Microbial BMAA elicits mitochondrial dysfunction, innate immunity activation, and Alzheimer's disease features in cortical neurons
JOURNAL OF NEUROINFLAMMATION
Authors: Silva, Diana F.; Candeias, Emanuel; Esteves, A. Raquel; Magalhaes, Joao D.; Ferreira, I. Luisa; Nunes-Costa, Daniela; Rego, A. Cristina; Empadinhas, Nuno; Cardoso, Sandra M.
Abstract
BackgroundAfter decades of research recognizing it as a complex multifactorial disorder, sporadic Alzheimer's disease (sAD) still has no known etiology. Adding to the myriad of different pathways involved, bacterial neurotoxins are assuming greater importance in the etiology and/or progression of sAD. beta -N-Methylamino-l-alanine (BMAA), a neurotoxin produced by some microorganisms namely cyanobacteria, was previously detected in the brains of AD patients. Indeed, the consumption of BMAA-enriched foods has been proposed to induce amyotrophic lateral sclerosis-parkinsonism-dementia complex (ALS-PDC), which implicated this microbial metabolite in neurodegeneration mechanisms.MethodsFreshly isolated mitochondria from C57BL/6 mice were treated with BMAA and O-2 consumption rates were determined. O-2 consumption and glycolysis rates were also measured in mouse primary cortical neuronal cultures. Further, mitochondrial membrane potential and ROS production were evaluated by fluorimetry and the integrity of mitochondrial network was examined by immunofluorescence. Finally, the ability of BMAA to activate neuronal innate immunity was quantified by addressing TLRs (Toll-like receptors) expression, p65 NF-kappa B translocation into the nucleus, increased expression of NLRP3 (Nod-like receptor 3), and pro-IL-1 beta. Caspase-1 activity was evaluated using a colorimetric substrate and mature IL-1 beta levels were also determined by ELISA.ResultsTreatment with BMAA reduced O-2 consumption rates in both isolated mitochondria and in primary cortical cultures, with additional reduced glycolytic rates, decrease mitochondrial potential and increased ROS production. The mitochondrial network was found to be fragmented, which resulted in cardiolipin exposure that stimulated inflammasome NLRP3, reinforced by decreased mitochondrial turnover, as indicated by increased p62 levels. BMAA treatment also activated neuronal extracellular TLR4 and intracellular TLR3, inducing p65 NF-kappa B translocation into the nucleus and activating the transcription of NLRP3 and pro-IL-1 beta. Increased caspase-1 activity resulted in elevated levels of mature IL-1 beta. These alterations in mitochondrial metabolism and inflammation increased Tau phosphorylation and A beta peptides production, two hallmarks of AD.ConclusionsHere we propose a unifying mechanism for AD neurodegeneration in which a microbial toxin can induce mitochondrial dysfunction and activate neuronal innate immunity, which ultimately results in Tau and A beta pathology. Our data show that neurons, alone, can mount inflammatory responses, a role previously attributed exclusively to glial cells.
Effectiveness of Combining Compensatory Cognitive Training and Vocational Intervention vs. Treatment as Usual on Return to Work Following Mild-to-Moderate Traumatic Brain Injury: Interim Analysis at 3 and 6 Month Follow-Up
FRONTIERS IN NEUROLOGY
Authors: Howe, Emilie Isager; Fure, Silje C. R.; Lovstad, Marianne; Enehaug, Heidi; Sagstad, Kjersti; Hellstrom, Torgeir; Brunborg, Cathrine; Roe, Cecilie; Nordenmark, Tonje Haug; Soberg, Helene L.; Twamley, Elizabeth; Lu, Juan; Andelic, Nada
Abstract
Aims: Knowledge regarding the most effective return to work (RTW) approaches after traumatic brain injury (TBI) is lacking. This trial aimed to compare the effectiveness of a combined cognitive and vocational intervention to treatment as usual (TAU) on RTW and work stability after TBI. Methods: We performed a parallel-group randomized controlled trial (RCT) at a TBI outpatient clinic at Oslo University Hospital (OUH), Norway. Patients with a history of mild-to-moderate TBI (n = 116) aged 18-60 were randomized (1:1) by an independent investigator to receive group-based compensatory cognitive training (CCT) and supported employment (SE) (n = 60) or TAU consisting of individualized multidisciplinary treatment (n = 56). Participants were enrolled 2-3 months post-injury. The nature of the intervention prevented blinding of patients and therapists, however, outcome assessors were blinded to group allocation. The primary outcome measure was RTW at 3 and 6 months following study inclusion. Secondary outcomes were work percentage, stability, and productivity. The present study provides results from an interim analysis from the first two planned follow ups, while subsequent publications will present results up to 12 months following study inclusion. Results: Mixed effects models showed no between-group differences in the RTW proportion, work percentage, and hours worked between CCT-SE and TAU from baseline to 6 months. A significantly higher proportion of participants in CCT-SE had returned to work at 3 months when adjusting for baseline differences. The majority of participants who were employed at 3 and 6 months were stably employed. There was a statistically significant within-group improvement on RTW proportion, hours worked and work percentage in both groups. Conclusion: The results revealed no difference between CCT-SE and TAU on work-related outcomes from baseline to 6 months. However, there was a higher RTW proportion in the CCT-SE group compared to TAU at 3 months. Future publications will assess the effectiveness of CCT-SE vs. TAU up to 12 months.