α1-Antitrypsin Binds to the Glucocorticoid Receptor with Anti-Inflammatory and Antimycobacterial Significance in Macrophages.

α1-Antitrypsin (AAT), a serine protease inhibitor, is the third most abundant protein in plasma. Although the best-known function of AAT is irreversible inhibition of elastase, AAT is an acute-phase reactant and is increasingly recognized to have a panoply of other functions, including as an anti-inflammatory mediator and a host-protective molecule against various pathogens. Although a canonical receptor for AAT has not been identified, AAT can be internalized into the cytoplasm and is known to affect gene regulation. Because AAT has anti-inflammatory properties, we examined whether AAT binds the cytoplasmic glucocorticoid receptor (GR) in human macrophages. We report the finding that AAT binds to GR using several approaches, including coimmunoprecipitation, mass spectrometry, and microscale thermophoresis. We also performed in silico molecular modeling and found that binding between AAT and GR has a plausible stereochemical basis. The significance of this interaction in macrophages is evinced by AAT inhibition of LPS-induced NF-κB activation and IL-8 production as well as AAT induction of angiopoietin-like 4 protein, which are, in part, dependent on GR. Furthermore, this AAT-GR interaction contributes to a host-protective role against mycobacteria in macrophages. In summary, this study identifies a new mechanism for the gene regulation, anti-inflammatory, and host-defense properties of AAT.

Alpha-1 antitrypsin inhibits fractalkine-mediated monocyte-lung endothelial cell interactions.

Chronic obstructive pulmonary disease (COPD) is characterized by nonresolving inflammation fueled by breach in the endothelial barrier and leukocyte recruitment into the airspaces. Among the ligand-receptor axes that control leukocyte recruitment, the full-length fractalkine ligand (CX3CL1)-receptor (CX3CR1) ensures homeostatic endothelial-leukocyte interactions. Cigarette smoke (CS) exposure and respiratory pathogens increase expression of endothelial sheddases, such as a-disintegrin-and-metalloproteinase-domain 17 (ADAM17, TACE), inhibited by the anti-protease α-1 antitrypsin (AAT). In the systemic endothelium, TACE cleaves CX3CL1 to release soluble CX3CL1 (sCX3CL1). During CS exposure, it is not known whether AAT inhibits sCX3CL1 shedding and CX3CR1+ leukocyte transendothelial migration across lung microvasculature. We investigated the mechanism of sCX3CL1 shedding, its role in endothelial-monocyte interactions, and AAT effect on these interactions during acute inflammation. We used two, CS and lipopolysaccharide (LPS) models of acute inflammation in transgenic Cx3cr1gfp/gfp mice and primary human endothelial cells and monocytes to study sCX3CL1-mediated CX3CR1+ monocyte adhesion and migration. We measured sCX3CL1 levels in plasma and bronchoalveolar lavage (BALF) of individuals with COPD. Both sCX3CL1 shedding and CX3CR1+ monocytes transendothelial migration were triggered by LPS and CS exposure in mice, and were significantly attenuated by AAT. The inhibition of monocyte-endothelial adhesion and migration by AAT was TACE-dependent. Compared with healthy controls, sCX3CL1 levels were increased in plasma and BALF of individuals with COPD, and were associated with clinical parameters of emphysema. Our results indicate that inhibition of sCX3CL1 as well as AAT augmentation may be effective approaches to decrease excessive monocyte lung recruitment during acute and chronic inflammatory states.NEW & NOTEWORTHY Our novel findings that AAT and other inhibitors of TACE, the sheddase that controls full-length fractalkine (CX3CL1) endothelial expression, may provide fine-tuning of the CX3CL1-CX3CR1 axis specifically involved in endothelial-monocyte cross talk and leukocyte recruitment to the alveolar space, suggests that AAT and inhibitors of sCX3CL1 signaling may be harnessed to reduce lung inflammation.

Macrophage programming is regulated by a cooperative interaction between fatty acid binding protein 5 and peroxisome proliferator-activated receptor γ.

