FOXO1 and pulmonary arterial hypertension: To date, numerous studies have confirmed that IL-6 can activate various signaling pathways that drive the progression of PAH, such as CD4 + T cell/IL-6/glycoprotein 130 (gp130) [165], IRF-4/IL-6/ C-X3-C-Motif Receptor 1 (CX3CR1) [166], and IL-6/Forkhead box protein O1 (FoxO1) [167].