Effect of pravastatin on cholesteryl esters in foam cells and the relation with caveolin-1 / 生理学报

The purpose of the present study was to investigate the effect of pravastatin on cholesteryl esters in foam cells of murine macrophages and the relation with caveolin-1. RAW 264.7 murine macrophages were coincubated with 80 mg/L oxidized low density lipoprotein (ox-LDL) and pravastatin (0~100 mumol/L) respectively for 24 h. When the best control concentration of pravastatin was confirmed, RAW 264.7 murine macrophages were coincubated with 80 mg/L ox-LDL and pravastatin of the best concentration respectively for 0, 6, 12, 24 h. Oil red O dyeing experiment was used to show the lipid droplets in foam cells. High performance liquid chromatography (HPLC) analysis was performed to determine the content of cellular cholesterol. The level of caveolin-1 was determined by Western blot analysis. The result showed that when macrophages were incubated with 80 mg/L ox-LDL, the ratio of cellular cholesteryl ester to total cholesterol (CE/TC) was beyond 50% through HPLC analysis, and a great deal of lipid droplets displayed in cells through Oil red O dyeing experiment, which manifested the formation of the foam cells. Pravastatin could decrease CE in foam cells in a concentration-dependent manner (1~100 mumol/L). At the concentration of 100 mumol/L, pravastatin decreased cellular CE more than 50%. The effects of pravastatin on the decrease of CE in murine macrophages also displayed a time-dependent manner (incubated with 100 mumol/L pravastatin from 6 to 24 h). Moreover, the expression of caveolin-1 was decreased when the macrophages were incubated with ox-LDL (80 mg/L), while treatment with pravastatin increased the level of caveolin-1 and displayed a concentration- and time-dependent manner. These results suggest that pravastatin could inhibit the development of foam cells through the decrease of cellular CE, which may be related to the upregulation of caveolin-1.

Preparation and identification of monoclonal antibody against human thrombomodulin / 生理学报

To produce specific monoclonal antibody (McAb) against human thrombomodulin (hTM), the full-length hTM cDNA-expressing plasmid pThr402 was transfected into CHO cells by Lipofectamine 2000 reagent. The hTM-expressing CHO cells, which was confirmed by flow cytometry and Western blot, were obtained by G418 selection. Then the McAb against hTM was prepared with classic hybridoma technique. A cell line of CHO-TM5 with high level of hTM was used to immunize female Balb/c mice 3 times at an interval of 4 weeks. On the third day after the third immunization, mice were sacrificed and spleen cells were harvested to prepare hybridoma cells with SP2/0 cells at the ratio of 10 to 1. Hybridoma cells were then cultured at 96-well plates for screening. Cellular enzyme-linked immunoabsorbent assay (CELISA) was applied twice. The first CELISA was done with polythene ELISA plate with a monolayer of CHO-TM5 cells. The positive clones from the first screen were then selected by reacting with similar screening ELISA plate but with CHO cell monolayer instead. Only clones that were positive for the first screening and negative for the second screening were kept, and called as CHO-TM5(+)CHO(-) hybridoma cells. Balb/c mice were intraperitoneally injected with the selected hybridoma cells. Ascites were collected and monoclonal antibodies were purified using FPLC, and its Ig class, subclass, and titer were then determined respectively. The specificity of the yielded McAb was identified with CELISA, flow cytometry, ABC immunohistochemistry and immunoblotting. One line of hybridoma cells with high expression of specific McAb against hTM, NH-1, was obtained. The Ig subclass of the McAb was IgG1 and the titer of ascitic McAb was 1x10(-6). Flow cytometry, CELISA and Western blot assays demonstrated that McAb NH-1 could specifically recognize hTM expressed in CHO-TM5 cells and human umbilical vascular endothelial cells. Meanwhile, the tissue specificity of antigen recognized by McAb NH-1 was identified by immunohistochemical ABC staining. NH-1 can specifically recognize the natural hTM expressed mainly in vascular endothelial cells, which will potentially be useful for investigation of the functions and clinic values of hTM.

