Search Results (861)

Background and Objectives: Cardiac transplantation is currently the elective treatment choice in end-stage heart failure, and cellular rejection is a predictive factor for morbidity and mortality after surgery. We proposed an evaluation of the clinicopathologic factors involved in the mechanism of rejection. Materials and Methods: This study included 146 patients who underwent transplantation at the Institute of Cardiovascular Diseases and Transplantation in Targu Mures between 2010 and 2023, and we evaluated the function and structure of the myocardium after surgery by using endomyocardial biopsy. Results: Overall, 120 men and 26 women underwent transplantation, with an approximately equal proportion under and over 40 years old (48.6% and 51.4%). Evaluating the degree of acute cellular rejection according to the International Society for Heart and Lung Transplantation classification showed that most of the patients presented with acute cellular rejection (ACR) and antibody-mediated rejection (AMR) grade 0, and most cases of ACR and AMR were reported with mild changes (13% or 10.3% patients). Therefore, the most frequent histopathologic diagnoses were similar to lesions unrelated to rejection (45.2% of patients) and ischemia–reperfusion lesions (25.3% patients), respectively. Conclusions: Although 82.2% of the transplanted cases showed no rejection (ISHLT score 0), non-rejection-related lesion-like changes were present in 45.2% of cases, and because more of the non-rejection-related criteria could be detected, it may be necessary to adjust the grading of the rejection criteria. The histopathologic changes that characterize rejection are primarily represented by the mononuclear inflammatory infiltrate; in our study, inflammatory changes were mostly mild (71.9%), with myocyte involvement in all cases. These changes are associated with and contribute to the maintenance of the rejection phenomenon. Full article

Background/Objectives: The incidence of cardiac morbimortality in patients with relapsed/refractory (R/R) acute myeloid leukemia (AML) is unknown. Methods: We analyze the characteristics, incidence, risk factors, and outcomes of cardiac events in AML patients treated for second-line (2L) or third-line (3L) episodes. Results: Among 327 2L AML patients (median age 62 years old), 135 experienced cardiac events, with an incidence of 38.6% non-fatal and 1.3% fatal events at 6 months. The grade 1–2 incidence was 16.8%, and the grade 3–4 incidence was 23.5% at 6 months. Overall, 207 cardiac events occurred in the 2L cohort, the most frequent being hypertension (n = 45), bradycardia (n = 39), QTc prolongation (n = 35), heart failure (n = 33), syncope/presyncope (n = 22), arrhythmia (n = 18), and myocardial ischemia (n = 8). Median OS in the 2L cohort was 9.4 months, 21.4 months in patients with grade 1–2, 8.8 months in patients without a cardiac event, 7.6 months in grade 3–4 patients, and 2.1 months with in 5 patients (p = 0.0035). The multivariate analysis showed prior cardiologic antecedents (p = 0.013), intensive 2L chemotherapy (p = 0.01), and inclusion in a 2L clinical trial (p < 0.001) as independent risk factors for non-fatal cardiac events. Among 189 patients of the 3L cohort, the incidence of non-fatal and fatal cardiac events was 49.2% and 0% at 6 months, respectively. Non-fatal cardiac events were more frequent in patients with prior cardiac antecedents (p = 0.004). Conclusions: In summary, cardiotoxicity is a frequent and challenging complication in R/R AML patients. We identified the risk factors that could be relevant to implementing risk-adapted management guidelines, aiming to reduce morbi-mortality in this difficult-to-treat setting. Full article

Cardiovascular diseases (CVD), such as myocardial hypertrophy, heart failure, atherosclerosis, and myocardial ischemia/reperfusion (I/R) injury, are among the major threats to human health worldwide. Post-translational modifications alter the function of proteins through dynamic chemical modification after synthesis. This mechanism not only plays an important role in maintaining homeostasis and plays a crucial role in maintaining normal cardiovascular function, but is also closely related to the pathological state of various diseases. Histone deacetylases (HDACs) play an important role in the epigenetic regulation of gene expression, and play important roles in post-translational modification by catalyzing the deacetylation of key lysine residues in nucleosomal histones, which are closely associated with the occurrence and development of cardiovascular diseases. Recent studies indicate that HDAC inhibitors (HDACis) may represent a new class of drugs for the treatment of cardiovascular diseases by influencing post-translational modifications. In this review, we systematically summarize the mechanism of action of HDACs and HDACis in post-translational modifications related to common cardiovascular diseases, providing new ideas for the treatment of CVD, and explore possible future research directions on the relationship between HDAC and HDACi in post-translational modifications and cardiovascular diseases. Full article

