Cell-type specific modulation of NMDA receptors triggers antidepressant actions.

Both the NMDA receptor (NMDAR) positive allosteric modulator (PAM), and antagonist, can exert rapid antidepressant effects as shown in several animal and human studies. However, how this bidirectional modulation of NMDARs causes similar antidepressant effects remains unknown. Notably, the initial cellular trigger, specific cell-type(s), and subunit(s) of NMDARs mediating the antidepressant-like effects of a PAM or an antagonist have not been identified. Here, we used electrophysiology, microdialysis, and NMR spectroscopy to evaluate the effect of a NMDAR PAM (rapastinel) or NMDAR antagonist, ketamine on NMDAR function and disinhibition-mediated glutamate release. Further, we used cell-type specific knockdown (KD), pharmacological, and behavioral approaches to dissect the cell-type specific role of GluN2B, GluN2A, and dopamine receptor subunits in the actions of NMDAR PAM vs. antagonists. We demonstrate that rapastinel directly enhances NMDAR activity on principal glutamatergic neurons in medial prefrontal cortex (mPFC) without any effect on glutamate efflux, while ketamine blocks NMDAR on GABA interneurons to cause glutamate efflux and indirect activation of excitatory synapses. Behavioral studies using cell-type-specific KD in mPFC demonstrate that NMDAR-GluN2B KD on Camk2a- but not Gad1-expressing neurons blocks the antidepressant effects of rapastinel. In contrast, GluN2B KD on Gad1- but not Camk2a-expressing neurons blocks the actions of ketamine. The results also demonstrate that Drd1-expressing pyramidal neurons in mPFC mediate the rapid antidepressant actions of ketamine and rapastinel. Together, these results demonstrate unique initial cellular triggers as well as converging effects on Drd1-pyramidal cell signaling that underlie the antidepressant actions of NMDAR-positive modulation vs. NMDAR blockade.

Neurobiology of rapid-acting antidepressants: convergent effects on GluA1-synaptic function.

Efforts to develop efficacious antidepressant agents with novel mechanisms have been largely unsuccessful since the 1950's until the discovery of ketamine, an N-methyl-D-aspartate (NMDA) receptor antagonist that produces rapid and sustained antidepressant actions even in treatment-resistant patients. This finding has ushered in a new era for the development of novel rapid-acting antidepressants that act at the NMDA receptor complex, but without dissociative and psychotomimetic side effects of ketamine. Here, we review the current state of rapid-acting antidepressant drug development, including NMDA channel blockers, glycine site agents, and allosteric modulators, as well as ketamine stereoisomers and metabolites. In addition, we focus on the neurobiological mechanisms underlying the actions of these diverse agents and discuss evidence of convergent mechanisms including increased brain-derived neurotrophic factor signaling, increased synthesis of synaptic proteins, and most notably increased GluR1 and synaptic connectivity in the medial prefrontal cortex. These convergent mechanisms provide insight for potential additional novel targets for drug development (e.g., agents that increase synaptic protein synthesis and plasticity). Importantly, the convergent effects on synapse formation and plasticity also reverse the well-documented neuronal and synaptic deficits associated with stress and depression, and thereby target the underlying pathophysiology of major depressive disorder.

Uptake and Tissue Distribution of Pharmaceuticals and Personal Care Products in Wild Fish from Treated-Wastewater-Impacted Streams.

A fish plasma model (FPM) has been proposed as a screening technique to prioritize potential hazardous pharmaceuticals to wild fish. However, this approach does not account for inter- or intraspecies variability of pharmacokinetic and pharmacodynamic parameters. The present study elucidated the uptake potency (from ambient water), tissue distribution, and biological risk of 20 pharmaceutical and personal care product (PPCP) residues in wild cyprinoid fish inhabiting treated-wastewater-impacted streams. In order to clarify the uncertainty of the FPM for PPCPs, we compared the plasma bioaccumulation factor in the field (BAFplasma = measured fish plasma/ambient water concentration ratio) with the predicted plasma bioconcentration factor (BCFplasma = fish plasma predicted by use of theoretical partition coefficients/ambient water concentration ratio) in the actual environment. As a result, the measured maximum BAFplasma of inflammatory agents was up to 17 times higher than theoretical BCFplasma values, leading to possible underestimation of toxicological risk on wild fish. When the tissue-blood partition coefficients (tissue/blood concentration ratios) of PPCPs were estimated, higher transportability into tissues, especially the brain, was found for psychotropic agents, but brain/plasma ratios widely varied among individual fish (up to 28-fold). In the present study, we provide a valuable data set on the intraspecies variability of PPCP pharmacokinetics, and our results emphasize the importance of determining PPCP concentrations in possible target organs as well as in the blood to assess the risk of PPCPs on wild fish.

