Gene therapy for acute lung injury

Rap1 mediates protective effects of iloprost against ventilator-induced lung injury

Prostaglandin I(2) (PGI(2)) has been shown to attenuate vascular constriction, hyperpermeability, inflammation, and acute lung injury. However, molecular mechanisms of PGI(2) protective effects on pulmonary endothelial cells (EC) are not well understood. We tested a role of cAMP-activated Epac-Rap1 pathway in the barrier protective effects of PGI(2) analog iloprost in the murine model of ventilator-induced lung injury. Mice were treated with iloprost (2 microg/kg) after onset of high tidal volume ventilation (30 ml/kg, 4 h). Bronchoalveolar lavage, histological analysis, and measurements of Evans blue accumulation were performed. In vitro, microvascular EC barrier function was assessed by morphological analysis of agonist-induced gap formation and monitoring of Rho pathway activation and EC permeability. Iloprost reduced bronchoalveolar lavage protein content, neutrophil accumulation, capillary filtration coefficient, and Evans blue albumin extravasation caused by high tidal volume ventilation. Small-interfering RNA-based Rap1 knockdown inhibited protective effects of iloprost. In vitro, iloprost increased barrier properties of lung microvascular endothelium and alleviated thrombin-induced EC barrier disruption. In line with in vivo results, Rap1 depletion attenuated protective effects of iloprost in the thrombin model of EC permeability. These data describe for the first time protective effects for Rap1-dependent signaling against ventilator-induced lung injury and pulmonary endothelial barrier dysfunction.

Airway gene therapy

Given both the accessibility and the genetic basis of several pulmonary diseases, the lungs and airways initially seemed ideal candidates for gene therapy. Several routes of access are available, many of which have been refined and optimized for nongene drug delivery. Two respiratory diseases, cystic fibrosis (CF) and alpha1-antitrypsin (alpha1-AT) deficiency, are relatively common; the single gene responsible has been identified and current treatment strategies are not curative. This type of inherited disease was the obvious initial target for gene therapy, but it has become clear that nongenetic and acquired diseases, including cancer, may also be amenable to this approach. The majority of preclinical and clinical studies in the airway have involved viral vectors, although for diseases such as CF, likely to require repeated application, non-viral delivery systems have clear advantages. However, with both approaches a range of barriers to gene expression have been identified that are limiting success in the airway and alveolar region. This chapter reviews these issues, strategies aimed at overcoming them, and progress into clinical trials with non-viral vectors in a variety of pulmonary diseases.

Repeated gene transfer of naked prostacyclin synthase plasmid into skeletal muscles attenuates monocrotaline-induced pulmonary hypertension and prolongs survival in rats

A safer, less invasive method for repeated transgene administration is desirable for clinical application of gene therapy targeting chronic diseases, including pulmonary hypertension (PH). Thus, effects of prostaglandin I2 (prostacyclin) synthase (PGIS) gene transfer by the naked DNA method into skeletal muscle were investigated in monocrotaline (MCT)-induced PH rats. A single injection of rat PGIS cDNA-encoding plasmid into thigh muscle 3 days after bupivacaine pretreatment transiently increased muscle PGIS protein expression and muscle and serum levels of a stable prostacyclin metabolite (6-keto-prostaglandin F1). The muscle 6-keto-prostaglandin F1 level peaked on day 2 but was still elevated on day 7; prostacyclin selectively increased lung cyclic AMP levels as compared with liver and kidney. MCT induced a marked rise in right ventricular (RV) systolic pressure, pulmonary arterial wall thickening, and RV hypertrophy. Repeated PGIS gene transfer every week lowered RV systolic pressure and ameliorated RV and pulmonary artery remodeling in MCT-induced PH rats. Furthermore, repeated PGIS gene transfer significantly improved the survival rate of MCT-induced PH rats. In conclusion, repeated PGIS gene transfer into skeletal muscle not only attenuated the development of PH and cardiovascular remodeling but also improved the prognosis for MCT-induced PH rats. This study may provide insight into a new treatment strategy for PH.

