The function of substance P (SP) in myocardial ischemia is well understood, but its effects on congestive heart failure are unclear. The present study aimed to use in vitro and in vivo approaches to investigate the effects of SP on doxorubicin‑induced cardiomyocyte injury. Pathological changes, apoptosis, cardiomyocyte ultrastructure and molecular mechanisms were evaluated in vitro and in vivo. The effects of SP on cell viability of H9c2 myocardial cells were evaluated using the Cell Counting Kit‑8 and flow cytometry. B‑cell lymphoma 2 (Bcl‑2), Bcl‑2‑associated X protein (Bax), Beclin‑1 and microtubule‑associated protein 1A/1B‑light chain 3 (LC3) were detected by western blotting. Heart failure in rats was established by intraperitoneal injection of doxorubicin. The in vitro data demonstrated that SP at concentrations of 1 µg/ml inhibited doxorubicin‑induced apoptosis of H9c2 cells. Administration of doxorubicin reduced Bcl‑2, Beclin‑1 and LC3 expression levels in H9c2 cells, while having no effect on Bax levels. Administration of SP to these doxorubicin‑treated cells did not affect Bcl‑2 or Bax expression, but further reduced Beclin‑1 while inhibiting the reduction in LC3 expression. In vivo, food intake was significantly increased in rats in the SP group compared with the model group. Cardiomyocytes in the heart‑failure group underwent dysfunctional autophagy as ascertained by transmission electron microscopy. Compared with the heart‑failure group, these pathological changes, including loss of striations and vacuolation, were inhibited by SP treatment, which promoted Bax expression, reduced Beclin‑1 expression and inhibited the reduction in LC3 expression. Taken together, SP reduced cardiomyocyte apoptosis in doxorubicin‑induced cardiomyocyte injury, likely by promoting autophagy, which suggested that SP is a potential therapeutic target for doxorubicin‑induced heart failure.
Keywords: apoptosis; autophagy; heart failure; substance P.