Increased number of monocytes and plasma levels of MCP-1 and YKL-40 in first-episode psychosis.

OBJECTIVE: Accumulating evidence implicates immune activation in the development of schizophrenia. Here, monocyte numbers, monocyte chemoattractant protein-1 (MCP-1) and chitinase-3-like protein 1 (YKL-40) were investigated in plasma and cerebrospinal fluid (CSF) in first-episode psychosis (FEP) patients. METHOD: CSF and blood were sampled from 42 first-episode psychosis (FEP) patients and 22 healthy controls. The levels of YKL-40 and MCP-1 were measured using electrochemiluminescence assay, and blood monocytes were counted using an XN-9000-hematology analyzer. RESULTS: We found higher plasma levels of MCP-1 and YKL-40 in FEP patients compared with healthy controls, a condition that was unrelated to antipsychotic and/or anxiolytic medication. This was combined with an increased number of blood monocytes and a borderline significant increase in YKL-40 levels in the CSF of tobacco-free FEP patients. Plasma or CSF chemokines or blood monocytes did not correlate with the severity of symptoms or the level of functioning. CONCLUSION: These data demonstrate activation of monocytes in FEP and strengthens the idea of an immune dysfunction of psychotic disorders. Further studies are required to perceive a role of YKL-40 and MCP-1 in the initiation and progression of schizophrenia.

CSF GABA is reduced in first-episode psychosis and associates to symptom severity.

Schizophrenia is characterized by a multiplicity of symptoms arising from almost all domains of mental function. γ-Aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the brain and is increasingly recognized to have a significant role in the pathophysiology of the disorder. In the present study, cerebrospinal fluid (CSF) concentrations of GABA were analyzed in 41 first-episode psychosis (FEP) patients and 21 age- and sex-matched healthy volunteers by high-performance liquid chromatography. We found lower CSF GABA concentration in FEP patients compared with that in the healthy volunteers, a condition that was unrelated to antipsychotic and/or anxiolytic medication. Moreover, lower CSF GABA levels were associated with total and general score of Positive and Negative Syndrome Scale, illness severity and probably with a poor performance in a test of attention. This study offers clinical in vivo evidence for a potential role of GABA in early-stage schizophrenia.

LPS-induced cortical kynurenic acid and neurogranin-NFAT signaling is associated with deficits in stimulus processing during Pavlovian conditioning.

The N-Methyl-d-Aspartate receptor (NMDAR) antagonist kynurenic acid (KYNA) and the post-synaptic calmodulin binding protein neurogranin (Nrgn) have been implicated in neurological and neuropsychiatric conditions including Alzheimer's disease and schizophrenia. This study indicates that systemic dual-lipopolysaccharide (LPS) injections increases KYNA in the medial prefrontal cortex (mPFC), which is accompanied with increased phosphorylation of nuclear factor kappa chain of activated B cells (NFκB) and activation of the nuclear factor of activated T- cells (NFAT). Our results also indicate that dual-LPS increases Nrgn phosphorylation and concomitantly reduces phosphorylation of calmodulin kinase-II (CaMKII). We confirmed that systemic blockade of kynurenine-3 monooxygenase in conjunction with kynurenine administration results in significant increases in Nrgn phosphorylation and a significant reduction of CaMKII phosphorylation in the mPFC. Consequently, dual-LPS administration induced significant impairments in stimulus processing during Pavlovian conditioning. Taken together, our study indicates that elevations in KYNA in the mPFC can directly regulate NMDA-Nrgn-CaMKII signaling, suggesting that neuroinflammatory conditions affecting this pathway may be associated with cognitive dysfunction.

Maternal and fetal risk factors for bladder exstrophy: A nationwide Swedish case-control study.

