Irene Gracia-Rubio

Maternal separation induces neuroinflammation and long-lasting emotional alterations in mice.

Early life experiences play a key role in brain function and behaviour. Adverse events during childhood are therefore a risk factor for psychiatric disease during adulthood, such as mood disorders. Maternal separation is a validated mouse model for maternal neglect, producing negative early life experiences that result in subsequent emotional alteration. Mood disorders have been found to be associated with neurochemical changes and neurotransmitter deficits such as reduced availability of monoamines in discrete brain areas. Emotional alterations like depression result in reduced serotonin availability and enhanced kynurenine metabolism through the action of indoleamine 2, 3-dioxygenase in response to neuroinflammatory factors. This mechanism involves regulation of the neurotransmitter system by neuroinflammatory agents, linking mood regulation to neuroinmunological reactions. In this context, the aim of this study was to investigate the effects of maternal separation with early weaning on emotional behaviour in mice. We investigated neuroinflammatory responses and the state of the tryptophan-kynurenine metabolic pathway in discrete brain areas following maternal separation. We show that adverse events during early life increase risk of long-lasting emotional alterations during adolescence and adulthood. These emotional alterations are particularly severe in females. Behavioural impairments were associated with microglia activation and disturbed tryptophan-kynurenine metabolism in brain areas related to emotional control. This finding supports the preeminent role of neuroinflammation in emotional disorders.

Targeting tryptophan and tyrosine metabolism by liquid chromatography tandem mass spectrometry

An imbalance in tryptophan (Trp) and tyrosine (Tyr) metabolites is associated with neurological and inflammatory disorders. The accurate and precise measurement of these compounds in biological specimens is a powerful tool to understand the biochemical state in several diseases. In this study, a rapid, accurate and sensitive method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the targeted analysis of the metabolism of Trp and Tyr has been developed and validated. The method allows for the adequate quantification of Trp, Tyr and, eight Trp metabolites, three Tyr metabolites, together with four competitive large neutral amino acids. Serotonin, 5-hydroxyindoleacetic acid, kynurenine, kynurenic acid, dopamine, and homovanilic acid were among the targeted compounds. Sample preparation, chromatographic separation and mass spectrometric detection were optimized in human urine, human plasma and mice prefrontal cortex extracts. The method was shown to be linear (r>0.98) in the range of endogenous concentrations for all studied metabolites. In general, the limits of detection were suitable for the detection of the endogenous levels. Intra- and inter-assay precisions below 25% and accuracies ranging from 80 to 120% were found for most of the analytes. The use of labeled internal standards corrected the moderate matrix effect observed for some compounds. The applicability of the method was confirmed by analyzing urine samples collected from 13 healthy volunteers and comparing the results with previously established normal ranges. In addition, urine samples from two patients and a heterozygous carrier of a family with disturbed monoamine metabolism due to a loss of function mutation in the MAOA gene (X-linked) were analyzed and compared with samples from controls. All data together show the potential of the developed approach for targeted metabolomic studies.

Genetic blockade of adenosine A2A receptors induces cognitive impairments and anatomical changes related to psychotic symptoms in mice

Schizophrenia is a chronic severe mental disorder with a presumed neurodevelopmental origin, and no effective treatment. Schizophrenia is a multifactorial disease with genetic, environmental and neurochemical etiology. The main theories on the pathophysiology of this disorder include alterations in dopaminergic and glutamatergic neurotransmission in limbic and cortical areas of the brain. Early hypotheses also suggested that nucleoside adenosine is a putative affected neurotransmitter system, and clinical evidence suggests that adenosine adjuvants improve treatment outcomes, especially in poorly responsive patients. Hence, it is important to elucidate the role of the neuromodulator adenosine in the pathophysiology of schizophrenia. A2A adenosine receptor (A2AR) subtypes are expressed in brain areas controlling motivational responses and cognition, including striatum, and in lower levels in hippocampus and cerebral cortex. The aim of this study was to characterize A2AR knockout (KO) mice with complete and specific inactivation of A2AR, as an animal model for schizophrenia. We performed behavioral, anatomical and neurochemical studies to assess psychotic-like symptoms in adult male and female KO and wild-type (WT) littermates. Our results show impairments in inhibitory responses and sensory gating in A2AR KO animals. Hyperlocomotion induced by d-amphetamine and MK-801 was reduced in KO animals when compared to WT littermates. Moreover, A2AR KO animals show motor disturbances, social and cognitive alterations. Finally, behavioral impairments were associated with enlargement of brain lateral ventricles and decreased BDNF levels in the hippocampus. These data highlight the role of adenosine in the pathophysiology of schizophrenia and provide new possibilities for the therapeutic management of schizophrenia.

