TY - JOUR
T1 - β2-adrenergic receptor-coupled phosphoinositide 3-kinase constrains cAMP-dependent increases in cardiac inotropy through phosphodiesterase 4 activation
AU - Gregg, Christopher J.
AU - Steppan, Jochen
AU - Gonzalez, Daniel R.
AU - Champion, Hunter C.
AU - Phan, Alexander C.
AU - Nyhan, Daniel
AU - Shoukas, Artin A.
AU - Hare, Joshua M.
AU - Barouch, Lili A.
AU - Berkowitz, Dan E.
N1 - Funding Information:
This work was supported in part by a grant from the National Space Biomedical Research Institute ( CA00405 ) through National Aeronautics & Space Administration (AS) and a National Institutes of Health grant ( R01 AG 021,523 ) (DEB).
PY - 2010/10
Y1 - 2010/10
N2 - BACKGROUND: Emerging evidence suggests that phosphoinositide 3-kinase (PI3K) may modulate cardiac inotropy; however, the underlying mechanism remains elusive. We hypothesized that β2-adrenergic receptor (AR)-coupled PI3K constrains increases in cardiac inotropy through cyclic adenosine monophosphate (cAMP)-dependent phosphodiesterase (PDE) activation. METHODS: We tested the effects of PI3K and PDE4 inhibition on myocardial contractility by using isolated murine cardiac myocytes to study physiologic functions (sarcomere shortening [SS] and intracellular Ca+ transients), as well as cAMP and PDE activity. RESULTS: PI3K inhibition with the reversible inhibitor LY294002 (LY) resulted in a significant increase in SS and Ca2+ handling, indicating enhanced contractility. This response depended on Giα protein activity, because incubation with pertussis toxin (an irreversible Giα inhibitor) abolished the LY-induced hypercontractility. In addition, PI3K inhibition had no greater effect on SS than both a PDE3,4 inhibitor (milrinone) and LY combined. Furthermore, LY decreased PDE4 activity in a concentration-dependent manner (58.0% of PDE4 activity at LY concentrations of 10 μM). Notably, PI3K γ coimmunoprecipitated with PDE4D. The β2-AR inverse agonist, ICI 118,551 (ICI), abolished induced increases in contractility. CONCLUSIONS: PI3K modulates myocardial contractility by a cAMP-dependent mechanism through the regulation of the catalytic activity of PDE4. Furthermore, basal agonist-independent activity of the β2-AR and its resultant cAMP production and enhancement of the catalytic activity of PDE4 through PI3K represents an example of integrative cellular signaling, which controls cAMP dynamics and thereby contractility in the cardiac myocyte. These results help to explain the mechanism by which milrinone is able to increase myocardial contractility in the absence of direct β-adrenergic stimulation and why it can further augment contractility in the presence of maximal β-adrenergic stimulation.
AB - BACKGROUND: Emerging evidence suggests that phosphoinositide 3-kinase (PI3K) may modulate cardiac inotropy; however, the underlying mechanism remains elusive. We hypothesized that β2-adrenergic receptor (AR)-coupled PI3K constrains increases in cardiac inotropy through cyclic adenosine monophosphate (cAMP)-dependent phosphodiesterase (PDE) activation. METHODS: We tested the effects of PI3K and PDE4 inhibition on myocardial contractility by using isolated murine cardiac myocytes to study physiologic functions (sarcomere shortening [SS] and intracellular Ca+ transients), as well as cAMP and PDE activity. RESULTS: PI3K inhibition with the reversible inhibitor LY294002 (LY) resulted in a significant increase in SS and Ca2+ handling, indicating enhanced contractility. This response depended on Giα protein activity, because incubation with pertussis toxin (an irreversible Giα inhibitor) abolished the LY-induced hypercontractility. In addition, PI3K inhibition had no greater effect on SS than both a PDE3,4 inhibitor (milrinone) and LY combined. Furthermore, LY decreased PDE4 activity in a concentration-dependent manner (58.0% of PDE4 activity at LY concentrations of 10 μM). Notably, PI3K γ coimmunoprecipitated with PDE4D. The β2-AR inverse agonist, ICI 118,551 (ICI), abolished induced increases in contractility. CONCLUSIONS: PI3K modulates myocardial contractility by a cAMP-dependent mechanism through the regulation of the catalytic activity of PDE4. Furthermore, basal agonist-independent activity of the β2-AR and its resultant cAMP production and enhancement of the catalytic activity of PDE4 through PI3K represents an example of integrative cellular signaling, which controls cAMP dynamics and thereby contractility in the cardiac myocyte. These results help to explain the mechanism by which milrinone is able to increase myocardial contractility in the absence of direct β-adrenergic stimulation and why it can further augment contractility in the presence of maximal β-adrenergic stimulation.
UR - http://www.scopus.com/inward/record.url?scp=77957721465&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=77957721465&partnerID=8YFLogxK
U2 - 10.1213/ANE.0b013e3181ee8312
DO - 10.1213/ANE.0b013e3181ee8312
M3 - Article
C2 - 20705779
AN - SCOPUS:77957721465
SN - 0003-2999
VL - 111
SP - 870
EP - 877
JO - Anesthesia and analgesia
JF - Anesthesia and analgesia
IS - 4
ER -