INTRODUCTION: Bladder exstrophy is a rare, congenital, complex malformation where the underlying cause is largely unknown. Both environmental and genetic mechanisms are thought to be involved. There are divergent results concerning the prevalence, birth descriptive data, and potential maternal risk factors for bladder exstrophy. Few previous studies have reflected nationwide populations, population registers, or spanned a longer period of time. OBJECTIVE: To describe and assess bladder exstrophy and the potential maternal risk factors, for a time period of four decades, by conducting a nationwide register study of bladder exstrophy in Sweden. METHODS: A matched-design, case-control, linkage-analysis study nested within the entire pool of live births in Sweden between 1973 and 2011 was performed. Cases with bladder exstrophy were identified using nationwide population-based birth and health registers. Inclusion criteria were people born in Sweden with the classification of bladder exstrophy according to the ICD coding system. Cases were matched with five controls per patient, based on birth year and sex. Prevalence was assessed and birth descriptive data were compiled. Potential maternal risk factors were obtained from medical birth registers of cases and assessed using conditional and multivariate logistic regression models to obtain odds ratios as a measure of the relative risk. Classification of the diagnosis in the registers constituted a possible limitation for determining the correct study population, which demanded strict validation and inclusion criteria. All data were collected prospectively, thereby avoiding potential recall bias. RESULTS: The prevalence was calculated to be approximately 3 per 100,000 live births, with a male-to-female ratio of 1.14:1. In 92.5% of the cases, bladder exstrophy was an isolated malformation without associated major malformations. However, 41% had had surgery for congenital inguinal hernia and 11% of the male subjects had been operated on for cryptorchidism. A significantly higher proportion of cases had a birth weight <1500 g compared with controls, but other characteristics were comparable with controls. High maternal age was the only significant potential associated maternal risk factor. CONCLUSIONS: One hundred and twenty children born with bladder exstrophy in Sweden during the last four decades were identified; this resulted in prevalence in Sweden of 3 per 100,000. The prevalence was stable over time and the sex ratio was equal. Birth characteristics were comparable to controls, and bladder exstrophy generally occurred as an isolated malformation without major associated malformations. Advanced maternal age was the only significant potential maternal risk factor.

Repeated LPS Injection Induces Distinct Changes in the Kynurenine Pathway in Mice.

The immune system has been recognized as a potential contributor to psychiatric disorders. In animals, lipopolysaccharide (LPS) is used to induce inflammation and behaviors analogous to some of the symptoms in these disorders. Recent data indicate that the kynurenine pathway contributes to LPS-induced aberrant behaviors. However, data are inconclusive regarding optimal LPS dose and treatment strategy. Here, we therefore aimed to evaluate the effects of single versus repeated administration of LPS on the kynurenine pathway. Adult C57BL6 mice were given 0.83 mg/kg LPS as a single or a repeated injection (LPS + LPS) and sacrificed after 24, 48, 72, or 120 h. Mice receiving LPS + LPS had significantly elevated brain kynurenine levels at 24 and 48 h, and elevated serum kynurenine at 24, 48 and 72 h. Brain kynurenic acid and quinolinic acid were significantly increased at 24 and 48 h in mice receiving LPS + LPS, whereas serum kynurenic acid levels were significantly decreased at 24 h. The increase of brain kynurenic acid by LPS + LPS was likely unrelated to the higher total dose as a separate group of mice receiving 1.66 mg/kg LPS as single injection 24 h prior to sacrifice did not show increased brain kynurenic acid. Serum quinolinic acid levels were not affected by LPS + LPS compared to vehicle. Animals given repeated injections of LPS showed a more robust induction of the kynurenine pathway in contrast to animals receiving a single injection. These results may be valuable in light of data showing the importance of the kynurenine pathway in psychiatric disorders.

A genome-wide association study of kynurenic acid in cerebrospinal fluid: implications for psychosis and cognitive impairment in bipolar disorder.

