Abnormal levels of seven amino neurotransmitters in depressed rat brain and determination by HPLC-FLD

Novel insight into astrocyte-mediated gliotransmission modulates the synaptic plasticity in major depressive disorder

Major depressive disorder (MDD) is a form of glial cell-based synaptic dysfunction disease in which glial cells interact closely with neuronal synapses and perform synaptic information processing. Glial cells, particularly astrocytes, are active components of the brain and are responsible for synaptic activity through the release gliotransmitters. A reduced density of astrocytes and astrocyte dysfunction have both been identified the brains of patients with MDD. Furthermore, gliotransmission, i.e., active information transfer mediated by gliotransmitters between astrocytes and neurons, is thought to be involved in the pathogenesis of MDD. However, the mechanism by which astrocyte-mediated gliotransmission contributes to depression remains unknown. This review therefore summarizes the alterations in astrocytes in MDD, including astrocyte marker, connexin 43 (Cx43) expression, Cx43 gap junctions, and Cx43 hemichannels, and describes the regulatory mechanisms of astrocytes involved in synaptic plasticity. Additionally, we investigate the mechanisms acting of the glutamatergic, gamma-aminobutyric acidergic, and purinergic systems that modulate synaptic function and the antidepressant mechanisms of the related receptor antagonists. Further, we summarize the roles of glutamate, gamma-aminobutyric acid, d-serine, and adenosine triphosphate in depression, providing a basis for the identification of diagnostic and therapeutic targets for MDD.

New bithiophene derivative attenuated Alzheimer's disease induced by aluminum in a rat model via antioxidant activity and restoration of neuronal and synaptic transmission

BACKGROUND

One of the hypotheses that leads to an increased incidence of Alzheimer's disease (AD) is the accumulation of aluminum in the brain's frontal cortex. The present study aimed to evaluate the therapeutic role of a novel bithiophene derivative at two doses against AlCl3-induced AD in a rat model.

METHODOLOGY

Adult male rats were divided into six groups, 18 rats each. Group 1: naïve animals, group 2: animals received a daily oral administration of bithiophene dissolved in DMSO (1 mg/kg) for 30 days every other day, groups 3-6: animals received a daily oral administration of AlCl3 (100 mg/kg/day) for 45 consecutive days. Groups 4 and 5 received an oral administration of low or high dose of the bithiophene (0.5 or 1 mg/kg, respectively). Group 6; Animals were treated with a daily oral dose of memantine (20 mg/kg) for 30 consecutive days.

MAIN FINDINGS

Al disturbed the antioxidant milieu, elevated the lipid peroxidation, and depleted the antioxidants. It also disturbed the synaptic neurotransmission by elevating the activities of acetylcholine esterase and monoamine oxidase resulting in the depletion of dopamine and serotonin and accumulation of glutamate and norepinephrine. Al also deteriorated the expression of genes involved in apoptosis and the production of amyloid-β plaques as well as phosphorylation of tau. The new bithiophene at the low dose reversed most of the previous deleterious effects of aluminum in the cerebral cortex and was in many instances superior to the reference drug; memantine.

CONCLUSION

Taking together, the bithiophene modulated the AD etiology through antioxidant activity, prevention of neuronal and synaptic loss, and probably mitigating the formation of amyloid-β plaques and phosphorylation of tau.

Determination of Multiple Neurotransmitters through LC-MS/MS to Confirm the Therapeutic Effects of Althaea rosea Flower on TTX-Intoxicated Rats

