NO Production In Endothelial Cells Research Articles

Deformation-induced release of ATP from erythrocytes in a poly(dimethylsiloxane)-based microchip with channels that mimic resistance vessels.

The ability of nitric oxide to relax smooth muscle cells surrounding resistance vessels in vivo is well documented. Here, we describe a series of studies designed to quantify amounts of adenosine triphosphate (ATP), a known stimulus of NO production in endothelial cells, released from erythrocytes that are mechanically deformed as these cells traverse microbore channels in lithographically patterned microchips. Results indicate that micromolar amounts of ATP are released from erythrocytes flowing through channels having cross sectional dimensions of 60 x 38 micron (2.22 +/- 0.50 microM ATP). Microscopic images indicate that erythrocytes, when being pumped through the microchip channels, migrate toward the center of the channels, leaving a cell-free or skimming layer at the walls of the channel, a profile known to exist in circulatory vessels in vivo. A comparison of the amounts of ATP released from RBCs mechanically deformed in microbore tubing (2.54 +/- 0.15 microM) vs a microchip (2.59 +/- 0.32 microM) suggests that channels in microchips may serve as functional biomimics of the microvasculature. Control studies involving diamide, a membrane-stiffening agent, suggest that the RBC-derived ATP is not due to cell lysis but rather physical deformation.

The caveolar nitric oxide synthase/arginine regeneration system for NO production in endothelial cells.

The enzyme endothelial nitric oxide synthase (eNOS) catalyzes the conversion of arginine, oxygen and NADPH to NO and citrulline. Previous results suggest an efficient, compartmentalized system for recycling of citrulline to arginine utilized for NO production. In support of this hypothesis, the recycling enzymes, argininosuccinate synthase (AS) and argininosuccinate lyase (AL), have been shown to colocalize with eNOS in caveolae, a subcompartment of the plasma membrane. Under unstimulated conditions, the degree of recycling is minimal. Upon stimulation of NO production by bradykinin, however, recycling is co-stimulated to the extent that more than 80% of the citrulline produced is recycled to arginine. These results suggest an efficient caveolar recycling complex that supports the receptor-mediated stimulation of endothelial NO production. To investigate the molecular basis for the unique location and function of endothelial AS and AL, endothelial AS mRNA was compared with liver AS mRNA. No differences were found in the coding region of the mRNA species, but significant differences were found in the 5'-untranslated region (5'-UTR). The results of these studies suggest that sequence in the endothelial AS-encoding gene, represented by position -92 nt to -43 nt from the translation start site in the extended AS mRNA 5'-UTRs, plays an important role in differential and tissue-specific expression. Overall, a strong evidential case has been developed supporting the proposal that arginine availability, governed by a caveolar-localized arginine regeneration system, plays a key role in receptor-mediated endothelial NO production.

Free fatty acid overload attenuates Ca2+ signaling and NO production in endothelial cells.

Hyperlipidemia represents a major risk factor for development of vascular dysfunction and atherosclerosis. Although the unfortunate role of low-density lipoprotein has been clearly demonstrated, the mechanistic pathways through which triglyceride-derived free fatty acids (FFAs) contribute to vascular disorders are not completely understood. Thus, the present study was designed to elucidate the effects of FFAs on cultured endothelial cells. The Ca(2+) signaling, endothelial nitric oxide synthase (eNOS) activity, and production of superoxide anions (.O(2)(-)) were monitored in cells treated with bovine serum albumin-conjugated FFA. FFA-loaded cells showed enhanced intracellular Ca(2+) release in response to ATP, histamine, or the SERCA inhibitor thapsigargin. This effect corresponded to an overall increase in intracellularly stored Ca(2+). In contrast, autacoid-triggered elevation of cytosolic free Ca(2+) concentration was blunted in FFA-loaded cells due to inhibition of capacitative Ca(2+) entry. In agreement with the reduced Ca(2+) signaling, the Ca(2+)-dependent activity of eNOS was reduced under basal conditions and if cells were stimulated with ATP, histamine, or thapsigargin. The attenuated eNOS activity was associated with.O(2)(-) release in FFA-loaded cells. These data indicate that FFAs significantly affect endothelial Ca(2+) signaling, eNOS activity, and.O(2)(-) release and, thus, might contribute to vascular dysfunction in atherogenesis.

