Bioeffects of low-intensity ultrasound in vitro: apoptosis, protein profile alteration, and potential molecular mechanism

Effects of low-frequency ultrasound combined with microbubbles on breast cancer xenografts in nude mice

The aim of this study was to explore the effects of low-frequency ultrasound (US) combined with microbubbles (MBs) on breast cancer xenografts and explain its underlying mechanisms. A total of 20 xenografted nude mice were randomly divided into four groups: a group treated with US plus MBs (the US + MBs group), a group treated with US alone (the US group), a group treated with MBs alone (the MBs group), and a control group. In different groups, mice were treated with different US and injection regimens on an alternate day, three times in total. Histological changes, apoptosis of cells, microvascular changes, and the apoptosis index (AI) and microvascular density (MVD) of the breast cancer xenograft were analyzed after the mice were sacrificed. Results indicated that the tumor volume in the US + MBs group was smaller than that in the other three groups (p < 0.001 for all). The rate of tumor growth inhibition in the US + MBs group was significantly higher than that in the US and MBs groups (p < 0.001 for both). There were no significant differences in histological changes among the four groups. However, the AI was higher in the US + MBs group than that in the other three groups while the MVD was lower (p < 0.001 for all). All in all, low-frequency US combined with MBs can effectively slow down the growth of breast cancer in nude mice. In summary, low-frequency US combined with MBs has a significant effect on breast cancer treatment. Cavitation, thermal effects, and mechanical effects all play a vital role in the inhibition of tumor growth.

Harnessing External Irradiation for Precise Activation of Metal-Based Agents in Cancer Therapy

Cancer is a significant global health issue. Platinum-based chemotherapy drugs, including cisplatin, are crucial in clinical anti-cancer treatment. However, these drugs have limitations such as drug resistance, non-specific distribution, and irreversible toxic and side effects. In recent years, the development of metal-based agents has led to the discovery of other anti-cancer effects beyond chemotherapy. Precise spatiotemporal controlled external irradiation can activate metal-based agents at specific sites and play a different role from traditional chemotherapy. These strategies can not only enhance the anti-cancer efficiency, but also show fewer side effects and non-cross-drug resistance, which are ideal approaches to solve the problems caused by traditional platinum-based chemotherapy drugs. In this review, we focus on various metal-based agent-mediated cancer therapies that are activated by three types of external irradiation: near-infrared (NIR) light, ultrasound (US), and X-ray, and give some prospects. We hope that this review will promote the generation of new kinds of metal-based anti-cancer agents.

Study on the effect of a triple cancer treatment of propolis, thermal cycling-hyperthermia, and low-intensity ultrasound on PANC-1 cells

To reduce side effects and enhance treatment efficacy, study on combination therapy for pancreatic cancer, a deadly cancer, has gained much attraction in recent years. In this study, we propose a novel triple treatment combining propolis and two physical stimuli-thermal cycling-hyperthermia (TC-HT) and low-intensity ultrasound (US). The study found that, after the triple treatment, the cell viability of a human cancer cell line PANC-1 decreased to a level 80% less than the control, without affecting the normal pancreatic cells. Another result was excessive accumulation of reactive oxygen species (ROS) after the triple treatment, leading to the amplification of apoptotic pathway through the MAPK family and mitochondrial dysfunction. This study, to the best of our knowledge, is the first attempt to combine TC-HT, US, and a natural compound in cancer treatment. The combination of TC-HT and US also promotes the anticancer effect of the heat-sensitive chemotherapy drug cisplatin on PANC-1 cells. It is expected that optimized parameters for different agents and different types of cancer will expand the methodology on oncological therapy in a safe manner.

GHz Ultrasound and Electrode Chip-Scale Arrays Stimulate and Influence Morphology of Human Neural Cells

This study describes the effects of chip-scale gigahertz (GHz) ultrasound (US) and electrical stimulus on the morphology, functionality, and viability of neural cells in vitro. The GHz frequency stimulation is achieved using aluminum nitride piezoelectric transducers fabricated on a silicon wafer, operating at 1.47 GHz, corresponding to the film's thickness mode resonance. These devices are used to stimulate SH-SY5Y neural cells in vitro and observe effects on the morphology and viability of the stimulated cells. It is possible to use these devices to deliver either ultrasonic stimulus alone or US stimulus in conjunction with electrical stimulus. Viability tests demonstrated that the neurons retained structural integrity and viability across a wide range of GHz US stimulus intensities (0-1.2 W/cm²), validating that measurements occur at nontoxic doses of US. Neural stimulation is validated with these devices following the outputs of a previous study, with the normalized fluorescence intensity of activated cells between 1.9 and 2.4. The 300-s ultrasonic stimulation at 1.47 GHz and 0.05 W/cm² peak intensity led to a decrease in nuclear elongation by 17.5% and a cross-sectional area decrease by 17.8% across three independent trials of over 150 cells per category ( ). The F-actin governed cellular elongation increased in length by up to 16.3% in cells exposed to an ultrasonic stimulus or costimulus ( ). Neurite length increased following ultrasonic stimulation compared with control by 75.8% ( ). This article demonstrates new GHz US and electrical chip-scale arrays with apparent effects in both neural excitation and cell morphology.

System and method for applying physiotherapeutic focused ultrasound

Despite many years of clinical use of ultrasound, the results of different reviews of controlled trials on the efficacy of ultrasound physical therapy for different musculoskeletal injuries continue to question its efficacy. However, "in vitro" experiments with well-controlled cell cultures and experiments with animal models show positive results. The question is whether the commercial systems used by physiotherapists can deliver the required ultrasonic dose to the exact location on the body. The object of this work is the design, realization and testing of a new concept of ultrasound system for Physiotherapy capable of focusing the ultrasound beam to apply the required ultrasonic energy dose at the point targeted by the physiotherapist. The system is designed for non-thermal effects Physiotherapy. The system consists of conceptually new piezocomposite arrays with a metallic delay line, multi-pulser electronics for emission focusing, parallel robots for mechanical steering and positioning of the array transducers, and linear and angular encoders to allow the physiotherapist to direct the focus to the target. The multi-pulser and parallel robot angulation are controlled by the computer, using a graphical interface software.

