The Healthy and Diseased Retina Seen through Neuron-Glia Interactions.

The retina is the sensory tissue responsible for the first stages of visual processing, with a conserved anatomy and functional architecture among vertebrates. To date, retinal eye diseases, such as diabetic retinopathy, age-related macular degeneration, retinitis pigmentosa, glaucoma, and others, affect nearly 170 million people worldwide, resulting in vision loss and blindness. To tackle retinal disorders, the developing retina has been explored as a versatile model to study intercellular signaling, as it presents a broad neurochemical repertoire that has been approached in the last decades in terms of signaling and diseases. Retina, dissociated and arranged as typical cultures, as mixed or neuron- and glia-enriched, and/or organized as neurospheres and/or as organoids, are valuable to understand both neuronal and glial compartments, which have contributed to revealing roles and mechanisms between transmitter systems as well as antioxidants, trophic factors, and extracellular matrix proteins. Overall, contributions in understanding neurogenesis, tissue development, differentiation, connectivity, plasticity, and cell death are widely described. A complete access to the genome of several vertebrates, as well as the recent transcriptome at the single cell level at different stages of development, also anticipates future advances in providing cues to target blinding diseases or retinal dysfunctions.

Dopamine promotes NMDA receptor hypofunction in the retina through D1 receptor-mediated Csk activation, Src inhibition and decrease of GluN2B phosphorylation.

Dopamine and glutamate are critical neurotransmitters involved in light-induced synaptic activity in the retina. In brain neurons, dopamine D1 receptors (D1Rs) and the cytosolic protein tyrosine kinase Src can, independently, modulate the behavior of NMDA-type glutamate receptors (NMDARs). Here we studied the interplay between D1Rs, Src and NMDARs in retinal neurons. We reveal that dopamine-mediated D1R stimulation provoked NMDAR hypofunction in retinal neurons by attenuating NMDA-gated currents, by preventing NMDA-elicited calcium mobilization and by decreasing the phosphorylation of NMDAR subunit GluN2B. This dopamine effect was dependent on upregulation of the canonical D1R/adenylyl cyclase/cAMP/PKA pathway, of PKA-induced activation of C-terminal Src kinase (Csk) and of Src inhibition. Accordingly, knocking down Csk or overexpressing a Csk phosphoresistant Src mutant abrogated the dopamine-induced NMDAR hypofunction. Overall, the interplay between dopamine and NMDAR hypofunction, through the D1R/Csk/Src/GluN2B pathway, might impact on light-regulated synaptic activity in retinal neurons.

ATP activates a reactive oxygen species-dependent oxidative stress response and secretion of proinflammatory cytokines in macrophages.

Secretion of the proinflammatory cytokines, interleukin (IL)-1beta and IL-18, usually requires two signals. The first, due to microbial products such as lipopolysaccharide, initiates transcription of the cytokine genes and accumulation of the precursor proteins. Cleavage and secretion of the cytokines is mediated by caspase-1, in association with an inflammasome containing Nalp3, which can be activated by binding of extracellular ATP to purinergic receptors. We show that treatment of macrophages with ATP results in production of reactive oxygen species (ROS), which stimulate the phosphatidylinositol 3-kinase (PI3K) pathway and subsequent Akt and ERK1/2 activation. ROS exerts its effect through glutathionylation of PTEN (phosphatase and tensin homologue deleted from chromosome 10), whose inactivation would shift the equilibrium in favor of PI3K. ATP-dependent ROS production and PI3K activation also stimulate transcription of genes required for an oxidative stress response. In parallel, ATP-mediated ROS-dependent PI3K is required for activation of caspase-1 and secretion of IL-1beta and IL-18. Thus, an increase in ROS levels in ATP-treated macrophages results in activation of a single pathway that promotes both adaptation to subsequent exposure to oxidants or inflammation, and processing and secretion of proinflammatory cytokines.

Sistema colinérgico: revisitando receptores, regulação e a relação com a doença de Alzheimer, esquizofrenia, epilepsia e tabagismo: [revisão] / Colinergic system: revisiting receptors, regulation and the relationship with Alzheimer disease, schizophrenia, epilepsy and smoking: [review]

OBJETIVO: Revisar a estrutura e o funcionamento do sistema colinérgico central ressaltando seu papel na fisiologia e na fisiopatologia das doenças de Alzheimer e Parkinson, esquizofrenia, epilepsia e tabagismo. MÉTODO: Foi realizada uma pesquisa bibliográfica no MedLine, LILACS, PubMed e ISI, e na Biblioteca da Fundação Oswaldo Cruz, RJ, selecionando-se o período de 1914 a 2009, utilizando os descritores: "receptors", "cholinergic", "Alzheimer disease", "schizophrenia", "epilepsy" e "smoking", além de referências cruzadas dos artigos selecionados e análise adicional de referências na literatura específica do tema. RESULTADOS: Efeitos importantes da ativação de receptores colinérgicos nicotínicos e muscarínicos sobre o desenvolvimento do sistema nervoso central (SNC) têm sido descritos. A dessensibilização e a internalização dos receptores acoplados à proteína G mediadas pela ativação de proteínas cinases têm sido descritas em proliferação, diferenciação e morte celular, além de síndromes neuropsiquiátricas. CONCLUSÃO: As informações produzidas a partir de estudos do sistema de neurotransmissão colinérgica podem auxiliar no desenvolvimento de medicamentos mais específicos para o tratamento da doença de Alzheimer, esquizofrenia, epilepsia e tabagismo.

OBJECTIVES: To review articles regarding important topics about cholinergic system and its ionotropic and G-protein coupled receptors as well as their regulation, also enlightening its importance in central nervous system (CNS) development and in several neuropsychiatric conditions such as Alzheimer disease, schizophrenia, epilepsy and smoking. METHOD: Bibliographical research was completed through MedLine, LILACS, PubMed, ISI and the Fundação Oswaldo Cruz Library, RJ, specifically for 1914 to 2009, using the descritors: "receptors", "cholinergic", Alzheimer "disease", "schizophrenia", "epilepsy" and "smoking", in addition to the cross-reference of the articles selected and further analyses of bibliographical references on the theme. RESULTS: Currently literature describes important effects of nicotinic and muscarinic receptors activation on development of central nervous system (CNS). The protein G coupled receptors dessensibilization and internalization mediated by kinases have been described in proliferation, differentiation and cell death, and also in neurologic disorders. DISCUSSION: The importance of the cholinergic system and its relationship with pathologies such as Alzheimer disease, schizophrenia, epilepsy is evident. The data produced so far may help on planning medicaments more specific for these pathologies treatment.