Comparative Study of HIF-1α- and HIF-2α-Immunopositive Neurons and Capillaries in Rat Cortex under Conditions of Tissue Hypoxia.

We measured the content of HIF-1α and HIF-2α-immunopositive neurons and microvessels in the brain of Wistar rats during the first 24 h of tissue hypoxia induced by subcutaneous injection of cobalt dichloride (50 mg/kg). In control rats (without hypoxia), immunohistochemical marker HIF-2α in cortex of parietal lobe was not detected, and HIF-1α was detected only in few weakly stained pale neurons and capillaries. In 30 min after injection of the cobalt salt, the number of HIF-1α+ neurons increased by 25.6% (in capillaries by 12.3%), many of these were characterized by intensive reaction; the quantitative parameters reached their maximum level within 1-3 h. However, the concentration of immunopositive neurons returned to the control values in 6 h after hypoxia modeling (capillaries in 9 h). In contrast to HIF-1α, the number of neurons and capillaries containing HIF-2α reached a maximum level in 6-12 h of hypoxia. The relative density of HIF-2α+ capillaries increased most pronouncedly (by 23.6%); the relative density of neurons increased by 18.9%. The relative density of HIF-2α+ cells did not change significantly to the end of the experiment. Thus, HIF-1α is more essential for regulation of adaptation to hypoxia in neurons and HIF-2α is more important for the endothelium of microvessels.

[The distribution of matrix metalloproteinases and their tissue inhibitors in the brain vascular bed exposed to chronic tobacco smoke]. / Ékspressiia matriksnykh metalloproteinaz i ikh tkanevykh ingibitorov v sosudistom rusle golovnogo mozga pri khronicheskoi intoksikatsii tabachnym dymom v éksperimente.

AIM: To study the distribution of MMP-2 and MMP-9 and their inhibitors (TIMP-2 and TIMP-1 respectively) in the brain vascular bed of rats exposed to chronic tobacco smoke. MATERIAL AND METHODS: Localization and expression of MMP-2, MMP-9, TIMP-2 and TIMP-1 in the pial branches (I-V order vessels), intracerebral arteries and capillaries of rats exposed to tobacco smoke were studied for 36 weeks. The level of enzymatic activity was assessed by the relative quantity of enzymopositive arteries and amount of fragments per 1 mm2 and rate of immunohistochemical reaction. Specific capillary density per mm2 of brain tissue and optical density of the immunohistochemical product were calculated. RESULTS: MMP-2 and TIMP-2 were found in all segments of the arterial course in control animals. In rats exposed to tobacco smoking, the expression of MMP-2 increased only in intracerebral arteries and capillaries while TIMP-2 level decreased. MMP-9 and TIMP-1 were noted only in single vessels, mainly small pial and intracerebral arteries, in intact animals. In rats exposed to tobacco smoke, MMP-9 expression significantly increased in all segments of the arterial course whereas the increase in TIMP-1 was observed mainly in large pial arteries. CONCLUSION: In physiological conditions, the dynamic balance between MMP-2 and TIMP-2 maintains basic tissue metabolism. Products of tobacco combustion are inductors of the inducible MMP-9 which promotes morphofunctional changes. The imbalance in MMP-9 - TIMP-1 system causes the degradation of extracellular matrix in different segments of the brain arterial course promoting the development of cerebral dysfunction.

Dynamics of Distribution of Capillaries with Matrix Metalloproteinase-2 and Its Tissue Inhibitor in Rat Brain during Development of Experimental Hypertension.

The capillaries containing MMP-2 and its tissue inhibitor TIMP-2 were examined in cerebral cortex and white matter obtained from intact Wistar rats (n=5) and the rats with progressing experimental renovascular hypertension (n=35). In hypertensive rats, the changes in intensity of the immunohistochemical reaction and in the density of capillaries expressing TIMP-2 significantly differed from the corresponding values in MMP-2-positive capillaries, which resulted in pronounced deviation of MMP-2/TIMP-2 index from the control level (especially in cerebral cortex) probably attesting to enhanced risk of complications in cases with arterial hypertension.

[The cellular and molecular mechanisms of angiogenesis regulation in the brain]. / Kletochno-molekuliarnye mekhanizmy reguliatsii angiogeneza v golovnom mozge.

