Effects of dissolved gases and an echo contrast agent on apoptosis induced by ultrasound and its mechanism via the mitochondria-caspase pathway

Calcium ion delivery by microbubble-assisted sonoporation stimulates cell death in human gastrointestinal cancer cells

Ultrasound-mediated cell membrane permeabilization - sonoporation, enhances drug delivery directly to tumor sites while reducing systemic side effects. The potential of ultrasound to augment intracellular calcium uptake - a critical regulator of cell death and proliferation - offers innovative alternative to conventional chemotherapy. However, calcium therapeutic applications remain underexplored in sonoporation studies. This research provides a comprehensive analysis of calcium sonoporation (CaSP), which combines ultrasound treatment with calcium ions and SonoVue microbubbles, on gastrointestinal cancer cells LoVo and HPAF-II. Initially, optimal sonoporation parameters were determined: an acoustic wave of 1 MHz frequency with a 50 % duty cycle at intensity of 2 W/cm2. Subsequently, various cellular bioeffects, such as viability, oxidative stress, metabolism, mitochondrial function, proliferation, and cell death, were assessed following CaSP treatment. CaSP significantly impaired cancer cell function by inducing oxidative and metabolic stress, evidenced by increased mitochondrial depolarization, decreased ATP levels, and elevated glucose uptake in a Ca2+ dose-dependent manner, leading to activation of the intrinsic apoptotic pathway. Cellular response to CaSP depended on the TP53 gene's mutational status: colon cancer cells were more susceptible to CaSP-induced apoptosis and G1 phase cell cycle arrest, whereas pancreatic cancer cells showed a higher necrotic response and G2 cell cycle arrest. These promising results encourage future research to optimize sonoporation parameters for clinical use, investigate synergistic effects with existing treatments, and assess long-term safety and efficacy in vivo. Our study highlights CaSP's clinical potential for improved safety and efficacy in cancer therapy, offering significant implications for the pharmaceutical and biomedical fields.

Focal opening of the neuronal plasma membrane by shock-induced bubble collapse for drug delivery: a coarse-grained molecular dynamics simulation

Cell permeabilization using shock-induced bubble collapse provides an attractive choice for drug delivery systems. In this work, based on a realistically human brain plasma membrane (PM) model, we investigated the focal opening of this complex model by the jet from cavitation, focusing on the effect of characteristic membrane components, particle velocity (u_p) and bubble diameters (D). Both high levels of cholesterol and specific cerebrosides in the PM model limit the pore opening of cavitation jets. Sphingomyelin is the opposite, but has little effect due to its low content. Two adjustable parameters of u_p and D can be coupled to control the opening size. The relationship between them and the maximum pore area was provided for the first time. The maximum pore area increases with the u_p (or the impulse that is positively related to u_p) in the low-speed range, which agrees with the experimentally observed impulse determinism. However, the maximum area drops in the high-speed range. Combined with D, we proposed that the jet size determines the pore size, not the impulse. Larger bubbles that can create a larger pore in the membrane have a larger jet size, but their impulse is relatively small. Finally, the recovery simulation shows that the membrane with a small pore can be quickly recovered within 300 ps, while that with a larger pore did not recover until 2 μs. These rules from this work may be helpful to optimize the choice of shock waves for the delivery of different drugs across membranes.

Estimation of the number density of active cavitation bubbles in a sono-irradiated aqueous solution using a thermodynamic approach

An alternative semi-empirical technique is developed to determine the number density of active cavitation bubbles (N) formed in sonicated solutions. This was achieved by relating the acoustic power supplied to the solution (i.e., determined experimentally) to the released heat by a single bubble. The energy dissipation via heat exchange is obtained by an advanced cavitation model accounting for the liquid compressibility and viscosity, the non-equilibrium condensation/evaporation of water vapor, and heat conduction across the bubble wall and heats of chemical reactions resulting within the bubble at the collapse. A good concordance was observed between our results and those found in the literature. It was found that the number of active bubbles increased proportionally with a rise in ultrasound frequency. Additionally, the increase of acoustic intensity increases the number of active bubbles, whatever the sonicated solution's volume. On the other hand, it was observed that the rise of the irradiated solution volume causes the number of active bubbles to be reduced even when the acoustic power is increased. A decrease in acoustic energy accelerates this negative impact.

Landscape of Cellular Bioeffects Triggered by Ultrasound-Induced Sonoporation

Sonoporation is the process of transient pore formation in the cell membrane triggered by ultrasound (US). Numerous studies have provided us with firm evidence that sonoporation may assist cancer treatment through effective drug and gene delivery. However, there is a massive gap in the body of literature on the issue of understanding the complexity of biophysical and biochemical sonoporation-induced cellular effects. This study provides a detailed explanation of the US-triggered bioeffects, in particular, cell compartments and the internal environment of the cell, as well as the further consequences on cell reproduction and growth. Moreover, a detailed biophysical insight into US-provoked pore formation is presented. This study is expected to review the knowledge of cellular effects initiated by US-induced sonoporation and summarize the attempts at clinical implementation.

Ultrasound-Induced DNA Damage and Cellular Response: Historical Review, Mechanisms Analysis, and Therapeutic Implications

The biological effects of ultrasound may be classified into thermal and nonthermal mechanisms. The nonthermal effects may be further classified into cavitational and noncavitational mechanisms. DNA damage induced by ultrasound is considered to be related to nonthermal cavitations. For this aspect, many in vitro studies on DNA have been conducted for evaluating the safety of diagnostic ultrasound, particularly in fetal imaging. Technological advancement in detecting DNA damage both in vitro and in vivo have elucidated the mechanism of DNA damage formation and their cellular response. Damage to DNA, and the residual damages after DNA repair are implicated in the biological effects. Here, we discuss the historical evidence of ultrasound on DNA damage and the mechanism of DNA damage formation both in vitro and in vivo, compared with those induced by ionizing radiation. We also offer a commentary on the safety of ultrasound over X-ray-based imaging. Also, understanding the various mechanisms involved in the bioeffects of ultrasound will lead us to alternative strategies for use of ultrasound for therapy.

Investigation of the Therapeutic Effect of Doxorubicin Combined With Focused Shockwave on Glioblastoma

BACKGROUND

Glioblastoma multiforme (GBM) is currently the most devastating brain tumor globally and produces a high mortality rate. GBM is also challenging to eradicate using surgery due to its invasive characteristics. Moreover, the blood-brain barrier (BBB) increases the difficulty of transporting most therapeutic drugs to tumor sites. The use of transcranial focused ultrasound (FUS) has recently been investigated for opening the BBB to facilitate drug delivery. A special form of FUS, the shockwave (SW), has also been shown to open BBB efficiently. SW has several advantages including no heating effect, less reactive oxygen species production, good transcranial ability, and no need to supply microbubbles.

METHODS

We employed a commercial SW device, which is a common tool used for musculoskeletal disorders, to improve doxorubicin delivery across the BBB and evaluated its therapeutic efficacy on GBM rat models. SW emits relatively short but stronger mechanical pulses comparing with FUS.

RESULTS

The results demonstrated that doxorubicin combined with SW treatment substantially inhibited tumor growth and prolonged overall survival.

CONCLUSIONS

The present study shows the non-invasive transcranial SW may have potential for the treatment of GBM in future clinical setting.

