Chemokine response of pulmonary artery endothelial cells to hypoxia and reoxygenation 1 1Presented at the annual meeting of the Association for Academic Surgery, Boston, MA, November 7–9, 2002

Inhibition of DNA methylation attenuates lung ischemia-reperfusion injury after lung transplantation

OBJECTIVE

DNA methylation plays an important role in inflammation and oxidative stress. This study aimed to investigate the effect of inhibiting DNA methylation on lung ischemia-reperfusion injury (LIRI).

METHODS

We adopted a completely random design for our study. Thirty-two rats were randomized into the sham, LIRI, azathioprine (AZA), and pluripotin (SC1) groups. The rats in the LIRI, AZA, and SC1 groups received left lung transplantation and intravenous injection of saline, AZA, and SC1, respectively. After 24 hours of reperfusion, histological injury, the arterial oxygen partial pressure to fractional inspired oxygen ratio, the wet/dry weight ratio, protein and cytokine concentrations in lung tissue, and DNA methylation in lung tissue were evaluated. The pulmonary endothelium that underwent hypoxemia and reoxygenation was treated with AZA or SC1. Endothelial apoptosis, chemokines, reactive oxygen species, nuclear factor-κB, and apoptotic proteins in the endothelium were studied.

RESULTS

Inhibition of DNA methylation by AZA attenuated lung injury, inflammation, and the oxidative stress response, but SC1 aggravated LIRI injury. AZA significantly improved endothelial function, suppressed apoptosis and necrosis, reduced chemokines, and inhibited nuclear factor-κB.

CONCLUSIONS

Inhibition of DNA methylation ameliorates LIRI and apoptosis and improves pulmonary function via the regulation of inflammation and oxidative stress.

NAADP-induced intracellular calcium ion is mediated by the TPCs (two-pore channels) in hypoxia-induced pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a form of obstructive vascular disease. Chronic hypoxic exposure leads to excessive proliferation of pulmonary arterial smooth muscle cells and pulmonary arterial endothelial cells. This condition can potentially be aggravated by [Ca²⁺] _i mobilization. In the present study, hypoxia exposure of rat's model was established. Two‐pore segment channels (TPCs) silencing was achieved in rats' models by injecting Lsh‐TPC1 or Lsh‐TPC2. The effects of TPC1/2 silencing on PAH were evaluated by H&E staining detecting pulmonary artery wall thickness and ELISA assay kit detecting NAADP concentrations in lung tissues. TPC1/2 silencing was achieved in PASMCs and PAECs, and cell proliferation was detected by MTT and BrdU incorporation assays. As the results shown, NAADP‐activated [Ca²⁺]_i shows to be mediated via two‐pore segment channels (TPCs) in PASMCs, with TPC1 being the dominant subtype. NAADP generation and TPC1/2 mRNA and protein levels were elevated in the hypoxia‐induced rat PAH model; NAADP was positively correlated with TPC1 and TPC2 expression, respectively. In vivo, Lsh‐TPC1 or Lsh‐TPC2 infection significantly improved the mean pulmonary artery pressure and PAH morphology. In vitro, TPC1 silencing inhibited NAADP‐AM‐induced PASMC proliferation and [Ca²⁺]_i in PASMCs, whereas TPC2 silencing had minor effects during this process; TPC2 silencing attenuated NAADP‐AM‐ induced [Ca²⁺]_i and ECM in endothelial cells, whereas TPC1 silencing barely ensued any physiological changes. In conclusion, TPC1/2 might provide a unifying mechanism within pulmonary arterial hypertension, which can potentially be regarded as a therapeutic target.

The Effect of Cyclosporine A on Dermal Fibroblast Cell - Transcriptomic Analysis of Inflammatory Response Pathway

BACKGROUND

The first immunosuppressive drug - cyclosporine A (CsA) has many unquestioned merits in maintaining organ transplants in patients, as well as, in the treatment of many inflammatory diseases, also associated with cutaneous manifestations. The main task of this drug is to suppress the inflammatory response at the sites of action, which is not well known.

