Age Specifics of Homeostasis Response to Cold Stress in Wistar Rats: Endurance Improvement or Disorganization?

Cold exposure, especially in combination with exercise, is a common procedure to fortify the body. However, its effects in old age are poorly understood. Using the homeostasis stability coefficient as an indicator, the body response to a 20-min swim in cold water was for the first time studied comprehensively in old and young Wistar rats. Effects on the hormonal, hematological, and morphofunctional systems of the liver and thymus were assessed. Unfavorable age-related changes in the stability of homeostasis were observed in old rats. The changes complicated the recovery after cold stress and required the involvement of a greater number of homeostatic mechanisms than in young rats. The liver was found to be the most vulnerable to cold stress. It was concluded that fortifying the body by cold exposure is possible to use in old age, but with due regard to age-related restrictions.

Physical Fatigue and Morphofunctional State of the Myocardium in Experimental Chronic Stress.

The relationship between the development of skeletal muscle fatigue of a specific type in male Wistar rats and morphofunctional alterations in the myocardium in the posttraumatic stress disorder (PTSD) model has been investigated for the first time. The aggravation of oxidative stress in the cardiomyocytes and the related transformation of the cell structural components and the depletion of energy reserves in PTSD has been identified as one of the main factors that accelerate the onset of musculoskeletal fatigue.

[Effect of adaptation to hypoxia on expression of NO synthase isoforms in rat myocardium].

Previously we have shown that adaptation to hypoxia (AH) is cardio- and vasoprotective in myocardial ischemic and reperfusion injury and this protection is associated with restriction of nitrosative stress. The present study was focused on further elucidation of NO-dependent mechanisms of AH by identifying specific NO synthases (NOS) that could play the major role in AH protection. AH was performed in a normobaric hypoxic chamber by breathing hypoxic gas mixture (9.5-10% O2) for 5-10 min with intervening 4 min normoxia (5-8 cycles daily for 21 days). Expression of neuronal (nNOS), inducible (iNOS), and endothelial (eNOS) protein was measured in the left ventricular myocardium using Western blot analysis with respective antibodies. AH educed iNOS protein expression by 71% (p < 0.05) whereas eNOS protein expression tended to be reduced by 41% compared to control (p < 0.05). nNOS protein expression remained unchanged after AH. Selective iNOS inhibition can mimic the AH-induced protection. Therefore protective effects of AH could be at least partially due to restriction of iNOS and, probably, eNOS expression.

[Vasoprotective effect of adaptation to hypoxia in myocardial ischemia and reperfusion injury].

Adaptation to hypoxia is known to be cardioprotective in ischemic and reperfusion (IR) injury of the myocardium. This study was focused on investigating a possibility for prevention of endothelial dysfunction in IR injury of the rat heart using adaptation to intermittent hypoxia, which was performed in a cyclic mode (5-10 min of hypoxia interspersed with 4 min of normoxia, 5-8 cycles daily) for 21 days. Endothelial function of coronary blood vessels was evaluated after the in vitro IR of isolated heart (15 min of ischemia and 10 min of reperfusion) by the increment of coronary flow rate in response to acetylcholine. Endothelium-dependent relaxation of isolated rat aorta was evaluated after the IR myocardial injury in situ (30 min of ischemia and 60 min of reperfusion) by a relaxation response of noradrenaline-precontracted vessel rings to acetylcholine. The following major results were obtained in this study: 1) IR myocardial injury induced endothelial dysfunction of coronary blood vessels and the aorta, a non-coronary blood vessel, remote from the IR injury area; and 2) adaptation to hypoxia prevented the endothelial dysfunction of both coronary and non-coronary blood vessels associated with the IR injury. Therefore, adaptation to hypoxia is not only cardioprotective but also vasoprotective in myocardial IR injury.

[Resistance to acute hypoxia and changes in the phenotype and phenotypic plasticity of macrophages in mice of different genetic strains].

