The intrinsic apoptotic pathway is required for lipopolysaccharide-induced lung endothelial cell death

LPS has been implicated in the pathogenesis of endothelial cell death associated with Gram-negative bacterial sepsis. The binding of LPS to the TLR-4 on the surface of endothelial cells initiates the formation of a death-inducing signaling complex at the cell surface. The subsequent signaling pathways that result in apoptotic cell death remain unclear and may differ among endothelial cells in different organs. We sought to determine whether LPS and cycloheximide-induced cell death in human lung microvascular endothelial cells (HmVECs) was dependent upon activation of the intrinsic apoptotic pathway and the generation of reactive oxygen species. We found that cells overexpressing the anti-apoptotic protein Bcl-X(L) were resistant to LPS and cycloheximide-induced death and that the proapoptotic Bcl-2 protein Bid was cleaved following treatment with LPS. The importance of Bid was confirmed by protection of Bid-deficient (bid(-/-)) mice from LPS-induced lung injury. Neither HmVECs treated with the combined superoxide dismutase/catalase mimetic EUK-134 nor HmVECs depleted of mitochondrial DNA (rho(0) cells) were protected against LPS and cycloheximide-induced death. We conclude that LPS and cycloheximide-induced death in HmVECs requires the intrinsic cell death pathway, but not the generation of reactive oxygen species.

Alveolar epithelial beta2-adrenergic receptors

beta(2)-adrenergic receptors are present throughout the lung, including the alveolar airspace, where they play an important role for regulation of the active Na(+) transport needed for clearance of excess fluid out of alveolar airspace. beta(2)-adrenergic receptor signaling is required for up-regulation of alveolar epithelial active ion transport in the setting of excess alveolar edema. The positive, protective effects of beta(2)-adrenergic receptor signaling on alveolar active Na(+) transport in normal and injured lungs provide substantial support for the use of beta-adrenergic agonists to accelerate alveolar fluid clearance in patients with cardiogenic and noncardiogenic pulmonary edema. In this review, we summarize the role of beta(2)-adrenergic receptors in the alveolar epithelium with emphasis on their role in the regulation of alveolar active Na(+) transport in normal and injured lungs.

Electroporation-mediated gene transfer of the Na+,K+ -ATPase rescues endotoxin-induced lung injury

RATIONALE

Acute lung injury and acute respiratory distress syndrome are common clinical syndromes resulting largely from the accumulation of and inability to clear pulmonary edema, due to injury to the alveolar epithelium. Gene therapy may represent an important alternative for the treatment and prevention of these diseases by restoring alveolar epithelial function. We have recently developed an electroporation strategy to transfer genes to the lungs of mice, with high efficiency and low inflammation.

OBJECTIVES

We asked whether electroporation-mediated transfer of genes encoding subunits of the Na+,K+ -ATPase could protect from LPS-induced lung injury or be used to treat already injured lungs by up-regulating mechanisms of pulmonary edema clearance.

METHODS

Plasmids were delivered to the lungs of mice using transthoracic electroporation. Lung injury was induced by intratracheal administration of LPS (4 mg/kg body weight). Biochemical, cellular, and physiologic measurements were taken to assess gene transfer and lung injury.

MEASUREMENTS AND MAIN RESULTS

Improvements in wet-to-dry ratios, pulmonary effusions, bronchoalveolar lavage protein levels and cellularity, alveolar fluid clearance, and respiratory mechanics were seen after delivery of plasmids expressing Na+,K+ -ATPase subunits, but not control plasmids, in LPS-injured lungs. Delivery of plasmids expressing Na+,K+ -ATPase subunits both protected from subsequent lung injury and partially reversed existing lung injury by these measures.

CONCLUSIONS

These results demonstrate that electroporation can be used effectively in healthy and injured lungs to facilitate gene delivery and expression. To our knowledge, this is the first successful use of gene delivery to treat existing lung injury, and may have future clinical potential.

Severe pseudomonal infections

PURPOSE OF REVIEW

To review the most recent data on severe Pseudomonas aeruginosa infections. The focus will be on clinical studies with an emphasis on the critically ill.

RECENT FINDINGS

The frequency of P. aeruginosa as the etiologic agent of infections associated with high morbidity and mortality in hospitalized patients continues to increase. Unfortunately, pan-resistant isolates are now emerging as a significant clinical problem. Highly or pan-resistant isolates are associated with more frequent inappropriate initial therapy and increased mortality. Prevention relies on limitation of antibiotic pressure. Unfortunately, antibiotic class rotation has not resulted in persistent decreases in resistant isolates and the increased use of treatment protocols may actually increase selection.

