Hemodynamic effects of metalloporphyrin catalytic antioxidants: structure-activity relationships and species specificity

Superoxide plays a role in blood pressure regulation in certain vascular diseases, however, its involvement in regulating basal blood pressure is uncertain. Vascular superoxide concentrations are limited by extracellular superoxide dismutase (EC-SOD), which is highly expressed in the vasculature of most animal species. Metalloporphyrins are low molecular weight, synthetic, redox-active, catalytic antioxidants that act as SOD mimetics. We evaluated the effects of metalloporphyrins on blood pressure in different animal species. The metalloporphyrin AEOL10113 (5-10 micro /kg iv), but not native or polyethylene glycol-CuZnSOD, caused a dose-dependent reduction in blood pressure in anesthetized rats. AEOL10113 had no effect on blood pressure in mice (wild-type or EC-SOD knockouts), guinea pigs, dogs, or baboons at doses up to 5 mg/kg iv Structure-activity studies indicated that metalloporphyrins with high SOD activity were more effective in lowering rat blood pressure than low-activity analogs. The blood pressure effect of AEOL10113 was not attributable to the release of manganese, nor was it affected by inhibitors of nitric oxide synthase (L-NAME) and guanylate cyclase (ODQ, 8-bromo-cGMP, and methylene blue) or nitric oxide scavengers (HbAo). Chlorpheniramine attenuated the effect, suggesting that the blood pressure response in rats is related to histamine release rather than the protection of nitric oxide.

Regulation of the brain's vascular responses to oxygen

The mechanism of oxygen-induced cerebral vasoconstriction has been sought for more than a century. Using genetically altered mice to enhance or disrupt extracellular superoxide dismutase (EC-SOD, SOD3), we tested the hypothesis that this enzyme plays a critical role in the physiological response to oxygen in the brain by regulating nitric oxide (NO*) availability. Cerebral blood flow responses in these genetically altered mice to changes in PO2 demonstrate that SOD3 regulates equilibrium between superoxide (*O2-) and NO*, thereby controlling vascular tone and reactivity in the brain. That SOD3 opposes inactivation of NO* is shown by absence of vasoconstriction in response to PO2 in the hyperbaric range in SOD3+/+ mice, whereas NO-dependent relaxation is attenuated in SOD3-/- mutants. Thus, EC-SOD promotes NO* vasodilation by scavenging *O2- while hyperoxia opposes NO* and promotes constriction by enhancing endogenous *O2- generation and decreasing basal vasodilator effects of NO*.

Iron increases expression of iron-export protein MTP1 in lung cells

Accumulation of reactive iron in acute and chronic lung disease suggests that iron-driven free radical formation could contribute to tissue injury. Safe transport and sequestration of this metal is likely to be of importance in lung defense. We provide evidence for the expression and iron-induced upregulation of the metal transporter protein-1 (MTP1) genes in human and rodent lung cells at both the protein and mRNA levels. In human bronchial epithelial cells, a 3.8-fold increase in mRNA level and a 2.4-fold increase in protein level of MTP1 were observed after iron exposure. In freshly isolated human macrophages, as much as an 18-fold increase in the MTP1 protein level was detected after incubation with an iron compound. The elevation in expression of MTP1 gene was also demonstrated in iron-instilled rat lungs and in hypotransferrinemic mouse lungs. This is similar to our previous findings with divalent metal transporter-1 (DMT1), an iron transporter that is required for iron uptake and intracellular iron trafficking. These studies suggest the presence of iron mobilization and/or detoxification pathways in the lung that are crucial for iron homeostasis and lung defense.

Alveolar barrier function assessed by hydrophobic and hydrophilic fluorescent solutes in rabbit lung

