Respiration-triggered olfactory stimulation reduces obstructive sleep apnea severity: A prospective pilot study.

Obstructive sleep apnea is a prevalent sleep-disordered breathing condition characterized by repetitive reduction in breathing during sleep. The current care standard for obstructive sleep apnea is continuous positive air pressure devices, often suffering from low tolerance due to limited adherence. Capitalizing on the unique neurocircuitry of olfactory perception and its retained function during sleep, we conducted a pilot study to test transient, respiration-based olfactory stimulation as a treatment for obstructive sleep apnea markers. Thirty-two patients with obstructive sleep apnea (apnea-hypopnea index ≥ 15 events per hr) underwent two polysomnography sessions, "Odour" and "Control", in random order. In "Odour" nights, patients were presented with transient respiratory-based olfactory stimulation delivered via a computer-controlled commercial olfactometer (Scentific). The olfactometer, equipped with a wireless monitoring, analysed respiratory patterns and presented odour upon detection of respiratory events. No odours were presented in "Control" nights. Following exclusions, 17 patients entered the analysis (four women, 47.4 (10.5) years, body mass index: 29.4 (6.3) kg m-2). We observed that olfactory stimulation during sleep reduced the apnea-hypopnea index ("Odour": 17.2 (20.9), "Control": 28.2 (18.6), z = -3.337, p = 0.000846, BF10 [Bayesian Factor 10]= 57.9), reflecting an average decrease of 31.3% in the number of events. Relatedly, stimulation reduced the oxygen desaturation index by 26.9% ("Odour": 12.5 (15.8), "Control": 25.7 (25.9), z = -3.337, p = 0.000846, BF10 = 9.522). This effect was not linked to the severity of baseline obstructive sleep apnea markers (ρ = -0.042, p = 0.87). Olfactory stimulation did not arouse from sleep or affect sleep structure, measured as time per sleep stage (F1,16 = 0.088, p = 0.77). In conclusion, olfactory stimulation during sleep was effective in reducing the severity of obstructive sleep apnea markers without inducing arousals, and may provide a novel treatment for obstructive sleep apnea, prompting continued research.

Association of the risk of obstructive sleep apnoea with the severity of COVID-19.

Patients with coronavirus 2019 (COVID-19) and obstructive sleep apnoea (OSA) have a worse prognosis than COVID-19 patients without OSA. This study aimed to examine the relationship between OSA risk and the severity of COVID-19 in patients undiagnosed with OSA. Patients diagnosed with COVID-19 and hospitalized or admitted to a community hotel were recruited for the study after recovery during a clinic check-up visit 6-8 weeks after discharge. At this visit, they answered the Epworth Sleeping Scale (ESS) and Berlin questionnaire. Demographic and clinical details were collected from electronic medical records. OSA risk was observed in 37 of 119 included patients (31.1%). Patients with high OSA risk were male, significantly older, had a higher body mass index (BMI), and had higher rates of hypertension and snoring than patients with low OSA risk. Moreover, OSA risk was associated with COVID-19 severity; 48.6% of patients with high risk for OSA suffered from severe COVID-19 compared to 22% of patients with low risk for OSA (p = 0.007). The duration of hospitalization for patients with a high OSA risk was 10.97±9.43 days, while that for those with a low OSA risk was 4.71±6.86 days (p = 0.001). After adjusting for BMI, age, hypertension, and chronic disease, the odds ratio was 4.3 (95%CI, 1.2-16, p = 0.029). A high OSA risk was associated with severe COVID-19 and longer hospitalization. Thus, we recommend that the Berlin and ESS questionnaires be completed for every COVID-19-infected patient at hospitalization, especially in the presence of comorbidities.

Prevalence and Persistence of Symptoms in Adult COVID-19 Survivors 3 and 18 Months after Discharge from Hospital or Corona Hotels.

