S100A12, also called EN-RAGE (extracellular newly identified receptor for advanced glycation end products binding protein) or calcium-binding protein in amniotic fluid-1, is a ligand for RAGE. It has been shown that S100A12 induces adhesion molecules such as vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 in the vascular endothelial cell and mediates migration and activation of monocytes/macrophages through RAGE binding and that infusion of lipopolysaccharide into mice causes time-dependent increase of S100A12 in the plasma. Therefore, circulating S100A12 protein may be involved in chronic inflammation in the atherosclerotic lesion. In this study, we developed an ELISA system that uses specific monoclonal antibodies against recombinant human S100A12 to measure plasma S100A12 levels in patients with diabetes. On using our S100A12 ELISA system, the coefficients of variation of intra- and interassay were less than 4 and 9%, respectively. The analytical lower detection limit was 0.2 ng/ml. When plasma S100A12 levels were measured by this system, the concentrations were more than twice as high in the patients with diabetes, compared with those without. Using univariate analysis in all subjects, plasma S100A12 concentrations correlated with hemoglobin A1c, fasting glucose, high-sensitivity C-reactive protein and white blood cell count. Stepwise multiple regression analyses, however, revealed that only white blood cell count and hemoglobin A1c remained significant independent determinants of plasma S100A12 concentration. These results suggest that plasma S100A12 protein levels are regulated by factors related to subclinical inflammation and glucose control in patients with type 2 diabetes.

No abstract

No abstract

Abstract-Angiotensin (Ang) II has 2 major receptor isoforms, Ang type 1 (AT 1 ) and Ang type (AT 2 ). AT 1 transphosphorylates epidermal growth factor receptor (EGFR) to activate extracellular signal-regulated kinase (ERK).Although AT 2 was shown to inactivate ERK, the action of AT 2 on EGFR activation remains undefined. Using AT 2 -overexpressing vascular smooth muscle cells from AT 2 transgenic mice, we studied these undefined actions of AT 2 . Maximal ERK activity induced by Ang II was increased 1.9-and 2.2-fold by AT 2 inhibition, which was abolished by orthovanadate but not okadaic acid or pertussis toxin. AT 2 inhibited AT 1 -mediated EGFR tyrosine phosphorylation by 63%. The activity of SHP-1 tyrosine phosphatase was significantly upregulated 1 minute after AT 2 stimulation and association of SHP-1 with EGFR was increased, whereas AT 2 failed to tyrosine phosphorylate SHP-1. Stable overexpression of SHP-1-dominant negative mutant completely abolished AT 2 -mediated inhibition of EGFR and ERK activation. AT 1 -mediated c-fos mRNA accumulation was attenuated by 48% by AT 2 stimulation. Induction of fibronectin gene containing an AP-1 responsive element in its 5Ј-flanking region was decreased by 37% after AT 2 stimulation, corresponding to the results of gel mobility assay with the AP-1 sequence of fibronectin as a probe. These findings suggested that AT 2 inhibits ERK activity by inducing SHP-1 activity, leading to decreases in AP-1 activity and AP-1-regulated gene expression, in which EGFR dephosphorylation plays an important role via association of SHP-1. Key Words: angiotensin II Ⅲ angiotensin II receptors Ⅲ angiotensin II type 2 receptor Ⅲ tyrosinephosphatase Ⅲ SHP-1 Ⅲ epidermal growth factor receptor A ngiotensin (Ang) II plays a critical role in regulation of the cardiovascular system via 2 main Ang II receptor subtypes, Ang type 1(AT 1 ) and Ang type 2(AT 2 ). 1,2 Most of the Ang II-mediated vasoconstrictive actions are mediated by AT 1 , although little information is available regarding signal transduction by AT 2 . 3 AT 2 is abundantly and widely expressed in fetal tissues and is reexpressed in myocardial infarction and vascular injury. 4 Although the level of expression of AT 2 is low in large vessels, AT 2 is present in high levels in vascular smooth muscle cells (VSMCs) of microvessels. 5 AT 2 antagonizes the in vivo effects of AT 1 on blood pressure 6 and renal natriuresis 7 and mediates growth inhibition, 8,9 differentiation, 10 and/or apoptosis 11 in VSMCs and in endothelial, neuronal, and fibroblast R3T3 cells.These effects of AT 2 are mediated mainly by the activation of protein tyrosine phosphatases (PTP), resulting in the inactivation of AT 1 -activated extracellular signal-regulated kinase (ERK). [12][13][14] Recently, Ang II-induced ERK activation was shown to be mediated by epidermal growth factor receptor (EGFR) transactivated via AT 1 in a Ca 2ϩ signaldependent manner in cardiac fibroblasts, 15 VSMCs, 16 and liver epithelial cells. 17 In contrast, activation of c-Jun NH 2 -termina...