Benzo[a]pyrene [B(a)P], a well-known environmental carcinogen, promotes oxidative stress and DNA damage. Thymoquinone (TQ), the main active constituent of black seed essential oil, exhibits promising effects against inflammatory diseases and cancer. The present study was designed to investigate the possible protective effect of TQ on [B(a)P] -induced lung cancer in mice. One hundred male Swiss Albino mice were divided into four equal groups. Group Ι :( Control group) received no drugs. Group Π :( lung cancer- induced group) mice administered with a single dose of [B(a)P] (100 mg/ kg b.wt, intraperitoneally). Group III :( lung cancer + TQ treated group) mice injected with [B(a)P] as in group II and treated with TQ (20 mg/kg b.wt/day, orally) from 22th week to 30th weeks. Group IV: (lung cancer + TQ protected group) mice received TQ (20 mg/kg b.wt. / Orally) on alternate days from 1 day prior to [B(a)P] injection and were treated continuously with TQ until 30th week (end of experiment). Blood samples and lung tissue specimens were collected at the end of experimental period (30 week) for determination of serum carcino-embryonic antigen (CEA), Haptoglobin (HPT) and Gamma glutamyl transferase (ɤ-GT) in addition to catalase (CAT), Super oxide dismutase(SOD), L-Malondialdehyde (L-MDA), Caspase3, DNA fragmentation(DF), Cycloxygenase -2(COX-2) in lung tissues. The obtained results revealed that, [B(a)P] potentially increased serum ɤ- GT activity, HP and CEA levels in addition to lung tissues COX-2, Caspase 3 gene, L-MDA and DNA fragmentation. However, SOD and GST activities in lung tissues were significantly decreased. TQ treatment was able to mitigate lung cancer induced by [B(a)P] through enhanced the activity of SOD, CAT and attenuated the increased caspase 3 gene, DNA fragmentation, COX-2 and L-MDA in lung tissues and serum CEA, HP and ɤ- GT. It could be concluded that, TQ may be effective in reducing lung cancer by its radical scavenging activity and anti-inflammatory effect, regenerating endogenous antioxidant mechanisms and decreased caspase-3 gene and DNA fragmentation in lung tissues. These results suggest that, the possible efficiency of TQ as an distinct chemo-preventive agent in lung carcinogenesis.
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