Elevated cerebrospinal fluid (CSF) levels of the glia-derived N-methyl-D-aspartic acid receptor antagonist kynurenic acid (KYNA) have consistently been implicated in schizophrenia and bipolar disorder. Here, we conducted a genome-wide association study based on CSF KYNA in bipolar disorder and found support for an association with a common variant within 1p21.3. After replication in an independent cohort, we linked this genetic variant-associated with reduced SNX7 expression-to positive psychotic symptoms and executive function deficits in bipolar disorder. A series of post-mortem brain tissue and in vitro experiments suggested SNX7 downregulation to result in a caspase-8-driven activation of interleukin-1ß and a subsequent induction of the brain kynurenine pathway. The current study demonstrates the potential of using biomarkers in genetic studies of psychiatric disorders, and may help to identify novel drug targets in bipolar disorder.

The KMO allele encoding Arg452 is associated with psychotic features in bipolar disorder type 1, and with increased CSF KYNA level and reduced KMO expression.

The kynurenine pathway metabolite kynurenic acid (KYNA), modulating glutamatergic and cholinergic neurotransmission, is increased in cerebrospinal fluid (CSF) of patients with schizophrenia or bipolar disorder type 1 with psychotic features. KYNA production is critically dependent on kynurenine 3-monooxygenase (KMO). KMO mRNA levels and activity in prefrontal cortex (PFC) are reduced in schizophrenia. We hypothesized that KMO expression in PFC would be reduced in bipolar disorder with psychotic features and that a functional genetic variant of KMO would associate with this disease, CSF KYNA level and KMO expression. KMO mRNA levels were reduced in PFC of bipolar disorder patients with lifetime psychotic features (P=0.005, n=19) or schizophrenia (P=0.02, n=36) compared with nonpsychotic patients and controls. KMO genetic association to psychotic features in bipolar disorder type 1 was studied in 493 patients and 1044 controls from Sweden. The KMO Arg(452) allele was associated with psychotic features during manic episodes (P=0.003). KMO Arg(452) was studied for association to CSF KYNA levels in an independent sample of 55 Swedish patients, and to KMO expression in 717 lymphoblastoid cell lines and 138 hippocampal biopsies. KMO Arg(452) associated with increased levels of CSF KYNA (P=0.03) and reduced lymphoblastoid and hippocampal KMO expression (P≤0.05). Thus, findings from five independent cohorts suggest that genetic variation in KMO influences the risk for psychotic features in mania of bipolar disorder patients. This provides a possible mechanism for the previous findings of elevated CSF KYNA levels in those bipolar patients with lifetime psychotic features and positive association between KYNA levels and number of manic episodes.

Elevated levels of kynurenic acid in the cerebrospinal fluid of male patients with schizophrenia.

Previous studies have shown that endogenous brain levels of kynurenic acid (KYNA), a glutamate receptor antagonist, are elevated in patients with schizophrenia. Here we analyse KYNA in the cerebrospinal fluid (CSF) from a large cohort, including male healthy controls (n=49) and male patients with schizophrenia (n=90). We found that male patients with schizophrenia had significantly higher levels of CSF KYNA compared to healthy male controls (1.45 nM+/-0.10 vs. 1.06 nM+/-0.06 in the control group). Furthermore, when the patients with schizophrenia were divided into subgroups we found that CSF KYNA levels were significantly elevated in drug-naïve, first episode patients (1.53 nM+/-0.19, n=37) and in patients undergoing treatment with antipsychotic drugs (1.53 nM+/-0.17, n=34) compared to healthy male controls. No elevated CSF KYNA levels were detected in drug-free patients with schizophrenia, i.e. patients previously undergoing antipsychotic medications but drug-free at time of sampling (1.16 nM+/-0.10, n=19). Present results confirm that CSF KYNA concentration is elevated in patients with schizophrenia and are consistent with the hypothesis that KYNA contributes to the pathophysiology of the disease.

Prostaglandin-mediated control of rat brain kynurenic acid synthesis--opposite actions by COX-1 and COX-2 isoforms.

