Peripheral Inflammation Enhances Microglia Response and Nigral Dopaminergic Cell Death in an in vivo MPTP Model of Parkinson’s Disease

The impact of systemic inflammation in nigral dopaminergic cell loss remains unclear. Here, we have investigated the role of peripheral inflammation induced by systemic lipopolysaccharide (LPS) administration in the MPTP-based model of Parkinson’s disease. Brain inflammation, microglia and astroglia activation, disruption of the blood–brain barrier (BBB) and integrity of the nigrostriatal dopaminergic system were evaluated in response to i.p. injection of LPS, MPTP or the combination of both. Our results showed that combinative treatment exacerbates microglia activation and enhances (i) the appearance of galectin-3-positive microglia, recently identified as microglial disease-associated phenotypic marker, (ii) the up-regulation of pro-inflammatory cytokines, (iii) the occurrence of A1 neurotoxic astrocytes, (iv) the breakdown of the BBB, and (v) the loss of dopaminergic neurons in the substantia nigra. Microglia activation was triggered earlier than other degenerative events, suggesting that over-activation of microglia (including different polarization states) may induce dopaminergic neuron loss by itself, initiating the endless cycle of inflammation/degeneration. Our study revitalizes the importance of peripheral inflammation as a potential risk factor for Parkinson’s disease and raises the possibility of using new anti-inflammatory therapies to improve the course of neurodegenerative diseases, including those directly aimed at modulating the deleterious activity of disease-associated microglia.España MINECO y FEDER SAF2015-64171-

Reformulating Pro-Oxidant Microglia in Neurodegeneration

In neurodegenerative diseases, microglia-mediated neuroinflammation and oxidative stress are central events. Recent genome-wide transcriptomic analyses of microglial cells under different disease conditions have uncovered a new subpopulation named disease-associated microglia (DAM). These studies have challenged the classical view of the microglia polarization state's proinflammatory M1 (classical activation) and immunosuppressive M2 (alternative activation). Molecular signatures of DAM and proinflammatory microglia (highly pro-oxidant) have shown clear differences, yet a partial overlapping gene profile is evident between both phenotypes. The switch activation of homeostatic microglia into reactive microglia relies on the selective activation of key surface receptors involved in the maintenance of brain homeostasis (a.k.a. pattern recognition receptors, PRRs). Two relevant PRRs are toll-like receptors (TLRs) and triggering receptors expressed on myeloid cells-2 (TREM2), whose selective activation is believed to generate either a proinflammatory or a DAM phenotype, respectively. However, the recent identification of endogenous disease-related ligands, which bind to and activate both TLRs and TREM2, anticipates the existence of rather complex microglia responses. Examples of potential endogenous dual ligands include amyloid β, galectin-3, and apolipoprotein E. These pleiotropic ligands induce a microglia polarization that is more complicated than initially expected, suggesting the possibility that different microglia subtypes may coexist. This review highlights the main microglia polarization states under disease conditions and their leading role orchestrating oxidative stress

Galectin-3 Deletion Reduces LPS and Acute Colitis-Induced Pro-Inflammatory Microglial Activation in the Ventral Mesencephalon