OBJECTIVE

The objective of this study was to evaluate the influence of CsA in therapeutic concentration on the expression of genes associated with the inflammatory response pathway in normal human dermal fibroblasts (NHDF; CC-2511), and this study attempted to determine the mechanism of its action.

METHODS

The cytotoxicity MTT test was performed. The expression of the inflammatory response pathway genes was determined using HG-U133A_2.0 oligonucleotide microarrays. Statistical analysis was performed by GeneSpring 13.0 software using the PL-Grid platform.

RESULTS

Among the 5,300 mRNA, only 573 were changed significantly in response to CsA compared to the control fibroblasts (P≤0.05). CsA inhibited the expression of most genes associated with the inflammatory response in NHDFs. There were only 19 genes with a fold change (FC) lower than -2.0, among which EGR1, FOS, PBK, CDK1 and TOP2A had the lowest expression, as did CXCL2 which can directly impact inflammation. Furthermore, ZNF451 was strongly induced, and COL1A1, COL3A1, IL33, TNFRSFs were weakly up-regulated (FC lower than 2.0).

CONCLUSION

The CsA in therapeutic concentration influences the genes linked to the inflammatory response (in the transcriptional level) in human dermal fibroblasts. The findings suggest that the potential mechanism of CsA action in this concentration and on these genes can be associated with a profibrotic and proapoptotic, and genotoxic effects.

Role of toll-like receptor-4 in lung ischemia-reperfusion injury

BACKGROUND

Toll-like receptor-4 has been implicated in modulating ischemia-reperfusion injury in cardiac, hepatic, renal, and cerebral models. However, its role in lung ischemia-reperfusion injury is unknown. We hypothesize that toll-like receptor-4 has a key role in initiating the inflammatory cascade in lung ischemia-reperfusion injury.

METHODS

We used toll-like receptor-4 specific short interference RNA to achieve toll-like receptor-4 knockdown in rats prior to undergoing ischemia and reperfusion. Lungs were explanted and studied for protein expression and markers of lung injury. Additional animals were evaluated for cellular uptake of toll-like receptor-4 short interference RNA. Toll-like receptor-4 short interference RNA localized to the alveolar macrophage.

RESULTS

In animals pretreated with toll-like receptor-4 short interference RNA, toll-like receptor-4 expression and mitogen-activated protein kinase phosphorylation were suppressed. Markers of lung injury including permeability index, myeloperoxidase content, and bronchoalveolar lavage inflammatory cell counts were all reduced with toll-like receptor-4 knockdown.

CONCLUSIONS

Toll-like receptor-4 is critical in the development of lung ischemia-reperfusion injury and its activation in the alveolar macrophage may be the initiating step.

Differential toll-like receptor activation in lung ischemia reperfusion injury

OBJECTIVE

The requirement for toll-like receptors (TLRs) in lung ischemia reperfusion injury (LIRI) has been demonstrated but not fully characterized. Previously, we reported that TLR-4 is required by alveolar macrophages but not pulmonary endothelial or epithelial cells for development of LIRI. Additionally, we demonstrated differential patterns of mitogen-activated protein kinase (MAPK) activation and cytokine release in these cell types during LIRI. Here, we sought to determine whether these differences in activation responses are related to cell-specific TLR activation requirements.

METHODS

Primary cultures of alveolar macrophages, pulmonary endothelial, and immortalized epithelial cells were pretreated with TLR-2 or TLR-4 short interference RNA (ribonucleic acid) before hypoxia and reoxygenation. Cell lysates and media were analyzed for receptor knockdown, MAPK activation, and cytokine production. Rats were pretreated with TLR-2 or TLR-4 short interference RNA before lung ischemia reperfusion and changes in lung vascular permeability were assessed.

RESULTS

Knockdown of TLR-2 in alveolar macrophages did not affect MAPK phosphorylation or cytokine secretion. Conversely, TLR-2 knockdown in pulmonary endothelial and epithelial cells demonstrated significant reductions in extracellular signal-regulated kinase 1/2 activation and cytokine secretion. The lung permeability index in LIRI was decreased by TLR-4 but not TLR-2.