Maternal Separation Impairs Cocaine-Induced Behavioural Sensitization in Adolescent Mice.

Adverse early-life conditions induce persistent disturbances that give rise to negative emotional states. Therefore, early life stress confers increased vulnerability to substance use disorders, mainly during adolescence as the brain is still developing. In this study, we investigated the consequences of maternal separation, a model of maternal neglect, on the psychotropic effects of cocaine and the neuroplasticity of the dopaminergic system. Our results show that mice exposed to maternal separation displayed attenuated behavioural sensitization, while no changes were found in the rewarding effects of cocaine in the conditioned place preference paradigm and in the reinforcing effects of cocaine in the self-administration paradigm. The evaluation of neuroplasticity in the striatal dopaminergic pathways revealed that mice exposed to maternal separation exhibited decreased protein expression levels of D2 receptors and increased levels of the transcriptional factor Nurr1. Furthermore, animals exposed to maternal separation and treated with cocaine exhibited increased DA turnover and protein expression levels of DAT and D2R, while decreased Nurr1 and Pitx3 protein expression levels were observed when compared with saline-treated mice. Taken together, our data demonstrate that maternal separation caused an impairment of cocaine-induced behavioural sensitization possibly due to a dysfunction of the dopaminergic system, a dysfunction that has been proposed as a factor of vulnerability for developing substance use disorders.

Modulation of cAMP-Specific PDE without Emetogenic Activity: New Sulfide-Like PDE7 Inhibitors

A forward chemical genetic approach was followed to discover new targets and lead compounds for Parkinsons disease (PD) treatment. By analysis of the cell protection produced by some small molecules, a diphenyl sulfide compound was revealed to be a new phosphodiesterase 7 (PDE7) inhibitor and identified as a new hit. This result allows us to confirm the utility of PDE7 inhibitors as a potential pharmacological treatment of PD. On the basis of these data, a diverse family of diphenyl sulfides has been developed and pharmacologically evaluated in the present work. Moreover, to gain insight into the safety of PDE7 inhibitors for human chronic treatment, we evaluated the new compounds in a surrogate emesis model, showing nonemetic effects.

Maternal alcohol binge drinking induces persistent neuroinflammation associated with myelin damage and behavioural dysfunctions in offspring mice

&NA; Alcohol binge drinking is on the increase in the young adult population, and consumption during pregnancy can be deleterious for foetal development. Maternal alcohol consumption leads to a wide range of long‐lasting morphological and behavioural deficiencies known as foetal alcohol spectrum disorders (FASD), associated with neurodevelopmental disabilities. We sought to test the effects of alcohol on neuroimmune system activation and its potential relation to alcohol‐induced neurodevelopmental and persistent neurobehavioural effects in offspring after maternal alcohol binge drinking during the prenatal period or in combination with lactation. Pregnant C57BL/6 female mice underwent a procedure for alcohol binge drinking either during gestation or both the gestation and lactation periods. Adult male offspring were assessed for cognitive functions and motor coordination. Early alcohol exposure induced motor coordination impairments in the rotarod test. Object recognition memory was not affected by maternal alcohol binge drinking, but Y‐maze performance was impaired in pre‐ and early postnatal alcohol‐exposed mice. Behavioural effects were associated with an upregulation of pro‐inflammatory signalling (Toll‐like receptor 4, nuclear factor‐kappa B p65, NOD‐like receptor protein 3, caspase‐1, and interleukin‐1&bgr;), gliosis, neuronal cell death and a reduction in several structural myelin proteins (myelin‐associated glycoprotein, myelin basic protein, myelin proteolipid protein and myelin regulatory factor) in both the prefrontal cortex and hippocampus of adult mice exposed to alcohol. Altogether, our results reveal that maternal binge‐like alcohol consumption induces neuroinflammation and myelin damage in the brains of offspring and that such effects may underlie the persistent cognitive and behavioural impairments observed in FASD. HighlightsMaternal alcohol binge drinking induces neuroinflammation in offspring.Motor coordination impairments are found in early alcohol‐exposed mice.Prenatal and early postnatal alcohol exposure induces cognitive deficits.Myelin damage is found in mice developmentally exposed to alcohol.

