Asthma exacerbations are among the most frequent causes of hospitalization during childhood, but the underlying mechanisms are poorly understood. We performed a genome-wide association study of a specific asthma phenotype characterized by recurrent, severe exacerbations occurring between 2 and 6 years of age in a total of 1,173 cases and 2,522 controls. Cases were identified from national health registries of hospitalization, and DNA was obtained from the Danish Neonatal Screening Biobank. We identified five loci with genome-wide significant association. Four of these, GSDMB, IL33, RAD50 and IL1RL1, were previously reported as asthma susceptibility loci, but the effect sizes for these loci in our cohort were considerably larger than in the previous genome-wide association studies of asthma. We also obtained strong evidence for a new susceptibility gene, CDHR3 (encoding cadherin-related family member 3), which is highly expressed in airway epithelium. These results demonstrate the strength of applying specific phenotyping in the search for asthma susceptibility genes.

No abstract

Matrix stiffening with downstream activation of mechanosensitive pathways is strongly implicated in progressive fibrosis; however, pathologic changes in extracellular matrix (ECM) that initiate mechano-homeostasis dysregulation are not defined in human disease. By integrated multiscale biomechanical and biological analyses of idiopathic pulmonary fibrosis lung tissue, we identify that increased tissue stiffness is a function of dysregulated post-translational collagen cross-linking rather than any collagen concentration increase whilst at the nanometre-scale collagen fibrils are structurally and functionally abnormal with increased stiffness, reduced swelling ratio, and reduced diameter. In ex vivo and animal models of lung fibrosis, dual inhibition of lysyl oxidase-like (LOXL) 2 and LOXL3 was sufficient to normalise collagen fibrillogenesis, reduce tissue stiffness, and improve lung function in vivo. Thus, in human fibrosis, altered collagen architecture is a key determinant of abnormal ECM structure-function, and inhibition of pyridinoline cross-linking can maintain mechano-homeostasis to limit the self-sustaining effects of ECM on progressive fibrosis.

In this study we addressed the role of the nuclear factor (NF)-kappaB1/p50 subunit in chronic injury of the liver by determining the inflammatory and fibrotic responses of nfkappab1-null mice in an experimental model that mimics chronic liver disease. Mice received repeated hepatic injuries throughout 12 weeks by intraperitoneal injection of the hepatotoxin carbon tetrachloride. In response nfkappab1(-/-) mice developed more severe neutrophilic inflammation and fibrosis compared to nfkappab1(+/+) mice. This phenotype was associated with elevated hepatic expression of tumor necrosis factor (TNF)-alpha, which was localized to regions of the liver associated with inflammation and fibrosis. Hepatic stellate cells are important regulators of hepatic inflammatory and fibrogenic events but normally do not express TNF-alpha. Hepatic stellate cells derived from nfkappab1(-/-) mice expressed TNF-alpha promoter activity, mRNA, and protein. By contrast the expression of other NF-kappaB-responsive genes (ICAM1 and interleukin-6) was similar between nfkappab1(-/-) and nfkappab1(+/+) cells. We provide experimental evidence that the inappropriate expression of TNF-alpha by nfkappab1(-/-) cells is because of lack of a p50-dependent histone deacetylase 1 (HDAC1)-mediated repression of TNF-alpha gene transcription. Taken together these data indicate that the p50 NF-kappaB subunit plays a critical protective role in the injured liver by limiting the expression of TNF-alpha and its recruitment of inflammatory cells.

In the injured liver hepatic stellate cells (HSCs) undergo a dramatic phenotypic transformation known as ''activation'' in which they become myofibroblast-like and express high levels of the tissue inhibitor of metalloproteinase 1 (TIMP-1). HSC activation is accompanied by transactivation of the TIMP-1 promoter. Truncation mutagenesis studies delineated a minimal active promoter consisting of nucleotides ؊102 to ؉60 relative to the major start site for transcription. Removal of an AP-1 site located at nucleotides ؊93 to ؊87 caused almost a complete loss of promoter activity.

Hepatic stellate cells (HSCs)1 represent up to 15% of the resident cells of the liver and play a pivotal role in the cellular pathology underlying hepatic fibrosis (1). In response to liver injury of any etiology, the normally quiescent HSC undergoes a progressive process of trans-differentiation into a proliferating myofibroblast-like activated HSC (1). Through increased secretion of extracellular matrix proteins and the tissue inhibitor of metalloproteinases (TIMP)-1 and TIMP-2, activated HSCs are responsible for deposition and accumulation of the majority of the excess extracellular matrix in the fibrotic liver (2). Furthermore, activated HSCs can contribute to the fibrogenic process through their ability to secrete and respond to a wide range of cytokines and growth factors (3).Details of the molecular events that regulate HSC activation are beginning to be unraveled, as is the potential for specific members of the AP-1, NF-B, and Kruppel-like transcription factor families to control key profibrogenic features of the activated HSCs (1, 4 -6). Putative AP-1 and NF-B sites are found in the promoters of many genes that are induced upon HSC activation and contribute to the fibrotic process, including TIMP-1 (AP-1), IL-6 (AP-1 and NF-B), and ICAM-1 (NF-B) (4, 5, 7). Since in vivo activation of HSCs can be closely mimicked by culturing HSCs isolated from normal rat liver on plastic and in the presence of serum, it has been possible to investigate the transcriptional control of potential profibrotic genes during HSC activation (1). Investigators including ourselves have previously demonstrated that basal and cytokine/ growth factor-inducible transcription of these genes is dependent on interaction of specific AP-1 and NF-B (Rel) protein dimers with their putative promoter-binding sites (4 -6). These observations indicate that these inducible transcription factors are likely to play a key role in the activation and/or persistence of myofibroblast-like HSCs. Recent studies have identified target genes of NF-B (IL-6 and ICAM-1) and have also indicated that NF-B may protect activated HSCs against apoptosis (5,6,8). Less attention has been directed at studying the role played by AP-1 in HSC activation. Although in vitro studies have shown that activated HSCs express inducible AP-1 DNA-binding activity (4, 9, 10), there is little direct evidence that AP-1 plays a key role in the transcriptional regulation of the activated HSC phenotype. Chen and Davis (11, 12) recently re-

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Idiopathic pulmonary fibrosis (IPF) is a progressive disease that usually affects elderly people. It has a poor prognosis and there are limited therapies. Since epigenetic alterations are associated with IPF, histone deacetylase (HDAC) inhibitors offer a novel therapeutic strategy to address the unmet medical need. This study investigated the potential of romidepsin, an FDA-approved HDAC inhibitor, as an anti-fibrotic treatment and evaluated biomarkers of target engagement that may have utility in future clinical trials. The anti-fibrotic effects of romidepsin were evaluated both in vitro and in vivo together with any harmful effect on alveolar type II cells (ATII). Bronchoalveolar lavage fluid (BALF) from IPF or control donors was analyzed for the presence of lysyl oxidase (LOX). In parallel with an increase in histone acetylation, romidepsin potently inhibited fibroblast proliferation, myofibroblast differentiation and LOX expression. ATII cell numbers and their lamellar bodies were unaffected. In vivo, romidepsin inhibited bleomycin-induced pulmonary fibrosis in association with suppression of LOX expression. LOX was significantly elevated in BALF of IPF patients compared to controls. These data show the anti-fibrotic effects of romidepsin, supporting its potential use as novel treatment for IPF with LOX as a companion biomarker for evaluation of early on-target effects.