title: Cellular effects of low-intensity pulsed ultrasound and X-irradiation in combination in two human leukaemia cell lines.
abstract: Previously, we have shown that a combination between X-irradiation and low-intensity pulsed ultrasound (US) could synergistically suppress cell survival post exposure (Buldakov et al., 2014). In this study, the cellular effects underlying the enhanced cell killing are investigated. U937 and Molt-4 cell lines were exposed to 1.0 MHz US with 50% duty factor at 0.3 W/cm(2) and pulsed at 1, 5 and 10 Hz immediately after exposure to X-rays at 0, 0.5, 2.5 and 5 Gy. The cells were assayed at different time points to depict the major cellular events that culminated in cell death. For instance, membrane damage and cell lysis were estimated immediately following exposure and 24 h later. Intracellular reactive oxygen species (ROS) were also determined flow cytometrically after treatment. Moreover, the extent of DNA damage and cell cycle progression were determined at 6 and 24 h, respectively. Despite the general trend for synergism, there was a disproportionation of mediating factors depending on the cell type and its specific biological makeup. Immediately, US could induce appreciable necrotic cell death through extensive membrane damage in U937 but induced cell lysis in Molt-4 cells. ROS might have contributed to cell killing in Molt-4 but not in U937 cells. Although both of the physical modalities are significantly DNA-damaging alone, no additional damage was observed in combination. Moreover, override in some arrested cell cycle phases was also observed following combination. Collectively, the interaction between X-rays and US seems to depend mainly on the acoustic environment determined by the setup and this might explain the contradictory data among reports.
authors.affiliation: Department of Radiological Sciences, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama 930-0194, Japan; Cancer Research Institute of Siberian Вranch of the Russian Academy of Medical Sciences, Tomsk, Russia; Tomsk State University, Tomsk, Russia. Electronic address: buldakov@oncology.tomsk.ru.
authors.forename: Mikhail A
authors.initials: MA
authors.lastname: Buldakov
authors.affiliation: Department of Radiological Sciences, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama 930-0194, Japan; Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmacy, Cairo University, Kasr Al-Aini Str., Cairo 11562, Egypt. Electronic address: mariame.ali@staff.cu.edu.eg.
authors.forename: Mariame A
authors.initials: MA
authors.lastname: Hassan
authors.affiliation: Department of Radiological Sciences, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama 930-0194, Japan.
authors.forename: Paras
authors.initials: P
authors.lastname: Jawaid
authors.affiliation: Cancer Research Institute of Siberian Вranch of the Russian Academy of Medical Sciences, Tomsk, Russia.
authors.forename: Nadejda V
authors.initials: NV
authors.lastname: Cherdyntseva
authors.affiliation: Department of Radiological Sciences, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama 930-0194, Japan. Electronic address: kondot@med.u-toyama.ac.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kondo
mesh_terms: D002453:Cell Cycle / Q000528:radiation effects; D016923:Cell Death / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects; D004249:DNA Damage; D006801:Humans; D007938:Leukemia / Q000473:pathology*; D011829:Radiation Dosage; D020298:U937 Cells; D014465:Ultrasonics; D014965:X-Rays
keywords: Cell killing; Cell lysis; DNA damage; Ionizing radiation; Membrane damage; Ultrasound