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Down-regulation of protein kinase C alpha/ezrin signals in light-induced phagocytic crisis of retinal pigment epithelium cells.

AIM
To investigate the roles of PKC-α/ezrin signals in phagocytosis crisis of retinal pigment epithelium (RPE) cells in light damage model.


METHODS
Light induced mice RPE injury model was established by continuously irradiating cool white light at different exposure time (0, 4, 8h light intensity: 4.18×10-6 J/cm2). In vitro, human ARPE-19 cells treated with the doses and intensity (1.57×10-6 J/cm2) of laser irradiation. Histology analysis was evaluated by hematoxylin and eosin (HE) staining. In vivo RPE phagocytosis was quantified by measuring the accumulation of photoreceptor outer segments in the sub-retinal space. In vitro RPE phagocytosis was assessed by calculating the relative fluorescence intensity of FITC-labeled microspheres in ARPE-19 cells. To further investigate the molecular mechanism, the activation of PKC-α/ezrin signal was evaluated by Western blot in vivo and in vitro.


RESULTS
HE staining revealed that the thickness of outer nuclear layer decreased significantly after 4 and 8h light exposure. By immunostaining with rhodopsin, a significant greater accumulation of photoreceptor outer segment was noticed after light injury. In vitro, light injured RPE cells had less phagocytic activity in a dose dependent manner than that of the normal control (P<0.01). Western blot suggested the activation of PKC-α/ezrin signaling was down-regulated in a dose-dependent manner after light exposure.


CONCLUSION
Our data suggest that light induced phagocytic crisis of RPE cells may result from the down-regulation of PKC-α/ezrin signaling.