Co-Localization of Glia Maturation Factor with NLRP3 Inflammasome and Autophagosome Markers in Human Alzheimer’s Disease Brain

Abstract

Alzheimer’s disease (AD) is a progressive neurodegenerative disease characterized by the presence of intracellular neurofibrillary tangles (NFTs) containing hyper-phosphorylated tau, and the extracellular deposition of amyloid plaques (APs) with misfolded amyloid–β (Aβ) peptide. Glia maturation factor (GMF), a highly conserved pro-inflammatory protein, isolated and cloned in our laboratory has been shown to activate glial cells leading to neuroinflammation and neurodegeneration in AD. We hypothesized that inflammatory reactions promoted by NLRP3-Caspase-1inflammasome pathway trigger dysfunction in autophagy and accumulation of Aβ which is amplified and regulated by GMF in AD. In this study, using immunohistochemical techniques we analyzed components of the NLRP3 inflammasome and autophagy-lysosomal markers in relation to Aβ, p-tau and GMF in human post-mortem AD and age-matched non-AD brains. Tissue sections were prepared from the temporal cortex of human post-mortem brains. Here, we demonstrate an increased expression of the inflammasome components NLRP3 and Caspase-1 and the products of inflammasome activation IL-1β and IL-18 along with GMF in the temporal cortex of AD brains. These inflammasome components and the pro-inflammatory cytokines co-localized with GMF in the vicinity and periphery of the amyloid plaques and NFTs. Moreover, using double immunofluorescence staining, AD brain displayed an increase in the autophagy SQSTM1/p62 and LC3 positive vesicles and the lysosomal marker LAMP1 that also co-localized with GMF, amyloid beta and hyper-phosphorylated p-tau. Our results indicate that in AD, the neuroinflammation promoted by the NLRP3 inflammasome may be amplified and regulated by GMF, which further impairs clearance of protein aggregates mediated by the autophagosomal pathway.

Targeted Gene Editing of Glia Maturation Factor in Microglia: a Novel Alzheimer’s Disease Therapeutic Target

“…Neuroinflammation plays a crucial role during AD progression. We have previously shown that GMF plays a crucial role in the AD pathophysiology including neurodegeneration [17,23,24]. Therefore, we believe that GMF could potentially be an attractive therapeutic target against AD.…”

“…The activation of the microglial cells initiates a cascade of events that ultimately lead to neurodegeneration and AD pathophysiology. Proinflammatory mediator GMF has been shown to be expressed at elevated levels in AD patients [17,22-25,27]. We therefore believe that GMF represents a novel and an attractive therapeutic target to disrupt glia-neuron interactions and possibly delay and/or halt the progression of AD.…”

“…In addition, other studies have uncovered the role of microglia in high fat diet induced neuroinflammation [80-83]. We have recently reported that in human AD brain, dysfunctional lysosomal-autophagy pathway triggered and regulated by GMF and the NLRP3 inflammasome along with pro-inflammatory cytokines result in aggregated Aβ and tauopathy [17]. Therefore, we believe that targeted GMF gene editing in microglia could be exploited for halting the progression of neuroinflammation-mediated neurodegeneration in a wide variety of neurodegenerative diseases especially AD, diet-induced metabolic dysfunction including obesity and post-operative cognitive decline.…”

“…Microglia are the key players in neuroinflammation [13-16]. GMF, a proinflammatory molecule, discovered and characterized by our research group has been shown to be highly expressed in AD brain and is associated with neurodegeneration [17-28]. Our prior studies have demonstrated that GMF plays an important role in Parkinson’s disease (PD) pathogenesis and GMF deficiency protects the dopaminergic neuronal loss in the mouse model of Parkinson’s disease [29].…”

Dementia risk genes engage gene networks poised to tune the immune response towards chronic inflammatory states

“…3G, 3H), which we accordingly named the "inflammasome" and "anti-inflammasome" modules. The NLRP3 inflammasome is assembled downstream of cellular stressors and activated by the detection of various stimuli 13 , including pathological Abeta 49,50 , to promote pro-inflammatory states. Similarly, pathological Abeta rapidly and specifically stimulates the expression of the inflammasome module eigengene in microglia, both in vivo and in vitro ( Fig.…”