Methyl-CpG binding protein 2 dysfunction provides stress vulnerability with sex- and zygosity-dependent outcomes.

Stress vulnerability is a critical factor for the development of trauma-related disorders; however, its biological underpinnings are not clear. We demonstrated that dysfunctions in the X-linked epigenetic factor methyl-CpG binding protein 2 (MeCP2) provide trauma vulnerability in male mice. Given the prominent role of sex in stress outcomes, we explored the effects of MeCP2 hypofunctionality in females. Female mice carrying truncated MeCP2 (heterozygous and homozygous) and wild type controls (wt) were tested for fear memory. Stress-induced corticosterone release and brain expression of hypothalamic-pituitary-adrenal (HPA) axis regulatory genes were also evaluated in wt and mutant mice of both sexes. Although heterozygous females displayed a normal stress-related behavioural profile, homozygous mice showed enhanced memory recall for the threatening context compared to wt, thus recapitulating the phenotype previously evidenced in hemizygous males. Interestingly, MeCP2 truncation abolished the sex differences in stress-induced corticosterone release, which was found increased in mutant males, whereas blunted in mutant females in a zygosity-independent manner. Although heterozygous mice did not differ from controls, homozygous females and hemizygous males showed increased hypotalamic Crh and Avp mRNAs and a differentially altered expression of Fkbp5 in cortical areas. Present results demonstrate that in female mice carrying truncated MeCP2, altered stress responsivity is driven by homozygosity, whereas heterozygosity does not lead to maladaptive stress outcomes. MeCP2 dysfunctions thus provide stress vulnerability in mice with sex- and zygosity-dependent outcomes.

Treatment with the Bacterial Toxin CNF1 Selectively Rescues Cognitive and Brain Mitochondrial Deficits in a Female Mouse Model of Rett Syndrome Carrying a MeCP2-Null Mutation.

Rett syndrome (RTT) is a rare neurological disorder caused by mutations in the X-linked MECP2 gene and a major cause of intellectual disability in females. No cure exists for RTT. We previously reported that the behavioural phenotype and brain mitochondria dysfunction are widely rescued by a single intracerebroventricular injection of the bacterial toxin CNF1 in a RTT mouse model carrying a truncating mutation of the MeCP2 gene (MeCP2-308 mice). Given the heterogeneity of MECP2 mutations in RTT patients, we tested the CNF1 therapeutic efficacy in a mouse model carrying a null mutation (MeCP2-Bird mice). CNF1 selectively rescued cognitive defects, without improving other RTT-related behavioural alterations, and restored brain mitochondrial respiratory chain complex activity in MeCP2-Bird mice. To shed light on the molecular mechanisms underlying the differential CNF1 effects on the behavioural phenotype, we compared treatment effects on relevant signalling cascades in the brain of the two RTT models. CNF1 provided a significant boost of the mTOR activation in MeCP2-308 hippocampus, which was not observed in the MeCP2-Bird model, possibly explaining the differential effects of CNF1. These results demonstrate that CNF1 efficacy depends on the mutation beared by MeCP2-mutated mice, stressing the need of testing potential therapeutic approaches across RTT models.

Stimulation of the Serotonin Receptor 7 Restores Brain Histone H3 Acetylation and MeCP2 Corepressor Protein Levels in a Female Mouse Model of Rett Syndrome.

Rett syndrome (RTT) is a rare neurological disorder caused by mutations in the X-linked MECP2 gene, characterized by severe behavioral and physiological impairments for which no cure is available. The stimulation of serotonin receptor 7 (5-HT7R) with its selective agonist LP-211 (0.25 mg/kg/day for 7 days) was proved to rescue neurobehavioral alterations in a mouse model of RTT. In the present study, we aimed at gaining insight into the mechanisms underpinning the efficacy of 5-HT7R pharmacological stimulation by investigating its epigenetic outcomes in the brain of RTT female mice bearing a truncating MeCP2 mutation. Treatment with LP-211 normalized the reduced histone H3 acetylation and HDAC3/NCoR levels, and increased HDAC1/Sin3a expression in RTT mouse cortex. Repeated 5-HT7R stimulation also appeared to strengthen the association between NCoR and MeCP2 in the same brain region. A different profile was found in RTT hippocampus, where LP-211 rescued H3 hyperacetylation and increased HDAC3 levels. Overall, the present data highlight a new scenario on the relationship between histone acetylation and serotoninergic pathways. 5-HT7R is confirmed as a pivotal therapeutic target for the recovery of neuronal function supporting the translational value of this promising pharmacological approach for RTT.