Loss of alveolar barrier function is important in the development of pulmonary edema, but quantitation of its integrity has been difficult in the intact lung. We report a new non-radioactive method to assess paracellular and transcellular permeability of alveolar barrier in buffer-perfused rabbit lungs. Changes in alveolar barrier parameters were then correlated with different types of lung edema formation. The paracellular and transcellular barrier function was quantified by calculating the apparent epithelial permeability-surface area products (PS) for a fluorescent hydrophilic solute, FITC-dextran (FD-4), and a hydrophobic solute, rhodamine B, respectively. In control lungs, the apparent epithelial PS for FD-4 and rhodamine B were 0.7+/-0.05 x 10(-4) and 40.0+/-4.1 x 10(-4) ml/sec, respectively. The apparent epithelial PS of FD-4 could be increased 25-fold by inhibition of epithelial anion exchange with 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) without affecting the PS of rhodamine B. The apparent epithelial PS of FD-4 could be increased 6- and 1.7-fold by disrupting microtubules with nocodazole and colchicine respectively, but microtubule agents decreased PS for rhodamine B. A pattern similar was produced when ATP production in the lung was inhibited by 2-deoxyglucose or when oxidative injury was induced by ischemia-reperfusion. Neither DIDS nor nocodazole altered endothelial permeability to albumin. DIDS, but not nocodazole, increased transcapillary liquid filtration and calculated interstitial compliance of the lung during hydrostatic challenge. We conclude that epithelial permeability in the intact lung can be assessed using fluorescent solutes, and that increased permeation of hydrophilic solutes may enhance lung edema formation.

Oxidative stress activates anion exchange protein 2 and AP-1 in airway epithelial cells

Anion exchange protein 2 (AE2) is a membrane-bound protein that mediates chloride-bicarbonate exchange. In addition to regulating intracellular pH and cell volume, AE2 exports superoxide (O.) to the extracellular matrix in an HCO-dependent process. Given this ability to export O., we hypothesized that expression of AE2 in the lung is regulated by oxidative stress. AE2 mRNA and protein expression was measured by RT-PCR and Western blot analysis, respectively, in differentiated human bronchial epithelial cells exposed to H(2)O(2) (100 microM). Alterations in in vivo AE2 protein expression were evaluated in lung tissue of rats exposed to 70% O(2). The role of transcription factor activator protein (AP)-1 in oxidant regulation of AE2 was evaluated by EMSA and by immunoblotting of nuclear phospho-c-jun. Results show increased AE2 mRNA and protein expression after oxidant exposure. This was preceded by transient increases in DNA binding of AE2-specific AP-1 and phosphorylation of c-jun. This study demonstrates that AE2 expression is regulated by oxidative stress in airway epithelial cells and that this regulation correlates with activation of AP-1.

Prenatal hypoxia decreases lung extracellular superoxide dismutase expression and activity

Extracellular superoxide dismutase (EC-SOD), which scavenges extracellular superoxide (O.), is highly regulated in the developing lung. In the prenatal rabbit, EC-SOD is predominantly intracellular and inactive, and postnatally, active EC-SOD is secreted. We hypothesized that prenatal hypoxia would delay the normal postnatal secretion of active EC-SOD in the lung. Pregnant New Zealand White rabbits were exposed to hypobaric hypoxia (15,000 ft x 36 h) to alter fetal O(2) tension or were maintained in room air. Lungs were harvested from preterm (28 days), term (30 +/- 1 day), and 1-wk-old kits. After prenatal hypobaric hypoxia, EC-SOD mRNA expression was significantly decreased in lungs of full-term kits, whereas EC-SOD protein decreased at all ages. Immunohistochemical staining for EC-SOD showed that hypoxia delayed secretion of the isoenzyme in the airways and pulmonary vasculature. Furthermore, pulmonary EC-SOD enzyme activity was significantly decreased in the 1-wk-old kits exposed to prenatal hypoxia. We conclude that prenatal hypoxia downregulates EC-SOD expression at both the transcriptional and posttranslational levels. Furthermore, prenatal hypoxia delays secretion of active EC-SOD enzyme. These findings have important implications for the effects of prenatal asphyxia on postnatal response to oxidant stress.

