Our own study as well as others have previously reported that hypoxia activates 15-lipoxygenase (15-LO) in the brain, causing a series of chain reactions, which exacerbates ischemic stroke. 15-hydroxyeicosatetraenoic acid (15-HETE) and 15-oxoeicosatetraenoic acid (15-oxo-ETE/15-KETE) are 15-LO-specific metabolites of arachidonic acid (AA). 15-HETE was found to be rapidly converted into 15-oxo-ETE by 15-hydroxyprostaglandin dehydrogenase (15-PGDH) in some circumstances. We have demonstrated that 15-HETE promotes cerebral vasoconstriction during hypoxia. However, the effect of 15-oxo-ETE upon the contraction of cerebral vasculature remains unclear. To investigate this effect and to clarify the underlying mechanism, we performed immunohistochemistry and Western blot to test the expression of 15-PGDH in rat cerebral tissue, examined internal carotid artery (ICA) tension in isolated rat ICA rings. Western blot and reverse transcription polymerase chain reaction (RT-PCR) were used to analyze the expression of voltage-gated potassium (Kv) channels (Kv2.1, Kv1.5, and Kv1.1) in cultured cerebral arterial smooth muscle cells (CASMCs). The results showed that the levels of 15-PGDH expression were drastically elevated in the cerebral of rats with hypoxia, and 15-oxo-ETE enhanced ICA contraction in a dose-dependent manner. This effect was more significant in the hypoxic rats than in the normoxic rats. We also found that 15-oxo-ETE significantly attenuated the expression of Kv2.1 and Kv1.5, but not Kv1.1. In conclusion, these results suggest that 15-oxo-ETE leads to the contraction of the ICA, especially under hypoxic conditions and that specific Kv channels may play an important role in 15-oxo- ETE-induced ICA constriction., Di Wang, Yu Liu, Ping Lu, Daling Zhu, Yulan Zhu., and Obsahuje bibliografii
Hypoxic pulmonary vasoconstric tion (HPV) is an important homeostatic mechanism in which increases of [Ca2+] i are primary events. In this study, primary cultured, human pulmonary artery smooth muscle cells (hPASMC) were used to examine the role of TRPC channels in mediating [Ca2+] i elevations during hypoxia. Hypoxia (PO2 about 20 mm Hg) evoked a transient [Ca2+] i elevation that was reduced by removal of extracellular calcium. Nifedipine and verapamil, blockers of vo ltage-gated calcium channels (VGCCs), attenuated th e hypoxia-induced [Ca2+] i elevation by about 30 %, suggesting the presence of alternate Ca2+ entry pathways. Expression of TRPC1 an d TRPC6 in hPASMC were found by RT-PCR and confirmed by Western blot analysis. Antagonists for TRPC, 2APB and SKF96365, significantly reduced hypoxia-induced [Ca2+] i elevation by almost 60 %. Both TRPC6 and TRPC1 were knocked down by siRNA, the loss of TRPC6 decreased hypoxic response down to 21 % of control, whereas the knockdown of TRPC1 reduced the hypoxia respon se to 85 %, suggesting that TRPC6 might play a central role in mediating hypoxia response in hPASMC. However, blockade of PLC pathway caused only small inhibition of the hypoxia response. In contrast, AICAR, the agonist of AMP-activated kinase (AMPK), induced a gradual [Ca2+] i elevation, whereas compound C, an antagonist of AMPK, almost abolished the hypoxia response. Ho wever, co-immunoprecipitation revealed that AMPK α was not colocalized with TRPC6. Our data supports a role for TRPC6 in mediation of the [Ca2+] i elevation in response to hypoxia in hPASMC and suggests that this response may be linked to cellular energy status via an activation of AMPK., C. Tang, W. K To, F. Meng, Y. Wang, Y. Gu., and Obsahuje bibliografii
The effect of chronic hypercapnia on cardioprotection induced by chronic hypoxia was investigated in adult male Wistar rats exposed to isobaric hypoxia (10 % O2) for three weeks. In the first experimental group, CO2 in the chamber was fully absorbed; in the second group, its level was increased to 4.1 %. Normoxic controls were kept in atmospheric air. Anesthetized open-chest animals were subjected to 20-min LAD coronary artery occlusion and 3-h reperfusion for infarct size determination (TTC staining). Chronic hypoxia alone reduced body weight and increased hematocrit; these effects were significantly attenuated by hypercapnia. The infarct size was reduced from 61.9 ± 2.2 % of the area at risk in the normoxic controls to 44.5±3.3 % in the hypoxic group (P<0.05). Hypercapnia blunted the infarct size-limiting effect of hypoxia (54.8±2.4 %; P<0.05). It is concluded that increased CO2 levels in the inspired air suppress the development of the chronic hypoxia-induced cardioprotective mechanism, possibly by interacting with ROS signalling pathways., J. Neckář, O. Szárszoi, J. Herget, B. Ošťádal, F. Kolář., and Obsahuje bibliografii
