Nitric oxide mediates stretch-induced Ca2+ release via activation of phosphatidylinositol 3-kinase-Akt pathway in smooth muscle.
BACKGROUND
Hollow smooth muscle organs such as the bladder undergo significant changes in wall tension associated with filling and distension, with attendant changes in muscle tone. Our previous study indicated that stretch induces Ca(2+) release occurs in the form of Ca(2+) sparks and Ca(2+) waves in urinary bladder myocytes. While, the mechanism underlying stretch-induced Ca2+ release in smooth muscle is unknown.


RESULTS
We examined the transduction mechanism linking cell stretch to Ca(2+) release. The probability and frequency of Ca(2+) sparks induced by stretch were closely related to the extent of cell extension and the time that the stretch was maintained. Experiments in tissues and single myocytes indicated that mechanical stretch significantly increases the production of nitric oxide (NO) and the amplitude and duration of muscle contraction. Stretch-induced Ca(2+) sparks and contractility increases were abrogated by the NO inhibitor L-NAME and were also absent in eNOS knockout mice. Furthermore, exposure of eNOS null mice to exogenously generated NO induced Ca(2+) sparks. The soluble guanylyl cyclase inhibitor ODQ did not inhibit SICR, but this process was effectively blocked by the PI3 kinase inhibitors LY494002 and wortmannin; the phosphorylation of Akt and eNOS were up-regulated by 204+/-28.6% and 258+/-36.8% by stretch, respectively. Moreover, stretch significantly increased the eNOS protein expression level.


CONCLUSIONS
Taking together, these results suggest that stretch-induced Ca2+ release is NO dependent, resulting from the activation of PI3K/Akt pathway in smooth muscle.
Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
Bin
B
Wei
Zheng
Z
Chen
Xu
X
Zhang
Morris
M
Feldman
Xian-zhi
XZ
Dong
Robert
R
Doran
Bao-Lu
BL
Zhao
Wen-xuan
WX
Yin
Michael I
MI
Kotlikoff
Guangju
G
Ji
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D009130:Muscle, Smooth / Q000201:enzymology / Q000378:metabolism*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000502:physiology*; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism; D010069:Oxadiazoles / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011810:Quinoxalines / Q000494:pharmacology; D019459:Urothelium / Q000201:enzymology / Q000378:metabolism*; D000077191:Wortmannin
D000730:Androstadienes; D002118:Calcium; D004791:Enzyme Inhibitors; D019331:NG-Nitroarginine Methyl Ester; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; D010069:Oxadiazoles; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D011810:Quinoxalines; D000077191:Wortmannin; C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one