Ultrasound Protects Human Chondrocytes from Biochemical and Ultrastructural Changes Induced by Oxidative Stress

The aim of the study was to assess the effects of therapeutic ultrasound (US) on oxidative stress (OS)-induced changes in cultured human chondrocytes (HCH). For this, monolayer HCH were randomized in three groups: a control group (CG), a group exposed to OS (OS group), and a group exposed to US and OS (US-OS group). US exposure of the chondrocytes was performed prior to OS induction by hydrogen peroxide. Transmission electron microscopy (TEM) was used to assess the chondrocytes ultrastructure. OS and inflammatory markers were recorded. Malondialdehyde (MDA) and tumor necrosis factor (TNF)-α were significantly higher (p < 0.05) in the OS group than in CG. In the US-OS group MDA and TNF-α were significantly lower (p < 0.05) than in the OS group. Finally, in the US-OS group MDA and TNF-α were lower than in CG, but without statistical significance. TEM showed normal chondrocytes in CG. In the OS group TEM showed necrotic chondrocytes and chondrocytes with a high degree of vacuolation and cell organelles damages. In the US-OS group the chondrocytes ultrastructure was well preserved, and autophagosomes were generated. In conclusion, US could protect chondrocytes from biochemical (lipid peroxidation, inflammatory markers synthesis) and ultrastructural changes induced by OS and could stimulate autophagosomes development.

Ultrasounds in cancer therapy: A summary of their use and unexplored potential

Ultrasounds (US) are a non-ionizing mechanical wave, with less adverse effects than conventional pharmacological or surgical treatments. Different biological effects are induced in tissues and cells by ultrasound actuation depending on acoustic parameters, such as the wave intensity, frequency and treatment dose. This non-ionizing radiation has considerable applications in biomedicine including surgery, medical imaging, physical therapy and cancer therapy. Depending on the wave intensity, US are applied as high-intensity ultrasounds (HIUS) and low-intensity pulsed ultrasounds (LIPUS), with different effects on cells and tissues. HIUS produce thermal and mechanical effects, resulting in a large localized temperature increase, leading to tissue ablation and even tumor necrosis. This can be achieved by focusing low intensity waves emitted from different electrically shifted transducers, known as high-intensity focused ultrasounds (HIFU). LIPUS have been used extensively as a therapeutic, surgical and diagnostic tool, with diverse biological effects observed in tissues and cultured cells. US represent a non-invasive treatment strategy that can be applied to selected areas of the body, with limited adverse effects. In fact, tumor ablation using HIFU has been used as a curative treatment in patients with an early-stage pancreatic tumor and is an effective palliative treatment in patients with advanced stage disease. However, the biological effects, dose standardization, benefit-risk ratio and safety are not fully understood. Thus, it is an emerging field that requires further research in order to reach its full potential.

Non-contact ultrasound oocyte denudation

Cumulus removal (CR) is a central prerequisite step for many protocols involved in the assisted reproductive technology (ART) such as intracytoplasmic sperm injection (ICSI) and preimplantation genetic testing (PGT). The most prevalent CR technique is based upon laborious manual pipetting, which suffers from inter-operator variability and therefore a lack of standardization. Automating CR procedures would alleviate many of these challenges, improving the odds of a successful ART or PGT outcome. In this study, a chip-scale ultrasonic device consisting of four interdigitated transducers (IDT) on a lithium niobate substrate has been engineered to deliver megahertz (MHz) range ultrasound to perform denudation. The acoustic streaming and acoustic radiation force agitate COCs inside a microwell placed on top of the LiNbO₃ substrate to remove the cumulus cells from the oocytes. This paper demonstrates the capability and safety of the denudation procedure utilizing surface acoustic wave (SAW), achieving automation of this delicate manual procedure and paving the steps toward improved and standardized oocyte manipulation.

Advances in Nanoliposomes for the Diagnosis and Treatment of Liver Cancer

The mortality rate of liver cancer is gradually increasing worldwide due to the increasing risk factors such as fatty liver, diabetes, and alcoholic cirrhosis. The diagnostic methods of liver cancer include ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI), among others. The treatment of liver cancer includes surgical resection, transplantation, ablation, and chemoembolization; however, treatment still faces multiple challenges due to its insidious development, high rate of recurrence after surgical resection, and high failure rate of transplantation. The emergence of liposomes has provided new insights into the treatment of liver cancer. Due to their excellent carrier properties and maneuverability, liposomes can be used to perform a variety of functions such as aiding in imaging diagnoses, combinatorial therapies, and integrating disease diagnosis and treatment. In this paper, we further discuss such advantages.

Effect of 1-MHz ultrasound on the proinflammatory interleukin-6 secretion in human keratinocytes

Keratinocytes, the main cell type of the skin, are one of the most exposed cells to environmental factors, providing a first defence barrier for the host and actively participating in immune response. In fact, keratinocytes express pattern recognition receptors that interact with pathogen associated molecular patterns and damage associated molecular patterns, leading to the production of cytokines and chemokines, including interleukin (IL)-6. Herein, we investigated whether mechanical energy transported by low intensity ultrasound (US) could generate a mechanical stress able to induce the release of inflammatory cytokine such IL-6 in the human keratinocyte cell line, HaCaT. The extensive clinical application of US in both diagnosis and therapy suggests the need to better understand the related biological effects. Our results point out that US promotes the overexpression and secretion of IL-6, associated with the activation of nuclear factor-κB (NF-κB). Furthermore, we observed a reduced cell viability dependent on exposure parameters together with alterations in membrane permeability, paving the way for further investigating the molecular mechanisms related to US exposure.

