[Ventilatory management of SARS-CoV-2 acute respiratory failure]

COVID-19 pneumonia presents several particularities in its clinical presentation (cytokine storm, silent hypoxemia, thrombo-embolic risk) and may lead to a number of acute respiratory distress syndrome (ARDS) phenotypes. While the optimal oxygenation strategy in cases of hypoxemic acute respiratory failure (ARF) is still under debate, ventilatory management of COVID-19-related ARF has confirmed the efficacy of high-flow oxygen therapy and restored interest in other ventilatory approaches such as continuous positive airway pressure (CPAP) and noninvasive ventilation involving a helmet, which due to patient overflow are sometimes implemented outside of critical care units. However, further studies are still needed to determine which patients should be given which oxygenation technique, and under which conditions they require invasive mechanical ventilation, given that delayed initiation potentially burdens prognosis. During invasive mechanical ventilation, ventral decubitus and extracorporeal membrane oxygenation have become increasingly prevalent. While innovative therapies such as awake prone position or lung transplantation have likewise been developed, their indications, modalities and efficacy remain to be determined.

Influence of socio-economic status on functional recovery after ARDS caused by SARS-CoV-2: the multicentre, observational RECOVIDS study

PURPOSE

Survivors after acute respiratory distress syndrome (ARDS) due to coronavirus disease 2019 (COVID-19) are at high risk of developing respiratory sequelae and functional impairment. The healthcare crisis caused by the pandemic hit socially disadvantaged populations. We aimed to evaluate the influence of socio-economic status on respiratory sequelae after COVID-19 ARDS.

METHODS

We carried out a prospective multicenter study in 30 French intensive care units (ICUs), where ARDS survivors were pre-enrolled if they fulfilled the Berlin ARDS criteria. For patients receiving high flow oxygen therapy, a flow ≥ 50 l/min and an FiO2 ≥ 50% were required for enrollment. Socio-economic deprivation was defined by an EPICES (Evaluation de la Précarité et des Inégalités de santé dans les Centres d'Examens de Santé - Evaluation of Deprivation and Inequalities in Health Examination Centres) score ≥ 30.17 and patients were included if they performed the 6-month evaluation. The primary outcome was respiratory sequelae 6 months after ICU discharge, defined by at least one of the following criteria: forced vital capacity < 80% of theoretical value, diffusing capacity of the lung for carbon monoxide < 80% of theoretical value, oxygen desaturation during a 6-min walk test and fibrotic-like findings on chest computed tomography.

RESULTS

Among 401 analyzable patients, 160 (40%) were socio-economically deprived and 241 (60%) non-deprived; 319 (80%) patients had respiratory sequelae 6 months after ICU discharge (81% vs 78%, deprived vs non-deprived, respectively). No significant effect of socio-economic status was identified on lung sequelae (odds ratio (OR), 1.19 [95% confidence interval (CI), 0.72-1.97]), even after adjustment for age, sex, most invasive respiratory support, obesity, most severe P/F ratio (adjusted OR, 1.02 [95% CI 0.57-1.83]).

CONCLUSIONS

In COVID-19 ARDS survivors, socio-economic status had no significant influence on respiratory sequelae 6 months after ICU discharge.

Interest of TAPSE/sPAP ratio for noninvasive pulmonary arterial hypertension risk assessment

BACKGROUND

Although ventriculoarterial coupling is associated with better survival in pulmonary arterial hypertension (PAH), existing PAH risk assessment method has not considered echocardiographic criteria of right ventricular to pulmonary artery coupling. We aimed to test the prognostic value of the echocardiographic tricuspid annular plane systolic excursion/systolic pulmonary artery pressure (TAPSE/sPAP) ratio for noninvasive PAH risk assessment.

METHODS

We retrospectively studied a cohort of 659 incident PAH patients from 4 independent French PH centers (training cohort: n = 306, validation cohort n = 353) who underwent follow-up TAPSE/sPAP measurement in addition to previously validated noninvasive risk stratification variables. The primary composite outcome was 3-year all-cause mortality or lung transplantation from re-evaluation.

