Sonodynamically-induced Anticancer Effects of Polyethylene Glycol-Modified Carbon Nano Tubes.

BACKGROUND/AIM: Sonodynamic cancer therapy is based on the preferential uptake and/or retention of a sonosensitizing drug (sonosensitizer) in tumor tissues and the subsequent activation of the drug by ultrasound irradiation. In the present study, we investigated the sonodynamically-induced antitumoral effect with functionalized carbon nanotubes, such as poly-ethylene glycol-modified carbon nanotubes (PEG-modified CNTs). MATERIALS AND METHODS: Antitumor effects were evaluated using histological observation and assessing tumor growth following sonodynamic exposure to PEG-modified CNTs. RESULTS: The combined treatment of 100 µM PEG-modified CNT and ultrasound induced a 2-fold cytotoxicity. Sodium azide, which quenches singlet oxygen, significantly inhibited ultrasonication induced cell damage in the presence of PEG-modified CNTs. This suggests that singlet oxygen produced by the combined use of PEG-modified CNTs and ultrasound is involved in the induction of antitumoral effects. The destruction of tumor tissue was observed with the ultrasonic treatment in combination with PEG-modified CNTs, while neither the treatment with PEG-modified CNTs alone nor ultrasound alone caused any necrosis. CONCLUSION: These results indicate that PEG-modified CNT functions as a sonosensitizer and is effective for sonochemical treatment of solid tumors.

Apoptosis Induced by Ultraviolet A Exposure in the Presence of Enoxacin in HL-60 Cells.

BACKGROUND: The ultraviolet A (UVA) spectrum mainly includes the region associated with the phototoxicity of fluoroquinolone antimicrobial agents. This study investigated apoptosis induced with UVA light and enoxacin in HL-60 cells. MATERIALS AND METHODS: HL-60 cells were irradiated by UVA (1.1 mW/cm2) for 20 min in the presence or absence of enoxacin. The induction of apoptosis was investigated by analysing cell morphology, flow cytometry of annexin V-positive cells, DNA ladder formation, and caspase-3 activation. RESULTS: Significant induction of apoptosis, DNA fragmentation, and caspase-3 activation were observed in cells treated with both UVA and enoxacin. UVA-induced apoptosis was significantly suppressed when NaN3, a singlet oxygen scavenger, was present. CONCLUSION: Apoptosis was induced by the combination of UVA and enoxacin in HL-60 cells, and singlet oxygen appears to play an important role in photodynamically-induced apoptosis.

Glutamine Deprivation Enhances Acetyl-CoA Carboxylase Inhibitor-induced Death of Human Pancreatic Cancer Cells.

BACKGROUND/AIM: Acetyl-CoA carboxylase (ACC) is a rate-limiting enzyme in fatty acid synthesis. In this study, we investigated the effect of ACC inhibition on survival of pancreatic cancer cells. MATERIAL AND METHODS: AsPC-1, BxPC-3 and PANC-1 were used as human pancreatic cancer cell lines. 5-(etradecyloxy)-2-furoic acid (TOFA) and bis-2-(5-phenylacetamido-1,2,4-thiadiazol-2-yl) ethyl sulfide (BPTES) were used as inhibitors of ACC and glutaminase (GLS) respectively. Apoptotic and live cells were distinguished by annexin-V staining. The activity of caspase-3 was evaluated by measuring the fluorescence intensity of the degradation product of the substrate, N-acetyl-Asp-Glu-Val-Asp-7-amido-4-trifluoromethylcoumarin. RESULTS: TOFA increased the number of annexin V-positive cells and enhanced caspase-3 activity in AsPC-1 and BxPC-3, but not in PANC-1 cells. The number of PANC-1 cells increased after 48 h in Earle's balanced salt solution. Interestingly, proliferation of PANC-1 cells was drastically suppressed by glutamine deprivation, but not by inhibition of glycolysis. BPTES also induced cell death to the same extent as glutamine deprivation. In addition, TOFA induced cell death of PANC-1 cells, both in the presence of BPTES and with glutamine deprivation, suggesting that inhibition of glutaminolysis causes cell death and enhances the effect of TOFA in PANC-1 cells. CONCLUSION: These findings suggest that glutaminolysis is important for the survival of pancreatic cancer cells showing tolerance to nutrient starvation such as PANC-1 cells, and use of a combination of inhibitors of ACC and GLS may be a new strategy for treatment of pancreatic cancer.

Comparison of Drug Metabolism and Its Related Hepatotoxic Effects in HepaRG, Cryopreserved Human Hepatocytes, and HepG2 Cell Cultures.

