Arterial vascular cell line expressing SSAO: a new tool to study the pathophysiology of vascular amine oxidases

Semicarbazide-sensitive amine oxidase (SSAO) widely exists in nature, mainly expressed at significant levels in vasculature. It plays a detrimental role in vascular diseases, particularly atherosclerosis, which occurs mainly in arteries. Herein we for the first time present SSAO expression in arterial lineage of vascular cell line, i.e., human umbilical arterial endothelial cell (HUAEC). Firstly, two commercially available gene transfection reagents were compared to determine high transfection efficiency and then the expression behavior of HUAEC:SSAO was characterized. Furthermore, our model was also been compared with commonly used human embryonic kidney (HEK) cell transfected with the same vector. For enzymatic assay, an in-house developed highly sensitive high performance liquid chromatography electron spray ionization mass spectrometry method was applied. Results indicated that the maximal transfection efficiency in HUAEC was detected by JetPEI™ and transfected protein was expressed at membrane and cytosol of different clones. No significant variations were observed in HUAEC between cell passages 1 and 7, although HEK cell displayed twofold higher SSAO expression level than HUAEC. The transfected SSAO was shown to be released into the cell-culture medium. Both cellular and released types of SSAO exhibited monomer and dimer structural forms. The cytotoxicity determination exhibited large number of viable cells after transfection with JetPEI™. Differential expression characterization of this new cell line demonstrates the correct behavior of SSAO in arterial endothelial cells and also provides a real physiological environment to elucidate the unclear role of this enzyme. In addition, our cellular model could partly solve the problems raised by the loss of enzyme expression found in cultured endothelial cells. This model could also be a useful tool for proteomic base study, screening of interacting protein and analysis of compounds that could modify its activity for therapeutic purposes.