Coagulation and inflammation in acute lung injury

The acute respiratory distress syndrome (ARDS) is a severe lung injury in patients with sepsis and other acute inflammatory insults, which is characterized by fibrin deposition in the pulmonary parenchyma, vasculature, and airspaces. Recent evidence suggests that progressive ARDS is closely linked to activation of inflammation and coagulation. Coagulation becomes activated by circulating endotoxin or bacteria, and a procoagulant state develops in the vascular and the alveolar compartments of the lung. This state is Tissue Factor (TF)-dependent and associated with increased elaboration of inflammatory cytokines. A similar procoagulant state is found in bronchoalveolar lavage of patients with ARDS, suggesting that extravascular coagulation contributes to lung inflammation. TF and other coagulation proteins, including Factor Xa, thrombin, and fibrin, also contribute to the pathogenesis of acute lung injury through multi-level interactions with inflammatory effectors, in which these proteins coordinately act as regulators of tissue injury responses. Each coagulation protein has direct and independent effects on inflammatory events that influences lung injury through changes in cytokine elaboration, inflammatory cell migration and activation, surfactant function, and repair mechanisms. New interventional strategies directed at procoagulant activity highlight the importance of the coagulation system to acute lung injury and suggest that blockade of initiation of coagulation may have therapeutic benefit in patients with ARDS.

Nitric oxide in the human respiratory cycle

Interactions of nitric oxide (NO) with hemoglobin (Hb) could regulate the uptake and delivery of oxygen (O(2)) by subserving the classical physiological responses of hypoxic vasodilation and hyperoxic vasconstriction in the human respiratory cycle. Here we show that in in vitro and ex vivo systems as well as healthy adults alternately exposed to hypoxia or hyperoxia (to dilate or constrict pulmonary and systemic arteries in vivo), binding of NO to hemes (FeNO) and thiols (SNO) of Hb varies as a function of HbO(2) saturation (FeO(2)). Moreover, we show that red blood cell (RBC)/SNO-mediated vasodilator activity is inversely proportional to FeO(2) over a wide range, whereas RBC-induced vasoconstriction correlates directly with FeO(2). Thus, native RBCs respond to changes in oxygen tension (pO2) with graded vasodilator and vasoconstrictor activity, which emulates the human physiological response subserving O(2) uptake and delivery. The ability to monitor and manipulate blood levels of NO, in conjunction with O(2) and carbon dioxide, may therefore prove useful in the diagnosis and treatment of many human conditions and in the development of new therapies. Our results also help elucidate the link between RBC dyscrasias and cardiovascular morbidity.

Extrinsic coagulation blockade attenuates lung injury and proinflammatory cytokine release after intratracheal lipopolysaccharide

Initiation of coagulation by tissue factor (TF) is a potentially powerful regulator of local inflammatory responses. We hypothesized that blockade of TF-factor VIIa (FVIIa) complex would decrease lung inflammation and proinflammatory cytokine release after tracheal instillation of Escherichia coli lipopolysaccharide (LPS 0111:B4). At the time of injury, rats received one dose of site-inactivated FVIIa (FFR-FVIIa) or saline intravenously. At 0, 6,12, 24, and 48 h after injury, lungs were examined for histologic changes and bronchoalveolar lavage (BAL) was performed to assess protein, lactate dehydrogenase (LDH) activity, cell counts, and cytokine levels. LPS-injured rats treated with FFR-FVIIa showed decreased intra-alveolar inflammation and fibrin deposition by light microscopy compared with untreated rats. This was accompanied by decreased protein leakage (P < 0.0001), LDH activity (P < 0.0001), and local elaboration of interleukin (IL)-1beta, IL-6, and IL-10 (all P < 0.0001), but not tumor necrosis factor (TNF)-alpha. Protection was associated with reduction of TF mRNA expression in whole lung, but not with changes in nuclear translocation of nuclear factor (NF)-kappaB. FFR-FVIIa given 6 h after LPS afforded equivalent lung protection. Therefore, blockade of TF-FVIIa complex protects the lung from injury by LPS in part by reducing local expression of proinflammatory cytokines and may offer promise for therapy of acute lung injury.

