Homozygotic mutations in the GBA gene cause Gaucher’s disease, moreover, both patients and heterozygotic carriers have been associated with 20- to 30-fold increased risk of developing Parkinson’s disease. In homozygosis, these mutations impair the activity of beta-glucocerebrosidase, the enzyme encoded by GBA, and generate a lysosomal disorder in macrophages, which changes morphology towards an engorged phenotype, considered the hallmark of Gaucher’s disease. In the brain, most of the pathological effects caused by GBA mutations have been attributed to the beta-glucocerebrosidase deficit in neurons, while a microglial phenotype for these mutations has never been reported. Here, we applied the bioluminescence imaging technology, immunohistochemical and gene expression analysis to investigate the consequences of microglial beta-glucocerebrosidase inhibition in the brain of reporter mice, in primary neuron/microglia co-cultures and in cell lines. Our data demonstrate the existence of a novel mechanism by which microglia sustain the antioxidant/detoxifying response mediated by the nuclear factor erythroid 2-related factor 2 in neurons. The central role played by microglia in this neuronal response in vivo was proven by pharmacological depletion of the lineage in the brain, while co-cultures experiments provided insight on the nature of this cell-to-cell communication showing that this mechanism requires a direct microglia-to-neuron contact supported by functional actin structures. Pharmacological inhibition of microglial beta-glucocerebrosidase was proven to induce morphological changes, turn on an anti-inflammatory/repairing pathway and hinder the microglia ability to activate the anti-oxidant/detoxifying response, thus increasing the neuronal susceptibility to neurotoxins. Altogether, our data suggest that microglial beta-glucocerebrosidase inhibition impairs microglia-to-neuron communication increasing the sensitivity of neurons to oxidative or toxic insults, thus providing a possible mechanism for the increased risk of neurodegeneration observed in carriers of GBA mutations.
bioRxiv Subject Collection: Neuroscience