Biology subjects

Fleury, S.

Publications and source records attributed to Fleury, S..

8 recordsLinked to original sources

bioRxiv2026

cGAS integrates Toll-like receptor signaling in platelets to promote thromboinflammation

Thromboinflammation is driven by innate immune signaling and promotes tissue injury during sepsis. Activation of platelets by bacterial products and alarmins amplifies inflammation, coagulation, and thrombotic dysfunction. However, the mechanisms by which these diverse inflammatory signals converge to elicit common platelet responses remain largely undefined. Mitochondria are key integrators of cellular stress responses and can activate innate immune pathways through the release of mitochondrial DNA and engagement of the DNA sensor cGAS. We therefore hypothesized that stimulation of innate immune receptors generates endogenous cGAS ligands within platelets, providing a unifying mechanism by which distinct inflammatory cues converge on cGAS-STING signaling. Here, we demonstrate that activation of TLR4, TLR1/2, and TLR5 engages a platelet-intrinsic mtDNA-cGAS-STING axis that promotes platelet activation. In a model of endotoxemia, genetic deletion of cGAS reduced platelet activation, thrombocytopenia, pyroptosis and the early systemic inflammatory response. Platelet transfer experiments further established that platelet-intrinsic cGAS is sufficient to amplify inflammatory responses in vivo. Mechanistically, we demonstrated that cytosolic accumulation of mtDNA and activation of cGAS-STING signaling pathway in platelets are dependent on mitochondrial calcium uniporter (MCU) and correlated with the loss of mitochondrial membrane potential and the production of mitochondrial reactive oxygen species. In contrast, canonical platelet agonists activated platelets independently of cGAS and failed to induce substantial cytosolic mtDNA accumulation. Importantly, this signaling architecture was conserved in human platelets, where TLR1/2-mediated activation required MCU- and STING-dependent signaling, whereas responses to thrombin receptor-activating peptide and collagen-related peptide remained largely unaffected. Together, these findings identify cGAS as an intracellular signal integration node that allows diverse innate immune receptors to converge on a common platelet activation pathway through sensing of mitochondria-derived DNA, allowing a rapid platelet response to microbial products.

cell biology↗

bioRxiv2026

Identifying factors that contribute to the behavioral effects of psilocybin in preclinical mouse models

Psychedelic drugs offer a potentially promising avenue for novel therapeutics for the treatment of psychiatric conditions, including for mood and anxiety disorders. Emerging clinical studies have prompted increased preclinical research into mechanisms of action. However, post-acute behavioral outcomes in rodents remain inconsistent and difficult to reproduce across laboratories. To address this, we collected a large dataset of behavioral responses to psilocybin in mice (N=693) and used data-driven analyses to identify biological and experimental factors that modulated behavioral readouts. We examined the effects of sex, age, strain, stress protocol, and 5-HT1B signaling on the response to a single high dose of psilocybin measured in acute (head twitch responding and locomotion) or post-acute (sucrose preference, elevated plus maze, novelty-suppressed feeding) behavioral outcomes. We found that psilocybin displays a robust acute behavioral response and a more variable post-acute behavioral profile with a most robust response in sucrose preference. Sex, stress model, and 5-HT1BR activation emerged as key modulators of post-acute antidepressant-like and anxiolytic effects. Random forest classification was narrowly able to predict drug treatment based on post-acute behavioral outcomes and biological and experimental factors. These findings suggest that the heterogeneity seen in the response to psilocybin in mice reflects meaningful biological and experimental variables. Accounting for these factors may enhance translational relevance by identifying the conditions under which therapeutic-like effects are most robust and can support more reproducible models for understanding the neural mechanisms underlying the persisting behavioral effects of psilocybin.

neuroscience↗

bioRxiv2025

Localized immunomodulation with cytokine-producing cells to mitigate host immune rejection responses in rodents and a non-human primate