Enhanced tumor cell killing by ultrasound after microtubule depolymerization

Recent studies show that tumor cells are vulnerable to mechanical stresses and undergo calcium-dependent apoptosis (mechanoptosis) with mechanical perturbation by low-frequency ultrasound alone. To determine if tumor cells are particularly sensitive to mechanical stress in certain phases of the cell cycle, inhibitors of the cell-cycle phases are tested for effects on mechanoptosis. Most inhibitors show no significant effect, but inhibitors of mitosis that cause microtubule depolymerization increase the mechanoptosis. Surprisingly, ultrasound treatment also disrupts microtubules independent of inhibitors in tumor cells but not in normal cells. Ultrasound causes calcium entry through mechanosensitive Piezo1 channels that disrupts microtubules via calpain protease activation. Myosin IIA contractility is required for ultrasound-mediated mechanoptosis and microtubule disruption enhances myosin IIA contractility through activation of GEF-H1 and RhoA pathway. Further, ultrasound promotes contractility-dependent Piezo1 expression and localization to the peripheral adhesions where activated Piezo1 allows calcium entry to continue feedback loop. Thus, the synergistic action of ultrasound and nanomolar concentrations of microtubule depolymerizing agents can enhance tumor therapies.

Effects of Non-thermal Ultrasound on a Fibroblast Monolayer Culture: Influence of Pulse Number and Pulse Repetition Frequency

Despite the use of therapeutic ultrasound in the treatment of soft tissue pathologies, there remains some controversy regarding its efficacy. In order to develop new treatment protocols, it is a common practice to carry out in vitro studies in cell cultures before conducting animal tests. The lack of reproducibility of the experimental results observed in the literature concerning in vitro experiments motivated us to establish a methodology for characterizing the acoustic field in culture plate wells. In this work, such acoustic fields are fully characterized in a real experimental configuration, with the transducer being placed in contact with the surface of a standard 12-well culture plate. To study the non-thermal effects of ultrasound on fibroblasts, two different treatment protocols are proposed: long pulse (200 cycles) signals, which give rise to a standing wave in the well with the presence of cavitation (I_SPTP max = 19.25 W/cm²), and a short pulse (five cycles) of high acoustic pressure, which produces a number of echoes in the cavity (I_SPTP = 33.1 W/cm², with P_max = 1.01 MPa). The influence of the acoustic intensity, the number of pulses, and the pulse repetition frequency was studied. We further analyzed the correlation of these acoustic parameters with cell viability, population, occupied surface, and cell morphology. Lytic effects when cavitation was present, as well as mechanotransduction reactions, were observed.

Nanoparticle-Assisted Sonosensitizers and Their Biomedical Applications

As a non-invasive strategy, sonodynamic therapy (SDT) which utilizes sonosensitizers to generate reactive oxygen species (ROS) has received significant interest over recent years due to its ability to break depth barrier. However, intrinsic limitations of traditional sonosensitizers hinder the widespread application of SDT. With the development of nanotechnology, various nanoparticles (NPs) have been designed and used to assist sonosensitizers for SDT. This review first summarizes the possible mechanisms of SDT, then classifies the NPs-assisted sonosensitizers and discusses their biomedical applications in ultrasonography, drug delivery, high intensity focused ultrasound and SDT-based combination treatment. Finally, some challenges and future perspectives of NPs-assisted SDT has also been discussed.

GHz Ultrasonic Chip-Scale Device Induces Ion Channel Stimulation in Human Neural Cells

Emergent trends in the device development for neural prosthetics have focused on establishing stimulus localization, improving longevity through immune compatibility, reducing energy re-quirements, and embedding active control in the devices. Ultrasound stimulation can single-handedly address several of these challenges. Ultrasonic stimulus of neurons has been studied extensively from 100 kHz to 10 MHz, with high penetration but less localization. In this paper, a chip-scale device consisting of piezoelectric Aluminum Nitride ultrasonic transducers was engineered to deliver gigahertz (GHz) ultrasonic stimulus to the human neural cells. These devices provide a path towards complementary metal oxide semiconductor (CMOS) integration towards fully controllable neural devices. At GHz frequencies, ultrasonic wavelengths in water are a few microns and have an absorption depth of 10-20 µm. This confinement of energy can be used to control stimulation volume within a single neuron. This paper is the first proof-of-concept study to demonstrate that GHz ultrasound can stimulate neurons in vitro. By utilizing optical calcium imaging, which records calcium ion flux indicating occurrence of an action potential, this paper demonstrates that an application of a nontoxic dosage of GHz ultrasonic waves [Formula: see text] caused an average normalized fluorescence intensity recordings >1.40 for the calcium transients. Electrical effects due to chip-scale ultrasound delivery was discounted as the sole mechanism in stimulation, with effects tested at α = 0.01 statistical significance amongst all intensities and con-trol groups. Ionic transients recorded optically were confirmed to be mediated by ion channels and experimental data suggests an insignificant thermal contributions to stimulation, with a predicted increase of 0.03 ^oC for [Formula: see text] This paper paves the experimental framework to further explore chip-scale axon and neuron specific neural stimulation, with future applications in neural prosthetics, chip scale neural engineering, and extensions to different tissue and cell types.

In vitro potentiation of doxorubicin by unseeded controlled non-inertial ultrasound cavitation

Ultrasound-generated non-inertial cavitation has the ability to potentiate the therapeutic effects of cytotoxic drugs. We report a novel strategy to induce and regulate unseeded (without nucleation agents) non-inertial cavitation, where cavitation is initiated, monitored and regulated using a confocal ultrasound setup controlled by an instrumentation platform and a PC programmed feedback control loop. We demonstrate, using 4T1 murine mammary carcinoma as model cell line, that unseeded non-inertial cavitation potentiates the cytotoxicity of doxorubicin, one of the most potent drugs used in the treatment of solid tumors including breast cancer. Combined treatment with doxorubicin and unseeded non-inertial cavitation significantly reduced cell viability and proliferation at 72 h. A mechanistic study of the potential mechanisms of action of the combined treatment identified the presence of cavitation as required to enhance doxorubicin efficacy, but ruled out the influence of changes in doxorubicin uptake, temperature increase, hydroxyl radical production and nuclear membrane modifications on the treatment outcome. The developed strategy for the reproducible generation and maintenance of unseeded cavitation makes it an attractive method as potential preclinical and clinical treatment modality to locally potentiate doxorubicin.

