3'UTR shortening of HAS2 promotes hyaluronan hyper-synthesis and bioenergetic dysfunction in pulmonary hypertension.

Pulmonary hypertension (PH) comprises a diverse group of disorders that share a common pathway of pulmonary vascular remodeling leading to right ventricular failure. Development of anti-remodeling strategies is an emerging frontier in PH therapeutics that requires a greater understanding of the interactions between vascular wall cells and their extracellular matrices. The ubiquitous matrix glycan, hyaluronan (HA), is markedly elevated in lungs from patients and experimental models with PH. Herein, we identified HA synthase-2 (HAS2) in the pulmonary artery smooth muscle cell (PASMC) layer as a predominant locus of HA dysregulation. HA upregulation involves depletion of NUDT21, a master regulator of alternative polyadenylation, resulting in 3'UTR shortening and hyper-expression of HAS2. The ensuing increase of HAS2 and hyper-synthesis of HA promoted bioenergetic dysfunction of PASMC characterized by impaired mitochondrial oxidative capacity and a glycolytic shift. The resulting HA accumulation stimulated pro-remodeling phenotypes such as cell proliferation, migration, apoptosis-resistance, and stimulated pulmonary artery contractility. Transgenic mice, mimicking HAS2 hyper-synthesis in smooth muscle cells, developed spontaneous PH, whereas targeted deletion of HAS2 prevented experimental PH. Pharmacological blockade of HAS2 restored normal bioenergetics in PASMC, ameliorated cell remodeling phenotypes, and reversed experimental PH in vivo. In summary, our results uncover a novel mechanism of HA hyper-synthesis and downstream effects on pulmonary vascular cell metabolism and remodeling.

Transcriptomic and Epigenetic Profiling of Fibroblasts in Idiopathic Pulmonary Fibrosis.

Idiopathic pulmonary fibrosis (IPF), a devastating, fibroproliferative, chronic lung disorder, is associated with expansion of fibroblasts/myofibroblasts, which leads to excessive production and deposition of extracellular matrix. IPF is typically clinically identified as end-stage lung disease, after fibrotic processes are well-established and advanced. Fibroblasts have been shown to be critically important in the development and progression of IPF. We hypothesize that differential chromatin access can drive genetic differences in IPF fibroblasts relative to healthy fibroblasts. To this end, we performed assay of transposase-accessible chromatin sequencing to identify differentially accessible regions within the genomes of fibroblasts from healthy and IPF lungs. Multiple motifs were identified to be enriched in IPF fibroblasts compared with healthy fibroblasts, including binding motifs for TWIST1 and FOXA1. RNA sequencing identified 93 genes that could be annotated to differentially accessible regions. Pathway analysis of the annotated genes identified cellular adhesion, cytoskeletal anchoring, and cell differentiation as important biological processes. In addition, single nucleotide polymorphism analysis showed that linkage disequilibrium blocks of IPF risk single nucleotide polymorphisms with IPF-accessible regions that have been identified to be located in genes that are important in IPF, including MUC5B, TERT, and TOLLIP. Validation studies in isolated lung tissue confirmed increased expression for TWIST1 and FOXA1 in addition to revealing SHANK2 and CSPR2 as novel targets. Thus, modulation of differential chromatin access may be an important mechanism in the pathogenesis of lung fibrosis.

Regulation of IL-4 receptor signaling by STUB1 in lung inflammation.

