Biology subjects

Marrelli, S. P.

Publications and source records attributed to Marrelli, S. P..

9 recordsLinked to original sources

bioRxiv2026

Capsinoids (non-pungent TRPV1 agonists) promote mild hypothermia and improved outcome following stroke in aged mice

Background and PurposeMild hypothermia provides potent neuroprotection in experimental ischemic stroke, however, its implementation in awake stroke patients is hampered by the induction of intense shivering and inconsistent body temperature control. Pharmacological activation of peripheral/peritoneal TRPV1 channels with non-pungent capsinoids offers a means to induce hypothermia while minimizing TRPV1 activation in the injury region. We tested whether capsinoid-mediated mild hypothermia, initiated within the post-stroke period, reduces brain injury and improves functional outcomes in aged mice. MethodsAged (18-20 months) male and female C57BL/6 mice underwent either permanent distal middle cerebral artery (MCA) occlusion (pdMCAO) or 60-minute MCA occlusion/reperfusion (MCAO/R). At 2 or 4 hours after stroke, mice received intraperitoneal injections of vehicle or capsinoids (>97% purity; 40 mg/kg) every 90 minutes to induce mild hypothermia for 4.5-6 hours. Core temperature was monitored by wireless probe. After pdMCAO, infarct volume was quantified at post-stroke day 3 (PSD3) by TTC and brain atrophy at PSD30 by iodine-enhanced microCT; sensorimotor function (DigiGait, forelimb grip strength, foot fault) was assessed at PSD7 and PSD30. Survival was the primary measured outcome for MCAO/R. ResultsCapsinoids induced a rapid and sustained reduction in core temperature of 2-4{degrees}C, independent of sex. In the pdMCAO model, capsinoid-induced hypothermia reduced infarct volume by 48% at PSD3 and decreased chronic cortical tissue loss by 44% at PSD30. Capsinoid-treated mice showed significant improvements in gait, grip strength, and contralateral foot fault performance at PSD7 and PSD30. In the MCAO/R model, survival was significantly higher in capsinoid-treated mice (80%) versus vehicle controls (33%) through PSD3. ConclusionsIntraperitoneal capsinoid administration after stroke induces mild hypothermia in aged mice and confers robust acute neuroprotection and improved chronic functional outcome and survival. These preclinical findings add support for the use of capsinoids as a means to target peripheral thermoeffectors for promoting neuroprotective hypothermia in conscious stroke subjects.

neuroscience↗

bioRxiv2026

Repeated Mild Head Injury Establishes a Senescent Cranial Bone Marrow Niche that Impairs Brain Metabolism

Traumatic brain injury (TBI) of any severity is associated with long-term systemic inflammation and increased risk of peripheral comorbidities, yet the mechanisms driving immune dysregulation and accelerated aging after repeated mild head impacts remain poorly defined. Here, we investigated the acute and chronic effects of repeated mild TBI (rmTBI) on distal and proximal bone marrow compartments in the femur and calvaria, respectively. Using a modified weight-drop mouse model delivering rotational and acceleration-deceleration forces (3 hits/week for up to 16 weeks), rmTBI produced no mortality, skull fracture, hemorrhage, or brain leukocyte infiltration. One day after three consecutive impacts, rmTBI induced robust proliferation of LSK stem/progenitor cells in both femoral and calvarial marrow, evidenced by Ki67 expression, BrdU incorporation, and increased monocyte output. By 8 weeks (24 impacts), injury-induced proliferation subsided and LSK cells exhibited increased senescence-associated {beta}-galactosidase activity and upregulation of tumor suppressor genes. At 16 weeks (48 impacts), LSK populations were depleted at both sites, displaying reduced proliferative capacity, telomere shortening, and pancytopenia in otherwise young adult mice. Calvarial bone marrow cells exposed to rmTBI released a distinct cytokine and proteomic secretome marked by elevated IL-6, suppressed mitochondrial and metabolic signaling, and enhanced DNA repair pathways. Notably, skull-derived secretome factors impaired cortical and hippocampal mitochondrial metabolism, and reduced microglial mitochondrial membrane potential. Together, these findings identify replicative senescence of the brain-adjacent bone marrow niche as an early and progressive consequence of repeated mild head injury, linking rmTBI to long-lasting metabolic dysfunction, impaired immunity, and accelerated aging. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/699107v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@683c8eorg.highwire.dtl.DTLVardef@15fc42forg.highwire.dtl.DTLVardef@48f398org.highwire.dtl.DTLVardef@170bbcc_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2025

