Aims Cardiac miR-132 activation leads to adverse remodelling and pathological hypertrophy. CDR132L is a synthetic lead-optimized oligonucleotide inhibitor with proven preclinical efficacy and safety in heart failure (HF) early after myocardial infarction (MI), and recently completed clinical evaluation in a Phase 1b study (NCT04045405). The aim of the current study was to assess safety and efficacy of CDR132L in a clinically relevant large animal (pig) model of chronic heart failure following MI. Methods and results In a chronic model of post-MI HF, slow-growing pigs underwent 90 min left anterior descending artery occlusion followed by reperfusion. Animals were randomized and treatment started 1-month post-MI. Monthly intravenous (IV) treatments of CDR132L over 3 or 5 months (3× or 5×) were applied in a blinded randomized placebo-controlled fashion. Efficacy was evaluated based on serial magnetic resonance imaging, haemodynamic, and biomarker analyses. The treatment regime provided sufficient tissue exposure and CDR132L was well tolerated. Overall, CDR132L treatment significantly improved cardiac function and reversed cardiac remodelling. In addition to the systolic recovery, diastolic function was also ameliorated in this chronic model of HF. Conclusion Monthly repeated dosing of CDR132L is safe and adequate to provide clinically relevant exposure and therapeutic efficacy in a model of chronic post-MI HF. CDR132L thus should be explored as treatment for the broad area of chronic heart failure.

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Purpose Myocardial infarction (MI) triggers a local inflammatory response which orchestrates cardiac repair and contributes to concurrent neuroinflammation. Angiotensin-converting enzyme (ACE) inhibitor therapy not only attenuates cardiac remodeling by interfering with the neurohumoral system, but also influences acute leukocyte mobilization from hematopoietic reservoirs. Here, we seek to dissect the anti-inflammatory and anti-remodeling contributions of ACE inhibitors to the benefit of heart and brain outcomes after MI. Methods C57BL/6 mice underwent permanent coronary artery ligation (n = 41) or sham surgery (n = 9). Subgroups received ACE inhibitor enalapril (20 mg/kg, oral) either early (anti-inflammatory strategy; 10 days treatment beginning 3 days prior to surgery; n = 9) or delayed (anti-remodeling; continuous from 7 days post-MI; n = 16), or no therapy (n = 16). Cardiac and neuroinflammation were serially investigated using whole-body macrophage-and microglia-targeted translocator protein (TSPO) PET at 3 days, 7 days, and 8 weeks. In vivo PET signal was validated by autoradiography and histopathology. Results Myocardial infarction evoked higher TSPO signal in the infarct region at 3 days and 7 days compared with sham (p < 0.001), with concurrent elevation in brain TSPO signal (+ 18%, p = 0.005). At 8 weeks after MI, remote myocardium TSPO signal was increased, consistent with mitochondrial stress, and corresponding to recurrent neuroinflammation. Early enalapril treatment lowered the acute TSPO signal in the heart and brain by 55% (p < 0.001) and 14% (p = 0.045), respectively. The acute infarct signal predicted late functional outcome (r = 0.418, p = 0.038). Delayed enalapril treatment reduced chronic myocardial TSPO signal, consistent with alleviated mitochondrial stress. Early enalapril therapy tended to lower TSPO signal in the failing myocardium at 8 weeks after MI (p = 0.090) without an effect on chronic neuroinflammation. Conclusions Whole-body TSPO PET identifies myocardial macrophage infiltration and neuroinflammation after MI, and altered cardiomyocyte mitochondrial density in chronic heart failure. Improved chronic cardiac outcome by enalapril treatment derives partially from acute anti-inflammatory activity with complementary benefits in later stages. Whereas early ACE inhibitor therapy lowers acute neuroinflammation, chronic alleviation is not achieved by early or delayed ACE inhibitor therapy, suggesting a more complex mechanism underlying recurrent neuroinflammation in ischemic heart failure.

