Long-term treatment with royal jelly improves bleomycin-induced pulmonary fibrosis in rats

This study investigated the anti-fibrotic potential of royal jelly (RJ) powder against bleomycin-induced pulmonary fibrosis in rats. The rats were given RJ orally (25, 50, and 100 mg/kg per day) for 7 consecutive days before the administration of single intratracheal instillation of bleomycin (BLM) at 7.5 IU/kg. RJ doses were continued for 21 days after BLM exposure. Fibrotic changes in the lungs were studied by cell count and analysis of cytokine levels in the bronchoalveolar lavage fluid (BALF), histopathological examination, and assaying oxidative stress biomarkers in lung tissue. The results showed that BLM administration significantly increased the fibrotic changes, collagen content, and levels of malondialdehyde and decreased total thiol and glutathione peroxidase antioxidant contents in the rats' lung tissue. An increase in the level of cell counts and pro-inflammatory and pro-fibrotic cytokines such as TNF-α and TGF-β in BALF was observed. Also, it significantly decreased IFN-γ, an anti-fibrotic cytokine, in BALF. However, RJ (50 and 100 mg/kg) reversed all of these biochemical indices as well as histopathological alterations induced by BLM. The present study demonstrates that RJ, by its antioxidant and anti-inflammatory properties, attenuates oxidative damage and fibrosis induced by BLM.