Mesenchymal Stromal Cells Facilitate Tip Cell Fusion Downstream of BMP-Mediated Venous Angiogenesis-Brief Report.

BACKGROUND: The goal of this study was to identify and characterize cell-cell interactions that facilitate endothelial tip cell fusion downstream of BMP (bone morphogenic protein)-mediated venous plexus formation. METHODS: High resolution and time-lapse imaging of transgenic reporter lines and loss-of-function studies were carried out to study the involvement of mesenchymal stromal cells during venous angiogenesis. RESULTS: BMP-responsive stromal cells facilitate timely and precise fusion of venous tip cells during developmental angiogenesis. CONCLUSIONS: Stromal cells are required for anastomosis of venous tip cells in the embryonic caudal hematopoietic tissue.

Role of endocannabinoid signaling in a septohabenular pathway in the regulation of anxiety- and depressive-like behavior.

Enhancing endocannabinoid signaling produces anxiolytic- and antidepressant-like effects, but the neural circuits involved remain poorly understood. The medial habenula (MHb) is a phylogenetically-conserved epithalamic structure that is a powerful modulator of anxiety- and depressive-like behavior. Here, we show that a robust endocannabinoid signaling system modulates synaptic transmission between the MHb and its sole identified GABA input, the medial septum and nucleus of the diagonal band (MSDB). With RNAscope in situ hybridization, we demonstrate that key enzymes that synthesize or degrade the endocannabinoids 2-arachidonylglycerol (2-AG) or anandamide are expressed in the MHb and MSDB, and that cannabinoid receptor 1 (CB1) is expressed in the MSDB. Electrophysiological recordings in MHb neurons revealed that endogenously-released 2-AG retrogradely depresses GABA input from the MSDB. This endocannabinoid-mediated depolarization-induced suppression of inhibition (DSI) was limited by monoacylglycerol lipase (MAGL) but not by fatty acid amide hydrolase. Anatomic and optogenetic circuit mapping indicated that MSDB GABA neurons monosynaptically project to cholinergic neurons of the ventral MHb. To test the behavioral significance of this MSDB-MHb endocannabinoid signaling, we induced MSDB-specific knockout of CB1 or MAGL via injection of virally-delivered Cre recombinase into the MSDB of Cnr1loxP/loxP or MgllloxP/loxP mice. Relative to control mice, MSDB-specific knockout of CB1 or MAGL bidirectionally modulated 2-AG signaling in the ventral MHb and led to opposing effects on anxiety- and depressive-like behavior. Thus, depression of synaptic GABA release in the MSDB-ventral MHb pathway may represent a potential mechanism whereby endocannabinoids exert anxiolytic and antidepressant-like effects.

T-Type Calcium Channels Contribute to Burst Firing in a Subpopulation of Medial Habenula Neurons.

Action potential (AP) burst firing caused by the activation of low-voltage-activated T-type Ca2+ channels is a unique mode of neuronal firing. T-type channels have been implicated in diverse physiological and pathophysiological processes, including epilepsy, autism, and mood regulation, but the brain structures involved remain incompletely understood. The medial habenula (MHb) is an epithalamic structure implicated in anxiety-like and withdrawal behavior. Previous studies have shown that MHb neurons fire tonic APs at a frequency of ∼2-10 Hz or display depolarized low-amplitude membrane oscillations. Here, we report in C57BL/6J mice that a subpopulation of MHb neurons are capable of firing transient, high-frequency AP bursts mediated by T-type channels. Burst firing was observed following rebounding from hyperpolarizing current injections or during depolarization from hyperpolarized membrane potentials in ∼20% of MHb neurons. It was rarely observed at baseline but could be evoked in MHb neurons displaying different initial activity states. Further, we show that T-type channel mRNA, in particular Cav3.1, is expressed in the MHb in both cholinergic and substance P-ergic neurons. Pharmacological Cav3 antagonism blocked both burst firing and evoked Ca2+ currents in MHb neurons. Additionally, we observed high-frequency AP doublet firing at sustained depolarized membrane potentials that was independent of T-type channels. Thus, there is a greater diversity of AP firing patterns in MHb neurons than previously identified, including T-type channel-mediated burst firing, which may uniquely contribute to behaviors with relevance to neuropsychiatric disease.

[Application of wireless neuronal recording system in fear conditioning of Alzheimer's disease mice - hippocampal Theta oscillation observation].

