Molecular neurobiology of loss: a role for basolateral amygdala extracellular matrix.

Psychological loss is a common experience that erodes well-being and negatively impacts quality of life. The molecular underpinnings of loss are poorly understood. Here, we investigate the mechanisms of loss using an environmental enrichment removal (ER) paradigm in male rats. The basolateral amygdala (BLA) was identified as a region of interest, demonstrating differential Fos responsivity to ER and having an established role in stress processing and adaptation. A comprehensive multi-omics investigation of the BLA, spanning multiple cohorts, platforms, and analyses, revealed alterations in microglia and the extracellular matrix (ECM). Follow-up studies indicated that ER decreased microglia size, complexity, and phagocytosis, suggesting reduced immune surveillance. Loss also substantially increased ECM coverage, specifically targeting perineuronal nets surrounding parvalbumin interneurons, suggesting decreased plasticity and increased inhibition within the BLA following loss. Behavioral analyses suggest that these molecular effects are linked to impaired BLA salience evaluation, leading to a mismatch between stimulus and reaction intensity. These loss-like behaviors could be rescued by depleting BLA ECM during the removal period, helping us understand the mechanisms underlying loss and revealing novel molecular targets to ameliorate its impact.

Differential vulnerability of anterior cingulate cortex cell types to diseases and drugs.

In psychiatric disorders, mismatches between disease states and therapeutic strategies are highly pronounced, largely because of unanswered questions regarding specific vulnerabilities of different cell types and therapeutic responses. Which cellular events (housekeeping or salient) are most affected? Which cell types succumb first to challenges, and which exhibit the strongest response to drugs? Are these events coordinated between cell types? How does disease and drug effect this coordination? To address these questions, we analyzed single-nucleus-RNAseq (sn-RNAseq) data from the human anterior cingulate cortex-a region involved in many psychiatric disorders. Density index, a metric for quantifying similarities and dissimilarities across functional profiles, was employed to identify common or salient functional themes across cell types. Cell-specific signatures were integrated with existing disease and drug-specific signatures to determine cell-type-specific vulnerabilities, druggabilities, and responsiveness. Clustering of functional profiles revealed cell types jointly participating in these events. SST and VIP interneurons were found to be most vulnerable, whereas pyramidal neurons were least. Overall, the disease state is superficial layer-centric, influences cell-specific salient themes, strongly impacts disinhibitory neurons, and influences astrocyte interaction with a subset of deep-layer pyramidal neurons. In absence of disease, drugs profiles largely recapitulate disease profiles, offering a possible explanation for drug side effects. However, in presence of disease, drug activities, are deep layer-centric and involve activating a distinct subset of deep-layer pyramidal neurons to circumvent the disease state's disinhibitory circuit malfunction. These findings demonstrate a novel application of sn-RNAseq data to explain drug and disease action at a systems level.

Schizophrenia: a disorder of broken brain bioenergetics.

A substantial and diverse body of literature suggests that the pathophysiology of schizophrenia is related to deficits of bioenergetic function. While antipsychotics are an effective therapy for the management of positive psychotic symptoms, they are not efficacious for the complete schizophrenia symptom profile, such as the negative and cognitive symptoms. In this review, we discuss the relationship between dysfunction of various metabolic pathways across different brain regions in relation to schizophrenia. We contend that several bioenergetic subprocesses are affected across the brain and such deficits are a core feature of the illness. We provide an overview of central perturbations of insulin signaling, glycolysis, pentose-phosphate pathway, tricarboxylic acid cycle, and oxidative phosphorylation in schizophrenia. Importantly, we discuss pharmacologic and nonpharmacologic interventions that target these pathways and how such interventions may be exploited to improve the symptoms of schizophrenia.

Antipsychotics impair regulation of glucose metabolism by central glucose.