Parkinson’s disease is a highly prevalent neurological disorder for which there is currently no cure. Therefore, the knowledge of risk factors as well as the development of new putative molecular targets is mandatory. In this sense, peripheral inflammation, especially the originated in the colon, is emerging as a predisposing factor for suffering this disease. We have largely studied the pleiotropic roles of galectin-3 in driving microglia-associated immune responses. However, studies aimed at elucidating the role of galectin-3 in peripheral inflammation in terms of microglia polarization are lacking. To achieve this, we have evaluated the effect of galectin-3 deletion in two different models of acute peripheral inflammation: intraperitoneal injection of lipopolysaccharide or gut inflammation induced by oral administration of dextran sodium sulfate. We found that under peripheral inflammation the number of microglial cells and the expression levels of pro-inflammatory mediators take place specifically in the dopaminergic system, thus supporting causative links between Parkinson’s disease and peripheral inflammation. Absence of galectin-3 highly reduced neuroinflammation in both models, suggesting an important central regulatory role of galectin-3 in driving microglial activation provoked by the peripheral inflammation. Thus, modulation of galectin-3 function emerges as a promising strategy to minimize undesired microglia polarization states.This work was supported by grants from the Spanish Ministerio de Ciencia, Innovación y Universidades (RTI 2018-098830-B-I00), from the Consejería de Economía y Conocimiento of Junta de Andalucía (P18-RT-1372 and US-1264806). MJP, MDVC and PGM were supported by a grant from the Junta de Andalucía (CTS 5884) and AEC by an associated post-doctoral grant

Galectin-3, a novel endogenous TREM2 ligand, detrimentally regulates inflammatory response in Alzheimer’s disease

Alzheimer’s disease (AD) is a progressive neurodegenerative disease in which the formation of extracellular aggregates of amyloid beta (Aβ) peptide, fibrillary tangles of intraneuronal tau and microglial activation are major pathological hallmarks. One of the key molecules involved in microglial activation is galectin-3 (gal3), and we demonstrate here for the first time a key role of gal3 in AD pathology. Gal3 was highly upregulated in the brains of AD patients and 5xFAD (familial Alzheimer’s disease) mice and found specifically expressed in microglia associated with Aβ plaques. Single-nucleotide polymorphisms in the LGALS3 gene, which encodes gal3, were associated with an increased risk of AD. Gal3 deletion in 5xFAD mice attenuated microglia-associated immune responses, particularly those associated with TLR and TREM2/DAP12 signaling. In vitro data revealed that gal3 was required to fully activate microglia in response to fibrillar Aβ. Gal3 deletion decreased the Aβ burden in 5xFAD mice and improved cognitive behavior. Interestingly, a single intrahippocampal injection of gal3 along with Aβ monomers in WT mice was sufficient to induce the formation of long-lasting (2 months) insoluble Aβ aggregates, which were absent when gal3 was lacking. High-resolution microscopy (stochastic optical reconstruction microscopy) demonstrated close colocalization of gal3 and TREM2 in microglial processes, and a direct interaction was shown by a fluorescence anisotropy assay involving the gal3 carbohydrate recognition domain. Furthermore, gal3 was shown to stimulate TREM2–DAP12 signaling in a reporter cell line. Overall, our data support the view that gal3 inhibition may be a potential pharmacological approach to counteract AD.This work was supported by Grants from the Swedish Research Council, and the Strong Research Environment MultiPark (Multidisciplinary Research in Parkinson’s and Alzheimer’s Disease at Lund University), Bagadilico (Linné consortium sponsored by the Swedish Research Council), the Swedish Alzheimer’s Foundation, Swedish Brain Foundation, A.E. Berger Foundation, Gyllenstiernska Krapperup Foundation, the Royal Physiographic Society, Crafoord Foundation, Olle Engkvist Byggmästare Foundation, Wiberg Foundation, G&J Kock Foundation, Stohnes Foundation, Swedish Dementia Association and the Medical Faculty at Lund University. This work was supported by Grant SAF2015-64171R (Spanish MINECO/FEDER, UE), by Instituto de Salud Carlos III (ISCiii) of Spain, co-financed by FEDER funds from European Union through grants PI15/00796 and PI18/01557 (to AG), PI15/00957 and PI18/01556 (to JV), and CIBERNED (to AG and JV), by Consejería de Economía, Innovación, Ciencia y Empleo, Junta de Andalucia Proyecto de Excelencia (CTS-2035) (to JV and AG), and by Malaga University grant PPIT.UMA.B1.2017/26 (to RSV). AV and GCB received funding from the Innovative Medicines Initiative 2 Joint Undertaking under Grant agreement no. 115976 (PHAGO). CIBERNED “Centro de Investigacion Biomedica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid (Spain)”. HL and AF were supported by the Swedish Research Council, the Swedish Brain Foundation, the Alzheimer Foundation and the Åhlén Foundation. UJN was supported by Grants from the Knut and Alice Wallenberg Foundation (KAW 2013.0022) and the Swedish Research Council (Grant no. 621-2012-2978).Peer reviewe