Pulmonary vasoconstriction by serotonin is inhibited by S-nitrosoglutathione

Nitric oxide (NO) functions as an endothelium-derived relaxing factor by activating guanylate cyclase to increase cGMP levels. However, NO and related species may also regulate vascular tone by cGMP-independent mechanisms. We hypothesized that naturally occurring NO donors could decrease the pulmonary vascular response to serotonin (5-HT) in the intact lung through chemical interactions with 5-HT(2) receptors. In isolated rabbit lung preparations and isolated pulmonary artery (PA) rings, 50-250 microM S-nitrosoglutathione (GSNO) inhibited the response to 0.01-10 microM 5-HT. The vasoconstrictor response to 5-HT was mediated by 5-HT(2) receptors in the lung, since it could be blocked completely by the selective inhibitor ketanserin (10 microM). GSNO inhibited the response to 5-HT by 77% in intact lung and 82% in PA rings. In PA rings, inhibition by GSNO could be reversed by treatment with the thiol reductant dithiothreitol (10 mM). 3-Morpholinosydnonimine (100-500 microM), which releases NO and O simultaneously, also blocked the response to 5-HT. Its chemical effects, however, were distinct from those of GSNO, because 5-HT-mediated vasoconstriction was not restored in isolated rings by dithiothreitol. In the intact lung, neither NO donor altered the vascular response to endothelin, which activates the same second-messenger vasoconstrictor system as 5-HT. These findings, which did not depend on guanylate cyclase, are consistent with chemical modification by NO of the 5-HT(2) G protein-coupled receptor system to inhibit vasoconstriction, possibly by S-nitrosylation of the receptor or a related protein. This study demonstrates that GSNO can regulate vascular tone in the intact lung by a reversible mechanism involving inhibition of the response to 5-HT.

Iron uptake and Nramp2/DMT1/DCT1 in human bronchial epithelial cells

The capacity of natural resistance-associated macrophage protein-2 [Nramp2; also called divalent metal transporter-1 (DMT1) and divalent cation transporter-1 (DCT1)] to transport iron and its ubiquitous expression make it a likely candidate for transferrin-independent uptake of iron in peripheral tissues. We tested the hypothesis that non-transferrin-bound iron uptake by airway epithelial cells is associated with Nramp2/DMT1/DCT1 and that exposure to iron can increase Nramp2/DMT1/DCT1 mRNA and protein expression and transport of this metal. Exposure of BEAS-2B cells to ferric ammonium citrate (FAC) resulted in a decrease in Fe(3+) concentration in the supernatant that was dependent on time and initial iron concentration. In the presence of internalized calcein, FAC quenched the fluorescent signal, indicating intracellular transport of the metal. The Nramp2/DMT1/DCT1 mRNA isoform without an iron-response element (IRE) increased with exposure of BEAS-2B cells to FAC. RT-PCR demonstrated no change in the mRNA for the isoform with an IRE. Similarly, Western blot analysis for the isoform without an IRE confirmed an increased expression of this protein after FAC exposure, whereas the isoform with an IRE exhibited no change. Finally, immunohistochemistry revealed an increase in the isoform without an IRE in the rat lung epithelium after instillation of FAC. Comparable to mRNA and protein increases, iron transport was elevated after pretreatment of BEAS-2B cells with iron-containing compounds. We conclude that airway epithelial cells increase mRNA and expression of the Nramp2/DMT1/DCT1 without an IRE after exposure to iron. The increase results in an elevated transport of iron and its probable detoxification by these cells.

Carbon monoxide promotes hypoxic pulmonary vascular remodeling

CO is a biologically active gas that produces cellular effects by multiple mechanisms. Because cellular binding of CO by heme proteins is increased in hypoxia, we tested the hypothesis that CO interferes with hypoxic pulmonary vascular remodeling in vivo. Rats were exposed to inspired CO (50 parts/million) at sea level or 18,000 ft of altitude [hypobaric hypoxia (HH)], and changes in vessel morphometry and pulmonary pressure-flow relationships were compared with controls. Vascular cell single strand DNA (ssDNA) and proliferating cell nuclear antigen (PCNA) were assessed, and changes in gene and protein expression of smooth muscle alpha-actin (sm-alpha-actin), beta-actin, and heme oxygenase-1 (HO-1) were evaluated by Western analysis, RT-PCR, and immunohistochemistry. After 21 days of HH, vascular pressure at constant flow and vessel wall thickness increased and lumen diameter of small arteries decreased significantly. The presence of CO, however, further increased both pulmonary vascular resistance (PVR) and the number of small muscular vessels compared with HH alone. CO + HH also increased vascular PCNA and nuclear ssDNA expression compared with hypoxia, suggesting accelerated cell turnover. CO in hypoxia downregulated sm-alpha-actin and strongly upregulated beta-actin. CO also increased lung HO activity and HO-1 mRNA and protein expression in small pulmonary arteries during hypoxia. These data indicate an overall propensity of CO in HH to promote vascular remodeling and increase PVR in vivo.