Hypothalamic detection of elevated circulating glucose triggers suppression of endogenous glucose production (EGP) to maintain glucose homeostasis. Antipsychotics alleviate symptoms associated with schizophrenia but also increase the risk for impaired glucose metabolism. In the current study, we examined whether two acutely administered antipsychotics from different drug classes, haloperidol (first generation antipsychotic) and olanzapine (second generation antipsychotic), affect the ability of intracerebroventricular (ICV) glucose infusion approximating postprandial levels to suppress EGP. The experimental protocol consisted of a pancreatic euglycemic clamp, followed by kinomic and RNA-seq analyses of hypothalamic samples to determine changes in serine/threonine kinase activity and gene expression, respectively. Both antipsychotics inhibited ICV glucose-mediated increases in glucose infusion rate during the clamp, a measure of whole-body glucose metabolism. Similarly, olanzapine and haloperidol blocked central glucose-induced suppression of EGP. ICV glucose stimulated the vascular endothelial growth factor (VEGF) pathway, phosphatidylinositol 3-kinase (PI3K) pathway, and kinases capable of activating KATP channels in the hypothalamus. These effects were inhibited by both antipsychotics. In conclusion, olanzapine and haloperidol impair central glucose sensing. Although results of hypothalamic analyses in our study do not prove causality, they are novel and provide the basis for a multitude of future studies.

mTOR kinase activity disrupts a phosphorylation signaling network in schizophrenia brain.

The AKT-mTOR signaling transduction pathway plays an important role in neurodevelopment and synaptic plasticity. mTOR is a serine/threonine kinase that modulates signals from multiple neurotransmitters and phosphorylates specific proteins to regulate protein synthesis and cytoskeletal organization. There is substantial evidence demonstrating abnormalities in AKT expression and activity in different schizophrenia (SZ) models. However, direct evidence for dysregulated mTOR kinase activity and its consequences on downstream effector proteins in SZ pathophysiology is lacking. Recently, we reported reduced phosphorylation of mTOR at an activating site and abnormal mTOR complex formation in the SZ dorsolateral prefrontal cortex (DLPFC). Here, we expand on our hypothesis of disrupted mTOR signaling in the SZ brain and studied the expression and activity of downstream effector proteins of mTOR complexes and the kinase activity profiles of SZ subjects. We found that S6RP phosphorylation, downstream of mTOR complex I, is reduced, whereas PKCα phosphorylation, downstream of mTOR complex II, is increased in SZ DLPFC. In rats chronically treated with haloperidol, we showed that S6RP phosphorylation is increased in the rat frontal cortex, suggesting a potential novel mechanism of action for antipsychotics. We also demonstrated key differences in kinase signaling networks between SZ and comparison subjects for both males and females using kinome peptide arrays. We further investigated the role of mTOR kinase activity by inhibiting it with rapamycin in postmortem tissue and compared the impact of mTOR inhibition in SZ and comparison subjects using kinome arrays. We found that SZ subjects are globally more sensitive to rapamycin treatment and AMP-activated protein kinase (AMPK) contributes to this differential kinase activity. Together, our findings provide new insights into the role of mTOR as a master regulator of kinase activity in SZ and suggest potential targets for therapeutic intervention.

Similarities and dissimilarities between psychiatric cluster disorders.

The common molecular mechanisms underlying psychiatric disorders are not well understood. Prior attempts to assess the pathological mechanisms responsible for psychiatric disorders have been limited by biased selection of comparable disorders, datasets/cohort availability, and challenges with data normalization. Here, using DisGeNET, a gene-disease associations database, we sought to expand such investigations in terms of number and types of diseases. In a top-down manner, we analyzed an unbiased cluster of 36 psychiatric disorders and comorbid conditions at biological pathway, cell-type, drug-target, and chromosome levels and deployed density index, a novel metric to quantify similarities (close to 1) and dissimilarities (close to 0) between these disorders at each level. At pathway level, we show that cognition and neurotransmission drive the similarity and are involved across all disorders, whereas immune-system and signal-response coupling (cell surface receptors, signal transduction, gene expression, and metabolic process) drives the dissimilarity and are involved with specific disorders. The analysis at the drug-target level supports the involvement of neurotransmission-related changes across these disorders. At cell-type level, dendrite-targeting interneurons, across all layers, are most involved. Finally, by matching the clustering pattern at each level of analysis, we showed that the similarity between the disorders is influenced most at the chromosomal level and to some extent at the cellular level. Together, these findings provide first insights into distinct cellular and molecular pathologies, druggable mechanisms associated with several psychiatric disorders and comorbid conditions and demonstrate that similarities between these disorders originate at the chromosome level and disperse in a bottom-up manner at cellular and pathway levels.

