Proinflammatory Cytokines Are Soluble Mediators Linked with Ventricular Arrhythmias and Contractile Dysfunction in a Rat Model of Metabolic Syndrome

Implications for neutrophils in cardiac arrhythmias

Cardiac arrhythmias commonly occur as a result of aberrant electrical impulse formation or conduction in the myocardium. Frequently discussed triggers include underlying heart diseases such as myocardial ischemia, electrolyte imbalances, or genetic anomalies of ion channels involved in the tightly regulated cardiac action potential. Recently, the role of innate immune cells in the onset of arrhythmic events has been highlighted in numerous studies, correlating leukocyte expansion in the myocardium to increased arrhythmic burden. Here, we aim to call attention to the role of neutrophils in the pathogenesis of cardiac arrhythmias and their expansion during myocardial ischemia and infectious disease manifestation. In addition, we will elucidate molecular mechanisms associated with neutrophil activation and discuss their involvement as direct mediators of arrhythmogenicity.

Oxidative stress in early metabolic syndrome impairs cardiac RyR2 and SERCA2a activity and modifies the interplay of these proteins during Ca2+ waves

We investigated how oxidative stress (OS) alters Ca2+ handling in ventricular myocytes in early metabolic syndrome (MetS) in sucrose-fed rats. The effects of N-acetyl cysteine (NAC) or dl-Dithiothreitol (DTT) on systolic Ca2+ transients (SCaTs), diastolic Ca2+ sparks (CaS) and Ca2+ waves (CaW), recorded by confocal techniques, and L-type Ca2+ current (ICa), assessed by whole-cell patch clamp, were evaluated in MetS and Control cells. MetS myocytes exhibited decreased SCaTs and CaS frequency but unaffected CaW propagation. In Control cells, NAC/DTT reduced RyR2/SERCA2a activity blunting SCaTs, CaS frequency and CaW propagation, suggesting that basal ROS optimised Ca2+ signalling by maintaining RyR2/SERCA2a function and that these proteins facilitate CaW propagation. Conversely, NAC/DTT in MetS recovered RyR2/SERCA2a function, improving SCaTs and CaS frequency, but unexpectedly decreasing CaW propagation. We hypothesised that OS decreases RyR2/SERCA2a activity at early MetS, and while decreased SERCA2a favours CaW propagation, diminished RyR2 restrains it.

Soluble factors in COVID-19 mRNA vaccine-induced myocarditis causes cardiomyoblast hypertrophy and cell injury: a case report

BACKGROUND

Inflammation affecting the heart and surrounding tissues is a clinical condition recently reported following COVID-19 mRNA vaccination. Assessing trends of these events related to immunization will improve vaccine safety surveillance and best practices for forthcoming vaccine campaigns. However, the causality is unknown, and the mechanisms associated with cardiac myocarditis are not understood.

CASE PRESENTATION

After the first dose, we reported an mRNA vaccine-induced perimyocarditis in a young patient with a history of recurrent myocardial inflammation episodes and progressive loss of cardiac performance. We tested this possible inflammatory cytokine-mediated cardiotoxicity after vaccination in the acute phase (ten days), and we found a significant elevation of MCP-1, IL-18, and IL-8 inflammatory mediators. Still, these cytokines decreased considerably at the recovery phase (42 days later). We used the cardiomyoblasts cell line to test the effect of serum on cell viability, observing that serum from the acute phase reduced the cell viability to 75%. We did not detect this toxicity in cells when we tested serum from the patient in the recovery phase. We also tested serum-induced hypertrophy, a phenomenon in myocarditis and heart failure. We found that acute phase-serum has hypertrophy effects, increasing 25% of the treated cardiac cells' surface and significantly increasing B-type natriuretic peptide. However, we did not observe the hypertrophic effect in the recovery phase or sera from healthy controls.

CONCLUSION

Our results opened the possibility of the inflammatory cytokines or serum soluble mediators as key factors for vaccine-associated myocarditis. In this regard, identifying anti-inflammatory molecules that reduce inflammatory cytokines could help avoid vaccine-induced myocardial inflammation.