Seasonal and diurnal variation of organic ultraviolet filters from personal care products used along the Japanese coast.

This study aimed to investigate the behavior of organic ultraviolet (UV) filters released by recreational activities along the Japanese coastline. Seasonal variations of organic UV filters in seawater were investigated at four different recreational beaches (Mogushi, Wakamiya, Tsurugahama, and Otachimisaki beaches) in both summer (July through August) and winter (December). Moreover, short time scale diurnal changes were monitored at Otachimisaki beach in summer. Of the four sunscreen agents tested in this study, two agents-2-ethylhexyl-4-methoxycinnamate (EHMC) and 2-ethylhexyl salicylate (EHS)-were detected in all samples, whereas octyl-dimethyl-p-aminobenzonic acid and 3-(4-methylbenzylidene)-camphor were lower than detection limits. In particular, EHMC, one of the most popular organic UV filters, was dominant. The highest concentration of EHMC was observed at 1,080 ng L(-1), a level that exceeds those of previous studies. Both EHMC and EHS concentrations showed significant (p < 0.05) seasonal variations with advancing summer suggesting direct input from recreational activities. The subsequent examination showed short time scale diurnal changes of organic UV filters on the beach. The results showed that diurnal changes in EHMC concentrations were correlated to the number of bathers. EHMC concentrations increased during the afternoon and decreased during the night, although complete attenuation during the night did not occur. EHMC persists along the coast due to low mobility and may persist the next day. This is the first study to show the natural attenuation behavior of organic UV filters along recreational beaches.

EphA4-dependent axon retraction and midline localization of Ephrin-B3 are disrupted in the spinal cord of mice lacking mDia1 and mDia3 in combination.

mDia is an actin nucleator and polymerization factor regulated by the small GTPase Rho and consists of three isoforms. Here, we found that mice lacking mDia1 and mDia3, two isoforms expressed in the brain, in combination (mDia-DKO mice) show impaired left-right limb coordination during locomotion and aberrant midline crossing of axons of corticospinal neurons and spinal cord interneurons. Given that mice lacking Ephrin-B3-EphA4 signaling show a similar impairment in locomotion, we examined whether mDia is involved in Ephrin-B3-EphA4 signaling for axon repulsion. In primary cultured neurons, mDia deficiency impairs growth cone collapse and axon retraction induced by chemo-repellants including EphA ligands. In mDia-DKO mice, the Ephrin-B3-expressing midline structure in the spinal cord is disrupted, and axons aberrantly cross the spinal cord midline preferentially through the region devoid of Ephrin-B3. Therefore, mDia plays multiple roles in the proper formation of the neural network in vivo.

Occurrence and source of chlorinated polycyclic aromatic hydrocarbons (Cl-PAHs) in tidal flats of the Ariake Bay, Japan.

In this study, we hypothesize that natural photochemical reactions of polycyclic aromatic hydrocarbons (PAHs) in tidal flats are responsible for the occurrence of chlorinated polycyclic aromatic hydrocarbons (Cl-PAHs). This study aims to survey the impact of photochemical reactions using a combination of field surveys and lab-scale experiments. Concentrations and profiles of PAHs and Cl-PAHs in road dust and sediments collected from seven tunnels and two watersheds, respectively, were determined. In the lab-scale experiments, anthracene was irradiated with ultraviolet (UV) light under various salinity conditions. No detectable Cl-PAHs were found in the road dust. However, Cl-PAHs were detected in the sediments from 700 to 6.1 × 10(3) pg g(-1) and specifically from downstream sites. 2-Monochloroanthracene (2-Cl-ANT) and 9,10-dichloroanthracene (9,10-di-Cl-ANT) were dominant in the sediments. In the Domen River watershed, the ∑Cl-PAHs and the salinity showed a significant positive correlation (p < 0.01) in the sediments, while such a correlation was not found for PAHs. 2-Cl-ANT, 9-monochloroanthracene, and 9,10-di-Cl-ANT were identified as transformation products in the UV irradiation experiments. Production of these Cl-PAHs was dependent on the solution salinity. These results support our hypothesis, and we conclude that photochemical reactions significantly contribute to the occurrence of Cl-PAHs in the studied tidal flats.

