The effect of eosinophils on collagen gel contraction and implications for tissue remodelling

Asthma is characterized by an eosinophilic inflammation and a subepithelial fibrosis in the airways. Eosinophils contain several cytotoxic substances, such as eosinophil cationic protein (ECP), which can promote inflammation and cause tissue damage. This has generated the hypothesis that eosinophils may drive remodelling of extracellular matrix (ECM). To investigate the role of eosinophils we used an in vitro model for remodelling, the three-dimensional collagen gel contraction assay. Two sources of eosinophils were used in this study, isolated human peripheral eosinophils (purity > 95%) and stimulated [interleukin (IL)-5, IL-3 and granulocyte macrophage–colony stimulating factor (GM-CSF)] HL-60 clone 15 cells. Human eosinophils or HL-60 cells were cast together with human lung fibroblasts (HFL1) in type I collagen gels. Both types of eosinophils augmented fibroblast-mediated collagen gel contraction in a time and concentration-dependent manner. At 48 h, the gel area in HFL1/eosinophil co-culture was 46·5% ± 0·5 (mean ± s.e.m.) of initial area and in HFL1 culture 52·3% ± 0·1 (P < 0·001). Respective figures for HFL1/stimulated HL-60 co-culture and HFL1 culture only were 44·1% ± 0·5 and 52·4% ± 0·4 (P < 0·001). The release of ECP was increased when fibroblasts were cultured with eosinophils compared to eosinophils cultured alone. In addition, native ECP added to fibroblast gel cultures also augmented contraction. Our results suggest that eosinophils may interact with mesenchymal cells, promoting remodelling of ECM and that ECP constitutes one potential eosinophil-derived mediator driving this process. We conclude that this may be one important mechanism by which eosinophil–ECM interactions will lead to airway tissue remodelling in asthma

Modulation of the Maladaptive Stress Response to Manage Diseases of Protein Folding

<div><p>Diseases of protein folding arise because of the inability of an altered peptide sequence to properly engage protein homeostasis components that direct protein folding and function. To identify global principles of misfolding disease pathology we examined the impact of the local folding environment in alpha-1-antitrypsin deficiency (AATD), Niemann-Pick type C1 disease (NPC1), Alzheimer's disease (AD), and cystic fibrosis (CF). Using distinct models, including patient-derived cell lines and primary epithelium, mouse brain tissue, and <i>Caenorhabditis elegans</i>, we found that chronic expression of misfolded proteins not only triggers the sustained activation of the heat shock response (HSR) pathway, but that this sustained activation is maladaptive. In diseased cells, maladaptation alters protein structure–function relationships, impacts protein folding in the cytosol, and further exacerbates the disease state. We show that down-regulation of this <u>m</u>aladaptive <u>s</u>tress <u>r</u>esponse (MSR), through silencing of HSF1, the master regulator of the HSR, restores cellular protein folding and improves the disease phenotype. We propose that restoration of a more physiological proteostatic environment will strongly impact the management and progression of loss-of-function and gain-of-toxic-function phenotypes common in human disease.</p></div

Functional characterization of putative cilia genes by high-content analysis

siRNA-mediated knockdown of 40 putative ciliome genes reveals distinct roles in cilia formation, cilia elongation, ciliary transport of different cargoes, and signaling capability. Depletion of a subset of genes allows cilia transport to be uncoupled from cilia formation, whereas most genes are required for efficient signaling function