Tetrodotoxin (TTX) inhibits neurotransmission in animals, and there is no specific antidote. In clinical practice in China, Althaea rosea (A. rosea flower) extract has been used to treat TTX poisoning. In this work, the efficacy of the ethyl acetate fraction extract of A. rosea flower in treating TTX poisoning in rats was investigated. A high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to determine nine neurotransmitters in rat brain tissue, including γ-aminobutyric acid (GABA), dopamine (DA), 5-hydroxytryptamine (5-HT), noradrenaline (NE), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), 5-hydroxyindole-3-acetic acid (5-HIAA), epinephrine (E), and tyramine (Tyn). The detoxifying effect of A. rosea flower was verified by comparing the changes in neurotransmitters' content in brain tissue before and after poisoning in rats. The assay was performed in multiple reaction monitoring mode. The quantification method was performed by plotting an internal-standard working curve with good linearity (R² > 0.9941) and sensitivity. Analyte recoveries were 94.04-107.53% (RSD < 4.21%). Results indicated that the levels of 5-HT, DA, E, and NE in the brains of TTX-intoxicated rats decreased, whereas the levels of GABA, Tyn, and 5-HIAA showed an opposite trend, and HVA and DOPAC were not detected. The levels of all seven neurotransmitters returned to normal after the gavage administration of ethyl acetate extract of A. rosea flower to prove that the ethyl acetate extract of A. rosea flower had a therapeutic effect on TTX poisoning. The work provided new ideas for studies on TTX detoxification.

Rapid and sensitive HPLC-MS/MS method for the quantification of dopamine, GABA, serotonin, glutamine and glutamate in rat brain regions after exposure to tobacco cigarettes

Tobacco smoking is a preventable main cause of fatal diseases. Accurate measurements of the effects it has on neurotransmitters are essential in developing new strategies for smoking cessation. Moreover, measurements of neurotransmitter levels can aid in developing drugs that counteract the effects of smoking. The aim of this study is to develop and validate a fast, simultaneous and sensitive method for measuring the levels of neurotransmitters in rat brain after the exposure of tobacco cigarettes. The selected neurotransmitters include dopamine, GABA, serotonin, glutamine and glutamate. The method is based on high-performance liquid chromatography-tandem mass spectrometry. Chromatographic separation was achieved within 3 min using a Zorbax SB C₁₈ column (3.0 × 100 mm, 1.8 μm particle size). The mobile phase consisted of HPLC-grade water and acetonitrile each containing 0.3% heptafluorobutyric acid and 0.5% formic acid at gradient conditions. The linear range was 0.015-0.07, 825-7,218, 140-520, 63.42-160.75 and 38.25 × 10³ to 110.35 × 10³  ng/ml for dopamine, GABA, serotonin, glutamine and glutamate, respectively. Inter- and intra-run accuracy were in the range 97.82-103.37% with a precision (CV%) of ≤0.90%. The results revealed that 4 weeks of cigarette exposure significantly increased neurotransmitter levels after exposure to tobacco cigarettes in various brain regions, including the hippocampus and the amygdala. This increase in neurotransmitters levels may in turn activate the nicotine dependence pathway.

The variation in the levels of 18 amino acids in the cortex and plasma of cerebral ischemia C57BL/6 mice

Emerging evidence suggests that amino acid (AA) neurotransmitters play important roles in the pathophysiological processes of cerebral ischemia. In this work, an HPLC with fluorescence detection (HPLC-FLR) method was developed for the simultaneous determination of 18 AAs in the cortex and plasma after cerebral ischemia in mice. The ischemia model was prepared by bilateral common carotid artery occlusion, and then the cortex and plasma of the sham, ischemia, and naringenin groups were collected. Based on the protein precipitation method, a simple and effective sample preparation method was developed. The treated sample contained minimal proteins and lipids. The analysis of the sample was performed by the proposed HPLC-FLR method in combination with o-phthalaldehyde. The results showed a statistically significant increase in excitatory AAs (aspartic acid and glutamic acid), inhibitory AAs (glycine and 4-aminobutyric acid), phenylalanine, citrulline, isoleucine, and leucine levels, and a decrease of glutathione and phenylalanine levels when compared with the sham group in the cortex. Besides, the administration of naringenin had significant effects on excitatory AAs, inhibitory AA (glycine), glutamine, tyrosine, phenylalanine, and leucine levels when compared with the sham group in the cortex. These findings could be utilized in studying and clarifying the mechanisms of ischemia.

