Stretch-induced injury alters mitochondrial membrane potential and cellular ATP in cultured astrocytes and neurons

Energy deficit after traumatic brain injury (TBI) may alter ionic homeostas is, neurotransmission, biosynthesis, and cellular transport. Using an in vi tro model for TBI, we tested the hypothesis that stretch-induced injury alt ers mitochondrial membrane potential (Delta psi(m)) and ATP in astrocytes a nd neurons. Astrocytes, pure neuronal cultures, and mixed neuronal plus gli al cultures grown on Silastic membranes were subjected to mild, moderate, a nd severe stretch. After injury, Delta psi(m), was measured using rhodamine -123, and ATP was quantified with a luciferin-luciferase assay. In astrocyt es, Delta psi(m) dropped significantly, and ATP content declined 43-52% 15 min after mild or moderate stretch but recovered by 24 h. In pure neurons, Delta psi(m) declined at 15 min only in the severely stretched group. At 48 h postinjury, Delta psi(m) remained decreased in severely stretched neuron s and dropped in moderately stretched neurons. Intracellular ATP content di d not change in any group of injured pure neurons. We also found that astro cytes and neurons release ATP extracellularly following injury. In contrast to pure neurons, Delta psi(m) in neurons of mixed neuronal plus glial cult ures declined 15 min after mild, moderate, or severe stretch and recovered by 24-48 h. ATP content in mixed cultures declined 22-28% after mild to sev ere stretch with recovery by 24 h. Our findings demonstrate that injury cau ses mitochondrial dysfunction in astrocytes and suggest that astrocyte inju ry alters mitochondrial function in local neurons.