CONCLUSIONS

Differential TLR signaling and MAPK activation in response to LIRI seem to be cell specific. Short interference RNA provides an outstanding tool for examination of the underlying mechanism.

Functional roles of tumor necrosis factor-alpha and interleukin 1-Beta in hypoxia and reoxygenation

BACKGROUND

Intercellular signaling plays an important role in the development of lung ischemia-reperfusion injury. However, the role of specific mediators remains poorly characterized. Alveolar macrophages (AM) produce soluble mediators early in reperfusion, which modulate the responses of endothelial and epithelial cells to oxidative stress. There is a burst of proinflammatory cytokine production in a variety of cells; however, interleukin 1-beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) localize to the AM. We hypothesized that these cytokines account for the costimulatory effects that AM exert on endothelial and epithelial cells.

METHODS

Activated AM media was placed on cultured rat type 2 pneumocytes and pulmonary artery endothelial cells, which were then subjected to hypoxia and reoxygenation. To assess the contributions of IL-1β and TNF-α, the cells were treated with control media or media that had been depleted of IL-1β or TNF-α. To deplete specific cytokines, activated media was passed through a column with immobilized IL-1β or TNF-α antibodies. Nuclear translocation of transcription factors, mitogen-activated protein kinase activation, and cytokine and chemokine production were assessed.

RESULTS

Depletion of IL-1β or TNF-α effectively eliminated the ability of AM media to enhance the response of endothelial and epithelial cells to oxidative stress. There were significant reductions in monocyte chemotactic protein 1 and cytokine-induced neutrophil chemoattractant (CINC) production (p < 0.05) at 4 hours of reperfusion. Additionally there was decreased nuclear translocation of nuclear factor-kappa B, and extracellular signal-regulated kinase phosphorylation.

CONCLUSIONS

Interleukin 1-beta and TNF-α are critical mediators in the intercellular communication pathways that allow the AM to enhance the response of surrounding cells to oxidative stress.

Synergistic protection in lung ischemia-reperfusion injury with calcineurin and thrombin inhibition

BACKGROUND

Ischemia-reperfusion injury impairs lung transplant outcomes. The transcription factors, activator protein-1, and nuclear factor kappa B, are activated early in reperfusion and drive the development of injury. Thrombin inhibition with hirudin, and calcineurin inhibition with tacrolimus have independently been shown to ameliorate lung ischemia-reperfusion injury by reducing activator protein-1 and nuclear factor kappa B activation, respectively. However, high doses were required to achieve protection using individual agents, raising concerns about potential toxicities. We sought to determine if low-dose combination therapy reduced injury through synergistic inhibition of pretranscriptional signaling events.

METHODS

Rats were pretreated with either intravenous hirudin or tacrolimus at low doses or high doses, or both at low doses, prior to undergoing left lung ischemia and reperfusion. Lungs were assessed for markers of lung injury, including bronchoalveolar lavage cytokine-chemokine content and transcription factor transactivation of activator protein-1 and nuclear factor kappa B.

RESULTS

High-dose monotherapy with hirudin or tacrolimus reduced lung injury and transactivation of activator protein-1 and nuclear factor kappa B activation, respectively, whereas low-dose monotherapy with either agent did not alter transcription factor activation or lung injury compared with positive controls. Low-dose combination therapy was more protective than high-dose monotherapy with either drug, and correlated with a reduction in activation of both transcription factors and their associated cytokines.

CONCLUSIONS

The significant decrease in lung injury severity and transcription factor activation with combined pathway inhibition suggests pretranscriptional signaling redundancy between the calcineurin and thrombin dependent pathways in lung reperfusion injury.

Alveolar macrophage secretory products effect type 2 pneumocytes undergoing hypoxia-reoxygenation

BACKGROUND

Activation of the alveolar macrophage is centrally important to the development of lung ischemia reperfusion injury. Alveolar macrophages and type 2 pneumocytes secrete a variety of proinflammatory mediators in response to oxidative stress. The manner in which they interact and how the macrophage may influence pneumocyte responses in lung ischemia reperfusion injury is unknown. Utilizing an in vitro model of hypoxia and reoxygenation, we sought to determine if the proinflammatory response of type 2 pneumocytes to oxidative stress would be amplified by alveolar macrophage secretory products.

