Red and near-infrared light induces intracellular Ca2+ flux via the activation of glutamate N-methyl-D-aspartate receptors.

Red and near-infrared (NIR) light effect on Ca2+ ions flux through the influence on N-methyl-D-aspartate receptors (NMDARs) and their functioning in HeLa cells was studied in vitro. Cells were irradiated by 650 and 808 nm laser light at different power densities and doses and the obtained effect was compared with that caused by the pharmacological agents. The laser light was found to elevate Ca2+ influx into cell cytoplasm in a dose-dependent manner without changes of the NMDAR functioning. Furthermore, the light of both wavelengths demonstrated the ability to elevate Ca2+ influx under the pharmacological blockade of NMDARs and also might partially abolish the blockade enhancing Ca2+ influx after selective stimulation of the receptors with NMDA. Simultaneously, the light at moderate doses demonstrated a photobiostimulating effect on cells. Based on our experiments and data reported in the literature, we suggest that the low-power visible and NIR light can instigate a cell membrane depolarization via nonthermal activation, resulting in the fast induction of Ca2+ influx into cells. The obtained results also demonstrate that NIR light can be used for nonthermal and nonpharmacological stimulation of NMDARs in cancer cells.