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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 inhibition of repolarizing K+-currents does not involve the initial G-protein stimulation that follows receptor activation.Internalization of AT1Rs by incubation in 5 μM SII caused reductions in Ito,fast(A) and IK,slow(B). Based on ANOVA statistical analyses, the overall responses differ significantly (Ito,fast P = 0.004, and IK,slow P = 0.025). Post hoc statistical analyses of SII induced changes at each voltage were significant (P < 0.05) with exceptions of the results for IK,slow obtained at 10 mV and 20 mV, which did not reach statistical significance.
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pone.0138711.g007: AT1R-mediated inhibition of repolarizing K+-currents does not involve the initial G-protein stimulation that follows receptor activation.Internalization of AT1Rs by incubation in 5 μM SII caused reductions in Ito,fast(A) and IK,slow(B). Based on ANOVA statistical analyses, the overall responses differ significantly (Ito,fast P = 0.004, and IK,slow P = 0.025). Post hoc statistical analyses of SII induced changes at each voltage were significant (P < 0.05) with exceptions of the results for IK,slow obtained at 10 mV and 20 mV, which did not reach statistical significance.

Mentions: Additionally, K+ currents were recorded from CON and SII treated cells to examine the effect on peak Ito,fast and IK,slow (Fig 7). Compared with CON cells, peak Ito,fast (Fig 7A) and IK,slow (Fig 7B) densities were significantly attenuated in SII treated cells (Ito,fast 41%, IK,slow 44% inhibition at Vtest = +50 mV). These inhibitions are essentially the same as A2-mediated inhibitions reported for the data in Fig 2 or Table 1. Thus, consistent with the AP results (Fig 6), the effect of AT1R activation on Ito,fast and IK,slow appear to be through β-arrestin2 dependent AT1R internalization without the involvement of AT1R G-protein signaling.


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 inhibition of repolarizing K+-currents does not involve the initial G-protein stimulation that follows receptor activation.Internalization of AT1Rs by incubation in 5 μM SII caused reductions in Ito,fast(A) and IK,slow(B). Based on ANOVA statistical analyses, the overall responses differ significantly (Ito,fast P = 0.004, and IK,slow P = 0.025). Post hoc statistical analyses of SII induced changes at each voltage were significant (P < 0.05) with exceptions of the results for IK,slow obtained at 10 mV and 20 mV, which did not reach statistical significance.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0138711.g007: AT1R-mediated inhibition of repolarizing K+-currents does not involve the initial G-protein stimulation that follows receptor activation.Internalization of AT1Rs by incubation in 5 μM SII caused reductions in Ito,fast(A) and IK,slow(B). Based on ANOVA statistical analyses, the overall responses differ significantly (Ito,fast P = 0.004, and IK,slow P = 0.025). Post hoc statistical analyses of SII induced changes at each voltage were significant (P < 0.05) with exceptions of the results for IK,slow obtained at 10 mV and 20 mV, which did not reach statistical significance.
Mentions: Additionally, K+ currents were recorded from CON and SII treated cells to examine the effect on peak Ito,fast and IK,slow (Fig 7). Compared with CON cells, peak Ito,fast (Fig 7A) and IK,slow (Fig 7B) densities were significantly attenuated in SII treated cells (Ito,fast 41%, IK,slow 44% inhibition at Vtest = +50 mV). These inhibitions are essentially the same as A2-mediated inhibitions reported for the data in Fig 2 or Table 1. Thus, consistent with the AP results (Fig 6), the effect of AT1R activation on Ito,fast and IK,slow appear to be through β-arrestin2 dependent AT1R internalization without the involvement of AT1R G-protein signaling.

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