Differential effects of dexamethasone and roflumilast on asthma in mice with or without short cigarette smoke exposure

Appropriate drug treatment for smoking asthmatics is uncertain because most smokers with asthma are less sensitive to treatment with glucocorticoids compared with non-smokers with asthma. We hypothesized that roflumilast (Rof), a selective phosphodiesterases-4 inhibitor regarded as an add-on therapy for chronic obstructive pulmonary disease, might be more effective than glucocorticoids for improving asthma in smokers. To investigate this hypothesis, we compared the therapeutic effects of dexamethasone (Dex) and Rof in a mouse model of ovalbumin-induced asthma with or without concurrent cigarette smoke (CS) exposure for 2 weeks. We found that recurrent asthma attacks increased lung tissue resistance. CS exposure in asthmatic mice decreased the central airway resistance, increased lung compliance, and attenuated airway hyper-responsiveness (AHR). CS exposure in asthmatic mice also increased the number of neutrophils and macrophages in the bronchoalveolar fluid. Treatment with Dex in asthmatic mice without CS exposure reduced airway resistance, AHR and airway eosinophilia. In asthmatic mice with CS exposure, however, Dex treatment unexpectedly increased lung tissue resistance and restored AHR that had been otherwise suppressed. Dex treatment in asthmatic mice with CS exposure inhibited eosinophilic inflammation but conversely exacerbated neutrophilic inflammation. On the other hand, treatment with Rof in asthmatic mice without CS exposure reduced airway resistance and airway eosinophilia, although the inhibitory effect of Rof on AHR was unremarkable. In asthmatic mice with CS exposure, Rof treatment did not exacerbate lung tissue resistance but modestly restored AHR, without any significant effects on airway inflammation. These results suggest that CS exposure mitigates sensitivity to both Dex and Rof. In asthmatic mice with CS exposure, Dex is still effective in reducing eosinophilic inflammation but increases lung tissue resistance, AHR and neutrophilic inflammation. Rof is ineffective in improving lung function and inflammation in asthmatic mice with CS exposure. This study did not support our initial hypothesis that Rof might be more effective than glucocorticoids for improving asthma in smokers. However, glucocorticoids may have a detrimental effect on smoking asthmatics.

Fenofibrate inhibits TGF-β-induced myofibroblast differentiation and activation in human lung fibroblasts in vitro

Fenofibrate (FF), a peroxisome proliferator-activated receptor-alpha (PPAR-α) agonist and a lipid-lowering agent, can decrease experimental pulmonary fibrosis. However, the mechanisms underlying the antifibrotic effect of FF remain unknown. Hence, this study was conducted to evaluate the effects of FF on transforming growth factor-beta (TGF-β)-induced myofibroblast differentiation and activation in lung fibroblasts. The results showed that FF inhibited alpha-smooth muscle actin (α-SMA) and connective tissue growth factor expression, collagen production, cell motility, SMAD3 phosphorylation and nuclear translocation, and metabolic reprogramming in TGF-β-exposed cells. The inhibitory effect of FF did not decrease with the addition of a PPAR-α antagonist. Moreover, the inhibitory effect given by FF could not be reproduced with the addition of an alternative PPAR-α agonist. FF inhibited mitochondrial respiration. However, rotenone, a complex I inhibitor, did not suppress TGF-β-induced myofibroblast differentiation. Furthermore, the TGF-β-induced nuclear reduction of protein phosphatase, Mg²⁺ /Mn²⁺ -dependent 1A (PPM1A), a SMAD phosphatase, was inhibited by FF. These results showed that FF suppressed TGF-β-induced myofibroblast differentiation and activation independent of PPAR-α activation and impaired mitochondrial respiration. In conclusion, this study provides information on the effects of FF on anti-TGF-β mechanisms.

Glasgow prognostic score for prediction of chemotherapy-triggered acute exacerbation interstitial lung disease in patients with small cell lung cancer

BACKGROUND

Predicting the incidence of chemotherapy-triggered acute exacerbation of interstitial lung disease (AE-ILD) in patients with lung cancer is important because AE-ILD confers a poor prognosis. The Glasgow prognostic score (GPS), which is an inflammation-based index composed of serum levels of C-reactive protein and albumin, predicts prognosis in patients with small cell lung cancer (SCLC) without ILD. In this study, we investigated AE-ILD and survival outcome based on the GPS in patients with ILD associated with SCLC who were receiving chemotherapy.

METHODS

Medical records of patients who received platinum-based first-line chemotherapy between June 2010 and May 2019 were retrospectively reviewed to compare the incidence of AE-ILD and overall survival (OS) between GPS 0, 1, and 2.

RESULTS

Among our cohort of 31 patients, six (19.3%) experienced chemotherapy-triggered AE-ILD. The AE-ILD incidence increased from 9.5% to 25.0% and 50.0% with increase in GPS of 0, 1, and 2, respectively. Univariate and multivariate analyses revealed remarkable associations between GPS 2 and both AE-ILD (odds ratio for GPS 2, 18.69; p = 0.046) and prognosis (hazard ratio of GPS 2, 13.52; p = 0.002). Furthermore, median OS in the GPS 0, 1, and 2 groups was 16.2, 9.8, and 7.1 months, respectively (p < 0.001).