Microbubble-Mediated Cavitation Promotes Apoptosis and Suppresses Invasion in AsPC-1 Cells

The aim of this study was to identify the potential and mechanisms of microbubble-mediated cavitation in promoting apoptosis and suppressing invasion in cancer cells. AsPC-1 cells were used and divided into four groups: control group, microbubble-only (MB) group, ultrasound-only (US) group and ultrasound plus microbubble (US + MB) group. Pulse ultrasound was used at a frequency of 360 kHz and a SPPA (spatial peak, pulse average) intensity of 1.4 W/cm² for 1 min (duty rate = 50%). Then cells in the four groups were cultured for 24 h. Cell Counting Kit‑8 (Biosharp, Hefei, Anhui, China) revealed decreased cell viability in the US + MB group. Western blot confirmed that there were increased cleaved caspase‑3 and Bcl-2-associated X protein levels and decreased B‑cell lymphoma‑2 (Bcl-2) levels, as well as increased intracellular calcium ions and downregulated cleaved caspase-8, in the US + MB group. With respect to proliferation, cells in the US + MB group had lower expression of Ki67 and the weakened colony formation ability. The transwell invasion assay revealed that invasion ability could be decreased in AsPC-1 cells in the US + MB group. Further, it was found that cells in the US + MB group had lower levels of hypoxia-inducible factor-1α (HIF-1α) and vimentin and higher levels of E-cadherin compared with the other three groups. Finally, the US + MB cells had less invadopodium formation. In conclusion, these results suggest that microbubble-mediated cavitation promotes apoptosis and suppresses invasion in AsPC-1 cells.

Inhibition of Human Breast Cancer Cell Proliferation by Low-Intensity Ultrasound Stimulation

OBJECTIVES

Cancer is characterized by uncontrolled cell proliferation, which makes novel therapies highly desired. In this study, the effects of near-field low-intensity pulsed ultrasound (LIPUS) stimulation on T47D human breast cancer cell and healthy immortalized MCF-12A breast epithelial cell proliferation were investigated in monolayer cultures.

METHODS

A customized ultrasound (US) exposure setup was used for the variation of key US parameters: intensity, excitation duration, and duty cycle. Cell proliferation was quantified by 5-bromo-2'-deoxyuridine and alamarBlue assays after LIPUS excitation.

RESULTS

At a 20% duty cycle and 10-minute excitation period, we varied LIPUS intensity from to 100 mW/cm² (spatial-average temporal-average) to find a gradual decrease in T47D cell proliferation, the decrease being strongest at 100 mW/cm² . In contrast, healthy MCF-12A breast cells showed an increase in proliferation when exposed to the same conditions. Above a 60% duty cycle, T47D cell proliferation decreased drastically. Effects of continuous wave US stimulation were further explored by varying the intensity and excitation period.

CONCLUSIONS

These experiments concluded that, irrespective of the waveform (pulsed or continuous), LIPUS stimulation could inhibit the proliferation of T47D breast cancer cells, whereas the same behavior was not observed in healthy cells. The study demonstrates the beneficial bioeffects of LIPUS on breast cancer cells and offers the possibility of developing novel US-mediated cancer therapy.

TRPV4 promotes acoustic wave-mediated BBB opening via Ca2+/PKC-δ pathway

Introduction

Numerous studies have shown the ability of low-energy acoustic waves such as focused ultrasound or shockwave to transiently open blood-brain barrier (BBB) and facilitate drug delivery to the brain. Preclinical and clinical evidences have well demonstrated the efficacy and safety in treating various brain disorders. However, the molecular mechanisms of acoustic waves on the BBB are still not fully understood.

Objectives

The present study aimed at exploring the possible molecular mechanisms of acoustic wave stimulation on brains.

Methods: Briefly describe the experimental design

The left hemisphere of the rat‘s brain was treated with pulsed ultrasound from a commercial focused shockwave or a planar ultrasound device, and the right hemisphere served as a control. One hour after the mechanical wave stimulation or overnight, the rats were sacrificed and the brains were harvested for protein or histological analysis. Agonists and antagonists related to the signal transduction pathways of tight junction proteins were used to investigate the possible intracellular mechanisms.

Results

Intracellular signal transduction analysis shows calcium influx through transient receptor potential vanilloid 4 (TRPV4) channels, and the activation of PKC-δ pathway to mediate dissociation of ZO-1 and occludin after acoustic wave stimulation. The activation of TRPV4 or PKC-δ signaling further increased the expression level of TRPV4, suggesting a feedback loop to regulate BBB permeability. Moreover, the tight junction proteins dissociation can be reversed by administration of PKC-δ inhibitor and TRPV4 antagonist.

Conclusion

The present study shows the crucial role of TRPV4 in acoustic wave-mediated BBB permeability, specifically its effect on compromising tight junction proteins, ZO-1 and occludin. Our findings provide a new molecular perspective to explain acoustic wave-mediated BBB opening. Moreover, activation of TRPV4 by agonists may reduce the threshold intensity level of acoustic waves for BBB opening, which may prevent undesirable mechanical damages while maintaining efficient BBB opening.

The Long-Term Fate of the Sonoporated Pancreatic Cancer Cells is Uncorrelated With the Degree of Model Molecular Loading

Studies have determined that ultrasound-activated microbubbles can increase the membrane permeability of tumor cells by triggering membrane perforation (sonoporation) to improve drug loading. However, because of the distinct cavitation events adjacent to each cell, the degree of drug loading appeared to be heterogeneous. The relationship between the long-term fate trend and the degree of drug loading remains unclear. To investigate the time-lapse viability of diversity loading cells, fluorescein isothiocyanate-dextran (FITC-dextrans) was used as a molecular model mixed with 2% v/v SonoVue microbubbles (Bracco, Milan, Italy) and exposed to various peak negative pressures (0.25 MPa, 0.6 MPa, 1.2 MPa), 1 MHz frequency and 300 μs pulse duration. To select a suitable parameter, the cavitation activity was measured, and the cell analysis was performed by flow cytometry under these acoustic pressures. The sonoporated cells were then categorized into 3 sub-groups by flow cytometry according to the various fluorescence intensity distributions to analyze their long-term fate. We observed that the stable cavitation occurred at 0.25 MPa and microbubbles underwent ultra-harmonic emission, and obvious broadband signals were observed at 0.6 MPa and 1.2 MPa, suggesting the occurs of inertial cavitation. The cell analysis further showed the maximum delivery efficiency and cell viability at 0.6 MPa, and it was selected for the following experiment. The categorization displayed that the fluorescence intensity of FITC-dextrans in sub-groups 2 and 3 were approximate 5.62-fold and 19.53-fold higher than that in sub-group 1, respectively. After separation of these sub-groups, the apoptosis and necrosis ratios in all 3 sub-groups of sonoporated cells gradually increased with increasing culture time and displayed no significant difference in either the apoptosis (p > 0.05) or necrosis (p > 0.05) ratio after 6 h and 24 h of culture, respectively. Further analysis using Western blot verified that the long-term fate of sonoporated cells involves the mitochondrial signaling proteins. These results provide better insight into the role of cavitation-enhanced permeability and a critical guide for acoustic cavitation designs.

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.

Generation of Reactive Oxygen Species in Heterogeneously Sonoporated Cells by Microbubbles with Single-Pulse Ultrasound

To develop and realize sonoporation-based macromolecule delivery, it is important to understand the underlying cellular bioeffects involved. It is known that an appropriate level of reactive oxygen species (ROS) is necessary to maintain normal physiologic function, but excessive ROS triggers adverse downstream bioeffects. However, it is still unclear whether a relationship exists between intracellular ROS levels and sonoporation. Using a customized platform for 1.5-MHz ultrasound exposure (13.33 µs duration and 0.70 MPa peak negative pressure) and imaging the dynamics of sonoporation and intracellular ROS at the single-cell level, we quantified the exogenous molecular uptake and the concentration of intracellular ROS indicator to evaluate the extent of sonoporation and ROS change, respectively. Our results revealed that the intracellular ROS level was correlated with the degree of the sonoporation. (i) Within ~120 s of the onset of ultrasound, during which membrane perforation and complete membrane resealing occurred, intracellular ROS rapidly decreased because of extracellular diffusion of dichlorofluorescein through the perforated membrane and positively correlated with the degree of the sonoporation. (ii) In the following 270 s (120-390 s post-exposure), ROS generation in reversibly sonoporated cells gradually increased and was positively correlated with the degree of the sonoporation. (iii) The ROS level in irreversibly sonoporated cells reduced to depletion during this time interval. It is possible that ROS generation in reversibly sonoporated cells can impact their long-term fate. These results thus provide new insight into the biological response to sonoporation.