The efficacy of cell-based therapeutics is often compromised by host immune recognition of implanted cells and biomaterials, resulting in fibrotic encapsulation and loss of function. Here, we address this challenge with an immunomodulatory cell-based therapy, in which alginate-encapsulated retinal pigment epithelial cells continuously secrete cytokines to locally modulate the implant microenvironment. In a healthy rodent model, the localized production of interleukin-10 (IL-10) or IL-12 from encapsulated cytokine-producing cells prevented host immune rejection and fibrosis of alginate capsules. Mechanistically, treatment was associated with reduced expression of pro-fibrotic genes and immune shifts consistent with macrophage and T-cell regulation, supporting a cytokine-mediated mitigation of foreign body response. In a diabetic murine model (streptozotocin-induced C57BL/6J), co-implantation of human islets with IL-10-producing cells attenuated pericapsular fibrosis, preserved islet viability, and restored normoglycemia for up to 100 days (4.76 times longer than islets alone). Significantly, IL-10-producing cells were also effective in enabling the durability and function of encapsulated cells in a healthy non-human primate, showing translational feasibility. Collectively, these findings suggest that localized cytokine delivery can reduce fibrotic encapsulation and support durable graft function, offering a path to lessen reliance on systemic immunosuppression in islets transplantation and other implantable biomaterial therapies. TeaserEncapsulated IL-10-producing cells locally suppress fibrosis and extend graft function in rodent models and a non-human primate.

bioengineering↗

bioRxiv2025

Evidence for age-related vulnerability in dopamine-glutamate projections to the lateral entorhinal cortex

The lateral entorhinal cortex (LEC) supports novelty detection and episodic memory and is selectively vulnerable to aging. Dopamine signals novelty in LEC, but how aging alters this input is unclear. Using intersectional viral strategies to distinguish ventral tegmental area (VTA) dopamine neurons with or without glutamate co-release, we find that co-releasing neurons are a minority ([~]30%) in the VTA, yet provide [~]93% of the dopaminergic projections to LEC. In aged mice, dopamine-glutamate labeling in VTA and LEC decreases [~]80%, whereas pan-dopaminergic labeling of LEC axons remains, consistent with functional silencing rather than degeneration. In LEC dopaminergic axons, dopamine synthesis is reduced while glutamate vesicular packaging is relatively spared. Optogenetic stimulation combined with a dopamine sensor reveals diminished dopamine release at high frequencies, when synthesis demand is greatest. These findings identify selective vulnerability of dopamine-glutamate neurons as a cell- and circuit-specific mechanism that weakens dopamine signaling within memory circuits.

neuroscience↗

bioRxiv2024

The non-hallucinogenic serotonin 1B receptor is necessary for the antidepressant-like effects of psilocybin in mice

Recent studies highlight the promising use of psychedelic therapies for psychiatric disorders, including depression. The persisting clinical effects of psychedelics such as psilocybin are commonly attributed to activation of the serotonin 2A receptor (5-HT2AR) based on its role in the acute hallucinatory effects. However, the active metabolite of psilocybin binds to many serotonin receptor subtypes, including the serotonin 1B receptor (5-HT1BR). Given the known role of 5-HT1BR in mediating depressive phenotypes and promoting neural plasticity, we hypothesized that it mediates the effects of psilocybin on neural activity and behavior. We first examined the acute neural response to psilocybin in mice lacking 5-HT1BR. We found that 5-HT1BR expression influenced brain-wide activity following psilocybin administration, measured by differences in the patterns of the immediate early gene c-Fos, across regions involved in emotional processing and cognitive function, including the amygdala and prefrontal cortex. Functionally, we demonstrated that 5-HT1BR mediates some of the acute and persisting behavioral effects of psilocybin. Although there was no effect of 5-HT1BR expression on the acute head twitch response, mice lacking 5-HT1BRs had attenuated hypolocomotion to psilocybin. We also measured the persisting effects of psilocybin on anhedonia and anxiety-like behavior using transgenic and pharmacological 5-HT1BR loss-of-function models and found that 5-HT1B is involved in mediating the decreased anhedonia and reduced anxiety-like behavior. Finally, using a network analysis, we identified neural circuits through which 5-H1BR may modulate the response to psilocybin. Overall, our research implicates the 5-HT1BR, a non-hallucinogenic serotonin receptor, as a mediator of the behavioral and neural effects of psilocybin in mice.

