Koshiro Umemura

Mechanism of Cell Damage by Ultrasound in Combination with Hematoporphyrin

The mechanism of cell damage by ultrasound in combination with hematoporphyrin was studied. Mouse sarcoma 180 cell suspensions were exposed to ultrasound for up to 60 s in the presence and absence of hematoporphyrin, with and without active oxygen scavengers. The cell damage enhancement by hematoporphyrin was suppressed by adding histidine but not by mannitol. The enhancement was doubled in rate by substitution of deuterium oxide medium for normal water. Sonoluminescence was produced in a saline solution under similar acoustic conditions and observed to have spectral components that can excite hematoporphyrin molecules. These results suggest that cell damage enhancement is probably mediated via singlet oxygen generated by ultrasonically activated hematoporphyrin.

Synergistic Effect of Ultrasound and Hematoporphyrin on Sarcoma 180

The antitumor effects of combined use of ultrasound (US) and a photosensitizer, hematoporphyrin (Hp), were determined in mice bearing sarcoma 180. In order to find the optimum timing of the US irradiation after the administration of Hp, the Hp concentrations in the tumor and in the plasma were determined and were analyzed pharmacokinetically. Antitumor effects were evaluated by measuring the tumor size and the tumor weight. Hp alone showed no antitumor effect but US alone showed a slight antitumor effect. The combined treatment with US and Hp showed marked synergistic effects on sarcoma 180 (inhibition ratio was 74% of the control). From these results, the enhancement of antitumor effect is thought to be caused by the sensitization of tumor cells to US mediated by Hp.

Sonodynamically induced effect of rose bengal on isolated sarcoma 180 cells

Purpose: The ultrasonically induced effect of rose bengal (RB) on isolated tumor cells was investigated. Methods: Sarcoma 180 cells were suspended in air-saturated phosphate-buffered saline and exposed to ultrasound in standing wave mode for up to 60 s in the presence and absence of RB. Cell viability was determined by the ability to exclude trypan blue. Results: The rate of inducing cell damage by ultrasound was enhanced two to three times with 160 μM RB, while no cell damage was observed with RB alone. This enhancement was significantly inhibited by histidine. Conclusions: Ultrasonically induced in vitro cell damage was significantly enhanced by RB. A sonochemical mechanism may be suggested since the enhancement was significantly inhibited by an active oxygen scavenger.

Recent advances in sonodynamic approach to cancer therapy

Abstract Chemical agents such as porphyrins were found to be activated by ultrasound, producing significant antitumor effects. Hematoporphyrin (Hp) enhanced ultrasonically induced damage on sarcoma cells and shown a synergistic inhibitory effect on the tumor growth in combination with ultrasound at 2 MHz. Recently, other types of porphyrins such as protoporphyrin were also found to have such sonodynamic activities. Furthermore, it was found that sonochemical reactions can be greatly accelerated by superimposing the second harmonic onto the fundamental. The highest rate of iodine release from aqueous iodide was obtained at an acoustic intensity ratio between 1 MHz and 2 MHz of 1:1 while either one of the frequency components alone could not induce significant iodine release at the same total acoustic intensity. Second-harmonic superimposition in combination with sonodynamically active antitumor agents may have the potential for selective tumor treatment.

Studies on sonodynamic cancer therapy

Chemical agents such as hematoporphyrin have been found to have a sonochemical activity to induce anti-tumor effects. The same kind of sonochemical reactions producing active oxygen species has been demonstrated to be localized with a highly focused ultrasound in a specially developed tissue-mimicking phantom. These results suggest that the focused ultrasound irradiation to a tumor combined with administration of such a sonochemically active agent can be a potential low-invasive modality for cancer therapy.

