- Luis Barbeito (MD, Head)
- Monique Richter (PhD)
- Emiliano Trías (PhD student)
- Valentina Varela (Msc student)
- Romina Barreto (Msc student)
- Sofía Ibarbouru (Msc student)
Modulation of disease progression in Amyotrophic Lateral Sclerosis (ALS)
In most neurodegenerative diseases, neuronal death begins as a focal process that spreads contiguously along brain regions in an ineluctable manner. This implicates an acquired pathogenic mechanism involving neuronal damage and subsequent chronic inflammation. The mechanisms underlying such disease progression remain largely unknown as well as the potential therapeutic strategies to halt the process and prevent symptom aggravation. There is no cure for the neurodegenerative diseases. However, if their progression would be slowed during early symptomatic stages by interventions in glial cells, neurodegenerative diseases would become a minor chronic disabilitiy and no longer a death sentence.
We study neurodegeneration in an inherited model of ALS expressing SOD1 mutations. ALS is caused by the progressive death of motor neurons, leading to serious debility, paralysis and ultimately death within a few years. Because microglia and reactive astrocytes accumulate in the spinal cord of rats expressing the ALS-linked SOD1G93A mutation, we originally proposed that disease progression was mediated by the emergence of inflammatory glial cells. In fact, glial cells isolated from rodent models as well as ALS patients are toxic to motor neurons. In 2011, we identified a new type of glial cell referred as “AbA cells” (from aberrant astrocytes) from degenerating spinal cord from SOD1G93A rats, their appearance being closely associated with the progression of paralysis in SOD1G93A rats. Phenotypically AbA cells appear as atypical astrocytes. Functionally, AbA cellsare the most toxiccells yet identified to motor neurons. AbA cells actively proliferateafter the onset of progressive paralysis and make intimate contact with degeneratingmotor neurons. By analyzing the population of proliferating glial cells in theventral horn of symptomatic SOD1 rats, we found that microglia are the most likelycellular origin of AbA cells. Of considerable interest, AbA cells share some characteristics with glioblastoma cells, including the high proliferation rate in vivo and vitro, as well as lack of contact inhibition and predominant glycolytic metabolism.
The understanding of the mediators inducing such phenotypic transition may allow intervention to slow the progressive spread of disease in ALS patients.
One goal of our research is to develop new therapeutic agents for the treatment of ALS using mechanistic insights drawn from understanding how different cells and molecules contribute to progressive neuronal death. 20 years of animal testing have so far failed to yield an effective therapy for motor neuron disease. Such failure might be explained by the fact that, until recently, research has been mainly focused on motor neuron degeneration, the concomitant pathological changes in other cell types including glial cells being mostly neglected.
Our central hypothesis is that the spread of motor neuron disease is dependent on the formation of a neurodegenerative microenvironment surrounding damaged neurons, organized around AbA cells, with the ability to replicate and expand the inflammatory and neurotoxic process to contiguous or distant areas of the CNS. The objective is to characterize such cellular microenvironment, unraveling the cells types involved, cell-cell interactions and the role of specific trophic factors like nitroNGF. The outcomes of these studies will strongly influence our approach to other neurodegenerative disease by providing new tools to define appropriate in vivo and in vitro models for therapeutic interventions.
Targeting AbA cells with the tyrosine-kinase inhibitor Masitinb
We have recently provided evidence that Masitinib mesilate (AB1010) exerts a disease-modifying effect in ALS animal models by controlling secondary neuroinflammation that causes paralysis progression and spread. Masitinib is a selective tyrosine kinase inhibitor that targets c-Kit, platelet-derived growth factor receptors (PDGF-R), and, to a lesser extent, Lyn and Fyn pathways. By combined targeting of c-Kit and Lyn, Masitinib is particularly efficient in controlling mast cell survival, differentiation, and degranulation. Our hypothesis establishes that Masitinib also decreases the appearance of inflammatory aberrant glial cells through a specific mechanism.
Nitrated-NGF as a novel glial factor mediating neuronal apoptosis
We reported that activated astrocytes in ALS express increased levels of NGF, which triggers p75-dependent motor neuron apoptosis. Although adult motor neurons lack TrkA and p75NTR receptors, they re-express p75NTR following nerve injury or in ALS, thus becoming sensitive to NGF-induced apoptosis. We found that spinal cord extracts from ALS-affected SODG93A mice contained a hundred fold more active form of NGF than the mature factor. Becausereactive astrocytes and microglial cells expressing NGF also exhibit nitroxidative stress, we hypothesized that NGF could undergo post-translational nitrative modification by reaction with peroxynitrite to make it more active. This approach has allowed us to identify nitrated NGF species (nitroNGF) that are likely secreted by reactive astrocytes and exhibit apoptotic activity. In support to our hypothesis, other authors have reported the formation of nitroNGF in the brain of Alzheimer’s disease patients.
