Although antiretrovirals are the mainstay of therapy against HIV infection, neurological complications associated with the virus continue to hamper quality of life of the infected individuals. Drugs of abuse in the infected individuals further fuel the epidemic. Epidemiological studies have demonstrated that abuse of cocaine resulted in acceleration of HIV infection and the progression of NeuroAIDS. Cocaine has not only been shown to play a crucial role in promoting virus replication, but also has diverse but often deleterious effects on various cell types of the CNS. In the neuronal system, cocaine exposure results in neuronal toxicity and also potentiates gp120-induced neurotoxicity. In the astroglia and microglia, cocaine exposure leads to up-regulation of pro-inflammatory mediators such as cytokines and chemokines. These in turn, can lead to neuroinflammation and transmission of toxic responses to the neurons. Additionally, cocaine exposure can also lead to leakiness of the blood-brain barrier that manifests as enhanced transmigraiton of leukocytes/monocytes into the CNS. Both in vitro and in vivo studies have provided valuable tools in exploring the role of cocaine in mediating HIV-associated neuropathogenesis. This review summarizes previous studies on the mechanism(s) underlying the interplay of cocaine and HIV as it relates to the CNS.
HIV; AIDS; cocaine; Glial cell; neuron; HIV-1-associated neurocognitive disorders
The neuronal PAS domain protein 4 (Npas4) is a transcription factor that is almost exclusively expressed in the mammalian brain. As an activity-dependent transcription factor, Npas4 regulates the transcription of discrete genes and transcriptionally controls the experience-dependent learning and memory. In this study, we explored the impact of the psychostimulant amphetamine (AMPH) on Npas4 protein expression in the rat striatum. We found that acute systemic injection of AMPH had a minimal effect on protein levels of Npas4 in the caudate putamen (CPu) and nucleus accumbens (NAc), while AMPH readily increased protein products of the immediate early gene c-Fos in these regions. In contrast, repeated administration of AMPH (5 mg/kg, once daily for 5 days) triggered a significant increase in Npas4 expression in the NAc, although repeated AMPH did not alter Npas4 in the CPu. These data demonstrate that Npas4 is an AMPH-sensitive transcription factor. It is inducible selectively in the NAc in response to repeated AMPH administration.
Immediate early gene; transcription factor; c-Fos; Le-PAS; NXF; PASD10; striatum; caudate
The current research tested the hypothesis that individuals engaged in long-term efforts to limit food intake (e.g., individuals with high eating restraint) would have reduced capacity to regulate eating when self-control resources are limited. In the current research, body mass index (BMI) was used as a proxy for eating restraint based on the assumption that individuals with high BMI would have elevated levels of chronic eating restraint. A preliminary study (Study 1) aimed to provide evidence for the assumed relationship between eating restraint and BMI. Participants (N = 72) categorized into high or normal-range BMI groups completed the eating restraint scale. Consistent with the hypothesis, results revealed significantly higher scores on the weight fluctuation and concern for dieting subscales of the restraint scale among participants in the high BMI group compared to the normal-range BMI group. The main study (Study 2) aimed to test the hypothesized interactive effect of BMI and diminished self-control resources on eating behavior. Participants (N = 83) classified as having high or normal-range BMI were randomly allocated to receive a challenging counting task that depleted self-control resources (ego-depletion condition) or a non-depleting control task (no depletion condition). Participants then engaged in a second task in which required tasting and rating tempting cookies and candies. Amount of food consumed during the taste-and-rate task constituted the behavioral dependent measure. Regression analyses revealed a significant interaction effect of these variables on amount of food eaten in the taste-and-rate task. Individuals with high BMI had reduced capacity to regulate eating under conditions of self-control resource depletion as predicted. The interactive effects of BMI and self-control resource depletion on eating behavior were independent of trait self-control. Results extend knowledge of the role of self-control in regulating eating behavior and provide support for a limited-resource model of self-control.
A novel design and facile synthesis process for carbon based hybrid materials, i.e., cobalt monoxide (CoO)-doped graphitic porous carbon microspheres (Co-GPCMs), have been developed. With the synthesis strategy, the mixture of cobalt gluconate, α-cyclodextrin and poly (ethylene oxide)106-poly (propylene oxide)70-poly (ethylene oxide)106 is treated hydrothermally, followed by pyrolysis in argon. The resultant Co-GPCMs exhibits a porous carbon matrix with localized graphitic structure while CoO nanodots are embedded in the carbon frame. Thus, the Co-GPCMs effectively combine the electric double-layer capacitance and pseudo-capacitance when used as the electrode in supercapacitor, which lead to a higher operation voltage (1.6 V) and give rise to a significantly higher energy density. This study provides a new research strategy for electrode materials in high energy density supercapacitors.
