Microglial phagocytosis dysfunction in stroke is driven by energy depletion and induction of autophagy
Creators: name: Beccari, Sol
name: Sierra-Torre, Virginia
name: Valero, Jorge
name: Pereira-Iglesias, Marta
name: García-Zaballa, Mikel
name: Soria, Federico N.
name: De Las Heras-Garcia, Laura
name: Carretero-Guillen, Alejandro
name: Capetillo-Zarate, Estibaliz
name: Domercq, Maria
name: Huguet, Paloma R.
name: Ramonet, David
name: Osman, Ahmed
name: Han, Wei
name: Dominguez, Cecilia
name: Faust, Travis E.
name: Touzani, Omar
name: Pampliega, Olatz
name: Boya, Patricia
name: Schafer, Dorothy
name: Mariño, Guillermo
name: Canet-Soulas, Emmanuelle
name: Blomgren, Klas
name: Plaza-Zabala, Ainhoa
name: Sierra, Amanda
Publisher: name: Taylor & Francis
Year: 2023
Subjects: subject: Physical Sciences not elsewhere classified
subject: Medicine
subject: Cell Biology
subject: Genetics
subject: FOS: Biological sciences
subject: Neuroscience
subject: Physiology
subject: Pharmacology
subject: Evolutionary Biology
subject: Immunology
subject: FOS: Clinical medicine

description: Microglial phagocytosis of apoptotic debris prevents buildup damage of neighbor neurons and inflammatory responses. Whereas microglia are very competent phagocytes under physiological conditions, we report their dysfunction in mouse and preclinical monkey models of stroke (macaques and marmosets) by transient occlusion of the medial cerebral artery (tMCAo). By analyzing recently published bulk and single cell RNA sequencing databases, we show that the phagocytosis dysfunction was not explained by transcriptional changes. In contrast, we demonstrate that the impairment of both engulfment and degradation was related to energy depletion triggered by oxygen and nutrient deprivation (OND), which led to reduced process motility, lysosomal exhaustion, and the induction of a protective macroautophagy/autophagy response in microglia. Basal autophagy, in charge of removing and recycling intracellular elements, was critical to maintain microglial physiology, including survival and phagocytosis, as we determined both in vivo and in vitro using pharmacological and transgenic approaches. Notably, the autophagy inducer rapamycin partially prevented the phagocytosis impairment induced by tMCAo in vivo but not by OND in vitro, where it even had a detrimental effect on microglia, suggesting that modulating microglial autophagy to optimal levels may be a hard to achieve goal. Nonetheless, our results show that pharmacological interventions, acting directly on microglia or indirectly on the brain environment, have the potential to recover phagocytosis efficiency in the diseased brain. We propose that phagocytosis is a therapeutic target yet to be explored in stroke and other brain disorders and provide evidence that it can be modulated in vivo using rapamycin. <b>Abbreviations:</b> AIF1/IBA1: allograft inflammatory factor 1; AMBRA1: autophagy/beclin 1 regulator 1; ATG4B: autophagy related 4B, cysteine peptidase; ATP: adenosine triphosphate; BECN1: beclin 1, autophagy related; CASP3: caspase 3; CBF: cerebral blood flow; CCA: common carotid artery; CCR2: chemokine (C-C motif) receptor 2; CIR: cranial irradiation; <i>Csf1r/v-fms</i>: colony stimulating factor 1 receptor; CX3CR1: chemokine (C-X3-C motif) receptor 1; DAPI: 4’,6-diamidino-2-phenylindole; DG: dentate gyrus; GO: Gene Ontology; HBSS: Hanks’ balanced salt solution; HI: hypoxia-ischemia; LAMP1: lysosomal-associated membrane protein 1; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MCA: medial cerebral artery; MTOR: mechanistic target of rapamycin kinase; OND: oxygen and nutrient deprivation; Ph/A coupling: phagocytosis-apoptosis coupling; Ph capacity: phagocytic capacity; Ph index: phagocytic index; SQSTM1: sequestosome 1; RNA-Seq: RNA sequencing; TEM: transmission electron microscopy; tMCAo: transient medial cerebral artery occlusion; ULK1: unc-51 like kinase 1.