Microglial-glucocorticoid receptor depletion alters the response of hippocampal microglia and neurons in a chronic unpredictable mild stress paradigm in female mice

Picard K, Bisht K, Poggini S, Garofalo S, Golia MT, Basilico B, Abdallah F, Ciano Albanese N, Amrein I, Vernoux N, Sharma K, Hui CW, C. Savage J, Limatola C, Ragozzino D, Maggi L, Branchi I, Tremblay MÈ. Microglial-glucocorticoid receptor depletion alters the response of hippocampal microglia and neurons in a chronic unpredictable mild stress paradigm in female mice. Brain, Behavior, and Immunity.

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Author
Picard, Katherine; Bisht, Kanchan; Poggini, Silvia; Garofalo, Stefano; Golia, Maria Teresa; Basilico, BernadetteIST Austria; Abdallah, Fatima; Ciano Albanese, Naomi; Amrein, Irmgard; Vernoux, Nathalie; Sharma, Kaushik; Hui, Chin Wai
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Abstract
Chronic psychological stress is one of the most important triggers and environmental risk factors for neuropsychiatric disorders. Chronic stress can influence all organs via the secretion of stress hormones, including glucocorticoids by the adrenal glands, which coordinate the stress response across the body. In the brain, glucocorticoid receptors (GR) are expressed by various cell types including microglia, which are its resident immune cells regulating stress-induced inflammatory processes. To study the roles of microglial GR under normal homeostatic conditions and following chronic stress, we generated a mouse model in which the GR gene is depleted in microglia specifically at adulthood to prevent developmental confounds. We first confirmed that microglia were depleted in GR in our model in males and females among the cingulate cortex and the hippocampus, both stress-sensitive brain regions. Then, cohorts of microglial-GR depleted and wild-type (WT) adult female mice were housed for 3 weeks in a standard or stressful condition, using a chronic unpredictable mild stress (CUMS) paradigm. CUMS induced stress-related behavior in both microglial-GR depleted and WT animals as demonstrated by a decrease of both saccharine preference and progressive ratio breakpoint. Nevertheless, the hippocampal microglial and neural mechanisms underlying the adaptation to stress occurred differently between the two genotypes. Upon CUMS exposure, microglial morphology was altered in the WT controls, without any apparent effect in microglial-GR depleted mice. Furthermore, in the standard environment condition, GR depleted-microglia showed increased expression of pro-inflammatory genes, and genes involved in microglial homeostatic functions (such as Trem2, Cx3cr1 and Mertk). On the contrary, in CUMS condition, GR depleted-microglia showed reduced expression levels of pro-inflammatory genes and increased neuroprotective as well as anti-inflammatory genes compared to WT-microglia. Moreover, in microglial-GR depleted mice, but not in WT mice, CUMS led to a significant reduction of CA1 long-term potentiation and paired-pulse ratio. Lastly, differences in adult hippocampal neurogenesis were observed between the genotypes during normal homeostatic conditions, with microglial-GR deficiency increasing the formation of newborn neurons in the dentate gyrus subgranular zone independently from stress exposure. Together, these findings indicate that, although the deletion of microglial GR did not prevent the animal’s ability to respond to stress, it contributed to modulating hippocampal functions in both standard and stressful conditions, notably by shaping the microglial response to chronic stress.
Publishing Year
Date Published
2021-07-31
Journal Title
Brain, Behavior, and Immunity
Acknowledgement
We acknowledge that Université Laval stands on the traditional and unceded land of the Huron-Wendat peoples; and that the University of Victoria exists on the territory of the Lekwungen peoples and that the Songhees, Esquimalt and WSÁNEÆ peoples have relationships to this land. We thank Emmanuel Planel for the access to the epifluorescence microscope and Julie-Christine Lévesque at the Bioimaging Platform of CRCHU de Québec-Université Laval for technical assistance. We also thank the Centre for Advanced Materials and Related Technology for the access to the confocal microscope with Airyscan. K.P. was supported by a doctoral scholarship from Fonds de Recherche du Québec – Santé (FRQS), an excellence award from Fondation du CHU de Québec, as well as from Centre Thématique de Recherche en Neurosciences and from Fondation Famille-Choquette. K.B. was supported by excellence scholarships from Université Laval and Fondation du CHU de Québec. S.G. is supported by FIRC-AIRC fellowship for Italy 22329/2018 and by Pilot ARISLA NKINALS 2019. C.W.H. and J.C.S. were supported by postdoctoral fellowships from FRQS. This study was funded by a Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery grant (RGPIN-2014-05308) awarded to M.E.T., by ERANET neuron 2017 MicroSynDep to M.E.T. and I.B., and by the Italian Ministry of Health, grant RF-2018-12367249 to I.B, by PRIN 2017, AIRC 2019 and Ministero della Salute RF2018 to C.L. M.E.T. is a Tier II Canada Research Chair in Neurobiology of Aging and Cognition.
ISSN
IST-REx-ID

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Picard K, Bisht K, Poggini S, et al. Microglial-glucocorticoid receptor depletion alters the response of hippocampal microglia and neurons in a chronic unpredictable mild stress paradigm in female mice. Brain, Behavior, and Immunity. doi:10.1016/j.bbi.2021.07.022
Picard, K., Bisht, K., Poggini, S., Garofalo, S., Golia, M. T., Basilico, B., … Tremblay, M. È. (n.d.). Microglial-glucocorticoid receptor depletion alters the response of hippocampal microglia and neurons in a chronic unpredictable mild stress paradigm in female mice. Brain, Behavior, and Immunity. Elsevier. https://doi.org/10.1016/j.bbi.2021.07.022
Picard, Katherine, Kanchan Bisht, Silvia Poggini, Stefano Garofalo, Maria Teresa Golia, Bernadette Basilico, Fatima Abdallah, et al. “Microglial-Glucocorticoid Receptor Depletion Alters the Response of Hippocampal Microglia and Neurons in a Chronic Unpredictable Mild Stress Paradigm in Female Mice.” Brain, Behavior, and Immunity. Elsevier, n.d. https://doi.org/10.1016/j.bbi.2021.07.022.
K. Picard et al., “Microglial-glucocorticoid receptor depletion alters the response of hippocampal microglia and neurons in a chronic unpredictable mild stress paradigm in female mice,” Brain, Behavior, and Immunity. Elsevier.
Picard K, Bisht K, Poggini S, Garofalo S, Golia MT, Basilico B, Abdallah F, Ciano Albanese N, Amrein I, Vernoux N, Sharma K, Hui CW, C. Savage J, Limatola C, Ragozzino D, Maggi L, Branchi I, Tremblay MÈ. Microglial-glucocorticoid receptor depletion alters the response of hippocampal microglia and neurons in a chronic unpredictable mild stress paradigm in female mice. Brain, Behavior, and Immunity.
Picard, Katherine, et al. “Microglial-Glucocorticoid Receptor Depletion Alters the Response of Hippocampal Microglia and Neurons in a Chronic Unpredictable Mild Stress Paradigm in Female Mice.” Brain, Behavior, and Immunity, Elsevier, doi:10.1016/j.bbi.2021.07.022.

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