Homocysteine modulates sodium channel currents in human atrial myocytes

Linking homocysteine and ferroptosis in cardiovascular disease: insights and implications

Homocysteine (Hcy) is a metabolic intermediate product derived from methionine. Hyperhomocysteinemia is a condition associated with various diseases. Hcy is recognized as a risk factor for cardiovascular disease (CVD). Ferroptosis, a novel form of cell death, is primarily characterized by substantial iron accumulation and lipid peroxidation. Recent research indicates a close association between ferroptosis and the pathophysiological processes of tumors, neurological diseases, CVD, and other ailments. However, limited research has been conducted on the impact of Hcy on ferroptosis. Therefore, this paper aimed to investigate the potential roles and mechanisms of homocysteine and ferroptosis in the context of cardiovascular disease. By conducting comprehensive literature research and analysis, we aimed to summarize recent advancements in understanding the effects of homocysteine on ferroptosis in cardiovascular diseases. This research contributes to a profound understanding of this critical domain.

Lowering serum homocysteine in H-type hypertensive patients with atrial fibrillation after radiofrequency catheter ablation to prevent atrial fibrillation recurrence

Background

Prior investigation revealed that elevated serum total homocysteine (tHcy) are strongly correlated with atrial fibrillation (AF) recurrence. Herein, the goal of this study was to elucidate whether folic acid (FA) treatment reduced AF recurrence following radiofrequency catheter ablation (RFCA).

Methods

To conduct this retrospective research, we included consecutive H-type hypertensive AF patients, who were treated with first RFCA, between January 2010 and January 2022. We assessed the AF recurrence risk between patients who were taking 10 mg enalapril and 0.8 mg FA in a single-pill combination (enalapril–FA) daily and those who were taking a pill of 10 mg enalapril only. Outcomes were compared using the propensity-score matched analysis. Cox regression model was employed for the evaluation of AF recurrence events.

Results

Out of 2,714 patients, 645 patients receiving enalapril and 282 patients receiving enalapril-FA were included for analysis. Following propensity score matching, 239 patients remained in each group. These patients were followed-up for a median of 379 (137–596) days, and revealed that the enalapril-FA patients had drastically reduced AF recurrence, compared to the enalapril patients [adjusted hazard ratio (HR), 0.68; 95% confidence interval (CI), 0.48–0.97; P = 0.029]. Apart from this, no interactions were detected in the subgroup analysis.

Conclusion

In H-type hypertensive AF patients who were treated with first RFCA, FA supplementation was correlated with a reduced AF recurrence risk.

Homocysteine as a Predictor of Paroxysmal Atrial Fibrillation-Related Events: A Scoping Review of the Literature

High levels of homocysteine (Hcy) have been linked with adverse cardiovascular outcomes, such as arrhythmias and stroke. In the context of paroxysmal atrial fibrillation (PAF), hyperhomocysteinemia has been demonstrated to be an independent predictor of future events. The aim of this report was to address the potential value of Hcy levels in predicting future paroxysms of atrial fibrillation (AF), as well as to identify the potential mechanisms of action. We searched PubMed and the Cochrane Database on 16 January 2022. Keywords used were homocysteine or hyperhomocysteinemia paired with a total of 67 different keywords or phrases that have been implicated with the pathogenesis of AF. We included primary reports of clinical and non-clinical data in the English language, as well as systematic reviews with or without meta-analyses. We placed no time constraints on our search strategy, which yielded 3748 results. Following title review, 3293 reports were excluded and 455 reports were used for title and abstract review, after which 109 reports were finally used for full-text review. Our review indicates that Hcy levels seem to hold a predictive value in PAF. Herein, potential mechanisms of action are presented and special considerations are made for clinically relevant diagnostic procedures that could complement plasma levels in the prediction of future PAF events. Finally, gaps of evidence are identified and considerations for future clinical trial design are presented.

Homocysteine (HCY) levels in patients with atrial fibrillation (AF): A meta-analysis

PURPOSE

Atrial fibrillation (AF) is one of the most common persistent arrhythmia, and its complications include cerebral embolism, arterial embolism and heart failure. Some studies have found that elevated Homocysteine (HCY) levels is a new risk factor for AF. Currently, there is no meta-analysis to explore whether the HCY levels is related to AF. Therefore, a meta-analysis was conducted to evaluate the relationship between the HCY levels and AF, in order to draw the attention of clinicians to the HCY levels.