METHODS

Cultured pneumocytes were exposed to control media or media from cultured macrophages exposed to hypoxia and reoxygenation. Pneumocytes were subsequently subjected to hypoxia and reoxygenation and assessed for both nuclear translocation of nuclear factor kappa B and inflammatory cytokine and chemokine secretion. To examine for any reciprocal interactions, we reversed the experiment, exposing macrophages to conditioned pneumocyte media.

RESULTS

In the presence of media from stimulated macrophages, production of proinflammatory mediators by type 2 pneumocytes was dramatically enhanced. In contrast, exposure of the macrophage to conditioned pneumocyte media had an inhibitory effect on macrophage responses subsequently exposed to hypoxia and reoxygenation.

CONCLUSIONS

The alveolar macrophage drives the development of lung reperfusion injury in part through amplification of the inflammatory response of type 2 pneumocytes subjected to hypoxia and reoxygenation.

Alveolar macrophage secretory products augment the response of rat pulmonary artery endothelial cells to hypoxia and reoxygenation

BACKGROUND

Endothelial cell activation is an important response to ischemia and reperfusion in a variety of vascular beds. Endothelial cells secrete a multitude of proinflammatory mediators and express adhesion molecules that promote leukocyte recruitment into injured tissues. Pulmonary artery endothelial cell response to lung ischemia-reperfusion injury does not appear robust enough to drive the development of lung injury independently. Rather, the alveolar macrophage is the key cell in the development of ischemia-reperfusion injury of the lung. Macrophages are known to be a rich source of inflammatory mediators, but the precise mechanism whereby they amplify injury is unknown. The aim of this study was to determine whether alveolar macrophage secretory products amplify the response of the endothelial cell using an in vitro model of lung reperfusion injury.

METHODS

Macrophages were exposed to hypoxia and reoxygenation and the media collected. Cultured endothelial cells were then exposed to macrophage media and maintained at normoxia or subjected to hypoxia and reoxygenation. To assess any reciprocal effects of endothelial cell products on macrophage activation, macrophages were likewise exposed to activated endothelial cell media.

RESULTS

Exposure of endothelial cells to activated alveolar macrophage media enhanced chemokine secretion in response to hypoxia and reoxygenation. In the reciprocal experiment, activated endothelial cell media increased the production of macrophage inflammatory protein 1alpha from macrophages.

CONCLUSIONS

Alveolar macrophages drive the development of lung reperfusion injury, by enhancing the production of proinflammatory chemokines from endothelial cells, which impart a degree of positive feedback on alveolar macrophages.

Regulation of nicotine-induced apoptosis of pulmonary artery endothelial cells by treatment of N-acetylcysteine and vitamin E

This study investigated the frequency of apoptosis in rat pulmonary artery endothelial cells after intraperitoneal nicotine injection, examining the roles of the inflammatory markers myeloperoxidase (MPO), tumour necrosis factor alpha (TNF-alpha), and vascular endothelial growth factor (VEGF) in nicotine-induced vascular damage and the protective effects of two known antioxidant agents, N-acetylcysteine (NAC) and vitamin E. Female Wistar rats were divided into four groups, each composed of nine rats: negative control group, positive control group, NAC-treated group (500 mg/kg), and vitamin E-treated group (500 mg/kg). Nicotine was intraperitoneally injected at a dosage of 0.6 mg/kg for 21 days. Following nicotine injection, the antioxidants were administered orally; treatment was continued until the rats were killed. Lung tissue samples were stained with hematoxylin-eosin (H&E) for histopathological assessments. Apoptosis level in endothelial cells was determined by using TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling) method. Staining of cytoplasmic TNF-alpha and VEGF in endothelial cells, and perivascular MPO activity were evaluated by immunohistochemistry. The treatments with NAC and vitamin E significantly reduced the rate of nicotine-induced endothelial cell apoptosis. NAC and vitamin E significantly reduced the increases in the local production of TNF-alpha and VEGF, and perivascular MPO activity. This findings suggest that NAC can be as effective as vitamin E in protecting against nicotine-induced endothelial cell apoptosis.

