Molecular Mechanisms of Angiotensin II‐Induced Leptin Synthesis in Vascular Smooth Muscle
Authors: Azrak Zeina , Kfouri Cassandra , Ghantous Crystal , Zeidan Asad 
Published: November 2023

Background and aims

Angiotensin II (Ang II) and the obesity‐associated adipokine leptin playing an important role in the pathogenesis of vascular hypertrophy. 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 not been investigated. In this study, we explored whether Ang II induced leptin synthesis in vascular smooth muscle cells (VSMCs) and attempted to identify the molecular and cellular mechanisms in the hypertrophic response.

Methods

A VSMC culture and blood vessels (rat portal vein; RPV) organ culture were performed in the absence/presence of Ang II (1 μM), some studies involved the pretreatment of VSMCs and RPVs with different inhibitors. Western blot analysis was performed to detect Ang II‐induced leptin expression and p‐cofilin, p‐p38, p‐Akt phosphorylation. The effect of Ang II on Reactive Oxygen Species (ROS) formation and the G/F actin (Globular/Filamentous actin) ratio was detected by immunohistochemical analysis on VSMCs. The actin depolymerization agent cytochalasin D (CD) and the ROCK inhibitor Y‐27632 (10 μM), the NADPH oxidase (NOX) inhibitor apocynin (1 mM) and the epidermal growth factor receptor (EGFR) 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 was done to study the effect of Ang II on leptin synthesis and the GATA‐4 nuclear translocation (activation index) in the VSMCs.

Results

Ang II significantly increased leptin synthesis in both RPV and VSMCs. Treatment with AG‐1478 or Y‐27632 prevented Ang II‐induced leptin synthesis indicating the involvement of EGFR and ROCK activation in this process. Inhibition of Ang II –induced leptin synthesis was associated with inhibition of VSMC hypertrophy as evaluated by leucine incorporation and wet weight changes. The role of ROS in Ang II‐induced leptin protein synthesis was studied with pretreatment of the NADPH oxidase inhibitor apocynin, which potently inhibited Ang II‐induced leptin synthesis. In addition, Ang II significantly increased actin cytoskeleton polymerization, as reflected by a decrease in the G‐/F‐actin ratio, effects that were significantly inhibited by apocynin. The effect of Ang II on GATA‐4 (a transcription factor) activation in VSMCs was studied. Pretreating VSMC with Ang II for 1 h significantly induced GATA‐4 nuclear translocation, which was potently inhibited by apocynin and Y‐27632.

Conclusion

The results advanced our understanding of the molecular mechanisms underlying the Ang II–induced vascular hypertrophy either directly or via the induction of leptin synthesis. Ang II‐induced leptin synthesis is mediated by ROS production, actin cytoskeleton dynamics, RhoA pathway and GATA‐4 activation.

Support or Funding Information

This work was supported by Medical Practice Plan (MPP), Faculty of Medicine at AUB, and the National Council for Scientific Research (CNRS) in Lebanon to Asad Zeidan.