Tetraspanin heterogeneity of small extracellular vesicles in human biofluids and brain tissue.

Extracellular vesicles (EVs) are particles released from most cell types delimited by a lipid bilayer. Small EVs (sEVs) are nanosized (<200 nm) and include exosomes. Brain-derived sEVs may provide a source for new biomarkers of brain status. CD9, CD63, and CD81 are major members of the tetraspanin family frequently used as sEV markers. However, according to a recent report, tetraspanins were not equally expressed in all sEVs, but rather show heterogeneity that reflects the expression levels in their secretory cells. We therefore investigated tetraspanin heterogeneity of sEVs in biofluids commonly used for clinical laboratory tests, and those in the brain. Expression levels and distributions of CD9, CD63 and CD81 on sEVs were determined in serum, plasma, and cerebrospinal fluid (CSF) samples collected from each healthy donor, and in post-mortem brain tissue samples. We found heterogeneous mixes of sEVs with various tetraspanin combinations among sEVs, and the predominant types and heterogeneous patterns of tetraspanins were specific to sample type. Hierarchical clustering revealed that brain sEVs were similar to those in the CSF, but different from those in peripheral blood. Our findings both provide basic information and contribute to the development of biomarkers for neurological and psychiatric disorders.

Reduced Cerebrospinal Fluid Levels of Lysophosphatidic Acid Docosahexaenoic Acid in Patients With Major Depressive Disorder and Schizophrenia.

BACKGROUND: Lysophosphatidic acid (LPA) is involved in numerous biological processes, including neurodevelopment, chronic inflammation, and immunologic response in the central nervous system. Autotaxin (ATX) is a secreted enzyme that produces LPA from lysophosphatidylcholine (LPC). Previous studies have demonstrated decreased protein levels of ATX in cerebrospinal fluid (CSF) of patients with major depressive disorder (MDD). Based on those studies, the current study investigated the levels of lysophospholipids species including LPA and related metabolic enzymes, in CSF of patients with MDD and schizophrenia (SCZ). METHODS: The levels of lysophospholipids species and related metabolic enzymes were measured with either liquid chromatography-tandem mass spectrometry or enzyme-linked immunosorbent assay. Japanese patients were diagnosed with DSM-IV-TR. CSF was obtained from age- and sex-matched healthy controls (n = 27) and patients with MDD (n = 26) and SCZ (n = 27). RESULTS: Of all lysophospholipids species, the levels of LPA 22:6 (LPA - docosahexaenoic acid) were significantly lower in patients with MDD and SCZ than in healthy controls. These levels were negatively correlated with several clinical symptomatic scores of MDD, but not those of SCZ. In addition, the levels of LPA 22:6 were significantly correlated with the levels of LPC 22:6 among all 3 groups. On the other hand, the levels of LPA 22:6 were not correlated with ATX activity in patients with MDD and SCZ. CONCLUSION: The lower levels of LPA 22:6 in patients with MDD and SCZ suggest an abnormality of LPA 22:6 metabolism. In addition, several depressive symptoms in patients with MDD were significantly associated with the lower levels of LPA 22:6, suggesting an involvement of LPA 22:6 in the pathophysiology of MDD.

Differential anatomical and cellular expression of lysophosphatidic acid receptor 1 in adult mouse brain.

Lysophosphatidic acid (LPA) is a bioactive phospholipid that acts as an extracellular signaling molecule through six G-protein-coupled receptors: LPA1-LPA6. Recent studies have demonstrated that LPA signaling via LPA1 receptor plays a crucial role in cognition and emotion. However, because of limited availability of reliable antibodies, it is currently difficult to identify the cell types expressing LPA1 receptor in the brain. The current study explored the cellular distribution pattern of LPA1 receptor in the brain using the LPA1 lacZ-knock-in reporter mice. In situ hybridization and immunohistochemistry revealed that LacZ gene expression in these mice reflected the expression of endogenous LPA1 receptor in the brain. Overall, some brain nuclei contained higher levels of LPA1 receptor than others. The majority of LPA1 receptor-expressing cells were Olig2+ oligodendrocytes. In addition, ALDH1l1+ astrocytes and CD31+ vascular endothelial cells also expressed LPA1 receptor. By contrast, NeuN+ neuron and Iba1+ microglia expressed little or no LPA1 receptor. The current neuroanatomical findings will aid in elucidating a role of brain LPA1 receptor, especially those involved in cognition and emotion.

