CYCS and diabetic retinopathy: We have shown that MAP kinase plays a significant role in activation of small molecular weight G-protein, H-Ras-mediated activation of matrix metalloproteinase-9 (MMP-9) in retinal capillary cells in diabetes; activated MMP-9 damages the mitochondria, allowing cytochrome-C to leak out and initiate the apoptosis process [25, 26, 43, 44], a phenomenon which precedes the development of histopathology characteristic of diabetic retinopathy [45].