Neural conditional ablation of the protein tyrosine phosphatase receptor Delta PTPRD impairs gliogenesis in the developing mouse brain cortex.

Neurodevelopmental disorders are characterized by alterations in the development of the cerebral cortex, including aberrant changes in the number and function of neural cells. Although neurogenesis is one of the most studied cellular processes in these pathologies, little evidence is known about glial development. Genetic association studies have identified several genes associated with neurodevelopmental disorders. Indeed, variations in the PTPRD gene have been associated with numerous brain disorders, including autism spectrum disorder, restless leg syndrome, and schizophrenia. We previously demonstrated that constitutive loss of PTPRD expression induces significant alterations in cortical neurogenesis, promoting an increase in intermediate progenitors and neurons in mice. However, its role in gliogenesis has not been evaluated. To assess this, we developed a conditional knockout mouse model lacking PTPRD expression in telencephalon cells. Here, we found that the lack of PTPRD in the mouse cortex reduces glial precursors, astrocytes, and oligodendrocytes. According to our results, this decrease in gliogenesis resulted from a reduced number of radial glia cells at gliogenesis onset and a lower gliogenic potential in cortical neural precursors due to less activation of the JAK/STAT pathway and reduced expression of gliogenic genes. Our study shows PTPRD as a regulator of the glial/neuronal balance during cortical neurodevelopment and highlights the importance of studying glial development to understand the etiology of neurodevelopmental diseases.

LAR Receptor Tyrosine Phosphatase Family in Healthy and Diseased Brain.

Protein phosphatases are major regulators of signal transduction and they are involved in key cellular mechanisms such as proliferation, differentiation, and cell survival. Here we focus on one class of protein phosphatases, the type IIA Receptor-type Protein Tyrosine Phosphatases (RPTPs), or LAR-RPTP subfamily. In the last decade, LAR-RPTPs have been demonstrated to have great importance in neurobiology, from neurodevelopment to brain disorders. In vertebrates, the LAR-RPTP subfamily is composed of three members: PTPRF (LAR), PTPRD (PTPδ) and PTPRS (PTPσ), and all participate in several brain functions. In this review we describe the structure and proteolytic processing of the LAR-RPTP subfamily, their alternative splicing and enzymatic regulation. Also, we review the role of the LAR-RPTP subfamily in neural function such as dendrite and axon growth and guidance, synapse formation and differentiation, their participation in synaptic activity, and in brain development, discussing controversial findings and commenting on the most recent studies in the field. Finally, we discuss the clinical outcomes of LAR-RPTP mutations, which are associated with several brain disorders.

Comparative Efficacy of a High-Dose vs Standard-Dose Hepatitis B Revaccination Schedule Among Patients With HIV: A Randomized Clinical Trial.

Importance: Active immunization for hepatitis B virus (HBV) infection is recommended in patients living with HIV. Limited evidence is available about the most appropriate regimen of HBV vaccination among those who have not responded to an initial schedule. Objective: To determine the efficacy of a high-dose schedule compared with a standard dose of HBV vaccination. Design, Setting, and Participants: This double-masked, parallel-group, randomized controlled trial included patients living with HIV at a single outpatient HIV and hepatology clinic in Chile for whom previous HBV vaccination had failed. Patients with hepatitis B surface antibody (anti-HBs) titers less than 10 IU/L after an initial HBV vaccination regimen were included. Consecutive patients were recruited between December 2013 and March 2018. Data were analyzed in June 2018 using intention-to-treat analysis. Intervention: The high-dose HBV vaccination group consisted of 3 doses of 40 µg recombinant hepatitis B vaccine at 0, 1, and 2 months. The standard-dose group received 3 doses 20 µg each at 0, 1, and 2 months. Main Outcomes and Measures: Primary outcome was the serologic response to HBV vaccination (anti-HBs greater than 10 IU/L) 4 to 8 weeks after completion of the schedule. Secondary outcomes were anti-HBs greater than 100 IU/L and seroprotective anti-HBs at 1 year follow up. Results: A total of 107 patients underwent randomization (55 to the standard-dose group, 52 to the high-dose group); 81 (75.7%) were men, and the mean (SD) patient age was 47.0 (13.3) years. Nearly all patients were receiving antiretroviral therapy (105 patients [98%]) and 92 patients (86%) had an undetectable HIV viral load. Mean (SD) CD4 count was 418 (205) cells/mm3. There were no differences in baseline characteristics between groups. Serological response in the high-dose group was found in 36 of 50 patients (72%; 95% CI, 56.9%-82.9%) compared with 28 of 55 patients in the standard-dose group (51%; 95% CI, 37.1%-64.6%) (odds ratio, 2.48; 95% CI, 1.02-6.10; P = .03). Mean (SD) anti-HB levels were 398.0 (433.4) IU/L in the high-dose group and 158.5 (301.4) IU/L in the standard-dose group (P < .001). Of patients with a serological response in the high-dose group, 29 of 36 (80.6%) had anti-HBs titers greater than 100 IU/L compared with 14 of 28 responders (50.0%) in the standard-dose group (P = .02). At 1-year follow-up, 20 of 25 patients (80.0%) with a serological response in the high-dose group had protective anti-HBs vs 9 of 23 patients (39.1%) in the standard-dose group (P = .01). Conclusions and Relevance: The results of this randomized clinical trial suggest that use of a high-dose regimen for HBV revaccination for patients with HIV achieves a higher and longer-lasting serological response as compared with a standard-dose regimen. Trial Registration: ClinicalTrials.gov Identifier: NCT02003703.

