Moreover, the expressions of transcription factors snail family transcriptional repressor 1 (SNAI1) and snail family transcriptional repressor 2 (SNAI2, previously known as SLUG), which are key regulators mediated TGF-β1/SMAD signaling triggered the ECM proteins overexpression and deposition in pulmonary fibrosis, were downregulated by the treatment of apelin (Figure 7C). Here, APLN is linked to pulmonary fibrosis.