Experimental Data-Mining Analyses Reveal New Roles of Low-Intensity Ultrasound in Differentiating Cell Death Regulatome in Cancer and Non-cancer Cells via Potential Modulation of Chromatin Long-Range Interactions

Background: The mechanisms underlying low intensity ultrasound (LIUS) mediated suppression of inflammation and tumorigenesis remain poorly determined. Methods: We used microarray datasets from NCBI GEO Dataset databases and conducted a comprehensive data mining analyses, where we studied the gene expression of 299 cell death regulators that regulate 13 different cell death types (cell death regulatome) in cells treated with LIUS. Results: We made the following findings: (1) LIUS exerts a profound effect on the expression of cell death regulatome in cancer cells and non-cancer cells. Of note, LIUS has the tendency to downregulate the gene expression of cell death regulators in non-cancer cells. Most of the cell death regulator genes downregulated by LIUS in non-cancer cells are responsible for mediating inflammatory signaling pathways; (2) LIUS activates different cell death transcription factors in cancer and non-cancer cells. Transcription factors TP-53 and SRF- were induced by LIUS exposure in cancer cells and non-cancer cells, respectively; (3) As two well-accepted mechanisms of LIUS, mild hyperthermia and oscillatory shear stress induce changes in the expression of cell death regulators, therefore, may be responsible for inducing LIUS mediated changes in gene expression patterns of cell death regulators in cells; (4) LIUS exposure may change the redox status of the cells. LIUS may induce more of antioxidant effects in non-cancer cells compared to cancer cells; and (5) The genes modulated by LIUS in cancer cells have distinct chromatin long range interaction (CLRI) patterns to that of non-cancer cells. Conclusions: Our analysis suggests novel molecular mechanisms that may be utilized by LIUS to induce tumor suppression and inflammation inhibition. Our findings may lead to development of new treatment protocols for cancers and chronic inflammation.

Nonuniform Bessel-Based Radiation Distributions on A Spherically Curved Boundary for Modeling the Acoustic Field of Focused Ultrasound Transducers

Therapeutic focused ultrasound is a technique that can be used with different intensities depending on the application. For instance, low intensities are required in nonthermal therapies, such as drug delivering, gene therapy, etc.; high intensity ultrasound is used for either thermal therapy or instantaneous tissue destruction, for example, in oncologic therapy with hyperthermia and tumor ablation. When an adequate therapy planning is desired, the acoustic field models of curve radiators should be improved in terms of simplicity and congruence at the prefocal zone. Traditional ideal models using uniform vibration distributions usually do not produce adequate results for clamped unbacked curved radiators. In this paper, it is proposed the use of a Bessel-based nonuniform radiation distribution at the surface of a curved radiator to model the field produced by real focused transducers. This proposal is based on the observed complex vibration of curved transducers modified by Lamb waves, which have a non-negligible effect in the acoustic field. The use of Bessel-based functions to approximate the measured vibration instead of using plain measurements simplifies the rationale and expands the applicability of this modeling approach, for example, when the determination of the effects of ultrasound in tissues is required.

Mitochondrial inner membrane protein, Mic60/mitofilin in mammalian organ protection

The identification of the mitochondrial contact site and cristae organizing system (MICOS) in the inner mitochondrial membrane shed light on the intricate components necessary for mitochondria to form their signature cristae in which many protein complexes including the electron transport chain are localized. Mic60/mitofilin has been described as the core component for the assembly and maintenance of MICOS, thus controlling cristae morphology, protein transport, mitochondrial DNA transcription, as well as connecting the inner and outer mitochondrial membranes. Although Mic60 homologs are present in many species, mammalian Mic60 is only recently gaining attention as a critical player in several organ systems and diseases with mitochondrial-defect origins. In this review, we summarize what is currently known about the ever-expanding role of Mic60 in mammals, and highlight some new studies pushing the field of mitochondrial cristae organization towards potentially new and exciting therapies targeting this protein.

Low‑frequency ultrasound and microbubbles combined with simvastatin promote the apoptosis of MCF‑7 cells by affecting the LATS1/YAP/RHAMM pathway

Ultrasound scanning has widespread used in clinical practice and also has therapeutic applications. Simvastatin is a statins that is able to competitively inhibit the activity of 3‑hydroxy‑3‑methylglutaryl‑coenzyme A reductase. The aim of the present study was to investigate the roles and mechanisms of low‑frequency ultrasound (LFU) and microbubbles combined with simvastatin on MCF‑7 cell growth and apoptosis. Cell viability, apoptosis and cell cycle were evaluated using an MTT assay and flow cytometry, respectively. The expression of related proteins was measured by western blot assay. The results revealed that simvastatin and LFU with microbubbles reduces the viability of MCF‑7 cells. The combination of LFU and microbubbles with simvastatin promoted the apoptosis of MCF‑7 cells. Furthermore, it was confirmed that LFU and microbubbles combined with simvastatin affected the large tumor suppressor 1 (LATS1)/yes‑associated protein (YAP)/receptor of the hyaluronan‑mediated motility (RHAMM) pathway in MCF‑7 cells. It was determined that LATS1 acts as a negative regulator in the LATS1/YAP/RHAMM pathway in MCF‑7 cells. In conclusion, the results of the present study indicate that LFU and microbubbles combined with simvastatin promotes the apoptosis of MCF‑7 cells via the LATS1/YAP/RHAMM pathway. The present study suggested a possible strategy for the treatment of breast cancer.

