Chitinase 3-like 1 is neurotoxic in primary cultured neurons

Chitinase 3-like 1 (CHI3L1) is known to play a role as prognostic biomarker in the early stages of multiple sclerosis (MS), and patients with high cerebrospinal fluid CHI3L1 levels have an increased risk for the development of neurological disability. Here, we investigated its potential neurotoxic effect by adding recombinant CHI3L1 in vitro to primary cultures of mouse cortical neurons and evaluating both neuronal functionality and survival by immunofluorescence. CHI3L1 induced a significant neurite length retraction after 24 and 48 hours of exposure and significantly reduced neuronal survival at 48 hours. The cytotoxic effect of CHI3L1 was neuron-specific and was not observed in mouse immune or other central nervous system cells. These results point to a selective neurotoxic effect of CHI3L1 in vitro and suggest a potential role of CHI3L1 as therapeutic target in MS patients

Identification of the Immunological Changes Appearing in the CSF During the Early Immunosenescence Process Occurring in Multiple Sclerosis

Immunitat adaptativa; Envelliment; Esclerosi múltipleInmunidad adaptativa; Envejecimiento; Esclerosis múltipleAdaptive immunity; Aging; Multiple sclerosisPatients with multiple sclerosis (MS) suffer with age an early immunosenescence process, which influence the treatment response and increase the risk of infections. We explored whether lipid-specific oligoclonal IgM bands (LS-OCMB) associated with highly inflammatory MS modify the immunological profile induced by age in MS. This cross-sectional study included 263 MS patients who were classified according to the presence (M+, n=72) and absence (M-, n=191) of LS-OCMB. CSF cellular subsets and molecules implicated in immunosenescence were explored. In M- patients, aging induced remarkable decreases in absolute CSF counts of CD4+ and CD8+ T lymphocytes, including Th1 and Th17 cells, and of B cells, including those secreting TNF-alpha. It also increased serum anti-CMV IgG antibody titers (indicative of immunosenescence) and CSF CHI3L1 levels (related to astrocyte activation). In contrast, M+ patients showed an age-associated increase of TIM-3 (a biomarker of T cell exhaustion) and increased values of CHI3L1, independently of age. Finally, in both groups, age induced an increase in CSF levels of PD-L1 (an inductor of T cell tolerance) and activin A (part of the senescence-associated secretome and related to inflammaging). These changes were independent of the disease duration. Finally, this resulted in augmented disability. In summary, all MS patients experience with age a modest induction of T-cell tolerance and an activation of the innate immunity, resulting in increased disability. Additionally, M- patients show clear decreases in CSF lymphocyte numbers, which could increase the risk of infections. Thus, age and immunological status are important for tailoring effective therapies in MS.This work was supported by grants FIS-PI15/00513, FIS-PI18/00572 and RD16/0015/0001 from the Instituto de Salud Carlos III. Ministerio de Ciencia e Innovación, Spain and FEDER: "Una manera de hacer Europa"