The aim of study was to investigate the effect of hypoxia on the macrophage phenotype and phenotypic plasticity and to determine the resistance to acute hypoxia in C57/BL mice, which have the pro-inflammatory M1 macrophage phenotype, and in BALB/c mice, which have the anti-inflammatory M2 macrophage phenotype. The following results were obtained. 1) The response of macrophages to acute hypoxia has two successive phases, the immediate, anti-inflammatory phase, and the delayed, pro-inflammatory phase. This response was more distinctly inverted in C57/BL6 M1 macrophages than in BALB/c M2 macrophages; 2) the effect of acute hypoxia on macrophage phenotypic plasticity depends on the genetically predetermined, original macrophage phenotype. In this process, a clear regularity was observed: hypoxia increased the capability of macrophages for changing into the pro-inflammatory M1 phenotype, while their capability for changing into the anti-inflammatory M2 phenotype remained virtually unaffected. 3) BALB/c mice were more resistant to acute hypoxia than C57/BL6 mice. Taken together, these data expand our understanding of mechanisms for pathogenetic effects of hypoxia.

[Role of restricted nitric oxide overproduction in the cardioprotective effect of adaptation to intermittent hypoxia].

Adaptation to intermittent normobaric hypoxia is cardioprotective and can stimulate nitric oxide (NO) synthesis. However the role of nitric oxide (NO) in prevention of ischemia-reperfusion (IR) injury of myocardium is controversial. This study was focused on evaluating the effect of adaptation to hypoxia and IR on NO production and development of nitrative stress in the myocardium. Adaptation to hypoxia tended to increase NO production, which was determined by the total level of plasma nitrite and nitrate, and prevented IR-induced NO overproduction. The IR-induced NO overproduction was associated with significant 3-nitrotyrosine (3-NT) accumulation in the left ventricle but not in septum or aorta. In hypoxia-adapted rats, 3-NT after IR was similar to that of control rats without IR. IHC induced marked accumulation of HIF-1alpha in the left ventricle. We suggest that HIF-1alpha contributes to NO-synthase expression during adaptation to hypoxia and thereby facilitates the increase in NO production. NO, in turn, may subsequently prevent NO overproduction during IR by a negative feedback mechanism.

Erratum to: "Anxiety and neurometabolite levels in the hippocampus and amygdala after prolonged exposure to predator-scent stress".

Vavilovskii Zhurnal Genetiki i Selektsii = Vavilov Journal of Genetics and Breeding. 2019;23(5):582-587 (in Russian) Page 587, in Acknowledgements instead of The animals and behavioral testing are supported by the budget project (No. 0324-2019-0041). The MRI study is supported by the budget project (No. 0259-2019-0004). All studies are implemented using the equipment of Center for Genetic Resources of Laboratory Animals at ICG SB RAS, supported by the Ministry of Education and Science of Russia (Unique ID# of the project: RFMEFI62117X0015). should read The animals and behavioral testing are supported by the budget project (No. 0324-2019-0041). The MRI study is supported by the budget project (No. 0259-2019-0004). All studies are implemented using the equipment of Center for Genetic Resources of Laboratory Animals at ICG SB RAS, supported by the Ministry of Education and Science of Russia (Unique ID# of the project: RFMEFI62117X0015). The study was conducted within the basic part of the state task of the Ministry of Science and Higher Education of the Russian Federation (No. 17.7255.2017/8.9). The original article can be found under DOI 10.18699/VJ19.528.

[Protective and damaging effects of periodic cerebral hypoxia: the role of nitric oxide].

Low oxygen delivery to organs and tissues is one of the most life-threatening situations. Periodic hypoxic episodes may have not only damaging, but also protective effects on the organism depending on how long and intensive this factor is. In both cases an important role is played by changes in the synthesis and metabolism of NO. The direction of NO synthesis and, finally, the direction of periodic hypoxia effect is determined by the regimen of hypoxic impact. The effect of NO depends on its concentration. Both NO excess and deficit are very unfavorable to the organism. Sleep apnea syndrome and pulmonary hypertension are typical examples of NO-dependent damaging effects of periodical hypoxia. NO-dependent protective effects of adaptation to periodic hypoxia are underlied by moderate stimulation of NO synthesis, which provides both compensation for NO deficit and the limitation of its hyperproduction. In turn, NO may increase the expression of other protective factors, which makes adaptive protection more reliable and durable. Understanding the mechanisms of adaptation to hypoxia will help develop new approaches to the prevention of hypoxia and ischemic lesions and the improvement of adaptive abilities of the organism.

