Mahn, S. | Search bioRxiv

bioRxiv2024

Peripheral immune cell response to stimulation stratifies Parkinson's disease progression from prodromal to clinical stages

The motor stage of idiopathic Parkinsons disease (iPD) can be preceded for years by a prodromal stage characterized by non-motor symptoms like REM sleep behavior disorder (RBD). Here, we show that multiple stages of iPD, including the pre-motor prodromal stage, can be stratified according to the inflammatory and immunometabolic responses to stimulation of peripheral blood mononuclear cells ex vivo. We identified increased stimulation-dependent secretion of TNF, IL-1{beta}, and IL-8 in monocytes from RBD patients and showed diminished proinflammatory cytokine secretion in monocytes and T cells in early and moderate stages of PD. Mechanistically, immune activation revealed deficits in CD8+ T-cell mitochondrial health in moderate PD, and relative mitochondrial health in CD8+ T cells was positively correlated with stimulation-dependent T-cell cytokine secretion across the PD spectrum. Dysregulated immunometabolism may drive peripheral inflammation and PD progression, and ex vivo stimulation-based assays have potential to reveal novel biomarkers for patient stratification and progression with immune endophenotypes.

neuroscience↗

bioRxiv2024

ASO-mediated knockdown of GPNMB in mutant-GRN and Grn-deficient peripheral myeloid cells disrupts lysosomal function and immune responses

BackgroundIncreases in GPNMB are detectable in FTD-GRN cerebrospinal fluid (CSF) and post-mortem brain, and brains of aged Grn-deficient mice. Although no upregulation of GPNMB is observed in the brains of young Grn-deficient mice, peripheral immune cells of these mice do exhibit this increase in GPNMB. Importantly, the functional significance of GPNMB upregulation in progranulin-deficient states is currently unknown. Given that GPNMB has been discussed as a potential therapeutic target in GRN-mediated neurodegeneration, it is vital for the field to determine what the normal function of GPNMB is in the immune system, and whether targeting GPNMB will elicit beneficial or deleterious effects. MethodsThe effects of GPNMB knock-down via antisense oligonucleotide (ASO) were assessed in peripheral blood mononuclear cells (PBMCs) from 25 neurologically healthy controls (NHCs) and age- and sex-matched FTD-GRN patients, as well as peritoneal macrophages (pMacs) from progranulin-deficient (Grn-/-) and B6 mice. Lysosomal function, antigen presentation and MHC-II processing and recycling were assessed, as well as cytokine release and transcription. ResultsWe demonstrate here that ASO-mediated knockdown of GPNMB increases lysosomal burden and cytokine secretion in FTD-GRN carrier and neurologically healthy controls (NHCs) monocytes. ASO-mediated knockdown of GPNMB in Grn-deficient macrophages decreased lysosomal pan-cathepsin activity and protein degradation. In addition, ASO-mediated knockdown of GPNMB increased MHC-II surface expression, which was driven by decreased MHC-II uptake and recycling, in macrophages from Grn-deficient females. Finally, ASO-mediated knockdown of GPNMB dysregulated IFN{gamma}-stimulated cytokine transcription and secretion by mouse macrophages due to the absence of regulatory actions of the GPNMB extracellular fragment (ECF). ConclusionsOur data herein reveals that GPNMB has a regulatory effect on multiple immune effector functions, including capping inflammation and immune responses in myeloid cells via secretion of its ECF. Therefore, in progranulin-deficient states, the drastic upregulation in GPNMB transcript and protein may represent a compensatory mechanism to preserve lysosomal function in myeloid cells. These novel findings indicate that targeted depletion in FTD-GRN would not be a rational therapeutic strategy because it is likely to dysregulate important immune cell effector functions.

immunology↗