Purinergic signaling modulates human visceral adipose inflammatory responses: implications in metabolically unhealthy obesity.

Obesity is accompanied by chronic inflammation of VAT, which promotes metabolic changes, and purinergic signaling has a key role in a wide range of inflammatory diseases. Therefore, we addressed whether fat inflammation could be differentially modulated by this signaling pathway in the MUO and in individuals who remain MHO. Our results show that the necrotized VAT of both groups released greater levels of ATP compared with lean donors. Interestingly, MUO tissue SVCs showed up-regulation and engagement of the purinergic P2X7R. The extracellular ATP concentration is regulated by an enzymatic process, in which CD39 converts ATP and ADP into AMP, and CD73 converts AMP into adenosine. In VAT, the CD73 ectoenzyme was widely distributed in immune and nonimmune cells, whereas CD39 expression was restricted to immune CD45PAN+ SVCs. Although the MUO group expressed the highest levels of both ectoenzymes, no difference in ATP hydrolysis capacity was found between the groups. As expected, MUO exhibited the highest NLRP3 inflammasome expression and IL-1ß production. MUO SVCs also displayed up-regulation of the A2AR, allowing extracellular adenosine to increase IL-1ß local secretion. Additionally, we demonstrate that metabolic parameters and BMI are positively correlated with purinergic components in VAT. These findings indicate that purinergic signaling is a novel mechanism involved in the chronic inflammation of VAT underlying the metabolic changes in obesity. Finally, our study reveals a proinflammatory role for adenosine in sustaining IL-1ß production in this tissue.

Gating kinetics of the alpha1I T-type calcium channel.

The alpha1I T-type calcium channel inactivates almost 10-fold more slowly than the other family members (alpha1G and alpha1H) or most native T-channels. We have examined the underlying mechanisms using whole-cell recordings from rat alpha1I stably expressed in HEK293 cells. We found several kinetic differences between alpha1G and alpha1I, including some properties that at first appear qualitatively different. Notably, alpha1I tail currents require two or even three exponentials, whereas alpha1G tails were well described by a single exponential over a wide voltage range. Also, closed-state inactivation is more significant for alpha1I, even for relatively strong depolarizations. Despite these differences, gating of alpha1I can be described by the same kinetic scheme used for alpha1G, where voltage sensor movement is allosterically coupled to inactivation. Nearly all of the rate constants in the model are 5-12-fold slower for alpha1I, but the microscopic rate for channel closing is fourfold faster. This suggests that T-channels share a common gating mechanism, but with considerable quantitative variability.

Mg(2+) block unmasks Ca(2+)/Ba(2+) selectivity of alpha1G T-type calcium channels.

We have examined permeation by Ca(2+) and Ba(2+), and block by Mg(2+), using whole-cell recordings from alpha1G T-type calcium channels stably expressed in HEK 293 cells. Without Mg(o)(2+), inward currents were comparable with Ca(2+) and Ba(2+). Surprisingly, three other results indicate that alpha1G is actually selective for Ca(2+) over Ba(2+). 1) Mg(2+) block is approximately 7-fold more potent with Ba(2+) than with Ca(2+). With near-physiological (1 mM) Mg(o)(2+), inward currents were approximately 3-fold larger with 2 mM Ca(2+) than with 2 mM Ba(2+). The stronger competition between Ca(2+) and Mg(2+) implies that Ca(2+) binds more tightly than Ba(2+). 2) Outward currents (carried by Na(+)) are blocked more strongly by Ca(2+) than by Ba(2+). 3) The reversal potential is more positive with Ca(2+) than with Ba(2+), thus P(Ca) > P(Ba). We conclude that alpha1G can distinguish Ca(2+) from Ba(2+), despite the similar inward currents in the absence of Mg(o)(2+). Our results can be explained by a 2-site, 3-barrier model if Ca(2+) enters the pore 2-fold more easily than Ba(2+) but exits the pore at a 2-fold lower rate.

