Gram-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.

1. Cytosolic free calcium ion concentration ([Ca2+]i) and whole-cell L-type Ca2" channel currents were measured during excitation-contraction (E-C) coupling in single voltageclamped rat cardiac ventricular cells. The measurements were used to compute the total cellular efflux of calcium ions through sarcoplasmic reticulum (SR) Ca2" release channels (FsR,rel) Ca2" influx through co-associated L-type neighbouring SR release channels.

The ionic currents of carotid body type I cells and their possible involvement in the detection of oxygen tension (Po2) in arterial blood are unknown. The electrical properties of these cells were studied with the whole-cell patch clamp technique, and the hypothesis that ionic conductances can be altered by changes in PO2 was tested. The results show that type I cells have voltage-dependent sodium, calcium, and potassium channels. Sodium and calcium currents were unaffected by a decrease in PO2 from 150 to 10 millimeters of mercury, whereas, with the same experimental protocol, potassium currents were reversibly reduced by 25 to 50 percent. The effect of hypoxia was independent of internal adenosine triphosphate and calcium. Thus, ionic conductances, and particularly the O2-sensitive potassium current, play a key role in the transduction mechanism of arterial chemoreceptors.

7Kv channels constitute a large and ubiquitous family of membrane proteins present in both excitable and nonexcitable cells. In nonexcitable cells, their function as feedback regulators of resting V M has been proposed to participate in many cellular functions ranging from secretion to cell migration, proliferation, and apoptotic death. Kv channel genes can give rise to an even larger number of functional Kv currents, via heteromultimerization, association with accessory subunits, Kv1 .3 Channels Can Modulate Cell Proliferation during Phenotypic switch by an ion-Flux independent MechanismPilar Cidad,* Laura Jiménez-Pérez,* Daniel García-Arribas, Eduardo Miguel-Velado, Sendoa Tajada, Christian Ruiz-McDavitt, José R. López-López, † M. Teresa Pérez-García † Objective-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

Abstract-Hypoxic inhibition of large-conductance Ca 2ϩ -dependent K ϩ channels (maxiK) of rat carotid body type I cells is a well-established fact. However, the molecular mechanisms of such inhibition and the role of these channels in the process of hypoxic transduction remain unclear. We have examined the mechanisms of interaction of O 2 with maxiK channels exploring the effect of hypoxia on maxiK currents recorded with the whole-cell and the inside-out configuration of the patch-clamp technique. Hypoxia inhibits channel activity both in whole-cell and in excised membrane patches. This effect is strongly voltage-and Ca 2ϩ -dependent, being maximal at low [Ca 2ϩ ] and low membrane potential. The analysis of single-channel kinetics reveals a gating scheme comprising three open and five closed states. Hypoxia inhibits channel activity increasing the time the channel spends in the longest closed states, an effect that could be explained by a decrease in the Ca 2ϩ sensitivity of those closed states. Reducing maxiK channels with dithiothreitol (DTT) increases channel open probability, whereas oxidizing the channels with 2,2Ј-dithiopyridine (DTDP) has the opposite effect. These results suggest that hypoxic inhibition is not related with a reduction of channel thiol groups. However, CO, a competitive inhibitor of O 2 binding to hemoproteins, fully reverts hypoxic inhibition, both at the whole-cell and the single-channel level. We conclude that O 2 interaction with maxiK channels does not require cytoplasmic mediators. Such interaction could be mediated by a membrane hemoprotein that, as an O 2 sensor, would modulate channel activity.

1. Confocal microscopy and the fluorescent Ca2+ indicator fluo-3 (K+ salt) were used to measure cytosolic free calcium ion concentration ([Ca`+]

Voltage-gated K+ (KV) channels are protein complexes composed of ion-conducting integral membrane α subunits and cytoplasmic modulatory β subunits. The differential expression and association of α and β subunits seems to contribute significantly to the complexity and heterogeneity of KV channels in excitable cells, and their functional expression in heterologous systems provides a tool to study their regulation at a molecular level. Here, we have studied the effects of Kvβ1.2 coexpression on the properties of Shaker and Kv4.2 KV channel α subunits, which encode rapidly inactivating A-type K+ currents, in transfected HEK293 cells. We found that Kvβ1.2 functionally associates with these two α subunits, as well as with the endogenous KV channels of HEK293 cells, to modulate different properties of the heteromultimers. Kvβ1.2 accelerates the rate of inactivation of the Shaker currents, as previously described, increases significantly the amplitude of the endogenous currents, and confers sensitivity to redox modulation and hypoxia to Kv4.2 channels. Upon association with Kvβ1.2, Kv4.2 can be modified by DTT (1,4 dithiothreitol) and DTDP (2,2′-dithiodipyridine), which also modulate the low pO2 response of the Kv4.2+β channels. However, the physiological reducing agent GSH (reduced glutathione) did not mimic the effects of DTT. Finally, hypoxic inhibition of Kv4.2+β currents can be reverted by 70% in the presence of carbon monoxide and remains in cell-free patches, suggesting the presence of a hemoproteic O2 sensor in HEK293 cells and a membrane-delimited mechanism at the origin of hypoxic responses. We conclude that β subunits can modulate different properties upon association with different KV channel subfamilies; of potential relevance to understanding the molecular basis of low pO2 sensitivity in native tissues is the here described acquisition of the ability of Kv4.2+β channels to respond to hypoxia.

Essential hypertension involves a gradual and sustained increase in total peripheral resistance, reflecting an increased vascular tone. This change associates with a depolarization of vascular myocytes, and relies on a change in the expression profile of voltage-dependent ion channels (mainly Ca 2+ and K + channels) that promotes arterial contraction. However, changes in expression and/or modulation of voltage-dependent K + channels (Kv channels) are poorly defined, due to their large molecular diversity and their vascular bed-specific expression. Here we endeavor to characterize the molecular and functional expression of Kv channels in vascular smooth muscle cells (VSMCs) and their regulation in essential hypertension, by using VSMCs from resistance (mesenteric) or conduit (aortic) arteries obtained from a hypertensive inbred mice strain, BPH, and the corresponding normotensive strain, BPN. Real-time PCR reveals a differential distribution of Kv channel subunits in the different vascular beds as well as arterial bed-specific changes under hypertension. In mesenteric arteries, the most conspicuous change was the de novo expression of Kv6.3 (Kcng3) mRNA in hypertensive animals. The functional relevance of this change was studied by using patch-clamp techniques. VSMCs from BPH arteries were more depolarized than BPN ones, and showed significantly larger capacitance values. Moreover, Kv current density in BPH VSMCs is decreased mainly due to the diminished contribution of the Kv2 component. The kinetic and pharmacological profile of Kv2 currents suggests that the expression of Kv6.3 could contribute to the natural development of hypertension.