Ultrasonically induced cell damage and membrane lipid peroxidation by photofrin II: mechanism of sonodynamic activation

Purpose Ultrasonically induced cell damage and active oxygen generation with photofrin II were compared using the same in vitro insonation setup.Methods Sarcoma 180 cells suspended in an air-saturated phosphate-buffered saline solution were exposed to ultrasound at 2 MHz for not more than 60 s in the presence and absence of photofrin II. The trypan blue exclusion test was used to determine viability. Lipid peroxidation in cell membranes was estimated by measuring the quantity of reactive substance produced from thiobarbituric acid added immediately after the cells had been exposured to ultrasound.Results Significant enhancement of the rates of ultrasonically induced cell damage and lipid peroxidation was demonstrated with photofrin II (20-80 µg/ml), and the two rates were closely associated. Enhancement of both rates by photofrin II was suppressed by 10 mM of histidine.Conclusion These results suggest that ultrasonically generated active oxygen is a primary factor in ultrasonically induced cell damage in the presence of photofrin II.