COVID-19 is characterized by persistent symptoms beyond acute illness. In this prospective cohort study of patients with COVID-19, we sought to characterize the prevalence and persistence of symptoms up to 18 months after diagnosis. We followed 166 patients and assessed their symptoms during acute illness, and at 3 and 18 months after disease onset. The mean number of symptoms per patient during acute disease was 2.3 (SD:1.2), dropping to 1.8 (SD:1.1) at 3 months after recovery and to 0.6 (SD:0.9) at 18 months after recovery. However, this decrease was not unidirectional. Between acute illness and 3 months, the frequency of symptoms decreased for cough (64.5%→24.7%), ageusia (21.7% to6%), anosmia (17.5%→5.4%), and generalized pain (10.8% to 5.4%) but increased for dyspnea (53%→57.2%) weakness (47%→54.8%), and brain fog (3%→8.4%). Between 3 and 18 months, the frequency of symptoms decreased for all symptoms but remained relatively high for dyspnea (15.8%), weakness (21.2%), and brain fog (7.3%). Symptoms may persist for at least 18 months after acute COVID-19 infection. During the medium- to long-term recovery period, the prevalence of some symptoms may decrease or remain stable, and the prevalence of others may increase before slowly decreasing thereafter. These data should be considered when planning post-acute care for these patients.

Varenicline for Gradual Versus Abrupt Smoking Cessation in Poorly Motivated Smokers With COPD: A Prematurely Terminated Randomized Controlled Trial.

Background: Although smoking is the leading cause of chronic obstructive pulmonary disease (COPD), many patients with COPD smoke, highlighting the need for effective smoking cessation interventions in this population. This study examined the efficacy and safety of varenicline in increasing smoking cessation rates through "gradual" versus "abrupt" cessation in COPD patients with low motivation to quit smoking. Methods: A randomized, open label, 30-week, controlled trial (ClinicalTrials.gov identifier: NCT02894957) was conducted between January 2019 and October 2020 at a center in Israel. Smokers with COPD, poorly motivated to quit, were randomized to 6 weeks of varenicline for smoking reduction and a target quit day (TQD) at the end of week 6 (gradual cessation group) or ad libitum smoking for 5 weeks, 1 week of varenicline, and a TQD at the end of week 6 (abrupt cessation group). After the pre-quit phase, both groups received 12-week regular varenicline treatment and 12-week follow-up. Primary outcome was biochemically-validated continuous abstinence for weeks 6-30. Secondary outcomes were: (1) biochemically-confirmed7-day point prevalence abstinence for weeks 4-30, (2) efficient smoking reduction (≥50% in number of cigarettes/day) in the pre-quit phase; and (3) number of cigarettes/day, motivation to quit, and changes in respiratory symptoms and spirometry from baseline through week 30. Results: A drug recall issued by the study sponsor stopped the study after 70/242 (28.9%) patients had been enrolled. The gradual cessation group (n=29) had significantly higher continuous abstinence rates from TQD through week 30 versus the abrupt cessation group (n=41): 20.7% versus 4.9% (odds ratio [OR]=5.09; 95% confidence interval [CI] 0.89-29.17; p=0.048) and higher 7-day point prevalence abstinence levels at all time points but week 18 (p=0.027 at week 6, 0.056 at week 7, and 0.096 at week 9). Motivation to quit increased (p=0.002) and the number of cigarettes/day decreased (p=0.002) over time in both groups. Respiratory symptoms, but not spirometry, improved in both groups at week 30. Treatment was safe and well tolerated. Conclusion: In poorly motivated smokers with COPD, using varenicline for a 6-week gradual smoking cessation before TQD, compared with abrupt cessation, significantly increased quit rates up to 6 months. Results were not affected by the smaller-than-expected sample size. Further studies are needed to confirm these data.

Haematocrit level in obesity hypoventilation syndrome: a predictor of mortality?