Resolution of inflammation is an active process that is tightly regulated to achieve repair and tissue homeostasis. In the absence of resolution, persistent inflammation underlies the pathogenesis of chronic lung disease such as chronic obstructive pulmonary disease (COPD) with recurrent exacerbations. Over the course of inflammation, macrophage programming transitions from pro-inflammatory to pro-resolving, which is in part regulated by the nuclear receptor Peroxisome Proliferator-Activated Receptor γ (PPARγ). Our previous work demonstrated an association between Fatty Acid Binding Protein 5 (FABP5) expression and PPARγ activity in peripheral blood mononuclear cells of healthy and COPD patients. However, a role for FABP5 in macrophage programming has not been examined. Here, using a combination of in vitro and in vivo approaches, we demonstrate that FABP5 is necessary for PPARγ activation. In turn, PPARγ acts directly to increase FABP5 expression in primary human alveolar macrophages. We further illustrate that lack of FABP5 expression promotes a pro-inflammatory macrophage programming with increased secretion of pro-inflammatory cytokines and increased chromatin accessibility for pro-inflammatory transcription factors (e.g., NF-κB and MAPK). And finally, real-time cell metabolic analysis using the Seahorse technology shows an inhibition of oxidative phosphorylation in FABP5-deficient macrophages. Taken together, our data indicate that FABP5 and PPARγ reciprocally regulate each other's expression and function, consistent with a novel positive feedback loop between the two factors that mediates macrophage pro-resolving programming. Our studies highlight the importance of defining targets and regulatory mechanisms that control the resolution of inflammation and may serve to inform novel interventional strategies directed towards COPD.

Pharmacological sphingosine-1 phosphate receptor 1 targeting in cigarette smoke-induced emphysema in mice.

Primarily caused by chronic cigarette smoking (CS), emphysema is characterized by loss of alveolar cells comprising lung units involved in gas exchange and inflammation that culminate in airspace enlargement. Dysregulation of sphingolipid metabolism with increases of ceramide relative to sphingosine-1 phosphate (S1P) signaling has been shown to cause lung cell apoptosis and is emerging as a potential therapeutic target in emphysema. We sought to determine the impact of augmenting S1P signaling via S1P receptor 1 (S1P1) in a mouse model of CS-induced emphysema. DBA2 mice were exposed to CS for 4 or 6 mo and treated with pharmacological agonists of S1P1: phosphonated FTY720 (FTY720-1S and 2S analogs; 0.01-1.0 mg/kg) or GSK183303A (10 mg/kg). Pharmacological S1P1 agonists ameliorated CS-induced lung parenchymal apoptosis and airspace enlargement as well as loss of body weight. S1P1 agonists had modest inhibitory effects on CS-induced airspace inflammation and lung functional changes measured by Flexivent, improving lung tissue resistance. S1P1 abundance was reduced in chronic CS-conditions and remained decreased after CS-cessation or treatment with FTY720-1S. These results support an important role for S1P-S1P1 axis in maintaining the structural integrity of alveoli during chronic CS exposure and suggest that increasing both S1P1 signaling and abundance may be beneficial to counteract the effects of chronic CS exposure.

Altered Macrophage Function Associated with Crystalline Lung Inflammation in Acid Sphingomyelinase Deficiency.

Deficiency of ASM (acid sphingomyelinase) causes the lysosomal storage Niemann-Pick disease (NPD). Patients with NPD type B may develop progressive interstitial lung disease with frequent respiratory infections. Although several investigations using the ASM-deficient (ASMKO) mouse NPD model revealed inflammation and foamy macrophages, there is little insight into the pathogenesis of NPD-associated lung disease. Using ASMKO mice, we report that ASM deficiency is associated with a complex inflammatory phenotype characterized by marked accumulation of monocyte-derived CD11b+ macrophages and expansion of airspace/alveolar CD11c+ CD11b- macrophages, both with increased size, granularity, and foaminess. Both the alternative and classical pathways were activated, with decreased in situ phagocytosis of opsonized (Fc-coated) targets, preserved clearance of apoptotic cells (efferocytosis), secretion of Th2 cytokines, increased CD11c+/CD11b+ cells, and more than a twofold increase in lung and plasma proinflammatory cytokines. Macrophages, neutrophils, eosinophils, and noninflammatory lung cells of ASMKO lungs also exhibited marked accumulation of chitinase-like protein Ym1/2, which formed large eosinophilic polygonal Charcot-Leyden-like crystals. In addition to providing insight into novel features of lung inflammation that may be associated with NPD, our report provides a novel connection between ASM and the development of crystal-associated lung inflammation with alterations in macrophage biology.

