The decrease in maternal plasma total (free + albumin-bound) tryptophan (Trp) during the third pregnancy trimester is attributed to induction of indoleamine 2,3-dioxygenase (IDO). When measured, free [Trp] is increased because of albumin depletion and non-esterified fatty acid elevation. The Trp depletion concept in pregnancy is therefore not supported because of incorrect interpretation of changes in Trp disposition and also for not addressing mouse strain differences in Trp-related responses and potential inhibition of Trp transport by the IDO inhibitor 1-methyl tryptophan. Application of the Trp utilization concept in pregnancy offers several physiological advantages favoring fetal development and successful outcome, namely provision of Trp for fetal protein synthesis and growth, serotonin for signaling pathways, kynurenic acid for neuroprotection, quinolinic acid for NAD+ synthesis, and other kynurenines for suppression of T cell responses. An excessive increase in Trp availability could compromise pregnancy by undermining T cell suppression, e.g., in pre-eclampsia.
Animals ; Female ; Fetal Development ; Humans ; Indoleamine-Pyrrole 2,3,-Dioxygenase ; Kynurenic Acid ; Mice ; Plasma ; Pre-Eclampsia ; Pregnancy Trimester, Third ; Pregnancy* ; Quinolinic Acid ; Serotonin ; Tryptophan*

To explore the correlation between kynurenine (KYN) metabolites and postpartum depression (PPD), and to provide new possible explanation for the pathogenesis of postpartum depression (PPD).
 Methods: A total of 726 Chinese women, who received cesarean section, were enrolled in this study. PPD was diagnosed with an Edinburgh Postnatal Depression Scale (EPDS) score ≥13. Twenty-four women with PPD and 48 matched women without PPD were randomly selected. The perinatal serum concentrations of KYN, quinolinic acid (QUIN) and kynurenic acid (KYNA) were measured. Subsequently, the puerperants were compared for the differences in the serum concentrations of KYN, QUIN and KYNA at the end of term, day 1 and day 3 after cesarean section, respectively.
 Results: The incidence of PPD was 7.99%. Of clinical characteristics, pressure during pregnancy was significantly different between subjects with or without PPD (P<0.01). Patients with PPD showed significantly increased serum KYN concentration (P<0.05) at the end of term, increased serum QUIN concentration (P<0.05) and decreased KYNA concentration (P<0.05) on the third day after cesarean section as compared with the control women. Furthermore, the KYNA/QUIN ratio was significantly higher in patients with PPD as compared to the control women on the third day after cesarean section (P<0.01).
 Conclusion: The contribution of alterations in plasma levels of KYN, QUIN and KYNA is closely related with the incidence of PPD, and correction of KYNA/QUIN ratio could be a new strategy for the prevention and treatment of postpartum depressive symptoms.
Biomarkers ; blood ; Cesarean Section ; psychology ; China ; epidemiology ; Depression, Postpartum ; blood ; epidemiology ; Female ; Humans ; Incidence ; Kynurenic Acid ; blood ; Kynurenine ; blood ; Pregnancy ; Quinolinic Acid ; blood

Accumulating evidence has suggested the existence of reciprocal communication between immune, endocrine, and neurotransmitter system. Cytokine hypothesis of depression implies that increased pro-inflammatory cytokine such as -1, IL-6, IL-12, TNF-alpha, and IFN-gamma in major depression, acting neuromodulators, play a key role in the mediation of behavioral, neuroendocrine, and neurochemical disturbances in depression. Concerning the relation between cytokines and serotonin metabolism, pro-inflammatory cytokines have profound effects on the metabolism of brain serotonin through the enzyme indoleamine-2,3-dioxygenase(IDO) that metabolizes tryptophan, the precursor of 5-HT to neurodegenerative quinolinate and neuroprotective kynurenate. The neurodegeneration process is reinforced by the neurotoxic effect of the hypercortisolemia during depression. From this perspective, it is possible that efficacy of antidepressants in the treatment of depression may, at least in part, rely on downregulation of pro-inflammatory cytokine synthesis. So, the use of cytokine synthesis inhibitors or cytokine antagonists may be a new treatment approach in depression. However, at present the question whether cytokines play a causal role in the onset of depression or are mere epiphenomena sustaining depressive symptoms remains to be elucidated. Nevertheless, cytokine hypothesis has created new perspectives in the study of psychological and pathophysiological mechanism that are associated with major depression, as well as the prospect for developing a new generation antidepressants.
Antidepressive Agents ; Brain ; Cytokines ; Depression ; Down-Regulation ; Interleukin-12 ; Interleukin-6 ; Kynurenic Acid ; Negotiating ; Neurotransmitter Agents ; Psychoneuroimmunology ; Quinolinic Acid ; Serotonin ; Tryptophan ; Tumor Necrosis Factor-alpha

