Transcriptomic changes during TGF-ß-mediated differentiation of airway fibroblasts to myofibroblasts.

Asthma is the most common chronic lung disease in children and young adults worldwide. Airway remodelling (including increased fibroblasts and myofibroblasts in airway walls due to chronic inflammation) differentiates asthmatic from non-asthmatic airways. The increase in airway fibroblasts and myofibroblasts occurs via epithelial to mesenchymal transition (EMT) where epithelial cells lose their tight junctions and are transdifferentiated to mesenchymal cells, with further increases in myofibroblasts occurring via fibroblast-myofibroblast transition (FMT). Transforming growth factor (TGF)-ß is the central EMT- and FMT-inducing cytokine. In this study, we have used next generation sequencing to delineate the changes in the transcriptome induced by TGF-ß treatment of WI-38 airway fibroblasts in both the short term and after differentiation into myofibroblasts, to gain an understanding of the contribution of TGF-ß induced transdifferentiation to the asthmatic phenotype. The data obtained from RNAseq analysis was confirmed by quantitative PCR (qPCR) and protein expression investigated by western blotting. As expected, we found that genes coding for intermediates in the TGF-ß signalling pathways (SMADs) were differentially expressed after TGF-ß treatment, SMAD2 being upregulated and SMAD3 being downregulated as expected. Further, genes involved in cytoskeletal pathways (FN1, LAMA, ITGB1) were upregulated in myofibroblasts compared to fibroblasts. Importantly, genes that were previously shown to be changed in asthmatic lungs (ADAMTS1, DSP, TIMPs, MMPs) were similarly differentially expressed in myofibroblasts, strongly suggesting that TGF-ß mediated differentiation of fibroblasts to myofibroblasts may underlie important changes in the asthmatic airway. We also identified new intermediates of signalling pathways (PKB, PTEN) that are changed in myofibroblasts compared to fibroblasts. We have found a significant number of genes that are altered after TGF-ß induced transdifferentiation of WI-38 fibroblasts into myofibroblasts, many of which were expected or predicted. We also identified novel genes and pathways that were affected after TGF-ß treatment, suggesting additional pathways are activated during the transition between fibroblasts and myofibroblasts and may contribute to the asthma phenotype.

Molecular changes during TGFß-mediated lung fibroblast-myofibroblast differentiation: implication for glucocorticoid resistance.

Airway remodeling is an important process in response to repetitive inflammatory-mediated airway wall injuries. This is characterized by profound changes and reorganizations at the cellular and molecular levels of the lung tissue. It is of particular importance to understand the mechanisms involved in airway remodeling, as this is strongly associated with severe asthma leading to devastating airway dysfunction. In this study, we have investigated the transforming growth factor-ß (TGFß, a proinflammatory mediator)-activated fibroblast to myofibroblast transdifferentiation pathway, which plays a key role in asthma-related airway remodeling. We show that TGFß induces fibroblast to myofibroblast transdifferentiation by the expression of αSMA, a specific myofibroblast marker. Furthermore, Smad2/Smad3 gene and protein expression patterns are different between fibroblasts and myofibroblasts. Such a change in expression patterns reveals an important role of these proteins in the cellular phenotype as well as their regulation by TGFß during cellular transdifferentiation. Interestingly, our data show a myofibroblastic TGFß-mediated increase in glucocorticoid receptor (GR) expression and a preferential localization of GR in the nucleus, compared to in fibroblasts. Furthermore, the GRß (nonfunctional GR isoform) is increased relative to GRα (functional isoform) in myofibroblasts. These results are interesting as they support the idea of a GRß-mediated glucocorticoid resistance observed in the severe asthmatic population. All together, we provide evidence that key players are involved in the TGFß-mediated fibroblast to myofibroblast transdifferentiation pathway in a human lung fibroblast cell line. These players could be the targets of new treatments to limit airway remodeling and reverse glucocorticoid resistance in severe asthma.

Nucleocytoplasmic transport of nucleocapsid proteins of enveloped RNA viruses.

Most viruses with non-segmented single stranded RNA genomes complete their life cycle in the cytoplasm of infected cells. However, despite undergoing replication in the cytoplasm, the structural proteins of some of these RNA viruses localize to the nucleus at specific times in the virus life cycle, primarily early in infection. Limited evidence suggests that this enhances successful viral replication by interfering with or inhibiting the host antiviral response. Nucleocapsid proteins of RNA viruses have a well-established, essential cytoplasmic role in virus replication and assembly. Intriguingly, nucleocapsid proteins of some RNA viruses also localize to the nucleus/nucleolus of infected cells. Their nuclear function is less well understood although significant advances have been made in recent years. This review will focus on the nucleocapsid protein of cytoplasmic enveloped RNA viruses, including their localization to the nucleus/nucleolus and function therein. A greater understanding of the nuclear localization of nucleocapsid proteins has the potential to enhance therapeutic strategies as it can be a target for the development of live-attenuated vaccines or antiviral drugs.

