Rat Lung Epithelial Cells Research Articles

Mechanical ventilation-induced apoptosis in newborn rat lung is mediated via FasL/Fas pathway

Mechanical ventilation induces pulmonary apoptosis and inhibits alveolar development in preterm infants, but the molecular basis for the apoptotic injury is unknown. The objective was to determine the signaling mechanism(s) of ventilation (stretch)-induced apoptosis in newborn rat lung. Seven-day-old rats were ventilated with room air for 24 h using moderate tidal volumes (8.5 ml/kg). Isolated fetal rat lung epithelial and fibroblast cells were subjected to continuous cyclic stretch (5, 10, or 17% elongation) for up to 12 h. Prolonged ventilation significantly increased the number of apoptotic alveolar type II cells (i.e., terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling and anti-cleaved caspase-3 immunochemistry) and was associated with increased expression of the apoptotic mediator Fas ligand (FasL). Fetal lung epithelial cells, but not fibroblasts, subjected to maximal (i.e., 17%, but not lesser elongation) cyclic stretch exhibited increased apoptosis (i.e., nuclear fragmentation and DNA laddering), which appeared to be mediated via the extrinsic pathway (increased expression of FasL and cleaved caspase-3, -7, and -8). The intrinsic pathway appeared not to be involved [minimal mitochondrial membrane depolarization (JC-1 flow analysis) and no activation of caspase-9]. Universal caspases inhibition and neutralization of FasL abrogated the stretch-induced apoptosis. Prolonged mechanical ventilation induces apoptosis of alveolar type II cells in newborn rats and the mechanism appears to involve activation of the extrinsic death pathway via the FasL/Fas system.

Protective effect of quercetin on acrolein-induced COX-2 expression in lung epithelial cells

The purpose of this study was to determine whether quercetin can protect against acrolein-induced cyclooxygenase-2 (COX-2) expression using rat lung epithelial (LE) cells. The LE cells were exposed to 20 or 60 μM quercetin and 20 μM acrolein for 24 hr. Cell viability was reduced by acrolein, while quercetin 20 μM reduced the adverse effect produced by acrolein. Quercetin alone at 20 μM did not markedly affect cell viability. Acrolein-induced toxicity in LE cells was evidenced by the presence of inflammatory mediators. It was previously reported that exposure of LE cells to 20 μM acrolein produced an upregulation in COX-2 expression that was reduced by 20 μM quercetin. To determine the underlying mechanism of activation of inflammation, the protein expression of NFκB (phosphorylated p65), ERK and MEK, and MAP kinases was determined. These inflammatory mediators were upregulated by acrolein while quercetin reduced the expression of these mediators. Data suggest that quercetin, a flavonoid, may be beneficial in counteracting acrolein-mediated adverse insults to cells via an ERK/MEK/NFκB-mediated inflammatory pathway.

Induction of Apoptosis in Rat Lung Epithelial Cells by Multiwalled Carbon Nanotubes

Induction of Apoptosis in Rat Lung Epithelial Cells by Multiwalled Carbon Nanotubes

Extracellular Secretion of Suppressor of Cytokine Signaling (SOCS) Proteins by Alveolar Macrophages (AMs)

Many proteins once thought to be exclusively intracellular have been shown to be secreted into the extracellular space via unconventional pathways. SOCS proteins serve as critical brakes on immune activation by targeting STAT proteins, and have never been identified in the extracellular space. Here we investigated i) if SOCS proteins are secreted by AMs in vitro and in vivo; ii) if secreted SOCS proteins are biologically active; and iii) if their secretion proceeds by conventional or unconventional pathways.SOCS1 and 3 proteins were secreted constitutively by primary rat AMs and this was not explained by toxicity. In vivo, SOCS3 could be identified in BAL fluid of naïve mice. SOCS‐enriched conditioned medium from AMs inhibited IL‐6‐induced STAT3 and IFNγ‐induced STAT1 protein phosphorylation/activation in rat lung epithelial cells. Monensin, an inhibitor of conventional secretion, decreased secretion of TNF‐α but not that of SOCS proteins, suggesting unconventional secretion mechanisms are involved. Differential centrifugation revealed that SOCS3 protein was found in microparticles rather than exosomes.These studies show that SOCS 1 and 3 are secreted from AMs in vitro and in vivo, via the release of microparticles. We speculate that this represents a novel means of intercellular communication by which AMs can modulate lung immunity, for example by inhibiting JAK/STAT pathway in epithelial cells.This work was supported by U.S. National Institutes of Health grant HL058897 (M.P.‐G.) and an American Lung Association Senior Research Training Fellowship (E.B.).