Binge ethanol drinking during adolescence modifies cocaine responses in mice

Binge ethanol drinking is an emerging pattern of excessive consumption among adolescents and young adults. Repeated ethanol intoxication has negative consequences during critical periods of brain development. Therefore, binge ethanol intake represents a vulnerability factor that promotes subsequent manifestations of neuropsychiatric disorders. In this study, we investigated the effects of oral binge ethanol intake during adolescence on the subsequent effects of cocaine in C57BL/6 mice. Firstly, we evaluated the oral ethanol intake of two binge ethanol procedures with different ethanol concentrations (20% v/v versus 30%, v/v). The highest ethanol intake was found in mice exposed to the lower ethanol concentration (20% v/v). In a second experiment, mice exposed to binge ethanol procedure were evaluated to study the effects of cocaine on locomotor activity, behavioural sensitization, and the reinforcing effects of cocaine in the self-administration paradigm. Mice exposed to ethanol binging showed discrete detrimental effects in responses to cocaine in the different experiments evaluated. Our findings revealed that the pattern of binge ethanol consumption in adolescent mice here evaluated produced a weak facilitation of cocaine responses. The present study highlights the importance of interventions to limit the deleterious effects of binge ethanol drinking during adolescence.

Cognitive impairments associated with alterations in synaptic proteins induced by the genetic loss of adenosine A2A receptors in mice

&NA; The study of psychiatric disorders usually focuses on emotional symptoms assessment. However, cognitive deficiencies frequently constitute the core symptoms, are often poorly controlled and handicap individuals quality of life. Adenosine receptors, through the control of both dopamine and glutamate systems, have been implicated in the pathophysiology of several psychiatric disorders such as schizophrenia and attention deficit/hyperactivity disorder. Indeed, clinical data indicate that poorly responsive schizophrenia patients treated with adenosine adjuvants show improved treatment outcomes. The A2A adenosine receptor subtype (A2AR) is highly expressed in brain areas controlling cognition and motivational responses including the striatum, hippocampus and cerebral cortex. Accordingly, we study the role of A2AR in the regulation of cognitive processes based on a complete cognitive behavioural analysis coupled with the assessment of neurogenesis and sub‐synaptic protein expression in adult and middle‐aged A2AR constitutional knockout mice and wild‐type littermates. Our results show overall cognitive impairments in A2AR knockout mice associated with a decrease in new‐born hippocampal neuron proliferation and concomitant changes in synaptic protein expression, in both the prefrontal cortex and the hippocampus. These results suggest a deficient adenosine signalling in cognitive processes, thus providing new opportunities for the therapeutic management of cognitive deficits associated with psychiatric disorders. HighlightsDeletion of A2AR induces overall cognitive deficits in adult and middle‐aged mice.Deficits in cognition are associated to decreases in neurogenesis.A2AR deletion induces changes in synaptic proteins in the PFC and hippocampus.

Maternal separation increases alcohol-drinking behaviour and reduces endocannabinoid levels in the mouse striatum and prefrontal cortex

Childhood adversity is associated with an increased risk of mood, anxiety and substance use disorders. Maternal separation is a reliable rodent model of early life adversity that leads to depression-like symptoms, which may increase the vulnerability to alcohol consumption during adolescence. However, the specific alterations in the pattern of alcohol consumption induced by maternal separation and the underlying molecular mechanisms are still unclear. The purpose of this study is to evaluate the long-term effects of maternal separation with early weaning (MSEW) on emotional and social behaviour, alcohol rewarding properties, and alcohol consumption, abstinence and relapse in adolescent male C57BL/6 mice. In addition, endocannabinoid and monoamine levels were analysed in discrete brain areas. Results showed that MSEW mice presented emotional alterations related to depressive-like behaviour and modified endocannabinoid levels in the striatum and the prefrontal cortex. MSEW mice also showed impairments in alcohol-induced conditioned place preference and higher alcohol intake in a model of binge drinking. Moreover, MSEW animals displayed a higher propensity to relapse in the two-bottle choice paradigm following a period of alcohol abstinence associated with reduced monoamine levels in the striatum. Such results indicate that exposure to early life stress increased the vulnerability to alcohol binge-drinking during adolescence, which may be partially explained by decreased sensitivity to alcohol rewarding properties and the ability to potentiate alcohol intake following a period of abstinence.