Prion-Like Propagation Mechanisms in Tauopathies and Traumatic Brain Injury: Challenges and Prospects

Antiepileptic Drugs as Potential Dementia Prophylactics Following Traumatic Brain Injury

Seizures and other forms of neurovolatility are emerging as druggable prodromal mechanisms that link traumatic brain injury (TBI) to the progression of later dementias. TBI neurotrauma has both acute and long-term impacts on health, and TBI is a leading risk factor for dementias, including chronic traumatic encephalopathy and Alzheimer's disease. Treatment of TBI already considers acute management of posttraumatic seizures and epilepsy, and impressive efforts have optimized regimens of antiepileptic drugs (AEDs) toward that goal. Here we consider that expanding these management strategies could determine which AED regimens best prevent dementia progression in TBI patients. Challenges with this prophylactic strategy include the potential consequences of prolonged AED treatment and that a large subset of patients are refractory to available AEDs. Addressing these challenges is warranted because the management of seizure activity following TBI offers a rare opportunity to prevent the onset or progression of devastating dementias.

Delivering Traumatic Brain Injury to Larval Zebrafish

We describe a straightforward, scalable method for administering traumatic brain injury (TBI) to zebrafish larvae. The pathological outcomes appear generalizable for all TBI types, but perhaps most closely model closed-skull, diffuse lesion (blast injury) neurotrauma. The injury is delivered by dropping a weight onto the plunger of a fluid-filled syringe containing zebrafish larvae. This model is easy to implement, cost-effective, and provides a high-throughput system that induces brain injury in many larvae at once. Unique to vertebrate TBI models, this method can be used to deliver TBI without anesthetic or other metabolic agents. The methods simulate the main aspects of traumatic brain injury in humans, providing a preclinical model to study the consequences of this prevalent injury type and a way to explore early interventions that may ameliorate subsequent neurodegeneration. We also describe a convenient method for executing pressure measurements to calibrate and validate this method. When used in concert with the genetic tools readily available in zebrafish, this model of traumatic brain injury offers opportunities to examine many mechanisms and outcomes induced by traumatic brain injury. For example, genetically encoded fluorescent reporters have been implemented with this system to measure protein misfolding and neural activity via optogenetics.

Systematic Analysis of tRNA-Derived Small RNAs Reveals the Effects of Xuefu-Zhuyu Decoction on the Hippocampi of Rats after Traumatic Brain Injury

Background

Traumatic brain injury (TBI) is one of the most common neurosurgical diseases and refers to brain function impairment or brain pathological changes induced by external causes. A traditional Chinese medicine, Xuefu-Zhuyu Decoction (XFZYD), has been indicated to harbor therapeutic properties against TBI. Transfer RNA (tRNA)-derived small RNAs, that is, tsRNAs (a group of small RNAs derived from tRNAs), are multifunctional regulatory noncoding RNAs generated under pressure and implicated in the progression of TBI.

Methods

A TBI model was successfully constructed using rats. We further performed sequencing and omics analyses to identify novel tsRNAs as drug targets for XFZYD therapy against TBI in the rat hippocampus. qPCR assays were used to further verify the experimental results. Gene Ontology (GO) was used to analyze the signaling pathways of downstream target genes of tsRNAs in the XFZYD-regulated TBI model. qPCR was used to detect the influence of overexpressed tsRNA mimics/inhibitors on their target genes in PC12 cells.

Results

Our RNA-Seq data illustrate that 11 tsRNAs were mediated by XFZYD. The experimental data revealed AS-tDR-002004 and AS-tDR-002583 as potential targets for XFZYD therapy and showed that they influenced TBI via the cadherin signaling pathway, cocaine addiction, circadian entrainment, and the nicotine pharmacodynamics pathway. We also confirmed that Pi4kb, Mlh3, Pcdh9, and Ppp1cb were target genes of 2 XFZYD-regulated tsRNAs in the hippocampus of a rat model and PC12 cells. Furthermore, biological function analysis revealed the potential therapeutic effects of tsRNAs, and the results showed that Mapk1 and Gnai1 were related genes for XFZYD therapy against TBI.

Conclusion

Our work successfully illuminates the efficiency of XFZYD in the treatment of TBI. The experimental data revealed AS-tDR-002004 and AS-tDR-002583 as potential targets for XFZYD therapy and showed that they influenced TBI via the cadherin signaling pathway, cocaine addiction, circadian entrainment, and the nicotine pharmacodynamics pathway in a TBI rat model.

Oligomeropathies, inflammation and prion protein binding

The central role of oligomers, small soluble aggregates of misfolded proteins, in the pathogenesis of neurodegenerative disorders is recognized in numerous experimental conditions and is compatible with clinical evidence. To underline this concept, some years ago we coined the term oligomeropathies to define the common mechanism of action of protein misfolding diseases like Alzheimer, Parkinson or prion diseases. Using simple experimental conditions, with direct application of synthetic β amyloid or α-synuclein oligomers intraventricularly at micromolar concentrations, we could detect differences and similarities in the biological consequences. The two oligomer species affected cognitive behavior, neuronal dysfunction and cerebral inflammatory reactions with distinct mechanisms. In these experimental conditions the proposed mediatory role of cellular prion protein in oligomer activities was not confirmed. Together with oligomers, inflammation at different levels can be important early in neurodegenerative disorders; both β amyloid and α-synuclein oligomers induce inflammation and its control strongly affects neuronal dysfunction. This review summarizes our studies with β-amyloid or α-synuclein oligomers, also considering the potential curative role of doxycycline, a well-known antibiotic with anti-amyloidogenic and anti-inflammatory activities. These actions are analyzed in terms of the therapeutic prospects.

Structural Bases of Prion Variation in Yeast

Amyloids are protein aggregates with a specific filamentous structure that are related to a number of human diseases, and also to some important physiological processes in animals and other kingdoms of life. Amyloids in yeast can stably propagate as heritable units, prions. Yeast prions are of interest both on their own and as a model for amyloids and prions in general. In this review, we consider the structure of yeast prions and its variation, how such structures determine the balance of aggregated and soluble prion protein through interaction with chaperones and how the aggregated state affects the non-prion functions of these proteins.