Abstract Body (Do not enter title and authors here): Background: Tyrosine kinase inhibitors (TKIs), such as sunitinib, are highly effective in treating cancers. However, they have severe cardiovascular (CV) side effects that include cardiotoxicity via cardiomyocyte injury and death resulting in myocardial dysfunction. There are no FDA-approved drugs to prevent or treat cardiotoxicity, which have been linked mechanistically to mitochondrial dysfunction and oxidative stress, highlighting the need for new therapeutics. Two recognized CV protective pathways are the particulate guanylyl cyclase A receptor (GC-A)/cGMP and the Mas receptor (MasR)/cAMP pathways. We recently engineered NPA7 a novel peptide that activates both pathways.
Aim: Here we investigated NPA7’s ability to protect against sunitinib-induced cardiotoxicity in human cardiomyocytes (HCMs) and defined its role on mitochondrial function.
Methods: HCMs were treated with DMSO or sunitinib (10 µM) together with PBS or NPA7 (10 µM). Intracellular reactive oxygen species (ROS) was assessed by DHE staining. CCK8 assay was performed to measure cell viability. TOM20 staining were performed by immunofluorescence and the mitochondrial length was analyzed. The protein levels of mitochondrial dynamics markers (fission: MFF, Fis1; fusion: OPA1 and MFN1) proteins were measured by western blot. Cell surface area was assessed by phalloidin staining with mRNA levels of hypertrophic gene markers (NPPA and MYH7) in HCMs using real-time PCR.

Results: Sunitinib increased DHE staining and intracellular ROS in HCMs, which was decreased with NPA7 treatment. NPA7 enhanced HCM cell viability in the presence of sunitinib. TOM20 staining showed a marked reduction in mitochondrial length in sunitinib group, compared to DMSO group, whereas NPA7 treatment rescued mitochondria length (DMSO= 6.15 ± 0.94 μm, Sunitinib= 2.42 ± 0.63 μm, NPA7= 5.4 ± 1.19 μm; P < 0.05). Moreover, NPA7 inhibited mitochondrial fission protein levels (MFF and Fis1) and increased mitochondrial fusion protein levels (OPA1, MFN1) in HCMs treated with sunitinib. Sunitinib treatment notably increased HCM cell surface area and hypertrophic gene markers (NPPA and MYH7), whereas NPA7 abolished these markers of hypertrophy.

Conclusions: We report, for the first time, that NPA7 protects against sunitinib induced oxidative stress, mitochondrial fragmentation, hypertrophy and cell death in HCMs. These data support a novel therapeutic approach against TKI-induced cardiotoxicity with NPA7 to which no therapies exist.