CONCLUSIONS

Our results suggest that GPS 2 is both a predictor of risk of chemotherapy-triggered AE-ILD and a prognostic indicator in patients with ILD associated with SCLC. We propose that GPS may be used as a guide to distinguish chemotherapy-tolerant patients from those at high risk of AE-ILD.

Glasgow Prognostic Score predicts chemotherapy-triggered acute exacerbation-interstitial lung disease in patients with non-small cell lung cancer

BACKGROUND

Interstitial lung disease (ILD) in patients with non-small cell lung cancer (NSCLC) worsens the prognosis for overall survival (OS) due to chemotherapy-triggered acute exacerbation (AE)-ILD. The Glasgow Prognostic Score (GPS), which is based on serum C-reactive protein and albumin levels, has been suggested as a reliable prognostic tool for mortality in cancer patients, including NSCLC. In this study, we investigated whether GPS is a predictor for chemotherapy-triggered AE-ILD and the prognosis in patients with NSCLC and pre-existing ILD.

METHODS

We conducted a retrospective review on 56 NSCLC and ILD patients at our hospital who received platinum agent-based treatment as first-line chemotherapy between June 2010 and May 2019. We categorized these patients according to their GPS (0-2) and compared the incidence of chemotherapy-triggered AE-ILD and OS.

RESULTS

The GPS 0, 1, and 2 groups included 31, 16, and nine patients, respectively, out of 56. A total of 12 (21.4%) patients showed chemotherapy-triggered AE-ILD. The median OS was at 11.5 months (95% confidence interval: 8.0-15.1). The incidence of chemotherapy-triggered AE-ILD within the first year of chemotherapy in the GPS 0, 1, and 2 groups was three (9.6%), four (25.0%), and five (55.5%), and the median OS time was 16.9, 9.8 and 7.6 months, respectively. Univariate and multivariate analyses indicated that only GPS 2 could predict both chemotherapy-triggered AE-ILD and OS (P < 0.05).

CONCLUSIONS

GPS assessment of patients with NSCLC and pre-existing ILD is a valuable prognostic tool for predicting chemotherapy-triggered AE-ILD and OS.

KEY POINTS

SIGNIFICANT FINDINGS OF THE STUDY: We found that GPS 2 was an independent risk factor for chemotherapy-triggered AE-ILD and prognosis in patients with ILD associated with NSCLC.

WHAT THIS STUDY ADDS

GPS may potentially enable the discrimination of patients tolerant of chemotherapy from those at an increased risk of AE-ILD and predict the prognosis in patients with NSCLC and ILD receiving chemotherapy.

Anti-cancer strategy targeting the energy metabolism of tumor cells surviving a low-nutrient acidic microenvironment

OBJECTIVE

Tumor cells experience hypoxia, acidosis, and hypoglycemia. Metabolic adaptation to glucose shortage is essential to maintain tumor cells' survival because of their high glucose requirement. This study evaluated the hypothesis that acidosis might promote tumor survival during glucose shortage and if so, explored a novel drug targeting metabolic vulnerability to glucose shortage.

METHODS

Cell survival and bioenergetics metabolism were assessed in lung cancer cell lines. Our in-house small-molecule compounds were screened to identify those that kill cancer cells under low-glucose conditions. Cytotoxicity against non-cancerous cells was also assessed. Tumor growth was evaluated in vivo using a mouse engraft model.

RESULTS

Acidosis limited the cellular consumption of glucose and ATP, causing tumor cells to enter a metabolically dormant but energetically economic state, which promoted tumor cell survival during glucose deficiency. We identified ESI-09, a previously known exchange protein directly activated by cAMP (EAPC) inhibitor, as an anti-cancer compound that inhibited cancer cells under low-glucose conditions even when associated with acidosis. Bioenergetic studies showed that independent of EPAC inhibition, ESI-09 was a safer mitochondrial uncoupler than a classical uncoupler and created a futile cycle of mitochondrial respiration, leading to decreased ATP production, increased ATP dissipation, and fuel scavenging. Accordingly, ESI-09 exhibited more cytotoxic effects under low-glucose conditions than under normal glucose conditions. ESI-09 was also more effective than actively proliferating cells on quiescent glucose-restricted cells. Cisplatin showed opposite effects. ESI-09 inhibited tumor growth in lung cancer engraft mice.

CONCLUSIONS

This study highlights the acidosis-induced promotion of tumor survival during glucose shortage and demonstrates that ESI-09 is a novel potent anti-cancer mitochondrial uncoupler that targets a metabolic vulnerability to glucose shortage even when associated with acidosis. The higher cytotoxicity under lower-than-normal glucose conditions suggests that ESI-09 is safer than conventional chemotherapy, can target the metabolic vulnerability of tumor cells to low-glucose stress, and is applicable to many cancer cell types.

Can DLNO/DLCO ratio offset prejudicial effects of functional heterogeneities in acinar regions?

OBJECTIVES

(1) To establish the general equation that describes relationship of DM_CO/Vc versus DL_NO/DL_CO under conditions with no functional heterogeneities. (2) To examine the effects of functional heterogeneities, including parallel and series (stratified) heterogeneities, on DL_NO/DL_CO.

