Abstract 14698: Identifying Sources of Prostacyclin Outside the Vascular Wall and Their Contribution to Cardiovascular Protection

Abstract

Introduction: Prostacyclin is a key anti-thrombotic hormone synthesised through cyclooxygenase (COX) enzymes. Historically, its production has been almost universally associated with the endothelium however the role of non-vascular sources has not been systematically evaluated due to a lack of suitable tools. This has resulted in an underappreciation of its cardiovascular biology and role in other contexts. Hypothesis: We hypothesised that cells outside the vascular wall contribute to generation of prostacyclin which can enter the circulation to provide anti-thrombotic protection. Methods: Global, endothelial and fibroblast COX1 or COX2 knockout mice were studied alongside freshly isolated healthy human lung tissue and primary cell cultures. Prostacyclin levels in plasma and released from cells/tissue ex vivo were measured by ELISA. Individual cell populations were isolated by FACS. Thrombosis in vivo was measured using a FeCl 3 -carotid artery injury model. Results: Vascular endothelial COX1 deletion strongly reduced prostacyclin release from mouse aorta and heart, but not from isolated lung, colon, kidney or spleen (Fig A). This non-vascular prostacyclin required COX1 as it was abolished by global COX1 and not COX2 deletion. Freshly isolated lung fibroblasts exhibited greater prostacyclin synthesis than endothelial or other cell types (Fig B) and this was confirmed in primary human lung cell cultures. Deletion of COX1 from fibroblasts in mice reduced lung prostacyclin release (Fig C) and plasma prostacyclin levels (Fig D) and this was associated with accelerated thrombotic occlusion after carotid artery injury (Fig E). Conclusions: These findings define a new paradigm in prostacyclin biology in which fibroblast/non-vascular-derived prostacyclin works in parallel with endothelium-derived prostanoids to control thrombosis. This may have particular relevance to understanding how local diseases of the lung result in cardiovascular risk.