Functional roles of CD26/DPP4 in lipopolysaccharide-induced lung injury.

Acute respiratory distress syndrome (ARDS) is characterized by dysregulated inflammation and increased permeability of lung microvascular cells. CD26/dipeptidyl peptidase-4 (DPP4) is a type II membrane protein that is expressed in several cell types and mediates multiple pleiotropic effects. We previously reported that DPP4 inhibition by sitagliptin attenuates lipopolysaccharide (LPS)-induced lung injury in mice. The current study characterized the functional role of CD26/DPP4 expression in LPS-induced lung injury in mice, isolated alveolar macrophages, and cultured lung endothelial cells. In LPS-induced lung injury, inflammatory responses [bronchoalveolar lavage fluid (BALF) neutrophil numbers and several proinflammatory cytokine levels] were attenuated in Dpp4 knockout (Dpp4 KO) mice. However, multiple assays of alveolar capillary permeability were similar between the Dpp4 KO and wild-type mice. TNF-α and IL-6 production was suppressed in alveolar macrophages isolated from Dpp4 KO mice. In contrast, in cultured mouse lung microvascular endothelial cells (MLMVECs), reduction in CD26/DPP4 expression by siRNA resulted in greater ICAM-1 and IL-6 expression after LPS stimulation. Moreover, the LPS-induced vascular monolayer permeability in vitro was higher in MLMVECs treated with Dpp4 siRNA, suggesting that CD26/DPP4 plays a protective role in endothelial barrier function. In summary, this study demonstrated that genetic deficiency of Dpp4 attenuates inflammatory responses but not permeability in LPS-induced lung injury in mice, potentially through differential functional roles of CD26/DPP4 expression in resident cellular components of the lung. CD26/DPP4 may be a potential therapeutic target for ARDS and warrants further exploration to precisely identify the multiple functional effects of CD26/DPP4 in ARDS pathophysiology.NEW & NOTEWORTHY We aimed to clarify the functional roles of CD26/DPP4 in ARDS pathophysiology using Dpp4-deficient mice and siRNA reduction techniques in cultured lung cells. Our results suggest that CD26/DPP4 expression plays a proinflammatory role in alveolar macrophages while also playing a protective role in the endothelial barrier. Dpp4 genetic deficiency attenuates inflammatory responses but not permeability in LPS-induced lung injury in mice, potentially through differential roles of CD26/DPP4 expression in the resident cellular components of the lung.

Functional Roles of CD26/DPP4 in Bleomycin-Induced Pulmonary Hypertension Associated with Interstitial Lung Disease.

Pulmonary hypertension (PH) with interstitial lung diseases (ILDs) often causes intractable conditions. CD26/Dipeptidyl peptidase-4 (DPP4) is expressed in lung constituent cells and may be related to the pathogenesis of various respiratory diseases. We aimed to clarify the functional roles of CD26/DPP4 in PH-ILD, paying particular attention to vascular smooth muscle cells (SMCs). Dpp4 knockout (Dpp4KO) and wild type (WT) mice were administered bleomycin (BLM) intraperitoneally to establish a PH-ILD model. The BLM-induced increase in the right ventricular systolic pressure and the right ventricular hypertrophy observed in WT mice were attenuated in Dpp4KO mice. The BLM-induced vascular muscularization in small pulmonary vessels in Dpp4KO mice was milder than that in WT mice. The viability of TGFß-stimulated human pulmonary artery SMCs (hPASMCs) was lowered due to the DPP4 knockdown with small interfering RNA. According to the results of the transcriptome analysis, upregulated genes in hPASMCs with TGFß treatment were related to pulmonary vascular SMC proliferation via the Notch, PI3K-Akt, and NFκB signaling pathways. Additionally, DPP4 knockdown in hPASMCs inhibited the pathways upregulated by TGFß treatment. These results suggest that genetic deficiency of Dpp4 protects against BLM-induced PH-ILD by alleviating vascular remodeling, potentially through the exertion of an antiproliferative effect via inhibition of the TGFß-related pathways in PASMCs.

Abr, a Rho-regulating protein, modulates osteoclastogenesis by enhancing lamellipodia formation by interacting with poly(ADP-ribose) glycohydrolase.