neuroscience↗

bioRxiv2023

Role of Dopamine Neurons in Familiarity

Dopamine neurons signal the salience of environmental stimuli, influencing learning and motivation. However, research has not yet identified whether dopamine neurons also modulate the salience of memory content. Dopamine neuron activity in the ventral tegmental area (VTA) increases in response to novel objects and diminishes as objects become familiar through repeated presentations. We proposed that the declined rate of dopamine neuron activity during familiarization affects the salience of a familiar objects memory. This, in turn, influences the degree to which an animal distinguishes between familiar and novel objects in a subsequent novel object recognition (NOR) test. As such, a single familiarization session may not sufficiently reduce dopamine activity, allowing the memory of a familiar object to maintain its salience and potentially attenuating NOR. In contrast, multiple familiarization sessions could lead to more pronounced dopamine activity suppression, strengthening NOR. Our data in mice reveals that, compared to a single session, multiple sessions result in decreased VTA dopamine neuron activation, as indicated by c-Fos measurements, and enhanced novelty discrimination. Critically, when VTA dopamine neurons are chemogenetically inhibited during a single familiarization session, NOR improves, mirroring the effects of multiple familiarization sessions. In summary, our findings highlight the pivotal function of dopamine neurons in familiarity and suggest a role in modulating the salience of memory content.

animal behavior and cognition↗

bioRxiv2023

Electrocatalytic on-site oxygenation for transplanted cell-based-therapies

Implantable cell therapies and tissue transplants require sufficient oxygen supply to function and are limited by a delay or lack of vascularization from the transplant host1, 2. Exogenous oxygen production can support cells and tissues, such as pancreatic islets and engineered therapeutic cells. Previous oxygenation strategies have targeted gas circulation or decomposition of solid peroxides. These strategies however require bulky implants, transcutaneous supply lines, and are limited in their total oxygen production or regulation3, 4. Readily integrated and controlled production of oxygen has eluded cell therapy devices. Here, we show an electrocatalytic approach that enables bioelectronic control of oxygen generation in complex cellular environments to sustain engineered cell viability and therapy production under hypoxic stress and at high cell densities. Nanostructured sputtered iridium oxide serves as an ideal catalyst for oxygen evolution reaction (OER) at neutral pH. It enables a lower OER onset and shows selective oxygen production without evolution of toxic side products over a 300 mV window of operation. This electrocatalytic on site oxygenator (ecO2) can sustain high cell loadings (>60k cells/mm3) in hypoxic conditions in vitro and in vivo. Our results demonstrate that exogenous oxygen production devices can be readily integrated into bioelectronic platforms and enable high cell loadings in smaller device footprints with broad applicability.

bioengineering↗

bioRxiv2021

Single dose of amphetamine induces delayed subregional attenuation of striatal cholinergic interneuron activity

Psychostimulants such as amphetamine target dopamine neuron synapses to engender drug-induced plasticity. While dopamine neurons modulate the activity of striatal cholinergic interneurons (ChIs) with regional heterogeneity, how amphetamine affects ChI activity has not been elucidated. Here, we applied quantitative fluorescence imaging approaches to map the dose-dependent effects of a single dose of amphetamine on ChI activity at 2.5 and 24 hours after injection across the mouse striatum using the activity-dependent marker phosphorylated ribosomal protein S6 (p-rpS6). We found that amphetamine did not induce neurotoxic effects on ChIs, as their distribution and morphology were not affected. While low- or high-dose amphetamine did not affect ChI activity after 2.5 hours, ChI activity was significantly reduced in all striatal subregions after 24 hours, with a dose-dependent effect in the nucleus accumbens. Thus, our findings suggest that a single dose of amphetamine has delayed regionally heterogeneous effects on ChI activity. Significance statementUsing the activity dependent marker phosphorylated ribosomal protein S6 (p-rpS6), we mapped amphetamine effects on the activity of cholinergic interneurons (ChIs) across the striatum. Amphetamine caused a delayed attenuation of ChI activity in all striatal subregions, and a dose-dependent effect in the ventral striatum/nucleus accumbens, a critical site of psychostimulant action.

neuroscience↗