P2X7 receptors and pannexin1 hemichannels shape presynaptic transmission.

Over the last decades, since the discovery of ATP as a transmitter, accumulating evidence has been reported about the role of this nucleotide and purinergic receptors, in particular P2X7 receptors, in the modulation of synaptic strength and plasticity. Purinergic signaling has emerged as a crucial player in orchestrating the molecular interaction between the components of the tripartite synapse, and much progress has been made in how this neuron-glia interaction impacts neuronal physiology under basal and pathological conditions. On the other hand, pannexin1 hemichannels, which are functionally linked to P2X7 receptors, have appeared more recently as important modulators of excitatory synaptic function and plasticity under diverse contexts. In this review, we will discuss the contribution of ATP, P2X7 receptors, and pannexin hemichannels to the modulation of presynaptic strength and its impact on motor function, sensory processing, synaptic plasticity, and neuroglial communication, with special focus on the P2X7 receptor/pannexin hemichannel interplay. We also address major hypotheses about the role of this interaction in physiological and pathological circumstances.

Astroglial gliotransmitters released via Cx43 hemichannels regulate NMDAR-dependent transmission and short-term fear memory in the basolateral amygdala.

Astrocytes release gliotransmitters via connexin 43 (Cx43) hemichannels into neighboring synapses, which can modulate synaptic activity and are necessary for fear memory consolidation. However, the gliotransmitters released, and their mechanisms of action remain elusive. Here, we report that fear conditioning training elevated Cx43 hemichannel activity in astrocytes from the basolateral amygdala (BLA). The selective blockade of Cx43 hemichannels by microinfusion of TAT-Cx43L2 peptide into the BLA induced memory deficits 1 and 24 h after training, without affecting learning. The memory impairments were prevented by the co-injection of glutamate and D-serine, but not by the injection of either alone, suggesting a role for NMDA receptors (NMDAR). The incubation with TAT-Cx43L2 decreased NMDAR-mediated currents in BLA slices, effect that was also prevented by the addition of glutamate and D-serine. NMDARs in primary neuronal cultures were unaffected by TAT-Cx43L2, ruling out direct effects of the peptide on NMDARs. Finally, we show that D-serine permeates through purified Cx43 hemichannels reconstituted in liposomes. We propose that the release of glutamate and D-serine from astrocytes through Cx43 hemichannels is necessary for the activation of post-synaptic NMDARs during training, to allow for the formation of short-term and subsequent long-term memory, but not for learning per se.

Effects of an Auxin and a brassinosteroid on physical, chemical and biochemical attributes of Galaxy apples / Ação da auxina e do brassinosteroide nos atributos físico-químicos e bioquímicos de maçãs ‘Galaxy

The aim of this study was to study the effect of the auxin naphthalene acetic acid (NAA) and the brassinosteroid 28-homocastasterone (28-HCS) applied every 15 days (harvest 2015/16) or every 21 days (harvest 2016/17) after full bloom, on the physical, chemical and biochemical attributes of the ‘Galaxy apples. The study was performed at a commercial orchard at Vacaria county, Rio Grande do Sul State, Brazil. The following treatments were applied: water (control), NAA (0.1%), 28-HCS (10‒6 M) and NAA (0.1%) + 28-HCS (10‒6 M). For this purpose, 300 μL of the plant growth regulator solutions were applied to the fruit peduncles. Fruits treated with NAA every 21 days presented higher starch-iodine index and lower total soluble solids (TSS), titratable acidity (TA), lightness index (L) and hue angle (h°) than 28-HCS-treated fruits. Fruits treated every 15 days with NAA presented reduced skin rupture force (SRF), total antioxidant activities (TAA) of the skin and flesh, and hydrogen peroxide content compared to the control fruits. In addition, NAA application every 15 and 21 days resulted in increased anthocyanin content in the skin. Application of NAA + 28-HCS reduced superoxide dismutase activity. 28-HCS applications increased TSS, color attributes (C and h°) of the skin, total antioxidant activity of the skin and flesh and peroxidase activity compared to control fruits. These results are expected to help to understand how plant growth regulators affect apple quality. In addition, results described here are also expected to help on the development of strategies to reduce post harvest losses and to increase fruit shelf life.(AU)