Ceramide and sphingosine-1 phosphate in COPD lungs.

Studies of chronic obstructive pulmonary disease (COPD) using animal models and patient plasma indicate dysregulation of sphingolipid metabolism, but data in COPD lungs are sparse. Mass spectrometric and immunostaining measurements of lungs from 69 COPD, 16 smokers without COPD and 13 subjects with interstitial lung disease identified decoupling of lung ceramide and sphingosine-1 phosphate (S1P) levels and decreased sphingosine kinase-1 (SphK1) activity in COPD. The correlation of ceramide abundance in distal COPD lungs with apoptosis and the inverse correlation between SphK1 activity and presence of emphysema suggest that disruption of ceramide-to-S1P metabolism is an important determinant of emphysema phenotype in COPD.

Influenza virus infection increases ACE2 expression and shedding in human small airway epithelial cells.

BACKGROUND: Patients with coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) demonstrate high rates of co-infection with respiratory viruses, including influenza A (IAV), suggesting pathogenic interactions. METHODS: We investigated how IAV may increase the risk of COVID-19 lung disease, focusing on the receptor angiotensin-converting enzyme (ACE)2 and the protease TMPRSS2, which cooperate in the intracellular uptake of SARS-CoV-2. RESULTS: We found, using single-cell RNA sequencing of distal human nondiseased lung homogenates, that at baseline, ACE2 is minimally expressed in basal, goblet, ciliated and secretory epithelial cells populating small airways. We focused on human small airway epithelial cells (SAECs), central to the pathogenesis of lung injury following viral infections. Primary SAECs from nondiseased donor lungs apically infected (at the air-liquid interface) with IAV (up to 3×105 pfu; ∼1 multiplicity of infection) markedly (eight-fold) boosted the expression of ACE2, paralleling that of STAT1, a transcription factor activated by viruses. IAV increased the apparent electrophoretic mobility of intracellular ACE2 and generated an ACE2 fragment (90 kDa) in apical secretions, suggesting cleavage of this receptor. In addition, IAV increased the expression of two proteases known to cleave ACE2, sheddase ADAM17 (TACE) and TMPRSS2 and increased the TMPRSS2 zymogen and its mature fragments, implicating proteolytic autoactivation. CONCLUSION: These results indicate that IAV amplifies the expression of molecules necessary for SARS-CoV-2 infection of the distal lung. Furthermore, post-translational changes in ACE2 by IAV may increase vulnerability to lung injury such as acute respiratory distress syndrome during viral co-infections. These findings support efforts in the prevention and treatment of influenza infections during the COVID-19 pandemic.

Role of Glucosylceramide in Lung Endothelial Cell Fate and Emphysema.

Rationale: The loss of pulmonary endothelial cells in emphysema is associated with increased lung ceramide. Ceramide perturbations may cause adaptive alterations in other bioactive sphingolipids, with pathogenic implications. We previously reported a negative correlation between emphysema and circulating glycosphingolipids (GSLs). Glucosylceramide (GlcCer), the initial GSL synthesized from ceramide by GCS (GlcCer synthase), is required for embryonic survival, but its role in the lung is unknown.Objectives: To determine if cigarette smoke (CS) alters lung GlcCer and to elucidate the role of GCS in lung endothelial cell fate.Methods: GlcCer was measured by tandem mass spectrometry in BAL fluid of CS- or elastase-exposed mice, and GCS was detected by Western blotting in chronic obstructive pulmonary disease lungs and CS extract-exposed primary human lung microvascular endothelial cells (HLMVECs). The role of GlcCer and GCS on mTOR (mammalian target of rapamycin) signaling, autophagy, lysosomal function, and cell death were studied in HLMVECs with or without CS exposure.Measurements and Main Results: Mice exposed to chronic CS or to elastase, and patients with chronic obstructive pulmonary disease, exhibited significantly decreased lung GlcCer and GCS. In mice, lung GlcCer levels were negatively correlated with airspace size. GCS inhibition in HLMVEC increased lysosomal pH, suppressed mTOR signaling, and triggered autophagy with impaired lysosomal degradation and apoptosis, recapitulating CS effects. In turn, increasing GlcCer by GCS overexpression in HLMVEC improved autophagic flux and attenuated CS-induced apoptosis.Conclusions: Decreased GSL production in response to CS may be involved in emphysema pathogenesis, associated with autophagy with impaired lysosomal degradation and lung endothelial cell apoptosis.