METHODS

A meta-analysis was performed in the study to evaluated the association between the HCY levels and AF. In order to identify eligible original articles, The EMBASE, PubMed, and web of science were systematically searched until November 2020. All data were analyzed with Review Manager 5.3. The meta-analysis results were evaluated depending on standardized mean differences (SMD) with 95% confidence intervals (CI). Moreover, the subgroup analysis and sensitivity analysis were also analyzed.

RESULTS

The HCY levels was significantly associated with AF (WMD = 0.81, 95% CI: 0.58 to 1.03; P < .00001). In the analysis, there was a medium degree of heterogeneity (I² = 73%). Subgroup analysis showed that female < 60, BMI≥25, BMI <25, age ≥60 and publication year ≥2010 were identified as possible sources of heterogeneity. Sensitivity analysis showed that the main results remained unchanged after omitting any single study or converting the random effects model (REM) to fixed effects model (FEM).

CONCLUSIONS

The meta-analysis showed that there is a significant correlation between the HCY levels and AF, and the role of HCY in AF patients should not be ignored in clinical.

No causal association between plasma homocysteine levels and atrial fibrillation: A Mendelian randomization study

BACKGROUND AND AIMS

Although several studies have shown an association between plasma homocysteine (Hcy) levels and atrial fibrillation (AF), the causality remains unclear. We undertook a Mendelian randomization (MR) study to investigate the causal association between Hcy and AF.

METHODS AND RESULTS

Single-nucleotide polymorphisms (SNPs) which genome-wide significantly associated with plasma Hcy levels were obtained from a genome-wide meta-analysis (N = 44 147). MR analyses including the random-effect inverse variance-weighted (IVW) meta-analysis, weighted median analysis, and MR-Egger regression were used to estimate the associations between the selected SNPs and AF based on a meta-analysis of genome-wide association study for AF (N = 588 190). The MR analyses revealed no causal role of genetically elevated plasma Hcy levels with AF risk (random-effect IVW, odds ratio per 1 SD increase in Hcy levels = 0.972, 95% confidence interval = 0.919 to 1.027, P = 0.308). The results were consistent with the weighted median method, MR-Egger and the analysis after excluding the pleiotropic SNPs. No heterogeneity and directional pleiotropy were observed in sensitivity analyses.

CONCLUSION

The findings suggested that plasma Hcy levels were not causally associated with AF.

Elevated Homocysteine Levels Associated with Atrial Fibrillation and Recurrent Atrial Fibrillation

There is increasing evidence linking plasma homocysteine levels and atrial fibrillation (AF). The association between an elevated level of plasma homocysteine and AF was examined by meta-analysis in this study.The PubMed and ScienceDirect databases until August 2019 were utilized to collect previous literature on homocysteine and the potential relation to AF. The pooled effects were evaluated depending on standardized mean differences (SMDs) or odds ratios (ORs) with 95% confidence intervals (CIs), and the calculation was performed using Stata 12 software.A total of 11 validated articles were included in the meta-analysis. For pooled effect, the results confirmed that AF patients had higher homocysteine levels than control subjects (SMD: 0.58, 95%CI: 0.09-1.06). Compared with control subjects, homocysteine levels were higher in paroxysmal AF (SMD: 0.45, 95%CI: 0.18-0.72) and persistent AF patients (SMD: 1.21, 95%CI: 0.50-1.92). The pooled analysis suggested that patients with elevated homocysteine levels had markedly higher risk of AF compared with lower homocysteine levels in the categorical variable (OR: 2.21, 95%CI: 1.16-4.21) and continuous variable analyses (OR: 1.13, 95%CI: 1.00-1.27), respectively. In addition, the pooled analysis indicated that recurrent AF patients had significantly higher homocysteine levels than those without recurrence (SMD: 0.65, 95%CI: 0.42-0.88). The pooled analysis of the categorical variables indicated that elevated homocysteine levels were associated with increased risk of AF recurrence (OR: 3.81, 95%CI: 3.11-4.68). However, the association was weak in the pooled analysis of continuous variables (OR: 1.88, 95%CI: 0.74-4.81).Our meta-analysis identified that plasma homocysteine levels were significantly elevated in AF and recurrent AF patients. Elevated homocysteine is associated with increased risk of AF and AF recurrence.

