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Angiotensin II Type 1 Receptor-Mediated Electrical Remodeling in Mouse Cardiac Myocytes.

Kim J, Gao J, Cohen IS, Mathias RT - PLoS ONE (2015)

Bottom Line: Pre-application of the microtubule destabilizing agent colchicine eliminated A2 effects on Ito and AP duration, suggesting these effects depend on intracellular trafficking.Application of the biased agonist SII ([Sar1-Ile4-Ile8]A2), which stimulates receptor internalization without G protein activation, caused Ito reduction and AP prolongation similar to A2-induced changes.Moreover, all measured properties parallel those measured in dog heart, suggesting an autocrine RAS may be a fundamental feedback system that is present across species.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology & Biophysics, State University of New York at Stony Brook, Stony Brook, New York, United States of America.

ABSTRACT
We recently characterized an autocrine renin angiotensin system (RAS) in canine heart. Activation of Angiotensin II Type 1 Receptors (AT1Rs) induced electrical remodeling, including inhibition of the transient outward potassium current Ito, prolongation of the action potential (AP), increased calcium entry and increased contractility. Electrical properties of the mouse heart are very different from those of dog heart, but if a similar system existed in mouse, it could be uniquely studied through genetic manipulations. To investigate the presence of a RAS in mouse, we measured APs and Ito in isolated myocytes. Application of angiotensin II (A2) for 2 or more hours reduced Ito magnitude, without affecting voltage dependence, and prolonged APs in a dose-dependent manner. Based on dose-inhibition curves, the fast and slow components of Ito (Ito,fast and IK,slow) appeared to be coherently regulated by [A2], with 50% inhibition at an A2 concentration of about 400 nM. This very high K0.5 is inconsistent with systemic A2 effects, but is consistent with an autocrine RAS in mouse heart. Pre-application of the microtubule destabilizing agent colchicine eliminated A2 effects on Ito and AP duration, suggesting these effects depend on intracellular trafficking. Application of the biased agonist SII ([Sar1-Ile4-Ile8]A2), which stimulates receptor internalization without G protein activation, caused Ito reduction and AP prolongation similar to A2-induced changes. These data demonstrate AT1R mediated regulation of Ito in mouse heart. Moreover, all measured properties parallel those measured in dog heart, suggesting an autocrine RAS may be a fundamental feedback system that is present across species.

No MeSH data available.


Related in: MedlinePlus

AT1R-mediated effects on AP duration do not involve the initial G-protein stimulation that follows receptor activation.(A) Representative traces of AP morphology in CON and 5 μM SII incubated cells. SII induced increases in APD, which appears to occur through a G-protein independent β-arrestin2 mediated pathway involving AT1R internalization. APDs measured from SII treated cells display significant prolongations in both APD50(B) and APD90(C). Based on the student’s t-test, APDs at both levels of repolarization are significantly increased (P < 0.05).
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pone.0138711.g006: AT1R-mediated effects on AP duration do not involve the initial G-protein stimulation that follows receptor activation.(A) Representative traces of AP morphology in CON and 5 μM SII incubated cells. SII induced increases in APD, which appears to occur through a G-protein independent β-arrestin2 mediated pathway involving AT1R internalization. APDs measured from SII treated cells display significant prolongations in both APD50(B) and APD90(C). Based on the student’s t-test, APDs at both levels of repolarization are significantly increased (P < 0.05).

Mentions: Cells were incubated with 5 μM SII ([Sar1-Ile4-Ile8]A2), which selectively activates β-arrestin2 dependent signaling and receptor internalization without G protein stimulation [13,14]. APs were recorded from CON and SII treated cells (Fig 6). APs from SII treated cells were significantly prolonged compared with controls (CON 4.26 ± 0.53 ms and SII 5.89 ± 0.51 ms for APD50; CON 17.55 ± 1.70 ms and SII 33.81 ± 5.39 ms for APD90), similar to the prolongations observed in cells treated with A2 (Fig 1). These results suggest electrical remodeling occurs through β-arrestin2 dependent AT1R internalization without the involvement of AT1R activated G proteins.