RESULTS AND DISCUSSIONS

(1) Given that "true" θ_NO in pulmonary capillaries is represented by surface absorption-related θ_NO, relationship between DM_CO/Vc and DL_NO/DL_CO does not differ significantly from that obtained on premise of infinite θ_NO. DL_NO/DL_CO decided physiologically may mirror morphometric DM_CO/Vc actually working for gas exchange but not "total" morphometric ratio of DM_CO/Vc. (2) There are three parallel heterogeneities that affect diffusing capacity (D)-related parameters. Of them, only the heterogeneity of D/V_A, where V_A is alveolar volume, underestimates DL_CO and DL_NO. DL_NO/DL_CO does not alleviate negative impact of D/V_A heterogeneity, indicating that DM_CO/Vc estimated from DL_NO/DL_CO does not mirror "true" morphometric DM_CO/Vc in diseased lungs with D/V_A maldistribution. (3) Stratified heterogeneity underrates morphometric DM_CO, DM_NO, and DM_NO/DM_CO maximally by 1.4 %, 2.8 %, and 1.4 %, respectively, under conditions similar to single-breath D measurements, suggesting that effect of stratified heterogeneity on D measures is no longer needed to be considered in normal subjects but may be in patients having lung diseases with destructive lesions of acinar structures.

What are appropriate values of relative krogh diffusion Constant of NO against CO and of theta-NO in alveolar septa?

OBJECTIVES

To propose new physical constants for NO and CO (Krogh diffusion constant ratio (KD_NO/CO) and specific blood conductance for NO (θ_NO)) for calculating DMCO and Vc, according to Roughton-Forster's equation (Roughton and Forster, J. Appl. Physiol. 11: 290-302, 1957) from simultaneous DLNO and DLCO measurements.

RESULTS AND CONCLUSIONS

(1) The Graham's law is unacceptable for determining KD_NO/CO because CO does not fulfil all the conditions of an "ideal" gas. We have re-estimated KD_NO/CO in a new way based on difference in molar volumes of two gases (molar volume theory). The KD_NO/CO thus decided is 2.34. (2) θ_NO measured with rapid-reaction, constant-flow method by Carlsen and Comroe (J. Gen. Physiol. 42: 83-107, 1958) may be underestimated by about 40 % due to unstirred water layer surrounding the erythrocyte. (3) Erythrocyte θ_O2 can be harvested from O₂ release kinetics in presence of high concentration of dithionite, which effectively removes the unstirred water layer-elicited effect. Multiplication of erythrocyte θ_O2 by erythrocyte KD_NO/O2 equals erythrocyte θ_NO, the value of which is 6.2 mL/min/mmHg/(mL⋅blood). According to the concepts of Kang et al. (RESPNB. 241: 62-71, 2017) and Borland et al. (RESPNB. 241: 58-61, 2017), in vitro θ_NO decided from rapid-mixing experiments may mirror bulk absorption of NO by erythrocytes. (4) In pulmonary capillaries, NO uptake takes place predominantly in the surface rim of the erythrocyte. This surface absorption of NO increases the θ_NO 10-fold versus bulk absorption of NO to about 60 mL/min/mmHg/(mL⋅blood).

Hypercapnic tumor microenvironment confers chemoresistance to lung cancer cells by reprogramming mitochondrial metabolism in vitro

The tumor microenvironment has previously been reported to be hypercapnic (as high as ~84 mmHg), although its effect on tumor cell behaviors is unknown. In this study, high CO₂ levels, ranging from 5% to 15%, protected lung cancer cells from anticancer agents, such as cisplatin, carboplatin and etoposide, by suppressing apoptosis. The cytoprotective effect of a high CO₂ level was independent of acidosis and was due to mitochondrial metabolic reprogramming that reduced mitochondrial respiration, as assessed by oxygen consumption, oxidative phosphorylation, mitochondrial membrane and oxidative potentials, eventually leading to reduced reactive oxidant species production. In contrast, high CO₂ levels did not affect cisplatin-mediated DNA damage responses or the expression of Bcl-2 family proteins. Although high CO₂ levels inhibited glycolysis, this inhibition was not mechanistically involved in high CO₂-mediated reductions in mitochondrial respiration, because a high CO₂ concentration inhibited isolated mitochondria. A cytoprotective effect of high CO₂ levels on mitochondria DNA-depleted cells was not noted, lending support to our conclusion that high CO₂ levels act on mitochondria to reduce the cytotoxicity of anticancer agents. High CO₂-mediated cytoprotection was also noted in a 3D culture system. In conclusion, the hypercapnic tumor microenvironment reprograms mitochondrial respiratory metabolism causing chemoresistance in lung cancer cells. Thus, tumor hypercapnia may represent a novel target to improve chemosensitivity.

Arousal index as a marker of carotid artery atherosclerosis in patients with obstructive sleep apnea syndrome

PURPOSE

It was shown in a previous cohort study that men with internal carotid artery (ICA) plaque, defined as focal wall thickness of ≥ 1.5 mm, had a threefold higher risk of stroke than those without plaque. We examined the relationship between arousal indices and sleep stages in patients with obstructive sleep apnea syndrome (OSAS) and carotid atherosclerosis.