MAPK pathway mediates EGR-1-HSP70-dependent cigarette smoke-induced chemokine production

Cigarette smoking, a major risk factor for chronic obstructive pulmonary disease, can cause airway inflammation, airway narrowing, and loss of elasticity, leading to chronic airflow limitation. In this report, we sought to define the signaling pathways activated by smoke and to identify molecules responsible for cigarette smoke-induced inflammation. We applied cigarette smoke water extract (CSE) to primary human lung fibroblasts and found that CSE significantly increased CXC chemokine IL-8 production. Meanwhile, 70-kDa heat shock protein (HSP70) was also induced by CSE in a dose- and time-dependent manner. CSE treatment stimulated HSP70 secretion by primary fibroblasts, which augmented IL-8 production. This was further confirmed by exogenously added recombinant HSP70. Using HSP70 small interfering RNA, we confirmed that CSE-induced chemokine production was dependent on heat shock protein expression. Further investigation showed that CSE could also stimulate early growth response-1 (EGR-1) in an ERK-dependent manner and that the expression of HSP70 was EGR-1 dependent. In view of these findings, we hypothesize that the MAPK-EGR-1-HSP70 pathway regulates the cigarette smoke-induced inflammatory process.

Perinatal increases in TGF-α disrupt the saccular phase of lung morphogenesis and cause remodeling: microarray analysis

Transforming growth factor-α (TGF-α) and its receptor, the epithelial growth factor receptor (EGFR), have been associated with lung remodeling in premature infants with bronchopulmonary dysplasia (BPD). The goal of this study was to target TGF-α overexpression to the saccular phase of lung morphogenesis and determine early alterations in gene expression. Conditional lung-specific TGF-α bitransgenic mice and single-transgene control mice were generated. TGF-α overexpression was induced by doxycycline (Dox) treatment from embryonic day 16.5 (E16.5) to E18.5. After birth, all bitransgenic pups died by postnatal day 7 (P7). Lung histology at E18.5 and P1 showed abnormal lung morphogenesis in bitransgenic mice, characterized by mesenchymal thickening, vascular remodeling, and poor apposition of capillaries to distal air spaces. Surfactant levels (saturated phosphatidylcholine) were not reduced in bitransgenic mice. Microarray analysis was performed after 1 or 2 days of Dox treatment during the saccular (E17.5, E18.5) and alveolar phases (P4, P5) to identify genes induced by EGFR signaling that were shared or unique to each phase. We found 196 genes to be altered (>1.5-fold change; P < 0.01 for at least 2 time points), with only 32% similarly altered in both saccular and alveolar phases. Western blot analysis and immunostaining showed that five genes selected from the microarrays (egr-1, SP-B, SP-D, S100A4, and pleiotrophin) were also increased at the protein level. Pathological changes in TGF-α-overexpressing mice bore similarities to premature infants born in the saccular phase who develop BPD, including remodeling of the distal lung septae and arteries.

Early immunological changes associated with laryngeal transplantation in a major histocompatibility complex-matched pig model

Laryngeal transplantation is an increasingly viable proposition for patients with irreversible diseases of the larynx. One human transplant has been performed successfully, but many questions remain before routine transplantation can begin. In order to measure the immunological changes in mismatched transplants, it is first necessary to know the immediate combined effects of ischaemia-reperfusion injury (IRI) plus the added insult of major surgery in a fully matched setting. We measured the changes in immunologically active mucosal cells following 3 h of cold ischaemia and 8 h of in situ reperfusion in a major histocompatibility complex (MHC)-matched minipig model (n = 4). Biopsies were prepared for quantitative, multiple-colour immunofluorescence histology. The number of immunologically active cells was significantly altered above (supraglottis) and below (subglottis) the vocal cords following transplantation and reperfusion (P < 0.05, P < 0.001, respectively). However, the direction of the change differed between the two subsites: cell numbers decreased post-transplant in the supraglottis and increased in the subglottis. Despite the statistical evidence for IRI, these changes were less than the large normal inter- and intrapig variation in cell counts. Therefore, the significance of IRI in exacerbating loss of function or rejection of a laryngeal allograft is open to question. Longer-term studies are required.

