High mitochondrial calcium levels precede neuronal death in vivo in Alzheimer's disease.

Alzheimer's disease (AD), the most common cause of dementia, affects millions of people worldwide. Suggested mechanisms of neurotoxicity in AD include impaired calcium (Ca²⁺) homeostasis and mitochondrial dysfunction, both contributing to neuronal damage. Little was known about the exact mitochondrial Ca²⁺ homeostasis in the living brain, particularly in AD. Only now, with the development of intravital imaging techniques and transgenic mouse models of the disease, we are able to directly observe Ca²⁺ levels in specific regions or particular subcellular compartments of cells, such as mitochondria. Using multiphoton microscopy, a Ca²⁺ reporter targeted to mitochondria and a mouse model of cerebral β amyloidosis (APP/PS1), our recent study (Nat Comms 2020, 11:2146) found elevated mitochondrial Ca²⁺ concentration in the transgenic mouse after plaque deposition, and after topical application of natural soluble amyloid beta (Aβ) oligomers to the healthy mouse brain at concentrations similar to those found in the human brain. Elevated Ca²⁺ in mitochondria preceded neuronal death and could be targeted for neuroprotective therapies in AD. Here, we describe our main findings and pose new questions for future studies aimed at better understanding mitochondrial Ca²⁺ dyshomeostasis in AD.