Figure 7

Modulation of ERK1/2 and AKT signaling in the diabetic retina after peptide treatment. (A) The confocal micrographs show that ERK1/2 and AKT signaling were decreased in diabetic retinas (AT) compared with ND controls (ND). Treatment with the PEDF derivatives induced activation of both ERK and AKT in diabetic retinas. Similar to the nondisease controls, ERK signaling was confined to Muller glia processes in the outer retina and AKT activation in Muller glia cell processes of the inner retina. (B) Higher magnification of the micrographs in (A) showing pERK (outer retina) and pAKT (inner retina) immunolocalization in Muller processes in animals receiving the peptide eye drops (n = 5) (scale bar = 50 µmol/L). (C) The Western blots show that ERK and AKT activation were also evident in retinal explants cultured for 24 h in high glucose (HG) (25 mmol/L) and were then treated with P60 or P78 for 15–120 min. (D, E) Densitometric analyses of the Western blots indicate that P60 induced rapid activation of ERK1/2. P78 reduced ERK1 phosphorylation below the HG controls but had no effect on ERK2 activation, and P78 (F) promoted and sustained activation of AKT throughout the treatment period (n = 3; p < 0.05) (NG, normal glucose). Statistically significant comparisons for P60 and P78 are indicated in the figures. All values are means ± SD.