via downregulation of p38 and JNK MAPKs, but the role of α7nAChR on Aβ-induced anxiety and depressive-like behaviors and the effect of α7nAChR on the regulation of MAPKs pathways remain unknown. To examine the effects of α7nAChR and MAPKs pathways on Aβ-induced anxiety and depression-like behaviors and to explore their relationships between them, elevated plus maze, open field and forced swim tests were performed. Protein levels of 5-HT_1A receptor, 5-HT_2C receptor, α7nAChR, t-ERK1/2 and p-ERK1/2 in the amygdala were analyzed by western blotting and immunostaining. Our study found out that Aβ oligomers induced anxiety and depression-like behaviors in C56BL/6 mice with open field, elevated plus maze and forced swim tests. However, activation of α7nAChR or inhibition of ERK pathways showed significant antidepressant and anxiolytic-like effects on Aβ-injected mice. Moreover, Aβ significantly decreased the level of 5-HT_1A receptor but increased the level of 5-HT_2C receptor in the basolateral amygdala. Treatment with α7nAChR agonist PNU282987 or ERK inhibitor U0126 reversed Aβ-induced 5-HT_1A and 5-HT_2C receptor changes. Moreover, activation of α7nAChR inhibited ERK pathway in the amygdala of Aβ_1-42-injected mice. Our study provides a new insight into the mechanism of α7nAChR in Aβ-induced depression and anxiety-related symptoms through the regulation of ERK1/2 pathway and the potential association with serotonin receptors. Together, our data suggests that α7nAChR is protective against Aβ-induced anxiety and depression-like behaviors in mice.

Gallic acid affects blood-brain barrier permeability, behaviors, hippocampus local EEG, and brain oxidative stress in ischemic rats exposed to dusty particulate matter

Dust storms are environmental natural events that transport high concentrations of particulate matter (PM) in living spaces. Recent epidemiological studies have shown that air pollution is associated with stroke. In the present study we aimed to investigate the probable protective effects of gallic acid (GA) on blood-brain barrier (BBB) disruption, brain oxidative stress, anxiety, depression, locomotion behaviors, and changes of hippocampal local electroencephalogram (local EEG) power induced by 4-vessel transient occlusion (4VO I/R) following exposure to dusty PM in rats. Male Wistar rats were divided randomly into eight groups: (1) vehicle+Sham (Veh + Sh), (2) vehicle+4VO I/R (Veh + I/R), (3) gallic acid+sham (GA + Sh), (4) gallic acid+4VO I/R (GA + I/R), (5) vehicle+PM (Veh + PM), (6) PM + 4VO I/R (PM + I/R), (7) gallic acid+PM + Sham (GA + PM + Sh), and (8) gallic acid+PM + 4Vo I/R (GA + PM + I/R). 4VO type of I/R was induced after 10 days of pretreatment by GA 100 mg/kg/2 ml/ip, or 2 ml/kg/ip, normal saline as vehicle (Veh) and exposure to dust storm composed of dusty PM (DPM, 2000-8000 μg/m3), 60 min daily for consecutive 10 days) simultaneously. Seventy-two hours after I/R induction, all behavioral tests and BBB permeability evaluation were done. Hippocampus local EEG was recorded just before and 72 h after I/R induction, and finally brain tissue oxidative stress was assayed. Data showed that 4VO I/R following exposure to DPM increased BBB permeability (p < 0.001), brain oxidative stress (p < 0.001), induced anxiety (p < 0.001), depression (p < 0.01), locomotion impairment (p < 0.001), superoxide dismutase (SOD) activity, and local EEG power also were decreased in PM + Sh (p < 0.001). Pretreatment with GA reversed BBB permeability and MDA. Our findings suggest that GA is a probable protective agent against adverse effects of both I/R and exposure to DPM and also in I/R subjects exposed to DPM. The beneficial effects of GA may induce by its antioxidative and anti-inflammatory properties.

