Oxidized LDL Mediates the Release of Fibroblast Growth Factor-1

Abstract

Fibroblast growth factor-1 (FGF-1) and lipoproteins play an important role in atherogenesis. In the present study, we explored a possible mechanism by which abnormal lipid metabolism could be linked to the proliferative aspects of the disease. We tested oxidized LDL (oxLDL) as a possible pathophysiological mediator of the release of FGF-1, using FGF-1-transfected mouse NIH 3T3 cells and FGF-1-transfected rabbit smooth muscle cells, and compared it with the release caused by elevated temperature. Immunoblot analysis showed that oxLDL induced the release of FGF-1 in a concentration-dependent manner from 10 to 100 micrograms/mL. The effect correlated with the extent of oxidative modification of LDL and was maximal within 4 hours of exposure of cells to oxLDL. In contrast to the temperature stress-induced FGF-1 secretion pathway, FGF-1 released in response to oxLDL (1) appeared in the conditioned medium as a monomer, (2) appeared independently of the presence of either actinomycin D or cycloheximide, and (3) was neither enhanced nor inhibited by brefeldin A. We did not detect cell loss, significant morphological changes, changes in growth characteristics, or other indications of lethal toxicity in oxLDL-treated cells. Although the level of lactate dehydrogenase activity was elevated after oxLDL exposure, the calculations showed that > 90% of the FGF-1 was released by viable cells. We propose that oxLDL-induced FGF-1 release is mediated by sublethal and apparently transient changes in cell membrane permeability. In the environment of an atherosclerotic lesion, oxLDL-induced FGF-1 release may be among the mediators of endothelial and smooth muscle cell proliferation.

Potential role of leptin in angiogenesis: leptin induces endothelial cell proliferation and expression of matrix metalloproteinases in vivo and in vitro

“…Interestingly, the immunoreactivity of VEGFR-1 was colocalized in atheromatous plaques and observed in foam cell-rich regions adjacent to the lipid core or the basal regions of plaque consisting predominantly of VSMCs. Ananyeva et al (1997) recently demonstrated that ox-LDL induced the release of aFGF from aFGF-transfected VSMCs. VEGF receptor (flt-1) expression in monocyte and VSMCs has recently been confirmed; this receptor mediates chemotaxis and tissue factor production associated with up-regulation of MMPs to contribute to the lateral expansion of new blood vessels.…”

Requirement of Phosphatidylinositol 3-Kinase Activity for Translocation of Exogenous aFGF to the Cytosol and Nucleus

“…2 In this paper we use phosphorylation of aFGF as a measure of translocation to the cytosol and nucleus, since these are the only places in the cell where protein kinase C is known to exist. In untransfected COS cells, which express little or no FGFR, aFGF is not translocated to the cytosol and nucleus, and hence, it is also not phosphorylated.…”

“…Acidic fibroblast growth factor (aFGF) 1 is considered to be involved in several important physiological and pathological processes, such as angiogenesis, wound healing (1), and atheromatosis (2)(3)(4)(5)(6). In cell cultures it can stimulate growth, cell migration, and differentiation.…”

“…It depends on FGFR and, at least in the case of FGFR4, also on the intactness of the C terminus of its cytosolic part. 2 Human PI 3-kinases phosphorylate PI in the 3Ј position of the inositol ring and can be divided into three main classes on the basis of in vitro substrate specificity (23). Class I phosphorylates PI, PI 4-phosphate and PI 4,5-diphosphate and includes the p85/p110 heterodimeric PI 3-kinases and the G-protein ␤␥ subunit-activated PI 3-kinases.…”

Release of FGF1 and p40 synaptotagmin 1 correlates with their membrane destabilizing ability

“…Thus, FGF1 export through exocytotic fusion of secretory vesicles with the cell membrane is unlikely. FGF1 is secreted from cells upon stress stimulation such as heat shock [14], hypoxia [17], serum starvation [18], and treatment with oxidized LDL [19]. The availability of free intracellular copper ions is necessary for FGF1 release, and in vitro data suggest the formation of a copper-and stress-dependent multiprotein export complex [20], which contains the calcium-binding proteins, S100A13 and p40 Syt1 [21,22].…”