Loïc Guillot

Cutting Edge: The Immunostimulatory Activity of the Lung Surfactant Protein-A Involves Toll-Like Receptor 4

The collectin surfactant protein-A (SP-A) is involved in the innate host defense and the regulation of inflammatory processes in the lung. In this work we investigated the molecular mechanisms related to the immunostimulatory activity of SP-A using macrophages from C3H/HeJ mice, which carry an inactivating mutation in the Toll-like receptor (TLR)4 gene, and TLR4-transfected Chinese hamster ovary cells. We demonstrate that SP-A-induced activation of the NF-κB signaling pathway and up-regulation of cytokine synthesis such as TNF-α and IL-10 are critically dependent on the TLR4 functional complex. These findings support the concept that TLR4 is a pattern recognition receptor that signals in response to both foreign pathogens and endogenous host mediators.

Genome-wide association meta-analysis identifies five modifier loci of lung disease severity in cystic fibrosis

The identification of small molecules that target specific CFTR variants has ushered in a new era of treatment for cystic fibrosis (CF), yet optimal, individualized treatment of CF will require identification and targeting of disease modifiers. Here we use genome-wide association analysis to identify genetic modifiers of CF lung disease, the primary cause of mortality. Meta-analysis of 6,365 CF patients identifies five loci that display significant association with variation in lung disease. Regions on chr3q29 (MUC4/MUC20; P=3.3 × 10−11), chr5p15.3 (SLC9A3; P=6.8 × 10−12), chr6p21.3 (HLA Class II; P=1.2 × 10−8) and chrXq22-q23 (AGTR2/SLC6A14; P=1.8 × 10−9) contain genes of high biological relevance to CF pathophysiology. The fifth locus, on chr11p12-p13 (EHF/APIP; P=1.9 × 10−10), was previously shown to be associated with lung disease. These results provide new insights into potential targets for modulating lung disease severity in CF.

NKX2-1 Mutations Leading to Surfactant Protein Promoter Dysregulation Cause Interstitial Lung Disease in "Brain-Lung-Thyroid Syndrome''

NKX2‐1 (NK2 homeobox 1) is a critical regulator of transcription for the surfactant protein (SP)‐B and ‐C genes (SFTPB and SFTPC, respectively). We identified and functionally characterized two new de novo NKX2‐1 mutations c.493C>T (p.R165W) and c.786_787del2 (p.L263fs) in infants with closely similar severe interstitial lung disease (ILD), hypotonia, and congenital hypothyroidism. Functional analyses using A549 and HeLa cells revealed that NKX2‐1‐p.L263fs induced neither SFTPB nor SFTPC promoter activation and had a dominant negative effect on wild‐type (WT) NKX2‐1. In contrast,NKX2‐1‐p.R165W activated SFTPC, to a significantly greater extent than did WTNKX2‐1,whileSFTPB activation was only significantly reduced in HeLa cells. In accordance with our in vitro data, we found decreased amounts of SP‐B and SP‐C by western blot in bronchoalveolar lavage fluid (patient with p.L263fs) and features of altered surfactant protein metabolism on lung histology (patient with NKX2‐1‐p.R165W). In conclusion, ILD in patients with NKX2‐1 mutations was associated with altered surfactant protein metabolism, and both gain and loss of function of the mutated NKX2‐1 genes on surfactant protein promoters were associated with ILD in “Brain‐Lung‐Thyroid syndrome”.

