Role of caveolar compartmentation in endothelium-derived hyperpolarizing factor-mediated relaxation: Ca2+ signals and gap junction function are regulated by caveolin in endothelial cells.

BACKGROUND: In endothelial cells, caveolin-1, the structural protein of caveolae, acts as a scaffolding protein to cluster lipids and signaling molecules within caveolae and, in some instances, regulates the activity of proteins targeted to caveolae. Specifically, different putative mediators of the endothelium-derived hyperpolarizing factor (EDHF)-mediated relaxation are located in caveolae and/or regulated by the structural protein caveolin-1, such as potassium channels, calcium regulatory proteins, and connexin 43, a molecular component of gap junctions. METHODS AND RESULTS: Comparing relaxation in vessels from caveolin-1 knockout mice and their wild-type littermates, we observed a complete absence of EDHF-mediated vasodilation in isolated mesenteric arteries from caveolin-1 knockout mice. The absence of caveolin-1 is associated with an impairment of calcium homeostasis in endothelial cells, notably, a decreased activity of Ca2+-permeable TRPV4 cation channels that participate in nitric oxide- and EDHF-mediated relaxation. Moreover, morphological characterization of caveolin-1 knockout and wild-type arteries showed fewer gap junctions in vessels from knockout animals associated with a lower expression of connexins 37, 40, and 43 and altered myoendothelial communication. Finally, we showed that TRPV4 channels and connexins colocalize with caveolin-1 in the caveolar compartment of the plasma membrane. CONCLUSIONS: We demonstrated that expression of caveolin-1 is required for EDHF-related relaxation by modulating membrane location and activity of TRPV4 channels and connexins, which are both implicated at different steps in the EDHF-signaling pathway.

Rosuvastatin restores superoxide dismutase expression and inhibits accumulation of oxidized LDL in the aortic arch of obese dyslipidemic mice.

BACKGROUND AND PURPOSE: Our goal was to elucidate mechanisms of the inhibitory effect of rosuvastatin on the accumulation of plaque oxidized low density lipoproteins (oxLDL) and on plaque volume, without lowering cholesterol, in mice with combined leptin and LDL-receptor deficiency (DKO). EXPERIMENTAL APPROACH: Twelve-week old DKO mice were treated with rosuvastatin (10 mg kg(-1) day(-1), s.c.) or placebo or no treatment for 12 weeks. The effect on blood variables, aortic plaque volume and composition and gene expression in the aorta and in THP-1 cells was assessed. KEY RESULTS: Rosuvastatin lowered free fatty acids (FFA), triglycerides, and increased insulin sensitivity, without affecting cholesterol. Rosuvastatin lowered the plaque volume, inhibited macrophage, lipid and oxLDL accumulation, and decreased the oxLDL-to-LDL ratio of plaques in the aortic arch. It increased superoxide dismutase 1 (SOD1), CD36, LXR-alpha, ABCA-1 and PPAR-gamma RNA expression in aortic extracts. SOD1 was the strongest inverse correlate of oxLDL. In THP-1 macrophages and foam cells, expression of SOD1 was lower than in THP-1 monocytes. Rosuvastatin restored expression of SOD1 in THP-1 macrophages and foam cells. CONCLUSIONS AND IMPLICATIONS: Rosuvastatin restored SOD1 expression in THP-1 macrophages and foam cells in vitro and in the aorta of DKO mice. The latter was associated with less oxLDL accumulation within atherosclerotic plaques and inhibition of plaque progression. This effect was obtained at a dose not affecting cholesterol levels but improving insulin sensitivity. SOD1 is a potentially important mediator of the prevention of oxLDL accumulation within atherosclerotic plaques.

Nitric oxide-dependent endothelial function and cardiovascular disease.

Nitric oxide produced by three different isoforms of nitric oxide synthase (NOS) widely expressed in virtually all vascular cell types is mostly produced by the endothelial isoform (eNOS) in endothelial cells where it plays a crucial role in vascular tone and structure regulation. It also exerts an anti-inflammatory influence, inhibits platelets adhesion and aggregation, and prevents smooth muscle cells proliferation and migration. Several lines of evidence link endothelial dysfunction, characterized by decreased bioavailability of nitric oxide, with the development of many pathological conditions such as heart failure, hypertension, diabetes and atherosclerosis. This review focuses on nitric oxide-dependent endothelial dysfunction in cardiovascular diseases, its clinical detection and relevance, potential pathogenic mechanisms and possible therapies.

Inhaled prostacyclin reduces cardiopulmonary bypass-induced pulmonary endothelial dysfunction via increased cyclic adenosine monophosphate levels.

OBJECTIVE: Cardiopulmonary bypass triggers a systemic inflammatory response that alters pulmonary endothelial function, which can contribute to pulmonary hypertension. This study was designed to demonstrate that inhaled prostacyclin, a selective pulmonary vasodilator prostaglandin, prevents pulmonary arterial endothelial dysfunction induced by cardiopulmonary bypass. METHODS: Three groups of Landrace swine were compared: control without cardiopulmonary bypass (control group); 90 minutes of normothermic cardiopulmonary bypass (bypass group); 90 minutes of cardiopulmonary bypass and treated with prostacyclin during cardiopulmonary bypass (continuous nebulization with continuous positive airway pressure until the end of the cardiopulmonary bypass; prostacyclin group). After 60 minutes of reperfusion, swine were put to death and pulmonary arteries harvested. After contraction to phenylephrine, endothelium-dependent relaxation to bradykinin and acetylcholine was studied in standard organ chamber experiments. The pulmonary artery intravascular cyclic adenosine monophosphate content was compared between the 3 groups (post-cardiopulmonary bypass). RESULTS: There was a statistically significant improvement of the endothelium-dependent relaxation to bradykinin in the prostacyclin group when compared with the bypass group (P <.05). There was no statistically significant difference for endothelium-dependent relaxation to acetylcholine (P >.05) between the prostacyclin and the bypass groups. There was a statistically significant decrease in the cyclic adenosine monophosphate content and a statistically significant increase of the mean pulmonary artery pressure in the bypass group only (P <.05). CONCLUSION: Prophylactic use of inhaled prostacyclin has a favorable impact on the pulmonary endothelial dysfunction induced by cardiopulmonary bypass associated with preservation of pulmonary intravascular cyclic adenosine monophosphate content and the pulmonary vascular tone.

