An estimated 25 million people in the US alone rely on implanted medical devices, ∼2.5 million implanted within the nervous system. Even though many devices perform adequately for years, the host ...response to medical devices often severely limits tissue integration and long-term performance. This host response is believed to be particularly limiting in the case of intracortical microelectrodes, where it has been shown that glial cell encapsulation and localized neuronal cell loss accompany intracortical microelectrode implantation. Since neuronal ensembles must be within ∼50 µm of the electrode to obtain neuronal spikes and local field potentials, developing a better understanding of the molecular and cellular environment at the device-tissue interface has been the subject of significant research. Unfortunately, immunohistochemical studies of scar maturation in correlation to device function have been inconclusive. Therefore, here we present a detailed quantitative study of the cellular events and the stability of the blood-brain barrier (BBB) following intracortical microelectrode implantation and cortical stab injury in a chronic survival model. We found two distinctly inverse multiphasic profiles for neuronal survival in device-implanted tissue compared to stab-injured animals. For chronically implanted animals, we observed a biphasic paradigm between blood-derived/trauma-induced and CNS-derived inflammatory markers driving neurodegeneration at the interface. In contrast, stab injured animals demonstrated a CNS-mediated neurodegenerative environment. Collectively these data provide valuable insight to the possibility of multiple roles of chronic neuroinflammatory events on BBB disruption and localized neurodegeneration, while also suggesting the importance to consider multiphasic neuroinflammatory kinetics in the design of therapeutic strategies for stabilizing neural interfaces.
Abstract The current study seeks to elucidate a biological mechanism which may mediate neuroinflammation, and decreases in both blood–brain barrier stability and neuron viability at the intracortical ...microelectrode-tissue interface. Here, we have focused on the role of pro-inflammatory reactive oxygen species. Specifically, adult rats implanted within intracortical microelectrodes were systemically administered the anti-oxidant, resveratrol, both the day before and the day of surgery. Animals were sacrificed at two or four weeks post-implantation for histological analysis of the neuroinflammatory and neurodegenerative responses to the microelectrode. At two weeks post-implantation, we found animals treated with resveratrol demonstrated suppression of reactive oxygen species accumulation and blood–brain barrier instability, accompanied with increased density of neurons at the intracortical microelectrode-tissue interface. Four weeks post-implantation, animals treated with resveratrol exhibited indistinguishable levels of markers for reactive oxygen species and neuronal nuclei density in comparison to untreated control animals. However, of the neurons that remained, resveratrol treated animals were seen to display reductions in the density of degenerative neurons compared to control animals at both two and four weeks post-implantation. Initial mechanistic evaluation suggested the roles of both anti-oxidative enzymes and toll-like receptor 4 expression in facilitating microglia activation and the propagation of neurodegenerative inflammatory pathways. Collectively, our data suggests that short-term attenuation of reactive oxygen species accumulation and blood–brain barrier instability can result in prolonged improvements in neuronal viability around implanted intracortical microelectrodes, while also identifying potential therapeutic targets to reduce chronic intracortical microelectrode-mediated neurodegeneration.
Tauopathies constitute a group of neurodegenerative diseases characterized by abnormal aggregation of the protein tau, progressive neuronal and synaptic loss, and eventual cognitive and motor ...impairment. In this review, we will highlight the latest efforts investigating the intricate interplay between the gut microbiome and tauopathies. We discuss the physiological interactions between the microbiome and the brain as well as clinical and experimental evidence that suggests that the presence of tauopathy alters the composition of gut microbiota. We explore both animal and human studies that define causative relationships between the gut microbiome and tauopathy by directly manipulating or transferring gut microbiota. This review highlights future directions into identifying and mechanistically elucidating microbial species causally linked to tauopathies, with an ultimate goal of devising therapeutic targets towards the gut microbiome to treat tauopathies.
