Thymoquinone, the main constituent of Nigella sativa, affects adenosine receptors in asthmatic guinea pigs

Objective(s): For determining the mechanism of anti-asthmatic effect of thymoquinone, this investigation evaluated the effect of thymoquinone in the presence of selective A۲A and A۲B adenosine receptor antagonists (ZM۲۴۱۳۸۵ and MRS۱۷۰۶, respectively). Materials and Methods: Seventy guinea pigs were randomly divided to ۷ groups; control (C), sensitized with ovalbumin (S), sensitized groups pretreated with thymoquinone (S+TQ), ZM۲۴۱۳۸۵ (S+Anta A۲A), MRS۱۷۰۶ (S+Anta A۲B), thymoquinone and antagonists (S+Anta A۲A+TQ and S+Anta A۲B+TQ). Thymoquinone and each of these antagonists with ۳ mg/kg dose were injected i.p. on ۱۰th day of sensitization protocol. Tracheal responsiveness (TR) to methacholine and ovalbumin (OA), and total and differential cell count in lung lavage fluid (LLF) in different groups were measured. Results: Increased EC۵۰ and LLF neutrophil count and decreased TR to methacholine and OA, LLF eosinophil and basophil counts were observed in S+TQ group compared to S group (PP<۰.۰۵). Significant decrease in EC۵۰ (P<۰.۰۱), LLF neutrophil, lymphocyte and monocyte count (PP<۰.۰۱), LLF total WBC (P<۰.۰۱) and eosinophil count (P<۰.۰۰۱) were observed in S+A۲A group compared to S+TQ group. There was significant increase in LLF eosinophil and monocyte counts in S+Anta A۲B group compared with S+TQ group (P۲A group, there was significant increase in LLF eosinophil (P<۰.۰۰۱) and significant decrease in LLF neutrophil (P<۰.۰۱) and monocyte (P<۰.۰۰۱) counts compared with S+TQ group. Conclusion: Thymoquinone affects adenosine receptors, which suggest that some of its anti-inflammatory effects may be mediated by these receptors.

Keywords:

Asthma , Adenosine receptor , MRS۱۷۰۶ , Thymoquinone , ZM۲۴۱۳۸۵