| Background:Major depressive disorder(MDD)and bipolar disorder(BD)are two main subtypes of mood disorders,which are great challenge to personal suffering,society and medicine.Research on their pathogenesis is the focus of the present study.The diagnosis of MDD and BD has a significant clinical symptoms dependence.The difference between the clinical symptoms of these two types of mood disorders(MDD:depression;BD:mania,depression)suggests that their pathogenesis has similarities and differences.Both MDD and BD show dysfunction of the stress response system.The stress molecule/neuropeptide,i.e.corticotropin-releasing hormone,secreted by the paraventricular nucleus of the hypothalamus plays an important role in mood disorders.The protein that regulates CRH expression and its molecular mechanism,such as the mechanism of sex hormones regulating CRH expression is the focus of our research.Clinical researches in recent years and our previous studies revealed that another neuropeptide,i.e.oxytocin(OXT)may be a key molecule in the pathogenesis od BD.We will further investigate the alterations and expression regulation mechanism of these key stress response molecules in the pathogenesis of MDD and BD based upon our previous research.On the other hand,in order to clarify the pathological mechanisms that occur in protein network interaction,we will conduct proteomics research on the brain tissue of patients with mood disorders for the first time.Therefore,in the first chapter,we further studied several stress-related receptors,that is,the mechanism of estrogen membrane receptors regulating CRH;as well as the CRH receptors(CRHR1,CRHR2),OXT receptor mRNA expression alterations in prefrontal cortex of MDD and BD patients,including the dorsolateral prefrontal cortex(DLPFC)and the anterior cingulate cortex(ACC)and its correlation with clinical symptoms.In the second chapter,we conduct a proteomics study in the DLPFC and ACC of MDD and BD patients and well-matched controls.The aim of our study is to reveal the differential neurobiological pathogenetic alterations in MDD and BD from the expression level of single molecules to the whole proteome.Material and Methods:(1)Cell pharmacological experiments were used to study the regulation mechanism of membrane-initiated estrogen signaling pathway(MIES),i.e MIES-PI3K-nitric oxide(NO)and MIES-PKC,on CRH secretion in neuroma cell line SK-N-SH cells.(2)Quantitative real-time PCR technology was used to detect the changes in the mRNA levels of CRH receptors and OXT receptors and study their relation with psychotic symptoms and suicide in DLPFC and ACC of MDD and BD patients.(3)Frozen tissue was cut and sections were thionin stained to quantify the proportion of gray and white matter.The proteome of individual samples was identified by Tandemn mass tag(TMT)and high-performance liquid chromatography-mass spectrometry system(LC-MS/MS),and the protein expression level was quantified as well.Bioinformatics analysis was used for functional enrichment analysis of differentially expressed proteins.Western blot was used for verification of the results about protein expression levels from quantitative proteomics analysis.Result:(1)1 nM estradiol-bovine serum albumin(E2-BSA)can significantly stimulate the secretion of NO(p=0.019)and CRH(p<0.01)at 30 min.The PI3K pathway promotes the secretion of CRH by stimulating the production of NO.PKC can stimulate the secretion of CRH independent of NO.(2)The level of OXTR-mRNA in the PFC of BD patients has an upward trend compared with the control group(DLPFC:p=0.10;ACC:p=0.056),especially in male BD patients(BD,n=15;Control group,n=25)(DLPFC:p<0.01;ACC:p=0.069).Compared with the control group,the CRHR2mRNA level of MDD patients only showed a downward trend in DLPFC(p=0.056).The level of CRHR2-mRNA in MDD suicide patients was significantly lower than that in the control group(p=0.011).The ratio of OXTR-mRNA/CRHR2-mRNA in BD patients increased significantly in ACC and showed an upward trend in DLPFC(ACC:p=0.035;DLPFC:p=0.078),especially in male BD patients(ACC:p=0.043;DLPFC:p=0.007).The ratio of OXTR-mRNA/CRHR1-mRNA in male BD patients was also significantly higher in DLPFC than in the male control group(p=0.040).(3)The ratios of gray matter/white matter were around 2.5 both in the DLPFC and the ACC of MDD,BD and their respective controls without significant differences(DLPFC:p=0.54;ACC:p=0.30).It was found that the neuron signature marker,MAP2,was expressed in a significantly higher level than the prototypic markers for astrocytes,oligodendrocytes,endotheliocytes,and macrophages(p<0.0001).In the DLPFC of MDD,enrichment analysis showed a decreased activity of the energy metabolism functional cluster.In the ACC of MDD,enrichment analysis showed decreased activity of synaptic function,cytoskeleton organization,adhesion process and immune inflammatory response.In the DLPFC of BD,enrichment analysis showed decreased activity of cytoskeleton organization,adhesion process and neuronal projection.In the ACC of BD,no specific functional cluster changed.Western blot results showed that the expression levels SUCLA2 was not significantly different between MDD patients and the control group.Conclusion:Estrogen can upregulate the secretion of CRH through multiple intracellular membrane receptor kinase pathways.The differential changes of OXTR-,CRHR1-,CRHR2-mRNA levels in the prefrontal cortex of MDD and BD patients suggest a differential pathogenesis of MDD and BD,and support the idea that hyperactivity of the OXT system may be a characteristic of BD.The DLPFC and ACC proteomics of MDD and BD patients showed significant proteomic differences and several similarities between diseases and between different brain regions of the same disease,revealing further differences in the pathogenesis of MDD and BD,and providing important novel evidence for further elucidation of the pathogenesis of mood disorders. |
