Pulmonary Hypertension (PH) is a severe disease leading to right heart failure and death. We have previously shown that blockade of the nerve growth factor NGF may be of therapeutic interest in PH, since NGF contributes to pulmonary arterial (PA) hyperreactivity, remodelling and inflammation.

In this study, we have started to explore the possible links between NGF, inflammation and PA remodelling. More precisely, we have investigated whether interleukin-1β (IL-1β), whose expression is upregulated by NGF, may participate in PA remodelling and inflammation induced by NGF.

In vitro, control human PA smooth muscle (hPASMC) or endothelials cells (hPAEC) in primary culture were treated with exogenous IL-1β (10ng/ml or 100ng/ml, 24h). Cell proliferation (cell counting, ki67 staining), cell migration (Transwell assays), cell apoptosis (caspase 3/7 activity assay) and interleukin-6 (IL-6) secretion (ELISA) were then assessed. In hPAEC, IL-1β effects on endothelial nitric oxide synthase (eNOS) and intercellular adhesion molecule-1 (ICAM-1) expression were also investigated (Western Blotting). In vivo, PH was induced in the rat by chronic hypoxia (0.5 atm, 28 days). IL-1β seric and PA levels were assessed (ELISA), and expression of the inflammasome components NLRP3, caspase-1 and pro-IL-1β were evaluated in lung homogenates (Western Blotting).

In vitro, in hPASMC, IL-1β significantly increased cell proliferation, cell migration, cell resistance to apoptosis and IL-6 secretion. In hPAEC, IL-1β significantly increased cell proliferation, IL-6 secretion and ICAM-1 expression, and significantly decreased eNOS expression. In vivo, IL-1β seric and PA levels, as well as NLRP3, caspase-1 and pro-IL-1β expression in lung homogenates were significantly increased of chronic hypoxic rats compared to controls.

In conclusion, our in vitro results suggest that IL-1β may stimulate both PA smooth muscle and endothelial cells to contribute to PA inflammation, altered reactivity and remodelling. Our in vivo results show inflammasome increased activity and increased IL-1β levels in rat hypoxic PH. Since NGF contributes to IL-1β increased levels in PH, IL-1β may therefore play a role in NGF-dependent PA alterations in this disease.