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Acta Neuropathologica Communications May 2024Neurons pose a particular challenge to degradative processes like autophagy due to their long and thin processes. Autophagic vesicles (AVs) are formed at the tip of the...
Neurons pose a particular challenge to degradative processes like autophagy due to their long and thin processes. Autophagic vesicles (AVs) are formed at the tip of the axon and transported back to the soma. This transport is essential since the final degradation of the vesicular content occurs only close to or in the soma. Here, we established an in vivo live-imaging model in the rat optic nerve using viral vector mediated LC3-labeling and two-photon-microscopy to analyze axonal transport of AVs. Under basal conditions in vivo, 50% of the AVs are moving with a majority of 85% being transported in the retrograde direction. Transport velocity is higher in the retrograde than in the anterograde direction. A crush lesion of the optic nerve results in a rapid breakdown of retrograde axonal transport while the anterograde transport stays intact over several hours. Close to the lesion site, the formation of AVs is upregulated within the first 6 h after crush, but the clearance of AVs and the levels of lysosomal markers in the adjacent axon are reduced. Expression of p150Glued, an adaptor protein of dynein, is significantly reduced after crush lesion. In vitro, fusion and colocalization of the lysosomal marker cathepsin D with AVs are reduced after axotomy. Taken together, we present here the first in vivo analysis of axonal AV transport in the mammalian CNS using live-imaging. We find that axotomy leads to severe defects of retrograde motility and a decreased clearance of AVs via the lysosomal system.
Topics: Animals; Axonal Transport; Optic Nerve; Rats; Autophagy; Optic Nerve Injuries; Male; Axons; Nerve Degeneration; Rats, Sprague-Dawley; Female
PubMed: 38812004
DOI: 10.1186/s40478-024-01791-2 -
Communications Biology May 2024Neurons grow neurites of several tens of micrometers in length, necessitating active transport from the cell body by motor proteins. By tracking fluorophores as...
Neurons grow neurites of several tens of micrometers in length, necessitating active transport from the cell body by motor proteins. By tracking fluorophores as minimally invasive labels, MINFLUX is able to quantify the motion of those proteins with nanometer/millisecond resolution. Here we study the substeps of a truncated kinesin-1 mutant in primary rat hippocampal neurons, which have so far been mainly observed on polymerized microtubules deposited onto glass coverslips. A gentle fixation protocol largely maintains the structure and surface modifications of the microtubules in the cell. By analyzing the time between the substeps, we identify the ATP-binding state of kinesin-1 and observe the associated rotation of the kinesin-1 head in neurites. We also observed kinesin-1 switching microtubules mid-walk, highlighting the potential of MINFLUX to study the details of active cellular transport.
Topics: Kinesins; Animals; Rats; Neurites; Microtubules; Hippocampus; Cells, Cultured
PubMed: 38811803
DOI: 10.1038/s42003-024-06358-4 -
Endocrine Journal May 2024Post-traumatic pituitary stalk transection syndrome (PSTS) is an extremely rare cause of combined pituitary hormone deficiency (CPHD), affecting approximately 9 per...
Post-traumatic pituitary stalk transection syndrome (PSTS) expeditiously manifested after a fall from a height combined with acute traumatic spinal cord injury: a rare case report with review of literature.
Post-traumatic pituitary stalk transection syndrome (PSTS) is an extremely rare cause of combined pituitary hormone deficiency (CPHD), affecting approximately 9 per 100,000 cases of traumatic brain injury. In contrast, pituitary stalk interruption syndrome (PSIS) is also a rare cause of CPHD. Importantly, these conditions are often confused due to their similar names and resembling findings on magnetic resonance imaging (MRI). PSIS has been thought to be a prenatal developmental event resulting from a couple of genetic aberrations. In typical PSIS, anterior pituitary hormone deficiencies are restricted to growth hormone (GH) and gonadotropin during the pediatric age, gradually and generally progressing to panhypopituitarism in most cases. In contrast, global deficiencies of the anterior pituitary hormones in PSTS are temporally associated with trauma. To the best of our knowledge, no case reports of PSTS combined with acute traumatic spinal cord injury have been reported. A 34-year-old female was transferred to our hospital after jumping from the fourth building floor. She was diagnosed as an acute traumatic spinal cord injury and underwent the operation of elective posterior spinal fusion. On postoperative day 7, the blood tests revealed considerable hyperkalemia, hyponatremia and eosinophilia. Notably, menstruation stopped after falling from a height. Pituitary function tests revealed GH deficiency, hypogonadism, hypothyroidism and hypoadrenocorticism. MRI revealed loss of the pituitary stalk, whilst the hyperintense signal from distal axon of hypothalamus was still identified. Based on these findings, she was diagnosed as PSTS. Our case highlights endocrinological landscape of transection of the pituitary stalk by acute trauma.
