New approaches to acute lung injury.
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Anti-Inflammatory Agents↗
Biomedical subjects
W M Zapol
Publications and source records attributed to W M Zapol.
Hyporesponsiveness to inhaled nitric oxide in isolated, perfused lungs from endotoxin-challenged rats.
Inhaled nitric oxide (iNO) causes selective pulmonary vasodilation and improves oxygenation in patients with the adult respiratory distress syndrome (ARDS). Approximately 30% of ARDS patients fail to respond to iNO. Because sepsis syndrome often accompanies a decreased response to iNO, we investigated NO responsiveness in isolated, perfused lungs from rats exposed to lipopolysaccharide (LPS). Eighteen hours after intraperitoneal injection of 0.5 mg/kg LPS, rat lungs were isolated, perfused, and preconstricted with U-46619. Ventilation with 0.4, 4, and 40 parts per million by volume NO vasodilated LPS-pretreated lungs 75, 47, and 42% less than control lungs (P < 0.01 value differs at each concentration). The diminished vasodilatory response to iNO was associated with decreased NO-stimulated guanosine 3',5'-cyclic monophosphate (cGMP) release into the perfusate. Soluble guanylate cyclase activity did not differ in lung extracts from LPS-pretreated and control rats. LPS increased pulmonary cGMP-phosphodiesterase (PDE) activity by 40%. The PDE-sensitive cGMP analogue 8-bromoguanosine 3',5'-cyclic monophosphate vasodilated lungs from LPS-pretreated rats less than lungs from control rats. In contrast, the PDE-insensitive 8-para-chlorophenylthioguanosine 3',5'-cyclic monophosphate vasodilated lungs equally from both groups. After LPS challenge, the rat pulmonary vasculature becomes hyporesponsive to iNO. Hyporesponsiveness to iNO appears partly attributable to increased pulmonary cGMP-PDE activity.
Administration, Inhalation↗
Splenic contraction, catecholamine release, and blood volume redistribution during diving in the Weddell seal.
The spleen of the Weddell seal (Leptonychotes weddelli) may contract and inject red blood cells (RBCs) into the peripheral circulation during diving, but evidence for this hypothesis is indirect. Accordingly, we measured splenic dimensions by ultrasonography, plasma catecholamine concentrations, hemoglobin concentration, and hematocrit in five Weddell seals before and after intravenous epinephrine during halothane anesthesia and while awake at the surface after voluntary dives. Spleen size was reduced immediately after epinephrine injection or after the seal surfaced. Within the first 2 min after the seal surfaced, cephalocaudal splenic length was 71 +/- 2% (mean +/- SD; P < 0.05) and splenic thickness was 71 +/- 4% (P < 0.05) of the maximal resting values. Splenic size increased (half-time = 6-9 min) after the seal surfaced and was inversely correlated with plasma epinephrine and norepinephrine concentrations. Hemoglobin concentration increased from 17.5 +/- 5.3 g/dl (measured during general anesthesia) to 21.9 +/- 3.7 g/dl (measured in the first 2 min after surfacing). At these same times, the hematocrit increased from 44 +/- 12 to 55 +/- 8%. These values decreased (half-time = 12-16 min) after the seal surfaced. We estimate 20.1 liters of RBCs were sequestered at rest, presumably in the spleen, and released either on epinephrine injection or during diving. Catecholamine release and splenic contraction appear to be an integral part of the voluntary diving response of Weddell seals.
Animals↗
Chronic inhalation of nitric oxide inhibits neointimal formation after balloon-induced arterial injury.
