Tissue fibrosis is characterized by uncontrolled deposition and diminished clearance of fibrous connective tissue proteins, ultimately leading to organ scarring. Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) have recently emerged as pivotal drivers of mesenchymal cell activation in human fibrosis. Therapeutic strategies inhibiting YAP and TAZ have been hindered by the critical role that these proteins play in regeneration and homeostasis in different cell types. Here, we find that the Gαs-coupled dopamine receptor D1 (DRD1) is preferentially expressed in lung and liver mesenchymal cells relative to other resident cells of these organs. Agonism of DRD1 selectively inhibits YAP/TAZ function in mesenchymal cells and shifts their phenotype from profibrotic to fibrosis resolving, reversing in vitro extracellular matrix stiffening and in vivo tissue fibrosis in mouse models. Aromatic l-amino acid decarboxylase [DOPA decarboxylase (DDC)], the enzyme responsible for the final step in biosynthesis of dopamine, is decreased in the lungs of subjects with idiopathic pulmonary fibrosis, and its expression inversely correlates with disease severity, consistent with an endogenous protective role for dopamine signaling that is lost in pulmonary fibrosis. Together, these findings establish a pharmacologically tractable and cell-selective approach to targeting YAP/TAZ via DRD1 that reverses fibrosis in mice.

Idiopathic pulmonary fibrosis (IPF) is a fatal ageing-related disease linked to mitochondrial dysfunction. The present study aimed to determine whether peroxisome proliferator activated receptor gamma co-activator 1-alpha (PPARGC1A, encoding PGC1α), a master regulator of mitochondrial biogenesis, is diminished in IPF and controls pathologic fibroblast activation. Primary human IPF, control lung fibroblasts and fibroblasts sorted from bleomycin-injured mice were used to evaluate the expression and function of PGC1α. In vitro PGC1α manipulation was performed by small interfering RNA knockdown or overexpression. Fibroblast activation was assessed by quantitative PCR, Western blotting, matrix deposition, secreted cytokine array, immunofluorescence and traction force microscopy. Mitochondrial function was assessed by Seahorse analyzer and mitochondria mass and number by flow cytometry, mitochondrial DNA quantification and transmission electron microscopy (TEM). We found that PGC1α levels are stably repressed in IPF fibroblasts. After bleomycin injury in young mice, PGC1α expression drops transiently but then increases prior to fibrosis resolution. In contrast, PGC1α expression fails to recover in aged mice with persistent fibrosis. PGC1α knockdown alone in normal human lung fibroblasts reduces mitochondrial mass and function while enhancing contractile and matrix synthetic fibroblast activation, senescence-related gene expression and soluble profibrotic and prosenescence signalling. Re-expression of PGC1α in IPF fibroblasts ameliorates all of these pathological cellular functions. Pharmacological treatment of IPF fibroblasts with rosiglitazone, but not thyroid hormone, elevated PGC1α expression and attenuated fibroblast activation. The sustained repression of PGC1α and beneficial effects of its rescue in IPF fibroblasts identifies PGC1α as an important regulator of the fibroblast’s pathological state in IPF.

Vascular dysfunction is a hallmark of chronic diseases in elderly. The contribution of the vasculature to lung repair and fibrosis is not fully understood. Here, we performed an epigenetic and transcriptional analysis of lung endothelial cells (ECs) from young and aged mice during the resolution or progression of bleomycin-induced lung fibrosis. We identified the transcription factor ETS-related gene (ERG) as putative orchestrator of lung capillary homeostasis and repair, and whose function is dysregulated in aging. ERG dysregulation is associated with reduced chromatin accessibility and maladaptive transcriptional responses to injury. Loss of endothelial ERG enhances paracrine fibroblast activation in vitro, and impairs lung fibrosis resolution in young mice in vivo. scRNA-seq of ERG deficient mouse lungs reveales transcriptional and fibrogenic abnormalities resembling those associated with aging and human lung fibrosis, including reduced number of general capillary (gCap) ECs. Our findings demonstrate that lung endothelial chromatin remodeling deteriorates with aging leading to abnormal transcription, vascular dysrepair, and persistent fibrosis following injury.

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Background Recent studies reported abnormal alpha‐synuclein deposition in biopsy‐accessible sites of the peripheral nervous system in Parkinson's disease (PD). This has considerable implications for clinical diagnosis. Moreover, if deposition occurs early, it may enable tissue diagnosis of prodromal PD. Objective The aim of this study was to develop and test an automated bright‐field immunohistochemical assay of cutaneous pathological alpha‐synuclein deposition in patients with idiopathic rapid eye movement sleep behavior disorder, PD, and atypical parkinsonism and in control subjects. Methods For assay development, postmortem skin biopsies were taken from 28 patients with autopsy‐confirmed Lewy body disease and 23 control subjects. Biopsies were stained for pathological alpha‐synuclein in automated stainers using a novel dual‐immunohistochemical assay for serine 129‐phosphorylated alpha‐synuclein and pan‐neuronal marker protein gene product 9.5. After validation, single 3‐mm punch skin biopsies were taken from the cervical 8 paravertebral area from 79 subjects (28 idiopathic rapid eye movement sleep behavior disorder, 20 PD, 10 atypical parkinsonism, and 21 control subjects). Raters blinded to clinical diagnosis assessed the biopsies. Results The immunohistochemistry assay differentiated alpha‐synuclein pathology from nonpathological‐appearing alpha‐synuclein using combined phosphatase and protease treatments. Among autopsy samples, 26 of 28 Lewy body samples and none of the 23 controls were positive. Among living subjects, punch biopsies were positive in 23 (82%) subjects with idiopathic rapid eye movement sleep behavior disorder, 14 (70%) subjects with PD, 2 (20%) subjects with atypical parkinsonism, and none (0%) of the control subjects. After a 3‐year follow‐up, eight idiopathic rapid eye movement sleep behavior disorder subjects phenoconverted to defined neurodegenerative syndromes, in accordance with baseline biopsy results. Conclusion Even with a single 3‐mm punch biopsy, there is considerable promise for using pathological alpha‐synuclein deposition in skin to diagnose both clinical and prodromal PD. © 2020 International Parkinson and Movement Disorder Society

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