Regulation of swelling-activated Cl(-) current by angiotensin II signalling and NADPH oxidase in rabbit ventricle.
OBJECTIVE
We assessed whether hypoosmotic swelling of cardiac myocytes activates volume-sensitive Cl(-) current (I Cl,swell) via the angiotensin II (AngII)-reactive oxygen species (ROS) signalling cascade. The AngII-ROS pathway previously was shown to elicit I(Cl,swell) upon mechanical stretch of beta(1D) integrin. Integrin stretch and osmotic swelling are, however, distinct stimuli. For example, blocking Src kinases stimulates swelling-induced but inhibits stretch-induced I Cl,swell.


RESULTS
I Cl,swell was measured in rabbit ventricular myocytes by whole-cell voltage clamp. Swelling-induced I Cl,swell was completely blocked by losartan and eprosartan, AngII type I receptor (AT1) antagonists. AT1 stimulation transactivates epidermal growth factor receptor (EGFR) kinase. Blockade of EGFR kinase with AG1478 abolished both I Cl,swell and AngII-induced Cl(-) current, whereas exogenous EGF evoked a Cl(-) current that was suppressed by osmotic shrinkage. Phosphatidylinositol 3-kinase (PI-3K) is downstream of EGFR kinase, and PI-3K inhibitors LY294002 and wortmannin blocked I Cl,swell. Ultimately, AngII signals via NADPH oxidase (NOX) and superoxide anion, O2*. NOX inhibitors, diphenyleneiodonium, apocynin and gp91ds-tat, eliminated I Cl,swell, whereas scramb-tat, an inactive gp91ds-tat analogue, was ineffective. O2* rapidly dismutates to H2O2. Consistent with H2O2 being a downstream effector, catalase inhibited I Cl,swell, and exogenous H2O2 overcame suppression of I Cl,swell by AT1 receptor, EGFR kinase, and PI-3K blockers. H2O2-induced current was not blocked by osmotic shrinkage, however.


CONCLUSIONS
Activation of I Cl,swell by osmotic swelling is controlled by the AngII-ROS cascade, the same pathway previously implicated in I Cl,swell activation by integrin stretch. This in part explains why I Cl,swell is persistently activated in several models of cardiac disease.
Ren
Zuojun
Z
Department of Physiology, Pauley Heart Center, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA 23298-0551, USA.
Raucci
Frank J
FJ
Browe
David M
DM
Baumgarten
Clive M
CM
D000804:Angiotensin II / Q000502:physiology*; D000818:Animals; D048429:Cell Size; D018118:Chloride Channels / Q000502:physiology*; D002867:Chromones / Q000494:pharmacology; D066246:ErbB Receptors / Q000502:physiology; D006352:Heart Ventricles / Q000378:metabolism*; D009025:Morpholines / Q000494:pharmacology; D032383:Myocytes, Cardiac / Q000378:metabolism*; D019255:NADPH Oxidases / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D011493:Protein Kinase C / Q000502:physiology; D011817:Rabbits; D017382:Reactive Oxygen Species / Q000378:metabolism; D044140:Receptor, Angiotensin, Type 1 / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D019061:src-Family Kinases / Q000502:physiology
D018118:Chloride Channels; D002867:Chromones; D009025:Morpholines; D017382:Reactive Oxygen Species; D044140:Receptor, Angiotensin, Type 1; D000804:Angiotensin II; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D019255:NADPH Oxidases; D019869:Phosphatidylinositol 3-Kinases; D066246:ErbB Receptors; D019061:src-Family Kinases; D011493:Protein Kinase C