Idiopathic Pulmonary Fibrosis (IPF) is a chronic parenchymal lung disease characterized by repetitive alveolar cell injury, myofibroblast proliferation, and excessive extracellular matrix deposition for which unmet need persists for effective therapeutics. The bioactive eicosanoid, prostaglandin F2a, and its cognate receptor FPr (Ptfgr) are implicated as a TGFβ1 independent signaling hub for IPF. To assess this, we leveraged our published murine PF model (IER-SftpcI73T) expressing a disease-associated missense mutation in the surfactant protein C (Sftpc) gene. Tamoxifen treated IER-SftpcI73T mice develop an early multiphasic alveolitis and transition to spontaneous fibrotic remodeling by 28 days. IER-SftpcI73T mice crossed to a Ptgfr null (FPr-/-) line showed attenuated weight loss and gene dosage dependent rescue of mortality compared to FPr+/+ cohorts. IER-SftpcI73T/FPr-/- mice also showed reductions in multiple fibrotic endpoints for which administration of nintedanib was not additive. Single cell RNA sequencing, pseudotime analysis, and in vitro assays demonstrated Ptgfr expression predominantly within adventitial fibroblasts which were reprogrammed to an “inflammatory/transitional” cell state in a PGF2a/ FPr dependent manner. Collectively, the findings provide evidence for a role for PGF2a signaling in IPF, mechanistically identify a susceptible fibroblast subpopulation, and establish a benchmark effect size for disruption of this pathway in mitigating fibrotic lung remodeling.
Luis R. Rodriguez, Soon Yew Tang, Willy Roque Barboza, Aditi Murthy, Yaniv Tomer, Tian-Quan Cai, Swati Iyer, Katrina Chavez, Ujjalkumar Subhash Das, Soumita Ghosh, Charlotte Cooper, Thalia T. Dimopoulos, Apoorva Babu, Caitlin F. Connelly, Garret A. FitzGerald, Michael F. Beers
Aberrant fibroblast function plays a key role in the pathogenesis of Idiopathic Pulmonary Fibrosis, a devastating disease of unrelenting extracellular matrix deposition in response to lung injury. Platelet-derived growth factor alpha-positive (PDGFRα+) lipofibroblasts (LipoFBs) are essential for lung injury response and maintenance of a functional alveolar stem cell niche. Little is known about the effects of lung injury on LipoFB function. Here, we used scRNA-Seq technology and PDGFRαGFP lineage tracing to generate a transcriptomic profile of PDGFRα+ fibroblasts in normal and injured mouse lungs 14 days after bleomycin exposure, generating eleven unique transcriptomic clusters that segregated according to treatment. While normal and injured LipoFBs shared a common gene signature, injured LipoFBs acquired fibrogenic pathway activity with an attenuation of lipogenic pathways. In a 3D organoid model, injured PDGFRα+ fibroblast- supported organoids were morphologically distinct from those cultured with normal FBs, and scRNA-Seq analysis suggested distinct transcriptomic changes in alveolar epithelia supported by injured PDGFRα+ fibroblasts. In summary, while LipoFBs in injured lung have not migrated from their niche and retain their lipogenic identity, they acquire a potentially reversible fibrogenic profile, which may alter the kinetics of epithelial regeneration and potentially contribute to dysregulated repair, leading to fibrosis.
Carol S. Trempus, Brian N. Papas, Maria I. Sifre, Carl D. Bortner, Erica Scappini, Charles J. Tucker, Xin Xu, Katina L. Johnson, Leesa J. Deterding, Jason G Williams, Dylan J. Johnson, Jian-Liang Li, Deloris Sutton, Charan K. Ganta, Debabrata Mahapatra, Muhammad Arif, Abhishek Basu, Lenny Pommerolle, Resat Cinar, Anne-Karina T. Perl, Stavros Garantziotis
Primary graft dysfunction (PGD) limits clinical benefit after lung transplantation, a life-prolonging therapy for patients with end-stage disease. PGD is the clinical syndrome resulting from pulmonary ischemia-reperfusion injury (IRI), driven by innate immune inflammation. We recently demonstrated a key role for NK cells in the airways of mouse models and human tissue samples of IRI. Here we used 2 mouse models paired with human lung transplant samples to investigate the mechanisms whereby NK cells migrate to the airways to mediate lung injury. We demonstrate that chemokine receptor ligand transcripts and proteins are increased in mouse and human disease. CCR5 ligand transcripts were correlated with NK cell gene signatures independent of NK cell CCR5 ligand secretion. NK cells expressing CCR5 were increased in the lung and airways during IRI and had increased markers of tissue residency and maturation. Allosteric CCR5 drug blockade reduced the migration of NK cells to the site of injury. CCR5 blockade also blunted quantitative measures of experimental IRI. Additionally, in human lung transplant bronchoalveolar lavage samples, we found that CCR5 ligand was associated with increased patient morbidity and that the CCR5 receptor was increased in expression on human NK cells following PGD. These data support a potential mechanism for NK cell migration during lung injury and identify a plausible preventative treatment for PGD.
