authors: Curatolo P., Aronica E., Jansen A., Jansen F., Kotulska K., Lagae L., Moavero R., Jozwiak S.
Eur J Paediatr Neurol. 2016 Mar;20(2):203-11. doi: 10.1016/j.ejpn.2015.12.005.
Background: In tuberous sclerosis complex (TSC) a relationship has been shown between early and refractory seizures and intellectual disability. However, it is uncertain whether epilepsy in TSC is simply a marker in infants who are destined to develop an encephalopathic process or if seizures play a causal role in developing encephalopathy.
Methods: This paper summarizes the key points discussed during a European TSC workshop held in Rome and reviews the experimental and clinical evidence in support of the two theories.
Results/conclusion: There are many factors that influence the appearance of both early seizure onset and the encephalopathy resulting in neurodevelopmental deficits. Experimental studies show that as a consequence of the TSC genes mutation, mammalian target of Rapamycin (mTOR) overactivation determines an alteration in cellular morphology with cytomegalic neurons, altered synaptogenesis and an imbalance between excitation/inhibition, thus providing a likely neuroanatomical substrate for the early appearance of refractory seizures and for the encephalopathic process. At the clinical level, early signs of altered developmental trajectories are often unrecognized before 12 months of age. Evidence from experimental research shows that encephalopathy in TSC might have a genetic cause, and mTOR activation caused by TSC gene mutation can be directly responsible for the early appearance of seizures and encephalopathy.
authors: Boison D., Aronica E.
Neuropharmacology. 2015 Oct;97:18-34. doi:10.1016/j.neuropharm.2015.04.031
Comorbidities in Neurology represent a major conceptual and therapeutic challenge. For example, temporal lobe epilepsy (TLE) is a syndrome comprised of epileptic seizures and comorbid symptoms including memory and psychiatric impairment, depression, and sleep dysfunction. Similarly, Alzheimer's disease (AD), Parkinson's disease (PD), and Amyotrophic Lateral Sclerosis (ALS) are accompanied by various degrees of memory dysfunction. Patients with AD have an increased likelihood for seizures, whereas all four conditions share certain aspects of psychosis, depression and sleep dysfunction. This remarkable overlap suggests common pathophysiological mechanisms, which include synaptic dysfunction and synaptotoxicity, as well as glial activation and astrogliosis. Astrogliosis is linked to synapse function via the tripartite synapse, but astrocytes also control the availability of gliotransmitters and adenosine. Here we will specifically focus on the adenosine hypothesis of comorbidities' implying that astrocyte activation, via overexpression of adenosine kinase (ADK), induces a deficiency in the homeostatic tone of adenosine. We present evidence from patient-derived samples showing astrogliosis and overexpression of ADK as common pathological hallmark of epilepsy, AD, PD and ALS. We discuss a transgenic 'comorbidity model', in which brain-wide overexpression of ADK and resulting adenosine deficiency produces a comorbid spectrum of seizures, altered dopaminergic function, attentional impairment, and deficits in cognitive domains and sleep regulation. We conclude that dysfunction of adenosine signaling is common in neurological conditions, that adenosine dysfunction can explain co-morbid phenotypes, and that therapeutic adenosine augmentation might be effective for the treatment of comorbid symptoms in multiple neurological conditions.
authors: Vezzani A., Lang B., Aronica E.
Cold Spring Harb Perspect Med. 2015 Dec 18; 6(2). pii: a022699. doi: 10.1101/cshperspect.a022699
This review reports the available evidence on the activation of the innate and adaptive branches of the immune system and the related inflammatory processes in epileptic disorders and the putative pathogenic role of inflammatory processes developing in the brain, as indicated by evidence from experimental and clinical research. Indeed, there is increasing knowledge supporting a role of specific inflammatory mediators and immune cells in the generation and recurrence of epileptic seizures, as well as in the associated neuropathology and comorbidities. Major challenges in this field remain: a better understanding of the key inflammatory pathogenic pathways activated in chronic epilepsy and during epileptogenesis, and how to counteract them efficiently without altering the homeostatic tissue repair function of inflammation. The relevance of this information for developing novel therapies will be highlighted.
authors: van Scheppingen J., Iyer AM., Prabowo AS., Mühlebner A., Anink JJ., Scholl T., Feucht M., Jansen FE., Spliet WG., Krsek P., Zamecnik J., Buccoliero AM., Giordano F., Genitori L., Kotulska K., Jozwiak S., Jaworski J., Liszewkska E., van Vliet EA., Aronica E.