O objetivo deste estudo foi avaliar a ação do ácido naftaleno acético (ANA) e do brassinosteroide (catasterona), aplicados a cada 15 (safra 2015/16) ou 21 (safra 2016/17) dias a partir dos 40 dias após a plena floração, nos atributos físico-químicos e bioquímicos de maçãs ‘Galaxy. O estudo foi realizado em um pomar comercial de macieiras ‘Galaxy no município de Vacaria, RS. Os tratamentos avaliados foram: água (controle), ANA (0,1%), catasterona (10‒6 M) e ANA (0,1%) + catasterona (10‒6 M). As aplicações foram realizadas no pedúnculo dos frutos, utilizando 300 µL de solução por pedúnculo. Frutos tratados com ANA a cada 21 dias tiveram maior índice de iodo-amido e menores valores de sólidos solúveis (SS), acidez titulável e dos atributos de cor L e ângulo hue (h°) do que os frutos tratados com catasterona. Aplicações de ANA a cada 15 dias reduziu a força de ruptura da casca (FRC), atividade antioxidante (AAT) da casca, da polpa e conteúdo de peróxido de hidrogênio. Além disso, ANA aplicada a cada 15 ou 21 dias aumentaram o teor de antocianinas na casca. ANA + catasterona reduziu a atividade da enzima superóxido dismutase. Entretanto, aplicações de catasterona a cada 15 dias aumentou o teor de SS, atributos de cor (C e h°) na casca, atividade antioxidante da casca e da polpa, compostos fenólicos totais (CFT) e atividade da enzima peroxidase dos frutos de maçãs. Portanto, estudos adicionais devem ser realizados para confirmar a ação desses fitorreguladores na manutenção da qualidade e redução das perdas pós-colheitas de maçãs ‘Galaxy.(AU)

Oligopeptidases activity in bipolar disorder: Ndel1 and angiotensin I converting enzyme.

BACKGROUND: Abnormal activity of two enzymes relevant to neurodevelopment, namely nuclear-distribution element-like 1 (Ndel1) and angiotensin I-converting enzyme (ACE), was reported in individuals with schizophrenia; to our knowledge, these oligopeptidases were never measured in bipolar disorder (BD). AIMS: Evaluate the enzyme activity of Ndel1 and ACE in euthymic individuals with BD type 1 which was compare to healthy control (HC) group. METHODS: Ndel1 and ACE activities were assessed in the serum of individuals with BD type 1 according to DSM-IV criteria (n = 70) and a HC group (n = 34). The possible differences between BD type 1 and HC groups were evaluated using Analysis of Covariance (ANCOVA), and the results were adjusted for age, gender and body mass index. RESULTS: We observed a positive correlation between Ndel1 activity and the total YMRS score in BD group (p = 0.030) and a positive correlation between ACE activity and Ham-D score (p = 0.047). ANCOVA analysis showed lower Ndel1 activity in BDs compared to HCs. Interestingly, we did not observe between-groups differences in ACE activity, despite the recognized correlation of ACE activity levels with cognitive functions, also described to be worsened in psychiatric patients. CONCLUSION: Oligopeptidases, especially Ndel1, which has been strongly correlated with neurodevelopment and brain formation, are potentially a good new target in the study of the neurobiology of BD. LIMITATIONS: The relatively small sample size did not permit to examine the cause-effect relationship of clinical dimensions of BD and the enzymatic activity.

Effects of an Auxin and a brassinosteroid on physical, chemical and biochemical attributes of 'Galaxy' apples / Ação da auxina e do brassinosteroide nos atributos físico-químicos e bioquímicos de maçãs 'Galaxy'

ABSTRACT: The aim of this study was to study the effect of the auxin naphthalene acetic acid (NAA) and the brassinosteroid 28-homocastasterone (28-HCS) applied every 15 days (harvest 2015/16) or every 21 days (harvest 2016/17) after full bloom, on the physical, chemical and biochemical attributes of the 'Galaxy' apples. The study was performed at a commercial orchard at Vacaria county, Rio Grande do Sul State, Brazil. The following treatments were applied: water (control), NAA (0.1%), 28-HCS (10‒6 M) and NAA (0.1%) + 28-HCS (10‒6 M). For this purpose, 300 μL of the plant growth regulator solutions were applied to the fruit peduncles. Fruits treated with NAA every 21 days presented higher starch-iodine index and lower total soluble solids (TSS), titratable acidity (TA), lightness index (L) and hue angle (h°) than 28-HCS-treated fruits. Fruits treated every 15 days with NAA presented reduced skin rupture force (SRF), total antioxidant activities (TAA) of the skin and flesh, and hydrogen peroxide content compared to the control fruits. In addition, NAA application every 15 and 21 days resulted in increased anthocyanin content in the skin. Application of NAA + 28-HCS reduced superoxide dismutase activity. 28-HCS applications increased TSS, color attributes (C and h°) of the skin, total antioxidant activity of the skin and flesh and peroxidase activity compared to control fruits. These results are expected to help to understand how plant growth regulators affect apple quality. In addition, results described here are also expected to help on the development of strategies to reduce post harvest losses and to increase fruit shelf life.