Systemic and local intravascular NO administration inhibits neointimal formation after vascular injury in animal models. NO appears to attenuate smooth muscle proliferation both directly and indirectly by preventing the release of growth factors. Inhalation of low concentrations of NO dilates pulmonary vascular smooth muscle but does not cause systemic vasodilatation. Recently, NO inhalation was found to inhibit platelet function in vivo. We studied the effects of NO inhalation on neointimal formation after balloon-induced injury of the adult rat carotid artery. Beginning 60 minutes before carotid injury, rats breathed either air with 0 or 80 ppm NO for 14 days. Rats were killed, carotid arteries were fixed and paraffin-embedded, and neointimal formation was measured by analyzing the ratio of intimal to medial areas (I/M ratio) in carotid artery cross sections. Intimal hyperplasia was evident in both groups of animals, but I/M ratios were 43% less in animals breathing 80 ppm NO for 2 weeks than in animals breathing air alone (0.78 +/- 0.12 and 1.37 +/- 0.11 [mean +/- SE], respectively; P < .02). Similarly, 1 week after carotid injury, neointimal formation was less in rats breathing 80 ppm NO than in rats breathing air alone (I/M ratio, 0.39 +/- 0.11 versus 0.76 +/- 0.06; P < .02). Breathing 20 ppm NO for 2 weeks or 80 ppm NO for 1 week followed by air alone for 1 week did not attenuate neointimal formation measured at 14 days. In anesthetized rats breathing 80 ppm NO or air alone for 1 hour, neither systemic blood pressure nor bleeding time differed. These observations demonstrate that inhaling 80 ppm NO inhibits neointimal formation after balloon-induced carotid artery injury in rats. NO inhalation may represent a safe and novel method of preventing restenosis after percutaneous angioplasty.
Administration, Inhalation↗
Inhaled nitric oxide. A bronchodilator in mild asthmatics with methacholine-induced bronchospasm.
Nitric oxide (NO) reduces airway tone in the methacholine-treated guinea pig. We examined whether low levels of inhaled NO gas would relax airway smooth muscle tone in patients with mild asthma subjected to methacholine-induced bronchospasm. Thirteen adult volunteers with mild asthma inspired increasing concentrations of methacholine until their baseline forced expiratory volume in one second (FEV1, 3.29 +/- 0.17 L, mean +/- SEM) decreased by > or = 20% (2.33 +/- 0.18 L, p < 0.01). Thereafter, they sequentially inhaled 100 parts per million (ppm) NO, 40% O2; 40% O2; and 100 ppm NO, 40% O2 while spirometry was performed. Subsequent inhalation of isoproterenol returned the FEV1 levels to baseline. Inhaling 100 ppm NO increased FEV1 to 2.66 +/- 0.18 L (p < 0.01), and this increase was maintained after NO was discontinued. FEV1 did not change during the second period of NO inhalation. Similar results were observed for vital capacity, but no significant effect was noted on forced expiratory flow at 25% of vital capacity or peak expiratory flow. Subjects were then divided into a responder subgroup, which showed a mean increase in FEV1 after initial NO inhalation of 560 +/- 150 ml, and a nonresponder subgroup, which showed a mean increase in FEV1 of 129 +/- 29 ml. Our data suggest that inhalation of nitric oxide by patients with mild asthma with methacholine-induced bronchospasm results in a minor but significant relaxation of airway tone.
Administration, Inhalation↗
Inhaled nitric oxide.
The major objective of this lecture is to describe the effects of inhaling low levels of nitric oxide (NO) on the hemodynamic and gas exchange function of both the normal and diseased lung. Considerable attention will be paid to safety and hazards of inhaled NO therapy. During the past few years remarkable progress has been made in understanding the NO-guanylate cyclase signal transduction system. NO has been given considerable clinical investigation in pulmonary artery hypertension and the adult respiratory distress syndrome (ARDS) patients. This lecture concentrates on this area of clinical research.
Administration, Inhalation↗
Hormonal regulatory adjustments during voluntary diving in Weddell seals.
Subadult male Weddell seals were instrumented with microcomputer-based backpacks and were then monitored during voluntary diving and recovery periods in McMurdo Sound, Antarctica. Depth and duration of diving, swim speed, and dive pattern were routinely monitored. An indwelling venous catheter was used to collect plasma samples at various time periods before and following diving episodes, so that changes in plasma concentrations of hormones and of metabolites could be measured. Adrenergic and nitroxidergic regulatory effects were assessed indirectly by measuring concentration changes in catecholamine and cyclic guanosine monophosphate (cGMP), respectively. The studies found that (i), except for dives of less than several minutes, epinephrine and norepinephrine both increased as a function of diving duration, then rapidly decreased during recovery (with a half time of about 10 min), (ii) that the changes in catecholamine concentrations correlated with splenic contraction and an increase in circulating red blood cell mass (hematocrit), (iii) that the changes in catecholamines, especially [epinephrine], were inversely related to insulin/glucagon ratios, which mediated a postdiving hyperglycemia, and (iv) that in long dives (but not short ones) the changes in catecholamines correlated with increasing reliance on anaerobic metabolism, indicated by increased plasma lactate concentrations. These diving-catecholamine relationships during voluntary diving at sea were similar to those observed during enforced submergence (simulated diving) under controlled laboratory conditions. At the end of diving, even while catecholamine concentrations were still high, many of the above effects were rapidly reversed and the reversal appeared to correlate with accelerated nitric oxide production, indirectly indicated by increased plasma cGMP concentrations. Taken together, the data led to the hypothesis of important adrenergic regulation of the diving response in seals, with rapid reversal at the end of diving and during recovery being regulated by nitroxidergic mechanisms.
