Newly Developed Mimetic Peptides for Angiotensin II Type 1 Receptor Attenuate Doxorubicin-Induced c-Jun N-Terminal Kinase Activation, a Marker of Pro-Apoptotic Stress Signaling

Objectives: An ideal cardiotoxicity inhibitor targeting the angiotensin (Ang) II type 1 (AT1) receptor would be a β-arrestin-biased orthostatic ligand, which inhibits the G protein pathway and activates the β-arrestin pathway. Therefore, this study examined seven Ang II mimetic peptides (MP1–7), Ang A and TRV027 as potential β-arrestin-biased AT1 receptor ligands to prevent doxorubicin (Dox)-induced cardiotoxicity. Methods: Competition binding study, inositol phosphate (IP) production assay and extracellular signal-regulated kinase (ERK) 1/2 activation were performed using COS7 cells. Changes in phosphorylated Akt (Ser473), c-Jun N-terminal kinase (JNK) (Thr183/Tyr185), Bad (Ser112), Bcl-2 (Ser70), p53 (Ser46), active caspase-8 (Asp384) and active caspase-9 (Asp315) in cell lysates were measured using AT1 receptor-transfected H9C2 cells. Results: Binding assays showed Ang II and Ang A had the highest affinity, with MP2 and MP7 similar to TRV027. IP production was strong for Ang II and Ang A, minimal for MP1 and MP7, and no stimulation for MP2 and TRV027. Ang II and Ang A significantly activated ERK1/2 in this cell system. MP2 and MP7 in addition to TRV027 also significantly activated ERK1/2, whereas MP1 did not activate it. Dox-activated JNK and Bad, while Ang A, TRV027, MP2, and MP7 inhibited JNK activation without affecting Bad or Akt. Conclusions: MP2, which is a candidate biased ligand for the AT1 receptor and has similar amino acid sequence to TRV027, along with TRV027, attenuated Dox-induced JNK activation while avoiding excessive G protein-mediated activation. Interestingly, MP7, which showed minimal G protein-mediated activation with β-arrestin-mediated ERK activation, also attenuated Dox-induced JNK activation, a marker of pro-apoptotic stress signaling.