Zaragozic acid attenuates the acute increase in cellular cholesterol resulting from exposure of NB4 cells to radiation and chemotherapy, with a concomitant increase in cytotoxicity.

(A) NB4 cells were treated with zaragozic acid A (ZGA; 64 or 256 μM) for 24 or 48 hours, cytarabine (ARA; 0.5 μM) for 24 or 48 hours, or γ-irradiation (RAD; 390 cGy) at 24 or 48 hours before analysis, alone or in combination. Cell death was assayed microscopically by trypan blue uptake (TB+). As can be seen, the addition of ZGA increased radiation and cytarabine cytotoxicity in cotreated cells. Data are presented with standard errors and represent the mean of 2 to 5 independent replicates. (B) NB4 cells treated as described for panel A were assayed for cellular cholesterol using the Amplex Red assay. As can be seen, the addition of ZGA to cells treated with radiation or cytarabine attenuated the cellular cholesterol increments normally seen after irradiation or chemotherapeutic exposure. Cellular cholesterol measures are expressed relative to that of untreated NB4 cells (UN). Data are presented with standard errors and represent the mean of 2 to 5 independent replicates. (C) To determine the toxicity of ZGA as a function of time, NB4 cells were treated with ZGA (64 or 256 μM) for up to 120 hours and assayed for cell death by trypan blue uptake (TB+). The cultures were divided every 48 hours to maintain optimal cell densities.