Neuroimmune responses and therapeutics of alpha-synucleinopathies of the aging population

National Institute On Aging

Investigators

Linked publications & trials

Abstract

The main objective of the Molecular Neuropathology section (MNS) at Laboratory of Neurogenetics (LNG) is to harness the immune system to better understand the mechanisms of neurodegeneration and to develop therapies for synucleinopathies of the aging population such as DLB, PD and AD. We propose 3 Aims, the first investigating the role of innate immune responses and combinatorial immunotherapy targeting LRRK2, Toll-like receptors, p38, NFAT and the protein aggregates (eg: a-synuclein, Abeta, tau) in PD/DLB; the second assessing downstream pro-inflammatory signaling pathways including MAPK-p38, NFAT and NFkB and the third evaluating the role of aging in T cell mediated adaptive immune cell responses in PD/DLB pathogenesis and for developing immunotherapies for synucleinopathies. During this period we published over 20 manuscripts mostly focusing understanding the pathogenesis of PD/DLB and developing novel pharmacological and immunotherapeutical approaches. Progress for Aim1. Previous studies have identified several immune receptors that mediate neuroinflammation in synucleinopathies, such as Toll-like receptor 2 (TLR2). However, the species of -syn aggregates varies from study to study, and how different -syn aggregate species interact with innate immune receptors has yet to be addressed. We recently published a new study (Kim et al, Exp Mol Med 2021), where we investigated whether innate immune receptors can facilitate the uptake of different species of a-syn aggregates. We reported that stimulation of TLR2 in vitro accelerated a-syn fibril uptake in neurons and glia while delaying the degradation of a-syn in neurons and astrocytes. Internalized a-syn was rapidly degraded in microglia regardless of whether TLR2 was stimulated. However, cellular a-syn uptake and degradation kinetics were not altered by TLR4 stimulation. In addition, upregulation of TLR2 expression in a DLB/PD mouse models increased the density of Lewy-body-like pathology and induced morphological changes in microglia. Together, these results suggest that cell type-specific modulation of TLR2 may be a multifaceted and promising therapeutic strategy for synucleinopathies; inhibition of neuronal and astroglial TLR2 decreases pathogenic a-syn transmission, but activation of microglial TLR2 enhances microglial extracellular a-syn clearance. The next steps will investigate the effects of aging and deleting microglia with the PLX3387 (a compound that targets CSF1R) on synucleinopathies in DLB/PD models. Progress for Aim 2. In collaboration with the Cookson group we are investigating the cross talk between TLR2 and LRRK2 and downstream signaling involving NFATC leading to neurodegeneration and inflammation in PD/DLB. We recently published a manuscript (Kim et al Science TM 2020) showing that LRRK2) plays a critical role in the activation of microglia by extracellular a-synuclein. Exposure to a-synuclein was found to enhance LRRK2 phosphorylation and activity in mouse primary microglia. Furthermore, genetic and pharmacological inhibition of LRRK2 markedly diminished a-synuclein-mediated microglial neurotoxicity via lowering of tumor necrosis factor- and interleukin-6 expression in mouse cultures. We determined that LRRK2 promoted a neuroinflammatory cascade by selectively phosphorylating and inducing nuclear translocation of the immune transcription factor nuclear factor of activated T cells, cytoplasmic 2 (NFATc2). NFATc2 activation was seen in patients with synucleinopathies and in a mouse model of synucleinopathy, where administration of an LRRK2 pharmacological inhibitor restored motor behavioral deficits. Our results suggest that modulation of LRRK2 and its downstream signaling mediator NFATc2 might be therapeutic targets for treating synucleinopathies. The next steps include developing specific antibodies that recognize pNFAT phosphorylated by activation of the TLR2-LRKK2 pathway and to test the effects of compounds and genetic manipulations targeting NFAT. Progress for Aim 3. In collaboration with the Sen laboratory we recently published (Iba et al J Neuroinflammation 2020) one of the first studies in the field demonstrating that neuroinflammation in synucleinopathies involves considerable T cell infiltration with potential participation of NKT cells. Next, we explored the role of aging in the pathogenesis of PD/DLB by analyzing, behavior, neuropathology and transcriptomics and immune responses in young and aged wildtype mice that received intrastriatal injections with a-syn preformed fibrils (pff). We found that aged mice showed more extensive accumulation of a-syn and behavioral deficits that was associated with greater infiltration of T cells and microgliosis. Distinct inflammatory patterns of gene expression in microglia showed that a-syn pff-induced genes networks in young mice (eg: CSF2, TNF, IL1b, IL6) that overlaps with genes differentially expressed in microglia in the aged mice. These results indicate that the aged and more inflamed brain micro-environment directly influences the disease outcome of pathological accumulation of a-syn in age-related chronic diseases such as DLB and PD. This manuscript is under revision in Nature Aging. Along these lines, in another recent publication (Roshanbin et al Neurobiology of Dis 2021) we found that in our -syn transgenic model of DLB/PD there is and age dependent increase in a-syn oligomers and motor dysfunction. Taken together, our data indicate that a-syn oligomers are central to the development of brain pathology and behavioral deficits in the L61 tg -syn mouse model. The next steps will be to investigate the effects of aging and inflammation in models where T cells and microglia are deleted or where CSF1 and CSF2 are modulated. Other collaborations at LNG are with Drs. Cookson, Singleton, Traynor and Scholz on the genetic architecture of FTD, DLB and MSA by providing expert neuropathological assessment, animal models and human postmorten brain tissues. In addition to the collaborations with LNG, we have been collaborating with the laboratory of Dr. Avi Nath at NINDS investigating the neuropathology of COVID19 that resulted on a recent publication on the microvascular alterations in NeuroCOVID (Nath et al NEJM 2021), we plan to continue these studies and investigate the role of SARS-CoV2 at accelerating the pathology of AD/ADRD in particular inflammation and protein aggregation