Glia. 2016 Mar 25. doi: 10.1002/glia.22983.
Tuberous sclerosis complex (TSC) is a genetic disease presenting with multiple neurological symptoms including epilepsy, mental retardation and autism. Abnormal activation of various inflammatory pathways has been observed in astrocytes in brain lesions associated with TSC. Increasing evidence supports the involvement of miRNAs in the regulation of astrocyte-mediated inflammatory response. To study the role of inflammation-related microRNAs in TSC, we employed real-time qPCR and in situ hybridization to characterize the expression of miR21, miR146a, and miR155 in TSC lesions (cortical tubers and subependymal giant cell astrocytomas, SEGAs). We observed an increased expression of miR21, miR146a, and miR155 in TSC tubers compared with control and perituberal brain tissue. Expression was localized in dysmorphic neurons, giant cells, and reactive astrocytes and positively correlated with IL-1B expression. In addition, cultured human astrocytes and SEGA-derived cell cultures were used to study the regulation of the expression of these miRNAs in response to the proinflammatory cytokine IL-1B and to evaluate the effects of overexpression or knockdown of miR21, miR146a, and miR155 on inflammatory signaling. IL-1B stimulation of cultured glial cells strongly induced intracellular miR21, miR146a, and miR155 expression, as well as miR146a extracellular release. IL-1B signaling was differentially modulated by overexpression of miR155 or miR146a, which resulted in pro- or anti-inflammatory effects, respectively. This study provied supportive evidence that inflammation-related microRNAs play a role in TSC. In particular, miR146a and miR155 appear to be key players in the regulation of astrocyte-mediated inflammatory response, with miR146a as most interesting anti-inflammatory therapeutic candidate.
authors: Mühlebner A., Iyer AM., van Scheppingen J., Anink JJ., Jansen FE., Veersema TJ., Braun KP., Spliet WG., Van Hecke W., Söylemezoglu F., Feucht M., Krsek P., Zamecnik J., Bien CG., Polster T., Coras R., Blümcke I., Aronica E.
J Neurodev Disord. 2016 Apr 2;8:9. doi: 10.1186/s 11689-016-9142-0.
Background: Tuberous sclerosis complex (TSC) is a multisystem disorder that results from mutations in the TSC1 or TSC genes, leading to constitutive activation of the mammalian target of rapamycin (mTOR) signaling pathway. Cortical tubers represent typical lesions of the central nervous system (CNS) in TSC. The pattern of cortical layering disruption observed in brain tissue of TSC patients is not yet fully understood, and little is known about the origin and phenotype of individual abnormal cell types recognized in tubers.
Methods: In the present study, we aimed to characterize dysmorphic neurons (DNs) and giant cells (GCs) of cortical tubers using neocortical layer-specific markers (NeuN, SMI32, Tbr1, Satb2, Cux2, ER81 and RORB) and to compare the features with the histo-morphologically similar focal cortical dysplacia (FCD) type IIb. We studied a cohort of nine surgically resected cortical tubers, five FCD type IIb, and four samples using immunohistochemistry and in situ hybridization.
Results: Cortical tuber displayed a prominent cell loss in all cortical layers. Moreover, we observed altered proportions of layer-specific markers within the dysplastic region. DNs, in both tubers and FCD type IIb, were found positive for different cortical layer markers, regardless of their laminar location, and their immunophenotype resembles that of cortical projection neurons.
Conclusions: These findings demonstrate that, similar to FCD type IIb, cortical layering is markedly disturbed in cortical tubers of TSC patients. Distribution of these disturbances is comparable in all tubers and suggests a dysmaturation affecting early and late migratory patterns, with a more severe impairment of the late stage of maturation.