Important role for Rac1 in regulating reactive oxygen species generation and pulmonary arterial smooth muscle cell growth

Sandip Patil, Melisa Bunderson, Jason Wilham, Stephen M. Black

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


Vascular NADPH oxidases have been shown to be a major source of reactive oxygen species (ROS). Recent studies have also implicated ROS in the proliferation of vascular smooth muscle cells. However, the components required for activation of the NADPH oxidase complex have not been clearly elucidated. Here we demonstrate that ROS generation in ovine pulmonary arterial smooth muscle cells (PASMCs) requires the activation of Rac1, implicating this protein as an important subunit of the NADPH oxidase complex. Our results, using a geranylgeranyl transferase inhibitor (GGTI-287), demonstrated a dose-dependent inhibition of Rac1 activity and ROS production. This was associated with an inhibition of PASMC proliferation with an arrest at G2/M. The inhibition of Rac1 by GGTI-287 led us to more specifically target Rac1 to investigate its role in the generation of ROS and cellular proliferation. To accomplish this, we utilized a dominant negative Rac1 (N17Rac1) and a constitutively active Rac1 (V12Rac1). These two forms of Rac1 were transiently expressed in PASMCs using adenovirus-mediated gene transfer. N17Rac1 expression resulted in decreased cellular Rac1 activity, whereas V12Rac1 infection showed increased activity. Compared with controls, the V12Rac1-expressing cells had higher levels of ROS production and increased proliferation, whereas the N17Rac1-expressing cells had decreased ROS generation and proliferation and cell cycle arrest at G2/M. However, the inhibition of cell growth produced by N17Rac1 overexpression could be overcome if cells were co-incubated with the Cu5,Zn superoxide dismutase inhibitor DETC. These results indicate the importance of Rac1 in ROS generation and proliferation of vascular smooth muscle cells.

Original languageEnglish (US)
Pages (from-to)L1314-L1322
JournalAmerican Journal of Physiology - Lung Cellular and Molecular Physiology
Issue number6 31-6
StatePublished - Dec 2004
Externally publishedYes


  • Vascular reduced nicotinamide adenine dinucleotide phosphate oxidase

ASJC Scopus subject areas

  • Physiology
  • Pulmonary and Respiratory Medicine
  • Physiology (medical)
  • Cell Biology


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