Chenglong Rao

Metabolomic analysis reveals metabolic disturbances in the prefrontal cortex of the lipopolysaccharide-induced mouse model of depression.

Major depressive disorder (MDD) is a debilitating illness. However, the underlying molecular mechanisms of depression remain largely unknown. Increasing evidence supports that inflammatory cytokine disturbances may be associated with the pathophysiology of depression in humans. Systemic administration of lipopolysaccharide (LPS) has been used to study inflammation-associated neurobehavioral changes in rodents, but no metabonomic study has been conducted to assess differential metabolites in the prefrontal cortex (PFC) of a LPS-induced mouse model of depression. Here, we employed a gas chromatography-mass spectrometry-based metabonomic approach in the LPS-induced mouse model of depression to investigate any significant metabolic changes in the PFC. Multivariate statistical analysis, including principal component analysis (PCA), partial least squares-discriminate analysis (PLS-DA), and pair-wise orthogonal projections to latent structures discriminant analysis (OPLS-DA), was implemented to identify differential PFC metabolites between LPS-induced depressed mice and healthy controls. A total of 20 differential metabolites were identified. Compared with control mice, LPS-treated mice were characterized by six lower level metabolites and 14 higher level metabolites. These molecular changes were closely related to perturbations in neurotransmitter metabolism, energy metabolism, oxidative stress, and lipid metabolism, which might be evolved in the pathogenesis of MDD. These findings provide insight into the pathophysiological mechanisms underlying MDD and could be of valuable assistance in the clinical diagnosis of MDD.

Quantitative proteomics analysis of the liver reveals immune regulation and lipid metabolism dysregulation in a mouse model of depression.

Major depressive disorder (MDD) is a highly prevalent and debilitating mental illness with substantial impairments in quality of life and functioning. However, the pathophysiology of major depression remains poorly understood. Combining the brain and body should provide a comprehensive understanding of the etiology of MDD. As the largest internal organ of the human body, the liver has an important function, yet no proteomic study has assessed liver protein expression in a preclinical model of depression. Using the chronic unpredictable mild stress (CUMS) mouse model of depression, differential protein expression between CUMS and control (CON) mice was examined in the liver proteome using isobaric tag for relative and absolute quantitation (iTRAQ) coupled with tandem mass spectrometry. More than 4000 proteins were identified and 66 most significantly differentiated proteins were used for further bioinformatic analysis. According to the ingenuity pathway analysis (IPA), we found that proteins related to the inflammation response, immune regulation, lipid metabolism and NFκB signaling network were altered by CUMS. Moreover, four proteins closely associated with these processes, hemopexin, haptoglobin, cytochrome P450 2A4 (CYP2A4) and bile salt sulfotransferase 1 (SULT2A1), were validated by western blotting. In conclusion, we report, for the first time, the liver protein expression profile in the CUMS mouse model of depression. Our findings provide novel insight (liver-brain axis) into the multifaceted mechanisms of major depressive disorder.

Pioglitazone attenuates lipopolysaccharide-induced depression-like behaviors, modulates NF-κB/IL-6/STAT3, CREB/BDNF pathways and central serotonergic neurotransmission in mice

&NA; Immune activation and inflammation are closely associated with the development of depression. Pioglitazone (PIO), a peroxisome proliferator‐activated receptor gamma (PPAR‐&ggr;) agonist, has exhibited antidepressant‐like effects in a couple of studies. However, the underlying mechanisms are far from being fully elucidated. The study aimed to investigate the effects of PIO on depression‐like behaviors induced by lipopolysaccharide (LPS) and to explore the possible underlying mechanisms. The results showed that PIO pretreatment attenuated the depression‐like behaviors in mice challenged with intracerebroventricular (i.c.v.) LPS administration. Moreover, Western blot analysis revealed the effects of PIO on inhibiting activation of the nuclear factor kappa B/interleukin 6/signal transducer and activator of transcription 3 (NF‐&kgr;B/IL‐6/STAT3) pathway, improving down‐regulation of the cAMP response‐element‐binding protein/brain derived neurotrophic factor (CREB/BDNF) pathway, as well as regulating disturbed expression of proteins involved in central serotonergic neurotransmission following LPS administration. The beneficial effects of PIO, at both the behavioral and molecular level, were significantly inhibited by the PPAR‐&ggr; specific antagonist GW9662. In summary, our data reveals for the first time that the modulation of the NF‐&kgr;B/IL‐6/STAT3 and CREB/BDNF pathways, as well as the potential impact on central serotonergic neurotransmission, may be involved in the PPAR‐&ggr;‐dependent effects of PIO on depression‐like behaviors induced by LPS. Additionally, our findings may provide a novel therapeutic target for the treatment of depression‐like behaviors in patients with inflammatory status. Graphical abstract Figure. No caption available. HighlightsPIO attenuated depression‐like behaviors induced by LPS.PIO inhibited LPS‐induced activation of the NF‐&kgr;B/IL‐6/STAT3 pathway.PIO improved LPS‐induced down‐regulation of the CREB/BDNF pathway.PIO potentially impacted on serotonergic neurotransmission in LPS‐treated mice.

