Response of pheochromocytoma neuronal cells to varying intensity of continuous wave terahertz radiation

The effects of varying intensities of Australian Synchrotron source terahertz (THz) radiation on pheochromocytoma (PC 12) neuronal cells were investigated. PC 12 cells were exposed to THz radiation at beam incident power intensities of 0.25 W m^-2 (low intensity, LI), 0.5 W m^-2 (medium intensity, MI) and 1 W m^-2 (high intensity, HI) for 10 min. After exposure, the morphological and physiological status of the cells was evaluated using scanning electron microscopy (SEM) and confocal laser scanning microscopy. SEM imaging revealed that, after exposure to LI THz radiation, the cells exhibited membrane protrusions (blebs) measuring 70-120 nm in diameter. In contrast, cells exposed to HI THz radiation demonstrated increased uptake of FITC-dextran and nanospheres. Analysis of single-cell populations counterstained with 4',6-diamidino-2-phenylindole (DAPI) showed a decrease in the proportion of DAPI-positive cells, with approximately 90, 80 and 50% remaining positive after exposure to LI, MI and HI THz radiation, respectively. However, only a slight increase in the proportion of dead cells was observed at varying THz intensities. Proteomic analysis of the cell changes following exposure to LI and HI THz irradiation indicated that THz radiation activated the CaN complex and upregulated genes involved in ribosome biogenesis and DNA damage repair.