Isquemia miocárdica silenciosa / Silent myocardial ischemia

A isquemia miocárdica é o evento fisiopatológico final da doença arterial coronária (DAC). Quando desprovida de sintomatologia é denominada "isquemia miocárdica silenciosa", sendo a responsável pela maior parte dos eventos isquêmicos totais. Ainda permanecem incertos os porquês da näo percepçäo dolorosa ("angina") de certos episódios isquêmicos, bem como dos mecanismos fisiopatológicos que as desencadeiam. Claro está, no entanto, que os eventos silenciosos e sintomáticos näo se diferem quanto às alteraçöes miocárdicas estruturais e funcionais. O diagnóstico de isquemia silenciosa se estabelece quando da detecçäo de alteraçöes objetivas e características de dano miocárdico isquêmico. Dentre os métodos se configuram, principalmente, a eletrocardiografia de esforço, a monitorizaçäo eletrocardiográfica ambulatorial, o teste de perfusäo com tálio-201 e o ecocardiograma de esforço. Há outros, porém de menor utilizaçäo. Destaca-se a isquemia silenciosa pela sua importante relaçäo com o prognóstico dos portadores de DAC. Muitos estudos relatam participaçäo significativa daquela nos variados desfechos da DAC (angina, infarto agudo do miocárdio e morte súbita). O enfoque terapêutico varia para cada paciente, podendo iniciar-se com a mudança do estilo de vida (alteraçäo dos fatores de risco). A terapêutica medicamentosa se baseia na utilizaçäo de drogas antiisquêmicas (nitratos, beta-bloqueadores e antagonistas dos canais de cálcio) e antiplaquetários. o tratamento mais agressivo inclui a angioplastia coronária, a colocaçäo de stents e a cirurgia de revascularizaçäo do miocárdio.

State-dependent inactivation of the alpha1G T-type calcium channel.

We have examined the kinetics of whole-cell T-current in HEK 293 cells stably expressing the alpha1G channel, with symmetrical Na(+)(i) and Na(+)(o) and 2 mM Ca(2+)(o). After brief strong depolarization to activate the channels (2 ms at +60 mV; holding potential -100 mV), currents relaxed exponentially at all voltages. The time constant of the relaxation was exponentially voltage dependent from -120 to -70 mV (e-fold for 31 mV; tau = 2.5 ms at -100 mV), but tau = 12-17 ms from-40 to +60 mV. This suggests a mixture of voltage-dependent deactivation (dominating at very negative voltages) and nearly voltage-independent inactivation. Inactivation measured by test pulses following that protocol was consistent with open-state inactivation. During depolarizations lasting 100-300 ms, inactivation was strong but incomplete (approximately 98%). Inactivation was also produced by long, weak depolarizations (tau = 220 ms at -80 mV; V(1/2) = -82 mV), which could not be explained by voltage-independent inactivation exclusively from the open state. Recovery from inactivation was exponential and fast (tau = 85 ms at -100 mV), but weakly voltage dependent. Recovery was similar after 60-ms steps to -20 mV or 600-ms steps to -70 mV, suggesting rapid equilibration of open- and closed-state inactivation. There was little current at -100 mV during recovery from inactivation, consistent with

[Determination of micro and macronutrients in the cattle of the Venezuelan plains and their influence on the origin of bovine paraplegic syndrome]. / Micro y macronutrientes en el ganado bovino de los llanos venezolanos y su posible relacion con el origen del sindrome paraplejico del bovino.

We report a study carried out in three livestock-producing regions of Venezuela to determine the mineral status of grazing cattle and its relationship to the Síndrome Parpléjico del Bovino (SPB). Animal tissue samples from blood and liver were collected from a total of 17 farms within three regions: southwest (Apure), central (Guárico) and southeast (Bolívar) both during the dry and rainy seasons. In SPB free animals, the serum levels of sodium, potassium, chloride, magnesium, total and ionized calcium, phosphorus, and creatinine, were within the normal range. Glucose was found to be deficient in cattle from Bolívar and Guárico states and normal in Apure. With the exception of liver copper and serum zinc, all the other microelements analyzed (liver cobalt, and molybdenum, and serum iron) were found to be normal. Copper was found to be low in all regions studied with a mean value of 74.8 ppm indicating a moderate deficiency of this element. Similarly, in the central and southwest regions, zinc was found to be close to 0.34 ppm, significantly lower than the critical level of 0.7 ppm. In order to determine the effect of the dry and rainy seasons on the content of macro and microelements, controlled group of cattle from the three regions were followed in their contents of magnesium, calcium, copper and iron. In the dry season all of these elements tended to be much lower, showing a significant increase in the rainy season. This increase was much greater in cattle that received mineral supplementation and sanitary treatment. Bovines with diagnosis of SPB showed: low liver copper content, low serum magnesium and phosphorus levels significantly higher that control cattle.