Localization of lysosomal enzymes in the retina and retinal pigment epithelium of RCS rats

Isolation of intact lysosomes from human RPE cells and effects of A2-E on the integrity of the lysosomal and other cellular membranes

“…Although lysosomal enzymes have their maximum activity around pH 5 and exhibit only little residual activity at the neutral cytoplasmic environment, disruption of the lysosomal membrane has already been associated with pathological conditions and drug-induced tissue destruction [1,19,30,31,34]. A possible potentiation of the detergent effect of A2-E by its interaction with phototoxic destabilization [5,23,30,33] or age-related fragility [8] of the lysosomal membrane remains to be elucidated.…”

Distribution of Cathepsin D in Human Eyes with or without Age-related Maculopathy

“…3. Cathepsin D (CatD) Tamai, 1990) and it has been suggested that it plays a role in the development of retinal dystrophies (Hayasaka, Takahashi and Mizuno, 1977 ;El-Hifnawi et al, 1994). The concept of an age-related decrease of lysosomal enzyme activity as a cause of senescence, have been well documented (Rothstein, 1975 ;Berman, 1994).…”

“…3(C)]. The presence of secreted active CatD has been linked to retinal degeneration in RCS rats (El-Hifnawi et al, 1994) and an increased CatD activity has been found in Spontaneously Dystrophic Rats (SDR) (Hayasaka et al, 1977). In the RCS rat, the release of CatD from the RPE cells into the subretinal space is due to the fragility of the lysosomal membranes.…”

“…In the human eye, CatD activity has been demonstrated by enzymatic assays (Hayasaka, Takahashi and Mizuno, 1977 ;Hayasaka and Shiono, 1982 ;Boulton et al, 1994) and recent immunohistochemical studies (Zimmerman, Godchaux III and Belkin, 1983 ;El-Hifnawi et al, 1994) described the presence of CatD in a wide range of ocular cells. However, these immunohistochemical studies fell short of clearly identifying CatD in pigment laden cells such as retinal pigment epithelial (RPE) cells due to the dark brown color of the melanin pigment.…”

Effects of Tamoxifen, Toremifene and Chloroquine on the Lysosomal Enzymes in Cultured Retinal Pigment Epithelial Cells

“…It removes the shed rod outer segments by phagocytosis (Kennedy et al 1994). The retinal pigment epithelial cells have a very active lysosomal system, which is responsible for the degradation of ingested rod outer segment material (el Hifnawi et al 1994). Deficiencies in rod outer segment phagocytosis can result in retinal degeneration and eventual blindness.…”