Neuropathological hallmarks during the chronic phase of ischemic stroke in mice and humans

BackgroundImprovements in acute stroke treatment, including endovascular thrombectomy and critical care management, have increased survival rates post-stroke. However, stroke remains a leading cause of long-term disability and many survivors have significant neurological and cognitive deficits. Despite this, the chronic neurological sequelae and underlying secondary injury mechanisms induced by ischemic stroke remain understudied. MethodsThis study examined long-term neurobehavioral recovery and neuropathology at 2- and 6- months post-stroke in young (12-week-old) male C57Bl/6 mice after a 60-minute transient middle cerebral artery occlusion (MCAO) or sham surgery. Behavioral testing included the open field test (OFT), novel object recognition test (NORT), fear conditioning (FC), nesting activity, and tail suspension. Post-mortem brain samples from patients with chronic ischemic stroke were also assessed. Immunohistochemistry (IHC) was performed to assess demyelination (MBP), neuronal apoptosis (TUNEL), and A{beta}42 in human brains. Flow cytometric analysis was performed to assess microglial phenotypes, the chronic neuroimmune landscape, and to evaluate senescent-like phenotypes (SA-{beta}Gal and lipofuscin). Transcriptomic profiling was performed using RNA isolated from the ipsilateral hemisphere in stroke mice. ResultsExperimental stroke caused progressive cognitive and motor decline up to 6 months post-MCAO. IHC and flow cytometric analyses revealed a significant increase in TUNEL-positive neurons, cortical and hippocampal gliosis, white matter degradation, senescent cell accumulation, and altered microglial function. IHC analysis of postmortem human brains shows significantly increased levels of microgliosis, senescent cells and amyloid burden. Transcriptomic analysis revealed that pathways involving apoptosis, microglial activation and the complement pathway were chronically upregulated after stroke. ConclusionOur findings demonstrate that ischemic stroke induces a non-resolving microglial response and accelerated inflamm-aging in the brain, evidenced by premature senescence and elevated production of cytokines within the chronic infarct microenvironment. Senescent-like phenotypes and chronic neurodegenerative disease signatures may contribute to the progressive worsening of cognitive function post-stroke. These results suggest that chronic, ongoing neurodegeneration occurs late after stroke, even in younger mice. Mitigating these detrimental changes may offer viable targets for delayed treatment strategies for stroke.

neuroscience↗

bioRxiv2024

Serum metabolome profiling in patients with mild cognitive impairment reveals sex differences in lipid metabolism

Alzheimers disease (AD) affects more women than men. Although women live longer than men, it is not longevity alone, but other factors, including metabolic changes, that contribute to the higher risk of AD in women. Metabolic pathways have been implicated in AD progression, but studies to date examined targeted pathways, leaving many metabolites unmeasured. Sex is often a neglected biological variable, and most metabolomic studies were not designed to investigate sex differences in metabolomic profiles. Here, we performed untargeted metabolomic profiling of sera from male and female patients with mild cognitive impairment (MCI), a common precursor to AD, and matched controls. We discovered significant metabolic changes in individuals with MCI, and found several pathways that were strongly associated with sex. Peptide energy metabolism demonstrated sexual dimorphism. Lipid pathways exhibited the strongest differences between female and male MCI patients, including specific phosphatidylcholine lipids, lysophospholipids, long-chain fatty acids, and monoacylglycerols. 1-palmitoleoyl glycerol and 1-arachidonoyl glycerol were higher in female MCI subjects than in male MCI subjects with no differences between control males and females. Conversely, specific dicarboxylic fatty acids were lower in female MCI subjects than male MCI subjects. In cultured astrocytes, 1-arachidonoyl glycerol promoted phosphorylation of the transcriptional regulator sphingosine kinase 2, which was inhibited by the transient receptor potential vanilloid 1 receptor antagonists, as well as chromatin remodelling. Overall, we identified novel sex-specific metabolites in MCI patients that could serve as biomarkers of MCI in both sexes, help further define AD etiology, and reveal new potential prevention strategies for AD. Highlights{blacksquare} Individuals with MCI experience significant metabolic changes. {blacksquare}Lipid pathways demonstrated the strongest sexual dimorphism in MCI. {blacksquare}1-monoacylglycerols showed a robust sex association, being higher in MCI females. {blacksquare}Sex-specific metabolites may be MCI biomarkers in each sex.

