Protective effects of Nigella sativa oil, thymoquinone and dexamethasone on bleomycin-induced lung fibrosis in rats

Pulmonary fibrosis (PF) is a chronic interstitial lung disease with a progressive damage to the air sacs and deposition of collagen fibers in the lung tissue. The study aimed to explore the effects of Nigella sativa oil (NSO) or thymoquinone (TQ), alone or in combination with dexamethasone (DEX), on the development of bleomycin (BLM)-induced PF. Forty-two male rats were divided into seven groups: Control (CTRL); BLM, received a single dose of BLM on day 0, intratracheally; all remaining groups received BLM, as well. DEX, received DEX daily, intraperitoneally, 1 day before BLM and continued for 14 days; NSO and TQ groups, received daily NSO and TQ, respectively, 7 days before BLM and continued for 35 days; DEX + TQ, received both DEX and TQ; DEX + NSO, received both DEX and NSO. At the end, lung tissues were used for histopathological and biochemical analyses. BLM significantly increased the severity of fibrosis and inflammation compared to the CTRL. Bleomycin also significantly increased the amount of hydroxyproline, however, decreased most antioxidant enzymes in the lung tissue compared to the other groups. Group TQ + DEX significantly reduced the severity of BLM-induced PF as well as alterations in biochemical parameters, lung weight and O2 saturation. Nigella sativa oil slightly reduced BLM-induced PF, however, it caused non-significant hyperemia in lung tissue. Thymoquinone potentiated the effects of DEX on most biochemical and pathological alterations of BLM-induced lung injury much better than NSO. More studies are needed to support the use of NSO and TQ as potential protective agents against PF.