PubMed: 38811206
DOI: 10.1507/endocrj.EJ24-0091 -
Science Advances May 2024Transporting and translating mRNAs in axons is crucial for neuronal viability. Local synthesis of nuclear-encoded mitochondrial proteins protects long-lived axonal...
Transporting and translating mRNAs in axons is crucial for neuronal viability. Local synthesis of nuclear-encoded mitochondrial proteins protects long-lived axonal mitochondria from damage; however, the regulatory factors involved are largely unknown. We show that CLUH, which binds mRNAs encoding mitochondrial proteins, prevents peripheral neuropathy and motor deficits in the mouse. CLUH is enriched in the growth cone of developing spinal motoneurons and is required for their growth. The lack of CLUH affects the abundance of target mRNAs and the corresponding mitochondrial proteins more prominently in axons, leading to ATP deficits in the growth cone. CLUH interacts with ribosomal subunits, translation initiation, and ribosome recycling components and preserves axonal translation. Overexpression of the ribosome recycling factor ABCE1 rescues the mRNA and translation defects, as well as the growth cone size, in CLUH-deficient motoneurons. Thus, we demonstrate a role for CLUH in mitochondrial quality control and translational regulation in axons, which is essential for their development and long-term integrity and function.
Topics: Animals; Motor Neurons; Mitochondria; Axons; Protein Biosynthesis; Mice; Peripheral Nervous System Diseases; Growth Cones; RNA, Messenger; Mitochondrial Proteins; Mice, Knockout
PubMed: 38809982
DOI: 10.1126/sciadv.adn2050 -
Science Advances May 2024While our understanding of the nanoscale architecture of anterograde synaptic transmission is rapidly expanding, the qualitative and quantitative molecular principles...
While our understanding of the nanoscale architecture of anterograde synaptic transmission is rapidly expanding, the qualitative and quantitative molecular principles underlying distinct mechanisms of retrograde synaptic communication remain elusive. We show that a particular form of tonic cannabinoid signaling is essential for setting target cell-dependent synaptic variability. It does not require the activity of the two major endocannabinoid-producing enzymes. Instead, by developing a workflow for physiological, anatomical, and molecular measurements at the same unitary synapse, we demonstrate that the nanoscale stoichiometric ratio of type 1 cannabinoid receptors (CBRs) to the release machinery is sufficient to predict synapse-specific release probability. Accordingly, selective decrease of extrasynaptic CBRs does not affect synaptic transmission, whereas in vivo exposure to the phytocannabinoid Δ-tetrahydrocannabinol disrupts the intrasynaptic nanoscale stoichiometry and reduces synaptic variability. These findings imply that synapses leverage the nanoscale stoichiometry of presynaptic receptor coupling to the release machinery to establish synaptic strength in a target cell-dependent manner.
Topics: Animals; Synaptic Transmission; Receptor, Cannabinoid, CB1; Synapses; Signal Transduction; Presynaptic Terminals; Mice; Endocannabinoids; Dronabinol
PubMed: 38809980
DOI: 10.1126/sciadv.ado0077 -
PloS One 2024Benfotiamine provides an important novel therapeutic direction in Alzheimer's disease (AD) with possible additive or synergistic effects to amyloid targeting therapeutic... (Randomized Controlled Trial)
Randomized Controlled Trial
Protocol for a seamless phase 2A-phase 2B randomized double-blind placebo-controlled trial to evaluate the safety and efficacy of benfotiamine in patients with early Alzheimer's disease (BenfoTeam).
BACKGROUND
Benfotiamine provides an important novel therapeutic direction in Alzheimer's disease (AD) with possible additive or synergistic effects to amyloid targeting therapeutic approaches.
OBJECTIVE
To conduct a seamless phase 2A-2B proof of concept trial investigating tolerability, safety, and efficacy of benfotiamine, a prodrug of thiamine, as a first-in-class small molecule oral treatment for early AD.