Corticostriatal dysfunction and social interaction deficits in mice lacking the cystine/glutamate antiporter.

The astrocytic cystine/glutamate antiporter system xc- represents an important source of extracellular glutamate in the central nervous system, with potential impact on excitatory neurotransmission. Yet, its function and importance in brain physiology remain incompletely understood. Employing slice electrophysiology and mice with a genetic deletion of the specific subunit of system xc-, xCT (xCT-/- mice), we uncovered decreased neurotransmission at corticostriatal synapses. This effect was partly mitigated by replenishing extracellular glutamate levels, indicating a defect linked with decreased extracellular glutamate availability. We observed no changes in the morphology of striatal medium spiny neurons, the density of dendritic spines, or the density or ultrastructure of corticostriatal synapses, indicating that the observed functional defects are not due to morphological or structural abnormalities. By combining electron microscopy with glutamate immunogold labeling, we identified decreased intracellular glutamate density in presynaptic terminals, presynaptic mitochondria, and in dendritic spines of xCT-/- mice. A proteomic and kinomic screen of the striatum of xCT-/- mice revealed decreased expression of presynaptic proteins and abnormal kinase network signaling, that may contribute to the observed changes in postsynaptic responses. Finally, these corticostriatal deregulations resulted in a behavioral phenotype suggestive of autism spectrum disorder in the xCT-/- mice; in tests sensitive to corticostriatal functioning we recorded increased repetitive digging behavior and decreased sociability. To conclude, our findings show that system xc- plays a previously unrecognized role in regulating corticostriatal neurotransmission and influences social preference and repetitive behavior.

Transcriptional profile of pyramidal neurons in chronic schizophrenia reveals lamina-specific dysfunction of neuronal immunity.

While the pathophysiology of schizophrenia has been extensively investigated using homogenized postmortem brain samples, few studies have examined changes in brain samples with techniques that may attribute perturbations to specific cell types. To fill this gap, we performed microarray assays on mRNA isolated from anterior cingulate cortex (ACC) superficial and deep pyramidal neurons from 12 schizophrenia and 12 control subjects using laser-capture microdissection. Among all the annotated genes, we identified 134 significantly increased and 130 decreased genes in superficial pyramidal neurons, while 93 significantly increased and 101 decreased genes were found in deep pyramidal neurons, in schizophrenia compared to control subjects. In these differentially expressed genes, we detected lamina-specific changes of 55 and 31 genes in superficial and deep neurons in schizophrenia, respectively. Gene set enrichment analysis (GSEA) was applied to the entire pre-ranked differential expression gene lists to gain a complete pathway analysis throughout all annotated genes. Our analysis revealed overrepresented groups of gene sets in schizophrenia, particularly in immunity and synapse-related pathways, suggesting the disruption of these pathways plays an important role in schizophrenia. We also detected other pathways previously demonstrated in schizophrenia pathophysiology, including cytokine and chemotaxis, postsynaptic signaling, and glutamatergic synapses. In addition, we observed several novel pathways, including ubiquitin-independent protein catabolic process. Considering the effects of antipsychotic treatment on gene expression, we applied a novel bioinformatics approach to compare our differential expression gene profiles with 51 antipsychotic treatment datasets, demonstrating that our results were not influenced by antipsychotic treatment. Taken together, we found pyramidal neuron-specific changes in neuronal immunity, synaptic dysfunction, and olfactory dysregulation in schizophrenia, providing new insights for the cell-subtype specific pathophysiology of chronic schizophrenia.

Consequences of NMDA receptor deficiency can be rescued in the adult brain.

N-methyl-D-aspartate receptors (NMDARs) are required to shape activity-dependent connections in the developing and adult brain. Impaired NMDAR signalling through genetic or environmental insults causes a constellation of neurodevelopmental disorders that manifest as intellectual disability, epilepsy, autism, or schizophrenia. It is not clear whether the developmental impacts of NMDAR dysfunction can be overcome by interventions in adulthood. This question is paramount for neurodevelopmental disorders arising from mutations that occur in the GRIN genes, which encode NMDAR subunits, and the broader set of mutations that disrupt NMDAR function. We developed a mouse model where a congenital loss-of-function allele of Grin1 can be restored to wild type by gene editing with Cre recombinase. Rescue of NMDARs in adult mice yields surprisingly robust improvements in cognitive functions, including those that are refractory to treatment with current medications. These results suggest that neurodevelopmental disorders arising from NMDAR deficiency can be effectively treated in adults.