SUMMARY

Because of the frequency of antibiotic resistance in clinical isolates of P. aeruginosa and the high associated mortality, combination, broad-spectrum antibiotic therapy should be used for empiric coverage of suspected P. aeruginosa infections. Accurate diagnostic testing can help to discontinue unnecessary antibiotics and decrease the overall selective pressure. Increasing resistance without new antibiotic classes on the horizon suggests the need for better use of available antibiotics and an emphasis on innovative treatment strategies in the future.

Leptin resistance protects mice from hyperoxia-induced acute lung injury

RATIONALE

Human data suggest that the incidence of acute lung injury is reduced in patients with type II diabetes mellitus. However, the mechanisms by which diabetes confers protection from lung injury are unknown.

OBJECTIVES

To determine whether leptin resistance, which is seen in humans with diabetes, protects mice from hyperoxic lung injury.

METHODS

Wild-type (leptin responsive) and db/db (leptin resistant) mice were used in these studies. Mice were exposed to hyperoxia (100% O(2)) for 84 hours to induce lung injury and up to 168 hours for survival studies. Alveolar fluid clearance was measured in vivo.

MEASUREMENTS AND MAIN RESULTS

Lung leptin levels were increased both in wild-type and leptin receptor-defective db/db mice after hyperoxia. Hyperoxia-induced lung injury was decreased in db/db compared with wild-type mice. Hyperoxia increased lung permeability in wild-type mice but not in db/db mice. Compared with wild-type control animals, db/db mice were resistant to hyperoxia-induced mortality (lethal dose for 50% of mice, 152 vs. 108 h). Intratracheal instillation of leptin at a dose that was observed in the bronchoalveolar lavage fluid during hyperoxia caused lung injury in wild-type but not in db/db mice. Intratracheal pretreatment with a leptin receptor inhibitor attenuated leptin-induced lung edema. The hyperoxia-induced release of proinflammatory cytokines was attenuated in db/db mice. Despite resistance to lung injury, db/db mice had diminished alveolar fluid clearance and reduced Na,K-ATPase function compared with wild-type mice.

CONCLUSIONS

These results indicate that leptin can induce and that resistance to leptin attenuates hyperoxia-induced lung injury and hyperoxia-induced inflammatory cytokines in the lung.

Predictors of acute lung injury and severe hypoxemia in patients undergoing operative talc pleurodesis

BACKGROUND

Acute lung injury (ALI) is a life-threatening complication of talc pleurodesis. This study defines characteristics that predispose patients to ALI and severe hypoxemia in patients after video-assisted thoracoscopic surgery (VATS) talc pleurodesis.

METHODS

Charts of patients who underwent talc pleurodesis at Northwestern Memorial Hospital between January 1, 1997 and December 31, 2003 were retrospectively reviewed. We sought variables associated with the development of postoperative ALI or severe hypoxemia, defined as an increase in fraction of the inspired oxygen by more than 0.15 within 24 hours after the surgery. The analysis included 84 patients (58 women, 26 men) who underwent VATS talc pleurodesis for malignant (n = 74) or benign (n = 10) indications.

RESULTS

ALI developed in 5 patients (5.9%), severe hypoxemia developed in 25 (29.8%), and 54 (64.3%) did not have postoperative complications. In multivariate analysis, the presence of peripheral edema before pleurodesis (p = 0.005), any preoperative requirement for supplemental oxygen (p = 0.032), and chemotherapy within 14 days before pleurodesis (p = 0.04) were identified as predictors of ALI or severe postoperative hypoxemia.

CONCLUSIONS

Oxygen supplementation, recent chemotherapy, and presence of peripheral edema were independent predictors of a combined outcome of ALI or severe hypoxemia after VATS talc pleurodesis. Patients with these characteristics might be at risk for adverse outcomes of talc pleurodesis and should be considered for alternative therapy for their effusions.

p53 mediates particulate matter-induced alveolar epithelial cell mitochondria-regulated apoptosis

RATIONALE

Exposure to particulate matter (PM) causes lung cancer by mechanisms that are unknown, but p53 dysfunction is implicated.

OBJECTIVE

We determined whether p53 is required for PM-induced apoptosis in both human and rodent alveolar type (AT) 2 cells.

