Biology subjects

Frye, J.

Publications and source records attributed to Frye, J..

4 recordsLinked to original sources

bioRxiv2026

Neuroprotective activity of sub-anesthetic ketamine in a preclinical model of Parkinson's disease is not blocked by antagonizing brain-derived neurotrophic factor signaling

Treatment with low-dose ketamine is neuroprotective in rodent models of acute damage, while high doses of ketamine can be neurotoxic. Our group has previously shown that sub-anesthetic ketamine treatment leads to long-term reduction of L-DOPA-induced dyskinesia (LID) via brain-derived neurotrophic factor (BDNF)-signaling in a rat 6-hydroxydopamine (6-OHDA) model of Parkinson's disease (PD). In this report, we investigated if sub-anesthetic ketamine is also neuroprotective in a progressive 6-OHDA model of PD via neurotrophic action through the tropomyosin receptor kinase B (TrkB) receptor. We demonstrated that ketamine-treatment (20 mg/kg, i.p.) prior to striatal administration of the neurotoxin 6-OHDA is neuroprotective, providing near complete protection against development of parkinsonian motor deficits. This robust behavioral efficacy occurred in the presence of only modest preservation of tyrosine hydroxylase (TH) striatal levels (~50-60% loss). Interestingly, based on data from an additional cohort treated with ketamine and ANA-12 (TrkB antagonist) we found that the neuroprotective effects of ketamine are not mediated by TrkB receptors. Semi-quantitative western analysis showed that the relative tyrosine hydroxylase content in the striatum was not significantly increased in ketamine-treated rats compared to vehicle. Unbiased stereology of dopamine neurons in the substantia nigra pars compacta (SNc) revealed no significant differences between any of the groups. The role of BDNF was evaluated with in situ hybridization for RNA of BDNF and TrkB. While BDNF expression was not changed, co-administration of ketamine and ANA-12 led to a significant decrease in TrkB receptor expression compared to ketamine-only on the lesioned but not the intact hemisphere in the SNc. In conclusion, we show that ketamine at the low dose currently pursued for therapeutic benefit for LID led to robust behavioral motor improvement in this rodent PD degeneration model, yet these protective effects were not driven by neurotrophic BDNF-signaling, indicating complex mechanisms are underlying neuroprotective activities of low-dose ketamine.

neuroscience↗

bioRxiv2026

ABERRANT HIPPOCAMPAL NEUROGENESIS IS A CONSERVED RESPONSE TO STROKE IN MICE: A MULTI-CENTER MULTIMODEL STUDY

BackgroundAdult hippocampal neurogenesis is markedly altered after cerebral ischemia. Although stroke increases the production of newborn neurons, many of these cells display aberrant morphological and positional features that impair their functional integration and contribute to long-term cognitive decline. Given the clinical heterogeneity of ischemic stroke and the persistent translational failures of preclinical approaches relying on single-model studies it remains unknown whether post-stroke neurogenic alterations are conserved across different experimental paradigms. This study aimed to define common and model-specific features of hippocampal neurogenesis across complementary focal ischemia models. MethodsWe performed a multi-center, multimodel analysis within the STROKE-IMPaCT consortium using permanent and transient middle cerebral artery occlusion (MCAO) paradigms (MCAO via ligation or cauterization under normoxic (dMCAO) or hypoxic conditions (dMCAO+Hypoxia); and filament-based tMCAO across six international sites. Brains from adult C57BL/6J mice were collected 3 days, 7 days, or 2 months after ischemia, sham, or naive conditions. Hippocampal cell proliferation (Ki67) and neuroblast density (DCX) were quantified, and the morphological maturation of newborn neurons was evaluated using high-resolution analyses of dendritic architecture and somatodendritic polarity. All analyses were performed blind to experimental group. ResultsAcross all stroke models, ischemia induced a robust bilateral increase in hippocampal cell proliferation, most pronounced at 3 days and still elevated at 7 days, with levels returning to baseline by 2 months. Neuroblast density was similarly increased at 7 days, particularly in the ipsilateral hippocampus, but normalized by 2 months. Despite recovery in cell number, long-term morphological analysis revealed a consistent reduction in apical dendrite length and a higher proportion of neurons exhibiting aberrant features including ectopic localization, multipolar or inverted polarity, and abnormal lateral growth across all models. These abnormalities were observed both when pooling data across sites and when analyzing each model or center individually. ConclusionsIschemia induces an early, transient increase in hippocampal neurogenesis across diverse stroke paradigms, but the newborn neurons generated after stroke consistently display maladaptive morphological features. These cross-model, cross-site abnormalities indicate that aberrant hippocampal neurogenesis represents a robust hallmark of post-stroke pathology within the investigated species, independent of ischemia type or surgical approach, despite known differences in the spatial distribution of primary injury across experimental stroke models. Our findings support the concept that maladaptive neurogenesis may contribute to chronic post-stroke cognitive impairment and underscore the need to consider the quality not only the quantity of newborn neurons when developing therapeutic strategies.

