Autophagy proteins regulate innate immune responses by inhibiting the release of mitochondrial DNA mediated by the NALP3 inflammasome.

Autophagy, a cellular process for organelle and protein turnover, regulates innate immune responses. Here we demonstrate that depletion of the autophagic proteins LC3B and beclin 1 enhanced the activation of caspase-1 and secretion of interleukin 1ß (IL-1ß) and IL-18. Depletion of autophagic proteins promoted the accumulation of dysfunctional mitochondria and cytosolic translocation of mitochondrial DNA (mtDNA) in response to lipopolysaccharide (LPS) and ATP in macrophages. Release of mtDNA into the cytosol depended on the NALP3 inflammasome and mitochondrial reactive oxygen species (ROS). Cytosolic mtDNA contributed to the secretion of IL-1ß and IL-18 in response to LPS and ATP. LC3B-deficient mice produced more caspase-1-dependent cytokines in two sepsis models and were susceptible to LPS-induced mortality. Our study suggests that autophagic proteins regulate NALP3-dependent inflammation by preserving mitochondrial integrity.

Protein kinase R-like endoplasmatic reticulum kinase is a mediator of stretch in ventilator-induced lung injury.

BACKGROUND: Acute respiratory distress syndrome (ARDS) is a severe form of lung injury characterized by damage to the epithelial barrier with subsequent pulmonary edema and hypoxic respiratory failure. ARDS is a significant medical problem in intensive care units with associated high care costs. There are many potential causes of ARDS; however, alveolar injury associated with mechanical ventilation, termed ventilator-induced lung injury (VILI), remains a well-recognized contributor. It is thus critical to understand the mechanism of VILI. Based on our published preliminary data, we hypothesized that the endoplasmic reticulum (ER) stress response molecule Protein Kinase R-like Endoplasmic Reticulum Kinase (PERK) plays a role in transmitting mechanosensory signals the alveolar epithelium. METHODS: ER stress signal responses to mechanical stretch were studied in ex-vivo ventilated pig lungs. To explore the effect of PERK inhibition on VILI, we ventilated live rats and compared lung injury parameters to non-ventilated controls. The effect of stretch-induced epithelial ER Ca2+ signaling on PERK was studied in stretched alveolar epithelial monolayers. To confirm the activation of PERK in human disease, ER stress signaling was compared between ARDS and non-ARDS lungs. RESULTS: Our studies revealed increased PERK-specific ER stress signaling in response to overstretch. PERK inhibition resulted in dose-dependent improvement of alveolar inflammation and permeability. Our data indicate that stretch-induced epithelial ER Ca2+ release is an activator of PERK. Experiments with human lung tissue confirmed PERK activation by ARDS. CONCLUSION: Our study provides evidences that PERK is a mediator stretch signals in the alveolar epithelium.

Integrated Stress Response Mediates Epithelial Injury in Mechanical Ventilation.

Ventilator-induced lung injury (VILI) is a severe complication of mechanical ventilation that can lead to acute respiratory distress syndrome. VILI is characterized by damage to the epithelial barrier with subsequent pulmonary edema and profound hypoxia. Available lung-protective ventilator strategies offer only a modest benefit in preventing VILI because they cannot impede alveolar overdistension and concomitant epithelial barrier dysfunction in the inflamed lung regions. There are currently no effective biochemical therapies to mitigate injury to the alveolar epithelium. We hypothesize that alveolar stretch activates the integrated stress response (ISR) pathway and that the chemical inhibition of this pathway mitigates alveolar barrier disruption during stretch and mechanical ventilation. Using our established rat primary type I-like alveolar epithelial cell monolayer stretch model and in vivo rat mechanical ventilation that mimics the alveolar overdistension seen in acute respiratory distress syndrome, we studied epithelial responses to mechanical stress. Our studies revealed that the ISR signaling pathway is a key modulator of epithelial permeability. We show that prolonged epithelial stretch and injurious mechanical ventilation activate the ISR, leading to increased alveolar permeability, cell death, and proinflammatory signaling. Chemical inhibition of protein kinase RNA-like endoplasmic reticulum kinase, an upstream regulator of the pathway, resulted in decreased injury signaling and improved barrier function after prolonged cyclic stretch and injurious mechanical ventilation. Our results provide new evidence that therapeutic targeting of the ISR can mitigate VILI.

Ventilator Weaning in Prolonged Mechanical Ventilation-A Narrative Review.

