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Biomedical subjects

K R Stenmark

Publications and source records attributed to K R Stenmark.

At least 73 records · Page 4Linked to original sources
PubMed1991

Hypoxia-induced inhibition of tropoelastin synthesis by neonatal calf pulmonary artery smooth muscle cells.

Animals chronically exposed to hypoxia develop characteristic structural changes in the pulmonary arterial vasculature including cell hypertrophy, hyperplasia, and increased deposition of extracellular matrix proteins. The medial smooth muscle cells' (SMC) increase in tropoelastin mRNA expression and elastin deposition as determined by in situ hybridization and histologic examination appears to contribute significantly to this increase in matrix protein accumulation. The primary stimulus for the increased tropoelastin production, which persists in vitro, is unknown but mechanical forces and hypoxia seem to play a role. In order to determine the direct effects of hypoxia on tropoelastin production by pulmonary artery SMC, cultured neonatal bovine pulmonary artery SMC were exposed to 3%, 10%, and 21% O2 concentrations for 48, 72, and 120 h and soluble tropoelastin was measured by direct immunoassay. Tropoelastin mRNA levels were also determined by Northern and slot blot analysis after 48 h of incubation under hypoxic conditions. SMC cultured in 3% and 10% O2 for 120 h showed dose-dependent decreases (11-fold and 2-fold, respectively) in measured tropoelastin levels compared with SMC cultured in 21% O2 conditions. This decrease was not due to cell damage or accumulation of toxic metabolites while under hypoxic conditions nor to a change in tropoelastin partitioning between the cell and media. Tropoelastin mRNA levels were also decreased under hypoxic conditions. Secreted, cell layer, and total protein synthesis determined by L-[3H]leucine incorporation again showed a dose-dependent decrease under hypoxic conditions but not to the same extent as tropoelastin production.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Insulin-like growth factor I and protein kinase C activation stimulate pulmonary artery smooth muscle cell proliferation through separate but synergistic pathways.

Smooth muscle cell (SMC) hyperplasia is an important component of vascular remodeling in chronic hypoxic pulmonary hypertension. The mechanisms underlying SMC proliferation in the remodeling process are poorly understood, but may involve insulin-like growth factor I (IGF-I). This study investigates the potential proliferative effects of IGF-I on SMC cultured from the pulmonary arteries (PA) of neonatal calves. We hypothesized that IGF-I stimulates PA SMC proliferation through a protein kinase C (PKC)-independent pathway, but that PKC activation would augment this proliferative response. Incorporation of 3H-thymidine was used as an index of cellular proliferation, and was correlated with subsequent changes in cell counts. Under serum-free conditions, IGF-I (100 ng/ml) induced a 6-fold increase in thymidine incorporation by quiescent PA SMC. This stimulation was not blocked by dihydrosphingosine, an inhibitor of PKC activation. Phorbol myristate acetate (PMA) (1 nM), a membrane-permeable PKC activator, induced a 12-fold increase in thymidine incorporation which was 70% inhibited by dihydrosphingosine. Co-incubation with IGF-I and PMA caused a 60-fold increase in thymidine incorporation, which was 30% inhibited by dihydrosphingosine. This synergistic increase in thymidine incorporation was associated with a subsequent significant increase in cell number. PKC-downregulated cells (1,000 nM PMA x 30 hr) proliferated in response to IGF-I but not PMA, and did not demonstrate synergism with the combination of IGF-I and PMA. The threshold concentrations of IGF-I and PMA for synergism were approximately 1 ng/ml and 1 pM, respectively. We conclude that IGF-I stimulates neonatal PA SMC proliferation via a PKC-independent pathway, and that trace amounts of PKC activators are capable of synergistically augmenting this response. We speculate that the synergistic stimulation of SMC proliferation by IGF-I and PKC activators may play an important role in hypertensive pulmonary vascular remodeling.

Animals↗
PubMed1990

Alpha-skeletal actin messenger RNA increases in acute right ventricular hypertrophy.

Newborn calves exposed to hypobaric hypoxia develop severe pulmonary hypertension. Right ventricular hypertrophy and failure occur as a consequence of the increased pressure load. Alterations in right ventricular myocyte performance or differentiation could be reflected by the changes in the expression of contractile protein genes. We studied expression of contractile actin isotypes by measuring mRNA levels in total cellular RNA purified from right (RV) and left ventricles (LV) of calves with severe pulmonary hypertension after a 2-wk exposure to hypobaric hypoxia and age-matched controls. alpha-Skeletal actin mRNA was increased greater than 10-fold in the RV of hypertensive animals, whereas alpha-cardiac actin mRNA did not appear to change. alpha-Skeletal actin mRNA and alpha-cardiac actin mRNA did not increase in the LV of any of the hypoxic animals. After a 2-wk hypoxic exposure, calves were removed from the chamber. Two days later, RV alpha-skeletal actin mRNA decreased dramatically but was apparently elevated above that of an age-matched control. Thirty days after hypoxia, there appeared to be a persistent increase in RV alpha-skeletal actin mRNA. Although the physiological significance of these changes are unknown, an alteration in the RV myocyte phenotype has occurred.

