The absence of p53 accelerates atherosclerosis by increasing cell proliferation in vivo.

The tumor suppressor protein p53 is an essential molecule in cell proliferation and programmed cell death (apoptosis), and has been postulated to play a principal part in the development of atherosclerosis. We have examined the effect of p53 inactivation on atherogenesis in apoE-knockout mice, an animal model for atherosclerosis. We found that, compared with p53+/+/apoE-/- mice, p53-/-/apoE-/- mice developed considerably accelerated aortic atherosclerosis in the presence of a similar serum cholesterol in response to a high-fat diet. Furthermore, the atherosclerotic lesions in p53-/-/apoE-/- mice had a significant (approximately 280%) increase in cell proliferation rate and an insignificant (approximately 180%) increase in apoptosis compared with those in p53+/+/apoE-/- mice. Our observations indicate that the role of p53 in atherosclerotic lesion development might be associated with its function in cell replication control, and that p53-independent mechanisms can mediate the apoptotic response in atherosclerosis.