Jesse Santos, Ping Wang, Avishai Shemesh, Fengchun Liu, Tasha Tsao, Oscar A. Aguilar, Simon J. Cleary, Jonathan P. Singer, Ying Gao, Steven R. Hays, Jeffrey Golden, Lorriana E. Leard, Mary Ellen Kleinhenz, Nicholas A. Kolaitis, Rupal J. Shah, Aida Venado, Jasleen Kukreja, S. Sam Weigt, John A. Belperio, Lewis L. Lanier, Mark R. Looney, John R. Greenland, Daniel R. Calabrese
Lung contusion and gastric aspiration (LC and GA) are major risk factors for developing acute respiratory distress following trauma. Hypoxia from lung injury is mainly regulated by hypoxia-inducible factor 1α (HIF-1α). Published data from our group indicate that HIF-1α regulation in airway epithelial cells (AEC) drives the acute inflammatory response following LC and GA. Metabolomic profiling and metabolic flux of Type II AEC following LC revealed marked increases in glycolytic and TCA intermediates in vivo and in vitro that were HIF-1α dependent. GLUT-1/4 expression was also increased in HIF-1α+/+ mice, suggesting that increased glucose entry may contribute to increased intermediates. Importantly, lactate incubation in vitro on Type II cells did not significantly increase the inflammatory byproduct IL-1β. Contrastingly, succinate had a direct proinflammatory effect on human small AEC by IL-1β generation in vitro. This effect was reversed by dimethylmalonate, suggesting an important role for succinate dehydrogenase in mediating HIF-1α effects. We confirmed the presence of the only known receptor for succinate binding, SUCNR1, on Type II AEC. These results support the hypothesis that succinate drives HIF-1α–mediated airway inflammation following LC. This is the first report to our knowledge of direct proinflammatory activation of succinate in nonimmune cells such as Type II AEC in direct lung injury models.
Madathilparambil V. Suresh, Sinan Aktay, George Yalamanchili, Sumeet Solanki, Dily Thazhath Sathyarajan, Manikanta Swamy Arnipalli, Subramaniam Pennathur, Krishnan Raghavendran
Acute lung injury (ALI) and its most severe form, acute respiratory distress syndrome (ARDS), cause severe endothelial dysfunction in the lung, and vascular endothelial growth factor (VEGF) is elevated in ARDS. We found that the levels of a VEGF-regulated microRNA, microRNA-1 (miR-1), were reduced in the lung endothelium after acute injury. Pulmonary endothelial cell–specific (EC-specific) overexpression of miR-1 protected the lung against cell death and barrier dysfunction in both murine and human models and increased the survival of mice after pneumonia-induced ALI. miR-1 had an intrinsic protective effect in pulmonary and other types of ECs; it inhibited apoptosis and necroptosis pathways and decreased capillary leak by protecting adherens and tight junctions. Comparative gene expression analysis and RISC recruitment assays identified miR-1 targets in the context of injury, including phosphodiesterase 5A (PDE5A), angiopoietin-2 (ANGPT2), CNKSR family member 3 (CNKSR3), and TNF-α–induced protein 2 (TNFAIP2). We validated miR-1–mediated regulation of ANGPT2 in both mouse and human ECs and found that in a 119-patient pneumonia cohort, miR-1 correlated inversely with ANGPT2. These findings illustrate a previously unknown role of miR-1 as a cytoprotective orchestrator of endothelial responses to acute injury with prognostic and therapeutic potential.