Honeysuckle flowers extract loaded Bombyx mori silk fibroin films for inducing apoptosis of HeLa cells

This study aimed to prepare silk fibroin (SF) films loaded with honeysuckle flowers extract (HFE) for inducing apoptosis of HeLa cells. We mixed solution of SF and HFE by air-drying for preparing the honeysuckle flowers extract loaded silk fibroin (SFH) films. The physical properties including morphologies, contact angle, roughness, and Z range were characterized. MTS assay and fluorescence micrographs proved that SFH films inhibited the proliferation rate of HeLa cells due to induction of HFE into SF films. Furthermore, cell apoptosis assay and cell cycle analysis confirmed that the apoptosis of HeLa cells resulted from SFH films. Therefore, SFH films designed in our study might be a promising candidate material for cancer therapy.

Modeling the effect of carbon-dioxide gas on cavitation

One of the controlling parameters of the physical and chemical effects produced by acoustic cavitation is the use of dissolved gas as it affects the temperature and pressure obtained at cavity collapse and, the reactions happening in a bubble. It also enhances the nucleation rates by decreasing the threshold required for cavitation by providing dissolved gas nuclei. The present study looks into the effect of carbon dioxide gas on cavitation using a diffusion limited model. The model couples the dynamics of a single bubble with 11 chemical reactions involving 8 reactive species. The effect of mass transport (diffusion of water vapor and radical species) and heat transport (by conduction) is included in the model. Simulations were carried out for different initial compositions of an Ar-CO₂^- bubble and the results were compared with an experimental study reported in the earlier literature. The results have indicated that intensity of collapse decreases with an increase in CO₂ composition in the bubble thereby decreasing the yield of the oxidizing radicals like OH. This is due to the lower polytropic coefficient and higher specific heat of CO₂ compared to that of argon. Also, the bubbles grows to a larger extent with an increase in the dissolved CO₂ concentration thereby accommodating higher amounts of water vapor and ultimately decreasing the temperature obtained at collapse. Simulations were done for a bubble containing a mole fraction of 95% Ar and 5% CO₂ at different values of driving frequencies (213, 355, 647 and 1000kHz) and driving pressure amplitudes (3.22, 5, 7.5 and 10bar). Higher production rate of OH radicals was predicted at a lower driving frequency, for a given driving pressure amplitude and it increased with an increase in the driving pressure amplitude. At a given driving pressure amplitude, the yield of OH radicals decreased with an increase in the CO₂ concentration in the bubble for all the driving frequencies used in the simulations.

Investigation of Microbubble Cavitation-Induced Calcein Release from Cells In Vitro

In the present study, microbubble (MB) cavitation signal analysis was performed together with calcein release evaluation in both pressure and exposure duration domains of the acoustic field. A passive cavitation detection system was used to simultaneously measure MB scattering and attenuation signals for subsequent extraction efficiency relative to MB cavitation activity. The results indicate that the decrease in the efficiency of extraction of calcein molecules from Chinese hamster ovary cells, as well as cell viability, is associated with MB cavitation activity and can be accurately predicted using inertial cavitation doses up to 0.18 V × s (R² > 0.9, p < 0.0001). No decrease in additional calcein release or cell viability was observed after complete MB sonodestruction was achieved. This indicates that the optimal exposure duration within which maximal sono-extraction efficiency is obtained coincides with the time necessary to achieve complete MB destruction. These results illustrate the importance of MB inertial cavitation in the sono-extraction process. To our knowledge, this study is the first to (i) investigate small molecule extraction from cells via sonoporation and (ii) relate the extraction process to the quantitative characteristics of MB cavitation acoustic spectra.

Ultrasound: A Chemotherapy Sensitizer

Chemotherapy plays a very important role in cancer treatment. However, there are still some barriers in the successful use of such therapies, mainly because of the adverse side effects of the anticancer agents and due to the development of chemoresistance. This paper focuses on the use of ultrasound to enhance chemotherapy and to overcome drug resistance. The action of many anticancer agents can be improved with the use of ultrasonic exposure either in vitro or in vivo. Drug resistance can be circumvented using ultrasound alone. Furthermore, the reversal attributable to chemoresistance modifiers, such as verapamil and PSC 833, is augmented by ultrasound. Ultrasound-mediated chemosensitization is usually achieved via increasing intracellular drug accumulation, although other mechanisms are also involved. Ultrasound also can play a role in targeted chemotherapy, releasing anticancer chemicals directly and efficiently into the lesions. However, this promising modality has not been clinically adopted so far and the reasons are discussed.

Tumor growth suppression by the combination of nanobubbles and ultrasound

We previously developed novel liposomal nanobubbles (Bubble liposomes [BL]) that oscillate and collapse in an ultrasound field, generating heat and shock waves. We aimed to investigate the feasibility of cancer therapy using the combination of BL and ultrasound. In addition, we investigated the anti-tumor mechanism of this cancer therapy. Colon-26 cells were inoculated into the flank of BALB/c mice to induce tumors. After 8 days, BL or saline was intratumorally injected, followed by transdermal ultrasound exposure of tumor tissue (1 MHz, 0-4 W/cm2 , 2 min). The anti-tumor effects were evaluated by histology (necrosis) and tumor growth. In vivo cell depletion assays were performed to identify the immune cells responsible for anti-tumor effects. Tumor temperatures were significantly higher when treated with BL + ultrasound than ultrasound alone. Intratumoral BL caused extensive tissue necrosis at 3-4 W/cm2 of ultrasound exposure. In addition, BL + ultrasound significantly suppressed tumor growth at 2-4 W/cm2 . In vivo depletion of CD8+ T cells (not NK or CD4+ T cells) completely blocked the effect of BL + ultrasound on tumor growth. These data suggest that CD8+ T cells play a critical role in tumor growth suppression. Finally, we concluded that BL + ultrasound, which can prime the anti-tumor cellular immune system, may be an effective hyperthermia strategy for cancer treatment.

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.

Apoptosis Induced by Microbubble-Assisted Acoustic Cavitation in K562 Cells: The Predominant Role of the Cyclosporin A-Dependent Mitochondrial Permeability Transition Pore

Acoustic cavitation of microbubbles has been described as inducing tumor cell apoptosis that is partly associated with mitochondrial dysfunction; however, the exact mechanisms have not been fully characterized. Here, low-intensity pulsed ultrasound (1 MHz, 0.3-MPa peak negative pressure, 10% duty cycle and 1-kHz pulse repetition frequency) was applied to K562 chronic myelogenous leukemia cells for 1 min with 10% (v/v) SonoVue microbubbles. After ultrasound exposure, the apoptotic index was determined by flow cytometry with annexin V-fluorescein isothiocyanate/propidium iodide. In addition, mitochondrial membrane potential (ΔΨm) was determined with the JC-1 assay. Translocation of apoptosis-associated protein cytochrome c was evaluated by Western blotting. We found that microbubble-assisted acoustic cavitation can increase the cellular apoptotic index, mitochondrial depolarization and cytochrome c release in K562 cells, compared with ultrasound treatment alone. Furthermore, mitochondrial dysfunction and apoptosis were significantly inhibited by cyclosporin A, a classic inhibitor of the mitochondrial permeability transition pore; however, the inhibitor of Bax protein, Bax-inhibiting peptide, could not suppress these effects. Our results suggest that mitochondrial permeability transition pore opening is involved in mitochondrial dysfunction after exposure to microbubble-assisted acoustic cavitation. Moreover, the release of cytochrome c from the mitochondria is dependent on cyclosporin A-sensitive mitochondrial permeability transition pore opening, but not formation of the Bax-voltage dependent anion channel complex or Bax oligomeric pores. These data provide more insight into the mechanisms underlying mitochondrial dysfunction induced by acoustic cavitation and can be used as a basis for therapy.