Kynurenic acid (KYNA), an endogenous glutamate-receptor antagonist preferentially blocking NMDA-receptors, has analgesic properties and has also been implicated in the pathophysiology of schizophrenia. Recently, the non-steroid anti-inflammatory drug (NSAID) diclofenac was found to increase rat brain KYNA. Here, we analyze whether cyclooxygenase (COX)-1 or COX-2 modulate the levels of rat brain KYNA. The non-selective COX-inhibitor diclofenac (50 mg/kg, i.p.) or indomethacin (50 mg/kg, i.p.), a non-selective inhibitor with a preferential selectivity for COX-1, produced an elevation in brain KYNA. In contrast, the COX-2 selective inhibitors parecoxib (25 mg/kg, i.p.) or meloxicam (5 mg/kg, i.p.) decreased brain KYNA. Both elevation and lowering of brain KYNA by indomethacin or parecoxib, respectively, were prevented by the prostaglandin E1/E2 agonist misoprostol (1 mg/kg, s.c.). It is proposed that increased brain KYNA formation induced by NSAIDs displaying an inhibitory action on COX-1 contribute to their analgesic efficacy as well as to their psychiatric side effects.

The anaesthetic agent propofol interacts with GABA(B)-receptors: an electrophysiological study in rat.

The mode of action by which propofol induces anaesthesia is not fully understood, although several studies suggest that the compound acts via potentiation of brain GABA(A)-receptors. The aim of the present study is to investigate a putative GABA(B)-receptor agonistic action of propofol. For this purpose the action of propofol on a GABA-receptor mediated regulation of dopamine neurons was analyzed with extracellular single unit recordings of dopaminergic neurons of the substantia nigra in chloral hydrate anaesthetized rats. Intravenous administration of propofol (1-16 mg/kg) was found to dose-dependently decrease the firing rate and burst firing activity of nigral DA neurons. These effects by propofol were effectively antagonized by pretreatment with the selective GABA(B)-receptor antagonist CGP 35348 (200 mg/kg, i.v.) but not by pretreatment with the GABA(A)-receptor antagonist picrotoxin (4.5 mg/kg, i.v.). It is proposed that an activation of central GABA(B)-receptors may, at least partially, contribute to the anesthetic properties of propofol.

Increased phasic activity of dopaminergic neurones in the rat ventral tegmental area following pharmacologically elevated levels of endogenous kynurenic acid.

Kynurenic acid (KYNA) is an antagonist of ionotropic glutamate receptors, preferentially blocking the glycine-site of the N-methyl-D-aspartate (NMDA) receptor. In the present electrophysiological study, the firing pattern of dopamine (DA) neurones of rat ventral tegmental area (VTA) was investigated following pharmacologically elevated endogenous levels of KYNA by means of an inhibitor of kynurenine 3-hydroxylase (PNU 156561A). Pre-treatment with PNU 156561A (40 mg kg-1, i.v., 5-9 h) caused a threefold increase in endogenous KYNA in whole brain levels and also evoked a significant increase in firing rate and bursting activity of VTA DA neurones. Administration of D-cycloserine (2-128 mg kg-1, i.v.), a partial agonist at the glycine-site of the NMDA-receptor, was found to reverse the increase in firing rate and bursting activity as induced by elevated concentrations of KYNA. The electrophysiological effects of elevated KYNA levels were in all essential mimicked by administration of the NMDA-receptor antagonist MK 801 (0.05-1.6 mg kg-1, i.v.). Thus, the effects of elevated endogenous brain KYNA observed in the present study are likely to be carried out by NMDA receptor antagonism. In conclusion, this study shows that an increase in endogenous KYNA levels produces significant actions on the tonic afferent control of the firing pattern of VTA DA neurones. Given the psychotomimetic effects of NMDA-receptor antagonists, e.g. phencyclidine and ketamine, the state of hyperactivity of mesocorticolimbic DA system induced by elevated levels of KYNA may represent a pathophysiological condition analogous to that seen in schizophrenic patients.

Kynurenic acid levels are elevated in the cerebrospinal fluid of patients with schizophrenia.