Objective: This study aimed to investigate the cardioprotective effects of bosentan, an endothelin receptor antagonist, in a rat model of lung ischemia–reperfusion (I/R) injury, with a focus on myocardial tissue involvement. Methods: Twenty-four male Wistar rats were randomly assigned to four groups: sham, bosentan, I/R, and I/R + bosentan. Lung I/R injury was induced by hilar clamping for 45 min, followed by 60 min of reperfusion. Bosentan (30 mg/kg) was administered intraperitoneally 30 min prior to the procedure. Myocardial tissue was evaluated histopathologically for structural disorganization, inflammation, fibrosis, and edema. TGF-β1 protein levels in myocardial tissue were compared across the groups using β-actin as the loading control. ELISA was used to quantify ET-1, NF-κB, and p53 levels, while spectrophotometric analysis was employed to assess MDA levels and the activities of SOD and CAT enzymes in heart tissue. Results: The I/R group exhibited significant myocardial disorganization, inflammation, and interstitial edema compared to the sham and bosentan groups. Bosentan treatment markedly ameliorated these histopathological alterations. Additionally, the I/R group showed elevated levels of ET-1, NF-κB, p53, and MDA, along with reduced SOD and CAT activities; these changes were significantly attenuated by bosentan administration. Bosentan treatment significantly reduced myocardial ET-1 levels (from 136.88 ± 5.02 to 120.18 ± 2.67 nmol/g, p = 0.003), NF-κB levels (from 0.87 ± 0.04 to 0.51 ± 0.03 ng/mg, p = 0.002), and TGF-β1 expression (from 1.72 ± 0.10 to 0.91 ± 0.08 relative units, p = 0.001). Moreover, bosentan increased antioxidant enzyme activities, elevating SOD levels from 21.45 ± 1.23 to 32.67 ± 1.45 U/mg protein (p = 0.001) and CAT levels from 15.22 ± 0.98 to 25.36 ± 1.12 U/mg protein (p = 0.002). Conclusions: Bosentan exerts cardioprotective effects in rats subjected to lung I/R injury by reducing myocardial damage, inflammation, and oxidative stress. These findings suggest that bosentan may serve as a potential therapeutic agent for preventing remote organ injury associated with pulmonary I/R. Full article

Acute myocardial hypoxia/ischemia is associated with abnormal accumulation of myocardial lipids, including dihydroceramides. Here, we characterized how dihydroceramides are remodeled in response to hypoxia and assessed how dihydroceramide remodeling correlates to human cardiac pathophysiology. Hypoxia resulted in a marked accumulation of very-long-chain (VLC)-dihydroceramides in cultured HL-1 cardiomyocytes. In humans, we identified a correlation between the abundance of VLC-dihydroceramides in myocardial biopsies and arrhythmias and heart failure and showed that cardiac expression of CERS2, coding for an enzyme that promotes synthesis of VLC-dihydroceramides, was associated with signaling pathways linked to cardiac arrhythmia and cardiomyopathy. In cultured HL-1 cardiomyocytes, we showed that CerS2 knockdown reduced accumulation of VLC dihydroceramides and altered the expression of mediators regulating Ca²⁺ cycling and electrical conduction. In conclusion, our findings indicate that increased abundance of VLC-dihydroceramides, promoted by increased activity of CerS2 in response to hypoxia, could play a role in cardiac arrhythmias and heart failure. Full article

Cardiac remodeling in feline hypertrophic cardiomyopathy (HCM) is poorly understood. To investigate underlying molecular mechanisms, we determined microRNA–mRNA interactions, regulatory networks, and upstream regulators using left ventricle (LV) and left atrium (LA) mRNA and microRNA sequencing datasets from cats with HCM and controls. Upstream regulators, molecules, and pathways associated with ischemia, inflammation, fibrosis, and cellular changes were observed in the HCM heart. In both the HCM LV and LA, TNFα, IL1β, and TGFβ were identified as upstream regulators, along with FGF23, THBS4, and FAMB177 as the top increased molecules. Relevant microRNAs included upstream regulator miR-132, enriched miR-124-3p, miR-122b-3p, miR-146-5p (HCM LV and LA), miR-370, miR-1185-5p, miR-12194-3p (HCM LV), miR-153-3p, miR-185-5p, and miR-185-3p (HCM LA). Macrophage pathways were activated, and granulocyte and agranulocyte adhesion and diapedesis were the most connected pathways. The HIF1α signaling pathway in the HCM LV, upstream regulators miR-1-3p and miR-204, and reduced miR-29 and miR-122-5p suggest cardioprotective mechanisms. Observed in the healthy heart and suspected to be involved in cardiac homeostasis were upstream regulators miR-96, inhibited WNT3A and miR-145, as well as miR-140-5p, miR-141-3p, miR-208b-3p, and miR-885-3p. This study provides further insights into the pathogenesis of HCM, and identifies the factors involved in the maintenance of a healthy LV and LA. Full article