Immune Checkpoint Inhibitors Related to Cardiotoxicity

Immune checkpoint inhibitors (ICIs) have now emerged as a mainstay of treatment for various cancers. Along with development of ICIs, immune-related adverse effects (irAEs) have aroused wide attention. The cardiac irAE, one of the rare but potentially fatal effects, have been reported recently. However, the clinical comprehension of cardiac irAEs remains limited and guidelines are inadequate for cardio-oncologists to tackle the problem. In this review, we have summarized current classifications of, manifestations of, potential mechanisms of, and treatment for ICI-related myocardial injury in order to provide some clues for the understanding of cardiac irAEs in clinical work.

Integrating Evidence of the Traditional Chinese Medicine Collateral Disease Theory in Prevention and Treatment of Cardiovascular Continuum

Cardiovascular disease has become a major public health problem. The concept of “cardiovascular continuum” refers to the continuous process from the risk factors that lead to arteriosclerosis, vulnerable plaque rupture, myocardial infarction, arrhythmia, heart failure, and death. These characteristics of etiology and progressive development coincide with the idea of “preventing disease” in traditional Chinese medicine (TCM), which corresponds to the process of systemic intervention. With the update of the understanding via translational medicine, this article reviews the current evidence of the TCM collateral disease theory set prescriptions in both mechanical and clinical aspects, which could lead to the development of new therapeutic strategies for prevention and treatment.

P2X7 Receptor and Heart Function in a Mouse Model of Systemic Inflammation Due to High Fat Diet

Purpose

Low-grade inflammation contributes to heart failure in obesity or type 2 diabetes mellitus. The P2X7 receptor (P2X7R) is a key regulator of several pro-inflammatory responses in multiple tissues and organs; however, its involvement in the onset of heart dysfunction remains unclear. The study evaluated the role of P2X7R as a cardiac function regulator in C57BL/6J wild-type (WT) and P2X7R knockout (KO) mice by inducing systemic inflammation with high fat diet (HFD).

Methods

Specific parameters of systolic and diastolic function and heart morphology were measured in vivo before animal sacrifice by high-frequency ultrasonographic analysis. Gene and protein expression of cardiac biomarkers associated with inflammatory-oxidative pathways were evaluated by real-time PCR and Western Blotting.

Results

P2X7R-mediated up-regulation of the NLRP3-caspase-1 complex, increased expression of key oxidative stress (NOS-2, TNFα), and chemotactic (MCP-1) mediators were revealed in WT-HFD animals. In KO-HFD mice, such inflammatory-oxidative pathway was silent. Nevertheless, HFD induced in vivo a clear alteration of diastolic pattern (E/A: p < 0.03 vs WT-HFD) and a cardiac morphologic remodelling (left ventricular mass: p < 0.05 vs WT-HFD) only in P2X7R KO animals. Surprisingly, the transcriptional and protein expression of IL-1β and IL-6, usually regulated through P2X7R activation, were significantly higher in KO-HFD than in WT-HFD mice (both p < 0.05). Furthermore, an up-regulation of miR-214 and a down-regulation of miR-126 in heart of HFD-KO mice were observed, suggesting a link between such epigenetic dysregulation and cytokine overexpression as a potential pathophysiologic mechanism concurring to the progressive cardiac dysfunction.

Conclusion

These findings seem to suggest a cardioprotective role of P2X7R toward this tissue-specific inflammatory damage, likely through tissue homeostasis and organ functionality preservation.

A Systematic Review of the Mechanisms Involved in Immune Checkpoint Inhibitors Cardiotoxicity and Challenges to Improve Clinical Safety

Immune checkpoint inhibitors (ICIs) are monoclonal antibodies that block CTLA-4, PD-1, or PD-L1 and induce the activation of the immune system against cancer. Despite the efficacy of ICIs, which has improved the oncotherapy for patients with a variety of malignancies, several immune-related adverse events (irAEs) have been described, including those affecting the heart. Cardiac irAEs after ICI therapies, including myocarditis, can become life-threatening, and their pathogenic mechanisms remain unclear. Here, a systematic analysis was performed regarding the potential immune mechanisms underlying cardiac irAEs based on the immune adverse events induced by the ICIs: 1) recruitment of CD4⁺ and CD8⁺ T cells, 2) autoantibody-mediated cardiotoxicity, and 3) inflammatory cytokines. Furthermore, the impact of dual therapies in ICI-induced cardiac irAEs and the potential risk factors are reviewed. We propose that self-antigens released from cardiac tissues or cancer cells and the severity/advancement of cancer disease have an important role in ICI cardiotoxicity.

