Faculty Bibliography

There is an increasing awareness of the role of distal airways in the pathophysiology of obstructive lung diseases including asthma and chronic obstructive pulmonary disease. We hypothesize that during induced bronchoconstriction: 1) disparity between distal and proximal airway reactivity may occur; and 2) changes in distal airway function may explain symptom onset in subjects with minimal FEV(1) change. 185 subjects underwent methacholine challenge testing (MCT). In addition to spirometry, oscillometry was performed at baseline and after maximum dose of methacholine; 33/185 also underwent oscillometry after each dose. Oscillometric parameters included resistance at 5 and 20 Hz (R(5,) R(20)) and heterogeneity of distal airway mechanics assessed by frequency dependence of resistance 5-20 Hz (R(5-20)) and reactance area (AX). R(5) varied widely during MCT (range -0.8 - 11.3 cmH(2)O/L/s) and correlated poorly with change in FEV(1) (r = 0.17). Changes in R(5) reflected changes in both R(20) and R(5-20) (r = 0.59, p<0.05; r = 0.87, p<0.0001). However, R(20) increased only 0.3 cmH(2)O/L/s, while R(5-20) increased 0.7 cmH(2)O/L/s for every 1cmH(2)O/L/s change in R(5,) indicating predominant effect of distal airway mechanics. 9/33 subjects developed symptoms despite minimal FEV(1) change (<5%), while R(5) increased 42% due to increased distal airway heterogeneity. These data indicate disparate behavior of proximal airway resistance (FEV(1) and R(20)) and distal airway heterogeneity (R(5-20) and AX). Distal airway reactivity may be associated with methacholine-induced symptoms despite absence of change in FEV(1). This study highlights the importance of disparity between proximal and distal airway behavior, which has implications in understanding pathophysiology of obstructive pulmonary diseases and their response to treatment

Community-acquired pneumonia affects approximately 4 million people in the United States, with 40,000 deaths per year. The incidence is increased about 35-fold in HIV-infected individuals, and this rate has decreased since the antiretroviral era has begun. Bacterial pneumonia has decreased from 5 to 20 cases per 100 person-years to less than 1 to 5 cases per 100 person-years in the era of antiretroviral therapy. HIV-1 infection impairs the function of neutrophils in the lung and infects CD4(+) cells and alveolar macrophages. Opportunistic infections dramatically increase local HIV replication in the lung cells, especially alveolar macrophages and CD4(+) cells. This enhanced replication increases viral mutations and provides opportunities for viral escape from latent reservoirs. Mortality is increased with more comorbidities in this highly susceptible population. Immunization with vaccines is recommended, especially pneumococcal vaccines, although the vaccine itself may stimulate viral replication. Recent studies show that the lower respiratory tract is a microbial reservoir in HIV-infected individuals rather than being a sterile environment, as originally thought. This may provide new opportunities for preventing opportunistic infections in HIV-infected subjects. Bacterial pneumonia presents an ongoing challenge in these high-risk individuals, particularly in studying the functions of the innate and acquired immune response

Introduction: Airway dysfunction has been detected by oscillometry in obese subjects despite normal large airway function as assessed by spirometry. This has been attributed to lung/airway compression as reflected by reduced FRC; we previously demonstrated improvement of abnormalities towards normal upon voluntary inflation to predicted FRC (AJRCCM 2010; 181:A2532). However, other causes of airway dysfunction such as inflammation or concomitant intrinsic airway disease may coexist and could not be excluded. The present study re-evaluated these subjects following bariatric surgery induced weight loss to evaluate for residual abnormality. Methods: 22 morbidly obese subjects without history of smoking and/or cardiopulmonary disease, underwent evaluation pre/post bariatric surgery (20% reduction in weight). Spirometry, plethysmography and impulse oscillometry (IOS) were performed. IOS parameters included resistance at 5Hz (R5), resistance at 20Hz (R20) frequency dependence of resistance (R5-20) and reactance at 5Hz (X5).IOS was also performed at an elevated lung volume (~1 liter) targeted to restore FRC to predicted values. All IOS measurements were repeated post bronchodilator. Results: Baseline weight and BMI were 256+/-43 kg and 46+/-7 kg/m², respectively. All subjects lost >20% of body weight, but obesity persisted in all subjects (weight 182 kg, BMI 33 kg/ m2). FEV /FVC was normal at baseline and remained unchanged post weight loss 1 (81+/-3% vs 83+/-4%) indicating normal large airway function. FRC and ERV improved post weight loss but values remained abnormal (FRC from 60+/-12 to 77+/-21% predicted, ERV from 46+/-16 to 75+/-38% predicted, p<0.05). Although IOS parameters improved following weight loss, data remained above the upper limit of normal (R5 from 6.8+/-1.8 to 5.1+/-1.4 cmH₂O/l/s, R₂₀ from 4.7+/-1.1 to 3.9+/-0.9 cmH₂O/l/s, R_5-20 from 2.1+/-1.1 to 1.2+/-0.9 cmH_2O /l/s, X₅ from -3.2+/-1.7 to -1.8+/-0.9 cmH₂O /l/s, p<0.05). Since FRC remained abnormal following weight loss, IOS was repeated following voluntary lung inflation (FRC 142+/-30%). While R20 corrected to normal at the elevated FRC (R₂₀ 3.1+/-1.0 cmH₂ O/l/s), R5, R5-20 and X5 remained abnormal indicating residual distal airway dysfunction (R₅ 4.2+/-1.4 cmH₂O/l/s, , R_5-20 1.1+/-0.7 cmH₂O /l/s, X₅ -2.0+/-0.8 cmH₂O /l/s); these residual oscillometric abnormalities were present in 11/22 subjects. Residual airway dysfunction was demonstrated by low specific conductance (assessed at 5HZ) despite restoration of FRC to supranormal values. Conclusions: Distal airway dysfunction persisted following weight loss and was not attributable to persistent mass loading in a subgroup of patients without clinical evidence of airway disease. These abnormalities may represent either functional abnormalities due to persistent obesity and/or intrinsic airway disease

