Tenney, S. | Search bioRxiv

bioRxiv2025

Impact of chronic alcohol and stress on mid-life cognition and locus coeruleus integrity

BackgroundExcessive alcohol consumption and stress are associated with structural and functional alterations in the brain and impaired cognition. However, the persistence of long-term neural impacts after alcohol and stress are less understood. This study investigated midlife cognition and neuropathological changes following a history of alcohol and stress exposure. MethodsC57BL/6J mice acclimated to ethanol drinking (15% v/v) before exposure to four cycles of alternating chronic intermittent ethanol (CIE) vapor exposure and repeated forced swim stress (FSS), with control groups exposed to air and no stress (AIR/NS). After three months of abstinence, mice were evaluated at midlife (11 months old) on volitional drinking and a final CIE/FSS challenge for stress induced drinking. Spatial learning and cognitive flexibility were assessed using the Barnes maze before brains were collected to evaluate locus coeruleus integrity at 12 months old. ResultsCIE/FSS increased volitional alcohol intake, and this drinking phenotype persisted through to midlife despite extended abstinence. CIE/FSS mice showed intact spatial learning but impaired flexibility in the Barnes maze reversal phase. Flexibility impairments were driven by decreased time in the target quadrant and increased errors during the reversal test compared to AIR/NS. Furthermore, CIE/FSS mice showed pathological measures of reduced locus coeruleus integrity common to dementia related disorders, including elevated markers of oxidative stress, apoptosis and reduced autoinhibitory function. ConclusionsOur findings highlight the long-lasting impact of alcohol and stress exposure on cognition, with flexibility impairments persisting into midlife. In addition to cognitive changes, alcohol and stress history produced pathological changes in the locus coeruleus, an area known to mediate cognitive flexibility via its forebrain projections. Together, these results give an insight into the long-lasting impacts of chronic alcohol and stress and how they may accelerate age-related cognitive decline.

neuroscience↗

bioRxiv2025

Fluid shear stress promotes glial-mediated neurotoxicity in vitro via purinergic signaling

Interstitial fluid flow plays a critical role in maintaining function and homeostasis in neural tissue, and dysregulation of this flow due to injury or disease results in mechanical stress that is associated with several neuropathologies, including traumatic brain injury, ischemic stroke, and glioma. Glial cells such as astrocytes and microglia are known to respond to mechanical forces like fluid shear stress but the impact of this stress on their functionality and any subsequent impact on neurons remains poorly defined. To investigate how pathologically high fluid shear stress modulates astrocyte and microglia function and to determine whether glial responses to fluid shear influence neuronal survival and morphology, we applied low pathological levels of fluid shear stress (0.1 dynes/cm2) to cultured human astrocytes and microglia and assessed functional changes including metabolic activity, metabolite release, lipid droplet accumulation, and phagocytic activity. Conditioned media from these glia were then applied to differentiated SH-SY5Y neurons to evaluate effects on cell survival and neurite outgrowth. We then focused on identifying the soluble factor mediating the observed neurotoxicity. We found that fluid shear stress promotes distinct functional responses in astrocytes and microglia, including increased metabolic activity in astrocytes, increased lipid droplet accumulation in microglia, and heightened release of extracellular ATP in both cell types. Exposure to shear-conditioned glial media significantly reduced neuronal survival and neurite length. This neurotoxic effect was abolished by activated charcoal filtration but not by boiling and was prevented through P2x7 receptor inhibition in neurons, suggesting extracellular ATP as a causative agent. These findings indicate that high fluid shear stress promotes glial-mediated neurotoxicity via purinergic signaling. This study helps to characterize glial-neuronal mechanobiological interaction in the context of neuropathology and provides support for targeting purinergic signaling pathways as a therapeutic approach for neuropathologies associated with altered interstitial fluid flow. Statement of significanceGlial cells, until recently merely considered to support neurons, are now known to play critical roles in neural tissue development and function. Astrocytes and microglia play diverse roles in the central nervous system, adopting phenotypes that both promote and resolve pathology. Within brain tissue, disruptions to interstitial fluid flow are associated with brain injury, ischemic stroke, and glioma. This study identifies fluid shear stress as a modulator of glial cell function with downstream neurotoxic consequences. Namely, we found that increased release of extracellular ATP by glial cells under high shear promotes neurotoxicity via P2x7 receptor signaling. These findings help to characterize mechanobiological glial-neuronal communication and lend support for the therapeutic efficacy of P2x7 receptor inhibition in the treatment of neuropathology.

bioengineering↗