BACKGROUND: Osteoclasts are multinucleated bone-resorbing cells formed by the fusion of monocyte/macrophage lineage. During osteoclast differentiation, Rho GTPases are involved in various processes, including cell migration, adhesion, and polarity. However, the role of Rho-regulatory molecules in the regulation of osteoclast differentiation remains unclear. In this study, among these genes, we focused on active breakpoint cluster region-related (Abr) protein that is a multifunctional regulator of Rho GTPases. METHODS AND RESULTS: We examined using knockdown and overexpression experiments in RANKL-stimulated RAW-D macrophages whether Abr regulates osteoclast differentiation and cell morphology. We observed an increase in Abr expression during osteoclast differentiation and identified expression of a variant of the Abr gene in osteoclasts. Knockdown of Abr suppressed osteoclast differentiation and resorption. Abr knockdown markedly inhibited the expression of osteoclast markers, such as Nfatc1, c-fos, Src, and Ctsk in osteoclasts. Conversely, overexpression of Abr enhanced the formation of multinucleated osteoclasts, bone resorption activity, and osteoclast marker gene expression. Moreover, Abr overexpression accelerated lamellipodia formation and induced the formation of well-developed actin in osteoclasts. Importantly, the Abr protein interacted with poly(ADP-ribose) glycohydrolase (PARG) and Rho GTPases, including RhoA, Rac1/2/3, and Cdc42 in osteoclasts. CONCLUSIONS: Taken together, these results indicate that Abr modulates osteoclastogenesis by enhancing lamellipodia formation via its interaction with PARG.

Functional roles of CD26/DPP4 in bleomycin-induced pulmonary fibrosis.

The pathogenesis of pulmonary fibrosis involves complex interplay between cell types and signaling pathways. Recurrent alveolar epithelial injury can occur during pulmonary inflammation, causing dysregulation of epithelial repair. Dysregulated repair interacts with mesenchymal, inflammatory, and endothelial cells to trigger fibroblast-to-myofibroblast activation. CD26/dipeptidyl peptidase-4 (DPP4) is a type II membrane protein mediating pleiotropic effect. However, the mechanistic role of CD26/DPP4 in pulmonary fibrosis remains unclear. In this study, we aimed to characterize Dpp4 deficiency in a mouse bleomycin (BLM)-induced pulmonary fibrosis model and in cell culture systems of human lung fibroblasts (HLFs). Dpp4 knockout (Dpp4 KO) mouse lungs exhibited lower Ashcroft scale indices, collagen content, and numbers of fibroblasts and myofibroblasts compared with those in C57BL/6 wild-type (WT) mice. Upregulation of Tgfb1 and Tgfb2 mRNA levels in the lungs after BLM treatment was lower in Dpp4 KO mice compared with those in WT mice. Although TGF-ß-driven endothelial-to-mesenchymal transition (EndMT) has been implicated as one of the mechanisms of pulmonary fibrosis, a number of partial EndMT cells in lungs did not differ between Dpp4 KO mice and WT mice. The proliferation capacity and mRNA levels of COL1A1, a collagen deposition-related gene, in cultured HLFs were suppressed in DPP4 small interfering RNA-treated cells. This study indicates that the genetic deficiency of DPP4 has protective effects against BLM-induced pulmonary fibrosis, partly through the reduction in TGF-ß expression and inhibition of fibroblast activation in the lung. Our study suggests that CD26/DPP4 inhibition is a potential therapeutic strategy for pulmonary fibrosis.

Significance of Brain Imaging for Staging in Patients With Clinical Stage T1-2 N0 Non-Small-Cell Lung Cancer on Positron Emission Tomography/Computed Tomography.

BACKGROUND: Routine positron emission tomography/computed tomography (PET/CT) has been recommended even for clinical stage I non-small-cell lung cancer (NSCLC). In spite of the progress in the screening procedure, and revisions to TNM classification, there is no evidence to support brain imaging screening of patients assessed with the current staging protocol including PET/CT. MATERIALS AND METHODS: We retrospectively investigated the frequency of extrathoracic metastasis in 466 consecutive patients with clinical stage T1-2 N0 NSCLC with the complete staging assessment comprised of thin-section CT, PET/CT, and brain contrast-enhanced magnetic resonance imaging between 2008 and 2016. All patients were reclassified according to the eighth edition of the tumor, node, and metastasis (TNM) classification. RESULTS: Among all patients, 70% of the tumors were pure solid and 30% had part-solid ground-glass opacity on thin-section CT, and 388 (83%) and 78 (17%) were classified into clinical stages T1 and T2, respectively. Eight patients (1.7%) had extrathoracic metastasis, including 3 (0.6%) with brain metastasis, and all showed pure-solid tumors. The frequency of extrathoracic and brain metastasis was 1.0% and 0.5% in 388 T1 patients, and 5.0% and 3.0% in 78 T2 patients. Although brain metastases were detected in 2 of 7 patients (29%) with PET/CT detectable extrathoracic metastases and 1 of 459 patients (0.2%) without PET/CT detectable extrathoracic metastasis, there were no neurologically asymptomatic brain metastases in patients with early-stage NSCLC confirmed by PET/CT. CONCLUSION: Routine screening of brain imaging is unnecessary in patients with early-stage NSCLC, assessed with the current staging protocol including PET/CT.

Prognosis after acute exacerbation in patients with interstitial lung disease other than idiopathic pulmonary fibrosis.