Differentiated HepaRG cells maintain liver-specific functions such as drug-metabolizing enzymes. In this study, the feasibility of HepaRG cells as a human hepatocyte model for in vitro toxicity assessment was examined using selected hepatotoxic compounds. First, basal drug-metabolizing enzyme activities (CYP1A2, CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP3A4, uridine 5'-diphospho-glucuronosyltransferase [UGT], and sulfotransferases [SULT]) were measured in HepaRG, human hepatocytes, and HepG2 cells. Enzyme activities in differentiated HepaRG cells were comparable to those in human hepatocytes and much higher than those in HepG2 cells, except for SULT activity. Second, we examined the cytotoxicity of hepatotoxic compounds, acetaminophen (APAP), aflatoxin B1 (AFB1), cyclophosphamide (CPA), tamoxifen (TAM), and troglitazone (TGZ) in HepaRG cells and human hepatocytes. AFB1- and CPA-induced cytotoxicities against HepaRG cells were comparable to those against human hepatocytes. Furthermore, the cytotoxicities of these compounds were inhibited by 1-aminobenzotriazole (ABT), a broad CYP inhibitor, in both cells and were likely mediated by metabolic activation by CYP. Finally, toxicogenomics analysis of HepG2 and HepaRG cells after exposure to AFB1 and CPA revealed that numerous p53-related genes were upregulated- and the expression of these genes was greater in HepaRG than in HepG2 cells. These results suggest that gene expression profiles of HepaRG cells were affected more considerably by the toxic mechanisms of AFB1 and CPA than the profiles of HepG2 cells were. Therefore, our investigation shows that HepaRG cells could be useful human hepatic cellular models for toxicity studies.

Enoxacin with UVA Irradiation Induces Apoptosis in the AsPC1 Human Pancreatic Cancer Cell Line Through ROS Generation.

Pancreatic cancer is one of the deadliest human cancers. In the current study, we investigated the possibility of a new treatment strategy using a combination of the new fluoroquinolone, enoxacin, and mild ultraviolet A (UVA) irradiation. Enoxacin with UVA irradiation increased the number of annexin V-positive (apoptotic) pancreatic cancer cells in time- and concentration-dependent manners, whereas alone neither had these effects. In addition, enoxacin with UVA irradiation induced cleavage of poly (ADP-ribose) polymerase in AsPC1 human pancreatic cancer cells. Moreover, the singlet oxygen scavengers, histidine and sodium azide, and the hydroxyl radical scavenger, mannitol, significantly suppressed apoptosis induced by enoxacin and UVA irradiation, respectively. These results suggest that UVA irradiation activates enoxacin, after which activated enoxacin induces apoptosis of AsPC1 cells through generation of reactive oxygen species. Therefore, the combination of enoxacin with mild UVA irradiation may be a useful method for treating pancreatic cancer.

Photodynamically-induced Apoptosis Due to Ultraviolet A in the Presence of Lomefloxacin in Human Promyelocytic Leukemia Cells.

Lomefloxacin (LFX) is a widely used fluoroquinolone antimicrobial agent that plays an important role in the treatment of human and animal infections; however, it has been reported to cause phototoxicity. In this study, we investigated the induction of apoptosis due to ultraviolet A (UVA) light in the presence and absence of LFX in HL-60 human promyelocytic leukemia cells. HL-60 cells were exposed to UVA at an intensity of 1.1 mW/cm2 for 20 min in the presence and absence of LFX, and the induction of apoptosis was examined by analyzing cell morphology, DNA fragmentation, and caspase-3 activity. Cells treated with 100 µM LFX and UVA clearly showed membrane blebbing and cell shrinkage. The proportion of apoptotic cells was significantly higher in cells treated with both UVA and LFX than in those treated with UVA or LFX alone. In addition, DNA ladder formation and caspase-3 activation were observed in cells treated with both UVA and LFX. A significant reduction in the number of UVA-induced apoptotic cells and caspase-3 activation was observed when histidine was present, which suggested that photodynamically-generated singlet oxygen is an important mediator of apoptosis. These results indicate that the combination of UVA and LFX induces apoptosis in HL-60 cells.

Evaluation of the mutagenicity of alkylating agents, methylnitrosourea and temozolomide, using the rat Pig-a assay with total red blood cells or reticulocytes.

