Laquinimod Modulates Human Astrocyte Function and Dampens Astrocyte-Induced Neurotoxicity during Inflammation.

Emanuela Colombo,Daniela Triolo,Linda Ottoboni,Gianvito Martino,Giancarlo Comi,Anthea De Angelis,Francesca Ruffini,Claudia Bassani,Cinthia Farina,Rosaria Pascente

doi:10.3390/molecules25225403

Abstract

Astrocytes greatly participate to inflammatory and neurotoxic reactions occurring in neurodegenerative diseases and are valuable pharmacological targets to support neuroprotection. Here we used human astrocytes generated from reprogrammed fibroblasts as a cellular model to study the effect of the compound Laquinimod and its active metabolite de-Laquinimod on astrocyte functions and the astrocyte–neuron interaction. We show that human iAstrocytes expressed the receptor for the inflammatory mediator IL1 and responded to it via nuclear translocation of NFκB, an event that did not occur if cells were treated with Laquinimod, indicating a direct anti-inflammatory activity of the drug on the human astrocyte. Similarly, while exposure to IL1 downregulated glial glutamate transporters GLAST and GLT1, treatment with Laquinimod supported maintenance of physiological levels of these proteins despite the inflammatory milieu. Laquinimod also induced nuclear translocation of the aryl hydrocarbon receptor (AHR), suggesting that drug action was mediated by activation of the AHR pathway. However, the drug was effective despite AHR inhibition via CH223191, indicating that AHR signaling in the astrocyte is dispensable for drug responses. Finally, in vitro experiments with rat spinal neurons showed that laquinimod did not exert neuroprotection directly on the neuron but dampened astrocyte-induced neurodegeneration. Our findings indicate that fibroblast-derived human astrocytes represent a suitable model to study astrocyte–neuron crosstalk and demonstrate indirect, partial neuroprotective efficacy for laquinimod.

Highlights

Astrocytes are essential components of intrinsic innate immune responses of the central nervous system (CNS), and act as important mediators of neuronal damage in brain disorders [1,2]
Generation and Characterization of Human iAstrocytes iAstrocytes were generated from induced pluripotent stem cells-derived neural precursor cells as previously described [16]. iNPC differentiation induced cell size increase and typical morphology of astroglia (Figure 1A)
Astrocytes displayed strong expression of Interleukin 1 receptor (IL1R; Figure 1B,C), an inflammatory receptor upregulated under neuroinflammation [4], indicating that our in vitro human cell model could be responsive to inflammatory mediators

Summary

Introduction

Astrocytes are essential components of intrinsic innate immune responses of the central nervous system (CNS), and act as important mediators of neuronal damage in brain disorders [1,2]. They are able to sense any type of tissue insults and react activating a process defined as astrogliosis, characterized by a spectrum of molecular, cellular and functional changes that may either exacerbate tissue damage or contribute to CNS repair [3]. Human fibroblast-derived astrocytes (iAstrocytes) provide an unlimited cell source to explore the contributions of astrocytes to human diseases and test compounds modulating astrocyte activity and supporting neuroprotection. Our novel findings demonstrate that Laq and delaquinimod (de-Laq), the N-dealkylated active metabolite of Laq [15], dampen inflammatory signaling in astrocytes, preserve physiological astrocyte functions and prevent astrocyte-mediated neurodegeneration

Methods

Results

Conclusion