Introduction: Macrolides are associated with a significant reduction in exacerbations compared with placebo in both chronic obstructive lung disease and cystic fibrosis. However, this may be due anti-bacterial and/or anti-inflammatory effects. The mechanism of the anti-inflammatory effects of macrolides in the lung are poorly understood. Alveolar macrophages (AM) have a central role on innate immune homeostasis of the lung; AM have developed many mechanisms to prevent autonomous induction and excess production of inflammatory cytokines through an increased expression of immune inhibitors such as C/EBPbeta and MafB. Interferon induces inhibitory C/EBPbeta, is regulated by MafB and has anti-inflammatory effect in the lung. Here, we test the hypothesis that azithromycin suppresses innate immune response by induction of inhibitory transcription factors. Methods: Alveolar macrophages were obtained from five subjects and incubated with lipopolysaccharide (LPS), interferon (IFN)-alpha, azithromycin (AZM) and AZM+LPS for 24hrs. Thirty nine supernatant cytokines were measured using Luminex. Protein extracts were obtained from AM and used for immunoblots for C/EBPbeta and MafB. Results: LPS strongly induced TNF-alpha production by AM, while the combination AZM and LPS inhibited LPS induced TNF-alpha production (Figure 1, p=0.02). AZM by itself had minimal effect. AZM also inhibited LPS induced CCL22, MDC, IL-1b, IL-6, IL10, G-GSF and GM-CSF. The inhibitory C/EBPbeta transcription factor and MafB expression was induced when AZM was added with LPS (Figure 2). Conclusions: AZM inhibits inflammatory cytokine production after LPS stimulation and induces inhibitory C/EBPbeta and MafB in AM. We will investigate if induction of innate immune inhibitors that blocks TLR signaling pathways underlies the broad anti-inflammatory effect achieved by macrolides. (Figure presented)

Introduction:Regulatory T cells (Treg) play important roles in immunological self-tolerance, and are functionally immunosuppressive subsets of T cells. Th17 cells are critical in the defense against microbes, particularly at mucosal surfaces. It has been shown that the balance between Treg and Th17 cells is a key factor that regulates helper T-cell (CD4⁺ or Th) function. However, there is limited information on the balance between Treg and Th17 cells in bronchoalveolar lavage (BAL). We investigated the distribution of Th17 cells in relation to Treg in PBMC and BAL of healthy volunteers, emphysema patients and HIV-1 infected patients. Methods:BAL lymphocytes were obtained by plating BAL cells for >=1 hour to remove adherent alveolar macrophages. PBMC were isolated by Ficoll gradient fractionation. BAL and PB lymphocytes were stimulated with PMA and ionomycin, treated with monensin, permeabilized, then labeled with PerCP-anti-CD4, PE-anti-IL-17 and Alexa Fluor 647 anti-Foxp3, and analyzed on a FACSCalibur to determine the percentage of CD4⁺ lymphocytes expressing IL-17 and Foxp3 (mean+/-SD). Results:Ten subjects were available for analysis (2 healthy volunteers, 5 emphysema and 3 HIV-1 infected subjects). Both PB and BAL Th cells presented a wide range of FoxP3⁺ cells (19.2+/-18.6 and 6.3+/-5.9 respectively) and IL-17⁺ cells (9.5+/-8.1 and 8.8+/-4.6 respectively). There was a greater percentage of FoxP3⁺ in the HIV-infected group compared to the healthy volunteer and emphysema groups (11.7+/-6.4 vs. 1.7+/-1.1 and 4.9+/-4.7 respectively). Similarly, there was a trend towards higher percentage of IL-17⁺ cells in the BAL of HIV-infected subjects compared to the healthy volunteer and emphysema subjects (10.8+/-3.6 vs. 5.6+/-0.9 and 8.9+/-5.8 respectively). When the expression of FoxP3⁺ and IL-17⁺ cells in BAL was compared for each subject, a direct correlation with an r2 of 0.36 and a p-value of 0.06 was found Conclusions:We observed a relative preservation of FoxP3⁺ and IL-17⁺ cells in BAL CD4⁺ lymphocytes, despite prior evidence suggesting a preferential loss of both Treg and Th17 subsets in PBMC of HIV-1 infected subjects. The co-ordinated expression of these subsets in BAL Th cells warrants further investigation to evaluate its immune significance in the alveolar compartment