Chronic Treatment with Cannabidiolic Acid (CBDA) Reduces Thermal Pain Sensitivity in Male Mice and Rescues the Hyperalgesia in a Mouse Model of Rett Syndrome.

Rett syndrome (RTT) is a rare neurologic disorder, characterized by severe behavioural and physiological symptoms. RTT is caused by mutations in the MECP2 gene in about 95% of cases and to date no cure is available. Recent evidence suggests that non-euphoric phytocannabinoids (pCBs) extracted from Cannabis sativa may represent innovative therapeutic molecules for RTT, with the cannabinoid cannabidivarin having beneficial effects on behavioural and brain molecular alterations in RTT mouse models. The present study evaluated the potential therapeutic efficacy for RTT of cannabidiolic acid (CBDA; 0.2, 2, 20 mg/kg through intraperitoneal injections for 14 days), a pCB that has proved to be effective for the treatment of nausea and anxiety in rodents. This study demonstrates that systemic treatment with the low dose of CBDA has anti-nociceptive effects and reduces the thermal hyperalgesia in 8 month-old MeCP2-308 male mice, a validated RTT mouse model. CBDA did not affect other behavioural or molecular parameters. These results provide support to the antinociceptive effects of CBDA and stress the need for further studies aimed at clarifying the mechanisms underlying the abnormal pain perception in RTT.

Maternal Immune Activation in Mice Only Partially Recapitulates the Autism Spectrum Disorders Symptomatology.

Prenatal viral/bacterial infections are considered risk factors for autism spectrum disorders (ASD) and rodent models of maternal immune activation (MIA) have been developed and extensively used in preclinical studies. Poly inosinic-cytidylic acid (Poly I:C) was injected in C57BL6/J dams to mimic a viral infection on gestational day 12.5; the experimental design includes 10/12 litters in each treatment group and data were analysed always considering the litter-effect; neonatal (spontaneous motor behaviour and ultrasonic vocalizations) and adult [open field, marble burying, social approach, fear conditioning, prepulse inhibition (PPI)] offspring of both sexes were tested. In vivo magnetic resonance imaging/spectroscopy (MRI-MRS) and high-performance liquid chromatography (HPLC) to quantify both aminoacid and/or neurotransmitter concentration in cortical and striatal regions were also carried out. In both sexes high levels of repetitive motor responses and sensory gating deficits in PPI were the more striking effects of Poly I:C, whereas no alteration of social responses were evidenced. Poly I:C treatment did not affect mean values, but, intriguingly, increased variability in the levels of four aminoacids (aspartate glycine and GABA) selectively in males. As a whole prenatal Poly I:C induced relevant long-term alterations in explorative-stereotyped motor responses and in sensory gating, sparing cognitive and social competences. When systematically assessing differences between male and female siblings within each litter, no significant sex differences were evident except for increased variability of four aminoacid levels in male brains. As a whole, prenatal Poly I:C paradigms appear to be a useful tool to investigate the profound and translationally-relevant effects of developmental immune activation on brain and behavioural development, not necessarily recapitulating the full ASD symptomatology.

Methyl-CpG binding protein 2 functional alterations provide vulnerability to develop behavioral and molecular features of post-traumatic stress disorder in male mice.