Biological chemistry of carbon monoxide

Carbon monoxide (CO) has many effects in biology due to its complex biochemical activities. These actions of CO depend primarily on its ability to bind heme proteins (Hp) and to inhibit or alter their biochemical functions. Whether CO is derived from exogenous or endogenous sources, its cellular activity is related to its concentration and the concentration of molecular O(2), as well as to the availability of reduced transition metals such as Fe(II). In this respect, the CO/O(2) ratio and O(2)-dependent changes in local oxidation-reduction state assume critical importance in determining the physiological effects of CO by affecting the functions of specific Hp. By interacting with Hp, CO influences electron-transport reactions in a variety of ways, which can produce either prooxidant or antioxidant effects. Similarly, Hp relationships also govern how changes in CO concentration influence the physiological and pathological effects of nitric oxide and the relationships of the two biologically active gases to metal-catalyzed oxidations. This article provides a brief update on the biochemistry of CO as it relates to Hp binding, chemical oxidative processes, and cellular function.

Nitric oxide and differential effects of ATP on mitochondrial permeability transition

The mitochondrial permeability transition pore (PTP) undergoes a calcium-dependent transition (MPT) that disrupts membrane potential and releases apoptogenic proteins. Because PTP opening is enhanced by oxidation of thiols at the so-called "S-site," we hypothesized that nitrogen monoxide (NO*) could enhance the open probability of the PTP, e.g., by S-nitrosylation or S-thiolation. At low NO donor concentrations (1 to 20 microM), PTP opening in succinate-energized liver mitochondria at nonlimiting calcium was delayed or unaffected, while it was accelerated by NO donors at 20 to 100 microM. At low donor concentrations, PTP opening was facilitated twofold by adenosine triphosphate (ATP), which normally delays PTP opening. Among NO donors, the oxatriazole GEA 3162, with an activation constant (Ka) of 1.9 microM at 500 microM ATP was more effective at enhancing pore transition than SIN-1 or SNAP. NO donor effects were superseded by diamide, which induces disulfide formation, but independent of SH-adduct formation by alkylation. NO-related changes in PTP function were accompanied by protein mixed disulfide formation, inhibited by dithiothreitol (DTT), and reversed by DTT after donor addition. PTP opening was stimulated in the presence of ATP by L-arginine-dependent NO production, i.e., mitochondrial NOS activity. ATP-facilitated pore opening was sensitive to atractyloside and depended on nucleotide interactions but not on hydrolysis, because specific nonhydrolyzable ATP analogs accelerated pore opening. These data indicate NO can influence pore transition by oxidation of thiols that produce conformational changes governing the ATP interaction at the adenine nucleotide transporter.

Rapid mtDNA deletion by oxidants in rat liver mitochondria after hemin exposure

The amounts of superoxide and hydrogen peroxide generated by mitochondria under physiological conditions can be enhanced by cellular stress. This study tested the hypothesis that the response to hemin-induced stress, which includes heme oxygenase-1 (HO-1) induction, predisposes to oxidative damage of mitochondrial DNA (mtDNA). Hepatic mitochondria from control, hemin-, and CO-exposed rats were incubated with tert-butyl hydroperoxide (tert-BH) or the NO donor 1,2,3,4-oxatriazolium, 5-amino-3- (3,4-dichlorophenyl)-chloride (GEA 3162). Mitochondrial total and oxidized glutathione (GSH and GSSG), total and free iron, and 8-oxo-7, 8-dihydro-2' deoxyguanosine (8-OHdG) were determined with and without oxidants. As expected, oxidation by tert-BH induced significant GSH depletion and increased amounts of free iron and 8-OhdG. Oxidant exposure rapidly produced a large mtDNA deletion involving the coding regions for cytochrome c oxidase (COX 1) and NADH dehydrogenase (ND1 and ND2). Hemin and CO greatly exacerbated susceptibility to the deletion of mtDNA by tert-BH, and this was attenuated by preincubation with GSH methyl ester. Analysis of mitochondria-associated proteins Bax and Bcl-xl in hemin- and CO-exposed rats showed significant responses, revealing interactions with apoptotic pathways. Thus, hemin-induced mitochondrial events sensitize a specific region of the mitochondrial genome to deletion, which is related to depletion of GSH and is not explained by effects of CO. This mtDNA damage is associated with altered expression of mitochondrial cell death proteins, thereby suggesting a novel mechanism for systemic or environmental pro-oxidants to influence apoptosis.

