Alicja Braczko

Background: Cardiac fibrosis drives adverse myocardial remodelling through persistent fibroblast activation, ECM deposition, and impaired cardiac function. Current therapies offer limited protection against cardiac fibrosis progression. Elafibranor is a dual PPAR-α/δ agonist approved for the treatment of liver disease. However, its effects in human models of cardiac fibrosis remain insufficiently explored. Methods: Elafibranor was evaluated in complementary human in vitro TGF-β ₁ -induced cardiac fibrosis models: 2D primary fibroblasts, 3D fibroblast spheroids, spontaneously contracting 3D cardiac microtissues, and hiPSC-derived cardiomyocytes. Viability, apoptosis, fibroblast activation, ECM remodelling, mitochondrial respiration, nucleotide and NAD pools, calcium handling, contractility, and transcriptomic profiles were assessed. Results: At non-cytotoxic concentrations, elafibranor attenuated TGF-β ₁ -driven cardiac fibrosis responses. In 2D cardiac fibroblasts, it reduced myofibroblast differentiation, procollagen 1α1 secretion, and partially restored mitochondrial respiratory capacity. In 3D spheroids, it preserved viability, attenuated caspase-3/7 activation, and suppressed procollagen 1α1 release. In cardiac microtissues, elafibranor reduced ECM accumulation, shifted transcriptomic profiles toward redox-metabolic/cytoprotective pathways, altered adenine nucleotide and NAD pools, and partially recovered contraction parameters. In hiPSC-derived cardiomyocytes, elafibranor modulated calcium handling, contractility, and mitochondrial respiration. Conclusions: Elafibranor mitigates TGF-β ₁ -driven cardiac fibrosis by suppressing fibroblast activation and ECM remodelling while promoting adaptive metabolic, redox, and bioenergetic responses, supporting balanced PPAR-α/δ activation as a potential therapeutic strategy for cardiac fibrosis. Graphical

Aims: Cardiac stereotactic body radiotherapy (SBRT) has emerged as a promising non-invasive treatment for refractory ventricular tachycardia (VT). Intriguingly, the clinical benefit of SBRT often occurs within days of treatment, preceding the development of radiation-induced fibrosis, suggesting alternative underlying mechanisms. This study aimed to investigate the acute and persistent effects of ionizing radiation on cardiac bioenergetics and mitochondrial function, providing mechanistic insights into early cardiac responses to radiation exposure. Methods and results: We employed a translational multi-model approach, including HL-1 mouse cardiomyocytes and ex vivo mouse left ventricular living myocardial slices (LMS). Bioenergetic profiling, assessment of mitochondrial respiration and calcium handling were performed following exposure to clinically relevant radiation doses (10 Gy and 25 Gy). In HL-1 cardiomyocytes, 10 Gy induced acute bioenergetic stress, characterized by reduced adenylate energy charge, cytoskeletal disorganization, and impaired mitochondrial respiration, accompanied by increased calcium oscillation amplitude. 25 Gy exposure led to NAD ⁺ depletion but paradoxically enhanced mitochondrial respiratory capacity, suggesting an adaptive metabolic response. Murine myocardial slices demonstrated reduced creatine content while preserving energy balance as indicated by phosphocreatine/ATP ratio, indicating tissue-level metabolic resilience. These findings reveal model-specific metabolic perturbations induced by cardiac irradiation, underscoring the importance of tissue complexity in modulating the cardiac response to radiation. Conclusion: This study demonstrates that ionizing radiation at 10 Gy and 25 Gy induced dose- and model-dependent bioenergetic alterations in cardiac cells and tissues, including changes in mitochondrial respiration, nucleotide levels, and redox balance. While 10 Gy exacerbated metabolic disruption, 25 Gy triggered partial recovery, highlighting differential responses across cellular and tissue levels. These metabolic changes may contribute to the immediate effects of cardiac SBRT and potentially to long-term cardiotoxicity. Translational Perspective: Our study provides novel mechanistic insights into the metabolic effects of cardiac irradiation, revealing acute mitochondrial stress, redox imbalance and alterations in calcium homeostasis in cardiomyocytes. These early bioenergetic changes may contribute to both the immediate anti-arrhythmic effects and the potential long-term cardiotoxicity of stereotactic body radiation therapy. Understanding these molecular responses is essential to optimize the therapeutic window of cardiac radioablation and minimize adverse effects. GRAPHICAL