METHODS

A well-characterized form of urban PM was used to determine whether it induces mitochondrial dysfunction (mitochondrial membrane potential change [DeltaPsi m] and caspase-9 activation), p53 protein and mRNA expression, and apoptosis (DNA fragmentation and annexin V staining) in vitro using A549 cells and primary isolated human and rat AT2 cells. The role of p53 was assessed using inhibitors of p53-dependent transcription, pifithrin-alpha, and a genetic approach (overexpressing E6 or dominant negative p53). In mice, the in vivo effects of PM causing p53 expression and apoptosis were assessed 72 h after a single PM intratracheal instillation.

MEASUREMENTS AND MAIN RESULTS

PM-induced apoptosis in A549 cells was characterized by increased p53 mRNA and protein expression, mitochondrial translocation of Bax and p53, a reduction in DeltaPsi m, and caspase-9 activation, and these effects were blocked by inhibiting p53-dependent transcription. Similar findings were noted in primary isolated human and rat AT2 cells. A549-rho degrees cells that are incapable of mitochondrial reactive oxygen species production were protected against PM-induced DeltaPsi m, p53 expression, and apoptosis. In mice, PM induced p53 expression and apoptosis at the bronchoalveolar duct junctions.

CONCLUSIONS

These data suggest a novel interaction between p53 and the mitochondria in mediating PM-induced apoptosis that is relevant to the pathogenesis of lung cancer from air pollution.

Pulmonary adverse events of anti-tumor necrosis factor-alpha antibody therapy

It is well established that anti-tumor necrosis factor-alpha (TNFalpha) antibody is an efficacious disease-modifying drug for rheumatoid arthritis and Crohn's disease. Unfortunately, its long-term use can be associated with ominous pulmonary adverse events, most notably mycobacterial and fungal lung infections. To this end, reactivation of latent tuberculosis infection represents a serious concern of anti-TNFalpha antibody therapy. Given the anticipated increase in the approved indications for these drugs, community-based physicians should be made aware of these events for implementation of better patient selection for anti-TNFalpha antibody therapy and initiation of appropriate measures once these adverse events are observed. This review will address this issue by outlining: 1) the role of TNFalpha in host inflammatory response to injury, particularly during mycobacterial and fungal infections; 2) the salutary effects of anti-TNFalpha antibody therapy in human diseases; and 3) the ominous pulmonary adverse events associated with these drugs.

Clinical manifestations of sarcoidosis among inner-city African-American dwellers

OBJECTIVES

To characterize clinical, radiographic and physiological features of sarcoidosis among African Americans residing in inner-city Chicago.

METHODS

This is a retrospective review of medical records of 75 African Americans with biopsy-proven sarcoidosis from internal medicine and pulmonary clinics at three inner-city, acute care hospitals in Chicago.

RESULTS

The number of organs involved was 1.77 +/- 0.94 (mean +/- SD). The most common sites for tissue diagnosis were lung (49%), skin (19%) and lymph nodes (16%). Thirty-six (48%) patients had stage-2 and -3 disease on chest x-ray. Electrocardiographic changes and ocular involvement were detected in 23% and 21% of patients, respectively. Nineteen (25%) patients had obstructive defect (FEV1 1.71 +/- 0.78 L/s), 15 (20%) had a restrictive defect [TLC 4.1 +/- 1.2 L (63.9 +/- 9.2% predicted)]. Three patients had both restrictive and obstructive defect. Forced vital capacity and FEV1 declined by 0.26 L and 0.09 L/s per year, respectively, in patients with an obstructive defect. Most patients (91%) were treated with prednisone for 3.8 +/- 3.9 years (range 0-20 years).

CONCLUSIONS

African Americans with sarcoidosis residing in inner-city Chicago express a high rate of chronic progressive disease necessitating corticosteroid therapy. Further studies are warranted to elucidate the reasons underlying this paradigm.

Hyperalbuminemia and elevated transaminases associated with high-protein diet

While high protein diets are increasing in popularity, there is a lack of data on their potential adverse effects. We describe two patients on high protein supplements and exercising for physical fitness. Both developed intermittent abdominal pain, transient elevations in transaminases and hyperalbuminemia without there being any identifiable cause. The symptoms and abnormalities on the laboratory tests resolved after the high protein intake was discontinued. While the pathogenesis and importance of these abnormalities need further study, the findings raise concerns regarding the safety of high protein diets combined with high intensity exercise.