Internal carotid artery dissection in stroke from SCUBA diving: a case report

Although diving with compressed air is generally safe, neurological problems resulting from infarction in SCUBA diving are well known, including arterial gas embolism and decompression sickness (caisson's disease, bends) involving the brain and spinal cord. While air gas embolism forms the overwhelming majority of causes for stroke in divers, internal carotid artery (ICA) dissection is another potential mechanism for central nervous system infarction in the setting of SCUBA diving. A 38 year-old female, who presented with complaints of headache, nausea, vomiting, and left sided hemiparesis after rapid ascent to the surface from a depth of 120 feet of seawater was initially treated for decompression illness in a hyperbaric chamber. Further neurological workup revealed a right ICA dissection. This case demonstrates the dangers of ICA dissection following rapid ascent to the surface from underwater and emphasizes an interesting presentation of stroke associated with SCUBA diving.

Coagulation blockade prevents sepsis-induced respiratory and renal failure in baboons

Sepsis-induced tissue factor (TF) expression activates coagulation in the lung and leads to a procoagulant environment, which results in fibrin deposition and potentiates inflammation. We hypothesized that preventing initiation of coagulation at TF-Factor VIIa (FVIIa) complex would block fibrin deposition and control inflammation in sepsis, thereby limiting acute lung injury (ALI) and other organ damage in baboons. A model of ALI was used in which adult baboons were primed with killed Escherichia coli (1 x 10(9) CFU/kg), and bacteremic sepsis was induced 12 h later by infusion of live E. coli at 1 x 10(10) CFU/kg. Animals in the treatment group were given a competitive inhibitor of TF, site-inactivated FVIIa (FVIIai), intravenously at the time of the infusion of live bacteria and monitored physiologically for another 36 h. FVIIai dramatically protected gas exchange and lung compliance, prevented lung edema and pulmonary hypertension, and preserved renal function relative to vehicle (all p < 0.05). Treatment attenuated sepsis-induced fibrinogen depletion (p < 0.01) and decreased systemic proinflammatory cytokine responses, for example, interleukin 6 (p < 0.01). The protective effects of TF blockade in sepsis-induced ALI were confirmed by using tissue factor pathway inhibitor. The results show that TF-FVIIa complex contributes to organ injury in septic primates in part through selective stimulation of proinflammatory cytokine release and fibrin deposition.

Nitric oxide production is enhanced in rat brain before oxygen-induced convulsions

Central nervous system oxygen toxicity (CNS O2 toxicity) is preceded by release of hyperoxic vasoconstriction, which increases regional cerebral blood flow (rCBF). These increases in rCBF precede the onset of O2-induced convulsions. We have tested the hypothesis that hyperbaric oxygen (HBO2) stimulates NO* production in the brain that leads to hyperemia and anticipates electrical signs of neurotoxicity. We measured rCBF and EEG responses in rats exposed at 4 to 6 atmospheres (ATA) of HBO2 and correlated them with brain interstitial NO* metabolites (NO(x)) as an index of NO* production. During exposures to hyperbaric oxygen rCBF decreased at 4 ATA, decreased for the initial 30 min at 5 ATA then gradually increased, and increased within 30 min at 6 ATA. Changes in rCBF correlated positively with NO(x) production; increases in rCBF during HBO2 exposure were associated with large increases in NO(x) at 5 and 6 ATA and always preceded EEG discharges as a sign of CNS O2 toxicity. In rats pretreated with L-NAME, rCBF remained maximally decreased throughout 75 min of HBO2 at 4, 5 and 6 ATA. These data provide the first direct evidence that increased NO* production during prolonged HBO2 exposure is responsible for escape from hyperoxic vasoconstriction. The finding suggests that NO* overproduction initiates CNS O2 toxicity by increasing rCBF, which allows excessive O2 to be delivered to the brain.