Transitional human alveolar type II epithelial cells suppress extracellular matrix and growth factor gene expression in lung fibroblasts.

Epithelial-fibroblast interactions are thought to be very important in the adult lung in response to injury, but the specifics of these interactions are not well defined. We developed coculture systems to define the interactions of adult human alveolar epithelial cells with lung fibroblasts. Alveolar type II cells cultured on floating collagen gels reduced the expression of type 1 collagen (COL1A1) and α-smooth muscle actin (ACTA2) in fibroblasts. They also reduced fibroblast expression of hepatocyte growth factor (HGF), fibroblast growth factor 7 (FGF7, KGF), and FGF10. When type II cells were cultured at an air-liquid interface to maintain high levels of surfactant protein expression, this inhibitory activity was lost. When type II cells were cultured on collagen-coated tissue culture wells to reduce surfactant protein expression further and increase the expression of some type I cell markers, the epithelial cells suppressed transforming growth factor-ß (TGF-ß)-stimulated ACTA2 and connective tissue growth factor (CTGF) expression in lung fibroblasts. Our results suggest that transitional alveolar type II cells and likely type I cells but not fully differentiated type II cells inhibit matrix and growth factor expression in fibroblasts. These cells express markers of both type II cells and type I cells. This is probably a normal homeostatic mechanism to inhibit the fibrotic response in the resolution phase of wound healing. Defining how transitional type II cells convert activated fibroblasts into a quiescent state and inhibit the effects of TGF-ß may provide another approach to limiting the development of fibrosis after alveolar injury.

Rapid clearance of heavy chain-modified hyaluronan during resolving acute lung injury.

BACKGROUND: Several inflammatory lung diseases display abundant presence of hyaluronic acid (HA) bound to heavy chains (HC) of serum protein inter-alpha-inhibitor (IαI) in the extracellular matrix. The HC-HA modification is critical to neutrophil sequestration in liver sinusoids and to survival during experimental lipopolysaccharide (LPS)-induced sepsis. Therefore, the covalent HC-HA binding, which is exclusively mediated by tumor necrosis factor α (TNFα)-stimulated-gene-6 (TSG-6), may play an important role in the onset or the resolution of lung inflammation in acute lung injury (ALI) induced by respiratory infection. METHODS: Reversible ALI was induced by a single intratracheal instillation of LPS or Pseudomonas aeruginosa in mice and outcomes were studied for up to six days. We measured in the lung or the bronchoalveolar fluid HC-HA formation, HA immunostaining localization and roughness, HA fragment abundance, and markers of lung inflammation and lung injury. We also assessed TSG-6 secretion by TNFα- or LPS-stimulated human alveolar macrophages, lung fibroblast Wi38, and bronchial epithelial BEAS-2B cells. RESULTS: Extensive HC-modification of lung HA, localized predominantly in the peri-broncho-vascular extracellular matrix, was notable early during the onset of inflammation and was markedly decreased during its resolution. Whereas human alveolar macrophages secreted functional TSG-6 following both TNFα and LPS stimulation, fibroblasts and bronchial epithelial cells responded to only TNFα. Compared to wild type, TSG-6-KO mice, which lacked HC-modified HA, exhibited modest increases in inflammatory cells in the lung, but no significant differences in markers of lung inflammation or injury, including histopathological lung injury scores. CONCLUSIONS: Respiratory infection induces rapid HC modification of HA followed by fragmentation and clearance, with kinetics that parallel the onset and resolution phase of ALI, respectively. Alveolar macrophages may be an important source of pulmonary TSG-6 required for HA remodeling. The formation of HC-modified HA had a minor role in the onset, severity, or resolution of experimental reversible ALI induced by respiratory infection with gram-negative bacteria.