This review presents the data on cellular and molecular mechanisms of angiogenesis regulation linked to the vascular epithelium. According to current conceptions, activated endothelial cells and their predecessors (progenitor cells) are involved in the regulation of angiogenesis. These cells synthesize angiogenic molecules differing by the chemical structure and mechanism of biological effect and allowing a direct or indirect control over each stage of angiogenesis. Both the excess and insufficient angiogenesis can lead to fast and irreversible changes in nervous tissue under certain conditions. For this reason, the balance in the system of molecular stimulators and inhibitors of angiogenesis is especially important for brain function. Without adequate reperfusion of an affected brain area the post-stroke neuroreparation, which can be provided with timely stimulation of angiogenesis, is unattainable and the intensification of this process in tumors, on the contrary, has adverse consequences. Growth of a tumor and its metastatic spread are substantially associated with an increase in the level of tumor tissue vascularization, and blocking angiogenesis is often the only productive way to limit the growth of a tumor. However our knowledge of mechanisms of angiogenesis regulation in the brain on the cellular and molecular level in physiological and pathological conditions is still insufficient, and, therefore, the influence of angiogenic factors on tissue targets do not always cause the expected effects.

Effects of Chronic Tobacco Smoking on the Distribution of Tachykinin Receptors in Rat Pial Arteries.

Pial arteries of different diameter were studied in intact rats and after 6-month modeling of chronic tobacco smoking in rats. Expression of tachykinin NK1 receptors in pial arteries was studied by biomicroscopy and immunohistochemical methods. Chronic tobacco smoking induced considerable reorganizations of the arterial bed. The intensity of changes depended on the diameter of vessels. In small pial vessels that directly participate in the blood supply to the brain, pronounced vasodilatation and enhanced expression of NK1 receptors in the endothelium mediating the effects of substance P were observed; the number of these vessels also increased. The intensity of the response to tobacco smoke components decreased with increasing vessel diameter.

[Effects of chronic tabacco smoking on the cerebral blood flow]. / Vliyanie khronicheskogo tabakokureniya na tserebral'nuyu gemodinamiku.

AIM: To study an effect of chronic smoking on cerebral hemodynamics and cerebrovascular reactivity in different segments of the arterial system of the brain in men. MATERIAL AND METHODS: Male patients enrolled in the study were divided into two groups: controls (n=11) and smokers (n=24) with index 30.7 pack-year smoking history. Haemorheological parameters: viscosity of blood, aggregation of erythrocytes, hematocrit, fibrinogen were evaluated in both groups. Using carotid duplex ultrasound (MyLab 50 Esaote, Italy), intima-media thickness (IMT) of common carotid arteries (CCA) was measured. Parameters of cerebral hemodynamics were evaluated using transcranial Doppler ultrasound (Nicolet Companion Biomedikal, USA). Tests of the cerebrovascular reactivity were used to study arteries of three levels: common carotid arteries, middle cerebral arteries (MCA) and pial arteries. RESULTS: An increase in erythrocytes, hemoglobin, hematocrit, viscosity of blood, aggregation of erythrocytes and fibrinogen was found in the group of smokers compared to the control group. There were an increase in IMT of CCA by more than 50% and a decrease in the mean flow velocity in CCA in smokers. Also smoking decreased MCA mean flow velocity, but this decrease was 2-3 times smaller than in the common carotid arteries. Vasoconstrictor reactions prevailed in MCA, as indicated by the increase in the peripheral vascular resistance index. An increase in vasospastic reactions in pial arteries in smokers was discovered. At the same time, the vasodilatation reaction was maintained or not significantly reduced in pial arteries. CONCLUSION: Chronic smoking is one of the significant factors causing changes in haemorheological parameters, damage of vascular wall, initiation of atherogenesis and disturbance of cerebral hemodynamics. The study of velocity characteristics and peripheral vascular resistance indices in the group of smokers revealed different reactions of different segments of the brain arterial system.

Vasomotor activity of the aorta during chronic smoking modeling.

We studied vasomotor responses of aortic endothelium in a rat model of chronic smoking. It was found that long-term exposure to tobacco smoke (inhalation) impaired vasomotor function of the aortic endothelium leading to insufficient vasodilator activity and enhanced vasoconstriction. After the cessation of inhalations, vasomotor disturbances were not only preserved, but also exacerbated because of increased pathological endothelium-independent vasoconstriction.

[The state of cerebral blood flow in hypertensive crises and possibilities of its correction].

We examined 60 patients with arterial hypertension admitted to hospital during hypertensive crisis. Control group consisted of 30 patients with normal arterial pressure. We investigated parameters of cerebral blood flow with the method of transcranial dopplerography, content of NO and a row of cytokines (interleukin-6, interleukin-0, tumor necrosis factor) in blood serum during hypotensive therapy with inclusion of calcium antagonist amlodipine and cerebroprotector vinpocetine. After 12 weeks of hypotensive therapy we noted significant antihypertensive effect, improvement of parameters of cerebral blood flow, and elevation of NO content in all groups of studied persons most pronounced in patients receiving amlodipine as monotherapy or in combination with vinpocetine. Administration of vinpocetine in addition to hypotensive therapy is justified in patients with hypertensive disease, as this significantly improves blood flow in cerebral vessels. This appears as elevation of linear blood flow velocity, lowering of peripheral resistance and increase of content of NO in blood serum.