Interleukin-6 Regulation of Direct Lung Ischemia Reperfusion Injury

BACKGROUND

Lung ischemia reperfusion injury continues to adversely affect patient and graft survival after transplantation. While the role of interleukin-6 has been studied in ischemia-reperfusion models of intestine, liver, and heart, its participation in lung reperfusion injury has not been characterized.

METHODS

We administered recombinant interleukin-6 to rat lungs through the intratracheal route before inducing left lung ischemia and reperfusion. Multiple in-vivo indicators of left lung injury were studied, as were transactivation patterns for nuclear factor kappa B and signal transduction and activators of transcription-3. Downstream effects on the elaboration of proinflammatory chemokines and cytokines were also studied.

RESULTS

Recombinant interleukin-6 reduced endothelial disruption and neutrophil sequestration in left lung and alveolar spaces, resulting in improved oxygenation after ischemia and 4 hours of reperfusion. This protection was associated with decreased nuclear factor kappa B and signal transduction and activators of transcription-3 nuclear translocation early in reperfusion, and diminished proinflammatory mediator secretion late in reperfusion.

CONCLUSIONS

Further studies focusing on the effects of recombinant interleukin-6 in large animal models are warranted, as this may be a novel strategy to improve outcomes after lung transplantation. Intratracheal administration may focus its efficacy on the lung while reducing effects on other organ systems during organ procurement.

Crosstalk Between Thrombosis and Inflammation in Lung Reperfusion Injury

BACKGROUND

Activation of extravascular coagulation has been reported in acute lung injury models of sepsis and acute respiratory distress syndrome. Thrombin, the main effector protease of extravascular coagulation, activates proinflammatory cell types, including macrophages, endothelial cells, and neutrophils, each of which participates in lung ischemia-reperfusion injury. We used hirudin, a potent, specific direct thrombin inhibitor, to define the role of thrombin in lung ischemia-reperfusion injury.

METHODS

Rats were pretreated with hirudin 30 minutes before warm, in situ left lung ischemia and reperfusion. Multiple in vivo assessments of lung injury were determined, and mechanistic studies assessed transcriptional regulation early in reperfusion and proinflammatory protein secretion late in reperfusion. Immunohistochemistry localized thrombin activation.

RESULTS

Thrombin localized to macrophages and endothelial and epithelial cells early in reperfusion. Hirudin significantly limited lung ischemia-reperfusion injury-induced derangements in vascular permeability and intraalveolar inflammatory cell sequestration, resulting in improved arterial oxygenation after ischemia and 4 hours of reperfusion. The protection was transcriptionally mediated by attenuated activator protein-1 and early growth response-1 transactivation, but not nuclear factor kappa B transactivation. This was associated with reduced chemokine, but not tumor necrosis factor alpha, secretion late in reperfusion.

CONCLUSIONS

Thrombin promotes lung ischemia-reperfusion injury, as hirudin protected against experimental acute lung injury. Hirudin conferred protection through a mechanism independent of nuclear factor kappa B and tumor necrosis factor alpha, suggesting that its effects may be mediated by a parallel, synergistic inflammatory pathway through activator protein-1 and early growth response-1.

Cyclosporine modulates the response to hypoxia-reoxygenation in pulmonary artery endothelial cells

BACKGROUND

Depletion of macrophages, neutrophils, or lymphocytes confers only partial protection against experimental lung reperfusion injury, suggesting that inflammatory responses in other cell types contribute to tissue injury. Endothelial cell activation has previously been shown to be critical to the development of ischemia-reperfusion injury in other vascular beds. Furthermore, cyclosporine (CSA) reduces in vivo lung reperfusion injury through attenuated secretion of proinflammatory mediators. These studies determined whether pulmonary artery endothelial cells (PAEC), subjected to hypoxia and reoxygenation, promote inflammation and whether CSA afforded any modulation of that response.

