Journal of molecular and cellular cardiology plus最新文献

Methods

Results

Conclusion

Background

Methods

Results

Conclusions

Background

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a genetic arrhythmic syndrome caused by mutations in the calcium (Ca²⁺) release channel ryanodine receptor (RyR2) and its accessory proteins. These mutations make the channel leaky, resulting in Ca²⁺-dependent arrhythmias. Besides arrhythmias, CPVT hearts typically lack structural cardiac remodeling, a characteristic often observed in other cardiac conditions (heart failure, prediabetes) also marked by RyR2 leak. Recent studies suggest that mitochondria are able to accommodate more Ca²⁺ influx to inhibit arrhythmias in CPVT. Thus, we hypothesize that CPVT mitochondria can absorb diastolic Ca²⁺ to protect the heart from cardiac remodeling.

Methods and results

The Mitochondrial Ca²⁺ uniporter (MCU), the main mitochondrial Ca²⁺ uptake protein, was conditionally knocked out in a CPVT model of calsequestrin 2 (CASQ2) KO. In vivo cardiac function was impaired in the CASQ2^−/−-MCU^CKO model as assessed by echocardiography. Cardiac dilation and cellular hypertrophy were also observed in the CASQ2^−/−-MCU^CKO hearts. Live-cell imaging identified altered Ca²⁺ handling and increased oxidative stress in CASQ2^−/−-MCU^CKO myocytes. The activation status of Ca²⁺-dependent remodeling pathways (CaMKII, Calcineurin) was not altered in the CASQ2^−/−-MCU^CKO model. RNAseq identified changes in the transcriptome of the CASQ2^−/−-MCU^CKO hearts, distinct from the classic cardiac remodeling program of fetal gene re-expression.

Conclusions

We present genetic evidence that mitochondria play a protective role in CPVT. MCU-dependent Ca²⁺ uptake is crucial for preventing pathological cardiac remodeling in CPVT.

Background and aims

Cadherins are adhesion proteins, and their dysregulation may result in the development of atherosclerosis, plaque rupture, or lesions of the vascular wall. The aim of the present study was to detect the associations of cadherins-P, −E, and H, with atherosclerosis and pathological cardiovascular conditions.

Methods and results

The present study with 3-year follow up evaluated atherosclerosis and fasting levels of P-, E-, and H-cadherins in the serum samples of 214 patients in a hospital setting. Coronary lesions were assessed by coronary angiography as Gensini score. Serum proteomic profiling was performed using antibody microarrays. The contents of P-, E-, and H-cadherins in the serum were measured using indirect ELISA. High levels of P- and E-cadherins and low levels of H-cadherin were associated with severity of atherosclerosis. High levels of P- and E-cadherins were associated with higher incidence of nonfatal cardiovascular outcomes. E-cadherin was associated with higher incidence of recurrent revascularization during 3 year follow-up. The results of Spearman rank correlation analysis revealed various associations of the three cadherins with lipid, endothelial, and metabolic biomarkers.

Conclusions

The data indicated that classical and atypical cadherins were associated with atherosclerosis progression. Elevated levels of P-cadherin were associated with coronary atherosclerosis. The data indicated that various lipid, endothelial, and metabolic biomarkers may influence the levels of cadherins. Thus, P-, E-, and H-cadherins may be promising markers for the assessment of cardiovascular risk.

Dravet Syndrome (DS) is a pediatric-onset epilepsy with an elevated risk of Sudden Unexpected Death in Epilepsy (SUDEP). Most individuals with DS possess mutations in the voltage-gated sodium channel gene Scn1a, expressed in both the brain and heart. Previously, mutations in Scn1a have been linked to arrhythmia. We used a Scn1a^−/+ DS mouse model to investigate changes to cardiac mitochondrial function that may underlie arrhythmias and SUDEP. We detected significant alterations in mitochondrial bioenergetics that were sex-specific. Mitochondria from male Scn1a^−/+ hearts had deficits in maximal (p = 0.02) and Complex II-linked respiration (p = 0.03). Male Scn1a^−/+ mice were also more susceptible to cardiac arrhythmias under increased workload. When isolated cardiomyocytes were subjected to diamide, cardiomyocytes from male Scn1a^−/+ hearts were less resistant to thiol oxidation. They had decreased survivability compared to Scn1a^+/+ (p = 0.02) despite no whole-heart differences. Lastly, there were no changes in mitochondrial ROS production between DS and wild-type mitochondria at basal conditions, but Scn1a^−/+ mitochondria accumulated more ROS during hypoxia/reperfusion. This study determines novel sex-linked differences in mitochondrial and antioxidant function in Scn1a-linked DS. Importantly, we found that male Scn1a^−/+ mice are more susceptible to cardiac arrhythmias than female Scn1a^−/+ mice. When developing new therapeutics to address SUDEP risk in DS, sex should be considered.

