Antagonizing Neuronal Toll-like Receptor 2 Prevents Synucleinopathy by Activating Autophagy

Kim, Changyoun; Rockenstein, Edward; Spencer, Brian; Kim, Hyung Koo; Adame, Anthony; Trejo, Margarita; Stafa, Klodjan; Lee, He Jin; Lee, Seung-Jae; Masliah, Eliezer

doi:10.1016/j.celrep.2015.09.044

Cited by 120 publications

(138 citation statements)

References 42 publications

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“…Interestingly, activation of autophagy with rapamycin was able to ameliorate the TLR2-mediated increase in α-synuclein, suggesting that activating autophagy can help clear α-synuclein protein, as has been seen before in animal studies [2, 23, 25, 32]. It is also important to note that while our manuscript was in preparation, Kim and colleagues reported similar findings regarding the activation of TLR2 on cell culture neurons and the accumulation of α-synuclein in association with increased p62 [20]. While there are some similarities in this aspect, it is noteworthy that our study employed only endogenous proteins while Kim et al employed neuronal cells transduced with lenti-viral α-synuclein and treated with 10-fold higher amounts of PAM3CSK4.…”

Section: Discussionsupporting

confidence: 73%

“…While there are some similarities in this aspect, it is noteworthy that our study employed only endogenous proteins while Kim et al employed neuronal cells transduced with lenti-viral α-synuclein and treated with 10-fold higher amounts of PAM3CSK4. However, Kim et al, also extend their studies to animal models and show that α-synuclein-mediated neurodegeneration is attenuated by either knockout or knockdown of TLR2 in rodent PD models [20]. We have further added to this important proof of principal work by demonstrating that small molecule inhibitors targeting the TLR pathway can also ameliorate the TLR2-mediated increase in α-synuclein and, as such, TLR2 pathway inhibition could form the basis of new therapeutic interventions.…”

Section: Discussionmentioning

confidence: 99%

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Toll-like receptor 2 is increased in neurons in Parkinson’s disease brain and may contribute to alpha-synuclein pathology

et al. 2016

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Inflammation is likely a key contributor to the pathogenesis of Parkinson’s disease (PD), a progressively debilitating neurodegenerative disease that is accompanied by a pathological accumulation of the α-synuclein protein in a staged manner through the brain. What leads to the accumulation of α-synuclein in PD and how this relates to inflammatory pathways, however, is not entirely clear. Toll-like receptor (TLR) signaling is a major pathway mediating inflammation and, in particular, TLR2 is increasingly being implicated in PD. We have, therefore, examined the expression of TLR2 in postmortem brain tissue from PD patients and matched controls. We confirm that TLR2 is increased in PD brain, and find that levels of TLR2 correlate with the accumulation of pathological α-synuclein. TLR2 was expressed on neurons as well as microglia; however, the neuronal rather than glial expression of TLR2 was significantly increased in PD brain in accordance with disease staging, and TLR2 was strongly localized to α-synuclein positive Lewy bodies. In cell culture, activation of neuronal TLR2 induced an inflammatory response, including the secretion of inflammatory cytokines and microglial-activating chemokines, as well as the production of reactive oxygen species. Moreover, activation of neuronal TLR2 increased levels of endogenous α-synuclein protein, which was in turn associated with increased levels of the autophagy/lysosomal pathway marker p62. Finally, promoting autophagy with rapamycin or pharmacological inhibition of the TLR2 signaling pathway prevented the TLR2-mediated increase in α-synuclein in neuronal cell cultures. These results implicate neuronal TLR2 expression in human PD pathogenesis. In particular, the increased expression of TLR2 on neurons may provide new insight into disease pathogenesis and/or options for therapeutic intervention.Electronic supplementary materialThe online version of this article (doi:10.1007/s00401-016-1648-8) contains supplementary material, which is available to authorized users.

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Section: Discussionsupporting

confidence: 73%

Section: Discussionmentioning

confidence: 99%

Toll-like receptor 2 is increased in neurons in Parkinson’s disease brain and may contribute to alpha-synuclein pathology

et al. 2016

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“…Other studies have shown that TNFα and TLR activation in neurons increase α-synuclein levels by inhibiting autophagy [39, 40]. In this study, TNFα transiently increased α-synuclein levels, which could eventually favor protein aggregation and pathogenicity [41, 42].…”