Differential genetic associations and expression of PAPST1/SLC35B2 in bipolar disorder and schizophrenia.

Lithium's inhibitory effect on enzymes involved in sulfation process, such as inhibition of 3'(2')-phosphoadenosine 5'-phosphate (PAP) phosphatase, is a possible mechanism of its therapeutic effect for bipolar disorder (BD). 3'-Phosphoadenosine 5'-phosphosulfate (PAPS) is translocated from cytosol to Golgi lumen by PAPS transporter 1 (PAPST1/SLC35B2), where it acts as a sulfa donor. Since SLC35B2 was previously recognized as a molecule that facilitates the release of D-serine, a co-agonist of N-methyl-D-aspartate type glutamate receptor, altered function of SLC35B2 might be associated with the pathophysiology of BD and schizophrenia (SCZ). We performed genetic association analyses of the SLC35B2 gene using Japanese cohorts with 366 BD cases and 370 controls and 2012 SCZ cases and 2170 controls. We then investigated expression of SLC35B2 mRNA in postmortem brains by QPCR using a Caucasian cohort with 33 BD and 34 SCZ cases and 34 controls and by in situ hybridization using a Caucasian cohort with 37 SCZ and 29 controls. We found significant associations between three SNPs (rs575034, rs1875324, and rs3832441) and BD, and significantly reduced SLC35B2 mRNA expression in postmortem dorsolateral prefrontal cortex (DLPFC) of BD. Moreover, we observed normalized SLC35B2 mRNA expression in BD subgroups who were medicated with lithium. While there was a significant association of SLC35B2 with SCZ (SNP rs2233437), its expression was not changed in SCZ. These findings indicate that SLC35B2 might be differentially involved in the pathophysiology of BD and SCZ by influencing the sulfation process and/or glutamate system in the central nervous system.

Adenosine, Schizophrenia and Cancer: Does the Purinergic System Offer a Pathway to Treatment?

For over a century, a complex relationship between schizophrenia diagnosis and development of many cancers has been observed. Findings from epidemiological studies are mixed, with reports of increased, reduced, or no difference in cancer incidence in schizophrenia patients. However, as risk factors for cancer, including elevated smoking rates and substance abuse, are commonly associated with this patient population, it is surprising that cancer incidence is not higher. Various factors may account for the proposed reduction in cancer incidence rates including pathophysiological changes associated with disease. Perturbations of the adenosine system are hypothesized to contribute to the neurobiology of schizophrenia. Conversely, hyperfunction of the adenosine system is found in the tumor microenvironment in cancer and targeting the adenosine system therapeutically is a promising area of research in this disease. We outline the current biochemical and pharmacological evidence for hypofunction of the adenosine system in schizophrenia, and the role of increased adenosine metabolism in the tumor microenvironment. In the context of the relatively limited literature on this patient population, we discuss whether hypofunction of this system in schizophrenia, may counteract the immunosuppressive role of adenosine in the tumor microenvironment. We also highlight the importance of studies examining the adenosine system in this subset of patients for the potential insight they may offer into these complex disorders.

Bilirubin remodels murine white adipose tissue by reshaping mitochondrial activity and the coregulator profile of peroxisome proliferator-activated receptor α.

