In vitro investigation of ultrasound-induced oxidative stress on human lens epithelial cells

The effect of ultrasound exposure on human lens epithelial cells (HLE-B3) was investigated in vitro, specifically on the generation of oxidative stress upon ultrasound application using various clinically-relevant settings. In addition to ultrasound-induced heat effects, oxidative stress has been recently proposed as one of the main mechanisms for ultrasound-induced effects on human cells. In this work, the levels of biocompatibility and generation of oxidative stress by exposure of ultrasound to HLE-B3 were evaluated quantitatively and qualitatively by the MTT assay, Live/Dead assay, reactive oxygen species (ROS) and intracellular calcium level. Oxidative stress induction is traditionally achieved through administrations of H₂O₂ and thus the administration of H₂O₂ was used as the positive control group for comparison herein. Concerning the administrations of H₂O₂ are considered invasive and may potentially have side effects, ultrasound as physical stimulation could be a safer and non-invasive method to induce similar oxidative stress environments. The effect of ultrasound on cell viability and induction of oxidative stress increases with ultrasound intensity. The result reveals that the continuous ultrasound has a positive impact on the oxidative stress levels but does negatively on the cell viability, as compared to the pulsed ultrasound. Furthermore, our work demonstrates that the exposure of 58 kPa continuous ultrasound without microbubbles can maintain acceptable cell viability and produce oxidative stress effects similar to the traditional administrations of H₂O₂. In summary, exposure of ultrasound can generate oxidative stress comparable to traditional administrations of H₂O₂. The effect of generating oxidative stress is adjustable through ultrasound parameters, including the pulsed or continuous wave, the intensity of ultrasound and addition of microbubbles.