Strain dependence of diet-induced NASH and liver fibrosis in obese mice is linked to diabetes and inflammatory phenotype.

BACKGROUND & AIMS: Obese Alms1 mutant (foz/foz) NOD.B10 mice develop diabetes and fibrotic NASH when fed high-fat(HF) diet. To establish whether diabetes or obesity is more closely associated with NASH fibrosis, we compared diabetic foz/foz C57BL6/J with non-diabetic foz/foz BALB/c mice. We also determined hepatic cytokines, growth factors and related profibrotic pathways. METHODS: Male and female foz/foz BALB/c and C57BL6/J mice were fed HF or chow for 24 weeks before determining metabolic indices, liver injury, cytokines, growth factors, pathology/fibrosis and matrix deposition pathways. RESULTS: All foz/foz mice were obese. Hepatomegaly, hyperinsulinemia, hyperglycaemia and hypoadiponectinaemia occurred only in foz/foz C57BL6/J mice, whereas foz/foz BALB/c formed more adipose. Serum ALT, steatosis, ballooning, liver inflammation and NAFLD activity score were worse in C57BL6/J mice. In HF-fed mice, fibrosis was severe in foz/foz C57BL6/J, appreciable in WT C57BL6/J, but absent in foz/foz BALB/c mice. Hepatic mRNA expression of TNF-α, IL-12, IL-4, IL-10 was increased (but not IFN-γ, IL-1ß, IL-17A), and IL-4:IFN-γ ratio (indicating Th-2 predominance) was higher in HF-fed foz/foz C57BL6/J than BALB/c mice. In livers of HF-fed foz/foz C57BL6/J mice, TGF-ß was unaltered but PDGFα and CTGF were increased in association with enhanced α-SMA, CD147and MMP activity. CONCLUSIONS: In mice with equivalent genetic/dietary obesity, NASH development is linked to strain differences in hyperinsulinaemia and hyperglycaemia inversely related to lipid partitioning between adipose and liver. Diabetes-mediated CTGF-regulation of MMPs as well as cytokines/growth factors (Th-2 cytokine predominant, PDGFα, not TGF-ß) mobilized in the resultant hepatic necroinflammatory change may contribute to strain differences in NASH fibrosis.

Dietary modification dampens liver inflammation and fibrosis in obesity-related fatty liver disease.

BACKGROUND: Alms1 mutant (foz/foz) mice develop hyperphagic obesity, diabetes, metabolic syndrome, and fatty liver (steatosis). High-fat (HF) feeding converts pathology from bland steatosis to nonalcoholic steatohepatitis (NASH) with fibrosis, which leads to cirrhosis in humans. OBJECTIVE: We sought to establish how dietary composition contributes to NASH pathogenesis. DESIGN AND METHODS: foz/foz mice were fed HF diet or chow 24 weeks, or switched HF to chow after 12 weeks. Serum ALT, NAFLD activity score (NAS), fibrosis severity, neutrophil, macrophage and apoptosis immunohistochemistry, uncoupling protein (UCP)2, ATP, NF-κB activation/expression of chemokines/adhesion molecules/fibrogenic pathways were determined. RESULT: HF intake upregulated liver fatty acid and cholesterol transporter, CD36. Dietary switch expanded adipose tissue and decreased hepatomegaly by lowering triglyceride, cholesterol ester, free cholesterol and diacylglyceride content of liver. There was no change in lipogenesis or fatty acid oxidation pathways; instead, CD36 was suppressed. These diet-induced changes in hepatic lipids improved NAS, reduced neutrophil infiltration, normalized UCP2 and increased ATP; this facilitated apoptosis with a change in macrophage phenotype favoring M2 cells. Dietary switch also abrogated NF-κB activation and chemokine/adhesion molecule expression, and arrested fibrosis by dampening stellate cell activation. CONCLUSION: Reversion to a physiological dietary composition after HF feeding in foz/foz mice alters body weight distribution but not obesity. This attenuates NASH severity and fibrotic progression by suppressing NF-κB activation and reducing neutrophil and macrophage activation. However, adipose inflammation persists and is associated with continuing apoptosis in the residual fatty liver disease. Taken together, these findings indicate that other measures, such as weight reduction, may be required to fully reverse obesity-related NASH.

A truncating mutation of Alms1 reduces the number of hypothalamic neuronal cilia in obese mice.