Sonodynamically induced antitumor effect of pheophorbide a

The sonodynamically induced antitumor effect of pheophorbide a (Ph-a) was investigated. Both in vitro and in vivo effects on sarcoma 180 were tested in combination with ultrasound at 2 MHz. The rate of ultrasonically induced cell damage in air-saturated suspension was enhanced by twice with 80 microM Ph-a. This enhancement was significantly inhibited by histidine, which may suggest it was mediated by ultrasonically induced oxidation. For mice, 5 mg/kg Ph-a was administered before the insonation, and ultrasound stopped the tumor growth at an intensity with which ultrasound alone showed only a slight antitumor effect.

Sonochemical activation of hematoporphyrin: a potential modality for cancer treatment

In-vitro and in-vivo studies demonstrate the antitumor effect of hematoporphyrin sonochemically activated by ultrasound irradiation. Tumor cell suspensions with and without hematoporphyrin (Hp) are irradiated by continuous-wave ultrasound. Ultrasound cell damage with Hp is significantly greater than that without Hp, while no cell damage by Hp alone was detected. Growth of tumors implanted in mice is stopped by the ultrasound irradiation after Hp administration. Because the cell-damage enhancement by Hp is suppressed by adding histidine to the suspension but not by adding mannitol, the enhancement is most likely due to sonochemical generation of singlet oxygen.<<ETX>>

Sonodynamically-induced in vitro cell damage enhanced by adriamycin

Sonodynamically-induced cell damage and active oxygen generation enhanced by adriamycin (ADM) were compared in the same in vitro insonation set-up. Significant enhancement of the rates of both ultrasonically-induced cell damage and nitroxide generation was demonstrated with 40-160 microM ADM. Both rates correlated very well resulting in a correlation coefficient of more than 0.99. The enhancement of both rates was suppressed by 10 mM histidine. These results are consistent with the hypothesis that ultrasonically-generated active oxygen plays a major role in the sonodynamically-induced cell damage enhanced by ADM.

Membrane lipid peroxidation as a mechanism of sonodynamically induced erythrocyte lysis

Sonodynamically induced lipid peroxidation with haematoporphyrin (Hp) was studied using rat erythrocytes. Both suspensions of erythrocyte ghosts and of intact erythrocytes were exposed to ultrasound in the same way in the presence and absence of Hp (80 microM). The lipid peroxidation in erythrocyte ghost membranes was estimated by measuring the amount of reactive substance produced from thiobarbituric acid added immediately after the exposure. Haematoporphyrin multiplied the ultrasonically induced lipid peroxidation by three to five times, while Hp alone showed no peroxidation. A 24-h interval between the exposure and the preparation for measurement did not increase the measured amount of peroxide. In the presence of Hp the estimated peroxidation rate and the rate of erythrocyte lysis correlated quite well for each acoustic condition and for each chemical condition such as the presence or absence of active oxygen scavengers in the suspension. The sonodynamically induced lipid peroxidation with Hp was doubled by deuterium oxide substitution for suspension medium and was significantly reduced by histidine, by sodium azide, and also by nitrogen substitution for saturation gas, whereas superoxide dismutase and mannitol showed no significant inhibitory effect. These results are consistent with a hypothesis that lipid peroxidation in membranes by singlet oxygen is the primary mechanism of sonodynamically induced erythrocyte lysis with Hp.

Sonodynamic approach to tumor treatment

The localization of sonochemical reactions with focused ultrasound is investigated by developing a sonochemically active tissue mimicking phantom. It is demonstrated that the sonochemical effects can be localized within a region of size not larger than typical tumors to be treated. Sonochemically efficient methods of ultrasound irradiation, which may neither require standing wave situations nor extremely high ultrasound intensity in order to induce substantial sonochemical effects, are studied. The ultrasound intensity threshold for the sonochemical reaction is drastically decreased by the second harmonic superimposition. It is also demonstrated by in vitro experiments that a gallium-deuteroporphyrin complex, ATX-70, has three times higher sonochemical activity than hematoporphyrin (Hp) and induces cell damage at twice the rate of Hp in combination with ultrasound.<<ETX>>