Section: Discussionsupporting

confidence: 51%

Mutations in LRRK2 impair NF-κB pathway in iPSC-derived neurons

Maturana¹,

Lang²,

Zubiarrain³

et al. 2016

J Neuroinflammation

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BackgroundMutations in leucine-rich repeat kinase 2 (LRRK2) contribute to both familial and idiopathic forms of Parkinson’s disease (PD). Neuroinflammation is a key event in neurodegeneration and aging, and there is mounting evidence of LRRK2 involvement in inflammatory pathways. In a previous study, we described an alteration of the inflammatory response in dermal fibroblasts from PD patients expressing the G2019S and R1441G mutations in LRRK2.MethodsTaking advantage of cellular reprogramming, we generated induced pluripotent stem cell (iPSC) lines and neurons thereafter, harboring LRRK2G2019S and LRRK2R1441G mutations. We used gene silencing and functional reporter assays to characterize the effect of the mutations. We examined the temporal profile of TNFα-induced changes in proteins of the NF-κB pathway and optimized western blot analysis to capture α-synuclein dynamics. The effects of the mutations and interventions were analyzed by two-way ANOVA tests with respect to corresponding controls.ResultsLRRK2 silencing decreased α-synuclein protein levels in mutated neurons and modified NF-κB transcriptional targets, such as PTGS2 (COX-2) and TNFAIP3 (A20). We next tested whether NF-κB and α-synuclein pathways converged and found that TNFα modulated α-synuclein levels, although we could not detect an effect of LRRK2 mutations, partly because of the individual variability. Nevertheless, we confirmed NF-κB dysregulation in mutated neurons, as shown by a protracted recovery of IκBα and a clear impairment in p65 nuclear translocation in the LRRK2 mutants.ConclusionsAltogether, our results show that LRRK2 mutations affect α-synuclein regulation and impair NF-κB canonical signaling in iPSC-derived neurons. TNFα modulated α-synuclein proteostasis but was not modified by the LRRK2 mutations in this paradigm. These results strengthen the link between LRRK2 and the innate immunity system underscoring the involvement of inflammatory pathways in the neurodegenerative process in PD.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-016-0761-x) contains supplementary material, which is available to authorized users.

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“…Moreover, additive application of antagonists indicates that TLR2, TLR3, and TLR4 are differently involved in the α‐syn‐induced inflammatory process. Our result that blockage of α‐syn stimulation by TLR2 antagonist downregulated TLR3 expression is also consistent with the data from transgenic mice and in vitro models, which demonstrates that inactivation of TLR2 increases clearance of neuronal α‐syn by activation of autophagy and reduces intracellular accumulation of α‐syn (a TLR3 stimulator), and vice versa (Kim et al., ). Likewise, TLR4 knockout technique shows participation of TLR4 in activation of microglia and astrocytes induced by WT α‐syn (0.7 μM, 72 hr), but with no influence on uptake of α‐syn in astrocytes other than microglia (Fellner et al., ; Rannikko, Weber, & Kahle, ), indicating lack of direct involvement of TLR4 in intracellular accumulation of α‐syn linked to TLR3 activation, as observed in our study.…”

Section: Discussionsupporting

confidence: 91%

α‐Synuclein activates innate immunity but suppresses interferon‐γ expression in murine astrocytes

Wang

Chen

Walston

et al. 2018

Eur J of Neuroscience

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Glial activation and neuroinflammation contribute to pathogenesis of neurodegenerative diseases, linked to neuron loss and dysfunction. α-Synuclein (α-syn), as a metabolite of neuron, can induce microglia activation to trigger innate immune response. However, whether α-syn, as well as its mutants (A53T, A30P, and E46K), induces astrocyte activation and inflammatory response is not fully elucidated. In this study, we used A53T mutant and wild-type α-syns to stimulate primary astrocytes in dose- and time-dependent manners (0.5, 2, 8, and 20 μg/ml for 24 hr or 3, 12, 24, and 48 hr at 2 μg/ml), and evaluated activation of several canonical inflammatory pathway components. The results showed that A53T mutant or wild-type α-syn significantly upregulated mRNA expression of toll-like receptor (TLR)2, TLR3, nuclear factor-κB and interleukin (IL)-1β, displaying a pattern of positive dose-effect correlation or negative time-effect correlation. Such upregulation was confirmed at protein levels of TLR2 (at 20 μg/ml), TLR3 (at most doses), and IL-1β (at 3 hr) by western blotting. Blockage of TLR2 other than TLR4 inhibited TLR3 and IL-1β mRNA expressions. By contrast, interferon (IFN)-γ was significantly downregulated at mRNA, protein, and protein release levels, especially at high concentrations of α-syns or early time-points. These findings indicate that α-syn was a TLRs-mediated immunogenic agent (A53T mutant stronger than wild-type α-syn). The stimulation patterns suggest that persistent release and accumulation of α-syn is required for the maintenance of innate immunity activation, and IFN-γ expression inhibition by α-syn suggests a novel immune molecule interaction mechanism underlying pathogenesis of neurodegenerative diseases.

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Antagonizing Neuronal Toll-like Receptor 2 Prevents Synucleinopathy by Activating Autophagy

Cited by 120 publications

References 42 publications

Toll-like receptor 2 is increased in neurons in Parkinson’s disease brain and may contribute to alpha-synuclein pathology

Toll-like receptor 2 is increased in neurons in Parkinson’s disease brain and may contribute to alpha-synuclein pathology

Mutations in LRRK2 impair NF-κB pathway in iPSC-derived neurons

α‐Synuclein activates innate immunity but suppresses interferon‐γ expression in murine astrocytes

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