New surfactant protein C gene mutations associated with diffuse lung disease

Background: Mutations in the surfactant protein C gene (SFTPC) have been recently associated with the development of diffuse lung disease, particularly sporadic and familial interstitial lung disease (ILD). Objective: We have investigated the prevalence and the spectrum of SFTPC mutations in a large cohort of infants and children with diffuse lung disease and suspected with surfactant dysfunction. Method and results: 121 children were first screened for the common SFTPC mutation, p.Ile73Thr (I73T). Ten unrelated patients were shown to carry this mutation. The I73T mutation was inherited in six cases, and appeared de novo in four. The 111 patients without the I73T mutation were screened for the entire coding sequence of SFTPC. Of these, eight (seven unrelated) subjects were shown to carry a novel mutant allele of SFTPC. All these seven new mutations are located in the BRICHOS domain except the p.Val39Ala (V39A) mutation, which is in the surfactant protein C (SP-C) mature peptide. Conclusions: Our results confirm that SFTPC mutations are a frequent cause of diffuse lung disease, and that I73T is the most frequent SFTPC mutation associated with diffuse lung disease.

Characteristics of disorders associated with genetic mutations of surfactant protein C

Study objectives To present diagnosis and treatment modalities of children with interstitial lung disease associated with frequent or rare surfactant protein C gene (SFTPC) mutation. Patients Twenty-two children with chronic lung disease associated with SFTPC mutation in a heterozygous form. Results Mutations located in the BRICHOS domain (‘BRICHOS domain’ group) were identified in six children, whereas 16 children carried mutations located outside the BRICHOS domain (‘non-BRICHOS domain’ group). The median age of onset was 3 (0–24) months. Four patients had neonatal respiratory distress, and symptom onset was associated with acute bronchiolitis in nine patients. Cough, tachypnoea and failure to thrive were initially noticed in all the children. Physical examination at presentation revealed tachypnoea (n=22), clubbing (n=1) and crackles (n=5). Low oxygen saturation (<95%) was observed in 18 patients. The predominant findings on initial high-resolution CT (HRCT) scans were basal-predominant ground-glass opacity (n=21) and cystic spaces (n=3). Bronchoalveolar lavage fluid (BALF) cell counts showed 379±56×103 cells/ml with increased neutrophil percentage (18±4%) independent of the mutation status. The median follow-up was 3.2 (1–18.3) years. Eighteen patients were treated by monthly methylprednisolone pulses associated with oral prednisolone (n=16), hydroxychloroquine (n=11) and/or azithromycin (n=4). Fifteen patients benefited from enteral nutrition. Conclusion Initial diagnosis is based on clinical presentation, radiological features and BALF analysis, but the definitive diagnosis requires genetic analysis. Although progressive improvement was seen in most patients, the development of new therapeutic strategies with minimal side effects is needed.

Benign hereditary chorea: phenotype, prognosis, therapeutic outcome and long term follow-up in a large series with new mutations in the TITF1/NKX2-1 gene

Background Benign hereditary chorea (BHC) is a rare autosomal dominant disorder characterised by childhood onset that tends to improve in adulthood. The associated gene, NKX2-1 (previously called TITF1), is essential for organogenesis of the basal ganglia, thyroid and lungs. The aim of the study was to refine the movement disorders phenotype. We also studied disease course and response to therapy in a large series of genetically proven patients. Methods We analysed clinical, genetic findings and follow-up data in 28 NKX2-1 mutated BHC patients from 13 families. Results All patients had private mutations, including seven new mutations, three previously reported mutations and three sporadic deletions encompassing the NKX2-1 gene. Hypotonia and chorea were present in early infancy, with delayed walking ability (25/28); dystonia, myoclonus and tics were often associated. Attention deficit hyperactivity disorder (ADHD) was present in seven. Among the 14 patients followed-up until adulthood, nine had persistent mild chorea, two had near total resolution of chorea but persistent disabling prominent myoclonus and three recovered completely. Learning difficulties were observed in 20/28 patients, and three had mental retardation. Various combinations of BHC, thyroid (67%) and lung (46%) features were noted. We found no genotype–phenotype correlation. A rapid and sustained beneficial effect on chorea was obtained in 5/8 patients treated with tetrabenazine. Conclusion Early onset chorea preceded by hypotonia is suggestive of BHC. Associated thyroid or respiratory disorders further support the diagnosis and call for genetic studies. Tetrabenazine may be an interesting option to treat disabling chorea.