The metabotropic glutamate receptor 1 (mGluR1) is a Gαq protein-coupled receptor and is distributed in broad regions of the mammalian brain. As a key element in excitatory synaptic transmission, the receptor regulates a wide range of cellular and synaptic activities. In addition to regulating its targets, the receptor itself is believed to be actively regulated by intracellular signals, although underlying mechanisms are largely unknown. Here we found that a synapse- enriched protein kinase, Ca2+/calmodulin-dependent protein kinase IIα (CaMKIIα), directly binds to the intracellular C terminus (CT) of mGluR1a. This binding is augmented by Ca2+
in vitro. The direct interaction promotes CaMKIIα to phosphorylate mGluR1a at a specific threonine site (T871). In rat striatal neurons, the mGluR1 agonist triggers the receptor- associated phosphoinositide signaling pathway to induce Ca2+-dependent recruitment of CaMKIIα to mGluR1a-CT. This enables the kinase to inhibit the response of the receptor to subsequent agonist exposure. Our data identify an agonist-induced and Ca2+-dependent protein-protein interaction between a synaptic kinase and mGluR1, which constitutes a feedback loop facilitating desensitization of mGluR1a.
striatum; calcium; calmodulin; phosphoinositide; IP3; desensitization; mGluR; kinase; G protein-coupled receptor
Postsynaptic density 93 (PSD-93) is a protein enriched at postsynaptic sites. As a key scaffolding protein, PSD-93 forms complexes with the clustering of various synaptic proteins to construct postsynaptic signaling networks and control synaptic transmission. Extracellular signal-regulated kinase (ERK) is a prototypic member of a serine/threonine protein kinase family known as mitogen-activated protein kinase (MAPK). This kinase, especially ERK2 isoform, noticeably resides in peripheral structures of neurons, such as dendritic spines and postsynaptic density areas, in addition to its distribution in the cytoplasm and nucleus, although little is known about specific substrates of ERK at synaptic sites. In this study, we found that synaptic PSD-93 is a direct target of ERK. This was demonstrated by direct protein-protein interactions between purified ERK2 and PSD-93 in vitro. The accurate ERK2-binding region seems to locate at an N-terminal region of PSD-93. In adult rat striatal neurons in vivo, native ERK from synaptosomal fractions also associated with PSD-93. In phosphorylation assays, active ERK2 phosphorylated PSD-93. An accurate phosphorylation site was identified at a serine site (S323). In striatal neurons, immunoprecipitated PSD-93 showed basal phosphorylation at an ERK-sensitive site. Our data provide evidence supporting PSD-93 as a new substrate of the synaptic species of ERK. ERK2 possesses the ability to interact with PSD-93 and mediate phosphorylation of PSD-93 at a specific site.
PDZ; PSD-95; MAPK; JNK; synapse; signaling; striatum
14-3-3ε is implicated in regulating tumor progression, including hepatocellular carcinoma (HCC). Our earlier study indicated that elevated 14-3-3ε expression is significantly associated with higher risk of metastasis and lower survival rates of HCC patients. However, the molecular mechanisms of how 14-3-3ε regulates HCC tumor metastasis are still unclear.
Methodology and Principal Findings
In this study, we show that increased 14-3-3ε expression induces HCC cell migration and promotes epithelial-mesenchymal transition (EMT), which is determined by the reduction of E-cadherin expression and induction of N-cadherin and vimentin expression. Knockdown with specific siRNA abolished 14-3-3ε-induced cell migration and EMT. Furthermore, 14-3-3ε selectively induced Zeb-1 and Snail expression, and 14-3-3ε-induced cell migration was abrogated by Zeb-1 or Snail siRNA. In addition, the effect of 14-3-3ε-reduced E-cadherin was specifically restored by Zeb-1 siRNA. Positive 14-3-3ε expression was significantly correlated with negative E-cadherin expression, as determined by immunohistochemistry analysis in HCC tumors. Analysis of 14-3-3ε/E-cadherin expression associated with clinicopathological characteristics revealed that the combination of positive 14-3-3ε and negative E-cadherin expression is significantly correlated with higher incidence of HCC metastasis and poor 5-year overall survival. In contrast, patients with positive 14-3-3ε and positive E-cadherin expression had better prognostic outcomes than did those with negative E-cadherin expression.
