Phosphorylation of smooth muscle 22α facilitates angiotensin II-induced ROS production via activation of the PKCδ-P47phox axis through release of PKCδ and actin dynamics and is associated with hypertrophy and hyperplasia of vascular smooth muscle cells in vitro and in vivo.

Abstract

RATIONALE:

We have demonstrated that smooth muscle (SM) 22α inhibits cell proliferation via blocking Ras-ERK1/2 signaling in vascular smooth muscle cells (VSMCs) and in injured arteries. The recent study indicates that SM22α disruption can independently promote arterial inflammation through activation of reactive oxygen species (ROS)-mediated NF-κB pathways. However, the mechanisms by which SM22α controls ROS production have not been characterized.

OBJECTIVE:

To investigate how SM22α disruption promotes ROS production and to characterize the underlying mechanisms.

METHODS AND RESULTS:

ROS level was measured by dihydroethidium staining for superoxide and TBA assay for malondialdehyde, respectively. We showed that downregulation and phosphorylation of SM22α were associated with angiotensin (Ang) II-induced increase in ROS production in VSMCs of rats and human. Ang II induced the phosphorylation of SM22α at Serine 181 in an Ang II type 1 receptor-PKCδ pathway-dependent manner. Phosphorylated SM22α activated the protein kinase C (PKC)δ-p47phox axis via 2 distinct pathways: (1) disassociation of PKCδ from SM22α, and in turn binding to p47phox, in the early stage of Ang II stimulation; and (2) acceleration of SM22α degradation through ubiquitin-proteasome, enhancing PKCδ membrane translocation via induction of actin cytoskeletal dynamics in later oxidative stress. Inhibition of SM22α phosphorylation abolished the Ang II-activated PKCδ-p47phox axis and inhibited the hypertrophy and hyperplasia of VSMCs in vitro and in vivo, accompanied with reduction of ROS generation.

CONCLUSIONS:

These findings indicate that the disruption of SM22α plays pivotal roles in vascular oxidative stress. PKCδ-mediated SM22α phosphorylation is a novel link between actin cytoskeletal remodeling and oxidative stress and may be a potential target for the development of new therapeutics for cardiovascular diseases.

• Authors: Pin Lv, Sui-Bing Miao, Ya-Nan Shu, Li-Hua Dong, George Liu, Xiao-Li Xie, Min Gao, Yu-Can Wang, Ya-Juan Yin, Xiao-Juan Wang, Mei Han
• Journal: Circulation research (Circ Res) Vol. 111 Issue 6 Pg. 697-707 (Aug 31 2012) ISSN: 1524-4571 [Electronic] United States
• PMID: 22798525 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Actins
• Microfilament Proteins
• Muscle Proteins
• Reactive Oxygen Species
• transgelin
• Angiotensin II
• Green Fluorescent Proteins
• NADPH Oxidases
• neutrophil cytosolic factor 1
• Protein Kinase C-delta

Topics

• Actins (metabolism)
• Angiotensin II (pharmacology)
• Animals
• Blotting, Western
• Cells, Cultured
• Down-Regulation
• Enzyme Activation (drug effects)
• Green Fluorescent Proteins (genetics, metabolism)
• Humans
• Hyperplasia
• Hypertrophy
• Male
• Microfilament Proteins (genetics, metabolism)
• Microscopy, Confocal
• Muscle Proteins (genetics, metabolism)
• Muscle, Smooth, Vascular (metabolism, pathology)
• Myocytes, Smooth Muscle (drug effects, metabolism, pathology)
• NADPH Oxidases (metabolism)
• Phosphorylation
• Protein Binding
• Protein Kinase C-delta (metabolism)
• RNA Interference
• Rats
• Rats, Sprague-Dawley
• Reactive Oxygen Species (metabolism)