Scavenger receptor class B, type I-mediated uptake of A1AT by pulmonary endothelial cells.

In addition to exerting a potent anti-elastase function, α-1 antitrypsin (A1AT) maintains the structural integrity of the lung by inhibiting endothelial inflammation and apoptosis. A main serpin secreted in circulation by hepatocytes, A1AT requires uptake by the endothelium to achieve vasculoprotective effects. This active uptake mechanism, which is inhibited by cigarette smoking (CS), involves primarily clathrin- but also caveola-mediated endocytosis and may require active binding to a receptor. Because circulating A1AT binds to high-density lipoprotein (HDL), we hypothesized that scavenging receptors are candidates for endothelial uptake of the serpin. Although the low-density lipoprotein (LDL) receptor-related protein 1 (LRP1) internalizes only elastase-bound A1AT, the scavenger receptor B type I (SR-BI), which binds and internalizes HDL and is modulated by CS, may be involved in A1AT uptake. Transmission electron microscopy imaging of colloidal gold-labeled A1AT confirmed A1AT endocytosis in both clathrin-coated vesicles and caveolae in endothelial cells. SR-BI immunoprecipitation identified binding to A1AT at the plasma membrane. Pretreatment of human lung microvascular endothelial cells with SR-B ligands (HDL or LDL), knockdown of SCARB1 expression, or neutralizing SR-BI antibodies significantly reduced A1AT uptake by 30-50%. Scarb1 null mice exhibited decreased A1AT lung content following systemic A1AT administration and reduced lung anti-inflammatory effects of A1AT supplementation during short-term CS exposure. In turn, A1AT supplementation increased lung SR-BI expression and modulated circulating lipoprotein levels in wild-type animals. These studies indicate that SR-BI is an important mediator of A1AT endocytosis in pulmonary endothelium and suggest a cross talk between A1AT and lipoprotein regulation of vascular functions.

Marked elevations in lung and plasma ceramide in COVID-19 linked to microvascular injury.

The pathogenesis of the marked pulmonary microvasculature injury, a distinguishing feature of COVID-19 acute respiratory distress syndrome (COVID-ARDS), remains unclear. Implicated in the pathophysiology of diverse diseases characterized by endothelial damage, including ARDS and ischemic cardiovascular disease, ceramide and in particular palmitoyl ceramide (C16:0-ceramide) may be involved in the microvascular injury in COVID-19. Using deidentified plasma and lung samples from COVID-19 patients, ceramide profiling by mass spectrometry was performed. Compared with healthy individuals, a specific 3-fold C16:0-ceramide elevation in COVID-19 patient plasma was identified. Compared with age-matched controls, autopsied lungs of individuals succumbing to COVID-ARDS displayed a massive 9-fold C16:0-ceramide elevation and exhibited a previously unrecognized microvascular ceramide-staining pattern and markedly enhanced apoptosis. In COVID-19 plasma and lungs, the C16-ceramide/C24-ceramide ratios were increased and reversed, respectively, consistent with increased risk of vascular injury. Indeed, exposure of primary human lung microvascular endothelial cell monolayers to C16:0-ceramide-rich plasma lipid extracts from COVID-19, but not healthy, individuals led to a significant decrease in endothelial barrier function. This effect was phenocopied by spiking healthy plasma lipid extracts with synthetic C16:0-ceramide and was inhibited by treatment with ceramide-neutralizing monoclonal antibody or single-chain variable fragment. These results indicate that C16:0-ceramide may be implicated in the vascular injury associated with COVID-19.

