Biomedical subjects

Stephanie E Wölfle

Publications and source records attributed to Stephanie E Wölfle.

5 recordsLinked to original sources

PubMed2006

Impaired endothelium-derived hyperpolarizing factor-mediated dilations and increased blood pressure in mice deficient of the intermediate-conductance Ca2+-activated K+ channel.

The endothelium plays a key role in the control of vascular tone and alteration in endothelial cell function contributes to several cardiovascular disease states. Endothelium-dependent dilation is mediated by NO, prostacyclin, and an endothelium-derived hyperpolarizing factor (EDHF). EDHF signaling is thought to be initiated by activation of endothelial Ca(2+)-activated K(+) channels (K(Ca)), leading to hyperpolarization of the endothelium and subsequently to hyperpolarization and relaxation of vascular smooth muscle. In the present study, we tested the functional role of the endothelial intermediate-conductance K(Ca) (IK(Ca)/K(Ca)3.1) in endothelial hyperpolarization, in EDHF-mediated dilation, and in the control of arterial pressure by targeted deletion of K(Ca)3.1. K(Ca)3.1-deficient mice (K(Ca)3.1(-/-)) were generated by conventional gene-targeting strategies. Endothelial K(Ca) currents and EDHF-mediated dilations were characterized by patch-clamp analysis, myography and intravital microscopy. Disruption of the K(Ca)3.1 gene abolished endothelial K(Ca)3.1 currents and significantly diminished overall current through K(Ca) channels. As a consequence, endothelial and smooth muscle hyperpolarization in response to acetylcholine was reduced in K(Ca)3.1(-/-) mice. Acetylcholine-induced dilations were impaired in the carotid artery and in resistance vessels because of a substantial reduction of EDHF-mediated dilation in K(Ca)3.1(-/-) mice. Moreover, the loss of K(Ca)3.1 led to a significant increase in arterial blood pressure and to mild left ventricular hypertrophy. These results indicate that the endothelial K(Ca)3.1 is a fundamental determinant of endothelial hyperpolarization and EDHF signaling and, thereby, a crucial determinant in the control of vascular tone and overall circulatory regulation.

Acetylcholine↗

PubMed2006

Connexin-dependent communication within the vascular wall: contribution to the control of arteriolar diameter.

Communication between cells is important to the microcirculation and enables the coordination of cellular behavior along the length of the vessel. Arterioles span considerable distances within the microcirculatory network, and thus flow changes require the adaptation of vessel resistance over the whole length of the vessel in order to be effective. Such a task requires communication along the vessel wall, and gap junction channels that connect endothelial as well as smooth muscle cells with each other set the stage for this requirement. Communication along the vessel wall can be tested experimentally by confined local stimulation of arterioles either in vitro or in vivo. Certain vascular stimuli induce both a local response and a concomitant uniform remote response, confirming the rapid conduction of vasomotor stimuli along the vessel wall. Gap junctions in vascular tissue are composed of connexins (Cx) Cx40, Cx43, Cx37 and Cx45. Of these, Cx40 is of special importance: its lack results in a deficient conduction of vasodilator stimuli along the vessel wall. Interestingly, Cx40-deficient mice display an elevated mean arterial pressure, suggesting that Cx40-depending gap junctional coupling is necessary to regulate vascular behavior and peripheral resistance. While the role of other connexins is less well established, an abundance of experimental data has proven the necessity of gap junctional communication to coordinate vascular behavior during adaptive blood flow regulation.

Animals↗

PubMed2006

Endothelial mediators and communication through vascular gap junctions.

Cellular interaction in vessels is achieved by multiple communication pathways, including gap junctions (GJs). They provide intercellular channels, allowing direct interaction of endothelial and smooth muscle cells and the coordination of cellular behaviour along the vessel. The latter is a prerequisite for large flow increases because an adaptation of resistance along the vessel length is required. Longitudinal communication is studied by confined local stimulation of arterioles and the observation of responses at distant locations. Certain vascular stimuli induce local and concomitant remote responses of a similar type, verifying rapid longitudinal conduction of vasomotor signals, most likely changes in membrane potential. This is achieved for dilatory responses via the endothelium, possibly by an endothelium-derived hyperpolarising factor (EDHF) that induces local hyperpolarisation, which is then transferred to remote sites through GJs. In vessels, GJs are composed of different connexins (Cx), but Cx40 is of special importance because its lack impairs longitudinal conduction of vasodilations. Interestingly, Cx40-deficient mice are hypertensive, suggesting that Cx40-dependent coupling is necessary to regulate vascular behaviour and peripheral resistance. While the role of other connexins is less well established, an abundance of data has proven the necessity of GJ communication to coordinate vascular behaviour during blood flow regulation.