A collaborative study of the endogenous phosphatidylinositol glycan class A (Pig-a) gene mutation assay was conducted by the Japanese Environmental Mutagen Society/Mammalian Mutagenicity Study Group with a single-dosing regimen of test chemicals administered to male rats. As a part of the study, two DNA alkylating agents, methylnitrosourea (MNU) and temozolomide (TMZ), were dosed by single oral gavage at 25, 50, and 100mg/kg body weight. Pig-a mutant analysis of total red blood cells (RBCs; RBC Pig-a assay) and reticulocytes (RETs; PIGRET assay) was performed on Days 8, 15 and 29 after the administration. Both chemicals increased Pig-a mutants among RBCs and RETs with dose dependency on all days examined. The mutant frequencies were higher among RETs compared with RBCs, indicating that the PIGRET assay could detect mutagenicity more sensitively than the RBC Pig-a assay after a single dose of test chemicals.

Inhibition of Fatty Acid Synthesis Induces Apoptosis of Human Pancreatic Cancer Cells.

Cancer cells tend to have a high requirement for lipids, including fatty acids, cholesterol and triglyceride, because of their rapid proliferative rate compared to normal cells. In this study, we investigated the effects of inhibition of lipid synthesis on the proliferation and viability of human pancreatic cancer cells. Of the inhibitors of lipid synthesis that were tested, 5-(tetradecyloxy)-2-furoic acid (TOFA), which is an inhibitor of acetyl-CoA carboxylase, and the fatty acid synthase (FAS) inhibitors cerulenin and irgasan, significantly suppressed the proliferation of MiaPaCa-2 and AsPC-1 cells. Treatment of MiaPaCa-2 cells with these inhibitors significantly increased the number of apoptotic cells. In addition, TOFA increased caspase-3 activity and induced cleavage of poly (ADP-ribose) polymerase in MiaPaCa-2 cells. Moreover, addition of palmitate to MiaPaCa-2 cells treated with TOFA rescued cells from apoptotic cell death. These results suggest that TOFA induces apoptosis via depletion of fatty acids and that, among the various aspects of lipid metabolism, inhibition of fatty acid synthesis may be a notable target for the treatment of human pancreatic cancer cells.

Assessment of methyl methanesulfonate using the repeated-dose liver micronucleus assay in young adult rats.

A repeated-dose liver micronucleus assay using young adult rats was conducted with methyl methanesulfonate (MMS) as a part of a collaborative study supported by the Collaborative Study Group for the Micronucleus Test/the Japanese Environmental Mutagen Society-Mammalian Mutagenicity Study Group. MMS is a classical DNA-reactive carcinogen, but it is not a liver carcinogen. In the first experiment (14-day study), MMS was administered per os to 6-week-old male Crl:CD (SD) rats every day for 14 days at a dose of 12.5, 25, or 50mg/kg/day. In the second experiment (28-day study), 6-week-old male SD rats were treated with MMS at 7.5, 15, or 30mg/kg/day for 28 days, because the highest dose used in the 14-day study (50mg/kg/day) caused mortality. Hepatocyte and bone marrow cell specimens were prepared on the day after the final dose. The frequency of micronucleated hepatocytes (MNHEPs) in the liver and that of micronucleated immature erythrocytes (MNIMEs) in the bone marrow were evaluated. Exposure to 50mg/kg/day MMS for 14 days resulted in an increased frequency of MNHEPs, but MMS had no effect on the frequency of MNHEPs in the rats exposed to the chemical for 28 days at doses up to 30mg/kg/day. MMS induced MNIMEs production at doses of 25 and 50mg/kg/day in the 14-day study and at doses of 15 and 30mg/kg/day in the 28-day study. Overall, the effect of MMS on the frequency of MNHEPs was considered to be equivocal.

Chromosomal damage and micronucleus induction by MP-124, a novel poly(ADP-ribose) polymerase-1 (PARP-1) inhibitor: Evidence for a non-DNA-reactive mode of action.

MP-124, a novel poly(ADP-ribose) polymerase-1 (PARP-1) inhibitor that competes with the binding of the PARP substrate nicotinamide adenine dinucleotide (NAD), is being developed as a neuroprotective agent against acute ischemic stroke. MP-124 increased structural chromosomal aberration in CHL/IU cells, but showed negative results in the bacterial reverse mutation test, and the rat bone marrow micronucleus (MN) and the rat liver unscheduled DNA synthesis tests after the intravenous bolus injection. Thus, MP-124 did not appear to be direct-acting mutagen. Since, PARP-1 is a key enzyme in DNA repair, the effect of continuous PARP-1 inhibition by MP-124 was further examined in the rat MN test under 24-h intravenous infusion, and an increase in micronucleated immature erythrocytes (MNIE) was observed. The increase was clearly reduced by co-treatment with nicotinic acid, which resulted in increased intracellular NAD levels. This is consistent with the established activity of MP-124 as a competitive inhibitor of PARP and provides strong evidence that the DNA-damaging effect that leads to the increase in MNIE is a secondary effect of PARP-1 inhibition. This mechanism is expected to result in a threshold for the induction of MNIE by MP-124, and allows for the establishment of a safe margin of exposure for the therapeutic use of MP-124.

