Effect of Rapamycin on Staurosporine-Induced Cardiac Myofibroblast Death

Many cardiac diseases are associated with an excessive accumulation of myofibroblasts, characterized by increased production of extracellular matrix proteins and resistance to apoptosis, which leads to progression of fibrosis and cardiac dysfunction. Targeting the mechanisms of myofibroblast elimination is a promising strategy for treating fibrosis that requires further investigation.
The aim of this work was to determine the ability of the autophagy activator rapamycin to affect the staurosporin-induced death of cardiac myofibroblasts.
Materials and methods. In vivo modeling of cardiac fibrosis was performed using a mouse model of aortic arch ligation. In vitro studies used myofibroblasts obtained by differentiation of cardiac fibroblasts in presence of transforming growth factor beta 1 (TGFb1). To study the mechanism of myofibroblasts elimination, a cell model was developed using staurosporine, an alkaloid that can initiate apoptosis in a culture of cardiac myofibroblasts. The activity of apoptosis and autophagy was studied using immunofluorescence staining, immunoblotting, and flow cytometry.
Results. It was shown that pressure-induced cardiac overload causes the accumulation of myofibroblasts characterized by a low rate of apoptosis (annexin V+ cells in sham-operated hearts and after modeling pressure overload (0.0016 ± 0.0006% and 0.0019 ± 0.0009%; p = 0.32, n = 10), leading to marked interstitial fibrosis in the myocardium. It was found that rapamycin is able to enhance the effect of staurosporin and cause increased myofibroblast death due to autophagy-associated mechanisms (control 1.68 ± 0.66% (n = 4); staurosporin 65.8 ± 2.63% (n = 4); rapamycin + staurosporin 73.73 ± 0.67% (n = 4); control vs staurosporin p 0.0001; control vs rapamycin + staurosporin p 0.0001; staurosporin vs rapamycin + staurosporin p = 0.0071).
Conclusion. Rapamycin enhanced myofibroblast apoptosis induced by staurosporine, which may be related to regulation of the mTOR signaling and increased autophagy activity. The molecular mechanisms of this process require further research.

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