BACKGROUND: The connection between obstructive sleep apnea and secondary erythrocytosis is controversial. We hypothesised that there may be a higher prevalence of erythrocytosis in patients with obesity hypoventilation syndrome (OHS) due to persistent hypoxemia. METHODS: The study was a retrospective, cross-sectional review of patients with OHS derived from an established cohort of "non-invasive ventilation" patients at the Department of Sleep Medicine at the Royal Infirmary Medical Centre, Edinburgh (2004-2017). Relevant clinical data were obtained from patient records. RESULTS: The cohort comprised 74 patients with OHS, 44 men (60%), mean age at diagnosis 54 ± 10 years. The mean haematocrit level for the group overall was 0.44, in men 0.45, and in women 0.41. Of 11 patients with erythrocytosis (15%), 7 were men. Thirteen patients (18%) died during follow-up (2004-2017). There was a statistically significant increase in risk of death in patients with higher and lower haematocrit levels compared to that in patients with OHS who had normal haematocrits. CONCLUSIONS: This is the first study showing increased prevalence of erythrocytosis in OHS patients. There was a "U"-shaped correlation with mortality according to haematocrit levels.

Diffuse pulmonary calcifications: A case series and review of literature.

Pulmonary calcifications are usually incidental asymptomatic findings discovered on x-rays or computed tomography scans that can be easily overlooked, and their significance undermined, especially in a seemingly asymptomatic person. Calcifications can be a marker of chronicity or disease severity, and thus have diagnostic value. Rarely, calcification can be the direct cause of morbidity. Calcifications can be either localized or diffuse. Many diseases, in particular infectious diseases, can cause localized calcifications. Diffuse calcifications are less common and usually secondary to a handful of conditions such as dystrophic pulmonary calcifications, metastatic pulmonary calcifications, disseminated pulmonary ossifications and pulmonary alveolar microlithiasis. We describe three cases of diffuse pulmonary calcifications, review the different causes of diffuse pulmonary calcifications and provide some indicators on how to differentiate between them. Differentiating between the different types of pulmonary calcifications has significant implications on the management and prognosis of the patients, and thus it is important to distinguish between them.

[DIAPHRAGMATIC PARALYSIS].

INTRODUCTION: One-sided diaphragmatic paralysis is a common phenomenon which is usually a-symptomatic. In case of acute onset or if there is an underlying lung disease, the phenomenon may be symptomatic and even limiting. In this article, we present a patient who arrived with subacute shortness of breath when lying down. She underwent thorough investigations but, as happens in most cases, the cause of the paralysis was not identified and it remains idiopathic. The authors present an overview of the etiology, differential diagnosis and treatment of diaphragmatic paralysis.

Identification of Asthma-COPD Overlap, Asthma, and Chronic Obstructive Pulmonary Disease Phenotypes in Patients with Airway Obstruction: Influence on Treatment Approach.

BACKGROUND: Many studies have described asthma-COPD overlap (ACO) among patients diagnosed with asthma or chronic obstructive pulmonary disease (COPD), but less so in broad populations of patients with chronic airway obstruction. OBJECTIVE: This study aimed to (i) examine the prevalence of ACO, asthma, and COPD phenotypes among subjects referred for pulmonary function testing (PFT), who had airway obstruction in spirometry (forced expiratory volume in 1 s [FEV1]/forced vital capacity [FVC] <0.7); and (ii) delineate the therapeutic approach of each group. METHODS: Cross-sectional study of patients who were referred for PFT at the Rokach Institute, in Jerusalem. Working definitions were as follows: (a) COPD: post-bronchodilator (BD) FEV1/FVC <0.70; (b) asthma: physician-diagnosed asthma before age 40 and/or minimum post-BD increase in FEV1 or FVC of 12% and 200 mL; and (c) ACO: the combination of the 2. Demographics, smoking habits, episodes of exacerbation, health-related quality of life (HRQL), and respiratory medication utilization were analyzed. RESULTS: Of 3,669 referrals from January 1 to April 30, 2017, 1,220 had airway obstruction of which 215 were included. Of these, 82 (38.1%) had ACO, 49 (22.8%) asthma, and 84 (39.1%) COPD. ACO subjects tended to (a) be predominantly female; (b) be older than asthmatics, (c) be smokers; (d) have worse HRQL in the activity domain; and (d) have more exacerbations. Treatment of ACO and COPD patients differed from that of asthmatics, but not from each other, in the proportion of subjects on maintenance treatment, use of LABA, LAMA, and ICS, alone or in combination, and in the number of inhaler devices used by patients. CONCLUSION: ACO represented >1/3 of patients referred for PFT. Despite a clearly identifiable phenotype, ACO patients received treatment similar to COPD patients, suggesting poor ACO identification. Our data emphasize the need to raise the awareness of ACO among clinicians, in order to guide better recognition and appropriate treatment in individual patients.