Role of Oxidative Stress in the Genesis of Ventricular Arrhythmias

Ventricular arrhythmias, mainly lethal arrhythmias, such as ventricular tachycardia and fibrillation, may lead to sudden cardiac death. These are triggered as a result of cardiac injury due to chronic ischemia, acute myocardial infarction and various stressful conditions associated with increased levels of circulating catecholamines and angiotensin II. Several mechanisms have been proposed to underlie electrical instability of the heart promoting ventricular arrhythmias; however, oxidative stress which adversely affects ion homeostasis due to changes in the ion channel structure and function, seems to play a critical role in eliciting different types of ventricular arrhythmias. Prevention or mitigation of the severity of ventricular arrhythmias due to antioxidants has been indicated as the fundamental contribution in the field of preventive cardiology; however, novel interventions have to be developed for greater effectiveness and specificity in attenuating the adverse effects of oxidative stress. In this review, we have attempted to discuss proarrhythmic effects of oxidative stress differing in time and concentration dependence and highlight a molecular and cellular concept how it alters cardiac cell automaticity and conduction velocity sensitizing the probability of ventricular arrhythmias with resultant sudden cardiac death due to ischemic heart disease and other stressful situations. It is concluded that pharmacological approaches targeting multiple mechanisms besides oxidative stress might be more effective in the treatment of ventricular arrhythmias than current antiarrhythmic therapy.

Homocysteine in non-valvular atrial fibrillation: Role and clinical implications

Atrial fibrillation (AF), the most common sustained arrhythmia, is associated with a series of adverse complications that cause so-called AF socioeconomic burden. Apart from the classical risk factors, it seems to be novel factors that increase the risk of AF and AF-related stroke. Recently, more and more evidence has well documented the close relationships between homocysteine (Hcy) and AF. As a well-known marker for pro-oxidation and pro-inflammation, Hcy plays an important role in a number of vascular diseases having strong association with AF. This review will discuss the expression of Hcy and its association with ischemic stroke in AF patients especially for elderly patients, and the role and clinical implications of Hcy in the thromboembolic events and rhythm outcome in AF patients. The possible mechanisms linking elevated Hcy and cardiovascular events in AF patients will also be addressed, including oxidative stress, inflammatory response, atrial remodeling, etc.

Plasma homocysteine levels associated with a corrected QT interval

BACKGROUND

Little is known about the relationship between homocysteine (Hcy) levels and the QT interval. We examined the association of different Hcy levels with corrected QT (QTc) intervals in a general population.

METHODS

Plasma levels of Hcy were assessed in a population-based study of 7002 participants 35 years of age and older from 2012 to 2013. Twelve-lead ECGs were performed on all participants and analyzed automatically.

RESULTS

The distribution of Hcy levels was determined for an entire population after the data were grouped into quartiles (Q1: <=11.1umol/L; Q2: 11.1-13.8umol/L; Q3: 13.8-18.2 umol/L; Q4 > 18.2 umol/L). The mean value of the QTc interval in each quartile was 433.2 ± 23.8 ms, 430.0 ± 24.6 ms, 429.2 ± 24.5 ms and 430.6 ± 25.7 ms. Multiple logistic regression analyses showed that, compared with the second quartile, and after fully adjusting for potential confounding factors, the odds for QTc > 440 ms in the first and fourth quartile increased (P < 0.05), (OR: 1.23, 95% CI: 1.05-1.43 for Q1; OR: 1.40, 95% CI: 1.19-1.65 for Q4).

CONCLUSIONS

QTc interval was associated with the Hcy level in this general population.

Plasma homocysteine levels predict early recurrence after catheter ablation of persistent atrial fibrillation

AIMS

To assess the association and the predictive value of plasma homocysteine (Hcy) with early recurrence in persistent atrial fibrillation patients after a single ablation procedure.