Canagliflozin and renal outcomes in type 2 diabetes and nephropathy

BACKGROUND Type 2 diabetes mellitus is the leading cause of kidney failure worldwide, but few effective long-term treatments are available. In cardiovascular trials of inhibitors of sodium–glucose cotransporter 2 (SGLT2), exploratory results have suggested that such drugs may improve renal outcomes in patients with type 2 diabetes. METHODS In this double-blind, randomized trial, we assigned patients with type 2 diabetes and albuminuric chronic kidney disease to receive canagliflozin, an oral SGLT2 inhibitor, at a dose of 100 mg daily or placebo. All the patients had an estimated glomerular filtration rate (GFR) of 30 to <90 ml per minute per 1.73 m2 of body-surface area and albuminuria (ratio of albumin [mg] to creatinine [g], >300 to 5000) and were treated with renin–angiotensin system blockade. The primary outcome was a composite of end-stage kidney disease (dialysis, transplantation, or a sustained estimated GFR of <15 ml per minute per 1.73 m2), a doubling of the serum creatinine level, or death from renal or cardiovascular causes. Prespecified secondary outcomes were tested hierarchically. RESULTS The trial was stopped early after a planned interim analysis on the recommendation of the data and safety monitoring committee. At that time, 4401 patients had undergone randomization, with a median follow-up of 2.62 years. The relative risk of the primary outcome was 30% lower in the canagliflozin group than in the placebo group, with event rates of 43.2 and 61.2 per 1000 patient-years, respectively (hazard ratio, 0.70; 95% confidence interval [CI], 0.59 to 0.82; P=0.00001). The relative risk of the renal-specific composite of end-stage kidney disease, a doubling of the creatinine level, or death from renal causes was lower by 34% (hazard ratio, 0.66; 95% CI, 0.53 to 0.81; P<0.001), and the relative risk of end-stage kidney disease was lower by 32% (hazard ratio, 0.68; 95% CI, 0.54 to 0.86; P=0.002). The canagliflozin group also had a lower risk of cardiovascular death, myocardial infarction, or stroke (hazard ratio, 0.80; 95% CI, 0.67 to 0.95; P=0.01) and hospitalization for heart failure (hazard ratio, 0.61; 95% CI, 0.47 to 0.80; P<0.001). There were no significant differences in rates of amputation or fracture. CONCLUSIONS In patients with type 2 diabetes and kidney disease, the risk of kidney failure and cardiovascular events was lower in the canagliflozin group than in the placebo group at a median follow-up of 2.62 years

Caracterización del modelo condicional neuronal de caspasa 3 en condiciones fisiológicas y patológicas