Patients requiring mechanical ventilation (MV) beyond 21 days, usually referred to as prolonged MV, represent a unique group with significant medical needs and a generally poor prognosis. Research suggests that approximately 10% of all MV patients will need prolonged ventilatory care, and that number will continue to rise. Although we have extensive knowledge of MV in the acute care setting, less is known about care in the post-ICU setting. More than 50% of patients who were deemed unweanable in the ICU will be liberated from MV in the post-acute setting. Prolonged MV also presents a challenge in care for medically complex, elderly, socioeconomically disadvantaged and marginalized individuals, usually at the end of their life. Patients and their families often rely on ventilator weaning facilities and skilled nursing homes for the continuation of care, but home ventilation is becoming more common. The focus of this review is to discuss recent advances in the weaning strategies in prolonged MV, present their outcomes and provide insight into the complexity of care.

Inflammasome-regulated cytokines are critical mediators of acute lung injury.

RATIONALE: Despite advances in clinical management, there are currently no reliable diagnostic and therapeutic targets for acute respiratory distress syndrome (ARDS). The inflammasome/caspase-1 pathway regulates the maturation and secretion of proinflammatory cytokines (e.g., IL-18). IL-18 is associated with injury in animal models of systemic inflammation. OBJECTIVES: We sought to determine the contribution of the inflammasome pathway in experimental acute lung injury and human ARDS. METHODS: We performed comprehensive gene expression profiling on peripheral blood from patients with critical illness. Gene expression changes were assessed using real-time polymerase chain reaction, and IL-18 levels were measured in the plasma of the critically ill patients. Wild-type mice or mice genetically deficient in IL-18 or caspase-1 were mechanically ventilated using moderate tidal volume (12 ml/kg). Lung injury parameters were assessed in lung tissue, serum, and bronchoalveolar lavage fluid. MEASUREMENTS AND MAIN RESULTS: In mice, mechanical ventilation enhanced IL-18 levels in the lung, serum, and bronchoalveolar lavage fluid. IL-18-neutralizing antibody treatment, or genetic deletion of IL-18 or caspase-1, reduced lung injury in response to mechanical ventilation. In human patients with ARDS, inflammasome-related mRNA transcripts (CASP1, IL1B, and IL18) were increased in peripheral blood. In samples from four clinical centers, IL-18 was elevated in the plasma of patients with ARDS (sepsis or trauma-induced ARDS) and served as a novel biomarker of intensive care unit morbidity and mortality. CONCLUSIONS: The inflammasome pathway and its downstream cytokines play critical roles in ARDS development.

Mechanical Ventilator Liberation of Patients With COVID-19 in Long-term Acute Care Hospital.

BACKGROUND: Mechanical ventilation (MV) via tracheostomy is performed commonly for patients who are in long-term acute care hospitals (LTACHs) after respiratory failure. However, the outcome of MV in COVID-19-associated respiratory failure in LTACHs is not known. RESEARCH QUESTION: What is the ventilator liberation rate of patients who have received tracheostomy with COVID-19-associated respiratory failure compared with those with respiratory failure unrelated to COVID-19 in LTACHs? STUDY DESIGN AND METHODS: In this retrospective cohort study, we examined mechanically ventilated patients discharged between June 2020 and March 2021. Of 242 discharges, 165 patients who had undergone tracheostomy arrived and were considered for ventilator liberation. One hundred twenty-eight patients did not have COVID-19 and 37 patients were admitted for COVID-19. RESULTS: The primary outcome of the study was ventilator liberation; secondary outcomes were functional recovery, length of stay (LOS) at the LTACH, and discharge disposition. After controlling for demographics, the number of comorbidities, hemodialysis, vasopressor need, thrombocytopenia, and the LOS at the short-term acute care hospital, our results indicated that patients with COVID-19 showed a higher adjusted ventilator liberation rate of 91.4% vs 56.0% in those without COVID-19. Functional ability was assessed with the change of Functional Status Score for the Intensive Care Unit (FSS-ICU) between admission and discharge. The adjusted mean change in FSS-ICU was significantly higher in the COVID-19 group than in the non-COVID-19 group: 9.49 (95% CI, 7.38-11.6) vs 2.08 (95% CI, 1.05-3.11), respectively (P < .001). Patients with COVID-19 experienced a shorter adjusted LOS at the LTACH with an adjusted hazard ratio of 1.57 (95% CI, 1.0-2.46; P = .05) compared with patients without COVID-19. We did not observe significant differences between the two groups regarding discharge location, but a trend toward need for lower level of care was found in patients with COVID-19. INTERPRETATION: Our study suggests that patients with COVID-19 requiring MV and tracheostomy have a higher chance for recovery than those without COVID-19.

