Mechanistic attenuation by L-carnitine of trastuzumab-induced downregulation of adenosine monophosphate -activated protein kinase signal in cardiac H9c2 cells

Clinical usefulness of trastuzumab (TZ) is restrained owing to its cardiotoxic effect. This investigation was initiated to evaluate the potential protective impact of carnitine (CARN) against TZ-related cardiac influence; and to uncover the underlining mechanism. Cytotoxic effect of TZ, CARN and their combination was assessed in cardiac H9c2 cells. Carnitine pamlitoyltransferase-1B (CPT1B) and adenosine monophosphate activated protein kinase-α2 (AMPK-α2) expression were investigated using quantitative real-time Polymerase Chain Reaction (RT-PCR). Troponin I, creatine kinase-MB (CK-MB), Adenosine triphosphate (ATP), malonyl-CoA, acetyl-CoA carboxylase-2 (ACC2) and autophagy protein 5 (ATG-5) were investigated using Enzyme-linked immunosorbent assay (ELISA). Challenging cardiac cell with TZ resulted in concentration-dependent decrease in cell viability with inhibitory concentration 50 (IC 50 ) of (1.21 uM). Combining TZ’s IC 50 and CARN (5 mM) resulted in the most profound drop of cardiac cellular toxicity. Trastuzumab elevated Troponin I, CK-MB, ACC-2 and Malonyl-CoA, while CARN counteracted this elevation. TZ decreased mRNA expression of AMPK-α2 and CPT1B; as well as ATP and ATG-5 levels, but combination of TZ and CARN counteracted this reduction. TZ disorders AMPK-α2 downstream signaling with the consequent decrease of ATP production and disturbs autophagy. Carnitine tempers TZ-related cardiotoxicity and acts as guard against TZ-related cardiac impact. The current findings are preliminary and highlight the need for additional studies to answer this current research question.