Small Interfering RNA Targeting Dickkopf-1 Contributes to Neuroprotection After Intracerebral Hemorrhage in Rats

Excessive Dickkopf-1 (Dkk-1) plays a vital role in secondary brain injury following ischemic stroke and psychotic disease. However, it is unclear whether an increased expression of Dkk-1 occurred after intracerebral hemorrhage (ICH). The present study examined the potential role of Dkk-1 after ICH. ICH was induced by a single injection of autologous blood into the basal ganglia of rats. Dkk-1 protein levels in brain tissue and serum were detected by enzyme-linked immunosorbent assay after ICH. Rats were treated with small interfering RNA targeting Dkk-1 (siDkk-1) or vehicle following ICH. Behavioral deficits and brain water content were examined. Blood-brain barrier (BBB) integrity was detected by Evans blue extravasation and observed by transmission electron microscopy. Wnt-1 was evaluated by real-time RT-PCR. The tight junction protein zonula occludens-1 (ZO-1) was investigated by immunohistochemistry and Western blot assays. Serum level of Dkk-1 did not differ between the ICH and sham groups. However, the level of Dkk-1 in brain tissue was significantly increased at 24 and 72 h after ICH. BBB disruption and brain edema, as well as neurological deficits, were remarkably ameliorated by administration of siDkk-1. Moreover, siDkk-1 treatment significantly increased the transcription of Wnt-1 mRNA and upregulated the expression of ZO-1. These results provide the first evidence that siDkk-1 treatment is neuroprotective against secondary injury including brain edema and BBB permeability following ICH; the mechanism of neuroprotection may be associated with improvement of BBB integrity.