Celecoxib paradoxically induces COX-2 expression and astrocyte activation through the ERK/JNK/AP-1 signaling pathway in the cerebral cortex of rats

Previous studies have shown that celecoxib or NSAID may paradoxically induce cyclooxygenase-2 (COX-2) expression and trigger inflammation-like responses in airway smooth muscle cells and renal mesangial cells. Despite the extensive research on celecoxib, its atypical biological effect on the induction of COX-2 in astroglial cells within the central nervous system (CNS) remains unexplored. In the present study, we investigated the impact of celecoxib on COX-2 and Glial Fibrillary Acidic Protein (GFAP) expression and explored the mechanisms underlying celecoxib-regulated COX-2 expression in cortical astrocytes of rats.

Cortical astrocytes were treated with celecoxib (20 μM) for 24 h, resulting in a significant increase in COX-2 expression and up-regulation of GFAP, a marker of astrocyte activation, and the COX-2 induced by celecoxib is functionally active in prostaglandin E2 (PGE2) synthesis. Celecoxib also enhanced LPS-induced COX-2 expression, but its ability to inhibit PGE2 synthesis decreased at higher concentrations. Celecoxib induced phosphorylation of Extracellular signal-regulated Kinase (ERK) and c-Jun N-terminal Kinase (JNK) but not p38 Mitogen-Activated Protein Kinase (p38 MAPK), and inhibition of activity of ERK and JNK by U0126 and SP600125 effectively blocked COX-2 and GFAP induction by celecoxib. Celecoxib increased the accumulation of transcription factor AP-1 (composed of phosphorylated c-Jun and c-fos) in the nucleus. Inhibition of AP-1 activity with SR11302 significantly prevented celecoxib-induced COX-2 and GFAP expression. Additionally, the inhibiting activity of ERK and JNK can effectively suppress AP-1 expression and activity induced by celecoxib.

These findings demonstrated that celecoxib induces COX-2 expression and astrocyte activation through the ERK/JNK/AP-1 signaling pathway, highlighting its potential effect in modulating inflammatory responses in the central nervous system.