Pulmonary vascular cell mitochondrial dysfunction in response to hepcidin

Abstract

Vascular physiology predominates with endothelial cell-mediated smooth muscle responses to physiological conditions. Variations in cell-type responses are therefore important in vascular pathophysiology. Pulmonary Artery Hypertension (PAH) is characterised by vascular remodelling and proliferation of pulmonary artery smooth muscle cells (PASMC), increasing vascular resistance. Dysregulation of iron and elevated hepcidin are implicated in PAH and previously we have demonstrated hepcidin-mediated proliferation in PASMC. We hypothesise that responses to hepcidin induced iron overload are cell-type specific and we aim to comparatively analyse mitochondrial response in pulmonary arterial endothelial cells (PAEC) vs PASMC. Human PAEC or PASMC were treated with hepcidin (1 µg/ml) or IL-6 (10 ng/ml) for 24 hours. Mitochondria and mitochondrial Reactive Oxygen Species (mROS) were analysed with Mitotracker CMTMros and MitoSOX respectively, using confocal microscopy. Hepcidin treatment induced a significant reduction in fluorescence (***p = <0.0002), network fragmentation (****p = <0.0001) and per cell volume (***p = <0.0002) in PASMC. PAEC only exhibited significant reduction in per cell volume (*p = <0.01). mROS levels were raised significantly in PASMC (***p = 0.0002) and PAEC exhibited no significant change. Our results suggest that PAECs are able to maintain mitochondrial function following hepcidin treatment whereas PASMCs exhibit mitochondrial dysfunction. The driving force of this may be mitochondrial iron accumulation of which PAECs are able to accommodate compared to PASMCs.