Our findings show for the first time that E-cadherin is one of the downstream targets of 14-3-3ε in modulating HCC tumor progression. Thus, 14-3-3ε may act as an important regulator in modulating tumor metastasis by promoting EMT as well as cell migration, and it may serve as a novel prognostic biomarker or therapeutic target for HCC.
Newly synthesized protein kinase C (PKC) undergoes a series of phosphorylation to render a mature form of the enzyme. It is this mature PKC that possesses the catalytic competence to respond to second messengers for activation and downstream signaling. The first and rate-limiting phosphorylation occurs at a threonine residue in the activation loop (AL), which triggers the rest maturation processing of PKC and regulates PKC activity in response to cellular stimulation. Given the fact that PKC is enriched in striatal neurons, we investigated the regulation of PKC phosphorylation at the AL site in the rat striatum by the psychostimulant cocaine in vivo. We found that PKC was phosphorylated at the AL site at a moderate level in the normal rat brain. Acute systemic injection of cocaine increased the PKC-AL phosphorylation in the two striatal structures (caudate putamen and nucleus accumbens). Cocaine also elevated the PKC-AL phosphorylation in the medial prefrontal cortex. The cocaine-stimulated PKC phosphorylation in the striatum is rapid and transient. A reliable increase in PKC phosphorylation was seen 7 min after drug injection, which declined to the normal level by 1 h. This kinetics corresponds to that seen for another striatum-enriched protein kinase, mitogen-activated protein kinase/extracellular signal-regulated kinase, in response to cocaine. This study suggests a new model for exploring the impact of cocaine on protein kinases in striatal neurons. By modifying PKC phosphorylation at the AL site, cocaine is believed to possess the ability to alter the maturation processing of the kinase in striatal neurons in vivo.
protein kinase C; ERK; dopamine; stimulant; caudate; nucleus accumbens; prefrontal cortex; addiction
Ionotropic glutamate receptors, especially the α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor subtype, undergo dynamic trafficking between the surface membrane and intracellular organelles. This trafficking activity determines the efficacy and strength of excitatory synapses and is subject to modulation by changing synaptic inputs. Given the possibility that glutamate receptors in the central nervous system might be a sensitive target of anesthetic agents, this study investigated the possible impact of anesthesia on trafficking and subcellular expression of AMPA receptors in adult mouse brain neurons in vivo. We found that anesthesia induced by a systemic injection of pentobarbital did not alter total protein levels of three AMPA receptor subunits (GluR1–3) in cortical neurons. However, an anesthetic dose of pentobarbital reduced GluR1 and GluR3 proteins in the surface pool and elevated these proteins in the intracellular pool of cortical neurons. The similar redistribution of GluR1/3 was observed in mouse striatal neurons. Pentobarbital did not significantly alter GluR2 expression in the two pools. Chloral hydrate at an anesthetic dose also reduced surface GluR1/3 expression and increased intracellular levels of these proteins. The effect of pentobarbital on subcellular distribution of AMPA receptors was reversible. Altered subcellular distribution of GluR1/3 returned to normal levels after the anesthesia subsided. These data indicate that anesthesia induced by pentobarbital and chloral hydrate can alter AMPA receptor trafficking in both cortical and striatal neurons. This alteration is characterized by the concurrent loss and addition of GluR1/3 subunits in the respective surface and intracellular pools.
pentobarbital; chloral hydrate; glutamate; GluR1; GluR3; trafficking
Partitioning defective 3 (Par-3), a crucial component of partitioning-defective complex proteins, controls cell polarity and contributes to cell migration and cancer cell epithelial-to-mesenchymal transition. However, the clinical relevance of Par-3 in tumor progression and metastasis has not been well elucidated. In this study, we investigated the impact and association of Par-3 expression and clinical outcomes with hepatocellular carcinoma (HCC). We first confirmed that Par-3 was abundantly expressed in HCC cell lines by Western blot analysis. We used immunohistochemistry to analyze the association of Par-3 expression and clinicopathological characteristics in primary and subsequent metastatic tumors of patients with HCC. Par-3 was overexpressed in 47 of 111 (42.3%) primary tumors. Increased expression of Par-3 in primary tumors predicted an increased five-year cumulative incidence of extrahepatic metastasis. In addition, multivariate analysis revealed that Par-3 overexpression was an independent risk factor of extrahepatic metastasis. Increased Par-3 expression in primary tumors was associated with poor five-year overall survival rates and was an independent prognostic factor on Cox regression analysis. In conclusion, we show for the first time that increased Par-3 expression is associated with distant metastasis and poor survival rates in patients with HCC. Par-3 may be a novel prognostic biomarker and therapeutic target for HCC.