The Protein Tyrosine Phosphatase Receptor Delta Regulates Developmental Neurogenesis.

PTPRD is a receptor protein tyrosine phosphatase that is genetically associated with neurodevelopmental disorders. Here, we asked whether Ptprd mutations cause aberrant neural development by perturbing neurogenesis in the murine cortex. We show that loss of Ptprd causes increases in neurogenic transit-amplifying intermediate progenitor cells and cortical neurons and perturbations in neuronal localization. These effects are intrinsic to neural precursor cells since acute Ptprd knockdown causes similar perturbations. PTPRD mediates these effects by dephosphorylating receptor tyrosine kinases, including TrkB and PDGFRß, and loss of Ptprd causes the hyperactivation of TrkB and PDGFRß and their downstream MEK-ERK signaling pathway in neural precursor cells. Moreover, inhibition of aberrant TrkB or MEK activation rescues the increased neurogenesis caused by knockdown or homozygous loss of Ptprd. These results suggest that PTPRD regulates receptor tyrosine kinases to ensure appropriate numbers of intermediate progenitor cells and neurons, suggesting a mechanism for its genetic association with neurodevelopmental disorders.

The Role of the Rodent Insula in Anxiety.

The human insula has been consistently reported to be overactivated in all anxiety disorders, activation which has been suggested to be proportional to the level of anxiety and shown to decrease with effective anxiolytic treatment. Nonetheless, studies evaluating the direct role of the insula in anxiety are lacking. Here, we set out to investigate the role of the rodent insula in anxiety by either inactivating different insular regions via microinjections of glutamatergic AMPA receptor antagonist CNQX or activating them by microinjection of GABA receptor antagonist bicuculline in rats, before measuring anxiety-like behavior using the elevated plus maze. Inactivation of caudal and medial insular regions induced anxiogenic effects, while their activation induced anxiolytic effects. In contrast, inactivation of more rostral areas induced anxiolytic effects and their activation, anxiogenic effects. These results suggest that the insula in the rat has a role in the modulation of anxiety-like behavior in rats, showing regional differences; rostral regions have an anxiogenic role, while medial and caudal regions have an anxiolytic role, with a transition area around bregma +0.5. The present study suggests that the insula has a direct role in anxiety.

Scavenger Receptor-A deficiency impairs immune response of microglia and astrocytes potentiating Alzheimer's disease pathophysiology.

Late onset Alzheimer disease's (LOAD) main risk factor is aging. Although it is not well known which age-related factors are involved in its development, evidence points out to the involvement of an impaired amyloid-ß (Aß) clearance in the aged brain among possible causes. Glial cells are the main scavengers of the brain, where Scavenger Receptor class A (SR-A) emerges as a relevant player in AD because of its participation in Aß uptake and in the modulation of glial cell inflammatory response. Here, we show that SR-A expression is reduced in the hippocampus of aged animals and APP/PS1 mice. Given that Aß deposition increases in the aging brain, we generated a triple transgenic mouse, which accumulates Aß and is knockout for SR-A (APP/PS1/SR-A-/-) to evaluate Aß accumulation and the inflammatory outcome of SR-A depletion in the aged brain. The lifespan of APP/PS1/SR-A-/- mice was greatly reduced, accompanied by a 3-fold increase in plasmatic pro-inflammatory cytokines, and reduced performance in a working memory behavioral assessment. Microglia and astrocytes lacking SR-A displayed impaired oxidative response and nitric oxide production, produced up to 7-fold more pro-inflammatory cytokines and showed a 12-fold reduction in anti-inflammatory cytokines release, with conspicuous changes in lipopolysaccharide-induced glial activation. Isolated microglia from young and adult mice lacking SR-A showed a 50% reduction in phagocytic activity. Our results indicate that reduced expression of SR-A can deregulate glial inflammatory response and potentiate Aß accumulation, two mechanisms that could contribute to AD progression.