Soluble Epoxide Hydrolase Inhibitors Regulate Ischemic Arrhythmia by Targeting MicroRNA-1

Background: Soluble epoxide hydrolase inhibitors (sEHis) inhibit the degradation of epoxyeicosatrienoic acids (EETs) in cells, and EETs have antiarrhythmic effects. Our previous experiments confirmed that t-AUCB, a preparation of sEHis, inhibited ischemic arrhythmia by negatively regulating microRNA-1 (miR-1), but its specific mechanism remained unclear. Aim: This study aimed to examine the role of serum response factor (SRF) and the PI3K/Akt/GSK3β pathway in t-AUCB-mediated regulation of miR-1 and the interaction between them. Methods/Results: We used SRF small interfering RNA (siSRF), SRF small hairpin (shSRF) RNA sequence adenovirus, PI3K/Akt/GSK3β pathway inhibitors, t-AUCB, and 14,15-EEZE (a preparation of EETs antagonists) to treat mouse cardiomyocytes overexpressing miR-1 and mice with myocardial infarction (MI). We found that silencing SRF attenuated the effects on miR-1 and its target genes KCNJ2 and GJA1 in the presence of t-AUCB, and inhibition of the PI3K/Akt/GSK3β pathway antagonized the effects of t-AUCB on miR-1, KCNJ2, and GJA1, which were associated with PI3Kα, Akt, and Gsk3β but not PI3Kβ or PI3Kγ. Moreover, the PI3K/Akt/GSK3β pathway was involved in the regulation of SRF by t-AUCB, and silencing SRF inhibited the t-AUCB-induced increases in Akt and Gsk3β phosphorylation. Conclusions: Both the SRF and the PI3K/Akt/GSK3β pathway are involved in the t-AUCB-mediated regulation of miR-1, and these factors interact with each other.

Updates on epicardial adipose tissue mechanisms on atrial fibrillation

Obesity is a well-known risk factor for atrial fibrillation (AF). Local epi-myocardial or intra-myocardial adiposity caused by aging, obesity, or cardiovascular disease (CVD) is considered to be a better predictor of the risk of AF than general adiposity. Some of the described mechanisms suggest that epicardial adipose tissue (EAT) participates in structural remodeling owing to its endocrine activity or its infiltration between cardiomyocytes. Epicardial fat also wraps up the ganglionated plexi that reach the myocardium. Although the increment of volume/thickness and activity of EAT might modify autonomic activity, autonomic system dysfunction might also change the endocrine activity of epicardial fat in a feedback response. As a result, new preventive therapeutic strategies are focused on reducing adiposity and weight loss before AF ablation or inhibiting autonomic neurotransmitter secretion on fat pads during open-heart surgery to reduce the recurrence or postoperative risk of AF. In this manuscript, we review some of the novel findings regarding the pathophysiology and associated risk factors of AF, with special emphasis on the role of EAT in the electrical, structural, and molecular mechanisms of AF initiation and maintenance. In addition, we have included a brief note provided on epicardial fat preclinical models that could be useful for identifying new therapeutic targets.

Higher Serum Urate Levels Are Associated With an Increased Risk for Sudden Cardiac Death

OBJECTIVE

To determine the association of serum urate (SU) levels with sudden cardiac death and incident coronary heart disease (CHD), separately, among adults without a history of CHD.

METHODS

We conducted a case-cohort analysis of Black and White participants aged ≥ 45 years enrolled in the REason for Geographic And Racial Differences in Stroke (REGARDS) study without a history of CHD at baseline between 2003 and 2007. Participants were followed for sudden cardiac death or incident CHD (i.e., myocardial infarction [MI] or death from CHD excluding sudden cardiac death) through December 31, 2013. Baseline SU was measured in a random sample of participants (n = 840) and among participants who experienced sudden cardiac death (n = 235) or incident CHD (n = 851) during follow-up.