Prefrontal contributions to mental resilience: Lessons from rodent studies of stress and antidepressant actions.

Individual variability of stress susceptibility led to the concept of stress resilience to adapt well upon stressors. However, the neural mechanisms of stress resilience and its relevance to antidepressant actions remain elusive. In rodents, chronic stress induces dendritic atrophy and decreases dendritic spine density in the medial prefrontal cortex (mPFC), recapitulating prefrontal alterations in depressive patients, and the mPFC promotes stress resilience. Whereas dopamine neurons projecting to the nucleus accumbens potentiated by chronic stress promote stress susceptibility, dopamine neurons projecting to the mPFC activated upon acute stress contribute to dendritic growth of mPFC neurons via dopamine D1 receptors, leading to stress resilience. Rodent studies have also identified the roles of prefrontal D1 receptors as well as D1 receptor-expressing mPFC neurons projecting to multiple subcortical areas and dendritic spine formation in the mPFC for the sustained antidepressant-like effects of low-dose ketamine. Thus, understanding the cellular and neural-circuit mechanism of prefrontal D1 receptor actions paves the way for bridging the gap between stress resilience and the sustained antidepressant-like effects. The mechanistic understanding of stress resilience might be exploitable for developing antidepressants based on a naturally occurring mechanism, thus safer than low-dose ketamine.

Air contamination of therapeutic drug monitoring assay reagents results in falsely high plasma ammonia levels.

BACKGROUND: Accumulating evidence shows that contamination of blood samples by atmospheric ammonia affects blood ammonia test levels; however, reports on the effect of ammonia contamination of assay reagents are limited. Here, we aimed to clarify the effect of ammonia contamination of assay reagents, particularly the therapeutic drug monitoring (TDM) reagents, on the detection levels of blood ammonia using enzymatic assays. METHODS: Ammonia gas was measured in the refrigerator compartment of the automatic analyser and the reaction tank water, probe wash water and drain outlets connected to the automatic analyser. At different time points following the closure of the cold storage, ammonia levels in quality control plasma samples were measured using three commercial assay reagents to evaluate the effect of air contamination. The distribution of evaporated ammonia in the reagent was measured using the CicaLiquid NH3 assay kit containing the assay reagent most affected by air contamination. RESULTS: It was confirmed that ammonia gas was generated in the cold storage of the automatic analyser. More than half of the reagents detected >0.25 ppm ammonia, and the highest concentration was detected in the TDM reagent. The ammonia levels obtained using all three reagents increased significantly after 3 h of air contamination. The effect was resolved by measuring a 'dummy' sample or mixing the reagents by inversion. CONCLUSIONS: We demonstrated that air contamination by TDM reagents placed in cold storage could result in significantly falsely high ammonia measurements. Preventing this effect would improve the accuracy of ammonia measurements.

Chronic social defeat stress increases the amounts of 12-lipoxygenase lipid metabolites in the nucleus accumbens of stress-resilient mice.

Severe and prolonged social stress induces mood and cognitive dysfunctions and precipitates major depression. Neuroinflammation has been associated with chronic stress and depression. Rodent studies showed crucial roles of a few inflammation-related lipid mediators for chronic stress-induced depressive-like behaviors. Despite an increasing number of lipid mediators identified, systematic analyses of synthetic pathways of lipid mediators in chronic stress models have not been performed. Using LC-MS/MS, here we examined the effects of chronic social defeat stress on multiple synthetic pathways of lipid mediators in brain regions associated with stress susceptibility in mice. Chronic social defeat stress increased the amounts of 12-lipoxygenase (LOX) metabolites, 12-HETE and 12-HEPE, specifically in the nucleus accumbens 1 week, but not immediately, after the last stress exposure. The increase was larger in stress-resilient mice than stress-susceptible mice. The S isomer of 12-HETE was selectively increased in amount, indicating the role of 12S-LOX activity. Among the enzymes known to have 12S-LOX activity, only Alox12 mRNA was reliably detected in the brain and enriched in brain endothelial cells. These findings suggest that chronic social stress induces a late increase in the amounts of 12S-LOX metabolites derived from the brain vasculature in the nucleus accumbens in a manner associated with stress resilience.