CSF SERPINA3 Levels Are Elevated in Patients With Progressive MS

Multiple sclerosis; SERPINA3Esclerosi múltiple; SERPINA3Esclerosis múltiple; SERPINA3Objective To identify biomarkers associated with progressive phases of MS and with neuroprotective potential. Methods Combined analysis of the transcriptional and proteomic profiles obtained in CNS tissue during chronic progressive phases of experimental autoimmune encephalomyelitis (EAE) with the transcriptional profile obtained during the differentiation of murine neural stem cells into neurons. Candidate biomarkers were measured by ELISA in the CSF of 65 patients with MS (29 with relapsing-remitting MS [RRMS], 20 with secondary progressive MS, and 16 with primary progressive MS [PPMS]) and 30 noninflammatory neurologic controls (NINCs). Results Integrative analysis of gene and protein expression data identified 2 biomarkers, the serine protease inhibitor Serpina3n and the calcium-binding protein S100A4, which were upregulated in chronic progressive EAE and whose expression was induced during neuronal differentiation. Immunofluorescence studies revealed a primarily neuronal expression of S100A4 and Serpina3n during EAE. CSF levels of SERPINA3, the human ortholog of murine Serpina3n, and S100A4 were increased in patients with MS compared with NINCs (SERPINA3: 1,320 vs 838.6 ng/mL, p = 0.0001; S100A4: 1.6 vs 0.8 ng/mL, p = 0.02). Within the MS group, CSF SERPINA3 levels were significantly elevated in patients with progressive forms, mainly patients with PPMS compared with patients with RRMS (1,617 vs 1,129 ng/mL, p = 0.02) and NINCs (1,617 vs 838.6 ng/mL, p = 0.0001). Of interest, CSF SERPINA3 levels significantly correlated with CSF neurofilament light chain levels only in the PPMS group (r = 0.62, p = 0.01). Conclusion These results point to a role of SERPINA3 as a biomarker associated with the progressive forms of MS, particularly PPMS.This work was supported by grants from the Fondo de Investigación Sanitaria (FIS; grant number PI17/00596), Ministry of Science and Innovation, Spain; Generalitat de Catalunya Suport Grups de Recerca (2017 SGR 0527); and the Red Española de Esclerosis Múltiple (RD16/0015/0004) funded by the FIS

Comparison of direct and indirect models of early induced acute lung injury

The animal experimental counterpart of human acute respiratory distress syndrome (ARDS) is acute lung injury (ALI). Most models of ALI involve reproducing the clinical risk factors associated with human ARDS, such as sepsis or acid aspiration; however, none of these models fully replicates human ARDS. To compare different experimental animal models of ALI, based on direct or indirect mechanisms of lung injury, to characterize a model which more closely could reproduce the acute phase of human ARDS. Adult male Sprague-Dawley rats were subjected to intratracheal instillations of (1) HCl to mimic aspiration of gastric contents; (2) lipopolysaccharide (LPS) to mimic bacterial infection; (3) HCl followed by LPS to mimic aspiration of gastric contents with bacterial superinfection; or (4) cecal ligation and puncture (CLP) to induce peritonitis and mimic sepsis. Rats were sacrificed 24 h after instillations or 24 h after CLP. At 24 h, rats instilled with LPS or HCl-LPS had increased lung permeability, alveolar neutrophilic recruitment and inflammatory markers (GRO/KC, TNF-α, MCP-1, IL-1β, IL-6). Rats receiving only HCl or subjected to CLP had no evidence of lung injury. Rat models of ALI induced directly by LPS or HCl-LPS more closely reproduced the acute phase of human ARDS than the CLP model of indirectly induced ALI

CSF SERPINA3 Levels Are Elevated in Patients With Progressive MS

Objective: To identify biomarkers associated with progressive phases of MS and with neuroprotective potential. Methods: Combined analysis of the transcriptional and proteomic profiles obtained in CNS tissue during chronic progressive phases of experimental autoimmune encephalomyelitis (EAE) with the transcriptional profile obtained during the differentiation of murine neural stem cells into neurons. Candidate biomarkers were measured by ELISA in the CSF of 65 patients with MS (29 with relapsing-remitting MS [RRMS], 20 with secondary progressive MS, and 16 with primary progressive MS [PPMS]) and 30 noninflammatory neurologic controls (NINCs). Results: Integrative analysis of gene and protein expression data identified 2 biomarkers, the serine protease inhibitor Serpina3n and the calcium-binding protein S100A4, which were upregulated in chronic progressive EAE and whose expression was induced during neuronal differentiation. Immunofluorescence studies revealed a primarily neuronal expression of S100A4 and Serpina3n during EAE. CSF levels of SERPINA3, the human ortholog of murine Serpina3n, and S100A4 were increased in patients with MS compared with NINCs (SERPINA3: 1,320 vs 838.6 ng/mL, p = 0.0001; S100A4: 1.6 vs 0.8 ng/mL, p = 0.02). Within the MS group, CSF SERPINA3 levels were significantly elevated in patients with progressive forms, mainly patients with PPMS compared with patients with RRMS (1,617 vs 1,129 ng/mL, p = 0.02) and NINCs (1,617 vs 838.6 ng/mL, p = 0.0001). Of interest, CSF SERPINA3 levels significantly correlated with CSF neurofilament light chain levels only in the PPMS group (r = 0.62, p = 0.01). Conclusion: These results point to a role of SERPINA3 as a biomarker associated with the progressive forms of MS, particularly PPMS

