Effects of therapeutic ultrasound on the nuclear envelope and nuclear pore complexes

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.

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.

Effects of therapeutic ultrasound on the nucleus and genomic DNA

In recent years, data have been accumulating on the ability of ultrasound to affect at a distance inside the cell. Previous conceptions about therapeutic ultrasound were mainly based on compromising membrane permeability and triggering some biochemical reactions. However, it was shown that ultrasound can access deep to the nuclear territory resulting in enhanced macromolecular localization as well as alterations in gene and protein expression. Recently, we have reported on the occurrence of DNA double-strand breaks in different human cell lines exposed to ultrasound in vitro with some insight into the subsequent DNA damage response and repair pathways. The impact of these observed effects again sways between extremes. It could be advantageous if employed in gene therapy, wound and bone fracture-accelerated healing to promote cellular proliferation, or in cancer eradication if the DNA lesions would culminate in cell death. However, it could be a worrying sign if they were penultimate to further cellular adaptations to stresses and thus shaking the safety of ultrasound application in diagnosis and therapy. In this review, an overview of the rationale of therapeutic ultrasound and the salient knowledge on ultrasound-induced effects on the nucleus and genomic DNA will be presented. The implications of the findings will be discussed hopefully to provide guidance to future ultrasound research.