Actins↗
PubMed1990

Leukotrienes and prostaglandins in fetal lung liquid.

Several recent studies have suggested that peptidoleukotrienes are involved in or responsible for the pulmonary pressor response to hypoxia as well as the normally high pulmonary vascular resistance of fetal lambs. The present studies were carried out to test these hypotheses. Fetal lambs were prepared with indwelling vascular catheters and tracheal catheters for access to lung liquid. We measured lung liquid levels of leukotrienes C4 (LTC4) and D4 (LTD4) in control unanesthetized fetal lambs with blood gases and pH in the normal range. In the control series, LTC4 and LTD4 were either not detectable or their levels were close to the limit of resolution (LTC4, less than 80 pg/ml; LTD4, less than 50 pg/ml) of the techniques utilized. Leukotriene E4 was measured in a separate study by using pooled samples, and it was also found to be below the detection limit of that assay (10 pg/ml). In a second series of animals, a level of acute hypoxia was induced to decrease fetal arterial PO2 to 12 Torr for 20 min. After hypoxia, tracheal fluid levels of leukotrienes were again below detection limits of the assays used (LTC4, less than 80 pg/ml; LTD4, less than 142 pg/ml). In another study, methodology was altered to lower the detection limits of leukotrienes in lung fluid and to allow the measurement of total peptidoleukotriene concentrations. In this study, even when hypoxia was extended for up to 1 h, leukotriene levels were consistently below the limit of detection of the assay (less than 20 pg/ml for the sum of all leukotrienes).(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗
PubMed1990

Decreased pulmonary vasoreactivity in an animal model of chronic Pseudomonas pneumonia.

Chronic pulmonary infection/colonization caused by Pseudomonas aeruginosa accounts for much of the morbidity and mortality in cystic fibrosis (CF). The effect of chronic pulmonary P. aeruginosa infection on the pulmonary circulation has not been studied. Therefore, we investigated the effect of chronic P. aeruginosa infection on pulmonary hemodynamics in a rat model. Two groups of rats were inoculated with either agar beads containing 1.0 x 10(4) colony-forming units of P. aeruginosa (infected) or an equal volume of sterile beads alone (control). In vivo, pulmonary vasoreactivity measured as the percent change in total pulmonary resistance during hypoxia was decreased at 1 wk (22 +/- 7% versus 57 +/- 3%), 2 wk (29 +/- 5% versus 73 +/- 17%), 3 wk (41 +/- 8% versus 77 +/- 14%), and 6 to 9 wk (23 +/- 10 versus 53 +/- 7; p less than 0.05 all time points; mean +/- SEM) postinoculation in infected animals when compared with that in time-matched control animals. At 6 to 9 wk postinoculation, pulmonary artery pressure was significantly elevated in infected rats (25.8 +/- 1.6 versus 21.0 +/- 1.0 mm Hg; p less than 0.05) when compared with that in control animals. Histopathologic findings were characterized by bronchiectasis as well as by chronic bronchial, parenchymal, and perivascular inflammation at all time points in infected animals.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗
PubMed1990

Unilateral pulmonary hypertension as a result of chronic high flow to one lung.

The patient presented is a 27-month-old male with complex congenital heart disease consisting of severe left ventricular outflow tract obstruction and ventricular septal defect who had undergone a pulmonary trunk-to-aorta graft and a pulmonary artery banding procedure as a neonate. Sometime after this repair, but at least 15 months prior to presentation to this institution for placement of an aortic homograft, the pulmonary trunk band apparently slipped and migrated over the right pulmonary artery, severely limiting blood flow to the right lung and increasing flow to the left. Severe pulmonary hypertension developed, with a main pulmonary artery pressure of 94/53 mm Hg. We present clinical and radiographic evidence that the resulting chronic high blood flow and pressure in the left lung ultimately resulted in hypoperfusion of that lung, presumably secondary to chronic vascular changes with greatly increased vascular resistance. Upon surgical repair and removal of the constrictive band from the previously banded right PA, blood flow was increased to the low resistance right lung causing right-sided unilateral pulmonary edema, ventilation/perfusion mismatching, and severe hypoxemia. Perfusion studies documented that less than 10% of blood was directed to the left lung, with greater than 90% to the right. Perfusion studies 9 months postoperatively continued to demonstrate minimal blood flow to the left lung. Discussion focuses on the effects of mechanical forces and the interaction with hypoxia in causing pulmonary vascular remodeling.