Assessment of 8-methosypsoralen, lomefloxacin, sparfloxacin, and Pirfenidone phototoxicity in Long-Evans rats.

Phototoxicity has a strong impact on drug development. Although several animal models have been developed to quantitatively assess human risks, none have been validated for standardized use. In this study, we validated an in vivo phototoxicity model using Long-Evans (LE) rats treated with 4 well-known phototoxic drugs, namely 8-methoxypsoralen, lomefloxacin, sparfloxacin, and pirfenidone. Daily macroscopic observations of skin and eyes, ophthalmological examinations 4 days after dosing, and blood sampling for toxicokinetics (TKs) were performed after exposure of treated animals to ultraviolet, and dose-dependent eye and/or skin reactions were noted for all compounds. Margins of safety were calculated when possible and correlated well with known relative phototoxicity of the 4 compounds. We conclude that the present in vivo phototoxicity assay using LE rats with TK analysis can be used to quantitatively predict the risk of pharmaceutical phototoxicity in humans.

Involvement of reactive oxygen species in the enhancement of membrane lipid peroxidation by sonodynamic therapy with functionalized fullerenes.

BACKGROUND/AIM: Sonodynamic cancer therapy is based on the preferential uptake and/or retention of a sonosensitizing drug (sonosensitizer) in tumor tissues and subsequent activation of the drug by ultrasound irradiation. In the present study, we investigated the participation of lipid peroxidation in the mechanism of the sonodynamically-induced antitumor effect with functionalized fullerenes, such as polyhydroxy fullerene (PHF. MATERIALS AND METHODS: Ultrasonically-induced cell damage and lipid peroxidation with PHF were compared in the same in vitro insonation setup. Sarcoma 180 cells suspended in PBS were exposed to 2 MHz ultrasound in the presence and absence of PHF. Cell viability was determined by the Trypan Blue exclusion test. Lipid peroxidation in cell membranes was estimated by measuring the amount of malondialdehyde as the thiobarbituric acid-reactive-substances. RESULTS: Significant enhancement of the rates of both ultrasonically-induced cell damage and lipid peroxidation was observed in the presence of PHF, both of which were positively correlated with PHF. The enhancement of cell damage and lipid peroxidation with PHF was suppressed by reactive oxygen scavengers such as histidine and tryptophan. CONCLUSION: The good correlation observed in the presence of PHF suggests that membrane lipid peroxidation is one of the important intermediary events in sonodynamically-induced cellular damage. The inhibitory effects of histidine and tryptophan also provide evidence that singlet oxygen plays an important role in PHF-mediated sonosensitization of membranes and that this moiety may be an important mediator of cell destruction in sonodynamic therapy associated with PHF and ultrasound.

Usefulness of monitoring γ-H2AX and cell cycle arrest in HepG2 cells for estimating genotoxicity using a high-content analysis system.

Formation of the phosphorylated protein γ-H2AX is a well-established marker of DNA strand breakage induced by DNA-damaging compounds. Many of these genotoxic compounds also inhibit cell division, leading to arrest at specific points in the cell cycle. Detection of γ-H2AX in combination with cell cycle arrest may therefore be useful for estimating the genotoxicity of experimental compounds. In this study, we examined γ-H2AX formation and cell cycle arrest using high-content screening (HCS) as a method for determining genotoxicity. HepG2 cells were treated with a panel of compounds and then stained with Hoechst 33342 and anti-γ-H2AX, anti-phospho-histone H3, and anti-tubulin antibodies. In total, 19 genotoxic and 7 nongenotoxic compounds were tested in this study. γ-H2AX production was observed within 1 h posttreatment for the majority of Ames-positive compounds, topoisomerase inhibitors, and DNA polymerase inhibitors. Cell cycle arrest in either the S or G2 phase was detected for all DNA-damaging compounds 24 h posttreatment, whereas tubulin-targeting compounds were shown to induce cell cycle arrest in the mitotic phase. Together, these results show that HCS is a simple, rapid, and effective tool for estimating the genotoxicity of compounds through detection of γ-H2AX production and cell cycle arrest.