hepatocellular carcinoma; metastasis; Par-3; survival
Human immunodeficiency virus (HIV) infection is now being driven by drug-abusing populations. Epidemiological studies on drug abusers with AIDS link abuse of cocaine, even more than other drugs, to increased incidence of HIV seroprevalence and progression to AIDS. Both cell culture and animal studies demonstrate that cocaine can both potentiate HIV replication and can potentiate HIV proteins to cause enhanced glial cell activation, neurotoxicity, and breakdown of the blood-brain barrier. Based on the ability of both HIV proteins and cocaine to modulate NMDA receptor on neurons, NMDA R has been suggested as a common link underlying the crosstalk between drug addiction and HIV infection. While the role of dopamine system as a major target of cocaine cannot be overlooked, recent studies on the role of sigma receptors in mediating the effects of cocaine in both cell and organ systems warrants a deeper understanding of their functional role in the field. In this review, recent findings on the interplay of HIV infection and cocaine abuse and their possible implications in mode of action and/or addiction will be discussed.
Enterococci are used to evaluate the safety of beach waters and studies have identified beach sands as a source of these bacteria. In order to study and quantify the release of microbes from beach sediments, flow column systems were built to evaluate flow of pore water out of beach sediments. Results show a peak in enterococci (average of 10% of the total microbes in core) released from the sand core within one pore water volume followed by a marked decline to below detection. These results indicate that few enterococci are easily removed and that factors other than simple pore water flow control the release of the majority of enterococci within beach sediments. A significantly larger quantity and release of enterococci were observed in cores collected after a significant rain event suggesting the influx of fresh water can alter the release pattern as compared to cores with no antecedent rainfall.
enterococci; beach sand; pore water; sand cores; columns
The fragile X premutation provides a unique opportunity for the study of genetic and brain mechanisms of behavior and cognition in the context of neurodevelopment and neurodegeneration. Although the neurodegenerative phenotype, fragile X-associated tremor/ataxia syndrome (FXTAS), is well described, evidence of a causal link between the premutation and psychiatric disorder earlier in life, clear delineation of a behavioral/cognitive phenotype, and characterization of the physiological basis of observed symptoms have been elusive.
We completed functional magnetic resonance imaging (fMRI) targeting the amygdala with an emotion-matching task and concurrent infra-red eyetracking, FMR1 molecular genetic testing, and neuropsychological assessment in 23 men with the premutation (mean age = 32.9 years) and 25 male controls (mean age = 30.1).
Premutation carriers had significantly smaller left and right amygdala volume and reduced right amygdala activation during the task relative to controls. Although both elevated FMR1 mRNA and reduced FMR1 protein (FMRP) were associated with the reduced activation, multiple regression analysis suggested that reduced FMRP is the primary factor. Premutation carriers also had higher ratings of autism spectrum symptoms than controls that were associated with the reduced amygdala response.
Although prior studies have emphasized a toxic gain-of-function effect of elevated mRNA associated with the premutation, the current results point to the role of reduced FMRP in alterations of brain activity and behavior.
FMR1; fragile X; premutation; amygdala; insula; FXTAS
Melanoma is the most lethal form of skin cancer, but recent advances in molecularly targeted agents against the Ras/Raf/MAPK pathway demonstrate promise as effective therapies. Despite these advances, resistance remains an issue, as illustrated recently by the clinical experience with vemurafenib. Such acquired resistance appears to be the result of parallel pathway activation, such as PI3K, to overcome single-agent inhibition. In this report, we describe the cytotoxicity and anti-tumour activity of the novel MEK inhibitor, E6201, in a broad panel of melanoma cell lines (n = 31) of known mutational profile in vitro and in vivo. We further test the effectiveness of combining E6201 with an inhibitor of PI3K (LY294002) in overcoming resistance in these cell lines.