Child, Preschool↗
PubMed1989

Insulin-like growth factor I stimulates elastin synthesis by bovine pulmonary arterial smooth muscle cells.

Insulin-like growth factor I stimulates mitogenesis in smooth muscle cells, and upregulates elastin synthesis in embryonic aortic tissue. Increased smooth muscle elastin synthesis may play an important role in vascular remodeling in chronic pulmonary hypertension. Therefore, we studied the effect of IGF-I on elastin and total protein synthesis by pulmonary arterial smooth muscle cells in vitro. Tropoelastin synthesis was measured by enzyme immunoassay, and total protein synthesis was measured by [3H]-leucine incorporation. In addition, the steady-state levels of tropoelastin mRNA were determined by slot blot hybridization. Incubation of confluent cultures with various concentrations of IGF-I resulted in a dose-dependent stimulation of elastin synthesis, with a 2.4-fold increase over control levels at 1000 ng/ml of IGF. The increase in elastin synthesis was reflected by a stimulation of the steady-state levels of tropoelastin mRNA. We conclude that IGF-I has potent elastogenic effects on vascular smooth muscle cells, and speculate that it may contribute to vascular wall remodeling in chronic hypertension.

Animals↗
PubMed1989

Regulation of collagen production by medial smooth muscle cells in hypoxic pulmonary hypertension.

Pulmonary hypertension is associated with abnormal connective tissue deposition in the media of pulmonary arteries. Lobar arteries from calves maintained for up to 15 days at simulated high altitude showed a 35% increase in collagen and a greater than 40% increase in crosslinked elastin per microgram protein. Labeling of artery tissue with [14C]proline revealed a nearly twofold increase in relative collagen synthesis. There was increased incorporation into Types I, III, IV, and V collagen with an increase in the proportion of newly synthesized Type IV collagen. Quantitation of collagen mRNA by slot-blot assay demonstrated increased levels of Types I and IV collagen message. In addition, medial smooth muscle cells isolated from the hypertensive calves demonstrated a nearly twofold increase in relative collagen synthesis, a twofold increase in the accumulation of newly synthesized collagen per microgram DNA, and increased levels of Types I and IV collagen mRNA. Exposure of pulmonary artery smooth muscle cells, adventitial cells, and fetal calf ligament fibroblasts to conditioned calf serum harvested from cultures of medial cells from hypertensive animals increased their levels of collagen as well as elastin mRNA. These studies suggest that the increased production of collagen in hypertensive arteries is mediated at a pre-translational level by soluble factor(s) generated by medial smooth muscle cells.

Animals↗
PubMed1989

Response of lobar vessels to hypoxic pulmonary hypertension.

Lobar pulmonary arteries demonstrate increased production of extracellular matrix components in response to hypertension, but biosynthetic changes in lobar veins have not been described. We report here that steady-state levels of mRNAs for tropoelastin and type I procollagen in proximal lobar veins were decreased in calves with hypoxic pulmonary hypertension relative to levels detected in veins from normotensive animals. In contrast, transcript levels were elevated in lobar arteries from hypertensive calves. Histologically, medial thickening and hypertrophy were apparent in distal lobar arteries from pulmonary hypertensive calves, but at this level no structural changes were observed in veins. These results indicate that the synthetic response to hypoxic pulmonary hypertension is complex, with different alterations in the expression of extracellular matrix components in the pulmonary arterial and venous circulations.

Animals↗
PubMed1989

Decreased arterial wall prostaglandin production in neonatal calves with severe chronic pulmonary hypertension.

