Serotonin Transporter (SERT) Expression Modulates the Composition of the Western-Diet-Induced Microbiota in Aged Female Mice.

Background. The serotonin transporter (SERT), highly expressed in the gut and brain, is implicated in metabolic processes. A genetic variant of the upstream regulatory region of the SLC6A4 gene encoding SERT, the so-called short (s) allele, in comparison with the long (l) allele, results in the decreased function of this transporter, altered serotonergic regulation, an increased risk of psychiatric pathology and type-2 diabetes and obesity, especially in older women. Aged female mice with the complete (Sert-/-: KO) or partial (Sert+/-: HET) loss of SERT exhibit more pronounced negative effects following their exposure to a Western diet in comparison to wild-type (Sert+/+: WT) animals. Aims. We hypothesized that these effects might be mediated by an altered gut microbiota, which has been shown to influence serotonin metabolism. We performed V4 16S rRNA sequencing of the gut microbiota in 12-month-old WT, KO and HET female mice that were housed on a control or Western diet for three weeks. Results. The relative abundance of 11 genera was increased, and the abundance of 6 genera was decreased in the Western-diet-housed mice compared to the controls. There were correlations between the abundance of Streptococcus and Ruminococcaceae_UCG-014 and the expression of the pro-inflammatory marker Toll-like-Receptor 4 (Tlr4) in the dorsal raphe, as well as the expression of the mitochondrial activity marker perixome-proliferator-activated-receptor-cofactor-1b (Ppargc1b) in the prefrontal cortex. Although there was no significant impact of genotype on the microbiota in animals fed with the Control diet, there were significant interactions between diet and genotype. Following FDR correction, the Western diet increased the relative abundance of Intestinimonas and Atopostipes in the KO animals, which was not observed in the other groups. Erysipelatoclostridium abundance was increased by the Western diet in the WT group but not in HET or KO animals. Conclusions. The enhanced effects of a challenge with a Western diet in SERT-deficient mice include the altered representation of several gut genera, such as Intestinimonas, Atopostipes and Erysipelatoclostridium, which are also implicated in serotonergic and lipid metabolism. The manipulation of these genera may prove useful in individuals with the short SERT allele.

In FUS[1-359]-tg mice O,S-dibenzoyl thiamine reduces muscle atrophy, decreases glycogen synthase kinase 3 beta, and normalizes the metabolome.

Mutations in the gene encoding the RNA/DNA-binding protein Fused in Sarcoma (FUS) have been detected in familial amyotrophic lateral sclerosis (ALS) patients. FUS has been found to be a critical component of the oxidative damage repair complex that might explain its role in neurodegeneration. Here, we examined what impact antioxidant treatment with thiamine (vitamine B1), or its more bioavailable derivative O,S-dibenzoylthiamine (DBT), would have on the hallmarks of pathology in the FUS[1-359]-transgenic mouse model of ALS. From 8-weeks old, in the pre-symptomatic phase of disease, animals received either thiamine, DBT (200 mg/kg/day), or vehicle for 6 weeks. We examined physiological, behavioral, molecular and histological outcomes, as well as the serum metabolome using nuclear magnetic resonance (NMR). The DBT-treated mice displayed improvements in physiological outcomes, motor function and muscle atrophy compared to vehicle, and the treatment normalized levels of brain glycogen synthase kinase-3ß (GSK-3ß), GSK-3ß mRNA and IL-1ß mRNA in the spinal cord. Analysis of the metabolome revealed an increase in the levels of choline and lactate in the vehicle-treated FUS mutants alone, which is also elevated in the cerebrospinal fluid of ALS patients, and reduced glucose and lipoprotein concentrations in the FUS[1-359]-tg mice, which were not the case in the DBT-treated mutants. The administration of thiamine had little impact on the outcome measures, but it did normalize circulating HDL levels. Thus, our study shows that DBT therapy in FUS mutants is more effective than thiamine and highlights how metabolomics may be used to evaluate therapy in this model.

Predation Stress Causes Excessive Aggression in Female Mice with Partial Genetic Inactivation of Tryptophan Hydroxylase-2: Evidence for Altered Myelination-Related Processes.