RESULTS

Mean age was 55 ± 17 years-old with a majority of female (66%). The three main PAH causes were connective tissue disease (26%), idiopathic (24%) and porto-pulmonary (19%). The primary composite outcome occurred in 71 (23%) patients. Multivariable Cox regression analysis retained 3 noninvasive low-risk criteria as associated with the primary composite outcome: NYHA I-II (p = 0.001), NTproBNP <300 ng/L or BNP <50 ng/L (p = 0.004), and TAPSE/sPAP >0.33 mm/mmHg (p = 0.004). The more the low-risk criteria achieved at follow-up, the better the event-free survival both in the training and validation cohort (log-rank p < 0.001). In the training cohort, the c-index for these 3 criteria, for COMPERA 2.0 and for the noninvasive French Pulmonary Hypertension Network method were 0.75, 95%CI(0.70-0.82), 0.72 95%CI(0.66-0.75), 0.71 95%CI(0.62-0.73), respectively.

CONCLUSION

The 3 following dichotomized low-risk criteria: TAPSE/sPAP >0.33 mm/mmHg, NYHA I-II and NTproBNP <300 ng/L or BNP <50 ng/L allow to identify low-risk PAH patients at follow-up.

High flow nasal cannula oxygen therapy: P-SILI or not P-SILI?

We would like to thank A.S. Saini and co-workers for their interest and their valuable and constructive comments concerning our study [1]. We have shown that, assessed by pulmonary electrical impedance tomography (EIT), high-flow nasal cannula (HFNC) oxygen therapy and noninvasive ventilation (NIV) could generate comparable alveolar recruitment, but NIV generated larger lung volumes. This increase in lung volumes with NIV could be involved in alveolar lesions worsening, induced by the patient's spontaneous ventilation or “patient self-inflicted lung injury” (P-SILI) [2]. However, A.S. Saini and co-workers argue that HFNC could also generate P-SILI and describe the main pathophysiological determinants involved in this deleterious effect. If one can accept this potential risk with HFNC and share the arguments proposed by A.S. Saini and co-workers concerning its mechanisms, we nevertheless wish to make a few additional comments.

The risk of P-SILI with HFNC is controversial and may be less than with NIV. Some physiological mechanisms of the protective effect of HFNC are hypoxaemia correction, reduction of inspiratory efforts and homogeneity of lung volume distribution.https://bit.ly/3skOEKX

High-flow oxygen therapy versus noninvasive ventilation: a randomised physiological crossover study of alveolar recruitment in acute respiratory failure

High-flow nasal cannula (HFNC) oxygen therapy has recently shown clinical benefits in hypoxaemic acute respiratory failure (ARF) patients, while the value of noninvasive ventilation (NIV) remains debated. The primary end-point was to compare alveolar recruitment using global end-expiratory electrical lung impedance (EELI) between HFNC and NIV. Secondary end-points compared regional EELI, lung volumes (global and regional tidal volume variation (V_T)), respiratory parameters, haemodynamic tolerance, dyspnoea and patient comfort between HFNC and NIV, relative to face mask (FM).

A prospective randomised crossover physiological study was conducted in patients with hypoxaemic ARF due to pneumonia. They received alternately HFNC, NIV and FM.

16 patients were included. Global EELI was 4083 with NIV and 2921 with HFNC (p=0.4). Compared to FM, NIV and HFNC significantly increased global EELI by 1810.5 (95% CI 857–2646) and 826 (95% CI 399.5–2361), respectively. Global and regional V_T increased significantly with NIV compared to HFNC or FM, but not between HFNC and FM. NIV yielded a significantly higher pulse oxygen saturation/inspired oxygen fraction ratio compared to HFNC (p=0.03). No significant difference was observed between HFNC, NIV and FM for dyspnoea. Patient comfort score with FM was not significantly different than with HFNC (p=0.1), but was lower with NIV (p=0.001).

This study suggests a potential benefit of HFNC and NIV on alveolar recruitment in patients with hypoxaemic ARF. In contrast with HFNC, NIV increased lung volumes, which may contribute to overdistension and its potentially deleterious effect in these patients.

This study found a potential benefit of HFNC and NIV on alveolar recruitment in patients with hypoxaemic ARF, but NIV also increases lung volumes, which may give rise to overdistension, reinforcing the concept of patient self-inflicted lung injuryhttps://bit.ly/3iRcZDJ

Right ventricular improvement is associated with left ventricular diastolic function and size enhancement in PAH patients: an echocardiographic study

Background

While pulmonary vasodilation therapy improves right ventricular (RV) function in pulmonary arterial hypertension (PAH), data regarding left ventricular (LV) function remain sparse.

