Vol. 53, Issue 3, 385-391, March 1998

On the Induction of Cyclooxygenase-2, Inducible Nitric Oxide Synthase and Soluble Phospholipase A₂ in Rat Mesangial Cells by a Nonsteroidal Anti-Inflammatory Drug: The Role of Cyclic AMP

Thomas Klein, Volker Ullrich, Josef Pfeilschifter, and Rolf Nüsing

Department of Pediatrics, Philipps University, D-35033 Marburg, Germany (T.K., R.N.), Faculty of Biology, University of Konstanz, P. O. Box 5560, D-78434 Konstanz, Germany (V.U.), Centre of Pharmacology, Johann Wolfgang Goethe University, D-60590 Frankfurt, Germany (J.P.)

One of the challenges in the therapy with anti-inflammatory drugs is the avoidance of gastrointestinal side effects, which may be achieved by selective inhibition of cyclooxygenase (COX) -2. CGP 28238 is reported with these characteristics inhibiting selectively the COX-2 activity at nanomolar concentrations. However, we report here on a novel action of this compound uncovered during the application of higher concentrations. In rat mesangial cells, CGP 28238 induced the mRNA and the protein of COX-2 as well as those of inducible nitric oxide synthase and soluble phospholipase A₂. In the case of COX-2, this stimulation had no effect on the production of COX-2 metabolites because of the effective blockade of the enzyme. In contrast, the level of NO produced by the cells increased in a concentration-dependent manner from 1.2 to 12.5 nmol of nitrite/3 × 10⁵ cells. Furthermore, in combination with low doses of IL-1 CGP 28238 superinduced the formation of nitrite. The observed effects were independent of the inhibition of prostaglandin formation, as suggested by the failure of the potent COX inhibitor diclofenac to cause similar effects. Furthermore, the activity and expression of enzymes downstream of the COX step, such as prostacyclin synthase, were unaffected by CGP 28238. The inductive action of CGP 28238 could be blocked by inhibitors for tyrosine kinases and protein kinase A, such as genistein and KT5720, respectively. The increase in intracellular cAMP concentration in rat mesangial cells and the inhibition by CGP 28238 of phosphodiesterase 4 activity with an IC₅₀ value of 23 µM gave a rationale to explain the underlying mechanisms for the induction of the inflammatory response genes COX-2, soluble phospholipase A₂ and inducible NO synthase in rat mesangial cells.