The interaction between brain serotonin (5-HT) deficiency and environmental adversity may predispose females to excessive aggression. Specifically, complete inactivation of the gene encoding tryptophan hydroxylase-2 (Tph2) results in the absence of neuronal 5-HT synthesis and excessive aggressiveness in both male and female null mutant (Tph2-/-) mice. In heterozygous male mice (Tph2+/-), there is a moderate reduction in brain 5-HT levels, and when they are exposed to stress, they exhibit increased aggression. Here, we exposed female Tph2+/- mice to a five-day rat predation stress paradigm and assessed their emotionality and social interaction/aggression-like behaviors. Tph2+/- females exhibited excessive aggression and increased dominant behavior. Stressed mutants displayed altered gene expression of the 5-HT receptors Htr1a and Htr2a, glycogen synthase kinase-3 ß (GSK-3ß), and c-fos as well as myelination-related transcripts in the prefrontal cortex: myelin basic protein (Mbp), proteolipid protein 1 (Plp1), myelin-associated glycoprotein (Mag), and myelin oligodendrocyte glycoprotein (Mog). The expression of the plasticity markers synaptophysin (Syp) and cAMP response element binding protein (Creb), but not AMPA receptor subunit A2 (GluA2), were affected by genotype. Moreover, in a separate experiment, naïve female Tph2+/- mice showed signs of enhanced stress resilience in the modified swim test with repeated swimming sessions. Taken together, the combination of a moderate reduction in brain 5-HT with environmental challenges results in behavioral changes in female mice that resemble the aggression-related behavior and resilience seen in stressed male mutants; additionally, the combination is comparable to the phenotype of null mutants lacking neuronal 5-HT. Changes in myelination-associated processes are suspected to underpin the molecular mechanisms leading to aggressive behavior.

Sex-Specific ADHD-like Behaviour, Altered Metabolic Functions, and Altered EEG Activity in Sialyltransferase ST3GAL5-Deficient Mice.

A deficiency in GM3-derived gangliosides, resulting from a lack of lactosylceramide-alpha-2,3-sialyltransferase (ST3GAL5), leads to severe neuropathology, including epilepsy and metabolic abnormalities. Disruption of ganglioside production by this enzyme may also have a role in the development of neuropsychiatric disorders. ST3Gal5 knock-out (St3gal5-/-) mice lack a-, b-, and c-series gangliosides, but exhibit no overt neuropathology, possibly owing to the production of compensatory 0-series glycosphingolipids. Here, we sought to investigate the possibility that St3gal5-/- mice might exhibit attention-deficit/hyperactivity disorder (ADHD)-like behaviours. In addition, we evaluated potential metabolic and electroencephalogram (EEG) abnormalities. St3gal5-/- mice were subjected to behavioural testing, glucose tolerance tests, and the levels of expression of brain and peripheral A and B isoforms of the insulin receptor (IR) were measured. We found that St3gal5-/- mice exhibit locomotor hyperactivity, impulsivity, neophobia, and anxiety-like behavior. The genotype also altered blood glucose levels and glucose tolerance. A sex bias was consistently found in relation to body mass and peripheral IR expression. Analysis of the EEG revealed an increase in amplitude in St3gal5-/- mice. Together, St3gal5-/- mice exhibit ADHD-like behaviours, altered metabolic and EEG measures providing a useful platform for better understanding of the contribution of brain gangliosides to ADHD and associated comorbidities.

ASD-like behaviors, a dysregulated inflammatory response and decreased expression of PLP1 characterize mice deficient for sialyltransferase ST3GAL5.

