AlphaB-crystallin in the trabecular meshwork is inducible by transforming growth factor-beta

Abstract

Purpose: Because in glaucomatous eyes transforming growth factor-beta (TGF-beta) and alphaB-crystallin are increased in the anterior eye segment, the effect of TGF-beta1 and TGF-beta2 on the expression of alphaB-crystallin and its corresponding mRNA was studied in human trabecular meshwork (TM) cells.

Methods: Monolayer cultures of "cribriform" and "corneoscleral" TM cells of 5 human donors (12-73 years of age) were treated with either 1.0 ng/ml TGF-beta1, TGF-alpha2, or 5 X 10(-7) dexamethasone (DEX) for 12 to 96 hours. Induction of alphaB-crystallin and the related mRNA was investigated by western and northern blot analyses. For comparison, human foreskin fibroblasts (HFF) and NIH 3T3 cells were treated in the same way as the TM cells.

Results: An increase of alphaB-crystallin mRNA was observed after treatment of TM cells with TGF-beta1 and TGF-beta2, whereas DEX had no effect. In the cribriform TM cells with a high basal level, the enhancement ranged between 2 and 3 times; whereas in the corneoscleral TM cells alphaB-crystallin mRNA increased between 5 and 6 times. Using western blot analysis, the increase of alphaB-crystallin expression in the cribriform TM cells was only small compared with the significant increase in the corneoscleral TM cells. Treatment of HFF and NIH 3T3 cells with TGF-beta did not induce alphaB-crystallin mRNA.

Conclusions: This is the first time to show that alphaB-crystallin is not only induced by stress factors but also by TGF-beta in TM cell cultures. The difference in induction of mRNA and protein seems to be dependent on alphaB-crystallin concentration before treatment.