Intranasally Delivered Wnt3a Improves Functional Recovery after Traumatic Brain Injury by Modulating Autophagic, Apoptotic, and Regenerative Pathways in the Mouse Brain

Abstract

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.

STING-mediated type-I interferons contribute to the neuroinflammatory process and detrimental effects following traumatic brain injury

“…Both the STING and type-I IFN pathways have emerged as key players in autophagy activation in cellular and other disease models [ 47 , 51 ] but their interaction and regulation following brain injury is unknown. Our results demonstrated increased expression of autophagy markers in both WT and STING −/− mice at 2 h and 24 h after TBI as compared to their sham controls validating our CCI model in inducing autophagy as previously reported [ 44 , 73 , 74 ]. Interestingly, after CCI, we observed increased and sustained expression of LC3 and p62 in STING −/− brains as compared to their WT counterparts.…”

On the Role of Basal Autophagy in Adult Neural Stem Cells and Neurogenesis

“…Furthermore, the cortical phenotype observed following Atg5 silencing is fully rescued by β-catenin knockdown ( Lv et al, 2014 ). On the other hand, it has been reported that Wnt3A decreases autophagy in mature neurons after traumatic brain injury while increasing hippocampal neurogenesis ( Zhang et al, 2018a ). In contrast, Wnt3A increases autophagy in embryonic rat hippocampal neuronal cultures through the activation of AMPK ( Ríos et al, 2018 ).…”

WNT3A Promotes Neuronal Regeneration upon Traumatic Brain Injury

“…Although WNT3A is not likely to pass through the BBB in an uninjured brain due to its size, the BBB is compromised in response to TBI and may be permissive to WNT3A uptake after intravenous injection [23]. On the other hand, intranasal delivery of proteins is believed to bypass the BBB in animal models [24], and our results demonstrate that this method of WNT3A delivery can produce a promising outcome on regeneration of injured brain neurons. The clinical efficacy of systemic or intranasal administration of protein drugs to the brain of TBI patients remains to be tested [25,26].…”