Résumé
To systematically clarify the effects of apolipoprotein E (aopE) and low-density lipoprotein receptor (LDLR) gene mutant on hyperlipidemia, vascular inflammation impairment and pathogenesis of atherosclerosis (AS), total RNA was isolated from fresh aortas of young apoE/LDLR double knockout (apoE(-/-)/LDLR(-/-)) and wild type (WT) mice using TRIzol reagent. Then RNA was reversely transcribed to first-strand cDNA by reverse transcriptase for reverse transcription polymerase chain reaction (RT-PCR) and real-time RT-PCR. Primer pairs were designed using primer design software according to the gene sequences available in GenBank. β-actin was used as an internal control. Then RT-PCR assay was used to analyze the expression patterns of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), nuclear factor-κB (NF-κB), granulocyte-macrophage colony-stimulating factor (GM-CSF), CD36, endothelin-1 (ET-1), toll-like receptor 2 (TLR2), monocyte chemoattractant protein-1 (MCP-1), vascular adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1) and platelet-derived growth factor-α (PDGF-α). SYBR Green quantitative real-time RT-PCR was used to validate gene expressions identified by RT-PCR. Blood samples were taken from the retro-orbital venous plexus, and serum levels of total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL) and high-density lipoprotein (HDL) were measured by using biochemical techniques. Serum concentrations of circulating TNF-α, IL-1β and oxidized LDL (ox-LDL) were determined by ELISA. Frozen sections of aortic sinus were stained with Sudan IV to visualize intimal fatty lesions. The results showed that the relative expressions of IL-1β, GM-CSF, ET-1, TLR2, CD36, MCP-1, ICAM-1 and VCAM-1 in apoE(-/-)/LDLR(-/-) mice at the age of 1 month were higher than those in age-matched WT mice (P<0.05, P<0.01), respectively. The expressions of PDGF-α and TNF-α in apoE(-/-)/LDLR(-/-) mice at the age of 2 months were up-regulated compared to those in age-matched WT mice (P<0.05). All the expressions of target genes continued to be up-regulated (P<0.05, P<0.01) except that ET-1 expression at the age of 2 months, TLR2, VCAM-1 and ICAM-1 expressions at the age of 3 months were down-regulated to that in WT mice. NF-κB expression had no significant changes between two genotype mice at different ages. All the gene expressions kept unchanged in WT mice at different ages, except that IL-1b expressions were slightly up-regulated at the ages of 2 and 3 months. Serum levels of TC, TG, LDL, HDL, TNF-α, IL-1β and ox-LDL in apoE(-/-)/LDLR(-/-) mice at different ages were higher than those in age-matched WT mice (P<0.05, P<0.01), and were increasing with age. Primary atherosclerotic lesions were observed in 1-month old apoE(-/-)/LDLR(-/-) mice and were progressing with age. There were no lesions observed in all WT mice at different ages. The data suggest that hyperlipidemia due to apoE and LDLR gene mutant may stimulate the temporal expressions of AS-related genes and contribute to primary atherogenetic lesions and vascular inflammation impairment.