Divergent host innate immune response to the smooth-to-rough M. abscessus adaptation to chronic infection.

Mycobacterium abscessus is a nontuberculous mycobacterium emerging as a significant pathogen for individuals with chronic lung disease, including cystic fibrosis and chronic obstructive pulmonary disease. Current therapeutics have poor efficacy. New strategies of bacterial control based on host defenses are appealing, but anti-mycobacterial immune mechanisms are poorly understood and are complicated by the appearance of smooth and rough morphotypes with distinct host responses. We explored the role of the complement system in the clearance of M. abscessus morphotypes by neutrophils, an abundant cell in these infections. M. abscessus opsonized with plasma from healthy individuals promoted greater killing by neutrophils compared to opsonization in heat-inactivated plasma. Rough clinical isolates were more resistant to complement but were still efficiently killed. Complement C3 associated strongly with the smooth morphotype while mannose-binding lectin 2 was associated with the rough morphotype. M. abscessus killing was dependent on C3, but not on C1q or Factor B; furthermore, competition of mannose-binding lectin 2 binding with mannan or N-acetyl-glucosamine during opsonization did not inhibit killing. These data suggest that M. abscessus does not canonically activate complement through the classical, alternative, or lectin pathways. Complement-mediated killing was dependent on IgG and IgM for smooth and on IgG for rough M. abscessus. Both morphotypes were recognized by Complement Receptor 3 (CD11b), but not CR1 (CD35), and in a carbohydrate- and calcium-dependent manner. These data suggest the smooth-to-rough adaptation changes complement recognition of M. abscessus and that complement is an important factor for M. abscessus infection.

Effect of cigarette smoke exposure and structural modifications on the α-1 Antitrypsin interaction with caspases.

α-1 Antitrypsin (A1AT) is a serpin with a major protective effect against cigarette smoke-induced emphysema development, and patients with mutations of the A1AT gene display a markedly increased risk for developing emphysema. We reported that A1AT protects lung endothelial cells from apoptosis and inhibits caspase-3 activity. It is not clear if cigarette smoking or A1AT mutations alter the caspase-3 inhibitory activity of A1AT and if this serpin alters the function of other caspases. We tested the hypothesis that the caspase-3 inhibitory activity of A1AT is impaired by cigarette smoking and that the A1AT RCL, the key antiprotease domain of the serpin, is required for its interaction with the caspase. We examined the caspase-3 inhibitory activity of human A1AT purified from plasma of actively smoking and nonsmoking individuals, either affected or unaffected with chronic obstructive pulmonary disease. We also tested the caspase inhibitory activity of two mutant forms of A1AT, the recombinant human piZZ and the RCL-deleted (RCL-null) A1AT forms. A1AT purified from the blood of active smokers exhibited marked attenuation in its caspase-3 inhibitory activity, independent of disease status. In vitro exposure of the normal (MM) form of A1AT to cigarette smoke extract reduced its ability to interact with caspase-3, measured by isothermal titration calorimetry, as did the deletion of the RCL, but not the ZZ point mutation. In cell-free assays A1AT was capable of inhibiting all executioner caspases, -3, -7 and especially -6, but not the initiator or inflammatory caspases. The inhibitory effect of A1AT against caspase-6 was tested in vivo, where overexpression of both human MM and ZZ-A1AT via adeno-associated virus transduction significantly protected against apoptosis and against airspace damage induced by intratracheal instillation of caspase-6 in mice. These data indicate a specific inhibitory effect of A1AT on executioner caspases, which is profoundly attenuated by active exposure to cigarette smoking and is dependent on the protein RCL, but is not affected by the PiZZ mutation.

Akt activation induces hypertrophy without contractile phenotypic maturation in airway smooth muscle.