[The effects of adaptation to hypoxia on the resistance to neurodegenerative disorders in the brain of rats of different genetic strains].

The aim of the study was to compare the protective effects of adaptation to altitude hypoxia (AH) on neurodegenerative brain disorders (NBD) induced with infusion of beta-amyloid peptides (Abeta) into the brain (imitation of Alzheimer's disease) of rats belonging to two species: Wistar rats (WR) and August rats (AR). Previously it was shown by the authors that WR were less resistant to memory function impairment and open-field activities, induced with Abeta infusion compared with AR. This study showed that preliminary AH significantly restricted brain function impairment induced by Abeta in WR, so AH demonstrated the protective effect in WR. In contrast, in AR preliminary AH provoked those impairments induced by Abeta. The AH protective effect in WR was associated with activation of stress-limiting systems (antioxidant system, NO system). Lack of AH protective effect in AR was associated with lack of activation of these systems in these rats. Thus, the different AH effects on NBD development in WR and AR are obviously determined by hereditary peculiarities of stress-limiting systems in WR and AR.

[Clinical significance of nitric oxide levels in patients with chronic glomerulonephritis].

Nitric oxide (NO) takes an active part in the regulation of the main renal functions, water-salt metabolism, and system arterial pressure. Under pathological conditions, NO plays the leading role in the development and progression of nephrosclerosis. The aim of this study was to evaluate the clinical significance of serum and urine levels of stable NO metabolites in patients with various clinical forms of chronic glomerulonephritis (CGN), as well as CGN patients with chronic renal failure (CRF). Ninety-seven CGN patients, including 56 ones with preserved nitrogen excretion and 41 ones with CRF, were examined. The levels of stable NO metabolites (nitrites and nitrates) in serum and 24-hour urine were measured. The highest serum and urine NO levels were found in patients with nephrotic and hematuric CGN; patients suffering from latent and hypertonic CGN displayed the lowest levels. Patients with CRF had higher serum levels of NO compared with non-CRF patients. A reverse correlation between serum levels of creatinine and NO in patients with CRF was revealed. In CGN patients without CRF, the activity of inflammatory process, observed by high C-reactive protein levels, was associated with elevation of blood and urine levels of NO, while such an association was not found in patients with CRF.

Physical properties of dinitrosyl iron complexes with thiol-containing ligands in relation with their vasodilator activity.

When studying the vasodilator activity of dinitrosyl iron complexes (DNIC) with thiol-containing ligands as NO donors, it should be taken into consideration that these complexes depending on the content of thiols in the environment can occur in either of two forms that differ by their EPR, gamma-resonance and optical characteristics and also by their vasodilator effect on isolated blood vessels. The more stable diamagnetic form appears at the ratio Fe2+:RS- = 1:2. It reversibly dissociates to the monomeric paramagnetic form [(RS-)2Fe+(NO+)2] on increasing the thiol content to the level 20-times and more exceeding the quantity of iron. It is suggested that stabilization of the dimeric form is provided by formation of RS(-)-NO+ bonds between monomeric components of the dimer. This process is favored by a corresponding orientation of the monomers relative to each other. A high stability of the DNIC dimeric form correlates with more prolonged vasodilator effect of this complex as an NO source. Replacement of cysteine by reduced glutathione in dimeric and monomeric forms of DNIC increases both stability of the complexes and the duration of their vasodilator effect.

[Stress proteins in Alzheimer's disease].

Alzheimer's disease (AD) progression can be restricted by brain self-defense systems for a long time since the onset. Among these an exclusive role is played by the system of stress proteins, or heat shock proteins. In AD, stress proteins play primarily a neuroprotective role, which is realized through at least 7 mechanisms: 1) restriction of apoptosis; 2) restriction of NO overproduction; 3) disaggregation of extracellular Abeta aggregates; 4) acceleration of Abeta elimination from intercellular space; 5) restriction of tau-protein hyperphosphorylation; 6) protection of neurons from glutamate toxicity; 7) restriction of intracellular Abeta cytotoxicity. Results of studies on protective effects of heat shock proteins in AD allow creation of a new trend in the field of the treatment, related with developing methods of activation of stress protein self-defense system in order to restrict neurodegenerative disorders. The given review presents theoretical and experimental prerequisites for such an approach, and substantiates its possible efficiency.