COVID-19 is associated with long-term vascular complications, but the underlying mechanisms remain incompletely understood. During infection, NAD⁺ homeostasis becomes dys-regulated, with excessive NAD⁺ consumption and enhanced catabolic flux through nicotinamide methylation pathways. This imbalance leads to NAD⁺ depletion accompanied by accumulation of pyridone metabolites, including N-methyl-2-pyridone-5-carboxamide (Met2PY) and N-methyl-4-pyridone-3-carboxamide (Met4PY). These derivatives have been linked to oxidative stress, endothelial dysfunction, and cardiovascular risk, yet their role in long COVID remains unclear. We enrolled 26 post-COVID patients with persistent cardiovascular symptoms and 8 healthy controls. Serum concentrations of Met2PY and Met4PY were quantified by LC/MS. High-sensitivity C-reactive protein (hsCRP), tumor necrosis factor-alpha (TNFα), interleukin-10 (IL-10), and soluble intercellular adhesion molecule-1 (sICAM-1) were measured to assess systemic inflammation and endothelial activation. Statistical analyses included group comparisons and correlation analyses. We observed significantly elevated Met2PY levels (0.770 ± 0.08 vs. 0.389 ± 0.09 µmol/l) and a trend toward increased Met4PY (0.095 ± 0.01 vs. 0.055 ± 0.01 µmol/l) in post-COVID patients compared with controls. Both metabolites positively correlated with hsCRP. Importantly, Met2PY was associated with an unfavorable cytokine profile (higher TNFα/IL-10 ratio) and increased sICAM-1 levels, whereas no such associations were observed for Met4PY. Persistent dysregulation of NAD⁺ metabolism and accumulation of pyridone metabolites, particularly Met2PY, are associated with markers of chronic endothelial activation and inflammation in long COVID. These findings support the potential utility of Met2PY as a biomarker to identify patients at higher risk for endothelial dysfunction and cardiovascular events, enabling more personalized risk stratification and follow-up.

Classical Hodgkin lymphoma (cHL) is a biologically and clinically unique malignancy characterized by rare Hodgkin and Reed–Sternberg (HRS) cells surrounded by a dense and diverse inflammatory infiltrate. These malignant cells actively reshape the tumor microenvironment (TME) through metabolic reprogramming and immune evasion strategies. This review synthesizes current knowledge on how metabolic alterations contribute to tumor survival, immune dysfunction, and therapeutic resistance in cHL. We discuss novel therapeutic approaches aimed at disrupting these processes and examine the potential of combining metabolic interventions with immune-based strategies—such as immune checkpoint inhibitors (CPIs), epigenetic modulators, bispecific antibodies, and CAR-T/CAR-NK cell therapies—which may help overcome resistance and enhance anti-tumor responses. Several agents are currently under investigation for their ability to modulate immune cell metabolism and restore effective immune surveillance. Altogether, targeting metabolic vulnerabilities within both tumor and immune compartments offers a promising, multifaceted strategy to improve clinical outcomes in patients with relapsed or refractory cHL.

Hypercholesterolemia (Hch) is a risk factor for cerebrovascular and neurodegenerative diseases, manifesting with symptoms that vary depending on damage to specific brain regions. Hch triggers inflammatory responses and cell death. However, the progression of these processes in relation to the duration of Hch and the location of pathology in the central nervous system remains unclear. Therefore, we aimed to investigate (1) the impact of age and duration of Hch on neuroinflammatory responses and programmed cell death in the brain and (2) the intensity of these processes in various brain areas during Hch. In this study, we used 3-, 6-, and 12-month-old male Apo E^−/−/LDLR^−/− double-knockout mice and age-matched wild-type C57BL/6 mice (control group). Concentrations of cytokines IL-1β, IL-4, and IL-6, as well as apoptotic mediators AIF and Cas-3, were measured using enzyme-linked immunosorbent assay in the whole brain and separately in the prefrontal cortex (PFCx), hippocampus (HIP), and striatum (STR). The results showed that the Hch-induced release of cytokines IL-1β and IL-6, decreased expression of IL-4, and elevated level of apoptotic markers AIF and Cas-3 correlated with Hch duration. The inflammatory response and expression of apoptotic markers were more pronounced in the HIP and STR compared to the PFCx. Our results indicate a correlation between the neurodegenerative effects of Hch and its duration and highlight the varying susceptibility of different brain areas to Hch-induced damage. Graphical Abstract Hypercholesterolemia (Hch)-induced inflammatory response and programmed cell death activation in the prefrontal cortex (PFCx), hippocampus (HIP), and striatum (STR) of 3-, 6-, and 12-month-old, Apo E^−/−/LDLR^−/− double-knockout mice. In three age-groups the Hch-induced response involved release of inflammatory cytokines (IL-1ß and IL-6), a decrease of anti-inflammatory (IL-4) cytokine level, and activation of programmed cell death markers (AIF and Cas-3). The inflammatory response and expression of apoptotic markers were more pronounced in the HIP and STR, compared to the PFCx.