Primary cilia are ubiquitous cellular antennae whose dysfunction collectively causes various disorders, including vision and hearing impairment, as well as renal, skeletal, and central nervous system anomalies. One ciliopathy, Alström syndrome, is closely related to Bardet-Biedl syndrome (BBS), sharing amongst other phenotypic features morbid obesity. As the cellular and molecular links between weight regulation and cilia are poorly understood, we used the obese mouse strain foz/foz, bearing a truncating mutation in the Alström syndrome protein (Alms1), to help elucidate why it develops hyperphagia, leading to early onset obesity and metabolic anomalies. Our in vivo studies reveal that Alms1 localizes at the base of cilia in hypothalamic neurons, which are implicated in the control of satiety. Alms1 is lost from this location in foz/foz mice, coinciding with a strong postnatal reduction (∼70%) in neurons displaying cilia marked with adenylyl cyclase 3 (AC3), a signaling protein implicated in obesity. Notably, the reduction in AC3-bearing cilia parallels the decrease in cilia containing two appetite-regulating proteins, Mchr1 and Sstr3, as well as another established Arl13b ciliary marker, consistent with progressive loss of cilia during development. Together, our results suggest that Alms1 maintains the function of neuronal cilia implicated in weight regulation by influencing the maintenance and/or stability of the organelle. Given that Mchr1 and Sstr3 localization to remaining cilia is maintained in foz/foz animals but known to be lost from BBS knockout mice, our findings suggest different molecular etiologies for the satiety defects associated with the Alström syndrome and BBS ciliopathies.

A fresh look at NASH pathogenesis. Part 1: the metabolic movers.

The strong relationship between over-nutrition, central obesity, insulin resistance/metabolic syndrome and non-alcoholic fatty liver disease (NAFLD) suggest pathogenic interactions, but key questions remain. NAFLD starts with over-nutrition, imbalance between energy input and output for which the roles of genetic predisposition and environmental factors (diet, physical activity) are being redefined. Regulation of energy balance operates at both central nervous system and peripheral sites, including adipose and liver. For example, the endocannabinoid system could potentially be modulated to provide effective pharmacotherapy of NAFLD. The more profound the metabolic abnormalities complicating over-nutrition (glucose intolerance, hypoadiponectinemia, metabolic syndrome), the more likely is NAFLD to take on its progressive guise of non-alcoholic steatohepatitis (NASH). Interactions between steatosis and insulin resistance, visceral adipose expansion and subcutaneous adipose failure (with insulin resistance, inflammation and hypoadiponectinemia) trigger amplifying mechanisms for liver disease. Thus, transition from simple steatosis to NASH could be explained by unmitigated hepatic lipid partitioning with failure of local adaptive mechanisms leading to lipotoxicity. In part one of this review, we discuss newer concepts of appetite and metabolic regulation, bodily lipid distribution, hepatic lipid turnover, insulin resistance and adipose failure affecting adiponectin secretion. We review evidence that NASH only occurs when over-nutrition is complicated by insulin resistance and a highly disordered metabolic milieu, the same 'metabolic movers' that promote type 2 diabetes and atheromatous cardiovascular disease. The net effect is accumulation of lipid molecules in the liver. Which lipids and how they cause injury, inflammation and fibrosis will be discussed in part two.

Antibodies against the melanocortin-4 receptor act as inverse agonists in vitro and in vivo.

Functionally active antibodies (Abs) against central G-protein-coupled receptors have not yet been reported. We selected the hypothalamic melanocortin-4 receptor (MC4-R) as a target because of its crucial role in the regulation of energy homeostasis. A 15 amino acid sequence of the N-terminal (NT) domain was used as an antigen. This peptide showed functional activity in surface plasmon resonance experiments and in studies on HEK-293 cells overexpressing the human MC4-R (hMC4-R). Rats immunized against the NT peptide produced specific antibodies, which were purified and characterized in vitro. In HEK-293 cells, rat anti-NT Abs showed specific immunofluorescence labeling of hMC4-R. They reduced the production of cAMP under basal conditions and after stimulation with a synthetic MC4-R agonist. Rats immunized against the NT peptide developed a phenotype consistent with MC4-R blockade, that is, increased food intake and body weight, increased liver and fat pad weight, and elevated plasma triglycerides. In a separate experiment in rats, an increase in food intake could be produced after injection of purified Abs into the third ventricle. Similar results were obtained in rats injected with anti-NT Abs raised in rabbits. Our data show for the first time that active immunization of rats against the NT sequence of the MC4-R results in specific Abs, which appear to stimulate food intake by acting as inverse agonists in the hypothalamus.