Animals↗
Inhaled nitric oxide, clinical rationale and applications.
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Administration, Inhalation↗
Platelet factor 4 injection produces acute pulmonary hypertension in the awake lamb.
BACKGROUND: Reversal of heparin anticoagulation by intravenous protamine sulfate consistently produces acute pulmonary vasoconstriction mediated by the release of thromboxane in the awake lamb. Recently, recombinant platelet factor 4 (rPF4) has been cloned, expressed in Escherichia coli, and infused to reverse heparin anticoagulation in the rat, without producing adverse hemodynamic or pulmonary morphologic effects. The authors sought to learn whether intravenous administration of PF4 is devoid of side effects in the pulmonary circulation of lambs. METHODS: The authors evaluated the hemodynamic response and plasma release rates of thromboxane during intravenous challenges with heparin-rPF4 (n = 2), rPF-free carrier (n = 5), rPF4 (n = 5), rPF4 after indomethacin (n = 5), protamine (n = 5) and heparin-protamine (n = 5) in 17 awake, hemodynamically monitored lambs. Each lamb underwent up to three random challenges with a 2-h recovery period between each challenge. RESULTS: In two lambs, systemic anticoagulation with heparin followed by reversal of anticoagulation with an intravenous bolus of rPF4 (4 mg/kg) led to acute pulmonary vasoconstriction and hypertension with the release of thromboxane (peak pulmonary artery pressure [Ppa] 40 and 33 mmHg and peak plasma thromboxane B2 50 and 30 ng/ml, respectively). Intravenous administration of rPF4 (1.5 mg/kg) alone increased the Ppa from 17.2 +/- 0.7 mmHg (mean +/- SEM) at baseline to 31.2 +/- 2 mmHg at 1 min (n = 5, P < 0.05). This was associated with an increase of plasma thromboxane B2 from 0.06 +/- 0.02 to 3.96 +/- 1.21 ng/ml. Acute pulmonary vasoconstriction lasted approximately 5 min and was completely prevented by pre-treatment with oral indomethacin (10 mg/kg). Intravenous bolus administration of rPF4 carrier (n = 5) or protamine (2 mg/kg) alone (n = 5) did not induce pulmonary hypertension or the release of thromboxane. In five lambs, intravenous heparin (200 U/kg) followed by protamine (2 mg/kg) consistently produced acute pulmonary vasoconstriction and hypertension. CONCLUSIONS: Intravenous injection of human rPF4 into the awake lamb produces acute pulmonary vasoconstriction and hypertension associated with thromboxane release into circulating blood. The effects of rPF4 on the pulmonary vasculature should be evaluated in primates before rPF4 is substituted for protamine in reversing heparin anticoagulation in humans.
Animals↗
Effects of targeted neuronal nitric oxide synthase gene disruption and nitroG-L-arginine methylester on the threshold for isoflurane anesthesia.