Evaluation of inertial cavitation activity in tissue through measurement of oxidative stress

Ultrasound cavitation is an essential mechanism involved in the therapeutic local enhancement of drug delivery by ultrasound for cancer treatment. Inertial cavitation also triggers chemical reactions that generate free radicals and subsequent oxidative stress in the tissue. The aim of this study was to measure the oxidative stress induced by inertial cavitation in ex vivo tissue and to test the association between the exposure conditions and the oxidative stress. A confocal ultrasound setup was used to sonicate and create inertial cavitation in freshly excised adipose pig tissue. The ex vivo tissue samples were then processed to measure the quantity of malondialdehyde (MDA), an end-product of polyunsaturated free fatty acid oxidation. The creation of hydroxyterephthalic acid (HTA) from the reaction of terephthalic acid (TA) with free radicals in water was also quantified in vitro. Samples were sonicated for different durations using various amplitudes for the applied pressure. The results showed a minimum 2-fold increase in the amount of detected MDA in the sonicated tissue samples compared to baseline clearly suggesting the generation of free radicals by inertial cavitation. The method exhibited a moderate dependence of MDA generated upon the duration of exposure (R(2)=057,p<0.0001). The average increase in MDA concentration was approximately 2-fold, 5-fold, 6-fold, and 9-fold for exposure durations per unit of volume of 0.13, 0.17, 0.25, and 0.50s/mm(3), respectively. The results showed no statistically significant dependence on the amplitude of the pressure within the used range. Both pressure amplitude and exposure duration, however, influenced the HTA concentration (R(2)>0.95,p<0.0001). This biochemical method can be used on ex vivo tissue to detect the generation of free radicals induced by inertial cavitation. In large enough sample populations, the cavitation activity is linked to the exposure conditions of the sonication.

Induction of endoplasmic reticulum stress by sonoporation: linkage to mitochondria-mediated apoptosis initiation

The use of cavitational means to create transient membrane pores on living cells (i.e., sonoporation) may potentially induce a broad range of downstream bio-effects that disrupt the functioning of various organelles. Here we observed that on HL-60 leukemia cells, sonoporation may induce endoplasmic reticulum (ER) stress on a time-lapse basis and, in turn, signal the mitochondria to commit a cell toward apoptosis. Our observations were derived from in vitro ultrasound exposure experiments performed on HL-60 cells in the presence of lipid-shelled microbubbles (1:1 cell-to-bubble ratio; 1-MHz frequency; 0.45-MPa in situ peak negative pressure; 100-cycle pulse length; 1-kHz pulse repetition frequency; 60-s exposure period). Using flow cytometry, we found that sonoporated cells exhibited a progressive loss of functional ER mass over a 6-h period. Also, post-exposure Western blot assays (between 0 and 24 h) revealed various indications of post-sonoporation ER stress: (i) upregulation of ER-resident enzymes responsible for catalyzing protein folding; (ii) activation of trans-ER-membrane stress sensors; (iii) increased expression of ER-induced regulatory proteins that mediate pro-apoptotic signals to the mitochondria. These results corresponded to flow cytometry observations that depicted a progressive depolarization of a sonoporated cell's mitochondrial outer membrane potential. They were also consistent with another Western blot assay that found, in sonoporated cells, a time-lapse increase of caspase-9 (a mitochondria-activated apoptosis initiator protein). Taken together, our findings indicate that sonoporation may upset ER homeostasis, and this may ultimately result in initiation of apoptosis.

Effects of low-frequency ultrasound and microbubbles on angiogenesis-associated proteins in subcutaneous tumors of nude mice

It has been shown that 1 and 3 MHz low-intensity ultrasound was able to affect the fragile and leaky angiogenic blood vessels in a tumor. However, the biological effects of 21 kHz low-intensity ultrasound on tumors remain unclear. The aim of the present study was to explore the effects of 21 kHz ultrasound with microbubbles on the regulation of vascular endothelial growth factor (VEGF), cyclooxygenase-2 (COX-2) and apoptosis in subcutaneous prostate tumors in nude mice. The study included three parts, each with 20 tumor-bearing nude mice. Twenty nude mice were divided into four groups: control (sham treatment), microbubble ultrasound contrast agent (UCA), low-frequency ultrasound (US) and US+UCA groups. The UCA used was a microbubble contrast agent (SonoVue). The parameter of ultrasound: 21 kHz, an intensity of 26 mW/cm2, 40% duty cycle (on 2 sec, off 3 sec), 3 min, once every other day for 2 weeks. In the first study, all subcutaneous tumors were examined by contrast-enhanced ultrasonography (CEUS) at the initiation and completion of the experiments. Peak intensity (PI), time to peak intensity (TTP) and area under the curve (AUC) on the time intensity curve (TIC) were analyzed. In the second study, the intensity of VEGF and COX-2 protein expression in the vascular endothelium and cytoplasm was evaluated using immunohistochemistry and laser confocal microscopy. In the third study, terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) assay was used for the evaluation of cell apoptosis in tumor tissues. The tumor cells and vasculature were examined by transmission electron microscopy (TEM). Only in the US+UCA group, PI and AUC decreased. The intensity of COX-2 and VEGF in the US+UCA group in immunohistochemical staining and laser confocal microscopy was lower compared to that of the other three groups. More cell apoptosis was found in the US+UCA group compared to the other 3 groups. In the control, UCA and US groups, the tumors had intact vascular endothelium and vessel lumens in TEM. However, lumen occlusion of vessels was observed in the US+UCA group. Twenty-one kHz low-intensity ultrasound with microbubbles may have anti-angiogenic effects on subcutaneous tumors in nude mice.

Enhancing HSP70-ShRNA transfection in 22RV1 prostate cancer cells by combination of sonoporation, liposomes and HTERT/CMV chimeric promoter

Gene therapy is a potentially viable approach for treating hormone-refractory prostate cancer (HRPC), it requires efficient delivery systems and a target gene. Inducing carcinoma cell apoptosis by inhibition of heat shock protein 70 (HSP70) overexpression has been emerging as an attractive strategy for cancer therapy. In our study, the high tumor-specificity of human telomerase reverse transcriptase (HTERT) expression prompted the use of an HTERT/cytomegalovirus (CMV) chimeric promoter to drive HSP70-ShRNA expression to induce HRPC 22RV1 cell apoptosis. At the same time, sonoporation induced by ultrasound-targeted microbubble destruction (UTMD) was utilized for delivery of plasmid loaded with HTERT/CMV promoter. Our results indicated the combination of sonoporation, low-dose liposomes and HTERT/CMV chimeric promoter as a delivery system has the potential to promote efficient gene transfer with lower cytotoxicity.

Apoptosis of U937 cells induced by hematoporphyrin monomethyl ether-mediated sonodynamic action

PURPOSE

The present study aims to investigate apoptosis of U937 cells induced by hematoporphyrin monomethyl ether (HMME)-mediated sonodynamic therapy (SDT).

MATERIALS

HMME concentration was kept constant at 10 μg/mL. Tumor cells suspended in serum-free RPM1640 were exposed to ultrasound at 1.1 MHz for up to 60 seconds with an intensity of 1 W/cm(2) in the presence and absence of HMME. The viability of cells was determined by the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltertrazolium bromide tetrazolium (MTT) test. Apoptosis was analyzed using a flow cytometer with Annexin V-PE/7-ADD staining as well as fluorescence microscopy with 4'-6-diamidino-2-phenylindole (DAPI) staining. The DNA damage of U937 cells, intracellular reactive oxygen species (ROS), and mitochondria membrane potential (MMP) were also analyzed by a flow cytometer after exposures. Western blotting and reverse transcriptase-polymerase chain reaction were used to analyze the protein and mRNA expression level of caspase-3 and poly(ADP-ribose) polymerase (PARP).

