Vascular-Parenchymal Cross-Talk Promotes Lung Fibrosis through BMPR2 Signaling.

Rationale: Idiopathic pulmonary fibrosis (IPF) is a fatal lung disease characterized by progressive lung scarring. IPF-related pulmonary vascular remodeling and pulmonary hypertension (PH) result in a particularly poor prognosis. Objectives: To study the pathogenesis of vascular remodeling in fibrotic lungs and its contribution to progression of fibrosis. Methods: We used an experimental model of lung fibrosis associated with PH by transient overexpression of active TGF-ß1 (transforming growth factor-ß1). Samples from patients with fibrotic lung diseases were analyzed in depth using immunostaining, gene expression, and gene mutations. Measurements and Main Results: We found a reduction in endothelial cells (ECs) and activation of vascular smooth muscle cells (VSMCs) in fibrotic lungs. Coculturing fibroblasts with VSMCs or ECs from fibrotic lungs induced fibrotic phenotypes in fibroblasts. IPF fibroblasts induced EC death and activation of VSMCs in coculture systems. Decreased concentrations of BMPR2 (bone morphogenic protein receptor 2) and its signaling were observed in ECs and VSMCs from fibrotic lungs in both rats and humans. On fibroblasts treated with media from VSMCs, BMPR2 suppression in VSMCs led to fibrogenic effects. Tacrolimus activated BMPR2 signaling and attenuated fibrosis and PH in rodent lungs. Whole-exome sequencing revealed rare mutations in PH-related genes, including BMPR2, in patients with IPF undergoing transplantation. A unique missense BMPR2 mutation (p.Q721R) was discovered to have dysfunctional effects on BMPR2 signaling. Conclusions: Endothelial dysfunction and vascular remodeling in PH secondary to pulmonary fibrosis enhance fibrogenesis through impaired BMPR2 signaling. Tacrolimus may have value as a treatment of advanced IPF and concomitant PH. Genetic abnormalities may determine the development of PH in advanced IPF.

Intrinsic BMP inhibitor Gremlin regulates alveolar epithelial type II cell proliferation and differentiation.

Type 1 alveolar epithelial cells (AT1s) and type 2 alveolar epithelial cells (AT2s) regulate the structural integrity and function of alveoli. AT1s mediate gas exchange, whereas AT2s serve multiple functions, including surfactant secretion and alveolar repair through proliferation and differentiation into AT1s as progenitors. However, mechanisms regulating AT2 proliferation and differentiation remain unclear. Here we demonstrate that Gremlin, an intrinsic inhibitor of bone morphogenetic protein (BMP), induces AT2 proliferation and differentiation. Transient overexpression of Gremlin in rat lungs by adenovirus vector delivery suppressed BMP signaling, induced proliferation of AT2s and the production of Bmp2, which in turn led to the recovery of BMP signaling and induced AT2 differentiation into AT1s. Bleomycin-induced lung injury upregulated Gremlin and showed a similar time course of biomarker expression comparable to the adenovirus model. TGF-ß and IL-1ß induced Gremlin expression in fibroblasts. Taken together, our findings implicate that Gremlin expression during lung injury leads to precisely timed inhibition of BMP signaling and activates AT2s, leading to alveolar repair.

Connective-Tissue Growth Factor Contributes to TGF-ß1-induced Lung Fibrosis.

Idiopathic pulmonary fibrosis is a fatal lung disease characterized by progressive and excessive accumulation of myofibroblasts and in the lung. Connective-tissue growth factor (CTGF) exacerbates pulmonary fibrosis in radiation-induced lung fibrosis, and in this study, we demonstrate upregulation of CTGF in a rat lung fibrosis model induced by an adenovirus vector encoding active TGF-ß1 (AdTGF-ß1). We show that CTGF is also upregulated in patients with idiopathic pulmonary fibrosis. Expression of CTGF was upregulated in vascular smooth muscle cells cultured from fibrotic lungs on Days 7 and 14 as well as endothelial cells sorted from fibrotic lungs on Days 14 and 28. These findings suggest contributions of different cells in maintaining the fibrotic phenotype during fibrogenesis. Treatment of fibroblasts with recombinant CTGF along with TGF-ß increases profibrotic markers in fibroblasts, confirming the synergistic effect of recombinant CTGF with TGF-ß in inducing pulmonary fibrosis. Also, the fibrotic extracellular matrix upregulated CTGF expression, compared with the normal extracellular matrix, suggesting that not only profibrotic mediators but also a profibrotic environment contributes to fibrogenesis. We also showed that pamrevlumab, a CTGF inhibitory antibody, partially attenuates fibrosis in the model. These results suggest that pamrevlumab could be an option for treatment of pulmonary fibrosis.