Multifunctional Polymer-Coated Carbon Nanotubes for Safe Drug Delivery.

Though progress in the use carbon nanotubes in medicine has been most encouraging for therapeutic and diagnostic applications, any translational success must involve overcoming the toxicological and surface functionalization challenges inherent in the use of such nanotubes. Ideally, a carbon nanotube-based drug delivery system would exhibit low toxicity, sustained drug release, and persist in circulation without aggregation. We report a carbon nanotube (CNT) coated with a biocompatible block-co-polymer composed of poly(lactide)-poly(ethylene glycol) (PLA-PEG) to reduce short-term and long-term toxicity, sustain drug release of paclitaxel (PTX), and prevent aggregation. The copolymer coating on the surface of CNTs significantly reduces in vitro toxicity in human umbilical vein endothelial cells (HUVEC) and U-87 glioblastoma cells. Moreover, coating reduces in vitro inflammatory response in rat lung epithelial cells. Compared to non-coated CNTs, in vivo studies show no long-term inflammatory response with CNT coated with PLA-PEG (CLP) and the surface coating significantly decreases acute toxicity by doubling the maximum tolerated dose in mice. Using polymer coatings, we can encapsulate PTX and release over one week to increase the therapeutic efficacy compared to free drugs. In vivo biodistribution and histology studies suggests a lower degree of aggregation in tissues in that CLP accumulate more in the brain and less in the spleen than the CNT-PLA (CL) formulation.

Geminin Functions Downstream of p53 in K-ras–Induced Gene Amplification of Dihydrofolate Reductase

DNA strand breakage and perturbation of cell-cycle progression contribute to gene amplification events that can drive cancer. In cells lacking p53, DNA damage does not trigger an effective cell-cycle arrest and in this setting promotes gene amplification. This is also increased in cells harboring oncogenic Ras, in which cell-cycle arrest is perturbed and ROS levels that cause DNA single strand breaks are elevated. This study focused on the effects of v-K-ras and p53 on Methotrexate (MTX)-mediated DHFR amplification. Rat lung epithelial cells expressing v-K-ras or murine lung cancer LKR cells harboring active K-ras continued cell-cycle progression when treated with MTX. However, upon loss of p53, amplification of DHFR and formation of MTX-resistant colonies occurred. Expression levels of cyclin A, Geminin, and Cdt1 were increased in v-K-ras transfectants. Geminin was sufficient to prevent the occurrence of multiple replications via interaction with Cdt1 after MTX treatment, and DHFR amplification proceeded in v-K-ras transfectants that possess a functional p53 in the absence of geminin. Taken together, our findings indicate that p53 not only regulates cell-cycle progression, but also functions through geminin to prevent DHFR amplification and protect genomic integrity.

Signal change of surface acoustic wave (SAW) caused by H2O2 damage to SV40-T2 cells cultivated on SH-SAW sensor

We developed a cellular biosensing system based on the direct assembly of rat- or human-cultured cells onto a shear horizontal-surface acoustic wave (SH-SAW) device. This novel design enables the sensitive monitoring of changes in physical cell-characteristics, such as viscosity or density inside the cells. In our system, the change of phase of SAW and insertion loss was observed to be time-dependent when the rat lung epithelial cells were treated with 1.0mM H2O2. Immunofluorescence microscopy showed the disappearance of the zonula occludens protein from the cell–cell contact region. Furthermore, the transepithelial electrical resistance of the cells gradually decreased owing to this treatment. These results suggest the correlation between the change of SH-SAW phase, the insertion loss of the SH-SAW parameter, and the destruction of the tight junction of the cells on SH-SAW devices.

233 Mechanical Ventilation-Induced Apoptosis in Newborn Rat Lung is Mediated Via Fasl/Fas Pathway

RationaleMechanical ventilation induces pulmonary apoptosis and inhibits alveolar development in preterm infants, but the molecular basis for this apoptotic injury is unknown.ObjectiveTo determine the signaling mechanism(s) of ventilation(stretch)-induced apoptosis in...

