Correlation of Peroxisome Proliferator-Activated Receptor-γ (PPAR-γ) and Retinoid X Receptor-α (RXR-α) expression with clinical risk factors in patients with advanced carotid atherosclerosis

BACKGROUND Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) and its nuclear partners, the Retinoid X Receptors (RXRs), have been recognized as crucial players in the pathogenesis of atherosclerosis. The present study aimed to assess the clinical significance of PPAR-gamma and RXR-alpha expression in different cellular populations localized within advanced carotid atherosclerosis lesions. MATERIAL/METHODS PPAR-gamma and RXR-alpha expression was assessed by immunohistochemistry in 134 carotid atherosclerotic plaques obtained from an equal number of patients that underwent endarterectomy procedure for vascular repair, and was correlated with patients' medical history, risk factors and medication intake. RESULTS Increased incidence of low PPAR-gamma expression in both macrophages and smooth muscle cells was noted in patients presenting coronary artery disease (p=0.032 and p=0.046, respectively). PPAR-gamma expression in smooth muscle cells was borderline down-regulated in symptomatic compared to asymptomatic patients (p=0.061), reaching statistical significance when analyzing groups of patients with specific cerebrovascular events; amaurosis fugax (p=0.008), amaurosis fugax/stroke (p=0.020) or amaurosis fugax/transient ischemic attack patients (p=0.028) compared to asymptomatic patients. Low RXR-alpha expression in macrophages was more frequently observed in hypertensive (p=0.048) and hyperlipidemic patients (p=0.049). Increased incidence of low RXR-alpha expression in smooth muscle cells was also noted in patients presenting advanced carotid stenosis grade (p=0.015). CONCLUSIONS PPAR-gamma and RXR-alpha expression down-regulation in macrophages and smooth muscle cells was associated with a more pronounced disease progression in patients with advanced carotid atherosclerotic lesions.