Alveolar macrophages (AMs) are exposed to respirable microbial particles. Similar to phagocytes in the gastrointestinal tract, AMs can suppress inflammation after exposure to nonpathogenic organisms. IL-1R-associated kinase-M (IRAK-M) is one inhibitor of innate immunity, normally suppressing pulmonary inflammation. During pneumonia, polymorphonuclear neutrophils (PMNs) are recruited by chemotactic factors released by AMs to produce an intense inflammation. We report that intact IRAK-M is strongly expressed in resting human AMs but is cleaved in patients with pneumonia via PMN-mediated induction of caspase-6 (CASP-6) activity. PMN contact is necessary and PMN membranes are sufficient for CASP-6 induction in macrophages. PMNs fail to induce TNF-alpha fully in macrophages expressing CASP-6 cleavage-resistant IRAK-M. Without CASP-6 expression, PMN stimulation fails to cleave IRAK-M, degrade IkappaBalpha, or induce TNF-alpha. CASP-6(-/-) mice subjected to cecal ligation and puncture have impaired TNF-alpha production in the lung and decreased mortality. LPS did not induce or require CASP-6 activity demonstrating that TLR2/4 signaling is independent from the CASP-6 regulated pathway. These data define a central role for CASP-6 in PMN-driven macrophage activation and identify IRAK-M as an important target for CASP-6. PMNs de-repress AMs via CASP-6-mediated IRAK-M cleavage. This regulatory system will blunt lung inflammation unless PMNs infiltrate the alveolar spaces

BACKGROUND: Obstructive sleep apnea (OSA) is associated with prothrombotic effects that could lead to venous thromboembolic disease. We performed a prospective cross-sectional study to determine the prevalence of snoring and risk of OSA in patients with acute pulmonary embolism (PE). METHODS: We evaluated 270 consecutive patients who underwent a computed tomographic angiogram for suspected PE. Patients without PE served as a control group. Demographic and clinical characteristics were analyzed. The Berlin Questionnaire was used to determine the presence of snoring and the risk of OSA. A subset of patients also underwent formal nocturnal polysomnography. RESULTS: PE was present in 71 (26%) of the 270 patients who underwent a computed tomographic angiogram. When compared with patients without PE, patients with PE had a significantly higher prevalence of snoring (75% vs 50%, odds ratio = 2.91, 95% confidence interval: 1.60, 5.33, P = 0.001) and an increased risk of having OSA, as defined by the Berlin Questionnaire (65% vs 36%, odds ratio = 3.25, confidence interval: 1.84, 5.72, P < 0.001). Results from the multivariate analysis showed that PE was independently associated with risk of OSA (OR = 2.78, P = 0.001). CONCLUSIONS: We found a higher prevalence of snoring and high risk of OSA in patients diagnosed with acute PE, in comparison with patients in whom PE was suspected but ruled out. This association might be independent of other risks factors common to both OSA and PE. Therefore, OSA may represent a risk factor for the development of PE.

PURPOSE: Rapid shallow breathing may occur at any time during spontaneous breathing trials (SBT), questioning the utility of a single determination of the rapid shallow breathing index (RSBI). We hypothesize that change in RSBI during SBT may more accurately predict successful extubation than a single determination. METHODS: Prospective observational study. Seventy-two subjects were extubated. At 24 h, 63/72 remained extubated (Extubation Success), and 9 were re-intubated (Extubation Failure). Respiratory rate (RR), tidal volume (VT) and RSBI were measured every 30 min during 2-h T-piece SBT. Change in respiratory parameters was assessed as percent change from baseline. RESULTS: Initial RSBI was similar in Extubation Success and Extubation Failure groups (77.0 +/- 4.8, 77.0 +/- 4.8, p = ns). Nevertheless, RSBI tended to remain unchanged or decreased in the Extubation Success group; in contrast RSBI tended to increase in the Extubation Failure group because of either increased RR and/or decreased VT (p < 0.001 for mean percent change RSBI over time), indicating worsening of the respiratory pattern. Quantitatively, only 7/63 subjects of the Extubation Success group demonstrated increased RSBI >/=20% at any time during the SBT. In contrast, in the Extubation Failure group, RSBI increased in all subjects during the SBT, and eight of nine subjects demonstrated an increase greater than 20%. Thus, with a 2-h SBT the optimal threshold was a 20% increase (sensitivity = 89%, specificity = 89%). Similar results were obtained at 30 min (threshold = 5% increase). Percent change of RSBI predicted successful extubation even when initial values were >/=105. CONCLUSION: Percent change of RSBI during an SBT is a better predictor of successful extubation than a single determination of RSBI