The Role of Telomerase and Telomeres in Interstitial Lung Diseases: From Molecules to Clinical Implications.

Telomeres are distal chromosome regions associated with specific protein complexes that protect the chromosome against degradation and aberrations. Telomere maintenance capacity is an essential indication of healthy cell populations, and telomere damage is observed in processes such as malignant transformation, apoptosis, or cell senescence. At a cellular level, telomere damage may result from genotoxic stress, decreased activity of telomerase enzyme complex, dysfunction of shelterin proteins, or changes in expression of telomere-associated RNA such as TERRA. Clinical evidence suggests that mutation of telomerase genes (Tert/Terc) are associated with increased risk of congenital as well as age-related diseases (e.g., pneumonitis, idiopathic pulmonary fibrosis (IPF), dyskeratosis congenita, emphysema, nonspecific interstitial pneumonia, etc.). Thus, telomere length and maintenance can serve as an important prognostic factor as well as a potential target for new strategies of treatment for interstitial lung diseases (ILDs) and associated pulmonary pathologies.

The Effect of Pulmonary Rehabilitation on Non-chronic Obstructive Pulmonary Disease Patients.

BACKGROUND: Pulmonary rehabilitation has shown significant benefit for patients with chronic obstructive pulmonary disease (COPD). The effect on non-COPD pulmonary patients is less well established. OBJECTIVES: To determine whether pulmonary rehabilitation is also beneficial for non-COPD pulmonary patients. METHODS: Clinical and demographic data on non-COPD pulmonary patients who participated in our institutional pulmonary rehabilitation program between January 2009 and December 2016 were collected. Participants engaged in a 60-minute, twice-weekly, ambulatory hospital-based program lasting 12 to 24 sessions. Sessions included both endurance and muscle training as well as healthy lifestyle educational activities. The six-minute walk test (6MWT) and the St. George's Respiratory Questionnaire (SGRQ) were conducted before and after the rehabilitation program. RESULTS: We recruited 214 non-COPD patients, of whom 153 completed at least 12 sessions. Of these, 59 presented with interstitial lung disease (ILD), 18 with non-ILD restrictive lung defects, 25 with asthma, 30 with lung cancer, and 21 with other conditions (e.g., pulmonary hypertension, bronchiectasis) The groups demonstrated significant improvement in 6MWT and in SGRQ scores. Non-COPD patients gained a 61.9 meter (19%) improvement in the 6MWT (P < 0.0001) and 8.3 point reduction in their SGRQ score (P < 0.0001). CONCLUSIONS: Pulmonary rehabilitation is effective in non-COPD pulmonary patients. As such, it should be an integral part of the treatment armament provided to the vast majority of those suffering from chronic respiratory disease.

The effect of body position on pulmonary function: a systematic review.

