IL-6 in PH-LHDIn a rat model of PH-LHD, macrophage accumulation and increased IL-6 production were observed in the lung (8, 81). IL-6 activates STAT3 signaling, inducing PA SMC overproliferation (81).IL-6 and calcification in PAHMicroRNA-204 regulates BRD4 expression, which upregulates IL-6 and drives vascular calcification in PAH (86, 87).Coronary artery disease (CAD)CAD patients have increased osteoprotegerin, osteopontin, and IL-6 levels in serum (88). This evidence concerns the gene STAT3 and pulmonary arterial hypertension.