BACKGROUND: Acute exacerbation (AE) is recognized as a life-threatening condition with acute respiratory worsening in idiopathic pulmonary fibrosis (IPF). AE also occurs in fibrotic interstitial lung disease (ILD) other than IPF, including other types of idiopathic interstitial pneumonias (IIPs), ILD associated with collagen vascular disease (CVD-ILD), and chronic hypersensitivity pneumonia (CHP). However, the clinical impact after AE in those patients is still unclear. METHODS: A retrospective review of 174 consecutive first-episodes with AE of ILD in our institution from 2002 to 2016 was performed. AE was defined according to the revised definition and diagnostic criteria proposed by an international working group in 2016. Clinical characteristics, 90-day survival, and the requirement of long-term oxygen therapy (LTOT) after AE were evaluated in each underlying ILD. RESULTS: There were 102 patients with AE of IPF (AE-IPF) and 72 with AE of ILD other than IPF, including non-IPF IIPs (n = 29) and secondary ILD (n = 43) [CVD-ILD (n = 39), CHP (n = 4)]. In CVD-ILD, rheumatoid arthritis (n = 17) was most common. The 90-day mortality after AE was 57% in IPF, 29% in non-IPF IIPs, and 33% in secondary ILD. After AE, ILD other than IPF had a significantly better survival rate than IPF (P < 0.001). Among survivors, the rates of patients requiring LTOT after AE were 63% in IPF, 35% in non-IPF IIPs, and 46% in secondary ILD, respectively. CONCLUSIONS: AE of ILD other than IPF might have a better prognosis than AE-IPF, but both are fatal conditions that cause chronic respiratory failure.

Prognostic impact of an early marginal decline in forced vital capacity in idiopathic pulmonary fibrosis patients treated with pirfenidone.

BACKGROUND: Pirfenidone (PFD), an oral antifibrotic drug, is conditionally recommended for the treatment of idiopathic pulmonary fibrosis (IPF). This study aimed to investigate the prognostic factors in IPF patients treated with PFD and clarify the clinical significance of marginal physiological changes after PFD therapy. METHODS: We retrospectively reviewed 96 consecutive IPF patients treated with PFD. The physiological evaluation was performed at 3-6 months after PFD therapy, and the findings were classified into three groups based on the presence of a 5% change in %forced vital capacity (%FVC): improved, stable, and worsened. The clinical characteristics and prognostic outcomes were compared among groups, and the prognostic factors were evaluated by Cox proportional hazards analysis. RESULTS: Of the 96 patients, 25 (26.0%) showed acute exacerbation (AE) and 40 (41.6%) died during the observation period (median, 17 months). Physiological responses could be evaluated in 80 patients and the findings were as follows: improved, 23%; stable, 36%; and worsened, 41%. Time to the first AE and the survival rate were significantly shorter and lower, respectively, in the worsened group than in the improved/stable group (P = 0.002, P < 0.001, respectively). The prognostic analysis revealed that low %FVC at baseline (hazard ratio [HR]: 0.973 [0.950-0.996]), use of supplemental oxygen (HR: 2.180 [1.041-4.622]), and a "worsened" status after PFD therapy (HR: 5.253 [2.541-11.400]) were significantly associated with a poor prognosis. CONCLUSIONS: An early marginal decline in FVC may be important for survival outcomes in PFD-treated IPF patients.

IgG4-related disease presenting with combined pulmonary fibrosis and emphysema (CPFE).

A 64-year-old man was admitted to our hospital with an abnormal chest shadow. The patient was a current-smoker and had a past illness of autoimmune pancreatitis with a high serum level of IgG4, 348 mg/dL. Chest CT showed upper-lobe emphysema, and lower-lobe reticulation with honeycombing, suggestive of combined pulmonary fibrosis with emphysema (CPFE). Surgical lung biopsy was revealed a usual interstitial pneumonia pattern with marked infiltration of IgG4-positive plasma cells. The patient was diagnosed with IgG4 related disease (IgG4-RD) presenting with CPFE. Pulmonary manifestation was improved by corticosteroid therapy. IgG4-RD may be an underlying condition in patient with CPFE.

Anti-PL-7 Antisynthetase Syndrome with Eosinophilic Pleural Effusion.

A 68-year-old woman was admitted to our hospital with fever and pleural effusion. Her thoracentesis showed eosinophilic pleural effusion (EPE) without any evidence of malignancy, infection, or trauma. Pleural biopsy revealed pleuritis and intercostal myositis. Characteristic skin manifestations, including Gottron's sign, interstitial lung disease, and pericardial effusion, appeared later in the clinical course. She was finally diagnosed with anti-PL-7 antisynthetase syndrome (ASS) based on the presence of anti-PL-7 antibody, and she fulfilled the diagnostic criteria for dermatomyositis. These clinical manifestations improved with immunosuppressive therapy. EPE might therefore be one of the characteristic features of anti-PL-7 ASS.