Premna odorata extract as a protective agent on neurotoxic effect of aluminum: neurochemical, molecular, and histopathological alterations

Premna odorata Blanco (Lamiaceae) is an ethnomedicinal plant, where some reports claimed their anti-inflammatory, cytotoxic, and antituberculosis effects, without investigating its role on the brain. Therefore, forty mature male rats were equally divided into 4 groups; the 1st was kept as control. Rats in groups 2 and 4 were orally given P. odorata extract daily at a dose of 500 mg/kg B.W., while those in groups 3 and 4 were daily administrated aluminum chloride "AlCl₃" (70 mg/kg B.W.). The treatments extended for 30 successive days. At the end of the experimental period, brain samples were collected for biochemical assay of glutathione reductase (GSH), catalase, malondialdehyde (MDA), and acetylcholinesterase activity (AChE). Besides, monoamines (norepinephrine, dopamine, serotonin), amino acids (glutamine, serine, arginine, taurine and gamma-aminobutyric acid (GABA)), neurotransmitters, DNA damage, cyclooxygenase-2 (COX-2), and tumor necrosis factor (TNF)-α genes were estimated. Moreover, brain samples were obtained for histopathological investigation. Aluminum toxicity resulted in a decline of GSH concentration, elevation of MDA, and AChE activity. Except for GABA which exhibited a significant decrease, there was a marked increase in the measured amino acid and monoamine neurotransmitters. Also, an increase in mRNA expressions of TNF-α and COX-2 was detected. It was noticed that Premna odorata extract reduced the oxidative stress and counteracted the augmentations in AChE caused by AlCl₃. Marked improvements in most measured neurotransmitters with downregulation of pro-inflammatory gene expression were recorded in P. odorata + AlCl₃ group. Premna odorata restores the altered histopathological feature induced by AlCl₃. In conclusion, the present findings clarify that P. odorata extract could be important in improving and treatment of neurodegenerative disorders as it was able to reduce oxidative stress, DNA damage, biochemical alterations, and histopathological changes in rats exposed to AlCl₃ toxicity.

Simultaneous determination of five amino acid neurotransmitters in rat and porcine blood and brain by two-dimensional liquid chromatography

A method for the simultaneous determination of aspartic acid (Asp), glutamic acid (Glu), glycine (Gly), taurine (Tau) and gamma-aminobutyric acid (GABA) in animal blood and brain by two-dimensional liquid chromatography (2D-LC) combined with ultraviolet detection was established for the first time. First, the amino acid neurotransmitters (AANTs) were labeled on the corresponding fluorescent derivatives with 4-fluoro-7-nitrobenzofurazan (NBD-F), enriched on the extraction column and automatically transferred to the analytical column to achieve on-line extraction and complete separation of the target components. This method exhibited good selectivity, and the correlation coefficients for the analyte calibration curves of were > 0.99. The intra- and inter-day precisions were ≤ 16.03, and the accuracies were in the range of 70.59-116.20%. The system realizes the rapid detection and stability quantification of the five AANTs, which proves that the alternative dilution method is feasible. The results show that the system has high loading capacity, excellent resolution, and good peak shape and is not affected by other endogenous substances. Moreover, the developed method has been successfully applied to the analysis of biological samples in the blood and whole brain of rats and pigs. The content of AANTs in the hippocampus and cortex of rats was higher than that in those of pigs. This method is expected to provide applicability for the determination of AANTs in pharmacological, pharmaceutical and clinical research in nervous science.

Oxaloacetate reduces emotional symptoms in premenstrual syndrome (PMS): results of a placebo-controlled, cross-over clinical trial

Objective

Premenstrual syndrome (PMS) affects millions of women. While over-the-counter products have helped with the physical symptoms of PMS, emotional symptoms have been less well supported. The objective of this trial was to measure the effect of an oxaloacetate/vitamin C combination on the major emotional symptoms of PMS, including depression, anxiety, perceived stress, aggression, and suicidal ideation.

Methods

Forty-eight women experiencing PMS completed a baseline survey comprising the Beck's Depression Inventory, Cohen Perceived Stress Scale, Generalized Anxiety Disorder Test, and Buss-Perry Aggression Questionnaire. After baseline measurements, participants were randomly assigned to take either 2 capsules of 100 mg oxaloacetate/150 mg ascorbic acid, or 2 capsules of rice flour (placebo) for their entire menstrual cycle. At menstruation, the women completed the 4 surveys again. The women then switched capsules in a cross-over design and continued the study for an additional menstrual cycle. The final assessment was repeated at menstruation. Statistical analysis of the 4 surveys was performed to examine efficacy.

