SNAP, a NO donor, induces cortical neuron death by a mechanism in which the caspase pathway is implicated

In this paper, we present data which demonstrate that, in cortical neurons, SNAP induces loss in cell viability as evaluated by the XTT test. This cell death started at 250 μM SNAP when the treatment was performed in a serum-free medium and at 10 μM when the treatment was given in the presence of serum. This death was mediated, at least in part, by an apoptotic mechanism detected by flow cytometry and DNA fractionation. The highest SNAP concentrations induced a dual behavior on caspase-3 activity. Concentrations of 250 μM in the absence of serum and 10 μM to 300 μM in the presence of serum produced caspase-3 activation. This indicates that NO induces neuronal death by an apoptotic mechanism in which the caspase pathway is implicated. Higher SNAP concentrations (500 μM to 1 mM) diminished the caspase-3 activity to levels similar or even lower than control values. This profile was observed in the absence as well as in the presence of serum in the medium. The caspase-3 inhibition mediated by the highest SNAP concentrations did not imply NO cellular protection since the caspase-3 inhibition mediated by these SNAP concentrations neither correlated with cellular viability nor with cellular apoptosis. The possible mechanism of caspase-3 inhibition at the highest SNAP concentrations used is discussed.