Global Proteomic Analysis Reveals Alterations in Differentially Expressed Proteins between Cardiopathic Lamin A/C Mutations.

Lamin A/C (LMNA) is an important component of nuclear lamina. Mutations cause arrhythmia, heart failure, and sudden cardiac death. While LMNA-associated cardiomyopathy typically has an aggressive course that responds poorly to conventional heart failure therapies, there is variability in severity and age of penetrance between and even within specific mutations, which is poorly understood at the cellular level. Further, this heterogeneity has not previously been captured to mimic the heterozygous state, nor have the hundreds of clinical LMNA mutations been represented. Herein, we have overexpressed cardiopathic LMNA variants in HEK cells and utilized state-of-the-art quantitative proteomics to compare the global proteomic profiles of (1) aggregating Q353 K alone, (2) Q353 K coexpressed with WT, (3) aggregating N195 K coexpressed with WT, and (4) nonaggregating E317 K coexpressed with WT to help capture some of the heterogeneity between mutations. We analyzed each data set to obtain the differentially expressed proteins (DEPs) and applied gene ontology (GO) and KEGG pathway analyses. We found a range of 162 to 324 DEPs from over 6000 total protein IDs with differences in GO terms, KEGG pathways, and DEPs important in cardiac function, further highlighting the complexity of cardiac laminopathies. Pathways disrupted by LMNA mutations were validated with redox, autophagy, and apoptosis functional assays in both HEK 293 cells and in induced pluripotent stem cell derived cardiomyocytes (iPSC-CMs) for LMNA N195 K. These proteomic profiles expand our repertoire for mutation-specific downstream cellular effects that may become useful as druggable targets for personalized medicine approach for cardiac laminopathies.

Increased late sodium current in myocytes from a canine heart failure model and from failing human heart.

Electrophysiological remodeling of ion channels in heart failure causes action potential prolongation and plays a role in arrhythmia mechanism. The importance of down-regulation of potassium currents is well-known, but a role for Na current (I(Na)) in heart failure is less well established. We studied I(Na) in heart failure ventricular cells from a canine pacing model of heart failure and also from explanted failing human hearts. Peak I(Na) density was significantly decreased by 39% and 57% in the dog model and in human heart failure, respectively. The kinetics of peak I(Na) were not different in heart failure. Late I(Na) was measured 750 ms after the initial depolarization as the saxitoxin (STX)-sensitive current and also as the current remaining after contaminating currents were blocked. Late I(Na) as a percentage of the peak I(Na) was significantly increased in both conditions. In dogs, STX sensitive late I(Na) was 0.5 +/- 0.1% n = 16 cells from eight normal hearts and 3.4 +/- 1.4% n = 12 cells from seven failing hearts; in humans, it was 0.2 +/- 0.1% n = 4 cells from two normal hearts and 2.4 +/- 0.5% n = 10 cells from three human failing hearts (-40 mV). Quantitative measures of mRNA including RNase protection assays and real time quantitative PCR in the dog model showed no differences for different alpha subunit isoforms (NaV1.1, 1.3, 1.5) and for the beta1 and beta2 subunits. This suggests neither alpha subunit isoform switching nor altered beta subunit expression is a mechanism for increased late I(Na). We conclude that a peak I(Na) is decreased, and non-inactivating late I(Na) is increased in heart failure and this may contribute to action potential prolongation and the generation of arrhythmia.

Transseptal stent treatment of anastomotic stricture after repair of partial anomalous pulmonary venous return.

PURPOSE: To report the endovascular treatment of a stenosis of the pulmonary venous anastomosis following surgical treatment for partial anomalous pulmonary venous return. CASE REPORT: A 60-year-old man presented with recurrent pleural effusions after correction of a partial anomalous left pulmonary venous return. Magnetic resonance imaging demonstrated focal stenosis at the anastomosis of the anomalous pulmonary vein to the left atrial appendage. Using a transseptal approach, the pulmonary vein stenosis was accessed and successfully stented. The patient's symptoms improved, and follow-up imaging demonstrated a patent stent without residual pressure gradient. CONCLUSIONS: Endovascular repair of a stenosis at the anastomosis of an anomalous pulmonary vein is possible and should be considered as a treatment option for this lesion.