The majority of melanoma cell lines were either sensitive (IC50 < 500 nM, 24/31) or hypersensitive (IC50 < 100 nM, 18/31) to E6201. This sensitivity correlated with wildtype PTEN and mutant BRAF status, whereas mutant RAS and PI3K pathway activation were associated with resistance. Although MEK inhibitors predominantly exert a cytostatic effect, E6201 elicited a potent cytocidal effect on most of the sensitive lines studied, as evidenced by Annexin positivity and cell death ELISA. Conversely, E6201 did not induce cell death in the two resistant melanoma cell lines tested. E6201 inhibited xenograft tumour growth in all four melanoma cell lines studied to varying degrees, but a more pronounced anti-tumour effect was observed for cell lines that previously demonstrated a cytocidal response in vitro. In vitro combination studies of E6201 and LY294002 showed synergism in all six melanoma cell lines tested, as defined by a mean combination index < 1.
Our data demonstrate that E6201 elicits a predominantly cytocidal effect in vitro and in vivo in melanoma cells of diverse mutational background. Resistance to E6201 was associated with disruption of PTEN and activation of downstream PI3K signalling. In keeping with these data we demonstrate that co-inhibition of MAPK and PI3K is effective in overcoming resistance inherent in melanoma.
Melanoma; BRAF; PTEN; MEK inhibition; E6201; PI3K; MAPK
Methyl CpG-binding protein-2 (MeCP2) is a transcriptional regulator that binds to methylated DNA at CpG sites and functions to silence DNA transcription. MeCP2 is subject to the phosphorylation modification at serine 421 (S421), which releases MeCP2 from DNA and thus facilitates gene expression. As a transcriptional repressor densely expressed in limbic reward circuits of adult mammalian brains, MeCP2 is recently emerging as a critical epigenetic factor in experience-dependent neural plasticity and psychostimulant addiction. In this study, we investigated the regulation of MeCP2 phosphorylation in the rat striatum by the psychostimulant cocaine in vivo. We found that acute systemic injection of cocaine increased MeCP2 phosphorylation at S421 in the rat striatum, including both the caudate putamen and the nucleus accumbens, while cocaine did not affect MeCP2 phosphorylation in the medial prefrontal cortex. The cocaine-stimulated MeCP2 phosphorylation in the nucleus accumbens was a rapid and transient event, as it was evident at 20 min and returned to normal levels 3 h after drug injection. The cocaine effect in the caudate putamen was however relatively delayed. Reliable induction of MeCP2 phosphorylation in this region was detected at 60 min. Pretreatment with an N-methyl-D-aspartate (NMDA) glutamate receptor antagonist significantly reduced the cocaine-stimulated MeCP2 phosphorylation in the caudate putamen, although not in the nucleus accumbens. Our data support that MeCP2 is a sensitive target of psychostimulants. Its phosphorylation status is regulated by psychostimulant exposure. NMDA receptors play a region-specific role in linking cocaine to MeCP2 phosphorylation in striatal neurons in vivo.
Glutamate; dopamine; stimulant; caudate; nucleus accumbens; prefrontal cortex; transcription; CREB; addiction
Enterococci, are used nationwide as a water quality indicator of marine recreational beaches. Prior research has demonstrated that enterococci inputs to the study beach site (located in Miami, FL) are dominated by non-point sources (including humans and animals). We have estimated their respective source functions by developing a counting methodology for individuals to better understand their non-point source load impacts. The method utilizes camera images of the beach taken at regular time intervals to determine the number of people and animal visitors. The developed method translates raw image counts for weekdays and weekend days into daily and monthly visitation rates. Enterococci source functions were computed from the observed number of unique individuals for average days of each month of the year, and from average load contributions for humans and for animals. Results indicate that dogs represent the larger source of enterococci relative to humans and birds.