METHODS AND RESULTS

Two hundred and fifty-seven consecutive patients with persistent atrial fibrillation who underwent successful catheter ablation were enrolled. Early recurrence of atrial tachyarrhythmia was documented within 3 months after ablation. The logistic regression analysis and Kaplan-Meier curve analysis were used to evaluate the association of Hcy with early recurrence. During the 3-month follow-up, 75 (29.2%) patients experienced recurrence. Patients with early recurrence were older, more likely to have larger left atrial diameter and higher CHA₂DS₂-VASc score (all P< 0.001). Plasma Hcy levels were significantly elevated in patients with early recurrence compared with those without early recurrence (15.1 ± 4.1 vs. 12.4 ± 3.7 µmol/L, P< 0.001). In multivariate analysis, Hcy was significantly associated with early recurrence (OR 1.188, 95% CI 1.097-1.286, P< 0.001). Hcy demonstrated a predictive value with AUC of 0.688 (95% CI 0.623-0.753, P< 0.001). The optimal cut-off value was 14 µmol/L for Hcy (sensitivity 69%, specificity 59%). Patients with Hcy ≥14 µmol/L had higher early recurrence rate compared with those with Hcy <14 µmol/L (41 vs. 22%, P= 0.006).

CONCLUSION

Plasma Hcy levels are associated with early recurrence of atrial tachyarrhythmia after catheter ablation in persistent atrial fibrillation patients, thus it should be taken into account in prediction of early recurrence.

Ischemic Stroke after Heart Transplantation

Cerebrovascular complications after orthotopic heart transplantation (OHT) are more common in comparison with neurological sequelae subsequent to routine cardiac surgery. Ischemic stroke and transient ischemic attack (TIA) are more common (with an incidence of up to 13%) than intracranial hemorrhage (2.5%). Clinically, ischemic stroke is manifested by the appearance of focal neurologic deficits, although sometimes a stroke may be silent or manifests itself by the appearance of encephalopathy, reflecting a diffuse brain disorder. Ischemic stroke subtypes distribution in perioperative and postoperative period after OHT is very different from classical distribution, with different pathogenic mechanisms. Infact, ischemic stroke may be caused by less common and unusual mechanisms, linked to surgical procedures and to postoperative inflammation, peculiar to this group of patients. However, many strokes (40%) occur without a well-defined etiology (cryptogenic strokes). A silent atrial fibrillation (AF) may play a role in pathogenesis of these strokes and P wave dispersion may represent a predictor of AF. In OHT patients, P wave dispersion correlates with homocysteine plasma levels and hyperhomocysteinemia could play a role in the pathogenesis of these strokes with multiple mechanisms increasing the risk of AF. In conclusion, stroke after heart transplantation represents a complication with considerable impact not only on mortality but also on subsequent poor functional outcome.

Effect of Homocysteine on Voltage-Gated Sodium Channel Currents in Primary Cultured Rat Caudate Nucleus Neurons and Its Modulation by 2-Arachidonylglycerol

Homocysteine (Hcy) is an important risk factor for Alzheimer's disease (AD) and other neurodegenerative diseases. Caudate nucleus (CN), the largest nucleus in the brain, is also implicated in many neurological disorders. 2-Arachidonoylglycerol (2-AG), the most abundant endogenous cannabinoid, has been shown to exhibit neuroprotective effects from many stimuli in the central nervous system (CNS). Furthermore, it has been reported that voltage-gated sodium channels (VGSCs) are the common targets of many neuronal damages and drugs. However, it is still not clear whether VGSCs are involved in the neurotoxicity of Hcy and the neuroprotective effect of 2-AG in CN neurons. In the present study, whole-cell patch clamp recording was used to invest the action of Hcy on sodium currents in primary cultured rat CN neurons and its modulation by 2-AG. The results showed that in cultured CN neurons, pathological concentration of Hcy (100 μM) significantly increased the voltage-gated sodium currents (I(Na)) and produced a hyperpolarizing shift in the activation-voltage curve of I(Na). The further data demonstrated 2-AG is capable of suppressing elevation of Hcy-induced increase in I(Na) and hyperpolarizing shift of activation curves most partly through CB1 receptor-dependent way. Our study provides a better understanding of Hcy-associated neurological disorders and suggests the therapeutic potential for 2-AG for the treatment of these diseases.