Results

Oxaloacetate/vitamin C supplementation during PMS significantly improved depression, perceived stress, anxiety, aggression, and suicidal ideation. The mean improvement in depression was 54.1%, 35.8% for perceived stress, 51.43% for generalized anxiety, and 17.8% for aggression. Suicidal ideation was reduced by 47.9%. All results were highly significant.

Conclusion

A combination of oxaloacetate and vitamin C supplementation helped to alleviate depression, anxiety, perceived stress, aggression, and suicidal ideation symptoms associated with PMS.

Trial Registration

ClinicalTrials.gov Identifier: NCT03509714.

Simultaneous determination of thirteen substances related to NAFLD in mouse brain tissue using 3-aminobutyric acid as internal standard by HPLC-FLD

Disorders of certain branched-chain amino acids may be associated with the occurrence and development of non-alcoholic fatty liver disease. Measurement of related branched-chain amino acid levels could provide a reference for the clinical and scientific research of the non-alcoholic fatty liver disease. An established HPLC-FLD method was used to quantify aspartic acid, glutamate, glutamine, glycine, taurine, tyrosine, 4-amino butanoic acid, tryptophan, methionine, valine, phenylalanine, isoleucine and leucine in mouse brain tissue. Brain tissue samples mixed with internal standard (3-aminobutyric acid) were processed, then derivatized with 2-O-phthaldialdehyde, and finally separated on an ODS2 column through gradient elution at a flow rate of 1.0 ml·min^-1 . The excitation and emission wavelengths were set at 340 and 455 nm, respectively. The mobile phase A was 100% methanol and the mobile phase B consisted of 30 mmol·L^-1 sodium acetate (pH 6.8). The injection volume was 20 μl and the single run time was 45 min. Several parameters, accuracy, precision, and stability, were verified and the results showed the established method had good sensitivity and resolution for all of the 13 compounds and internal standard in mouse brain.

Relationship Among Dietary Taurine Intake, Dietary Attitudes, Dietary Behaviors, and Life Stress by Depression in Korean Female College Students

This study was conducted to investigate the correlation between dietary taurine intake, nutrients intake, dietary attitudes, dietary behaviors, and life stress by depression in Korean female college students. Depression was measured by self-reported symptoms of depression on the CES-D (Center for Epidemiologic Studies Depression) scale. The subjects of this cross-sectional study included 56 female college students with depression (depression group, DG) and 122 female students without depression (control group, CG). Self-reported life stress score was determined using the life stress scale developed for Korean college students. Intakes of dietary taurine and nutrients were assessed using 3-day food records (2 weekdays and 1 weekend day) and evaluated using the computer aided nutrition program 4.0 version. Statistical analysis was performed using SPSS 24.0. We observed no significant difference in the average dietary taurine intake between DG (87.6 mg/day) and CG (92.3 mg/day). The average dietary intakes of vitamin A and calcium in DG were significantly lower as compared to CG (p < 0.05). The average total scores of dietary attitudes (p < 0.01) and dietary behaviors (p < 0.05) in DG were significantly lower as compared to CG. The average total life stress score (p < 0.001) and all stress categories were significantly higher in DG as compared to CG. No significant correlation was observed between the CES-D scale score and dietary taurine intake. However, there were significant negative correlations between the CES-D scale score and vitamin A, folic acid, vitamin C, and calcium intakes (p < 0.05), dietary attitudes, and dietary behaviors (p < 0.01). Scores of the CES-D scale and life stress showed a significantly positive correlation (p < 0.01). Therefore, continuous nutrition education and counseling for good dietary attitudes and behaviors are required. Future studies need to be undertaken to confirm the correlation between dietary taurine intake and depression by intervention with taurine.

