Oxidative stress induces axonal beading in cultured human brain tissue

Oxidative stress has been implicated in the pathogenesis of a number of human neurodegenerative disorders of the central nervous system (CNS), including Alzheimer's disease (AD). To better understand the pathological effects of oxidative stress on CNS neurons we used a primary human brain cell culture model of hydrogen peroxide-induced oxidative stress. Neuronal and astrocytic morphology was visualised by immunofluorescence with antibodies to the neuron-specific microtubule component beta-tubulin III and against glial fibrillary acidic protein (GFAP), respectively. After exposure to 40 mM H(2)O(2) for 60-90 min, axonal swelling was observed, which developed into axonal beading after 48 h. No beading was observed in GFAP-positive astrocytes. Despite the concentration of H(2)O(2) used, neurons remained attached to the substratum and showed no signs of apoptosis. This was attributed to the neuroprotective effect of the B-27 medium supplement, which contained antioxidants. The axonal swelling and beading was consistent with a disruption of microtubules by oxidative stress and subsequent hold-up of axonal transport.