Nanoparticle-assisted ultrasound: A special focus on sonodynamic therapy against cancer

At present, ultrasound radiation is broadly employed in medicine for both diagnostic and therapeutic purposes at various frequencies and intensities. In this review article, we focus on therapeutically-active nanoparticles (NPs) when stimulated by ultrasound. We first introduce the different ultrasound-based therapies with special attention to the techniques involved in the oncological field, then we summarize the different NPs used, ranging from soft materials, like liposomes or micro/nano-bubbles, to metal and metal oxide NPs. We therefore focus on the sonodynamic therapy and on the possible working mechanisms under debate of NPs-assisted sonodynamic treatments. We support the idea that various, complex and synergistics physical-chemical processes take place during acoustic cavitation and NP activation. Different mechanisms are therefore responsible for the final cancer cell death and strongly depends not only on the type and structure of NPs or nanocarriers, but also on the way they interact with the ultrasonic pressure waves. We conclude with a brief overview of the clinical applications of the various ultrasound therapies and the related use of NPs-assisted ultrasound in clinics, showing that this very innovative and promising approach is however still at its infancy in the clinical cancer treatment.

Ultrasound-triggered PLGA microparticle destruction and degradation for controlled delivery of local cytotoxicity and drug release

In this study, we investigated the low intensity ultrasound (US)-controlled delivery of local cytotoxicity and drug release via induced destruction and degradation of microparticles (MPs) made of poly(lactic-co-glycolic acid) (PLGA). This study was conducted in vitro with potential application towards tumor treatment in conjunction with direct injection. MPs, either loaded with or without doxorubicin (DOX), were prepared using a double-emulsion solvent-evaporation technique. First, the MPs were exposed to US with duty cycle (DC)-modulation. The destruction and degradation of MPs were evaluated using light and scanning electron microscopy. Second, the effects of US-mediated destruction/degradation of MPs on the local cytotoxicity as well as DOX release were evaluated. US-triggered MP destruction/degradation significantly enhanced nearby cell death and DOX release. These affects occurred in proportion to the DC. Our findings indicate that controlled cytotoxicity and DOX release by US could be useful in developing the minimally invasive therapeutic applications for tumor treatment.

Effect of platinum nanoparticles on cell death induced by ultrasound in human lymphoma U937 cells

In this study, we report on the potential use of platinum nanoparticles (Pt-NPs), a superoxide dismutase (SOD)/catalase mimetic antioxidant, in combination with 1MHz ultrasound (US) at an intensity of 0.4 W/cm(2), 10% duty factor, 100 Hz PRF, for 2 min. Apoptosis induction was assessed by DNA fragmentation assay, cell cycle analysis and Annexin V-FITC/PI staining. Cell killing was confirmed by cell counting and microscopic examination. The mitochondrial and Ca(2+)-dependent pathways were investigated. Caspase-8 expression and autophagy-related proteins were detected by spectrophotometry and western blot analysis, respectively. Intracellular reactive oxygen species (ROS) elevation was detected by flow cytometry, while extracellular free radical formation was assessed by electron paramagnetic resonance spin trapping spectrometry. The results showed that Pt-NPs exerted differential effects depending on their internalization. Pt-NPs functioned as potent free radical scavengers when added immediately before sonication while pre-treatment with Pt-NPs suppressed the induction of apoptosis as well as autophagy (AP), and resulted in enhanced cell killing. Dead cells displayed the features of pyknosis. The exact mode of cell death is still unclear. In conclusion, the results indicate that US-induced AP may contribute to cell survival post sonication. To our knowledge this is the first study to discuss autophagy as a pro-survival pathway in the context of US. The combination of Pt-NPs and US might be effective in cancer eradication.

Low intensity-pulsed ultrasound induced apoptosis of human hepatocellular carcinoma cells in vitro

The present study was conducted to determine whether low intensity-pulsed ultrasound (LIPUS) could induce apoptosis of human hepatocellular carcinoma cells, SMMC-7721, and to define the mechanism of ultrasound-induced apoptosis, in vitro. MTT assay was used to measure cell proliferation. Apoptosis was investigated by multiple methods such as flow cytometry, DNA fragmentation, Ca(2+) mobilizations, pro- and anti-apoptotic protein expression, and light as well as ultramicroscopic morphology. The results provide evidence that LIPUS induced a dose-dependent effect on cell viability and apoptosis of SMMC-7721 cells. Specifically, exposure of cells to >0.5 W/cm(2) intensity significantly increased cell apoptosis, caused shifts in cell cycle phase, and induced structural changes. Ultrasound significantly increased intracellular Ca(2+) concentrations and modulated expression of caspase-3, Bcl-2 and Bax. The findings suggest that this novel technology can be used to induce SMMC-7721 apoptosis via the Ca(2+)/mitochondrial pathway and could potentially be of clinical use for the treatment of hepatocellular carcinoma (SMMC-7721 cell line) and other cancers.

Upregulation of Beclin-1 expression in DU-145 cells following low-frequency ultrasound irradiation combined with microbubbles

Castration-resistant prostate cancer (PCa) is difficult to treat. Autophagy, which is an evolutionarily conserved mechanism, plays an important role in cancer development. The balance between cell death and survival in different stages varies in cancer development. The role of autophagy in PCa development has not yet been fully elucidated. Ultrasound may be of value in the treatment of PCa. The aim of the present study was to investigate the association between autophagy and ultrasound combined with microbubbles. The MTT assay was used to evaluate cell viability. Autophagy was observed by transmission electron microscopy. Reverse transcription-polymerase chain reaction and western blot analysis were used to assess the expression of autophagy-related genes. The results revealed that cell viability was significantly reduced by ultrasound combined with microbubbles in DU145 PCa cells. The present study demonstrated that ultrasound combined with microbubbles induced autophagy and autophagy-related DU-145 cell death. Notably, these findings highlighted additional mechanisms that suggest the potential of ultrasound-modulated autophagy as a novel therapeutic strategy for PCa.