Intra-/inter-laboratory validation study on reactive oxygen species assay for chemical photosafety evaluation using two different solar simulators.

A previous multi-center validation study demonstrated high transferability and reliability of reactive oxygen species (ROS) assay for photosafety evaluation. The present validation study was undertaken to verify further the applicability of different solar simulators and assay performance. In 7 participating laboratories, 2 standards and 42 coded chemicals, including 23 phototoxins and 19 non-phototoxic drugs/chemicals, were assessed by the ROS assay using two different solar simulators (Atlas Suntest CPS series, 3 labs; and Seric SXL-2500V2, 4 labs). Irradiation conditions could be optimized using quinine and sulisobenzone as positive and negative standards to offer consistent assay outcomes. In both solar simulators, the intra- and inter-day precisions (coefficient of variation; CV) for quinine were found to be below 10%. The inter-laboratory CV for quinine averaged 15.4% (Atlas Suntest CPS) and 13.2% (Seric SXL-2500V2) for singlet oxygen and 17.0% (Atlas Suntest CPS) and 7.1% (Seric SXL-2500V2) for superoxide, suggesting high inter-laboratory reproducibility even though different solar simulators were employed for the ROS assay. In the ROS assay on 42 coded chemicals, some chemicals (ca. 19-29%) were unevaluable because of limited solubility and spectral interference. Although several false positives appeared with positive predictivity of ca. 76-92% (Atlas Suntest CPS) and ca. 75-84% (Seric SXL-2500V2), there were no false negative predictions in both solar simulators. A multi-center validation study on the ROS assay demonstrated satisfactory transferability, accuracy, precision, and predictivity, as well as the availability of other solar simulators.

Sonodynamically-induced anticancer effects by functionalized fullerenes.

BACKGROUND: Functionalized fullerenes, such as polyhydroxy fullerenes (PHF), have attracted particular attention due to their water solubility and their potential application in tumor imaging and therapy as carbon nanomaterials. In this study, the sonodynamically-induced antitumor effect of PHF was investigated. MATERIALS AND METHODS: Sonodynamically-induced antitumor effects of PHF in combination with ultrasound were investigated using isolated sarcoma 180 cells and solid tumor from colon 26 carcinoma cells. RESULTS: The cell damage induced by sonication was enhanced by two-fold in the presence of 80 µM PHF. Histidine significantly inhibited this enhancement. This inhibitory effect suggests that the sonodynamically-induced antitumor effect was mediated by sonodynamically-generated reactive oxygen species. The combined treatment of ultrasonic exposure with PHF suppressed the growth of implanted colon 26 tumors. The destruction of tumor tissue was observed with the ultrasonic treatment in combination with PHF, while neither the treatment with PHF alone nor that with ultrasound alone caused necrosis. CONCLUSION: These results suggest that PHF is a potential sonosensitizer for sonodynamic treatment of solid tumors.

Establishment and intra-/inter-laboratory validation of a standard protocol of reactive oxygen species assay for chemical photosafety evaluation.

A reactive oxygen species (ROS) assay was previously developed for photosafety evaluation of pharmaceuticals, and the present multi-center study aimed to establish and validate a standard protocol for ROS assay. In three participating laboratories, two standards and 42 coded chemicals, including 23 phototoxins and 19 nonphototoxic drugs/chemicals, were assessed by the ROS assay according to the standardized protocol. Most phototoxins tended to generate singlet oxygen and/or superoxide under UV-vis exposure, but nonphototoxic chemicals were less photoreactive. In the ROS assay on quinine (200 µm), a typical phototoxic drug, the intra- and inter-day precisions (coefficient of variation; CV) were found to be 1.5-7.4% and 1.7-9.3%, respectively. The inter-laboratory CV for quinine averaged 15.4% for singlet oxygen and 17.0% for superoxide. The ROS assay on 42 coded chemicals (200 µm) provided no false negative predictions upon previously defined criteria as compared with the in vitro/in vivo phototoxicity, although several false positives appeared. Outcomes from the validation study were indicative of satisfactory transferability, intra- and inter-laboratory variability, and predictive capacity of the ROS assay.

Involvement of reactive oxygen species in sonodynamically induced apoptosis using a novel porphyrin derivative.

