Effects of low-level laser exposure on calcium channels and intracellular release in cultured astrocytes

Prompted by a study of traumatic brain injury (TBI) in a model system of cultured astrocytes, we discovered that low level laser illumination (LLL) at 660nm elevates the level of intracellular Ca²⁺. The coherence of the illumination was not essential since incoherent red light also worked. For cells bathed in low Ca²⁺ saline so that influx was suppressed, the Ca²⁺ level rose with no significant latency following illumination and consistent with a slow leak of Ca²⁺ from storage such as from the endoplasmic reticulum and/or mitochondria. When the cells were bathed in normal Ca²⁺ saline, the internal Ca²⁺ rose, but with a latency of about 17 seconds from the beginning of illumination. Pharmacologic studies with ryanodine inhibited the light effect. Testing the cells with fluid shear stress as used in the TBI model showed that mechanically induced elevation of cell Ca²⁺ was unaffected by illumination.