Exploration of the mechanism by which icariin modulates hippocampal neurogenesis in a rat model of depression.

Icariin (ICA) has a significant capacity to protect against depression and hippocampal injury, but it cannot effectively cross the blood-brain barrier and accumulate in the brain. Therefore, the mechanism by which ICA protects against hippocampal injury in depression remains unclear. In this study, we performed proteomics analysis of cerebrospinal fluid to investigate the mechanism by which ICA prevents dysfunctional hippocampal neurogenesis in depression. A rat model of depression was established through exposure to chronic unpredictable mild stress for 6 weeks, after which 120 mg/kg ICA was administered subcutaneously every day. The results showed that ICA alleviated depressive symptoms, learning and memory dysfunction, dysfunctional neurogenesis, and neuronal loss in the dentate gyrus of rats with depression. Neural stem cells from rat embryonic hippocampi were cultured in media containing 20% cerebrospinal fluid from each group of rats and then treated with 100 µM corticosterone. The addition of cerebrospinal fluid from rats treated with ICA largely prevented the corticosterone-mediated inhibition of neuronal proliferation and differentiation. Fifty-two differentially expressed proteins regulated by chronic unpredictable mild stress and ICA were identified through proteomics analysis of cerebrospinal fluid. These proteins were mainly involved in the ribosome, PI3K-Akt signaling, and interleukin-17 signaling pathways. Parallel reaction monitoring mass spectrometry showed that Rps4x, Rps12, Rps14, Rps19, Hsp90b1, and Hsp90aa1 were up-regulated by chronic unpredictable mild stress and down-regulated by ICA. In contrast, HtrA1 was down-regulated by chronic unpredictable mild stress and up-regulated by ICA. These findings suggest that ICA can prevent depression and dysfunctional hippocampal neurogenesis through regulating the expression of certain proteins found in the cerebrospinal fluid. The study was approved by the Experimental Animal Ethics Committee of Guangzhou University of Chinese Medicine of China in March 2017.

[Preliminary study on cerebrospinal fluid proteomics of Erxian Decoction against neurogenesis impairment in late-onset depression].

This study aims to elucidate the underlying mechanism of Erxian Decoction(EXD) against neurogenesis impairment in late-onset depression(LOD) rats based on cerebrospinal fluid(CSF) proteomics. A total of 66 20-21-month-old male Wistar rats were randomized into naturally aged(AGED) group, LOD group, and EXD group. All rats received chronic unpredictable mild stress(CUMS) for 6 weeks for LOD modeling except for the AGED group. During the modeling, EXD group was given EXD(ig, twice a day at 4 g·kg~(-1)) and other groups received equivalent amount of normal saline(ig). After modeling, a series of behavioral tests, such as sucrose preference test(SPT), open-field test(OFT), forced swimming test(FST), and Morris water maze test(MWMT) were performed. Immunofluorescence method was used to detect the number of Ki-67/Nesti-positive cells and BrdU/DCX-positive cells in the hippocampal DG area of each group. High-concentration corticosterone(CORT) was combined with D-galactose(D-gal) to simulate the changes of LOD-related stress and aging and the proliferation and differentiation of primary neural stem cells of hippocampus in each group were observed. Data independent acquisition(DIA)-mass spectrometry(MS) was used to analyze the differential proteins in CSF among groups and bioinformatics analysis was performed to explore the biological functions of the proteins. Behavioral tests showed that sucrose consumption in SPT, total traveling distance in OFT, and times of crossing the platform in MWMT were all reduced(P<0.01) and the immobility time in FST was prolonged(P<0.01) in the LOD group compared with those in the AGED group, suggesting that LOD rats had developed depression symptoms such as anhedonia, decreased locomotor activity ability, and cognitive dysfunction. Behavioral abnormalities were alleviated(P<0.01, P<0.05) in the EXD group as compared with those in the LOD group. Immunofluorescence results demonstrated that Ki-67/Nesti-positive cells and BrdU/DCX-positive cells in the hippocampal DG area were fewer(P<0.05) in LOD group than in the AGED group, and the positive cells in the EXD group were more(P<0.05) than those in the LOD group. In vitro experiment showed that the proliferation and differentiation of primary hippocampal neural stem cells under the CORT+D-gal treatment were reduced(P<0.01). The proliferation rate of neural stem cells decreased(P<0.05) in CORT+D-gal+LOD-CSF group but increased(P<0.01) in CORT+D-gal+EXD-CSF group compared with that in the CORT+D-gal group. A total of 2 620 proteins were identified from rat CSF, with 135 differential proteins between the LOD group and AGED group and 176 between EXD group and LOD group. GDF11, NrCAM, NTRK2, and GhR were related to neurogenesis and 39 differential proteins were regulated by both LOD and EXD. EXD demonstrated obvious anti-LOD effect, as it improved the locomotor activity ability and cognitive function of LOD rats and protected the proliferation and differentiation of hippocampal neural stem cells. EXD exerts anti-LOD effect by regulating the proteins related to neurogenesis in CSF, such as GDF11, NrCAM, NTRK2, and GhR and maintaining hippocampal neurogenesis.