Purpose

We aimed to investigate whether PAH therapy improve LV function in PAH patients.

Methods

Between 2002 and 2020, all incident PAH patients from one PH referral centers were included, treated and followed-up according to current ESC/ERS guidelines. All patients had comprehensive echocardiography both investigating right and left ventricular function before and after 1-year of vasodilation therapy. In addition to RV echocardiographic evaluation, we focused on LV ejection fraction from Modified Simpson method, LV diameters by M-mode, transmitral pulsed-wave E/A ratio, Flow to tissue Doppler imaging E/e' ratio, and left atrial size.

Results

126 patients were included (63% female, 57±17 yo), mainly from connectivite tissue associated and idiopathic PAH (24% and 28% respectively) causes. Compared to baseline, 1-year NYHA functional class (p&lt;0.01), NTproBNP plasma level (p&lt;0.001), invasive mean pulmonary arterial pressure (p&lt;0.01) and cardiac index (p&lt;0.01) significantly improved. While LV ejection fraction (p=0.68), LV end-diastolic diameter (p=0.11) as well as LA area and volume (p=0.09) were not significantly enhanced under vasodilation therapy, LV diastolic function, assessed by mitral E wave (p&lt;0.01), tissue doppler imaging mitral e' wave (p=0.04), and E/A ratio (p=0.045) were significantly improved at 1-year. There was a significant correlation between LV end-diastolic diameter (p&lt;0.001) and RV end-diastolic area (p&lt;0.001) owing to the normalization of right- to left ventricular interdependence, as well as between mitral E wave and TAPSE (p=0.045).

Conclusion

By improving RV function, PAH vasodilation therapy enhances LV size and diastolic function and normalizes the biventricular interdependence.

Funding Acknowledgement

Type of funding sources: None.

Inclusion of echocardiographic measure of right ventricular function in the non-invasive French pulmonary arterial hypertension risk stratification method

Background

Although preserved right ventricular (RV) function is consistently associated with better survival in pulmonary arterial hypertension (PAH), the French risk assessment method has not yet considered echocardiographic criteria of RV function.

Purpose

In the present study, we tested the value of tricuspid annular plane systolic excursion (TAPSE) measured by echocardiography for non-invasive PAH risk assessment.

Methods

We retrospectively studied a cohort of 306 incident PAH patients treated in two French expert centers who underwent follow-up TAPSE measurement from echocardiographic apical 4-chamber view in addition to previously validated invasive and non-invasive risk stratification variables. The primary composite outcome was 3-year lung transplantation free survival after follow-up assessment.

Results

At re-evaluation, 66% of patients were in NYHA functional class I-II and mean pulmonary arterial pressure, cardiac index, N-Terminal pro brain natriuretic peptide (NTproBNP), and 6-minute walk distance (6MWD) were 40±16 mmHg, 3.5±1.1 L/min/m2, 270 [interquartile range (IQR) 896] ng/L and 401 (IQR 213) meters, respectively. The primary outcome occurred in 58 (19%) patients. In multivariable Cox regression analysis, NYHA functional class I-II (p=0.02), NTproBNP &lt;300 ng/L or BNP &lt;50 ng/L (p=0.02), 6MWD &gt;440m (p=0.049) and TAPSE≥17 mm (p=0.02) were associated with lung transplantation free survival. TAPSE provided similar information over 6MWD when both were used alternatively to stratify PAH patients at low risk (log-rank&lt;0.001); Harrell's c-index 0.73.

Conclusion

Three dichotomized low-risk criteria (TAPSE, 6MWD and NTproBNP or BNP plasma levels) allow non-invasive risk assessment in PAH.

Funding Acknowledgement

Type of funding sources: None. 3-years transplant-free survival

Right ventricular reverse remodeling assessed by echocardiography as a new goal-oriented treatment strategy in PAH patients

Background

While in heart failure with reduced ejection fraction, left ventricular reverse remodeling assessed by transthoracic echocardiography (TTE) is associated with better prognosis, right ventricular reverse remodeling (RVRR) was less investigated in pulmonary arterial hypertension (PAH)

Purpose

We aimed to investigate whether RVVR assessed by echocardiography could help to stratify PAH patient's prognosis.