Mitochondrial dysfunction in failing hearts has been described as a driving force for energy deprivation and cardiomyocyte energy supply-demand imbalance. Isoproterenol (ISO), the β1/β2-adrenergic receptor agonist that leads to myocardial stress and mitochondrial damage, is extensively used for in vitro and in vivo studies to test the efficacy of therapeutic strategies in heart failure (HF). This study evaluated the cell morphology, nucleotide concentrations, and mitochondrial function of ISO-treated cardiomyocytes stimulated with the activators of mitochondrial biogenesis and nucleotide precursors. H9c2 rat cardiomyocyte line cells were treated with ISO in the presence of mitochondrial biogenesis stimuli quercetin (Que), rosiglitazone (Ros), S-Nitroso-N-acetyl-DL-penicillamin (SNAP), and NAD⁺ precursor, nicotinamide riboside (NR). The intracellular concentrations of nucleotides were analyzed using high-performance liquid chromato-graphy, and the Seahorse metabolic flux analyzer determined the mitochondrial function. ISO decreased intracellular ATP concentration in H9c2 cells as compared to control. The treatment with SNAP increased ATP concentration compared to ISO-only treated cells, while Que, Ros, and NR had no effect. NR treatment led to the elevation of intracellular NAD⁺ concentration, while the treatment with SNAP, Ros, and NR stimulated the mitochondrial respiration in ISO-pretreated H9c2 cells. In conclusion, mitochondrial biogenesis activators consistently improved cardiomyocyte mitochondrial function, but only selected molecules helped to improve ATP or NAD⁺ concentrations. This information may help to optimize treatment to ameliorate energy imbalance in failing cardiomyocytes.

4-pyridone-3-carboxamide-1-β-D-ribonucleoside (4PYR) is a nicotinamide derivative, considered a new oncometabolite. 4PYR formation induced a cytotoxic effect on the endothelium. Elevated blood 4PYR concentration was observed in patients with cancer. Still, little is known about the metabolic and functional effects of 4PYR in this pathology. The study aimed to investigate whether this toxic accumulation of 4PYR may affect the activity of anticancer therapy with cyclophosphamide in the orthotropic model of breast cancer. Female Balb/c mice were injected with 4T1 breast cancer cells and assigned into three groups: treated with PBS (Control), cyclophosphamide-treated (+CP), 4PYR-treated (+4PYR), and mice treated with both 4PYR and CP(+4PYR+CP) for 28 days. Afterward, blood and serum samples, liver, muscle, spleen, heart, lungs, aortas, and tumor tissue were collected for analysis of concentrations of nucleotides, nicotinamide metabolites, and 4PYR with its metabolites, as well as the liver level of cytochrome P450 enzymes. 4PYR treatment caused elevation of blood 4PYR, its monophosphate and a nicotinamide adenine dinucleotide (NAD+) analog—4PYRAD. Blood 4PYRAD concentration in the +4PYR+CP was reduced in comparison to +4PYR. Tumor growth and final tumor mass were significantly decreased in +CP and did not differ in +4PYR in comparison to Control. However, we observed a substantial increase in these parameters in +4PYR+CP as compared to +CP. The extracellular adenosine deamination rate was measured to assess vascular inflammation, and it was higher in +4PYR than the Control. Treatment with 4PYR and CP caused the highest vascular ATP hydrolysis and adenosine deamination rate. 4PYR administration caused significant elevation of CYP2C9 and reduction in CYP3A4 liver concentrations in both +4PYR and +4PYR+CP as compared to Control and +CP. In additional experiments, we compared healthy mice without cancer, treated with 4PYR (4PYR w/o cancer) and PBS (Control w/o cancer), where 4PYR treatment caused an increase in the serum proinflammatory cytokine expression as compared to Control w/o cancer. 4PYR accumulation in the blood interferes with cyclophosphamide anticancer activity and induces a pro-inflammatory shift of endothelial extracellular enzymes, probably by affecting its metabolism by cytochrome P450 enzymes. This observation may have crucial implications for the activity of various anticancer drugs metabolized by cytochrome P450.

