cGMP-dependent protein kinase (PKG) plays a crucial role in vasodilatation induced by cGMP-elevating agents. Akt has been demonstrated to be involved in modulating vasoreactivity. The present study was to determine the interaction between PKG and Akt and their influences on nitric oxide (NO)–induced vasodilatation. Isolated fourth-generation porcine pulmonary arteries were dissected from the lung and cut into rings in ice-cold modified Krebs–Ringer bicarbonate buffer. The relaxant responses of vessels were determined by organ chamber technique, cGMP was assayed by using enzyme-linked immunosorbent assay kit, the protein levels of phosphorylated Akt were examined by Western blotting, and the activity of phosphodiesterase type 5 (PDE5) was assayed by measuring the rate of cGMP degradation. Incubation with DETA NONOate (a stable NO donor) and 8-Br-cGMP (a cell membrane permeable analog of cGMP) attenuated Akt phosphorylation at Ser-473, which was prevented by Rp-8-Br-PET-cGMPS (a specific inhibitor of PKG) and calyculin A (an inhibitor of protein phosphatase 1 and 2A) but not by okadaic acid (a selective inhibitor of protein phosphatase 2A). Inhibition of Akt enhanced the relaxation and cGMP elevation of porcine pulmonary arteries induced by DETA NONOate or sodium nitroprusside, which was prevented by zaprinast, a specific inhibitor of PDE5. Incubation with LY294002 or Akt inhibitor reduced PDE5 activity in porcine pulmonary arteries. The present study indicates that PKG may attenuate Akt phosphorylation through protein phosphatase 1, which leads to an augmented cGMP elevation by inhibition of PDE5. The increased cGMP in turn activates PKG. Such a positive feedback may play an important role in NO-induced pulmonary vasodilatation.
*Department of Physiology and Pathophysiology, Peking University Health Science Center, Beijing, China;
†Department of Physiology, Heze Medical College, Heze, China; and
‡Key Laboratory of Molecular Cardiovascular Science, Ministry of Education, Peking University, Beijing, China.
Reprints: Dou Dou, PhD, Department of Physiology and Pathophysiology, Peking University Health Science Center, 38 Xueyuan Road, Beijing 100191, China (e-mail: firstname.lastname@example.org).
Supported by the National Natural Science Foundation of China (Grant No. 81001433, 81270341 and 81373404), Doctoral Fund of Ministry of Education for New Teachers (Grant No. 20100001120037), and Beijing Higher Education Young Elite Teacher Project (Grant No. YETP0054).
The authors report no conflicts of interest.
Received January 25, 2014
Accepted June 11, 2014