Abstract 17204: Nucleostemin and Nucleophosmin Express with Up-regulating Telomere Reverse Transcriptase in the Arteriosclerotic Lesions

Abstract

Introduction: Nucleostemin (NS) and nucleophosmin (NPM) are the nucleolar proteins which not only regulate the proliferation of stem cells, but also protect myocardial cells from oxidative stress. Hypothesis: We hypothesize that NS and NPM regulate the proliferation of the arterial smooth muscle cell (SMC) and contribute to their survival in the process of arteriosclerosis. This study investigated for the first time the expression pattern of them and consider their roles in arteriosclerosis. Methods and Results: Immunohistochemical examination revealed the expression of NS and NPM in the nuclei of SMCs and endothelial cells (ECs) both in the media and the intima of the human autopsy coronary arteries and the aorta of the apo E-deficient mice. Immunoreactivity was especially strong in the SMCs and ECs constructing the fibrous cap covering the plaques. The immunoreactivity of telomere reverse transcriptase (TERT) was at once observed in these NS- and NPM-positive nuclei, indicating of the strong proliferating activities. In the fibro-muscular proliferating intima after denudation of the endothelium of rat abdominal aorta confirmed the same localization of NS and NPM with TERT. In order to investigate the roles of NS in the SMC, mRNA of NS was knocked down with siRNA in cultured human arterial SMC. The 47S ribosomal RNA reduced to 35%, without reducing 18S ribosomal RNA (real-time PCR), indicating the promoting effect of NS on the pre-ribosomal RNA processing necessary for total protein synthesis. Knocking down of NS mRNA also reduced the expression of TERT to 65% and on the contrary up-regulated p21 mRNA to 150%, indicating anti-senescence activity of NS. Subculture of human SMCs ultimately to the replicative senescence gradually reduced the number of NS positive nucleoli from four to only one per cell, maybe reflecting the reduced activity of NS in the senescence process. Conclusion: These results indicate that NS and NPM promote the proliferation of arterial SMCs and ECs in the arteriosclerotic lesions, collaborating with TERT.