RESULTS

Fluorescent imaging revealed that HMME mainly localized in the mitochondria. MTT assay showed 55.6% of cell survival at 4 hours post-SDT. Flow cytometric analysis displayed a significant increase in the early- and late-apoptotic cell populations (35.6%) of U937 cells by HMME-mediated SDT. Compared with the control, ultrasound-alone, and HMME-alone groups, the intracellular ROS and the MMP loss were greatly increased in the combined SDT group. Obvious nuclear condensation was also found with DAPI staining, and the DNA fragment increased to 33.9% at 2 hours post-SDT treatment. Immunofluorescent staining indicated obvious Bax translocation after SDT. Western blot showed visible enhancement of caspase-3 and PARP cleavage. In addition, caspase-3 and PARP mRNA expression of U937 cells increased remarkably after SDT treatment.

CONCLUSIONS

The findings demonstrated that HMME-mediated sonodynamic action (HMME-SDT) significantly induced apoptosis of U937 cells, suggesting that HMME may be a good sonosensitizer, and HMME-SDT might be a potential therapeutic strategy for cancer treatment.

Study of the UTMD-based delivery system to induce cervical cancer cell apoptosis and inhibit proliferation with shRNA targeting Survivin

Apoptosis induction by short hairpin RNA (shRNA) expression vectors could be an efficient and promising strategy for cancer gene therapy. Ultrasound-targeted microbubble destruction (UTMD) is an appealing technique. In this study, we investigated the apoptosis induction and suppression of cell proliferation in vivo transfected by the UTMD-based shRNA delivery system. Nude mice with transplanted tumors of cervical cancer were randomly arranged into three groups: control group, plasmid injection and ultrasound (P + US), P + UTMD group. Expressions of Survivin and proliferating cell nuclear antigen (PCNA), Bcl-2, Bax, Caspase-3, Ki-67, nucleostemin (NS) were investigated by immunohistochemistry. Furthermore, microvessel density (MVD) was detected by CD34 protein expressions and apoptotic index (AI) was measured by TUNEL. As compared with those in the control and P + US groups, protein expressions of PCNA, Ki-67, Bcl-2, Survivin and NS in P + UTMD groups were down-regulated markedly, while those of Bax, Caspase-3 were up-regulated significantly (p < 0.05). MVD decreased significantly, whereas AI increased remarkably (p < 0.05). We suggested that UTMD-based shRNA delivery system could induce apoptosis and inhibit proliferation significantly, without causing any apparently adverse effect, representing a new, promising technology that would be used in the future gene therapy and research.

Subcellular impact of sonoporation on plant cells: issues to be addressed in ultrasound-mediated gene transfer

Sonoporation (membrane perforation via ultrasonic cavitation) is known to be realizable in plant cells on a reversible basis. However, cell viability may concomitantly be affected over the process, and limited knowledge is now available on how such cytotoxic impact comes about. This work has investigated how sonoporation may affect plant cells at a subcellular level and in turn activate programmed cell death (PCD). Tobacco BY-2 cells were used as the plant model, and sonoporation was applied through a microbubble-mediated approach with 100:1 cell-to-bubble ratio, free-field peak rarefaction pressure of either 0.4 or 0.9 MPa, and 1 MHz ultrasound frequency (administered in pulsed standing-wave mode at 10% duty cycle, 1 kHz pulse repetition frequency, and 1 min duration). Fluoroscopy results showed that sonoporated tobacco cells may undergo plasma membrane depolarization and reactive oxygen species elevation (two cellular disruption events closely connected to PCD). It was also found that the mitochondria of sonoporated tobacco cells may lose their outer membrane potential over time (observed using confocal microscopy) and consequently release stores of cytochrome-c proteins (determined by Western Blotting) into the cytoplasm to activate PCD. These findings provide insight into the underlying mechanisms responsible for sonoporation-induced cytotoxicity in plant cells. They should be taken into account when using this membrane perforation approach for gene transfection applications in plant biotechnology.

Targeted delivery of biodegradable nanoparticles with ultrasound-targeted microbubble destruction-mediated hVEGF-siRNA transfection in human PC-3 cells in vitro

A potentially viable approach for treating late-stage prostate cancer is gene therapy. Successful gene therapy requires safe and efficient delivery systems. In this study, we report the efficient delivery of small interfering RNA (siRNA) via the use of biodegradable nanoparticles (NPs) made from monomethoxypoly(ethylene glycol)-poly(lactic-co-glycolic acid)-poly-l-lysine (mPEG-PLGA-PLL) triblock copolymers. On the basis of previous findings, cyclic Arg-Gly-Asp (cRGD) peptides were conjugated to NPs to recognize the target site, integrin αvβ3, expressed in high levels in PC-3 prostate cancer cells. The suppression of angiogenesis by the downregulation of vascular endothelial growth factor (VEGF) expression has been widely used to inhibit the growth of malignant tumors. In our study, human VEGF (hVEGF)-siRNA was encapsulated in NPs to inhibit VEGF expression in PC-3 cells. Concurrently, sonoporation induced by ultrasound-targeted microbubble destruction (UTMD) was utilized for the delivery of siRNA-loaded NPs. Our results showed low cytotoxicity and high gene transfection efficiency, demonstrating that the targeted delivery of biodegradable NPs with UTMD may be potentially applied as new vector system for gene delivery.

Ultrasound activates ataxia telangiectasia mutated- and rad3-related (ATR)-checkpoint kinase 1 (Chk1) pathway in human leukemia Jurkat cells

Low-intensity ultrasound (US) has been shown to induce death of cancer cells; however, the underlying mechanism remains unclarified. Here, we provide novel evidence that the inhibition of checkpoint kinase 1 (Chk1) by a selective inhibitor or small interfering RNA (siRNA) enhances US-induced apoptosis in Jurkat cells. Jurkat cells showed insignificant lysis immediately after US at any applied intensity, whereas approximately 70% of the cells were γH2AX-positive 30min after US at 0.4W/cm(2). Regarding DNA damage response (DDR), Chk1, known as a target of ataxia telangiectasia mutated (ATM) and rad3-related (ATR), was phosphorylated in cells after US exposure. An ATM inhibitor showed nearly no effect on Chk1 phosphorylation, whereas chemicals showing the ATR inhibitory effect markedly abrogated the phosphorylation, indicating that Chk1 phosphorylation is preferentially more dependent on ATR than on ATM in cells exposed to US. The pharmacological inhibition of Chk1 promoted caspase-3 cleavage and increased the percentage of cells in SubG1 after US exposure. siRNA targeting Chk1 abrogated approximately 55% of Chk1 expression and also promoted apoptosis, suggesting that Chk1 plays anti-apoptotic roles in response to US. These findings revealed, for the first time, that US activates Chk1 dependently on ATR and the activated Chk1 is involved in apoptosis of cells exposed to US. Moreover, we propose that Chk1 may be a promising target in US-aided therapy.

Targeted microbubbles in the experimental and clinical setting

BACKGROUND

Microbubbles have improved ultrasonography imaging techniques over the past 2 decades. Their safety, versatility, and easiness of use have rendered them equal or even superior in some instances to other imaging modalities such as computed tomography and magnetic resonance imaging. Herein, we conducted a literature review to present their types, general behavior in tissues, and current and potential use in clinical practice.

METHODS

A literature search was conducted for all preclinical and clinical studies involving microbubbles and ultrasonography.

RESULTS

Different types of microbubbles are available. These generally improve the enhancement of tissues during ultrasonography imaging. They also can be attached to ligands for the target of several conditions such as inflammation, angiogenesis, thrombosis, apoptosis, and might have the potential of carrying toxic drugs to diseased sites, thereby limiting the systemic adverse effects.

