Abstract 13521: Novel Protective Role of Cu Transporter ATP7A Against Cardiac Fibrosis by Inhibiting Endothelial-Mesenchymal Transition Mediated Through Snail and Antioxidant-1

Abstract

Cardiac fibrosis is attributed to excess pathological deposition of extracellular-matrix (ECM) components; however, it is also mediated through endothelial-mesenchymal transition (EndMT) and fibroblast-myofibroblast transition (FMT) with unknown mechanisms. Copper (Cu), essential micronutrient, has been implicated in fibrosis. Bioavailability of Cu is tightly controlled by Cu-transporter ATP7A which obtains Cu from Cu chaperone Antioxidant-1 (Atox1), and delivers Cu to the ECM secretory Cu enzyme lysysl oxidase (LOX) or exclude Cu. Atox1 also functions as a Cu-dependent transcription factor. However, role of ATP7A in cardiac fibrosis remains unknown. Here we show that high dose angiotensin II infusion (740ng/kg/min for 10 days) to ATP7A mutant (ATP7Amut) mice with reduced Cu transport function significantly increased cardiac fibrosis (200%) and Cu (170%) compared to wild type mice. Blood pressure and heart/body weight were similar between each group. ATP7Amut mice showed increased Isolectin B4+/αSMA+ cells, indicating EndMT in fibrosis region, which was associated with increase in fibrosis-related genes (αSMA, TGFβ1/2/3, CTGF). In ATP7Amut fibroblasts, although LOX activity was reduced, phenotypic conversion to αSMA+ myofibroblasts (FMT) was accelerated. In ECs isolated from ATP7Amut mice or ATP7A-depleted HUVECs, EC phenotype was converted to mesenchymal phenotype with reduced expression of ECs markers (VE-cadherin, VEGFR2) and increased mesenchymal markers (αSMA, TGFβ2) and Cu levels. Functionally, conditioned media from ATP7A-depleted HUVECs promoted cardiac fibroblast differentiation to myofibroblasts (FMT). Mechanistically, ATP7A knockdown in ECs increased expression of EndMT master regulatory transcription factor Snail as well as Atox1 (2 fold). Atox1 overexpression by adenovirus increased EndMT-inducing genes (αSMA, TGFβ2, Hey2) via binding to their promoters at Atox1 binding sites (GAAAGA) without affecting EC markers or Snail which is shown to reduce EC markers. In summary, ATP7A limits cardiac fibrosis by inhibiting EndMT and FMT via suppressing transcription factors Snail and Atox1. Thus, ATP7A is a potential therapeutic target for fibrosis-dependent cardiovascular diseases.