Phytoestrogen genistein supplementation increases eNOS and decreases caveolin-1 expression in ovariectomized rat hearts / 生理学报

This study examined whether genistein influences the production of nitric oxide (NO) and expression of endothelial nitric oxide synthase (eNOS) and the modulators of eNOS activity in ovariectomized (OVX) rat hearts. Female mature Sprague-Dawley rats were subjected to bilateral ovariectomy, OVX rats were randomly divided into four groups: 17beta-estradiol (0.1 mg/kg, s.c. daily) was used as the positive control; low dose of genistein (0.5 mg/kg, s.c. daily); high dose of genistein (5.0 mg/kg, s.c. daily) and model. Sham operations as controls, the treatment lasted 6 weeks. Blood pressure, heart rate, plasma estradiol, heart and uterine weights were measured. Nitrite production in the myocardium was determined by nitrate reductase method. Protein level of eNOS, caveolin-1 and calmodulin was determined by Western blot. The results showed that nitrite production and eNOS protein in homogenized ventricular tissue was attenuated by approximately 53% and 67% in OVX rats compared with those in sham rats, respectively. Genistein increased nitrite production in rat heart in a dose-dependent manner, genistein at the dose of 5 mg/kg.d(-1) resumed nitrite production to a level similar to that in sham operated rats. Administration of genistein also increased eNOS protein expression in OVX rats myocardium with a concomitant decrease in the expression of caveolin-1, an endogenous eNOS inhibitory protein. Another eNOS stimulatory protein, calmodulin, was unchanged in these treatments. These effects were also observed in rats treated with 17beta-estradiol. Genistein at the dose of 5.0 mg/kg.d(-1) augmented uterine weight but this side effect in reproductive system was less than that of 17beta-estradiol. These results suggest that genistein supplementation and estrogen replacement therapy directly increase eNOS functional activity and NO production in the hearts of the OVX rats, but genistein has less side effects on the reproductive system than 17beta-estradiol.

Cyclosporin A inhibits the adhesion of neutrophil with ECV-304 induced by hypoxia/reoxygenation via ROS-Cyclophilin A-ERK1/2 pathway / 生理学报

To investigate the inhibition of cyclosporin A (CsA) on neutrophil adhesion to human umbilical vein endothelial cells (HUVECs, ECV-304) induced by hypoxia/reoxygenation and further explore its mechanism, a 1 h hypoxia/4 h reoxygenation model was reproduced using ECV-304. The adhesion rate of neutrophils to ECV-304 was determined by measuring the activity of endogenous hexosaminidase. The expression of endothelial cell adhesion molecules of E-selectin and ICAM-1 was measured by flow cytometry. The expression of cyclophilin A (CyPA) and the activation of ERK1/2 was compared among experimental groups by Western blot. The content of reactive oxygen species (ROS) was measured by Fenton reaction. After being stimulated with 1 h hypoxia/4 h reoxygenation, ECV-304 showed an enhanced neutrophil adhensiveness in association with an increased surface expression of E-selectin and ICAM-1. In parallel, the content of ROS was also increased. These effects were significantly suppressed by the addition of CsA. Most importantly, the expression of CyPA was significantly increased following 1 h hypoxia/4 h reoxygenation, which was accompanied with an increased activation of ERK1/2. Treatment with CyPA inhibitor CsA and CyPA antisense oligonucleotides significantly inhibited the activation of ERK1/2 and decreased the adhesion of neutrophils to ECV-304. The specific ERK1/2 inhibitor PD98059 caused an inhibition of neutrophil adhesion to hypoxia/reoxygenation-stimulated ECV-304. Our data confirm that CsA inhibits neutrophil adhesion to hypoxia/reoxygenation stimulated ECV-304 by a mechanism involving inhibition of the signal transduction of ROS, CyPA and ERK1/2.