METHODS

Carotid atherosclerosis severity was evaluated using the maximal carotid wall intima-media thickness of the ICA (ICA-maxIMT) and plaque in 83 patients with OSAS.

RESULTS

The ICA-maxIMT values were positively correlated with the apnea hypopnea index (AHI) (ρ = 0.294, P = 0.007), arousal index (ρ = 0.289, P = 0.008), oxygen desaturation index (ρ = 0.298, P = 0.006), percentage of visually scored total sleep time spent in nocturnal oxygen saturation < 90% (SpO₂ < 90%) (ρ = 0.246, P = 0.025), and the percentage of visually scored total sleep time spent in non-REM sleep stage 1 (ρ = 0.326, P = 0.003) and were negatively correlated with the percentage of visually scored total sleep time spent in non-REM sleep stages 2 and 3. Arousal index, diabetes mellitus, and age were found to be independent predictors of ICA plaque presence (OR 1.052, P = 0.003; OR 8.705, P = 0.026; OR 1.064, P = 0.023, respectively).

CONCLUSIONS

Several PSG variables that are indicative of sleep fragmentation, sleep disordered breathing, and poor sleep quality correlated with the occurrence of atherosclerosis, but total arousal index was the only independent predictive factor.

Anatomical backgrounds on gas exchange parameters in the lung

Many problems regarding structure-function relationships have remained unsolved in the field of respiratory physiology. In the present review, we highlighted these uncertain issues from a variety of anatomical and physiological viewpoints. Model A of Weibel in which dichotomously branching airways are incorporated should be used for analyzing gas mixing in conducting and acinar airways. Acinus of Loeschcke is taken as an anatomical gas-exchange unit. Although it is difficult to define functional gas-exchange unit in a way entirely consistent with anatomical structures, acinus of Aschoff may serve as a functional gas-exchange unit in a first approximation. Based on anatomical and physiological perspectives, the multiple inert-gas elimination technique is thought to be highly effective for predicting ventilation-perfusion heterogeneity between acini of Aschoff under steady-state condition. Changes in effective alveolar P_O2, the most important parameter in classical gas-exchange theory, are coherent with those in mixed alveolar P_O2 decided from the multiple inert-gas elimination technique. Therefore, effective alveolar-arterial P_O2 difference is considered useful for assessing gas-exchange abnormalities in lung periphery. However, one should be aware that although alveolar-arterial P_O2 difference sensitively detects moderately low ventilation-perfusion regions causing hypoxemia, it is insensitive to abnormal gas exchange evoked by very low and high ventilation-perfusion regions. Pulmonary diffusing capacity for CO (D_LCO) and the value corrected for alveolar volume (V_AV), i.e., D_LCO/V_AV (K_CO), are thought to be crucial for diagnosing alveolar-wall damages. D_LCO-related parameters have higher sensitivity to detecting abnormalities in pulmonary microcirculation than those in the alveolocapillary membrane. We would like to recommend four categories derived from combining behaviors of D_LCO with those of K_CO for differential diagnosis on anatomically morbid states in alveolar walls: type-1 abnormality defined by decrease in both D_LCO and K_CO; type-2 abnormality by decrease in D_LCO but increase in K_CO; type-3 abnormality by decrease in D_LCO but restricted rise in K_CO; and type-4 abnormality by increase in both D_LCO and K_CO.

Classical regression equations of spirometric parameters are not applicable for diagnosing spirometric abnormalities in adipotic adults

The prevalence of overweighing and obese adults (defined as “adipotic” adults), has markedly increased over the world. A remarkable increase in the adipotic population urgently needs developing the regression equations for predicting spirometric parameters (SPs), which are specifically applicable to adipotic adults. Unfortunately, however, the reliable equations suitable for adipotic adults have not been reported to date. Recently, Yamaguchi et al have proposed the quantitative method to estimate the effects of adiposity on deciding the SPs incorporating with age-specific contributions of various explanatory, independent variables such as age (A), standing height (H), body weight (BW), and fat fraction of body mass (F). Extending the method proposed by Yamaguchi et al, we attempted to elaborate the novel regression equations applicable for diagnosing the spirometric abnormality in adipotic adults. For accomplishing this purpose, never-smoking, adipotic adults with body mass index (BMI) over 25 kg/m² and no respiratory illness were recruited from the general population in Japan (n = 3696, including men: 1890 and women: 1806). Introducing the four explanatory variables of A, H, BW, and F, gender-specific and age-dependent regression equations that allowed for prescribing the SPs in adipotic adults were constructed. Comparing the results obtained for non-adipotic adults (i.e., those with normal BMI), the negative or positive impact of height on SPs was preserved in adipotic adults, as well. However, the negative impact of age on SPs was blunted in adipotic men and the positive effect of BW on SPs was impeded in adipotic men and women. The fat fraction of body mass-elicited negative impact on SPs vanished in adipotic women. These results indicate that the regression equations of SPs for adipotic adults differ significantly from those for non-adipotic adults, leading to the conclusion that the regression equations for non-adipotic adults should not be used while judging the spirometric abnormalities in adipotic adults.