Gangliosides are glycosphingolipids, which are abundant in brain, are known to modulate ion channels and cell-to-cell communication. Deficiencies can result in aberrant myelination and altered immune responses, which can give rise to neurodevelopmental psychiatric disorders. However, to date, little mechanistic data is available on how ganglioside deficiencies contribute to the behavioural disorders. In humans, the loss of lactosylceramide-alpha-2,3-sialyltransferase (ST3Gal5) leads to a severe neuropathology, but in ST3Gal5 knock-out (St3gal5-/-) mice the absence of GM3 and associated a-, b- and c-series gangliosides is partially compensated by 0-series gangliosides and there is no overt behavioural phenotype. Here, we sought to examine the behavioural and molecular consequences of GM3 loss more closely. Mutants of both sexes exhibited impaired conditioned taste aversion in an inhibitory learning task and anxiety-like behaviours in the open field, moderate motor deficits, abnormal social interactions, excessive grooming and rearing behaviours. Taken together, the aberrant behaviours are suggestive of an autism spectrum disorder (ASD)-like syndrome. Molecular analysis showed decreased gene and protein expression of proteolipid protein-1 (Plp1) and over expression of proinflammatory cytokines, which has been associated with ASD-like syndromes. The inflammatory and behavioural responses to lipopolysaccharide (LPS) were also altered in the St3gal5-/- mice compared to wild-type, which is indicative of the importance of GM3 gangliosides in regulating immune responses. Together, the St3gal5-/- mice display ASD-like behavioural features, altered response to systemic inflammation, signs of hypomyelination and neuroinflammation, which suggests that deficiency in a- and b-series gangliosides could contribute to the development of an ASD-like pathology in humans.

Exposure to bacterial lipopolysaccharidein early life affects the expression of ionotropic glutamate receptor genes and is accompanied by disturbances in long-term potentiation and cognitive functions in young rats.

Infections in childhood play an essential role in the pathogenesis of cognitive and psycho-emotional disorders. One of the possible mechanisms of these impairments is changes in the functional properties of NMDA and AMPA glutamate receptors in the brain. We suggest that bacterial infections during the early life period, which is critical for excitatory synapse maturation, can affect the subunit composition of NMDA and AMPA receptors. In the present study, we investigated the effect of repetitive lipopolysaccharide (LPS) intraperitoneal (i.p.) administration (25 µg/kg/day on P14, 16, and 18), mimicking an infectious disease, on the expression of subunits of NMDA and AMPA receptors in young rats. We revealed a substantial decrease of GluN2B subunit expression in the hippocampus at P23 using Western blot analysis and real-time polymerase chain reaction assay. Moderate changes were also found in GluN1, GluN2A, and GluA1 mRNA expression. The LPS-treated rats exhibited decreased exploratory and locomotor activity in the open field test and the impairment of spatial learning in the Morris water maze. Behavioral impairments were accompanied by a significant reduction in long-term hippocampal synaptic potentiation. Our data indicate that LPS-treatment in the critical period for excitatory synapse maturation alters ionotropic glutamate receptor gene expression, disturbs synaptic plasticity, and alters behavior.

Stress-induced aggression in heterozygous TPH2 mutant mice is associated with alterations in serotonin turnover and expression of 5-HT6 and AMPA subunit 2A receptors.

BACKGROUND: The contribution of gene-environment interactions that lead to excessive aggression is poorly understood. Environmental stressors and mutations of the gene encoding tryptophan hydroxylase-2 (TPH2) are known to influence aggression. For example, TPH2 null mutant mice (Tph2-/-) are naturally highly aggressive, while heterozygous mice (Tph2+/-) lack a behavioral phenotype and are considered endophenotypically normal. Here we sought to discover whether an environmental stressor would affect the phenotype of the genetically 'susceptible' heterozygous mice (Tph2+/-). METHODS: Tph2+/- male mice or Tph2+/+ controls were subjected to a five-day long rat exposure stress paradigm. Brain serotonin metabolism and the expression of selected genes encoding serotonin receptors, AMPA receptors, and stress markers were studied. RESULTS: Stressed Tph2+/- mice displayed increased levels of aggression and social dominance, whereas Tph2+/+ animals became less aggressive and less dominant. Brain tissue concentrations of serotonin, its precursor hydroxytryptophan and its metabolite 5-hydroxyindoleacetic acid were significantly altered in all groups in the prefrontal cortex, striatum, amygdala, hippocampus and dorsal raphe after stress. Compared to non-stressed animals, the concentration of 5-hydroxytryptophan was elevated in the amygdala though decreased in the other brain structures. The overexpression of the AMPA receptor subunit, GluA2, and downregulation of 5-HT6 receptor, as well as overexpression of c-fos and glycogen-synthase-kinase-3ß (GSK3-ß), were found in most structures of the stressed Tph2+/- mice. LIMITATIONS: Rescue experiments would help to verify causal relationships of reported changes. CONCLUSIONS: The interaction of a partial TPH2 gene deficit with stress results in pathological aggression and molecular changes, and suggests that the presence of genetic susceptibility can augment aggression in seemingly resistant phenotypes.