Increased matrix metalloproteinases in cerebrospinal fluids of patients with major depressive disorder and schizophrenia.

BACKGROUND: Chronic inflammation of the brain has a pivotal role in the pathophysiology of major depressive disorder (MDD) and schizophrenia (SCZ). Matrix metalloproteinases (MMPs) are extracellular proteases involved in pro-inflammatory processes and interact with IL-6, which is increased in the cerebrospinal fluid (CSF) of patients with MDD and SCZ. However, MMPs in the CSF in patients with MDD and SCZ remains unclear. Therefore, we compared MMPs in the CSF of patients with MDD and SCZ to those of healthy controls (HC). METHODS: Japanese patients were diagnosed with DSM-IV-TR and clinical symptoms were assessed with the Hamilton Rating Scale for Depression for MDD and the Positive and Negative Syndrome Scale for SCZ. CSF was obtained from MDD (n=90), SCZ (n=86) and from age- and sex-matched HC (n=106). The levels of MMPs in CSF were measured with multiplex bead-based immunoassay. RESULTS: The levels of MMP-2 in CSF were higher in both MDD and SCZ than HC and were positively correlated with clinical symptomatic scores in MDD, but not in SCZ. Regardless of diagnosis, the levels of MMP-2, -7 and -10 were positively correlated with each other, and the levels of MMP-7 and -10 were higher in MDD, but not in SCZ, compared to HC. CONCLUSION: Increased CSF levels of MMP-2 in MDD and SCZ may be associated with brain inflammation. State-dependent alteration of MMP-2 and activation of cascades involving MMP-2, -7, and -10 appeared to have a role in the pathophysiology of MDD.

Shared preventive factors associated with relapse after a response to electroconvulsive therapy in four major psychiatric disorders.

AIM: The efficacy of electroconvulsive therapy (ECT) has been established in psychiatric disorders but the high rate of relapse is a critical problem. The current study sought preventative factors associated with relapse after a response to ECT in a continuum of four major psychiatric disorders. METHODS: The records of 255 patients with four psychiatric disorders (83 unipolar depression, 60 bipolar depression, 91 schizophrenia, 21 schizoaffective disorder) were retrospectively reviewed. RESULTS: The relapse-free rate of all patients at 1 year was 56.3% in the four psychiatric disorders without a difference. As a result of univariate analysis, three items could be considered as preventative factors associated with relapse: a small number of psychiatric symptom episodes before an acute course of ECT, the use of mood stabilizers, and the use of maintenance ECT. Multivariate analysis was performed, keeping age, sex, and diagnosis constant in addition to the three items, and small number of psychiatric symptom episodes before an acute course of ECT (P = 0.003), the use of lithium (P = 0.025), the use of valproate (P = 0.027), and the use of maintenance ECT (P = 0.001) were found to be significant preventative measures against relapse. CONCLUSION: The use of mood stabilizers, such as lithium and valproate, and maintenance ECT could be shared preventive factors associated with relapse after a response to ECT in four major psychiatric disorders.

Serum levels of high mobility group box-1 protein (HMGB1) and soluble receptors of advanced glycation end-products (RAGE) in depressed patients treated with electroconvulsive therapy.