neuroscience↗

bioRxiv2024

MEK signaling represents a viable therapeutic vulnerability of KRAS-driven somatic brain arteriovenous malformations

Brain arteriovenous malformations (bAVMs) are direct connections between arteries and veins that remodel into a complex nidus susceptible to rupture and hemorrhage. Most sporadic bAVMs feature somatic activating mutations within KRAS, and endothelial-specific expression of the constitutively active variant KRASG12D models sporadic bAVM in mice. By leveraging 3D-based micro-CT imaging, we demonstrate that KRASG12D-driven bAVMs arise in stereotypical anatomical locations within the murine brain, which coincide with high endogenous Kras expression. We extend these analyses to show that a distinct variant, KRASG12C, also generates bAVMs in predictable locations. Analysis of 15,000 human patients revealed that, similar to murine models, bAVMs preferentially occur in distinct regions of the adult brain. Furthermore, bAVM location correlates with hemorrhagic frequency. Quantification of 3D imaging revealed that G12D and G12C alter vessel density, tortuosity, and diameter within the mouse brain. Notably, aged G12D mice feature increased lethality, as well as impaired cognition and motor function. Critically, we show that pharmacological blockade of the downstream kinase, MEK, after lesion formation ameliorates KRASG12D-driven changes in the murine cerebrovasculature and may also impede bAVM progression in human pediatric patients. Collectively, these data show that distinct KRAS variants drive bAVMs in similar patterns and suggest MEK inhibition represents a non-surgical alternative therapy for sporadic bAVM.

molecular biology↗

bioRxiv2023

Astrocytic Slc4a4 regulates blood-brain barrier integrity in healthy and stroke brains via a NO-CCL2-CCR2 pathway

Astrocytes play vital roles in blood-brain barrier (BBB) maintenance, yet how they support BBB integrity under normal or pathological conditions remains poorly defined. Recent evidence suggests pH homeostasis is a new cellular mechanism important for BBB integrity. In the current study, we investigated the function of an astrocyte-specific pH regulator, Slc4a4, in BBB maintenance and repair. We show that astrocytic Slc4a4 is required for normal astrocyte morphological complexity and BBB function. Multi-omics analyses identified increased astrocytic secretion of CCL2 coupled with dysregulated arginine-NO metabolism after Slc4a4 deletion. Using a model of ischemic stroke, we found that loss of Slc4a4 exacerbates BBB disruption and reactive gliosis, which were both rescued by pharmacological or genetic inhibition of the NO-CCL2 pathway in vivo. Together, our study identifies the astrocytic Slc4a4-NO-CCL2 axis as a pivotal mechanism controlling BBB integrity and repair, while providing insights for a novel therapeutic approach against BBB-related CNS disorders.

neuroscience↗

bioRxiv2021

A low-cost mouse cage warming system provides improved intra-ischemic and post-ischemic body temperature control &ndash: application for reducing variability in experimental stroke studies

