Lipopolysaccharide From E. coli Increases Glutamate-Induced Disturbances of Calcium Homeostasis, the Functional State of Mitochondria, and the Death of Cultured Cortical Neurons

Zanda Bakaeva; Natalia Lizunova; Ivan Tarzhanov; Dmitrii Boyarkin; Svetlana Petrichuk; Vsevolod Pinelis; Andrey Fisenko; Alexander Tuzikov; Rinat Sharipov; Alexander Surin

doi:10.3389/fnmol.2021.811171

Lipopolysaccharide From E. coli Increases Glutamate-Induced Disturbances of Calcium Homeostasis, the Functional State of Mitochondria, and the Death of Cultured Cortical Neurons

Front Mol Neurosci. 2022 Jan 5:14:811171. doi: 10.3389/fnmol.2021.811171. eCollection 2021.

Authors

Zanda Bakaeva^{1

2}, Natalia Lizunova^{1

3}, Ivan Tarzhanov^{1

4}, Dmitrii Boyarkin¹, Svetlana Petrichuk¹, Vsevolod Pinelis¹, Andrey Fisenko¹, Alexander Tuzikov⁵, Rinat Sharipov⁶, Alexander Surin^{1

6}

Affiliations

¹ Laboratory of Neurobiology, "National Medical Research Center of Children's Health", Russian Ministry of Health, Moscow, Russia.
² Department of General Biology and Physiology, Kalmyk State University named after B.B. Gorodovikov, Elista, Russia.
³ Department of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia.
⁴ Institute of Pharmacy, The Sechenov First Moscow State Medical University, Ministry of Health of the Russian Federation, Moscow, Russia.
⁵ M.M. Shemyakin and Yu.A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia.
⁶ Laboratory of Fundamental and Applied Problems of Pain, Institute of General Pathology and Pathophysiology, Moscow, Russia.

Abstract

Lipopolysaccharide (LPS), a fragment of the bacterial cell wall, specifically interacting with protein complexes on the cell surface, can induce the production of pro-inflammatory and apoptotic signaling molecules, leading to the damage and death of brain cells. Similar effects have been noted in stroke and traumatic brain injury, when the leading factor of death is glutamate (Glu) excitotoxicity too. But being an amphiphilic molecule with a significant hydrophobic moiety and a large hydrophilic region, LPS can also non-specifically bind to the plasma membrane, altering its properties. In the present work, we studied the effect of LPS from Escherichia coli alone and in combination with the hyperstimulation of Glu-receptors on the functional state of mitochondria and Ca²⁺ homeostasis, oxygen consumption and the cell survival in primary cultures from the rats brain cerebellum and cortex. In both types of cultures, LPS (0.1-10 μg/ml) did not change the intracellular free Ca²⁺ concentration ([Ca²⁺]_i) in resting neurons but slowed down the median of the decrease in [Ca²⁺]_i on 14% and recovery of the mitochondrial potential (ΔΨm) after Glu removal. LPS did not affect the basal oxygen consumption rate (OCR) of cortical neurons; however, it did decrease the acute OCR during Glu and LPS coapplication. Evaluation of the cell culture survival using vital dyes and the MTT assay showed that LPS (10 μg/ml) and Glu (33 μM) reduced jointly and separately the proportion of live cortical neurons, but there was no synergism or additive action. LPS-effects was dependent on the type of culture, that may be related to both the properties of neurons and the different ratio between neurons and glial cells in cultures. The rapid manifestation of these effects may be the consequence of the direct effect of LPS on the rheological properties of the cell membrane.

Keywords: cell survival; glutamate excitotoxicity; intracellular free Ca2+ concentration ([Ca2+]i); lipopolysaccharide E. coli (LPS); mitochondrial potential (ΔΨm); oxygen consumption rates (OCR); primary neuronal cultures.