BACKGROUND: Considerable evidence suggests that nitric oxide plays a role in synaptic transmission in the central and peripheral nervous system. Nonselective inhibition of nitric oxide synthase by nitroG-L-arginine methylester (L-NAME) reduces the minimum alveolar concentration of halothane anesthesia. The effects of selective neuronal nitric oxide synthase inhibition on the anesthetic requirements in mice congenitally deficient in neuronal nitric oxide synthase (knockout mice) were examined. METHODS: Isoflurane minimum alveolar concentration and righting reflex ED50 (RRED50) were determined in knockout and wild-type mice. Subsequently, the effects of intraperitoneal L-NAME on minimum alveolar concentration and RRED50 of knockout and wild-type mice were examined. In a separate experiment, the effects of week-long administration of L-NAME were examined in wild-type mice. Isoflurane minimum alveolar concentration and RRED50 were measured on the 8th day and were repeated after an acute intraperitoneal dose of L-NAME. RESULTS: Targeted disruption of the neuronal nitric oxide synthase gene did not modify isoflurane minimum alveolar concentration and RRED50 of knockout mice. Acute intraperitoneal L-NAME decreased the minimum alveolar concentration and RRED50 of wild-type but did not alter those values in knockout mice. The wild-type mice, when given L-NAME for a week, showed a minimum alveolar concentration and RRED50 identical to that of untreated wild-type mice. CONCLUSIONS: Although acute nonselective inhibition of nitric oxide synthase reduces the anesthetic requirements of wild-type mice, a chronic congenital deficiency of neuronal nitric oxide synthase or a week of L-NAME treatment of wild-type mice does not produce a state of greater sensitivity to the effects of isoflurane anesthesia.
Amino Acid Oxidoreductases↗
Constitutive endothelial nitric oxide synthase gene expression is regulated during lung development.
Nitric oxide (NO), a potent vasodilator, is a free-radical gas synthesized from L-arginine by nitric oxide synthases (NOS). NO appears to have an important role in perinatal changes in pulmonary vascular resistance. We previously identified mRNA encoding the constitutive endothelial NOS (ceNOS) isoform in human pulmonary tissue. To begin investigating functions of this enzyme in perinatal pulmonary development, we measured ceNOS mRNA and immunoreactivity in the developing rat lung. With the use of RNA blot hybridization, abundant pulmonary ceNOS mRNA was detected during the late fetal and postnatal period. The highest levels were detected within 24 h after birth, and elevated mRNA levels persisted for 16 days. In contrast, much lower levels of ceNOS mRNA were found in adult rat lung. With the use of immunoblot techniques, ceNOS protein levels were found to be correlated with mRNA levels. To identify the pulmonary cell types expressing the ceNOS gene, in situ hybridization with a digoxigenin-labeled cRNA probe was performed on sections from lungs of 1-day-old and adult rats. In lungs from 1-day-old rats, ceNOS mRNA was detected in alveolar and serosal epithelial cells as well as in endothelial cells lining small and medium-sized blood vessels. In contrast, in adult lungs, ceNOS gene transcripts were detected in rare endothelial cells. These observations suggest that ceNOS gene expression is regulated during lung development and that ceNOS is available to participate in the postnatal reduction of pulmonary vascular resistance. ceNOS gene expression in nonendothelial cells in the neonatal rat lung suggests that NO may also contribute to nonvascular functions in the developing lung.
Amino Acid Oxidoreductases↗
In vivo lipopolysaccharide pretreatment inhibits cGMP release from the isolated-perfused rat lung.
Administration of bacterial lipopolysaccharide (LPS) to rats stimulates synthesis of nitric oxide (NO), a free radical molecule that activates soluble guanylate cyclase, thereby increasing intracellular guanosine 3',5'-cyclic monophosphate (cGMP) concentration and inducing systemic vasodilatation. To investigate the effect of endotoxemia on the pulmonary NO/cGMP signal transduction system, we measured the release of cGMP by isolated-perfused lungs of rats that received an intraperitoneal injection of LPS (1 mg/kg) or saline 2 days earlier. Over 90 min, 1.4 +/- 0.78 and 0.079 +/- 0.016 nmol cGMP accumulated in pulmonary perfusates of saline- and LPS-treated rats, respectively (P < 0.05). Despite addition to the perfusate of Zaprinast, superoxide dismutase, or A23187, markedly less cGMP was released from the lungs of rats exposed to LPS than from the lungs of control rats. In contrast, after ventilation with 100 parts per million NO gas, cGMP accumulating in the perfusate of the lungs of both groups of rats was markedly increased, and the quantity of cGMP released from the lungs of LPS-treated rats was similar to that released by control rat lungs (2.8 +/- 0.57 vs. 3.3 +/- 0.88 nmol, P = NS). With the use of immunoblot techniques, equal concentrations of constitutive endothelial NO synthase were detected in the lungs of rats treated with saline or LPS. These results demonstrate that the NO/cGMP signal transduction system is abnormal in the lungs of rats exposed to LPS, at least in part, at the level of endothelial NO synthase activation.