Acute respiratory distress syndrome after early successful primary percutaneous coronary intervention therapy in acute myocardial infarction: a case report

Acute respiratory distress syndrome (ARDS) is characterized by acute-onset dyspnea, diffuse bilateral pulmonary infiltration, low pulmonary capillary wedge pressure (PCWP), and an arterial oxygen tension/inspired oxygen fraction (PaO2/FiO2) ratio of less than 200 mmHg. Acute myocardial infarction (AMI), whether complicated by circulatory arrest, cardiogenic shock, and hypotension or not, was reported as an etiologic factor in the development of ARDS in the prethrombolytic era. In the thrombolytic era, two cases of AMI complicated with ARDS have been reported. ARDS in these two patients resulted from anaphylactic reaction to the thrombolytic agent and not from the hemodynamic consequences of AMI. Development of ARDS during the AMI period has not been reported after early successful primary percutaneous coronary intervention (PCI). Herein, we report a 61-year-old male patient with persistent chest pain who was diagnosed with Killip II anterior ST-segment elevation AMI. He was treated successfully with primary PCI 2.5 hours after the onset of chest pain. Unfortunately, on the third hospital day, acute-onset dyspnea (respiratory rate, 33 beats/min), fever (38.5 degrees C), leukocytosis (white blood cell count, 18,360/microL), and diffuse bilateral pulmonary infiltration were noted. ARDS was diagnosed from the low PCWP (8 mmHg) and a PaO2/FiO2 of less than 200 mmHg (160 mmHg). No usual causes of ARDS such as infection, aspiration, trauma, shock, or drug reactions were noted. We assumed that, in this particular patient, the systemic inflammatory response syndrome frequently induced by AMI might have caused this episode of ARDS. This may imply that AMI itself is a possible etiology of ARDS.

Transfection of lung cells in vitro and in vivo: effect of antioxidants and intraliposomal bFGF

We hypothesized that constitutive formation of reactive oxygen species by respiratory cells is a barrier to gene transfer when liposome-DNA complexes are used, by contributing to rapid degradation of plasmid DNA. When plasmid DNA is complexed to liposomes it is protected against H(2)O(2)-mediated degradation but not that mediated by the hydroxyl radical. Treatment of distal rat fetal lung epithelial cells (RFL(19)Ep) with the vitamin E analog Trolox (50 microM) reduced intracellular plasmid degradation. Both Trolox (50 microM) and an iron chelator, phenanthroline (0.1 microM), significantly increased transgene expression in RFL(19)Ep approximately twofold, consistent with a hydroxyl radical-mediated inhibition of transgene expression. When basic fibroblast growth factor (bFGF; 20 ng/ml), a growth factor with antioxidant properties, was included within liposomes, we observed a significantly greater enhancement of RFL(19)Ep transgene expression (approximately 2-fold) over that seen with Trolox or phenanthroline. Inclusion of bFGF within liposomes also significantly enhanced (approximately 4-fold) transgene expression in mice following intratracheal instillation.

Pharmacology of acute lung injury

The acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a clinical syndrome that affects both medical and surgical patients. To date, despite improved understanding of the pathogenesis of ALI/ARDS, pharmacological modalities have been unsuccessful in decreasing mortality. However, several pharmacological agents for ARDS are in development and have shown great promise. In addition to the anti-inflammatory category including late corticosteroids, inhaled nitric oxide, alveolar surfactant, and vasodilators are being evaluated. Replacements of anticoagulation mediators have also suggested beneficial effects on the patient outcome. This article provides an overview of pharmacological treatments of ALI/ARDS.

Gene transfer of human prostacyclin synthase into the liver is effective for the treatment of pulmonary hypertension in rats

BACKGROUND

As one of the future strategies of advanced pulmonary hypertension, intrinsic prostacyclin drug delivery using gene therapy may be useful. We investigated whether transfer of the prostacyclin synthase gene into the liver could ameliorate monocrotaline-induced pulmonary hypertension in rats.

METHODS

The human prostacyclin synthase gene was transfected into the liver of rats with monocrotaline-induced pulmonary hypertension. Hemodynamic indices, blood samples, lung tissues, and survival curves were evaluated between rats receiving the gene and control rats.

