Regulating astrocyte phenotype by Lcn2 inhibition toward ischemic stroke therapy

Astrocytes can be reacted to "reactive astrocytes" after ischemia-reperfusion injury, in which A1 phenotype causes neuronal and oligodendrocyte death, whereas the A2 phenotype exerts neuroprotective effects, thus regulating reactive astrocyte to A2 type is a potential target for stroke therapy. Lcn2 level is highly associated with the phenotypic polarization of astrocytes. We found that silencing the Lcn2 gene by adeno-associated virus (AAV)-Lcn2 shRNA adenovirus resulted in a dramatic decrease in A1-type astrocytes and increase in A2 astrocytes in MCAO mice. Hence, a nanoplatform was developed for stroke therapy by inhibiting Lcn2. This system was fabricated by N-acetyl Pro-Gly-Pro peptide-decorated rod-shaped poly (lactic-co-glycolic acid) nanoparticles loading with rolipram (AP@R). The nanodrug can be efficiently taken up by neutrophils simultaneously through morphology-mediated passive targeting and Cxcr2 receptor-mediated active targeting, subsequently crossing the blood-brain barrier (BBB) by hitchhiking neutrophils. When accumulating at the brain parenchyma, the released rolipram can inhibit the Lcn2 level, thereby reversing the astrocyte phenotype to alleviate neuroinflammation and promote BBB repair. This work provides a new strategy for treating ischemic stroke.