Acute heart failure (AHF) is a clinical syndrome characterized by the sudden onset or rapid worsening of heart failure signs and symptoms, frequently triggered by myocardial ischemia, pressure overload, or cardiotoxic injury. A central component of its pathophysiology is the activation of intracellular signal transduction cascades that translate extracellular stress into cellular responses. Among these, the mitogen-activated protein kinase (MAPK) pathways have received considerable attention due to their roles in mediating inflammation, apoptosis, hypertrophy, and adverse cardiac remodeling. The canonical MAPK cascades—including extracellular signal-regulated kinases (ERK1/2), p38 MAPK, and c-Jun N-terminal kinases (JNK)—are activated by upstream stimuli such as angiotensin II (Ang II), aldosterone, endothelin-1 (ET-1), and sustained catecholamine release. Additionally, emerging evidence highlights the role of receptor-mediated signaling, cellular stress, and myeloid cell-driven coagulation events in linking MAPK activation to fibrotic remodeling following myocardial infarction. The phosphatidylinositol 3-kinase (PI3K)/Akt signaling cascade plays a central role in regulating cardiomyocyte survival, hypertrophy, energy metabolism, and inflammation. Activation of the PI3K/Akt pathway has been shown to confer cardioprotective effects by enhancing anti-apoptotic and pro-survival signaling; however, aberrant or sustained activation may contribute to maladaptive remodeling and progressive cardiac dysfunction. In the context of AHF, understanding the dual role of this pathway is crucial, as it functions both as a marker of compensatory adaptation and as a potential therapeutic target. Recent reviews and preclinical studies have linked PI3K/Akt activation with reduced myocardial apoptosis and attenuation of pro-inflammatory cascades that exacerbate heart failure. Among the multiple signaling pathways involved, glycogen synthase kinase-3β (GSK-3β) has emerged as a key regulator of apoptosis, inflammation, metabolic homeostasis, and cardiac remodeling. Recent studies underscore its dual function as both a negative regulator of pathological hypertrophy and a modulator of cell survival, making it a compelling therapeutic candidate in acute cardiac settings. While earlier investigations focused primarily on chronic heart failure and long-term remodeling, growing evidence now supports a critical role for GSK-3β dysregulation in acute myocardial stress and injury. This comprehensive review discusses recent advances in our understanding of the MAPK signaling pathway, the PI3K/Akt cascade, and GSK-3β activity in AHF, with a particular emphasis on mechanistic insights, preclinical models, and emerging therapeutic targets. Full article