La caspasa 3 (casp 3) es una proteasa ampliamente conocida por su papel clave como mediadora en la apoptosis neuronal. En la actualidad, se han puesto de manifiesto funciones de la casp 3 en el Sistema Nervioso Central (SNC) no relacionadas con la apoptosis, destacando su papel regulador en la neurogénesis y en la actividad sináptica. De esta manera, la función de la casp 3 no se reduciría al proceso de apoptosis, sino que la activación limitada de la casp 3 sería crítica para la función sináptica en el cerebro adulto sano, participando en la regulación de la plasticidad sináptica y en los mecanismos moleculares del aprendizaje y la memoria. Las enfermedades neurodegenerativas como la enfermedad de Alzheimer (EA) están caracterizadas por la pérdida selectiva de poblaciones neuronales específicas, lo que a su vez desencadena la aparición de déficits cognitivos y/o motores. Además, varias proteínas relacionadas con la EA (APP, presenilinas) son procesadas por la casp 3 y por ello, en la actualidad, se postula que el procesamiento de estas proteínas por parte de la casp 3 podría estar directamente relacionado tanto con el inicio de la enfermedad, como con la ejecución final de la apoptosis neuronal (D´Amelio y cols. 2010). La casp 3 también ha sido relacionada con el incremento de la producción del péptido Aβ (Beta-amiloide), contribuyendo así a la patogénesis asociada a la EA (Tesco y cols. 2007). El objetivo principal de esta tesis ha sido la generación de un modelo murino condicional neuronal de casp 3 que nos permitiese estudiar la implicación de esta caspasa en la plasticidad sináptica en el SNC y con él, que pudiésemos generar una línea de ratones en la que poder estudiar la implicación de la casp 3 en la EA. Para ello, una vez que conseguimos desarrollar nuestro modelo KO condicional de casp 3, se comprobó a través de un análisis funcional y una caracterización conductual, que estos ratones no presentaban ninguna anomalía excepto en la memoria a largo plazo. Tras estos resultados, mediante la realización de la tinción de Golgi-Cox de las espinas dendríticas, se observó que nuestro modelo murino presentaba diferencias en la densidad de las espinas dendríticas y en el porcentaje de cada tipo de espina, presentano menor porcentaje de espinas cortas (maduras) y mayor porcentaje de espinas largas y delgadas (inmaduras). Finalmente, se estudió a través de técnicas electrofisiológicas, cómo la potenciación a largo plazo (LTP) se encontraba inhibida en esta línea de ratones. Estos resultados sugieren que la casp 3 tendría un papel fundamental en los procesos de aprendizaje y memoria, afectando a la LTP y a la plasticidad de las espinas denríticas. Además, habríamos conseguido un modelo murino condicional neuronal de casp 3 que alcanza la edad adulta y no presenta cambios neuropatológicos, pudiendo ser la base de estudios futuros sobre la influencia de la casp 3 en la plasticidad sináptica y sobre los mecanismos moleculares que provocan dichas alteraciones. En el ratón KO condicional de casp 3 APP/PS1, se comenzó comprobando, al igual que en el primer modelo, a través de una pequeña batería de comportamiento, que no existían anomalías que tuvierámos que tener en cuenta a lo largo del estudio. En este caso nos centramos en el análisis de la implicación de casp 3 en la generación de las placas de AB y en el estudio de la microglía presente en ratones de 6 meses. Para ello, analizamos a través de una inmunofluorescencia de triple marcaje, distintos parámetros morfológicos de las placas de A además del porcentaje de microglía por área de A, sin obtener resultados significativos en estos casos. Estudios a edades más avanzadas serían necesarios para completar el análisis de la influencia de casp 3 en la EA

Galectin‑3, a novel endogenous TREM2 ligand, detrimentally regulates infammatory response in Alzheimer’s disease