BACKGROUND: Pulmonary function tests (PFTs) are routinely performed in the upright position due to measurement devices and patient comfort. This systematic review investigated the influence of body position on lung function in healthy persons and specific patient groups. METHODS: A search to identify English-language papers published from 1/1998-12/2017 was conducted using MEDLINE and Google Scholar with key words: body position, lung function, lung mechanics, lung volume, position change, positioning, posture, pulmonary function testing, sitting, standing, supine, ventilation, and ventilatory change. Studies that were quasi-experimental, pre-post intervention; compared ≥2 positions, including sitting or standing; and assessed lung function in non-mechanically ventilated subjects aged ≥18 years were included. Primary outcome measures were forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC, FEV1/FVC), vital capacity (VC), functional residual capacity (FRC), maximal expiratory pressure (PEmax), maximal inspiratory pressure (PImax), peak expiratory flow (PEF), total lung capacity (TLC), residual volume (RV), and diffusing capacity of the lungs for carbon monoxide (DLCO). Standing, sitting, supine, and right- and left-side lying positions were studied. RESULTS: Forty-three studies met inclusion criteria. The study populations included healthy subjects (29 studies), lung disease (nine), heart disease (four), spinal cord injury (SCI, seven), neuromuscular diseases (three), and obesity (four). In most studies involving healthy subjects or patients with lung, heart, neuromuscular disease, or obesity, FEV1, FVC, FRC, PEmax, PImax, and/or PEF values were higher in more erect positions. For subjects with tetraplegic SCI, FVC and FEV1 were higher in supine vs. sitting. In healthy subjects, DLCO was higher in the supine vs. sitting, and in sitting vs. side-lying positions. In patients with chronic heart failure, the effect of position on DLCO varied. CONCLUSIONS: Body position influences the results of PFTs, but the optimal position and magnitude of the benefit varies between study populations. PFTs are routinely performed in the sitting position. We recommend the supine position should be considered in addition to sitting for PFTs in patients with SCI and neuromuscular disease. When treating patients with heart, lung, SCI, neuromuscular disease, or obesity, one should take into consideration that pulmonary physiology and function are influenced by body position.

Sex-linked difference in blood oxygen saturation.

BACKGROUND: It is not known whether SpO2 in healthy volunteers is affected by sex. OBJECTIVE: To evaluate whether there are differences in SpO2 between young healthy adult males and females and to evaluate whether the differences are already present at birth. METHODS: We studied two cohorts of patients. The first one consisted of young adult volunteers (105 males and 102 females). In these patients, SpO2 was measured as well as selected anthropometric variables (height, weight), vital signs (respiratory rate, pulse rate and body temperature) and obtained data on menstrual cycle phase of the female participants. For the second cohort, we reanalyzed data from a previous prospective study that was performed to compare SpO2 of newborns infants born at different altitudes (sea level or 760 m above sea level). MEASUREMENTS AND MAIN RESULTS: In young male adults, mean SpO2 was 97.1% ± 1.2% versus 98.6% ± 1.0% in females (P < .001). This difference remained significant (P = .002) after correction for BMI, BSA and age, variables that were significantly different between sexes in univariate analysis. The SpO2 in females was unaffected by menstrual phase. In contrast to findings in adults, there were no significant differences in SpO2 measurements in newborn infants attributable to sex. CONCLUSIONS: Healthy young female adults have a higher (1.5%) SpO2 than their male counterparts. This difference is not yet present at birth. Further studies are needed to determine the timing of sex-differences, and to better define the mechanism(s) behind this observation.

The association between osteopontin gene polymorphisms, osteopontin expression and sarcoidosis.

BACKGROUND: Sarcoidosis is a systemic inflammatory disease of unknown etiology. Osteopontin (SPP1, OPN) is an extra cellular matrix glycoprotein and cytokine with a known role in granuloma formation and in autoimmune and inflammatory diseases. OBJECTIVE: To determine whether plasma OPN levels are elevated in patients with sarcoidosis and compare the frequency of four single nucleotide polymorphism (SNPs) variants in the OPN gene in sarcoidosis patients compared to healthy controls. METHODS: Demographic and clinical information, radiological studies and pulmonary function tests were evaluated in 113 patients with sarcoidosis and in 79 healthy controls. Blood samples were analyzed for SNPs of the OPN gene and for plasma OPN and CRP levels. Association between clinical features of disease and OPN levels as well as SNP frequencies was determined. RESULTS: Plasma OPN levels were higher in sarcoidosis patients than in healthy subjects, (median: 217 vs 122ng/ml, p<0.001). Area under the curve for receiver operator curves (ROC) was 0.798 (0.686-0.909 95% CI.) No differences were observed between sarcoidosis patients and controls in the frequency of any of the SNPs evaluated. Presence of lung parenchymal involvement was associated with SNP distribution at rs1126772 (p = 0.02). We found no correlation between SNPs distribution and plasma OPN levels. CONCLUSIONS: Osteopontin protein levels are elevated in sarcoidosis. We found no evidence for an association between SNPs on the osteopontin gene and plasma OPN levels or the presence of sarcoidosis, however, an association between genotype and several phenotypic clinical parameters of disease was observed.

