Combined Preconditioning Reduces the Negative Influence of Cerebral Ischemia on the Morphofunctional Condition of CNS.

We studied the influence of combined preconditioning (compound pQ-4 and moderate hypoxia) on morphometrical parameters of neuronal populations in hippocampal fields CA1 and CA3 in rats after bilateral ligation of the common carotid artery. Preconditioning produced a neuroprotective effect, improved survival of pyramidal neurons in the early and delayed periods of modeled ischemia, prevented the formation of necrotic and apoptotic neurons and hyperactivation of microglia, and protected endotheliocytes. The positive influence of preconditioning factors on the morphometric parameters of the brain under ischemic conditions agrees with the results of behavioral tests (open field and elevated plus maze) that demonstrated increased locomotor activity and exploratory behavior of animals.

[Erythropoietin and vascular endothelial growth factor level in normoxia and in cerebral ischemia under pharmacological and hypoxic preconditioning]. / Soderzhanie éritropoétina i faktora rosta éndoteliia sosudov v usloviiakh normoksii i pri ishemii golovnogo mozga pod deistviem farmakologicheskogo i gipoksicheskogo prekonditsionirovaniia.

The level of erythropoietin (EPO) and vascular endothelial growth factor (VEGF-A) was investigated in blood serum and brain of Wistar rats by the enzyme immunoassay with specific rat antibodies. These growth factors are actively studied as biomarkers of ischemia or cytoprotection, as well as targets for agents initiating preconditioning (PreC). Pharmacological (amtizol administration), hypoxic (hypobaric hypoxia), and combined PreC (amtizol+hypobaric hypoxia) were used as neuroprotective approaches in this experimental work. In normoxia groups blood and brain tissue were collected 1 h (early period) or 48 h (delayed period) after the PreC. In addition we studied groups of animals with cerebral ischemia (induced by bilateral ligation of the common carotid arteries) 1 h and 48 h after the combined PreC: the levels of EPO and VEGF-A in the blood serum and the brain supernatant were determined in one day after the ligation. Experiments have shown that amtizol (3,5-diamino-1,2,4-thiadiazole) in normoxia increased the EPO level in the brain, and did not change EPO in blood serum and VEGF-A levels in both serum and the brain. A three-day (60 min exposure with 48 h intervals) hypobaric hypoxia (410 mm Hg) increased EPO and VEGF-A in the blood serum and brain tissues, but in most experimental groups differences did not reach the level of statistical significance versus intact control. The combined PreC was accompanied by a significant increase of EPO and VEGF-A in normoxia conditions both in early and delayed period of PreC. In cerebral ischemia the EPO level in the blood serum and brain tissues was higher than in intact control. The serum level of VEGF-A of the ischemia control group tended to increase while the brain level of VEGF-A remained basically unchanged versus the intact control group. In combined PreC before ischemia, the EPO level was lower in serum as compared with the ischemia control in the delayed PreC period, but did not differ significantly from the ischemia control in serum in early period and in brain tissues in both PreC periods. The VEGF-A level in the groups of combined PreC was significantly lower in serum as compared with the ischemia control in both the early and delayed PreC; in brain tissues it did not differ from the level of both the intact and ishemia control in early PreC period and was higher than in both control groups in the delayed PreC period.

Signal Mechanism of the Protective Effect of Combined Preconditioning by Amtizole and Moderate Hypoxia.

The content of regulatory proteins involved in adaptation to hypoxia and ischemia was studied in brain rat homogenate under conditions of normoxia and after bilateral ligation of the common carotid arteries. Preconditioning with amtizole in combination with moderate hypoxia increased the levels of HIF-1α, erythropoietin, vascular endothelial growth factor under conditions of normoxia. During experimental ischemia, combined preconditioning led to stabilization of the content of these regulatory proteins at the level of intact control and to a decrease in glycogen synthase-3ß kinase activity. This pattern of changes in regulatory proteins was noted during the early and late periods of preconditioning.

Neuroprotective Effect of Antioxidants and Moderate Hypoxia as Combined Preconditioning in Cerebral Ischemia.

We studied combined effect of moderate hypoxia and compounds pQ-4, pQ-915, pQ-1032, and pQ-1104 on neurological deficit and survival of rats after bilateral ligation of common carotid arteries. Preconditioning including moderate hypoxia and treatment with compound pQ-4 produced a neuroprotective effect and increased animal survival during the early (by 51%) and late (by 33.5%) periods of modeled ischemia and reduced neurological deficit (by 50% and 41%, respectively). Moreover, this combination of preconditioning factors prevented postischemic excessive activation of free radical oxidation in brain hemispheres and blood serum.

[INFLUENCE OF COMBINED PHARMACOLOGICAL AND HYPOXIC PRECONDITIONING ON ANIMAL SURVIVAL AND FUNCTIONAL ACTIVITY OF CNS DURING MODEL CEREBRAL ISCHEMIA.]

The combined action of amthizole administration and hypoxia conditions on the survival of rats and the functional state of the central nervous system has been studied on a model of bilateral common carotid artery occlusion. It is established that this combined preconditioning produces cerebroprotective action, increases animal survival after surgery (estimated 72 h upon the onset of ischemia) by 38% (p = 0.029) in early and by 29% (p = 0.078) in late period of the ischemia modeling, reduces neurological deficiency by 55% (p = 0.006) in early and by 43 % (p = 0.028) in late period of the ischemia modeling, and decreases severity of behavioral changes in rats caused by cerebral ischemia in both periods of ischemia modeling.

[Promising directions of search for antihypoxants and targets of their action].

The modem notions about mechanisms of the organism adaptation to hypoxia are reviewed. Promising new directions in the search for effective medicinal agents with antihypoxant action are proposed. Probable targets for antihypoxant action, including mitochondrial ATP-dependent potassium channel (mito-KATP), mitochondrial megapore (mPTP), and hypoxia-inducible factor-1alfa (HIF-1alpha) are discussed.