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Calcium channels are involved in EphB/ephrinB reverse signalinginduced apoptosis in a rat chronic ocular hypertension model

Dong, L;Cheng, X;Zhou, L;Hu, Y;

Erythropoietin-producing hepatocyte receptor B (EphB)/ephrinB reverse signaling has been revealed to be activated in chronic ocular hypertension (COH) by increasing the apoptosis of retinal ganglion cells (RGCs). However, the exact mechanism is not well understood. The present study investigated the involvement of Ca2+ channels in the apoptosis of RGCs induced by EphB/ephrinB reverse signaling in a rat CHO model, which was established by cauterizing 3 out of the 4 episcleral veins. The expression levels of four voltagegated Ca2+ channel subunits (Cav3.13.3 and Cav1.2) were detected using immunofluorescence and western blot analysis. TUNEL staining was performed to assess RGC apoptosis following an injection with the T type Ca2+ channel blocker. Ca2+ channels, mainly the T type, were upregulated in COH rat retinas when compared with the sham group (P<0.01). Additionally, the Cav3.2 subunit of T type calcium channels was predominantly expressed in Mller cells and RGCs, such as ephrinB2. Furthermore, an intravitreal injection of the Ca2+ channel blocker Mibefradil (3 M) reduced EphB2fragment crystallizable regioninduced RGC apoptosis in normal rats. Thus, the results suggest that Ca2+ channels in a COH model may be a pathway involved in ephrinB/EphB signalinginduced RGC apoptosis.