Indirect clews pointed that serotonin levels in lung homogenates increased significantly during bleomycin-induced pulmonary fibrosis, and blockage of 5-HT2A and 5-HT2B receptors could alleviate the fibrotic changes [14] Pulmonary fibrosis is characterized pathologically by ECM accumulation and pulmonary architecture remodeling. This evidence concerns the gene HTR2A and pulmonary fibrosis.