Neurobiology of the Rapid-Acting Antidepressant Effects of Ketamine: Impact and Opportunities.

The discovery of the rapid-acting antidepressant effects of ketamine has 1) led to a paradigm shift in our perception of what is possible in treating severe depression; 2) spurred a wave of basic, translation, and clinical research; and 3) provided an unprecedented investigational tool to conduct longitudinal mechanistic studies that may capture behavioral changes as complex as clinical remission and relapse within hours and days of treatment. Unfortunately, these advances did not yet translate into clinical biomarkers or novel treatments, beyond ketamine. In contrast to slow-acting antidepressants, in which targeting monoaminergic receptors identified several efficacious drugs with comparable mechanisms, the focus on the receptor targets of ketamine has failed in several clinical trials over the past decade. Thus, it is becoming increasingly crucial that we concentrate our effort on the downstream molecular mechanisms of ketamine and their effects on the brain circuitry and networks. Honoring the legacy of our mentor, friend, and colleague Ron Duman, we provide a historical note on the discovery of ketamine and its putative mechanisms. We then detail the molecular and circuits effect of ketamine based on preclinical findings, followed by a summary of the impact of this work on our understanding of chronic stress pathology across psychiatric disorders, with particular emphasis on the role of synaptic connectivity and its brain network effects in the pathology and treatment of clinical depression.

The degradation of diethyl phthalate (DEP) during ozonation: oxidation by-products study.

The degradation of diethyl phthalate (DEP) in an aqueous solution during ozonation was investigated by identifying the oxidation intermediates using GC-MS. The experiments were carried out in semi-batch mode with a 1.5 mg l(-1)-min ozone dose. The proposed degradation pathways were divided into hydrolysis of the aliphatic chain (pathway (A)) and hydroxylation resulting from OH attack in the aromatic ring (pathway (B)). With increasing ozone dose, the aromatic ring of DEP was opened and acidic compounds, such as malonic acid, succinic acid and glutaric acid were formed. In addition, the ozonation of DEP for 18 min induced hydrogen peroxide (H(2)O(2)) generation at levels six times higher than pure water. Of the intermediates indentified, phthalic acid (PA) and phthalic anhydride (PAH) enhanced the degradation of DEP by promoting ozone decomposition.

Social defeat stress-specific increase in c-Fos expression in the extended amygdala in mice: Involvement of dopamine D1 receptor in the medial prefrontal cortex.

We recently reported that dopamine D1 receptor in the medial prefrontal cortex (mPFC) is activated by subthreshold social defeat stress and suppresses the induction of depressive-like behavior in mice. However, which mPFC projection(s) mediates this antidepressant-like effect remains poorly understood. Here we show that social defeat stress specifically increased c-Fos expression, a marker for neuronal activity, in distinct brain regions involved in emotional regulation, relative to novelty-induced exploration. Among these brain areas, D1 knockdown in the mPFC decreased social defeat stress-induced c-Fos expression in the interstitial nucleus of the posterior limb of the anterior commissure (IPAC), a subregion of the extended amygdala. Using retrograde adeno-associated virus vectors and transgenic mice expressing Cre recombinase under the D1 promoter, we also found that D1-expressing deep-layer pyramidal neurons in the mPFC send direct projections to the IPAC. These findings indicate that social defeat stress specifically activates neurons in distinct brain areas, among which the IPAC is regulated by dopamine D1 receptor in the mPFC perhaps through direct projections. Thus, this study provides hints toward identifying neural circuits that underlie antidepressant-like effects of stress-induced dopamine D1 receptor signaling in the mPFC.

Social defeat stress induces phosphorylation of extracellular signal-regulated kinase in the leptomeninges in mice.

