Synaptophysin and the dopaminergic system in hippocampus are involved in the protective effect of rutin against trimethyltin-induced learning and memory impairment

Post-exposure self-recovery reverses oxidative stress, ameliorates pathology and neurotransmitters imbalance and rescues spatial memory after time-dependent aluminum exposure in rat brain

Aluminum is a potent neurotoxin, responsible for memory impairment and cognitive dysfunction. The neurotoxic effect of aluminum on cognitive impairment is well documented, however, exposure to aluminum in a time-dependent manner and post-exposure self-recovery still needs to be elaborated. This research aimed to (1) study the time-dependent effect of aluminum exposure by administering a total dose of 5850 mg/kg of Al over two different time periods: 30 and 45 days (130 and 195 mg/kg of AlCl3 respectively), and (2) study 20 days post-exposure self-recovery effect in both aluminum-exposed groups by giving distilled water. Cognitive abilities were investigated through Morris water maze test and hole board test and compared in both exposure and recovery groups. Oxidative stress markers and neurotransmitter levels were measured for both exposure and recovery groups. To understand the mechanism of aluminum exposure and recovery, immunohistochemical analysis of synaptophysin (Syp) and glial fibrillary acidic protein (GFAP) was performed. Results showed cognitive dysfunction, oxidative stress-induced damage, reduced neurotransmitter levels, decreased immunoreactivity of Syp, and increased GFAP. However, these parameters showed a larger improvement in the recovery group where rats were given aluminum for 30 days period in comparison to recovery group followed by 45 days of aluminum exposure. These results suggest that restoration of cognitive ability is affected by the duration of aluminum exposure. The study findings provide us with insight into the adverse effects of aluminum exposure and can be utilized to guide future preventive and therapeutic strategies against aluminum neurotoxicity.

The effect of olanzapine on spatial memory impairment, depressive-like behavior, pain perception, and BDNF and synaptophysin expression following childhood chronic unpredictable mild stress in adult male and female rats

Chronic unpredictable mild stress (CUMS) method has been introduced as a rodent model of depression. On the other hand, olanzapine, as an antipsychotic, can induce antidepressant and antipsychotic effects. Also, olanzapine may improve cognitive functions. Both CUMS and olanzapine can also affect the expression level of brain-derived neurotrophic factor (BDNF) and synaptophysin, the molecular factors involved in synaptic function, and learning and memory. In this study, we investigated the effect of olanzapine on locomotor activity (using open field test), pain threshold (using hot plate), depressive-like behavior (using forced swim test), spatial learning and memory (using Morris water maze), and BDNF and synaptophysin hippocampal expression (using real-time PCR) in both male and female CUMS rats. CUMS was performed for three consecutive weeks. Olanzapine was also injected intraperitoneally at the dose of 5 mg/kg. Our data showed that olanzapine can reverse the effects of CUMS on behavioral functions and BDNF and synaptophysin expression levels in the hippocampus of both males and females. It was also shown that olanzapine effects on spatial memory, pain perception, and BDNF and synaptophysin level were stronger in females than males. In conclusion, we suggested that the therapeutic effects of olanzapine in CUMS rats may be closely related to the function of BDNF and synaptophysin. Also, the therapeutic effects of olanzapine may be stronger in females. Therefore, and for the first time, we showed that there may be a sex difference in the effects of olanzapine on behavioral and molecular changes following CUMS.

IGF-1's protective effect on OSAS rats' learning and memory

PURPOSE

Patients with obstructive sleep apnea syndrome (OSAS) frequently experience cognitive dysfunction, which may be connected to chronic intermittent hypoxia (CIH). Insulin-like growth factor-1 (IGF-1) is thought to be closely associated with cognitive function, but its role in cognitive impairment caused by OSAS is unclear. The purpose of this study was to investigate the potential protective effect of IGF-1 on cognitive impairment in OSAS rats.