Chaperone-Mediated Autophagy Suppresses Apoptosis via Regulation of the Unfolded Protein Response during Chronic Obstructive Pulmonary Disease Pathogenesis.

Cigarette smoke (CS) induces accumulation of misfolded proteins with concomitantly enhanced unfolded protein response (UPR). Increased apoptosis linked to UPR has been demonstrated in chronic obstructive pulmonary disease (COPD) pathogenesis. Chaperone-mediated autophagy (CMA) is a type of selective autophagy for lysosomal degradation of proteins with the KFERQ peptide motif. CMA has been implicated in not only maintaining nutritional homeostasis but also adapting the cell to stressed conditions. Although recent papers have shown functional cross-talk between UPR and CMA, mechanistic implications for CMA in COPD pathogenesis, especially in association with CS-evoked UPR, remain obscure. In this study, we sought to examine the role of CMA in regulating CS-induced apoptosis linked to UPR during COPD pathogenesis using human bronchial epithelial cells (HBEC) and lung tissues. CS extract (CSE) induced LAMP2A expression and CMA activation through a Nrf2-dependent manner in HBEC. LAMP2A knockdown and the subsequent CMA inhibition enhanced UPR, including CHOP expression, and was accompanied by increased apoptosis during CSE exposure, which was reversed by LAMP2A overexpression. Immunohistochemistry showed that Nrf2 and LAMP2A levels were reduced in small airway epithelial cells in COPD compared with non-COPD lungs. Both Nrf2 and LAMP2A levels were significantly reduced in HBEC isolated from COPD, whereas LAMP2A levels in HBEC were positively correlated with pulmonary function tests. These findings suggest the existence of functional cross-talk between CMA and UPR during CSE exposure and also that impaired CMA may be causally associated with COPD pathogenesis through enhanced UPR-mediated apoptosis in epithelial cells.

Involvement of GPx4-Regulated Lipid Peroxidation in Idiopathic Pulmonary Fibrosis Pathogenesis.

The imbalanced redox status in lung has been widely implicated in idiopathic pulmonary fibrosis (IPF) pathogenesis. To regulate redox status, hydrogen peroxide must be adequately reduced to water by glutathione peroxidases (GPx). Among GPx isoforms, GPx4 is a unique antioxidant enzyme that can directly reduce phospholipid hydroperoxide. Increased lipid peroxidation products have been demonstrated in IPF lungs, suggesting the participation of imbalanced lipid peroxidation in IPF pathogenesis, which can be modulated by GPx4. In this study, we sought to examine the involvement of GPx4-modulated lipid peroxidation in regulating TGF-ß-induced myofibroblast differentiation. Bleomycin-induced lung fibrosis development in mouse models with genetic manipulation of GPx4 were examined. Immunohistochemical evaluations for GPx4 and lipid peroxidation were performed in IPF lung tissues. Immunohistochemical evaluations showed reduced GPx4 expression levels accompanied by increased 4-hydroxy-2-nonenal in fibroblastic focus in IPF lungs. TGF-ß-induced myofibroblast differentiation was enhanced by GPx4 knockdown with concomitantly enhanced lipid peroxidation and SMAD2/SMAD3 signaling. Heterozygous GPx4-deficient mice showed enhancement of bleomycin-induced lung fibrosis, which was attenuated in GPx4-transgenic mice in association with lipid peroxidation and SMAD signaling. Regulating lipid peroxidation by Trolox showed efficient attenuation of bleomycin-induced lung fibrosis development. These findings suggest that increased lipid peroxidation resulting from reduced GPx4 expression levels may be causally associated with lung fibrosis development through enhanced TGF-ß signaling linked to myofibroblast accumulation of fibroblastic focus formation during IPF pathogenesis. It is likely that regulating lipid peroxidation caused by reduced GPx4 can be a promising target for an antifibrotic modality of treatment for IPF.