APP/PS1/tau triple transgenic (3xTg) mouse is a classical animal model of Alzheimer's disease (AD), which has abnormalities in recognition and electrophysiological properties at early 6-month-old age. However, few studies were performed by using simultaneously recording cognitive behavior and brain electrical activity in the conscious 3xTg mice. By using a new wireless recording system, we recorded hippocampal Theta oscillations in 3xTg mice during the process of fear conditioning test. The results showed that: (1) in training session, no significant difference in the fear behavior and hippocampal Theta activity was found between 3xTg mice and WT mice; (2) in test session, 3xTg mice showed a significant decrease in freezing ratio compared with WT mice when they were exposed to conditioning stimulus (CS); (3) the 3xTg mice showed lower peak power in Theta oscillation in both Pre-CS and CS duration compared with WT mice; (4) CS effectively induced an increase in the peak frequency of Theta oscillation in WT mice, but not in 3xTg mice. These results indicated that the impairment of cognition behavior in 3xTg mice was accompanied with the decreased peak power and peak frequency of Theta oscillation in the hippocampus, suggesting that a decline in Theta oscillation might be involved in the impairments of the fear conditioning, and the enhanced hippocampal Theta oscillation may be beneficial for improving AD cognitive function.

Cerebral inoculation of human A53T α-synuclein reduces spatial memory decline and amyloid-ß aggregation in APP/PS1 transgenic mice of Alzheimer's disease.

Amyloid-ß (Aß) peptide and α-synuclein (α-syn) are major components of senile plaques in Alzheimer's disease (AD) and Lewy bodies in Parkinson's disease (PD), respectively. Co-occurrence of Aß and α-syn in the senile brains of AD and LB diseases suggests interactions between the two proteins. However, the significance of the overlapping deposition, especially the effects of α-syn on the Aß aggregation, still remains to be clarified. In the present study, we investigated the effects of α-syn pre-formed fibrils (PFFs) injection on the cognitive behaviors and Aß deposition in the brain of APP/PS1 transgenic AD mice by using Morris water maze (MWM) test, immunohistochemistry and western blot techniques. We found that APP/PS1 transgenic mice exhibited an obvious elevation in the α-syn load, as well as Aß deposition in the brain compared with wild type of C57 BL littermates. 5 months after cerebral injection of exogenous α-syn, MWM tests showed an alleviation in cognitive impairments in APP/PS1 mice; western blot and immunohistochemistry experiments also exhibited a significant reduction in Aß level in the brain of APP/PS1 mice injected with α-syn. These results suggest that α-syn aggregated in the brain of AD may act as a protective factor and defend the brain tissue from early Aß deposition and cognitive deficits.

Sex Differences in Neuropathology and Cognitive Behavior in APP/PS1/tau Triple-Transgenic Mouse Model of Alzheimer's Disease.

Alzheimer's disease (AD) is the most common form of dementia among the elderly, characterized by amyloid plaques, neurofibrillary tangles, and neuroinflammation in the brain, as well as impaired cognitive behaviors. A sex difference in the prevalence of AD has been noted, while sex differences in the cerebral pathology and relevant molecular mechanisms are not well clarified. In the present study, we systematically investigated the sex differences in pathological characteristics and cognitive behavior in 12-month-old male and female APP/PS1/tau triple-transgenic AD mice (3×Tg-AD mice) and examined the molecular mechanisms. We found that female 3×Tg-AD mice displayed more prominent amyloid plaques, neurofibrillary tangles, neuroinflammation, and spatial cognitive deficits than male 3×Tg-AD mice. Furthermore, the expression levels of hippocampal protein kinase A-cAMP response element-binding protein (PKA-CREB) and p38-mitogen-activated protein kinases (MAPK) also showed sex difference in the AD mice, with a significant increase in the levels of p-PKA/p-CREB and a decrease in the p-p38 in female, but not male, 3×Tg-AD mice. We suggest that an estrogen deficiency-induced PKA-CREB-MAPK signaling disorder in 12-month-old female 3×Tg-AD mice might be involved in the serious pathological and cognitive damage in these mice. Therefore, sex differences should be taken into account in investigating AD biomarkers and related target molecules, and estrogen supplementation or PKA-CREB-MAPK stabilization could be beneficial in relieving the pathological damage in AD and improving the cognitive behavior of reproductively-senescent females.

Amyloid ß protein injection into medial septum impairs hippocampal long-term potentiation and cognitive behaviors in rats.