Asawari Korde, Maria Haslip, Prachi Pednekar, Alamzeb Khan, Maurizio Chioccioli, Sameet Mehta, Francesc Lopez-Giraldez, Santos Bermejo, Mauricio Rojas, Charles Dela Cruz, Michael A. Matthay, Jordan S. Pober, Richard W. Pierce, Shervin S. Takyar
A hallmark of idiopathic pulmonary fibrosis (IPF) and other interstitial lung diseases is dysregulated repair of the alveolar epithelium. The Hippo pathway effector transcription factors YAP and TAZ are implicated as essential for type 1 and type 2 alveolar epithelial cell (AT1 and AT2) differentiation in the developing lung, yet aberrant activation of YAP/TAZ is a prominent feature of the dysregulated alveolar epithelium in IPF. In these studies, we sought to define the functional role of YAP/TAZ activity during alveolar regeneration. We demonstrated that Yap and Taz are normally activated in AT2 cells shortly after injury, and deletion of Yap/Taz in AT2 cells led to pathologic alveolar remodeling, failure of AT2 to AT1 cell differentiation, increased collagen deposition, exaggerated neutrophilic inflammation, and increased mortality following injury induced by a single dose of bleomycin. Loss of Yap/Taz activity prior to a LPS injury prevented AT1 cell regeneration, led to intra-alveolar collagen deposition, and resulted in persistent innate inflammation. Together these findings established that AT2 cell Yap/Taz activity is essential for functional alveolar epithelial repair and prevention of fibrotic remodeling.
Gianluca T. DiGiovanni, Wei Han, Taylor P. Sherrill, Chase J. Taylor, David S. Nichols, Natalie M. Geis, Ujjal K. Singha, Carla L. Calvi, A. Scott McCall, Molly M. Dixon, Yang Liu, Ji-Hoon Jang, Sergey S. Gutor, Vasiliy V. Polosukhin, Timothy S. Blackwell, Jonathan A. Kropski, Jason J. Gokey
Alveolar epithelial type II (AEC2) cells strictly regulate lipid metabolism to maintain surfactant synthesis. Loss of AEC2 cell function and surfactant production are implicated in the pathogenesis of the smoking-related lung disease chronic obstructive pulmonary disease (COPD). Whether smoking alters lipid synthesis in AEC2 cells and whether altering lipid metabolism in AEC2 cells contributes to COPD development are unclear. In this study, high-throughput lipidomic analysis revealed increased lipid biosynthesis in AEC2 cells isolated from mice chronically exposed to cigarette smoke (CS). Mice with a targeted deletion of the de novo lipogenesis enzyme, fatty acid synthase (FASN), in AEC2 cells (FasniΔAEC2) exposed to CS exhibited higher bronchoalveolar lavage fluid (BALF) neutrophils, higher BALF protein, and more severe airspace enlargement. FasniΔAEC2 mice exposed to CS had lower levels of key surfactant phospholipids but higher levels of BALF ether phospholipids, sphingomyelins, and polyunsaturated fatty acid–containing phospholipids, as well as increased BALF surface tension. FasniΔAEC2 mice exposed to CS also had higher levels of protective ferroptosis markers in the lung. These data suggest that AEC2 cell FASN modulates the response of the lung to smoke by regulating the composition of the surfactant phospholipidome.
Li-Chao Fan, Keith McConn, Maria Plataki, Sarah Kenny, Niamh C. Williams, Kihwan Kim, Jennifer A. Quirke, Yan Chen, Maor Sauler, Matthias E. Möbius, Kuei-Pin Chung, Estela Area Gomez, Augustine M.K. Choi, Jin-Fu Xu, Suzanne M. Cloonan
Optimal lung repair and regeneration is essential for recovery from viral infections including influenza A virus (IAV). We have previously demonstrated that acute inflammation and mortality induced by IAV is under circadian control. However, it is not known if the influence of the circadian clock persists beyond the acute outcomes. Here, we utilize the UK Biobank to demonstrate an association between poor circadian rhythms and morbidity from lower respiratory tract infections including the need for hospitalization and post-discharge mortality; this persists even after adjusting for common confounding factors. Further, we use a combination of lung organoid assays, single cell RNA sequencing (Sc-seq) and IAV infection in different models of clock disruption to investigate the role of the circadian clock in lung repair and regeneration. We show for the first time that lung organoids have a functional circadian clock, and the disruption of this clock impairs regenerative capacity. Finally, we find that the circadian clock acts through distinct pathways in mediating lung regeneration- in tracheal cells via the Wnt/β-catenin pathway and through IL1β in alveolar epithelial cells. We speculate, that adding a circadian dimension to the critical process of lung repair and regeneration will lead to novel therapies and improve outcomes.