Tissue factor in experimental acute lung injury

Acute lung injury (ALI) is characterized by fibrin deposition in the tissue and vascular spaces. Coagulation is activated after exposure to endotoxin or bacteria, and a procoagulant environment rapidly develops in the vascular, interstitial, and alveolar spaces of the lung. These changes are tissue factor (TF)-dependent and associated with increases in inflammatory cytokines. Procoagulant changes also occur in the lungs of patients with the acute respiratory distress syndrome (ARDS), suggesting that epithelial inflammation activates the extrinsic pathway. Many inflammatory mediators have specific effects on coagulation; however, the role of TF in regulation of pulmonary inflammatory responses is less clear. Here we report initial data on blockade of TF-initiated coagulation in baboons with Escherichia coli sepsis-induced ALI, using active site-inactivated FVIIa (FVIIai ASIS). Treatment with FVIIai prevented plasma fibrinogen depletion and attenuated fibrin deposition in the tissues. The drug also decreased systemic cytokine responses and inflammatory changes in the lung, including neutrophil infiltration, and decreased edema. Coagulation blockade with FVIIai improved lung function by preserving gas exchange and compliance, decreased pulmonary hypertension, and enhanced renal function. These results show that TF-FVIIa complex is an important regulatory site for the pathologic response of the lung to sepsis.

Inhaled carbon monoxide and hyperoxic lung injury in rats

Because carbon monoxide (CO) has been proposed to have anti-inflammatory properties, we sought protective effects of CO in pulmonary O(2) toxicity, which leads rapidly to lung inflammation and respiratory failure. Based on published studies, we hypothesized that CO protects the lung against O(2) by selectively increasing expression of antioxidant enzymes, thereby decreasing oxidative injury and inflammation. Rats exposed to O(2) with or without CO [50-500 parts/million (ppm)] for 60 h were compared for lung wet-to-dry weight ratio (W/D), pleural fluid volume, myeloperoxidase (MPO) activity, histology, expression of heme oxygenase-1 (HO-1), and manganese superoxide dismutase (Mn SOD) proteins. The brains were evaluated for histological evidence of damage from CO. In O(2)-exposed animals, lung W/D increased from 4.8 in normal rats to 6.3; however, only CO at 200 and 500 ppm decreased W/D significantly (to 5.9) during O(2) exposure. Large volumes of pleural fluid accumulated in all rats, with no significant CO treatment effect. Lung MPO values increased after O(2) and were not attenuated by CO treatment. CO did not enhance lung expression of oxidant-responsive proteins Mn SOD and HO-1. Animals receiving O(2) and CO at 200 or 500 ppm showed significant apoptotic cell death in the cortex and hippocampus by immunochemical staining. Thus significant protection by CO against O(2)-induced lung injury could not be confirmed in rats, even at CO concentrations associated with apoptosis in the brain.

Antibody to intercellular adhesion molecule 1 (CD54) decreases survival and not lung injury in baboons with sepsis

Neutrophil influx into the lung is an important event in the pathogenesis of acute lung injury in gram-negative sepsis. We hypothesized that administration of a monoclonal antibody to intercellular adhesion molecule 1 (ICAM-1, CD54), a molecule mediating neutrophil adhesion to endothelial cells, would decrease neutrophil sequestration and transmigration in the lung and attenuate lung injury in Escherichia coli sepsis. Sepsis was induced in 12 baboons primed with heat-killed E. coli (1 x 10(9) CFU/kg) 12 h before infusion of live bacteria (1 x 10(10) CFU/kg). Six animals received monoclonal antibody to CD54 (1 mg/kg) intravenously at the time of live E. coli infusion. After 48 h or when blood pressure could not be maintained, tissues were harvested and bronchoalveolar lavage (BAL) samples were obtained. Median survival time was decreased in anti-CD54-treated animals. This group also had decreased mean arterial pressure, increased metabolic acidosis, and decreased urine output. Measures of lung injury including gas exchange, lung lavage protein and lactate dehydrogenase (LDH), lung thiobarbituric acid-reactive species, and lung histology, including alveolar neutrophil volumes, were unaffected by treatment. The effect of anti-CD54 on neutrophil influx into tissues as measured by myeloperoxidase was organ specific. These data show that monoclonal antibody to CD54 does not ameliorate acute lung injury in E. coli sepsis, and septic primates given anti-CD54 have worsened metabolic parameters and decreased survival.