Inflammation in multiple sclerosis induces a specific reactive astrocyte state driving non-cell-autonomous neuronal damage

An in‐depth understanding of the neurodegenerative component of multiple sclerosis (MS) is crucial for the design of therapeutic approaches that may stop disease progression. Astrocytes have emerged as key contributors to the pathogenesis of MS. 1 However, the mechanisms underlying the regulation of maladaptive astrocytic responses remain unknown. In this report, we show that a high inflammatory activity in MS patients at disease onset induces a specific reactive astrocyte state that triggers synaptopathy and contributes to neuronal damage in vitro and ex vivo suggesting potential mechanisms that may ultimately lead to neurodegeneration. To investigate whether astrocytes are essential contributors to neuronal damage in MS, we cultured purified astrocytes with cerebrospinal fluid (CSF) samples from MS patients with high inflammatory activity at disease onset (MS‐High, Table S1). Then, we examined the effect of astrocytic secretomes on neurons (Figure 1A). Astrocytes became reactive upon high inflammatory CSF exposure (Figure 1B) and induced morphological alterations typically observed in neurodegenerative disorders, such as a less complex dendritic tree due to decreased arborisation (Figure 1C, D). Moreover, these abnormalities were accompanied with synaptic plasticity impairment (Figure 1E, F). Considering that a high lesion load at disease onset has been associated with an increased risk of neurological disability development, 2 we assessed whether the non‐cell‐autonomous effect on neuronal plasticity could be influenced by the degree of inflammatory activity of MS patients (Figure 2A and Table S1). Interestingly, we observed a direct correlation between the degree of inflammatory exposure and the extent of both astrocyte‐mediated synaptopathy (Figure 2B, C) and dendrite arborisation impairment

Identification of the Immunological Changes Appearing in the CSF During the Early Immunosenescence Process Occurring in Multiple Sclerosis

Patients with multiple sclerosis (MS) suffer with age an early immunosenescence process, which influence the treatment response and increase the risk of infections. We explored whether lipid-specific oligoclonal IgM bands (LS-OCMB) associated with highly inflammatory MS modify the immunological profile induced by age in MS. This cross-sectional study included 263 MS patients who were classified according to the presence (M+, n=72) and absence (M-, n=191) of LS-OCMB. CSF cellular subsets and molecules implicated in immunosenescence were explored. In M- patients, aging induced remarkable decreases in absolute CSF counts of CD4+ and CD8+ T lymphocytes, including Th1 and Th17 cells, and of B cells, including those secreting TNF-alpha. It also increased serum anti-CMV IgG antibody titers (indicative of immunosenescence) and CSF CHI3L1 levels (related to astrocyte activation). In contrast, M+ patients showed an age-associated increase of TIM-3 (a biomarker of T cell exhaustion) and increased values of CHI3L1, independently of age. Finally, in both groups, age induced an increase in CSF levels of PD-L1 (an inductor of T cell tolerance) and activin A (part of the senescence-associated secretome and related to inflammaging). These changes were independent of the disease duration. Finally, this resulted in augmented disability. In summary, all MS patients experience with age a modest induction of T-cell tolerance and an activation of the innate immunity, resulting in increased disability. Additionally, M- patients show clear decreases in CSF lymphocyte numbers, which could increase the risk of infections. Thus, age and immunological status are important for tailoring effective therapies in MS.This work was supported by grants FIS-PI15/00513, FIS-PI18/00572 and RD16/0015/0001 from the Instituto de Salud Carlos III. Ministerio de Ciencia e Innovación, Spain and FEDER: "Una manera de hacer Europa"

Targeting astrocytes to prevent neurodegeneration in patients with multiple sclerosis