Involvement of Lamin B1 Reduction in Accelerated Cellular Senescence during Chronic Obstructive Pulmonary Disease Pathogenesis.

Downregulation of lamin B1 has been recognized as a crucial step for development of full senescence. Accelerated cellular senescence linked to mechanistic target of rapamycin kinase (MTOR) signaling and accumulation of mitochondrial damage has been implicated in chronic obstructive pulmonary disease (COPD) pathogenesis. We hypothesized that lamin B1 protein levels are reduced in COPD lungs, contributing to the process of cigarette smoke (CS)-induced cellular senescence via dysregulation of MTOR and mitochondrial integrity. To illuminate the role of lamin B1 in COPD pathogenesis, lamin B1 protein levels, MTOR activation, mitochondrial mass, and cellular senescence were evaluated in CS extract (CSE)-treated human bronchial epithelial cells (HBEC), CS-exposed mice, and COPD lungs. We showed that lamin B1 was reduced by exposure to CSE and that autophagy was responsible for lamin B1 degradation in HBEC. Lamin B1 reduction was linked to MTOR activation through DEP domain-containing MTOR-interacting protein (DEPTOR) downregulation, resulting in accelerated cellular senescence. Aberrant MTOR activation was associated with increased mitochondrial mass, which can be attributed to peroxisome proliferator-activated receptor γ coactivator-1ß-mediated mitochondrial biogenesis. CS-exposed mouse lungs and COPD lungs also showed reduced lamin B1 and DEPTOR protein levels, along with MTOR activation accompanied by increased mitochondrial mass and cellular senescence. Antidiabetic metformin prevented CSE-induced HBEC senescence and mitochondrial accumulation via increased DEPTOR expression. These findings suggest that lamin B1 reduction is not only a hallmark of lung aging but is also involved in the progression of cellular senescence during COPD pathogenesis through aberrant MTOR signaling.

Involvement of PARK2-Mediated Mitophagy in Idiopathic Pulmonary Fibrosis Pathogenesis.

Fibroblastic foci, known to be the leading edge of fibrosis development in idiopathic pulmonary fibrosis (IPF), are composed of fibrogenic myofibroblasts. Autophagy has been implicated in the regulation of myofibroblast differentiation. Insufficient mitophagy, the mitochondria-selective autophagy, results in increased reactive oxygen species, which may modulate cell signaling pathways for myofibroblast differentiation. Therefore, we sought to investigate the regulatory role of mitophagy in myofibroblast differentiation as a part of IPF pathogenesis. Lung fibroblasts were used in in vitro experiments. Immunohistochemical evaluation in IPF lung tissues was performed. PARK2 was examined as a target molecule for mitophagy regulation, and a PARK2 knockout mouse was employed in a bleomycin-induced lung fibrosis model. We demonstrated that PARK2 knockdown-mediated mitophagy inhibition was involved in the mechanism for activation of the platelet-derived growth factor receptor (PDGFR)/PI3K/AKT signaling pathway accompanied by enhanced myofibroblast differentiation and proliferation, which were clearly inhibited by treatment with both antioxidants and AG1296, a PDGFR inhibitor. Mitophagy inhibition-mediated activation of PDGFR signaling was responsible for further autophagy suppression, suggesting the existence of a self-amplifying loop of mitophagy inhibition and PDGFR activation. IPF lung demonstrated reduced PARK2 with concomitantly increased PDGFR phosphorylation. Furthermore, bleomycin-induced lung fibrosis was enhanced in PARK2 knockout mice and subsequently inhibited by AG1296. These findings suggest that insufficient mitophagy-mediated PDGFR/PI3K/AKT activation, which is mainly attributed to reduced PARK2 expression, is a potent underlying mechanism for myofibroblast differentiation and proliferation in fibroblastic foci formation during IPF pathogenesis.

Pirfenidone inhibits myofibroblast differentiation and lung fibrosis development during insufficient mitophagy.

