Constitutive signalling pathway activity in trabecular meshwork cells from glaucomatous eyes

We recently described an IL-1-regulated stress response specific to the eye's aqueous outflow pathways that is diagnostic of glaucomas of diverse etiology. The goal of this study was to further identify IL-1-regulated signalling pathways in normal TM cells and determine whether their activity is altered in glaucomatous TM cells. Activity of the MAPK, p38, and JNK signalling pathways, represented by protein kinases ERK1/2, p38, and JNK-1, was followed by western blotting using antibodies specific for the active phosphorylated forms, after treatment of normal (N=5) or glaucomatous (N=5) cell lines by IL-1. Active forms of each of these kinases could be detected in normal and glaucomatous cells prior to treatment. When normal cells were stimulated with exogenous IL-1, an increase in activity of each of the kinases was observed. In contrast, treatment of glaucomatous cells with IL-1 resulted in little or no change in kinase activity. This difference was shown to be statistically significant by use of the paired two-tailed Student's t-test. Interference with IL-1 autocrine signalling in glaucomatous cell lines by treatment with IL-1 receptor antagonist (IL-1ra) had no effect on constitutive p38 or JNK activity (ERK was not examined). The results suggest that the MAPK, p38 and JNK signal transduction pathways are relatively unresponsive in glaucomatous cells as compared to normal cells. These results provide new information about the behaviour of glaucomatous TM cells, which may be important for understanding the pathophysiology of high-tension glaucoma.