Neonatal calves exposed to chronic hypobaric hypoxia develop severe pulmonary hypertension associated with altered vascular reactivity, cellular proliferation, and increased elastin and collagen production. We hypothesized that prostaglandin (PG) production would be decreased in the pulmonary arterial vessel wall of these calves. Further, because of the possibility that the hemodynamic stresses of hypoxic pulmonary hypertension might change along the longitudinal axis of the pulmonary circulation, we measured prostaglandin synthetic capability in tissues isolated from proximal pulmonary artery, distal pulmonary artery, and pulmonary vein. We found that PGI2 production was decreased in both proximal and distal pulmonary artery rings isolated from pulmonary hypertensive calves compared to controls. PGI2 production was greater in distal than in proximal lobar pulmonary artery. In contrast, pulmonary veins from hypertensive calves, which are protected from the hemodynamic stress of pulmonary arterial hypertension, did not demonstrate altered PGI2 production compared to controls. PGE2 production was also decreased in proximal hypertensive pulmonary arterial rings as compared to controls. To determine if this decrease in vessel wall production of prostaglandins was due to changes in cellular prostaglandin production, we studied prostaglandin production by the three major cell types comprising hypertensive and control arteries. Endothelial cells cultured from hypertensive main pulmonary artery produced less PGI2 than did those from control artery, and there appeared to be a shift from PGI2 production to PGE2 production in endothelial cells isolated from hypertensive artery. Explanted advential fibroblasts from hypertensive artery produced less PGE2 than did controls. Smooth muscle cell PGI2 production did not differ between cells isolated from hypertensive and control arteries in these brief 30-min incubations. We conclude that there is a relative deficit in PGI2 and PGE2 production in the pulmonary arteries of calves with hypoxia-induced pulmonary hypertension and speculate that this contributes to altered vascular tone and vessel remodeling.

Animals↗
PubMed1989

Regional heterogeneity of elastin and collagen gene expression in intralobar arteries in response to hypoxic pulmonary hypertension as demonstrated by in situ hybridization.

In situ hybridization was used to determine the morphologic distribution of tropoelastin and alpha 1(I) procollagen mRNA expression in elastic intralobar arteries from neonatal calves with hypoxic pulmonary hypertension induced by a 15-day exposure to a simulated altitude of 1500 m. In vessels from normotensive control animals, low levels of hybridizable tropoelastin mRNA were detected in smooth muscle cells (SMC) of the inner media associated with large elastic lamellae. Compared to control arteries, vessels from hypertensive animals demonstrated a markedly different pattern of hybridization. In these arteries, strong hybridization signals for tropoelastin mRNA were seen in SMC lying between the elastic lamellae of the outer media, and the density of labeling associated with these medial cells decreased progressively toward the lumen. Endothelial and adventitial cells in both control and hypertensive arteries were negative for tropoelastin mRNA. Type I procollagen mRNA was dispersed through the media of control arteries, and in hypertensive calves, the hybridization signal was more intense and was unevenly distributed through the media similarly to that for tropoelastin mRNA. Adventitial cells were strongly positive for procollagen mRNA, and the signal was equally intense for both control and hypertensive arteries. Cells that had no detectable tropoelastin mRNA were noted in the outer media of both control and hypertensive vessels. These cells occurred as broad circumferential bands in the normotensive artery and as nodular foci in the hypertensive artery. Immunocytochemical studies with antibodies to smooth muscle specific actin, desmin, and vimentin demonstrated that cells within these foci, as well as tropoelastin mRNA-positive cells, were SMC. These studies demonstrate that expression of tropoelastin and procollagen mRNA was differentially stimulated by pulmonary hypertension within specific regions and SMC populations of the vascular wall.

Animals↗
PubMed1989

Lung eicosanoid metabolism.

Eicosanoids are metabolites of the essential fatty acid, arachidonic acid, which is an integral part of all cell membranes. Membrane damage (as in lung injury) and stretching of tissues are recognized stimuli for lung prostaglandin release, indicating a spectrum of possible roles of eicosanoids in the function of the normal and diseased lung. This article reviews the most pertinent issues regarding the roles of arachidonic acid metabolites in the lung.

Animals↗
PubMed1988

Pulmonary vasodilation with structurally altered pulmonary vessels and pulmonary hypertension.

To evaluate pulmonary vasodilation in a structurally altered pulmonary vascular bed, we gave endothelium-dependent (acetylcholine) and endothelium-independent [sodium nitroprusside, prostaglandin I2 (PGI2)] vasodilators in vivo and to isolated lobar pulmonary arteries from neonatal calves with severe pulmonary hypertension. Acetylcholine, administered by pulmonary artery infusion, decreased pulmonary arterial pressure from 120 +/- 7 to 71 +/- 6 mmHg and total pulmonary resistance from 29.4 +/- 2.6 to 10.4 +/- 0.9 mmHg.l-1.min without changing systemic arterial pressure (90 +/- 5 mmHg). Although both sodium nitroprusside and PGI2 lowered pulmonary arterial pressure to 86 +/- 4 and 96 +/- 4 mmHg, respectively, they also decreased systemic arterial pressure to 65 +/- 4 and 74 +/- 3 mmHg, respectively. Neither sodium nitroprusside nor PGI2 was as effective as acetylcholine at lowering total pulmonary resistance (18.0 +/- 3.6 and 19.1 +/- 2.2 mmHg.l-1.min, respectively). Right-to-left cardiac shunt through the foramen ovale was decreased by acetylcholine from 1.6 +/- 0.4 to 0.1 +/- 0.2 l/min but was not changed by sodium nitroprusside or PGI2. Isolated lobar pulmonary arteries from pulmonary hypertensive calves did not relax in response to acetylcholine, whereas isolated pulmonary arteries from age-matched control calves did relax in response to acetylcholine. Control and pulmonary hypertensive lobar pulmonary arteries relaxed equally well in response to sodium nitroprusside. We concluded that acetylcholine vasodilation was impaired in vitro in isolated lobar pulmonary arteries but was enhanced in vivo in resistance pulmonary arteries in neonatal calves with pulmonary hypertension.