Growth inhibition of Mycobacterium tuberculosis by polyoxyethylene stearate present in the BACTEC pyrazinamide susceptibility test.

We have previously found that approximately 3.5% of 428 clinical isolates of Mycobacterium tuberculosis yield uninterpretable results in the BACTEC pyrazinamide (PZA) susceptibility test system, because of inadequate growth. We tested the hypothesis that polyoxyethylene stearate (POES), the ingredient of the reconstituting fluid for the test, was the cause of this growth inhibition. A total of 15 isolates known for their previously uninterpretable results and 100 randomly chosen clinical isolates were tested in parallel both with and without POES. Repeat testing of the isolates with previously uninterpretable results yielded results in the presence of POES in only seven (47%). In the absence of POES, all gave interpretable results but one such result showed false resistance. For the other 100 clinical isolates, interpretable results were obtained with and without POES, but growth was enhanced in the absence of POES, especially in the PZA-susceptible strains. This was evidenced by a decreased time to attain a growth index of 200 in the control vial (4.9 days without POES versus 5.8 days with POES; P < 0.001) and a higher mean growth index ratio on the day of interpretation of the test (7.4% without POES versus 2.2% with POES; P < 0.001). However, the enhanced growth without POES led to 20 susceptible strains being misinterpreted as either resistant or borderline. We suggest that isolates of M. tuberculosis which yield uninterpretable results in the BACTEC PZA test system should be retested both with and without POES. If interpretable results indicating PZA resistance are obtained only in the absence of POES, the result should be confirmed by a pyrazinamidase assay or by the conventional proportion method. Routine omission of POES from the BACTEC test for all clinical strains is discouraged because of the unacceptably high false-resistance rates.

Testing of susceptibility of Mycobacterium tuberculosis to pyrazinamide: comparison of Bactec method with pyrazinamidase assay.

The susceptibility of 428 clinical isolates of Mycobacterium tuberculosis to pyrazinamide was assessed by the Bactec method and the Wayne pyrazinamidase assay. The correlation between the two tests was 98.2 and 100% for susceptible and resistant strains, respectively. False resistance was seen in four (0.8%) strains with the Bactec test, and false-susceptible results occurred in two (0.5%) pyrazinamidase assays. The Bactec test is rapid and reliable, and the Bactec results correlate well with the pyrazinamidase test results, although some strains did not grow well in the test medium.

Smooth pursuit along a solid line: a new variation on the theme of efference-copy-bound eye tracking.

Theoretical considerations of the physiology of eye tracking have long implied that the kinematics of smooth pursuit need not parallel those of the pursued target, with pursuit in the absence of a physically moving target as an extreme case. Yet these theoretical implications have been largely ignored, with the consequence that observed kinematic discrepancies between target and pursuit have generally been presented as somewhat surprising, and this view has maintained unnecessary diversity among reported smooth-pursuit phenomena. The case of yet another stimulus-discrepant smooth-pursuit phenomenon is presented and is used to suggest a role which recognized eye-tracking theory might advantageously play in classifying smooth-pursuit phenomena. The new phenomenon, smooth pursuit along a stationary solid straight line under continuous illumination, was demonstrated in a study where eye movements were documented by continuous recordings of the electrooculogram. All twelve subjects were able to initiate smooth pursuit along the line and to maintain it in the absence of any other source of stimulation, and all reported experiencing apparent movement during smooth pursuit. It is suggested that smooth-pursuit phenomena can best be classified in terms of degree of efference-copy dependency.

Workers' exposure to isocyanates.

A model of exposure to isocyanates, based on knowledge of industrial processes and starting materials and the results of industrial hygiene surveys, is proposed. This model of exposure suggests the concentration and physical form of airborne isocyanate monomers and oligomers. A new sampling and analytical system was developed that is capable of determining the physical and chemical characteristics of occupational exposure to a variety of aliphatic and aromatic isocyanates as required by the exposure model. The sampling system consisted of a dual-filter 37-mm cassette, in which the first filter captured aerosol phase contaminants and the second captured vapor phase isocyanates through derivatization with 9-(N-methylaminomethyl) anthracene (MAMA). Urea derivative recovery by the sampling system, isocyanate-MAMA reactivity, and linearity of the calibration curve were evaluated in the laboratory. The practicality of the system was evaluated during field trials. Sampling times are reduced to 15 min, and the detection limit for TDI, HDI, and MDI was 1.0 micrograms/m3. A partial validation of the new sampling system was performed for HDI vapor by comparison to a standard method in field trials and for TDI vapor in a controlled test atmosphere. The analytical system may also be used to measure the concentration of oligomeric isocyanates. Airborne concentrations of isocyanates were measured in two foam plants, nine paint shops, and two foundries to verify the usefulness of the model. Exposure in foam plants was predominantly to gaseous monomeric isocyanates. Exposure to oligomer isocyanates was higher than expected in paint shops. Both monomer and oligomer isocyanates were undetectable in foundries.