La fisiopatologia della parete vasale:implicazioni terapeutiche

Our group is involved in the study of the mechanisms regulating vascular smooth muscle cell (VSMC) growth and the signaling pathways activated by anti-proliferative agents used in drug eluting stents (DES) (G i o r d a n o et al, Am. J Phys Heart and Circulatory Phys 2006; Giordano et al, Cardiovasc Res. 2008). Although DES technology has dramatically reduced the incidence of post-stent restenosis, on the other hand, it can predispose to late thrombotic events due lack of endothelization of vessels in which DES have been implanted. Apoptosis is a very important mechanism for the control of tissue omeostasis and the effectiveness of some agents, such as those used in DES, in preventing neointima formation is ascribable also to induction of programmed cell death of VSMC. Identifying drugs that selectively promote VSMC apoptosis and at the same time preserve the endothelium, could significantly improve the outcome of interventistic cardiology procedures. Preliminary results from our laboratory showed that statins, the most efficient agents available for lowering plasma levels of low-density lipoprotein cholesterol, sensitize VSMC, but not cells of the endothelial cell line ECV, to TNF-α-induced apoptosis. Noteworthy, TNF-α is a potent pro-inflammatory and apoptotic cytokine, which is released at high levels in the very early phases of angioplasty, due to arterial injury. It plays an important role in promoting the formation of neointima by stimulating migration and proliferation of VSMC. We found that atorvastatin activated low levels of apoptosis in both VSMC and ECV in a dose/dependent manner, by using doses comprised between 1-10 μM. However, VSMC appeared to be more sensitive to atorvastatin pro-apoptotic effect. Very surprisingly, when TNF-α was added to the cultures, we found a cooperative effect of the cytokine and atorvastatin in VSMC, but not ECV. When VSMC were cultured with 3 μM atorvastatin or TNF-α alone, the extent of apoptosis was 7%, 15% and 22%, in unstimulated, TNF-α-stimulated and atorvastatin-stimulated cells respectively, whereas it increased up to 35 % in cells stimulated with TNF-α+atorvastatin. We also found that statins clearly increased the levels of phospho-Jun in TNF-α-stimulated VSMC, compared to unstimulated cells or to cells stimulated with TNF-α alone. Such increase in phospho-Jun levels was not found in ECV. This results suggested that atorvastatin enhanced TNF-α-induced apoptosis of VSMC by stimulating the activity of cJun N-terminal kinase (JNK). Our preliminary results suggested that a proper treatment with statins, in these very early phases, may have a great impact in preventing neointima formation, by enhancing selectively TNF-α-induced apoptosis of VSMC, without affecting endothelial cell viability. Aim of our research is to confirm such important results of a different regulation of apoptosis in vascular smooth muscle cells and endothelial cells, by statins. In this regard, the experiments will be performed also with the primary umbilical vein endotelial cell line HUVEC. Furthermore, the mechanism underlying such a cell context dependent regulation of cell death will be also investigated, with particular focus on the JNK and NF-κB signaling pathways.