Acetylcholine↗
PubMed1988

Vascular remodeling in neonatal pulmonary hypertension. Role of the smooth muscle cell.

We suggest that hypoxia-induced pulmonary hypertension in the newborn calf is an attractive model for studying the mechanisms underlying alterations in extracellular matrix accumulation which occur in pulmonary vascular disease. Our data support a model (Fig 7) in which the SMC, perhaps as a result of hypoxic and/or pressure-induced vessel wall injury, becomes phenotypically altered. This phenotypically altered SMC generates a factor, termed smooth muscle derived extracellular matrix factor (SMEF), and possibly other factors. SMEF, in turn, stimulates or induces elastin and collagen synthesis in fibroblasts and endothelial cells. SMEF, or an associated activity derived from phenotypically altered smooth muscle cells, also induces elastin receptor expression on the cell surface and affects the chemotactic responsiveness of vascular cells. Thus, the SMC may be able to affect both the secretory and responsive properties of cell types in the vascular wall. The SMC may be critical in the vascular remodeling in pulmonary hypertension. The possible autocrine or paracrine alteration of cellular phenotypes by smooth muscle-derived mediators provides an important new direction for future research into molecular and cellular mechanisms of connective tissue regulation in diseased vessels.

Altitude↗
PubMed1987

Smooth muscle-mediated connective tissue remodeling in pulmonary hypertension.

Abnormal accumulation of connective tissue in blood vessels contributes to alterations in vascular physiology associated with disease states such as hypertension and atherosclerosis. Elastin synthesis was studied in blood vessels from newborn calves with severe pulmonary hypertension induced by alveolar hypoxia in order to investigate the cellular stimuli that elicit changes in pulmonary arterial connective tissue production. A two- to fourfold increase in elastin production was observed in pulmonary artery tissue and medial smooth muscle cells from hypertensive calves. This stimulation of elastin production was accompanied by a corresponding increase in elastin messenger RNA consistent with regulation at the transcriptional level. Conditioned serum harvested from cultures of pulmonary artery smooth muscle cells isolated from hypertensive animals contained one or more low molecular weight elastogenic factors that stimulated the production of elastin in both fibroblasts and smooth muscle cells and altered the chemotactic responsiveness of fibroblasts to elastin peptides. These results suggest that connective tissue changes in the pulmonary vasculature in response to pulmonary hypertension are orchestrated by the medial smooth muscle cell through the generation of specific differentiation factors that alter both the secretory phenotype and responsive properties of surrounding cells.

Animals↗
PubMed1987

Neither anticoagulant nor nonanticoagulant heparin affects monocrotaline lung injury.

The administration of monocrotaline to rats causes pulmonary vascular leak within 1 wk followed in 2-3 wk by perivascular proliferation and fatal pulmonary hypertension. Possibly blocking the proliferation might block the pulmonary hypertension, providing insight into its mechanism. Because heparin, given as an antiproliferative agent, reduced hypoxic pulmonary hypertension in mice, it might also block monocrotaline-induced pulmonary hypertension. Alternatively, anticoagulation could worsen the lung injury. We found that heparin (300 and 600 U/kg sc twice daily) inhibited clotting in rats given monocrotaline but did not change the vascular leak, the right ventricular pressure, the right ventricular hypertrophy, the increased medial thickness of the pulmonary arterioles, or the production of a slow-reacting substance of anaphylaxis-like material by the lungs. A nonanticoagulant heparin fragment (2 mg/kg sc twice daily), given to avoid anticoagulation also did not influence the monocrotaline injury. Thus neither anticoagulant nor nonanticoagulant heparin either attenuated or worsened the measured effects of monocrotaline.

Animals↗