Beneficial Effect of Fingolimod in a Lafora Disease Mouse Model by Preventing Reactive Astrogliosis-Derived Neuroinflammation and Brain Infiltration of T-lymphocytes

Lafora disease (LD; OMIM#254780) is a rare, devastating, and fatal form of progressive myoclonus epilepsy that affects young adolescents and has no treatment yet. One of the hallmarks of the disease is the accumulation of aberrant poorly branched forms of glycogen (polyglucosans, PGs) in the brain and peripheral tissues. The current hypothesis is that this accumulation is causative of the pathophysiology of the disease. Another hallmark of LD is the presence of neuroinflammation. We have recently reported the presence of reactive glia-derived neuroinflammation in LD mouse models and defined the main inflammatory pathways that operate in these mice, mainly TNF and IL-6 signaling pathways. In addition, we described the presence of infiltration of peripheral immune cells in the brain parenchyma, which could cooperate and aggravate the neuroinflammatory landscape of LD. In this work, we have checked the beneficial effect of two compounds with the capacity to ameliorate neuroinflammation and reduce leukocyte infiltration into the brain, namely fingolimod and dimethyl fumarate. Our results indicate a beneficial effect of fingolimod in reducing reactive astrogliosis-derived neuroinflammation and T-lymphocyte infiltration, which correlated with the improved behavioral performance of the treated Epm2b-/- mice. On the contrary, dimethyl fumarate, although it was able to reduce reactive astrogliosis, was less effective in preventing neuroinflammation and T-lymphocyte infiltration and in modifying behavioral tests.

Deciphering the Polyglucosan Accumulation Present in Lafora Disease Using an Astrocytic Cellular Model

Lafora disease (LD) is a neurological disorder characterized by progressive myoclonus epilepsy. The hallmark of the disease is the presence of insoluble forms of glycogen (polyglucosan bodies, or PGBs) in the brain. The accumulation of PGBs is causative of the pathophysiological features of LD. However, despite the efforts made by different groups, the question of why PGBs accumulate in the brain is still unanswered. We have recently demonstrated that, in vivo, astrocytes accumulate most of the PGBs present in the brain, and this could lead to astrocyte dysfunction. To develop a deeper understanding of the defects present in LD astrocytes that lead to LD pathophysiology, we obtained pure primary cultures of astrocytes from LD mice from the postnatal stage under conditions that accumulate PGBs, the hallmark of LD. These cells serve as novel in vitro models for studying PGBs accumulation and related LD dysfunctions. In this sense, the metabolomics of LD astrocytes indicate that they accumulate metabolic intermediates of the upper part of the glycolytic pathway, probably as a consequence of enhanced glucose uptake. In addition, we also demonstrate the feasibility of using the model in the identification of different compounds that may reduce the accumulation of polyglucosan inclusions.

TNF and IL6/Jak2 signaling pathways are the main contributors of the glia-derived neuroinflammation present in Lafora disease, a fatal form of progressive myoclonus epilepsy

Lafora disease (LD; OMIM#254780) is a rare form of progressive myoclonus epilepsy (prevalence <1:1,000,000) characterized by the accumulation of insoluble deposits of aberrant glycogen (polyglucosans), named Lafora bodies, in the brain but also in peripheral tissues. LD is the most severe form of the group of progressive myoclonus epilepsies, since patients present a rapid deterioration and dementia with amplification of seizures, leading to death after a decade from the onset of the first symptoms. We have recently described that reactive glia-derived neuroinflammation should be considered a novel hallmark of LD since we observed a florid upregulation of differentially expressed genes in both LD mouse lines, which were mainly related to mediators of inflammatory response. In this work, we define an upregulation of the expression of mediators of the TNF and IL6/JAK2 signaling pathways in LD. In addition, we describe the activation of the non-canonical form of the inflammasome. Furthermore, we describe the infiltration of peripheral immune cells in the brain parenchyma, which could aggravate glia-derived neuroinflammation. Finally, we describe CXCL10 and S100b as blood biomarkers of the disease, which will allow the study of the progression of the disease using serum blood samples. We consider that the identification of these initial inflammatory changes in LD will be very important to implement possible anti-inflammatory therapeutic strategies to prevent the development of the disease.