Angiotensin II Type 1 Receptor-Mediated Electrical Remodeling in Mouse Cardiac Myocytes.

Kim J, Gao J, Cohen IS, Mathias RT - PLoS ONE (2015)

AT1R-mediated effects on AP duration do not involve the initial G-protein stimulation that follows receptor activation.(A) Representative traces of AP morphology in CON and 5 μM SII incubated cells. SII induced increases in APD, which appears to occur through a G-protein independent β-arrestin2 mediated pathway involving AT1R internalization. APDs measured from SII treated cells display significant prolongations in both APD50(B) and APD90(C). Based on the student’s t-test, APDs at both levels of repolarization are significantly increased (P < 0.05).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4591968&req=5

pone.0138711.g006: AT1R-mediated effects on AP duration do not involve the initial G-protein stimulation that follows receptor activation.(A) Representative traces of AP morphology in CON and 5 μM SII incubated cells. SII induced increases in APD, which appears to occur through a G-protein independent β-arrestin2 mediated pathway involving AT1R internalization. APDs measured from SII treated cells display significant prolongations in both APD50(B) and APD90(C). Based on the student’s t-test, APDs at both levels of repolarization are significantly increased (P < 0.05).
Mentions: Cells were incubated with 5 μM SII ([Sar1-Ile4-Ile8]A2), which selectively activates β-arrestin2 dependent signaling and receptor internalization without G protein stimulation [13,14]. APs were recorded from CON and SII treated cells (Fig 6). APs from SII treated cells were significantly prolonged compared with controls (CON 4.26 ± 0.53 ms and SII 5.89 ± 0.51 ms for APD50; CON 17.55 ± 1.70 ms and SII 33.81 ± 5.39 ms for APD90), similar to the prolongations observed in cells treated with A2 (Fig 1). These results suggest electrical remodeling occurs through β-arrestin2 dependent AT1R internalization without the involvement of AT1R activated G proteins.

Bottom Line: Pre-application of the microtubule destabilizing agent colchicine eliminated A2 effects on Ito and AP duration, suggesting these effects depend on intracellular trafficking.Application of the biased agonist SII ([Sar1-Ile4-Ile8]A2), which stimulates receptor internalization without G protein activation, caused Ito reduction and AP prolongation similar to A2-induced changes.Moreover, all measured properties parallel those measured in dog heart, suggesting an autocrine RAS may be a fundamental feedback system that is present across species.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology & Biophysics, State University of New York at Stony Brook, Stony Brook, New York, United States of America.

ABSTRACT
We recently characterized an autocrine renin angiotensin system (RAS) in canine heart. Activation of Angiotensin II Type 1 Receptors (AT1Rs) induced electrical remodeling, including inhibition of the transient outward potassium current Ito, prolongation of the action potential (AP), increased calcium entry and increased contractility. Electrical properties of the mouse heart are very different from those of dog heart, but if a similar system existed in mouse, it could be uniquely studied through genetic manipulations. To investigate the presence of a RAS in mouse, we measured APs and Ito in isolated myocytes. Application of angiotensin II (A2) for 2 or more hours reduced Ito magnitude, without affecting voltage dependence, and prolonged APs in a dose-dependent manner. Based on dose-inhibition curves, the fast and slow components of Ito (Ito,fast and IK,slow) appeared to be coherently regulated by [A2], with 50% inhibition at an A2 concentration of about 400 nM. This very high K0.5 is inconsistent with systemic A2 effects, but is consistent with an autocrine RAS in mouse heart. Pre-application of the microtubule destabilizing agent colchicine eliminated A2 effects on Ito and AP duration, suggesting these effects depend on intracellular trafficking. Application of the biased agonist SII ([Sar1-Ile4-Ile8]A2), which stimulates receptor internalization without G protein activation, caused Ito reduction and AP prolongation similar to A2-induced changes. These data demonstrate AT1R mediated regulation of Ito in mouse heart. Moreover, all measured properties parallel those measured in dog heart, suggesting an autocrine RAS may be a fundamental feedback system that is present across species.

No MeSH data available.


Related in: MedlinePlus