Thymic Stromal Lymphopoietin Promotes Proliferation and Contractility of Human Pulmonary Artery Smooth Muscle

Hypoxia is a well-recognized risk factor in several pulmonary vascular diseases including pulmonary hypertension (PH). Furthermore, hypoxia-associated inflammatory changes enhance the structural and functional changes in the pulmonary artery (PA) of PH patients. Understanding the mechanisms that link hypoxia and inflammation, particularly early in disease, is key to development of novel therapeutic avenues for PH. Thymic stromal lymphopoietin (TSLP) is an “early” inflammatory mediator thought to be critical in diseases such as asthma, chronic obstructive pulmonary disease and atopic dermatitis. TSLP has canonical effects on the immune system, but can also have non-canonical effects on resident lung cells, e.g. airway smooth muscle. Currently, the expression and role of TSLP in the PA is unknown. We hypothesized that locally-produced TSLP potentiates the effects of hypoxia in PA remodeling and contractility relevant to PH. Experiments in human PA endothelial cells (PAECs) and smooth muscle cells (PASMCs) found PAECs to be a larger source of TSLP which targets PASMCs to enhance intracellular Ca2+ responses to vasoconstrictor agonist as well as cell proliferation, acting via a number of signaling cascades including Stat3 and PI3/Akt. Hypoxia, acting via HIF1?, enhanced PAEC production of TSLP, and promoted TSLP effects on PASMCs. Interestingly, TSLP per se enhance HIF1?. Overall, these novel data highlight a role for TSLP in hypoxia effects on the PA, and thus relevance for inflammation in PH.