Enhanced release of acid sphingomyelinase-enriched exosomes generates a lipidomics signature in CSF of Multiple Sclerosis patients

Abstract

Multiple Sclerosis (MuS) is a complex multifactorial neuropathology, resulting in heterogeneous clinical presentation. A very active MuS research field concerns the discovery of biomarkers helpful to make an early and definite diagnosis. The sphingomyelin pathway has emerged as a molecular mechanism involved in MuS, since high levels of ceramides in cerebrospinal fluid (CSF) were related to axonal damage and neuronal dysfunction. Ceramides are the hydrolysis products of sphingomyelins through a reaction catalyzed by a family of enzymes named sphingomyelinases, which were recently related to myelin repair in MuS. Here, using a lipidomic approach, we observed low levels of several sphingomyelins in CSF of MuS patients compared to other inflammatory and non-inflammatory, central or peripheral neurological diseases. Starting by this result, we investigated the sphingomyelinase activity in CSF, showing a significantly higher enzyme activity in MuS. In support of these results we found high number of total exosomes in CSF of MuS patients and a high number of acid sphingomyelinase-enriched exosomes correlated to enzymatic activity and to disease severity. These data are of diagnostic relevance and show, for the first time, high number of acid sphingomyelinase-enriched exosomes in MuS, opening a new window for therapeutic approaches/targets in the treatment of MuS.

Neutral Sphingomyelinase Inhibition Alleviates LPS-Induced Microglia Activation and Neuroinflammation after Experimental Traumatic Brain Injury

“…Recent studies indicate that myeloid cells can release EVs/MP that spread inflammatory signals both in vitro and in vivo to alter neuronal functions (Harrison-Brown et al, 2016;Nigro et al, 2016;Beneventano et al, 2017;Kumar et al, 2017). Importantly, EV levels are significantly increased following TBI in humans and animal models, as well as in chronic neurodegenerative and autoimmune disorders such as Alzheimer's disease (AD) and multiple sclerosis, supporting the concept that spreading inflammation via EVs release may play a role in these neuropathologies (Taylor and Gercel-Taylor, 2014;Xiao et al, 2017;Pieragostino et al, 2018). Thus, nSMase inhibitors have emerged as new pharmacological agents for preventing release of EVs and thus can modulate inflammation and oxidative stress.…”

Extracellular Vesicles as Signaling Mediators and Disease Biomarkers across Biological Barriers

“…The cargo varies depending on type and differentiation of the parent cell, microenvironmental variables, and agents that triggers EV release. Cargo contents include lipid mediators (e.g., eicosanoids), proteins (e.g., cytokines, chemokines, growth factors or other mediators of signal transduction), genetic material (e.g., mRNAs, long/short noncoding RNAs, nuclear and mt DNA) and, in the case of larger vesicles, whole organelles (e.g., mitochondria) [16][17][18]. While the mechanisms that mediate the biological effects of EVs on their cellular targets remain poorly known, it is clear that EVs are implicated in most, if not all, physiopathological processes, including signal transduction, cell growth, and differentiation, metabolic regulation, embryofetal development, organogenesis, tissue homeostasis and repair/regeneration, antigen presentation and immune response, ageing, pathogen-host interactions, carcinogenesis, tumor invasion/metastasis, cardiovascular dysfunction, etc.…”

“…Due to their substantial stability, EVs circulate systemically and have been detected in basically all body fluids, including blood, urine, cerebrospinal fluid, saliva, milk, and tears [16,[42][43][44][45][46][47][48]. Moreover, there is clear indication that EVs can cross multiple biological barriers, as demonstrated by the finding of glial/neuronal EVs in the cerebrospinal fluid, blood, tears, and urine [44].…”

The Transfer of Sphingomyelinase Contributes to Drug Resistance in Multiple Myeloma

“…The secreted SMase amount measured in the supernatant after 24 h of cell culture ( Figure 2B) was most consistent with the mRNA levels of SMPD1, coding for ASM. Therefore we focused further on ASM and determined whether ASM could also be packaged into sEVs, or exosomes, similar to what was described for exosomes in the cerebrospinal fluid of multiple sclerosis patients [9]. The ASM content in the exosome enriched fraction differed from cell line to cell line.…”

“…As Carpinteiro et al showed in a melanoma model, a higher secretion of ASM could result in the formation of ceramide-enriched membrane platforms on tumor cells, allowing integrins to cluster on these platforms and thus allowing diffuse metastasis of melanoma cells [8]. In multiple sclerosis, a higher secretion of ASM was attributed to the secretion of ASM-enriched exosomes in the cerebrospinal fluid of these patients [9]. Exosomes are a type of small extracellular vesicles (sEVs) formed inside multivesicular endosomes.…”