Background: Coronary heart disease (CHD) remains the most prevalent pathology within the circulatory system. Among its chronic complications, ischemic mitral valve regurgitation (IMR) is observed in approximately 15% of patients with sustained myocardial ischemia. The presence of this complex valvular defect significantly increases both overall mortality and the incidence of adverse cardiovascular events. Notably, the presence of moderate to severe mitral regurgitation in patients undergoing surgical revascularization has been shown to double the risk of death. Despite the well-established etiology of IMR, data regarding the efficacy of surgical interventions and the determinants of postoperative outcomes remain inconclusive. Methods: The objective of the present study was to evaluate both early and long-term outcomes of surgical treatment of mitral regurgitation in patients undergoing coronary artery bypass grafting (CABG) due to ischemic heart disease. Particular attention was given to the influence of the severity of regurgitation, left ventricular ejection fraction (LVEF), and the dimensions of the left atrium (LA) and left ventricle (LV) on the postoperative prognosis. An additional aim was to identify preoperative risk factors associated with increased postoperative mortality and morbidity. A retrospective analysis was conducted on 421 patients diagnosed with ischemic mitral regurgitation who underwent concomitant mitral valve surgery and CABG. Exclusion criteria included emergent and urgent procedures as well as non-ischemic etiologies of mitral valve dysfunction. Results: The study cohort comprised 34.9% women and 65.1% men, with the mean age of 65.7 years (±7.57). A substantial proportion (76.7%) of patients were aged over 60 years. More than half (51.5%) presented with severe heart failure symptoms, classified as NYHA class III or IV, while over 70% were categorized as CCS class II or III. Among the surgical procedures performed, 344 patients underwent mitral valve repair, and 77 patients required mitral valve replacement. Additionally, 119 individuals underwent concomitant tricuspid valve repair. Short-term survival was significantly affected by the presence of hypertension, prior cerebrovascular events, and chronic kidney disease. In contrast, hypertension and chronic obstructive pulmonary disease were identified as significant predictors of adverse late-term outcomes. Conclusions: Interestingly, neither the preoperative severity of mitral regurgitation nor the echocardiographic measurements of LA and LV dimensions were found to significantly influence surgical outcomes. The perioperative risk, as assessed by the EuroSCORE II (average score: 10.0%), corresponded closely with observed mortality rates following mitral valve repair (9.9%) and replacement (10.4%). Notably, the need for concomitant tricuspid valve surgery was associated with an elevated mortality rate (12.4%). Furthermore, the preoperative echocardiographic evaluation of LA regurgitation severity, as well as LA and LV dimensions, did not exhibit a statistically significant impact on either early or long-term surgical outcomes. However, a reduced LVEF was correlated with increased long-term mortality. The presence of advanced clinical symptoms and the necessity for tricuspid valve repair were independently associated with a poorer late-term prognosis. Importantly, the annual mortality rate observed in the late-term follow-up of patients who underwent surgical treatment of ischemic mitral regurgitation was lower than rates reported in the literature for patients managed conservatively. The EuroSCORE II scale proved to be a reliable and precise tool in predicting surgical risk and outcomes in this patient population. Full article

Background/Objectives: Ischemic postconditioning (IP) is a well-established intervention that mitigates this damage by activating endogenous cardioprotective pathways. However, the presence of comorbidities such as dyslipidemia can disrupt these protective mechanisms and abolish the infarct-sparing effect typically induced by IP. In this context, identifying pharmacological strategies to restore cardioprotection is of clinical relevance. This study aimed to evaluate whether N-acetylcysteine (NAC), a glutathione precursor with antioxidant properties, can restore the infarct-limiting effect of IP compromised by HFD-induced oxidative stress. Methods: Male mice were fed a control diet (CD) or HFD for 12 weeks. NAC (10 mM) was administered in drinking water for 3 weeks before ex vivo myocardial ischemia/reperfusion (I/R) injury (30 min ischemia/60 min reperfusion). In IP groups, six cycles of brief I/R were applied at the onset of reperfusion. Infarct size, ventricular function, redox status (GSH/GSSG), lipid profile, and histology were evaluated. Results: NAC improved the lipid profile (HDL/non-HDL ratio) and enhanced the infarct-sparing effect of IP in CD-fed mice. In HFD-fed mice, NAC restored the efficacy of IP, significantly reducing infarct size (HFD-I/R-NAC: 39.7 ± 4.5% vs. HFD-IP-NAC: 26.4 ± 2.0%, p < 0.05) without changes in ventricular function. The ratio of oxidized/reduced glutathione (GSSG/GSH) is depicted. Under basal conditions, the hearts of mice fed an HFD exhibited a shift towards a more oxidized state compared to the control diet CD group. In the I/R protocol, a significant shift towards a more oxidized state was observed in both CD and HFD-fed animals. In the IP protocol, the GSSG/GSH ratio revealed a tendency to basal values in comparison to the I/R protocol. The analysis indicates that animals subjected to I/R and IP protocols in conjunction with NAC show a tendency to reach basal values, thus suggesting a potential for the reduction in ROS. Conclusions: NAC treatment mitigates oxidative stress and restores the cardioprotective effect of ischemic postconditioning in a model of early-stage atherosclerosis. These findings support NAC as a potential adjunct therapy to improve myocardial resistance to reperfusion injury under dyslipidemic conditions Full article

