Effect of preventive or therapeutic treatment with angiotensin 1-7 in a model of bleomycin-induced lung fibrosis in mice

Idiopathic pulmonary fibrosis is characterized by aberrant fibroblast activation and excessive collagen deposition that may eventually lead to organ dysfunction. Lung fibrosis is frequently observed in cancer patients undergoing bleomycin (BLM) treatment. Therefore, BLM instillation in mice is the most frequent model used to investigate pulmonary fibrosis. Angiotensin 1-7 [Ang-(1-7)] is a heptapeptide with anti-inflammatory and proresolving activity. Here, we studied the effects of preventive and therapeutic oral administration of Ang-(1-7) in a model of BLM-induced lung fibrosis in mice. Male C57Bl/6j mice were instilled with BLM and followed for weight loss and survival or euthanized to examine pulmonary inflammation, fibrosis, and lung function. For preventive treatment, mice were treated with Ang-(1-7) 1 h before instillation and then twice daily. We observed that preventive treatment with Ang-(1-7) decreased weight loss, inflammation and collagen deposition, increased survival, and ameliorated lung function. Therapeutic treatment with Ang-(1-7), starting 3 days after BLM instillation resulted in decreased inflammation, decreased collagen deposition, and ameliorated lung function, although the effects were of lower magnitude than the preventive treatment. Therapeutic treatment with Ang-(1-7) starting 7 or 14 days after BLM instillation failed to alter any of the changes observed. Therefore, although oral preventive treatment with Ang-(1-7) is effective to decrease pulmonary inflammation, fibrosis, and functional changes induced by BLM, therapeutic effects are much less significant, arguing against its use in patients with chronic fibrosis. It remains to be determined whether other proresolving molecules will have better therapeutic effects in the context of chronic pulmonary fibrosis.