Therapeutic benefits of 9-amino acid peptide derived from prothymosin alpha against ischemic damages

Prothymosin alpha (ProTα), a nuclear protein, plays multiple functions including cell survival. Most recently, we demonstrated that the active 30-amino acid peptide sequence/P₃₀ (amino acids 49–78) in ProTα retains its substantial activity in neuroprotection in vitro and in vivo as well as in the inhibition of cerebral blood vessel damages by the ischemic stress in retina and brain. But, it has remained to identify the minimum peptide sequence in ProTα that retains neuroprotective activity. The present study using the experiments of alanine scanning suggested that any amino acid in 9-amino acid peptide sequence/P₉ (amino acids 52–60) of P₃₀ peptide is necessary for its survival activity of cultured rat cortical neurons against the ischemic stress. In the retinal ischemia-perfusion model, intravitreous injection of P₉ 24 h after ischemia significantly inhibited the cellular and functional damages at day 7. On the other hand, 2,3,5-triphenyltetrazolium chloride (TTC) staining and electroretinogram assessment showed that systemic delivery with P₉ 1 h after the cerebral ischemia (1 h tMCAO) significantly blocks the ischemia-induced brain damages. In addition, systemic P₉ delivery markedly inhibited the cerebral ischemia (tMCAO)-induced disruption of blood vessels in brain. Taken together, the present study provides a therapeutic importance of 9-amino acid peptide sequence against ischemic damages.