Despite significant advances in understanding and management, cardiovascular diseases remain the leading cause of mortality worldwide. Historically, diagnostic and therapeutic strategies have typically targeted obstructive coronary arteries. However, growing evidence supports the pivotal role of non-obstructive mechanisms in myocardial ischemia, prompting a new classification that distinguishes Acute Myocardial Ischemic Syndromes from Non-Acute Myocardial Ischemic Syndromes. In this evolving context, Optical Coherence Tomography (OCT) plays an important diagnostic role in the assessment of both obstructive and non-obstructive ischemic mechanisms. In Acute Myocardial Ischemic Syndromes, OCT enables the identification of major plaque destabilization mechanisms and contributes to the diagnosis of Myocardial Infarction with Non-Obstructive Coronary Arteries, helping to differentiate between atherosclerotic and non-atherosclerotic causes. In Non-Acute Myocardial Ischemic Syndromes, OCT assists in evaluating stenosis severity, plaque morphology, vulnerability, and healing, and may contribute to the diagnosis of Ischemia with Non-Obstructive Coronary Arteries, identifying myocardial bridge and epicardial spasm alongside conventional functional assessment of intermediate stenoses. This narrative review outlines the expanding clinical applications of OCT across the full spectrum of ischemic syndromes, emphasizing its role in bridging obstructive and non-obstructive pathophysiology and supporting a more comprehensive diagnostic approach to ischemic heart disease. Full article

Chronic total occlusions (CTOs), defined as complete coronary artery blockages persisting for over three months, are frequently encountered in up to 25% of coronary angiograms. Although percutaneous coronary intervention (PCI) for CTO remains technically challenging, advancements in guidewires, microcatheters, re-entry devices, and intravascular imaging, along with the expertise of specialized operators, have significantly improved procedural success rates, now exceeding 90% in expert centers. While recent evidence, such as the SYNTAX II study, emphasizes the importance of complete revascularization, over half of CTO cases continue to be managed conservatively with optimal medical therapy (OMT), partly due to the limited high-quality randomized evidence supporting revascularization. Observational studies have demonstrated that successful CTO-PCI is associated with improved angina relief, quality of life, left ventricular function, and possibly long-term survival. Extended observational follow-up, such as the Korean and Canadian registries, suggests long-term reductions in cardiac and all-cause mortality with CTO revascularization. However, randomized controlled trials (RCTs) have primarily shown symptomatic benefit, with no consistent reduction in major adverse cardiac events (MACE) or mortality, likely due to limited sample sizes, short follow-up, and treatment crossovers. Various strategies, including the hybrid algorithm, guide CTO interventions by balancing antegrade and retrograde techniques based on lesion complexity. Imaging modalities such as coronary CT angiography and intravascular ultrasound play a pivotal role in planning and optimizing these procedures. Future innovations, such as real-time fusion imaging of CCTA with coronary angiography, may enhance lesion visualization and guidewire navigation. While current guidelines recommend CTO-PCI in selected symptomatic patients with demonstrable ischemia or viable myocardium, the decision should be individualized, incorporating anatomical feasibility, comorbidities, patient preferences, and input from a multidisciplinary Heart Team. Looking ahead, adequately powered RCTs with extended follow-up are essential to determine the long-term clinical impact of CTO-PCI on hard outcomes such as mortality and myocardial infarction. Full article

(1) Background: Previous studies indicate that individuals who engage in regular physical activity have a higher pain threshold than those who do not exercise. However, it remains unclear how this phenomenon behaves in individuals exposed to chronic hypoxia. This study evaluates pain perception at high altitude between high-altitude natives who exercised regularly and those who did not practice physical activity. (2) Methods: Eighty-four healthy volunteers aged 20 to 30 years old with a body mass index (BMI) within the normal range (18.5–24.9) residing in the city of Puno (3825 m) were recruited. The unilateral ischemia pain provocation test was used, applying pressure with a manual sphygmomanometer to generate transient ischemia in the arm while the patient opens and closes their hand. Onset, peak, and resolution times of pain, heart rate, and oxygen saturation were recorded. (3) Results: The average time to pain onset in the right arm was 30.2 s ± 14.1 during light physical activity, whereas, during moderate physical activity, it increased to 32.5 s ± 15.4. In the left arm, the average time until pain sensation was 27.9 s ± 16.8 during light physical activity and increased to 34.6 s ± 18.5 with moderate physical activity. Regarding the progression of pain intensity, the average time to reach unbearable pain in the right arm was 54.1 s ± 16.4 during light physical activity and 53.8 s ± 19.6 during moderate physical activity; in the left arm, it was 53.0 s ± 19.6 during light physical activity, increasing to 59.3 s ± 24.5 during moderate physical activity. (4) Conclusions: A more stable and slightly higher pain tolerance in the dominant arm was observed. Full article