Elevated Expression of Fn14 in Non-Small Cell Lung Cancer Correlates with Activated EGFR and Promotes Tumor Cell Migration and Invasion

Lung cancer is the leading cause of cancer deaths worldwide; approximately 85% of these cancers are non-small cell lung cancer (NSCLC). Patients with NSCLC frequently have tumors harboring somatic mutations in the epidermal growth factor receptor (EGFR) gene that cause constitutive receptor activation. These patients have the best clinical response to EGFR tyrosine kinase inhibitors (TKIs). Herein, we show that fibroblast growth factor-inducible 14 (Fn14; TNFRSF12A) is frequently overexpressed in NSCLC tumors, and Fn14 levels correlate with p-EGFR expression. We also report that NSCLC cell lines that contain EGFR-activating mutations show high levels of Fn14 protein expression. EGFR TKI treatment of EGFR-mutant HCC827 cells decreased Fn14 protein levels, whereas EGF stimulation of EGFR wild-type A549 cells transiently increased Fn14 expression. Furthermore, Fn14 is highly expressed in EGFR-mutant H1975 cells that also contain an EGFR TKI-resistance mutation, and high TKI doses are necessary to reduce Fn14 levels. Constructs encoding EGFRs with activating mutations induced Fn14 expression when expressed in rat lung epithelial cells. We also report that short hairpin RNA-mediated Fn14 knockdown reduced NSCLC cell migration and invasion in vitro. Finally, Fn14 overexpression enhanced NSCLC cell migration and invasion in vitro and increased experimental lung metastases in vivo. Thus, Fn14 may be a novel therapeutic target for patients with NSCLC, in particular for those with EGFR-driven tumors who have either primary or acquired resistance to EGFR TKIs.

Identification of the amino-acid region involved in the intercellular interaction between the Na,K-ATPase β1 subunits

Epithelial junctions depend on intercellular interactions between β(1) subunits of the Na(+)/K(+)-ATPase molecules of neighboring cells. The interaction between dog and rat subunits is less effective than the interaction between two dog β(1) subunits, indicating the importance of species-specific regions for β(1)-β(1) binding. To identify these regions, the species-specific amino acid residues were mapped on a high-resolution structure of the Na(+)/K(+)-ATPase β(1) subunit to select those exposed towards the β(1) subunit of the neighboring cell. These exposed residues were mutated in both dog and rat YFP-linked β(1) subunits (YFP-β(1)) and also in the secreted extracellular domain of the dog β(1) subunit. Five rat-like mutations in the amino acid region spanning residues 198-207 of the dog YFP-β(1) expressed in Madin-Darby canine kidney (MDCK) cells decreased co-precipitation of the endogenous dog β(1) subunit with YFP-β(1) to the level observed between dog β(1) and rat YFP-β(1). In parallel, these mutations impaired the recognition of YFP-β(1) by the dog-specific antibody that inhibits cell adhesion between MDCK cells. Accordingly, dog-like mutations in rat YFP-β(1) increased both the (YFP-β(1))-β(1) interaction in MDCK cells and recognition by the antibody. Conversely, rat-like mutations in the secreted extracellular domain of the dog β(1) subunit increased its interaction with rat YFP-β(1) in vitro. In addition, these mutations resulted in a reduction of intercellular adhesion between rat lung epithelial cells following addition of the secreted extracellular domain of the dog β(1) subunit to a cell suspension. Therefore, the amino acid region 198-207 is crucial for both trans-dimerization of the Na(+)/K(+)-ATPase β(1) subunits and cell-cell adhesion.

Molecular changes during arsenic-induced cell transformation

Arsenic and its derivatives are naturally occurring metalloid compounds widely distributed in the environment. Arsenics are known to cause cancers of the skin, liver, lung, kidney, and bladder. Although numerous carcinogenic pathways have been proposed, the exact molecular mechanisms remain to be delineated. To further characterize the role of oxidative stress in arsenite-induced cell transformation via the reactive oxygen species (ROS)-mediated Ras/Erk pathway, here we demonstrated arsenite-induced rat lung epithelial cell (LEC) transformation, epithelial-mesenchymal transition, stimulation of the extracellular signal-regulated kinase signaling pathway, and enhancement of cell proliferation. However, there was no evidence of activation of the phosphoinositide 3-kinase/protein kinase B pathway in arsenite-induced transformed LECs. Since ROS is involved in arsenite-induced LEC cell transformation, Redox-status regulatory proteins (Cu/Zn SOD and thioredoxin) and arsenite-induced LEC cell transformation were significantly inhibited by concurrent treatment with the antioxidants. Our experimental results clearly demonstrated that induction of p-ERK and cell proliferation by arsenite is mediated via oxidative stress, since antioxidants can inhibit arsenite-induced cell transformation.