BACKGROUND: Pirfenidone (PFD) is an anti-fibrotic agent used to treat idiopathic pulmonary fibrosis (IPF), but its precise mechanism of action remains elusive. Accumulation of profibrotic myofibroblasts is a crucial process for fibrotic remodeling in IPF. Recent findings show participation of autophagy/mitophagy, part of the lysosomal degradation machinery, in IPF pathogenesis. Mitophagy has been implicated in myofibroblast differentiation through regulating mitochondrial reactive oxygen species (ROS)-mediated platelet-derived growth factor receptor (PDGFR) activation. In this study, the effect of PFD on autophagy/mitophagy activation in lung fibroblasts (LF) was evaluated, specifically the anti-fibrotic property of PFD for modulation of myofibroblast differentiation during insufficient mitophagy. METHODS: Transforming growth factor-ß (TGF-ß)-induced or ATG5, ATG7, and PARK2 knockdown-mediated myofibroblast differentiation in LF were used for in vitro models. The anti-fibrotic role of PFD was examined in a bleomycin (BLM)-induced lung fibrosis model using PARK2 knockout (KO) mice. RESULTS: We found that PFD induced autophagy/mitophagy activation via enhanced PARK2 expression, which was partly involved in the inhibition of myofibroblast differentiation in the presence of TGF-ß. PFD inhibited the myofibroblast differentiation induced by PARK2 knockdown by reducing mitochondrial ROS and PDGFR-PI3K-Akt activation. BLM-treated PARK2 KO mice demonstrated augmentation of lung fibrosis and oxidative modifications compared to those of BLM-treated wild type mice, which were efficiently attenuated by PFD. CONCLUSIONS: These results suggest that PFD induces PARK2-mediated mitophagy and also inhibits lung fibrosis development in the setting of insufficient mitophagy, which may at least partly explain the anti-fibrotic mechanisms of PFD for IPF treatment.

Metformin attenuates lung fibrosis development via NOX4 suppression.

BACKGROUND: Accumulation of profibrotic myofibroblasts in fibroblastic foci (FF) is a crucial process for development of fibrosis during idiopathic pulmonary fibrosis (IPF) pathogenesis, and transforming growth factor (TGF)-ß plays a key regulatory role in myofibroblast differentiation. Reactive oxygen species (ROS) has been proposed to be involved in the mechanism for TGF-ß-induced myofibroblast differentiation. Metformin is a biguanide antidiabetic medication and its pharmacological action is mediated through the activation of AMP-activated protein kinase (AMPK), which regulates not only energy homeostasis but also stress responses, including ROS. Therefore, we sought to investigate the inhibitory role of metformin in lung fibrosis development via modulating TGF-ß signaling. METHODS: TGF-ß-induced myofibroblast differentiation in lung fibroblasts (LF) was used for in vitro models. The anti-fibrotic role of metfromin was examined in a bleomycin (BLM)-induced lung fibrosis model. RESULTS: We found that TGF-ß-induced myofibroblast differentiation was clearly inhibited by metformin treatment in LF. Metformin-mediated activation of AMPK was responsible for inhibiting TGF-ß-induced NOX4 expression. NOX4 knockdown and N-acetylcysteine (NAC) treatment illustrated that NOX4-derived ROS generation was critical for TGF-ß-induced SMAD phosphorylation and myofibroblast differentiation. BLM treatment induced development of lung fibrosis with concomitantly enhanced NOX4 expression and SMAD phosphorylation, which was efficiently inhibited by metformin. Increased NOX4 expression levels were also observed in FF of IPF lungs and LF isolated from IPF patients. CONCLUSIONS: These findings suggest that metformin can be a promising anti-fibrotic modality of treatment for IPF affected by TGF-ß.

Interstitial Pneumonia Associated with Nodal T-follicular Helper Cell Lymphoma: A Case Report.

Nodal T-follicular helper cell lymphoma (nTFHL), a hematologic neoplasm originating from T-follicular helper (TFH) cells, occasionally presents with pulmonary radiographic abnormalities, without neoplastic cellular infiltration. However, the precise mechanisms underlying non-neoplastic pulmonary opacities in patients with nTFHL remain unclear. Previous reports have shown that TFH cell abnormalities are associated with collagen disease and interstitial pneumonia with autoimmune features (IPAF). We herein report a patient with nTFHL accompanied by interstitial pneumonia diagnosed via lung and lymph node biopsies. These findings suggest the need to rule out nTFHL before diagnosing IPAF.

Lemborexant-induced interstitial lung disease: A case report.

