Paeonol suppresses oxidized low-density lipoprotein induced endothelial cell apoptosis via activation of LOX-1/p38MAPK/NF-κB pathway.

Paeonol is an active compound isolated from traditional Chinese medicine, and has been shown to have anti-atherosclerosis, anti-inflammatory, antioxidant effects. The present investigation was undertaken to determine the suppression effects of paeonol on oxidized low-density lipoprotein (ox-LDL) induced endothelial cell line HUVEC apoptosis and to uncover some of the underlying mechanisms of these effects. Cell viability and lactate dehydrogenase (LDH) were measured to evaluate the cell injuries. Apoptosis was evaluated by Hoechst 33342 staining and flow cytometry. Intracellular reactive oxygen species (ROS) generation was detected by 2',7'-dichlorofluorescein diacetate (DCFH-DA). Real-time PCR was used to confirm the expression of LOX-1 mRNA. Western blotting was used to evaluate the protein expression of LOX-1 and Bcl-2, as well as caspase-3 cleavage, p38-mitogen-activated protein kinase (p38MAPK) phosphorylation. NF-κB nuclear translocation was detected by Western blotting and immunofluorescence. Caspase-3 activity was measured using a colorimetric protease assay kit. The results showed that ox-LDL significantly decreased cell viability and increased the LDH release, as well as the apoptotic rate (P<0.01). Pre-treatment of paeonol resulted in remarkable increase of cell viability, decrease of LDH release and cell apoptosis in a concentration-dependent manner. Besides, ox-LDL caused the up-regulation of LOX-1, the down-regulation of Bcl-2, the phosphorylation of p38MAPK, the translocation of NF-κB and the activation of caspase-3. Paeonol pre-treatment reversed these effects introduced by ox-LDL. Moreover, paeonol also showed its inhibition effects on ox-LDL induced ROS overproduction. These results indicate the preventive effects of paeonol on ox-LDL induced endothelial cell apoptosis. The effects might, at least partly, be obtained via inhibition of LOX-1-ROS- p38MAPK-NF-κB signaling pathway.

Bao MH ，Zhang YW ，Zhou HH 《-》

Puerarin protects endothelial cells from oxidized low density lipoprotein induced injuries via the suppression of LOX-1 and induction of eNOS.

Bao MH ，Zhang YW ，Lou XY ，Xiao Y ，Cheng Y ，Zhou HH ... -  《-》

Lipopolysaccharide induced LOX-1 expression via TLR4/MyD88/ROS activated p38MAPK-NF-κB pathway.

Lectin-like receptor for oxidized low density lipoprotein (LOX-1) plays a key role in endothelial ox-LDL endocytosis, endothelial dysfunction and atherogenesis. In the present study, the effect of lipopolysaccharide (LPS) on LOX-1 expression and the underlying molecular pathways were investigated. Human umbilical vein endothelial cells (HUVECs) were treated with LPS and the protein expressions of LOX-1, TLR4, TLR2, MyD88, Nox4, Nox2, PI3K, p38MAPK, JNK, ERK, Nrf1, Nrf2 and p65 were examined by Western blotting. The intracellular reactive oxygen species (ROS) production was examined by flow cytometry with fluorescence probe DCFH2-DA. The role of TLR4, MyD88 and Nox4 were determined with specific siRNA. The endothelial ox-LDL uptake and the endothelial-monocyte adhesion were evaluated with DiI-ox-LDL and Hoechst 33342 respectively. The effect of LPS on LOX-1 expression in aorta tissue was also studied with male C57/BL6 mice by intraperitoneal injection of LPS. The results showed that LPS induced LOX-1 protein expression in a time- and concentration-dependent manner. The mRNA expression of LOX-1 was also upregulated. The protein expression of LOX-1 and phosphorylated p38MAPK, p65 was significantly enhanced by LPS both in vitro and in vivo. LPS induced LOX-1 expression was blocked by siRNA for TLR4, MyD88, and Nox4 and inhibitors for p38MAPK, NF-κB, cyclooxygenase-2, and NADPH oxidase. Both LPS induced ox-LDL uptake and endothelial-monocyte adhesion were significantly inhibited by anti-LOX-1 antibody. LPS dramatically induced LOX-1 protein expression in aorta tissues. In conclusion, our data suggested that LPS induces LOX-1 expression via TLR4/MyD88/ROS activated p38MAPK/NF-κB pathway in endothelial cells, which provides new regulatory mechanisms for LOX-1 expression.

Zhao W ，Ma G ，Chen X 《-》

Isorhamnetin prevent endothelial cell injuries from oxidized LDL via activation of p38MAPK.

Bao M ，Lou Y 《EUROPEAN JOURNAL OF PHARMACOLOGY》

Ox-LDL-induced LOX-1 expression in vascular smooth muscle cells: role of reactive oxygen species.

Oxidized low density lipoprotein (ox-LDL) and lectin-like oxidized low density lipoprotein receptor-1 (LOX-1) have been implicated in the development of atherosclerosis. This study was designed to investigate the expression regulation of LOX-1 by ox-LDL and the potential underlying mechanisms in cultured rat vascular smooth muscle cells (VSMCs). VSMCs were treated with ox-LDL, and the expressions of LOX-1 mRNA and proteins were determined by RT-PCR and western blotting, respectively. The intracellular reactive oxygen species (ROS) production was monitored by flow cytometry with fluorescence probe, DCFH(2) -DA. The effect of several inhibitors including aspirin, NDGA, allopurinol, apocynin, and rotenone on ox-LDL-induced ROS formation and LOX-1 expression was also investigated. The roles of NF-κB p65 and JNK were explored. Ox-LDL significantly induced LOX-1 expression at both mRNA and protein levels in a dose-dependent and time-dependent manner. Aspirin, NDGA, and preconditioned apocynin suppressed ox-LDL-induced intracellular ROS production and LOX-1 expression, while allopurinol and rotenone failed to do so. Vitamin C and N-acetyl-l-cysteine demonstrated similar effect. Furthermore, both NF-κB p65 expression and phosphorylated JNK (p-JNK) to JNK expression ratio were elevated after ox-LDL treatment. In addition, the NF-κB inhibitor PDTC and JNK inhibitor SP600125 pretreatment partly abolished ox-LDL-induced LOX-1 expression. These findings suggested that ROS mediated ox-LDL-induced LOX-1 expression in VSMCs through NF-κB and JNK signaling pathways.

Sun Y ，Chen X 《-》