Investigating the molecular mechanisms of Angiotensin II-induced leptin synthesis in vascular smooth muscle cells -

Abstract

Background and aims: There is considerable evidence supporting the role of Ang II and the obesity-associated adipokine leptin, in the pathogenesis of vascular hypertrophy and remodeling. Both proteins appear to mediate the hypertrophic effect of one another, possibly through a crosstalk or feedback mechanism. The correlation between Ang II and leptin has been scarcely investigated. In this study, we aimed to investigate whether Ang II induced leptin synthesis in vascular smooth muscle cells (VSMCs), to define the molecular mechanisms and pathways underlying this process; and to explore the particular molecular mechanisms that mediate the Ang II-induced hypertrophy and link them to leptin synthesis. Finally, we explored the role of the anti-atherosclerotic adipokine, adiponectin, in inhibiting the Ang II-induced vascular remodeling and hypertrophy. Methods: A VSMC cell culture and RPV (Rat Portal Vein) organ culture was performed in the absence-presence of Ang II; some studies involved the pretreatment of VSMCs and RPVs (before adding Ang II) with an inhibitor or with adiponectin. Western blot analysis was performed to detect Ang II-induced leptin, p-cofilin, p-p38, p-Akt and p-ERK1-2 expression. The effect of Ang II on ROS (Reactive Oxygen Species) formation and the G-F actin (Globular-Filamentous actin) ratio was detected by immunohistochemical analysis (via laser confocal microscopy) on VSMCs of the rat aorta. The actin depolymerization agent cytochalasin D (CD) and the RhoA-ROCK pathway inhibitor y-27632, the NOX inhibitor apocynin and the EGFR (Epidermal Growth Factor receptor) inhibitor AG-1478, were used to investigate the involvement of the intact actin cytoskeleton, the RhoA-ROCK pathway, NOX and EGFR activation respectively. Immunocytochemical analysis (via laser confocal microscopy) was done to study both, the effect of Ang II on leptin synthesis and the GATA-4 nuclear translocation in the VSMCs. The mRNA expressions of AdipoR1, AdipoR2 and adiponectin were deduced by qPCR analysis. Results: We were a