WNT5A Signaling Contributes to Ab-Induced Neuroinflammation and Neurotoxicity Bei Li1,2., Ling Zhong2., Xiangling Yang2, Tommy Andersson 3 , Min Huang2, Shao-Jun Tang 1 * 1 Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, Texas, United States of America, 2 School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou, People’s Republic of China, 3 Department of Laboratory Medicine, Lund University, Clinical Research Centre, Ska˚ne University Hospital, Malmo¨ , Sweden Abstract Neurodegenration is a pathological hallmark of Alzheimer’s disease (AD), but the underlying molecular mechanism remains elusive. Here, we present evidence that reveals a crucial role of Wnt5a signaling in this process. We showed that Wnt5a and its receptor Frizzled-5 (Fz5) were up-regulated in the AD mouse brain, and that beta-amyloid peptide (Ab), a major constituent of amyloid plaques, stimulated Wnt5a and Fz5 expression in primary cortical cultures; these observations indicate that Wnt5a signaling could be aberrantly activated during AD pathogenesis. In support of such a possibility, we observed that inhibition of Wnt5a signaling attenuated while activation of Wnt5a signaling enhanced Ab-evoked neurotoxicity, suggesting a role of Wnt5a signaling in AD-related neurodegeneration. Furthermore, we also demonstrated that Ab-induced neurotoxicity depends on inflammatory processes, and that activation of Wnt5a signaling elicited the expression of proinflammatory cytokines IL-1b and TNF-a whereas inhibition of Wnt5a signaling attenuated the Ab-induced expression of the cytokines in cortical cultures. Our findings collectively suggest that aberrantly up-regulated Wnt5a signaling is a crucial pathological step that contributes to AD-related neurodegeneration by regulating neuroinflammation. Citation: Li B, Zhong L, Yang X, Andersson T, Huang M, et al. (2011) WNT5A Signaling Contributes to Ab-Induced Neuroinflammation and Neurotoxicity. PLoS ONE 6(8): e22920. doi:10.1371/journal.pone.0022920 Editor: Colin Combs, University of North Dakota, United States of America Received February 8, 2011; Accepted July 7, 2011; Published August 17, 2011 Copyright: 2011 Li et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by the start-up funds from the University of Texas Medical Branch to S-JT and by grant No. 30873457 from the National Natural Science Foundation of China and No. 2008A060202010 and 2010B050700019 from the Scientific Technology Project of Guangdong Province of China to LZ. BL is a Ph.D. student fellow supported by China Scholarship Council. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: shtang@utmb.edu . These authors contributed equally to this work. Introduction Beta-Amyloid (Ab) peptide is a dominant candidate of the causative agents for Alzheimer’s disease (AD) [1,2]. According to the widely-held amyloid hypothesis of AD, Ab initiates an array of molecular and cellular cascades that eventually lead to progressive neuronal dysfunction and degeneration [1,2]. However, mecha- nistic molecular processes that link Ab and neurodegeneration remain to be firmly established. Chronic neuroinflammation associated with persistent glial activation is a major disease process evoked by Ab and intimately associated with the progress of AD pathologies [3,4]. Previous studies suggest that neuroinflammation contributes to the development of neurodegenerative hallmarks in AD brains, including Ab plaques [4] and tau tangles [5,6,7]. AD therapeutic approaches that target neuroinflammation are under develop- ment [8,9,10,11]. AD neuroinflammation is likely triggered by Ab-mediated activation of microglia and astrocytes [3,4, 12,13,14]. It was reported that Ab induces the expression of cytokines (including IL-1b, TNF-a, IL-6, and IL-8) in cultured astrocytes and microglia [15,16,17,18]. Mounting evidence suggests that Ab may activate glial cells via specific sensor receptors such as toll-like receptors (TLR), receptors for advanced glycoxidation end-products (RAGE) and NOD-like receptors (NLR) [4]. Despite the significant understandings on the induction of AD neuroinflammation, the downstream molecular processes that are elicited by Ab and regulate the inflammation remain poorly understood. Wnts are secreted signaling proteins that play important roles in neural development and plasticity [19,20,21,22]. Multiple lines of evidence indicate a critical role of Wnt signaling in AD [22]. b- catenin, a key downstream effector protein in the canonical Wnt signaling pathway, interacts with and is regulated by presenilin [23,24,25]. Glycogen synthase kinase (GSK)-3, a central serine/ threnine kinase in the canonical Wnt signaling pathway, plays a critical role in the regulation of Ab production [26] and aggregation [27] and in tau phosphorylation [28]. Genetic studies revealed that LRP6 polymorphisms are causally linked to AD [29]. In AD brains, canonical Wnt signaling is impaired [30], and DKK1, an antagonist of Wnt signaling, is upregulated [31,32]. Importantly, Ab was reported to inhibit Wnt signaling by directly binding to the Frizzled receptors [33]. The impairment of canonical Wnt signaling is likely etiologically significant, because forced up-regulation of the canonical Wnt signaling pathway has rescuing effects on the development of AD-related phenotypes in both neuron cultures and animal models [27,30,34,35]. In contrast to the canonical pathway, the involvement of non-canonical Wnt signaling pathways in the regulation of AD pathogenesis is less clear. A recent study indicates that Wnt5a-activated non-canonical Wnt signaling antagonizes Ab synaptotoxicity [36]. PLoS ONE | www.plosone.org 1 August 2011 | Volume 6 | Issue 8 | e22920