ИСТИНА

Metabolism and signaling processes in neurons and astrocytes are closely related to local hemodynamic response. The activity of ATP synthesis must precisely match the current energy needs of cells, and the oxygen supply to brain tissue must correspond the rate of O2 reduction at complex IV in the mitochondrial respiratory chain (electron transport chain, ETC). Mitochondrial ETC activity also affects the redox state of cells due to the generation of superoxide-anion radical O2- in complexes I and III. In brain cells (in astrocytes, in particular) the generation of O2- with subsequent formation of other reactive oxygen species (ROS) can be used in signaling processes or can lead to the development of oxidative stress. To understand the relationship of mitochondria activity with ROS generation and with hemodynamic response in brain, methods are needed for in vivo assessment of local blood oxygenation, investigation of the ETC redox state and monitoring of ROS generation in neurons and glial cells. We developed an approach based on Raman microspectroscopy to estimate ETC loading with electrons in identified neurons and astrocytes and to monitor quantitatively blood oxygenation in arterioles and venules of somatosensory cortex of awake mice. We demonstrated that during physical activity of mice, the relative amount of reduced electron carriers in ETC of astrocytes increased and accompanied by the generation of H2O2. In neurons, on the contrary, the ETC loading with electrons was decreased and H2O2 production did not change. At the same time, we observed vasodilation and the increase in local blood oxygenation in venules and, to a lesser extent, in arterioles. We found that local blood oxygenation and its regulation in response to movements change with aging or under Alzheimer disease. We also observed changes in the redox state of ETC in neurons and astrocytes. We assume that under normal conditions hydrogen peroxide formed in astrocytes is necessary for signaling processes between astrocytes and other components of the brain. The proposed approach can be successfully used to study metabolic processes and hemodynamic response in brain under physiological stimuli and various pathologies. We acknowledge financial support from RSF (grants 23-44-00015, 23-74-00006).