scholarly journals Agents which increase cyclic AMP have diverse effects on low-density-lipoprotein-receptor function in human vascular smooth-muscle cells and skin fibroblasts

1990 ◽  
Vol 267 (3) ◽  
pp. 607-614 ◽  
Author(s):  
A Middleton ◽  
B Middleton
Keyword(s):  
Smooth Muscle ◽  
Cyclic Amp ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Vascular Smooth Muscle Cells ◽  
Ldl Receptor ◽  
Muscle Cells ◽  
Skin Fibroblasts ◽  
Receptor Expression ◽  
Low Density

Receptor-mediated binding and metabolism of low-density lipoproteins (LDL) in cultured human vascular smooth-muscle cells and skin fibroblasts are altered by increased cellular cyclic AMP concentrations. However, the LDL receptor does not respond to changes in cyclic AMP concentration in a simple manner. The activation of adenylate cyclase with forskolin, or the addition of membrane-permeant cyclic AMP analogues, initially decreases the expression of the LDL receptor, but is followed by a substantial increase in receptor expression after 24 h. This increase does not occur in the presence of inhibitors of RNA or protein synthesis, and is due to doubling of the Bmax. of the LDL receptor, without alteration of its affinity for LDL. By contrast, elevation of cyclic AMP concentration by inhibition of phosphodiesterases results in decreased receptor expression throughout the 24 h period. These two response patterns are reproducible phenomena, consistently observed in low-passaged cells derived from seven unrelated individuals.

scholarly journals Cyclic AMP stimulates the synthesis and function of the low-density lipoprotein receptor in human vascular smooth-muscle cells and fibroblasts

1992 ◽  
Vol 282 (3) ◽  
pp. 853-861 ◽  
Author(s):  
B Middleton ◽  
A Middleton
Keyword(s):  
Smooth Muscle ◽  
Cyclic Amp ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Vascular Smooth Muscle Cells ◽  
Free Cholesterol ◽  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Muscle Cells

1. Cyclic AMP-elevating agents stimulate low-density lipoprotein (LDL) receptor activity in human vascular smooth-muscle cells by increasing the rate of receptor protein synthesis. The stimulation is not secondary to the decrease in the regulatory pool of free cholesterol, since it is unaffected, or even enhanced, by inhibition of cholesterol synthesis and esterification, or inhibition of the conversion of cholesterol into its repressor metabolites. The cyclic AMP-mediated up-regulation of the receptor is maintained at low concentrations of inhibitory sterols, but is eventually over-ridden at high concentrations of these sterols. 2. Cyclic AMP-elevating agents also stimulate the hydrolysis of lysosomal cholesterol esters, thus increasing the cellular cholesterol pool and repressing the expression of the LDL receptor. This cholesterol-mediated repressive effect of cyclic AMP can be prevented by chloroquine, which inhibits lysosomal actions, or by ketoconazole, which inhibits conversion of free cholesterol into its repressor metabolite. Thus the cyclic AMP stimulation of the LDL receptor can be masked by the rapid mobilization of free cholesterol from existing cholesterol esters within cultured cells. 3. We have observed that elevated cyclic AMP concentrations will up-regulate the LDL receptor in cholesterol-depleted human vascular smooth-muscle cells, skin fibroblasts and foetal-lung fibroblasts. We propose that our results are evidence for a cyclic AMP-stimulated, sterol-independent, control of LDL-receptor synthesis which is of widespread occurrence in human cells.

Abstract 638: Urotensin II Promotes Calcification in Vascular Smooth Muscle Cells

2014 ◽  
Vol 34 (suppl_1) ◽  
Author(s):  
Isabella Albanese ◽  
Zhipeng You ◽  
Bin Yu ◽  
Bianca Barratt ◽  
Dominique Shum-Tim ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Vascular Smooth Muscle Cells ◽  
Muscle Cells ◽  
Receptor Expression ◽  
Urotensin Ii ◽  
Aortic Valves ◽  
Receptor System ◽  
Positive Correlations

Introduction: Atherosclerosis is a leading cause of death in Western societies. Vasoactive peptide urotensin II (UII) is upregulated in atherosclerosis and several other cardiovascular diseases however further research is required to develop a complete understanding of UII’s role in the pathogenesis of atherosclerosis. Hypothesis: We hypothesized that UII stimulates calcification in vascular smooth muscle cells and that UII, urotensin II related peptide (URP) and UT receptor expression are upregulated in calcified aortic valves. Methods and Results: Human aortic smooth muscle cells (HASMC) were cultured in phosphate media (2.6mmol/L) for 13 days in the presence of varying concentrations of UII (0, 10, 50, 100nm) and the amount of calcium was measured with a calcium assay kit. Protein was extracted and measured with a protein assay kit. HASMC calcification was assessed as the ratio of calcium (μg)/protein (mg). HASMC calcification increased with increasing UII concentration and was significantly elevated in 100nm of UII (N=6, P<0.05) 13 days after incubation. We also examined UII, URP and UT protein expression in 90 carotid endarterectomies and 87 mitral, non-calcified and calcified aortic valves by immunohistochemistry. Multivariant Spearman correlation analyses in carotids revealed significant positive correlations between UII, URP and UT overall staining with calcification, remodeling and inflammation (P<0.05). In valves there was significant positive correlations between UII, URP and UT overall staining with calcification, fibrosis, remodeling, inflammation, lipid score and microvessels (P<0.05). Conclusion: The stimulatory effect of UII on vascular smooth muscle cell calcification as well as the upregulated expression of UII, URP and UT in calcified aortic valves suggests that the UT receptor system plays a key role in the pathogenesis of atherosclerosis and valve calcification.

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