Effect of 40 Hz Light Stimulation on Calcium Dynamics of Astrocytes

Astrocytes are glial cells with intracellular calcium dynamics essential for brain homeostasis, synaptic modulation, and cognition and altered in neuropathology and neuroinflammation. Growing evidence indicates these calcium signals can be triggered by chemophysical stimuli. Photonic, label free optical stimulation could provide unique opportunities to study astrocytic calcium signaling in physiological and pathological conditions and responses to external cues. This study describes the effects of visible LED light technology, called 40 Hz invisible spectral flicker (ISF), on calcium dynamics in primary rat cortical astrocytes. We demonstrate that ISF and continuous visible light (CL, used as control) can efficiently trigger calcium dynamics in astrocyte, through recruiting distinct molecular pathways. Specifically, extracellular calcium influx is essential for the response to 40 Hz ISF stimulation to occur but not to CL. In addition,the channels TRPV4 and TRPA1, as well as IP 3 Rs and ryanodine receptors pathways, are differentially implicated in the observed effects in response to ISF and CL. These findings respond to the need for novel methods to trigger calcium signaling in astrocytes, showing that ISF visible, nonlaser light is an effective approach with potential modulation capability simply varying light stimulation frequency.