Multiwall carbon nanotubes induce apoptosis in rat lung epithelial cells through activation of caspases

Carbon nanotubes (CNTs), the most promising material with unique characteristics, find its application in different fields ranging from composite materials to medicine and from electronics to energy storage. However, little is known about the mechanism behind the interaction of these particles with cells and their biocompatibility. Therefore, in the present study, we treated rat lung epithelial cells (LE) with 0.5 to 10μg/ml of multiwall carbon nanotubes (MWCNTs) and investigated their effects on cell proliferation and cell death. MTT assay showed a significant dose dependent inhibition of cell proliferation in MWCNT treated cells as compared to control cells, which is also reconfirmed using live-dead cell assay. MWCNT induces reactive oxygen species in a dose dependent manner in LE cells. Dose dependent increase in the level of lipid peroxidation was observed in these cells, which directly correlates with increased ROS levels. The reductions of glutathione and superoxide dismutase level also were detected in cells treated with MWCNT than control. The time dependent and dose dependent increase in the level of caspase 3 and 8 activities was observed in treated cells as compared to control. DNA fragmentation was increased in a dose dependent manner with corresponding increased concentration of MWCNT than control cells. TUNEL assay showed no significant incorporation of dUTPs in cells incubated with z-VAD-fmk, the caspase inhibitor, which confirmed the role of caspases in DNA fragmentation. Together, our results show that that MWCNTs induce the generation of reactive radicals and activates the initiator and effectors caspases in LE cells and that this sequence of events triggers apoptosis cascade. This work was supported by NASA: NCC-1-02038 and NIH-1P20MD001822-1.

Role of ascorbate in lung cellular toxicity mediated by light-exposed parenteral nutrition solution

Neonatal lung injury has been induced experimentally by infusion of multivitamin-containing light-exposed parenteral nutrition (PN) solutions. The objective was to explore the role of ascorbate in toxic effects of light-exposed PN on primary cultured foetal rat lung epithelial cells. Hydroperoxides were measured in 3% amino acid solutions at baseline, immediately after addition of either multivitamins or ascorbate alone (400 μg/mL) and again after a 24-h period of exposure to (or protection from) ambient light. Cellular toxicity was assessed by [C14]adenine release. Multivitamins or ascorbate alone increased hydroperoxides in PN, which was attenuated by light protection. Light-exposed PN containing multivitamins was more toxic to cells than baseline or light-protected PN. Exposure to ascorbate at concentrations both lower (< 5 μg/mL) and higher (> 1000 μg/mL) than normally contained in PN-induced oxidant-mediated cell death, as indicated by protective effects of hydroperoxide and hydroxyl radical scavengers. This study concludes that ascorbate generates toxic amounts of peroxide in PN solutions. The types and physiological importance of hydroperoxides induced by pro-oxidant effects of ascorbate require further evaluation in vivo.

Loss of gap junctional intercellular communication in rat lung epithelial cells exposed to carbon or silica-based nanoparticles

The aim of this study was to investigate whether fine and ultrafine carbon black (fC and ufC), and fine and ultrafine silica (fS, ufS) particles affect gap junctional intercellular communication (GJIC) in rat lung epithelial cells. Exposure of cells to subcytotoxic doses of ufC, fS and ufS resulted in a 63%, 59% and 77% reduction of GJIC, respectively, as determined in a dye transfer assay. In contrast to ufC, fC did not significantly alter GJIC. Changes in subcellular localization of the major gap junction protein in RLE cells, connexin-43 (Cx43), and of β-catenin were observed in cells exposed to ufC, fS or ufS. The loss of GJIC was counteracted by N-acetyl cysteine and was largely prevented by specific inhibitors of epidermal growth factor receptor-dependent signaling, pointing to the crucial role of two known major mediators of nanoparticle action, namely reactive oxygen species and membrane-receptor signaling, in particle-induced modulation of GJIC.

