Abstract Brain radiation can occur from treatment of brain tumors or accidental exposures. Brain radiation has been rarely considered, though, as a possible tool to alter protein levels involved in neurodegenerative disorders. We analyzed possible molecular and neuropathology changes of phosphorylated-Tau (pTau), all-Tau forms, β -tubulin, amyloid precursor protein (APP), glial fibrillary acidic protein (GFAP), ionized calcium binding adaptor molecule 1 (IBA-1), myelin basic protein (MBP), and GAP43 in Frontal Cortex (FC), Hippocampus (H) and Cerebellum (CRB) of swine brains following total-body low-dose radiation (1.79 Gy). Our data show that radiated-animals had lower levels of pTau in FC and H, APP in H and CRB, GAP43 in CRB, and higher level of GFAP in H versus sham-animals. These molecular changes were not accompanied by obvious neurohistological changes, except for astrogliosis in the H. These findings are novel, and might open new perspectives on brain radiation as a potential tool to interfere with the accumulation of specific proteins linked to the pathogenesis of various neurodegenerative disorders.
ABSTRACT Multidimensional MRI is an emerging approach that simultaneously encodes water relaxation ( T 1 and T 2 ) and mobility (diffusion) and replaces voxel-averaged values with subvoxel distributions of those MR properties. While conventional (i.e., voxel-averaged) MRI methods cannot adequately quantify the microscopic heterogeneity of biological tissue, using subvoxel information allows to selectively map a specific T 1 - T 2 -diffusion spectral range that corresponds to a group of tissue elements. The major obstacle to the adoption of rich, multidimensional MRI protocols for diagnostic or monitoring purposes is the prolonged scan time. Our main goal in the present study is to evaluate the performance of a nonlocal estimation of multispectral magnitudes (NESMA) filter on reduced datasets to limit the total acquisition time required for reliable multidimensional MRI characterization of the brain. Here we focused and reprocessed results from a recent study that identified potential imaging biomarkers of axonal injury pathology from the joint analysis of multidimensional MRI, in particular voxelwise T 1 - T 2 and diffusion- T 2 spectra in human Corpus Callosum, and histopathological data. We tested the performance of NESMA and its effect on the accuracy of the injury biomarker maps, relative to the co-registered histological reference. Noise reduction improved the accuracy of the resulting injury biomarker maps, while permitting data reduction of 35.7% and 59.6% from the full dataset for T 1 - T 2 and diffusion- T 2 cases, respectively. As successful clinical proof-of-concept applications of multidimensional MRI are continuously being introduced, reliable and robust noise removal and consequent acquisition acceleration would advance the field towards clinically-feasible diagnostic multidimensional MRI protocols.
Rodent models are important research tools for studying the pathophysiology of traumatic brain injury (TBI) and developing new therapeutic interventions for this devastating neurological disorder. However, the failure rate for the translation of drugs from animal testing to human treatments for TBI is 100%. While there are several potential explanations for this, previous clinical trials have relied on extrapolation from preclinical studies for critical design considerations, including drug dose optimization, post-injury drug treatment initiation and duration. Incorporating clinically relevant biomarkers in preclinical studies may provide an opportunity to calibrate preclinical models to identical (or similar) measurements in humans, link to human TBI biomechanics and pathophysiology, and guide therapeutic decisions. To support this translational goal, we conducted a systematic literature review of preclinical TBI studies in rodents measuring blood levels of clinically used GFAP, UCH-L1, NfL, t-Tau, or p-Tau, published in PubMed/EMBASE up to April 10th, 2024. Although many factors influence clinical TBI outcomes, many of those cannot routinely be assessed in rodent studies (e.g., ICP monitoring), thus we focused on blood biomarkers' temporal trajectories and discuss our findings in the context of the latest clinical TBI biomarker data. Out of the 805 original preclinical studies, 74 met the inclusion criteria, with a median quality score of 5 (25th-75th percentiles: 4-7) on the CAMARADES checklist. GFAP was measured in 43 studies, UCH-L1 in 21, NfL in 20, t-Tau in 19, and p-Tau in seven. Data in rodent models indicate that all biomarkers exhibited injury severity-dependent elevations with distinct temporal profiles. GFAP and UCH-L1 peaked within the first day after TBI (30- and 4-fold increases, respectively, in moderate-to-severe TBI versus sham) with the highest levels observed in the contusion TBI model. NfL peaked within days (18-fold increase) and remained elevated up to 6 months post-injury. GFAP and NfL show a pharmacodynamic response in 64.7% and 60%, respectively, of studies evaluating neuroprotective therapies in preclinical models. However, GFAP's rapid decline post-injury may limit its utility for understanding the response to new therapeutics beyond the hyperacute phase after experimental TBI. Furthermore, as in humans, subacute NfL levels inform on chronic white matter loss after TBI. t-Tau and p-Tau levels increased over weeks after TBI (up to 6- and 16-fold, respectively); however, their relationship with underlying neurodegeneration has yet to be addressed. Further investigation into biomarker levels in the subacute and chronic phases after TBI will be needed to fully understand the pathomechanisms underpinning blood biomarkers' trajectories and select the most suitable experimental model to optimally relate preclinical mechanistic studies to clinical observations in humans. This new approach could accelerate the translation of neuroprotective treatments from laboratory experiments to real-world clinical practices.