The safety profile of a protocolized transbronchial cryobiopsy program utilizing a 2.4 mm cryoprobe for interstitial lung disease.

INTRODUCTION: Transbronchial lung cryobiopsy (TBLC) has emerged as a promising alternative to surgical lung biopsy for the diagnosis of interstitial lung disease. However, uncertainty remains regarding its overall complications due to a lack of procedural standardization including the size of cryoprobe utilized. METHODS: This is a prospective cohort study of a protocolized transbronchial cryobiopsy program utilizing a 2.4 mm cryoprobe. 201 consecutive subjects were enrolled at a single academic center. RESULTS: The average biopsy size was 106.2 ± 39.3 mm2. Complications included a total pneumothorax rate of 4.9% with 3.5% undergoing chest tube placement. Severe bleeding defined by the Nashville Working Group occurred in 0.5% of cases. There were no deaths at 30-days. DISCUSSION: A protocolized transbronchial cryobiopsy program utilizing a 2.4 mm cryoprobe in can achieve a high diagnostic yield with a favorable safety profile.

Quantitative image analysis in COVID-19 acute respiratory distress syndrome: a cohort observational study.

Background Acute respiratory distress syndrome (ARDS) is a severe form of acute lung injury commonly associated with pneumonia, including coronavirus disease-19 (COVID-19). The resultant effect can be persistent lung damage, but its extent is not known. We used quantitative high resolution computed tomography (QHR-CT) lung scans to radiographically characterize the lung damage in COVID-19 ARDS (CARDS) survivors. Methods Patients with CARDS (N=20) underwent QHR-CT lung scans 60 to 90 days after initial diagnosis, while hospitalized at a long-term acute care hospital (LTACH). QHR-CT assessed for mixed disease (QMD), ground glass opacities (QGGO), consolidation (QCON) and normal lung tissue (QNL). QMD was correlated with respiratory support on admission, tracheostomy decannulation and supplementary oxygen need on discharge. Results Sixteen patients arrived with tracheostomy requiring invasive mechanical ventilation. Four patients arrived on nasal oxygen support. Of the patients included in this study 10 had the tracheostomy cannula removed, four remained on invasive ventilation, and two died. QHR-CT showed 45% QMD, 28.1% QGGO, 3.0% QCON and QNL=23.9%. Patients with mandatory mechanical ventilation had the highest proportion of QMD when compared to no mechanical ventilation. There was no correlation between QMD and tracheostomy decannulation or need for supplementary oxygen at discharge. Conclusions Our data shows severe ongoing lung injury in patients with CARDS, beyond what is usually expected in ARDS. In this severely ill population, the extent of mixed disease correlates with mechanical ventilation, signaling formation of interstitial lung disease. QHR-CT analysis can be useful in the post-acute setting to evaluate for interstitial changes in ARDS.

Post-COVID recovery: characteristics of chronically critically ill patients admitted to a long-term acute care hospital.

Background: Survivors of COVID-19 pneumonia often suffer from chronic critical illness (CCI) and require long-term hospitalization. Long-term acute care (LTAC) hospitals are vital in the care of CCI patients, but their role for patients post COVID-19 infection is not known. Barlow Respiratory Hospital (BRH) is a 105-bed, LTAC hospital network serving ventilator-dependent and medically-complex patients transferred from the ICUs of hospitals in southern California. We report patient characteristics of our first series of COVID-19 survivors admitted to the post-acute venue of an LTAC hospital. Methods: Single-center observational descriptive report of patients recovering from acute infectious complications of COVID-19 pneumonia requiring long-term respiratory support. Results: From 28 April to 7 September 2020, 41 patients were admitted to BRH for continued recovery from COVID-19 pneumonia. Median age: 68 [44-94] years, 25/41 (61%) male, 33/41 (80.5%) with tracheostomy, 21/41 (51.2%) on invasive mechanical ventilation, 9/41 (22%) receiving hemodialysis. All mechanical ventilation and hemodialysis interventions were initiated at the transferring hospital. Conclusions: To our knowledge, this is the first report to characterize CCI and medically complex COVID-19 patients transferred to the post-acute venue of an LTAC hospital. Patients on average spent over six weeks in the transferring hospital mostly in the ICU, are largely elderly, carry the known risk factors for COVID-19 infection, and experienced respiratory failure necessitating prolonged mechanical ventilation via tracheostomy. Our findings suggest that these patients will continue to require considerable medical interventions and treatments, including weaning from mechanical ventilation, owing to the numerous sequelae of the infection and the burden of acute-on-chronic diseases. As ICU survival rates improve, this research further emphasizes the important role of the LTAC hospital in responding to the COVID-19 crisis.

