Vascular fibrosis enhanced by embryonic signal switching: a novel mechanism of placental growth factor-induced coronary artery sclerosis

Abstract

Purpose: Placental growth factor (PlGF) is a member of the vascular endothelial growth factor family, has been reported to be rapidly produced in acute phase of myocardial infarction and that the loss of PlGF reduces lesion growth in atherosclerosis animal models. On the other hand, it is known that the proliferation of cardiac fibroblasts (CFs) lead the fibrosis to coronary vessels which are associated with the progression of atherosclerosis. However, the molecular signals of PlGF in fibroblasts for the development of atherosclerosis are still unclear. Therefore, we analyzed cellular biological function of PlGF under Angiotensin II (AngII) stimulation, a potent inflammatory agent, using mouse cardiac and retrovirally introduced PlGF embryonic fibroblasts. Materials and methods: Retrovirally introduced PlGF mouse embryonic fibroblasts derived from C57BL/6 mice, were made by deficient retrovirus vector and were designated as C57/PlGF. Only retrovirus vector introduced C57 cells (C57/EV) were used as control. After AngII stimulation, cell migration, proliferation, reactive oxygen species (ROS), NF-kB activation, IL-6 and TNF-α production of C57/PlGF were evaluated. Cell proliferation was also measured in presence of MAPK-p38 inhibitor, SB205580. Then we assessed AngII-induced cell proliferation of mouse CFs incubated with10% supernatant of C57/PlGF. Results: The products of introduced PlGF in C57/PlGF were confirmed by ELISA (1093.48±3.5 pg/ml, mean ±SE). AngII-induced cell migration, proliferation and H2O2 production were significantly increased in C57/PlGF compared with C57/EV (6.5-time for migration, 1.3-time for proliferation, 1.9-time higher for H2O2 production, respectively). SB205580 inhibited the AngII-induced cell proliferation in C57/PlGF (32% decrease). In C57/PlGF cells, NF-kB activation was dramatically high, followed by significant up-regulation of IL-6 production. TNF-α production was also significantly increased in C57/PlGF cells compared to C57EV (1.8-time higher). CFs cell proliferation increased significantly in cells stimulated with C57/PlGF supernatant (1.3 times higher than those with 10% C57/EV supernatant, P<0.05). Conclusions: These data suggest that the activation of fibroblast concerning atherosclerosis, at least part of those activation might stimulate by PlGF signaling via NF-kB pathway accompanied by elevation of ROS and inflammatory signal activation through MAPK-p38 pathway. Furthermore, these signals could stimulate the activation of CFs, indicating that high circulating level of PlGF is possible to progress atherosclerosis.