Mr. Reinhard Knerr Profile

Reinhard Knerr

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Proceedings Article | 11 March 2020 Paper

Evaluating muscular membrane perturbation upon pulsed electric field exposure

Reinhard Knerr, James Mancillas, Anna Sedelnikova, Bryan Gamboa, Mara Casebeer, Ronald Barnes, Gleb Tolstykh, Bennett Ibey, Christoper Valdez

Proceedings Volume 11238, 112380X (2020) https://doi.org/10.1117/12.2552741

KEYWORDS: Receptors, Defense and security, Electrodes, Control systems, Cell death, Modulation, In vitro testing, Confocal microscopy, Physics, Calcium

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Nanosecond pulsed electric fields (nsPEF) are high voltage (1-15 kV/cm) nanosecond energy waveforms that can impact cellular activity. On a physical level, a nsPEF generates transient membrane perturbations in the form of nanopores to allow cation influx resulting in localized membrane depolarization. On a physiological level, a nsPEF exposure can activate receptors and channels on the membrane as well as second messenger cascades, both of which results in subcellular modulation that lasts beyond the nsPEF duration. An ongoing challenge is to characterize the extent/sequence of physiological events induced by nsPEF exposure, and potential to interplay with physical effects induced by the pulse. In our laboratory, C2C12 mouse myoblast cells have been demonstrated to be a useful in vitro model, as it is feasible to differentiate these immortalized progenitors into terminally transformed myotubes. From previous efforts, we quantified YO-PRO -1 (YO-PRO-1) uptake as a measurement of membrane perturbation, and concluded that membrane damage is proportional to applied pulsed electric field voltage. To expand upon these findings, we evaluated to what extent YOPRO-1 uptake at the membrane is physical or physiological in nature. Interestingly, the P2X7 receptor complex has been extensively studied utilizing YO-PRO-1 uptake as marker of apoptotic activity. For this reason, we tested the role of P2X7 receptor complex activation to mediate YO-PRO-1 uptake during pulsed electric field exposure. By blocking the P2X7 receptor, we reduced nsPEF-induced YO-PRO-1 uptake by 31.57%. Our results demonstrate that the P2X7 receptor complex is a subcellular candidate responsible for YO-PRO-1 uptake upon nsPEF exposure in myotubes.

Proceedings Article | 11 March 2020 Paper

Evaluating muscular calcium dynamics upon pulsed electric field exposure

James Mancillas, Reinhardt Knerr, Anna Sedelnikova, Bryan Gamboa, Mara Casebeer, Ronald Barnes, Gleb Tolstykh, Bennett Ibey, Christopher Valdez

Proceedings Volume 11238, 112380Y (2020) https://doi.org/10.1117/12.2553090

KEYWORDS: Calcium, Luminescence, Receptors, Confocal microscopy, Modulation, Electrodes, Astatine, Amplitude modulation, Physics, In vitro testing

Read Abstract +

Nanosecond pulsed electric fields (nsPEF) are high voltage (1-15 kV/cm) nanosecond energy waveforms that can impact cellular activity. On a physical level, nsPEF generates transient membrane perturbations in the form of nanopores to allow cation influx resulting in localized membrane depolarization. On a physiological level, nsPEF exposure can activate second messenger cascades resulting in subcellular modulation that lasts beyond the nsPEF duration. An ongoing challenge is to characterize the physiological events induced by nsPEF exposure, and potential to interplay with physical effects induced by the pulse. In our laboratory, C2C12 immortalized mouse myoblast cells have been demonstrated to be a useful in vitro model, by differentiating these progenitors into terminally transformed myotubes. We are not only able to further investigate the fundamental subcellular mechanisms activated by pulsed electric fields, but monitor muscle contraction as a functional output. From our previous efforts, we quantified calcium-green uptake as a measurement of cellular calcium uptake across a sweep of applied pulsed electric field voltages. To extend on these findings, we evaluated calcium dynamics in the intracellular space of myotubes. Given that sarcoplasmic reticulum efflux is required for muscle contraction, we tested the physiological role of the ryanodine receptor during pulsed electric field exposure on myotubes. By blocking the Ryanodine receptor with a competitive antagonist, we reduced nsPEF -induced calcium dynamics activation by 58.36% in media with calcium. Our results are the first to demonstrate that the Ryanodine receptor complex is a subcellular candidate responsible for generating calcium responses upon nsPEF exposure in myotubes.

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