L’esclerosi múltiple (EM) es una malaltia autoimmune i desmielinitzant del sistema nerviós central (SNC). La majoria dels pacients presenten una fase inicial inflamatòria que alterna períodes d’exacerbacions i remissions. Al llarg del temps, una gran proporció de pacients entrarà a una fase de la malaltia de neurodegeneració progressiva que es caracteritza per un deteriorament neurològic mantingut i irreversible. Els tractaments actualment disponibles pels pacients amb EM són molt efectius en la supressió de la inflamació, però altament ineficients en la prevenció del component neurodegeneratiu que inevitablement condueix a la progressió de la malaltia. Tot i que l’astrogliosis reactiva és ara una de les característiques patològiques de l’EM, els astròcits sempre s’han considerat cèl·lules estàtiques de suport. No obstant, els astròcits estan involucrats en moltes funcions importants del SNC, com l’homeòstasi d’ions, pH i aigua, el manteniment de les propietats de la barrera hemato-encefàlica, el control del subministrament energètic a les neurones, i la regulació de la funció i formació de les sinapsis. A més, evidències convincents apunten als astròcits com a contribuents clau al component neurodegeneratiu que s’observa a l’EM. No obstant, els mecanismes subjacents a la regulació de les respostes astrocítiques segueixen sent desconeguts. En el present estudi, ens vàrem proposar investigar com la inflamació en l’EM indueix l’astrogliosi reactiva, modulant la resposta astrocítica que condueix al dany neuronal. Presentem una caracterització molecular i funcional exhaustiva de la reactivitat dels astròcits exposats a líquid cefalorraquidi (LCR) de pacients amb EM classificats segons el grau d’activitat inflamatòria. Demostrem que els astròcits de ratolí exposats a LCR de pacients amb una alta activitat inflamatòria (MS-High) exhibien un estat reactiu pro-inflamatori específic caracteritzat per una major senyalització de nuclear factor kappa B (NF-кB). Aquest estat de reactivitat dels astròcits va conferir una resposta aberrant mitjançant un secretoma alterat i pro-inflamatori que condueix a la disfunció neuronal i al deteriorament de la plasticitat sinàptica. La SerpinE1 es va identificar com un mediador potencial de l’efecte tòxic paracrí sobre la funció neuronal en base a la seva expressió augmentada al secretoma dels astròcits exposats a LCR de pacients amb MS-High. A més, vàrem identificar la proteïna chitinase 3-like 1 (CHI3L1) com a possible modulador de la reactivitat astrocítica a través de l’activació de la senyalització de NF-кB, en funció dels seus nivells significativament augmentats al LCR de pacients amb MS-High. Conjuntament, els nostres descobriments indiquen que el microambient inflamatori al SNC dels pacients amb EM pot induir estats de reactivitat astrocítica específics que desencadenen la degeneració neuronal i, en última instància, poden contribuir a la progressió de la malaltia.La esclerosis múltiple (EM) es una enfermedad autoinmune y desmielinizante del sistema nervioso central (SNC). La mayoría de los pacientes presentan una fase inicial inflamatoria que alterna períodos de exacerbaciones y remisiones. A lo largo del tiempo, una gran proporción de pacientes entrará en una fase de la enfermedad de neurodegeneración progresiva que se caracteriza por un deterioro neurológico mantenido e irreversible. Los tratamientos actualmente disponibles para los pacientes con EM son muy efectivos en la supresión de la inflamación, pero altamente ineficientes en la prevención del componente neurodegenerativo que inevitablemente conlleva a la progresión de la enfermedad. A pesar de que la astrogliosis reactiva es ahora una de las características patológicas de la EM, los astrocitos siempre se han considerado células estáticas de soporte. Sin embargo, los astrocitos están involucrados en muchas funciones importantes del SNC, como la homeostasis de iones, pH y agua, el mantenimiento de las propiedades de la barrera hemato-encefálica, el control del suministro energético a las neuronas, y la regulación de la función y formación de las sinapsis. Además, evidencias convincentes apuntan a los astrocitos como contribuyentes clave al componente neurodegenerativo observado en la EM. Sin embargo, los mecanismos subyacentes a la regulación de las respuestas astrocíticas siguen siendo