In this study, we investigated the induction of apoptosis by ultrasound in the presence of the novel porphyrin derivative DCPH-P-Na(I). HL-60 cells were exposed to ultrasound for up to 3 min in the presence and absence of DCPH-P-Na(I), and the induction of apoptosis was examined by analyzing cell morphology, DNA fragmentation, and caspase-3 activity. Reactive oxygen species were measured by means of ESR and spin trapping technique. Cells treated with 8 µM DCPH-P-Na(I) and ultrasound clearly showed membrane blebbing and cell shrinkage, whereas significant morphologic changes were not observed in cells exposed to either ultrasound or DCPH-P-Na(I) alone. Also, DNA ladder formation and caspase-3 activation were observed in cells treated with both ultrasound and DCPH-P-Na(I) but not in cells treated with ultrasound or DCPH-P-Na(I) alone. In addition, the combination of DCPH-P-Na(I) and the same acoustical arrangement of ultrasound substantially enhanced nitroxide generation by the cells. Sonodynamically induced apoptosis, caspase-3 activation, and nitroxide generation were significantly suppressed by histidine. These results indicate that the combination of ultrasound and DCPH-P-Na(I) induced apoptosis in HL-60 cells. The significant reduction in sonodynamically induced apoptosis, nitroxide generation, and caspase-3 activation by histidine suggests active species such as singlet oxygen are important in the sonodynamic induction of apoptosis. These experimental results support the possibility of sonodynamic treatment for cancer using the induction of apoptosis.

Sonodynamically-induced antitumor effect of mono-l-aspartyl chlorin e6 (NPe6).

BACKGROUND: The sonodynamically-induced in vitro and in vivo antitumor effects of mono-l-aspartyl chlorin e6 (NPe6) was investigated. MATERIALS AND METHODS: Both in vitro and in vivo antitumor effects were tested in combination with ultrasound at 2 MHz. RESULTS: The rate of ultrasonically-induced damage on isolated sarcoma 180 cells in air-saturated suspension was enhanced two-fold with 80 µM NPe6. The co-administration of 25 mg/kg NPe6 followed by ultrasonic exposure at 2 MHz suppressed the growth of implanted colon 26 cell tumors at an intensity at which ultrasound alone showed only a slight antitumor effect. CONCLUSION: These in vitro and in vivo results suggest that NPe6 is a potential sensitizer for sonodynamic tumor treatment. The enhancement of cell damage by NPe6 was significantly inhibited by histidine, which may suggest reactive oxygen species plays a primary role in sonodynamically-induced antitumor effect.

Sonodynamically induced cell damage using rose bengal derivative.

AIM: The ultrasonically induced effect of a tumor accumulative derivative of rose bengal (RB) on isolated tumor cells was investigated to clarify whether the RB derivative (RBD) maintains the sonosensitizing ability of RB. MATERIALS AND METHODS: Sarcoma 180 cells were suspended in air-saturated phosphate-buffered saline and were exposed to ultrasound in standing wave mode for up to 60 s in the presence and absence of RBD or RB. The viability of the cells was determined by the ability to exclude trypan blue. RESULTS: The ultrasonically induced cell-damaging rate with 100 µM RBD was one order of magnitude higher than that with the same concentration of RB. This increase was significantly inhibited by the active oxygen scavengers histidine, tryptophan and N-acetyl-L-cysteine. CONCLUSION: Chemical modification of RB to RBD for tumor accumulation significantly increased the sonodynamically induced antitumor effect of RB.

Sonodynamically induced cell damage and membrane lipid peroxidation by novel porphyrin derivative, DCPH-P-Na(I).

BACKGROUND: Ultrasonically induced cell damage and active oxygen generation with a novel porphyrin derivative DCPH-P-Na(I), were compared in the same in vitro insonation setup. MATERIALS AND METHODS: Sarcoma 180 cells suspended in air-saturated PBS were exposed to ultrasound at 2 MHz for up to 60 s in the presence and absence of DCPH-P-Na(I). Cell viability was determined with the trypan blue exclusion test. Lipid peroxidation in cell membranes was estimated by measuring the amount of reactive substance produced immediately following the addition of thiobarbituric acid. RESULTS: Significant enhancement of the rates of both ultrasonically induced cell damage and lipid peroxidation was observed in the presence of 2-8 muM DCPH-P-Na(I). Both rates correlated very well. CONCLUSION: The enhancement of both rates with DCPH-P-Na(I) was suppressed by 10 mM histidine. These results suggest that ultrasonically generated active oxygen plays a primary role in the ultrasonically induced cell damage in the presence of DCPH-P-Na(I).