Nuclear translocation of
annexin A1 (ANXA1) has recently been reported to participate in neuronal apoptosis after
cerebral ischemia. Prevention of the nuclear translocation of ANXA1 should therefore inhibit neuronal apoptosis and protect against
cerebral stroke. Here, we found that, in the repeat III domain of ANXA1, the
amino-acid residues from R228 to F237 function as a unique nuclear translocation signal (NTS) and are required for nuclear translocation of ANXA1. Intriguingly, we synthesized a
cell-penetrating peptide derived by conjugating the
trans-activator of transcription (Tat) domain to the NTS sequence. This Tat-NTS
peptide specifically blocked the interaction of ANXA1 with
importin β and, consequently, the nuclear translocation of ANXA1 without affecting the nucleocytoplasmic shuttling of other
proteins. The Tat-NTS
peptide inhibited the transcriptional activity of p53, decreased Bid expression, suppressed activation of the
caspase-3 apoptosis pathway and improved the survival of hippocampal neurons subjected to
oxygen-
glucose deprivation and reperfusion in vitro. Moreover, using a focal
brain ischemia animal model, we showed that the Tat-NTS
peptide could be efficiently infused into the ischemic hippocampus and cortex by unilateral intracerebroventricular injection. Injection of the Tat-NTS
peptide alleviated neuronal apoptosis in the ischemic zone. Importantly, further work revealed that administration of the Tat-NTS
peptide resulted in a dramatic reduction in
infarct volume and that this was correlated with a parallel improvement in neurological function after reperfusion. Interestingly, the effects of Tat-NTS were injury specific, with little impact on neuronal apoptosis or cognitive function in
sham-treated nonischemic animals. In conclusion, based on its profound neuroprotective and cognitive-preserving effects, it is suggested that the Tat-NTS
peptide represents a novel and potentially promising new therapeutic candidate for the treatment of
ischemic stroke.