Airway smooth muscle (ASM) hypertrophy is a cardinal feature of severe asthma, but the underlying molecular mechanisms remain uncertain. Forced protein kinase B/Akt 1 activation is known to induce myocyte hypertrophy in other muscle types, and, since a number of mediators present in asthmatic airways can activate Akt signaling, we hypothesized that Akt activation could contribute to ASM hypertrophy in asthma. To test this hypothesis, we evaluated whether Akt activation occurs naturally within airway myocytes in situ, whether Akt1 activation is sufficient to cause hypertrophy of normal airway myocytes, and whether such hypertrophy is accompanied by excessive accumulation of contractile apparatus proteins (contractile phenotype maturation). Immunostains of human airway sections revealed concordant activation of Akt (reflected in Ser(473) phosphorylation) and of its downstream effector p70(S6Kinase) (reflected in Thr(389) phosphorylation) within airway muscle bundles, but there was no phosphorylation of the alternative Akt downstream target glycogen synthase kinase (GSK) 3ß. Artificial overexpression of constitutively active Akt1 (by plasmid transduction or lentiviral infection) caused a progressive increase in size and protein content of cultured canine tracheal myocytes and increased p70(S6Kinase) phosphorylation but not GSK3ß phosphorylation; however, constitutively active Akt1 did not cause disproportionate overaccumulation of smooth muscle (sm) α-actin and SM22. Furthermore, mRNAs encoding sm-α-actin and SM22 were reduced. These results indicate that forced Akt1 signaling causes hypertrophy of cultured airway myocytes without inducing further contractile phenotypic maturation, possibly because of opposing effects on contractile protein gene transcription and translation, and suggest that natural activation of Akt1 plays a similar role in asthmatic ASM.

Protein Biomarkers for COPD Outcomes.

COPD is a clinically heterogeneous syndrome characterized by injury to airways, airspaces, and lung vasculature and usually caused by tobacco smoke and/or air pollution exposure. COPD is also independently associated with nonpulmonary comorbidities (eg, cardiovascular disease) and malignancies (eg, GI, bladder), suggesting a role for systemic injury. Since not all those with exposure develop COPD, there has been a search for plasma and lung biomarkers that confer increased cross-sectional and longitudinal risk. This search typically focuses on clinically relevant COPD outcomes such as FEV1, FEV1 decline, CT measurements of emphysema, or exacerbation frequency. The rapid advances in omics technology and the molecular phenotyping of COPD cohorts now permit large-scale evaluation of genetic, transcriptomic, proteomic, and metabolic biomarkers. This review focuses on protein biomarkers associated with clinically relevant COPD outcomes. The prototypic COPD protein biomarker is alpha-1 antitrypsin; however, this biomarker only accounts for 1% to 5% of COPD. This article reviews and summarizes the evidence for other validated biomarkers for each COPD outcome, and discusses their advantages, weaknesses, and required regulatory steps to move the biomarker from the bench into clinic. Although we highlight the emergence of many novel biomarkers (eg, fibrinogen, soluble receptor for advanced glycation, surfactant protein D, club cell secretory protein), there is increasing evidence that individual biomarkers only explain a fraction of the increased COPD risk and that multiple biomarker panels are needed to completely explain clinical variation and risk in individuals and populations.

A 56-Year-Old Man With Emphysema, Rash, and Arthralgia.

CASE PRESENTATION: A 56-year-old man presented to the pulmonary clinic with dyspnea and hypoxemia on exertion. He was an avid biker and skier who had noticed a significant decrease in high-level physical activity over the past 3 years. He reported dyspnea, desaturations at altitudes higher than 9,000 feet, dry cough, tachycardia, and palpitations with exercise. Review of systems was also notable for gluten-intolerance, Raynaud's phenomenon, recurrent skin lesions and joint swelling, pain, and stiffness in the areas overlying the jaw, wrists, knees, and ankles (after capsaicin exposure). He denied fever, chills, anorexia, weight loss, hair loss, ocular symptoms, jaw claudication, chest pain, or lower extremity swelling. He had a five pack-year smoking history, no history of prematurity, childhood asthma, recurrent infections, or environmental and occupational exposure. Based on pulmonary function tests from an outside provider, he had received a diagnosis of exercise-induced asthma and had been prescribed an albuterol inhaler to use on an as-needed basis, which failed to improve his symptoms. He was later prescribed a mometasone-formoterol inhaler, still with no symptomatic improvement.