High blood pressure associates with the remodelling of inward rectifier K+ channels in mice mesenteric vascular smooth muscle cells

Producción CientíficaThe increased vascular tone that defines essential hypertension is associated with depolarization of vascular smooth muscle cells (VSMCs) and involves a change in the expression profile of ion channels promoting arterial contraction. As a major regulator of VSMC resting membrane potential (VM), K+channel activity is an important determinant of vascular tone and vessel diameter. However, hypertension-associated changes in the expression and/or modulation of K+channels are poorly defined, due to their large molecular diversity and their bed-specific pattern of expression. Moreover, the impact of these changes on the integrated vessel functionand their contribution to the development of altered vascular tone under physiological conditions need to be confirmed. Hypertensive (BPH) and normotensive (BPN) mice strains obtained by phenotypic selection were used to explore whether changes in the functional expression of VSMC inward rectifier K+channels contribute to the more depolarized resting VM and the increased vascular reactivity of hypertensive arteries. We determined the expression levels of inward rectifierK+channel mRNA in several vascular beds from BPN and BPH animals, and their functional contribution to VSMC excitability and vascular tone in mesenteric arteries. We found a decrease in the expression of Kir2.1, Kir4.1, Kir6.x and SUR2 mRNA in BPH VSMCs, and a decreased functional contribution of both KIRand KATP channels in isolated BPH VSMCs. However, only the effect of KATP channel modulators was impaired when exploring vascular tone, suggesting that decreased functional expression of KATP channels may be an important element in the remodelling of VSMCs in essential hypertension.Ministerio de Sanidad, Consumo y Bienestar Social - Instituto de Salud Carlos III (grant R006/009)Ministerio de Ciencia, Innovación y Universidades (grant BFU2010-15898)Junta de Castilla y León (grant VA094A11-2

Kv1.3 channels can modulate cell proliferation during phenotypic switch by an ion-flux independent mechanism

Producción CientíficaObjective: Phenotypic modulation of vascular smooth muscle cells has been associated with a decreased expression of all voltage-dependent potassium channel (Kv)1 channel encoding genes but Kcna3 (which encodes Kv1.3 channels). In fact, upregulation of Kv1.3 currents seems to be important to modulate proliferation of mice femoral vascular smooth muscle cells in culture. This study was designed to explore if these changes in Kv1 expression pattern constituted a landmark of phenotypic modulation across vascular beds and to investigate the mechanisms involved in the proproliferative function of Kv1.3 channels. Methods and Results: Changes in Kv1.3 and Kv1.5 channel expression were reproduced in mesenteric and aortic vascular smooth muscle cells, and their correlate with protein expression was electrophysiologicaly confirmed using selective blockers. Heterologous expression of Kv1.3 and Kv1.5 channels in HEK cells has opposite effects on the proliferation rate. The proproliferative effect of Kv1.3 channels was reproduced by “poreless” mutants but disappeared when voltagedependence of gating was suppressed. Conclusion: These findings suggest that the signaling cascade linking Kv1.3 functional expression to cell proliferation is activated by the voltage-dependent conformational change of the channels without needing ion conduction. Additionally, the conserved upregulation of Kv1.3 on phenotypic modulation in several vascular beds makes this channel a good target to control unwanted vascular remodeling.Instituto de Salud Carlos III (grant R006/009)Ministerio de Ciencia, Innovación y Universidades (grant BFU2010-15898)Junta de Castilla y León (grant VA094A11-2

TRPA1 channels mediate acute neurogenic inflammation and pain produced by bacterial endotoxins

Producción CientíficaGram-negative bacterial infections are accompanied by inflammation and somatic or visceral pain. These symptoms are generally attributed to sensitization of nociceptors by inflammatory mediators released by immune cells. Nociceptor sensitization during inflammation occurs through activation of the Toll-like receptor 4 (TLR4) signalling pathway by lipopolysaccharide (LPS), a toxic by-product of bacterial lysis. Here we show that LPS exerts fast, membrane delimited, excitatory actions via TRPA1, a transient receptor potential cation channel that is critical for transducing environmental irritant stimuli into nociceptor activity. Moreover, we find that pain and acute vascular reactions, including neurogenic inflammation (CGRP release) caused by LPS are primarily dependent on TRPA1 channel activation in nociceptive sensory neurons, and develop independently of TLR4 activation. The identification of TRPA1 as a molecular determinant of direct LPS effects on nociceptors offers new insights into the pathogenesis of pain and neurovascular responses during bacterial infections and opens novel avenues for their treatment.Projects SAF2010-14990 and PROMETEO2010-046. Instituto de Salud Carlos III. CONSOLIDER-INGENIO 2010. ISCIII grants R006/009 (Red Heracles), the Spanish Fundación Marcelino Botín and Belgian Federal Government (IUAP P6/28 and P7/13), the Research Foundation-Flanders and the Research Council of the KU Leuven

Role of Ca2+ and K+ channels in a model of essential hypertension

En este trabajo se han investigado los mecanismos que provocan la disfunción vascular en un modelo de ratón con hipertensión genética. La hipertensión esencial implica un aumento gradual y sostenido de las resistencias periféricas, lo que provoca un tono vascular aumentado. Este cambio se asocia con una despolarización de las células del músculo liso vascular (Vascular Smooth Muscle Cells, VSMCs) y se produce como consecuencia de un cambio en el perfil de expresión de los canales iónicos dependientes de voltaje (principalmente canales de K+ y Ca2+) que promueven la contracción arterial. Nosotros hemos caracterizado la expresión molecular y funcional de los canales de K+ “inwar rectifier” así como de los canales de Ca2+ dependiente de voltaje en miocitos vasculares de animales hipertensión (BPH) y normotensos (BPN) y su contribución a la excitabilidad de las VSMCs y al tono vascular en arterias mesentéricas.Departamento de Bioquímica y Biología Molecular y Fisiologí