RESUMO: O objetivo deste estudo foi avaliar a ação do ácido naftaleno acético (ANA) e do brassinosteroide (catasterona), aplicados a cada 15 (safra 2015/16) ou 21 (safra 2016/17) dias a partir dos 40 dias após a plena floração, nos atributos físico-químicos e bioquímicos de maçãs 'Galaxy'. O estudo foi realizado em um pomar comercial de macieiras 'Galaxy' no município de Vacaria, RS. Os tratamentos avaliados foram: água (controle), ANA (0,1%), catasterona (10‒6 M) e ANA (0,1%) + catasterona (10‒6 M). As aplicações foram realizadas no pedúnculo dos frutos, utilizando 300 µL de solução por pedúnculo. Frutos tratados com ANA a cada 21 dias tiveram maior índice de iodo-amido e menores valores de sólidos solúveis (SS), acidez titulável e dos atributos de cor L e ângulo hue (h°) do que os frutos tratados com catasterona. Aplicações de ANA a cada 15 dias reduziu a força de ruptura da casca (FRC), atividade antioxidante (AAT) da casca, da polpa e conteúdo de peróxido de hidrogênio. Além disso, ANA aplicada a cada 15 ou 21 dias aumentaram o teor de antocianinas na casca. ANA + catasterona reduziu a atividade da enzima superóxido dismutase. Entretanto, aplicações de catasterona a cada 15 dias aumentou o teor de SS, atributos de cor (C e h°) na casca, atividade antioxidante da casca e da polpa, compostos fenólicos totais (CFT) e atividade da enzima peroxidase dos frutos de maçãs. Portanto, estudos adicionais devem ser realizados para confirmar a ação desses fitorreguladores na manutenção da qualidade e redução das perdas pós-colheitas de maçãs 'Galaxy'.

From Hyperactive Connexin26 Hemichannels to Impairments in Epidermal Calcium Gradient and Permeability Barrier in the Keratitis-Ichthyosis-Deafness Syndrome.

The keratitis-ichthyosis-deafness (KID) syndrome is characterized by corneal, skin, and hearing abnormalities. KID has been linked to heterozygous dominant missense mutations in the GJB2 and GJB6 genes, encoding connexin26 and 30, respectively. In vitro evidence indicates that KID mutations lead to hyperactive (open) hemichannels, which in some cases is accompanied by abnormal function of gap junction channels. Transgenic mouse models expressing connexin26 KID mutations reproduce human phenotypes and present impaired epidermal calcium homeostasis and abnormal lipid composition of the stratum corneum affecting the water barrier. Here we have compiled relevant data regarding the KID syndrome and propose a mechanism for the epidermal aspects of the disease.

The ATP required for potentiation of skeletal muscle contraction is released via pannexin hemichannels.

During repetitive stimulation of skeletal muscle, extracellular ATP levels raise, activating purinergic receptors, increasing Ca2+ influx, and enhancing contractile force, a response called potentiation. We found that ATP appears to be released through pannexin1 hemichannels (Panx1 HCs). Immunocytochemical analyses and function were consistent with pannexin1 localization to T-tubules intercalated with dihydropyridine and ryanodine receptors in slow (soleus) and fast (extensor digitorum longus, EDL) muscles. Isolated myofibers took up ethidium (Etd+) and released small molecules (as ATP) during electrical stimulation. Consistent with two glucose uptake pathways, induced uptake of 2-NBDG, a fluorescent glucose derivative, was decreased by inhibition of HCs or glucose transporter (GLUT4), and blocked by dual blockade. Adult skeletal muscles apparently do not express connexins, making it unlikely that connexin hemichannels contribute to the uptake and release of small molecules. ATP release, Etd+ uptake, and potentiation induced by repetitive electrical stimulation were blocked by HC blockers and did not occur in muscles of pannexin1 knockout mice. MRS2179, a P2Y1R blocker, prevented potentiation in EDL, but not soleus muscles, suggesting that in fast muscles ATP activates P2Y1 but not P2X receptors. Phosphorylation on Ser and Thr residues of pannexin1 was increased during potentiation, possibly mediating HC opening. Opening of Panx1 HCs during repetitive activation allows efflux of ATP, influx of glucose and possibly Ca2+ too, which are required for potentiation of contraction. This article is part of the Special Issue Section entitled 'Current Pharmacology of Gap Junction Channels and Hemichannels'.