Discovery of the gene signature for acute lung injury in patients with sepsis.

The acute respiratory distress syndrome (ARDS)/acute lung injury (ALI) was described 30 yr ago, yet making a definitive diagnosis remains difficult. The identification of biomarkers obtained from peripheral blood could provide additional noninvasive means for diagnosis. To identify gene expression profiles that may be used to classify patients with ALI, 13 patients with ALI + sepsis and 20 patients with sepsis alone were recruited from the Medical Intensive Care Unit of the University of Pittsburgh Medical Center, and microarrays were performed on peripheral blood samples. Several classification algorithms were used to develop a gene signature for ALI from gene expression profiles. This signature was validated in an independently obtained set of patients with ALI + sepsis (n = 8) and sepsis alone (n = 1). An eight-gene expression profile was found to be associated with ALI. Internal validation found that the gene signature was able to distinguish patients with ALI + sepsis from patients with sepsis alone with 100% accuracy, corresponding to a sensitivity of 100%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 100%. In the independently obtained external validation set, the gene signature was able to distinguish patients with ALI + sepsis from patients with sepsis alone with 88.9% accuracy. The use of classification models to develop a gene signature from gene expression profiles provides a novel and accurate approach for classifying patients with ALI.

Carbon monoxide prevents ventilator-induced lung injury via caveolin-1.

OBJECTIVES: Carbon monoxide (CO) can confer anti-inflammatory protection in rodent models of ventilator-induced lung injury (VILI). Caveolin-1 exerts a critical role in cellular responses to mechanical stress and has been shown to mediate cytoprotective effects of CO in vitro. We sought to determine the role of caveolin-1 in lung susceptibility to VILI in mice. Furthermore, we assessed the role of caveolin-1 in the tissue-protective effects of CO in the VILI model. DESIGN: Prospective experimental study. SETTING: University laboratory. SUBJECTS: Wild type (wt) and caveolin-1 deficient (cav-1) mice. INTERVENTIONS: Mice were subjected to tracheostomy and arterial cannulation. Wt and cav-1 mice were ventilated with a tidal volume of 12 mL/kg body weight and a frequency of 80/minute for 5 minutes as control or for 8 hours with air in the absence or presence of CO (250 parts per million). Bronchoalveolar lavage and histology were used to determine lung injury. Lung sections or homogenates were analyzed for caveolin-1 expression by immunohistochemical staining or Western blotting, respectively. MEASUREMENTS AND MAIN RESULTS: Ventilation led to an increase in bronchoalveolar lavage protein concentration, cell count, neutrophil recruitment, and edema formation, which was prevented in the presence of CO. Although ventilation alone slightly induced caveolin-1 expression in epithelial cells, the application of CO during the ventilation significantly increased the expression of caveolin-1. In comparison with wt mice, mechanical ventilation of cav-1 mice led to a significantly higher degree of lung injury when compared with wt mice. In contrast to its effectiveness in wt mice, CO administration failed to reduce lung-injury markers in cav-1 mice. CONCLUSIONS: Caveolin-1 null mice are more susceptible to VILI. CO executes lung-protective effects during mechanical ventilation that are dependent, in part, on caveolin-1 expression.

Carbon monoxide protects against ventilator-induced lung injury via PPAR-gamma and inhibition of Egr-1.