METHODS

Isolated rat PAEC were subjected in vitro to 2 hours hypoxia followed by up to 4 hours reoxygenation. Cells were pretreated with CSA or a cremaphor vehicle. Differences in activation of signaling kinases and transcription factors were assessed, as was cytokine-chemokine protein secretion.

RESULTS

There was significant signaling kinase (extracellular signal regulated kinase [ERK 1/2]) activation by 15 minutes reoxygenation, which was temporally associated with marked activation of the transcription factors nuclear factor kappa B (NFkappaB) and early growth response one (EGR-1). At 4 hours reoxygenation there were significant increases in chemokine protein secretion. The CSA decreased ERK 1/2 phosphorylation and significantly attenuated transcription factor transactivation at 15 minutes reoxygenation. The CSA was found to be selective in reducing cytokine-chemokine elaboration at 4 hours reoxygenation.

CONCLUSIONS

Hypoxia-reoxygenation induces ERK 1/2 phosphorylation, as well as transactivation of the transcription factors NFkappaB and EGR-1 in PAEC. Cyclosporine selectively reduces proinflammatory mediator secretion, likely by transcriptional regulation through NFkappaB and EGR-1. This is the first demonstration of ERK 1/2 inhibition afforded by CSA.

Inhaled carbon monoxide confers antiinflammatory effects against ventilator-induced lung injury

Ventilator-induced lung injury (VILI) is a major cause of morbidity and mortality in intensive care units. The stress-inducible gene product, heme oxygenase-1, and carbon monoxide (CO), a major by-product of heme oxygenase catalysis of heme, have been shown to confer potent antiinflammatory effects in models of tissue and cellular injury. In this study, we observed increased expression of heme oxygenase-1 mRNA and protein in a rat model of VILI. To assess the physiologic function of heme oxygenase-1 induction in VILI, we determined whether low concentration of inhaled CO could serve to protect the lung against VILI. Low concentration of inhaled CO significantly reduced tumor necrosis factor-alpha levels and total cell count in lavage fluid, while simultaneously elevating levels of antiinflammatory interleukin-10 levels. To better characterize the mechanism of CO-mediated antiinflammatory effects, we examined key signaling pathways, which may mediate CO-induced antiinflammatory effects. We demonstrate that inhaled CO exerts antiinflammatory effects in VILI via the p38 mitogen-activated protein kinase pathway but independent of activator protein-1 and nuclear factor-kappaB pathways. Our data lead to a tempting speculation that inhaled CO might be useful in minimizing VILI.

Proinflammatory response of alveolar type II pneumocytes to in vitro hypoxia and reoxygenation

Type II pneumocytes (T2P) are integral in preserving the integrity of the alveolar space by modulating the fluid composition surrounding the alveolar epithelium. There is also mounting evidence supporting their contribution to the development of acute inflammatory lung injury subsequent to oxidative stress. This study characterized the response of T2P to in vitro hypoxia and reoxygenation (H&R). Rat T2P from a cultured cell line (RLE-6TN) were rendered hypoxic for 2 h, and reoxygenated for up to 6 h. Activation of signaling kinases, the nuclear translocation of proinflammatory transcription factors, and quantification of secreted cytokine and chemokine protein content were assessed. Type II pneumocytes expressed activated extracellular signal regulated kinase (ERK) 1/2 maximally at 15 min of reoxygenation. C-jun n-terminal kinase (JNK) and p38 activation was minimal at all time points studied. The nuclear translocation of nuclear factor kappa B (NFkappaB) and activator protein (AP)-1 were dramatic after 15 min of reoxygenation. There was a significant increase in the protein secretion of CINC (p = 0.03), IL-1beta (p = 0.02), and monocyte chemoattractant protein-1 (p < 0.001) at 6 h of reoxygenation. Type II pneumocytes respond directly to H&R. ERK 1/2 activity peaks at 15 min of reoxygenation, and correlates temporally with the nuclear translocation of NFkappaB and AP-1. These signaling cascades likely promote the elaboration of proinflammatory mediators.