Activation of lipid-burning pathways in the fat-storing white adipose tissue (WAT) is a promising strategy to improve metabolic health and reduce obesity, insulin resistance, and type II diabetes. For unknown reasons, bilirubin levels are negatively associated with obesity and diabetes. Here, using mice and an array of approaches, including MRI to assess body composition, biochemical assays to measure bilirubin and fatty acids, MitoTracker-based mitochondrial analysis, immunofluorescence, and high-throughput coregulator analysis, we show that bilirubin functions as a molecular switch for the nuclear receptor transcription factor peroxisome proliferator-activated receptor α (PPARα). Bilirubin exerted its effects by recruiting and dissociating specific coregulators in WAT, driving the expression of PPARα target genes such as uncoupling protein 1 (Ucp1) and adrenoreceptor ß 3 (Adrb3). We also found that bilirubin is a selective ligand for PPARα and does not affect the activities of the related proteins PPARγ and PPARδ. We further found that diet-induced obese mice with mild hyperbilirubinemia have reduced WAT size and an increased number of mitochondria, associated with a restructuring of PPARα-binding coregulators. We conclude that bilirubin strongly affects organismal body weight by reshaping the PPARα coregulator profile, remodeling WAT to improve metabolic function, and reducing fat accumulation.

Role of Astrocytes in Major Neuropsychiatric Disorders.

Astrocytes are the primary homeostatic cells of the central nervous system, essential for normal neuronal development and function, metabolism and response to injury and inflammation. Here, we review postmortem studies examining changes in astrocytes in subjects diagnosed with the neuropsychiatric disorders schizophrenia (SCZ), major depressive disorder (MDD), and bipolar disorder (BPD). We discuss the astrocyte-related changes described in the brain in these disorders and the potential effects of psychotropic medication on these findings. Finally, we describe emerging tools that can be used to study the role of astrocytes in neuropsychiatric illness.

Oxytocin's anti-inflammatory and proimmune functions in COVID-19: a transcriptomic signature-based approach.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a worldwide pandemic, infecting over 16 million people worldwide with a significant mortality rate. However, there is no current Food and Drug Administration-approved drug that treats coronavirus disease 2019 (COVID-19). Damage to T lymphocytes along with the cytokine storm are important factors that lead to exacerbation of clinical cases. Here, we are proposing intravenous oxytocin (OXT) as a candidate for adjunctive therapy for COVID-19. OXT has anti-inflammatory and proimmune adaptive functions. Using the Library of Integrated Network-Based Cellular Signatures (LINCS), we used the transcriptomic signature for carbetocin, an OXT agonist, and compared it to gene knockdown signatures of inflammatory (such as interleukin IL-1ß and IL-6) and proimmune markers (including T cell and macrophage cell markers like CD40 and ARG1). We found that carbetocin's transcriptomic signature has a pattern of concordance with inflammation and immune marker knockdown signatures that are consistent with reduction of inflammation and promotion and sustaining of immune response. This suggests that carbetocin may have potent effects in modulating inflammation, attenuating T cell inhibition, and enhancing T cell activation. Our results also suggest that carbetocin is more effective at inducing immune cell responses than either lopinavir or hydroxychloroquine, both of which have been explored for the treatment of COVID-19.

Neurotransmitter changes after traumatic brain injury: an update for new treatment strategies.

Traumatic brain injury (TBI) is a pervasive problem in the United States and worldwide, as the number of diagnosed individuals is increasing yearly and there are no efficacious therapeutic interventions. A large number of patients suffer with cognitive disabilities and psychiatric conditions after TBI, especially anxiety and depression. The constellation of post-injury cognitive and behavioral symptoms suggest permanent effects of injury on neurotransmission. Guided in part by preclinical studies, clinical trials have focused on high-yield pathophysiologic mechanisms, including protein aggregation, inflammation, metabolic disruption, cell generation, physiology, and alterations in neurotransmitter signaling. Despite successful treatment of experimental TBI in animal models, clinical studies based on these findings have failed to translate to humans. The current international effort to reshape TBI research is focusing on redefining the taxonomy and characterization of TBI. In addition, as the next round of clinical trials is pending, there is a pressing need to consider what the field has learned over the past two decades of research, and how we can best capitalize on this knowledge to inform the hypotheses for future innovations. Thus, it is critically important to extend our understanding of the pathophysiology of TBI, particularly to mechanisms that are associated with recovery versus development of chronic symptoms. In this review, we focus on the pathology of neurotransmission after TBI, reflecting on what has been learned from both the preclinical and clinical studies, and we discuss new directions and opportunities for future work.

Neuron-specific deficits of bioenergetic processes in the dorsolateral prefrontal cortex in schizophrenia.

