Differential effect of prostaglandins on γ-glutamyltranspeptidase activity and glutamate/cystine uptake in trabecular meshwork cells.

Abstract

Purpose : To investigate the effects of prostaglandin (PG) treatment on γ-glutamyltranspeptidase (GGT; plays key extracellular role in recapture of Cys for glutathione synthesis) activity and glutamate (Glu) and cystine (Cys) uptake in trabecular meshwork cells (TMC).

Methods : The effect of PG treatment on TMC GGT activity was determined by standard GGT assay utilizing conversion of γ-glutamyl p-nitroanilide in the presence of glycyl-gylcine with or without acivicin (AT¹²⁵, GGT inhibitor). The Na⁺-independent uptake of radiolabeled Cys and Glu by Xc^- antiporter was determined in replicate TMC cultures treated with different concentrations of PG A₂, D₂, F₁ and F_2.

Results : TMC GGT activity was inhibited 50±16% by 10-300 ng/mL PGF₁ and AT¹²⁵. GGT activity was inhibited 23-41% by 1 ug/mL of PGA₂, D₂ or F₂. Concomitantly, PGA₂, and PGF₁ treatment of TMC did not significantly affect Na⁺-independent uptake of radiolabeled Glu or Cys. However, PGD₂ increased Na⁺-independent radiolabeled Glu uptake by 39±11%, but not Cys uptake (<2.5%). In contrast, PGF₂ treatment induced a dose-dependent decrease in TMC Na⁺-independent radiolabeled Glu uptake (up to 37±9%) and radiolabeled Cys uptake (up to 12±7%).

Conclusions : TMC GGT and Xc^- antiporter activity can be modulated by prostaglandins. The results suggest that endogenous and exogenous prostaglandins may regulate TMC function in vivo via modulation of GGT and Xc^- antiporter coordinated activities.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.