Rac1 activation induces tumour necrosis factor-α expression and cardiac dysfunction in endotoxemia

J Cell Mol Med. 2011 May;15(5):1109-21. doi: 10.1111/j.1582-4934.2010.01095.x. Epub 2010 May 26.


Induction of tumour necrosis factor-α (TNF-α) expression leads to myocardial depression during sepsis. However, the underlying molecular mechanisms are not fully understood. The aim of this study was to investigate the role of Rac1 in TNF-α expression and cardiac dysfunction during endotoxemia and to determine the involvement of phosphoinositide-3 kinase (PI3K) in lipopolysaccharide (LPS)-induced Rac1 activation. Our results showed that LPS-induced Rac1 activation and TNF-α expression in cultured neonatal mouse cardiomyocytes. The response was inhibited in Rac1 deficient cardiomyocytes or by a dominant-negative Rac1 (Rac1N17). To determine whether PI3K regulates Rac1 activation, cardiomyocytes were treated with LY294002, a PI3K selective inhibitor. Treatment with LY294002 decreased Rac1 activity as well as TNF-α expression stimulated by LPS. Furthermore, inhibition of PI3K and Rac1 activity decreased LPS-induced superoxide generation which was associated with a significant reduction in ERK1/2 phosphorylation. To investigate the role of Rac1 in myocardial depression during endotoxemia in vivo, wild-type and cardiomyocyte-specific Rac1 deficient mice were treated with LPS (2 mg/kg, i.p.). Deficiency in Rac1 significantly decreased myocardial TNF-α expression and improved cardiac function during endotoxemia. We conclude that PI3K-mediated Rac1 activation is required for induction of TNF-α expression in cardiomyocytes and cardiac dysfunction during endotoxemia. The effect of Rac1 on TNF-α expression seems to be mediated by increased NADPH oxidase activity and ERK1/2 phosphorylation.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Endotoxemia / complications
  • Endotoxemia / metabolism*
  • Enzyme Activation
  • Heart Diseases / etiology
  • Heart Diseases / genetics
  • Heart Diseases / metabolism*
  • Lipopolysaccharides / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3 / metabolism
  • Neuropeptides / genetics
  • Neuropeptides / metabolism*
  • Phosphoinositide-3 Kinase Inhibitors
  • Phosphorylation
  • Sepsis / etiology
  • Sepsis / pathology
  • Signal Transduction
  • Superoxides / analysis
  • Superoxides / metabolism
  • Tumor Necrosis Factor-alpha / biosynthesis*
  • Tumor Necrosis Factor-alpha / genetics
  • rac GTP-Binding Proteins / genetics
  • rac GTP-Binding Proteins / metabolism*
  • rac1 GTP-Binding Protein


  • Lipopolysaccharides
  • Neuropeptides
  • Phosphoinositide-3 Kinase Inhibitors
  • Rac1 protein, mouse
  • Tumor Necrosis Factor-alpha
  • Superoxides
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • rac GTP-Binding Proteins
  • rac1 GTP-Binding Protein