Oxidative stress increases A1 adenosine receptor expression by activating nuclear factor κB

The A(1) adenosine receptor (A(1)AR) contributes to the cytoprotective action of adenosine under conditions known to generate reactive oxygen species (ROS). Pharmacological manipulation of A(1)AR expression has been shown to modulate this cytoprotective role. In this study, we provide evidence that ROS generated could increase the expression of the A(1)AR and thereby offset the detrimental effects of ROS. Incubation of DDT1MF-2 smooth muscle cells with ROS-generating chemotherapeutic agents, such as cisplatin (2.5 mu M) or H2O2 (10 mu M), elicited an increase in A(1)AR expression within 24 hr. The induction by H2O2 was reduced by the ROS scavenger catalase but not superoxide dismutase. Inhibition of nuclear factor kappa B (NF kappa B) by pyrrolidine dithiocarbamate (200 mu M), dexamethasone (100 nM), or genistein (1 mu M) abrogated the cisplatin-mediated increase in A(1)AR. Cisplatin promoted rapid translocation of NF kappa B (but not AP-1) to the nucleus, as detected by electrophoretic mobility shift assays and by Western blotting. A putative NF kappa B sequence in the A,AR promoter effectively competed with labeled KB probe for binding in nuclear preparations derived from DDT1MF-2 cells. Transient transfection of DDT1MF-2 cells with the A,AR promoter coupled to firefly luciferase reporter gene led to cisplatin-inducible and pyrrolidine dithiocarbamate-sensitive luciferase activity, suggesting the presence of functional NF kappa B binding site(s) in the A(1)AR promoter sequence. Treatment of cells with (R)-phenylisopropyladenosine (1 mu M), an agonist of the A(1)AR, reduced cisplatin-mediated lipid peroxidation, which was reversed after blockade of the A(1)AR. These data suggest that ROS can increase the expression of the A(1)AR by activating NF kappa B regulatory site(s) on this gene and thereby enhance the cytoprotective role of adenosine.