Molecular and cellular characteristics of ABCA3 mutations associated with diffuse parenchymal lung diseases in children

ABCA3 (ATP-binding cassette subfamily A, member 3) is expressed in the lamellar bodies of alveolar type II cells and is crucial to pulmonary surfactant storage and homeostasis. ABCA3 gene mutations have been associated with neonatal respiratory distress (NRD) and pediatric interstitial lung disease (ILD). The objective of this study was to look for ABCA3 gene mutations in patients with severe NRD and/or ILD. The 30 ABCA3 coding exons were screened in 47 patients with severe NRD and/or ILD. ABCA3 mutations were identified in 10 out of 47 patients, including 2 homozygous, 5 compound heterozygous and 3 heterozygous patients. SP-B and SP-C expression patterns varied across patients. Among patients with ABCA3 mutations, five died shortly after birth and five developed ILD (including one without NRD). Functional studies of p.D253H and p.T1173R mutations revealed that p.D253H and p.T1173R induced abnormal lamellar bodies. Additionally, p.T1173R increased IL-8 secretion in vitro. In conclusion, we identified new ABCA3 mutations in patients with life-threatening NRD and/or ILD. Two mutations associated with ILD acted via different pathophysiological mechanisms despite similar clinical phenotypes.

Lung alveolar epithelium and interstitial lung disease

Interstitial lung diseases (ILDs) comprise a group of lung disorders characterized by various levels of inflammation and fibrosis. The current understanding of the mechanisms underlying the development and progression of ILD strongly suggests a central role of the alveolar epithelium. Following injury, alveolar epithelial cells (AECs) may actively participate in the restoration of a normal alveolar architecture through a coordinated process of re-epithelialization, or in the development of fibrosis through a process known as epithelial-mesenchymal transition (EMT). Complex networks orchestrate EMT leading to changes in cell architecture and behaviour, loss of epithelial characteristics and gain of mesenchymal properties. In the lung, AECs themselves may serve as a source of fibroblasts and myofibroblasts by acquiring a mesenchymal phenotype. This review covers recent knowledge on the role of alveolar epithelium in the pathogenesis of ILD. The mechanisms underlying disease progression are discussed, with a main focus on the apoptotic pathway, the endoplasmic reticulum stress response and the developmental pathway.

Alveolar epithelial cells: master regulators of lung homeostasis.

The lung interfaces with the environment across a continuous epithelium composed of various cell types along the proximal and distal airways. At the alveolar structure level, the epithelium, which is composed of type I and type II alveolar epithelial cells, represents a critical component of lung homeostasis. Indeed, its fundamental role is to provide an extensive surface for gas exchange. Additional functions that act to preserve the capacity for such unique gas transfer have been progressively identified. The alveolar epithelium represents a physical barrier that protects from environmental insults by segregating inhaled foreign agents and regulating water and ions transport, thereby contributing to the maintenance of alveolar surface fluid balance. The homeostatic role of alveolar epithelium relies on the regulated/controlled production of the pulmonary surfactant, which is not only a key determinant of alveolar mechanical stability but also a complex structure that participates in the cross-talk between local cells and the lung immune and inflammatory response. In regard to these critical functions, a major point is the maintenance of alveolar surface integrity, which relies on the renewal capacity of type II alveolar epithelial cells, and the contribution of progenitor populations within the lung.

Azithromycin analogue CSY0073 attenuates lung inflammation induced by LPS challenge

Azithromycin is a macrolide antibiotic with anti‐inflammatory and immunomodulating effects. Long‐term azithromycin therapy in patients with chronic lung diseases such as cystic fibrosis has been associated with increased antimicrobial resistance, emergence of hypermutable strains, ototoxicity and cardiac toxicity. The aim of this study was to assess the anti‐inflammatory effects of the non‐antibiotic azithromycin derivative CSY0073.