Differential regulation of pregnancy associated plasma protein-A in human coronary artery endothelial cells and smooth muscle cells.
BACKGROUND
Pregnancy-associated plasma protein-A (PAPP-A), a metalloproteinase that serves to modulate local insulin-like growth factor (IGF) action, is upregulated in atherosclerotic plaque. However, little is known about the cellular mechanisms underlying this elevated PAPP-A.


OBJECTIVE
To continue study of PAPP-A expression and its regulation in human vascular cells, with a focus on endothelial cells.


METHODS
Primary cultures of human coronary artery endothelial cells (ECs) were treated without and with cytokines, growth factors, or low density lipoprotein (LDL). PAPP-A mRNA, protein, and protease activity were assessed using real-time PCR, ultra-sensitive PAPP-A ELISA and cell-free proteolysis of IGF binding protein (IGFBP-4), respectively. In addition, vascular cell adhesion molecule (VCAM), intercellular adhesion molecule (ICAM), monocyte chemotactic protein (MCP-1), IGF-I, IGF-I receptor, and IGFBP-4 and -5 mRNA expression levels were determined.


RESULTS
ECs in culture show little basal PAPP-A expression. The pro-inflammatory cytokines, tumor necrosis factor (TNF)-alpha and interleukin (IL)-beta, stimulated PAPP-A expression (TNF-alpha>>IL-1beta), whereas there was no effect of IL-6, transforming growth factor-beta, IGF-I, insulin, fibroblast growth factor or epidermal growth factor in these cells. Stimulation of PAPP-A expression by TNF-alpha was associated with significantly increased VCAM, ICAM, and MCP-1 expression but without major changes in other IGF system components. TNF-alpha-induced VCAM, ICAM, and MCP-1 expression (4h) preceded PAPP-A expression (24h). The anti-oxidant, N-acetyl cysteine, inhibited TNF-alpha-induced PAPP-A expression without altering the induction in VCAM, ICAM, and MCP-1. Treatment with native or oxidized LDL had no effect on PAPP-A expression in ECs. Comparative results in human coronary smooth muscle cells indicated qualitative and quantitative differences in PAPP-A expression and regulation between the two vascular cell types.


CONCLUSIONS
Human coronary artery ECs express PAPP-A mRNA and functional protein when activated by the pro-inflammatory cytokine, TNF-alpha. This study complements work on PAPP-A expression in human coronary artery SMCs and human monocyte-derived macrophages and suggests an interactive model of PAPP-A regulation and action in human atherosclerotic plaque.
Conover
Cheryl A
CA
Endocrine Research Unit, Department of Medicine, Mayo Clinic, College of Medicine, 200 First Street SW, 5-194 Joseph, Rochester, MN 55905, United States. Conover.Cheryl@Mayo.edu
Harrington
Sean C
SC
Bale
Laurie K
LK
D002478:Cells, Cultured; D003331:Coronary Vessels / Q000166:cytology*; D016207:Cytokines / Q000494:pharmacology; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology; D008077:Lipoproteins, LDL / Q000494:pharmacology; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000201:enzymology*; D011266:Pregnancy-Associated Plasma Protein-A / Q000235:genetics / Q000378:metabolism*
D016207:Cytokines; D036341:Intercellular Signaling Peptides and Proteins; D008077:Lipoproteins, LDL; D011266:Pregnancy-Associated Plasma Protein-A