CONCLUSIONS

The use of microbubbles is evolving rapidly and can have a significant impact on the management of various conditions. The potential for their use as targeting agents and gene and drug delivery vehicles looks promising.

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.

Ultrasound-microbubble mediated cavitation of plant cells: effects on morphology and viability

The interaction between ultrasound pulses and microbubbles is known to generate acoustic cavitation that may puncture biological cells. This work presents new experimental findings on the bioeffects of ultrasound-microbubble mediated cavitation in plant cells with emphasis on direct observations of morphological impact and analysis of viability trends in tobacco BY-2 cells that are widely studied in higher plant physiology. The tobacco cell suspensions were exposed to 1 MHz ultrasound pulses in the presence of 1% v/v microbubbles (10% duty cycle; 1 kHz pulse repetition frequency; 70 mm between probe and cells; 1-min exposure time). Few bioeffects were observed at low peak negative pressures (<0.4 MPa) where stable cavitation presumably occurred. In contrast, at 0.9 MPa peak negative pressure (with more inertial cavitation activities according to our passive cavitation detection results), random pores were found on tobacco cell wall (observed via scanning electron microscopy) and enhanced exogenous uptake into the cytoplasm was evident (noted in our fluorescein isothiocyanate dextran uptake analysis). Also, instant lysis was observed in 23.4% of cells (found using trypan blue staining) and programmed cell death was seen in 23.3% of population after 12 h (determined by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling [TUNEL]). These bioeffects generally correspond in trend with those for mammalian cells. This raises the possibility of developing ultrasound-microbubble mediated cavitation into a targeted gene transfection paradigm for plant cells and, conversely, adopting plant cells as experimental test-beds for sonoporation-based gene therapy in mammalian cells.

Cellular signal transduction can be induced by TRAIL conjugated to microcapsules

The extracellular agent tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) can induce apoptosis in tumor cells but spare normal cells. Ligation of TRAIL to a nanoparticle would serve to facilitate targeting to an extravascular site. Polymeric ultrasound contrast agents (UCA) (microencapsulated gas bubbles) can be tracked by ultrasound imaging, and fragmented into nanoparticles by focused ultrasound. This tumor-targeted delivery system has been shown to deliver more efficiently than solid nanoparticles. Additionally, small molecule inhibitors such as bortezomib, shown to sensitize TRAIL-resistant cells, could be co-administered within these UCA. In this pilot study, TRAIL was conjugated to UCA while preserving the agent's sensitivity to ultrasound. Human cancer cell lines, OVCAR-3 and A2058, were bathed with the TRAIL-UCA with and without the addition of bortezomib. Apoptosis was quantified using flow cytometry. OVCAR-3 treated with TRAIL-UCA exhibit significant (p < 0.05) apoptotosis compared to unmodified UCA, equal to positive controls, but no synergistic effect when combined with bortezomib. A2058 cells treated with TRAIL-UCA also exhibited significant apoptosis (p < 0.01) compared to unmodified UCA, similar to positive controls and bortezomib significantly increased apoptosis in combination with TRAIL-UCA. We conclude that TRAIL-ligated UCA show exciting potential as a new therapy.

Cellular damage and apoptosis along with changes in NF-kappa B expression were induced with contrast agent enhanced ultrasound in gastric cancer cells and hepatoma cells

Background

The effect of cell injury and apoptosis induced by ultrasound with contrast agent has been verified. Contrast agent enhanced apoptosis and expression of genes that related to apoptosis and are responsive to ultrasound. This effect was associated with reactive oxygen species (ROS) production induced by the sonochemical reaction, as reported in previous studies. NF-kappa B may be one of the factors involved in oxidizing reactions or modulation during the process of ultrasound inducing apoptosis.

Results

Ultrasound irradiated gastric cancer cells (SGC7901 cell line) and hepatocellular carcinoma cells (SMMC-771 cell line) cultured in medium containing contrast agent. Significant cellular damage and apoptosis were observed in the bath cells incubated for 24 hours following 120 seconds ultrasonic irradiation. I kappa B alfa expression synchronously increased in the treatment groups of both the cell lines, and the down-regulated expression of NF-kappa B influenced its-regulated expression of genes that related to apoptosis. Production of intracellular ROS and elevation of NF-kappa B level occurred after incubation of the cells for 1 hour following ultrasonic treatment.

Conclusions

Our result suggested that contrast agent enhanced the biological effect of ultrasound. Their reaction might stimulate the transitory expression of NF-kappaB, and subsequent elevation in IκBalfa expression could lead to the apoptosis of SGC7901 cells and SMMC-771 cells.

Inhibition of DNA-dependent protein kinase promotes ultrasound-induced cell death including apoptosis in human leukemia cells

Ultrasound (US) has been shown to induce cell death in cancer cells; however, the underlying mechanism remains elusive. Here, we report a set of novel findings on the molecular mechanism. We found that Akt (also known as protein kinase B), a substrate of DNA-dependent protein kinase (DNA-PK), was phosphorylated in U937 cells nullified with p53 or Molt-4 cells artificially abrogated with p53 after US exposure. On the contrary, Akt phosphorylation was transiently down-regulated then recovered in Molt-4 cells harboring wild-type p53 in US-exposed cells, possibly due to a mutual regulation between p53 and Akt. Inhibition of ataxia-telangiectasia mutated (ATM) or DNA-PK revealed that DNA-PK, rather than ATM, was preferentially involved in Akt phosphorylation and cell survival after US-exposure in all cell lines. These results indicate that DNA-PK plays a protective role against US-induced cell death regardless of p53 phenotype. In conclusion, our findings provide the first delineation of the role of DNA-PK in US-induced cell death and suggest that targeting DNA-PK might be a promising strategy to augment cancer eradication by US.

DNA double-strand breaks induced by cavitational mechanical effects of ultrasound in cancer cell lines

Ultrasonic technologies pervade the medical field: as a long established imaging modality in clinical diagnostics; and, with the emergence of targeted high intensity focused ultrasound, as a means of thermally ablating tumours. In parallel, the potential of [non-thermal] intermediate intensity ultrasound as a minimally invasive therapy is also being rigorously assessed. Here, induction of apoptosis in cancer cells has been observed, although definitive identification of the underlying mechanism has thus far remained elusive. A likely candidate process has been suggested to involve sonochemical activity, where reactive oxygen species (ROS) mediate the generation of DNA single-strand breaks. Here however, we provide compelling new evidence that strongly supports a purely mechanical mechanism. Moreover, by a combination of specific assays (neutral comet tail and staining for γH2AX foci formation) we demonstrate for the first time that US exposure at even moderate intensities exhibits genotoxic potential, through its facility to generate DNA damage across multiple cancer lines. Notably, colocalization assays highlight that ionizing radiation and ultrasound have distinctly different signatures to their respective γH2AX foci formation patterns, likely reflecting the different stress distributions that initiated damage formation. Furthermore, parallel immuno-blotting suggests that DNA-PKcs have a preferential role in the repair of ultrasound-induced damage.

