The protective effects of thymoquinone on lung damage caused by cigarette smoke.

Chronic obstructive pulmonary disease (COPD) is characterized by systemic inflammation that usually is caused by exposure to noxious particles or gases. Thymoquinone (TQ) prevents the production of inflammatory mediators, such as thromboxane B2 and leukotriene, by altering arachidonic acid metabolism. We investigated the preventive and curative effects of TQ on lung damage in rats caused by cigarette smoke (CS). We used 50 adult male rats, 30 of which were exposed to CS every day for 3 months. TQ in dimethylsulfoxide (DMSO) was administered intraperitoneally (i.p.) every day to ten animals to investigate the protective effects of TQ, and to ten other animals during the last 21 days to investigate the curative effect. Ten rats received saline for the last 21 days. Ten subjects were untreated controls. Ten controls that were not exposed to CS received TQ for the last ten days. Serum IL-8, IL-6, IL-1β and MMP-9 levels were measured using ELISA. IL-1β and IL-8 levels were elevated in the group exposed to CS compared to controls. IL-8 levels were decreased in the group that received only TQ compared to controls, which indicated the anti-inflammatory effect of TQ. The apoptotic index (AI) was increased in all groups that were exposed to CS compared to controls. The AI index was decreased in the group that received TQ for the last 21 days compared to the other CS groups. AI was increased in the group that received TQ daily compared to the other CS groups. Our findings indicate that TQ exerts curative effects for the inflammation caused by CS and may prevent apoptosis if administered in appropriate doses; however, long term TQ or DMSO exposure may produce cumulative toxic effects.