RATIONALE: Ventilator-induced lung injury (VILI) leads to an unacceptably high mortality. In this regard, the antiinflammatory properties of inhaled carbon monoxide (CO) may provide a therapeutic option. OBJECTIVES: This study explores the mechanisms of CO-dependent protection in a mouse model of VILI. METHODS: Mice were ventilated (12 ml/kg, 1-8 h) with air in the absence or presence of CO (250 ppm). Airway pressures, blood pressure, and blood gases were monitored. Lung tissue was analyzed for inflammation, injury, and gene expression. Bronchoalveolar lavage fluid was analyzed for protein, cell and neutrophil counts, and cytokines. MEASUREMENTS AND MAIN RESULTS: Mechanical ventilation caused significant lung injury reflected by increases in protein concentration, total cell and neutrophil counts in the bronchoalveolar lavage fluid, as well as the induction of heme oxygenase-1 and heat shock protein-70 in lung tissue. In contrast, CO application prevented lung injury during ventilation, inhibited stress-gene up-regulation, and decreased lung neutrophil infiltration. These effects were preceded by the inhibition of ventilation-induced cytokine and chemokine production. Furthermore, CO prevented the early ventilation-dependent up-regulation of early growth response-1 (Egr-1). Egr-1-deficient mice did not sustain lung injury after ventilation, relative to wild-type mice, suggesting that Egr-1 acts as a key proinflammatory regulator in VILI. Moreover, inhibition of peroxysome proliferator-activated receptor (PPAR)-gamma, an antiinflammatory nuclear regulator, by GW9662 abolished the protective effects of CO. CONCLUSIONS: Mechanical ventilation causes profound lung injury and inflammatory responses. CO treatment conferred protection in this model dependent on PPAR-gamma and inhibition of Egr-1.

Diurnal Rhythms Spatially and Temporally Organize Autophagy.

Circadian rhythms are a hallmark of physiology, but how such daily rhythms organize cellular catabolism is poorly understood. Here, we used proteomics to map daily oscillations in autophagic flux in mouse liver and related these rhythms to proteasome activity. We also explored how systemic inflammation affects the temporal structure of autophagy. Our data identified a globally harmonized rhythm for basal macroautophagy, chaperone-mediated autophagy, and proteasomal activity, which concentrates liver proteolysis during the daytime. Basal autophagy rhythms could be resolved into two antiphase clusters that were distinguished by the subcellular location of targeted proteins. Inflammation induced by lipopolysaccharide reprogrammed autophagic flux away from a temporal pattern that favors cytosolic targets and toward the turnover of mitochondrial targets. Our data detail how daily biological rhythms connect the temporal, spatial, and metabolic aspects of protein catabolism.

Carbon monoxide in sepsis.

Despite modern practices in critical care medicine, sepsis or systemic inflammatory response syndrome remains a leading cause of morbidity and mortality in the intensive care unit. Thus, the need to identify new therapeutic tools for the treatment of sepsis is urgent. In this context, carbon monoxide has become a promising therapeutic molecule that can potentially prevent uncontrolled inflammation in sepsis. In humans, carbon monoxide arises endogenously from the degradation of heme by heme oxygenase enzymes. Both endogenously synthesized and exogenously applied carbon monoxide can exert antiinflammatory and antiapoptotic effects in cells and tissues. Based on these properties, carbon monoxide, when applied at low concentration, conferred protection in a variety of cellular and rodent models of sepsis, and furthermore reduced morbidity and mortality in vivo. Therefore, application of carbon monoxide may have a major impact on the future of sepsis treatment. This review summarizes evidence for salutary effects of carbon monoxide in sepsis of various organs, including lung, heart, kidney, liver, and intestine, and discusses the potential translation of the data into human clinical trials.

Gene expression profiling of target genes in ventilator-induced lung injury.

In the lungs, high-pressure mechanical ventilation induces an inflammatory response similar to that observed in acute respiratory distress syndrome. To further characterize these responses and to compare them with classical inflammatory pathways, we performed gene expression profiling analysis of 20,000 mouse genes in isolated blood-free (to exclude genes from sequestered leukocytes) perfused mouse lungs exposed to low-pressure ventilation (10 cmH2O), high-pressure ventilation (25 cmH2O, overventilation), and LPS treatment. A large number of inflammatory and apoptotic genes were increased by both overventilation and LPS. However, certain growth factor-related genes, as well as genes related to development, cellular communication, and the cytoskeleton, were only regulated by overventilation. We validated and confirmed increased mRNA expression pattern of five genes (amphiregulin, gravin, Nur77, Cyr61, interleukin-11) by real-time PCR; furthermore, we confirmed increased protein expression of amphiregulin by immunohistochemistry and immunoblotting assays. These genes represent novel candidate genes in ventilator-induced lung injury.

