Abstract 538: Reduced Protein and mRNA Levels of Velosin Containing Protein in Left Ventricular Myocardium of Dogs With Advanced Heart Failure Are Restored Following Chronic Therapy With Elamipretide

Abstract

Introduction: The failing heart manifests abnormalities of mitochondrial function characterized by reduced respiration, reduced membrane potential and opening of permeability transition pore (mPTP). Recent studies have shown that velosin containing protein (VCP), an ATPase associate protein, preserves mitochondrial respiration and prevents opening of the mPTP. Long-term therapy with elamipretide (ELAM), a novel mitochondria-targeting tetra-peptide, was previously shown improve mitochondrial respiration, membrane potential and prevent opening of the mPTP in dogs with intracoronary microembolization-induced heart failure (HF). Hypothesis: This study tested the hypothesis that mRNA and protein levels of VCP are decreased in left ventricular (LV) myocardium of dogs with HF and that chronic therapy with ELAM reverses this dysregulation. Methods: Studies were performed using LV tissue from 14 HF dogs randomized to 3 months monotherapy with subcutaneous injections of ELAM (HF+ELAM, 0.5 mg/kg once daily, n=7) or no therapy at all (control, HF-CON, n=7). LV tissue from 6 normal (NL) dogs was used for comparisons. Protein levels of VCP and GAPDH, an internal loading control, were determined in LV SDS-extracts using Western blotting coupled with chemiluminescence detection and band intensity was expressed in densitometric units (du). Using isolated RNA and specific primers, mRNA expression of VCP normalized to GAPDH. Results: mRNA and protein levels of GAPDH in LV tissue remained unchanged among the 3 study groups. Compared to NL, mRNA expression of VCP was reduced by 3.67 fold in HF-CON. Compared to NL, protein level of VCP was significantly reduced compared to HF-CON (0.30 ± 0.04 vs. 1.77 ± 0.31 du, p<0.05). In HF+ELAM treated dogs, mRNA expression of VCP was reduced by only 1.07 fold compared to HF-CON (p<0.05). Similarly, in HF+ELAM, protein levels of VCP were significantly higher than in HF-CON (1.03 ± 0.16 du, p<0.05). Conclusions: VCP mRNA and protein levels are significantly reduced in LV myocardium of dogs with chronic HF. Long-term therapy with ELAM reverses this dysregulation. The findings support the observations of improved mitochondrial respiration and reduced mPTP opening in dogs with advanced HF following chronic therapy with ELAM.