https://doi.org/10.1007/s00392-024-02526-y
1Institute of Physiology, Ruhr University Bochum Department of Cellular and Translational Physiology, Bochum, Deutschland; 2Charité - Universitätsmedizin Berlin BIH Center für regenerative Therapien (BCRT) Berlin, Deutschland; 3Charité - Universitätsmedizin Berlin CC11: Med. Klinik m.S. Kardiologie Berlin, Deutschland; 4Kath. Klinikum Bochum Molekulare und experimentelle Kardiologie (IFL) Bochum, Deutschland; 5Medical College of Georgia Department of Physiology Augusta, USA; 6Klinikum der Ruhr-Universität Bochum Medizinische Klinik II, Kardiologie Bochum, Deutschland; 7From the Heart Center, Division Cardiology of the OLVG Hospital Department of Cardiology Amsterdam, Niederlande
Introduction: Diastolic left ventricular (LV) dysfunction, characterized by impaired relaxation and increased diastolic stiffness, is a defining feature of heart failure with preserved ejection fraction (HFpEF). HFpEF accounts for over 50% of all heart failure cases and is closely associated with comorbidities. These comorbidities contribute to a systemic inflammatory state, which leads to endothelial dysfunction, reactive oxygen species (ROS) production, nitrosative stress, reduced nitric oxide (NO) availability, and downregulation of cGMP-dependent protein kinase G (PKG). We hypothesize that oxidative stress and inflammation contribute to the pathophysiology of HFpEF by affecting LV stiffness, in part through modulation of the myocardial cGMP-PKG pathway. Our objective is to assess posttranslational modifications, specifically PDE9 oxidation, and to investigate how treatment strategies might reverse this oxidation and improve diastolic dysfunction.
Methods: We measured cardiomyocyte function, PDE9 oxidation and its distribution in different cell compartments, pro-inflammatory cytokines, oxidative stress levels, protein expression, and phosphorylation in human HFpEF samples before and after acute treatment of myocardial biopsies with the PDE9A inhibitor PF04447943, as well as in the ZSF1 obese rat model of HFpEF. Chronic treatment (2 weeks) with the PDE9A inhibitor (3 mg/kg) or vehicle was administered to 18-week-old HFpEF rats via daily oral gavage. At 20 weeks of age, LV diastolic dysfunction in HFpEF rats was assessed by transthoracic echocardiography.
Results: Both HFpEF patients and HFpEF rats exhibited significantly higher PDE9 oxidation, particularly in the membrane compartment, compared to control groups. Pro-inflammatory cytokines (e.g., ICAM-1, VCAM-1, IL-6, TNF-α) and oxidative stress markers (e.g., 3-Nitrotyrosine, lipid peroxidase, hydrogen peroxide) were significantly elevated in HFpEF patients and rats. These changes were associated with increased PDE9 activity due to oxidation, reduced NO and soluble guanylyl cyclase levels, and decreased PKG activity. Oxidized PDE9 significantly increased passive stiffness (Fpassive) in healthy cardiomyocytes, while it did not affect HFpEF cardiomyocytes (which are already elevated at baseline), indicating that increased PDE9 activity resulting from oxidation partially contributes to the elevated passive stiffness in HFpEF. Key signaling pathways involved in titin phosphorylation were differentially regulated in HFpEF compared to controls, with phosphorylation of myofilament proteins (e.g., myosin light chain, troponin I, myosin binding protein C, titin) significantly lower in HFpEF. Treatment with the PDE9A inhibitor reduced PDE9 oxidation, improved cardiomyocyte function, and increased myofilament protein phosphorylation. These improvements were associated with reduced inflammation and oxidative stress.
Conclusion: This study demonstrates that oxidative stress and inflammation play a critical role in the pathophysiology of HFpEF by modulating LV stiffness through the myocardial cGMP-PKG pathway. Targeting PDE9 oxidation with specific inhibitors can reverse diastolic dysfunction, highlighting a potential therapeutic strategy for HFpEF that addresses both oxidative stress and inflammation.