Plasma Level Of LOX-1in Patients With Essential Hypertension And Role Of LOX-1in Endothelial Cell Apoptosis Induced By Static Pressure

BACKGROUNDHypertension is a common cardiovascular disease. Renin-angiotensin-aldosterone system (RAAS) and oxidative stress play important roles in the pathologenesis of hypertension. Under the state of oxidative stress, ROS oxidatively modify native low-density lipoprotein, resulting in the formation of oxidized low-density lipoprotein (ox-LDL). Angiotensin Ⅱ via its type1receptor (AT1R) activation up-regulates lectin-like oxidized low-density lipoprotein receptor-1(LOX-1) expression through redox-sensitive pathways, and activation of LOX-1up-regulates ATIR expression. The interaction between angiotensin Ⅱ/AT1R and ox-LDL/LOX-1operates in a positive feedback loop with the generation of ROS, suggesting that LOX-1plays an important role in the pathogenesis of hypertension.LOX-1, a type C scavenger receptor, was initially cloned from bovine aortic endothelial cells in1997by Sawamura et al. It is the major receptor responsible for uptake and metabolism of ox-LDL in endothelial cells, and plays an important role in the pro-inflammatory signaling, endothelial dysfunction and atherosclerosis. Studies have shown that LOX-1mediates ox-LDL-induced apoptosis of endothelial cells.In the present study, we measured the plasma soluble LOX-1level in patients with essential hypertension, and observed the role of LOX-1in injury and apoptosis of endothelial cell induced by static pressure and the underlying mechanisms.Chapter I Chang in plasma soluble LOX-1level in patients with essential hypertensionObjectives:This study was aimed to measure the plasma soluble LOX-1(sLOX-1) level in patients with essential hypertension.Methods:There were four groups of subjects:control group (n=27), hypertension group (n=62), hyperlipemia group (n=24), hypertension combined with hyperlipemia group (n=56). The level of plasma sLOX-1and ox-LDL were measured by enzyme-linked immunosorbent assay.Results:The plasma ox-LDL levels in patients with hyperlipemia were significantly higher than that of the control group (P<0.01), but there was no difference between hypertension group and control group (P>0.05). The plasma ox-LDL levels in patients with hypertension combined with hyperlipemia were significantly higher than that of patients with hypertension (P<0.01), but no difference compared with hyperlipemia group (P>0.05). The plasma sLOX-1levels in patients with hypertension or hyperlipemia were significantly higher than that of the control group (P<0.01). Tthe plasma sLOX-1levels in patients with hypertension combined with hyperlipemia were significantly higher than that of patients with hypertension (P<0.01), but no difference compared with hyperlipemia group (P>0.05).Conclusion:The plasma sLOX-1level in pathients with essential hypertension was significantly elevated.Chapter II Role of LOX-1in static pressure induced endothelial cell apoptosis and the underlying mechanismsObjective:To explore the role of LOX-1in endothelial cell apoptosis induced by static pressure and the underlying mechanism.Methods:After cultured with the serum-free medium for24h, HUVEC-C cells were pretreated with LOX-1-neutralizing antibody TS20(10μg/ml), DPI (20μmol/L), SN50(18μmol/L), and DMSO for1h prior to exposure to static pressure (180mmHg). Cell injury was evaluated by laxtate dehydrogenase (LDH) leakage. Cell apoptosis was determined by flow cytometry assay and caspase-3activity. The level of intracellular reactive oxygen species (ROS) was determined using fluorescent ROS detection kit and cytometry assay. The level of LOX-1mRNA was detected by real time PCR. The level of LOX-1protein was determined by Western Blot.Results:LOX-1mRNA and protein expression in endothelial cells was up-regulated by static pressure in a pressure-and time-dependent manner. Static pressure at180mmHg for6h increased the leakage of LDH in endothelial cells, an effect that was inhibited by the LOX-1-neutralizing antibody, the NADPH oxidase inhibitor DPI and the NF-κB inhibitor SN50. Treatment with static pressure at180mmHg for6h increased the ratio of apoptotic cells, the caspase-3activity, and ROS production. All these effects were also inhibited by the LOX-1-neutralizing antibody, DPI, and SN50.Conclusion:Static pressure induces endothelial cell apoptosis, which is related to activation of LOX-1-NADPH oxidase-ROS-NF-KB-caspase-3pathway.