Adenine nucleotides play a critical role in maintaining essential functions of red blood cells (RBCs), including energy metabolism, redox status, shape fluctuations and RBC-dependent endothelial and microvascular functions. Recently, it has been shown that infection with the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) might lead to morphological and metabolic alterations in erythrocytes in both mild and severe cases of coronavirus disease (COVID-19). However, little is known about the effects of COVID-19 on the nucleotide energetics of RBCs nor about the potential contribution of nucleotide metabolism to the long COVID syndrome. This study aimed to analyze the levels of adenine nucleotides in RBCs isolated from patients 12 weeks after mild SARS-CoV-2 infection who suffered from long COVID symptoms and to relate them with the endothelial and microvascular function parameters as well as the rate of peripheral tissue oxygen supply. Although the absolute quantities of adenine nucleotides in RBCs were rather slightly changed in long COVID individuals, many parameters related to the endothelial and microcirculatory function showed significant correlations with RBC adenosine triphosphate (ATP) and total adenine nucleotide (TAN) concentration. A particularly strong relationship was observed between ATP in RBCs and the serum ratio of arginine to asymmetric dimethylarginine—an indicator of endothelial function. Consistently, a positive correlation was also observed between the ATP/ADP ratio and diminished reactive hyperemic response in long COVID patients, assessed by the flow-mediated skin fluorescence (FMSF) technique, which reflected decreased vascular nitric oxide bioavailability. In addition, we have shown that patients after COVID-19 have significantly impaired ischemic response parameters (IR max and IR index), examined by FMSF, which revealed diminished residual bioavailability of oxygen in epidermal keratinocytes after brachial artery occlusion. These ischemic response parameters revealed a strong positive correlation with the RBC ATP/ADP ratio, confirming a key role of RBC bioenergetics in peripheral tissue oxygen supply. Taken together, the outcomes of this study indicate that dysregulation of metabolic processes in erythrocytes with the co-occurring endothelial and microvascular dysfunction is associated with diminished intracellular oxygen delivery, which may partly explain long COVID-specific symptoms such as physical impairment and fatigue.

Endothelial cells are a preferential target for SARS-CoV-2 infection. Previously, we have reported that vascular adenosine deaminase 1 (ADA1) may serve as a biomarker of endothelial activation and vascular inflammation, while ADA2 plays a critical role in monocyte and macrophage function. In this study, we investigated the activities of circulating ADA isoenzymes in patients 8 weeks after mild COVID-19 and related them to the parameters of inflammation and microvascular/endothelial function. Post-COVID patients revealed microvascular dysfunction associated with the changes in circulating parameters of endothelial dysfunction and inflammatory activation. Interestingly, serum total ADA and ADA2 activities were diminished in post-COVID patients, while ADA1 remained unchanged in comparison to healthy controls without a prior diagnosis of SARS-CoV-2 infection. While serum ADA1 activity tended to positively correspond with the parameters of endothelial activation and inflammation, sICAM-1 and TNFα, serum ADA2 activity correlated with IL-10. Simultaneously, post-COVID patients had lower circulating levels of ADA1-anchoring protein, CD26, that may serve as an alternative receptor for virus binding. This suggests that after the infection CD26 is rather maintained in cell-attached form, enabling ADA1 complexing. This study points to the possible role of ADA isoenzymes in cardiovascular complications after mild COVID-19.

Myocardial ischemic adenosine production decreases in subsequent events that may blunt its protective functions. To test the relation between total or mitochondrial cardiac adenine nucleotide pool (TAN) on the energy status with adenosine production, Langendorff perfused rat hearts were subjected to three protocols: 1 min ischemia at 40 min, 10 min ischemia at 50 min, and 1 min ischemia at 85 min in Group I; additional infusion of adenosine (30 µM) for 15 min after 10 min ischemia in Group I-Ado, and 1 min ischemia at 40 and 85 min in the controls (Group No I). A ³¹P NMR and an HPLC were used for the analysis of nucleotide and catabolite concentrations in the heart and coronary effluent. Cardiac adenosine production in Group I measured after 1 min ischemia at 85 min decreased to less than 15% of that at 40 min in Group I, accompanied by a decrease in cardiac ATP and TAN to 65% of the initial results. Adenosine production at 85 min was restored to 45% of that at 40 min in Group I-Ado, accompanied by a rebound of ATP and TAN by 10% vs. Group I. Mitochondrial TAN and free AMP concentrations paralleled that of total cardiac TAN. Changes in energy equilibrium or mitochondrial function were minor. This study highlights that only a fraction of the cardiac adenine nucleotide pool is available for adenosine production, but further studies are necessary to clarify its nature.