Simultaneous measurement of pulmonary diffusing capacity for carbon monoxide and nitric oxide

In Europe and America, the newly-developed, simultaneous measurement of diffusing capacity for CO (D_LCO) and NO (D_LNO) has replaced the classic D_LCO measurement for detecting the pathophysiological abnormalities in the acinar regions. However, simultaneous measurement of D_LCO and D_LNO is currently not used by Japanese physicians. To encourage the use of D_LNO in Japan, the authors reviewed aspects of simultaneously-estimated D_LCO and D_LNO from previously published manuscripts. The simultaneous D_LCO-D_LNO technique identifies the alveolocapillary membrane-related diffusing capacity (membrane component, D_M) and the blood volume in pulmonary microcirculation (V_C); V_C is the principal factor constituting the blood component of diffusing capacity (D_B,D_B=θ·V_C where θ is the specific gas conductance for CO or NO in the blood). As the association velocity of NO with hemoglobin (Hb) is fast and the affinity of NO with Hb is high in comparison with those of CO, θ_NO can be taken as an invariable simply determined by diffusion limitation inside the erythrocyte. This means that θ_NO is independent of the partial pressure of oxygen (PO₂). However, θ_CO involves the limitations by diffusion and chemical reaction elicited by the erythrocyte, resulting in θ_CO to be a PO₂-dependent variable. Furthermore, D_LCO is determined primarily by D_B (∼77%), while D_LNO is determined equally by D_M (∼55%) and D_B (∼45%). This suggests that D_LCO is more sensitive for detecting microvascular diseases, while D_LNO can equally identify alveolocapillary membrane and microcirculatory abnormalities.

Hypercapnia Accelerates Adipogenesis: A Novel Role of High CO2 in Exacerbating Obesity

Obesity is a major risk factor for the development of obstructive sleep apnea (OSA) and obesity hypoventilation syndrome (OHS), which manifest as intermittent hypercapnia and sustained plus intermittent hypercapnia, respectively. In this study, we investigated whether CO₂ affects adipocyte differentiation (adipogenesis) and maturation (hypertrophy). Human visceral or subcutaneous preadipocytes were grown to confluence and then induced to differentiate to adipocytes under hypocapnia, normocapnia, and hypercapnia with or without hypoxia. Adipogenesis was also induced under intermittent or sustained hypercapnia. Differentiated adipocytes were maintained to maturity under normocapnia or hypercapnia. Our main findings are as follows: (1) hypercapnia accelerated adipogenesis in visceral and subcutaneous preadipocytes, whereas hypocapnia inhibited adipogenesis; (2) hypercapnia did not affect adipocyte hypertrophy; (3) hypercapnia-accelerated adipogenesis was independent of extracellular acidosis, oxygen concentration, or either intermittent or sustained exposure to high CO₂; and (4) the mechanisms underlying hypercapnia-accelerated adipogenesis involved increased production of cyclic adenosine monophosphate (cAMP) via soluble adenylyl cyclase, leading to the activation of protein kinase A and exchanger protein directly activated by cAMP, which, in turn, activated proadipogenic transcription factors, such as cAMP response element binding protein, CCAAT/enhancer binding protein β, and peroxisome proliferator-activated receptor γ. This study reveals a novel role of high CO₂ in promoting adipogenesis, which provides mechanistic clues to a pathoetiological interaction between OSA/OHS and obesity. Our data suggest a vicious cycle of disease progression via the following mechanism: OSA/OHS → hypoventilation → hypercapnia → increased adipogenesis → increased fat mass → exacerbated OSA/OHS.

Improvement of metabolic disorders by an EP2 receptor agonist via restoration of the subcutaneous adipose tissue in pulmonary emphysema

Chronic obstructive pulmonary disease (COPD) is often associated with co-morbidities. Metabolic disorders like hyperlipidemia and diabetes occur also in underweight COPD patients, although the mechanism is uncertain. Subcutaneous adipose tissue (SAT) plays an important role in energy homeostasis, since restricted capacity to increase fat cell number with increase in fat cell size occurring instead, is associated with lipotoxicity and metabolic disorders. The aim of this study is to show the protective role of SAT for the metabolic disorders in pulmonary emphysema of a murine model. We found ectopic fat accumulation and impaired glucose homeostasis with wasting of SAT in a murine model of elastase-induced pulmonary emphysema (EIE mice) reared on a high-fat diet. ONO-AE1-259, a selective E-prostanoid (EP) 2 receptor agonist, improved angiogenesis and subsequently adipogenesis, and finally improved ectopic fat accumulation and glucose homeostasis with restoration of the capacity for storage of surplus energy in SAT. These results suggest that metabolic disorders like hyperlipidemia and diabetes occured in underweight COPD is partially due to the less capacity for storage of surplus energy in SAT, though the precise mechanism is uncertained. Our data pave the way for the development of therapeutic interventions for metabolic disorders in emphysema patients, e.g., use of pro-angiogenic agents targeting the capacity for storage of surplus energy in the subcutaneous adipose tissue.