Animals↗

PubMed2005

Myoendothelial coupling is not prominent in arterioles within the mouse cremaster microcirculation in vivo.

A smooth muscle hyperpolarization is essential for endothelium-dependent hyperpolarizing factor-mediated dilations. It is debated whether the hyperpolarization is induced by a factor (endothelium-derived hyperpolarizing factor) and/or is attributable to direct current transfer from the endothelium via myoendothelial gap junctions. Here, we measured membrane potential in endothelial cells (EC) and smooth muscle cells (SMC) in vivo at rest and during acetylcholine (ACh) application in the cremaster microcirculation of mice using sharp microelectrodes before and after application of specific blockers of Ca2+-dependent K+ channels (K(Ca)). Moreover, diameter changes in response to ACh were studied. Membrane potential at rest was lower in EC than SMC (-46.6+/-1.0 versus -36.5+/-1.0mV, P<0.05). Bolus application of ACh induced robust hyperpolarizations in EC and SMC, but the amplitude (11.1+/-0.9 versus 5.1+/-0.9mV, P<0.05) and duration of the response (10.7+/-0.8 versus 7.5+/-1.0s, P<0.05) were larger in EC. Blockers of large conductance K(Ca) (charybdotoxin or iberiotoxin) abrogated ACh-induced hyperpolarizations in SMC but did not alter endothelial hyperpolarizations. In contrast, apamin, a blocker of small conductance K(Ca) abolished ACh-induced hyperpolarizations in EC and had only small effects on SMC. ACh-induced dilations were strongly attenuated by iberiotoxin but only slightly by apamin. We conclude that myoendothelial coupling in arterioles in vivo in the murine cremaster is weak, as EC and SMC behaved electrically different. Small conductance K(Ca) mediate endothelial hyperpolarization in response to ACh, whereas large conductance K(Ca) are important in SMC. Because tight myoendothelial coupling was found in vitro in previous studies, we suggest that it is differentially regulated between vascular beds and/or by mechanisms acting in vivo.

Acetylcholine↗

PubMed2005

Intact endothelium-dependent dilation and conducted responses in resistance vessels of hypercholesterolemic mice in vivo.

Atherosclerosis and hyperlipidemia impair endothelium-dependent nitric oxide (NO)-mediated dilations in conducting arteries. In addition to NO, the endothelium releases an endothelium-derived hyperpolarizing factor (EDHF) in response to acetylcholine (ACh), which is particularly important in microvessels and initiates a dilation that conducts along the vessel through gap junctional communication. The expression of connexins is, however, altered by hypercholesterolemia. Therefore, we studied endothelium-dependent dilations and their conduction in murine hypercholesterolemic models. Dilations were assessed by intravital microscopy in arterioles with a diameter of approximately 35 microm in ApoE and LDL receptor (LDLR(-/-))-deficient mice after superfusion or locally confined application of ACh. ACh induced comparable concentration-dependent dilations in wild-type, LDLR(-/-), and ApoE(-/-) mice fed a normal or high-cholesterol diet, however EC(50) was slightly higher in ApoE(-/-) mice. Furthermore, the NO donor sodium-nitroprusside dilated arterioles to a similar extent (approximately 60%). Locally initiated ACh dilations (approximately 68%) conducted up to a distance of 1,100 microm without significant attenuation even under severe hypercholesterolemic conditions. Since ACh dilation in the arterioles of mice is mainly mediated via EDHF, we conclude that hypercholesterolemia does not alter EDHF release and efficacy. This conclusion is confirmed by an intact conducted response since EDHF is a prerequisite for this response. The intact conduction also suggests that gap-junctional communication is functionally preserved in these models.

Acetylcholine↗