Visible light induces matrix metalloproteinase-9 expression in rat eye

Up-regulation of matrix metalloproteinase-9 (MMP-9, gelatinase B) in the nervous system has been demonstrated when excitotoxicity-induced tissue remodeling and neuronal death occurs. Induction of MMP-9 by a natural stimulus has not been observed yet. Using RT-PCR and gelatin-zymography we demonstrated MMP-9 induction at transcriptional and protein levels in different structures of the rat eye following over-stimulation with white light. MMP-9 elevation occurred in the retina without reduction in photoreceptor number or major anatomical reorganization. A transient decrease in electroretinogram b-wave indicated the functional recovery. Retrobulbar injection of a broad-spectrum MMP-inhibitor GM6001, slowed the recovery rate of b-wave amplitude. Even room-light applied to dark-adapted awake animals induced MMP-9 increase in the retina, which suggests a role for MMP-9 in physiological functional plasticity of the nervous system, such as light adaptation. This is the first demonstration of MMP-9 induction by a sensory stimulus.