Characteristics of Sarcoidosis in Patients with Previous Malignancy: Causality or Coincidence?

BACKGROUND: The association between sarcoidosis and malignancy is poorly defined. Sarcoidosis can precede, be diagnosed concurrently with, or follow malignancy. OBJECTIVES: We describe the clinical and radiological features of patients with sarcoidosis following malignancy to determine whether this association is causal or coincidental. METHODS: We performed a search for all patients with confirmed sarcoidosis following malignancy in our institution during 2001-2015. Clinical and radiological features, bronchoscopic findings, bronchoalveolar lavage cell counts, and pulmonary function tests (PFTs) were reviewed to evaluate patterns of disease involvement. Details of the histological type of cancer, staging, treatment, and follow-up were reviewed. RESULTS: Twenty-nine patients were identified. The most prevalent malignancies were breast cancer and lymphoma (24% each). Based on the incidence of these malignancies, we estimated the incidence of sarcoidosis was 175 times higher after lymphoma and 38 times higher after breast cancer as compared to the general population. Most patients had early stage cancer (stage I, II) (75%), and only 2 patients (7%) had recurrence of their malignancy after diagnosis of sarcoidosis. Sarcoidosis was diagnosed within 5 years of malignancy in over half the patients, 76% were asymptomatic and 69% had normal PFTs. Mediastinal lymphadenopathy was present in 81% of cases, hilar lymphadenopathy in 67%, and pulmonary parenchymal involvement in 41%. Fifty percent of patients had received Adriamycin, 38% cyclophosphamide, and 33% vincristine. CONCLUSIONS: Sarcoidosis following malignancy is indistinguishable from "idiopathic" sarcoidosis, although it is frequently asymptomatic. The high frequency of sarcoidosis after specific cancers but not others, suggests a causative association between malignancy and development of sarcoidosis.

Avoiding Routine Chest Radiography after Transbronchial Biopsy Is Safe.

BACKGROUND: Fiberoptic bronchoscopy (FOB) with transbronchial biopsy (TBB) is complicated by a pneumothorax in 1-4% of cases. Performance of routine post-TBB chest radiography (CXR) results in an extremely low diagnostic yield but nevertheless is the common clinical practice prevailing today. It has previously been suggested that routine post-TBB CXR could be avoided in asymptomatic patients. OBJECTIVE: The objective of this study was to prospectively assess the feasibility and safety of this approach. METHODS: The study group included 201 consecutive patients who underwent FOB with TBB at our institution between January 2009 and September 2014. All subjects completed a preprocedural, a 2-hour postprocedural, and a 24- to 48-hour postprocedural symptom questionnaire (chest pain, dyspnea, and cough). Post-TBB CXR was ordered by the treating physician only if indicated. All cases of pneumothorax were documented. Additionally, the following information was recorded: sex, age, immune status, indication for FOB, total number of biopsies done, lobe sampled, and pulse oxygen saturation. RESULTS: Sixteen CXRs were ordered by the treating physician due to suspected pneumothorax (8%). Early-onset pneumothorax (i.e. within 2 h of TBB) was diagnosed radiologically in 6 patients (3%). Two late-onset pneumothoraxes (1%) were diagnosed more than 24 h after TBB. No pneumothoraxes of clinical significance were diagnosed among asymptomatic patients without significant oxygen desaturation events. CONCLUSIONS: Among asymptomatic patients without significant desaturation events, pneumothorax is rare and usually of negligible clinical significance. Therefore, performance of routine CXR after TBB is not necessary and can be safely avoided in this category of patients.

Overexpression of Telomerase Protects Human and Murine Lung Epithelial Cells from Fas- and Bleomycin-Induced Apoptosis via FLIP Upregulation.