Metabolic, Molecular, and Behavioral Effects of Western Diet in Serotonin Transporter-Deficient Mice: Rescue by Heterozygosity?

Reduced function of the serotonin transporter (SERT) is associated with increased susceptibility to anxiety and depression and with type-2 diabetes, which is especially true in older women. Preference for a "Western diet" (WD), enriched with saturated fat, cholesterol, and sugars, may aggravate these conditions. In previous studies, decreased glucose tolerance, central and peripheral inflammation, dyslipidemia, emotional, cognitive, and social abnormalities were reported in WD-fed young female mice. We investigated the metabolic, molecular, and behavioral changes associated with a 3-week-long dietary regime of either the WD or control diet in 12-month-old female mice with three different Sert genotypes: homozygous (Slc6a4) gene knockout (Sert -/-: KO), heterozygous (Sert +/-: HET), or wild-type mice (Sert +/+: WT). In the WT-WD and KO-WD groups, but not in HET-WD-fed mice, most of changes induced by the WD paralleled those found in the younger mice, including brain overexpression of inflammatory marker Toll-like receptor 4 (Tlr4) and impaired hippocampus-dependent performance in the marble test. However, the 12-month-old female mice became obese. Control diet KO mice exhibited impaired hippocampal-dependent behaviors, increased brain expression of the serotonin receptors Htr2c and Htr1b, as well as increased Tlr4 and mitochondrial regulator, peroxisome proliferator-activated receptor gamma-coactivator-1a (Ppargc1a). Paradoxically, these, and other changes, were reversed in KO-WD mutants, suggesting a complex interplay between Sert deficiency and metabolic factors as well as potential compensatory molecular mechanisms that might be disrupted by the WD exposure. Most, but not all, of the changes in gene expression in the brain and liver of KO mice were not exhibited by the HET mice fed with either diet. Some of the WD-induced changes were similar in the KO-WD and HET-WD-fed mice, but the latter displayed a "rescued" phenotype in terms of diet-induced abnormalities in glucose tolerance, neuroinflammation, and hippocampus-dependent performance. Thus, complete versus partial Sert inactivation in aged mice results in distinct metabolic, molecular, and behavioral consequences in response to the WD. Our findings show that Sert +/- mice are resilient to certain environmental challenges and support the concept of heterosis as evolutionary adaptive mechanism.

Prefrontal cortex inflammation and liver pathologies accompany cognitive and motor deficits following Western diet consumption in non-obese female mice.

AIMS: The high sugar and lipid content of the Western diet (WD) is associated with metabolic dysfunction, non-alcoholic steatohepatitis, and it is an established risk factor for neuropsychiatric disorders. Our previous studies reported negative effects of the WD on rodent emotionality, impulsivity, and sociability in adulthood. Here, we investigated the effect of the WD on motor coordination, novelty recognition, and affective behavior in mice as well as molecular and cellular endpoints in brain and peripheral tissues. MAIN METHODS: Female C57BL/6 J mice were fed the WD for three weeks and were investigated for glucose tolerance, insulin resistance, liver steatosis, and changes in motor coordination, object recognition, and despair behavior in the swim test. Lipids and liver injury markers, including aspartate-transaminase, alanine-transaminase and urea were measured in blood. Serotonin transporter (SERT) expression, the density of Iba1-positive cells and concentration of malondialdehyde were measured in brain. KEY FINDINGS: WD-fed mice exhibited impaired glucose tolerance and insulin resistance, a loss of motor coordination, deficits in novel object exploration and recognition, increased helplessness, dyslipidemia, as well as signs of a non-alcoholic steatohepatitis (NASH)-like syndrome: liver steatosis and increased liver injury markers. Importantly, these changes were accompanied by decreased SERT expression, elevated numbers of microglia cells and malondialdehyde levels in, and restricted to, the prefrontal cortex. SIGNIFICANCE: The WD induces a spectrum of behaviors that are more reminiscent of ADHD and ASD than previously recognized and suggests that, in addition to the impairment of impulsivity and sociability, the consumption of a WD might be expected to exacerbate motor dysfunction that is also known to be associated with adult ADHD and ASD.