Porphyrin derivatives-mediated sonodynamic therapy for malignant gliomas in vitro

Because it is highly infiltrative, malignant glioma is a cancer with a poor prognosis despite multidisciplinary treatment strategies, such as aggressive surgery and chemoradiotherapy, necessitating new therapeutic approaches to control migration of tumor cells. In our study, we investigated the efficacy of sonodynamic therapy of glioma cells in vitro using porphyrin derivatives, including 5-aminolevulinic acid, protoporphyrin IX and talaporfin sodium, as sonosensitizers. These substances have been known to accumulate in glioma cells and are expected to have cytotoxic effects on sonication. Our study found that the cytotoxicity of sonication of glioma cells is enhanced by each sonosensitizer and that the efficacy of sonodynamic therapy may depend on the degree of intracellular accumulation of sonosensitizer. Also, the study suggests that induction of apoptosis is a major mechanism underlying cell death. Though further investigations are necessary, our preliminary result indicates a potential for sonodynamic therapy with sonosensitizers in glioma treatment.

Characterization of Dynamic Behaviour of MCF7 and MCF10A Cells in Ultrasonic Field Using Modal and Harmonic Analyses

Treatment options specifically targeting tumour cells are urgently needed in order to reduce the side effects accompanied by chemo- or radiotherapy. Differences in subcellular structure between tumour and normal cells determine their specific elasticity. These structural differences can be utilised by low-frequency ultrasound in order to specifically induce cytotoxicity of tumour cells. For further evaluation, we combined in silico FEM (finite element method) analyses and in vitro assays to bolster the significance of low-frequency ultrasound for tumour treatment. FEM simulations were able to calculate the first resonance frequency of MCF7 breast tumour cells at 21 kHz in contrast to 34 kHz for the MCF10A normal breast cells, which was due to the higher elasticity and larger size of MCF7 cells. For experimental validation of the in silico-determined resonance frequencies, equipment for ultrasonic irradiation with distinct frequencies was constructed. Differences for both cell lines in their response to low-frequent ultrasonic treatment were corroborated in 2D and in 3D cell culture assays. Treatment with ~ 24.5 kHz induced the death of MCF7 cells and MDA-MB-231 metastases cells possessing a similar elasticity; frequencies of > 29 kHz resulted in cytotoxicity of MCF10A. Fractionated treatments by ultrasonic irradiation of suspension myeloid HL60 cells resulted in a significant decrease of viable cells, mostly significant after threefold irradiation in intervals of 3 h. Most importantly in regard to a clinical application, combined ultrasonic treatment and chemotherapy with paclitaxel showed a significantly increased killing of MCF7 cells compared to both monotherapies. In summary, we were able to determine for the first time for different tumour cell lines a specific frequency of low-intensity ultrasound for induction of cell ablation. The cytotoxic effect of ultrasonic irradiation could be increased by either fractionated treatment or in combination with chemotherapy. Thus, our results will open new perspectives in tumour treatment.

Cellular effects of low-intensity pulsed ultrasound and X-irradiation in combination in two human leukaemia cell lines

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.

Combined treatment of PC-3 cells with ultrasound and microbubbles suppresses invasion and migration

The aim of the present study was to investigate whether ultrasound treatment combined with microbubbles inhibits cell invasion and migration in androgen-independent prostate cancer (PCa) cells and to identify the probable mechanism. Ultrasound was used in continuous wave mode at a frequency of 21 kHz and with a spatial-average temporal-average intensity of 46 mW/cm². Ultrasound combined with microbubbles (200 μl; SonoVue) was administered to androgen-independent human PCa PC-3 cells for 30 sec. The PC-3 cells were divided into three groups: The control group, the ultrasound group (US) and the ultrasound combined with microbubbles group (US + MB). Following treatment for 12, 24, 48 and 72 h, cell counting kit-8 was used to assess cell viability. Cell invasion and migration was measured 12 h after treatment using Transwell migration assays. Quantitative polymerase chain reaction and western blot analysis were used to evaluate the expression of the migration-associated proteins, matrix metalloproteinase (MMP)-2 and MMP-9. Cell reproduction levels in the US and US + MB groups were significantly suppressed when compared with the control group (P<0.01) following 24 h of treatment and this suppression was significantly higher in the US + MB group than in the US group (P<0.01). However, no significant differences in cell reproduction levels between the three groups were identified at 12 h (P>0.05). Ultrasound combined with microbubbles significantly suppressed the level of invasion and migration in the PC-3 cells compared with the control group (190.83±14.63 vs. 509.67±18.62, P<0.01; and 86.67±10.60 vs. 271.33±65.14; P<0.01, respectively). Furthermore, combined treatment with ultrasound and microbubbles suppressed the expression of MMP-2 and MMP-9. In conclusion, it was found that ultrasound combined with microbubbles suppressed invasion and migration in human PCa PC-3 cells via downregulation of MMP-2 and MMP-9.

Enhanced antitumor effects of low-frequency ultrasound and microbubbles in combination with simvastatin by downregulating caveolin-1 in prostatic DU145 cells