C-Src-mediated activation of Erk1/2 is a reaction of epithelial cells to carbon nanoparticle treatment and may be a target for a molecular preventive strategy

Owing to their specific physico/chemical properties, engineered as well as environmental nanoparticles can induce pathogenic endpoints in humans. Earlier studies demonstrated that pure carbon nanoparticles induce cell signaling events at the level of membrane receptor activation in lung epithelial cells. As a possible link between receptor activation and subsequent MAP-kinase signaling, the involvement of Src family kinases was investigated in cell lines of organs potentially exposed to environmental nanoparticles. Human cells from bronchus, intestine, and skin (keratinocytes) as well as rat lung epithelial cells showed similar time patterns for the activation of mitogen-activated protein kinases Erk1/2 as well as Src family kinases (SFK) when treated with carbon nanoparticles. Moreover, c-Src was identified as an integral part of the signaling mediating the transfer of information from membrane receptors to members of the proliferative signaling cascade in lung epithelial cells. Pretreatment of cells with the compatible solute ectoine, which is known to stabilize macromolecules, reduced the nanoparticle specific phosphorylation of SFK. Together with earlier in vivo and in vitro data, this demonstrates that compatible solutes prevent nanoparticle-induced signaling steps at the level of membrane-coupled signaling.

Multiwalled carbon nanotubes activate NF-κB and AP-1 signaling pathways to induce apoptosis in rat lung epithelial cells

Our previous report on multiwall carbon nanotubes (MWCNT) has demonstrated the generation of reactive radicals and depletion of intracellular antioxidants which in turn cause cell death through activation of caspases. The molecular mechanism of cellular death due to MWCNT is not clear yet. In this study, we investigated the signaling pathways implicated in MWCNT-induced apoptosis in rat lung epithelial cells. First, we assessed the DNA damage in response to MWCNT treatment and showed the significant DNA damage as compared to control. The collapse of the mitochondrial membrane integrity, release of cytochrome c into the cytosol, reduction in cellular ATP content, increased levels of mitochondrial apoptogenic factor and activation and nuclear translocation of NF-κB were observed in MWCNT treated cells. In addition, a time-dependent induction of phosphorylated IκBα and its degradation were detected in cells exposed to MWCNT. Furthermore, MWCNT activated several death related proteins including apoptosis inducing factor, p53, p21 and bax. Together, our results suggest that signaling pathways such as NF-κB and AP-1 are activated upon MWCNT treatment for cellular cytotoxicity.

Induction of Cell Death through Alteration of Oxidants and Antioxidants in Lung Epithelial Cells Exposed to High Energy Protons

Radiation affects several cellular and molecular processes, including double strand breakage and modifications of sugar moieties and bases. In outer space, protons are the primary radiation source that poses a range of potential health risks to astronauts. On the other hand, the use of proton irradiation for tumor radiation therapy is increasing, as it largely spares healthy tissues while killing tumor tissues. Although radiation-related research has been conducted extensively, the molecular toxicology and cellular mechanisms affected by proton irradiation remain poorly understood. Therefore, in this study, we irradiated rat lung epithelial cells with different doses of protons and investigated their effects on cell proliferation and death. Our data show an inhibition of cell proliferation in proton-irradiated cells with a significant dose-dependent activation and repression of reactive oxygen species and antioxidants glutathione and superoxide dismutase, respectively, compared with control cells. In addition, the activities of apoptosis-related genes such as caspase-3 and -8 were induced in a dose-dependent manner with corresponding increased levels of DNA fragmentation in proton-irradiated cells compared with control cells. Together, our results show that proton irradiation alters oxidant and antioxidant levels in cells to activate the apoptotic pathway for cell death.

NF-kappaB dependent and independent mechanisms of quartz-induced proinflammatory activation of lung epithelial cells.