Neuro-Cells therapy improves motor outcomes and suppresses inflammation during experimental syndrome of amyotrophic lateral sclerosis in mice.

AIMS: Mutations in DNA/RNA-binding factor (fused-in-sarcoma) FUS and superoxide dismutase-1 (SOD-1) cause amyotrophic lateral sclerosis (ALS). They were reproduced in SOD-1-G93A (SOD-1) and new FUS[1-359]-transgenic (FUS-tg) mice, where inflammation contributes to disease progression. The effects of standard disease therapy and anti-inflammatory treatments were investigated using these mutants. METHODS: FUS-tg mice or controls received either vehicle, or standard ALS treatment riluzole (8 mg/kg/day), or anti-inflammatory drug a selective blocker of cyclooxygenase-2 celecoxib (30 mg/kg/day) for six weeks, or a single intracerebroventricular (i.c.v.) infusion of Neuro-Cells (a preparation of 1.39 × 106 mesenchymal and hemopoietic human stem cells, containing 5 × 105 of CD34+ cells), which showed anti-inflammatory properties. SOD-1 mice received i.c.v.-administration of Neuro-Cells or vehicle. RESULTS: All FUS-tg-treated animals displayed less marked reductions in weight gain, food/water intake, and motor deficits than FUS-tg-vehicle-treated mice. Neuro-Cell-treated mutants had reduced muscle atrophy and lumbar motor neuron degeneration. This group but not celecoxib-FUS-tg-treated mice had ameliorated motor performance and lumbar expression of microglial activation marker, ionized calcium-binding adapter molecule-1 (Iba-1), and glycogen-synthase-kinase-3ß (GSK-3ß). The Neuro-Cells-treated-SOD-1 mice showed better motor functions than vehicle-treated-SOD-1 group. CONCLUSION: The neuropathology in FUS-tg mice is sensitive to standard ALS treatments and Neuro-Cells infusion. The latter improves motor outcomes in two ALS models possibly by suppressing microglial activation.

Platelets mediate protective neuroinflammation and promote neuronal plasticity at the site of neuronal injury.

It is generally accepted that inflammation within the CNS contributes to neurodegeneration after traumatic brain injury (TBI), but it is not clear how inflammation is initiated in the absence of infection and whether this neuroinflammation is predominantly beneficial or detrimental. We have previously found that brain-enriched glycosphingolipids within neuronal lipid rafts (NLR) induced platelet degranulation and secretion of neurotransmitters and pro-inflammatory factors. In the present study, we compared TBI-induced inflammation and neurodegeneration in wild-type vs. St3gal5 deficient (ST3-/-) mice that lack major CNS-specific glycosphingolipids. After TBI, microglial activation and CNS macrophage infiltration were substantially reduced in ST3-/- animals. However, ST3-/- mice had a larger area of CNS damage with marked neuronal/axonal loss. The interaction of platelets with NLR stimulated neurite growth, increased the number of PSD95-positive dendritic spines, and intensified neuronal activity. Adoptive transfer and blocking experiments provide further that platelet-derived serotonin and platelet activating factor plays a key role in the regulation of sterile neuroinflammation, hemorrhage and neuronal plasticity after TBI.

Insulin receptor in the brain: Mechanisms of activation and the role in the CNS pathology and treatment.

