ABSTRACT
Egr-1 and p53 are involved in pathology of both atherosclerosis and cancer. However, it is unknown whether p53 and Egr1 are interactively involved in apoptosis in atherosclerosis. We found that in human carotid plaques, the expression of p53 was inversely correlated with Egr1. In U937 cells, 7ß-hydroxycholesterol and 7-ketocholesterol induced production of reactive oxygen species (ROS), transient up-regulation of Egr1 followed by late induction of p53 and apoptosis. Cells with nuclear fragmentation induced by 7-oxysterol or p53 showed increased levels of p53, but decreased levels of Egr1. In conclusion, ROS induced by 7-oxysterols may function as an early initiator of Egr1 expression. The late induced p53 by 7-oxysterols contributes to apoptotic cell death and is linked to the reduction of Egr1 levels, which resembles the differential expression of p53 and Egr1 in human atheroma progression.
Subject(s)
Apoptosis/drug effects , Carotid Stenosis/chemically induced , Early Growth Response Protein 1/biosynthesis , Hydroxycholesterols/toxicity , Ketocholesterols/toxicity , Tumor Suppressor Protein p53/biosynthesis , Animals , Carotid Stenosis/metabolism , Carotid Stenosis/pathology , Cell Culture Techniques , Early Growth Response Protein 1/genetics , Humans , Immunohistochemistry , Mice , Reactive Oxygen Species/metabolism , Tumor Suppressor Protein p53/genetics , U937 CellsABSTRACT
OBJECTIVE: The expression of p53 has been associated with DNA damage, cell senescence, proliferation and apoptosis in human atherosclerotic plaques. However, it is largely unknown whether p53 expression is related to the stability and clinical manifestations of atherosclerotic plaques in humans. In the present study, we examined whether p53 expression is related to clinical symptoms and plaque integrity in patients with carotid atherosclerosis (n=62). We also investigated p53 expression and its relation to apoptosis and apoptosis-related cathepsin L and ferritin in the carotid lesions. METHODS AND RESULTS: We found that smooth muscle cells often had nuclear p53 in the shoulder region of carotid lesions while CD68-positive macrophages, which had both nuclear and cytoplasmic p53, frequently appeared in the surrounding areas of necrotic cores or plaque cap regions. Quantitative image analysis of immunohistochemistry showed that p53 expression was significantly increased in plaques with necrotic core formation or cap rupture and lesions from patients with transient ischemic attacks (TIAs). The levels of p53 expression was significantly increased in more severe stenosed lesions but decreased with prolonged time between symptom onset and carotid endarterectomy. Furthermore, p53 expression was significantly correlated with the expression of ferritin, lysosomal cathepsin L, and apoptosis. CONCLUSION: The increased p53 expression, particularly macrophage p53 levels, is associated with the enlargement of necrotic cores, plaque rupture and clinical manifestations of carotid plaques. Concomitant increases of lysosomal cathepsin, ferritin, and p53 levels may promote the apoptosis and atheroma progression in patients with carotid atherosclerosis.