In the initiation and progression of pulmonary inflammation, macrophages have classically been considered as a crucial cell type. However, evidence for the role of epithelial type II cells in pulmonary inflammation has been accumulating. In the current study, a combined in vivo and in vitro approach has been employed to investigate the mechanisms of quartz-induced proinflammatory activation of lung epithelial cells. In vivo, enhanced expression of the inflammation- and oxidative stress-related genes HO-1 and iNOS was found on the mRNA level in rat lungs after instillation with DQ12 respirable quartz. Activation of the classical NF-κB pathway in macrophages and type II pneumocytes was indicated by enhanced immunostaining of phospho-IκBα in these specific lung cell types. In vitro, the direct, particle-mediated effect on proinflammatory signalling in a rat lung epithelial (RLE) cell line was compared to the indirect, macrophage product-mediated effect. Treatment with quartz particles induced HO-1 and COX-2 mRNA expression in RLE cells in an NF-κB independent manner. Supernatant from quartz-treated macrophages rapidly activated the NF-κB signalling pathway in RLE cells and markedly induced iNOS mRNA expression up to 2000-fold compared to non-treated control cells. Neutralisation of TNFα and IL-1β in macrophage supernatant did not reduce its ability to elicit NF-κB activation of RLE cells. In addition the effect was not modified by depletion or supplementation of intracellular glutathione.The results from the current work suggest that although both oxidative stress and NF-κB are likely involved in the inflammatory effects of toxic respirable particles, these phenomena can operate independently on the cellular level. This might have consequences for in vitro particle hazard testing, since by focusing on NF-κB signalling one might neglect alternative inflammatory pathways.

HIV‐1‐related proteins decrease Nrf2 expression and alter tight junction protein localization in the plasma membranes of cultured alveolar epithelial cells

There is abundant evidence that HIV‐1‐related proteins can directly induce oxidative stress and impair tight junction (TJ) protein expression, causing serious consequences for the blood‐brain endothelial barrier and the alveolar epithelial air‐liquid barrier. Nrf2 is the redox‐sensitive transcription factor that regulates the expression of multiple antioxidants. We hypothesized that HIV‐1‐induced oxidative stress and barrier dysfunction could involve changes in Nrf2 expression. To test this hypothesis, we first determined that the gene and protein expression of Nrf2 and of the TJ proteins, occludin and ZO‐1, were significantly decreased in primary alveolar epithelial cells (AECs) isolated from HIV‐1 transgenic rats when compared to AECs from wild type (WT) littermates as assessed by real‐time PCR and western blot analysis. In parallel, exposing rat lung epithelial L2 cells to HIV‐1‐related proteins in vitro significantly inhibited Nrf2 gene expression. We then employed RNA silencing of Nrf2 in AECs isolated from WT rats to determine how this affected occludin and ZO‐1 expression. Consistent with our hypothesis, transfecting these cells with Nrf2 siRNA decreased the membrane localization of occludin and ZO‐1as assessed by immunocytochemistry, even though gene expression of occludin and ZO‐1 did not appear to be affected. Taken together, these data suggest that HIV‐1‐related proteins inhibit the expression of Nrf2 in the alveolar epithelium, and that as a consequence, tight junction assembly in the plasma membrane is somehow impaired. Whether this effect on TJ is mediated by oxidative stress is as yet unknown, but we speculate that Nrf2 expression is a redox‐sensitive target of HIV‐1‐related proteins that could mediate some of the cellular dysfunction in cells that are not directly infected by HIV‐1.

Activation of Akt Protects Alveoli from Neonatal Oxygen-Induced Lung Injury

Bronchopulmonary dysplasia (BPD) is the main complication of extreme prematurity, resulting in part from mechanical ventilation and oxygen therapy. Currently, no specific treatment exists for BPD. BPD is characterized by an arrest in alveolar development and increased apoptosis of alveolar epithelial cells (AECs). Type 2 AECs are putative distal lung progenitor cells, capable of regenerating alveolar homeostasis after injury. We hypothesized that the protection of AEC2 death via the activation of the prosurvival Akt pathway prevents arrested alveolar development in experimental BPD. We show that the pharmacologic inhibition of the prosurvival factor Akt pathway with wortmannin during the critical period of alveolar development impairs alveolar development in newborn rats, resulting in larger and fewer alveoli, reminiscent of BPD. Conversely, in an experimental model of BPD induced by oxygen exposure of newborn rats, alveolar simplification is associated with a decreased activation of lung Akt. In vitro studies with rat lung epithelial (RLE) cells cultured in hyperoxia (95% O(2)) showed decreased apoptosis and improved cell survival after the forced expression of active Akt by adenovirus-mediated gene transfer. In vivo, adenovirus-mediated Akt gene transfer preserves alveolar architecture in the newborn rat model of hyperoxia-induced BPD. We conclude that inhibition of the prosurvival factor Akt disrupts normal lung development, whereas the expression of active Akt in experimental BPD preserves alveolar development. We speculate that the modulation of apoptosis may have therapeutic potential in lung diseases characterized by alveolar damage.