While the insulin receptor (IR) was found in the CNS decades ago, the brain was long considered to be an insulin-insensitive organ. This view is currently revisited, given emerging evidence of critical roles of IR-mediated signaling in development, neuroprotection, metabolism, and plasticity in the brain. These diverse cellular and physiological IR activities are distinct from metabolic IR functions in peripheral tissues, thus highlighting region specificity of IR properties. This particularly concerns the fact that two IR isoforms, A and B, are predominantly expressed in either the brain or peripheral tissues, respectively, and neurons express exclusively IR-A. Intriguingly, in comparison with IR-B, IR-A displays high binding affinity and is also activated by low concentrations of insulin-like growth factor-2 (IGF-2), a regulator of neuronal plasticity, whose dysregulation is associated with neuropathologic processes. Deficiencies in IR activation, insulin availability, and downstream IR-related mechanisms may result in aberrant IR-mediated functions and, subsequently, a broad range of brain disorders, including neurodevelopmental syndromes, neoplasms, neurodegenerative conditions, and depression. Here, we discuss findings on the brain-specific features of IR-mediated signaling with focus on mechanisms of primary receptor activation and their roles in the neuropathology. We aimed to uncover the remaining gaps in current knowledge on IR physiology and highlight new therapies targeting IR, such as IR sensitizers.

Alterations in Properties of Glutamatergic Transmission in the Temporal Cortex and Hippocampus Following Pilocarpine-Induced Acute Seizures in Wistar Rats.

Temporal lobe epilepsy (TLE) is the most common type of focal epilepsy in humans, and is often developed after an initial precipitating brain injury. This form of epilepsy is frequently resistant to pharmacological treatment; therefore, the prevention of TLE is the prospective approach to TLE therapy. The lithium-pilocarpine model in rats replicates some of the main features of TLE in human, including the pathogenic mechanisms of cell damage and epileptogenesis after a primary brain injury. In the present study, we investigated changes in the properties of glutamatergic transmission during the first 3 days after pilocarpine-induced acute seizures in Wistar rats (PILO-rats). Using RT-PCR and electrophysiological techniques, we compared the changes in the temporal cortex (TC) and hippocampus, brain areas differentially affected by seizures. On the first day, we found a transient increase in a ratio of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and N-methyl d-aspartate (NMDA) receptors in the excitatory synaptic response in pyramidal neurons of the CA1 area of the dorsal hippocampus, but not in the TC. This was accompanied by an increase in the slope of input-output (I/O) curves for fEPSPs recorded in CA1, suggesting an enhanced excitability in AMPARs in this brain area. There was no difference in the AMPA/NMDA ratio in control rats on the third day. We also revealed the alterations in NMDA receptor subunit composition in PILO-rats. The GluN2B/GluN2A mRNA expression ratio increased in the dorsal hippocampus but did not change in the ventral hippocampus or the TC. The kinetics of NMDA-mediated evoked EPSCs in hippocampal neurons was slower in PILO-rats compared with control animals. Ifenprodil, a selective antagonist of GluN2B-containing NMDARs, diminished the area and amplitude of evoked EPSCs in CA1 pyramidal cells more efficiently in PILO-rats compared with control animals. These results demonstrate that PILO-induced seizures lead to more severe alterations in excitatory synaptic transmission in the dorsal hippocampus than in the TC. Seizures affect the relative contribution of AMPA and NMDA receptor conductances in the synaptic response and increase the proportion of GluN2B-containing NMDARs in CA1 pyramidal neurons. These alterations disturb normal circuitry functions in the hippocampus, may cause neuron damage, and may be one of the important pathogenic mechanisms of TLE.

Autism-Like Behaviours and Memory Deficits Result from a Western Diet in Mice.

Nonalcoholic fatty liver disease, induced by a Western diet (WD), evokes central and peripheral inflammation that is accompanied by altered emotionality. These changes can be associated with abnormalities in social behaviour, hippocampus-dependent cognitive functions, and metabolism. Female C57BL/6J mice were fed with a regular chow or with a WD containing 0.2% of cholesterol and 21% of saturated fat for three weeks. WD-treated mice exhibited increased social avoidance, crawl-over and digging behaviours, decreased body-body contacts, and hyperlocomotion. The WD-fed group also displayed deficits in hippocampal-dependent performance such as contextual memory in a fear conditioning and pellet displacement paradigms. A reduction in glucose tolerance and elevated levels of serum cholesterol and leptin were also associated with the WD. The peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PPARGC1a) mRNA, a marker of mitochondrial activity, was decreased in the prefrontal cortex, hippocampus, hypothalamus, and dorsal raphe, suggesting suppressed brain mitochondrial functions, but not in the liver. This is the first report to show that a WD can profoundly suppress social interactions and induce dominant-like behaviours in naïve adult mice. The spectrum of behaviours that were found to be induced are reminiscent of symptoms associated with autism, and, if paralleled in humans, suggest that a WD might exacerbate autism spectrum disorder.