Sonoporation induces apoptosis and cell cycle arrest in human promyelocytic leukemia cells

Despite being a transient biophysical phenomenon, sonoporation is known to disturb the homeostasis of living cells. This work presents new evidence on how sonoporation may lead to antiproliferation effects including cell-cycle arrest and apoptosis through disrupting various cell signaling pathways. Our findings were obtained from sonoporation experiments conducted on HL-60 human promyelocytic leukemia cells (with 1% v/v microbubbles; 1 MHz ultrasound; 0.3 or 0.5MPa peak negative pressure; 10% duty cycle; 1 kHz pulse repetition frequency; 1 min exposure period). Membrane resealing in these sonoporated cells was first verified using scanning electron microscopy. Time-lapse flow cytometry analysis of cellular deoxyribonucleic acid (DNA) contents was then performed at four post-sonoporation time points (4 h, 8 h, 12 h and 24 h). Results indicate that an increasing trend in the apoptotic cell population can be observed for at least 12 h after sonoporation, whilst viable sonoporated cells are found to temporarily accumulate in the G(2)/M (gap-2/mitosis) phase of the cell cycle. Further analysis using western blotting reveals that sonoporation-induced apoptosis involves cleavage of poly adenosine diphosphate ribose polymerase (PARP) proteins: a pro-apoptotic hallmark related to loss of DNA repair functionality. Also, mitochondrial signaling seems to have taken part in triggering this cellular event as the expression of two complementary regulators for mitochondrial release of pro-apoptotic molecules, Bcl-2 (B-cell lymphoma 2) and Bax (Bcl-2-associated X), are seen to be imbalanced in sonoporated cells. Furthermore, sonoporation is found to induce cell-cycle arrest through perturbing the expression of various cyclin and Cdk (cyclin-dependent kinase) checkpoint proteins that play an enabling role in cell-cycle progression. These bioeffects should be taken into account when using sonoporation for therapeutic purposes.

Sonodynamically induced anti-tumor effect with protoporphyrin IX on hepatoma-22 solid tumor

OBJECTIVE

The purpose of this study was to evaluate sonodynamically induced anti-tumor effect of protoporphyrin IX (PPIX) in mice bearing hepatoma-22 (H-22) solid tumors, and the possible in vivo cell damage mechanism was also investigated.

METHODS

The pharmacokinetics of PPIX was analyzed in plasma, skin, muscle and tumor of H-22 bearing mice. Tumors were irradiated with ultrasound (1.43MHz, I(SATA) 3W/cm(2), 3min) for three times at 8, 12 and 24h after 5.0mg/kg PPIX administration, respectively. The anti-tumor effects of sonodynamic therapy (SDT) were estimated by the tumor inhibition ratio (volume and weight). The bio-effects of SDT were evaluated by hematoxylin and eosin (H&E) staining, transmission electron microscope (TEM) observation, lipid peroxidation (LPO) measurement and anti-oxidative enzymes (glutathione peroxidase (GSH-PX), catalase (CAT) and superoxide dismutase (SOD)) assay.

RESULTS

A significant anti-tumor effect was obtained by PPIX-mediated sonodynamic therapy (PPIX-SDT). At the fifteenth day after PPIX-SDT, the tumor growth and tumor weight inhibition ratios were 53.84% and 45.86%, respectively. In addition, the structure of tumor tissues and the anti-oxidative enzymes were obviously destroyed after SDT treatment.

CONCLUSIONS

A biochemical mechanism was involved in PPIX-SDT in vivo, and the free radicals produced by the synergistic treatment destroying the anti-oxidative system of tumor cells in vivo may play an important role in this action. Also, the thermal effect could not be excluded in inducing damage of cellular structures, like membrane disruption and chromatin condensation under current evaluation in this paper.

Ultrasonic dispersion of nanoparticles for environmental, health and safety assessment--issues and recommendations

Studies designed to investigate the environmental or biological interactions of nanoscale materials frequently rely on the use of ultrasound (sonication) to prepare test suspensions. However, the inconsistent application of ultrasonic treatment across laboratories, and the lack of process standardization can lead to significant variability in suspension characteristics. At present, there is widespread recognition that sonication must be applied judiciously and reported in a consistent manner that is quantifiable and reproducible; current reporting practices generally lack these attributes. The objectives of the present work were to: (i) Survey potential sonication effects that can alter the physicochemical or biological properties of dispersed nanomaterials (within the context of toxicity testing) and discuss methods to mitigate these effects, (ii) propose a method for standardizing the measurement of sonication power, and (iii) offer a set of reporting guidelines to facilitate the reproducibility of studies involving engineered nanoparticle suspensions obtained via sonication.

Synergistic effects of sonoporation and taurolidin/TRAIL on apoptosis in human fibrosarcoma

Sonodynamic therapy, in combination with ultrasound contrast agents, proved to enhance the uptake of chemotherapeutics in malignant cells. HT1080 fibrosarcoma cells were treated in vitro with a combination of ultrasound SonoVue™-microbubbles and taurolidine (TRD) plus tumor necrosis factor related apoptosis inducing ligand (TRAIL). Apoptosis was measured by TdT-mediated dUTP-biotin nick end labelling (TUNEL) assay and fluorescence activated cell sorting (FACS) analysis. Gene expression was analysed by RNA-microarray. The apoptotic effects of TRD and TRAIL on human fibrosarcoma are enhanced by sonodynamic therapy and additional application of contrast agents, such as SonoVue™ by 25%. A broad change in the expression of genes related to apoptotic pathways is observed when ultrasound and microbubbles act synchronously in combination with the chemotherapeutics (e.g. BIRC3, NFKBIA and TNFAIP3). Some of these genes have already been proven to play a role in programmed cell death in human fibrosarcoma (HSPA1A/HSPA1B, APAF1, PAWR, SOCS2) or were associated with sonication induced apoptosis (CD44). Further studies are needed to explore the options of sonodynamic therapy on soft tissue sarcoma and its molecular mechanisms.

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

OBJECTIVE

The purpose of this study was to evaluate the potential molecular mechanism of low-intensity ultrasound-induced apoptosis by analyzing protein profile alteration in response to ultrasound exposure.

METHODS

Human hepatocarcinoma SMMC-7721 cells were used in this study. Cell viability was measured by a trypan blue dye exclusion test. Morphologic changes were examined by light microscopy. Apoptosis was assessed by phosphatidylserine externalization and DNA fragmentation. The pattern of the mitochondrial membrane potential decrease was determined by flow cytometry. Protein profile alteration was analyzed by comparative proteomics based on 2-dimensional polyacrylamide gel electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

RESULTS

Low-intensity ultrasound (3.0 W/cm(2), 1 minute, cells incubated for 6 hours after ultrasound exposure) induced early apoptosis (mean +/- SD, 26.5% +/- 6.2%) significantly (P < .05) with minimal lysis in human hepatocarcinoma cells in vitro. On a molecular level, several proteins, eg, cellular tumor antigen protein 53, BH3-interacting domain death agonist, apoptosis regulator Bcl-2, and heme oxygenase 1 were identified as responding to ultrasound irradiation, suggesting that mitochondrial dysfunction and oxidative stresses were involved in ultrasound-induced apoptosis. It was also assumed that mitofilin-regulated crista remodeling may be a potential channel of mitochondrial membrane permeabilization pore formation involved in low-intensity ultrasound-induced apoptosis.

CONCLUSIONS

This study suggests that 2 potential molecular signaling pathways are involved in ultrasound-induced apoptosis. It is a first step toward low-intensity ultrasound-induced apoptotic cancer therapy via understanding its relevant molecular signaling and key proteins.