The small splice variant of the sulfonylurea receptor protein isoform 2 A (SUR2A-55) targets mitochondria and enhances mitoK_ATP activity. In male mice the overexpression of this protein promotes cardioprotection, reducing myocardial injury after an ischemic insult. However, it is unclear what impact SUR2A-55 overexpression has on the female myocardium. To investigate the impact of SU2R2A-55 on the female heart, mice with cardiac specific transgenic overexpression of SUR2A-55 (TG^SUR2A-55) were examined by resting echocardiography and histopathology. In addition, hearts were subjected to ischemia reperfusion (IR) injury. Female TG^SUR2A-55 mice had resting LV dysfunction and worse hemodynamic recovery with increased infarct size after IR injury. RNA-seq analysis found 227 differential expressed genes between WT and TG^SUR2A-55 female mouse hearts that were enriched in pathways of cellular metabolism. This was in direct contrast to male mice that had only four differentially expressed genes. Female TG^SUR2A-55 mice compared to female WT mice had reduced cardiomyocyte mitochondrial membrane potential without a change in electron transport chain protein expression. In addition, isolated mitochondria from female TG^SUR2A-55 hearts displayed reduced sensitivity to ATP and diazoxide suggestive of increased mitoK_ATP activity. In conclusion, our data suggests that female TG^SUR2A-55 mice are unable to tolerate a more active mitoK_ATP channel leading to LV dysfunction and worse response to IR injury. This is in direct contrast to our prior report showing cardioprotection in male mice overexpressing SUR2A-55 in heart. Future research directed at examining the expression and activity of mitoK_ATP subunits according to sex may elucidate different treatments for male and female patients.

The adult mammalian heart is unable to undergo cardiac repair, limiting potential treatment options after cardiac damage. However, the fetal heart is capable of cardiac repair. In preparation for birth, cardiomyocytes (CMs) undergo major maturational changes that include exit from the cell cycle, hypertrophic growth, and mitochondrial maturation. The timing and regulation of such events in large mammals is not fully understood. In the present study, we aimed to assess this critical CM transition period using pigs as a preclinically relevant model. Left ventricular myocardium from Large White cross Landrace gilts was collected at 91, 98, 106 and 111–113 days gestation (d GA; term = 115d GA) and in piglets at 0–1, 4–5, 14–18, 19–20 days after birth. We found that miR-133a, which has known roles in CM proliferation, was significantly downregulated before birth, before rising postnatally. Likewise, gene expression of PCNA and CDK1 was repressed until birth with a rise postnatally, suggesting a decline in proliferation during late gestation followed by the onset of multinucleation in postnatal life. The timing of the switch in myocardial metabolism was unclear; however, complexes within the electron transport chain and mitochondrial biogenesis followed a similar pattern of decreasing abundance during late gestation and then a rise postnatally. These data suggest that CM maturation events such as cell cycle arrest and mitochondrial maturation occur around birth. These results may prove important to consider for preclinical applications such as the development of new therapeutics for cardiac repair.

Dynamin-related protein 1 (Drp1) is a mitochondrial fission protein and a viable target for cardioprotection against myocardial ischaemia-reperfusion injury. Here, we reported a novel Drp1 inhibitor (DRP1i1), delivered using a cardiac-targeted nanoparticle drug delivery system, as a more effective approach for achieving acute cardioprotection. DRP1i1 was encapsulated in cubosome nanoparticles with conjugated cardiac-homing peptides (NanoDRP1i1) and the encapsulation efficiency was 99.3 ± 0.1 %. In vivo, following acute myocardial ischaemia-reperfusion injury in mice, NanoDRP1i1 significantly reduced infarct size and serine-616 phosphorylation of Drp1, and restored cardiomyocyte mitochondrial size to that of sham group. Imaging by mass spectrometry revealed higher accumulation of DRP1i1 in the heart tissue when delivered as NanoDRP1i1. In human cardiac organoids subjected to simulated ischaemia-reperfusion injury, treatment with NanoDRP1i1 at reperfusion significantly reduced cardiac cell death, contractile dysfunction, and mitochondrial superoxide levels. Following NanoDRP1i1 treatment, cardiac organoid proteomics further confirmed reprogramming of contractile dysfunction markers and enrichment of the mitochondrial protein network, cytoskeletal and metabolic regulation networks when compared to the simulated injury group. These proteins included known cardioprotective regulators identified in human organoids and in vivo murine studies following ischaemia-reperfusion injury. DRP1i1 is a promising tool compound to study Drp1-mediated mitochondrial fission and exhibits promising therapeutic potential for acute cardioprotection, especially when delivered using the cardiac-targeted cubosome nanoparticles.