AIMS: Animal studies using various stress models have shown that excessive environmental stress induces depression? and anxiety?like behaviors through inflammatory responses in the brain and periphery. Although the leptomeningeal cells have multiple functions related to inflammatory responses in the brain, whether environmental stress influences the leptomeninges remains unknown. In this study, we aimed to examine phosphorylation of the extracellular signal-regulated kinase (ERK) in the leptomeninges. METHODS: We subjected C57BL/6 male mice to a single episode of social defeat stress and analyzed the expression of phosphorylated ERK in the leptomeninges by immunohistochemistry. RESULTS: Social defeat stress in mice induced phosphorylation of ERK in the leptomeninges, adjacent to vascular endothelial cells and the glia limitans. This ERK phosphorylation was maintained for at least one hour after the stress. CONCLUSIONS: This study shows the effect of environmental stress on the leptomeninges for the first time and paves the way for elucidating its functional role in stress-induced changes in neural functions.

Optogenetic stimulation of medial prefrontal cortex Drd1 neurons produces rapid and long-lasting antidepressant effects.

Impaired function in the medial prefrontal cortex (mPFC) contributes to depression, and the therapeutic response produced by novel rapid-acting antidepressants such as ketamine are mediated by mPFC activity. The mPFC contains multiple types of pyramidal cells, but it is unclear whether a particular subtype mediates the rapid antidepressant actions of ketamine. Here we tested two major subtypes, Drd1 and Drd2 dopamine receptor expressing pyramidal neurons and found that activating Drd1 expressing pyramidal cells in the mPFC produces rapid and long-lasting antidepressant and anxiolytic responses. In contrast, photostimulation of Drd2 expressing pyramidal cells was ineffective across anxiety-like and depression-like measures. Disruption of Drd1 activity also blocked the rapid antidepressant effects of ketamine. Finally, we demonstrate that stimulation of mPFC Drd1 terminals in the BLA recapitulates the antidepressant effects of somatic stimulation. These findings aid in understanding the cellular target neurons in the mPFC and the downstream circuitry involved in rapid antidepressant responses.

Repeated social defeat stress impairs attentional set shifting irrespective of social avoidance and increases female preference associated with heightened anxiety.

Repeated social defeat stress (R-SDS) induces multiple behavioral changes in mice. However, the relationships between these behavioral changes were not fully understood. In the first experiment, to examine how the social avoidance is related to R-SDS-impaired behavioral flexibility, 10-week-old male C57BL/6N mice received R-SDS followed by the social interaction test and the attentional set shifting task. R-SDS impaired attentional set shifting irrespective of the development of social avoidance. In the second experiment, to examine whether R-SDS affects sexual preference and how this behavioral change is related to the social avoidance and R-SDS-heightened anxiety, another group of 10-week-old male C57BL/6N mice were subjected to R-SDS followed by the social interaction test, the female encounter test and the elevated plus maze test. The anxiety was heightened in the defeated mice without social avoidance, but not in those which showed social avoidance. Furthermore, female preference was increased specifically in the defeated mice which showed heightened anxiety, but was not related to the level of social avoidance. Together, these results showed that attentional set shifting is more sensitive to R-SDS than social interaction, and that female preference is affected by R-SDS in association with heightened anxiety rather than the social avoidance.

Endocrine effects generated by photooxidation of coplanar biphenyls in water using titanium dioxide.

The oxidative photodegradation behaviors of selected three coplanar polychlorinated biphenyls (PCBs), (CB77, CB81, and CB169) using titanium dioxide (TiO(2)) in water were investigated. The main purposes were to clarify the structural relation between the original PCBs and the intermediates derived by TiO(2) oxidation and to evaluate the estrogenic and thyroid hormonal activity in the treated three coplanar PCBs during the oxidative reactions. Approximately 90% of the three coplanar PCBs decomposed within 180 min. Intermediates from the decomposition of the three coplanar PCBs, such as some hydroxylated-PCBs (OH-PCBs), carboxylic intermediates, phenolic intermediates, and other intermediates produced by the cleavage of a benzene ring were identified and quantified. In the degradation pathways, the produced amounts of OH-PCBs increased within 60 min of irradiation time. The estrogenic activity and thyroid hormonal activity of the intermediates from the three coplanar PCBs in water at 0, 60, 120, 180 and 240 min of irradiation time were assessed by using a yeast two-hybrid assay system for human estrogen receptor alpha (hERalpha) and human thyroid hormone receptor alpha (hTRalpha). The maximal estrogenic activities were induced by the solutions of decomposed PCBs with irradiation time at 60-120 min similar and slightly lower than those after the irradiation time. We found that the solutions occuring during the irradiation times of 60-120 min contained several 4-OH-PCBs substituted with OH and Cl at para- and para'-positions having estrogenic activity. The thyroid hormonal activity was not detected in the decomposed three coplanar PCBs solutions.

