Role Of Serum Amyloid A On Human Umbilical Vein Endothelial Cells

Coronary artery disease (CAD) is the most common cardiovascular disease, get more and more attention. Atherosclerosis is the pathological basis of CAD. To better manage and treat atherosclerosis, it is imperative that the process of atherogenesis be well understood. Over the years, studies have shown that inflammatory factors are involved in all stages of atherogenesis, and hence, atherosclerosis is now regarded as a chronic inflammatory disease. The two major human acute phase proteins C-reactive protein (CRP) and Serum Amyloid A (SAA), they both highly expressed when inflammatory stimulation exists. CRP is considered to directly contribute to atherogenesis. However, unlike CRP, SAA is relatively less well studied. We believe that SAA may directly contribute to atherogenesis.The aims of this thesis are:to examine the effects of SAA on endothelial proinflammation in human umbilical vein endothelial cells(HUVECs) and its mechanism; to determine the effects of SAA on eNOS expression and NO production in human umbilical vein endothelial cells; review and analysis the association between SAA and obesity. It might even lead to the identification of SAA as a potential novel treatment target for CAD or the prevention of CAD through SAA-lowering treatment.1 Serum amyloid A on the expression of cell adhesive molecules in human umbilical vein endothelial cellsTo investigate the effects of serum amyloid A on the expression of cell adhesive molecules in human umbilical vein endothelial cells and the potential signaling pathway. HUVECs were incubated with recombinant human SAA (0-40μg/mL). The transcriptional level of inter cellular adhesion molecule (ICAM-),vascular cell adhesion molecule (VCAM-1) and E-selectin were assayed by real time PCR. The protein cell surface expression and secretion were determined by ELISA assay. The interaction between DNA and nucleoprotein assayed by Electrophoretic Mobility Shift Assay (EMSA).Incubation with recombinant human SAA (20μg/mL) markedly induced gene transcription of CAMs, starting from 2 h, peaking at 4-6 h, and declining after 8 h. ELISA results showed cell surface expression of CAMs was highly induced after SAA treatment for 4 h. Incubation with SAA for 24 h significantly induced protein secretion of CAMs. Pretreatment with NFκB inhibitor (Bay-11-7082) could block SAA-dependent CAMs induction. Furthermore, EMSA results showed that SAA could directly induce the activation of NFκB. Conclusions:SAA induces CAMs expression in HUVECs through the NFκB pathway.2 The effects of SAA on endothelial dysfunctionIn this study, we tested the effect of SAA on eNOS expression and bioactivity in HUVECs to determine if SAA could impair eNOS expression, NO production and cell proliferation. HUVECs were incubated with recombinant human SAA (20μg/mL). The transcriptional level of endothelial nitric oxide synthase (eNOS) was assayed by real time PCR. The protein of eNOS was determined by western blot assay. The culture supernatants were collected and the total nitric oxide production was determined by colorimetric assay. HUVEC proliferation was assayed by MTT [3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] method. Incubation with SAA (20μg/mL) for 24 h markedly inhibited eNOS mRNA level and protein expression, NO production and cell proliferation was significantly decreased with SAA 20μg/mL for 24 h. In conclusion, SAA results in endothelial dysfunction by inhibiting eNOS expression and bioactivity, as well as suppressing HUVEC proliferation.3 Associations between Serum Amyloid A and ObesityHere we reviewed and summarized quantitatively the available data on the association between SAA and obesity. We systematically searched PubMed using words "serum amyloid A" and "obesity" and identified 81 relevant studies between January 1966 and July 2009. Among them,11 cross-sectional studies and 10 prospective studies with successful interventions were included for the meta-analysis. A strong association between BMI and SAA levels was found in the 11 cross-sectional studies. The overall correlation coefficient is 0.230 (95% CI 0.160-0.297, P<0.0005). The influence of weight loss on SAA levels was expressed in standardized mean difference (SDM) and the analysis showed that the change in SAA levels between before and after weight loss was-0.506 (95% CI-0.632 to-0.379, P=0.0001). Moreover, some potential underlying mechanisms and clinical application by reducing SAA levels in obesity are discussed in this review. In the meta-analysis, we demonstrated that SAA levels are positively associated with BMI levels and that weight loss led to decreased SAA level.