Selected group’s publications in ALS research
- Trias et el. (2013) Phenotypic transition of microglia into astrocyte-like cells associated with disease onset in a model of inherited ALS. Front. Cell. Neurosci.
- Miquel et al. (2012). Modulation of astrocytic mitochondrial function by dichloroacetate improves survival and motor performance in inherited amyotrophic lateral sclerosis. PLoS One. 7:e34776.
- Gandelman et al (2011) P2X7 receptor-induced death of motor neurons by a peroxynitrite/FAS-dependent pathway. J Neurochem. 126:382-8.
- Diaz-Amarilla et al (2011) Phenotypically aberrant astrocytes that promote motoneuron damage in a model of inherited ALS. Proc Natl Acad Sci U S. 108:18126-31.
- Garré et al (2010) FGF-1 induces ATP release from spinal astrocytes in culture and opens pannexin and connexin hemichannels. Proc Natl Acad Sci US107:22659-64
- GANDELMAN et al (2010) Extracellular ATP and the P2X(7) receptor in astrocyte-mediated motor neuron death: implications for amyotrophic lateral sclerosis. J. Neuroinflammation 9 :7-33
- BARBEITO et al (2010) Lead exposure stimulates VEGF expression in the spinal cord and extends survival in a mouse model of ALS. Neurobiol. of Disease 37:574-80.
- SOTELO-SILVEIRA et al (2009) Axonal mitochondrial clusters containing mutant SOD1 in transgenic models of ALS. Antioxidants & redox signaling 11:1535-1545.
- CASSINA,et al (2008) Mitochondrial dysfunction and oxidative stress in SOD1G93A –bearing astrocytes promote motoneuron degeneration. J. Neurosci. 28:4115-4122, 2008.
- DUPUIS et al (2008) Nogo receptor antagonizes p75NTR-dependent motor neuron death. Proc Natl Acad Sci 105:740-745.
- PEHAR et al (2007) Mitochondrial superoxide production and nuclear factor erythroid 2-related factor 2 activation in p75 neurotrophin receptor-induced motor neuron apoptosis. Journal of Neuroscience 29 :7777-7785.
- PEHARet al (2006) Modulation of p75-dependent motor neuron death by a small non-peptidyl mimetic of the neurotrophin loop 1 domain. European Journal of Neuroscience 6 :1575-1580.
- PEHAR et al (2006) Peroxynitrite transforms nerve growth factor into an apoptotic factor for motor neurons.. Free Radical Biology and Medicine 41:1632-1644.
- BARBEITOet al (2004) A Role for Astrocytes in Motor Neuron Loss in Amyotrophic Lateral Sclerosis. Brain Research Reviews 47:263-274.
- Regional Course & Symposium: ”Neuron Glia Interactions in health and disease: from basic Biology to translational Neuroscience – 2nd edition” 29 september-2 october, 2014.
- Fondo Clemente Estable ANII. FCE_1_2011_1_7342. Astrocitos fenotípicamente Aberrantes (células AbA): identificación de mecanismos y genes neurotóxicos. (2013-2014) Amount granted aprox USD 40.000
- Movilidad Bilateral Uruguay-Brasil – DICYT (MEC) (2013-2015) Amount Granted USD 6.000.
- Proyecto ECOS U014S02 “Mastocitos y neuroinflamación en enfermedades neurodegenerativas: caracteización de los mecanismos impllicados y nuevos blancos terapéuticos” 2014-2016.
- Isasi E, Barbeito L, Olivera-Bravo S. Increased blood-brain barrier permeability and alterations in perivascular astrocytes and pericytes induced by intracisternal glutaric acid. Fluids Barriers CNS. 2014 Jul 24;11:15.
- Miquel E, Cassina A, Martínez-Palma L, Souza JM, Bolatto C, Rodríguez-Bottero S, Logan A, Smith RA, Murphy MP, Barbeito L, Radi R, Cassina P. Neuroprotective effects of the mitochondria-targeted antioxidant MitoQ in a model of inherited amyotrophic lateral sclerosis. Free Radic Biol Med. 2014 70:204-13.