Age-Dependent Changes in the Activation and Regulation of Microglia.

As we age, a large number of physiological and molecular changes affect the normal functioning of cells, tissues, and the organism as a whole. One of the main changes is the establishment of a state of systemic inflammatory activation, which has been termed "inflamm-aging"; a mild chronic inflammation of the aging organism that reduces the ability to generate an efficient response against stressor stimuli. As any other system, the nervous system undergoes these aging-related changes; the neuroinflammatory state depends mainly on the dysregulated activation of microglia, the innate immune cells of the central nervous system (CNS) and the principal producers of reactive oxygen species. As the brain ages, microglia acquire a phenotype that is increasingly inflammatory and cytotoxic, generating a hostile environment for neurons. There is mounting evidence that this process facilitates development of neurodegenerative diseases, for which the greatest risk factor is age. In this chapter, we will review key aging-associated changes occurring in the central nervous system, focusing primarily on the changes that occur in aging microglia, the inflammatory and oxidative stressful environment they establish, and their impaired regulation. In addition, we will discuss the effects of aged microglia on neuronal function and their participation in the development of neurodegenerative pathologies such as Parkinson's and Alzheimer's diseases.

Expression Pattern of Scavenger Receptors and Amyloid-ß Phagocytosis of Astrocytes and Microglia in Culture are Modified by Acidosis: Implications for Alzheimer's Disease.

The pathological hallmarks of Alzheimer's disease (AD) are amyloid-ß (Aß) plaques, neurofibrillary tangles, and glia activation. The pathology also includes vascular amyloidosis and cerebrovascular disease. Vascular compromise can result in hypoperfusion, local tissue hypoxia, and acidosis. Activated microglia and astrocytes can phagocytose Aß through membrane receptors that include scavenger receptors. Changes in glial cells induced by extracellular acidosis could play a role in the development of AD. Here, we assess whether extracellular acidosis changes glial cell properties relevant for Aß clearance capacity. Incubation of glial cells on acidified culture medium (pH 6.9 or 6.5) for 24-48 h resulted in decreased cell diameter, with thinner branches in astrocytes, slight reduction in cell body size in microglia, a transient decrease in astrocyte adhesion to substrates, and a persistent decrease in microglia adhesion compared with control media (pH 7.4). Astrocyte Aß phagocytosis decreased at pH 6.9 and 6.5, whereas microglia phagocytosis only transiently decreased in acidified media. Scavenger receptors class B member I (SR-BI) increased and scavenger receptors-macrophage receptors with collagenous structures (SR-MARCO) decreased in astrocytes cultured at pH 6.5. In contrast, in microglia exposed to pH 6.5, expression of SR-BI and SR-MARCO increased and fatty acid translocase (CD-36) decreased. In conclusion, the acidic environment changed the adhesiveness and morphology of both microglia and astrocytes, but only astrocytes showed a persistent decrease in Aß clearance activity. Expression of scavenger receptors was affected differentially in microglia and astrocytes by acidosis. These changes in scavenger receptor patterns can affect the activation of glia and their contribution to neurodegeneration.

Role of TGFß signaling in the pathogenesis of Alzheimer's disease.

Aging is the main risk factor for Alzheimer's disease (AD); being associated with conspicuous changes on microglia activation. Aged microglia exhibit an increased expression of cytokines, exacerbated reactivity to various stimuli, oxidative stress, and reduced phagocytosis of ß-amyloid (Aß). Whereas normal inflammation is protective, it becomes dysregulated in the presence of a persistent stimulus, or in the context of an inflammatory environment, as observed in aging. Thus, neuroinflammation can be a self-perpetuating deleterious response, becoming a source of additional injury to host cells in neurodegenerative diseases. In aged individuals, although transforming growth factor ß (TGFß) is upregulated, its canonical Smad3 signaling is greatly reduced and neuroinflammation persists. This age-related Smad3 impairment reduces protective activation while facilitating cytotoxic activation of microglia through several cellular mechanisms, potentiating microglia-mediated neurodegeneration. Here, we critically discuss the role of TGFß-Smad signaling on the cytotoxic activation of microglia and its relevance in the pathogenesis of AD. Other protective functions, such as phagocytosis, although observed in aged animals, are not further induced by inflammatory stimuli and TGFß1. Analysis in silico revealed that increased expression of receptor scavenger receptor (SR)-A, involved in Aß uptake and cell activation, by microglia exposed to TGFß, through a Smad3-dependent mechanism could be mediated by transcriptional co-factors Smad2/3 over the MSR1 gene. We discuss that changes of TGFß-mediated regulation could at least partially mediate age-associated microglia changes, and, together with other changes on inflammatory response, could result in the reduction of protective activation and the potentiation of cytotoxicity of microglia, resulting in the promotion of neurodegenerative diseases.

