The Effects Of PCDH1 In Ventral Hippocampus In Chronic Restraint Stress-induced Anxiety And Depression-like Behaviors

Background:Affective disorder is the mental disorder, which is caused by several factors and characterized by emotional notable and sustained high and low. Environmental factors and genetic factors are two main factors of emotional disorder. Stress is an important environmental factor which can induce memory impairment and psychiatric disease, such as depression and anxiety. Studies have shown that chronic stress would result in neuroanatomical alteration, including decreased dendritic arborization and impaired synaptogenesis and spinogenesis in crucial brain areas, such as the prefrontal cortex and the hippocampus. Chronic stress can change the expression of mammalian target of rapamycin (mTOR), Brain-Derived Neurotrophic Factor (BDNF), Neuronal nitric oxide synthase (nNOS) through Norepinephrine (NE), 5-hydroxytryptamine (5-HT) and Hypothalamic-Pituitary-Adrenal axis (HPA), which resulted in synaptic structure and function alteration. However, the mechanism underlying chronic stress induced structural and functional alterations is extremely complicated.Synaptic cell adhesion molecules (CAMs) are constant component of synapse and it can be dynamic modulator when activation of synapse. Evidence indicates that dywsregulation of synaptic CAMs is related to structural modifications and emotional disorders. Cadherins are identified as calcium-dependent homophilic cell-cell adhesion molecule. In the central nervous system, cadherin regulates dendritic spine morphogenesis and is related to synaptic function. Protocadherin-1 (PCDH1), a member of the non-clustered protocadherins which belong to the cadherin superfamily, is strongly expressed in the hippocampus and prefrontal cortex. However, it is still unclear whether PCDH1 participate in emotion and structural remodeling.In the present study, we aimed to explore how chronic restraint stress (CRS) modulates PCDH1 expression in the ventral hippocampus. Using region specific knockdown and overexpression of PCDH1 technique, we tested whether PCDH1 participated in chronic restraint stress induced mood disorders.Objective:1. To investigate CRS-induced expression of PCDH1 in the hippocampus.2. To investigate whether PCDH1 is involved in CRS-induced anxiety and depression-like behaviors.Methods1. Chronic restraint stressThe stress group was restrained during the morning (9:00 A.M.-11:00 A.M.) for 2 h daily for 21 days.2. Stereotaxic surgery and Lentivirus Micro injectionMice were anesthetized and immobilized in a stereotaxic apparatus. Mice received ventral hippocampus (VH) micro-infusions,1 μl lentivirus/side and the injection coordinate was as follows:anterior-posterior (AP),-2.7 mm; lateral (L), ± 2.2 mm; dorsal-ventral (DV),-2.2 mm.3. Behavioral testsSpontaneous exploratory activity was assessed in the open field test (OFT). The anxiety-like behaviors were assessed in the OFT and elevated plus maze (EPM). The depression-like behaviors were assessed in the tail suspension test (TST) and forced swim test (FST).4. Quantitative Real-time PCRThe mRNA expression of PCDH1 was detected by Quantitative Real-time PCR.5. Protein extraction and Western blotSamples of mice brain were isolated and homogenized and were detected by western blot. Densitometry analysis on the bands was ca Iculated by Quantity one.6. ImmunohistochemistryMice were perfused with 4%paraformaldehyde (PFA). The brains were cut coronally using a frozen sliding microtome at 40 μm and brain sections were acquired for immunohistochemistry analysis. Images were acquired using a fluorescence microscopy.Results:1. CRS induced the reduction of PCDH1 in the VHPCDH1 mRNA level in CRS group was significantly decreased in the VH. However, the mRNA expression of PCDH 51 subfamily (PCDH7,9,11) were not significantly altered in both groups. The mRNA expression of PCDH1 in CRS group was also significantly decreased in the dorsal hippocampus (DH). PCDH1 mRNA level in both groups were not discrepant in the amygdala (AMY). Western blots also showed that the protein expression of PCDH1 have been significantly reduced after CRS inthe VH. But the protein expression of PCDH1 in both groups were not discrepant in the DH and AMY. These results suggested that CRS resulted in the reduction of PCDH1 expression specially in theVH.2. Knockdown of PCDH1 in the VH could imitate CRS-induced anxiety and depression-like behaviorsMice in PGW-siPCDH1-GFP group exerted decreased the time spent in center in the OFT, reduced the time in open arms and entries into the open arms in the EPM and increased immobility time in FST and TST compared with mice in PGW-ctr-GFP group. These results suggested that knockdown of PCDH1 in the VH resulted in anxiety and depression-like behavior.3. Overexpression of PCDH1 could alleviate CRS-induced anxiety and depression-like behaviorsAfter CRS, ADV-PCDH1-GFP group exerted increased the time spent in center in the OFT, enhanced the time in open arms and entries into the open arms in the EPM and decreased immobility time in FST and TST compared with mice in ADV-ctr-GFP group. These showed that overexpression of PCDH1 corrected CRS-induced anxiety and depression-like behaviors.Conclusion:1. CRS induced specifical reduction of mRNA and protein levels of PCDH1 in theVH.2. PCDH1 in the VH participated in CRS-induced anxiety and depression-like behaviors.Significance:In our study, we provide an evidence of PCDH1 involving in CRS-induced anxiety and depression-like behaviors, which may have potentical for clinical treatment of anxiety and depression in the future.