Effects of cytotoxic prostaglandin, ?12PGJ2 on protein synthesis and cytoskeleton in transformed epidermal cells in culture

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Abstract
Cyclopentenone prostaglandins (PGs) such as Δ12-PGJ2 and PGA are potent inducers of growth inhibition in a variety of cultured cells, including epidermal cells. These PGs are actively transported into cells by a specific carrier on cell membrane and accumulate in cell nuclei with binding to nuclear protein. To clarify the mechanism of cytotoxicity of these PGs in epidermal cells, we examined the effects of Δ12-PGJ2 on protein synthesis and cytoskeleton in the PAM 212 transformed mouse epidermal cell line. Cycloheximide at 1 Μg/ml culture medium exhibited a protective effect on cell growth inhibition of PAM 212 cells by Δ12-PGJ2. The analysis of cell lysate protein patterns by SDS-polyacrylamide gel electrophoresis revealed that 12-h incubation with Δ12-PGJ2 increased the amount of 70 kD protein in PAM 212 cells. The amount of 70 kD protein in Δ12-PGJ2-treated cells was markedly decreased by cotreatment with cycloheximide. This 70 kD protein was also induced in PAM 212 cells with treatment at 43‡C for 90 min, indicating that this synthesized protein belongs to the heat shock protein. The addition of Δ12-PGJ2 to confluent PAM 212 cells resulted in the disappearance of action filament, as visualized by fluorescent labeled phallacidine, but in contrast, keratin filament appeared to be intact during 12-h incubation with Δ12-PGJ2 at a concentration of 5 Μg/ml culture medium. These results suggest that the cytotoxicity of cyclopentenone PGs is at least in part due to induction of the synthesis of some protein(s), probably one of the heat shock proteins, and the damage to the actin filament in transformed cultured epidermal cells.