Animals↗
Nitric oxide responses of air-breathing and water-breathing fish.
Nitric oxide (NO), exogenously administered or endogenously produced by NO synthase (NOS), is an important regulator of lung ventilation and perfusion in mammals. This study attempts to investigate the evolutionary history of this system in fish and its possible relationship to air breathing. The gas bladder of Hoplerythrinus unitaeniatus (air-breathing teleost) and Oncorhynchus mykiss (non-air-breathing teleost) and the lung of Lepidosiren paradoxa (air-breathing dipnoan) all exhibited elevated guanosine 3',5'-cyclic monophosphate (cGMP) levels in response to 1 microM sodium nitroprusside. Only the H. unitaeniatus gas bladder responded to 10 microM acetylcholine chloride (ACh) with increased cGMP levels. The ACh response was inhibited by N omega-nitro-L-arginine methyl ester, which inhibits NOS. These data suggest that although tissues from each species may respond to exogenous NO, only the gas bladder of H. unitaeniatus appears to synthesize NO through NOS. This is the first report of constitutive NOS outside of the central nervous system in a teleost. These results also imply that NOS did not necessarily coevolve with air breathing in fish.
Acetylcholine↗
Prolonged pulmonary vasodilator action of inhaled nitric oxide by Zaprinast in awake lambs.
Inhaled nitric oxide (NO) has been shown to selectively dilate the pulmonary vasculature. Zaprinast, an inhibitor of guanosine 3',5'-cyclic monophosphate-specific phosphodiesterase, augments smooth muscle relaxation induced by endothelium-dependent vasodilators. The present study was designed to determine whether intravenous administration of Zaprinast potentiates the vasodilating effects or prolongs the duration of action of intermittent NO inhalation. Eight awake lambs with U-46619-induced pulmonary hypertension breathed three concentrations of NO (5, 10, and 20 ppm) in a random order before and during an intravenous Zaprinast infusion (0.1 mg.kg-1.min-1). Inhaled NO decreased pulmonary arterial pressure (PAP) in a dose-dependent fashion, with mean PAP reduction at 5, 10, and 20 ppm NO inhalation of 6 +/- 1, 7 +/- 1, and 9 +/- 1 (SE) mmHg, respectively. Although the Zaprinast infusion did not change the magnitude of mean PAP reduction, it caused a statistically significant reduction of pulmonary vascular resistance and prolonged the duration of action of inhaled NO (half-times of vasodilator response to 5, 10, and 20 ppm NO inhalation: 1.9 +/- 0.1, 2.1 +/- 0.2, and 2.1 +/- 0.2 min, respectively; half-times of NO inhalation with Zaprinast: 9.7 +/- 1.7, 11.5 +/- 2.2, and 12.3 +/- 2.0, respectively). Plasma concentrations as well as the transpulmonary differences of guanosine 3',5'-cyclic monophosphate were increased by the Zaprinast infusion during NO inhalation. A stable level of pulmonary vasodilation was demonstrated in four additional lambs by combining intermittent NO breathing with an intravenous infusion of Zaprinast.
15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
Inhaled nitric oxide does not alter endotoxin-induced nitric oxide synthase activity during rat lung perfusion.
Nitric oxide (NO) has been demonstrated to decrease its own synthesis in tissue preparations. We tested the hypothesis that endogenous NO synthesis induced by lipopolysaccharides (LPS) would be decreased by exogenous NO during isolated lung perfusion. Rats were pretreated with either saline or LPS 48 h before lung harvest. Endogenous NO synthase activity was measured as conversion of L-[14C]-arginine to L-[14C]citrulline during 90 min of perfusion. NO (100 ppm) was added to the ventilating gas during perfusion of lungs from one group of control or LPS-treated rats. A second group of control or LPS-treated rats was exposed chronically to 100 ppm NO for the 48 h before lung harvest, in addition to receiving 100 ppm NO added to the ventilating gas during lung perfusion. We conclude that conversion of L-[14C]arginine to L-[14C]citrulline was minimal in control lungs and increased in response to LPS pretreatment. NO added to the ventilating gas for the 90 min of ex vivo perfusion did not alter the rate of L-[14C]citrulline production. In vivo exposure to 100 ppm NO for 48 h did not alter the induction of inducible NO synthase activity as measured during ex vivo lung perfusion. This indicates that inhaled NO does not exert negative-feedback inhibition on inducible NO synthase in the ex vivo rat lung.
