LC-MS/MS based cellular pharmacokinetics to explore the mechanism of palmatine against doxorubicin-induced cardiotoxicity.

Doxorubicin (DOX) is an effective chemotherapeutic agent, but its use is limited by dose-dependent cardiotoxicity. Palmatine (PAL) has shown potential in preventing doxorubicin-induced cardiotoxicity (DIC); however, the underlying mechanism remains unclear. Since DOX accumulation in cardiomyocytes is a key factor in the development of cardiotoxicity, this study aims to explore the pharmacokinetic mechanisms through which PAL alleviates DIC. First, the effect of PAL on DIC was assessed based on H9c2 cardiomyocytes model using sulforhodamine B (SRB), lactate dehydrogenase (LDH), flow cytometry and Western blot assays, which demonstrated that PAL significantly attenuated DOX-induced cardiac toxicity and apoptosis. Second, a sensitive and efficient LC-MS/MS method was established to quantify DOX in H9c2 cells, with a lower limit of quantification of 10 nM and a total run time of 4 min per sample. Cellular pharmacokinetic study revealed that PAL significantly reduced DOX concentration in H9c2 cells. Finally, molecular docking analysis revealed that PAL exhibited low binding energies and formed hydrogen with uptake transporter proteins involved in DOX transport in cardiomyocytes, including organic cardi transporter (OCT) 1, OCT3, organic cation/carnitine transporter (OCTN) 1, OCTN2, and plasma membrane monoamine transporter (PMAT). This suggests a stable interaction between PAL and these transporters. In conclusion, PAL alleviates DIC, most likely by reducing myocardial DOX accumulation through the inhibition of uptake transporters. This study provides novel pharmacokinetic insights into the mechanism by which PAL mitigates DIC and underscores its potential as a complementary therapeutic agent in combination with DOX in clinical applications.