Schizophrenia is a devastating illness that affects over 2 million people in the United States and costs society billions of dollars annually. New insights into the pathophysiology of schizophrenia are needed to provide the conceptual framework to facilitate development of new treatment strategies. We examined bioenergetic pathways in the dorsolateral prefrontal cortex (DLPFC) of subjects with schizophrenia and control subjects using western blot analysis, quantitative real-time polymerase chain reaction, and enzyme/substrate assays. Laser-capture microdissection-quantitative polymerase chain reaction was used to examine these pathways at the cellular level. We found decreases in hexokinase (HXK) and phosphofructokinase (PFK) activity in the DLPFC, as well as decreased PFK1 mRNA expression. In pyramidal neurons, we found an increase in monocarboxylate transporter 1 mRNA expression, and decreases in HXK1, PFK1, glucose transporter 1 (GLUT1), and GLUT3 mRNA expression. These results suggest abnormal bioenergetic function, as well as a neuron-specific defect in glucose utilization, in the DLPFC in schizophrenia.

Kinome Array Profiling of Patient-Derived Pancreatic Ductal Adenocarcinoma Identifies Differentially Active Protein Tyrosine Kinases.

Pancreatic cancer remains one of the most difficult malignancies to treat. Minimal improvements in patient outcomes and persistently abysmal patient survival rates underscore the great need for new treatment strategies. Currently, there is intense interest in therapeutic strategies that target tyrosine protein kinases. Here, we employed kinome arrays and bioinformatic pipelines capable of identifying differentially active protein tyrosine kinases in different patient-derived pancreatic ductal adenocarcinoma (PDAC) cell lines and wild-type pancreatic tissue to investigate the unique kinomic networks of PDAC samples and posit novel target kinases for pancreatic cancer therapy. Consistent with previously described reports, the resultant peptide-based kinome array profiles identified increased protein tyrosine kinase activity in pancreatic cancer for the following kinases: epidermal growth factor receptor (EGFR), fms related receptor tyrosine kinase 4/vascular endothelial growth factor receptor 3 (FLT4/VEGFR-3), insulin receptor (INSR), ephrin receptor A2 (EPHA2), platelet derived growth factor receptor alpha (PDGFRA), SRC proto-oncogene kinase (SRC), and tyrosine kinase non receptor 2 (TNK2). Furthermore, this study identified increased activity for protein tyrosine kinases with limited prior evidence of differential activity in pancreatic cancer. These protein tyrosine kinases include B lymphoid kinase (BLK), Fyn-related kinase (FRK), Lck/Yes-related novel kinase (LYN), FYN proto-oncogene kinase (FYN), lymphocyte cell-specific kinase (LCK), tec protein kinase (TEC), hemopoietic cell kinase (HCK), ABL proto-oncogene 2 kinase (ABL2), discoidin domain receptor 1 kinase (DDR1), and ephrin receptor A8 kinase (EPHA8). Together, these results support the utility of peptide array kinomic analyses in the generation of potential candidate kinases for future pancreatic cancer therapeutic development.

Emerging Kinase Therapeutic Targets in Pancreatic Ductal Adenocarcinoma and Pancreatic Cancer Desmoplasia.

Kinase drug discovery represents an active area of therapeutic research, with previous pharmaceutical success improving patient outcomes across a wide variety of human diseases. In pancreatic ductal adenocarcinoma (PDAC), innovative pharmaceutical strategies such as kinase targeting have been unable to appreciably increase patient survival. This may be due, in part, to unchecked desmoplastic reactions to pancreatic tumors. Desmoplastic stroma enhances tumor development and progression while simultaneously restricting drug delivery to the tumor cells it protects. Emerging evidence indicates that many of the pathologic fibrotic processes directly or indirectly supporting desmoplasia may be driven by targetable protein tyrosine kinases such as Fyn-related kinase (FRK); B lymphoid kinase (BLK); hemopoietic cell kinase (HCK); ABL proto-oncogene 2 kinase (ABL2); discoidin domain receptor 1 kinase (DDR1); Lck/Yes-related novel kinase (LYN); ephrin receptor A8 kinase (EPHA8); FYN proto-oncogene kinase (FYN); lymphocyte cell-specific kinase (LCK); tec protein kinase (TEC). Herein, we review literature related to these kinases and posit signaling networks, mechanisms, and biochemical relationships by which this group may contribute to PDAC tumor growth and desmoplasia.