METHODS

Healthy male SD rats (n = 40) were randomly assigned into four groups: control group, CIH group, NS + CIH group, and IGF-1 + CIH group. All experimental rats except for those in the control group were exposed to intermittent hypoxic (IH) environments for 8 h per day over 28 days. Prior to daily exposure to IH, rats in the IGF-1 + CIH group received subcutaneous injections of IGF-1. The Morris water maze test was conducted on all experimental rats. Brain tissue testing methods included Enzyme-Linked Immunosorbent Assay, Hematoxylin and eosin staining, Immunohistochemistry, and Western blotting.

RESULTS

The rat model of OSAS was successfully established following exposure to CIH and exhibited significant cognitive impairment. However, daily subcutaneous injections of IGF-1 partially restored the impaired cognitive function in OSAS rats. Compared with the control group, there was a significant decrease in the expression levels of IGF-1, p-IGF-IR, and SYP in the CIH group; however, these expression levels increased significantly in the IGF-I + CIH group.

CONCLUSION

In OSAS rats, IGF-1 enhances learning memory; this effect may be linked to increased p-IGF-1R and SYP protein production in the hippocampus.

PK2/PKRs pathway is involved in the protective effect of artemisinin against trimethyltin chloride-induced hippocampal injury

Neuroinflammation is one of the important mechanisms of trimethyltin chloride (TMT) central neurotoxicity. Artemisinin (ARS) is a well-known antimalarial drug that also has significant anti-inflammatory effects. Prokineticin 2 (PK2) is a small molecule secreted protein that is widely expressed in the nervous system and plays a key role in the development of neuroinflammation. However, it remains unclear whether ARS can ameliorate neuroinflammation caused by TMT and whether PK2/PKRs signaling pathway plays a part in it. In this research, male Balb/c mice were administered TMT (2.8 mg/kg, i.p.) followed by immunohistochemistry to assess the expression of PK2, PKR1, and PKR2 proteins in the hippocampus. Network pharmacology was used to predict the intersection targets of ARS, central nervous system(CNS) injury and TMT. The neurobehavior of mice was evaluated by behavioral scores. Histopathological damage of the hippocampus was evaluated by HE, Nissl and Electron microscopy. Western blotting was used to identify the expression of synapse-related proteins (PSD95, SYN1, Synaptophysin), PK system-related proteins (PK2, PKR1, PKR2), and inflammation-related proteins (TNF-α, NF-κB p65). Immunohistochemistry showed that TMT resulted in elevated PK2 and PKR2 protein expression in the CA2 and CA3 regions of the hippocampus in mice, while PKR1 protein was not significantly altered. Network pharmacology showed that PK2 could interact with the intersectional targets of ARS, CNS injury, and TMT. ARS remarkably attenuated TMT-induced seizures and hippocampal histological damage. Further studies demonstrated that ARS treatment attenuated TMT-induced hippocampal ultrastructural damage, possibly by increasing the number of rough endoplasmic reticulum and mitochondria as well as upregulating the levels of synapse-associated proteins (PSD95, SYN1, Synaptophysin). Western blotting results revealed that ARS downregulated TMT-induced TNF-α and NF-κB p65 protein levels. In addition, ARS also decreased TMT-induced protein expression of PK2 and PKR2 in the mouse hippocampus, but had no significant effect on PKR1 protein expression. Our results suggested that ARS ameliorated TMT-induced abnormal neural behavior and hippocampal injury, which may be achieved by regulating PK2/PKRs inflammatory pathway and ameliorating synaptic injury. Therefore, we suggest that PK2/PKRs pathway may be involved in TMT neurotoxicity and ARS may be a promising drug that can relieve TMT neurotoxicity.

Mesenchymal stem cells act as stimulators of neurogenesis and synaptic function in a rat model of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is one of the most common NDs leading to cognitive dysfunctions and dementia which are progressively worsen with age. Cell therapy is currently of particular interest in treatment of neurodegenerative disease (ND) such as AD. However, the effective treatment for AD is yet to be found.

