Proteomic analysis of the lung in rats with hypobaric hypoxia-induced pulmonary hypertension.

Experimental pulmonary hypertension that develops in hypobaric hypoxia is characterized by structural remodeling of the lung. Proteomics - which may be the most powerful way to uncover unknown remodeling proteins involved in enhancing cardiovascular performance - was used to study 150 male Wistar rats housed for up to 21 days in a chamber at the equivalent of 5500 m altitude level. After 14 days' exposure to hypobaric hypoxia, pulmonary arterial pressure (PAP) was significantly increased. In lung tissue, about 140 matching protein spots were found among 8 groups (divided according to their hypobaric period) by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) (pH4.5-pH6.5, 30 kDa-100 kDa). In hypobaric rats, three spots were increased two-fold or more (vs. control rats) in two-dimensional differential in-gel electrophoresis (2D-DIGE). The increased proteins were identified, by matrix-assisted laser desorption ionization time of flight (MALDI-TOF), as one isoform of heat shock protein 70 (HSP70) and two isoforms of protein disulfide isomerase associated 3. This result was confirmed by Western blotting analysis of 2D-PAGE. Conceivably, HSP70 and PDIA3 may play roles in modulating the lung structural remodeling that occurs due to pulmonary hypertension in hypobaric hypoxia.

Expression of P2X4R mRNA and protein in rats with hypobaric hypoxia-induced pulmonary hypertension.

BACKGROUND: The experimental pulmonary hypertension that develops in hypobaric hypoxia is characterized by structural remodeling of the heart. The P2X4 receptor (P2X4R) controls vascular tone and vessel remodeling in several blood vessels, and it has emerged as a key factor in the enhancement of cardiovascular performance. METHODS AND RESULTS: To study the possible effects of hypobaric hypoxia on the P2X4R-synthesis system, 150 male Wistar rats were housed in a chamber at the equivalent of the 5,500 m altitude level for 21 days. After 14 days' exposure to hypobaric hypoxia, pulmonary arterial pressure (PAP) was significantly increased. In the right ventricle (RV) of the heart, P2X4R expression was significantly increased on days 1 and 14 (mRNA) and on days 7 and 21 (protein) of hypobaric hypoxic exposure. Immunohistochemical staining for P2X4R protein became more intense in RV in the late phase of exposure. These changes in P2X4R synthesis in RV occurred alongside the increase in PAP. In addition, P2X1R and P2Y2R mRNA levels in the RV were significantly increased on days 1, 14, and 21, and day 5, respectively, of exposure. The level of P2X1R protein in the RV was significantly increased on day 21 of exposure. CONCLUSIONS: Conceivably, P2 receptors, including P2X4R and P2X1R, might play roles in modulating the RV hypertrophy that occurs due to pulmonary hypertension in hypobaric hypoxia.

Urinary catecholamine responses in F-15 pilots: evaluation of the stress induced by long-distance flights.

Included in the Cooperative Cope Thunder exercises from Japan to Alaska is one of the longest distance flight missions carried out by Japan Air-Self Defense Force F-15 pilots. The magnitude of the flight stress of these pilots is considered to be quite high. The purpose of this study was to evaluate the flight stress induced by the long-distance flights. The subjects were eight pilots who participated on a volunteer basis. Samples of urine were collected approximately 30 minutes before (preflight) and 20 minutes after (postflight) the flights. The ratios (post-:preflight) of noradrenaline levels were 1.20 +/- 0.09 (Japan-Alaska) and 1.32 +/- 0.12 (Alaska-Japan), and those of adrenaline were 4.03 +/- 1.06 and 3.68 +/- 0.98. These results strongly suggest that psychological stress during the long-distance flights is increased in the fighter pilots.

Expression of endothelin-1 in the brain and lung of rats exposed to permanent hypobaric hypoxia.