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Acute myocardial infarction (MI) triggers a local and systemic inflammatory response. We recently showed microglia involvement using translocator protein imaging. Here, we evaluated whether 11 C-methionine provides further insight into heart-brain inflammation networking. Methods: Male C57BL/6 mice underwent permanent coronary artery ligation followed by 11 C-methionine PET at 3 and 7 d (n 5 3). In subgroups, leukocyte homing was blocked by integrin antibodies (n 5 5). The cellular substrate for PET signal was identified using brain section immunostaining. Results: 11 C-methionine uptake (percentage injected dose/cm 3 ) peaked in the MI region on day 3 (5.9 ± 0.9 vs. 2.4 ± 0.5), decreasing to the control level by day 7 (4.3 ± 0.6). Brain uptake was proportional to cardiac uptake (r 5 0.47, P , 0.05), peaking also on day 3 (2.9 ± 0.4 vs. 2.4 ± 0.3) and returning to baseline on day 7 (2.3 ± 0.4). Integrin blockade reduced uptake at every time point. Immunostaining on day 3 revealed colocalization of the L-type amino acid transporter, with glial fibrillary acidic protein-positive astrocytes but not CD68-positive microglia. Conclusion: PET imaging with 11 C-methionine specifically identifies an astrocyte component, enabling further dissection of the heart-brain axis in post-MI inflammation.

Persistent inflammation following myocardial infarction (MI) precipitates adverse outcome including acute ventricular rupture and chronic heart failure. Molecular imaging allows longitudinal assessment of immune cell activity in the infarct territory and predicts severity of remodeling. We utilized a multiparametric imaging platform to assess the immune response and cardiac healing following MI in mice. Suppression of circulating macrophages prior to MI paradoxically resulted in higher total leukocyte content in the heart, demonstrated by increased CXC motif chemokine receptor 4 (CXCR4) positron emission tomography imaging. This supported the formation of a thrombus overlying the injured region, as identified by magnetic resonance imaging. The injured and thrombotic region in macrophage depeleted mice subsequently showed active calcification, as evidenced by accumulation of 18F-fluoride and by cardiac computed tomography. Importantly, macrophage suppression triggered a prolonged inflammatory response confirmed by post-mortem tissue analysis that was associated with higher mortality from ventricular rupture early after occlusion and with increased infarct size and worse chronic contractile function at 6 weeks after reperfusion. These findings establish a molecular imaging toolbox for monitoring the interplay between adverse immune response and tissue repair after MI. This may serve as a foundation for development and monitoring of novel targeted therapies that may include immune modulation and endogenous healing support.

Background/Purpose Takotsubo syndrome (TTS) is characterized by acute transient left ventricular dysfunction in the absence of obstructive coronary lesions. We identified a higher sensitivity to catecholamine-induced stress toxicity as mechanism associated with the TTS phenotype in our former study, but the pathogenesis of TTS is still not completely understood. In this study our aim was to prove the hypothesis of an altered phosphodiesterase (PDE)-dependent 3',5'-cyclic adenosine monophosphate (cAMP)-signaling in TTS in patient-specific induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). Methods and results We generated functional TTS-iPSC-CMs and treated them with catecholamines to mimic a TTS-phenotype. To directly address the hypothesis that local cAMP dynamics might be altered in TTS, we used Förster resonance energy transfer (FRET) based cAMP sensors, which are specifically located in the cytosol or at the sarcoplasmic/endoplasmic reticulum calcium ATPase 2a (SERCA) micro domain. We demonstrated that β-adrenergic receptor (β-AR) stimulations resulted in stronger cytosolic FRET responses in TTS-CMs compared to controls. In contrast, no differences of cAMP level were observed in the SERCA-PLN micro domain between TTS- and control-iPSC-CMs. To analyze the interplay of β-AR signaling and specific PDE contribution to the cAMP signaling in TTS, specific PDE-inhibitors were used. We were able to show in the cytosol that after β-AR stimulation, the strong effects of the PDE4 family of control cells were significantly decreased in diseased TTS CMs, which is in line with previously described reduced PDE4 activity in failing mouse hearts. In contrast, the contribution of PDE3 to cytoplasmic cAMP degradation was increased in TTS (Figure 1 A). This is in line with increased PDE3A and down-regulated PDE4D protein expression in TTS-iPSC-CMs compared to control cells. Analysis of PDE-dependent cAMP level in the SERCA micro domain show also a significantly reduced PDE4 activity. But the dynamic cytosolic PDE contribution of PDE2 and PDE3 after catecholamine treatment in TTS is lost in SERCA micro domain (Figure1B). Conclusion Our data showed for the first time alterations of local cAMP signaling in healthy and diseased TTS-iPSC-CMs. We demonstrated an isozym shift from PDE4 in control to PDE3 and PDE2 in TTS and identified PDE4 as an important player in the β-adrenergic cAMP signaling in TTS. Therefore, PDE4 activators may be a possible new therapeutic target option in the treatment of TTS. Figure 1 Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): DZHK

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