Kynurenic acid is an endogenous glutamate antagonist with a preferential action at the glycine-site of the N-methyl D-aspartate-receptor. Mounting evidence indicate that the compound is significantly involved in basal neurophysiological processes in the brain. In the present investigation, cerebrospinal fluid (CSF) level of kynurenic acid was analyzed in 28 male schizophrenic patients and 17 male healthy controls by means of high pressure liquid chromatography and fluorescence detection. Schizophrenic patients showed elevated CSF levels of kynurenic acid (1.67+/-0.27 nM) compared to the control group (0.97+/-0.07 nM). Furthermore, CSF levels of kynurenic acid in schizophrenic patients were also found to correlate with age. The present finding is indicative of a contribution of kynurenic acid in the pathogenesis of schizophrenia.

Pharmacological elevation of endogenous kynurenic acid levels activates nigral dopamine neurons.

Inhibitors of kynurenine 3-hydroxylase have previously been used to increase endogenous levels of kynurenic acid, an excitatory amino acid receptor antagonist. In the present electrophysiological study PNU 156561A was utilized to elevate endogenous concentrations of kynurenic acid and subsequent effects on the firing pattern of dopamine (DA) neurons of rat substantia nigra (SN) were analyzed. Pretreatment with PNU 156561A (40 mg/kg, i.v., 5-7 h) caused a five-fold increase in endogenous kynurenic acid levels in whole brain five to seven hours after administration and also evoked a significant increase in firing rate and bursting activity of nigral DA neurons. The results of the present study show that a moderate increase in endogenous kynurenic acid levels produces significant actions on the tonic glutamatergic control of the firing pattern of nigral DA neurons, and implicate kynurenine 3-hydroxylase inhibitors as novel antiparkinsonian agents.

Inhibition of cytochrome P450 2E1 induces an increase in extracellular dopamine in rat substantia nigra: a new metabolic pathway?

We presented data previously on dopamine (DA) synthesis and catabolism in the rat substantia nigra (SN) suggesting that a substantial part of the synthesized DA in this brain part is metabolized by unknown nonclassical metabolic pathways. On the basis of that a relatively high density of cytochrome P450 2E1 (CYP 2E1) has been detected in rat SN the aim of the present study was to investigate the possibility that this enzyme is involved in the metabolism of DA. Systemic administration of either phenylethyl isothiocyanate (100 mg/kg ip), diethyldithiocarbamate (500 mg/kg, ip) or diallyl sulfide (200 mg/kg, sc or ip), three different inhibitors of cytochrome P450 2E1, induced an increase of the extracellular DA concentration in the SN, measured with microdialysis in awake rats, by 130%, 90%, and 35%, respectively. A tendency to increased concentrations of the classical DA metabolites in the dialysate from the SN was also observed in some experiments. In the striatum, no profound effects were induced by the drugs on the concentrations of DA or its metabolites. The results show that CYP 2E1 activity affects dopaminergic neurotransmission in the SN, possibly by participating in DA metabolism. Other mechanisms, such as the influence on the DA transporter or the release process cannot, however, be ruled out.

Pharmacologically elevated levels of endogenous kynurenic acid prevent nicotine-induced activation of nigral dopamine neurons.

Previous studies have shown that systemically administered nicotine is associated with an activation of rat midbrain dopamine neurons. The aim of the present electrophysiological study was to investigate if manipulation of brain kynurenic acid, an endogenous excitatory amino acid receptor antagonist, can affect the response of nigral dopamine neurons to nicotine. A potent inhibitor of kynurenine 3-hydroxylase, PNU 156561A (40 mg/kg, i.v., 4-7 h), was utilized to increase the levels of kynurenic acid in rat brain. This treatment, which caused a fourfold increase in brain kynurenic acid levels, abolished the increase in firing rate and burst activity of nigral dopamine neurons as induced by nicotine (25-400 microg/kg, i.v.). It is proposed that the excitation of dopamine neurons in the substantia nigra following nicotine administration is an indirect effect, mediated by glutamate release. In addition, our data highlight the role of brain kynurenic acid as a potentially important modulator of basic glutamatergic responses in brain.