Nitric oxide is involved in heat-induced HSP70 accumulation.

Heat shock potentiated the nitric oxide production (EPR assay) in the liver, kidney, heart, spleen, intestine, and brain. The heat shock-induced sharp transient increase in the rate of nitric oxide production preceded the accumulation of heat shock proteins (HSP70) (Western blot analysis) as measured in the heart and liver. In all organs the nitric oxide formation was completely blocked by the NO-synthase inhibitor N omega-nitro-L-arginine (L-NNA). L-NNA also markedly attenuated the heat shock-induced accumulation of HSP70. The results suggests that nitric oxide is involved in the heat shock-induced activation of HSP70 synthesis.

Nitric oxide donor induces HSP70 accumulation in the heart and in cultured cells.

As our group has shown, the NO-synthase inhibitor L-NNA decreased 2-3 times heat shock-induced synthesis of the heat shock protein HSP70 (FEBS Lett. 370 (1995) 159-162). It was suggested that NO is involved in such induction. In the present study, it was found that (1) injection of the NO donor dinitrosyl iron complex (DNIC) into rats results in accumulation of HSP70 in the heart; (2) heat shock is accompanied by increased generation of NO (EPR assay) and HSP70 accumulation in cultured cells; (3) DNIC induces HSP70 accumulation in cultured cells not exposed to heat shock.

Physical training limits the fall of blood pressure and the endothelium overactivation in acute myocardial infarction.

Physical training (PT) is beneficial in cardiovascular diseases associated with NO deficiency such as coronary disease, hypertension, etc. However, it is not known whether PT can also prevent pathological conditions associated with excess NO and fall of blood pressure (BP) such as acute myocardial infarction (AMI). The aim was to compare the effect of AMI on BP and functional state of the endothelium in rats trained by swimming and in untrained animals. After AMI, BP fell from 110 +/- 2 to 74 +/- 4 mm Hg (p < 0.05), the endothelium-dependent relaxation increased from 37 +/- 4 to 66 +/- 6% (p < 0.05) and the extent of contraction suppression by the endothelium was significantly greater than in the controls. PT itself increased the endothelium-dependent relaxation of rat aorta but left BP unaffected. PT limited the AMI-induced fall of BP to 87 +/- 3 mm Hg, the endothelium- dependent relaxation to 53 +/- 4% and prevented the hyporesponsiveness of the aorta to norepinephrine. We suggest that the protective effect of PT is related to inhibition of inducible NO synthase by a negative feedback mechanism.

Role of nitric oxide in adaptation to hypoxia and adaptive defense.

Adaptation to hypoxia is beneficial in cardiovascular pathology related to NO shortage or overproduction. However, the question about the influence of adaptation to hypoxia on NO metabolism has remained open. The present work was aimed at the relationship between processes of NO production and storage during adaptation to hypoxia and the possible protective significance of these processes. Rats were adapted to intermittent hypobaric hypoxia in an altitude chamber. NO production was determined by plasma nitrite/nitrate level. Vascular NO stores were evaluated by relaxation of the isolated aorta to diethyldithiocarbamate. Experimental myocardial infarction was used as a model of NO overproduction; stroke-prone spontaneously hypertensive rats (SHR-SP) were used as a model of NO shortage. During adaptation to hypoxia, the plasma nitrite/nitrate level progressively increased and was correlated with the increase in NO stores. Adaptation to hypoxia prevented the excessive endothelium-dependent relaxation and hypotension characteristic for myocardial infarction. At the same time, the adaptation attenuated the increase in blood pressure and prevented the impairment of endothelium-dependent relaxation in SHR-SP. The data suggest that NO stores induced by adaptation to hypoxia can either bind excessive NO to protect the organism against NO overproduction or provide a NO reserve to be used in NO deficiency.

Is HSP70 involved in nitric oxide-induced protection of the heart?

