| Background and purpose Minimally modified low density lipoprotein (mmLDL) is awell-known risk factor for coronary artery disease. Studies have shown that minimallymodified LDL up regulates endothelin type B receptors in rat coronary artery via ERK1/2MAPK and NF-κB pathway and in rat cerebral basilar artery via the PKC, MAPK andNF-κB signal pathways. Atherosclerosis is considered a chronic inflammatory disease inwhich monocytes and macrophages are critical. These cells express toll-like receptor (TLR)4on their surfaces, are activated by mmLDL and are capable of secretingpro-inflammatory cytokines. Nevertheless, the role of mmLDL impairedendothelium-dependent relaxation via inflammatory pathway in the vasculature has notbeen studied previously. Therefore, the object of our project is that explore mmLDLimpairments endothelium-dependent relaxation mechanisms through researching effect ofinflammatory on pro-inflammatory cytokines in IL-1β and TNF-α in order to provide sometheoretical guidance and experimental basis for anti-atherosclerosis research and give somenew ideas for the prevention and cure of atherosclerosis.Methods Wire myography was employed to examine endothelial function of mesentericarteries. Ultramicrostructure of mesenteric vascular beds were detected by transmissionelectron microscope. IL-1β and TNF-α level in serum were measured by mice ELISA Kit.mRNA and protein expression levels were determined using real-time PCR and WesternBlot, respectively.Results (1)The endothelium-dependent relaxation was decreased with the dosage andreached their peaks at1mg/kg and a plateau after72hours by using mmLDL, comparedwith normal arteries.(2) In endothelium derived hyperpolarizing factor (EDHF)-mediatedrelaxation, the pIC50and Rmaxwere decreased from6.42±0.03and (63±5)%of normalsaline control to5.67±0.07and (31±3)%in mmLDL group (P <0.001, P <0.001), Innitric oxide (NO)-mediated relaxation, the pIC50and Rmax were decreased from5.87±0.10and (47±4)%of normal saline control to5.44±0.12and (31±4)%in mmLDL group (P <0.01, P <0.01).(3)In small-conductance calcium-activated potassium channel(KCa2.3)-mediated relaxation, the pIC50and Rmaxwere decreased from6.44±0.11and (40±4)%of normal saline control to5.30±0.13and (18±3)%in mmLDL group (P <0.001,P<0.01). In intermediate-conductance calcium-activated potassium channel(KCa3.1)-mediated relaxation, the pIC50and Rmax were decreased from5.44±0.18and(21±4)%of normal saline control to4.72±0.13and (8±2)%in mmLDL group (P<0.01, P<0.01). There was no significant change of maxi-conductance calcium-activatedpotassium channel (maxi KCa) pathway between these two groups.(4) Ultramicrostructureof mesenteric vascular bed from mice was detected by transmission electron microscope.(5)TLR4receptor expression was significantly increased in mmLDL group.(6) mmLDLincreased serum and vascular levels of tumor necrosis factor-α and IL-1β, and significantlyupregulated in mesenteric arteries mRNA expression levels, adding to the injury mmLDLmesenteric artery.(6) The serum level of IL-1βwas higher in the mmLDL group comparedwith normal saline group (132.75±13.37vs.60.73±9.73pg/mL, respectively; P<0.01).TNF-α level was also significantly elevated (328.95±28.85) compared with normal salineanimals (140.15±22.68; P<0.001). Determination of TNF-α and IL-1β levels in vasculartissues with RT-PCR revealed similar resultsConclusions mmLDL significantly reduced endothelium-dependent vasodilation which themechanism with the following factors:(1) mmLDL impaired endothelial cellsultrastructure in mice mesenteric arteries via up-regulating the expression of TLR4, inwhich the inflammatory response was activated.(2) mmLDL inhibited of NO and EDHFsignaling pathways.(3) mmLDL down-regulated KCa2.3and KCa3.1protein expression. |
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