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Mechanismen der Regulation von K2P3.1 Kaliumkanälen und atrialer Aktionspotentialdauer bei Vorhofflimmern und Herzinsuffizienz - Implikationen für eine personalisierte antiarrhythmische Therapie

Fachliche Zuordnung Kardiologie, Angiologie
Förderung Förderung von 2017 bis 2020
Projektkennung Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 329726112
 
Erstellungsjahr 2021

Zusammenfassung der Projektergebnisse

Atrial fibrillation (AF) contributes significantly to cardiovascular morbidity and mortality. The coexistence of heart failure (HF) worsens prognosis of AF patients and poses a particular therapeutic challenge. The purpose of this study was to identify micro RNA-related signaling mechanisms that determine differential K2P3.1 remodeling in patients with AF and HF. Chronic (c)AF and severe left ventricular ejection fraction (LVEF) impairment were identified as important regulators of K2P3.1 expression in human atria. Atrial K2P3.1/KCNK3 mRNA, protein, and K+ current showed downregulation by severely reduced LVEF and antagonistic upregulation by cAF. Atrial action potential duration (APD) was prolonged in cases of LVEF reduction and shortened in cAF myocytes, consistent with K2P3.1 remodeling. The experimental K2P3.1 inhibitor A293 attenuated APD shortening in cAF patients in the absence of LV dysfunction. Furthermore, we observed progressive attenuation of class III antiarrhythmic APD prolongation following K2P3.1 blockade in patients with more advanced stages of LV dysfunction, indicating the need for patient-tailored antiarrhythmic AF management. A bioinformatical screening approach for miRNAs predicted to interact with the human KCNK3 mRNA yielded 16 potential miRNA candidates. Expression of miR-9, miR-28 and miR-485 was significantly reduced in pAF and cAF patients. Furthermore miR-338 was downregulated, whereas miR-23a, miR- 34a, and miR-124 were significantly upregulated in cAF patients. Differentially expressed miRNAs with highest expression levels (miR-9, miR-23a, miR-28, miR-34a, and miR-124) were subjected to further analyses in vitro. Regulation of endogenous KCNK3 mRNA and K2P3.1/TASK-1 protein expression by miR-9, miR-23a, miR-28, miR-34a, and miR-124 was assessed in HL-1 murine atrial cardiomyocytes. Application of a miR-23a inhibitor caused K2P3.1 upregulation at mRNA and protein levels, resembling findings in cAF patients. In addition, KCNK3 mRNA expression was enhanced by inhibition of microRNAs 9 and 124, similar to human data. Of note, miR-34a suppression caused similar KCNK3 upregulation despite enhanced microRNA expression in cAF; however, miR-34a overexpression did not affect KCNK3 abundance in HL-1 cells. Functional effects of miRNAs on K2P3.1 channels were assessed using the heterologous Xenopus laevis oocyte expression system following injection of KCNK3 mRNA and miRNA mimics or inhibitors. While no statistically significant changes in resting membrane potential (RMP) and potassium current level were observed after co-injecting mimics or inhibitors of miR-9, miR-23a, miR-28, and miR-124, this approach revealed functionally relevant interaction between miR-34a and K2P3.1 channels. RMP was depolarized upon miR-34a inhibition (with no significant K+ current changes) and hyperpolarized when miR-34a was expressed (with enhanced K+ current). Interestingly, miR-34a effects on KCNK3/K2P3.1 in humans versus Xenopus oocytes differed, indicating additional modulators of miR- 34a regulation of the channels that remain to be identified. To further establish the significance of LV dysfunction and other relevant comorbidities for miRNA remodeling a detailed statistical analyses of miRNA expression levels and patient characteristics was performed. To this end, additional miRNAs that were previously implicated in AF were included. Patient parameters associated with myocardial dilatation, HF, and AF (AF stage, LVESD, LVEDD, LA diameter) were associated with increased expression of miR-193a, miR-1, miR-133a, miR-125b, miR-23b, miR-29b, miR-23a, miR-34a, miR-21, miR-25, and miR-124. These parameters were further associated with reduced expression of miR-202, miR-708, miR-485, miR-338, miR-9, miR-26a, miR- 28, and miR-874. Indeed, miR-9/miR-28/miR-338/miR-485 suppression and miR-23a/miR-34a/miR-124 upregulation was similarly identified in our patient cohort and in the large-scale statistical analyses, highlighting a role for specific miRNA remodeling in AF complicated by HF. Follow-up investigations to specifically identify miRNA remodeling in patient subgroups stratified by multiple comorbidities that were predicted to affect miRNA expression based on the present work are currently in preparation.

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