We report the first case of drug-induced interstitial lung disease attributed to lemborexant. A 66-year-old man reported to our hospital with the acute onset of cough and breathlessness with ground-glass opacity on radiological examination. Symptoms were identified after taking lemborexant for 2 consecutive days. The patient had undergone lemborexant treatment 2 years prior and had exhibited no symptoms at that time. The drug-induced lymphocyte stimulation test for lemborexant was positive. He showed rapid improvement upon treatment with steroid. With the rise in prescriptions of lemborexant for insomnia, lemborexant should be considered as a possible cause of drug-induced interstitial lung disease.

Surfactant protein D prevents mucin overproduction in airway goblet cells via SIRPα.

Mucin overproduction is a common feature of chronic airway diseases such as asthma and chronic obstructive pulmonary disease (COPD), and exacerbates their underlying respiratory condition. Surfactant protein D (SP-D) protects against airway diseases through modulation of immune reactions, but whether it also exerts direct effects on airway epithelial cells has remained unclear. Therefore, we sought to investigate the inhibitory role of SP-D on mucin production in airway epithelial cells. We prepared air-liquid interface (ALI) cultures of human primary bronchial epithelial cells (HBECs), which recapitulated a well-differentiated human airway epithelium. Benzo(a)pyrene (BaP), a key toxicant in cigarette smoke, induced mucin 5AC (MUC5AC) production in ALI-cultured HBECs, airway secretory cell lines, and airway epithelia of mice. Then, the protective effects of SP-D against the BaP-induced mucin overproduction were examined. BaP increased MUC5AC production in ALI cultures of HBECs, and this effect was attenuated by SP-D. SP-D also suppressed the BaP-induced phosphorylation of extracellular signal-regulated kinase (ERK) and MUC5AC expression in NCI-H292 goblet-like cells, but not in NCI-H441 club-like cells. Signal regulatory protein α (SIRPα) was found to be expressed in HBECs and NCI-H292 cells but absent in NCI-H441 cells. In NCI-H292 cells, SP-D activated SH2 domain-containing tyrosine phosphatase-1 (SHP-1), downstream of SIRPα, and knockdown of SIRPα abolished the suppressive effects of SP-D on BaP-induced ERK phosphorylation and MUC5AC production. Consistent with these in vitro findings, intratracheal instillation of SP-D prevented the BaP-induced phosphorylation of ERK and Muc5ac expression in airway epithelial cells in a mouse model. SP-D acts directly on airway epithelial cells to inhibit mucin secretion through ligation of SIRPα and SHP-1-mediated dephosphorylation of ERK. Targeting of SIRPα is therefore a potential new therapeutic approach to suppression of mucin hypersecretion in chronic airway diseases such as COPD and asthma.

Therapeutic strategies to target connective tissue growth factor in fibrotic lung diseases.

The treatment of interstitial lung diseases, including idiopathic pulmonary fibrosis (IPF), remains challenging as current available antifibrotic agents are not effective in halting disease progression. Connective tissue growth factor (CTGF), also known as cellular communication factor 2 (CCN2), is a member of the CCN family of proteins that regulates cell signaling through cell surface receptors such as integrins, the activity of cytokines/growth factors, and the turnover of extracellular matrix (ECM) proteins. Accumulating evidence indicates that CTGF plays a crucial role in promoting lung fibrosis through multiple processes, including inducing transdifferentiation of fibroblasts to myofibroblasts, epithelial-mesenchymal transition (EMT), and cooperating with other fibrotic mediators such as TGF-ß. Increased expression of CTGF has been observed in fibrotic lungs and inhibiting CTGF signaling has been shown to suppress lung fibrosis in several animal models. Thus, the CTGF signaling pathway is emerging as a potential therapeutic target in IPF and other pulmonary fibrotic conditions. This review provides a comprehensive overview of the current evidence on the pathogenic role of CTGF in pulmonary fibrosis and discusses the current therapeutic agents targeting CTGF using a systematic review approach.

The Utility and Limitations of Universal Polymerase Chain Reaction Screening for SARS-CoV-2 During Hospital Admission.