Assessment of Left Atrial Function in Patients with Celiac Disease

BACKGROUND

There is some evidence suggesting increased risk of atrial fibrillation (AF) in patients with celiac disease (CD). Impaired left atrial function plays a significant role in the development of AF. This study aimed at assessing the electrical and mechanical functions of the left atrium in patients with CD.

METHODS

A total of 71 patients with biopsy-proven, antibody-positive CD and 52 age-matched healthy controls were included in this prospective study. P-wave dispersion (PWD) was measured to assess the electrical functions of the left atrium through the use of surface electrocardiography. A tissue Doppler echocardiography was performed to determine the atrial conduction and electromechanical delay (EMD) time. To evaluate the mechanical functions of the left atrium, maximum, minimum, and presystolic atrial volumes were estimated to calculate the contractile, conduit, and reservoir functions.

RESULTS

In terms of transthoracic echocardiographic parameters, CD and control subjects were not significantly different. However, as compared to controls, patients with CD had significantly increased PWD (median 52 ms [interquartile range 46-58 ms] vs. 38 [36-40], P < 0.001). Also, significantly higher interatrial (49 ms [32-60] vs. 26 ms [22-28], P < 0.001), intra-left atrial (26 ms [17-44] vs. 14 ms [12-18], P < 0.001), and intra-right atrial (15 ms [8-22] vs. 10 ms [8-14], P < 0.001) EMD was found among CD subjects than controls. Despite an increase in the left atrial volume in patients with CD, conduit and reservoir functions were comparable.

CONCLUSIONS

Although atrial mechanical functions are preserved in patients with CD, a slower electrical conduction was found, suggesting an increased risk of AF in this group of patients.

The effects of the modulation of NMDA receptors by homocysteine thiolactone and dizocilpine on cardiodynamics and oxidative stress in isolated rat heart

In light of the limited data concerning the role of N-methyl-D-aspartate (NMDA) receptors in cardiac function, the aim of the present study was to determine the role of NMDA receptors in cardiac function, as well as the possible role played by the oxidative stress induced by the overstimulation of NMDA receptors in isolated rat heart. The hearts of male, Wistar albino rats (n = 24, 12 in each experimental group, BM 180-200 g) were retrogradely perfused at a constant perfusion pressure (70 cm H₂O₂), using the Langendorff technique, and cardiodynamic parameters were determined during the subsequent administration of DL-homocysteine thiolactone (DL-Hcy TLHC) alone, the combination of DL-Hcy TLHC and dizocilpine (MK-801), and MK-801 alone. In the second experimental group, the order of the administration of each of the substances was reversed. The oxidative stress biomarkers, including thiobarbituric acid reactive substances (TBARS), NO(2)(-), O(2)(-) and H₂O₂, were each determined spectrophotometrically. DL-Hcy TLHC and MK-801 depressed cardiac function. DL-Hcy TLHC decreased oxidative stress, a finding that contrasted with the results of the experiments in which MK-801 was administered first. The findings of this study were suggestive of the likely role played by NMDA receptors in the regulation of cardiac function and coronary circulation in isolated rat heart.

Homocysteine induces procoagulant activity of red blood cells via phosphatidylserine exposure and microparticles generation

Increased homocysteine (Hcy) levels in plasma correlate with the risk of thromboic events. Red blood cells (RBCs), the most abundant blood cells in circulation, also play an active role in the process of thrombus formation. However, the effect of Hcy on procoagulant activity (PCA) of RBCs is unclear. In the present study, RBCs from healthy adults were treated with Hcy (8, 20, 80, 200, 800 μmol/L) for 24 h. Phosphatidylserine (PS) exposure of RBCs and red blood cell-derived microparticles (RMPs) release were detected using Alexa Fluor 488-lactadherin. PCA was assessed by coagulation time and purified clotting complexes testes. We found that Hcy treatment dose dependently enhanced PS exposure and consequent PCA of RBCs. Hcy also elevated the formation of procoagulant RMPs, with statistical significance at 800 μmol/L of Hcy. Moreover, 128 nmol/L lactadherin inhibited about 90% PCA of RBCs and RMPs. Our data suggest that PS exposure and RMPs shedding are key sources for Hcy-induced PCA of RBCs. Lactadherin could be used to modulate the anticoagulant and procoagulant balance in this process.

