No abstract

Wnt signaling is a conserved pathway involved in expansion of neural progenitors and lineage specification during development. However, the role of Wnt signaling in the post-stroke brain has not been well-elucidated. We hypothesized that Wnt-3a would play an important role for neurogenesis and brain repair. Adult male mice were subjected to a focal ischemic stroke targeting the sensorimotor cortex. Mice that received Wnt-3a (2 µg/kg/day, 1 h after stroke and once a day for the next 2 days, intranasal delivery) had reduced infarct volume compared to stroke controls. Wnt-3a intranasal treatment of seven days upregulated the expression of brain-derived growth factor (BDNF), increased the proliferation and migration of neuroblasts from the subventricular zone (SVZ), resulting in increased numbers of newly formed neurons and endothelial cells in the peri-infarct zone. Both the molecular and cellular effects of Wnt-3a were blocked by the Wnt specific inhibitors XAV-939 or Dkk-1. In functional assays, Wnt-3a treatment enhanced the local cerebral blood flow (LCBF) in the peri-infarct, as well as improved sensorimotor functions in a battery of behavioral tests. Together, our data demonstrates that the Wnt-3a signaling can act as a dual neuroprotective and regenerative factor for the treatment of ischemic stroke.

Traumatic brain injury (TBI) is a prevalent disorder, but no effective therapies currently exist. An underlying pathophysiology of TBI includes the pathological elevation of autophagy. β-Catenin, a downstream mediator of the canonical Wnt pathway, is a repressor of autophagy. The Wnt/β-catenin pathway plays a crucial role in cell proliferation and neuronal plasticity/repair in the adult brain. We hypothesized that activation of this pathway could promote neuroprotection and neural regeneration following TBI. In the controlled cortical impact (CCI) model of TBI in C57BL/6 mice (total n = 160), we examined intranasal application of recombinant Wnt3a (2 μg/kg) in a short-term (1 dose/day for 2 days) and long-term (1 dose/day for 7 days) regimen. Immunohistochemistry was performed at 1 to 14 days post-TBI to assess cell death and neurovascular regeneration. Western blotting measured canonical Wnt3a activity, expression of growth factors, and cell death markers. Longitudinal behavior assays evaluated functional recovery. In short-term experiments, Wnt3a treatment with a 60-min delay post-TBI suppressed TBI-induced autophagic activity in neurons (44.3 ± 6.98 and 4.25 ± 2.53 LC3+/NeuN+ double positive cells in TBI+Saline and TBI+Wnt3a mice, respectively; p < 0.0001, n = 5/group), reduced autophagic markers light chain 3 (LC3)-II and Beclin-1, as well as injury markers caspase-3 and matrix metalloproteinase 9 (MMP-9). The Wnt3a treatment reduced cell death and contusion volume (0.72 ± 0.07 mm and 0.26 ± 0.04 mm in TBI+Saline and TBI+Wnt3a mice, respectively; p < 0.001, n = 5/group). The 7-day Wnt3a treatment increased levels of β-catenin and growth factors glial-derived growth factor (GDNF) and vascular endothelial growth factor (VEGF). This chronic Wnt3a therapy augmented neurogenesis (0.52 ± 0.09 and 1.25 ± 0.13 BrdU+/NeuN+ co-labeled cells in TBI+Saline mice and TBI+Wnt3a mice, respectively; p < 0.01, n = 6/group) and angiogenesis (0.26 ± 0.07 and 0.74 ± 0.13 BrdU+/GLUT1+ co-labeled cells in TBI+Saline and TBI+Wnt3a mice, respectively; p = 0.014, n = 6/group). The treatment improved performance in the rotarod test and adhesive removal test. Targeting the Wnt pathway implements a unique combination of protective and regenerative approaches after TBI.

Hemorrhagic stroke is a devastating disease that lacks effective therapies. In the present investigation, we tested 6-bromoindirubin-3'-oxime (BIO) as a selective glycogen synthase kinase-3β (GSK-3β) inhibitor in a mouse model of intracerebral hemorrhage (ICH). ICH was induced by injection of collagenase IV into the striatum of 8- to 10-week-old C57BL/6 mice. BIO (8 μg/kg, IP) was administered following either an acute delivery (0-2 h delay) or a prolonged regimen (every 48 h starting at 3 days post-ICH). At 2 days post-ICH, the acute BIO treatment significantly reduced the hematoma volume. In the perihematoma regions, BIO administration blocked GSK-3β phosphorylation/activation, increased Bcl-2 and β-catenin levels, and significantly increased viability of neurons and other cell types. The prolonged BIO regimen maintained a higher level of β-catenin, upregulated VEGF and BDNF, and promoted neurogenesis and angiogenesis in peri-injury zones at 14 days after ICH. The BIO treatment also promoted proliferation of neural stem cells (NSCs) and migration of nascent DCX+ neuroblasts from the subventricular zone (SVZ) to the lesioned cortex. BIO improved functional outcomes on both the neurological severity score and rotarod tests. The findings of this study corroborate the neuroprotective and regenerative effects of BIO and suggest that the Wnt/GSK-3β/β-catenin pathway may be explored for the treatment of acute or chronic ICH.

The N-methyl-d-aspartate receptor (NMDAR) has been implicated in the pathophysiology of neurological diseases, such as schizophrenia, autism spectrum disorders (ASD), and Alzheimer's disease (AD), whose unique clinical hallmark is a constellation of impaired social and/or cognitive behaviors. GluN3A (NR3A) is a unique inhibitory subunit in the NMDAR complex. The role of GluN3A in social behavioral activities is obscure. In this study, we sought to evaluate altered social activities in adult GluN3A knockout (KO) mice. GluN3A KO mice spent less time in reciprocal social interaction in the social interaction test compared to wild-type (WT) mice. A social approach test using a three-chamber system confirmed that mice lacking GluN3A had lower sociability and did not exhibit a preference for social novelty. GluN3A KO mice displayed abnormal food preference in the social transmission of food preference task and low social interaction activity in the five-trial social memory test, but without social memory deficits. Using a home cage monitoring system, we observed reduced social grooming behavior in GluN3A KO mice. Signaling genes that might mediate the altered social behaviors were examined in the prefrontal cortex, hippocampus, and thalamus. Among nine genes examined, the expression of the oxytocin receptor was significantly lower in the prefrontal cortex of GluN3A KO mice than that in WT mice. Oxytocin treatment rescued social activity deficits in GluN3A KO mice. These findings support a novel idea that a chronic state of moderate increases in NMDAR activities may lead to downregulation of the oxytocin signaling and impaired behavioral activities that are seen in psychiatric/neurodegenerative disorders.