Cardiotoxicity is a leading cause of mortality in the growing populations of elderly breast cancer (BC) patients. Breast cancer treatment in the elderly is highly challenging due to its heterogeneous nature and the lack of specific evidence, as this population is usually underrepresented in randomized clinical trials. Decision making requires a comprehensive approach, considering the type and stage of BC, the patient’s overall health status, life expectancy, geriatric and frailty assessment, the risk of cancer recurrence, comorbidities, cardiotoxicity risk, and the patient’s preferences. The cardiotoxic effects of BC treatments cover the whole spectrum of cardiovascular diseases: heart failure, hypertension, arrhythmias, and myocardial ischemia. Cardiotoxicity risk in these patients is defined by several factors: anticancer therapies, polypharmacy, established cardiovascular disease, comorbidities, frailty, cellular senescence, hormonal changes, and genetic predisposition. Preventive oncological and cardio-oncological strategies, as well as patients’ education, are critical for improved outcomes. Prospective clinical trials in this population are urgently needed. Full article

Cardiovascular diseases remain the leading cause of death worldwide, highlighting the urgent need for novel therapeutic strategies. The Mediterranean diet is renowned for its cardiovascular benefits, largely attributed to extra virgin olive oil (EVOO) and its phenolic compounds, particularly hydroxytyrosol (HT). HT, a potent antioxidant and anti-inflammatory agent, has demonstrated significant therapeutic potential in mitigating myocardial damage following acute myocardial infarction (AMI). However, there is a notable lack of published evidence regarding the effects of HT administration in the context of acute ischemia/reperfusion (I/R) injury, making this study a novel contribution to the field. This study aimed to evaluate the cardioprotective effects of HT using the Langendorff technique in an isolated mouse heart ischemia/reperfusion (I/R) model. Mice were administered a single intraperitoneal dose of HT (10 mg/kg) 24 h prior to the I/R protocols, and parameters such as the infarct size, mitochondrial function, and redox balance were assessed. The results revealed a remarkable 57% reduction in infarct size in HT-treated mice compared to untreated controls. HT treatment also improved mitochondrial bioenergetics, as evidenced by the increased membrane potential (ΔΨm), enhanced oxygen consumption, and reduced hydrogen peroxide (H₂O₂) production. Furthermore, HT restored the activity of the mitochondrial respiratory complexes, notably Complex I, even under I/R conditions. These findings highlight the efficacy of HT in reducing oxidative stress and preserving mitochondrial function, critical factors in cardiac disease. In conclusion, HT emerges as a promising therapeutic agent for ischemic heart disease, demonstrating both preventive and restorative potential. Future research should explore its clinical applicability to advance cardiovascular disease management. Full article

Cardioprotection against ischemia is achieved using openers of mitochondrial ATP-sensitive K⁺ (mitoKATP) channels such as diazoxide (DZX), leading to pharmacological preconditioning (PPC). We previously reported that PPC decreases the abundance of ventricular Cav1.2 channels, but PPC’s effects on other channels remain largely unexplored. In this study, we hypothesized that DZX regulates the expression of hyperpolarization-activated cyclic nucleotide potassium channel 4 (HCN4) channels in sinoatrial node cells (SANCs), the specialized cardiomyocytes that generate the heartbeat. DZX increased the heart rate in intact adult rats. Patch-clamp experiments revealed an increase in the magnitude of ionic currents through HCN4 channels, which was abolished by the reactive oxygen species (ROS) scavenger N-acetylcysteine (NAC) and the selective mitoKATP channel inhibitor 5-hydroxydecanoate (5-HD). Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and Western blot assays showed that DZX increased HCN4 channel expression at the mRNA and protein levels. Immunofluorescence analyses revealed that PPC increased HCN4 fluorescence, which was abolished by NAC. DZX increased nuclear translocation of c-Fos and decreased protein abundance of RE1 silencing transcription factor (REST)/neuron-restrictive silencer factor (NRSF), suggesting the involvement of these factors. Our results suggest that PPC increases the heart rate by upregulating HCN4 channel expression through a mechanism involving c-Fos, REST, and ROS. Full article