Search

Cardiac two-pore domain potassium channels (K2P) exist in organisms from Drosophila to humans; however, their role in cardiac function is not known. We identified a K2P gene, CG8713 (sandman), in a Drosophila genetic screen and show that sandman is critical to cardiac function. Mice lacking an ortholog of sandman, TWIK-related potassium channel (TREK-1, also known Kcnk2), exhibit exaggerated pressure overload-induced concentric hypertrophy and alterations in fetal gene expression, yet retain preserved systolic and diastolic cardiac function. While cardiomyocyte-specific deletion of TREK-1 in response to in vivo pressure overload resulted in cardiac dysfunction, TREK-1 deletion in fibroblasts prevented deterioration in cardiac function. The absence of pressure overload-induced dysfunction in TREK-1-KO mice was associated with diminished cardiac fibrosis and reduced activation of JNK in cardiomyocytes and fibroblasts. These findings indicate a central role for cardiac fibroblast TREK-1 in the pathogenesis of pressure overload-induced cardiac dysfunction and serve as a conceptual basis for its inhibition as a potential therapy.

Introduction: Heart failure with preserved ejection fraction (HFpEF) is a major public health problem because of its high prevalence and the current lack of effective therapies. HFpEF is thought to develop through diastolic dysfunction caused by diminished ventricular compliance, which is strongly influenced by cardiac fibrosis. Our work identifies TWIK related potassium channel-1 (TREK-1) as a novel modulator of diastolic dysfunction and cardiac fibrosis. Methods & Results: TREK-1 is expressed in mammalian cardiac tissue, although its role in cardiac function is poorly understood. To assess the role of TREK-1 in mammalian cardiac function, we interrogated cardiac function in response to pressure overload in global TREK-1 knockout (KO) mice. TREK-1 KO mice showed normal cardiac function in the basal state. However, TREK-1 KO mice developed exaggerated concentric hypertrophy in response to pressure overload. Despite developing exaggerated hypertrophy, TREK-1 KO mice maintained normal systolic and diastolic function as measured by serial echocardiography and invasive hemodynamics. Invasive hemodynamics showed preservation of ventricular compliance in pressure overloaded TREK-1 KO mice, which was associated with significantly attenuated cardiac fibrosis. The limited fibrosis in the heart was indicative of a general impairment of the fibrotic response as measured by impairments in in vivo cutaneous wound healing and in vitro fibroblast migration assays. To determine the mechanism for how TREK-1 modulates fibrosis, we investigated the activation of signaling pathways in lung fibroblasts harvested from TREK-1 KO mice. In response to the profibrotic ligands TGF beta and TNF alpha, TREK-1 KO fibroblasts showed a significantly attenuated activation of the stress-activated kinases p38 alpha and c-Jun N-terminal kinase (JNK), known mediators of myofibroblast activation. These data suggest a critical role for TREK-1 in fibroblast function via the activation of stress-activated kinases. Conclusions: We identified TREK-1 as being critical to the development of diastolic dysfunction and chamber compliance by modulating the signaling pathways involved in the tissue fibrotic response.