CITED4 induces physiologic hypertrophy and promotes functional recovery after ischemic injury
Vassilios J. Bezzerides, Colin Platt, Carolin Lerchenmüller, Kaavya Paruchuri, Nul Loren Oh, Chunyang Xiao, Yunshan Cao, Nina Mann, Bruce M. Spiegelman, Anthony Rosenzweig
Vassilios J. Bezzerides, Colin Platt, Carolin Lerchenmüller, Kaavya Paruchuri, Nul Loren Oh, Chunyang Xiao, Yunshan Cao, Nina Mann, Bruce M. Spiegelman, Anthony Rosenzweig
View: Text | PDF
Research Article Cardiology

CITED4 induces physiologic hypertrophy and promotes functional recovery after ischemic injury

Abstract

The mechanisms by which exercise mediates its multiple cardiac benefits are only partly understood. Prior comprehensive analyses of the cardiac transcriptional components and microRNAs dynamically regulated by exercise suggest that the CBP/p300-interacting protein CITED4 is a downstream effector in both networks. While CITED4 has documented functional consequences in neonatal cardiomyocytes in vitro, nothing is known about its effects in the adult heart. To investigate the impact of cardiac CITED4 expression in adult animals, we generated transgenic mice with regulated, cardiomyocyte-specific CITED4 expression. Cardiac CITED4 expression in adult mice was sufficient to induce an increase in heart weight and cardiomyocyte size with normal systolic function, similar to the effects of endurance exercise training. After ischemia-reperfusion, CITED4 expression did not change initial infarct size but mediated substantial functional recovery while reducing ventricular dilation and fibrosis. Forced cardiac expression of CITED4 also induced robust activation of the mTORC1 pathway after ischemic injury. Moreover, pharmacological inhibition of mTORC1 abrogated CITED4’s effects in vitro and in vivo. Together, these data establish CITED4 as a regulator of mTOR signaling that is sufficient to induce physiologic hypertrophy at baseline and mitigate adverse ventricular remodeling after ischemic injury.

Authors

Vassilios J. Bezzerides, Colin Platt, Carolin Lerchenmüller, Kaavya Paruchuri, Nul Loren Oh, Chunyang Xiao, Yunshan Cao, Nina Mann, Bruce M. Spiegelman, Anthony Rosenzweig

×

Figure 7

Treatment with rapamycin inhibits the development of physiologic cardiac hypertrophy and cardioprotection from ischemic injury induced by CITED4.

Options: View larger image (or click on image) Download as PowerPoint
Treatment with rapamycin inhibits the development of physiologic cardiac...
(A) Measure of relative mass by echocardiography demonstrates an increase at baseline with CITED4 expression, which is inhibited by daily rapamycin (2 mg/kg) treatment. (B) Echocardiography demonstrates a nonsignificant trend toward improved function in animals receiving rapamycin versus those injected with vehicle (controls: with vehicle fractional shortening (FS) = 34.5% ± 1.6% vs. with rapamycin FS = 39.2% ± 2.1%, P = 0.1; iCITED4: with vehicle FS = 34.6% ± 3% vs. with rapamycin FS = 42.2% ± 1.8%, P = 0.08). Repeat echocardiography at 6 weeks after IRI demonstrated substantial recovery in CITED4 transgenics that was blocked by rapamycin treatment, **P < 0.01 by 1-way ANOVA. (iCITED4: with vehicle FS = 51.6% ± 2.8% vs. with rapamycin FS = 42.2% ± 1.8%, ‡P < 0.01) Comparison of control mice treated with rapamycin demonstrated recovery compared with mice receiving vehicle (controls: with vehicle % FS = 36.3% ± 1.2%, vs. with rapamycin FS = 41.5% ± 1.2%, *P = 0.01), n = 4–6 animals per group. (C) Representative images of cardiac sections stained with MTS demonstrated a reduction in the fibrosis in iCITED4 mice receiving vehicle. Scale bars: 1 mm. (D) Quantification of fibrosis 6 weeks after IRI revealed reduced fibrosis in CITED4 transgenics that was inhibited by rapamycin treatment (vehicle, controls: 9.9% ± 1.6% vs. iCITED4: 4.6% ± 0.4%, **P = 0.01; rapamycin, controls: 8.5% ± 1.6% vs. iCITED4: 7.1% ± 1.3%; n.s. designates P = 0.48). n = 4–6 animals per group. (E) Protein lysates from hearts 6 weeks after IRI demonstrate increased phosphorylation of S6 kinase in iCITED4 mice receiving vehicle, which was suppressed by administration of rapamycin, without a significant change in AKT1 activation. (F) Quantification of Western blotting reveals increased S6 kinase activation with CITED4 expression; *P < 0.05 by 1-way ANOVA. Rapamycin inhibits S6 kinase phosphorylation in control mice administered rapamycin by ratio of phosphorylated p70S6K to total p70S6K (P-p70S6K/p70S6K) (vehicle: 1 ± 0.26 vs. rapamycin: 0.44 ± 0.05, *P = 0.05) and blocks activation of S6 kinase by CITED4 (vehicle: 2.06 ± 0.22 vs. rapamycin: 0.85 ± 0.06, *P < 0.01). n.s. denotes no significant difference between CITED4 transgenics given rapamycin and controls. Student’s t test was used in paired groups unless otherwise specified.