5‑Aminosalicylic acid attenuates paraquat‑induced lung fibroblast activation and pulmonary fibrosis of rats

Early diagnosis and staging of paraquat-induced pulmonary fibrosis using [18F]F-FAPI-42 PET/CT imaging

BACKGROUND

Paraquat (PQ) -induced pulmonary fibrosis poses a significant medical challenge due to limited treatment options and high mortality rates. Consequently, there is an urgent need for early diagnosis and accurate staging to facilitate appropriate treatment strategies. In this study, we assessed the diagnostic potential of [18F]F-FAPI-42 PET/CT imaging for early detection and disease staging in a rat model of PQ-induced lung fibrosis.

METHODS

After administering 80 mg/kg of PQ orally to Sprague-Dawley rats, we intravenously injected 3-3.5 MBq of [18F]F-FAPI-42 on day 7, 14, and 21 post-dosing. Dynamic PET/CT imaging was carried out for one hour immediately after the administration of [18F]F-FAPI-42. Subsequently, the lung tissues were collected for Hematoxylin and Eosin (HE) staining, Masson's trichrome staining, and NOTA-FAPI-04-MB fluorescent probe staining. Data analysis was performed using the Imalytics preclinical software, and the mean standardized uptake value (SUVmean) was calculated.

RESULTS

PET signals revealed that in areas with evident lesions on CT, the SUVmean on day 14 was significantly higher than on day 7 and 21, indicating that changes in fibrosis activity levels contribute to the staging of pulmonary fibrosis. Additionally, the NOTA-FAPI-04-MB fluorescent probe staining also demonstrated the most pronounced probe uptake on day 14. In regions without apparent lesions on CT, the SUVmean gradually increased from day 7 to day 21, reflecting ongoing fibrotic activity. Moreover, HE staining and Masson's trichrome staining did not reveal pulmonary fibrosis, while PET imaging was able to detect it, serving the purpose of early diagnosis. At 30 min and 60 min, the target-to-background ratio (TBR) of the PQ groups on day 7, 14, and 21 was significantly higher than the control group, suggesting a high specificity of [18F]F-FAPI-42 binding to activated fibroblasts.

CONCLUSION

[18F]F-FAPI-42 PET/CT imaging enables early diagnosis and staging of PQ-induced pulmonary fibrosis, demonstrating its feasibility and potential for characterizing early disease stages.

Pathophysiological Changes in Rhesus Monkeys with Paraquat-Induced Pulmonary Fibrosis

Purpose

Pulmonary fibrosis is a life-threatening lung disorder. A comprehensive understanding of the pathophysiological changes in the development of pulmonary fibrosis will lead to new insights into its treatment.

Methods

We used a paraquat (PQ)-induced rhesus monkey model of pulmonary fibrosis to comprehensively investigate the process of pulmonary fibrosis development. Rhesus monkeys were orally administered PQ at concentrations of 25 mg/kg, 40 mg/kg, and 80 mg/kg. The dose was given once. Behavior and clinical data, such as PQ concentration, arterial oxygen saturation, biochemical evaluation, lung histopathology, and medical imaging, were continuously observed.

Results

Paraquat-exposed monkeys developed pulmonary fibrosis following an expected time course, especially at 25 mg/kg. CT images showed ground-glass lesions in the lung after 4 weeks, and pulmonary fibrosis persisted until the end of follow-up. Using pathological examination, the lung sustained collagen deposition and slight inflammatory cell infiltration. All rhesus monkeys had obvious inflammatory infiltration within 1 week according to the immunohistochemical results and the number of leukocytes in the blood. The CT results showed that pulmonary fibrosis had not formed, indicating that drugs with powerful anti-inflammatory ability are potential candidates for early pulmonary fibrosis treatment.

Conclusion

Our study describes the dynamic process of paraquat-induced pulmonary fibrosis in rhesus monkeys and provided a pathophysiological basis for the treatment of pulmonary fibrosis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00408-022-00572-9.