Advanced prostate cancer is difficult to treat due to androgen resistance, its deep location and blood tumor barriers. Low-frequency ultrasound (LFU) has potential clinical applications in the treatment of prostate cancer due to its strong penetrability and high sensitivity towards tumor cells. Simvastatin has often been administered as a preventive agent in prostate tumors. The aim of the present study was to investigate the enhanced effects of LFU and microbubbles in combination with simvastatin, in inhibiting cell viability and promoting apoptosis of androgen-independent prostatic DU145 cells. Cultured DU145 cells were divided into six groups based on the combination of treatments as follows: Control, LFU, LFU and microbubbles (LFUM), simvastatin, LFU and simvastatin, LFUM and simvastatin. The cells were treated by LFU (80 kHz) continuously for 30 sec with an ultrasound intensity of 0.45 W/cm² and a microbubble density of 20%. Simvastatin was added 30 h prior to the ultrasound exposure. The results indicated that cell viability was marginally reduced in the LFU and simvastatin alone treatment groups compared with the control 24 h following ultrasound exposure. The combination of LFU, with microbubbles or simvastatin, potentiated the growth inhibition; the greatest inhibition was observed in the cells that were subject to treatment with LFUM and simvastatin in combination. Furthermore, this inhibitory effect was enhanced in a time-dependent manner. For cell apoptosis, a low dose of simvastatin had no apparent affect on the DU145 cells, while LFU marginally promoted cell apoptosis. Microbubbles or simvastatin increased the apoptosis rate of the DU145 cells, however, the combination of LFUM and simvastatin induced a strong synergistic effect on cell apoptosis. Western blotting analysis demonstrated a high expression level of caveolin-1 in resting DU145 cells. LFUM or combined LFU and simvastatin resulted in a greater reduction in the expression compared with the control group (P<0.05). The expression of caveolin-1 was lowest in the LFUM combined with simvastatin treatment group. The expression of phospho-Akt (p-Akt) was consistent with caveolin-1, with the lowest expression levels of p-Akt observed in the cells that were treated with the combination of LFUM and simvastatin. The results indicate that LFUM in combination with simvastatin may additively or synergistically inhibit cell viability and induce apoptosis of DU145 cells by downregulating caveolin-1 and p-Akt protein expression.

Low intensity ultrasound promotes the sensitivity of rat brain glioma to Doxorubicin by down-regulating the expressions of p-glucoprotein and multidrug resistance protein 1 in vitro and in vivo

The overall prognosis for malignant glioma is extremely poor, and treatment options are limited in part because of multidrug resistant proteins. Our previous findings suggest low intensity ultrasound (LIUS) can induce apoptosis of glioma cells. Given this finding, we were interested in determining if LIUS could help treat glioma by inhibiting multidrug resistant proteins, and if so, which pathways are involved. In this study, the toxicity sensitivity and multidrug resistance proteins of glioma induced by LIUS were investigated using CCK-8, immunohistochemistry, immunofluorency, and RT-PCR in tissue samples and cultured cells. LIUS inhibited increase of C6 cells in an intensity- and time-dependent manner. The toxicity sensitivity of C6 cells increased significantly after LIUS sonication (intensity of 142.0 mW/cm²) or Doxorubicin (DOX) at different concentration, particularly by the combination of LIUS sonication and DOX. The expressions of P-gp and MRP1 decreased significantly post-sonication at intensity of 142.0 mW/cm² both in vitro and in vivo. The expressions of p110 delta (PI3K), NF-κB-p65, Akt/PKB, and p-Akt/PKB were downregulated by LIUS sonication and DOX treatment separately or in combination at the same parameters in rat glioma. These results indicate that LIUS could increase the toxicity sensitivity of glioma by down-regulating the expressions of P-gp and MRP1, which might be mediated by the PI3K/Akt/NF-κB pathway.

The induction of the apoptosis of cancer cell by sonodynamic therapy: a review

Ultrasound can be used not only in the examination, but also in the therapy, especially in the therapy of cancer, which has got effect in the treatment. Sonodynamic therapy is an experimental cancer therapy which uses ultrasound to enhance the cytotoxic effects of drugs known as sonosensitizers. It has been tested in vitro and in vivo. The ultrasound could penetrate the tissue and cell under some of conditions which directly changes the cell membranes permeability, thereby allowing the delivery of exogenous molecules into the cells in some degree. Ultrasound could inhibit the proliferation or induce the apoptosis of the cancer cell in vitro or in vivo. Recent research indicated low frequency and low intensity ultrasound could induce cells apoptosis, and which could be strengthened by sonodynamic sensitivities, microbubbles, chemotherapeutic drugs and so on. Most kinds of ultrasound suppressed the proliferation of cancer cell through inducing the apoptosis of cancer cell. The mechanism of apoptosis is not clear. In this review, we will focus on and discuss the mechanisms of the induction of the apoptosis of cancer cell by ultrasound.

Observations on the viability of C6-glioma cells after sonoporation with low-intensity ultrasound and microbubbles

Ultrasound (US) and microbubbles can be used to facilitate cellular uptake of drugs through a cavitationinduced enhancement of cell membrane permeability. The mechanism is, however, still incompletely understood. A direct contact between microbubbles and cell membrane is thought to be essential to create membrane perturbations lasting from seconds to minutes after US exposure of the cells. A recent study showed that the effect may even last up to 8 h after cavitation (with residual permeability up to 24 h after cavitation). In view of possible membrane damage, the purpose of this study was to further investigate the evolution of cell viability in the range of the 24-h temporal window. Furthermore, a description of the functional changes in tumor cells after US exposure was initiated to obtain a better understanding of the mechanism of membrane perturbation after sonication with microbubbles. Our results suggest that US does not reduce cell viability up to 24 h post-exposure. However, a perturbation of the entire cell population exposed to US was observed in terms of enzymatic activity and characteristics of the mitochondrial membrane. Furthermore, we demonstrated that US cavitation induces a transient loss of cell membrane asymmetry, resulting in phosphatidylserine exposure in the outer leaflet of the cell membrane.

