ABSTRACT: BACKGROUND: The Infiltration of leukocytes across the brain endothelium is a hallmark of various neuroinflammatory disorders. Under inflammatory conditions, there is increased expression of specific cell adhesion molecules (CAMs) on activated vascular endothelial cells which increases the adhesion and infiltration of leukocytes. TNFalpha is one of the major proinflammatory cytokines that causes endothelial dysfunction by various mechanisms including activation of transcription factor NF-kappaB, a key transcription factor that regulates expression of CAMs. Peroxisome proliferator-activated receptor gamma (PPARgamma) is a member of the nuclear hormone superfamily of ligand-activated transcriptional factors. 15-deoxy-delta 12, 14-prostaglandin J2 (15d-PGJ2) is a well recognized natural ligand of PPARgamma and possesses anti-inflammatory properties both in vitro and in vivo. This study aims to elucidate the mechanism of 15-PGJ2 on the adhesion of mononuclear cells to activated endothelial cells. METHODS: To delineate the signaling pathway of 15d-PGJ2 mediated effects, we employed an in vitro adhesion assay model of endothelial-monocyte interaction. Expression of CAMs was examined using flow cytometry and real time PCR techniques. To define the mechanism of 15d-PGJ2, we explored the role of NF-kappaB by EMSA (Electrophoretic Mobility Shift Assay) gels, NF-kappaB reporter and p65-transcriptional activities by transient transfection in the brain-derived endothelial cell line (bEND.3). RESULTS: Using an in vitro adhesion assay model, we demonstrate that 15d-PGJ2 inhibits TNFalpha induced monocyte adhesion to endothelial cells, which is mediated by downregulation of endothelial cell adhesion molecules in a PPARgamma independent manner. 15d-PGJ2 modulated the adhesion process by inhibiting the TNFalpha induced IKK-NF-kappaB pathway as evident from EMSA, NF-kappaB reporter and p65 mediated transcriptional activity results in bEND.3 cells. CONCLUSION: These findings suggest that 15d-PGJ2 inhibits inflammation at multiple steps and thus is a potential therapeutic target for various inflammatory diseases.