RATIONALE: IL-4Rα, the common receptor component for IL-4 and IL-13, plays a critical role in IL-4- and IL-13-mediated signaling pathways that regulate airway inflammation and remodeling. However, the regulatory mechanisms underlying IL-4Rα turnover and its signal termination remain elusive. OBJECTIVES: To evaluate the role of STUB1 (STIP1 homology and U-Box containing protein 1) in regulating IL-4R signaling in airway inflammation. METHODS: The roles of STUB1 in IL-4Rα degradation and its signaling were investigated by immunoblot, immunoprecipitation, and flow cytometry. The involvement of STUB1 in airway inflammation was determined in vivo by measuring lung inflammatory cells infiltration, mucus production, serum lgE levels, and alveolar macrophage M2 activation in STUB1(-/-) mice. STUB1 expression was evaluated in airway epithelium of patients with asthma and lung tissues of subjects with chronic obstructive pulmonary disease. MEASUREMENTS AND MAIN RESULTS: STUB1 interacted with IL-4Rα and targeted it for ubiquitination-mediated proteasomal degradation, terminating IL-4 or IL-13 signaling. STUB1 knockout cells showed increased levels of IL-4Rα and sustained STAT6 activation, whereas STUB1 overexpression reduced IL-4Rα levels. Mice deficient in STUB1 had spontaneous airway inflammation, alternative M2 activation of alveolar macrophage, and increased serum IgE. STUB1 levels were increased in airways of subjects with asthma or chronic obstructive pulmonary disease, suggesting that up-regulation of STUB1 might be an important feedback mechanism to dampen IL-4R signaling in airway inflammation. CONCLUSIONS: Our study identified a previously uncharacterized role for STUB1 in regulating IL-4R signaling, which might provide a new strategy for attenuating airway inflammation.

Autophagy and role in asthma.

PURPOSE OF REVIEW: Asthma is a common worldwide respiratory illness with significant morbidity and mortality. The disease is characterized by airway inflammation with involvement of multiple biological pathways. Genetic predisposition and increased susceptibility to severe respiratory viral infections are well known clinical features of asthma. Autophagy is an evolutionarily conserved cellular degradation process with significant impact on immunity and antiviral response. In this review we have described the role of autophagy in immune cell survival, proliferation and function. Autophagy has complex effects on immune response involved in inflammation, specifically Th2 immune response. Common respiratory viruses are associated with increased morbidity and mortality in asthmatic patients. RECENT FINDINGS: We describe recent studies showing the effect of autophagy on replication and immune response to common respiratory viruses. The role of autophagy in asthma has recently been investigated. Two studies have been published describing the association of autophagy with asthma. Genetic polymorphism in specific autophagy genes is associated with asthma and influences gene expression in an experimental in-vivo model. SUMMARY: These studies provide us with a window into the possible role of autophagy in asthma and offer new clues to pathogenesis. Modulation of autophagy has the potential to develop into a new therapeutic avenue to treat this common respiratory ailment.

Functional variant in the autophagy-related 5 gene promotor is associated with childhood asthma.

RATIONALE AND OBJECTIVE: Autophagy is a cellular process directed at eliminating or recycling cellular proteins. Recently, the autophagy pathway has been implicated in immune dysfunction, the pathogenesis of inflammatory disorders, and response to viral infection. Associations between two genes in the autophagy pathway, ATG5 and ATG7, with childhood asthma were investigated. METHODS: Using genetic and experimental approaches, we examined the association of 13 HapMap-derived tagging SNPs in ATG5 and ATG7 with childhood asthma in 312 asthmatic and 246 non-allergic control children. We confirmed our findings by using independent cohorts and imputation analysis. Finally, we evaluated the functional relevance of a disease associated SNP. MEASUREMENTS AND MAIN RESULTS: We demonstrated that ATG5 single nucleotide polymorphisms rs12201458 and rs510432 were associated with asthma (p = 0.00085 and 0.0025, respectively). In three independent cohorts, additional variants in ATG5 in the same LD block were associated with asthma (p<0.05). We found that rs510432 was functionally relevant and conferred significantly increased promotor activity. Furthermore, Atg5 expression was increased in nasal epithelium of acute asthmatics compared to stable asthmatics and non-asthmatic controls. CONCLUSION: Genetic variants in ATG5, including a functional promotor variant, are associated with childhood asthma. These results provide novel evidence for a role for ATG5 in childhood asthma.