Effects of chronic stress on intestinal amino acid pathways

Major depressive disorder (MDD) is a debilitating mental disorder with a high prevalence and severe impacts on quality of life. However, the pathophysiological mechanisms underlying MDD remain poorly understood. Here, we used high-performance liquid chromatography with ultraviolet detection-based targeted metabolomics to identify amino acid changes in the small intestine, in a rat model of chronic unpredictable mild stress (CUMS). Pearson's correlation analysis was conducted to investigate the correlations between amino acid changes and behavioral outcomes. Western blot analysis was employed to verify intestinal amino acid transport function. Moreover, we performed an integrated analysis of related differential amino acids in the hippocampus, peripheral blood mononuclear cells (PBMCs), urine and cerebellum identified in our previous studies using the CUMS rat model to further our understanding of amino acid metabolism in depression. Decreased concentrations of glutamine and glycine and upregulation of aspartic acid were found in CUMS model rats. These changes were significantly correlated with depressive-like behaviors. Western blot analysis revealed that CUMS rats exhibited a reduction in the expression levels of amino acid transporters ASCT2 and B⁰AT1, as well as an increase in LAT1 expression. Impaired transport of glycine and glutamine into the small intestine may contribute to a central deficiency. The current findings suggest that the glycine and glutamine uptake systems may be potential therapeutic targets for depression. The integrated analysis strategy used in the current study may provide new insight into the cellular and molecular mechanisms underlying the gut-brain axis, and help to elucidate the pathophysiological changes in central and peripheral systems in depression.

Xylazine Regulates the Release of Glycine and Aspartic Acid in Rat Brain

Introduction

Xylazine, a type of α₂-adrenoceptors, is a commonly used drug in veterinary medicine. Xylazine-induced changes in the content of amino acid neurotransmitters - glycine (Gly) and aspartic acid (Asp), in different brain regions and neurons were studied.

Material and Methods

Wistar rats were administered 50 mg/kg or 70 mg/kg of xylazine by intraperitoneal injection. In addition, in vitro experiments were conducted, in which neurons were treated with 15 μg/mL, 25 μg/mL, 35μg/mL, and 45 μg/mL of xylazine. Test methods were based on the enzyme-linked immunosorbent assays (ELISA).

Results

During anaesthesia, Asp levels in each brain area were significantly lower compared to the control group. Except for the cerebrum, levels of Gly in other brain areas were significantly increased during the anaesthesia period. In vitro, xylazine-related neuron secretion of Gly increased significantly compared to the control group at 60 min and 90 min. Moreover, xylazine caused a significant decrease in the levels of Asp secreted by neurons at 20 min, but gradually returned to the level of the control group.

Conclusion

The data showed that during anaesthesia the overall levels of Asp decreased and overall levels of Gly increased. In addition, the inhibitory effect of xylazine on Asp and the promotion of Gly were dose-dependent. Our data showed that different effects of xylazine on excitatory and inhibitory neurotransmitters provided a theoretical basis for the mechanism of xylazine activity in clinical anaesthesia.

Xylazine regulates the release of glycine and aspartic acid in rat brain

Introduction

Xylazine, a type of α2-adrenoceptors, is a commonly used drug in veterinary medicine. Xylazine-induced changes in the content of amino acid neurotransmitters – glycine (Gly) and aspartic acid (Asp), in different brain regions and neurons were studied.

Material and Methods

Wistar rats were administered 50 mg/kg or 70 mg/kg of xylazine by intraperitoneal injection. In addition, in vitro experiments were conducted, in which neurons were treated with 15 μg/mL, 25 μg/mL, 35μg/mL, and 45 μg/mL of xylazine. Test methods were based on the enzyme-linked immunosorbent assays (ELISA).

Results

During anaesthesia, Asp levels in each brain area were significantly lower compared to the control group. Except for the cerebrum, levels of Gly in other brain areas were significantly increased during the anaesthesia period. In vitro, xylazine-related neuron secretion of Gly increased significantly compared to the control group at 60 min and 90 min. Moreover, xylazine caused a significant decrease in the levels of Asp secreted by neurons at 20 min, but gradually returned to the level of the control group.

Conclusion

The data showed that during anaesthesia the overall levels of Asp decreased and overall levels of Gly increased. In addition, the inhibitory effect of xylazine on Asp and the promotion of Gly were dose-dependent. Our data showed that different effects of xylazine on excitatory and inhibitory neurotransmitters provided a theoretical basis for the mechanism of xylazine activity in clinical anaesthesia.