High-altitude hypoxia causes pulmonary hypertension in humans and animals. Endothelin-1 (ET-1) is a novel and long-lasting vasoconstrictor. However, no study has dealt with the effects of a hypobaric hypoxic environment (HHE) on ET-1 activity in the brain. We examined 134 male rats permanently exposed to the equivalent of 5500 m altitude for 1 to 8 weeks. In these HHE rats, the mean pulmonary arterial pressure was significantly raised. The level of ET-1 protein, measured by enzyme immunoassay, increased rapidly in the lungs on exposure to HHE, but decreased in the brain. The level of ET-1 mRNA, measured by semiquantitative RT-PCR, was raised at 1, 4, and 6 weeks' exposure in the lungs and at 4 or more weeks' exposure in 3 of 8 brain regions. By in situ hybridization and immunohistochemistry of brain sections, ET-1 mRNA and protein were detected in the endothelial cells, neurons, and astrocyte-like cells in control rats. In HHE rats, the immunoreactive intensity for ET-1 protein decreased rapidly with time in these cells within the brain, although a few weakly ET-1 protein-positive cells were detected until 8 weeks' exposure to HHE. Only a few weakly ET-1 mRNA-positive endothelial cells were detected in any HHE rats. Although the reactivity for ET-1 mRNA had decreased significantly in neurons and astrocyte-like cells at 1 and 2 weeks' exposure to HHE, it was again strong in both types of cells at 4 weeks' exposure to HHE. These results raise the possibility that during exposure to HHE, ET-1 production in the lung may play a role in the development of pulmonary hypertension, while a decrease in ET-1 production within the brain may help to protect neurons by preventing or limiting the constriction of cerebral microvessels during the hypoxia induced by HHE.

Expressions of adrenomedullin mRNA and protein in rats with hypobaric hypoxia-induced pulmonary hypertension.

Experimental pulmonary hypertension induced in a hypobaric hypoxic environment (HHE) is characterized by structural remodeling of the heart and pulmonary arteries. Adrenomedullin (AM) has diuretic, natriuretic, and hypotensive effects. To study the possible effects of HHE on the AM synthesis system, 150 male Wistar rats were housed in a chamber at the equivalent of a 5,500-m altitude level for 21 days. After 14 days of exposure to HHE, pulmonary arterial pressure (PAP) was significantly increased (compared with control rats). The plasma AM protein level was significantly increased on day 21 of exposure to HHE. In the right ventricle (RV), right atrium, and left atrium of the heart, the expressions of AM mRNA and protein were increased in the middle to late phase (5-21 days) of HHE, whereas in the brain and lung they were increased much earlier (0.5-5 days). In situ hybridization and immunohistochemistry showed AM mRNA and protein staining to be more intense in the RV in animals in the middle to late phase of HHE exposure than in the controls. During HHE, these changes in AM synthesis, which occurred strongly in the RV, occurred alongside the increase in PAP. Conceivably, AM may play a role in modulating pulmonary hypertension in HHE.

Changes in myosin heavy chain and its localization in rat heart in association with hypobaric hypoxia-induced pulmonary hypertension.

Experimental pulmonary hypertension induced in a hypobaric hypoxic environment (HHE) is characterized by structural remodelling of the heart. In rat cardiac ventricles, pressure and volume overload are well known to be associated with changes in cardiac myosin heavy chain (MHC) isoforms. To study the effects of HHE on the MHC profile in the ventricles, 83 male Wistar rats were housed in a chamber at the equivalent of 5500 m altitude for 1-8 weeks. Pulmonary arterial pressure, right ventricular free wall (RVFW) weight, the ratio of RVFW weight over body weight (BW), the ratio of left ventricular free wall (LVFW) weight over BW, and myocyte diameter in both ventricles showed significant increases after 1 week, 2 weeks, 1 week, 6 weeks, and 4 weeks of HHE, respectively. Semi-quantitative reverse transcriptase-polymerase chain reaction revealed that beta-MHC mRNA expression was increased significantly in both ventricles at 6 and 8 weeks of HHE, whereas alpha-MHC mRNA expression was decreased significantly at 6 and 8 weeks of HHE in the right ventricle (RV) and at 6 weeks of HHE in the left ventricle (LV). The percentage of myosin containing the beta-MHC isoform was increased significantly at 4-8 weeks of HHE in RV and at 6 weeks of HHE in LV. In situ hybridization showed that the area of strong staining for beta-MHC mRNA was increased in both ventricles at 8 weeks of HHE, and showed a decrease from RVFW to cardiac septum, and from cardiac septum to LVFW. These results suggest that HHE has a significant effect on the expression of both MHC mRNA and protein in the heart, particularly in RV. These changes may reflect a role for cardiac MHC in the response to pulmonary hypertension in HHE.