Modulation of CREB and NF-kappa B signal transduction by cannabinol in activated thymocytes

Cannabinoid compounds inhibit the cAMP signalling cascade in leukocytes. On e of these compounds, cannabinol (CBN has been shown to inhibit interleukin -2 (IL-2) expression and the activation of cAMP response element binding pr otein (CREB) and nuclear factor for immunoglobulin re chain in B cells (NF- kappaB) following phorbol-12-myristate-13 acetate (PMA) plus ionomycin Oo) treatment of thymocytes. Therefore, the objective of the present studies wa s to determine the role of cAMP and protein kinase A (PKA) in the CBN-media ted inhibition of IL-2, CREB, and NF-kappaB in PMA/Io-activated thymocytes. The inhibition of CREB/ATF-1 phosphorylation, or cAMP response element (CR E) or KB DNA binding activity produced by CBN in PMA/Io-activated thymocyte s, could not be reversed by DBcAMP costimulation. Furthermore, DBcAMP faile d to reverse the concentration-dependent inhibition of IL-2 protein secreti on by CBN. Pretreatment of thymocytes with H89 produced a modest inhibition of PMA/Io-induced CREB/ATF-1 phosphorylation and CRE DNA binding activity but H89 had no effect on protein binding to a kappaB motif. Additionally, H 89 modestly inhibited PMA/Io-induced IL-2 secretion. In light of the modest involvement of the cAMP pathway in CBN-mediated inhibition of CREB and IL- 2 in PMA/Io-activated thymocytes, PD098059 (PD), the MEK inhibitor, was uti lized to determine the role of ERK MAP kinases in thymocytes. ERKs play a c ritical role in IL-2 production but not for CREB phsophorylation. Collectiv ely these findings suggest that CBN may modulate several signalling pathway s in activated T cells. (C) 2001 Elsevier Science Inc. All rights reserved.