Abstract 13531: Cardiac-Specific Deletion of Phosphotase and Tensin Homolog Deleted on Chromosome 10 (PTEN) Triggers Cardiac Dysfunction and Hypertrophy through Impaired PTEN-Induced Activation of PTEN Induced Putative Kinase 1 (Pink1) and AMP-Activated Protein Kinase (AMPK)
PTEN is a negative regulator of insulin signaling and participates in many cardiac diseases including ischemia and diabetes. Targeting this enzyme pharmacologically becomes an attractive option although PTEN inactivation results in cardiac dysfunction, prompting the need for further investigation of the role of PTEN in the heart. Here we hypothesized that loss of PTEN in cardiomyocytes results in decreased Pink1 levels en route to cardiac dysfunction and hypertrophy. To this end, cardiomyocyte-specific PTEN knockout (PTENKO) mice were generated by crossing PTEN floxed mice with mice expressing CRE recombinase driven by α-myosin heavy chain promoter. Protein expression was assessed by immunobloting. Cardiac function was evaluted using echocardiography and isolated cardiomyocyte function. FITC conjugated lectin staining was used to measure cross sectional area and siRNA was employed to knockdown Pink1 in H9C2 cells. Western blot analysis revealed decreased Pink1 levels in PTENKO compared with wild type (WT) mice (0.028±0.004 vs. 0.084±0.012 respectively, p<0.05, n=3). Surprisingly, PTENKO mice displayed a decreased AMPK phosphorylation compared with WT group, (0.017±0.004 vs. 0.051±0.006 respectively, p<0.05, n=3) suggesting a tie among PTEN, Pink1 and AMPK. Pink1 knockdown in H9C2 cells decreased basal AMPK phosphorylation compared to control (0.27±0.03 vs. 0.38±0.02 for control, p<0.05, n=4-5) indicating a role of AMPK downstream of Pink1. To evaluate its role in vivo, the AMPK activator metformin (200 mg/kg/d) was given to PTENKO mice for 4 weeks prior to assessment of cardiac function. AMPK activation was sufficient to restore fractional shortening back WT levels (46.0±3.0 in WT vs. 35.5±2.1 in PTENKO vs. 42.8±1.6 in PTENKO+metformin, p<0.05, n≥3) and significantly decreased cardiomyocyte cross sectional area (310.0±6.6 for WT vs 401.1±8.3 for PTENKO vs 359.5±7.8 for PTENKO+metformin, p<0.05, n≥4). Cardiomyocyte function revealed that metformin was sufficient to restore decreased peak shortening, maximal velocity of shortening and relengthening, and increased TR90 in PTENKO back to WT levels (n=139-199 cells per group, p<0.05). These data suggest a novel PTEN-Pink1-AMPK pathway necessary for normal cardiac contractility.
- © 2012 by American Heart Association, Inc.