OBJECTIVE

In this study, the possible roles of human umbilical mesnchymal stromal cord (hUMSCs) and adipose mesenchymal stem cells (hAD-MSCs) in neurogenesis and synaptic function were investigated using a β-amyloid 1-42 (β A42)-induced AD rat model.

METHODS

hUMSCs and hAD-MSCs were isolated from umbilical cord stroma and adipose tissue, respectively. The expression of Mesenchymal (CD73, CD90 and CD105) and hematopoietic (CD45 and CD133) markers of hUMSCs and hAD-MSCs were confirmed by flow cytometry. Alzheimer's rat model was created by β-amyloid 1-42 injection into the hippocampus and confirmed by Morris Water Maze and immunohistochemical staining. hUMSCs and hAD-MSCs were injected in Alzheimer's rat model, intravenously. Deposition of β-amyloid in the CA1 of hippocampus was assayed 3 months after cell administration. The expression of synaptophysin and GAP43 proteins was assessed by Western blot. Neural death was assessed by Nissl staining.

RESULTS

The data obtained from flow cytometry showed that surface mesenchymal and hematopoteic markers of the fibroblastic like cells isolated from adipose tissue and umbilical cord were expressed highly in hUMSCs and mostly in hAD-SCs. Transplantation of MSCs reduced β-amyloid deposition in the hippocampus of the AD rats compared to the β-amyloid group. The rate of neuronal cell death in the hippocampus of the β-amyloid-treated rats was significantly increased compared to that of the control group. The percentage of apoptotic cells in this group was 72.98 ± 1.25, which was significantly increased compared to the control group. Transplantation of either hUMSCs or hAD-SCs, respectively, resulted in a significant reduction in the apoptotic rate of the neuronal cells in the hippocampus by 39.47 ± 0.01 (p = 0.0001) and 43.23 ± 0.577 (p = 0.001) compared to the β-amyloid group. MSC transplantation resulted in a significant up-regulation in the expression levels of both synaptogenic (synaptophysin) and neurogenic markers (GAP43) by 1.289 ± 0.112 (P = 0.02) and 1.112 ± 0.106 (P = 0.005) fold in the hUMSCs-treated group and 1.174 ± 0.105 (P = 0.04) and 0.978 ± 0.167 (P = 0.008) fold in the hAD-SCs-treated group, respectively.

CONCLUSION

Intravenous injection of hUMSCs and hAD-MSCs is a safe approach that improves synaptic function and neurogenesis via up-regulation of synaptophysin and GAP43 protein expression levels, respectively, in Alzheimer's model. Intravenous injection of both applied SCs could improve learning and cognitive impairment induced by β A42 injection.

KIF5A-dependent axonal transport deficiency disrupts autophagic flux in trimethyltin chloride-induced neurotoxicity

