CCL2 and pulmonary arterial hypertension: In fact, higher circulating levels of monocyte chemoattractant protein 1 (MCP-1), tumor necrosis factor α (TNF-α), and interleukins in patients with idiopathic PAH than in healthy controls are involved (Kimura et al., 2001; Itoh et al., 2006; Sanchez et al., 2007; Zabini et al., 2014; Sharma et al., 2016).