Post-traumatic stress disorder (PTSD) is a mental disorder characterized by symptoms of persistent anxiety arising after exposure to traumatic events. Stress susceptibility due to a complex interplay between genetic and environmental factors plays a major role in the disease etiology, although biological underpinnings have not been clarified. We hypothesized that aberrant functionality of the methyl-CpG binding protein 2 (MECP2), a master regulator of experience-dependent epigenetic programming, confers susceptibility to develop PTSD-like symptomatology in the aftermath of traumatic events. Transgenic male mice expressing a truncated form of MeCP2 protein (MeCP2-308) were exposed at adulthood to a trauma in the form of high-intensity footshocks. The presence and duration of PTSD-like symptoms were assessed and compared to those of trauma-exposed wild type littermates and MeCP2-308 mice subjected to a mild stressor. The effects of fluoxetine, a prime pharmacological PTSD treatment, on PTSD-like symptomatology were also explored. Trauma-exposed MeCP2-308 mice showed long-lasting hyperresponsiveness to both correct and incorrect predictors of the trauma and persistent increased avoidance of trauma-related cues. Traumatized MeCP2-308 mice also displayed abnormal post-traumatic plasma levels of the stress hormone corticosterone and altered peripheral gene expression mirroring that of PTSD patients. Fluoxetine improved PTSD-like symptoms in trauma-exposed MeCP2-308 mice. These findings provide evidence that MeCP2 dysfunction results in increased susceptibility to develop PTSD-like symptoms after trauma exposure, and identify trauma-exposed MeCP2-308 mice as a new tool to investigate the underpinnings of PTSD vulnerability.

Rett syndrome before regression: A time window of overlooked opportunities for diagnosis and intervention.

Rett syndrome (RTT) is a rare neurological disorder primarily affecting females, causing severe cognitive, social, motor and physiological impairments for which no cure currently exists. RTT clinical diagnosis is based on the peculiar progression of the disease, since patients show an apparently normal initial development with a subsequent sudden regression at around 2 years of age. Accumulating evidences are rising doubts regarding the absence of early impairments, hence questioning the concept of regression. We reviewed the published literature addressing the pre-symptomatic stage of the disease in both patients and animal models with a particular focus on behavioral, physiological and brain abnormalities. The emerging picture delineates subtle, but reliable impairments that precede the onset of overt symptoms whose bases are likely set up already during embryogenesis. Some of the outlined alterations appear transient, suggesting compensatory mechanisms to occur in the course of development. There is urgent need for more systematic developmental analyses able to detect early pathological markers to be used as diagnostic tools and precocious targets of time-specific interventions.

Rescue of prepulse inhibition deficit and brain mitochondrial dysfunction by pharmacological stimulation of the central serotonin receptor 7 in a mouse model of CDKL5 Deficiency Disorder.

Mutations in the X-linked cyclin-dependent kinase-like 5 (CDKL5) gene cause CDKL5 Deficiency Disorder (CDD), a rare neurodevelopmental syndrome characterized by severe behavioural and physiological symptoms. No cure is available for CDD. CDKL5 is a kinase that is abundantly expressed in the brain and plays a critical role in neurodevelopmental processes, such as neuronal morphogenesis and plasticity. This study provides the first characterization of the neurobehavioural phenotype of 1 year old Cdkl5-null mice and demonstrates that stimulation of the serotonin receptor 7 (5-HT7R) with the agonist molecule LP-211 (0.25 mg/kg once/day for 7 days) partially rescues the abnormal phenotype and brain molecular alterations in Cdkl5-null male mice. In particular, LP-211 treatment completely normalizes the prepulse inhibition defects observed in Cdkl5-null mice and, at a molecular level, restores the abnormal cortical phosphorylation of rpS6, a downstream target of mTOR and S6 kinase, which plays a direct role in regulating protein synthesis. Moreover, we demonstrate for the first time that mitochondria show prominent functional abnormalities in Cdkl5-null mouse brains that can be restored by pharmacological stimulation of brain 5-HT7R.

Chronic treatment with the phytocannabinoid Cannabidivarin (CBDV) rescues behavioural alterations and brain atrophy in a mouse model of Rett syndrome.

