MMP1 and pulmonary arterial hypertension: Our study shows that during the response to hypoxia, p42/p44 MAPK, p38 MAPK, JNK1/2, PI3K/AKT, and STAT3 are involved in the regulation of MMP-1 and MMP-10 expression in monocyte-derived M1 macrophages from patients with PAH.