Natural alkaloids from lotus plumule ameliorate lipopolysaccharide-induced depression-like behavior: integrating network pharmacology and molecular mechanism evaluation

Depression is a mental disorder that brings severe burdens to patients and their families. Neuroinflammation and neurotrophins are involved in depression. Lotus plumule is a nutritional food with medicinal values. In the present study, we tried to clarify the anti-depressive effect and molecular mechanism of lotus plumule. Network pharmacological analysis, behavior tests, qRT-PCR and western blotting were used. We found 7 potential active components and 91 targets from the TCMSP database. KEGG analysis suggested that lotus plumule significantly affected nitrogen metabolism, calcium signaling, and inflammatory mediator regulation signaling pathways. Consistent with those effects, total alkaloids of lotus plumule (TLA) and active alkaloids differently suppressed the nitric oxide (NO) production and pro-inflammatory mediators. TLA and higenamine significantly ameliorated LPS-induced depression-like behavior, increased BDNF levels, suppressed microglia activation, and inhibited the expression of ER stress-related proteins. Meanwhile, TLA and higenamine activated microglia autophagy by increasing the beclin-1 and LC3B-II expression. Additionally, in the presence of autophagy inhibitor 3-MA, TLA and higenamine did not reduce the LPS-induced NO production or pro-inflammatory mediators. Collectively, TLA and higenamine attenuated LPS-induced depression-like behavior by regulating BDNF-mediated ER stress and autophagy. Therefore, drinking tea of lotus plumule may provide a potential strategy for preventing depression.

TFEB Probably Involved in Midazolam-Disturbed Lysosomal Homeostasis and Its Induced β-Amyloid Accumulation

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases, and β-amyloid (Aβ) plays a leading role in the pathogenesis of AD. The transcription factor EB (TFEB), a main regulating factor of autophagy and lysosome biosynthesis, is involved in the pathogenesis of AD by regulating autophagy-lysosomal pathways. To date, the choice of anesthetics during surgery in patients with neurodegenerative diseases and evaluation of the effects and underlying mechanisms in these patients have rarely been reported. In this study, the HEK293-APP cells overexpressing APP and Hela cells were used. The cells were treated with midazolam at different concentrations and at different times, then lysosomes were stained by lysotracker and their morphology was observed under a fluorescence microscope. The number and size of lysosomes were analyzed using the ImageJ software. The levels of TFEB in the nucleus and APP-cleaved intracellular proteins were detected by nuclear separation and Western Blot. Finally, ELISA was used to detect the levels of Aβ40 and Aβ42 in the cells after drug treatment. We found that 30 μM midazolam decreased the number of lysosomes and increased its size in HEK293 and HeLa cells. However, 15 μM midazolam transiently disturbed lysosomal homeostasis at 24 h and recovered it at 36 h. Notably, there was no significant difference in the extent to which lysosomal homeostasis was disturbed between treatments of different concentrations of midazolam at 24 h. In addition, 30 μM midazolam prevents the transport of TFEB to the nucleus in either normal or starved cells. Finally, the intracellular C-terminal fragment β (CTFβ), CTFα, Aβ40 and Aβ42 levels were all significantly elevated in 30 μM midazolam-treated HKE293-APP cells. Collectively, the inhibition of TFEB transport to the nucleus may be involved in midazolam-disturbed lysosomal homeostasis and its induced Aβ accumulation in vitro. The results indicated the risk of accelerating the pathogenesis of AD by midazolam and suggested that TFEB might be a candidate target for reduction of midazolam-dependent neurotoxicity.

Effects of Maternal Deprivation on Anxiety, Depression, and Empathy in Male and Female Offspring of Wistar Rats in the Face of Novel Objects

Background:

Early life stress (ELS) models such as maternal deprivation (MD) are used to investigate behavioral changes in rodents under stressful situations. MD is a situation in which rat pups are separated from the dam; MD has different paradigms. The purpose of this research is to evaluate the effects of maternal deprivation on anxiety, depression, and empathy in adult Wistar rats.

Materials and Methods:

MD was applied to pups as per specifically designed protocol to compare rats of the control group with maternal deprivation rats and also the group, which faced novel objects. Each group consisted of eight rats. In this study, separation started from postnatal day (PND) 14 for various periods up to PND 60. EPM test was undertaken to measure anxiety; moreover, FST was used to indicate levels of depression. Also, changes in the empathy ratio were also demonstrated. One-way analysis of variance (ANOVA), Tukey’s post hoc analysis, and t-test were applied to analyze the results.

Results:

MD-treated rats showed a significant decrease in anxiety and empathy indexes compared with those in the control group (P<0.05). However, MD significantly increased depression in both male and female rats (P<0.05). Finally, exposure to novel objects decreased depression but did not have any effect on anxiety and empathy levels in MD rats (P<0.05).

Conclusion:

ELS may lead to various states of mood and behavior in adulthood. According to the findings of this study, depression increases due to MD, though both anxiety and empathy decrease in both male and female Wistar rats. Moreover, exposure to novel objects decreases depression, while anxiety and empathy do not change significantly with exposure to novel objects.