Experimental guidelines have been proposed to improve the rigor and reproducibility of experimental stroke studies in rodents. As brain temperature is a strong determinant of ischemic injury, tight management of brain or body temperature (Tcore) during the experimental protocol is highly recommended. However, little guidance is provided regarding how or for how long temperature support should be provided. We compared a commonly used heat support method (cage on heating pad) with a low-cost custom built warm ambient air cage (WAAC) system. Both heat support systems were evaluated for the middle cerebral artery occlusion (MCAo) model in mice. The WAAC system provided improved temperature control (more normothermic Tcore and less Tcore variation) during the intra-ischemic period (60 min) and post-ischemic period (3 hrs). Neurologic deficit score showed significantly less variance at post-stroke day 1 (PSD1) in WAAC system mice. Mean infarct volume was not statistically different by heat support system, however, standard deviation was 54% lower in the WAAC system group. In summary, we provide a simple low-cost heat support system that provides superior Tcore management in mice during the intra-ischemic and post-ischemic periods, which results in reduced variability of experimental outcomes. HighlightsO_LIWe describe the fabrication of a low-cost mouse cage warming system (warmed ambient air cage; WAAC system) that can be assembled and applied in any stroke laboratory. C_LIO_LIThe WAAC system provides more precise control of post-stroke mouse body temperature compared with traditional heating pad warming system. C_LIO_LIThe more precise control of post-stroke core temperature reduces variability in some experimental measures in more severely injured mice. C_LI

neuroscience↗

bioRxiv2020

Cortical stroke produces secondary injury and long-lasting gliosis in the ipsilateral thalamus

Remote secondary injury in the thalamus has been observed following cortical infarct, however the mechanisms are not well understood. We used the distal MCAO stroke model (pdMCAO) to explore the cellular and temporal gliosis response in secondary thalamic injury in mice. At 3 days post-stroke (PSD3), primary infarct was limited to the cortex, with no infarct in the thalamus. However, at 2 weeks after stroke (PSD14), the ipsilateral thalamus demonstrated degenerating and severely damaged neurons. Staining for GFAP (astrogliosis) or IBA-1 (microgliosis) was first apparent in the ipsilateral thalamus by PSD3, and showed a progressive increase through PSD14. The number of activated microglia was increased within the thalamus at PSD14, reflecting proliferation of resident microglia as well as infiltration of peripheral monocytes. Interestingly, astrogliosis within the thalamus was enduring, as it was still evident at two years post-stroke. Furthermore, the astrogliosis at two years (but not at 6 weeks) demonstrated glial scar-like characteristics. Lastly, we demonstrated that post-stroke treatment with an NMDA receptor antagonist (memantine) reduces gliosis in the thalamus at PSD14. These findings highlight the development of lasting secondary injury in the thalamus following cortical stroke and support the value of memantine treatment in the mitigation of this injury.

neuroscience↗

bioRxiv2017

A Novel Reporter Allele For Monitoring Dll4 Expression Within The Embryonic And Adult Mouse

Canonical Notch signaling requires the presence of a membrane bound ligand and a corresponding transmembrane Notch receptor. Receptor engagement induces multiple proteolytic cleavage events culminating in the nuclear accumulation of the Notch intracellular domain and its binding to a transcriptional co-factor to mediate gene expression. Notch signaling networks are essential regulators of vascular patterning and angiogenesis, as well as myriad other biological processes. Delta-like 4 (Dll4) encodes the earliest Notch ligand detected in arterial cells, and is enriched in sprouting endothelial tip cells. Dll4 expression has often been inferred by proxy using a lacZ knockin reporter allele. This is problematic, as a single copy of Dll4 is haploinsufficient. Additionally, Notch activity regulates Dll4 transcription, making it unclear whether these reporter lines accurately reflect Dll4 expression. Accordingly, accurately defining Dll4 expression is essential for determining its role in development and disease. To address these limitations, we generated a novel BAC transgenic allele with a nuclear-localized {beta}-galactosidase reporter (Dll4-BAC-nlacZ). Through a comparative analysis, we show the BAC line overcomes previous issues of haploinsufficiency, it recapitulates Dll4 expression in vivo, and allows superior visualization and imaging. As such, this novel Dll4 reporter is an important addition to the growing Notch toolkit.\n\nSummary Statement:\n\nWe have developed a novel reporter line, free from complicating factors associated with previous alleles, for monitoring Dll4 expression, at a cellular resolution, in the developing and adult mouse.

developmental biology↗