BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is a serious lung problem with 
advancing and diffusive pulmonary fibrosis as the pathologic basis, and with 
oxidative stress and inflammation as the key pathogenesis. 
Glycyl-L-histidyl-l-lysine (GHK) is a tripeptide participating into wound 
healing and regeneration. GHK-Cu complexes improve GHK bioavailability. Thus, 
the current study aimed to explore the therapeutic role of GHK-Cu on bleomycin 
(BLM)-induced pulmonary fibrosis in a mouse model.
METHODS: BLM (3 mg/kg) was administered via tracheal instillation (TI) to induce 
a pulmonary fibrosis model in C57BL/6j mice 21 days after the challenge of BLM. 
GHK-Cu was injected intraperitoneally (i.p.) at different dosage of 0.2, 2 and 
20 μg/g/day in 0.5 ml PBS on alternate day. The histological changes, 
inflammation response, the collagen deposition and epithelial-mesenchymal 
transition (EMT) was evaluated in the lung tissue. EMT was evaluated by ɑ-SMA 
and fibronectin expression in the lung tissue. NF-κB p65, Nrf2 and TGFβ1/Smad2/3 
signalling pathways were detected by immunoblotting analysis.
RESULTS: GHK-Cu complex inhibited BLM-induced inflammatory and fibrotic 
pathological changes, alleviated the inflammatory response in the BALF by 
reducing the levels of the inflammatory cytokines, TNF-ɑ and IL-6 and the 
activity of MPO as well as reduced collagen deposition. In addition, the GHK-Cu 
treatment significantly reversed the MMP-9/TIMP-1 imbalance and partially 
prevented EMT via Nrf2, NF-κB and TGFβ1 pathways, as well as Smad2/3 
phosphorylation.
CONCLUSIONS: GHK-Cu presented a protective effect in BLM-induced inflammation 
and oxidative stress by inhibiting EMT progression and suppressing TGFβ1/Smad2/3 
signalling in pulmonary fibrosis.