In vitro activity: Dexamethasone results in decrease in transmonolayer paracellular permeability mainly to sucrose, fluorescein and dextrans of up to 20 KDa in an immortalised rat brain endothelial cell line (GPNT). Dexamethasone results in filamentous actin and the cytoskeleton associated protein cortactin being highly concentrated in the regions of cell-cell contact with few F-actin stress fibres visible within the cytoplasm in cultured rat brain endothelial cells, an observation consistent with a more differentiated barrier phenotype induced by dexamethasone. Dexamethasone treatment has been shown to strongly stimulate the level of the Id-1 protein, which is a serum-inducible helix-loop-helix transcriptional repressor, involved in cell differentiation, and this effect was shown to be associated with reorganisation of ZO-1 to the cell periphery in Con8 mammary epithelial tumor cells. Dexamethasone prevents cytokine-induced enhanced expression of MMP-9 and alterations in the expression of ZO-1 in untreated GPNT monolayers. Dexamethasone depletes both basal and TNF-alpha-stimulated GSH levels by down-regulating the gamma-GCS-heavy subunit transcription via a mechanism involving AP-1 (c-Jun) in alveolar epithelial cells. Dexamethasone decreases both basal and stimulated GSH levels (TNF-α-treated) in alveolar epithelial cells (A549), without any change in GSSG.

Neurosci Lett. 2003 Jun 26;344(2):112-6; J Physiol. 2003 Feb 15;547(Pt 1):61-6.