High doses of bleomycin administered to patients with lymphomas and other tumors lead to significant lung toxicity in general, and to apoptosis of epithelial cells, in particular. Apoptosis of alveolar epithelium is an important step in the pathogenesis of bleomycin-induced pulmonary fibrosis. The Fas-FasL pathway is one of the main apoptotic pathways involved. Telomerase is a ribonucleoprotein RNA-dependent DNA polymerase complex consisting of an RNA template and a catalytic protein, telomerase reverse transcriptase (TERT). Telomerase also possess extra-telomeric roles, including modulation of transcription of anti-apoptotic genes, differentiation signals, and more. We hypothesized that telomerase overexpression affects Fas-induced epithelial cell apoptosis by an extra-telomeric role such as regulation of anti-apoptotic genes, specifically FLICE-like inhibitory protein (FLIP). Telomerase in mouse (MLE) and human (A549) lung epithelial cell lines was upregulated by transient transfection using cDNA hTERT expression vector. Telomerase activity was detected using a real-time PCR-based system. Bleomycin, and bleomycin-induced Fas-mediated apoptosis following treatment with anti-Fas activating mAb or control IgG, were assessed by Annexin V staining, FACS analysis, and confocal microscopy; caspase cleavage by Western blot; FLIP or Fas molecule detection by Western blot and flow cytometry. hTERT transfection of lung epithelial cells resulted in a 100% increase in their telomerase activity. Fas-induced lung epithelial cell apoptosis was significantly reduced in hTERT-transfected cells compared to controls in all experiments. Lung epithelial cells with increased telomerase activity had higher levels of FLIP expression but membrane Fas expression was unchanged. Upregulation of hTERT+ in human lung epithelial cells and subsequent downregulation of FLIP by shFLIP-RNA annulled hTERT-mediated resistance to apoptosis. Telomerase-mediated FLIP overexpression may be a novel mechanism to confer protection from apoptosis in bleomycin-exposed human lung epithelial cells.

Cutting edge: FasL(+) immune cells promote resolution of fibrosis.

Immune cells, particularly those expressing the ligand of the Fas-death receptor (FasL), e.g. cytotoxic T cells, induce apoptosis in 'undesirable' self- and non-self-cells, including lung fibroblasts, thus providing a means of immune surveillance. We aimed to validate this mechanism in resolution of lung fibrosis. In particular, we elucidated whether FasL(+) immune cells possess antifibrotic capabilities by induction of FasL-dependent myofibroblast apoptosis and whether antagonists of membrane (m) and soluble (s) FasL can inhibit these capabilities. Myofibroblast interaction with immune cells and its FasL-dependency, were investigated in vitro in coculture with T cells and in vivo, following transplantation into lungs of immune-deficient syngeneic Rag-/- as well as allogeneic SCID mice, and into lungs and air pouches of FasL-deficient (gld) mice, before and after reconstitution of the mice with wild-type (wt), FasL(+) immune cells. We found that myofibroblasts from lungs resolving fibrosis undergo FasL-dependent T cell-induced apoptosis in vitro and demonstrate susceptibility to in vivo immune surveillance in lungs of reconstituted, immune- and FasL-deficient, mice. However, immune-deficient Rag-/- and SCID mice, and gld-mice with FasL-deficiency, endure the accumulation of transplanted myofibroblasts in their lungs with subsequent development of fibrosis. Concomitantly, gld mice, in contrast to chimeric FasL-deficient mice with wt immune cells, accumulated transplanted myofibroblasts in the air pouch model. In humans we found that myofibroblasts from fibrotic lungs secrete sFasL and resist T cell-induced apoptosis, whereas normal lung myofibroblasts are susceptible to apoptosis but acquire resistance upon addition of anti-s/mFasL to the coculture. Immune surveillance, particularly functional FasL(+) immune cells, may represent an important extrinsic component in myofibroblast apoptosis and serve as a barrier to fibrosis. Factors interfering with Fas/FasL-immune cell-myofibroblast interaction such as sFasL secreted by fibrotic-lung myofibroblasts, may abrogate immune surveillance during fibrosis. Annulling these factors may pave a new direction to control human lung fibrosis.