Effect of adenosine on phorbol myristate acetate induced-reactive oxygen metabolite production in cultured mesangial cells

Cultured rat mesangial cells produced chemiluminescence in response to phorbol myristate acetate. Because 90% of this chemiluminescence was suppressed by 10 mU/ml superoxide dismutase, reactive oxygen metabolites are most likely involved in the chemiluminescence reaction. To clarify the role of cyclic AMP in the regulation of reactive oxygen metabolites production in cultured mesangial cells, we studied the effects of adenosine, an adenosine analog (2-chloroadenosine), and forskolin on phorbol myristate acetate-induced chemiluminescence. Exogenous adenosine suppressed the production of reactive oxygen metabolites in a dose-dependent manner (maximum at 1 mM adenosine: 70.6 ± 3.2% of control). Lower concentrations of 2-chloroadenosine (maximum at 100 μM 2-chloroadenosine: 63.2 ± 2.1% of control) and forskolin (maximum at 200 μM forskolin: 53.4 ± 2.6% of control) also significantly suppressed the production of reactive oxygen metabolites. In addition, adenosine analogs increased intracellular cyclic AMP in a dose-dependent manner in the order: 5′-N-ethylcarboxamidoadeno-sine)2-chloroadenosine)N6-cyclohexyladenosine. These results are in accordance with the probability that exogenous adenosine, by increasing intracellular cyclic AMP via the A2 receptor, inhibits the production of reactive oxygen metabolites through direct protein kinase C activation induced by phorbol myristate acetate in cultured rat mesangial cells.