In vitro evaluation of atmospheric particulate matter and sedimentation particles using yeast bioassay system.

Little information on the evaluation of airborne particulate matter (APM) and sedimentation particles from subway stations is available. The thermal metamorphism of train wheels generating toxic particles in subway stations is a possibility. In this study, the toxicity and physiological effects of particles from subway stations were evaluated using a yeast bioassay system. Estrogenic and antiestrogenic activities of APM in APM extracts from subway stations were determined. No estrogenic activity was found in the APM fractions and their S9-activated APM samples. Sedimentation dust samples also showed no estrogen activity. In contrast, extracts from sedimentation dust samples showed antiestrogen activity. Marked yeast toxicity was observed in the samples extracted from sedimentation dust. Potent yeast toxicity was also found in the S9-activated extracts from sedimentation dust. The results suggest that sedimentation dust from a semiclosed area of a subway system has antiestrogen activity, although both the origin and generation system of this activity are uncertain. These pollutants in sedimentation dust may change to a more toxic form in vivo by S9 activation.

Characterization of a Novel Rhamnose-containing Acidic Glycosphingolipid from the Ascidian Halocynthia aurantium.

Halocynthia aurantium, an edible ascidian species belonging to Urochordata, was subjected to structural characterization of acidic glycosphingolipids to investigate these molecules in ascidians: sulfatide from Ciona intestinalis and the glucuronic acid-containing acidic glycosphingolipid from H. roretzi. Acidic glycosphingolipids containing three or five sugars were isolated from soft parts of the ascidian H. aurantium by chloroform-methanol extraction, mild-alkaline hydrolysis, precipitation with cold acetone, and subsequent column chromatography using a DEAE-Sephadex A-25 column, a Florisil column, and an Iatrobead column. The structures of these glycosphingolipids were determined by methylation studies, sugar analysis, fatty acid analysis, sphingoid analysis, mass spectrometry, and proton nuclear magnetic resonance spectroscopy. A novel glucuronic acid-containing glycosphingolipid having a rhamnose residue was identified as Rhaα1-3GlcNAcß1-3Galß1-4(Fucα1-3)GlcAß1-Cer (UGL-2). This novel structure is particularly unusual given that it contains both a rhamnose residue and a reducing terminal glucuronic acid residue within a single molecule. Rhamnose is a characteristic sugar, which is a component of cell wall pectin in plants and exopolysaccharides in bacteria. Ascidians acquired the cellulose synthase gene via lateral gene transfer, and therefore, it can be speculated that they also acquired the rhamnosyltransferase gene in the same manner. We also detected Galß1-4(Fucα1-3)GlcAß1-Cer (UGL-1), which was already identified in another ascidian, H. roretzi.

Aqueous secondary formation of brominated, chlorinated, and mixed halogenated pyrene in presence of halide ions.

We examined the secondary production of halogenated derivatives of polycyclic aromatic hydrocarbons (PAHs) in surface seawater. Pyrene was selected as the model compound and exposed to UV irradiation in synthetic seawater for various irradiation times. Pyrene underwent rapid photochemical reactions that produced various halogenated derivatives including 1-chloropyrene, 1-bromopyrene, three unidentified dichloropyrenes, and three unidentified bromochloropyrenes. The production of 1-chloropyrene (220-360 nM) was higher than that of 1-bromopyrene (7.3-12 nM), reflecting the high chlorine content of seawater. A pilot field survey was conducted to test the environmental implications of these results, and fresh, brackish, and seawater samples were collected in southwestern Japan. The variation in the concentration ratios between 1-chloropyrene and pyrene implied the presence of a specific source of 1-chloropyrene in coastal water, which can be partly explained by the secondary production observed in our photolysis experiments. In sum, the photochemical reactions of PAHs are a potential secondary source of halogenated PAHs, especially in marine environments heavily contaminated with PAHs.