RESULTS

Participants with higher SU levels were older and more likely to be male or Black. The crude HR (95% CI) per 1 mg/dL higher SU level was 1.26 (1.14-1.40) for sudden cardiac death and 1.17 (1.09-1.26) for incident CHD. After adjustment for age, sex, race, and cardiovascular risk factors, the HR (95% CI) per 1 mg/dL higher SU level was 1.19 (1.03-1.37) for sudden cardiac death and 1.05 (0.96-1.15) for incident CHD. HRs for sudden cardiac death were numerically higher among participants aged 45-64 vs ≥ 65 years, without vs with diabetes, and among those of White vs Black race, although P values for effect modification were all ≥ 0.05.

CONCLUSION

Higher SU levels were associated with an increased risk for sudden cardiac death but not with incident CHD.

The traditional Chinese medicine formula Fufang-Zhenzhu-Tiaozhi protects myocardia from injury in diabetic minipigs with coronary heart disease

BACKGROUND AND PURPOSE

Diabetes mellitus (DM) is a major risk factor for coronary heart disease (CHD). Previous research has reported that the Fufang-Zhenzhu-Tiaozhi (FTZ) formula has obvious effects on the treatment of dyslipidemia and hyperglycemia. In the present study, we intended to establish a convenient DM-CHD model in minipigs and investigated the protective effect of FTZ against myocardial injury and its mechanism.

METHODS

The DM-CHD model was established by a high-fat/high-sucrose/high-cholesterol diet (HFSCD) combined with balloon injury in the coronary artery. Subsequently, sixteen Wuzhishan minipigs were assigned to three groups: control group, model group, and FTZ group. The model group and FTZ group were given a HFSCD, while the control group was given a normal diet (ND). FTZ was given with meals in the FTZ group. During this time, biochemical parameters, such as total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein (HDL-C), and fasting blood glucose (FBG), were measured by using testing kits. Insulin (INS) was determined by ELISA, and the homeostasis model assessment index of insulin resistance (HOMA-IR) was calculated to evaluate insulin resistance levels. After FTZ administration, the plasma levels of lactate dehydrogenase (LDH), creatine kinase isoenzyme MB (CK-MB), and cardiac troponin I (cTnI) were measured by using ELISA kits to evaluate myocardial injury. Coronary artery stenosis was analyzed by angiographic and HE staining. Myocardial ischemia was assayed with electrocardiogram (ECG). Moreover, cytokines, including interleukin-6 (IL-6), hypersensitive C-reactive protein (hs-CRP), and tumor necrosis factor-alpha (TNF-α), were measured by ELISA kits to assess inflammation. The myocardial tissue was collected, and the pathological morphology was observed by transmission electron microscopy (TEM), HE staining, and Masson staining. Western blots were used to detect the expression of PI3K, AKT, p-AKT, p-NF-κB, and NF-κB.

RESULTS

A DM-CHD model in minipigs with glucose-lipid metabolism disorder, coronary artery incrassation and myocardial damage was successfully established through balloon injury in the coronary artery combined with HFSCD. FTZ effectively inhibited coronary artery incrassation and protected the myocardium against injury in DM-CHD minipigs. FTZ decreased proinflammatory cytokine levels and upregulated the protein expression of the PI3K/Akt pathway in the myocardium.

CONCLUSIONS

A novel DM-CHD model in minipigs was successfully established through balloon injury in the coronary artery combined with HFSCD. FTZ has a protective effect against myocardial injury in DM-CHD by inhibiting inflammation and activating the PI3K/AKT signaling pathway.

Diagnostic Criteria for Metabolic Syndrome in Diet-Induced Rodent Models: A Systematic Review

BACKGROUND

Thousands of publications in recent years have addressed the induction of metabolic syndrome (MetS) in rodents. However, the criteria and the reference values for diagnosing this disease have not been defined.

OBJECTIVE

Our main objective was to carry out a systematic review to gather evidence about the criteria for biochemical and anthropometric parameters in which scientific studies have relied on to report that rats developed MetS from a previous dietary manipulation.

METHODS

We compiled characteristics and findings of diet-induced MetS with high-fat, high-carbohydrate, high-fat/high-carbohydrates, and cafeteria diet from PubMed and Science Direct databases published in the last 5 years.

RESULTS

The results on the principal determinants for the syndrome, published in the reviewed articles, were chosen to propose reference values in the rat models of food induction.