Bone marrow mesenchymal stem cells protected post-infarcted myocardium against arrhythmias via reversing potassium channels remodelling

Bone marrow mesenchymal stem cells (BMSCs) emerge as a promising approach for treating heart diseases. However, the effects of BMSCs-based therapy on cardiac electrophysiology disorders after myocardial infarction were largely unclear. This study was aimed to investigate whether BMSCs transplantation prevents cardiac arrhythmias and reverses potassium channels remodelling in post-infarcted hearts. Myocardial infarction was established in male SD rats, and BMSCs were then intramyocardially transplanted into the infarcted hearts after 3 days. Cardiac electrophysiological properties in the border zone were evaluated by western blotting and whole-cell patch clamp technique after 2 weeks. We found that BMSCs transplantation ameliorated the increased heart weight index and the impaired LV function. The survival of infarcted rats was also improved after BMSCs transplantation. Importantly, electrical stimulation-induced arrhythmias were less observed in BMSCs-transplanted infarcted rats compared with rats without BMSCs treatment. Furthermore, BMSCs transplantation effectively inhibited the prolongation of action potential duration and the reduction of transient and sustained outward potassium currents in ventricular myocytes in post-infarcted rats. Consistently, BMSCs-transplanted infarcted hearts exhibited the increased expression of K_V4.2, K_V4.3, K_V1.5 and K_V2.1 proteins when compared to infarcted hearts. Moreover, intracellular free calcium level, calcineurin and nuclear NFATc3 protein expression were shown to be increased in infarcted hearts, which was inhibited by BMSCs transplantation. Collectively, BMSCs transplantation prevented ventricular arrhythmias by reversing cardiac potassium channels remodelling in post-infarcted hearts.

Apoptosis of bone marrow mesenchymal stem cells caused by homocysteine via activating JNK signal

Bone marrow mesenchymal stem cells (BMSCs) are capable of homing to and repair damaged myocardial tissues. Apoptosis of BMSCs in response to various pathological stimuli leads to the attenuation of healing ability of BMSCs. Plenty of evidence has shown that elevated homocysteine level is a novel independent risk factor of cardiovascular diseases. The present study was aimed to investigate whether homocysteine may induce apoptosis of BMSCs and its underlying mechanisms. Here we uncovered that homocysteine significantly inhibited the cellular viability of BMSCs. Furthermore, TUNEL, AO/EB, Hoechst 333342 and Live/Death staining demonstrated the apoptotic morphological appearance of BMSCs after homocysteine treatment. A distinct increase of ROS level was also observed in homocysteine-treated BMSCs. The blockage of ROS by DMTU and NAC prevented the apoptosis of BMSCs induced by homocysteine, indicating ROS was involved in the apoptosis of BMSCs. Moreover, homocysteine also caused the depolarization of mitochondrial membrane potential of BMSCs. Furthermore, apoptotic appearance and mitochondrial membrane potential depolarization in homocysteine-treated BMSCs was significantly reversed by JNK inhibitor but not p38 MAPK and ERK inhibitors. Western blot also confirmed that p-JNK was significantly activated after exposing BMSCs to homocysteine. Homocysteine treatment caused a significant reduction of BMSCs-secreted VEGF and IGF-1 in the culture medium. Collectively, elevated homocysteine induced the apoptosis of BMSCs via ROS-induced the activation of JNK signal, which provides more insight into the molecular mechanisms of hyperhomocysteinemia-related cardiovascular diseases.

