AMP-activated protein kinase inhibits transforming growth factor-β-mediated vascular smooth muscle cell growth: implications for a Smad-3-dependent mechanism.
Dysfunctional vascular growth is a major contributor to cardiovascular disease, the leading cause of morbidity and mortality worldwide. Growth factor-induced activation of vascular smooth muscle cells (VSMCs) results in a phenotypic switch from a quiescent, contractile state to a proliferative state foundational to vessel pathology. Transforming growth factor-β (TGF-β) is a multifunctional signaling protein capable of growth stimulation via Smad signaling. Although Smad signaling is well characterized in many tissues, its role in VSM growth disorders remains controversial. Recent data from our lab and others implicate the metabolic regulator AMP-activated protein kinase (AMPK) in VSM growth inhibition. We hypothesized that AMPK inhibits VSMC proliferation by reducing TGF-β-mediated growth in a Smad-dependent fashion. Treatment of rat VSMCs with the AMPK agonist AICAR significantly decreased TGF-β-mediated activation of synthetic Smad2 and Smad3 and increased inhibitory Smad7. Flow cytometry and automated cell counting revealed that AICAR reversed TGF-β-mediated cell cycle progression at 24 h and elevated cell numbers at 48 h. TGF-β/Smad signaling increased the G0/G1 inducers cyclin D1/cyclin-dependent kinase (CDK) 4 and cyclin E/CDK2; however, AICAR reversed these events while increasing cytostatic p21. The specific role of Smad3 in AMPK-mediated reversal of TGF-β-induced growth was then explored using adenovirus-mediated Smad3 overexpression (Ad-Smad3). Ad-Smad3 cells increased cell cycle progression and cell numbers compared with Ad-GFP control cells, and these were restored to basal levels with concomitant AICAR treatment. These findings support a novel AMPK target in TGF-β/Smad3 for VSMC growth control and support continued investigation of AMPK as a possible therapeutic target for reducing vascular growth disorders.
Brody School of Medicine, East Carolina University, Greenville, North Carolina; and Carson-Newman University, Jefferson City, Tennessee.
Joshua D
JD
Stone
Brody School of Medicine, East Carolina University, Greenville, North Carolina; and.
Andrew W
AW
Holt
Brody School of Medicine, East Carolina University, Greenville, North Carolina; and.
Jackson R
JR
Vuncannon
Brody School of Medicine, East Carolina University, Greenville, North Carolina; and.
Jeffrey J
http://orcid.org/0000-0003-3503-0528
JJ
Brault
Brody School of Medicine, East Carolina University, Greenville, North Carolina; and tulisd@ecu.edu.
David A
DA
Tulis
D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D002453:Cell Cycle / Q000187:drug effects; D018797:Cell Cycle Proteins / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D020536:Enzyme Activators / Q000494:pharmacology; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D010766:Phosphorylation; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects; D051900:Smad3 Protein / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D014162:Transfection; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*
D018797:Cell Cycle Proteins; D020536:Enzyme Activators; D051900:Smad3 Protein; C497787:Smad3 protein, rat; D053773:Transforming Growth Factor beta1; D055372:AMP-Activated Protein Kinases
adenosine monophosphate-activated protein kinase; proliferation