METHODS
This is the protocol for a randomized, double-blind, placebo-controlled 72-week clinical trial of benfotiamine in 406 participants with early AD. Phase 2A determines the highest safe and well-tolerated dose of benfotiamine to be carried forward to phase 2B. During phase 2A, real-time monitoring of pre-defined safety stopping criteria in the first approximately 150 enrollees will help determine which dose (600 mg or 1200 mg) will be carried forward into phase 2B. The phase 2A primary analysis will test whether the rate of tolerability events (TEs) is unacceptably high in the high-dose arm compared to placebo. The primary safety endpoint in phase 2A is the rate of TEs compared between active and placebo arms, at each dose. The completion of phase 2A will seamlessly transition to phase 2B without pausing or stopping the trial. Phase 2B will assess efficacy and longer-term safety of benfotiamine in a larger group of participants through 72 weeks of treatment, at the selected dose. The co-primary efficacy endpoints in phase 2B are CDR-Sum of Boxes and ADAS-Cog13. Secondary endpoints include safety and tolerability measures; pharmacokinetic measures of thiamine and its esters, erythrocyte transketolase activity as blood markers of efficacy of drug delivery; ADCS-ADL-MCI; and MoCA.
CONCLUSION
The BenfoTeam trial utilizes an innovative seamless phase 2A-2B design to achieve proof of concept. It includes an adaptive dose decision rule, thus optimizing exposure to the highest and best-tolerated dose.
TRIAL REGISTRATION
ClinicalTrials.gov identifier: NCT06223360, registered on January 25, 2024. https://classic.clinicaltrials.gov/ct2/show/NCT06223360.
Topics: Humans; Alzheimer Disease; Thiamine; Double-Blind Method; Male; Female; Aged; Middle Aged; Treatment Outcome; Prodrugs
PubMed: 38809849
DOI: 10.1371/journal.pone.0302998 -
The Journal of Venomous Animals and... 2024In this experimental protocol, we evaluated the immediate and delayed repair of the buccal branch of the facial nerve (BBFN) with heterologous fibrin biopolymer (HFB) as...
BACKGROUND
In this experimental protocol, we evaluated the immediate and delayed repair of the buccal branch of the facial nerve (BBFN) with heterologous fibrin biopolymer (HFB) as a coaptation medium and the use of photobiomodulation (PBM), performing functional and histomorphometric analysis of the BBFN and perioral muscles.
METHODS
Twenty-eight rats were divided into eight groups using the BBFN bilaterally (the left nerve was used for PBM), namely: G1 - control group, right BBFN (without injury); G2 - control group, left BBFN (without injury + PBM); G3 - Denervated right BBFN (neurotmesis); G4 - Denervated left BBFN (neurotmesis + PBM); G5 - Immediate repair of right BBFN (neurotmesis + HFB); G6 - Immediate repair of left BBFN (neurotmesis + HFB + PBM); G7 - Delayed repair of right BBFN (neurotmesis + HFB); G8 - Delayed repair of left BBFN (neurotmesis + HFB + PBM). Delayed repair occurred after two weeks of denervation. All animals were sacrificed after six weeks postoperatively.
RESULTS
In the parameters of the BBFN, we observed inferior results in the groups with delayed repair, in relation to the groups with immediate repair, with a significant difference ( < 0.05) in the diameter of the nerve fiber, the axon, and the thickness of the myelin sheath of the group with immediate repair with PBM compared to the other experimental groups. In measuring the muscle fiber area, groups G7 (826.4 ± 69.90) and G8 (836.7 ± 96.44) were similar to G5 (882.8 ± 70.51). In the functional analysis, the G7 (4.10 ± 0.07) and G8 (4.12 ± 0.08) groups presented normal parameters.
CONCLUSION
We demonstrated that delayed repair of BBFN is possible with HFB, but with worse results compared to immediate repair, and that PBM has a positive influence on nerve regeneration results in immediate repair.
PubMed: 38808073
DOI: 10.1590/1678-9199-JVATITD-2023-0093 -
Cell Death & Disease May 2024Mitochondria dysfunctions and mitophagy failure have been associated with several Alzheimer's disease (AD) related molecular actors including amyloid beta (Aβ) and...