Potential antidepressant and resilience mechanism revealed by metabolomic study on peripheral blood mononuclear cells of stress resilient rats.

ABSTRACT Resilience is an active coping response to stress, which plays a very important role in major depressive disorder study. The molecular mechanisms underlying such resilience are poorly understood. Peripheral blood mononuclear cells (PBMCs) were promising objects in unveiling the underlying pathogenesis of resilience. Hereby we carried out successive study on PBMCs metabolomics in resilient rats of chronic unpredictable mild stress (CUMS) model. A gas chromatography–mass spectrometry (GC–MS) metabolomic approach coupled with principal component analysis (PCA) and orthogonal partial least‐squares discriminant analysis (OPLS‐DA) was used to detect differential metabolites in PBMCs of resilient rats. Ingenuity Pathways Analysis (IPA) was applied for pathway analysis. A set of differential metabolites including Malic acid, Ornithine, l‐Lysine, Stigmasterol, Oleic acid, &ggr;‐Tocopherol, Adenosine and N‐acetyl‐d‐glucosamine were significantly altered in resilient rats, meanwhile promoting antidepressant research. As revealed by IPA that aberrant energy metabolism, HIF&agr; signaling, neurotransmitter, O‐GlcNAcylation and cAMP signaling cascade in peripheral might be evolved in the pathogenesis of coping mechanism. The GC–MS based metabolomics may contribute to better understanding of resilience, as well as shedding light on antidepressant discovery.

Proteomic analysis reveals energy metabolic dysfunction and neurogenesis in the prefrontal cortex of a lipopolysaccharide‑induced mouse model of depression

Substantial evidence from previous studies has suggested an association between major depressive disorder (MDD) and inflammation, and previous studies have associated prefrontal cortex (PFC) dysfunction with MDD. Systemic administration of bacterial lipopolysaccharide has been used to study inflammation-associated behavioral changes in rodents. However, proteomic studies investigating PFC protein expression in an LPS-induced mouse model of depression have yet to be conducted. Using two-dimensional electrophoresis coupled with matrix-assisted laser desorption ionization-time of flight-tandem mass spectrometry, PFC proteomes were comparatively assessed in LPS-induced acute inflammation reaction mice, LPS-induced depressive-like behavior mice (Dep), and control mice. A total of 26 differentially expressed proteins were identified, two of which were selected for western blot analysis, the results of which revealed a significant increase in the expression levels of creatine kinase B and dihydropyrimidinase-like 3 in Dep mice, suggesting that changes in energy metabolism and neuro-genesis occur in the PFC of Dep mice. Further investigation on these processes and on the proteins of the PFC are required in order to elucidate the pathophysiological mechanism underlying MDD.

The Extrinsic Coagulation Pathway: a Biomarker for Suicidal Behavior in Major Depressive Disorder

Although an association between major depressive disorder (MDD) and suicide exists, most depressed patients never attempt suicide. An improved understanding of the factors contributing to suicidal risk in MDD can provide direction for suicide predictor development. In MDD suicide attempters (MDD-SA), MDD non-attempters (MDD-NA), and healthy controls (HC) (n = 12 each group), complementary plasma proteomics identified 45 differential proteins mapped to coagulation and inflammation, 25 of which underwent Western blotting. In another cohort including antidepressant-treated patients (n = 49 each group), seven additional extrinsic pathway proteins were selected for ELISA. Two inflammatory proteins and eight coagulatory proteins demonstrated alterations in MDD-SA relative to MDD-NA and HC. Applying a relative mass-action ratio, MDD-SA subjects displayed a higher relative prothrombinase activity than MDD-NA subjects, while healthy controls displayed higher relative prothrombinase activity than both MDD-SA and MDD-NA subjects. Consistent with our human findings, we found that heparin treatment significantly increased forced swimming test (FST) immobility time in rodents. MDD, independent of suicidality, is associated with a proinflammatory state accompanied by a hypothrombotic state. Suicidal behavior in MDD is associated with a more pronounced proinflammatory and prothrombotic phenotype accompanied by extrinsic pathway activation, revealing an extrinsic pathway biomarker that can be applied in predicting and monitoring suicidal risk.

