EFFECT OF TUMOR-NECROSIS-FACTOR-ALPHA ON RABBIT CORNEAL ENDOTHELIAL PERMEABILITY

Purpose. Tumor necrosis factor alpha (TNF alpha) is present in tile ir is and the lacrimal gland, and its concentration is increased during i nflammation and after corneal wounding. Although TNF alpha has been sh own to increase keratocyte and corneal epithelial interleukin producti on, no definitive effects of TNF alpha on corneal endothelial cells ha ve been reported. TNF alpha has been shown to disrupt barrier function in vascular endothelial monolayers through f-actin depolymerization. A reduction in intracellular cyclic adenosine monophosphate (cAMP) con centration may play a role in this response. This study was designed t o examine the role and signal transduction mechanisms of TNF alpha mod ulation of endothelial permeability in the cornea. In addition, it is the first examination of the effects of TNF alpha on the barrier funct ion of a noncultured cell monolayer. Methods. Rabbit corneal endotheli al superfusions were performed under an in vitro specular microscope. Corneas were processed for permeability measurements or f-actin staini ng. Results. TNF alpha superfused corneas had significantly higher per meabilities than controls. f-actin staining revealed that TNF alpha su perfusion disrupted f-actin filaments when compared to controls. Corne as superfused with the f-actin stabilizing agent phallacidin had signi ficantly lower permeabilities than TNF alpha superfused pairs. Permeab ilities of corneas superfused with TNF alpha plus 8-bromo-cAMP (0.01 t o 3 mM) were significantly lower than TNF alpha superfused pairs at al l concentrations, although only significantly lower at the 0.1 mM cAMP concentration. Conclusions. TNF alpha causes an increase in corneal e ndothelial permeability, and this increase is mediated by disruption o f f-actin filaments; cAMP appears to be involved in this response.