Cerebrospinal fluid proteomics reveal potential protein targets of JiaWeiSiNiSan in preventing chronic psychological stress damage.

CONTEXT: Chinese herbal formula JiaWeiSiNiSan (JWSNS) has been widely used to prevent stress-induced neuropsychiatric ailments in clinics and proven to have therapeutic anti-stress effects on rats. However, the mechanism remains unclear. OBJECTIVE: Based on the proteomics of cerebrospinal fluid (CSF), this study explores the possible mechanism and target proteins of JiaWeiSiNiSan raising stress resilience and preventing stress damage. MATERIALS AND METHODS: A 6-week Chronic Unpredictable Mild Stress (CUMS) model was applied on adult Wistar male rats to observe the effects of JWSNS on improving mental stress resilience. Tandem Mass Tag (TMT) proteomics and bioinformatics analysis were used to screen and analyze differentially expressed proteins (DEPs) in CSF. Parallel Reaction Monitoring (PRM) was used to validate target DEPs. RESULTS: Significantly decreased sucrose preference, locomotion activity level and accuracy of T-maze, as well as increased immobility time, were observed in CUMS rats compared to CON rats while JWSNS improved above depression-like behaviours. The quantitative proteomics and bioinformatics analysis showed that JWSNS decreased the expression of Rps4x, HSP90AA1, Rps12, Uba1, Rsp14, Tuba1b in CUMS rats CSF (p < 0.05, FDR < 0.5). Immunofluorescence results showed that the number of BrdU/DCX positive cells (p < 0.01) and the relative number of neurons (p < 0.01) in the hippocampus dentate gyrus (DG) of the JSWNS group significantly increased, compared with the CUMS group. CONCLUSIONS: JWSNS could increase mental stress resilience and prevent stress damage by regulating proteins in CSF. This study provides a scientific basis for further study on Chinese formulas preventing mental illness.

Dynamic changes of behaviors, dentate gyrus neurogenesis and hippocampal miR-124 expression in rats with depression induced by chronic unpredictable mild stress.

The depression-like behavior phenotype, neurogenesis in the dentate gyrus and miR-124 expression in the hippocampus are the focus of current research on the pathogenesis of depression and antidepressant therapy. The present study aimed to clarify the dynamic changes of depression-like behavior, dentate gyrus neurogenesis and hippocampal miR-124 expression during depression induced by chronic stress to reveal pathological features at different stages of depression and to further provide insight into depression treatment. Chronic unpredictable mild stress depression models were established by exposing Sprague-Dawley rats to various mild stressors, including white noise, thermal swimming, stroboscopic illumination, soiled cages, pairing with three other stressed animals, cold swimming, tail pinch, restraint and water and food deprivation. Chronic unpredictable mild stress model rats underwent dynamic observation from 1 to 8 weeks and were compared with a control group (normal feeding without any stressors). To observe changes in the depression-like behavior phenotype during chronic unpredictable mild stress-induced depression, a sucrose preference test was used to evaluate the degree of anhedonia. An open-field test was used to evaluate locomotor activity and anxiety status. Compared with the control group, chronic unpredictable mild stress rats lost weight but did not have a depression-like behavioral phenotype at 1-4 weeks. Chronic unpredictable mild stress rats presented decreased sucrose preference and locomotor activity at 5-8 weeks. In addition, chronic unpredictable mild stress rats did not have significant anxiety-like behavior during 1-8 weeks of modeling. To observe neurogenesis dysfunctions and changes in neuronal number in the dentate gyrus during chronic unpredictable mild stress-induced depression, markers (DCX and DCX/BrdU) of neural proliferation and differentiation and the neuronal marker NeuN were assessed by immunofluorescence. Compared with the control group, neurogenesis and the neuronal number in the dentate gyrus did not change from 2 to 6 weeks; however, neural proliferation and differentiation in the dentate gyrus decreased, and the number of neurons decreased until the eighth week in the chronic unpredictable mild stress group. Real-time quantitative reverse transcription polymerase chain reaction assays and fluorescence in situ hybridization were used to measure the expression of hippocampal miR-124 during chronic unpredictable mild stress-induced depression. The results showed that the expression of hippocampal miR-124 was unchanged during the first 4 weeks but increased from 5 to 6 weeks and decreased from 7 to 8 weeks compared with the control group. These findings indicate that during chronic unpredictable mild stress-induced depression, the behavioral phenotype, miR-124 expression in the hippocampus, neurogenesis in the dentate gyrus and neuronal numbers showed dynamic changes, which suggested that various pathological changes occur at different stages of depression. All experimental procedures and protocols were approved by the Experimental Animal Ethics Committee of Guangzhou University of Chinese Medicine of China in March 2015.