Mass spectrometry imaging uncovers drug-induced lipid alterations in the mouse heart

Clinically used drugs can adversely affect cardiac function. Doxorubicin (DOX), a chemotherapeutic drug, and efavirenz (EFV), an antiretroviral drug, are known to associate with adverse cardiovascular events and alterations of serum lipid profiles. In the heart, lipids serve as the main energy source and act as signaling molecules. Moreover, CYP2J2, a primary cytochrome P450 enzyme in the heart, metabolizes arachidonic acid. Drugs could alter the activity of CYP2J2, thereby modulating the levels of arachidonic acid. However, the effect of the above drugs on cardiac lipids is not fully elucidated. We hypothesized that DOX and EFV perturb endogenous lipid metabolism in heart tissues. In this work, we investigated lipid alterations in murine hearts following the above drug treatments using matrix-assisted laser desorption/ionization mass spectrometry imaging, which revealed region-specific localization of phosphatidylcholine (PC) and sphingomyelin (SM) in mouse heart tissues. Lipid molecules PC(34:2), PC(34:1), PC(32:0), and SM(37:1) showed alterations within mouse heart tissue in response to DOX treatment. Interestingly, hexosylceramide (42:2;O2), SM(40:2), and SM(40:3) showed increased abundance in the left ventricle of EFV-treated heart tissues relative to the control group. Notably, arachidonic acid, a precursor of various bioactive lipid mediators, was detected to be more abundant in drug-treated heart tissues as compared with controls. Proteomic analysis further demonstrated altered expression of cardiac proteins in response to drug treatments. The findings from in vitro inhibition assays suggest that EFV inhibits microsomal CYP2J2. Altogether, our results reveal the localized alterations of lipids in murine heart tissues following DOX and EFV treatments. SIGNIFICANCE STATEMENT: Clinically used drugs such as doxorubicin and efavirenz are known to associate with adverse cardiovascular events. Lipids play important roles in the cardiac function and both doxorubicin and efavirenz cause alterations of serum lipid levels. Using mass spectrometry imaging and bottom-up proteomics, we demonstrate the local region-specific alterations of phosphatidylcholine, sphingomyelin, hexosylceramide, and arachidonic acid in response to the above drugs in mouse heart tissues. Further, we performed in vitro inhibition assays to assess CYP2J2 inhibition by efavirenz.