Stem cells provide an important means for regenerative medicine due to the capacity to generate multiple types of differentiated cells and at the same time to maintain self-renewal. To identify the therapeutic effect of the transplantation of neural stem cells, differentiation and migration capacity of the neural stem cells that were isolated from E14 rat embryo and maintained in culture were examined after transplantation to the striatum of the quinolinic acid (QA)-induced Huntington's disease rat model. in vitro co-culture of the neural stem cells with the mixture of primary neurons and astrocytes promoted the maturation and the synapse formation of neuronal progenies of neural stem cells. Following the implantation, the neural stem cells survived, differentiated, and migrated in the damaged striatum region, exhibiting immunoreactivities against nestin, Tuj-1, GFAP, GAD(67) and synapsin 1 to a varying degree. These data provide clear evidence supporting that the neural stem cells isolated from the rat embryo and maintained in the primary culture have a multiple capacity to differentiate into neurons or glial cells both in vitro and in vivo.
Animals ; Astrocytes ; Brain ; Coculture Techniques ; Embryonic Structures ; Huntington Disease ; Intermediate Filament Proteins ; Nerve Tissue Proteins ; Neural Stem Cells ; Neuroglia ; Neurons ; Quinolinic Acid ; Rats ; Regenerative Medicine ; Synapses ; Transplants

OBJECTIVETo investigate the neurotoxicity and its mechanism of quinolinic acid (QA) to spiral ganglion cells (SGC) and observe the protectable potential of MgCl(2) on SGC.

METHODSSGC were cultured in vitro for 72 h, and then were divided into 4 groups: control group, QA group (1 mmol/L QA), MK-801 group (1 mmol/L QA + 20 µmol/L MK-801)and MgCl(2) protected group (1 mmol/L QA + 1 mmol/L MgCl(2)). SGC apoptosis rate was analyzed by Annexin V staining and PI staining measurements after 24 h exposure to different medium. SGC cultured as methods above were divided into 4 groups as following: 100 µmol/L QA, 1 mmol/L QA, 20 µmol/L MK-801+1 mmol/L QA and 1 mmol/L MgCl(2) + 1 mmol/L QA. The intracellular calcium concentration was measured by laser scanning confocal microscope finally.

RESULTSApoptosis rate in QA group was higher than that in both of control group (59.1% ± 7.5% vs 9.2% ± 0.9%, x ± s, q = 11.9, P < 0.05) and MgCl(2) group (59.1% ± 7.5% vs 27.5% ± 8.3%, q = 7.5, P < 0.05). There was no significant difference between apoptosis rate of control and MK-801 group (12.8% ± 5.7% vs 9.2% ± 0.9%, q = 0.9, P > 0.05). It was shown that there was a significant increase of Ca(2+) in SGC in the presence of QA by laser scanning confocal microscope. MK-801 may completely block the increase of Ca(2+), and the increase of Ca(2+) can be reduce by the application of MgCl(2).

CONCLUSIONSQA might injure SGC by excessive activating NMDA receptors on the cell membrane. Mg(2+) may have the function to reduce the neurotoxicity of QA.