AIMS: High mobility group box-1 (HMGB1) is one of the damage-associated molecular patterns produced by stress and induces inflammatory responses mediated by receptors of advanced glycation end-products (RAGE) on the cell surface. Meanwhile, soluble RAGE (sRAGE) exhibits an anti-inflammatory effect by capturing HMGB1. Animal models have shown upregulation of HMGB1 and RAGE in the brain or blood, suggesting the involvement of these proteins in depression pathophysiology. However, there have been no reports using blood from depressed patients, nor ones focusing on HMGB1 and sRAGE changes associated with treatment and their relationship to depressive symptoms. METHODS: Serum HMGB1 and sRAGE concentrations were measured by enzyme-linked immunosorbent assay in a group of patients with severe major depressive disorder (MDD) (11 males and 14 females) who required treatment with electroconvulsive therapy (ECT), and also in a group of 25 age- and gender-matched healthy subjects. HMGB1 and sRAGE concentrations were also measured before and after a course of ECT. Depressive symptoms were assessed using the Hamilton Rating Scale for Depression (HAMD). RESULTS: There was no significant difference in HMGB1 and sRAGE concentrations in the MDD group compared to healthy subjects. Although ECT significantly improved depressive symptoms, there was no significant change in HMGB1 and sRAGE concentrations before and after treatment. There was also no significant correlation between HMGB1 and sRAGE concentrations and the HAMD total score or subitem scores. CONCLUSION: There were no changes in HMGB1 and sRAGE in the peripheral blood of severely depressed patients, and concentrations had no relationship with symptoms or ECT.

Decreased serum levels of thrombospondin-1 in female depressed patients.

AIM: Thrombospondin-1 (TSP-1) is an astrocyte-derived synaptogenesis-related factor. It was previously reported to be increased by chronic treatment of electroconvulsive seizure, a model of electroconvulsive therapy (ECT), in rat hippocampus. The aim of this study was to examine whether serum levels of TSP-1 are associated with depression and ECT. METHODS: Serum TSP-1 levels of major depressive disorder (MDD) patients (n = 36) and age- and gender-matched healthy controls (n = 36) were measured by TSP-1 ELISA. MDD patients were diagnosed according to the Diagnostics and Statistical Manual of Mental Disorders-IV-TR and underwent ECT. MDD patients were also analyzed for serum TSP-1 levels pre- and post-ECT. Evaluation of symptoms was obtained using the Hamilton Rating Scale for Depression. RESULTS: Serum TSP-1 levels showed significant decreases specific to female MDD patients. However, TSP-1 did not change pre- and post-ECT, did not correlate with symptoms, nor was not affected by the dose of antidepressants. CONCLUSION: Serum TSP-1 is a possible female-specific factor that reflects depressive trait, but not state.

Antidepressant amitriptyline-induced matrix metalloproteinase-9 activation is mediated by Src family tyrosine kinase, which leads to glial cell line-derived neurotrophic factor mRNA expression in rat astroglial cells.

BACKGROUND: Astrocytes have been implicated in the pathophysiology of mood disorders and in the mechanism of the pharmacological effects of antidepressant drugs by the production of neurotrophic/growth factors. Previous studies have identified astrocyte-expressed Gαi/o -coupled lysophosphatidic acid receptor 1 (LPAR1), as being involved in antidepressant-induced production of glial cell line-derived neurotrophic factor (GDNF) and matrix metalloproteinase-9 (MMP-9) activation, an important step in the production of GNDF. However, the precise mechanism of MMP-9 activation by antidepressants has yet to be identified, in particular the intracellular signaling pathway between LPAR1/Gαi/o and MMP-9. METHODS AND RESULTS: Treatment of rat C6 astroglial cells (C6 cells) with amitriptyline increased Src family tyrosine kinase phosphorylation in a time and concentration-dependent manner. Amitriptyline-induced GDNF mRNA expression was blocked by Src family tyrosine kinase inhibitors. In addition, inhibiting Src family tyrosine kinase blocked amitriptyline-induced zymographic MMP-9 activation in C6 cells. The amitriptyline-induced zymographic MMP-9 activity was completely blocked by selective inhibition of Gαi/o protein and LPAR1. Furthermore, the amitriptyline-induced Src family tyrosine kinase phosphorylation was blocked by LPAR1, but not MMP-9 inhibition, indicating that Src family tyrosine kinase involvement is downstream of LPAR1. CONCLUSIONS: The current findings suggest that the pharmacological effect of antidepressant such as amitriptyline is mediated through an intracellular signaling pathway via the LPAR1/Gαi/o /Src family tyrosine kinase, which leads to MMP-9 activation and GDNF production.