Anti-RBP4 (native) polyclonal antibody

Recent studies have suggested that retinol binding protein 4 (RBP4), an adipocytokine related to insulin resistance (IR), may play an important role in the development of atherosclerosis and cardiovascular diseases (CVD). Abnormal proliferation and migration of vascular smooth muscle cells (VSMCs) is one of the most common causes of atherosclerosis. Hyperinsulinism promotes proliferation of VSMCs through the MAPK pathway. However, whether RBP4 is involved in insulin-induced proliferation of VSMCs leading to atherosclerosis remains unclear. In the present study, we evaluated the role of RBP4 and the potential relevance of signaling pathways in this process. Different concentrations of RBP4 (1 and 4 mu g/ml) were added to rat aortic smooth muscle cells (RASMCs) during insulin-induced proliferation. The levels of cell growth signaling pathway proteins ERK1/2, p-ERK1/2, JAK2, p-JAK2, STAT3 and p-STAT3 were assessed by western blotting in order to identify the pathway(s) that are activated during insulin-induced proliferation. The specific inhibitors of ERK1/2 (PD98059) and JAK2 (AG490) were used to confirm our findings. Insulin induced proliferation of RASMCs in a concentration- and time-dependent manner, and increased the expression of ERK1/2, p-ERK1/2, JAK2, p-JAK2, STAT3 and p-STAT3 in a time-dependent manner. RBP4 enhanced insulin-induced proliferation of RASMCs and expression of p-ERK1/2 and p-JAK2. RBP4-induced proliferation of RASMCs was reduced by the ERK1/2 inhibitor, while it was unaffected by the JAK2 inhibitor. These results suggest that RBP4 mediates VSMC proliferation induced by insulin via activation of the MAPK pathway, and highlight RBP4 as a modulator of atherosclerosis in hyperinsulinemia, therby enhancing our understanding on a number of unexpected aspects of CVD.

Objective: Preeclampsia (PE) is a disorder of pregnancy that is associated with maternal and fetal mortality and morbidity. Abnormal placental Retinol-binding protein 4 (RBP4) expression has been found in cases of PE. This study aimed to further investigate the possible role of RBP4 in the pathophysiology of PE. Study Design: RBP4 serum concentration was detected using enzyme-linked immunosorbent assays in eighteen patients with severe PE and twenty-five individuals with healthy pregnancies. JEG-3 cells were transiently transfected with a plasmid construct expressing RBP4 (pCMV-RBP4), an empty plasmid (p-CMV) or siRNA, and the MMP2 and MMP9 protein levels were analysed 48 h after transfection. MTT assays and transwell assays were used to explore the functional role of RBP4 in the proliferation and invasion of JEG-3 cells. Results: RBP4 serum concentration in patients with severe PE was significantly lower than that in individuals with healthy pregnancies. RBP4 over-expression enhanced the invasion and proliferation of JEG-3 cells and increased MMP2 and MMP9 in JEG-3 cells. Conclusions: RBP4 plays an important role in the regulation of trophoblast invasion and migration and represents a possible underlying pathological and molecular mechanism of PE.