Trimethyltin chloride (TMT) is widely used as a constituent of fungicides and plastic stabilizers in the industrial and agricultural fields, and is generally acknowledged to have potent neurotoxicity, especially in the hippocampus; however, the mechanism of induction of neurotoxicity by TMT remains elusive. Herein, we exposed Neuro-2a cells to different concentrations of TMT (2, 4, and 8 μM) for 24 h. Proteomic analysis, coupled with bioinformatics analysis, revealed the important role of macroautophagy/autophagy-lysosome machinery in TMT-induced neurotoxicity. Further analysis indicated significant impairment of autophagic flux by TMT via suppressed lysosomal function, such as by inhibiting lysosomal proteolysis and changing the lysosomal pH, thereby contributing to defects in autophagic clearance and subsequently leading to nerve cell death. Mechanistically, molecular interaction networks of Ingenuity Pathway Analysis identified a downregulated molecule, KIF5A (kinesin family member 5A), as a key target in TMT-impaired autophagic flux. TMT decreased KIF5A protein expression, disrupted the interaction between KIF5A and lysosome, and impaired lysosomal axonal transport. Moreover, Kif5a overexpression restored axonal transport, increased lysosomal dysfunction, and antagonized TMT-induced neurotoxicity in vitro. Importantly, in TMT-administered mice with seizure symptoms and histomorphological injury in the hippocampus, TMT inhibited KIF5A expression in the hippocampus. Gene transfer of Kif5a enhanced autophagic clearance in the hippocampus and alleviated TMT-induced neurotoxicity in vivo. Our results are the first to demonstrate KIF5A-dependent axonal transport deficiency to cause autophagic flux impairment via disturbance of lysosomal function in TMT-induced neurotoxicity; manipulation of KIF5A may be a therapeutic approach for antagonizing TMT-induced neurotoxicity.Abbreviations: 3-MA: 3-methyladenine; AAV: adeno-associated virus; ACTB: actin beta; AGC: automatic gain control; ATG: autophagy-related; ATP6V0D1: ATPase H+ transporting lysosomal V0 subunit D1; ATP6V1E1: ATPase H+ transporting lysosomal V1 subunit E1; CA: cornu ammonis; CQ: chloroquine; CTSB: cathepsin B; CTSD: cathepsin D; DCTN1: dynactin subunit 1; DG: dentate gyrus; DYNLL1: dynein light chain LC8-type 1; FBS: fetal bovine serum; GABARAP: GABA type A receptor-associated protein; GABARAPL1: GABA type A receptor associated protein like 1; GABARAPL2: GABA type A receptor associated protein like 2; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; IPA: Ingenuity Pathway Analysis; KEGG: Kyoto Encyclopedia of Genes and Genomes; KIF5A: kinesin family member 5A; LAMP: lysosomal-associated membrane protein; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; NBR1: NBR1 autophagy cargo receptor; OPTN: optineurin; PBS: phosphate-buffered saline; PFA: paraformaldehyde; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PRM: parallel reaction monitoring; siRNA: small interfering RNA; SQSTM1/p62: sequestosome 1; SYP: synaptophysin; TAX1BP1: Tax1 binding protein 1; TMT: trimethyltin chloride; TUB: tubulin.

Neuroinflammation Induction and Alteration of Hippocampal Neurogenesis in Mice Following Developmental Exposure to Gossypol

BACKGROUND

Neurogenesis in the neonatal period involves the proliferation and differentiation of neuronal stem/progenitor cells and the establishment of synaptic connections. This process plays a critical role in determining the normal development and maturation of the brain throughout life. Exposure to certain physical or chemical factors during the perinatal period can lead to many neuropathological defects that cause high cognitive dysfunction and are accompanied by abnormal hippocampal neurogenesis and plasticity. As an endocrine disruptor, gossypol is generally known to exert detrimental effects in animals exposed under experimental conditions. However, it is unclear whether gossypol affects neurogenesis in the hippocampal dentate gyrus during early developmental stages.

METHODS

Pregnant Institute of Cancer Research mice were treated with gossypol at a daily dose of 0, 20, and 50 mg/kg body weight from embryonic day 6.5 to postnatal day (P) 21. The changes of hippocampal neurogenesis as well as potential mechanisms were investigated by 5-bromo-2-deoxyuridine labeling, behavioral tests, immunofluorescence, quantitative reverse transcription-polymerase chain reaction, and western-blot analyses.

RESULTS

At P8, maternal gossypol exposure impaired neural stem cell proliferation in the dentate gyrus and decreased the number of newborn cells as a result of reduced proliferation of BLBP+ radial glial cells and Tbr2+ intermediate progenitor cells. At P21, the numbers of NeuN+ neurons and parvalbumin+ γ-aminobutyric acid-ergic interneurons were increased following 50 mg/kg gossypol exposure. In addition, gossypol induced hippocampal neuroinflammation, which may contribute to behavioral abnormalities and cognitive deficits and decrease synaptic plasticity.

