Abstract 275 Boosting endogenous small heat shock protein 70 prevents titin aggregation and improves titin-based cardiomyocyte stiffness in heart failure with preserved ejection fraction

Background:
Emerging evidence indicates a key role of oxidative stress in heart failure with preserved ejection fraction (HFpEF)-associated hypertrophy, fibrosis, and myocardial stiffness. Oxidative stress can damage cells, proteins, and DNA, thus contributing to premature senescence, deregulation of cytosolic heat shock response, mitochondrial and endoplasmic reticulum unfolded protein response, the ubiquitin-proteasome system, and autophagy. Here we aimed to investigate the regulation of heat shock protein 70 (HSP70) and its contribution to the modulation of cardiomyocyte function and the effect of HSP70 booster on titin and cardiomyocyte function in heart failure with preserved ejection fraction,

Results:
We explored the regulation of HSP70 and its effects on titin and cardiomyocyte function in left ventricular (LV) human HFpEF myocardium and before and after chronic treatment with BGP-17 a booster of HSP70.

We show here that HSP70 expression and phosphorylation are reduced in LV myocardium from HFpEF patients, this was associated with increased cardiomyocyte stiffness compared to non-failing human hearts. Increased cardiomyocyte stiffness is potentially due to aggregation of titin in HFpEF, as administration of the active recombinant HSP70 in vitro corrected increased cardiomyocyte stiffness. Also, we found that autophagy was enhanced in the HFpEF model, as indicated by the increased LC3 expression and decreased P62 expression. All of these changes were associated with increased oxidation of cardiac proteins in HFpEF. We used for this purpose in vivo redox state in LV from HFpEF patient's myocardium. Using the OxiCAT method coupled with mass spectrometry (MS), which involves using a cysteine-specific isotope-coded affinity tag (ICAT) reagent to differentially label oxidized and reduced cysteines and can then be detected with MS. Using MS, we were able to detect and compare many peptides in LV HFpEF and found an increase in oxidation in most of the detected peptides. Many peptides and from different cardiac proteins were highly oxidized and among them was the giant titin the main modulator of cardiomyocyte function. As BGP-15 has been suggested to increase HSP70/72 expression, we treated diastolic dysfunction model (Rabbits which were maintained on control or atherogenic diet-hypercholesterolemic for 16 weeks) with BGP-15 orally to assess the chronic effects. Boosting HSP70 chronically improved HSP70 expression, reduced autophagy, inflammation, and oxidative stress,

Conclusion:
Our data suggested that boosting endogenous small heat shock protein 70 could be a potential treatment option for HFpEF patients as it prevents titin aggregation and improves titin-based cardiomyocyte stiffness.

Clin Res Cardiol (2022). https://doi.org/10.1007/s00392-022-02087-y
Boosting endogenous small heat shock protein 70 prevents titin aggregation and improves titin-based cardiomyocyte stiffness in heart failure with preserved ejection fraction
N. Mostafi¹, M. Tangos¹, M. Varanitskaya¹, M. Begovic¹, M. Herwig², R. Hassoun³, H. Budde¹, Á. Kovács¹, A. Mügge⁴, Z. Zoltan Szilvassy⁵, B. Juhasz⁵, N. Hamdani²
¹Molecular and Experimental Cardiology, Institute for Forshung and Lehre, Bochum; ²Molekulare und Experimentelle Kardiologie, Institut für Forschung und Lehre (IFL), St. Josef Hospital, Ruhr-Universität Bochum, Bochum; ³Molecular and Experimental Cardiology, Institut für Forschung und Lehre (IFL), Ruhr University Bochum, Bochum; ⁴Medizinische Klinik II, Kardiologie, Klinikum der Ruhr-Universität Bochum, Bochum; ⁵Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Debrecen, Debrecen, HU;
Background: Emerging evidence indicates a key role of oxidative stress in heart failure with preserved ejection fraction (HFpEF)-associated hypertrophy, fibrosis, and myocardial stiffness. Oxidative stress can damage cells, proteins, and DNA, thus contributing to premature senescence, deregulation of cytosolic heat shock response, mitochondrial and endoplasmic reticulum unfolded protein response, the ubiquitin-proteasome system, and autophagy. Here we aimed to investigate the regulation of heat shock protein 70 (HSP70) and its contribution to the modulation of cardiomyocyte function and the effect of HSP70 booster on titin and cardiomyocyte function in heart failure with preserved ejection fraction, Results: We explored the regulation of HSP70 and its effects on titin and cardiomyocyte function in left ventricular (LV) human HFpEF myocardium and before and after chronic treatment with BGP-17 a booster of HSP70. We show here that HSP70 expression and phosphorylation are reduced in LV myocardium from HFpEF patients, this was associated with increased cardiomyocyte stiffness compared to non-failing human hearts. Increased cardiomyocyte stiffness is potentially due to aggregation of titin in HFpEF, as administration of the active recombinant HSP70 in vitro corrected increased cardiomyocyte stiffness. Also, we found that autophagy was enhanced in the HFpEF model, as indicated by the increased LC3 expression and decreased P62 expression. All of these changes were associated with increased oxidation of cardiac proteins in HFpEF. We used for this purpose in vivo redox state in LV from HFpEF patient's myocardium. Using the OxiCAT method coupled with mass spectrometry (MS), which involves using a cysteine-specific isotope-coded affinity tag (ICAT) reagent to differentially label oxidized and reduced cysteines and can then be detected with MS. Using MS, we were able to detect and compare many peptides in LV HFpEF and found an increase in oxidation in most of the detected peptides. Many peptides and from different cardiac proteins were highly oxidized and among them was the giant titin the main modulator of cardiomyocyte function. As BGP-15 has been suggested to increase HSP70/72 expression, we treated diastolic dysfunction model (Rabbits which were maintained on control or atherogenic diet-hypercholesterolemic for 16 weeks) with BGP-15 orally to assess the chronic effects. Boosting HSP70 chronically improved HSP70 expression, reduced autophagy, inflammation, and oxidative stress, Conclusion: Our data suggested that boosting endogenous small heat shock protein 70 could be a potential treatment option for HFpEF patients as it prevents titin aggregation and improves titin-based cardiomyocyte stiffness.
https://dgk.org/kongress_programme/ht2022/aP353.html