Excitation of nigral dopamine neurons by the GABA(A) receptor agonist muscimol is mediated via release of glutamate.

Previous electrophysiological studies have shown that the GABA(A)-receptor agonist muscimol is able to markedly increase the firing rate of rat nigral dopamine (DA) neurons. This action of the drug is paradoxical since local microiontophoretic application of the drug is associated with a clearcut inhibition of this neurons. In the present electrophysiological study, an attempt was made to analyze the mechanism of this action of the drug. Administration of muscimol (0.25-4.0 mg/kg, i.v.) was associated with a dose-dependent increase in firing rate as well as an increased bursting activity of the nigral DA neurons. Both these effects of muscimol were clearly antagonised by intravenous administration of the NMDA receptor antagonist MK 801(1 mg/kg) or by intracerebroventricular administration of the broad-spectrum excitatory amino acid receptor antagonist kynurenic acid. Furthermore, pretreatment with PNU 156561A (40 mg/kg, i.v., 5-8h), a compound that raised endogenous kynurenic acid levels about 9 times, also clearly antagonised the actions of muscimol. Indeed, this treatment reversed the excitatory action of muscimol into an inhibitory effect on the nigral DA neurons. Here, we report that the excitatory action of muscimol is mediated indirectly by release of glutamate.

Nicotine inhibits firing activity of dorsal raphe 5-HT neurones in vivo.

It is established that the brain monoaminergic systems are among the main targets of several dependence-inducing drugs, including nicotine. In the present study extracellular electrophysiological recordings were performed to investigate the effects of nicotine on dorsal raphe 5-HT neurones. Nicotine, administered systemically (50-400 microg/kg, i.v.) in chloral hydrate-anaesthetised rats, induced a transient inhibition of the majority of 5-HT neurones recorded (38 of 45). The inhibition was rapid in onset (about 30 s) and the firing rate returned to baseline within 1-3 min. No apparent tachyphylaxis was observed to this inhibitory effect. The centrally acting nicotine antagonist mecamylamine (4 mg/kg, i.v.), but not the peripherally acting nicotine antagonist chlorisondamine (0.3 mg/kg, i.v.) antagonised the nicotine-induced inhibition of 5-HT neurones. The inhibition of 5-HT neurones was also blocked with a selective 5-HT1A receptor antagonist (WAY 100635; 0.1 mg/kg, i.v.), indicating a possible involvement of somato-dendritic 5-HT1A receptors in the effect of nicotine. Interestingly, microiontophoretic application of nicotine into the dorsal raphe failed to inhibit 5-HT neurones, suggesting an indirect effect of nicotine on 5-HT neurones, possibly involving afferent pathways.

Nicotine-induced excitation of locus coeruleus neurons is blocked by elevated levels of endogenous kynurenic acid.

The present electrophysiological study shows that manipulation with endogenous brain kynurenic acid (KYNA) is able to affect the response of central noradrenergic neurons to nicotine. Previous studies have shown that systemically administered nicotine in low doses is associated with a marked, but short-lasting increase in the firing rate of rat noradrenergic neurons in the locus coeruleus (LC). This action of nicotine is of peripheral origin and finally mediated via a release of glutamate within the LC. KYNA is an endogenous glutamate receptor antagonist, which shows an uneven distribution in human brain. Previous studies have shown that a potent inhibitor of kynurenine 3-hydroxylase, PNU 156561A, is able to dose-dependently increase the levels of KYNA in brain. Anesthetized rats were given PNU 156561A in a dose that caused a 5-fold increase in brain KYNA levels after 3-6 hours (40 mg/kg, i.v. ). This treatment was found to abolish the increase in firing rate of LC neurons induced by nicotine (25-200 microg/kg, i.v.). The results of the present study show that an increased concentration of endogenous brain KYNA is able to inhibit the activation of central noradrenergic neurons by nicotine. In addition, our results highlight the role of endogenous KYNA in brain as a potentially important modulator of brain glutamatergic responses.