ER-associated Regulation of Astrocyte Mitochondrial Function during METH Exposure

Purpose: Astrocytes are key regulators of central nervous system (CNS) health and neuronal function. However, astrocyte mitochondrial dysfunction, such as induced by (METH)amphetamine, threatens the ability of astrocytes to provide the essential metabolic and antioxidant support to neurons. This study examined the endoplasmic reticulum (ER)-mitochondrial interface in response to METH to characterize changes in mitochondrial bioenergetics, the unfolded protein response (UPR), calcium signaling, and the regulation of mitochondria associated membranes (MAMs). We hypothesized that the ER regulates astrocyte mitochondrial function via calcium and UPR signaling during METH exposure. Methods: The effects of METH on astrocyte mitochondrial function were examined under both acute and chronic paradigms in primary human astrocytes. Mitochondrial bioenergetics was assessed using Seahorse assay while expression of UPR/MAM mediators were determined using RT-PCR and protein expression assays. Calcium signaling was measured by confocal microscopy using a genetically encoded calcium sensor. Finally, pharmacological inhibition of calcium and the UPR pathways were used to delineate the regulatory mechanisms mediating the changes on mitochondrial bioenergetics. Results: Our results show both acute and chronic METH increased Ca2+ flux, up-regulated the expression of UPR/MAM mediators, and altered mitochondrial bioenergetics in astrocytes. We further implicate a role for UPR signaling on mitochondrial activity. Conclusion: These findings illustrate novel cellular mechanisms in regulating astrocyte mitochondrial function during METH exposure. Additional studies will be required to assess whether these mechanisms can be therapeutically targeted to optimize the metabolic and antioxidant coupling between astrocytes and neurons to promote neuronal survival during neurodegenerative pathologies.