Shear stress-induced up-regulation of the intermediate-conductance Ca(2+)-activated K(+) channel in human endothelium

OBJECTIVE: Wall shear stress associated with blood flow is a major stimuli for generation of endothelial vasodilating and antithrombotic factors and it also regulates endothelial gene expression. Activation of endothelial intermediate-conductance Ca(2+)-activated K(+) channels (IK(Ca)) is important for the control of endothelial function by inducing cell hyperpolarization and thus generation of the endothelium-derived hyperpolarizing factor. In the present study we tested whether the IK(Ca) encoding IKCa1 gene is regulated by laminar shear stress (LSS). METHODS: Human umbilical vein endothelial cells (HUVEC) were subjected to LSS with a magnitude of 0.5-15 dyn/cm(2) and time intervals of 2-24 h in a flow cone apparatus. Expression of the IKCa1 gene and IK(Ca)-functions were determined by using real time RT-PCR and patch-clamp techniques. RESULTS: A short 2-4 h-or long 24 h-exposure to a LSS with a low (venous) magnitude of 0.5 dyn/cm(2) had no effect on IKCa1 expression levels. An exposure for 2 and 4 h to LSS with an intermediate magnitude of 5 dyn/cm(2) was also ineffective, whereas an exposure for 24 h induced a significant threefold up-regulation of IKCa1 expression levels. An exposure to LSS with a higher (arterial) magnitude of 15 dyn/cm(2), resulted in an eightfold up-regulation of IKCa1 expression levels after a 4 h-exposure and a fourfold increase of IKCa1 expression levels at 24 h. The increased IKCa1 expression levels following exposure to high levels of LSS resulted in enhanced IK(Ca) whole-cell currents and in an increased hyperpolarization of the endothelium in response to ATP and the IK(Ca) opener 1-EBIO. Inhibition of the mitogen-activated protein kinase/extracellular-signal-regulated kinase (ERK) kinase 1/2 (MEK/ERK) pathway by PD98059 prevented the LSS-induced up-regulation of IKCa1 expression levels and IK(Ca) whole-cell currents indicating that augmentation of IKCa1 expression levels is mediated by the LSS-induced activation of the MEK/ERK pathway. CONCLUSION: Long term exposure to LSS up-regulates expression and function of endothelial IK(Ca). This increase might represent a new important mechanism in endothelial adaptation to altered hemodynamics.     

Up-regulation of endothelial stretch-activated cation channels by fluid shear stress.

OBJECTIVE: Stretch-activated cation channels (SAC) have been suggested to act as endothelial mechanosensors for hemodynamic forces. Ca(2+) influx through SAC could induce an intracellular Ca(2+) signal stimulating Ca(2+)-dependent synthesis of vasodilators like NO, prostacyclin, or EDHF. In the present study we tested whether laminar shear stress (LSS) regulates SAC function. METHODS: Electrophysiological properties of SAC were investigated in human umbilical vein endothelial cells (HUVEC) subjected to defined levels of LSS in a flow-cone apparatus. RESULTS: In HUVEC, we identified a Ca(2+) permeable SAC that was activated by membrane stretch. Single-channel current densities of SAC in cell-attached patches were significantly increased in HUVEC exposed to an LSS of 5 dyn/cm(2) for 4 h (1.15+/-0.17 SAC/patch) compared to HUVEC kept in stationary culture (0.46+/-0.07 SAC/patch). Exposure of HUVEC to a higher LSS of 15 dyn/cm(2) for 4 h induced similar up-regulation of SAC (1.27+/-0.21 SAC/patch). After 24 h exposure to LSS of 15 dyn/cm(2), single-channel current densities of SAC remained up-regulated (1.07+/-0.18 SAC/patch) compared to controls. In addition, stretch-sensitivity of SAC (channel activity NP(o) at -30 mmHg) significantly increased after 2 h of exposure to LSS of 5 and 15 dyn/cm(2) and remained up-regulated after 24 h. Inhibition of protein kinases and tyrosine kinases by H7 and genistein, respectively, prevented LSS-induced alteration of SAC function. CONCLUSION: Single-channel current density and mechanosensitivity of SAC in HUVEC is up-regulated by LSS. Up-regulation of SAC function leads to enhanced mechanosensitive Ca(2+) influx, and represents a novel adaptive mechanism of the endothelium in the presence of altered hemodynamic forces.     

Obesity,dyslipidemia, and high blood pressure are associated with cardiovascular risk,determined using high-sensitivity C-reactive protein concentration,in young adults

ObjectiveFew studies have investigated the relationships between high-sensitivity C-reactive protein (hs-CRP) concentration and conventional cardiometabolic markers in young adults. The aim of this study was to characterize the cardiometabolic profile of young adults who are at high cardiovascular risk, according to hs-CRP concentration.MethodsA cross-sectional study was conducted in 300 young adults (18 to 30 years old) from southern Mexico (n = 150 normal-weight and n = 150 obese). Their circulating lipid and glucose concentrations were measured using colorimetric enzymatic assays, and their hs-CRP, ApoA, and ApoB concentrations were measured using turbidimetric assays.ResultsThe most prevalent abnormalities in the participants with high cardiovascular risk, determined using an hs-CRP >28.57 nmol/L, were high waist circumference (85.7%), obesity (83.9%), high low-density lipoprotein-cholesterol (64.3%), low high-density lipoprotein-cholesterol (50%), Apo B in the highest tertile (39.3%), hypertriglyceridemia (35.7%), and high blood pressure (30.4%). In addition, there were strong associations between hs-CRP >28.57 nmol/L and obesity (odds ratio [OR] = 13.9), high waist circumference (OR = 8.0), hypertriglyceridemia (OR = 4.0), high blood pressure (OR = 3.4), hypercholesterolemia (OR = 2.8), and Apo B in the highest tertile (OR = 2.4).ConclusionThe principal cardiometabolic alterations associated with high cardiovascular risk, determined using hs-CRP, are obesity, dyslipidemia, and high blood pressure in young adults.     

Comparison of Pulmonary Inflammatory and Antioxidant Responses to Intranasal Live and Heat-Killed Streptococcus pneumoniae in Mice

Inflammatory and antioxidant responses, in male C57Bl6J mice, to single intranasal inoculations with live or heat-killed Streptococcus pneumoniae were studied in order to tease out differences in responses. Heat-killed bacteria elicited weak lung neutrophil infiltration and raised concentrations (peak 6–8 h), in serum or lung tissue, of CXCL1 and 2, tumor necrosis factor alpha (TNFα), interleukin-6 (IL-6), and granulocyte-macrophage-colony stimulating factor, with later increases in CCL2 and IL-1β. Live bacteria induced profound pulmonary neutrophil infiltration and acute chemokine/cytokine elevations. After 72–96 h, live S. pneumoniae induced a delayed rise in chemokines CXCL2 and CCL2, preceded by increases in TNFα, IL-1β, and IL-6 and mononuclear infiltration of lungs. With both live and heat-killed bacteria, alveolar epithelial type II cells and alveolar macrophages were the main sources of TNFα and IL-1β. Only live bacteria caused an acute decrease in lung glutathione peroxidase, an increase in superoxide dismutase, and a sustained increase in serum amyloid protein A. Acute innate immune responses to live and heat-killed S. pneumoniae are similar. In response to live bacteria, inflammation is greater, accompanied by changes in antioxidant enzymes and has an additional, later mononuclear component.