Mitochondrial mitophagic mechanisms of myocardial matrix metabolism and remodelling

High levels of homocysteine (Hcy), known as hyperhomocysteinmia (HHcy), are correlated with an increase in extracellular matrix remodelling (ECM) via the matrix metalloproteinases (MMPs) and plasminogen/plasmin system. This results in an increase deposition of collagen that leads to endothelial-myocyte (EM) and myocyte-myocyte (MM) uncoupling; the physiological consequences are a plethora of cardiovascular pathologies. Homocysteine-induced increase in intracellular and mitochondrial Ca(2+) plays an important role in increasing reactive oxygen species (ROS) within mitochondria and instigating mitophagy within the cell. This occurs via several Hcy-mitigated processes: agonizing N-methyl-d-aspartate receptor-1 (NMDA-R1), decreasing expression of peroxisome proliferator activator receptor (PPAR) [thereby increasing oxidation], impairing Ca(2+) handling via Na(+)/Ca(2+) exchanger (NCX1) and Sarco endoplasmic reticulum Ca(2+) ATPase (SERCA-2a). The end result is an increase in ROS that directly or indirectly lead to MMP activation within mitochondria or the cytoplasm. Hcy induces a mitochondrial permeability transition that allows MMPs to be released from mitochondria thereby metabolizing matrix and impairing cardiac function. Further work remains to be elucidated concerning the specific mitochondrial mitophagic mechanisms under which matrix metabolism and remodelling occurs. Moreover, the therapeutic implications of NMDA and PPAR ligands are some promise to patient.

Homocysteine and P wave dispersion in patients with heart transplantation

BACKGROUND

Hyperhomocysteinemia (HHcy), a putative independent risk factor for the development of atherotrombosis in the general population, represents a very common finding in orthotopic heart transplantation (OHT) patients. Starting from previous studies suggesting a pro-arrhythmogenic activity of homocysteine (Hcy), we evaluated the possible correlation among Hcy plasma levels and P wave dispersion (PWD), corrected QT interval (QTc), and QTc dispersion (QTcD) as parameters of electric instability of the myocardium in patients undergone OHT whose hearts are therefore completely denervated, thus unresponsive to autonomic influences.

METHODS AND RESULTS

Homocysteine plasma levels, PWD, QTc, QTcD, and QTc dynamics were measured in 32 patients, who underwent OHT, and in 20 control subjects. In OHT patients, PWD (39.5 ± 11 vs. 34 ± 6 ms, p = 0.04) and QTc interval (438 ± 20 vs. 410 ± 10 ms, p < 0.001) were significantly higher in comparison with control subjects. Moreover, OHT subjects with HHcy had higher PWD values than those with normal Hcy plasma levels (44.1 ± 10.7 vs. 33.9 ± 8.8 ms, p = 0.007), but no difference was found between this latter OHT group and controls. Accordingly, in OHT patients, plasma Hcy level correlated significantly with PWD (Spearman r = 0.70; p < 0.0001), whereas no correlation was found with QTc, QTcD, and QTc circadian dynamics.

CONCLUSION

HHcy seems associated with an alteration in the electrical atrial conduction, possibly contributing, at least in part, to the increased risk of cardiac arrhythmias in the denervated hearts of OHT patients.

Difference of sodium currents between pediatric and adult human atrial myocytes: evidence for developmental changes of sodium channels

Voltage-gated calcium currents and potassium currents were shown to undergo developmental changes in postnatal human and animal cardiomocytes. However, so far, there is no evidence whether sodium currents also presented the developmental changes in postnatal human atrial cells. The aim of this study was to observe age-related changes of sodium currents between pediatric and adult atrial myocytes. Human atrial myocytes were acutely isolated and the whole-cell patch clamp technique was used to record sodium currents isolated from pediatric and adult atrial cardiomocytes. The peak amplitude of sodium currents recorded in adult atrial cells was significantly larger than that in pediatric atrial myocytes. However, there was no significant difference of the activation voltage for peak sodium currents between two kinds of atrial myocytes. The time constants for the activation and inactivation of sodium currents were smaller in adult atria than pediatric atria. The further study revealed that the voltage-dependent inactivation of sodium currents were more slow in adult atrial cardiomyocytes than pediatric atrial cells. A significant difference was also observed in the recovery process of sodium channel from inactivation. In summary, a few significant differences were demonstrated in sodium currents characteristics between pediatric and adult atrial myocytes, which indicates that sodium currents in human atria also undergo developmental changes.