Changes of AMPA receptor properties in the neocortex and hippocampus following pilocarpine-induced status epilepticus in rats.

Temporal lobe epilepsy (TLE) is the most common type of epilepsy in humans. The lithium-pilocarpine model in rodents reproduces some of the main features of human TLE. Three-week-old Wistar rats were used in this study. The changes in AMPA receptor subunit composition were investigated in several brain areas, including the medial prefrontal cortex (mPFC), the temporal cortex (TC), and the dorsal (DH) and ventral hippocampus (VH) during the first week following pilocarpine-induced status epilepticus (PILO-induced SE). In the hippocampus, GluA1 and GluA2 mRNA expression slightly decreased after PILO-induced SE and returned to the initial level on the seventh day. We did not detect any significant changes in mRNA expression of the GluA1 and GluA2 subunits in the TC, whereas in the mPFC we observed a significant increase of GluA1 mRNA expression on the third day and a decrease in GluA2 mRNA expression during the entire first week. Accordingly, the GluA1/GluA2 expression ratio increased in the mPFC, and the functional properties of the pyramidal cell excitatory synapses were disturbed. Using whole-cell voltage-clamp recordings, we found that on the third day following PILO-induced SE, isolated mPFC pyramidal neurons showed an inwardly rectifying current-voltage relation of kainate-evoked currents, suggesting the presence of GluA2-lacking calcium-permeable AMPARs (CP-AMPARs). IEM-1460, a selective antagonist of CP-AMPARs, significantly reduced the amplitude of evoked EPSC in pyramidal neurons from mPFC slices on the first and third days, but not on the seventh day. The antagonist had no effects on EPSC amplitude in slices from control animals. Thus, our data demonstrate that PILO-induced SE affects subunit composition of AMPARs in different brain areas, including the mPFC. SE induces transient (up to few days) incorporation of CP-AMPARs in the excitatory synapses of mPFC pyramidal neurons, which may disrupt normal circuitry functions.

Insulin receptor sensitizer, dicholine succinate, prevents both Toll-like receptor 4 (TLR4) upregulation and affective changes induced by a high-cholesterol diet in mice.

BACKGROUND: High cholesterol intake in mice induces hepatic lipid dystrophy and inflammation, signs of non-alcoholic fatty liver disease (NAFLD), depressive- and anxiety-like behaviors, and the up-regulation of brain and liver Toll-like receptor 4 (Tlr4). Here, we investigated whether dicholine succinate (DS), an insulin receptor sensitizer and mitochondrial complex II substrate would interact with these effects. METHODS: C57BL/6J mice were given a 0.2%-cholesterol diet for 3 weeks, alone or along with oral DS administration, or a control feed. Outcomes included behavioral measures of anxiety/depression, and Tlr4 and peroxisome-proliferator-activated-receptor-gamma coactivator-1b (PPARGC1b) expression. RESULTS: 50mg/kg DS treatment for 3 weeks partially ameliorated the cholesterol-induced anxiety- and depressive-like changes. Mice were next treated at the higher dose (180mg/kg), either for the 3-week period of dietary intervention, or for the last two weeks. Three-week DS administration normalized behaviors in the forced swim and O-maze tests and abolished the Tlr4 up-regulation in the brain and liver. The delayed, 2-week DS treatment had similar effects on Tlr4 expression and largely rescued the above-mentioned behaviors. Suppression of PPARGC1b, a master regulator of mitochondrial biogenesis, by the high cholesterol diet, was prevented with the 3-week administration, and markedly diminished by the a 2-week administration of DS. None of treatments prevented hepatic dystrophy and triglyceride accumulation. LIMITATIONS: Other conditions have to be tested to define possible limitations of reported effects of DS. CONCLUSIONS: DS treatment did not alter the patho-morphological substrates of NAFLD syndrome in mice, but ameliorated its molecular and behavioral consequences, likely by activating mitochondrial functions and anti-inflammatory mechanisms.