Low-intensity ultrasound enhances the anticancer activity of cetuximab in human head and neck cancer cells

The potential clinical use of ultrasound in inducing cell apoptosis and enhancing the effects of anticancer drugs in the treatment of cancers has previously been investigated. In this study, the combined effects of low-intensity ultrasound (LIU) and cetuximab, an anti-epidermal growth factor receptor (EGFR) antibody, on cell killing and induction of apoptosis in HSC-3 and HSC-4 head and neck cancer cells, and its mechanisms were investigated. Experiments were divided into 4 groups: non-treated (CNTRL), cetuximab-treated (CETU), ultrasound-treated (UST) and the combination of cetuximab and US-treated (COMB). Cell viability was assessed by trypan blue staining assay and induction of apoptosis was detected by fluorescein isothiocyanate (FITC)-Annexin V and propidium iodide (PI) staining assay at 24 h after cetuximab and/or US treatment. To elucidate the effect of cetuximab and US on EGFR signaling and apoptosis in head and neck cancer cells after the treatments, the expression of EGFR, phospho-EGFR, and the activation of caspase-3 were evaluated with western blotting. More cell killing features were evident in the COMB group in HSC-3 and HSC-4 cells compared with the other groups. No differences in EGFR expression among the CETU, UST and COMB groups was observed, while the expression of phospho-EGFR in the CETU group was downregulated compared with that in the CNTRL group. Phospho-EGFR expression was much more downregulated in the COMB group compared with that in the other groups. In addition, the activation of caspase-3 in the UST group was upregulated compared with that in the CNTRL group. Caspase-3 activation was much more upregulated in the COMB group than that in the other groups. These data indicated that LIU was able to enhance the anticancer effect of cetuximab in HSC-3 and HSC-4 head and neck cancer cells.

Low frequency and intensity ultrasound induces apoptosis of brain glioma in rats mediated by caspase-3, Bcl-2, and survivin

Low frequency and intensity ultrasound (LFU) sonication can selectively induce brain tumor cell apoptosis without damaging neural cells, while also enhancing drug delivery to brain tumors. To explore the underlying mechanisms of related pathways in LFU-induced apoptosis, we investigated the expression of proteins associated with LFU-induced apoptosis. C6 cells were used for in vitro experiments and C6 tumor-bearing rats were used during in vivo experiments. 3-[4.5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide; thiazolyl blue (MTT) assay was used to detect C6 cell viability in vitro. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) analysis was used to check the apoptotic cells, and they were counted and analyzed both in vitro and in vivo. Transmission electron microscopy (TEM) was used to illustrate the ultrastructure of apoptotic nuclei of cancer cells in vivo. The expressions of caspase-3, Bcl-2, and survivin proteins were assessed by immunofluorescence, immunohistochemistry and Western blot analysis in vivo. C6 cell viability decrease was statistically significant; the numbers of apoptotic C6 cells in the LFU sonication groups were higher than those in the control group both in vitro and in vivo. The expression of caspase-3 increased, yet the expressions of Bcl-2 and survivin decreased significantly 6h after LFU sonication, compared with the control group in vivo. This study suggests that LFU can induce apoptosis in vitro and in vivo, and that three signaling proteins, caspase-3, Bcl-2, and survivin, might be involved in LFU-induced apoptosis.

Effect of ultrasound treatment on brain edema in a traumatic brain injury model with the weight drop method

BACKGROUND

For the treatment of traumatic brain edema, an efficient modality has not yet emerged. There have been many studies to date which have reported the employment of low-frequency ultrasound for blood-brain barrier disruption (BBBD). However, the authors have observed that low-intensity ultrasound increases water permeability without cellular damage in cartilage cells. We have therefore attempted to observe the effects of applying this low-intensity ultrasound to an experimental animal model.

METHODS

A traumatic brain injury rat model was established according to the weight drop method developing the traumatic brain edema. The degree of BBBD was measured by the changes in the water content and spectrophotometric absorbance of Evans blue dye in the cerebrum after low-frequency ultrasound.

RESULTS

The cerebral water content levels showed that the BBBD gradually increased after impact and thereafter decreased after 6 h. After low-frequency ultrasound exposure, the values of water content and spectrophotometric absorbance of Evans blue dye were the lowest at 0 h, and were increased at 2 and 5 h of ultrasonic exposure (after impact).

CONCLUSION

We suggest that traumatic brain edema in the rat model may be alleviated by low-frequency ultrasound, and low-frequency ultrasound might be proposed as a novel treatment modality for brain edema.

Ultrasound reverses multidrug resistance in human cancer cells by altering gene expression of ABC transporter proteins and Bax protein

Multidrug resistance (MDR) is the major obstacle to successful chemotherapy of human malignancies and strategies for overcoming MDR phenomena are still unavailable to clinical use. Previous results showed that ultrasound (US) exposure could make MDR cancer cells become more sensitive to anticancer drugs, and the physical parameters of US exposure could adjust the uptake and retention of rhodamine 123 in MDR cells. In this study, we investigated the mechanisms of therapeutic ultrasound as a physical approach to overcoming MDR in a multidrug resistant human hepatocarcinoma cell line (HepG2/ADM). Our results demonstrated that the percentage of P-glycoprotein(+) (P-gp), multidrug resistance-associated protein(+) (MRP) and lung resistance-related protein(+) (LRP) cells was 96.97% ± 2.41%, 20.84% ± 3.12% and 1.16% ± 0.59% in HepG2/ADM cells, and 62.84% ± 3.42%, 10.26% ± 1.18% and 3.05% ± 0.37% in US-exposed HepG2/ADM cells, respectively. A significant decrease in the number of P-gp(+) and MRP(+) cells was observed between US-exposed HepG2/ADM and HepG2/ADM cells (p < 0.05). Using RT-PCR technique, we found that US could significantly downregulate the expression of P-glycoprotein (P-gp) and (MRP) at the mRNA level in HepG2/ADM cells. Compared with the control, the percentage of apoptotic cell death was significantly increased in HepG2/ADM after ultrasound exposure. Using immunocytochemistry, the percentage of Bcl-2(+) and Bax(+) cells was 21.7% and 4.1% in the control, and 18.46% and 8.1% in the US-exposed cells, respectively. The percentage of Bax(+) cells was significantly higher in US-exposed HepG2/ADM cells (p < 0.05), suggesting that US exposure could lead to cellular apoptosis in HepG2/ADM cells. It is concluded that US exposure could reverse MDR in HepG2/ADM cells via decreasing P-gp and MRP levels and their mRNA expressions and increasing expression of Bax protein. It may lead to the development of a novel strategy of using a targeted, noninvasive physical approach for the induction of MDR reversal in cancer cells.