Methods

Between 2002 and 2019, all consecutive PAH patients were included, treated and followed in a single PAH center in accordance with the current ESC/ERS guidelines. In addition to regular risk stratification parameters, we measured several echocardiographic RV systolic function and size parameters, including tricuspid annular plane systolic excursion (TAPSE, mm) or RV-end diastolic area (cm2) from apical-4 chamber view both at baseline, 1-year of follow-up as well as their change. Primary composite outcome was three-year transplant-free survival and death from all cause from the 1-year evaluation. Conditional inference trees were used to determine which TTE parameters and cutoffs values were associated with primary outcome from hierarchy of multiple covariates in multivariable Cox regression analysis. Kaplan-Meier curves were then drawn and compared with log-rank test.

Results

126 incident PAH patients were included (63% female, mean age 59±18 yo), mainly due to connectivite-tissue disease and idiopathic PAH (26% and 22% respectively). At baseline, mean pulmonary arterial pressure was 42 (33, 52) mmHg. At 1-y follow-up under pulmonary vasodilation therapy, NYHA (p&lt;0.01), NTproBNP (p&lt;0.01), mean pulmonary arterial pressure (p&lt;0.01) and cardiac index (p&lt;0.01) were significantly improved compared to baseline. Conditional inference trees showed that 1-year TAPSE gain &gt;1 mm and 1-year RV end-diastolic area decreased &gt;2 cm2 were associated with 3-year transplant-free survival in multivariable Cox regression analysis (HR=0.23, 95% CI [0.08–0.61] p=0,0035, HR=0.34, 95% CI [0.12–0.94], p=0.038). Simple score from 0 (absence of RVRR), 1 (partial RVRR) and 2 (complete RVRR), describing the number of TTE parameters reach at 1-year was then investigated. Patients with complete RVRR depicted better transplant-free survival than partial or absence of RVRR, log-rank p&lt;0.001 (figure).

Conclusion

Complete reverse remodeling from right ventricular size and function could represent a new goal-oriented treatment strategy in PAH patients.

Funding Acknowledgement

Type of funding sources: None. RVRR survival curves

Cardiopulmonary Exercise Testing to Assess Persistent Symptoms at 6 Months in People With COVID-19 Who Survived Hospitalization: A Pilot Study

OBJECTIVE

The aim of this pilot study was to assess physical fitness and its relationship with functional dyspnea in survivors of COVID-19 6 months after their discharge from the hospital.

METHODS

Data collected routinely from people referred for cardiopulmonary exercise testing (CPET) following hospitalization for COVID-19 were retrospectively analyzed. Persistent dyspnea was assessed using the modified Medical Research Council dyspnea scale.

RESULTS

Twenty-three people with persistent symptoms were referred for CPET. Mean modified Medical Research Council dyspnea score was 1 (SD = 1) and was significantly associated with peak oxygen uptake (VO2peak; %) (rho = -0.49). At 6 months, those hospitalized in the general ward had a relatively preserved VO2peak (87% [SD = 20]), whereas those who had been in the intensive care unit had a moderately reduced VO2peak (77% [SD = 15]). Of note, the results of the CPET revealed that, in all individuals, respiratory equivalents were high, power-to-weight ratios were low, and those who had been in the intensive care unit had a relatively low ventilatory efficiency (mean VE/VCO2 slope = 34 [SD = 5]). Analysis of each individual showed that none had a breathing reserve <15% or 11 L/min, all had a normal exercise electrocardiogram, and 4 had a heart rate >90%.

CONCLUSION

At 6 months, persistent dyspnea was associated with reduced physical fitness. This study offers initial insights into the mid-term physical fitness of people who required hospitalization for COVID-19. It also provides novel pathophysiological clues about the underlaying mechanism of the physical limitations associated with persistent dyspnea. Those with persistent dyspnea should be offered a tailored rehabilitation intervention, which should probably include muscle reconditioning, breathing retraining, and perhaps respiratory muscle training.