CONCLUSION

The values obtained will serve as reference cut-of points in the development of the disease; in addition, the compilation of data will be useful in planning and executing research protocols in animal models.

Therapeutic Applications of Cannabinoids in Cardiomyopathy and Heart Failure

A large number of cannabinoids have been discovered that could play a role in mitigating cardiac affections. However, none of them has been as widely studied as cannabidiol (CBD), most likely because, individually, the others offer only partial effects or can activate potential harmful pathways. In this regard, CBD has proven to be of great value as a cardioprotective agent since it is a potent antioxidant and anti-inflammatory molecule. Thus, we conducted a review to condensate the currently available knowledge on CBD as a therapy for different experimental models of cardiomyopathies and heart failure to detect the molecular pathways involved in cardiac protection. CBD therapy can greatly limit the production of oxygen/nitrogen reactive species, thereby limiting cellular damage, protecting mitochondria, avoiding caspase activation, and regulating ionic homeostasis. Hence, it can affect myocardial contraction by restricting the activation of inflammatory pathways and cytokine secretion, lowering tissular infiltration by immune cells, and reducing the area of infarct and fibrosis formation. These effects are mediated by the activation or inhibition of different receptors and target molecules of the endocannabinoid system. In the final part of this review, we explore the current state of CBD in clinical trials as a treatment for cardiovascular diseases and provide evidence of its potential benefits in humans.

The Role of Cardiac Macrophage and Cytokines on Ventricular Arrhythmias

In the heart, cardiac macrophages have widespread biological functions, including roles in antigen presentation, phagocytosis, and immunoregulation, through the formation of diverse cytokines and growth factors; thus, these cells play an active role in tissue repair after heart injury. Recent clinical studies have indicated that macrophages or elevated inflammatory cytokines secreted by macrophages are closely related to ventricular arrhythmias (VAs). This review describes the role of macrophages and macrophage-secreted inflammatory cytokines in ventricular arrhythmogenesis.

Type 2 diabetes mellitus alters cardiac mitochondrial content and function in a non-obese mice model

Type 2 diabetes mellitus (T2DM) is associated with an increase of premature appearance of several disorders such as cardiac complications. Thus, we test the hypothesis that a combination of a high fat diet (HFD) and low doses of streptozotocin (STZ) recapitulate a suitable mice model of T2DM to study the cardiac mitochondrial disturbances induced by this disease. Animals were divided in 2 groups: the T2DM group was given a HFD and injected with 2 low doses of STZ, while the CNTRL group was given a standard chow and a buffer solution. The combination of HFD and STZ recapitulate the T2DM metabolic profile showing higher blood glucose levels in T2DM mice when compared to CNTRL, and also, insulin resistance. The kidney structure/function was preserved. Regarding cardiac mitochondrial function, in all phosphorylative states, the cardiac mitochondria from T2DM mice presented reduced oxygen fluxes when compared to CNTRL mice. Also, mitochondria from T2DM mice showed decreased citrate synthase activity and lower protein content of mitochondrial complexes. Our results show that in this non-obese T2DM model, which recapitulates the classical metabolic alterations, mitochondrial function is impaired and provides a useful model to deepen study the mechanisms underlying these alterations.

Autonomous activation of CaMKII exacerbates diastolic calcium leak during beta-adrenergic stimulation in cardiomyocytes of metabolic syndrome rats

Autonomous Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) activation induces abnormal diastolic Ca²⁺ leak, which leads to triggered arrhythmias in a wide range of cardiovascular diseases, including diabetic cardiomyopathy. In hyperglycemia, Ca²⁺ handling alterations can be aggravated under stress conditions via the β-adrenergic signaling pathway, which also involves CaMKII activation. However, little is known about intracellular Ca²⁺ handling disturbances under β-adrenergic stimulation in cardiomyocytes of the prediabetic metabolic syndrome (MetS) model with obesity, and the participation of CaMKII in these alterations. MetS was induced in male Wistar rats by administering 30 % sucrose in drinking water for 16 weeks. Fluo 3-loaded MetS cardiomyocytes exhibited augmented diastolic Ca²⁺ leak (in the form of spontaneous Ca²⁺ waves) under basal conditions and that Ca²⁺ leakage was exacerbated by isoproterenol (ISO, 100 nM). At the molecular level, [³H]-ryanodine binding and basal phosphorylation of cardiac ryanodine receptor (RyR2) at Ser2814, a CaMKII site, were increased in heart homogenates of MetS rats with no changes in RyR2 expression. These alterations were not further augmented by Isoproterenol. SERCA pump activity was augmented 48 % in MetS hearts before β-adrenergic stimuli, which is associated to augmented PLN phosphorylation at T17, a target of CaMKII. In MetS hearts. CaMKII auto-phosphorylation (T287) was increased by 80 %. The augmented diastolic Ca²⁺ leak was prevented by CaMKII inhibition with AIP. In conclusion, CaMKII autonomous activation in cardiomyocytes of MetS rats with central obesity significantly contributes to abnormal diastolic Ca²⁺ leak, increasing the propensity for β-adrenergic receptor-driven lethal arrhythmias.

