Picralima nitida seeds suppress PGE2 production by interfering with multiple signalling pathways in IL 1β-stimulated SK-N-SH neuronal cells

Ethnopharmacological relevance
The dried seed of Picralima nitida is used in rheumatic fever and as an antipyretic in West Africa. In this study we have investigated the effects of an extract obtained from the seeds of Picralima nitida (PNE) on PGE2 production in IL-1β-stimulated cells.

Materials and methods
Prostaglandin E2 (PGE2) was measured in supernatants of IL-1β-stimulated SK-N-SH cells using enzyme immunoassay (EIA) for PGE2. In Cell ELISA and western blot were used to evaluate the effects of PNE on protein expressions of COX-2, mPGES-1, IκB and IKK. To determine the effect of the extract on NF-κB transactivation, a reporter gene assay was carried out in HEK293 cells stimulated with TNFα. An ELISA was used to measure the roles of p38, ERK1/2 and JNK Mitogen Activated Protein Kinases (MAPKs) on anti-neuroinflammatory actions of PNE.

Results
Results show that PNE significantly inhibited PGE2 production, as well as COX-2 and mPGES-1 protein expressions in IL-1β-stimulated SK-N-SH cells. Molecular targeting experiments showed that PNE interfered with NF-κB signalling pathway through attenuation of TNFα-stimulated NF-κB transcriptional activation in HEK 293 cells. Furthermore, IL-1β-mediated phosphorylation of IκB and IKK were inhibited in SK-N-SH cells. PNE (50–200 μg/ml) also produced significant inhibition of IL-1β-induced p38 MAPK phosphorylation in SK-N-SH cells. However, phosphorylation of ERK1/2 and JNK MAPKs were achieved at 100 and 200 μg/ml of the extract.

Conclusions
Taken together, these results clearly demonstrate that Picralima nitida suppresses PGE2 production by targeting multiple pathways involving NF-κB and MAPK signalling in IL-1β-stimulated SK-N-SH neuronal cells.