Pathology of chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease is one of the leading causes of death and morbidity worldwide. Despite intensive investigation, its pathology and pathophysiology are not well understood. The hallmarks of the disease are irreversible airflow limitation and chronic inflammation. Small airway obstruction due to progressive inflammation and fibrosis, and the loss of elastic recoil mediated by elastolysis and apoptosis equally contribute to pathologic changes. However, it is debated to what extent the obstruction of large airways leads to altered lung function. Three morphologic entities are described in the literature under one disease; chronic bronchitis, obstructive bronchiolitis and emphysema may appear in the same patient at the same time. The authors review pathologic changes observed in chronic obstructive pulmonary disease, including acute exacerbations and secondary pulmonary hypertension as severe but common complications of the disease. Furthermore, we detail recent scientific evidences for major cellular and molecular inflammatory pathway activation. These mechanisms result in accelerated apoptosis, remodeling and increased proinflammatory cytokine release. Targeting intracellular pathological changes may lead to the discovery of a new generation of drugs that could reduce chronic obstruction before airway irreversibility is established.

[Results in 42 non-resectable NSCLC IIA-B patients with initial concurrent Taxotere-Cisplatin chemoradiotherapy]. / IIIA-B stádiumú NSCLC elsovonalbeli Taxotere-Cisplatin konkuráló kemo-radioterápiájának eredményei 42 irreszekábilis daganatos beteg vizsgálata alapján.

GOALS: A prospective multicenter study to treat non-small cell lung cancer (NSCLC) with inductive chemoradiotherapy for improving chances of operability. If used as first-line therapy, combined treatment improves survival and it is well tolerated with a low rate of side effects. PATIENTS: 42 patients with stage IIIA-B NSCLC from which 36 could be followed. METHODS: A full dose Taxotere-Cisplatin chemotherapy was given to patients with concurrent radiotherapy in 2 Gy fractions up to 60 Gy via conformal irradiation. RESULTS: Local response was very high and 40.47% of patients became operable while in inoperable cases consolidation chemotherapy showed similar results as other protocols. We also found a low rate of side effects. The high rate of brain metastasis suggests that prophylactic cranial irradiation (PCI) should be considered.

[Randomised placebo controlled double blind study on the effect of prebiotic oligosaccharides on intestinal flora in healthy infants]. / Prebiotikus hatású oligoszacharidok egészséges csecsemok székletflórájára gyakorolt hatásának randomizált, placébóval kontrollált vizsgálata.

AIM: Effects of supplementing prebiotic oligosaccharides to formula for healthy infants were studied in this placebo controlled, randomised, double blind study. METHODS: Ninety-seven infants were included into the study; among them 42 breast-fed infants, 14 infants fed formula supplemented with 0.4 g/100ml oligosaccharides (9 to 1 mixture of galacto- and fructooligosaccharides) and 13 infants fed control formula were followed-up throughout the 12-week-long study period. The groups receiving formula were compared with statistical methods, whereas data of breast-fed infants served as reference values. RESULTS: Infants fed the two formulae did not differ in nutrient intakes, growth, occurrence rate of feeding difficulties and atopic manifestations, or in calcium excretion. The intestinal flora did not differ between the two formula fed groups at the beginning of the study. In contrast, numbers of Bifidobacteriae were significantly higher in infants receiving the formula supplemented with prebiotic oligosaccharides both at the 14th day (9 x 1011 versus 5 x 1010, colony forming units/g faeces, median, p < 0.05) and 28th day (9 x 1012 versus 5 x 1010, p < 0.05) of the study. CONCLUSION: In this study, supplementation of infant formula with prebiotic oligosaccharides resulted in ameliorating the difference in intestinal flora between formula fed and breast-fed healthy infants.

Heme Oxygenase-1/CO as protective mediators in cigarette smoke- induced lung cell injury and chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is a disease involving airways restriction, alveolar destruction, and loss of lung function, primarily due to cigarette smoke (CS) exposure. The inducible stress protein heme oxygenase-1 (HO-1) has been implicated in cytoprotection against the toxic action of many xenobiotics, including CS. HO-1 also protects against elastase-induced emphysema. Differential expression of HO-1 in epithelial cells and macrophages may contribute to COPD susceptibility. Genetic polymorphisms in the HO-1 gene, which may account for variations in HO-1 expression among subpopulations, may be associated with COPD pathogenesis. Carbon monoxide (CO), a primary reaction product of HO-1 has been implicated in cytoprotection in many acute lung injury models, though it's precise role in chronic CS-induced lung injury remains unclear. CO is a potential biomarker of CS exposure and of inflammatory lung conditions. To date, a single clinical trial has addressed the possible therapeutic potential of CO in COPD patients. The implications of the cytoprotective potential of HO-1/CO system in CS-induced lung injury and COPD are discussed.