Is There a Role of Autophagy in Depression and Antidepressant Action?

Autophagy has been recognized as evolutionary conserved intracellular pathway that ensures energy, organelle, and protein homeostasis through lysosomal degradation of damaged macromolecules and organelles. It is activated under various stress situations, e.g., food deprivation or proteotoxic conditions. Autophagy has been linked to several diseases, more recently also including stress-related diseases such as depression. A growing number of publications report on the role of autophagy in neurons, also referred to as "neuronal autophagy" on the one hand, and several studies describe effects of antidepressants-or of compounds that exert antidepressant-like actions-on autophagy on the other hand. This minireview highlights the emerging evidence for the involvement of autophagy in the pathology and treatment of depression and discusses current limitations as well as potential avenues for future research.

The regulation of pituitary-thyroid abnormalities by peripheral administration of levothyroxine increased brain-derived neurotrophic factor and reelin protein expression in an animal model of Alzheimer’s disease

Alzheimer’s disease (AD) is associated with decreased serum levels of thyroid hormones (THs), increased levels of thyroid-stimulating hormone (TSH), and decreased protein expression of brain-derived neurotrophic factor (BDNF) and reelin in the hippocampus. In this study, we have evaluated the effect of subcutaneous administration of levothyroxine (L-T4) on levels of THs and TSH as well as protein expression of BDNF and reelin in AD rats. To make an animal model of AD, amyloid-beta peptide (Aβ) plus ibotenic acid were infused intrahippocampally, and rats were treated with L-T4 and (or) saline for 10 days. The levels of THs and TSH were measured by ELISA kits. Protein synthesis was detected by Western blotting method. Results have been shown that serum level of THs, BDNF, and reelin protein expression in the hippocampus were significantly decreased (P < 0.001) in AD animals and elevated significantly in AD rats treated with L-T4 (P < 0.01). Data showed that TSH level significantly decreased in AD rats treated with L-T4 (P < 0.05). These findings indicated that L-T4 increased BDNF and reelin protein expression by regulation of serum THs and TSH level in Aβ-induced AD rats.

The effects of betulinic acid on neurobehavioral activity, electrophysiology and histological changes in an animal model of the Alzheimer's disease

Alzheimer's disease (AD) is a common disorder characterized by aggregation and conversion of amyloid beta (Aβ) monomers to fibrils. Betulinic acid (BA) strongly accelerated this pathway through circumventing the oligomeric intermediate state. BA at doses of 0.2 and 0.4μM/10μl/rat (intra-hippocampal or i.h injection, vehicle: DMSO) was bilaterally administrated 180 and 10min before co-administration of Aβ (0.1μM/5μl/rat, i.h injection, vehicle: PBS) and Streptozotocin (STZ, 1.5mg/kg/10μl/rat, intracerebroventricular or i.c.v. injection, vehicle: aCSF). The behavioral assessments (spatial and passive avoidance memory, anxiety, locomotion, depression, and motor coordination), electrophysiological evaluations (hippocampal long- term potentiation (LTP)) as well as histological changes were evaluated 30days after injections. The indices of spatial and passive avoidance memory, anxiety/depression and LTP records were significantly impaired in AD rats in comparison with the sham. Pretreatment of BA (0.4μM) showed a more significant effect on memory, anxiety, all LTP parameters, and histological damage compared to a low dose in contrast to the AD group. Overall, BA pretreatment was able to prevent AD-induced neurobehavioral and LTP deficits in rats and the best effect was observed in molar ratio of 1:4 (Aβ to BA).

Peripheral and central administration of T3 improved the histological changes, memory and the dentate gyrus electrophysiological activity in an animal model of Alzheimer's disease

