PB1265 - Role of a cellular antiprotease named Protease-Nexin-1 in the development of atherosclerosis

Background: The Protease/Antiprotease balance is involved in the development of atherosclerotic plaque and can particulary influence its stability. We have previously shown, that Protease Nexin-1 (PN-1), a serpin (Serine Protease Inhibitor) expressed by smooth muscle cells is significantly increased in human fatty streaks and fibrolipidic lesions.We have demonstrated that both platelets and intimal foam cells, including vascular smooth muscle cells (vSMCs), are the main sites of PN-1 presence in early atheroma. We have also observed that treatment of human vSMCs with modified LDL induce overexpression of PN-1 .

Aims: First, we have studied the impact of PN-1 in the development of atherosclerosis in vivo on LDL R-/- mice.Then, we studied the role of PN-1 in the responses of vSMCs during atherosclerosis: such as their ability to internalize oxidized LDLs, their proliferation potential, and their death.

Methods: We analysed the development of atherosclerosis plaques on PN-1 atherosclerotic deficient mice and WT atherosclerotic mice using oil red staining in en-face preparation of the aorta.We studied overexpression or underexpression of PN-1 by lentiviral transduction of SMCs incubated with increasing concentrations of oxidized LDLs. We analyzed the internalization of ox LDLs by Bodipy labeling, the PDGF-induced proliferation of SMCs by MTT proliferation test and the cell death induced by IL-1β by lactate deshydrogenase assay.

Results: Our in vitro results suggest that PN-1i) limits oxLDL internalization capacity by SMCs,ii) promotes SMC proliferation and iii) limits their death.
In vivo data show that PN-1 atherosclerotic deficient mice develop,a higher number of atherosclerotic lesions than the controls. Lesion size percentage is indeed 5 times higher in PN-1deficient mice compared to their relative controls.

Conclusion(s): The results obtained are promising and suggests a protective role of PN-1 in atherosclerosis.