Repeated exposure to 5-bromo-2'-deoxyuridine causes decreased proliferation and low-grade inflammation in the lungs of mice

Incorporation of 5-bromo-2'-deoxyuridine (BrdU) into proliferating cells has been used to label dividing cells in many tissues. Although BrdU has been shown to be genotoxic, teratogenic and mutagenic, such adverse effects have largely been ignored by researchers. We determined whether long-term BrdU exposure causes any histopathological changes in the lungs of mice. Eight-week-old male C57/BL6J mice were administered BrdU by intraperitoneal injection on 3 consecutive days of each week for 14 weeks. While no obvious structural changes such as tissue damage, fibrosis, emphysema, airway remodeling, vascular thickening or tumorigenesis were noted, a moderate degree of macrophage infiltration was observed in the airways and lung parenchyma in the lungs of the mice exposed repeatedly to BrdU (BrdU-exposed mice). The proliferative activities of the airway and alveolar epithelial and mesenchymal cells were reduced in the BrdU-exposed mice, although the numbers of these cells in the lungs were maintained. Double immunofluorescence study of the lungs of the BrdU-exposed mice showed overexpression of IL-6 in the airway epithelial and alveolar wall cells, some of which were also double-positive for BrdU. These results indicate that long-term exposure to BrdU inhibits cell proliferation and induces low-grade inflammation in the lungs of mice. Our findings underscore the need for caution in the interpretation of studies that involve long-term exposure to BrdU.

Correlation of a decline in aerobic capacity with development of emphysema in patients with chronic obstructive pulmonary disease: a prospective observational study

In patients with COPD, CT assessment of emphysema and airway disease is known to be associated with lung function and 6-minute walk distance. However, it remains to be determined whether low attenuation area (LAA) on CT is associated with aerobic capacity assessed using cardiopulmonary exercise testing (CPET). In this prospective observational study, we repeatedly conducted high-resolution CT and CPET using a treadmill in 81 COPD patients over a median interval of 3.5 years. Two investigators independently scored LAA on images obtained at the aortic arch level, tracheal bifurcation level, and supradiaphragmatic level. Grades for the images of each lung were added to yield the total LAA score. Total LAA score was negatively correlated with peak aerobic capacity ([Formula: see text]) (p<0.001, r = -0.485). LAA scores of the upper (aortic arch level) and the lower (supradiaphragmatic level) lungs were both significantly associated with peak [Formula: see text]. There was a significant correlation between total LAA score and peak CO2 output ([Formula: see text]) (p<0.001, r = -0.433). Total LAA score was correlated with oxygen saturation at peak exercise (p<0.001, r = -0.634) and the estimated dead space fraction (p<0.001, r = 0.416). The mean annual change in total LAA score was significantly correlated with those in peak [Formula: see text] (p<0.001, r = -0.546) and peak [Formula: see text] (p<0.001, r = -0.488). The extent of emphysema measured by CT was associated with the results of CPET. The time-dependent changes in CPET data were also correlated with that in total LAA score. CT assessment could be a non-invasive tool to predict aerobic capacity in patients with COPD.

An evolutionary medicine approach to understanding factors that contribute to chronic obstructive pulmonary disease

Although many studies have been published on the causes and mechanisms of chronic obstructive pulmonary disease (COPD), the reason for the existence of COPD and the reasons why COPD develops in humans have hardly been studied. Evolutionary medical approaches are required to explain not only the proximate factors, such as the causes and mechanisms of a disease, but the ultimate (evolutionary) factors as well, such as why the disease is present and why the disease develops in humans. According to the concepts of evolutionary medicine, disease susceptibility is acquired as a result of natural selection during the evolutionary process of traits linked to the genes involved in disease susceptibility. In this paper, we discuss the following six reasons why COPD develops in humans based on current evolutionary medical theories: (1) evolutionary constraints; (2) mismatch between environmental changes and evolution; (3) co-evolution with pathogenic microorganisms; (4) life history trade-off; (5) defenses and their costs, and (6) reproductive success at the expense of health. Our perspective pursues evolutionary answers to the fundamental question, 'Why are humans susceptible to this common disease, COPD, despite their long evolutionary history?' We believe that the perspectives offered by evolutionary medicine are essential for researchers to better understand the significance of their work.

Promotion of adipogenesis by an EP2 receptor agonist via stimulation of angiogenesis in pulmonary emphysema

Body weight loss is a common manifestation in patients with chronic obstructive pulmonary disease (COPD), particularly those with severe emphysema. Adipose angiogenesis is a key mediator of adipogenesis and use of pro-angiogenic agents may serve as a therapeutic option for lean COPD patients. Since angiogenesis is stimulated by PGE2, we examined whether ONO-AE1-259, a selective E-prostanoid (EP) 2 receptor agonist, might promote adipose angiogenesis and adipogenesis in a murine model of elastase-induced pulmonary emphysema (EIE mice). Mice were intratracheally instilled with elastase or saline, followed after 4 weeks by intraperitoneal administration of ONO-AE1-259 for 4 weeks. The subcutaneous adipose tissue (SAT) weight decreased in the EIE mice, whereas in the EIE mice treated with ONO-AE1-259, the SAT weight was largely restored, which was associated with significant increases in SAT adipogenesis, angiogenesis, and VEGF protein production. In contrast, ONO-AE1-259 administration induced no alteration in the weight of the visceral adipose tissue. These results suggest that in EIE mice, ONO-AE1-259 stimulated adipose angiogenesis possibly via VEGF production, and thence, adipogenesis. Our data pave the way for the development of therapeutic interventions for weight loss in emphysema patients, e.g., use of pro-angiogenic agents targeting the adipose tissue vascular component.