Rett syndrome (RTT) is a rare neurodevelopmental disorder, characterized by severe behavioural and physiological symptoms. RTT is caused by mutations in the MECP2 gene in about 95% of cases and to date no cure is available. The endocannabinoid system modulates several physiological processes and behavioural responses that are impaired in RTT and its deregulation has been associated with neuropsychiatric disorders which have symptoms in common with RTT. The present study evaluated the potential therapeutic efficacy for RTT of cannabidivarin (CBDV), a non-psychotropic phytocannabinoid from Cannabis sativa that presents antagonistic properties on the G protein-coupled receptor 55 (GPR55), the most recently identified cannabinoid receptor. Present results demonstrate that systemic treatment with CBDV (2, 20, 100 mg/Kg ip for 14 days) rescues behavioural and brain alterations in MeCP2-308 male mice, a validated RTT model. The CBDV treatment restored the compromised general health status, the sociability and the brain weight in RTT mice. A partial restoration of motor coordination was also observed. Moreover, increased levels of GPR55 were found in RTT mouse hippocampus, suggesting this G protein-coupled receptor as new potential target for the treatment of this disorder. Present findings highlight for the first time for RTT the translational relevance of CBDV, an innovative therapeutic agent that is under active investigation in the clinical setting.

HPLC Determination of Bioactive Sulfur Compounds, Amino Acids and Biogenic Amines in Biological Specimens.

There is an increasing interest for analytical methods aimed to detect biological sulfur-containing amines, because of their involvement in human diseases and metabolic disorders. This work describes an improved HPLC method for the determination of sulfur containing amino acids and amines from different biological matrices. We optimized a pre-column derivatization procedure using dabsyl chloride, in which dabsylated products can be monitored spectrophotometrically at 460 nm. This method allows the simultaneous analysis of biogenic amines, amino acids and sulfo-amino compounds including carnosine, dopamine, epinephrine, glutathione, cysteine, taurine, lanthionine, and cystathionine in brain specimens, urines, plasma, and cell lysates. Moreover, the method is suitable for the study of physiological and non-physiological derivatives of taurine and glutathione such as hypotaurine, homotaurine, homocysteic acid and S-acetylglutathione. The present method displays good efficiency of derivatization, having the advantage to give rise to stable products compared to other derivatizing agents such as o-phthalaldehyde and dansyl chloride.With this method, we provide a tool to study sulfur cycle from a metabolic point of view in relation to the pattern of biological amino-compounds, allowing researchers to get a complete scenario of organic sulfur and amino metabolism in tissues and cells.

Stimulation of the brain serotonin receptor 7 rescues mitochondrial dysfunction in female mice from two models of Rett syndrome.

Rett syndrome (RTT) is a rare neurodevelopmental disorder, characterized by severe behavioral and physiological symptoms. Mutations in the methyl CpG binding protein 2 gene (MECP2) cause more than 95% of classic cases, and currently there is no cure for this devastating disorder. Recently we have demonstrated that neurobehavioral and brain molecular alterations can be rescued in a RTT mouse model, by pharmacological stimulation of the brain serotonin receptor 7 (5-HT7R). This member of the serotonin receptor family, crucially involved in the regulation of brain structural plasticity and cognitive processes, can be stimulated by systemic repeated treatment with LP-211, a brain-penetrant selective agonist. The present study extends previous findings by demonstrating that LP-211 treatment (0.25 mg/kg, once per day for 7 days) rescues mitochondrial respiratory chain impairment, oxidative phosphorylation deficiency and the reduced energy status in the brain of heterozygous female mice from two highly validated mouse models of RTT (MeCP2-308 and MeCP2-Bird mice). Moreover, LP-211 treatment completely restored the radical species overproduction by brain mitochondria in the MeCP2-308 model and partially recovered the oxidative imbalance in the more severely affected MeCP2-Bird model. These results provide the first evidence that RTT brain mitochondrial dysfunction can be rescued targeting the brain 5-HT7R and add compelling preclinical evidence of the potential therapeutic value of LP-211 as a pharmacological approach for this devastating neurodevelopmental disorder.