V. P. Reutov

Nitrate and nitrite in biology, nutrition and therapeutics

Inorganic nitrate and nitrite from endogenous or dietary sources are metabolized in vivo to nitric oxide (NO) and other bioactive nitrogen oxides. The nitrate-nitrite-NO pathway is emerging as an important mediator of blood flow regulation, cell signaling, energetics and tissue responses to hypoxia. The latest advances in our understanding of the biochemistry, physiology and therapeutics of nitrate, nitrite and NO were discussed during a recent 2-day meeting at the Nobel Forum, Karolinska Institutet in Stockholm.

Effect of Inhibitors of Inducible and Neuronal NO Synthases on the Development of Audiogenic Stress-Induced Damage in Krushinskii–Molodkina Rats

Experiments on the models of epileptiform seizure and hemorrhagic stroke (Krushinskii–Molodkina rats) showed that selective inhibitors of inducible and neuronal NO synthases (aminoguanidine and 7-nitroindazole) significantly decrease the mortality rate, reduce the severity of motor disorders, and prevent the development of intracranial hemorrhages under conditions of audiogenic stress.

Role of glycogen in processes of cerebellar glial cells under conditions of its damage with sodium nitrite.

Ultrastructure of processes of glial cell, astrocytes of the molecular layer of cerebellar cortex in Rana temporaria frog, under conditions of damage to the cerebellum caused by NO-generating compound sodium nitrite was studied under an electron microscope. It is found that astrocytes have at least two types of processes: the first (fibrillar) primarily contained numerous fibrils and few glycogen granules and the second (granular) primarily containing glycogen granules. In the presence of NO-generating compound in toxic doses, fibrillar processes are damaged or completely degrade more rapidly than granular ones. The processes containing glycogen can protect both damaged synapses and individual synaptic buttons by forming a compact structure, wrapping, around them. We analyzed the possible role of glycogen of cerebellar glial cell processes in neuroglial interactions in the presence of sodium nitrite.

[Nitric oxide is involved in the protective effects of short-term adaptaion to hypoxia in the course of stress-induced disorders in Krushinsky-Molodkina rats].

A possible involvement of nitric oxide in the protective effect of short-term adaptation of Krushinsky-Molodkina rats to mild hypoxia simulating 5000 m above sea level was studied. Nitric oxide proved to have a considerable protective effect on stress-induced disorders in Krushinsky-Molodkina rats as demonstrated using NO-synthase inhibitors and NO monitoring by electron spin resonance under different experimental conditions.

Effects of Selective Inhibitors of Neuronal and Inducible NO-Synthase on ATP Content and Survival of Cultured Rat Cerebellar Neurons during Hyperstimulation of Glutamate Receptors

We studied the effects of selective inhibitors of neuronal and inducible NO-synthase (7-nitroindazole and aminoguanidine) and non-selective NO-synthase inhibitor L-NAME on ATP content and survival of cultured rat cerebellar neurons during hyperstimulation of glutamate receptors with toxic doses of glutamate. Application of 100 μM glutamate reduced ATP content in the primary culture of 7-8- and 14-15-day-old cerebellar granule cells by 66 and 49%, respectively, in comparison with the control. Inhibition of nitric oxide synthesis with 7-nitroindazole during glutamate exposure in the culture of 7-8-day-old neurons and with 7-nitroindazole and aminoguanidine in the culture of 14-15-day-old neurons ensured better protection of cells from ATP level decrease than non-specific inhibition with L-NAME. In addition, inhibition of neuronal and inducible NO-synthase during glutamate exposure decreased death of “young” neurons, whereas death of “old” neurons remained high under these conditions.

Sodium nitrate effect on development of neurological deficiency in rats after semi-global brain ischemia

Dose-dependent effects of sodium nitrate (NaNO3) on the dynamics of neurological disorders after brain ischemia induced by bilateral occlusion of the common carotid artery were investigated in rats of the Wistar line. NaNO3 at 50 and 500 mg/1000 g decreased mortality rates and neurological disorders. NaNO3 at 5 mg/1000 g had no effect.

Effect of cation type and concentration of nitrates on neurological disorders during experimental cerebral ischemia.

Experiments were performed on the model of ischemic stroke due to bilateral occlusion of the carotid arteries. Nitrates had various effects on the dynamics of neurological disorders and mortality rate of Wistar rats, which depended on the cation type and concentration.

Fusion of Frog Cerebellar Granule Cells Induced by the Toxic Effects of Glutamate and an NO-Generating Compound

Ultrastructural changes in cerebellar granule cells were studied in a model of stroke after the toxic action of glutamate (Glu) and an NO-generating compound. Toxic doses of glutamate produced two types of change in the nuclear chromatin. In some cases, cells with almost completely decondensed nuclear chromatin appeared; in others, cells with partially decondensed chromatin appeared. Pathological fusion of granule cells was seen in both cases. The toxic action of an NO-generating compound on granule cells also induced the appearance of cells with essentially complete and partial decondensation (flocculent) nuclear chromatin. Thus, Glu and NO, inducing changes in the nuclear chromatin, activate the process leading to the formation of clusters of granule cells able to undergo cytoplasmic fusion to form multinucleate conglomerates. The possible physiological role of the fusion of cerebellar granule cells in the presence of high concentrations of Glu and an NO-generating compound is discussed. This process is regarded as the realization of a compensatory-adaptive reaction in extreme conditions as seen in stroke and oxidative stress.

Effect of Locomotor Activity on Ultrastructure of Cerebellar Neurons, Neurological Disturbances, and Survival of Krushinsky–Molodkina Rats with Hemorrhagic Stroke

We studied the effect of locomotor activity on the ultrastructure of cerebellar neurons, neurological disturbances, and survival rate in Krushinsky–Molodkina rats during the development of hemorrhagic induced by acoustic stress. In animals with high spontaneous locomotor activity, severe edema of cerebellar neurons (resulting in the destruction of surrounding structures) and swelling of the synapses (terminals of mossy fi bers on granule cell dendrites) were observed. By contrast, the areas of intracerebral, subdural, and subarachnoid hemorrhages were lower in rats under conditions of forced rest.

Plastic Rearrangements of Synapse Ultrastructure in the Cerebellum in Toxicity due to Glutamate and NO-Generating Compounds

Ultrastructural changes in synaptic boutons of parallel fibers (PF) and the spines of Purkinje cell dendrites (PCD) in the frog cerebellum were stdied on exposure to high concentrations (1 mM) of glutamate (Glu) and NO-generating compounds, creating a model of stroke. Exposure to Glu led to envelopment of terminal boutons by spines, while NO-generating compounds, conversely, led to envelopment of spines by boutons. Morphological studies showed that in Glu solution, there was a dominance of synapses in which glial cells were surrounded by spines, while boutons were dominant in the presence of NO. On electrical stimulation of PF, the relative content of synapses whose boutons were enveloped by glial cells was greater than the proportion of synapses in which glial cells were enveloped by spines, by a factor of 10. These morphological changes reflect the functional state of PF and PCD synapses in response to the harmful influences of excess Glu and NO, apparent as different forms of synaptic contacts and neuron-glial structures.