Acute Alterations in [Ca2+]iin NG108-15 Cells Subjected to High Strain Rate Deformation and Chemical Hypoxia: Anin VitroModel for Neural Trauma

The short-term (less than 2 min) alterations in the intracellular free calcium concentration in differentiated NG108-15 (neuroblastoma cross glioma) cells exposed to dynamic mechanical deformation with and without superimposed chemical hypoxia were determined. A previously developed device, modified for these studies, was used to apply deformations at a magnitude and rate representative of those experienced by neural tissue in Traumatic Brain Injury. Chemical hypoxia was imposed using a combination of 2-deoxy-d-glucose and salicylate, anaerobic and aerobic metabolic blockers, respectively. Real time measurement of intracellular free calcium concentration using Fura-2 and a custom epifluorescence microscopy system provided a quantitative index of cell response. At high rates of deformation (∼10 sec-1), increases in intracellular free calcium concentration were exponentially related to the magnitude of the applied deformation. Chemical hypoxia had no effect on this acute response. At low rates of deformation, small increases in intracellular free calcium concentration were independent of the magnitude of the deformation. These findings indicate that strategies for reducing severity of TBI should focus on minimizing the rate of deformation of neural cells. Together with data from animal, physical, and finite element models, these data can be employed in the development of physiologic injury tolerance criteria for the whole head.