Indicator microbe organism; Enterococcus; recreational water quality; bather shedding; animal fecal load
HIV-associated increase in monocyte adhesion and trafficking is exacerbated by cocaine abuse. The underlying mechanisms involve cocaine-mediated up-regulation of adhesion molecules with subsequent disruption of the blood brain barrier (BBB). Recently, a novel activated leukocyte cell adhesion molecule (ALCAM) has been implicated in leukocyte transmigration across the endothelium. We now show that up-regulation of ALCAM in the brain endothelium seen in HIV+/cocaine drug abusers paralleled increased CD68 immunostaining compared with HIV+/no cocaine or uninfected controls, suggesting the important role of ALCAM in promoting leukocyte infiltration across the BBB. Furthermore, ALCAM expression was increased in cocaine-treated mice with concomitant increase in monocyte adhesion and transmigration in vivo, which was ameliorated by pre-treating with the neutralizing antibody to ALCAM, lending further support to the role of ALCAM. This new concept was further confirmed by in vitro experiments. Cocaine mediated induction of ALCAM in human brain microvascular endothelial cells through the translocation of sigma receptor to the plasma membrane, followed by phosphorylation of platelet-derived growth factor (PDGF)-β receptor. Downstream activation of mitogen-activated protein kinases, Akt, and NF- κB pathways resulted in induced expression of ALCAM. Functional implication of up-regulated ALCAM was confirmed using cell adhesion and transmigration assays. Neutralizing antibody to ALCAM ameliorated this effect. Taken together, these findings implicate cocaine-mediated induction of ALCAM as a mediator of increased monocyte adhesion/transmigration into the CNS.
Cocaine; ALCAM; sigma-1 receptor; platelet-derived growth factor-β receptor; monocyte adhesion; monocyte transmigration
The endoplasmic reticulum (ER) controls protein folding. Accumulation of unfolded and misfolded proteins in the ER triggers an ER stress response to accelerate normal protein folding or if failed to cause apoptosis. The ER stress response is a conserved cellular response in mammalian cells and is sensitive to various physiological or pathophysiological stimuli. Recent studies unravel that this response in striatal neurons is subject to the tight modulation by psychostimulants. Cocaine and amphetamines markedly increased expression of multiple ER stress reporter proteins in the dorsal striatum (caudate putamen) and other basal ganglia sites. This evoked ER stress response is mediated by activation of group I metabotropic glutamate receptors and N-methyl-D-aspartate receptors. Converging Ca2+ signals derived from activation of these receptors activate the c-Jun N-terminal kinase pathway to evoke ER stress responses. The discovery of robust ER stress responses to stimulant exposure establishes a previously unrecognized stimulant-ER coupling. This inducible coupling seems to contribute to neurotoxicity of stimulants related to various neuropsychiatric and neurodegenerative illnesses. Elucidating cellular mechanisms linking cocaine and other stimulants to ER is therefore important for the development of therapeutic agents for treating neurological disorders resulted from stimulant toxicity.
caudate putamen; mGluR; NMDA; chaperone; UPR; BiP; JNK; psychostimulant
This study is to determine if functional suppression of the catalytic domain of activation-induced cytidine deaminase (AID) can suppress the hyper-reactive germinal center responses in BXD2 mice.
A transgenic (Tg) BXD2 mouse expressing a dominant negative (DN) form of AID (Aicda-DN) at the somatic hypermutation (SHM) site was generated. Real-time RT-PCR was used to determine the expression of Aicda and DNA damage/repair genes. ELISA was used to measure sera levels of autoantibodies and immune complexes. Development of GCs and antibody containing immune complexes (ICs) as well as proliferative and apoptotic cells were determined using flow cytometry and/or immunohistochemistry analyses. Development of arthritis and kidney disease was evaluated histologically in 6-8 month-old mice.
Suppression of the SHM function of AID resulted in a significant decrease in autoantibody production without affecting the expression of DNA damage-related genes in GC B cells of BXD2-Aicda-DN Tg mice. There was decreased proliferation, increased apoptosis, increased expression of caspase 9 mRNA in GC B cells, and lower numbers of GCs in the spleen of BXD2-Aicda-DN Tg mice. Decreased GC response was associated with lower IgG containing ICs. Anti-IgM and anti-Ig plus anti-CD40-induced B cell proliferative responses were decreased in BXD2-Aicda-DN Tg mice.
Inhibition of AID SHM function in BXD2 mice suppressed development of spontaneous GCs, generation of autoantibody producing B cells, and autoimmunity in BXD2 mice. Suppression of AID catalytic function that limits selection-based survival of GC B cells could become a novel therapy for the treatment of autoimmune disease.
Palmitoylation is emerging as one of the most important posttranslational modifications of excitatory synaptic proteins in mammalian brain cells. As a reversible and regulatable modification sensitive to changing synaptic inputs, palmitoylation of ionotropic glutamate receptors contributes to not only the modulation of normal receptor and synaptic activities, but also the pathogenesis of various neuropsychiatric disorders. Here, we report that palmitoylation of the AMPA receptor is regulated by the psychostimulant, cocaine, and such regulation is involved in cocaine action.