Reduced dopamine and glutamate neurotransmission in the nucleus accumbens of quinpirole-sensitized rats hints at inhibitory D2 autoreceptor function.

Dopamine from the ventral tegmental area and glutamate from several brain nuclei converge in the nucleus accumbens (NAc) to drive motivated behaviors. Repeated activation of D2 receptors with quinpirole (QNP) induces locomotor sensitization and compulsive behaviors, but the mechanisms are unknown. In this study, in vivo microdialysis and fast scan cyclic voltammetry in adult anesthetized rats were used to investigate the effect of repeated QNP on dopamine and glutamate neurotransmission within the NAc. Following eight injections of QNP, a significant decrease in phasic and tonic dopamine release was observed in rats that displayed locomotor sensitization. Either a systemic injection or the infusion of QNP into the NAc decreased dopamine release, and the extent of this effect was similar in QNP-sensitized and control rats, indicating that inhibitory D2 autoreceptor function is maintained despite repeated activation of D2 receptors and decreased dopamine extracellular levels. Basal extracellular levels of glutamate in the NAc were also significantly lower in QNP-treated rats than in controls. Moreover, the increase in NAc glutamate release induced by direct stimulation of medial prefrontal cortex was significantly lower in QNP-sensitized rats. Together, these results indicate that repeated activation of D2 receptors disconnects NAc from medial prefrontal cortex and ventral tegmental area. Repeated administration of the dopamine D2 receptor agonist quinpirole (QNP) induces locomotor sensitization. We found that the NAc of QNP-sensitized rats has reduced glutamate levels coming from prefrontal cortex together with a decreased phasic and tonic dopamine neurotransmission but a conserved presynaptic D2 receptor function. We suggest that locomotor sensitization is because of increased affinity state of D2 post-synaptic receptors.

Role of scavenger receptors in glia-mediated neuroinflammatory response associated with Alzheimer's disease.

It is widely accepted that cells serving immune functions in the brain, namely, microglia and astrocytes, are important mediators of pathological phenomena observed in Alzheimer's disease. However, it is unknown how these cells initiate the response that results in cognitive impairment and neuronal degeneration. Here, we review the participation of the immune response mediated by glial cells in Alzheimer's disease and the role played by scavenger receptors in the development of this pathology, focusing on the relevance of class A scavenger receptor (SR-A) for A ß clearance and inflammatory activation of glial cell, and as a potential target for Alzheimer's disease therapy.

Repeated treatment with the kappa opioid receptor agonist U69593 reverses enhanced K+ induced dopamine release in the nucleus accumbens, but not the expression of locomotor sensitization in amphetamine-sensitized rats.

The effects after the acute activation of the kappa opioid receptor (KOR) can be distinguished from the effect after repeated administration of KOR agonist. Here, we report the effect of repeated administration of U69593 during abstinence after amphetamine-induced locomotor sensitization. Rats were injected once daily with amphetamine for five consecutive days. From day 6 to 9, rats that developed locomotor sensitization, received once daily injection of U69593 or vehicle. On day 10, all rats were injected with a challenging dose of amphetamine and locomotor activity was measured to assess the expression of sensitization. Microdialysis studies were carried out to assess dopamine extracellular levels in NAc. Rats that develop and express horizontal locomotor sensitization to amphetamine show increased dopamine release in the NAc induced by high K(+). The repeated treatment with U69593 reverses the sensitized depolarization-stimulated dopamine release in the NAc, but not the expression of locomotor sensitization induced by amphetamine. Thus, repeated activation of KORs during early amphetamine withdrawal dissociates the behavioral responses and the neurochemical responses that accompany the expression of sensitization to amphetamine.