Hypothalamic Proteomic Analysis Reveals Dysregulation of Glutamate Balance and Energy Metabolism in a Mouse Model of Chronic Mild Stress-Induced Depression

Hypothalamus–pituitary–adrenal (HPA) axis hyperactivity is observed in many patients suffering from depression. However, the mechanism underlying the dysfunction of the HPA axis is not well understood. Moreover, dysfunction of the hypothalamus, the key brain region of the HPA axis, has not been well-explored. The aim of our study was to examine possible alterations in hypothalamus protein expression in a model of depression using proteomic analysis. In order to achieve this aim, mice were exposed to chronic unpredictable mild stress (CUMS), as the paradigm results in hyperactivity of the HPA axis. Differential protein expression between the hypothalamic proteomes of CUMS and control mice was then assessed through two-dimensional electrophoresis followed by matrix-assisted laser desorption ionization-time of flight-tandem mass spectrometry. Thirty-seven proteins with a threshold of a 1.5-fold change and a p value ≤0.05 were identified as being differentially expressed between CUMS and control mice, and were quantified for bioinformatics analysis. Glycometabolism, citrate cycle (TCA cycle) and oxidation respiratory chain were found to have changed significantly. Glial fibrillary acidic protein and glutamine synthetase were further validated by Western Blot. Our results demonstrated that CUMS mice exhibited a dramatic protein change both in glutamate metabolism and energy mobilization, which may shed some light on the role of the hypothalamus in the pathology of stress-induced depression.

Identification and validation of argininosuccinate synthase as a candidate urinary biomarker for major depressive disorder

BACKGROUND Major depressive disorder (MDD) is a debilitating psychiatric mood disorder. However, no objective laboratory-based test is yet available to aid in the diagnosis of this disorder. METHODS In order to identify urinary protein biomarker candidates for MDD, the differential proteomic analysis of urine samples from first-episode drug-naïve MDD subjects and healthy controls (HC) was carried out by using two-dimensional gel electrophoresis separation followed by MALDI-TOF/TOF-MS/MS identification. Then, the differential expression levels of some candidate proteins were further validated by immunoblot analysis. RESULTS Through mass spectrometry and database searching, a total of 27 differential proteins were identified, primarily including enzymes, plasma proteins, serpins, and adhesion molecules. Five proteins were selected for subsequent validation by Western blotting. One arginine recycling enzyme - argininosuccinate synthase (ASS1) - was further confirmed to be significantly downregulated in the urine of 30 depressed subjects while remaining unchanged in the plasma. Importantly, receiver-operator curve analyses revealed that ASS1 displayed strong efficacy in distinguishing MDD subjects from HC. CONCLUSION The present study provides a range of urinary protein biomarker candidates for MDD, and further demonstrates that ASS1 has a potential for clinical diagnosis of this disorder.

2D-gel based proteomics unravels neurogenesis and energetic metabolism dysfunction of the olfactory bulb in CUMS rat model

Major depression is a devastating psychiatric disease worldwide currently. A reduced olfactory sensitivity in MDD patients was well evidenced. We previously interrogated the mechanism of decreasing hippocampus neurogenesis in CUMS rat model of depression. The Olfactory Bulb (OB) is crucial part of the olfactory system which functions in post-developmental neurogenesis. However, the mechanism of the dysfunction of OB induced by CUMS is still largely unknown. Herein, by using the chronic unpredictable mild stress (CUMS) rat model of depression, differential protein expression between the OB proteomes of CUMS and control group was interrogated through two-dimensional electrophoresis coupling with matrix-assisted laser desorption ionization-time of flight tandem mass spectrometry. Twenty nine differential protein expression was analyzed by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway over-representation and Ingenuity pathways analysis (IPA). Seven identified differential proteins were selected for Western blotting validation. This study provides insight that neurogenesis and Energy metabolism disorder is involved in OB dysfunction induced by CUMS.