Background Pulmonary fibrosis due to smoke inhalation is a common complication after fire, with high mortality rate and a lack of effective treatments, making it urgent to explore therapeutic agents and their mechanisms for this serious condition.

Objective To investigate whether HCQ exerts anti-pulmonary fibrosis effect through inhibiting Wnt/β-catenin signaling pathway by constructing a rat model of pulmonary fibrosis following smoke inhalation induced acute lung injury (SI-ALI).

Methods Totally 140 male SD rats were randomly divided into control group (C), model group (S), phosphate buffered saline group (S + PBS), methylprednisolone group (S + MP) and hydroxychloroquine group (S + HCQ), among which the S + HCQ group was divided into 3 subgroups according to different HCQ doses (5 mg/kg, 10 mg/kg, 20 mg/kg), with 20 rats in each group. Rats in each group were given intraperitoneal injections of corresponding doses of PBS, MP, and HCQ at 1 h before smoke inhalation in the chamber daily for 30 min and a total of 7 d, and continued to be housed normally until 28 d for comparison of survival rates and lung histopathological changes among rats in each group; The mRNA and protein levels of α-SMA, Col Ⅰ/Ⅲ, β-catenin and p-GSK-3β/GSK-3β were detected in rat lung tissues by qRT-PCR and western blotting.

Results Compared with the C group, the survival rate of rats in the S group and S + PBS group decreased significantly after smoke inhalation, and the survival rate remained at 70% after 72 h (P<0.05), and the pathology suggested an increase in pulmonary fibrosis. Compared with the S + PBS group, the survival rate of rats in the S + MP group and S + HCQ group increased and the degree of pulmonary fibrosis decreased, with 20 mg/kg HCQ and 4 mg/kg MP having obvious effects on the survival rate (90% and 95%), but only the 4 mg/kg MP group showed significant difference. Western blot results indicated that the expression of Collagen Ⅰ, Collagen Ⅲ, α-SMA and core protein β-catenin and p-GSK-3β/GSK-3β in Wnt/β-catenin signaling pathway in rat lung tissues decreased after HCQ and MP intervention (P<0.05), with 20 mg/kg HCQ having the most significant inhibitory effect on the proteins (P＜0.05). qRT-PCR results were generally consistent with western blot.

Conclusion HCQ has a protective effect on pulmonary fibrosis after smoke inhalation in rats, and the best effects are observed at 20 mg/kg HCQ, where part of the protective mechanism may be achieved through inhibition of the Wnt/β-catenin signaling pathway.