A murine model of airway fibrosis induced by repeated naphthalene exposure

The airway epithelium serves as a biological barrier essential for host defense against inhaled pollutants. While chronic epithelial injury, commonly associated with chronic obstructive pulmonary disease and bronchiolitis obliterans syndrome, often results in airway fibrosis, limited animal models of airway fibrosis have been established. Club cells (Clara cells) in the small airways represent an important population of epithelial progenitor cells and also the principal site of localization of the cytochrome P-450 monooxygenase system, which metabolically activates xenobiotic chemicals such as naphthalene by converting them to toxic epoxide intermediates. We hypothesized that repeated exposure to naphthalene may cause prolonged loss of club cells, triggering aberrant local epithelial repair mechanisms that lead to peribronchial fibrosis. We administered intraperitoneal injections of naphthalene to C57/BL6J mice once a week for 14 consecutive weeks. Repeated club cell injury caused by naphthalene triggered regional hyperproliferation of epithelial progenitor cells, while other regions remained denuded or squamated, resulting in fibroblast proliferation and peribronchial collagen deposition associated with upregulation of the fibrogenic cytokines transforming growth factor-β and connective tissue growth factor. The total collagen content of the lung assessed by measurement of the hydroxyproline content was also increased after repeated exposure to naphthalene. These results lend support to the relevance of repeated injury of airway epithelial cells as a trigger for resting fibroblast proliferation and airway fibrosis. This model of airway fibrosis is simple and easy to reproduce, and may be expected to advance our understanding of the pathogenesis and potential treatment of airway fibrotic disorders.

Systemic effects of acute cigarette smoke exposure in mice

CONTEXT

Cigarette smoke (CS) causes both pulmonary and extrapulmonary disorders.

OBJECTIVE

To determine the pulmonary and extrapulmonary effects of acute CS exposure in regard to inflammation, oxidative stress and DNA damage.

MATERIALS AND METHODS

Mice were exposed to CS for 10 days and then their lungs, heart, liver, pancreas, kidneys, gastrocnemius muscle and subcutaneous (inguinal and flank) and visceral (retroperitoneum and periuterus) adipose tissues were excised. Bronchoalveolar lavage fluid samples were obtained for differential cell analysis. Inflammatory cell infiltration of the tissues was assessed by immunohistochemistry for Mac-3(+) cells, F4/80(+) cells and CD45(+) cells. Oxidative stress was determined by immunohistochemistry for thymidine glycol (a marker of DNA peroxidation) and 4-hydroxy hexenal (a marker of lipid peroxidation), by enzyme-linked immunosorbent assay for protein carbonyls (a marker of protein peroxidation) and by measurements of enzyme activities of glutathione peroxidase, superoxide dismutase and catalase. DNA double-strand breaks were assessed by immunohistochemistry for γH2AX.

RESULTS

CS exposure-induced inflammatory cell infiltration, oxidative stress and DNA damage in the lung. Neither inflammatory cell infiltration nor DNA damage was observed in any extrapulmonary organs. However, oxidative stress was increased in the heart and inguinal adipose tissue.

DISCUSSIONS

Induction of inflammatory cell infiltration and DNA damage by acute CS exposure was confined to the lung. However, an increased oxidative burden occurred in the heart and some adipose tissue, as well as in the lung.

CONCLUSIONS

Although extrapulmonary effects of CS are relatively modest compared with the pulmonary effects, some extrapulmonary organs are vulnerable to CS-induced oxidative stress.

Estimation of parasympathetic nerve function during sleep in patients with obstructive sleep apnea by instantaneous time-frequency analysis

BACKGROUND AND OBJECTIVES

The pathophysiologic aspects of parasympathetic nerve (PN) function during sleep in patients with obstructive sleep apnea (OSA) studied by classical power spectrum analysis on heart rate variability (HRV) are highly controversial. The controversy is attributed to methodologic concerns, such as poor time resolution involved in power spectrum analysis. We aimed to establish the appropriate method for the investigation of PN function in OSA patients with apneas and hypopneas using instantaneous time-frequency analysis with complex demodulation (CD) and sufficient time resolution.

METHODS

A total of 30 patients with PSG-confirmed mild to severe OSA were recruited for the analysis of frequency spectra contained in R-R intervals (RRI) of overnight electrocardiograph (ECG) tracings. High-frequency (HF) domains ranging between 0.15 and 0.40 Hz were selected for analysis. Among these domains, the HF domain with the maximum instantaneous amplitude was defined as the main HF peak and was used as the surrogate marker of PN discharge. Based on density spectrum array (DSA) map for main HF peak constructed with a time scale of 1s and a frequency resolution of 0.002 Hz (HF-DSA map), the shift in central frequency (CF) of main HF peak over time was continuously monitored. When the main HF peak with the same CF lasted for more than 20 s or 5 min on HF-DSA map, the PN function was considered to be stable or very stable. The measurements were then repeated after continuous positive airway pressure (CPAP) treatment.

RESULTS

The extent of PN-evoked modulation of RRI was enhanced in nonrapid eye movement (NREM) sleep, though the stability was reduced in both NREM and rapid eye movement (REM) sleep. These peculiar behaviors of PN function were reversed by CPAP treatment.