Alzheimer’s disease (AD) is a progressive neurodegenerative disease in which the formation of extracellular aggregates of amyloid beta (Aβ) peptide, fibrillary tangles of intraneuronal tau and microglial activation are major pathological hallmarks. One of the key molecules involved in microglial activation is galectin-3 (gal3), and we demonstrate here for the first time a key role of gal3 in AD pathology. Gal3 was highly upregulated in the brains of AD patients and 5xFAD (familial Alzheimer’s disease) mice and found specifically expressed in microglia associated with Aβ plaques. Single-nucleotide polymorphisms in the LGALS3 gene, which encodes gal3, were associated with an increased risk of AD. Gal3 deletion in 5xFAD mice attenuated microglia-associated immune responses, particularly those associated with TLR and TREM2/DAP12 signaling. In vitro data revealed that gal3 was required to fully activate microglia in response to fibrillar Aβ. Gal3 deletion decreased the Aβ burden in 5xFAD mice and improved cognitive behavior. Interestingly, a single intrahippocampal injection of gal3 along with Aβ monomers in WT mice was sufficient to induce the formation of long-lasting (2 months) insoluble Aβ aggregates, which were absent when gal3 was lacking. High-resolution microscopy (stochastic optical reconstruction microscopy) demonstrated close colocalization of gal3 and TREM2 in microglial processes, and a direct interaction was shown by a fluorescence anisotropy assay involving the gal3 carbohydrate recognition domain. Furthermore, gal3 was shown to stimulate TREM2–DAP12 signaling in a reporter cell line. Overall, our data support the view that gal3 inhibition may be a potential pharmacological approach to counteract AD.Ministerio de Economía y Competitividad de España y fondos FEDER (MINECO/FEDER, UES). AF2015-64171RInstituto de Salud Carlos III (ISCiii) de España y fondos FEDER de la Unión Europea. PI15/00796, PI18/01557, PI15/00957 y PI18/01556Consejería de Economía, Innovación, Ciencia y Empleo de la Junta de Andalucía. CTS-2035Universidad de Málaga. PPIT.UMA.B1.2017/26Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED). 15976 (FAGO

Selective deletion of Caspase-3 gene in the dopaminergic system exhibits autistic-like behaviour

Apoptotic caspases are thought to play critical roles in elimination of excessive and non-functional synapses and removal of extra cells during early developmental stages. Hence, an impairment of this process may thus constitute a basis for numerous neurological and psychiatric diseases. This view is especially relevant for dopamine due to its pleiotropic roles in motor control, motivation and reward processing. Here, we have analysed the effect of caspase-3 depletion on the development of catecholaminergic neurons and performed a wide array of neurochemical, ultrastructural and behavioural assays. To achieve this, we performed selective deletion of the Casp3 gene in tyrosine hydroxylase (TH)-expressing cells using Cre-loxP-mediated recombination. Histological evaluation of most relevant catecholaminergic nuclei revealed the ventral mesencephalon as the most affected region. Stereological analysis demonstrated an increase in the number of TH-positive neurons in both the substantia nigra and ventral tegmental area along with enlarged volume of the ventral midbrain. Analysis of main innervating tissues revealed a rather contrasting profile. In striatum, basal extracellular levels and potassium-evoked DA release were significantly reduced in mice lacking Casp3, a clear indication of dopaminergic hypofunction in dopaminergic innervating tissues. This view was sustained by analysis of TH-labelled dopaminergic terminals by confocal and electron microscopy. Remarkably, at a behavioural level, Casp3-deficient mice exhibited impaired social interaction, restrictive interests and repetitive stereotypies, which are considered the core symptoms of autism spectrum disorder (ASD). Our study revitalizes the potential involvement of dopaminergic transmission in ASD and provides an excellent model to get further insights in ASD pathogenesis.This work was supported by grants from the Spanish Ministerio de Economía y Competitividad (SAF2015-64171-R and RTI2018-098645-B-I00). J.A.A. and E.P.V. was supported by a MINECO (BFU2015-64536) grant. I.S.P., E.B. and L.B. were co-financed by the “Fondo Europeo de Desarrollo Regional” (FEDER)-UE “A way to build Europe” from the “Ministerio de Ciencia, Innovación y Universidades” (RTI2018-099778-B-I00) and the Ministerio de Salud-Instituto de Salud Carlos III (PI18/01691), as well as funding from the “Consejería de Salud de la Junta de Andalucía” (PI-0134-2018); the “Programa Operativo de Andalucía FEDER, Iniciativa Territorial Integrada ITI 2014-2020 Consejería Salud, Junta de Andalucía” (PI-0080-2017); the “Consejería de Economía, Innovación, Ciencia y Empleo de la Junta de Andalucía” (CTS-510); and the “Centro de Investigación Biomédica en Red de Salud Mental- CIBERSAM” (CB/07/09/0033)