We tested palmitoylation and surface expression of AMPA receptors in striatal neurons and psychomotor behavior in responses to cocaine in rats.
All four AMPA receptor subunits (GluA1-4 or GluR1-4) are palmitoylated in the nucleus accumbens (NAc) of adult rats. Among them, GluA1 and GluA3 are preferentially upregulated in their palmitoylation levels by a systemic injection of cocaine. The upregulated GluA1 and 3 palmitoylation is a transient and reversible event. Consequently, it increases the susceptibility of surface-expressed GluA1 and 3 to internalization trafficking, leading to a temporal loss of surface receptor expression. Blockade of the regulated GluA1/3 palmitoylation with a palmitoylation inhibitor in the local NAc reverses the loss of surface GluA1/3. The inhibition of palmitoylation also concurrently sustains behavioral responsivity to cocaine.
Our data identify a novel drug-palmitoylation coupling in the center of limbic reward circuits. Through palmitoylating selective AMPA receptor subunits, cocaine activity-dependently regulates trafficking and subcellular localization of the receptor in NAc neurons and dynamically controls psychomotor sensitivity to the psychoactive drug in vivo.
Glutamate; dopamine; synapse; nucleus accumbens; addiction; drug abuse
Ionotropic glutamate receptors (iGluR) are ligand-gated ion channels and are densely expressed in broad areas of mammalian brains. Like iGluRs, acid-sensing ion channels (ASIC) are ligand (H+)-gated channels and are enriched in brain cells and peripheral sensory neurons. Both ion channels are enriched at excitatory synaptic sites, functionally coupled to each other, and subject to the modulation by a variety of signaling molecules. Central among them is a gasotransmitter, nitric oxide (NO). Available data show that NO activity-dependently modulates iGluRs and ASICs via either a direct or an indirect pathway. The former involves a NO-based and cGMP-independent post-translational modification (S-nitrosylation) of extracellular cysteine residues in channel subunits or channel-interacting proteins. The latter is achieved by NO activation of soluble guanylyl cyclase, which in turn triggers an intracellular cGMP-sensitive cascade to indirectly modulate iGluRs and ASICs. The NO modification is usually dynamic and reversible. Modified channels undergo significant, interrelated changes in biochemistry and electrophysiology. Since NO synthesis is enhanced in various neurological disorders, the NO modulation of iGluRs and ASICs is believed to be directly linked to the pathogenesis of these disorders. This review summarizes the direct and indirect modifications of iGluRs and ASICs by NO and analyzes the role of the NO-iGluR and NO-ASIC coupling in cell signaling and in the pathogenesis of certain related neurological diseases.
NMDA; AMPA; ASIC; nitrosylation; cGMP; NO; NOS; gasotransmitter
To investigate the role of CD86high marginal zone precursor (MZ-P) B cells in type I interferon (IFN)-induced T-dependent responses in autoimmune BXD2 mice.
Confocal imaging was used to determine the location of plasmacytoid dendritic cells (pDCs), MZ-P B cells and CD4 T cells in the spleens of BXD2 and BXD2-Ifnar−/− mice. Immunohistochemistry staining was used to determine IgGbright cells in BXD2 and BXD2-Ifnar−/− spleens. ELISA was used to determine serum levels of IFN-α, autoantibody, and NP-CGG- or NP-Ficoll-induced anti-NP2 antibody titers. Quantitative real-time (qRT)-PCR was used to determine the levels of type I IFN transcripts. [3H]-thymidine was used to measure T-cell proliferation. CD86 and CD80 expression was determined by FACS.
Type I IFN receptor (IFNR) deletion abrogated development of IgGbright cells and suppressed a T-dependent antibody response. Type I IFN signaling is associated with the expression of CD86, but not CD80, on follicular, MZ, and MZ-P B cells. However, MZ-P B cells demonstrated the highest expression of CD86 and the highest capacity for T-cell costimulation with intact type I IFNR. This effect was blocked by an antibody that neutralizes CD86. In IFNR intact BXD2 spleens, MZ-P B cells clustered at the T-B border. CD86 deletion suppressed germinal center formation, autoantibody production, and development of autoimmune diseases in BXD2 mice.
