Background Doxorubicin (DOXO) is an effective anthracycline chemotherapeutic, but its use is limited by cumulative dose-dependent cardiotoxicity. Neuregulin-1β (NRG1B) is an ErbB receptor family ligand that is effective against DOXO-induced cardiomyopathy in experimental models but is also pro-neoplastic. We previously showed that an engineered bivalent neuregulin-1β (NN) has reduced pro-neoplastic potential compared to the epidermal growth factor (EGF)-like domain of NRG1B (NRG), an effect mediated by receptor biasing towards ErbB3 homotypic interactions uncommonly formed by native NRG1B. Here, we hypothesized that a newly formulated, covalent NN would be cardioprotective with reduced pro-neoplastic effects compared to NRG. Methods and Results NN was expressed as a maltose-binding protein fusion in E. coli. As established previously, NN stimulated anti-neoplastic or cytostatic signaling and phenotype in cancer cells, whereas NRG stimulated pro-neoplastic signaling and phenotype. In neonatal rat cardiomyocytes (NRCM), NN and NRG induced similar downstream signaling. NN, like NRG, attenuated the double-stranded DNA breaks associated with DOXO exposure in NRCM and human cardiomyocytes derived from induced pluripotent stem cells. NN treatment significantly attenuated DOXO-induced decrease in fractional shortening as measured by blinded echocardiography in mice in a chronic cardiomyopathy model (57.7% ± 0.6% vs. 50.9% ± 2.6%, P=0.004), whereas native NRG had no significant effect (49.4% ± 3.7% vs. 50.9% ± 2.6%, P=0.813). Conclusions NN is a cardioprotective agent that promotes cardiomyocyte survival and improves cardiac function in DOXO-induced cardiotoxicity. Given the reduced pro-neoplastic potential of NN versus NRG, NN has translational potential for cardioprotection in cancer patients receiving anthracyclines.

Objective To assess the effects of empagliflozin, a selective SGLT2 inhibitor, on broad biological systems through proteomics. Research Design and Methods 3,713 proteins were quantified using aptamer-based proteomics in 144 paired plasma samples obtained from 72 participants across the spectrum of glucose tolerance, before and after 4 weeks of empagliflozin 25 mg/day. Biology of the plasma proteins significantly changed by empagliflozin (at false discovery rate-corrected p<0.05) was discerned through Ingenuity Pathway Analysis. Results Empagliflozin significantly affected levels of 43 proteins, 6 related to cardiomyocyte function (fatty acid binding protein 3 and 4 (FABPA), neurotrophic receptor tyrosine kinase (NTRK2), renin, thrombospondin-4, and leptin receptor), 5 to iron handling (ferritin heavy chain 1, transferrin receptor protein 1 (TFRC), neogenin, growth differentiation factor 2 (GDF-2), and ß2microglobulin) and 1 to spingosine/ceramide metabolism (neutral ceramidase), a known pathway of cardiovascular disease. Among the protein changes achieving the strongest statistical significance, insulin-like binding factor protein-1 (IGFBP-1), transgelin-2, FABPA, growth differentiation factor-15 (GDF15), and sulphydryl oxidase 2 precursor (QSOX2) were increased, while ferritin, thrombospondin-3, and REarranged during Transfection (RET) were decreased by empagliflozin administration Conclusion SGLT2 inhibition is associated, directly or indirectly, with multiple biological effects, including changes in markers of cardiomyocyte contraction/relaxation, iron handling, and other metabolic and renal targets. The most significant differences were detected in protein species (GDF15, ferritin, IGFBP-1 and FABP) potentially related to the clinical and metabolic changes that were actually measured in the same patients. These novel results may inform further studies, using targeted proteomics and a prospective design.