Shensong Yangxin Protects Against Metabolic Syndrome-Induced Ventricular Arrhythmias by Inhibiting Electrical Remodeling

Shensong Yangxin (SSYX) is a traditional Chinese medicine, which has been proven to improve the clinical symptoms of arrhythmia. However, the role of SSYX in metabolic syndrome (MetS)-induced electrical remodeling remains to be fully elucidated. Here, we sought to clarify whether SSYX can alter the electrophysiological remodeling of cardiac myocytes from MetS rats by regulating transient outward potassium current (I_to) and calcium current (I_Ca-L). Male Wistar rats were subjected to 16 weeks of high-carbohydrate, high-fat to produce a MetS model group. SSYX (0.4 g/kg) was administrated by daily gavage 8 weeks following high-carbohydrate, high-fat for 8 weeks. In vivo electrophysiological study was performed to evaluated ventricular arrhythmias (VA) vulnerability and electrophysiological properties. The potential electrical mechanisms were estimated by whole-cell patch-clamp and molecular analysis. The H9C2 cells were used to verify the protective role of SSYX in vitro. After 16-week high-carbohydrate, high-fat feeding, MetS model rats showed increased body weight (BW), blood pressure (BP), blood sugar (BS), heart rate (HR) and heart weights to tibia length (HW/TL) ratio. Furthermore, MetS rats depicted increased VA inducibility, shortened effective refractory period (ERP) and prolonged action potential duration (APD). Lower I_Ca-L and I_to current densities were observed in MetS rats than CTL rats. Additionally, MetS rats exhibited significantly increased cardiac fibrosis, decreased Cx43 expression and protein levels of Cav1.2, Kv4.2, Kv4.3 than CTL group. As expected, these MetS-induced effects above were reversed when SSYX was administrated. Mechanistically, SSYX administrated significantly down-regulated the TLR4/MyD88/CaMKII signaling pathway both in vivo and in vitro. Collectively, our data indicated that the electrical remodeling induced by MetS contributed to the increased VA susceptibility. SSYX protects against MetS-induced VA by inhibiting electrical remodeling through TLR4/MyD88/CaMKII signaling pathway.

Biochemical and nutritional overview of diet-induced metabolic syndrome models in rats: what is the best choice?

Metabolic syndrome (MS) is a condition that includes obesity, insulin resistance, dyslipidemias among other, abnormalities that favors type 2 Diabetes Mellitus (T2DM) and cardiovascular diseases development. Three main diet-induced metabolic syndrome models in rats exist: High carbohydrate diet (HCHD), high fat diet (HFD), and high carbohydrate-high fat diet (HCHHFD). We analyzed data from at least 35 articles per diet, from different research groups, to determine their effect on the development of the MS, aimed to aid researchers in choosing the model that better suits their research question; and also the best parameter that defines obesity, as there is no consensus to determine this condition in rats. For the HCHD we found a mild effect on body weight gain and fasting blood glucose levels (FBG), but significant increases in triglycerides, fasting insulin, insulin resistance and visceral fat accumulation. HFD had the greater increase in the parameters previously mentioned, followed by HCHHFD, which had a modest effect on FBG levels. Therefore, to study early stages of MS a HCHD is recommended, while HFD and HCHHFD better reproduce more severe stages of MS. We recommend the assessment of visceral fat accumulation as a good estimate for obesity in the rat.