Study On The Role Of Biologic Activity Changes Of PPARα In Senescent Endothelial Cell Dysfunction

Objectives:Peroxisome proliferators activated receptorsα(PPARα) is a ligand-dependent nuclear factor of the nuclear receptor superfamily,which plays an important role in adipocyte differentiation,energy metabolism and inflammation.Recent studies have shown that PPARα,as an important upstream regulating gene for such inflammatory transcription factors as NF-kB and AP-1,has potent anti-inflammatory and anti-atherosclerotic function and is crucial to maintain endothelial cell function.Atherosclerosis is a progressive, inflammatory disease secondary to endothelial cell dysfunction.Many studies have indicated that senescent endothelial cell dysfunction is an important pathologic basis for the incidence and development of atherosclerosis in the elderly.Hence,this study was aimed to investigate whether senescence-related endothelial cell dysfunction is closely associated with the biologic activity of PPARαin endothelial cells,so as to reveal the pathophysiological mechanism underlying senescent endothelial cell dysfunction and provide theoretical basis for the prevention and treatment of atherosclerosis in the elderly.Methods:Primary cultures of human umbilical vein endothelial cells(HUVECs) were propagated till cell senescence which was confirmed byβ-galactosidase staining and flow cytometry.HUVECs were divided into the youth group and the senescent group.NO synthesis levels of endothelial cells were measured by nitrate reductase assay;the transcription activity of NF-kB,AP-1,and PPARαin endothelial cells was determined by electrophoretic mobility shift assay(EMSA);the mRNA expression levels of PPARα, RXRα,and NCoR in endothelial cells were determined by semiquantitative reverse transcription-polymerase chain reaction(sqRT-PCR);ubiquitin expression levels in endothelial cells were measured by cytoimmunofluorescence assay;PPARαmRNA expression levels and the DNA-binding activity of PPARαin senescent HUVECs were determined by sqRT-PCR and EMSA,respectively,following the treatment of senescent HUVECs with various concentrations of PPARα-specific activator,CS207.Results:In vitro cultured HUVECs became senescent at the sixth generation,showing positive uponβ-galactosidase staining,arrest of 80%cells at G₀-G₁ phase,and virtually absence of cells at S phase.In senescent HUVECs,there were cell dysfunction,significant decreases in the NO synthesis level,and significant increases in the transcription activity of NF-kB and AP-1.Compared to the youth group,PPARαmRNA expression and the DNA-binding activity of PPARαwere significantly reduced in the senescent group,but RXRαmRNA expression did not change significantly.In contrast,the expression of NCoR mRNA and ubiquitin protein was significantly increased in the senescent group.CS207 effectively reversed the decreases in PPARαmRNA expression and the DNA-binding activity of PPARαin senescent HUVECs in a concentration-dependent manner.Conclusions:Senescence-related endothelial cell dysfunction is closely related to the decreased biologic activity of PPARαin senescent endothelial cells,and the PPARα-specific activator CS207 can effectively reverse the decreases in the biologic activity of PPARα.Therefore, CS207 should be effective in the prevention of senescent endothelial cell dysfunction.