Study of Appropriate Condition of Nanosecond Pulsed Electric Fields for Induction of Unfolded Protein Response Using GFP-Expressing Cell

Endoplasmic reticulum stress has been implicated as one of the causes of various diseases such as diabetes and neurodegenerative diseases. Living cells have an unfolded protein response (UPR) to relieve this stress. This UPR has been reported to be induced by the application of nanosecond pulsed electric fields (nsPEFs). Previous reports have shown that the induction of the UPR by a pulsed electric field is not significant. It is also believed that the conditions of pulsed electric field suitable for induction of UPR vary among cell lines. Therefore, in this study, we experimentally investigated the appropriate pulse electric field conditions for UPR induction using human-derived kidney cells (293A), which have been transfected to express GFP by UPR induction, and Blumlein pulse forming line (B-PFL) with adjustable pulse width. In this experiment, the induction of UPR was evaluated by the fluorescence of GFP expressed by UPR induction. Cell viability was also measured. Pulse voltages of 20 ns, 65 ns, and 200 ns were applied, and the GFP expressed 24 hours later was measured by fluorescence intensity using a microplate reader and fluorescence observation using a fluorescence microscope to evaluate UPR induction. A endoplasmic reticulum stress inducer: Tunicamycin at a final concentration of 2 μM was used for the positive control. The GFP fluorescence were observed in all pulse width conditions, but cell viability was reduced. The application of nsPEFs would be induced UPR on some level.