Key Points
- To determine whether anthracycline-induced cardiac toxicity occurs through calcium-dependent calpain activation targeting titin degradation.
- Cultured adult rat cardiomyocytes were treated with 1 or 3 µmol/L doxorubicin for up to 48 hours.
- Titin proteolysis was measured in cell lysates and visualized using domain-specific immunostaining directed against the spring-like PEVK domain and the M-line region.
- Calpain activity was quantified, and the protective effects of calpain versus caspase inhibitors were evaluated for titin preservation, myofibrillar organization, and cell survival.
- Doxorubicin triggered a rapid, approximately 3-fold increase in calpain activity within 1 hour that persisted at 48 hours, leading to selective proteolysis of titin's spring-like PEVK domain while sparing the M-line domain.
- Co-treatment with calpain inhibitors prevented titin breakdown, reduced myofibrillar disarray, and attenuated cardiomyocyte necrosis, whereas caspase inhibition failed to prevent titin degradation.
Structured PICO
PPopulationCultured adult rat cardiomyocytes
IInterventionDoxorubicin 1 or 3 micromol/liter for 1 to 48 hours, with or without calpain inhibitors or caspase inhibitor
CComparatorDoxorubicin alone (for inhibitor experiments)
OOutcomeTitin degradation and calpain activitysurrogate
Doxorubicin induces early calpain activation and targeted degradation of titin, which may predispose cardiomyocytes to diastolic dysfunction and necrosis.