The Prereceptor Regulation Mechanism Of GC On Protecting The Inflammtory Injury Of Vascular Endothelial Cells

Vascular endothelial cells (VEC) are a group of special cells and they play a important role in vascular barrier, immunity and inflammation. They can excrete many bioactivators or cytokines such as ICAM-1 and IL-6 that IL-6 was considered as a best molecular mark of inflammation in vascular endothelium. Endothelial cells as the target cells of lipopolysaccharide (LPS) play a pivotal role in the pathogenesis of sepsis , sepsis shock, MODS and so on. The disfunction or apoptosis of endothelial cells not only are the common onset of cardiac and brain vascular diseases but also are the main source of ARDS and MODS induced by sepsis, shock, trauma and so on. In the pathogenesis of ARDS, vascular endothelial cells serve as target and effector cells, so activated or injured VEC is the basic path of uncontrollable inflammatory reaction and high permeability pulmonary edema. For this reason VEC should be a target for the treatment of ARDS with glucocorticoid(GC).The research about the treatment of ARDS with GC were clinical trials in past decades, meanwhile the lab experiment mainly related to the injury of VEC and adhesion between leucocyte and VEC. On the other hand most of the researches about the mechanism of GC were in the field of glucocorticoid receptor(GR).For the present,the mechanism of treating ARDS in GC by protecting VEC ,especially the prereceptor regulation of GC has not reported. In this study, we firstly injured the human umbilical vein endothelial cell (HUVEC) in LPS in vitro and made a inflammatory injury model of VEC. Secondly, we observed the effect of GC (Dex) on the secretion of IL-6 and sICAM-1 in ELISA, apoptosis of HUVEC in TUNEL, and determined whether GC (Dex) could protect the HUVEC. Thirdly, we detected the expression of GR,MR and 11β-HSD(11-βhydroxysteroid dehydrogenase ,a key enzyme for the prereceptor regulation of GC) in HUVEC in RT-PCR or other methods. Finally, we observed the effect of glycyrrhizic acid(GA) on inhibiting the expression of 11β-HSD and enhancement of GC(Dex).We intended to explore the prereceptor regulation mechanism of GC on protection of the inflammatory injury in VEC and the prospect in treatment of ARDS. The main results and conclusions were summarized as follows: 1.HUVEC began to increase the secretion of IL-6 and sICAM-1 after 3h stimulating in different concentration of LPS, meanwhile occurred distinct necrosis and apoptosis. It could make the most conspicuous effect that LPS's concentration was 100ng/ml and treated 24h.So 100ng/ml of LPS could make a typical inflammatory injury model of VEC. 2.GC (Dex) could obviously inhibit the secretion of IL-6 and sICAM-1 and apoptosis of HUVEC with a does-dependent manner. When the concentration of Dex approached 10-6mol/L, the inhibited effects were maximal. Over 10-6mol/L ,Dex could not increase the effects again. It indicated that Dex could protect the injury of HUVEC induced by LPS with a does-dependent manner and 10-6mol/L was a top limit concentration of Dex to bring into full play. 3.HUVEC could express some mRNA and protein of GR and MR at the basic status. LPS and Dex could downregulate the expression of GR, but flushing does(10-6mol/L) of Dex could up regulate the expression of MR. It indicated that HUVEC could express constituted GR and MR,GC might access MR to produce the bioactive effects. It should be paid close attention to the non-GR dependent pathway. 4.HUVEC could express some mRNA of 11β-HSD at the basic status. GC(Dex) could up regulate the expression of both 11β-HSD1 and 11β-HSD2,but the expression of 11β-HSD1 was obviously more than 11β-HSD2(P<0.05).It indicated that HUVEC could express constituted 11β-HSD, which supplied the fundament for the prereceptor regulation of GC.Up regulation 11β-HSD1 could enhance the effect of GC by positive feedback with prereceptor regulation and it might be considered a mechanism of protecting the inflammatory injury in VEC. 5.LPS could up regulate the expression of both 11β-HSD2 and 11β-HSD1,but the expression of 11β-HSD2 was obviously more than 11β-HSD1(P<0.05).It indicated that LPS could attenuate the anti-inflammation effect of GC by prereceptor regulation and it might be considered a new pathway. 6.Glycyrrhizic acid(GA) could inhibit the expression of 11β-HSD2 in HUVEC but increase the expression of 11β-HSD1,meanwhile decreased the secretion of IL-6 and sICAM-1 and the apoptosis of HUVEC induced by LPS. Treated HUVEC with both GAand Dex could achieve a powerfuler effect than only Dex(P<0.05).It indicated that GA could enhance the effects of GC by prereceptor regulation. GC attached GA as a new treatment plan in GC should be spreaded in the future.