Amp-Activated Protein Kinase Reduces Vascular Smooth Muscle Growth By Inhibiting Tgf-Beta/Smad Signaling And Mmp Activity

Aberrant vascular smooth muscle cell (VSMC) growth and extracellular matrix synthesis provides mechanistic underpinning for many vascular disorders. One of the major contributors to these phenomena is transforming growth factor‐beta (TGF‐β) and its canonical Smad signaling cascade. Preliminary data suggest that activation of the metabolic sensor AMP‐activated protein kinase (AMPK) has ability to inhibit VSMC growth and neointima formation in the rat carotid artery. In the current study we explored the hypothesis that AMPK inhibits VSMC growth by inhibiting TGF‐β/Smad signaling and matrix turnover by the matrix metalloproteinases (MMPs)‐9. Treatment of VSMCs with the AMPK activator AICAR (1 mM) significantly reduced (~15%; p<0.05) TGF‐β expression in cell lysates after both 24 and 48 hours. AICAR significantly decreased (~15%; p<0.05) stimulatory Smad3 expression and significantly increased inhibitory Smad7 expression (~20%) over a 24 hr period. Furthermore, AICAR significantly decreased (~20%) MMP‐9 activity in 24 hour conditioned media as assessed by gel zymography. AICAR also significantly (p<0.05) inhibited cell proliferation (~40%) after 48 hours. These data support the theory that AMPK inhibits VSM growth by inhibiting the TGF‐β/Smad/MMP signaling cascade and provide solid support for the use of AMPK to halt the VSMC growth and matrix deposition inherent in vascular hypertrophy and stenosis.