Amruta Naik, Kaitlyn M. Forrest, Oindrila Paul, Yasmine Issah, Utham Kashyap Valekunja, Soon Yew Tang, Akhilesh B. Reddy, Elizabeth J. Hennessy, Thomas G. Brooks, Fatima N. Chaudhry, Apoorva Babu, Michael P. Morley, Jarod A. Zepp, Gregory R. Grant, Garret FitzGerald, Amita Sehgal, G. Scott Worthen, David B. Frank, Edward E. Morrisey, Shaon Sengupta
Proline and its synthesis enzyme pyrroline-5-carboxylate reductase 1 (PYCR1) are implicated in epithelial-mesenchymal transition (EMT), yet how proline and PYCR1 function in allergic asthmatic airway remodeling via EMT has not yet been addressed. In the present study, increased levels of plasma proline and PYCR1 were observed in asthmatic patients. Similarly, proline and PYCR1 in lung tissues were higher in a murine allergic asthma model induced by house dust mites (HDMs). Pycr1 knockout (KO) decreased proline in lung tissues, with reduced airway remodeling and EMT. Mechanistically, loss of Pycr1 restrained HDM-induced EMT by modulating mitochondrial fission, metabolic reprogramming, and the AKT/mTOR1 and WNT3a/β–catenin signaling pathways in airway epithelial cells. Therapeutic inhibition of PYCR1 in wild-type mice disrupted HDM-induced airway inflammation and remodeling. Deprivation of exogeneous proline partially relieved HDM-induced airway remodeling to some extent. Collectively, this study illuminates that proline and PYCR1 involved with airway remodeling in allergic asthma could be viable targets for asthma treatment.
Tingting Xu, Zhenzhen Wu, Qi Yuan, Xijie Zhang, Yanan Liu, Chaojie Wu, Meijuan Song, Jingjing Wu, Jingxian Jiang, Zhengxia Wang, Zhongqi Chen, Mingshun Zhang, Mao Huang, Ningfei Ji
Reducing inflammatory damage and improving alveolar epithelium regeneration are two key approaches to promoting lung repair in acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). Stimulation of cholinergic-α7nAChR (α7 nicotinic acetylcholine receptor, coded by Chrna7) signaling could dampen lung inflammatory injury. However, whether activation of α7nAChR in alveolar type II (AT2) cells promotes alveolar epithelial injury repair and underlying mechanisms are elusive. Here, we found that α7nAChR was expressed on AT2 cells and was upregulated in response to LPS-induced ALI. Meanwhile, deletion of Chrna7 in AT2 cells impeded lung repair process and worsened lung inflammation in ALI. Using in vivo AT2 lineage-labeled mice and ex vivo AT2-derived alveolar organoids, we demonstrated that activation of α7nAChR expressed on AT2 cells improved alveolar regeneration by promoting AT2 cells to proliferate and subsequently differentiate toward alveolar type I (AT1) cells. Then we screened out the WNT7B signaling pathway by the RNA sequencing analysis of in vivo AT2 lineage-labeled cells, and further confirmed its indispensability for α7nAChR activation-mediated alveolar epithelial proliferation and differentiation. Thus, we have identified an unrecognized pathway that cholinergic-α7nAChR signaling determines alveolar regeneration and repair, which might provide us a novel therapeutic target for combating ALI.
Xiaoyan Chen, Cuiping Zhang, Tianchang Wei, Jie Chen, Ting Pan, Miao Li, Lu Wang, Juan Song, Cuicui Chen, Yan Zhang, Yuanlin Song, Xiao Su
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