Biology subjects

Gosselet, F.

Publications and source records attributed to Gosselet, F..

3 recordsLinked to original sources

bioRxiv2025

Vitamin D differentially modulates effector and regulatory T-cell migration across the blood-brain barrier

Multiple sclerosis (MS) is an inflammatory disease of the CNS influenced by a combination of genetic predisposition and environmental factors. Vitamin D (VitD) deficiency is considered a major risk factor for MS. While VitD is associated with immunomodulatory roles, the exact mechanisms by which VitD protects from disease are still largely unknown. CD4 T cells play a key role in MS pathogenesis with autoimmune effector T cells (Teff) infiltrating the CNS across the blood-brain barrier (BBB) and regulatory T cells (Treg) displaying impaired functions. Here we show that treatment of human CD4 T cells with the active form of VitD (1,25-Dihydroxyvitamin D3; 1,25(OH)2D3) decreased cell-surface expression of 4{beta}1- and L{beta}2-integrins on Teff but not Treg and reduced Teff adhesion to their endothelial ligands VCAM-1 and ICAM-1. By employing live cell imaging, we observed that VitD treatment reduced arrest of Teff but not Treg to the BBB as well as ICAM-1 and VCAM-1 under physiological flow in vitro and differentially affected post-arrest behaviour of Teff versus Treg on the BBB under physiological flow. Furthermore, VitD treatment favoured the migration of Treg over Teff across the BBB under static and flow conditions in vitro. In vivo live cell imaging showed that VitD reduced T cell arrest on the inflamed BBB during autoimmune neuroinflammation. Finally, VitD also reduced expression of integrins mediating CNS homing on pathogenic CD4 T cells isolated from the CSF of persons with MS (PwMS). As VitD treatment did not alter barrier properties or adhesion molecule profile of our BBB model we propose a beneficial effect of VitD supplementation in PwMS by reducing CNS trafficking of pro-inflammatory T cells while leaving CNS entry of Treg unaffected.

immunology↗

bioRxiv2023

A small molecule cocktail for robust induction of blood-brain barrier properties

Blood-brain barrier (BBB) models derived from human stem cells are powerful tools to improve our understanding of cerebrovascular diseases and to facilitate drug development for the human brain. Yet providing stem cell-derived endothelial cells with the right signaling cues to acquire BBB characteristics while also retaining their vascular identity remains challenging. Here, we show that the simultaneous activation of cyclic AMP and Wnt/{beta}-catenin signaling, and inhibition of the TGF-{beta} pathway in endothelial cells robustly induce BBB properties in vitro. To target this novel interaction, we present a small molecule cocktail named cARLA, which synergistically enhances barrier tightness in a range of BBB models across species. Mechanistically, we reveal that the three pathways converge on Wnt/{beta}-catenin signaling to mediate the effect of cARLA via the tight junction protein claudin-5. We demonstrate that cARLA shifts the gene expressional profile of human stem cell-derived endothelial cells towards the in vivo brain endothelial signature, with a higher glycocalyx density and efflux pump activity, lower rates of endocytosis and a characteristic endothelial response to proinflammatory cytokines. Finally, we illustrate how cARLA can improve the predictive value of human BBB models regarding the brain penetration of drugs and targeted nanoparticles. Due to its synergistic effect, high reproducibility and ease of use, cARLA has the potential to advance drug development for the human brain by improving BBB models across laboratories. Significance StatementThe blood-brain barrier (BBB) hinders drug delivery to the brain and is implicated in neurological diseases. To better understand these processes in humans, there is a need for culture models that mimic the complexity of the BBB. However, state-of-the-art human BBB models either suffer from a non-physiological, mixed epithelial-endothelial identity or have weak barrier tightness, which greatly limits their usability. We identified a molecule combination that synergistically enhances barrier tightness in several in vitro models and induces complex BBB properties in human stem cell-derived endothelial cells by targeting a novel link between three signaling pathways. The molecule combination has the potential to improve BBB culture models across laboratories to advance both basic research and drug development for the human brain.

bioengineering↗

bioRxiv2020

Endothelial iron homeostasis regulates BBB integrity via the HIF2α-Ve-cadherin pathway

The blood-brain barrier (BBB) serves as the guardian of the CNS, tightly regulating the movement of ions, molecules, and cells between the circulatory system and brain. This barrier is critical in maintaining brain homeostasis, allowing proper neuronal function and protecting the brain from injury and disease. Chronic and acute exposure to various chemicals lead to BBB breakdown through pathways that are also affected in neurological diseases. Therefore, we have created an in-vitro BBB injury model to gain a better understanding of the mechanisms controlling BBB integrity. This model exposes a co-culture of human stem-cell derived brain-like endothelial cells (BLEC) and brain pericytes that mimic the BBB, to the organophosphate paraoxon. This exposure results in rapid lipid peroxidation, initiating a ferroptosis-like process and leading to endothelium cell toxicity. Mitochondrial ROS formation (MRF) and increase in mitochondrial membrane permeability (MMP), which occur 8 - 10 h post paraoxon-induced injury, also trigger apoptotic cell death. Yet, these processes do not directly result in damage to barrier functionality since blocking them does not reverse the increased permeability. Looking for a crucial pathway affecting barrier functionality we analyzed the iron homeostasis in our model since the iron chelator, Desferal(C) (DFO) rescued endothelial cell viability. Upon BBB insult, the liable iron pool (LIP) is rapidly increased, preventing the increased expression of the stress related hypoxia-induced factor 2 (HIF2) transcription factor. This results in a decrease in surface expression of the adherens junction and permeability master regulator protein, Ve-cadherin, ultimately damaging BBB integrity. Unlike the apoptosis inhibitor ZVAD that rescues BLEC from cell toxicity, yet exacerbates damage to the barrier functionality, DFO significantly decreases MRF and apoptosis subsequent to PX exposure, while also rescuing barrier integrity by inhibiting the liable iron pool increase, inducing HIF2 expression and preventing the degradation of Ve-cadherin on the cell surface. Moreover, the novel nitroxide JP4-039 significantly rescues both injury-induced endothelium cell toxicity and barrier functionality. Collectively, we have elucidated the cellular processes initiated by chemical injury to the endothelium barrier that result in cell toxicity; yet, inhibiting these processes does not necessarily protect BBB integrity which is regulated by the iron mediated HIF2 - Ve-Cadherin axis. DFO protects BBB integrity by inhibiting the injury-induced deregulation of this axis. Additionally, we have discovered a novel compound, JP4-039, that inhibits both damage to endothelium functionality and cell toxicity. Elucidating a regulatory pathway that maintains BBB integrity and discovering both a novel and an FDA approved compound that interfere with this pathway elucidates a potential therapeutic approach to protect the BBB degradation that is evident in many neurological diseases.

neuroscience↗