Animals ; Calcium ; analysis ; Cells, Cultured ; Magnesium Chloride ; pharmacology ; Neurotoxins ; toxicity ; Quinolinic Acid ; toxicity ; Rats ; Rats, Sprague-Dawley ; Spiral Ganglion ; cytology ; drug effects ; metabolism

The antidiabetic drug metformin has been found to have beneficial effects in various neurological disorders; however, the molecular mechanisms underlying these effects remain unclear. Here we report that metformin protects neuronal cells from quinolinic acid (QUIN)-induced excitotoxicity. For this, we pretreated N18D3 neuronal cells with metformin prior to QUIN for 24 h. We found that pretreating the cells with metformin significantly improved cell survival rate in a concentration-dependent manner and reduced apoptotic cell death, as revealed by a MTT assay and DAPI staining, respectively. Calcium imaging using fluo-4 showed that metformin (100 µM) inhibited the intracellular calcium increase that was induced by QUIN. In addition, mRNA expression of pro-apoptotic genes, p21 and Bax, was decreased and of anti-apoptotic genes, Bcl-2 and Bcl-xl, was increased with metformin treatment compared to QUIN-induced cells. The immunoreactivity of phosphorylated ERK1/2 was elevated in cells treated with metformin, indicating the ERK1/2 signaling pathway in the neuroprotective effects of metformin in QUIN-induced cell death. Collectively, our data demonstrates that metformin exerts its neuroprotective effects by inhibiting intracellular calcium increases, allowing it to regulate ERK1/2 signaling and modulate cell survival and death genes.
Apoptosis ; Calcium ; Cell Death ; Cell Survival ; Genes, bcl-2 ; Metformin ; Nervous System Diseases ; Neurons ; Neuroprotection ; Neuroprotective Agents ; Quinolinic Acid ; RNA, Messenger

A growing body of evidence suggests that major depression is associated with increased productions of pro-inflammatory cytokines such as IL-1, IL-6, IL-12 or TNF-alpha and increased concentrations of prostaglandin E2 and negative-regulatory cytokines such as IL-4 or IL-10. In major depression, interactions among brain 5-HT levels, the activity of its autoreceptors, and that of postsynaptic receptors play a critical role in mood changes and depression. Recently, the link between cytokines and serotonergic turnover has been explored. Cytokines such as IL-1, IL-2 and IFN-gamma reduce the production of 5-HT by stimulating the activity of indoleamine-2,3 dioxygenase (IDO), an enzyme which convert tryptophan, the precursor of 5-HT to kynurenine. The kynurenine is metabolized into quinolinic acid (quinolinate) and kynurenic acid (kynurenate), an excitotoxic NMDA receptor agonist and the antagonist of three ionotropic excitotatory aminoacid receptors, respectively. The cytokineserotonin interaction through IDO that leads to the challenge between quinolinate and kynurenate in the brain may finally induce the neurodegeneration in depression. The neurodegeneration hypothesis of depression can explain how people cope with psychological or physical stress at different stages according to severity and duration of stress and why major depression develops.
Autoreceptors ; Brain ; Cytokines ; Depression* ; Dinoprostone ; Interleukin-1 ; Interleukin-10 ; Interleukin-12 ; Interleukin-2 ; Interleukin-4 ; Interleukin-6 ; Kynurenic Acid ; Kynurenine ; N-Methylaspartate ; Neurogenesis ; Quinolinic Acid ; Serotonin ; Tryptophan ; Tumor Necrosis Factor-alpha

The present study was to investigate the role of the quinolinic acid (QUIN) and its relationship with N-methyl-D-aspartic acid (NMDA) receptor and metabotropic glutamate receptor 1 (mGluR1) in depression induced by chronic unpredictable mild stress (CUMS) in hippocampus. CUMS-induced depression model was established in Sprague-Dawley rats. Intrahippocampal injections of QUIN, QUIN antagonist Ro61-8048, non-competitive NMDA receptor antagonist MK-801 and mGluR1 antagonist AIDA were respectively adopted by rat brain stereotaxic coordinates. The behavioral observations were conducted by measurement of weight changes, sucrose preference test, open-field test and tail suspension test. The concentration of glutamic acid (Glu) and the expression of its receptor subunits in hippocampus were detected by HPLC and Western blot, respectively. The QUIN content in hippocampus was determined by enzyme linked immunosorbent assay (ELISA). The result showed that CUMS significantly induced the depressive-like behaviors in rats, increased the contents of QUIN and Glu, and upregulated the expression of NMDA receptor subunits NR2B and mGluR1 in hippocampus. Microinjection of QUIN into hippocampus resulted in animal depressive-like behaviors, and increased the content of Glu and the expression of NR2B and mGluR1 significantly. QUIN antagonist Ro61-8048 effectively restrained the depression-like behaviors induced by CUMS, and decreased the content of Glu and the expression of NR2B and mGluR1 significantly. Intrahippocampal injections of MK-801 and AIDA effectively improved the depression-like behaviors induced by CUMS and decreased the Glu content. The results suggest that CUMS may contribute to the production and release of QUIN in hippocampal microglia. QUIN results in elevation of Glu level via NMDA receptor and mGluR1, and the increase of expression of NR2B and mGluR1 in hippocampus, which leads to depression-like behaviors in the end.
Animals ; Behavior, Animal ; Depression ; drug therapy ; Dizocilpine Maleate ; pharmacology ; Glutamic Acid ; metabolism ; Hippocampus ; drug effects ; metabolism ; Quinolinic Acid ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Receptors, Metabotropic Glutamate ; metabolism ; Receptors, N-Methyl-D-Aspartate ; metabolism ; Stress, Psychological

