Biology subjects

Sipione, S.

Publications and source records attributed to Sipione, S..

3 recordsLinked to original sources

bioRxiv2025

Gangliosides Modulate the Secretion of Extracellular Vesicles and Their Misfolded Protein Cargo

Gangliosides are glycosphingolipids that play an integral role in cell signaling and provide neuroprotection. While present on extracellular vesicles (EVs) - key mediators of intercellular communication - their role in EV biogenesis remains unclear. Here, we identify gangliosides, both endogenously synthesized and exogenously administered, as key modulators of EV biogenesis, with the specific composition of their glycan headgroup and the presence or absence of sialic acid and N-acetyl-D-galactosamine residues dictating whether they promote or inhibit EV biogenesis. We show that GM1 and other complex gangliosides enhance EV secretion, while disruption of ganglioside synthesis impairs it. GM1 supplementation restores EV secretion in Huntingtons disease (HD) fibroblasts and HD cell models that have lower than normal levels of gangliosides, and in cells with a genetic block of ganglioside synthesis that models rare early-onset neurodegenerative diseases. Notably, GM1 also enhances EV-mediated secretion of pathogenic misfolded proteins, including mutant huntingtin (mHTT), -synuclein and tau, reducing intracellular burden and providing mechanistic insight into the mHTT-lowering effects of GM1 treatments in HD models. Our findings shed light on the neuroprotective roles of gangliosides and highlight their potential for therapeutic exploitation in misfolded protein disorders.

cell biology↗

bioRxiv2023

Naive Huntington's disease microglia mount a normal response to inflammatory stimuli but display impaired development of innate immune tolerance that can be counteracted by ganglioside GM1

Chronic activation and dysfunction of microglia have been implicated in the pathogenesis and progression of many neurodegenerative disorders, including Huntingtons Disease (HD). HD is a genetic condition caused by a mutation that affects the folding and function of huntingtin (HTT). Signs of microglia activation have been observed in HD patients even before the onset of symptoms. It is unclear, however, whether pro-inflammatory microglia activation in HD results from cell-autonomous expression of mutant HTT or is the response of microglia to a diseased brain environment, or both. In this study, we used primary microglia isolated from HD knock-in mice (Q140) and wild-type (Q7) mice to investigate their response to inflammatory conditions in vitro in the absence of confounding effects arising from brain pathology. We show that naive Q140 microglia do not undergo spontaneous pro-inflammatory activation and respond to inflammatory triggers, including stimulation of TLR4 and TLR2 and exposure to necrotic cells, with similar kinetics of pro-inflammatory gene expression as wild-type microglia. Upon termination of the inflammatory insult, the transcription of pro-inflammatory cytokines is tapered off in Q140 and wild-type microglia with similar kinetics. However, the ability of Q140 microglia to develop tolerance in response to repeated inflammatory stimulations is partially impaired, potentially contributing to the establishment of chronic neuroinflammation in HD. We further show that ganglioside GM1, a glycosphingolipid with anti-inflammatory effects in wild-type microglia, not only decreases the production of pro-inflammatory cytokines and nitric oxide in activated Q140 microglia, but also dramatically dampen microglia response to re-stimulation with LPS in an experimental model of tolerance. These effects are independent from the expression of interleukin 1 receptor associated kinase 3 (Irak-3), a strong modulator of LPS signaling involved in the development of innate immune tolerance and previously shown to be upregulated by immune cell treatment with gangliosides. Altogether, our data suggest that external triggers are required for HD microglia activation, but a cell-autonomous dysfunction that affects the ability of HD microglia to acquire tolerance might contribute to the establishment of neuroinflammation in HD. Administration of GM1 might be beneficial to attenuate chronic microglia activation and neuroinflammation.

neuroscience↗

bioRxiv2020

Anti-inflammatory role of GM1 and modulatory effects of gangliosides on microglia functions

Gangliosides are sialic acid-containing glycosphingolipids highly enriched in the brain. Located mainly at the plasma membrane, gangliosides play important roles in signaling and cell-to-cell communication. Lack of gangliosides causes severe early onset neurodegenerative disorders, while more subtle deficits have been reported in Parkinsons disease and in Huntingtons disease, two misfolded protein diseases with a neuroinflammatory component. On the other hand, administration of ganglioside GM1 provides neuroprotection in both diseases and in several other models of neuronal insult. While most studies have focused on the role of endogenous gangliosides and the effects of exogenously administered GM1 in neurons, their contribution to microglia functions that are affected in neurodegenerative conditions is largely unexplored. Microglia are the immune cells of the brain and play important homeostatic functions in health and disease. In this study, we show that administration of exogenous GM1 exerts a potent anti-inflammatory effect on microglia activated with LPS, IL-1{beta} or upon phagocytosis of latex beads. These effects are partially reproduced by L-t-PDMP, a compound that stimulates the activity of the ganglioside biosynthetic pathway, while inhibition of ganglioside synthesis with GENZ-123346 increases microglial transcriptional response to LPS. We further show that administration of GM1 increases the uptake of apoptotic bodies and latex beads by microglia, as well as microglia migration and chemotaxis in response to ATP. On the contrary, decreasing microglial ganglioside levels results in a partial impairment in both microglial activities. Finally, increasing cellular ganglioside levels results in decreased expression and secretion of microglial brain derived neurotrophic factor (BDNF). Altogether, our data suggest that gangliosides are important modulators of microglia functions that are crucial to healthy brain homeostasis, and reveal that administration of ganglioside GM1 exerts an important anti-inflammatory activity that could be exploited therapeutically.

neuroscience↗