Physiological levels of β-amyloid induce cerebral vessel dysfunction and reduce endothelial nitric oxide production

β-amyloid (Aβ), the major component of senile plaques in Alzheimer's disease (AD), normally circulates in the blood at nanomolar levels but is elevated in AD. Previous studies have found that high concentrations (10-5 -10-4 M) of Aβ result in neuronal cell death. Here we show that physiological levels of soluble Aβ can induce dysfunction in perfused rat cerebral vessels and in cultured endothelial cells. At concentrations of 10-9 -10-6 M, Aβ induced a significant concentration-dependent reduction of NO production in endothelial cells. At 10-8 M, Aβ significantly decreased the sensitivity of cerebral vessels to acetylcholine (ACh), an endothelium dependent vasodilator. At 10-7 M and higher concentrations, Aβ significantly reduced the maximum response of vessels to ACh, and induced significant endothelial cell death. Aβ (10-9 -10-5 M) did not cause any detectable change in nitric oxide synthase levels. The results suggest that a modest increase in the concentration of Aβ above its normal physiological level in the circulation, as found in the early stages of AD, results in decreased NO production and vessel sensitivity to endothelium-dependent vasodilation that could lead to constricted blood vessels and ischemia in the surrounding tissue. Further increases in Aβ concentration, which may occur in the later stages of AD, result in cell death and decreased maximum vasodilator response of cerebral vessels. [Neurol Res 2001; 23: 506-512]

Loss of ETB-receptor-mediated relaxation in basilar artery after cold lesion of the rat parietal cortex.

The endothelins (ETs) can exert both constrictor and dilator effects. These opposite actions have been attributed to the existence of different ET receptors. The ETA receptor has high affinity for ET-1 and ET-2 but low affinity for ET-3, while the ETB-receptor is non-selective in this respect. Stimulation of ETA receptors, which are located on vascular smooth muscle, causes vasoconstriction (Feger et al., 1994). This vasomotor reaction is mediated by activation of phospholipase C and protein kinase C (Görlach et al., 1998a). ETB receptors of arteries mediate vasodilation which is coupled to NO-production in endothelial cells (Schilling et al., 1995).

Dissecting the Interaction between Nitric Oxide Synthase (NOS) and Caveolin: FUNCTIONAL SIGNIFICANCE OF THE NOS CAVEOLIN BINDING DOMAININ VIVO

Endothelial nitric oxide synthase (eNOS) is a dually acylated peripheral membrane protein that targets to the Golgi region and caveolae of endothelial cells. Recent evidence has shown that eNOS can co-precipitate with caveolin-1, the resident coat protein of caveolae, suggesting a direct interaction between these two proteins. To test this idea, we examined the interactions of eNOS with caveolin-1 in vitro and in vivo. Incubation of endothelial cell lysates or purified eNOS with glutathione S-transferase (GST)-caveolin-1 resulted in the direct interaction of the two proteins. Utilizing a series of GST-caveolin-1 deletion mutants, we identified two cytoplasmic domains of caveolin-1 that interact with eNOS, the scaffolding domain (amino acids 61-101) and to a lesser extent the C-terminal tail (amino acids 135-178). Incubation of pure eNOS with peptides derived from the scaffolding domains of caveolin-1 and -3, but not the analogous regions from caveolin-2, resulted in inhibition of eNOS, inducible NOS (iNOS), and neuronal NOS (nNOS) activities. These results suggest a common mechanism and site of inhibition. Utilizing GST-eNOS fusions, the site of caveolin binding was localized between amino acids 310 and 570. Site-directed mutagenesis of the predicted caveolin binding motif within eNOS blocked the ability of caveolin-1 to suppress NO release in co-transfection experiments. Thus, our data demonstrate a novel functional role for caveolin-1 in mammalian cells as a potential molecular chaperone that directly inactivates NOS. This suggests that the direct binding of eNOS to caveolin-1, per se, and the functional consequences of eNOS targeting to caveolae are likely temporally and spatially distinct events that regulate NO production in endothelial cells. Additionally, the inactivation of eNOS and nNOS by the scaffolding domain of caveolin-3 suggests that eNOS in cardiac myocytes and nNOS in skeletal muscle are likely subject to negative regulation by this muscle-specific caveolin isoform.

P-205 - Relationship between cytosolic Ca2+ elevation and NO production in endothelial cells in situ: Comparison between thrombin (THR) and ionomycin (IM)

P-205 - Relationship between cytosolic Ca2+ elevation and NO production in endothelial cells in situ: Comparison between thrombin (THR) and ionomycin (IM)