OBJECTIVETo provide a useful biological index for clinical diagnosis of Alzheimer's disease (AD) by determination the functional changes in the central cholinergic nerve and their effects on the peripheral lymphatic system.

METHODSThe learning and memory impairment model was established through intraventricular injecting quinolinic acid (QA) repeatedly.

RESULTSThere was a significant decline of cholineacetyltransferase (ChAT) in cerebral cortex and hippocampus after QA injection. The significantly lower binding activities of acetylcholine muscarinic (M) and nicotinic (N) cholinergic receptors in the hippocampus and cortex in the QA group were found as compared with the sham-operated group (P < 0.01). Similar changes were found in the binding activities of M-and N-receptors on spleen lymphocytes.

CONCLUSIONCertain lesion of the central nervous system can be reflected in peripheral spleen lymphocytes, which may be an important reference to diagnose the changes of the central nervous system.

Alzheimer Disease ; etiology ; Animals ; Brain ; drug effects ; Choline O-Acetyltransferase ; metabolism ; Disease Models, Animal ; Learning ; drug effects ; Male ; Memory ; drug effects ; Nicotine ; metabolism ; Quinolinic Acid ; toxicity ; Quinuclidinyl Benzilate ; metabolism ; Rats ; Rats, Wistar ; Receptors, Cholinergic ; analysis ; drug effects

A double toxin-double lesion strategy is well-known to generate a rat model of striatonigral degeneration (SND) such as multiple system atrophy-parkinsonian type. However, with this model it is difficult to distinguish SND from Parkinson's disease (PD). In this study, we propose a new rat model of SND, which is generated by simultaneous injection of 6-hydroxydopamine into the medial forebrain bundle and quinolinic acid into the striatum. Stepping tests performed 30 min after intraperitoneal L-dopa administration at 6 weeks post-surgery revealed an L-dopa response in the PD group but not the SND group. Apomorphine-induced rotation tests revealed no rotational bias in the SND group, which persisted for 2 months, but contralateral rotations in the PD group. MicroPET scans revealed glucose hypometabolism and dopamine transporter impairment on the lesioned striatum in the SND group. Tyrosine hydroxylase immunostaining in the SND group revealed that 74.7% of nigral cells on the lesioned side were lost after lesion surgery. These results suggest that the proposed simultaneous double toxin-double lesion method successfully created a rat model of SND that had behavioral outcomes, multitracer microPET evaluation, and histological aspects consistent with SND pathology. This model will be useful for future study of SND.
Animals ; Apomorphine/pharmacology ; Behavior, Animal/drug effects ; Corpus Striatum/drug effects/pathology ; Disease Models, Animal ; Dopamine Plasma Membrane Transport Proteins/metabolism ; Glucose/metabolism ; Injections, Intraperitoneal ; Levodopa/pharmacology ; Male ; Medial Forebrain Bundle/drug effects/pathology ; Oxidopamine/*toxicity ; Parkinson Disease/metabolism/pathology ; Positron-Emission Tomography ; Quinolinic Acid/*toxicity ; Rats ; Rats, Wistar ; Striatonigral Degeneration/*chemically induced/metabolism/pathology ; Touch/drug effects