The purpose of the study was to check whether hypoxia of corneal tissue increases the collagenolytic activity due to release of reactive oxygen and nitrogen species. Rats were exposed to hypoxia 10 % O2 for 4, 14, and 21 days. The radical tissue injury was measured by the level of nitrotyrosine and changes in the lipoperoxide-related fluorophores. Collagen protein composition was analyzed by slab gel electrophoresis. The activity of gelatinolytic enzymes was studied using the zymography. The vascularization of the corneas was measured. We found no differences in the corneal tissue in the gel electrophoretic profile of collagenous proteins and gelatinolytic activity between normoxic and hypoxic rats. We did not find any sign of radical tissue injury. There were no changes in the vascularization of corneas after exposition to hypoxia. The environmental 10 % hypoxia does not induce radical tissue injury and an increase of collagenolytic activity in the rat cornea., G. Mahelková, J. Korynta, A. Moravová, J. Novotná, R. Vytášek, J. Wilhelm., and Obsahuje bibliografii a bibliografické odkazy
The aim of the present study was to test the hypothesis that chronic hypoxia would aggrav ate hypertension in Ren-2 transgenic rats (TGR), a well-defined monogenetic model of hypertension with increased ac tivity of endogenous renin- angiotensin system (RAS). Systolic blood pressure (SBP) in conscious rats and mean arterial pressure (MAP) in anesthetized TGR and normotensive Hannover Sprague-Dawley (HanSD) rats were determined under normoxia that was either continuous or interrupted by two weeks' hypoxi a. Expression, activities and concentrations of individual components of RAS were studied in plasma and kidney of TGR and HanSD rats under normoxic conditions and after exposure to chronic hypoxia. In HanSD rats two weeks' exposure to chroni c hypoxia did not alter SBP and MAP. Surprisingly, in TGR it de creased markedly SBP and MAP; this was associated with substantial reduction in plasma and kidney renin activities and also of angiotensin II (ANG II) levels, without altering angiotensin-converting enzyme (ACE) activities. Simultaneously, in TGR the exposu re to hypoxia increased kidney ACE type 2 (ACE2) activity and angiotensin 1-7 (ANG 1-7) concentrations as compared with TGR under continuous normoxia. Based on these results, we propose that suppression of the hypertensiogenic ACE-ANG II axis in the circulation and kidney tissue, combined with augmentation of the intrarenal vasodilator ACE2-ANG 1-7 axis, is the main mechanism responsible for the blood pressure-lowering effects of chronic hypoxia in TGR., L. Červenka, J. Bíbová, Z. Husková, Z. Vańourková, H. J. Kramer, J. Herget, Š. Jíchová, J. Sadowski, V. Hampl., and Obsahuje bibliografii
Hypoxia has been identified as an important stimulus for gene expression during embryogenesis and in various pathological situations. Its influence under physiological conditions, however, has only been studied occasionally. We therefore investigated the effect of intermittent high altitude hypoxia on the mRNA expression of different cytokines and protooncogenes, but also of other genes described to be regulated by hypoxia, in the left ventricle (LV), the right ventricle (RV), atria and the lung of adult rats after simulation of hypoxia in a barochamber (5000 m, 4 hours to 10 days). Heme oxygenase-1 as well as transforming growth factor-β1 showed an increased expression in all regions of the heart and the lung at different periods of hypoxia. For lactate dehydrogenase-A, we found a significant up-regulation in the RV and the lung, for lactate dehydrogenase-B up-regulation in the RV, but down-regulation in the LV and the atria. Vascular endothelial growth factor was up-regulated in the RV, the LV and the lung, but down-regulated in the atria. Its receptor Flk-1 mRNA was significantly increased in the atria and RV only. Expression of c-fos was found in the LV and RV only after 4 hours of hypoxia. The level of c-jun was significantly increased in the LV but decreased in the atria. Our data clearly demonstrate that intermittent hypoxia is a modulator of gene expression under physiological conditions. It differently regulates the expression of distinct genes not only in individual organs but even within one organ, i.e. in the heart., E. Deindl, F. Kolář, E. Neubauer, S Vogel, W. Schaper, B. Ošťádal., and Obsahuje bibliografii
Pregnant rats were exposed to intermittent hypobaric hypoxia (at a simulated altitude of 7000 m or 5000 m) and the excitability of cortical neurons of their pups was tested. Stimulation of the sensorimotor cortex of rats prenatally exposed to hypoxia shortened the duration of cortical afterdischarges in 12-day-old rats, but did not change the excitability in 25-day-old animals. Shortening of the first afterdischarge in 35-day-old rats but the prolongation of the first afterdischarge in adult rats (as compared to the duration of cortical afterdischarges in rats not exposed to prenatal hypoxia) were registered. The possible mechanisms of different excitability of cortical neurons in rats prenatally exposed to hypobaric hypoxia are discussed., D. Marešová, I. Valkounová, K. Jandová, J. Bortelová, S. Trojan., and Obsahuje bibliografii