Therapeutic strategies that target disease-associated transcripts are being developed for a variety of neurodegenerative syndromes. Protein levels change as a function of their half-life, a property ...that critically influences the timing and application of therapeutics. In addition, both protein kinetics and concentration may play important roles in neurodegeneration; therefore, it is essential to understand in vivo protein kinetics, including half-life. Here, we applied a stable isotope-labeling technique in combination with mass spectrometric detection and determined the in vivo kinetics of superoxide dismutase 1 (SOD1), mutation of which causes amyotrophic lateral sclerosis. Application of this method to human SOD1-expressing rats demonstrated that SOD1 is a long-lived protein, with a similar half-life in both the cerebral spinal fluid (CSF) and the CNS. Additionally, in these animals, the half-life of SOD1 was longest in the CNS when compared with other tissues. Evaluation of this method in human subjects demonstrated successful incorporation of the isotope label in the CSF and confirmed that SOD1 is a long-lived protein in the CSF of healthy individuals. Together, the results of this study provide important insight into SOD1 kinetics and support application of this technique to the design and implementation of clinical trials that target long-lived CNS proteins.
Objective
Accumulation of misfolded superoxide dismutase‐1 (SOD1) is a pathological hallmark of SOD1‐related amyotrophic lateral sclerosis (ALS) and is observed in sporadic ALS where its role in ...pathogenesis is controversial. Understanding in vivo protein kinetics may clarify how SOD1 influences neurodegeneration and inform optimal dosing for therapies that lower SOD1 transcripts.
Methods
We employed stable isotope labeling paired with mass spectrometry to evaluate in vivo protein kinetics and concentration of soluble SOD1 in cerebrospinal fluid (CSF) of SOD1 mutation carriers, sporadic ALS participants and controls. A deaminated SOD1 peptide, SDGPVKV, that correlates with protein stability was also measured.
Results
In participants with heterozygous SOD1A5V mutations, known to cause rapidly progressive ALS, mutant SOD1 protein exhibited ~twofold faster turnover and ~ 16‐fold lower concentration compared to wild‐type SOD1 protein. SDGPVKV levels were increased in SOD1A5V carriers relative to controls. Thus, SOD1 mutations impact protein kinetics and stability. We applied this approach to sporadic ALS participants and found that SOD1 turnover, concentration, and SDGPVKV levels are not significantly different compared to controls.
Interpretation
These results highlight the ability of stable isotope labeling approaches and peptide deamidation to discern the influence of disease mutations on protein kinetics and stability and support implementation of this method to optimize clinical trial design of gene and molecular therapies for neurological disorders.
Trial Registration
Clinicaltrials.gov: NCT03449212.
OBJECTIVES/SPECIFIC AIMS: We aimed to develop an assay to measure new protein synthesis after Antisense Oligonucleotide treatment, which we hypothesized to be the earliest biochemical identification ...of RNA-targeting therapy efficacy. METHODS/STUDY POPULATION: We treated 2 transgenic animal models expressing proteins implicated in neurodegenerative disease: human tau protein (hTau) and human superoxide dismutase 1 (hSOD1), with ASO against these mRNA transcripts. Animals received isotope-labeled 13C6-Leucine via drinking water to label newly synthesized proteins. We assayed target protein synthesis and concentration after ASO treatment to determine the earliest identification of ASO target engagement. RESULTS/ANTICIPATED RESULTS: hTau ASO treatment in transgenic mice lowered hTau protein concentration 23 days post-treatment in cortex (95% CI: 0.05%–64.0% reduction). In the same tissue, we observed lowering of hTau protein synthesis as early as 13 days (95% CI: 29.4%–123%). In hSOD1 transgenic rats, we observed lowering of 13C6-leucine-labeled hSOD1 in the cerebrospinal fluid 30 days after ASO treatment compared with inactive ASO control (95% CI: 12.0%–48.4%). DISCUSSION/SIGNIFICANCE OF IMPACT: In progressive neurodegenerative diseases, it is crucial to develop measurements that identify treatment efficacy early to improve patient outcomes. These data support the use of stable isotope labeling of amino acids to measure new protein synthesis as an early pharmacodynamics measurement for therapies that target RNA and inhibit the translation of proteins.
Objectives
Clinical trials for progressive neurodegenerative disorders such as Alzheimer's Disease and Amyotrophic Lateral Sclerosis have been hindered due to the absence of effective ...pharmacodynamics markers to assay target engagement. We tested whether measurements of new protein production would be a viable pharmacodynamics tool for RNA‐targeted therapies.