Type I IFN can promote autoimmune responses in BXD2 mice through upregulation of CD86high expression on MZ-P B cells and trafficking of MZ-P B cells to the T-B border to provide costimulation to CD4 T cells.
Chemotaxis is essential for shaping immune responses and chemokine-receptor antagonists are now being evaluated as therapies for various inflammatory and autoimmune diseases. However, the dysregulation of chemotaxis in autoimmune disease may involve both promotion and inhibition of B-cell migration. This review focuses on the disparate mechanisms by which two inflammatory cytokines that have been associated with autoimmune disease, namely interferon-α (IFNα) and interleukin-17 (IL-17), may regulate B-cell migratory responses. Chemotactic responses play a key role in orchestrating the cell-cell interactions in the germinal centers (GCs). This process involves ongoing shuttling of the antigen-carrying B cells between the marginal zone and the GCs. We have shown that in autoimmune BXD2 mice, the migration of marginal zone precursor B cells is promoted by high levels of interferon (IFN)-α produced by plasmacytoid dendritic cells in the marginal sinus that antagonize the activity of the S1P1 chemokine receptor. In contrast, within the GCs, interleukin-17A (IL-17A) upregulates the expression of regulators of G protein signaling (RGS) in B cells to desensitize the G protein-coupled receptor (GPCR) signaling pathway of CXCL12 and CXCL13 chemokines. This provides a prolonged stable interaction of B and T cells in the GC that induces high levels of activation-induced cytidine deaminase (AICDA) thereby enabling development of pathogenic autoantibody-producing B cells.
Previous functional MRI (fMRI) studies have shown that fragile X mental retardation 1 (FMR1) fragile X premutation allele carriers (FXPCs) exhibit decreased hippocampal activation during a recall task and lower inferior frontal activation during a working memory task compared to matched controls. The molecular characteristics of FXPCs includes 55–200 CGG trinucleotide expansions, increased FMR1 mRNA levels, and decreased FMRP levels especially at higher repeat sizes. In the current study, we utilized MRI to examine differences in hippocampal volume and function during an encoding task in young male FXPCs. While no decreases in either hippocampal volume or hippocampal activity were observed during the encoding task in FXPCs, FMRP level (measured in blood) correlated with decreases in parahippocampal activation. In addition, activity in the right dorsolateral prefrontal cortex during correctly encoded trials correlated negatively with mRNA levels. These results, as well as the established biological effects associated with elevated mRNA levels and decreased FMRP levels on dendritic maturation and axonal growth, prompted us to explore functional connectivity between the hippocampus, prefrontal cortex, and parahippocampal gyrus using a psychophysiological interaction analysis. In FXPCs, the right hippocampus evinced significantly lower connectivity with right ventrolateral prefrontal cortex (VLPFC) and right parahippocampal gyrus. Furthermore, the weaker connectivity between the right hippocampus and VLPFC was associated with reduced FMRP in the FXPC group. These results suggest that while FXPCs show relatively typical brain response during encoding, faulty connectivity between frontal and hippocampal regions may have subsequent effects on recall and working memory.
fragile X premutation; memory; prefrontal cortex; psychophysiological interaction analysis
Increases in extracellular proton concentrations, which takes place in physiological conditions such as synaptic signaling and pathological conditions such as tissue inflammation, ischemic stroke, traumatic brain injury, and epileptic seizure, activates a unique family of membrane ion channels; the acid-sensing ion channels (ASICs). All ASICs belong to amiloride-sensitive degenerin/epithelial Na+ channel superfamily. Four genes encoded at seven sub-units have been identified. ASICs are expressed primarily in neurons and have been shown to play critical roles in synaptic plasticity, learning/memory, fear conditioning, sensory transduction, pain perception, ischemic brain injury, seizure, and other neurological as well as psychological disorders. Although protons are the primary activator for ASICs, the properties and/or level of expression of these channels are modulated dramatically by neuropeptides, di-and polyvalent cations, inflammatory mediators, associated proteins, and protein phosphorylations, etc. Modulation of ASICs can result in profound changes in the activities and functions of these channels in both physiological and pathological processes. In this article, we provide an up to date review on the modulations of ASICs by exogenous agents and endogenous signaling molecules. A better understanding of how ASICs can be modulated should help define new strategies to counteract the deleterious effects of dysregulated ASIC activity.
Acid-sensing ion channel; acidosis; neuron; modulation