CaMKII-Dependent Contractile Dysfunction and Pro-Arrhythmic Activity in a Mouse Model of Obstructive Sleep Apnea

Abstract

Left ventricular contractile dysfunction and arrhythmias frequently occur in patients with sleep-disordered breathing (SDB). The CaMKII-dependent dysregulation of cellular Ca homeostasis has recently been described in SDB patients, but these studies only partly explain the mechanism and are limited by the patients’ heterogeneity. Here, we analyzed contractile function and Ca homeostasis in a mouse model of obstructive sleep apnea (OSA) that is not limited by confounding comorbidities. OSA was induced by artificial tongue enlargement with polytetrafluorethylene (PTFE) injection into the tongue of wildtype mice and mice with a genetic ablation of the oxidative activation sites of CaMKII (MMVV knock-in). After eight weeks, cardiac function was assessed with echocardiography. Reactive oxygen species (ROS) and Ca transients were measured using confocal and epifluorescence microscopy, respectively. Wildtype PTFE mice exhibited an impaired ejection fraction, while MMVV PTFE mice were fully protected. As expected, isolated cardiomyocytes from PTFE mice showed increased ROS production. We further observed decreased levels of steady-state Ca transients, decreased levels of caffeine-induced Ca transients, and increased pro-arrhythmic activity (defined as deviations from the diastolic Ca baseline) only in wildtype but not in MMVV PTFE mice. In summary, in the absence of any comorbidities, OSA was associated with contractile dysfunction and pro-arrhythmic activity and the inhibition of the oxidative activation of CaMKII conveyed cardioprotection, which may have therapeutic implications.

CRISPR-Cas9 base editing of pathogenic CaMKIIδ improves cardiac function in a humanized mouse model

“…However, permanent silencing of a pathomechanism might be suitable for patients with chronic diseases (e.g., coronary artery heart disease), where chronic disturbance of a pathogenic signaling cascade is perpetuated for many years. Future studies will aim to test additional nonviral delivery strategies and to determine whether CAMK2D editing is also beneficial to a broader range of cardiovascular diseases, as oxidized CaMKIIδ has been linked to numerous disorders like atrial fibrillation, diabetes mellitus, and sleep-disordered breathing ( 3 , 15 , 16 , 40 ).…”

“…While regulating cellular homeostasis and signaling at normal activation levels, sustained increased CaMKIIδ activation has been linked to impaired excitation-contraction coupling, disturbances in cellular Ca 2+ handling, inflammation, apoptosis, and fibrosis, all of which impair cardiac function ( 2 , 4 , 5 , 8 – 14 ). Accordingly, CaMKIIδ overactivation has been linked to myocardial infarction and ischemia/reperfusion (IR) injury, heart failure, arrhythmias, cardiac hypertrophy, and sleep-disordered breathing ( 2 , 3 , 6 – 11 , 15 , 16 ). Mechanistically, oxidation of 2 methionine residues at position 281 and 282 has been shown to activate CaMKIIδ by preventing association of the autoinhibitory region with the catalytic domain ( 3 , 10 , 15 – 17 ).…”

“…Accordingly, CaMKIIδ overactivation has been linked to myocardial infarction and ischemia/reperfusion (IR) injury, heart failure, arrhythmias, cardiac hypertrophy, and sleep-disordered breathing ( 2 , 3 , 6 – 11 , 15 , 16 ). Mechanistically, oxidation of 2 methionine residues at position 281 and 282 has been shown to activate CaMKIIδ by preventing association of the autoinhibitory region with the catalytic domain ( 3 , 10 , 15 – 17 ). Indeed, Camk2d knockin mice, in which both oxidation-sensitive methionines were replaced with oxidation-resistant valines in the germline, were protected from severe cardiac damage ( 3 , 15 , 16 ).…”

“…Mechanistically, oxidation of 2 methionine residues at position 281 and 282 has been shown to activate CaMKIIδ by preventing association of the autoinhibitory region with the catalytic domain ( 3 , 10 , 15 – 17 ). Indeed, Camk2d knockin mice, in which both oxidation-sensitive methionines were replaced with oxidation-resistant valines in the germline, were protected from severe cardiac damage ( 3 , 15 , 16 ). These studies suggested that preventing CaMKIIδ oxidation may offer a cardioprotective benefit to heart disease.…”

Insights into the Interaction of Heart Failure with Preserved Ejection Fraction and Sleep-Disordered Breathing

“…Therefore, our group has recently established a novel SDB mouse model by injecting polytetrafluoroethylene (PTFE) into the murine tongue [87]. PTFE is an inert substance that permanently enlarges the murine tongue, which results in spontaneous obstructive apneas, as well as inspiratory flow limitations that subsequently induce increased hypoxia and myocardial ROS production [87,113]. The frequency of apneas correlated with both heart weight (a surrogate for cardiac hypertrophy) and the severity of diastolic dysfunction (E/e') suggests a causal relationship [87].…”