Proapoptotic Bid is required for pulmonary fibrosis

The molecular mechanisms of pulmonary fibrosis are poorly understood. Previous reports indicate that activation of TGF-beta1 is essential for the development of pulmonary fibrosis. Here, we report that the proapoptotic Bcl-2 family member Bid is required for the development of pulmonary fibrosis after the intratracheal instillation of bleomycin. Mice lacking Bid exhibited significantly less pulmonary fibrosis in response to bleomycin compared with WT mice. The attenuation in pulmonary fibrosis was observed despite similar levels of inflammation, lung injury, and active TGF-beta1 in bronchoalveolar lavage fluid 5 days after the administration of bleomycin in mice lacking Bid and in WT controls. Bleomycin induced similar levels cell death in vitro in alveolar epithelial cells isolated from WT and bid(-/-) mice. By contrast, alveolar epithelial cells from bid(-/-) mice were resistant to TGF-beta1-induced cell death. These results indicate that Bcl-2 family members are critical regulators for the development of pulmonary fibrosis downstream of TGF-beta1 activation.

Airborne particulate matter inhibits alveolar fluid reabsorption in mice via oxidant generation

Ambient particulate matter is increasingly recognized as a significant contributor to human cardiopulmonary morbidity and mortality in the United States and worldwide. We sought to determine whether exposure to ambient particulate matter would alter alveolar fluid clearance in mice. Mice were exposed to a range of doses of a well-characterized particulate matter collected from the ambient air in Düsseldorf, Germany through a single intratracheal instillation, and alveolar fluid clearance and measurements of lung injury were made. Exposure to even very low doses of particulate matter (10 microg) resulted in a significant reduction in alveolar fluid clearance that was maximal 24 h after the exposure, with complete resolution after 7 d. This was paralleled by a decrease in lung Na,K-ATPase activity. To investigate the mechanism of this effect, we measured plasma membrane Na,K-ATPase abundance in A549 cells and Na,K-ATPase activity in primary rat alveolar type II cells after exposure to particulate matter in the presence or absence of the combined superoxide dismutase and catalase mimetic EUK-134 (5 microM). Membrane but not total protein abundance of the Na,K-ATPase was decreased after exposure to particulate matter, as was Na,K-ATPase activity. This decrease was prevented by the combined superoxide dismutase/catalase mimetic EUK-134. The intratracheal instillation of particulate matter results in alveolar epithelial injury and decreased alveolar fluid clearance, conceivably due to downregulation of the Na,K-ATPase.

Mechanisms of pulmonary edema clearance

The mechanisms of pulmonary edema resolution are different from those regulating edema formation. Absorption of excess alveolar fluid is an active process that involves vectorial transport of Na+out of alveolar air spaces with water following the Na+osmotic gradient. Active Na+transport across the alveolar epithelium is regulated via apical Na+and chloride channels and basolateral Na-K-ATPase in normal and injured lungs. During lung injury, mechanisms regulating alveolar fluid reabsorption are inhibited by yet unclear pathways and can be upregulated by pharmacological means. Better understanding of the mechanisms that regulate edema clearance may lead to therapeutic interventions to improve the ability of lungs to clear fluid, which is of clinical significance.

Cerebrospinal Fluid Leak and Meningitis Associated With Nasal Continuous Positive Airway Pressure Therapy

Clear rhinorrhea is a common symptom in patients with obstructive sleep apnea (OSA) and may worsen with continuous positive airway pressure therapy. Clear rhinorrhea can also be the presenting symptom of cerebrospinal fluid (CSF) leak, which is evidence of a communication between the subarachnoid space and the nasal cavity or sinuses. While CSF leak has been reported to occur with nasal continuous positive airway pressure (nCPAP) therapy following trauma to the skull base, its association with OSA and nCPAP therapy in the absence of trauma has not been previously described. We report two patients with OSA in whom CSF leak developed following the institution of nCPAP therapy. In one patient, the rhinorrhea was complicated by meningitis. Both patients underwent successful repair of their defects. One patient successfully restarted nCPAP therapy, while the other refused it.

Effects of body temperature on ventilator-induced lung injury

PURPOSE

To evaluate the effects of body temperature on ventilator-induced lung injury.