IMPACT

This study is the first, to our knowledge, to show that a persistent breathing disorder (in addition to muscle deconditioning) can explain persistent symptoms 6 months after hospitalization for COVID-19 infection and suggests that a specific rehabilitation intervention is warranted.

Long-term survival following initiation of home non-invasive ventilation: a European study

INTRODUCTION

Although home non-invasive ventilation (NIV) is increasingly used to manage patients with chronic ventilatory failure, there are limited data on the long-term outcome of these patients. Our aim was to report on home NIV populations and the long-term outcome from two European centres.

METHODS

Cohort analysis including all patients established on home NIV from two European centres between 2008 and 2014.

RESULTS

Home NIV was initiated in 1746 patients to treat chronic ventilatory failure caused by (1) obesity hypoventilation syndrome±obstructive sleep apnoea (OHS±OSA) (29.5%); (2) neuromuscular disease (NMD) (22.7%); and (3) obstructive airway diseases (OAD) (19.1%). Overall cohort median survival following NIV initiation was 6.6 years. Median survival varied by underlying aetiology of respiratory failure: rapidly progressive NMD 1.1 years, OAD 2.7 years, OHS±OSA >7 years and slowly progressive NMD >7 years. Multivariate analysis demonstrated higher mortality in patients with rapidly progressive NMD (HR 4.78, 95% CI 3.38 to 6.75), COPD (HR 2.25, 95% CI 1.64 to 3.10), age >60 years at initiation of home NIV (HR 2.41, 95% CI 1.92 to 3.02) and NIV initiation following an acute admission (HR 1.38, 95% CI 1.13 to 1.68). Factors associated with lower mortality were NIV adherence >4 hours per day (HR 0.64, 95% CI 0.51 to 0.79), OSA (HR 0.51, 95% CI 0.31 to 0.84) and female gender (HR 0.79, 95% CI 0.65 to 0.96).

CONCLUSION

The mortality rate following initiation of home NIV is high but varies significantly according to underlying aetiology of respiratory failure. In patients with chronic respiratory failure, initiation of home NIV following an acute admission and low levels of NIV adherence are poor prognostic features and may be amenable to intervention.

Prognostic importance of Kidney, Heart and Interstitial lung diseases (KHI triad) in PH: A machine learning study

BACKGROUND

Pulmonary hypertension (PH) is a heterogeneous, severe and progressive disease with an impact on quality of life and life-expectancy despite specific therapies.

AIMS

(i) to compare prognosis significance of each PH subgroup in a cohort from a referral center, (ii) to identify phenotypically distinct high-risk PH patient using machine learning.

METHODS

Patients with PH were included from 2002 to 2019 and routinely followed-up. We collected clinical, laboratory, imaging and hemodynamic variables. Four-year survival rate of each subgroups was then compared. Next, phenotypic domains were imputed with 5 eigenvectors for missing values and filtered if the Pearson correlation coefficient was>0.6. Thereafter, agglomerative hierarchical clustering was used for grouping phenotypic variables and patients: a heat map was generated and participants were separated using Penalized Model-Based Clustering. P<0.05 was considered significant.

RESULTS

328 patients were prospectively included (mean age 63±18 yo, 46% male). PH secondary to left heart disease (PH-LHD) and lung disease (PH-LD) had a significantly increased mortality compared to pulmonary arterial hypertension (PAH) patients: HR=2.43, 95%CI=(1.24-4.73) and 2.95, 95%CI=(1.43-6.07) respectively. 25 phenotypic domains were pinpointed and 3 phenogroups identified. Phenogroup 3 had a significantly increased mortality (log-rank P=0.046) compared to the others and was remarkable for predominant pulmonary disease in older male, accumulating cardiovascular risk factors, and simultaneous three major comorbidities: coronary artery disease, chronic kidney disease and interstitial lung disease.

CONCLUSION

PH-LHD and PH-LD has 2-fold and 3-fold increase in mortality, respectively compared with PAH. PH patients with simultaneous kidney-cardiac-pulmonary comorbidities were identified as having high-risk of mortality. Specific targeted therapy in this phenogroup should be prospectively evaluated.

Clinical phenotypes and outcomes of precapillary pulmonary hypertension of sickle cell disease

Rationale

Precapillary pulmonary hypertension (PH) is a devastating complication of sickle cell disease (SCD). Little is known about the influence of the SCD genotype on PH characteristics.