The amyloid beta (Aβ) induced Alzheimer's disease (AD) is associated with formation the amyloid plaques, cognitive impairments and decline in spontaneous discharge of neurons. In the current study, we evaluated the effect of subcutaneous (S. C) and intrahippocampal (I. H) administrations of triiodothyronine (T3) on the histological changes, memory and the dentate gyrus (DG) electrophysiological activity in an animal model of AD. Eighty adult male Wistar rats (250-300 g) were divided randomly into five groups: Sham-Operated (Sh-O), AD + Vehicle (S. C), AD + Vehicle (I. H), AD+ T3 (S. C) and AD + T3 (I. H). In order to induce animal model of AD, Aβ (10 ng/μl, bilaterally) were injected intrahippocampally. Rats were treated with T3 and/or normal saline for 10 days. Passive avoidance and spatial memory were evaluated in shuttle box apparatus and Morris water maze, respectively. Neuronal single unit recording was assessed from hippocampal DG. The percent of total time that animals spent in target quarter, the mean latency time (sec), the step through latency and the average number of spikes/bin were decreased significantly in AD rats compared with the Sh-O group (p < 0.001) and were increased significantly in AD groups that have received T3 (S. C and I. H) in compared with AD group (p < 0.01, p < 0.001). Also, formation of amyloid plaques was decreased in AD rats treated with T3.The results showed that T3 injection (S. C and I. H), by reduction of neural damage and increment of neuronal spontaneous activity improved the memory deficits in Aβ-induced AD rats.

Mechanism of depression as a risk factor in the development of Alzheimer's disease: the function of AQP4 and the glymphatic system

BACKGROUND

Many studies have indicated that a history of depression increases the risk of developing Alzheimer's disease (AD); however, the potential pathogenestic mechanism by which depression functions as a high risk factor for AD remains unknown. Recently, a "cerebral lymphatic system" referred to as "glymphatic system" has been demonstrated to be responsible for neuronal extracellular waste protein clearance via a paravascular pathway. However, the function of glymphatic pathway has not been determined in depressive disorders.

METHODS

The present study used an animal model of chronic unpredictable mild stress (CUMS) to determine the function of glymphatic pathway by using fluorescence tracers. Immunohistochemistry was used to assess the accumulation of endogenous mouse and exogenous human amyloid beta 42 (Aβ42) in CUMS-treated mice with or without treatment with antidepressant fluoxetine.

FINDINGS

Glymphatic pathway circulation was impaired in mice treated with CUMS; moreover, glymphatic pathway dysfunction suppressed Aβ42 metabolism, because the accumulation of endogenous and exogenous Aβ42 was increased in the brains of the CUMS-treated mice. However, treatment with fluoxetine reversed these destructive effects of CUMS on glymphatic system. In anhedonic mice, the expression of the water channel aquaporin 4 (AQP4), a factor in glymphatic pathway dysfunction, was down-regulated in cortex and hippocampus.

CONCLUSION

The dysfunction of glymphatic system suggested why a history of depression may be a strong risk factor for AD in anhedonic mice. We hope our study will contribute to an understanding of the risk mechanism of depressive disorder in the development of AD and the mechanisms of antidepressant therapies in AD.

Central and peripheral administrations of levothyroxine improved memory performance and amplified brain electrical activity in the rat model of Alzheimer's disease

Alzheimer's disease (AD) is associated with cognitive impairments and a decline in the spontaneous neuronal discharge. In the current study, we evaluated the effect of subcutaneous (S.C.) and intrahippocampal (I.H.) administrations of levothyroxine (LT-4) on the passive avoidance and spatial memory, as well as electrophysiological activity in an animal model of AD. One hundred-sixty male Wistar rats were divided into two main groups. The S.C. group included two Sham and four AD (vehicle or L-T4 25, 50 & 100μg/kg); and the I.H. had consisted of two Sham and two AD (vehicle or L-T4 10μg/kg) subgroups. To make an animal model of AD, amyloid beta (Aβ) plus ibotenic acid (Ibo) were injected I.H. Rats were treated with L-T4 and/or normal saline for ten days. Passive avoidance and spatial memory were evaluated in shuttle box and Morris water maze, respectively. Neuronal single unit recording was assessed from hippocampal dentate gyrus (DG). Results showed that the mean latency time (s) increased significantly (p<0.001) in AD animals and decreased significantly in both S.C. and I.H. L-T4 injected AD animals, compared with the AD group (p<0.001). The percentage of total time that animals spent in goal quarter and the step through latency decreased significantly in AD rats (p<0.001) and increased significantly in both S.C. and I.H. L-T4 injected AD animals in comparison with the AD group (p<0.01, p<0.001). Data showed that the average number of spikes/bin significantly decreased in the AD group (p<0.001). The S.C. and I.H. L-T4 injections in AD rats significantly increased the spike rate in comparison to the AD group (p<0.001). In conclusion, both S.C. and I.H. injections of L-T4 alleviated memory deficits and spontaneous neuronal activity in Aβ-induced AD rats. Also, I.H. microinjection of L-T4 had more beneficial effects on memory and neuronal electrophysiological activity in comparison to S.C. administration.