Autophagy is an important mechanism for the degradation of cytosolic proteins and organelles. We investigated how autophagy is regulated in the heart in response to pressure overload (PO). Mice were subjected to transverse aortic constriction (TAC) at multiple time points between 1 hours and 30 days. Left ventricular (LV) weight/tibial length (TL) was significantly elevated at Day 5 (6.21 ± 0.10 vs 4.59 ± 0.10, p<0.05) and thereafter. Ejection fraction (EF) was maintained at Day 7 (82.1±3.4 vs 78.4±3.2%), but gradually decreased thereafter (at Day 30; 51.0±4.5, p<0.05). The level of LC3II was rapidly increased and peaked at 3 hour (2.4 fold , p<0.05), returned to normal by 24 hours, and then significantly decreased at Day 5 (-40.0%, p<0.05) and thereafter. Autophagic flux was evaluated with tandem fluorescent LC3. At 6 hours, both GFP/RFP double positive (yellow) dots and RFP dots were significantly increased in the TAC group compared to the sham group with or without chloroquine (CQ) (yellow 12±2 vs 4±0 CQ(-), 23±3 vs 9±1 CQ(+); RFP 13±2 vs 5±1 CQ(-), 19±1 vs 13±1 CQ(+)). On the other hand, both yellow and RFP dots were significantly decreased at Day7 and thereafter in the TAC group compared to the sham group with or without CQ. These data suggest that autophagic flux is activated transiently after TAC, but is inactivated after Day 5. To examine the functional significance of autophagy during PO,
beclin1
heterozygous KO (
beclin1
-hetKO) mice,
atg7
cardiac specific KO (Atg7-CKO) mice, and cardiac-specific U6-shRNA
beclin1
(U6shRNA
beclin1
) mice were subjected to TAC. At Day 7 or 14, decreases in EF (60.7 ± 4.8%, 53.8 ± 2.1% and 46.7 ± 5.9%, p<0.05) and increases in lung weight/TL (8.43 ± 0.87, 11.04 ± 4.16 and 18.76 ± 3.77, p<0.05) were exacerbated in
beclin1
-hetKO,
atg7
-CKO and U6shRNA
beclin1
mice compared to in control mice. These results suggest that PO inhibits autophagy after Day5, which coincides with the development of cardiac dysfunction. Since heart failure is exacerbated by further suppression of autophagy, autophagy during PO protects the heart from cardiac dysfunction.