desconocidos. En el presente estudio, nos propusimos investigar cómo la inflamación en la EM induce astrogliosis reactiva, modulando la respuesta astrocítica que conduce al daño neuronal. Presentamos una caracterización molecular y funcional exhaustiva de la reactividad de los astrocitos tras la exposición al líquido cefalorraquídeo (LCR) de pacientes con EM clasificados según el grado de actividad inflamatoria. Demostramos que los astrocitos de ratón expuestos a LCR de pacientes con alta actividad inflamatoria (MS-High) exhibían un estado reactivo pro-inflamatorio específico caracterizado por una mayor señalización de nuclear factor kappa B (NF-kB). Este estado reactivo de los astrocitos confirió una respuesta aberrante a través de un secretoma alterado y pro-inflamatorio que conduce a la disfunción neuronal y al deterioro de la plasticidad sináptica. SerpinE1 se identificó como un mediador potencial del efecto tóxico paracrino sobre la función neuronal en base a su expresión aumentada en el secretoma de los astrocitos expuestos a LCR de pacientes con MS-High. Además, identificamos la proteína chitinase 3-like 1 (CHI3L1) como un posible modulador de la reactividad astrocítica a través de la activación de la señalización de NF-kB, en función de sus niveles significativamente aumentados en el LCR de pacientes con MS-High. Conjuntamente, nuestros hallazgos indican que el microambiente inflamatorio en el SNC de los pacientes con EM puede inducir estados de reactividad astrocítica específicos que desencadenan la degeneración neuronal y, en última instancia, pueden contribuir a la progresión de la enfermedad.Multiple sclerosis (MS) is a demyelinating autoimmune disease of the central nervous system (CNS). Most MS patients initially have an inflammatory phase characterized by periods of clinical relapses and remissions. Over time, a large proportion of patients will enter a progressive neurodegenerative phase of the disease characterized by sustained and irreversible neurological deterioration. Currently available therapies for MS patients are highly effective to suppress inflammation, but largely fail to prevent the neurodegenerative component that inevitably leads to disease progression. Despite that reactive astrogliosis is now one of the pathological hallmarks in MS, astrocytes have always been considered as static bystander cells. However, astrocytes are involved in many important CNS functions, such as ion, pH and water homeostasis, maintenance of blood-brain barrier properties, control of energy supply to neurons, and regulation of function and formation of synapses. Furthermore, compelling evidence points to astrocytes as key contributors to the neurodegenerative component observed in MS. However, the mechanisms underlying the regulation of astrocytic responses remain unknown. In the present study, we aimed to investigate how inflammation in MS induces astrocyte reactivity modulating the astrocytic response that leads to neuronal damage. We report an exhaustive molecular and functional characterization of astrocyte reactivity following exposure to cerebrospinal fluid (CSF) from MS patients classified according to the degree of inflammatory activity. We showed that mouse astrocytes exposed to CSF from patients with high inflammatory activity (MS-High) exhibited a specific pro-inflammatory reactive state that was characterized by enhanced nuclear factor kappa B (NF-кB) signalling. This reactive astrocyte state conferred an aberrant response through an altered pro-inflammatory secretome that drove neuronal dysfunction and impaired synaptic plasticity. SerpinE1 was identified as a potential downstream mediator of the non-cell-autonomous toxic effect on neuronal function based on its significant up-regulation in secretomes from astrocytes exposed to CSF from MS-High patients. Furthermore, we identified chitinase 3-like 1 (CHI3L1) as a potential upstream modulator of astrocyte reactivity via activation of NF-kB signalling based on its significantly increased levels in the CSF from MS-High patients. Taken together, our findings indicate that the inflammatory microenvironment in the CNS of MS patients can induce specific reactive astrocyte states that trigger neuronal degeneration and may ultimately contribute to disease progression.Universitat Autònoma de Barcelona. Programa de Doctorat en Medicin