Administration, Inhalation↗
Myoglobin saturation in free-diving Weddell seals.
Although the consumption of myoglobin-bound O2 (MbO2) stores in seal muscles has been demonstrated in seal muscles during laboratory simulations of diving, this may not be a feature of normal field diving in which measurements of heart rate and lactate production show marked differences from the profound diving response induced by forced immersion. To evaluate the consumption of muscle MbO2 stores during unrestrained diving, we developed a submersible dual-wavelength laser near-infrared spectrophotometer capable of measuring MbO2 saturation in swimming muscle. The probe was implanted on the surface of the latissimus dorsi of five subadult male Weddell seals (Leptonychotes weddelli) released into a captive breathing hole near Ross Island, Antarctica. Four seals had a monotonic decline of muscle O2 saturation during free diving to depths up to 300 m with median slopes of -5.12 +/- 4.37 and -2.54 +/- 1.95%/min for dives lasting < 17 and > 17 min, respectively. There was no correlation between the power consumed by swimming and the desaturation rate. Two seals had occasional partial muscle resaturations late in dives, indicating transfer of O2 from circulating blood to muscle myoglobin. Weddell seals partially consume their MbO2 stores during unrestrained free diving.
Animals↗
Continuous nitric oxide inhalation reduces pulmonary arterial structural changes, right ventricular hypertrophy, and growth retardation in the hypoxic newborn rat.
Breathing low oxygen levels for several weeks produces progressive pulmonary artery hypertension and smooth muscle hypertrophy and hyperplasia in many species. Because nitric oxide (NO) is an important regulator of pulmonary vascular tone, we examined whether the continuous inhalation of low levels of NO gas would attenuate pulmonary arterial structural changes in hypoxic rat pups. Nine-day-old rat pups and their mothers continuously breathed at FIO2 0.21 or 0.10 with or without adding 20 ppm (by volume) NO for 2 weeks. Lung tissue was obtained for vascular morphometric analysis, and the hearts were dissected to measure right ventricular weight and levels of mRNA encoding rat atrial natriuretic factor (rANF). In addition, femur and skull length were radiographically determined. Breathing at FIO2 0.10 for 14 days increased pulmonary arterial wall thickness and the proportion of muscular arteries in the lung periphery. Right ventricular weight and right ventricular rANF gene expression increased, whereas body weight and skeletal growth were reduced (all P < .05). Continuous inhalation of 20 ppm NO at FIO2 0.10 for 2 weeks decreased hypoxic pulmonary vascular structural changes and somatic growth retardation and prevented the increase of right ventricular weight and right ventricular rANF mRNA levels. These observations suggest that chronically breathing NO attenuates pulmonary vascular smooth muscle hypertrophy and/or hyperplasia and extension into distal arterial walls, right ventricular hypertrophy, and growth retardation of newborns breathing at a low oxygen level.
Administration, Inhalation↗
Effects of digoxin on regional diaphragm function after thoracotomy in awake sheep.
The effects of digoxin on diaphragmatic contraction were studied in 12 sheep, within 6 days after a right thoracotomy, during the period of intense diaphragmatic inhibition. Diaphragmatic function was assessed by implanting sonomicrometry crystals and electromyographic (EMG) electrodes in both the costal and crural diaphragmatic regions. Awake sheep were studied before and after intravenous digoxin (0.04 mg/kg) during both quiet breathing (QB) and during CO2 rebreathing, until the fractional concentration of expired CO2 (FETCO2) reached 0.10. After digoxin infusion, during both QB and at FETCO2 of 0.10, esophageal and transdiaphragmatic pressures increased (P < 0.05). After digoxin infusion no changes were measured for end-expiratory resting length, shortening fraction, shortening velocity or EMG activity of either diaphragmatic segment or for respiratory frequency, ventilation, tidal volume and FETCO2. We conclude that intravenous digoxin given to awake sheep after a thoracotomy increases Pdi, but does not alter diaphragmatic shortening nor alter the level of diaphragmatic activation either during QB or at FETCO2 of 0.10.
Animals↗