CONCLUSION

We found that instantaneous time-frequency analysis allowed estimation of transitional changes in PN function during sleep in OSA patients.

A large cohort study concerning age-dependent impacts of anthropometric variables on spirometric parameters in nonsmoking healthy adults

BACKGROUNDS

Although height (H) has been considered the principal anthropometric variable governing lung function, the age-dependent differences in its influences on determining spirometric parameters (SPs) have not been conclusively investigated. Moreover, there has been no study centered on age-dependent effects of other anthropometric variables, including body weight (BW) and body fat mass (BFM) on SPs. In addition, the age-dependent influences of these anthropometric variables are anticipated to differ quantitatively between male and female participants.

METHODS

A total of 16,919 nonsmoking healthy Japanese adults (men: 6,116, women: 10,803) were partitioned into six groups stratified by gender and age at intervals of 20-years: young-, middle-, and advanced-age groups of either gender. Using a model in which a SP was described by a logarithmic additive function of age, H, BW, and BFM, we determined the partial regression coefficients of the respective anthropometric variables to predict the reference means of SPs, including FVC, FEV1, FEV1/FVC, PEF, FEF50, and FEF75, in the six groups.

RESULTS/DISCUSSION

Although the impact of H on FVC and FEV1 was relatively homogeneous irrespective of gender and age, its homogeneity faded for flow parameters, particularly in the female middle- and advanced-age groups, indicating that the age-dependent contribution of H to SPs was enhanced more in women. The impact of BW on SPs differed depending on age, and this effect was also more conspicuous for female participants. H and BW generally exerted positive effects on SPs, whereas BFM had negative effects. Opposite effects of BW and BFM were observed in the female middle-age group in particular.

CONCLUSIONS

The effects of anthropometric variables on spirometric parameters are highly age-dependent, particularly in women, leading to the conclusion that the assumption of age-independent, constant partial regression coefficients of anthropometric variables while predicting the reference mean of a certain spirometric parameter may result in substantial errors.

Gender-specific impacts of apnea, age, and BMI on parasympathetic nerve dysfunction during sleep in patients with obstructive sleep apnea

BACKGROUND

The gender-specific influences of various confounding factors, including apnea, age, BMI, and cigarette consumption, on the function of the parasympathetic nerve system (PNS) during sleep in OSA patients has never been investigated.

METHODS

One hundred ninety-seven males and 63 females with OSA were subjected to full PSG examinations including assessment of R-R intervals (RRIs) during an overnight ECG. The PNS-derived modulatory effect on the RRIs and the variability of this effect were quantified during REM and NREM using instantaneous time-frequency analysis with complex demodulation. The spectral domain with the maximum instantaneous amplitude in the high-frequency band between 0.15 and 0.4 Hz was defined as the main HF peak and used as a surrogate marker of PNS discharge. Based on density-spectrum-array maps of the main HF peaks (HF-DSA map), shifts in the central frequency of the main HF peak over time were continuously observed. When the main HF peaks on the HF-DSA maps maintained the same central frequency for more than 20 sec or 5 min, the PNS functions were considered to be "stable" or "very stable", respectively.

RESULTS

Apneas enhanced PNS-derived cardiac-modulation during REM in males, but more importantly, they made PNS-function unstable during both REM and NREM in males and during NREM in females. Aging blunted the PNS-derived cardiac-modulation during both REM and NREM regardless of gender, but aging had no impact on the stability of PNS-function. BMI blunted PNS-eliciting cardiac-modulation during REM in males and during NREM in both males and females. BMI made the PNS unstable during REM in females. Neither height nor cigarette consumption influenced any PNS-related parameter.

CONCLUSIONS

The PNS-derived cardiac-modulation was generally inhibited by aging and obesity, in which the effect of obesity was gender-specific. The PNS instability at nighttime was mainly induced by apneas but by obesity particularly during REM in females.

The danger signal plus DNA damage two-hit hypothesis for chronic inflammation in COPD

Inflammation in chronic obstructive pulmonary disease (COPD) is thought to originate from the activation of innate immunity by a danger signal (first hit), although this mechanism does not readily explain why the inflammation becomes chronic. Here, we propose a two-hit hypothesis explaining why inflammation becomes chronic in patients with COPD. A more severe degree of inflammation exists in the lungs of patients who develop COPD than in the lungs of healthy smokers, and the large amounts of reactive oxygen species and reactive nitrogen species released from inflammatory cells are likely to induce DNA double-strand breaks (second hit) in the airways and pulmonary alveolar cells, causing apoptosis and cell senescence. The DNA damage response and senescence-associated secretory phenotype (SASP) are also likely to be activated, resulting in the production of pro-inflammatory cytokines. These pro-inflammatory cytokines further stimulate inflammatory cell infiltration, intensifying cell senescence and SASP through a positive-feedback mechanism. This vicious cycle, characterised by mutually reinforcing inflammation and DNA damage, may cause the inflammation in COPD patients to become chronic. Our hypothesis helps explain why COPD tends to occur in the elderly, why the inflammation worsens progressively, why inflammation continues even after smoking cessation, and why COPD is associated with lung cancer.