Calcium Dynamics in Astrocytes During Cell Injury

Abstract

The changes in intracellular calcium concentration ([Ca 2+ ]) following laser-induced cell injury in nearby cells were studied in primary mouse astrocytes selectively expressing the Ca 2+ sensitive GFAP-Cre Salsa6f fluorescent tandem protein, in an Ast1 astrocyte cell line, and in primary mouse astrocytes loaded with Fluo4. Astrocytes in these three systems exhibit distinct changes in [Ca 2+ ] following induced death of nearby cells. Changes in [Ca 2+ ] appear to result from release of Ca 2+ from intracellular organelles, as opposed to influx from the external medium. Salsa6f expressing astrocytes displayed dynamic Ca 2+ changes throughout the phagocytic response, including lamellae protrusion, cytosolic signaling during vesicle formation, vesicle maturation, and vesicle tract formation. Our results demonstrate local changes in [Ca 2+ ] are involved in the process of phagocytosis in astrocytes responding to cell corpses and/or debris.

Fluid Shear Stress Enhances the Phagocytic Response of Astrocytes

“…A previous study in epithelial cells demonstrate changes in calcium signaling in response to mechanical stimulation ( Sanderson et al, 1990 ), as well as astrocytes ( Charles et al, 1991 ). We have shown in previous studies significant calcium changes in astrocytes in response to photolysis ( Wakida et al, 2020 ). Follow up studies will combine the application of shear flow to calcium imaging to better understand how intercellular signaling, including calcium, is affected by shear flow.…”

“…In a previous study, we demonstrated the ability of astrocytes in vitro to phagocytose neighboring cellular debris released via targeted laser ablation ( Wakida et al, 2018 , 2020 ). In this study we elucidate the importance of mechanical forces on the phagocytic response of astrocytes by the application of laminar flow of media across the cell’s surface.…”

“…This is of critical importance to areas of research like traumatic brain injury and CNS repair. Our previous studies demonstrated the ability of astrocytes to respond to laser induced cell lysis via phagocytosis ( Wakida et al, 2018 , 2020 ). Membrane ruffling and subsequent vesicle formation in the responding astrocyte was associated with cellular debris from the targeted cell with the use of propidium iodide labeled DNA and pHrodo dye.…”

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“…Here we quantified the calcium response of the astrocyte network to laser-induced nuclear damage and investigated the relationship of PARP and calcium in response to nuclear damage. In vitro astrocyte model is known for the transmission of calcium elevation in response to cellular injury to network cells [2,18]. We found that nuclear damage specifically alters the whole cell calcium dynamics not only in the damaged cell, but also in the attached neighboring cells in a PARP-dependent manner.…”

“…Astrocytes respond to axon injury, cell death, and many other forms of brain injury through a process of reactive astrogliosis [1]. In previous studies we have utilized laser irradiation to mimic mild CNS damage and followed the response of astrocytes where laser ablation resulted in cell death of a targeted astrocyte within a network of cells [2,3].…”