RESULTS

High levels of prostacyclin synthase gene expression were found in the hepatocytes of the prostacyclin synthase group. The level of 6-keto-prostaglandin F(1alpha) was significantly higher in the prostacyclin synthase group (prostacyclin synthase, 35.4 +/- 4.4 ng/mL; control, 22.3 +/- 3.3 ng/mL; P =.0436). The right ventricular/femoral artery pressure ratio was significantly lower in the prostacyclin synthase group than in the control group (prostacyclin synthase, 0.60 +/- 0.039; control, 0.88 +/- 0.051; P =.0036). The endothelin-1 levels in the lung tissues were significantly lower in the prostacyclin synthase group than in the control group (prostacyclin synthase, 10.42 +/- 2.01 pg/mg protein; control, 19.94 +/- 2.82 pg/mg protein; P =.0176). The survival ratio was significantly higher in the prostacyclin synthase group than the control group (P =.0375).

CONCLUSION

This drug delivery system using gene transfer can be considered as an alternative for continuous intravenous prostacyclin infusion for pulmonary hypertension.

Vesicular stomatitis virus G-pseudotyped lentivirus vectors mediate efficient apical transduction of polarized quiescent primary alveolar epithelial cells

We investigated the use of lentivirus vectors for gene transfer to quiescent alveolar epithelial cells. Primary rat alveolar epithelial cells (AEC) grown on plastic or as polarized monolayers on tissue culture-treated polycarbonate semipermeable supports were transduced with a replication-defective human immunodeficiency virus-based lentivirus vector pseudotyped with the vesicular stomatitis virus G (VSV-G) protein and encoding an enhanced green fluorescent protein reporter gene. Transduction efficiency, evaluated by confocal microscopy and quantified by fluorescence-activated cell sorting, was dependent on the dose of vector, ranging from 4% at a multiplicity of infection (MOI) of 0.1 to 99% at an MOI of 50 for AEC grown on plastic. At a comparable titer and MOI, transduction of these cells by a similarly pseudotyped murine leukemia virus vector was approximately 30-fold less than by the lentivirus vector. Importantly, comparison of lentivirus-mediated gene transfer from the apical or basolateral surface of confluent AEC monolayers (R(t) > 2 kOmega. cm(2); MOI = 10) revealed efficient transduction only when VSV-G-pseudotyped lentivirus was applied apically. Furthermore, treatment with EGTA to increase access to the basolateral surface did not increase transduction of apically applied virus, indicating that transduction was primarily via the apical membrane domain. In contrast, differentiated tracheal epithelial cells were transduced by apically applied lentivirus only in the presence of EGTA and at a much lower overall efficiency (approximately 15-fold) than was observed for AEC. Efficient transduction of AEC from the apical cell surface supports the feasibility of using VSV-G-pseudotyped lentivirus vectors for gene transfer to the alveolar epithelium and suggests that differences exist between upper and lower airways in the polarity of available receptors for the VSV-G protein.

Adenovirus-mediated transfer of heme oxygenase-1 cDNA attenuates severe lung injury induced by the influenza virus in mice

Heme oxygenase-1 (HO-1) is an inducible heat shock protein that regulates heme metabolism to form bilirubin, ferritin and carbon monoxide. Based on recent evidence that HO-1 is involved in the resolution of inflammation by modulating apoptotic cell death or cytokine expression, the present study examined whether overexpression of exogenous HO-1 gene transfer provides a therapeutic effect on a murine model of acute lung injury caused by the type A influenza virus. We demonstrate herein that the transfer of HO-1 cDNA resulted in (1) suppression of both pathological changes and intrapulmonary hemorrhage; (2) enhanced survival of animals; and (3) a decrease of inflammatory cells in the lung. TUNEL analysis revealed that HO-1 gene transfer reduced the number of respiratory epithelial cells with DNA damage, and caspase assay suggested that HO-1 suppressed lung injury via a caspase-8-mediated pathway. These findings suggest the feasibility of HO-1 gene transfer to treat lung injury induced by a pathogen commonly seen in the clinical setting. Since oxidative stress and lung injury are involved in many lung disorders, such as pneumonia induced by a variety of microorganisms and pulmonary fibrosis, HO-1 may be useful for wider clinical applications in gene therapy targeting lung disorders including acute pneumonia and pulmonary fibrosis.