The specific loss of cholinergic neurons and the progressive deficits of cognitive function are the most primary characteristics of Alzheimer's disease (AD). Although the neurotoxicity of amyloid ß protein (Aß) in AD has been investigated extensively, it is still unclear whether the Aß aggregated in the medial septum (MS), a major cholinergic nucleus projecting to the hippocampus, could affect hippocampal synaptic plasticity and further impair the memory behaviors. The present study investigated the effects of Aß injection into the MS on hippocampal long-term potentiation (LTP) and cognitive behaviors of rats by using Morris water maze (MWM), Y maze and in vivo hippocampal LTP recording. The effects of kainic acid (KA), an agent with specific neurotoxicity to GABAergic neurons, were also observed. The results showed that: (1) Intra-MS injection of Aß25-35, not KA, impaired spatial learning and memory of rats in classical and reversal MWM tests; (2) Both Aß25-35 and KA impaired novelty-seeking behavior of rats in Y maze; (3) Intra-MS injection of Aß25-35, not KA, suppressed in vivo hippocampal LTP in the CA1 region of rats; (4) Both Aß25-35 and KA did not affect the motor ability in behavioral tests and the hippocampal paired-pulse facilitation (PPF) in electrophysiological recording. These results indicate that intra-MS injection of Aß could impair spatial memory, cognitive flexibility and exploratory motivation, as well as hippocampal LTP in rats, suggesting that the cholinergic neurons in the MS and the septo-hippocampal projection could be important targets of neurotoxic Aß, and the specific damage of cholinergic neurons in the MS is likely responsible for the impairments of hippocampal synaptic plasticity and cognitive function in AD.

DA5-CH, a novel GLP-1/GIP dual agonist, effectively ameliorates the cognitive impairments and pathology in the APP/PS1 mouse model of Alzheimer's disease.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder for which there is no cure. The early primary symptom of AD is the decline of memory ability, which gradually develops into complete dementia. Type 2 diabetes mellitus (T2DM) is an important risk factor of AD; and mimetics of the incretin hormone GLP-1 developed to treat diabetes are being tested as a novel therapeutic strategy for AD. In the present study, we reported for the first time the neuroprotective effects of a novel GLP-1/GIP dual agonist DA5-CH that activates the incretin hormone GLP-1 and GIP receptors in the APP/PS1 transgenic AD mouse model. We found that: (1) DA5-CH administration effectively improved working-memory and long-term spatial memory of 9-month-old AD mice in Y-maze and Morris water maze tests; (2) DA5-CH also reduced hippocampal amyloid senile plaques and phosphorylated tau protein levels; (3) DA5-CH basically reversed the deficits in hippocampal late-phase long-term potentiation; (4) DA5-CH up-regulated the levels of p-PI3K and p-AKT growth factor kinases and prevented excessive activation of p-GSK3ß in the hippocampus of APP/PS1 mice. Therefore, the neuroprotection of DA5-CH in alleviating cognitive impairments and pathological damages might be associated with the improvement of hippocampal synaptic plasticity and activation of the PI3K/AKT signaling pathway. We propose that DA5-CH may be beneficial for the treatment of AD patients, especially those with T2DM or hyperglycemia.

[The improvement effect of scFv17 on the gait of triple-transgenic mice].

OBJECTIVE: To observe the gait changes of Alzheimer's disease PS1M146V/APPswe/tauP301L triple-transgenic (3xTg-AD) mice and to investigate the improvement effect of single chain variable domain antibody fragment 17 (scFv17) on the gait. METHODS: In the present study, a selection of 6-month-old 3xTg-AD mice (n=18) and C57BL/6 wild-type mice (n=24) was performed. First, we observed their gait changes and found that the gait of 12-month-old 3xTg-AD mice was severely damaged. Then, the two groups of mice were randomly divided into four groups:WT+PBS(n=12), WT+scFv17(n=12), 3xTg-AD+PBS(n=9) and 3xTg-AD+scFv17(n=9). The gait behavior test and pathological test were performed after 12 weeks'continuous administration of scFv17 (1.5 mg/kg) or an equal volume of PBS (0.01 mol/L) by nasal gavage twice a week. RESULTS: Compared with the same month old wild type mice, the rear track width of 12 month old 3xTg-AD mice was increased(P<0.01), swing time percent was decreased (P<0.01), stance time percent was increased(P<0.01), so the ability of movement coordination and balance was seriously damaged. ScFv17 could improve the coordination and balance ability of 12 month old 3xTg-AD mice(P<0.01). The morphological structure of 3xTg-AD mice cerebellar Purkinje cells was improved. The treatment of scFv17 increased the Nissl body number of the cerebellar Purkinje cells of 3xTg-AD mice (P<0.01). scFv17 reduced the amyloid ß protein (Aß) plaques in the cerebellar cortex of 3xTg-AD mice (P<0.01), and scFv17 reduced the intracellular neurofibrillary tangles (NFT) of the cerebellar Purkinje cells of the 3xTg-AD mice (P<0.01). CONCLUSIONS: The coordination and balance ability of 3xTg-AD mice was significantly impaired. ScFv17 can improve gait behaviour in the 3xTg-AD significantly.The mechanism may be related to the improvement of the structure and protein function of cerebellar Purkinje cells, and the eliminating of the Aß plaques and the neurofibrillary tangles.