Regulation and modulation of the NCX1-PLM-NKA complex in heart failure

Regulation and modulation of the NCX1-PLM-NKA protein complex in heart failure: Development of a new therapeutic principle for heart failure patients with preserved ejection fraction (HFPEF). Heart failure (HF) is a common, costly, disabling and deadly disease. Diastolic dysfunction, which means that the heart is stiffer, has recently been recognized to be a major component of the HF condition in many patients (HF with preserved ejection fraction, HFPEF). Part of this stiffness can be ascribed to higher than normal intracellular Ca2+ in diastole. The HFPEF group constitutes 50% of the patients with HF. Today’s standard treatments of HF have no or little effect on diastolic dysfunction. In the present project, we propose upregulation of the Na+-Ca2+ exchanger 1 (NCX1) activity as a new therapeutic principle for HFPEF patients. We have previously demonstrated that the NCX1 activity, which regulates the intracellular Ca2+ level, is reduced in HF. Two mechanisms that results in reduction of NCX1 activity are: 1) Cleavage of NCX1 by calpain and 2) inhibition of NCX1 by binding to the inhibitory protein; phosphorylated phospholemman (p-PLM). We have shown that both calpain activity and p-PLM is upregulated in HF. To upregulate NCX1 activity, we have developed a peptide-based drug candidate (Opt-pep), which block the inhibitory p-PLM binding to NCX1. When we apply Opt-pep to cells in culture, PLM cannot longer inhibit NCX1, and the NCX1 activity is reversed back to normal. For in vivo administration and proof-of principle for this new therapy, we have also developed a smaller high affinity Opt-pep derivative with 12 times higher serum stability. This peptide derivative is very promising as it efficiently upregulates NCX1 activity in cardiomyocytes isolated from animals with HF. We further plan to administrate this peptide derivative into animals with HF (outside this project period). The expected outcome is improved cardiac function and increased survival. In a parallel project, we have also administrated the original peptide-based drug candidate (Opt-pep) into animals by adeno-associated virus technology and expressed it into transgenic mice. In the AAV animals, Opt-pep is successfully detected at mRNA level and it shows no toxicity in the animals after 4 month of administration. In addition, the AAV-Opt-pep mice showed a tendency to have a better cardiac function compared to the control group. Finally, we have identified the first NCX1-PLM-NKA proteome and identified additional therapeutic targets. Highly interestingly, one of the targets is able to maintain NCX1 integrity by blocking calpain cleavage of NCX1. We have recently determined the underlying molecular mechanisms behind this protective mechanism and further developed two novel protective peptides. The peptides might be tested in HF animals in future projects. This project has been performed at Institute for experimental medical research at Oslo University Hospital in collaboration with national and international laboratories. The work has during this project period resulted in three publications, two manuscripts (work completed) and one patent application. Long term: New theraphy for heart failure patients with preserved ejection fraction (HFPEF).