CONCLUSIONS

Our findings suggest that developmental gossypol exposure affects hippocampal neurogenesis by targeting the proliferation and differentiation of neuronal stem/progenitor cells, cognitive functions, and neuroinflammation. The present data provide novel insights into the neurotoxic effects of gossypol on offspring.

Flavonoids ameliorate aluminum chloride-induced learning and memory impairments via suppression of apoptosis and oxidative stress in rats

The study was to investigate the effects of flavonoids (rutin, puerarin, and silymarin) on learning and memory function in rats exposed to aluminum chloride (AlCl₃). Wistar rats were administered flavonoids at a dose of 100 mg/(kg·bw)/day or 200 mg/(kg·bw)/day after exposed to 281.40 mg/(kg·bw)/day AlCl₃·6H₂O. The results of Morris water maze suggested that rutin and puerarin increased the frequency of crossing the platform and swimming time spent in the target quadrant of AlCl₃-induced rats significantly. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay indicated that three flavonoids could alleviate apoptosis of hippocampal neurons induced by AlCl₃. Real time-PCR and western blot suggested that rutin, puerarin and 100 mg/(kg·bw)/day silymarin could decrease the AlCl₃-induced high expression of Bcl-2 associated X protein (Bax) mRNA and protein in hippocampus, but the expression of B cell lymphoma/leukemia-2 (Bcl-2) mRNA and protein was not significantly different among groups. Flavonoids could up regulate the low expression of autophagy related proteins (Beclin 1 (Bcl-2-interacting protein with a coiled-coil domain 1) and LC3 (microtubule-associated protein 1 light chain 3)) caused by AlCl₃ exposure. Flavonoids could also adjust the change in adenosine triphosphatase, superoxide dismutase, glutathione peroxidase and malondialdehyde induced by intake of AlCl₃. The results of inductively coupled plasma atomic emission spectroscopy (ICP-AES) suggested that flavonoids could effectively reduce the high Al level in brain and serum of AlCl₃ exposed rats. In conclusion, three flavonoids may improve learning and memory function by inhibiting excessive apoptosis and oxidative stress in AlCl₃ exposed rats.

Antiamnesic effects of tofisopam against scopolamine-induced cognitive impairments in rats

In this study, we investigated the potential therapeutic effects of tofisopam, a 2,3-benzodiazepine derivative anxiolytic, on cognitive deficits in rats with scopolamine-induced amnesia. Cognitive performance of the rats was investigated by using the Morris water maze and passive avoidance tests. Changes in motor activity were assessed by using the activity cage and Rota-rod tests and then morphological changes in the hippocampus were assessed via immunohistochemical stainings. The results indicated that scopolamine impaired learning and memory parameters in rats. Worsened cognitive performance, neuronal loss, and decreased hippocampal synaptophysin, Ki-67, and glial fibrillary acidic protein density were observed. Tofisopam administration at a dose of 50 mg/kg for seven days improved the impaired cognitive performance, enhanced the attenuated synaptic transmission in the hippocampus, increased proliferation in subgranular zones, and improved the decrease in astrocytes in amnesic rats. These findings point out the anti-amnesic effects of tofisopam with concomitant improvements in the hippocampal synaptogenesis, neurogenesis, and glial plasticity, for the first time. Presented beneficial effects of tofisopam on cognitive dysfunctions may have a notable clinical value considering the fact that one of the most important side effects of 1,4-benzodiazepines, which are classical anxiolytic drugs, is amnesia. However, these preclinical results need to be confirmed with further clinical studies, first.

