Acute and Delayed Effects of Mechanical Injury on Calcium Homeostasis and Mitochondrial Potential of Primary Neuroglial Cell Culture: Potential Causal Contributions to Post-Traumatic Syndrome.

In vitro models of traumatic brain injury (TBI) help to elucidate the pathological mechanisms responsible for cell dysfunction and death. To simulate in vitro the mechanical brain trauma, primary neuroglial cultures were scratched during different periods of network formation. Fluorescence microscopy was used to measure changes in intracellular free Ca2+ concentration ([Ca2+]i) and mitochondrial potential (ΔΨm) a few minutes later and on days 3 and 7 after scratching. An increase in [Ca2+]i and a decrease in ΔΨm were observed ~10 s after the injury in cells located no further than 150-200 µm from the scratch border. Ca2+ entry into cells during mechanical damage of the primary neuroglial culture occurred predominantly through the NMDA-type glutamate ionotropic channels. MK801, an inhibitor of this type of glutamate receptor, prevented an acute increase in [Ca2+]i in 99% of neurons. Pathological changes in calcium homeostasis persisted in the primary neuroglial culture for one week after injury. Active cell migration in the scratch area occurred on day 11 after neurotrauma and was accompanied by a decrease in the ratio of live to dead cells in the areas adjacent to the injury. Immunohistochemical staining of glial fibrillary acidic protein and ß-III tubulin showed that neuronal cells migrated to the injured area earlier than glial cells, but their repair potential was insufficient for survival. Mitochondrial Ca2+ overload and a drop in ΔΨm may cause delayed neuronal death and thus play a key role in the development of the post-traumatic syndrome. Preventing prolonged ΔΨm depolarization may be a promising therapeutic approach to improve neuronal survival after traumatic brain injury.

Isoliquiritigenin Protects Neuronal Cells against Glutamate Excitotoxicity.

It is considered that glutamate excitotoxicity may be a major factor in the pathological death of neurons and mediate the development of neurodegenerative diseases in humans. Here, we show that isoliquiritigenin (ILG) at a concentration of 0.5-5 µM protects primary neuroglial cell culture from glutamate-induced death (glutamate 100 µM). ILG (1 µM) prevented a sharp increase in [Ca2+]i and a decrease in mitochondrial potential (ΔΨm). With the background action of ILG (1-5 µM), there was an increase in oxygen consumption rate (OCR) in response to glutamate, as well as in reserve respiration. The neuroprotective effect of ILG (5 µM) was accompanied by an increase in non-mitochondrial respiration. The results show that ILG can protect cortical neurons from death by preventing the development of calcium deregulation and limiting mitochondrial dysfunction caused by a high dose of glutamate. We hypothesize that ILG will be useful in drug development for the prevention or treatment of neurodegenerative diseases accompanied by glutamate excitotoxicity.

The effect of DS16570511, a new inhibitor of mitochondrial calcium uniporter, on calcium homeostasis, metabolism, and functional state of cultured cortical neurons and isolated brain mitochondria.

BACKGROUND: Disorders of mitochondrial Ca2+ homeostasis play a key role in the glutamate excitotoxicity of brain neurons. DS16570511 (DS) is a new penetrating inhibitor of mitochondrial Ca2+ uniporter complex (MCUC). The paper examines the effects of DS on the cultivated cortical neurons and isolated mitochondria of the rat brain. METHODS: The functions of neurons and mitochondria were examined using fluorescence microscopy, XF24 microplate-based сell respirometry, ion-selective microelectrodes, spectrophotometry, and polarographic technique. RESULTS: At the doses of 30 and 45 µM, DS reliably slowed down the onset of glutamate-induced delayed calcium deregulation of neurons and suppressed their death. 30 µM DS caused hyperpolarization of mitochondria of resting neurons, and 45 µM DS temporarily depolarized neuronal mitochondria. It was also demonstrated that 30-60 µM DS stimulated cellular respiration. DS was shown to suppress Ca2+ uptake by isolated brain mitochondria. In addition, DS inhibited ADP-stimulated mitochondrial respiration and ADP-induced decrease in the mitochondrial membrane potential. It was found that DS inhibited the activity of complex II of the respiratory chain. In the presence of Ca2+, high DS concentrations caused a collapse of the mitochondrial membrane potential. CONCLUSIONS: The data obtained indicate that, in addition to the inhibition of MCUC, DS affects the main energy-transducing functions of mitochondria. GENERAL SIGNIFICANCE: The using DS as a tool for studying MCUC and its functional role in neuronal cells should be done with care, bearing in mind multiple effects of DS, a proper evaluation of which would require multivariate analysis.