The effect of endothelin-1 on the phagocytic function of human trabecular meshwork cells in vitro

Background Endothelin-1 (ET-1) is an active regulator of intraocular pressure.The ET-1 level in aqueous humor is elevated in primary open-angle glaucoma,normal intraocular tension glaucoma and the animal model of glaucoma.There is now accumulating evidence for a role of ET-1 in the pathogenesis of glaucoma.However,the effect of ET-1 on the phagocytic function in trabecular meshwork cells (TMCs) is unclear.ObjectiveThis study is to observe the effect of ET-1 on the phagocytic function in cultured human TMCs.Methods Human trabecular meshwork tissue was obtained from healthy donator and cultured and subcultured in vitro by the explant culture method.The third passage of human TMCs were incubated with fluoresent red-labeled latex beads for 0,4,8,12,24,48 and 72 hours.The phagocytic kinetics of human TMCs were continuously evaluated by counting the number of latex beads in TMCs using a fluorescence microscope.Depending on the concentrations of ET-1 in culture medium,the TMCs were divided into control group (without ET-1),low-dose ET-1 (10~(-9)mol/L) treatment group,middle-dose ET-1 (10~(-8)mol/L) treatment group and high-dose ET-1 (10~(-7) mol/L) treatment group.In addition,based on the addition of endothelin receptor (ETAR) antagonist,the TMCs were divided into control group (without ETAR antagonist),ET-1 (10~(-8)mol/L) treatment group,ETAR antagonist (1×10~(-7)mol/L BQ123+10~(-8)mol/L ET-1) treatment group and ETBR antagonist(1×10~(-7) mol/L BQ788+10~(-8) mol/L ET-1)treatment group.TMCs of each group were incubated with latex beads,and the numbers of latex beads in TMCs were counted under a fluorescent microscope.Results Cultured HTM cells showed positive reactions for FN,LN,NSE and negative response for FⅧRag.The phagocytic kinetics test revealed that the latex beads were detected 4 hours after incubation.The density of latex beads was gradually increased with the delay of incubation duration and peaked at 24 hours.The number of the latex beads saturated after 48 hours of incubation.However,the number of latex beads in TMCs was significantly reduced after the addition of ET-1 in a dose-dependent manner (F=28.91,P＜0.05).The number of latex beads in the ET-1 group was less than that in the control group and the ETAR receptor antagonist group (q=13.7228,q=9.4312,P＜0.05).No significant difference was found in latex beads number between the ET-1 group and the ETBR antagonist group (q=1.1600,P＞0.05).Conclusion ET-1 inhibits the phagocytic function of human TMCs and ETAR plays a partial role in the phagocytic function of human TMCs. Key words: trabecular human TMCs; meshwork cells; endothelin-1; phagocytosis; latex beads