Mitochondria dysfunctions and mitophagy failure have been associated with several Alzheimer's disease (AD) related molecular actors including amyloid beta (Aβ) and recently the amyloid precursor protein-C terminal fragments (APP-CTFs). The efficacy of the mitophagy process in neurons relies on regulated mitochondrial transport along axons involving a complex molecular machinery. The contribution of the amyloid precursor protein (APP) and its derived fragments to the mitochondrial transport machinery alterations in AD have not been investigated before. We report herein a change of the expression of mitochondrial transport proteins (SNPH and Miro1), motor adapters (TRANK1 and TRAK2), and components of the dynein and kinesin motors (i.e., IC1,2 and Kif5 (A, B, C) isoforms) by endogenous APP and by overexpression of APP carrying the familial Swedish mutation (APPswe). We show that APP-CTFs and Aβ concomitantly regulate the expression of a set of transport proteins as demonstrated in APPswe cells treated with β- and γ-secretase inhibitors and in cells Knock-down for presenilin 1 and 2. We further report the impact of APP-CTFs on the expression of transport proteins in AAV-injected C99 mice brains. Our data also indicate that both Aβ oligomers (Aβo) and APP-CTFs impair the colocalization of mitochondria and transport proteins. This has been demonstrated in differentiated SH-SY5Y naive cells treated with Aβo and in differentiated SH-SY5Y and murine primary neurons expressing APPswe and treated with the γ-secretase inhibitor. Importantly, we uncover that the expression of a set of transport proteins is modulated in a disease-dependent manner in 3xTgAD mice and in human sporadic AD brains. This study highlights molecular mechanisms underlying mitochondrial transport defects in AD that likely contribute to mitophagy failure and disease progression.
Topics: Alzheimer Disease; Amyloid beta-Protein Precursor; Animals; Mitochondria; Humans; Mice; Mice, Transgenic; Neurons; Amyloid beta-Peptides; Mitochondrial Proteins; Amyloid Precursor Protein Secretases; Kinesins; Biological Transport; Mitophagy; Nerve Tissue Proteins; rho GTP-Binding Proteins; Intracellular Signaling Peptides and Proteins
PubMed: 38806484
DOI: 10.1038/s41419-024-06742-2 -
Neurology International Apr 2024The development of the optic nerve and its surrounding tissues during the early fetal period is a convoluted period because it spans both the organogenesis period and...
The development of the optic nerve and its surrounding tissues during the early fetal period is a convoluted period because it spans both the organogenesis period and the fetal period. This study details the microscopic anatomy and histoembryology of the optic nerve in embryos during the early fetal period, including the second half of the first trimester of pregnancy. Serial sections through the orbit of variously aged embryos allowed us to analyze the nerve in both longitudinal and transverse aspects. A histological assessment and description of the structures surrounding and inside the nerve were performed, highlighting the cellular subtypes involved. By employing immunohistochemical techniques, we could characterize the presence and distribution of astrocytes within the optic nerve. Our findings suggest that by the 8th gestational week (WG) the structures are homologs to all the adult ones but with an early appearance so that maturation processes take place afterward. By this age, the axons forming the nerve are definitive adult axons. The glial cells do not yet exhibit adult phenotype, but their aspect becomes adult toward the 13th week. During its development the optic nerve increases in size then, at 14 weeks, it shrinks considerably, possibly through its neural maturation process. The morphological primordium of the blood-nerve barrier can be first noted at 10 WG and at 13 WG the morphological blood-nerve barrier is definitive. The meningeal primordium can be first noted as a layer of agglomerated fibroblasts, later toward 13 WG splitting in pachymeninx and leptomeninges and leaving space for intrinsic blood vessels.
PubMed: 38804475
DOI: 10.3390/neurolint16030035 -
Pain Research & Management 202430 male patients with primary inguinal hernias undergoing primary inguinal herniorrhaphy were prospectively recruited for ilioinguinal nerve resection and evaluation....
METHODS
30 male patients with primary inguinal hernias undergoing primary inguinal herniorrhaphy were prospectively recruited for ilioinguinal nerve resection and evaluation. Three samples of the resected ilioinguinal nerve (proximal, canal, and distal) were evaluated using Masson's trichrome stain to measure fascicle and total nerve cross-sectional area and detect changes in collagen.
RESULTS
The fascicle cross-sectional area in the canal segment was significantly decreased compared to the proximal control with a large effect size observed ( = 0.016, = 0.16). There was no significant difference in the nerve cross-sectional area between locations, but there was a moderate to large effect size observed between locations ( = 0.165, = 0.105). There was no significant difference in collagen content nor effect size observed between locations ( = 0.99, = 1.503 × 10). . The decrease in the fascicle cross-sectional area within the inguinal canal further suggests that there is chronic pressure applied by hernia tissue consistent with axon degeneration. Collagen content is uniformly distributed along the length of the nerve. Further studies with larger samples are needed to confirm the observed effect of nerve location on the total nerve cross-sectional area and axon loss.
Topics: Humans; Male; Hernia, Inguinal; Middle Aged; Nerve Compression Syndromes; Herniorrhaphy; Inguinal Canal; Aged; Adult; Collagen; Prospective Studies
PubMed: 38803624
DOI: 10.1155/2024/3339753