Rutin as Neuroprotective Agent: From Bench to Bedside

Flavonoids are major dietary constituents of plant-based food found ubiquitously in plant kingdom where they are usually present in substantial amounts. Rutin is a flavonol-type polyphenol which consists of the flavonol quercetin and the disaccharide rutinose. Rutin has been reported to exert diverse biological effects such as antitumor and antimicrobial mainly associated to its antioxidant and anti-inflammatory activities. Mental, neurological, and behavioural disorders are an important and growing cause of morbidity. Most of these disorders combine a high prevalence, early onset, progressive clinical course, and impairment of critical brain functions making them a major contributor to the global disease burden. In the present work, the biological in vitro and in vivo effects and the potential therapeutic applications of rutin in neurodegenerative processes are reviewed, as well as their bioavailability and pharmacokinetics, which are essential for a better understanding of its biological effectiveness. Moreover, the present review also provides an overview of the molecular mechanisms through which rutin is proposed to exert its neuroprotective effects.

Flavonoid Naringenin Attenuates Oxidative Stress, Apoptosis and Improves Neurotrophic Effects in the Diabetic Rat Retina

Diabetic retinopathy (DR) is one of the leading causes of decreased vision and blindness worldwide. Diabetes-induced oxidative stress is believed to be the key factor that initiates neuronal damage in the diabetic retina leading to DR. Experimental approaches to utilize dietary flavonoids, which possess both antidiabetic and antioxidant activities, might protect the retinal damage in diabetes. The aim of this study was to investigate the potential protective effects of naringenin in the retina of streptozotocin-induced diabetic rats. Diabetic rats were orally treated and untreated with naringenin (50 mg/kg/day) for five weeks and retinas were analyzed for markers of oxidative stress, apoptosis and neurotrophic factors. Systemic effects of naringenin treatments were also analyzed and compared with untreated groups. The results showed that elevated levels of thiobarbituric acid reactive substances (TBARs) and decreased level of glutathione (GSH) in diabetic rats were ameliorated with naringenin treatments. Moreover, decreased levels of neuroprotective factors (Brain derived neurotrophic factor (BDNF)), tropomyosin related kinase B (TrkB) and synaptophysin in diabetic retina were augmented with naringenin treatments. In addition, naringenin treatment ameliorated the levels of apoptosis regulatory proteins; B cell lymphoma 2 (Bcl-2), Bcl-2 associated X protein (Bax) and caspase-3 in the diabetic retina. Thus, the study demonstrates the beneficial effects of naringenin that possesses anti-diabetic, antioxidant and antiapoptotic properties, which may limit neurodegeneration by providing neurotrophic support to prevent retinal damage in diabetic retinopathy.

The mitochondrial division inhibitor Mdivi-1 rescues mammalian neurons from anesthetic-induced cytotoxicity

Background

Concerns have risen regarding the potential side effects of clinical exposure of the pediatric population to inhalational anesthetics, and how they might impact cognitive, learning, and memory functions. However, neither the mechanisms of anesthetic cytotoxicity, nor potential protective strategies, have yet been fully explored. In this study, we examined whether two of the most commonly used inhalational anesthetics, sevoflurane and desflurane, affect neuronal viability and synaptic network assembly between cultured rat cortical neurons.

Results

Primary rat cortical neuron cultures were exposed to equipotent sevoflurane or desflurane for 1 hour. Neuron viability, synaptic protein expression, mitochondrial morphology, and neurite growth were assayed with immunostaining and confocal microscopy techniques. The effects of anesthetics on the functional development of neural networks were evaluated with whole-cell patch clamp recordings of spontaneous synaptic currents. Our results demonstrate that an acute exposure to sevoflurane and desflurane inhibits the development of neurite processes, impacts the mitochondria, and compromises synaptic proteins - concomitant with a reduction in synaptic function in mature networks. Interestingly, pretreatment of neurons with a mitochondrial division inhibitor (Mdivi-1) not only protected mitochondria integrity but also played a protective role against anesthetic-induced structural and functional neurotoxicity.

Conclusions

We show that Mdivi-1 likely plays a protective role against certain harmful effects of general anesthetics on primary rat neuronal cultures. In addition, Mdivi-1 alone plays a direct role in enhancing growth and modulating synaptic activity. This study highlights the importance of further study into possible protective agents against anesthetic neurotoxicity.