MATERIAL AND METHODS

Thirty-four male Sprague-Dawley rats were randomized into 6 groups based on their body temperature (normothermia, 37 +/- 1 degrees C; hypothermia, 31 +/- 1 degrees C; hyperthermia, 41 +/- 1 degrees C). Ventilator-induced lung injury was achieved by ventilating for 1 hour with pressure-controlled ventilation mode set at peak inspiratory pressure (PIP) of 30 cmH2O (high pressure, or HP) and positive end-expiratory pressure (PEEP) of 0 cmH2O. In control subjects, PIP was set at 14 cmH2O (low pressure, or LP) and PEEP set at 0 cmH2O. Systemic chemokine and cytokine (tumor necrosis factor alpha , interleukin 1 beta , interleukin 6, and monocyte chemoattractant protein 1) levels were measured. The lungs were assessed for histological changes.

RESULTS

Serum chemokines and cytokines were significantly elevated in the hyperthermia HP group compared with all 3 groups, LP (control), normothermia HP, and hypothermia HP. Oxygenation was better but not statistically significant in hypothermia HP compared with other HP groups. Cumulative mean histology scores were higher in hyperthermia HP and normothermia HP groups compared with control and normothermia HP groups.

CONCLUSIONS

Concomitant hyperthermia increased systemic inflammatory response during HP ventilation. Although hypothermia decreased local inflammation in the lung, it did not completely attenuate systemic inflammatory response associated with HP ventilation.

Interdependency of beta-adrenergic receptors and CFTR in regulation of alveolar active Na+ transport

Beta-adrenergic receptors (betaAR) regulate active Na+ transport in the alveolar epithelium and accelerate clearance of excess airspace fluid. Accumulating data indicates that the cystic fibrosis transmembrane conductance regulator (CFTR) is important for upregulation of the active ion transport that is needed to maintain alveolar fluid homeostasis during pulmonary edema. We hypothesized that betaAR regulation of alveolar active transport may be mediated via a CFTR dependent pathway. To test this hypothesis we used a recombinant adenovirus that expresses a human CFTR cDNA (adCFTR) to increase CFTR function in the alveolar epithelium of normal rats and mice. Alveolar fluid clearance (AFC), an index of alveolar active Na+ transport, was 92% greater in CFTR overexpressing lungs than controls. Addition of the Cl- channel blockers NPPB, glibenclamide, or bumetanide and experiments using Cl- free alveolar instillate solutions indicate that the accelerated AFC in this model is due to increased Cl- channel function. Conversely, CFTR overexpression in mice with no beta1- or beta2-adrenergic receptors had no effect on AFC. Overexpression of a human beta2AR in the alveolar epithelium significantly increased AFC in normal mice but had no effect in mice with a non-functional human CFTR gene (Deltaphi508 mutation). These studies indicate that upregulation of alveolar CFTR function speeds clearance of excess fluid from the airspace and that CFTRs effect on active Na+ transport requires the betaAR. These studies reveal a previously undetected interdependency between CFTR and betaAR that is essential for upregulation of active Na+ transport and fluid clearance in the alveolus.

Pseudohypoxemia: interpretation of discrepancies between SaO(2) and SpO(2)

Pulse oximetry is an important tool in evaluation and management of patients with cardiopulmonary disease. It provides an accurate, continuous, non-invasive measurement of oxygenation, however it has some limitations. Pseudohypoxemia is an artifactual condition that has been reported in patients with extreme leukocytosis and thrombocytosis. It should be suspected in patients with a discrepancy between oxygen saturation measured by pulse oximetry and that in arterial blood. High level of suspicion is needed to diagnose this condition as not doing so may lead to unnecessary escalation of therapy (i.e., increased levels of oxygen and mechanical ventilation). We provide a review of the principles and limitations of pulse oximetry and discuss the pathophysiology and diagnosis of pseudohypoxemia.

Potential Genetic Therapies for Acute Lung Injury

Acute lung injury (ALI) is a common, highly lethal acquired disorder that affects over one hundred thousand people each year and for which there are no specific therapies. Extensive investigations in experimental models and humans with ALI have identified several maladaptive host responses and dysregulated protein systems that offer therapeutic opportunities for genetic intervention. Several lines of evidence suggest that gene transfer can be used to deliver protective proteins that improve alveolar epithelial and/or endothelial cell function or immunomodulators that augment lung defense mechanisms and speed clearance of infection. In many instances, gene transfer is the only avenue for producing localized expression of these pharmaceuticals. This article reviews recent translational, animal-based studies that tested the use of gene and cell based therapies to ameliorate or prevent ALI. The lack of effective therapies for ALI and the approachability of the lung for local gene transfer suggest that ALI is a unique example of an acute disease process that is suitable for gene therapy.