Rho-GDP dissociation inhibitor alpha downregulated by low shear stress promotes vascular smooth muscle cell migration and apoptosis: a proteomic analysis.
OBJECTIVE
Low shear stress (LSS) plays a significant role in vascular remodelling during atherogenesis, which involves migration, proliferation, and apoptosis of vascular smooth muscle cells (VSMCs). The aim of the present study is to elucidate the molecular mechanisms by which LSS induces vascular remodelling.


RESULTS
Using proteomic techniques, two-dimensional electrophoresis, and mass spectrometry, the protein profiles of Sprague-Dawley rat aorta cultured under two levels of shear stress, 5 and 15 dyn/cm(2), were determined. The results showed a significantly lower expression of protein-Rho-GDP dissociation inhibitor alpha (Rho-GDIalpha) in the LSS vessels. Rho-GDIalpha signalling mechanisms and effects on VSMC migration and apoptosis were then studied to understand the role of Rho-GDIalpha in the LSS-induced vascular remodelling. A decrease in Rho-GDIalpha expression by using target small interfering RNA (siRNA) transfection caused increases in the phosphorylation of Rac1 and Akt and enhancements of VSMC migration and apoptosis. Treatment with the PI3K/Akt-specific inhibitor wortmannin significantly decreased Akt phosphorylation, but had no effect on Rho-GDIalpha expression and Rac1 phosphorylation. Wortmannin was able to reverse the Rho-GDIalpha siRNA-induced enhancement of VSMC migration, but not VSMC apoptosis.


CONCLUSIONS
The results indicate that the LSS-induced VSMC migration and apoptosis are mediated by a downregulation of Rho-GDIalpha. The effect of Rho-GDIalpha on VSMC migration is mediated by the PI3K/Akt pathway, but its effect on VSMC apoptosis is not.
Qi
Ying-Xin
YX
Institute of Mechanobiology and Medical Engineering, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, PO Box 888, 800 Dongchuan Road, Minhang, Shanghai 200240, P.R. China.
Qu
Ming-Juan
MJ
Long
Ding-Kun
DK
Liu
Bo
B
Yao
Qing-Ping
QP
Chien
Shu
S
Jiang
Zong-Lai
ZL
D000818:Animals; D001013:Aorta, Thoracic / Q000166:cytology / Q000378:metabolism; D017209:Apoptosis; D002465:Cell Movement; D015536:Down-Regulation; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000502:physiology*; D040901:Proteomics; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D013314:Stress, Mechanical; D020741:rho GTP-Binding Proteins / Q000378:metabolism; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors
D020730:Guanine Nucleotide Dissociation Inhibitors; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D020741:rho GTP-Binding Proteins