Noujaim, S. F. | Search bioRxiv

bioRxiv2025

Oxidative stress mediates cardiac electrophysiological injury in inhalation exposure to flavored vaping products.

BackgroundElectronic nicotine delivery systems (ENDS) heat "E-liquids" to generate "E-vapor", an aerosolized mixture containing nicotine and flavors. Flavored ENDS are popular among teens who vape, however, the possible cardiac electrophysiological harm of inhalation exposure to flavored ENDS are not fully understood. ObjectiveTo test if inhalation exposure to flavoring carbonyls in E-liquids compromises mitochondrial integrity, increases oxidative stress, and leads to cardiac electrophysiological toxicity. MethodsGas chromatography mass spectrometry (GC/MS), flow cytometry, oxygen consumption rate (OCR) measurement, in-vivo programmed electrical stimulation (PES), and multielectrode array (MEA) were used in atrial like HL-1 myocytes, hiPSC derived cardiomyocytes, and mice overexpressing mitochondrial catalase (mCAT). ResultsWe compared the toxicity of E-vapor exposure from 30 differently flavored E-liquids in HL-1 cells using apoptotic annexin V flow cytometry. Most E-liquids were toxic. We identified the major flavoring carbonyls in these E-liquids and quantified their concentrations using GC/MS. Linear regression analysis showed that toxicity correlated with carbonyls concentration. Using flow cytometry of CellROX and TMRE staining, HL-1 cells exposed to flavored E-vapor showed increased reactive oxygen species and depolarized mitochondrial membrane potential. Additionally, exposure decreased OCR in these cells. In-vivo inhalation exposure to flavored E-vapor increased the inducible ventricular tachycardia duration in WT but not in mCAT mice compared to controls. MEA recordings in hiPSC derived cardiomyocytes exposed to flavored E-vapor, with or without nicotine, resulted in changes in the spontaneous beating rate. ConclusionsInhalation exposure to flavored ENDS negatively affects ventricular electrophysiology, in part via adverse mitochondrial remodeling, and increased oxidative stress.

physiology↗

bioRxiv2023

The Cardiac Calcium Handling Machinery is Remodeled in Friedreich's Ataxia

BackgroundFriedreichs ataxia (FA) is an inherited neurodegenerative disorder that causes progressive nervous system damage resulting in impaired muscle coordination. FA is the most common autosomal recessive form of ataxia and is caused by an expansion of the DNA triplet guanine-adenine-adenine (GAA) in the first intron of the Frataxin gene (FXN), located on chromosome 9q13. In the unaffected population, the number of GAA repeats ranges from 6 to 27 repetitions. In FA patients, GAA repeat expansions range from 44 to 1,700 repeats which decreases frataxin protein expression. Frataxin is a mitochondrial protein essential for various cellular functions, including iron metabolism. Reduced frataxin expression is thought to negatively affect mitochondrial iron metabolism, leading to increased oxidative damage. Although FA is considered a neurodegenerative disorder, FA patients display heart disease that includes hypertrophy, heart failure, arrhythmias, conduction abnormalities, and cardiac fibrosis. ObjectiveIn this work, we investigated whether abnormal Ca2+ handling machinery is the molecular mechanism that perpetuates cardiac dysfunction in FA. MethodsWe used the frataxin knock-out (FXN-KO) mouse model of FA as well as human heart samples from donors with FA and from unaffected donors. ECG and echocardiography were used to assess cardiac function in the mice. Expression of calcium handling machinery proteins was assessed with proteomics and western blot. In left ventricular myocytes from FXN-KO and FXN-WT mice, the IonOptix system was used for calcium imaging, the seahorse assay was utilized to measure oxygen consumption rate (OCR), and confocal imaging was used to quantify the mitochondrial membrane potential ({Delta}{psi}m) and reactive oxygen species (ROS). ResultsWe found that major contractile proteins, including SERCA2a and Ryr2, were downregulated in human left ventricular samples from deceased donors with FA compared to unaffected donors, similar to the downregulation of these proteins in the left ventricular tissue from FXN-KO compared to FXN-WT. On the ECG, the RR, PR, QRS, and QTc were significantly longer in the FXN-KO mice compared to FXN-WT. The ejection fraction and fractional shortening were significantly decreased and left ventricular wall thickness and diameter were significantly increased in the FXN-KO mice versus FXN-WT. The mitochondrial membrane potential {Delta}{psi}m was depolarized, ROS levels were elevated, and OCR was decreased in ventricular myocytes from FXN-KO versus FXN-WT. ConclusionThe development of left ventricular contractile dysfunction in FA is associated with reduced expression of calcium handling proteins and mitochondrial dysfunction.

physiology↗