A identidade da via de influxo de cálcio induzida por cafeína em neurônios sensitivos primários de ratos

Os transientes de Ca2+ induzidos por cafeína (CICTs) em neurônios sensitivos aferentes vagais (neurônios do gânglio nodoso) são produzidos por dois mecanismos distintos: liberação dos estoques intracelulares via receptores rianodina e influxo de Ca2+ através da membrana plasmática, por ativação de um receptor desconhecido. Utilizamos microfluorimetria de neurônios do GN de ratos para medirmos as mudanças da concentração intracelular de Ca2+ e testarmos a hipótese do receptor de potencial transiente vanilóide do tipo 1, TRPV1, ser a via de influxo de Ca2+. Aplicação de cafeína (10 mM) produziu CICTs em todos os neurônios testados, com uma média de 394 ± 32 nM. Os CICTs foram parcialmente dependentes da via de influxo de Ca2+, que variou de 33 a 98 % do transiente total de Ca2+ (média de 54 ± 9 %; n=6). Aplicação de dois antagonistas seletivos do TRPV1 (IRTX, 100 nM e BCTC, 175 nM) reduziu de forma significativa os CICTs para 45 ± 8% (n = 9) e 33 ± 4% (n = 8), respectivamente. Esses valores não apresentaram diferença significativa em relação às inibições dos CICTs observadas em meio extracelular nominalmente livre de Ca2+. As amplitudes médias dos CICTs em solução de Locke livre de Ca2+ e solução de Locke livre de Ca2+ com IRTX ou com BCTC não apresentaram diferenças significativas entre si (n = 5 e 7, respectivamente). Coletivamente, essas observações sugerem que a cafeína produz influxo de Ca2+ por ativação dos canais TRPV1Caffeine-induced Ca2+ transients (CICTs) in vagal sensory afferent neurons (nodose ganglion neurons) are produced by two distinct mechanisms: release from intracellular stores via ryanodine receptors and Ca2+ influx across the plasma membrane, due to activation of an unknown receptor. In isolated rat NGNs, we used single-cell microfluorimetry to measure changes in intracellular Ca2+ and to test whether TRPV1 receptors underlie the Ca2+ influx pathway. Caffeine (10 mM) evoked CICTs in all neurons tested (n=44) averaging 394 ± 32 nM. CICTs were partially dependent upon a Ca2+ influx pathway that ranged between 33 and 98 % (mean, 54 ± 9 %, n=6) of the total Ca2+ transient. Application of two selective TRPV1 antagonists (IRTX, 100 nM and BCTC, 175 nM) significantly attenuated CICTs by 45 ± 8% (n = 9) and 33 ± 4% (n = 8), respectively. These values were not significantly different from the inhibition of CICTs observed when recordings were made in nominally zero extracellular Ca2+. The peak average amplitudes of CICTs in Ca2+-free Locke solution and Ca2+-free Locke solution with IRTX or with BCTC were not significantly different from one another (n = 5 and 7, respectively). These observations suggest that caffeine can induce a Ca2+ influx by activating TR PV1 channels131f

Extracellular vesicles in Alzheimer's disease

Extracellular vesicles (EVs) are small vesicles released by cells that facilitate cell signaling. They are categorized based on their biogenesis and size. In the context of the central nervous system (CNS), EVs have been extensively studied for their role in both normal physiological functions and diseases like Alzheimer's disease (AD). AD is a neurodegenerative disorder characterized by cognitive decline and neuronal death. EVs have emerged as potential biomarkers for AD due to their involvement in disease progression. Specifically, EVs derived from neurons, astrocytes, and neuron precursor cells exhibit changes in quantity and composition in AD. Neuron-derived EVs have been found to contain key proteins associated with AD pathology, such as amyloid beta (Aß) and tau. Increased levels of Aß in neuron-derived EVs isolated from the plasma have been observed in individuals with AD and mild cognitive impairment, suggesting their potential as early biomarkers. However, the analysis of tau in neuron-derived EVs is still inconclusive. In addition to Aß and tau, neuron-derived EVs also carry other proteins linked to AD, including synaptic proteins. These findings indicate that EVs could serve as biomarkers for AD, particularly for early diagnosis and disease monitoring. However, further research is required to validate their use and explore potential therapeutic applications. To summarize, EVs are small vesicles involved in cell signaling within the CNS. They hold promise as biomarkers for AD, potentially enabling early diagnosis and monitoring of disease progression. Ongoing research aims to refine their use as biomarkers and uncover additional therapeutic applications

Óxido nítrico: inibição das plaquetas e participação na formação do trombo Nitric oxide: inhibition of platelets and participation in thrombus formation

Neste artigo faremos uma revisão bibliográfica de modo que entendamos como o óxido nítrico (NO) atua sobre as plaquetas, compreendendo assim mais um mecanismo antiplaquetário. Nos últimos 25 anos a função do NO na biologia evoluiu do seu reconhecimento como poluente ambiental para substância endógena envolvida em comunicação intracelular e intercelular e na transdução de sinais. O NO é uma molécula polivalente que exerce um papel na regulação da hemostasia, sendo responsável pela inibição das plaquetas em todos os seus níveis de atuação, desde adesão até agregação, impedindo, dessa forma, posterior formação de trombo. Inúmeras desordens clínicas têm sido reportadas em que a insuficiência da produção de NO endógeno e, portanto, a ausência de inibição de ação plaquetária, parece contribuir para os eventos trombóticos.<br>In this article we make a review above the way that nitric oxide (NO) influence platelets over the past 25 years. The role of NO in biology has evolved from being recognized as an environmental pollutant to an endogenously produced substance involved in intracellular and intercellular communication and signal transduction. NO is a multifunctional molecule that plays a role in the regulation of hemostasis. It is responsible for platelets inhibition in all levels of its action, from adhesion to aggregation, preventing in this manner, thrombus formation. Several clinical disorders have been reported in which endogenous NO production insufficiency and, as a consequence, the absence of platelets action inhibition, seems to contribute to thrombotic events