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IL-18 mediates sickle cell cardiomyopathy and inducible ventricular arrhythmias

ABSTRACT: Rationale. Sickle cell cardiomyopathy is characterized by prolonged QTc, myocardial fibrosis, diastolic dysfunction, and vulnerability to ventricular tachycardia (VT). Based on previous reports, IL-18 mediates cardiac fibrosis and its promoter SNPs are associated with sudden cardiac death in a non-sickle population. We, therefore, hypothesized that IL-18 may mediate cardiomyopathy and VT in sickle cell disease. Findings. Sickle cell patients with evidence of myocardial fibrosis demonstrated greater IL18 expression. Patients with higher IL18 gene expression levels also exhibited increased QTc intervals and overall mortality. A novel SNP within IL-18, rs5744285, was associated with both QTc and IL-18 expression levels. Similar to sickle cell patients, sickle mice demonstrated increased cardiac fibrosis and prolonged action potential duration (APD) associated with higher VT inducibility. Administration of exogenous IL-18 acutely ex vivo to hearts resulted in increased triggered activity and VTs while inhibition of IL-18 resulted in reduced cardiac NFkB expression, fibrosis, and dysfunction in sickle mice. Conclusions. IL-18 is associated with prolonged QTc, myocardial fibrosis, and mortality in sickle cell patients, and prolonged APD associated with heightened VT susceptibility in sickle mice. Inhibition of IL-18 improves cardiac function, in part, via NFκB. Inflammatory cytokines contribute to the development of sickle cardiomyopathy and inducible VT.

ORGANISM(S): Mus musculus

PROVIDER: GSE89373 | GEO | 2018/10/31

REPOSITORIES: GEO

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Project description:1.1 Introduction Cardiac fibrosis occurs in a wide range of cardiac diseases and is characterised by the transdifferentiation of cardiac fibroblasts into myofibroblasts these cells produce large quantities of extracellular matrix, resulting in myocardial scar. The profibrotic process is multi-factorial, meaning identification of effective treatments has been limited. The antifibrotic effect of the bile acid ursodeoxycholic acid (UDCA) is established in cases of liver fibrosis however its mechanism and role in cardiac fibrosis is less well understood. 1.2 Methods In this study, we used cellular models of cardiac fibrosis and living myocardial slices to characterise the macroscopic and cellular responses of the myocardium to UDCA treatment. We complemented this approach by conducting RNA-seq on cardiac fibroblasts isolated from dilated cardiomyopathy patients. This allowed us to gain insights into the mechanism of action and explore whether the IL-11 and TGFβ/ WWP2 profibrotic networks are influenced by UDCA. Finally, we used fibroblasts from a TGR5 KO mouse to confirm the mechanism of action. 1.3 Results and Discussion We found that UDCA reduced myofibroblast markers in rat and human fibroblasts and in living myocardial slices, indicating its antifibrotic action. Furthermore, we demonstrated that the treatment of UDCA successfully reversed the profibrotic IL-11 and TGFβ/ WWP2 gene networks. We also show that TGR5 is the most highly expressed UDCA receptor in cardiac fibroblasts. Utilising cells isolated from a TGR5 knock-out mouse, we identified that the antifibrotic effect of UDCA is attenuated in the KO fibroblasts. This study combines cellular studies with RNA-seq and state-of-the-art living myocardial slices to offer new perspectives on cardiac fibrosis. Our data confirm that TGR5 agonists, such as UDCA, offer a unique pathway of action for the treatment of cardiac fibrosis. Medicines for cardiac fibrosis have been slow to clinic and have the potential to be used in the treatment of multiple cardiac diseases. UDCA is well tolerated in the treatment of other diseases, indicating it is an excellent candidate for further in-human trials.

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IL-18 mediates sickle cell cardiomyopathy and inducible ventricular arrhythmias

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