OBJECTIVE: Universal polymerase chain reaction (PCR) screening for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on hospital admission is an effective approach to preventing coronavirus disease 2019 (COVID-19) outbreaks in medical facilities. However, false-positive test results due to a recent infection are a concern. We investigated the usefulness and limitations of universal PCR screening for SARS-CoV-2 on hospital admission in a real-world setting. METHODS: We retrospectively analyzed 1320 attempted hospital admissions for 775 patients at the Department of Respiratory Medicine, Kyushu University Hospital, between January 1, 2022, and May 2, 2023. RESULTS: Thirty-nine out of 1201 PCR tests (3.2%) yielded a positive result, with 22 of these results being considered false positives on the basis of a recent infection. We found that 39% of cases showed a positive PCR result between 31 and 60 days after the onset of COVID-19, although the threshold cycle (Ct) for target 1 (ORF1ab gene) of the Cobas SARS-CoV-2 test (Roche Diagnostics, Basel, Switzerland) was >30 in most instances. CONCLUSION: Hospital admission based on the results of PCR screening for SARS-CoV-2 should take into account not only PCR positivity but also the Ct value and recent COVID-19 history.

Exploratory mass cytometry analysis reveals immunophenotypes of cancer treatment-related pneumonitis.

Anticancer treatments can result in various adverse effects, including infections due to immune suppression/dysregulation and drug-induced toxicity in the lung. One of the major opportunistic infections is Pneumocystis jirovecii pneumonia (PCP), which can cause severe respiratory complications and high mortality rates. Cytotoxic drugs and immune-checkpoint inhibitors (ICIs) can induce interstitial lung diseases (ILDs). Nonetheless, the differentiation of these diseases can be difficult, and the pathogenic mechanisms of such diseases are not yet fully understood. To better comprehend the immunophenotypes, we conducted an exploratory mass cytometry analysis of immune cell subsets in bronchoalveolar lavage fluid from patients with PCP, cytotoxic drug-induced ILD (DI-ILD), and ICI-associated ILD (ICI-ILD) using two panels containing 64 markers. In PCP, we observed an expansion of the CD16+ T cell population, with the highest CD16+ T proportion in a fatal case. In ICI-ILD, we found an increase in CD57+ CD8+ T cells expressing immune checkpoints (TIGIT+ LAG3+ TIM-3+ PD-1+), FCRL5+ B cells, and CCR2+ CCR5+ CD14+ monocytes. These findings uncover the diverse immunophenotypes and possible pathomechanisms of cancer treatment-related pneumonitis.

Pleuroparenchymal fibroelastosis secondary to autologous peripheral blood stem cell transplantation: A case report.

Pleuroparenchymal fibroelastosis (PPFE) is a rare form of interstitial pneumonitis. Although most cases of PPFE are idiopathic, some cases of PPFE occur secondary to stem cell transplantation. We report a 41-year-old woman developed pneumonia after autologous peripheral blood system cell transplantation (PBSCT). Eleven years after PBSCT, she presented with dyspnea. A computed tomographic scan showed pleuroparenchymal thickening and predominantly in the upper lobes. She was diagnosed with PPFE secondary to PBSCT. She was started nintedanib and administered oxygen therapy. Most cases of PPFE secondary to stem cell transplantation have been reported. However, we experienced the case of PPFE post-autologous PBSCT.

Acute myeloid leukemia and myelodysplastic syndrome associated with a combination of immune checkpoint inhibitor and platinum-based chemotherapy.

Therapy related-acute myeloid leukemia (t-AML) and myelodysplastic syndrome (t-MDS) are complications of chemotherapy and/or radiation therapy for malignant diseases. In this report, we describe a patient with advanced lung adenocarcinoma who developed autoimmune hemolytic anemia and MDS associated with a combination of atezolizumab and platinum-based chemotherapy. The patient showed progression from t-MDS to t-AML 20 months after the treatment was initiated. A combination of immune checkpoint inhibitor (ICI) and chemotherapy may increase the risk of developing therapy-related myeloid neoplasms. As the prognosis of t-AML and t-MDS is poorer than that of de novo AML and MDS, proper surveillance, follow-up, and treatment are needed throughout the course of immunotherapy.

Expansion of ST2-expressing macrophages in a patient with bronchiolitis obliterans syndrome.

This case study of a patient with BOS after HSCT found increased ST2+CD64+ macrophages in BALF, a potential therapeutic target for treatment-refractory BOS, and reduced CCR2+CD14+ monocytes compared to other lung disorders https://bit.ly/406Uyy9.