Targeting astrocytes to prevent neurodegeneration in patients with multiple sclerosis

L'esclerosi múltiple (EM) es una malaltia autoimmune i desmielinitzant del sistema nerviós central (SNC). La majoria dels pacients presenten una fase inicial inflamatòria que alterna períodes d'exacerbacions i remissions. Al llarg del temps, una gran proporció de pacients entrarà a una fase de la malaltia de neurodegeneració progressiva que es caracteritza per un deteriorament neurològic mantingut i irreversible. Els tractaments actualment disponibles pels pacients amb EM són molt efectius en la supressió de la inflamació, però altament ineficients en la prevenció del component neurodegeneratiu que inevitablement condueix a la progressió de la malaltia. Tot i que l'astrogliosis reactiva és ara una de les característiques patològiques de l'EM, els astròcits sempre s'han considerat cèl·lules estàtiques de suport. No obstant, els astròcits estan involucrats en moltes funcions importants del SNC, com l'homeòstasi d'ions, pH i aigua, el manteniment de les propietats de la barrera hemato-encefàlica, el control del subministrament energètic a les neurones, i la regulació de la funció i formació de les sinapsis. A més, evidències convincents apunten als astròcits com a contribuents clau al component neurodegeneratiu que s'observa a l'EM. No obstant, els mecanismes subjacents a la regulació de les respostes astrocítiques segueixen sent desconeguts. En el present estudi, ens vàrem proposar investigar com la inflamació en l'EM indueix l'astrogliosi reactiva, modulant la resposta astrocítica que condueix al dany neuronal. Presentem una caracterització molecular i funcional exhaustiva de la reactivitat dels astròcits exposats a líquid cefalorraquidi (LCR) de pacients amb EM classificats segons el grau d'activitat inflamatòria. Demostrem que els astròcits de ratolí exposats a LCR de pacients amb una alta activitat inflamatòria (MS-High) exhibien un estat reactiu pro-inflamatori específic caracteritzat per una major senyalització de nuclear factor kappa B (NF-кB). Aquest estat de reactivitat dels astròcits va conferir una resposta aberrant mitjançant un secretoma alterat i pro-inflamatori que condueix a la disfunció neuronal i al deteriorament de la plasticitat sinàptica. La SerpinE1 es va identificar com un mediador potencial de l'efecte tòxic paracrí sobre la funció neuronal en base a la seva expressió augmentada al secretoma dels astròcits exposats a LCR de pacients amb MS-High. A més, vàrem identificar la proteïna chitinase 3-like 1 (CHI3L1) com a possible modulador de la reactivitat astrocítica a través de l'activació de la senyalització de NF-кB, en funció dels seus nivells significativament augmentats al LCR de pacients amb MS-High. Conjuntament, els nostres descobriments indiquen que el microambient inflamatori al SNC dels pacients amb EM pot induir estats de reactivitat astrocítica específics que desencadenen la degeneració neuronal i, en última instància, poden contribuir a la progressió de la malaltia.La esclerosis múltiple (EM) es una enfermedad autoinmune y desmielinizante del sistema nervioso central (SNC). La mayoría de los pacientes presentan una fase inicial inflamatoria que alterna períodos de exacerbaciones y remisiones. A lo largo del tiempo, una gran proporción de pacientes entrará en una fase de la enfermedad de neurodegeneración progresiva que se caracteriza por un deterioro neurológico mantenido e irreversible. Los tratamientos actualmente disponibles para los pacientes con EM son muy efectivos en la supresión de la inflamación, pero altamente ineficientes en la prevención del componente neurodegenerativo que inevitablemente conlleva a la progresión de la enfermedad. A pesar de que la astrogliosis reactiva es ahora una de las características patológicas de la EM, los astrocitos siempre se han considerado células estáticas de soporte. Sin embargo, los astrocitos están involucrados en muchas funciones importantes del SNC, como la homeostasis de iones, pH y agua, el mantenimiento de las propiedades de la barrera hemato-encefálica, el control del suministro energético a las neuronas, y la regulación de la función y formación de las sinapsis. Además, evidencias convincentes apuntan a los astrocitos como contribuyentes clave al componente neurodegenerativo observado en la EM. Sin embargo, los mecanismos