Objectives

To describe clinical phenotypes and outcomes of precapillary PH due to SCD according to disease genotype.

Methods

A nationwide multicentre retrospective study including all patients with SCD-related precapillary PH from the French PH Registry was conducted. Clinical characteristics and outcomes according to SCD genotype were analysed.

Results

58 consecutive SCD patients with precapillary PH were identified, of whom 41 had homozygous for haemoglobin S (SS) SCD, three had S-β0 thalassaemia (S-β0 thal) and 14 had haemoglobin SC disease (SC). Compared to SC patients, SS/S-β0 thal patients were characterised by lower 6-min walk distance (p=0.01) and lower pulmonary vascular resistance (p=0.04). Mismatched segmental perfusion defects on lung scintigraphy were detected in 85% of SC patients and 9% of SS/S-β0 thal patients, respectively, and 50% of SS/S-β0 thal patients had heterogeneous lung perfusion without segmental defects. After PH diagnosis, 31 patients (53%) received medical therapies approved for pulmonary arterial hypertension, and chronic red blood cell exchange was initiated in 23 patients (40%). Four patients were managed for chronic thromboembolic PH by pulmonary endarterectomy (n=1) or balloon pulmonary angioplasty (n=3). Overall survival was 91%, 80% and 60% at 1, 3 and 5 years, respectively, without influence of genotype on prognosis.

Conclusions

Patients with precapillary PH related to SCD have a poor prognosis. Thrombotic lesions appear as a major component of PH related to SCD, more frequently in SC patients.

Pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a chronic and progressive disease leading to right heart failure and ultimately death if untreated. The first classification of PH was proposed in 1973. In 2008, the fourth World Symposium on PH held in Dana Point (California, USA) revised previous classifications. Currently, PH is devided into five subgroups. Group 1 includes patients suffering from idiopathic or familial PAH with or without germline mutations. Patients with a diagnosis of PAH should systematically been screened regarding to underlying mutations of BMPR2 gene (bone morphogenetic protein receptor type 2) or more rarely of ACVRL1 (activine receptor-like kinase type 1), ENG (endogline) or Smad8 genes. Pulmonary veno occusive disease and pulmonary capillary hemagiomatosis are individualized and designated as clinical group 1'. Group 2 'Pulmonary hypertension due to left heart diseases' is divided into three sub-groups: systolic dysfonction, diastolic dysfonction and valvular dysfonction. Group 3 'Pulmonary hypertension due to respiratory diseases' includes a heterogenous subgroup of respiratory diseases like PH due to pulmonary fibrosis, COPD, lung emphysema or interstitial lung disease for exemple. Group 4 includes chronic thromboembolic pulmonary hypertension without any distinction of proximal or distal forms. Group 5 regroup PH patients with unclear multifactorial mechanisms. Invasive hemodynamic assessment with right heart catheterization is requested to confirm the definite diagnosis of PH showing a resting mean pulmonary artery pressure (mPAP) of ≥ 25 mmHg and a normal pulmonary capillary wedge pressure (PCWP) of ≤ 15 mmHg. The assessment of PCWP may allow the distinction between pre-capillary and post-capillary PH (PCWP > 15 mmHg). Echocardiography is an important tool in the management of patients with underlying suspicion of PH. The European Society of Cardiology and the European Respiratory Society (ESC-ERS) guidelines specify its role, essentially in the screening proposing criteria for estimating the presence of PH mainly based on tricuspid regurgitation peak velocity and systolic artery pressure (sPAP). The therapy of PAH consists of non-specific drugs including oral anticoagulation and diuretics as well as PAH specific therapy. Diuretics are one of the most important treatment in the setting of PH because right heart failure leads to fluid retention, hepatic congestion, ascites and peripheral edema. Current recommendations propose oral anticoagulation aiming for targeting an International Normalized Ratio (INR) between 1.5-2.5. Target INR for patients displaying chronic thromboembolic PH is between 2–3. Better understanding in pathophysiological mechanisms of PH over the past quarter of a century has led to the development of medical therapeutics, even though no cure for PAH exists. Several specific therapeutic agents were developed for the medical management of PAH including prostanoids (epoprostenol, trepoprostenil, iloprost), endothelin receptor antagonists (bosentan, ambrisentan) and phosphodiesterase type 5 inhibitors (sildenafil, tadalafil). This review discusses the current state of art regarding to epidemiologic aspects of PH, diagnostic approaches and the current classification of PH. In addition, currently available specific PAH therapy is discussed as well as future treatments.