In vitro activation of mitochondria-caspase signaling pathway in sonodynamic therapy-induced apoptosis in sarcoma 180 cells

Sonodynamic therapy (SDT) has been shown to mediate apoptosis in many experimental systems, but the detailed mechanism of this process is unclear. In this study, we aim to investigate the potential participation of the mitochondria-caspase signaling pathway in the SDT-induced apoptosis in isolated sarcoma 180 (S180) cells. The cell suspension was treated with 1.75MHz continuous ultrasound (US) at an acoustic intensity (I(SATA)) of 1.4W for 3min in the absence or presence of 20mug/ml hematoporphyrin (Hp). At different times after the SDT-treatment, the apoptotic cells were identified under a scanning electron microscope, and the apoptosis index (AI) was determined by flow cytometry. In addition, the mitochondrial membrane potential, permeabilization of the inner mitochondrial membrane, and translocation of apoptosis-related proteins were assessed by confocal microscopy. Simultaneously, the activation of some special apoptosis-associated proteins [caspase-9, caspase-3, polypeptide poly (ADP-ribose) polymerase (PARP), and Bax] was evaluated by western blotting. Our results indicate that the ultrasonically activated Hp can cause obvious cell apoptosis (AI, 57.66%) at 3h after treatment, and this effect can be significantly reduced by caspase-9 inhibitor (AI, 20.76%) and the oxygen scavenger NaN(3) (20.11%). However, the apoptosis induced by ultrasound alone was relatively lower (28.33%) and was not reduced by NaN(3). Further, SDT caused an 82.1% reduction in the mitochondrial membrane potential and a 70.7% reduction in the permeabilization of the inner mitochondrial membrane immediately after treatment, and these two effects were obviously prevented by NaN(3). In comparison with the control cells, the SDT-treated cells showed obvious cytochrome-c and Bax translocations, caspase activation, Bax expression, and PARP cleavage at 1h after SDT-treatment. However, in the cells treated with ultrasound alone, these phenomena partially and weakly occurred 3h after exposure. These results primarily showed that the mitochondria-caspase signaling pathway in S180 cells was activated in the US- and SDT-induced apoptosis. Moreover, Hp significantly accelerates the process of apoptosis and enhances the cytotoxic effect of ultrasonic treatment. Singlet oxygen may be responsible for the mitochondrial damage and the activation of the apoptotic signaling pathway.

High-intensity focused ultrasound induced apoptosis with caspase 3, 8, and 9/6 activation in rat hepatoma

PURPOSE

The purpose of the present study is to investigate anticancer efficacy and apoptosis confirmed by caspase under several exposure conditions of high-intensity focused ultrasound (HIFU).

MATERIALS AND METHODS

Twenty-five rats with KDH-8 hepatoma were treated by HIFU at several acoustic energies to evaluate treatment efficacy. Apoptosis was examined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) and Hoechst 33258 staining, and caspase 3, 8, and 9/6 activity was respectively assayed.

RESULTS

The KDH-8 subcutaneous tumors were reduced by HIFU, and these rats survived longer than the nontreatment rats (P < 0.01). The minimal threshold of HIFU energy was 30 W × 1.0 s for tumor control and long-term survival. The tumors exposed to HIFU exhibited marked apoptotic features under conditions of less than 10 W × 1.0 s. In cultured KDH-8 cells, apoptosis was caused at less than 30 W × 1.0 s (P < 0.01), and more was induced as the energy went down. Caspase 3, 8, and 9/6 were more activated at low energy under 10 W × 1.0 s (P < 0.01), and caspase 8, which is death receptor dependent, was significantly more activated than caspase 9/6, which is mitochondria dependent (P < 0.01).

CONCLUSION

HIFU-induced apoptosis in vivo and in vitro is one of the mechanisms for tumor control and is mediated by caspase 3, 8, and 9/6. The significantly greater activation of caspase 8 than of caspase 9/6 suggests that the apoptosis pathway induced by HIFU might be more mitochondria dependent than death receptor dependent. However, further examination will be needed.

The effect of high intensity focused ultrasound on luciferase activity on two tumor cell lines in vitro, under the control of a CMV promoter

In this study, we compared the effect of high intensity focused ultrasound (HIFU) and thermal stress on the luciferase activity, controlled by a cytomegaly virus (CMV) promoter in an in vitro model using two tumor cell lines (M21, SCCVII). HIFU was applied in a pulsed-wave mode with increasing voltage at constant pulse duration, or thermal stress was delivered over a range of temperatures (36-52 degrees C) for 5 min. The resulting luciferase activity was measured in live cells using a cooled CCD camera. Luciferase activity was measured at set time intervals over a total of 48 h post-stress. Compared to baseline, the luciferase activity of the M21 tumor cell line when exposed to HIFU was approximately 54.2+/-67.5% (p<0.01) higher at a temperature of 42 degrees C, and approximately 52.9+/-128.5% (p<0.01) higher at 44 degrees C. In the SCCVII tumor cell line, the luciferase activity after HIFU application was 55.4+/-66.6% (p<0.01) higher compared to baseline at a temperature of 42 degrees C. The M21 and SCCVII tumor cell line when exposed to thermal stress alone did not increase the luciferase activity. M21 and SCCVII tumor cells exposed to HIFU showed a maximum decrease in cell viability to 45.3+/-7.5% and 10.3+/-7.5%, respectively, and when exposed to thermal stress to 85.3+/-3.5% and 20.4+/-6.5%, respectively, compared to the untreated control. In M21 and SCCVII cells exposed to HIFU, free radicals could be detected using the dichlorofluorescein dye. Our findings demonstrate that HIFU can enhance the luciferase activity controlled by a CMV promoter. However it also has a higher damaging effect on the cells.

Evaluation and comparison of three novel microbubbles: enhancement of ultrasound-induced cell death and free radicals production

Three novel lipid-shell-type microbubbles (MBs), AS-0100, BG6356A and BG6356B, have been evaluated for their impact on ultrasound (US)-induced cell death and free radicals production. Previously studied and well-characterized US exposure conditions were employed in which human myelomonocytic lymphoma U937 cells were exposed to 1MHz pulsed US beam (0.3W/cm(2), 10% duty factor) for 1min with or without MBs. Three different concentrations of each MB were used. Apoptosis and cell lysis were assessed by examining phosphatidylserine externalization and by counting viable cells, respectively, 6h post-exposure. Free radicals production and scavenging activities were evaluated using electron paramagnetic resonance (EPR)-spin trapping. The results showed that only AS-0100 and BG6356A were able to enhance the US-induced apoptosis, mainly by increasing the secondary necrosis. Apoptosis and cell lysis seemed to depend more on mechanical forces exerted by oscillating MBs while free radicals played a trivial role. BG series MBs exhibited pronounced scavenging activities. Generally, despite the need for further optimization, AS-0100 and BG6356A appear to be promising as adjuncts in cases where US-induced cell death is required.

Induction of apoptosis in sonoporation and ultrasonic gene transfer

The role of apoptosis in sonoporation and ultrasound-enhanced gene transfection of cell suspensions was examined in vitro. Suspensions of HL-60 and of CHO-K1 cells were exposed to 2.25-MHz continuous ultrasound for 1 min in a 60-rpm rotating-tube exposure system, with ultrasound contrast media added to ensure nucleation of cavitation. Cell necrosis was measured by trypan blue dye exclusion (using a hemacytometer) and by propidium iodide nuclear staining (using flow cytometry). Apoptosis was detected by the annexin V method with Alexa Fluor 350 as the fluorescent label, and confirmed by Hoechst 33342 nuclear staining. Sonoporation cell loading was assessed by uptake of large fluorescent-dextran molecules from the medium. Transfection was demonstrated by expression of green fluorescent protein (GFP) from plasmids transferred into the cells by the treatment. Cell scoring was performed by flow cytometry, with necrotic cell events excluded. For HL-60 cells at 0.4 MPa, cell loading and transfection was significantly increased relative to shams at 2, 6 and 24 h post exposure, peaking at 19.0 +/- 5.5% and 9.6 +/- 4.2% of non-necrotic cells, respectively, at 6 h. However, about one third of the treatment-positive cells were identified as apoptotic. The cell loading and gene transfer effects increased for increasing peak rarefactional pressure amplitude, reaching 24.4 +/- 7.7% and 12.7 +/- 5.1% of non-necrotic cells, respectively, for 0.6-MPa exposure. However, the lethal cellular injury caused by cavitation in the rotating tube system reduced the overall apparent efficacy of cell loading and gene transfer to 5.1 +/- 2.1% and 2.1 +/- 0.9%, respectively, after accounting for necrosis and apoptosis. Similar tests with CHO cells showed increased sonoporation but mostly cell death by necrosis, rather than apoptosis. The induction of apoptosis by cavitation treatments should be considered as a possible confounding factor, in addition to necrosis, in sonoporation and ultrasonic gene transfer research.