It is known that HSP70 plays an important role in the antiischaemic effect of adaptation to stress. The aim of our study was to verify the hypothesis that nitric oxide (NO) may contribute to the activation of HSP70 synthesis and to enhance thereby the resistance of organism to the ischaemic and reperfusion damages. We observed that heat shock potentiated NO production in the heart. NO formation was completely blocked by the NO synthase inhibitor N omega-nitro-L-arginine (L-NNA). L-NNA also significantly attenuated the heat shock-induced accumulation of HSP70 (by 45% in heart). Both heat shock and NO donor induced time- and concentration-dependent HSP70 synthesis in the culture of human hepatoblastoma cells Hep G2. Prior injection of NO donor (30-100 mg per rat) exerted a dose-dependent protective effect on the isolated heart in ischaemia and reperfusion within 24 hours. We suggest that NO is involved in the activation of HSP70 synthesis which can play an important role in the delayed protective effect of NO donors.

Cross-talk between nitric oxide and HSP70 in the antihypotensive effect of adaptation to heat.

In this work, we evaluated the effect of adaptation to heat on the fall of blood pressure (BP) induced by heat shock (HS) and the interrelation between nitric oxide (NO) and heat shock protein, HSP70. Experiments were carried out on Wistar rats. It was shown that HS resulted in a generalized and transient increase in NO production (the electron paramagnetic resonance method) and a fall of BP from 113+/-3 to 88+/-1 mm Hg (p<0.05). Adaptation to heat itself did not affect BP, but completely prevented the NO overproduction and hypotension induced by HS. The adaptation simultaneously increased the brain NO-synthase content and induced HSP70 synthesis (the Western blot analysis) in various organs. Both the antihypotensive effects of adaptation and HSP70 accumulation were completely prevented by L-NNA, an inhibitor of NO synthesis, or quercetin, an inhibitor of HSP70 synthesis. The data suggest that adaptation to heat stimulates NO synthesis and NO activates synthesis of HSP70. HSP70, which hampers NO overproduction, thus restricts the BP fall induced by heat shock.

[Dimeric and monomeric forms of dinitrosyl iron complexes with thiol-containing ligands: physico-chemical properties and vasodilator activity]. / Dimernaia i monomernaia formy dinitrozil'nykh kompleksov zheleza s tiolsoderzhashchimi ligandami: fiziko-khimicheskie svoistva i vazodilatatornaia aktivnost'.

When studying the vasodilator activity of dinitrosyl iron complexes (DNIC) with thiol-containing ligands as NO donors, it should be taken into consideration that these complexes depending on the content of thiols in the environment can occur in either form that differ by their EPR, gamma-resonance and optical characteristics and also by their vasodilator effect on isolated blood vessels. The more stable diamagnetic form appears at the ratio Fe2+:RS(-)-1:2. It reversibly dissociates to the monomeric paramagnetic form [(RS-)2Fe+(NO+)2] on increasing the thiol content to the level 20 times and more exceeding the quantity of iron. It is suggested that stabilization of the dimeric form is provided by formation of RS(-)-NO+ bonds between monomeric components of the dimer. This process is favored by a corresponding orientation of the monomers relative to each other. A high stability of the DNIC dimeric form correlates with more prolonged vasodilator effect of this complex as an NO source. Replacement of cysteine by reduced glutathione in dimeric and monomeric forms of DNIC increases both stability of the complexes and the duration of their vasodilator effect.

[Nitric oxide in the cardiovascular system: its role in adaptive protection]. / Oksid azota v serdechno-sosudistoi sisteme: rol' v adaptatsionnoi zashchite.

Nitric oxide (NO) is involved virtually in all processes occurring in the body. In the cardiovascular system, it regulates cardiac contractility, blood coagulability, cell proliferation, vascular tone, and blood pressure (BP). NO deficiency leads to the development of severe cardiovascular diseases associated with endothelial dysfunction, abnormally increased vascular tone and BP (such as hypertension, angina pectoris, atherosclerosis, diabetic angiopathy, etc.) At the same time, NO hyperproduction makes a contribution to the development of septic, cardiogenic, thermal, and other shocks. The most effective non-drug stimulation of NO synthesis is a gradual adaptation to environmental factors. The adaptation-induced elevation of NO levels, followed by vascular wall NO deposition, on the one hand, limits the damaging action of excess NO in shocks by the feedback, and, on the other, makes up some NO reserve which may be used in NO deficiency. Further studies of NO-dependent adaptive mechanisms will allow the agent to be used in the prevention and treatment of cardiovascular diseases associated with NO metabolic disturbances.