animal behavior and cognition↗

bioRxiv2025

Manual lymph drainage massage of the head and neck improves cognition and reduces pathological biomarkers in the 5x-FAD mouse model of Alzheimers disease

Alzheimers disease (AD) affects 6.9 million people over the age of 65 in the US and is expected to double by 2060. While FDA approved immunotherapies slow cognitive decline in some individuals with AD, they do not improve cognition, are costly, and have significant side-effects. Therefore, new targets, approaches, and treatments for AD are a necessity. There are no FDA approved therapies for AD that target the brains lymphatic system. It is well established that the toxic protein, amyloid-beta (A{beta}), accumulates in the AD brain. Recent studies have shown that A{beta} is cleared via interstitial fluid and cerebrospinal fluid through a pathway involving the glymphatic system--meningeal lymphatic vessels--leading to deep and superficial cervical lymphatic vessels and nodes. Therefore, any blockage along this route can cause inefficient drainage and result in pathological buildup of A{beta}, which can lead to AD. Here, we propose a new approach to treating AD by manual lymph drainage (MLD), which is a light skin massage traditionally used to reduce fluid accumulation in lymphedema. This therapy has also been demonstrated to be safe in individuals with AD, but its effects on cognition and biomarkers of AD has never been investigated. In this study we demonstrate that repeated MLD of the head and neck, including the superficial cervical lymphatic vessels (scLVs), improves cognitive function in AD as measured in both the Y-maze and nest-building tests. We also show that this coincides with a reduction in plasma levels of neurofilament light chain (NfL), a non-specific biomarker for neuronal cell death and axonal damage. MLD was also shown to reduce A{beta} in the hippocampus of these mice. Combined, this data provides compelling proof-of-principle evidence for the potential of MLD as a standalone or adjunct therapy in the treatment of AD.

neuroscience↗

bioRxiv2018

Liquefaction of the brain following stroke shares a similar molecular and morphological profile with atherosclerosis and mediates secondary neurodegeneration in an osteopontin dependent mechanism

Here we used mouse models of heart and brain ischemia to compare the inflammatory response to ischemia in the heart, a protein rich organ, to the inflammatory response to ischemia in the brain, a lipid rich organ. We report that ischemia-induced inflammation resolves between 1 and 4 weeks in the heart compared to between 8 and 24 weeks in the brain. Importantly, we discovered that a second burst of inflammation occurs in the brain between 4 and 8 weeks following ischemia, which coincided with the appearance of cholesterol crystals within the infarct. This second wave shares a similar cellular and molecular profile with atherosclerosis and is characterized by high levels of osteopontin (OPN) and matrix metalloproteinases (MMPs). In order to test the role of OPN in areas of liquefactive necrosis, OPN-/- mice were subjected to brain ischemia. We found that at 7 weeks following stroke, the expression of pro-inflammatory proteins and MMPs was profoundly reduced in the infarct of the OPN-/- mice, although the number of cholesterol crystals was increased. OPN-/- mice exhibited faster recovery of motor function and a higher number of neuronal nuclei (NeuN) positive cells in the peri-infarct area at 7 weeks following stroke. Based on these findings we propose that the brain liquefies after stroke because phagocytic cells in the infarct are unable to efficiently clear cholesterol rich myelin debris, and that this leads to the perpetuation of an OPN-dependent inflammatory response characterized by high levels of degradative enzymes.\n\nSignificance StatementThe inflammatory response to ischemia in the brain is different to the response to ischemic injury in other organs. In the brain, and for unknown reasons, dead tissue liquefies in response to ischemia by the process of liquefactive necrosis. However, the data we present here demonstrate that there is overlap between the pathophysiology of liquefactive necrosis and atherosclerosis. Specifically, we show that chronic stroke infarcts contain foamy macrophages, cholesterol crystals, high levels of OPN and MMPs, and a similar cytokine profile to atherosclerosis. Therefore, because cholesterol is a central component of myelin, liquefactive necrosis in response to stroke may be caused by an inflammatory response to cholesterol-rich myelin debris that is driven in large part by OPN and MMPs.

neuroscience↗