PHOTOCHEMICAL TREATMENT WITH THE LYSOSOMALLY LOCALIZED DYE TETRA(4-SULFONATOPHENYL)PORPHINE RESULTS IN LYSOSOMAL RELEASE OF THE DYE BUT NOT OF BETA-N-ACETYL-D-GLUCOSAMINIDASE ACTIVITY

Tetra(4-sulfonatophenyl)porphine (TPPS4) sensitizes cells to photoinactivation mainly through formation of singlet oxygen. In human cervix carcinoma cells of the line NHIK 3025 TPPS4 localizes to a large extent in lysosomes as previously shown by fluorescence microscopical and spectroscopical techniques. In the present study photodamage to lysosomes was investigated. This was accomplished by measuring the activity of the lysosomal marker enzyme beta-N-acetyl-D-glucosaminidase (beta-AGA) after photochemical treatment (PCT). P-AGA activity was highly sensitive to light exposure in the presence of TPPS4. The enzymatic activity was reduced by similar to 70% by non-lethal doses of photochemical treatment, indicating that inactivation of lysosomal hydrolases is not likely to contribute significantly to the cytotoxic effects of PCT. Centrifugation studies showed that TPPS4, but not beta-AGA activity, was released from lysosomes after light exposure. 20-30% of the total beta-AGA activity was resistant to the photochemical treatment. This was due to beta-AGA activity in Golgi-derived vesicles (4-5%) and in vesicles with similar density as lysosomes but not containing TPPS4. The present results indicate that lysosomal hydrolases are inactivated by photochemical treatment before they eventually escape the lysosomal compartment.