// Diego Iacono 1,2,3,4 , Peter Zandi 5 , Myron Gross 6 , William R. Markesbery 7,8,9 , Olga Pletnikova 1 , Gay Rudow 1 and Juan C. Troncoso 1,10 1 Neuropathology Division, Department of Pathology, Johns Hopkins University, Baltimore, MD, USA 2 Neuropathology Research, Biomedical Research Institute of New Jersey, Cedar Knolls, NJ, USA 3 Atlantic Neuroscience Institute, Overlook Medical Center, Summit, NJ, USA 4 Department of Neurology, Icahn School of Medicine at Mount Sinai, Newyork, NY, USA 5 Department of Mental Health, Johns Hopkins University, Baltimore, MD, USA 6 Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN, USA 7 Department of Pathology, Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA 8 Department of Neurology, Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA 9 Alzheimer's Disease Center, Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA 10 Department of Neurology, Johns Hopkins University, Baltimore, MD, USA Correspondence to: Diego Iacono, email: // Keywords : Gerotarget, AD pathology, APOε2, higher education and language skills, neuronal hypertrophy, preserved cognition Received : March 11, 2015 Accepted : April 30, 2015 Published : May 12, 2015 Abstract Asymptomatic Alzheimer's disease (ASYMAD) subjects are individuals characterized by preserved cognition before death despite substantial AD pathology at autopsy. ASYMAD subjects show comparable levels of AD pathology, i.e. β-amyloid neuritic plaques (Aβ-NP) and tau-neurofibrillary tangles (NFT), to those observed in mild cognitive impairment (MCI) and some definite AD cases. Previous clinicopathologic studies on ASYMAD subjects have shown specific phenomena of hypertrophy in the cell bodies, nuclei, and nucleoli of hippocampal pyramidal neurons and other cerebral areas. Since it is well established that the allele APOε4 is a major genetic risk factor for AD, we examined whether specific alleles of APOE could be associated with the different clinical outcomes between ASYMAD and MCI subjects despite equivalent AD pathology. A total of 523 brains from the Nun Study were screened for this investigation. The results showed higher APOε2 frequency ( p < 0.001) in ASYMAD (19.2%) vs . MCI (0%) and vs. AD (4.7%). Furthermore, higher education in ASYMAD vs . MCI and AD ( p < 0.05) was found. These novel autopsy-verified findings support the hypothesis of the beneficial effect of APOε2 and education, both which seem to act as contributing factors in delaying or forestalling the clinical manifestations of AD despite consistent levels of AD pathology.
Traumatic brain injury generated by blast may induce long-term neurological and psychiatric sequelae. We aimed to identify molecular, histopathological, and behavioral changes in rats 2 weeks after explosive-driven double-blast exposure. Rats received two 30-psi (~ 207-kPa) blasts 24 h apart or were handled identically without blast. All rats were behaviorally assessed over 2 weeks. At Day 15, rats were euthanized, and brains removed. Brains were dissected into frontal cortex, hippocampus, cerebellum, and brainstem. Western blotting was performed to measure levels of total-Tau, phosphorylated-Tau (pTau), amyloid precursor protein (APP), GFAP, Iba1, αII-spectrin, and spectrin breakdown products (SBDP). Kinases and phosphatases, correlated with tau phosphorylation were also measured. Immunohistochemistry for pTau, APP, GFAP, and Iba1 was performed. pTau protein level was greater in the hippocampus, cerebellum, and brainstem and APP protein level was greater in cerebellum of blast vs control rats (p < 0.05). GFAP, Iba1, αII-spectrin, and SBDP remained unchanged. No immunohistochemical or neurobehavioral changes were observed. The dissociation between increased pTau and APP in different regions in the absence of neurobehavioral changes 2 weeks after double blast exposure is a relevant finding, consistent with human data showing that battlefield blasts might be associated with molecular changes before signs of neurological and psychiatric disorders manifest.
Early studies showed that the latency of P300 (P3) event related potential increases or diminishes when anticholinergic o cholinergic drugs are administered. We tested the hypothesis that new cholinesterase inhibitors like Donepezil (DPZ) may have an effect on the often abnormal P300 of patients with Alzheimer's Disease (AD), and therefore, that P300 recordings might simplify the evaluation of responses to cholinesterase inhibitor in patients with mild and moderate–severe AD. We evaluated 60 patients with AD: 30 patients with "mild" (Mini Mental State Examination 26–19) and 30 patients with "moderate–severe" (Mini Mental State Examination 18–10), according to the National Institute of Neurological and Communicative Disorders and Alzheimer's Disease and Related Disorders Association criteria in comparison with 40 age-matched controls. All subjects underwent P300 recordings and neuropsychologic examinations (Alzheimer's Disease Assessment Scale-Cognition and Wechsler Adult Intelligence Scale) during the 6-month follow-up. Patients were divided into four groups of 15 patients each: Group I DPZ (10 mg/day) and Group I Vitamin E (2000 IU/day) with "mild" AD; Group II DPZ and Group II Vitamin E with "moderate–severe" AD and same drug dosages. In patients treated with Vitamin E, we observed P3 latency increments (delta) by 11.8 ± 1.8 ms in Group I and by 12.8 ± 2.8 ms in Group II at 6 months; neuropsychologic test scores significantly worsened at 6 months (p < 0.001) in Group II patients. Donepezil induced significant P3 latency reductions (11.2 ± 2.4 ms) in nine patients of Group I and all patients of Group II (16.1 ± 4.0 ms), reaching a maximum at 3 months (23.2 ± 2.7 ms). Alzheimer's Disease Assessment Scale-Cognition and Wechsler Adult Intelligence Scale scores improved during the same period, and the difference between Vitamin E and DPZ treated patients was highly significant for P3 (analysis of variance) and for P3-Alzheimer's Diseases Assessment Scale-Cognition (analysis of covariance) with p < 0.001 for pooled groups of patients with AD and Group II (DPZ) versus Group II (Vitamin E). Combined P3 event related potentials measurements, neuropsychologic test comparison evidences significant effects of DPZ in mild and in moderate–severe AD.
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