The half‐lives of platelet‐derived growth factor A‐ and B‐chain mRNAS are similar in endothelial cells and unaffected by heparin‐binding growth factor‐1 or cycloheximide

Abstract

Platelet-derived growth factor (PDGF) is mitogenic and chemotactic for vascular smooth muscle cells cultured in vitro, and, thus, may play a role in the smooth muscle cell proliferation and migration that occurs during atherosclerotic lesion development. Two related PDGF polypeptides, designated as the A and B chains, form functionally active PDGF-AA, AB, or BB dimers. The PDGF A- and B-chain genes are both transcribed in human umbilical vein endothelial (HUVE) cells and their expression is regulated by cytokines, growth factors, endotoxin, and phorbol ester. We reported previously that the angiogenic polypeptide heparin-binding growth factor (HBGF)-1 induces PDGF A-chain gene expression, but does not affect PDGF B-chain gene expression. In this study, we determined whether mRNA stabilization contributed to this induction by measuring the half-life of PDGF A-chain mRNA in quiescent, HBGF-1-stimulated, and proliferating HUVE cells. PDGF A-chain mRNA levels increase when quiescent HUVE cells are treated with the protein synthesis inhibitor cycloheximide; therefore, the effect of cycloheximide on PDGF A-chain mRNA decay was also investigated. The half-life of PDGF A-chain transcripts in quiescent cells was approximately 2.4 h and neither HBGF-1 nor cycloheximide significantly altered this decay rate. We also estimated the half-life of PDGF B-chain mRNA under the three different growth conditions and in the absence or presence of cycloheximide. The half-life in quiescent cells was approximately 1.8 h and was unaffected by HBGF-1 or protein synthesis inhibition. Therefore, the PDGF mRNAs have similar decay rates in HUVE cells, even though the 3' untranslated region of B-chain transcripts, but not A-chain transcripts, contains AU-rich sequence motifs postulated to confer rapid turnover in vivo.

mRNA Expression of Growth Factors in Glomeruli From Diabetic Rats

“…Macrophages and bovine endothelial cells have been shown to express c-sis mRNA, which codes for the PDGF-B chain (49,50). Human endothelial cells and human mesangial cells express both PDGF-A and PDGF-B chain mRNA (51,52), whereas smooth muscle cells exclusively express the A-chain gene (53). PDGF originates from a variety of cell types within the glomerulus, including monocytes/macrophages, platelets, glomerular endothelial cells, and mesangial cells (54).…”

Post-transcriptional regulation of interleukin 1 alphain various strains of young and senescent human umbilical vein endothelialcells.

“…The bands were quantitated with the BioImage analytical imaging system (Millipore) and normalized for the amount of GAPDH mRNA present. RNA half-life was calculated as described (23), where the percent of IL-la mRNA remaining at various times after actinomycin D addition was calculated and linear regression analysis was performed using the time values and the natural logarithm of the percentages. The half-life was then estimated using the slope and y intercept.…”

Signals controlling the expression of PDGF

“…Basic fibrob last growth factor (bFGF) reversibly downregulates expression of PDGF B mRNA and secretion of PDGF by HUVECs [112], Acidic fibroblast growth factor (aFGF) transiently stimulates PDGF A gene transcrip tion and PDGF secretion, but does not affect the B gene [111]. The half-life of PDGF A and B mRNA in quiescent HUVECs (2.4 and 1.8 h, respectively) is not affected by aFGF [ 120]. Interferon-gamma (IFN-7 ) suppresses PDGF A and B mRNA levels and release of PDGF-like proteins in vascular endothelial cells [ 108,110].…”

“…The 5' untranslated sequence of the rat cDNA clone contains an ATG codon that is not in frame with the PDGF A open reading frame. Translation initiation endothelial cells [102,120] …”