Nucleoprotamine diet derived from salmon soft roe protects mouse hippocampal neurons from delayed cell death after transient forebrain ischemia

The nutritional benefits of nucleoprotamine (NP), the main component of fish soft roe, have been rarely addressed. In the present study, the preventive effect of oral supplements of nucleoprotamine and its derivatives, DNA and protamine (PT), extracted from salmon soft roe, on survival rate and hippocampal cell death induced by transient brain ischemia, was evaluated in mice. Artificially formulated nucleoprotamine-free (NF) diet with/without nucleoprotamine, DNA or protamine was fed orally. One week after commencement of respective diets, animals were subjected to transient brain ischemia, which was performed by common carotid artery (CCA) occlusion for 25 (severe) or 15min (mild). After severe ischemia, the survival rate of the NF group was lower than that in the group fed standard diet or NP. Morphological changes in the hippocampal CA1 region were estimated 48h after mild ischemia. The NP and PT groups significantly decreased the neuronal damage compared with the NF group. The number of cell death in the DNA group, however, was affected similar to that of the NF group. Our data suggests that the nucleoprotamine content in salmon soft roe could be a useful nutritional resource for the prevention of cell damage caused by ischemia such as those occurring with cerebral and/or heart infarction.