Pioglitazone improves working memory performance when administered in chronic TBI.

Traumatic brain injury (TBI) is a leading cause of long-term disability in the United States. Even in comparatively mild injuries, cognitive and behavioral symptoms can persist for years, and there are currently no established strategies for mitigating symptoms in chronic injury. A key feature of TBI-induced damage in acute and chronic injury is disruption of metabolic pathways. As neurotransmission, and therefore cognition, are highly dependent on the supply of energy, we hypothesized that modulating metabolic activity could help restore behavioral performance even when treatment was initiated weeks after TBI. We treated rats with pioglitazone, a FDA-approved drug for diabetes, beginning 46 days after lateral fluid percussion injury and tested working memory performance in the radial arm maze (RAM) after 14 days of treatment. Pioglitazone treated TBI rats performed significantly better in the RAM test than untreated TBI rats, and similarly to control animals. While hexokinase activity in hippocampus was increased by pioglitazone treatment, there was no upregulation of either the neuronal glucose transporter or hexokinase enzyme expression. Expression of glial markers GFAP and Iba-1 were also not influenced by pioglitazone treatment. These studies suggest that targeting brain metabolism, in particular hippocampal metabolism, may be effective in alleviating cognitive symptoms in chronic TBI.

Contrasting the Role of xCT and GLT-1 Upregulation in the Ability of Ceftriaxone to Attenuate the Cue-Induced Reinstatement of Cocaine Seeking and Normalize AMPA Receptor Subunit Expression.

Long-term treatment with ceftriaxone attenuates the reinstatement of cocaine seeking while increasing the function of the glutamate transporter 1 (GLT-1) and system xC- (Sxc) in the nucleus accumbens core (NAc). Sxc contributes the majority of nonsynaptic extracellular glutamate in the NAc, while GLT-1 is responsible for the majority of glutamate uptake. Here we used antisense to decrease the expression of GLT-1 and xCT (a catalytic subunit of Sxc) to determine the relative importance of both proteins in mediating the ability of ceftriaxone to prevent cue-induced reinstatement of cocaine seeking and normalize glutamatergic proteins in the NAc of rats. Intra-NAc xCT knockdown prevented ceftriaxone from attenuating reinstatement and from upregulating GLT-1 and resulted in increased surface expression of AMPA receptor subunits GluA1 and GluA2. Intra-NAc GLT-1 knockdown also prevented ceftriaxone from attenuating reinstatement and from upregulating xCT expression, without affecting GluA1 and GluA2 expression. In the absence of cocaine or ceftriaxone treatment, xCT knockdown in the NAc increased the expression of both GluA1 and GluA2 without affecting GLT-1 expression while GLT-1 knockdown had no effect. PCR and immunoprecipitation of GLT-1 revealed that ceftriaxone does not upregulate GLT-1 and xCT through a transcriptional mechanism, and their coregulation by ceftriaxone is not mediated by physical interaction. These data support important and distinct roles for xCT and GLT-1 in the actions of ceftriaxone and add to a body of literature finding evidence for coregulation of these transporters. Our results also point to xCT expression and subsequent basal glutamate levels as being a key mediator of AMPA receptor expression in the NAc.SIGNIFICANCE STATEMENT Ceftriaxone attenuates the reinstatement of cocaine, alcohol, and heroin seeking. The mechanism of action of this behavioral effect has been attributed to glutamate transporter 1 (GLT-1) and xCT (a catalytic subunit of Sxc)/Sxc upregulation in the nucleus accumbens core. Here we used an antisense strategy to knock down GLT-1 or xCT in the nucleus accumbens core and examined the behavioral and molecular consequences. While upregulation of both xCT and GLT-1 are essential to the ability of ceftriaxone to attenuate cue-induced reinstatement of cocaine seeking, each protein uniquely affects the expression of other glutamate receptor and transporter proteins. We also report that reducing basal glutamate levels through the manipulation of xCT expression increases the surface expression of AMPA receptor subunits, providing insight to the mechanism by which cocaine alters AMPA surface expression.