Methods
Transgenic animal models expressing human proteins implicated in neurodegenerative disorders – microtubule‐associated protein tau (hTau) or superoxide dismutase‐1 (hSOD1) – were treated with antisense oligonucleotides (ASOs) delivered to the central nervous system to target these human mRNA transcripts. Simultaneously, animals were administered 13C6‐leucine via drinking water to measure new protein synthesis after ASO treatment. Measures of new protein synthesis and protein concentration were assayed at designated time points after ASO treatment using targeted proteomics.
Results
ASO treatment lowered hTau mRNA and protein production (measured by 13C6‐leucine‐labeled hTau protein) earlier than total hTau protein concentration in transgenic mouse cortex. In the CSF of hSOD1 transgenic rats, ASO treatment lowered newly generated hSOD1 protein driven by decreases in newly synthesized hSOD1 protein, not overall protein concentration, 30 days after treatment. At later time points, decreases in newly generated protein were still observed after mRNA lowering reached a steady state after ASO treatment.
Interpretation
Measures of newly generated protein show earlier pharmacodynamics changes for RNA‐lowering therapeutics compared with total protein concentration. Early in ASO treatment, decreases in newly generated protein are driven by changes in newly synthesized protein. Measuring new protein production in CSF may be a promising early pharmacodynamics marker for RNA‐targeted therapeutics.
Endotracheal intubation (EI) is a potentially lifesaving but high-risk procedure in critically ill patients. While the ACGME mandates that trainees in pulmonary and critical care medicine (PCCM) ...achieve competence in this procedure, there is wide variation in EI training across the USA. One study suggests that 40% of the US PCCM trainees feel they would not be proficient in EI upon graduation. This article presents a review of the EI training literature; the recommendations of a national group of PCCM, anesthesiology, emergency medicine, and pediatric experts; and a call for further research, collaboration, and consensus guidelines.
For critically ill adults undergoing emergency tracheal intubation, failure to intubate the trachea on the first attempt occurs in up to 20% of cases and is associated with severe hypoxemia and ...cardiac arrest. Whether using a tracheal tube introducer ("bougie") increases the likelihood of successful intubation compared with using an endotracheal tube with stylet remains uncertain.
To determine the effect of use of a bougie vs an endotracheal tube with stylet on successful intubation on the first attempt.
The Bougie or Stylet in Patients Undergoing Intubation Emergently (BOUGIE) trial was a multicenter, randomized clinical trial among 1102 critically ill adults undergoing tracheal intubation in 7 emergency departments and 8 intensive care units in the US between April 29, 2019, and February 14, 2021; the date of final follow-up was March 14, 2021.
Patients were randomly assigned to use of a bougie (n = 556) or use of an endotracheal tube with stylet (n = 546).
The primary outcome was successful intubation on the first attempt. The secondary outcome was the incidence of severe hypoxemia, defined as a peripheral oxygen saturation less than 80%.
Among 1106 patients randomized, 1102 (99.6%) completed the trial and were included in the primary analysis (median age, 58 years; 41.0% women). Successful intubation on the first attempt occurred in 447 patients (80.4%) in the bougie group and 453 patients (83.0%) in the stylet group (absolute risk difference, -2.6 percentage points 95% CI, -7.3 to 2.2; P = .27). A total of 58 patients (11.0%) in the bougie group experienced severe hypoxemia, compared with 46 patients (8.8%) in the stylet group (absolute risk difference, 2.2 percentage points 95% CI, -1.6 to 6.0). Esophageal intubation occurred in 4 patients (0.7%) in the bougie group and 5 patients (0.9%) in the stylet group, pneumothorax was present after intubation in 14 patients (2.5%) in the bougie group and 15 patients (2.7%) in the stylet group, and injury to oral, glottic, or thoracic structures occurred in 0 patients in the bougie group and 3 patients (0.5%) in the stylet group.
Among critically ill adults undergoing tracheal intubation, use of a bougie did not significantly increase the incidence of successful intubation on the first attempt compared with use of an endotracheal tube with stylet.
ClinicalTrials.gov Identifier: NCT03928925
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