a1_Vascular repair in response to injury or stress (often referred to as remodeling) is a common complication of many cardiovascular abnormalities including pulmonary hypertension, systemic hypertension, atherosclerosis, vein graft remodeling and restenosis following balloon dilatation of the coronary artery. It is not surprising that repair and remodeling occurs frequently in the vasculature in that exposure of blood vessels to either excessive hemodynamic stress (e.g. hypertension), noxious blood borne agents (e.g. atherogenic lipids), locally released cytokines, or unusual environmental conditions (e.g. hypoxia), requires readily available mechanisms to counteract these adverse stimuli and to preserve structure and function of the vessel wall. The responses, which were presumably evolutionarily developed to repair an injured tissue, often escape self-limiting control and can result, in the case of blood vessels, in lumen narrowing and obstruction to blood flow. Each cell type (i. e. endothelial cells, smooth muscle cells, and fibroblasts) in the vascular wall plays a specific role in the response to injury. However, while the roles of the endothelial cells and smooth muscle cells (SMC) in vascular remodeling have been extensively studied, relatively little attention has been given to the adventitial fibroblasts. Perhaps this is because the fibroblast is a relatively ill-defined cell which, at least compared to the SMC, exhibits few specific cellular markers. Importantly though, it has been well demonstrated that fibroblasts possess the capacity to express several functions such as migration, rapid proliferation, synthesis of connective tissue components, contraction and cytokine production in response to activation or stimulation., a2_The myriad of responses exhibited by the fibroblasts, especially in response to stimulation, suggest that these cells could play a pivotal role in the repair of injury. This fact has been well documented in the setting of wound healing where a hypoxic environment has been demonstrated to be critical in the cellular responses. As such it is not surprising that fibroblasts may play an important role in the vascular response to hypoxia and/or injury. This paper is intended to provide a brief review of the changes that occur in the adventitial fibroblasts in response to vascular stress (especially hypoxia) and the role the activated fibroblasts might play in hypoxia-mediated pulmonary vascular disease., K. R. Stenmark, D. Bouchey, R. Nemonoff, E. C. Dempsey, M. Das., and Obsahuje bibliografii
Chronic hypoxia results in hypoxic pulmonary hypertension characterized by fibrotization and muscularization of the walls of peripheral pulmonary arteries. This vessel remodeling is accompanied by an increase in the amount of lung mast cells (LMC) and the presence of small collagen cleavage products in the vessel walls. We hypothesize that hypoxia activates LMC, which release matrix metalloproteinases (MMPs) cleaving collagen and starting increased turnover of connective tissue proteins. This study was designed to determine whether in vitro hypoxia stimulates production of MMPs in rat LMC and increases their collagenolytic activity. The LMC were separated on the Percoll gradient and then were divided into two groups and cultivated for 24 h in 21 % O2 + 5 % CO2 or in 10 % O2 + 5 % CO2. Presence of the rat interstitial tissue collagenase (MMP-13) in LMC was visualized by immunohistological staining and confirmed by Western blot analysis. Total MMPs activity and tryptase activity were measured in both cultivation media and cellular extracts. Exposure to hypoxia in vitro increased the amount of cells positively labeled by anti-MMP-13 antibody as well as activities of all measured enzymes. The results therefore support the concept that LMC are an important source of increased collagenolytic activity in chronic hypoxia., H. Maxová, J. Novotná, L. Vajner, H. Tomášová, R. Vytášek, M. Vízek, L. Bačáková, V. Valoušková, T. Eliášová, J. Herget., and Obsahuje bibliografii a bibliografické odkazy
Oxygen supply was corrected in rabbits during the hepatic ischemia/reperfusion by means of different breathing mixtures: hypoxic (14.8 % O2+85.2 % N2), hyperoxic (78 % O2+20.2 % N2+ 1.8 % CO2), or hypercapnic (5 % CO2 in air). Hepatic ischemia was induced for 30 min by ligation of hepatic artery, reperfusion period lasted 120 min. Indices of blood oxygen transport (p50act, pCO2, pH, pO2, etc.) and prooxidant-antioxidant balance (Schiff bases, conjugated dienes, catalase, retinol, a-tocopherol) were measured in the blood and liver. The severity of reperfusion damage was evaluated by the activities of alanine and aspartate aminotransferases (ALT, AST) in the blood. Hepatic ischemia/reperfusion resulted in higher p50act in hepatic venous and mixed venous blood in all experimental groups. The changes of p50act were most marked in the hypercapnic group and were the weakest in the hypoxic group. The rise in p50act was accompanied by higher levels of lipid peroxidation products, ALT and AST in blood and liver homogenates, and by a simultaneous fall of α-tocopherol and retinol concentrations, except in the hypoxic group. Catalase activity at the end of reperfusion increased under normoxia, decreased under hyperoxia or hypercapnia and did not change under hypoxia. The moderate hypoxia during reperfusion was accompanied by a better balance between the mechanisms of reactive oxygen species production and inactivation that may be observed by optimal changes in p50act and reduced the hepatic damage in this pathological condition., V. V. Zinchuk, M. N. Khodosovsky, D. A. Maslakov., and Obsahuje bibliografii