Nuclear factor erythroid 2-related factor 2 nuclear translocation induces myofibroblastic dedifferentiation in idiopathic pulmonary fibrosis

AIMS

Oxidants have been implicated in the pathophysiology of idiopathic pulmonary fibrosis (IPF), especially in myofibroblastic differentiation. We aimed at testing the hypothesis that nuclear factor erythroid 2-related factor 2 (Nrf2), the main regulator of endogenous antioxidant enzymes, is involved in fibrogenesis via myofibroblastic differentiation. Fibroblasts were cultured from the lungs of eight controls and eight IPF patients. Oxidants-antioxidants balance, nuclear Nrf2 expression, and fibroblast phenotype (α-smooth muscle actin and collagen I expression, proliferation, migration, and contraction) were studied under basal conditions and after Nrf2 knockdown or activation by Nrf2 or Keap1 siRNA transfection. The effects of sulforaphane (SFN), an Nrf2 activator, on the fibroblast phenotype were tested under basal and pro-fibrosis conditions (transforming growth factor β [TGF-β]).

RESULTS

Decreased Nrf2 expression was associated with a myofibroblast phenotype in IPF compared with control fibroblasts. Nrf2 knockdown induced oxidative stress and myofibroblastic differentiation in control fibroblasts. Conversely, Nrf2 activation increased antioxidant defences and myofibroblastic dedifferentation in IPF fibroblasts. SFN treatment decreased oxidants, and induced Nrf2 expression, antioxidants, and myofibroblastic dedifferentiation in IPF fibroblasts. SFN inhibited TGF-β profibrotic deleterious effects in IPF and control fibroblasts and restored antioxidant defences. Nrf2 knockdown abolished SFN antifibrosis effects, suggesting that they were Nrf2 mediated.

INNOVATION AND CONCLUSION

Our findings confirm that decreased nuclear Nrf2 plays a role in myofibroblastic differentiation and that SFN induces human pulmonary fibroblast dedifferentiation in vitro via Nrf2 activation. Thus, Nrf2 could be a novel therapeutic target in IPF.

[Protective role of Nrf2 in the lungs against oxidative airway diseases]

Airways are continually exposed to multiple inhaled oxidants and protect themselves with cellular and extracellular antioxidants throughout the epithelial lining fluid and tissues. Oxidative stress, resulting from the increased oxidative burden and decreased level of antioxidant proteins, is involved in cellular and tissue damage related to the pathogenesis of many acute and chronic respiratory diseases. Evidence suggested that nuclear factor erythroid-2-related factor 2 (Nrf2), a transcription factor that controls antioxidant response element (ARE)-regulated antioxidant and cytoprotective genes has an essential protective role in the lungs against oxidative airway diseases. Therefore, Nrf2 promises to be an attractive therapeutic target for intervention and prevention strategies in respiratory diseases. We have reviewed major findings on the mechanisms of lung protection against oxidative stress by Nrf2 and the current literature suggesting that Nrf2 is a valuable therapeutic target.

NRF2 targeting: a promising therapeutic strategy in chronic obstructive pulmonary disease

Several convergent destructive mechanisms such as oxidative stress, alveolar cell apoptosis, extracellular matrix proteolysis and chronic inflammation contribute to chronic obstructive pulmonary disease (COPD) development. Evidence suggests that oxidative stress contributes to the pathophysiology of COPD, particularly during exacerbations. Nuclear factor erythroid-2-related factor 2 (NRF2), a transcription factor expressed predominantly in epithelium and alveolar macrophages, has an essential protective role in the lungs through the activation of antioxidant response element-regulated antioxidant and cytoprotective genes. Animal models and human studies have identified NRF2 and several NRF2 target genes as a protective system against inflammation and oxidative stress from cigarette smoke, a major causative factor in COPD development. Hence, NRF2 targeting might provide clinical benefit by reducing both oxidative stress and inflammation in COPD.