subyacentes a la regulación de las respuestas astrocíticas siguen siendo desconocidos. En el presente estudio, nos propusimos investigar cómo la inflamación en la EM induce astrogliosis reactiva, modulando la respuesta astrocítica que conduce al daño neuronal. Presentamos una caracterización molecular y funcional exhaustiva de la reactividad de los astrocitos tras la exposición al líquido cefalorraquídeo (LCR) de pacientes con EM clasificados según el grado de actividad inflamatoria. Demostramos que los astrocitos de ratón expuestos a LCR de pacientes con alta actividad inflamatoria (MS-High) exhibían un estado reactivo pro-inflamatorio específico caracterizado por una mayor señalización de nuclear factor kappa B (NF-kB). Este estado reactivo de los astrocitos confirió una respuesta aberrante a través de un secretoma alterado y pro-inflamatorio que conduce a la disfunción neuronal y al deterioro de la plasticidad sináptica. SerpinE1 se identificó como un mediador potencial del efecto tóxico paracrino sobre la función neuronal en base a su expresión aumentada en el secretoma de los astrocitos expuestos a LCR de pacientes con MS-High. Además, identificamos la proteína chitinase 3-like 1 (CHI3L1) como un posible modulador de la reactividad astrocítica a través de la activación de la señalización de NF-kB, en función de sus niveles significativamente aumentados en el LCR de pacientes con MS-High. Conjuntamente, nuestros hallazgos indican que el microambiente inflamatorio en el SNC de los pacientes con EM puede inducir estados de reactividad astrocítica específicos que desencadenan la degeneración neuronal y, en última instancia, pueden contribuir a la progresión de la enfermedad.Multiple sclerosis (MS) is a demyelinating autoimmune disease of the central nervous system (CNS). Most MS patients initially have an inflammatory phase characterized by periods of clinical relapses and remissions. Over time, a large proportion of patients will enter a progressive neurodegenerative phase of the disease characterized by sustained and irreversible neurological deterioration. Currently available therapies for MS patients are highly effective to suppress inflammation, but largely fail to prevent the neurodegenerative component that inevitably leads to disease progression. Despite that reactive astrogliosis is now one of the pathological hallmarks in MS, astrocytes have always been considered as static bystander cells. However, astrocytes are involved in many important CNS functions, such as ion, pH and water homeostasis, maintenance of blood-brain barrier properties, control of energy supply to neurons, and regulation of function and formation of synapses. Furthermore, compelling evidence points to astrocytes as key contributors to the neurodegenerative component observed in MS. However, the mechanisms underlying the regulation of astrocytic responses remain unknown. In the present study, we aimed to investigate how inflammation in MS induces astrocyte reactivity modulating the astrocytic response that leads to neuronal damage. We report an exhaustive molecular and functional characterization of astrocyte reactivity following exposure to cerebrospinal fluid (CSF) from MS patients classified according to the degree of inflammatory activity. We showed that mouse astrocytes exposed to CSF from patients with high inflammatory activity (MS-High) exhibited a specific pro-inflammatory reactive state that was characterized by enhanced nuclear factor kappa B (NF-кB) signalling. This reactive astrocyte state conferred an aberrant response through an altered pro-inflammatory secretome that drove neuronal dysfunction and impaired synaptic plasticity. SerpinE1 was identified as a potential downstream mediator of the non-cell-autonomous toxic effect on neuronal function based on its significant up-regulation in secretomes from astrocytes exposed to CSF from MS-High patients. Furthermore, we identified chitinase 3-like 1 (CHI3L1) as a potential upstream modulator of astrocyte reactivity via activation of NF-kB signalling based on its significantly increased levels in the CSF from MS-High patients. Taken together, our findings indicate that the inflammatory microenvironment in the CNS of MS patients can induce specific reactive astrocyte states that trigger neuronal degeneration and may ultimately contribute to disease progression