Hisatoshi Asano

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.

BackgroundPirfenidone (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.MethodsTransforming growth factor-β (TGF-β)-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.ResultsWe 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-β. 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.ConclusionsThese 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.

Azithromycin attenuates myofibroblast differentiation and lung fibrosis development through proteasomal degradation of NOX4

ABSTRACT Accumulation of profibrotic myofibroblasts is involved in the process of fibrosis development during idiopathic pulmonary fibrosis (IPF) pathogenesis. TGFB (transforming growth factor β) is one of the major profibrotic cytokines for myofibroblast differentiation and NOX4 (NADPH oxidase 4) has an essential role in TGFB-mediated cell signaling. Azithromycin (AZM), a second-generation antibacterial macrolide, has a pleiotropic effect on cellular processes including proteostasis. Hence, we hypothesized that AZM may regulate NOX4 levels by modulating proteostasis machineries, resulting in inhibition of TGFB-associated lung fibrosis development. Human lung fibroblasts (LF) were used to evaluate TGFB-induced myofibroblast differentiation. With respect to NOX4 regulation via proteostasis, assays for macroautophagy/autophagy, the unfolded protein response (UPR), and proteasome activity were performed. The potential anti-fibrotic property of AZM was examined by using bleomycin (BLM)-induced lung fibrosis mouse models. TGFB-induced NOX4 and myofibroblast differentiation were clearly inhibited by AZM treatment in LF. AZM-mediated NOX4 reduction was restored by treatment with MG132, a proteasome inhibitor. AZM inhibited autophagy and enhanced the UPR. Autophagy inhibition by AZM was linked to ubiquitination of NOX4 via increased protein levels of STUB1 (STIP1 homology and U-box containing protein 1), an E3 ubiquitin ligase. An increased UPR by AZM was associated with enhanced proteasome activity. AZM suppressed lung fibrosis development induced by BLM with concomitantly reduced NOX4 protein levels and enhanced proteasome activation. These results suggest that AZM suppresses NOX4 by promoting proteasomal degradation, resulting in inhibition of TGFB-induced myofibroblast differentiation and lung fibrosis development. AZM may be a candidate for the treatment of the fibrotic lung disease IPF.

Feasibility of thoracoscopic thymectomy for treatment of early‐stage thymoma

The objective of this study was to evaluate the feasibility of thoracoscopic thymectomy (TT) for treatment of early‐stage thymoma and to compare the outcomes with those after open thymectomy (OT).

Anomalous Systemic Arterial Supply to the Basal Segments of the Lung: Feasible Thoracoscopic Surgery

BACKGROUND Anomalous systemic arterial supply to the basal segments of the lung is a rare anomaly. This study aimed to evaluate the outcomes of thoracoscopic surgery for this anomaly. METHODS We reviewed patients who underwent thoracoscopic surgery for anomalous systemic arterial supply to the basal segments of the lung between October 2007 and September 2012 at our institution. RESULTS Four patients (mean age 37.5 years; range, 22 to 54) underwent thoracoscopic surgery for anomalous systemic arterial supply to the basal segments of the lung. The mean diameter of the anomalous arteries was 14 mm (range, 10 to 16 mm). Two patients underwent thoracoscopic segmentectomy, 1 of whom had a complicated anomaly that necessitated conversion to thoracotomy. The other 2 patients underwent thoracoscopic lower lobectomy of the left lung. One of them had an aneurysm in the anomalous artery; therefore, endovascular devices were kept on standby in case massive hemorrhage occurred. The anomalous arteries were divided uneventfully using a vascular stapler in all patients. No patient had severe postoperative complications. CONCLUSIONS Thoracoscopic surgery for anomalous systemic arterial supply to the basal segments of the lung is feasible, safe, and minimally invasive, with confirmed effectiveness in typical cases.

Oncological outcomes of thoracoscopic thymectomy for the treatment of stages I–III thymomas

OBJECTIVES Thoracoscopic thymectomy has gradually replaced conventional sternotomy for resection of thymoma; however, a thoracoscopic approach for thymoma remains controversial. We evaluated the oncological outcomes of thoracoscopic thymectomy for the treatment of stages I-III thymomas. METHODS Sixty-two patients who underwent thoracoscopic thymectomy for the treatment of thymoma were retrospectively reviewed between July 2005 and September 2011 at Jikei University Hospital. Surgical outcomes and pathological results between stages I+II and stage III were compared. RESULTS Twenty-nine patients had Masaoka stage I, 28 had stage II and 5 had stage III. Three stage III patients needed conversions to open surgery. Masaoka stage III comprised pathological type B3 in 3 patients and thymic carcinoma in 2. For all patients, the 5-year overall survival rate was 100%. Three recurrences, diagnosed as thymic carcinoma, were observed in the Masaoka stage II or III patients. The 5-year disease-free survival rate was 94.2% for all patients, 100% for Masaoka stage I, 96.1% for stage II and 37.5% (55 months) for stage III (P=0.002). The 5-year disease-free survival rate was 100% for the World Health Organization classification types A, AB and B1-3 and 0% for thymic carcinoma (P<0.0001). Significant differences were found in the 5-year disease-free survival stratified by the Masaoka stage or WHO classification, but not by surgical procedures. CONCLUSIONS Thoracoscopic thymectomy for Masaoka stages I and II thymomas presented acceptable oncological outcomes. Further investigation in a large series with longer follow-up is required. Masaoka stage III thymoma requires careful consideration of the approaches, including median sternotomy.

Thoracoscopic resection of a mediastinal venous hemangioma: Report of a case

Mediastinal hemangioma is a rare tumor, accounting for 0.5% or fewer of all mediastinal tumors in most reports. We herein report a case of thoracoscopic resection of venous hemangioma in the middle mediastinum. A 48-year-old man was referred to our hospital for dysphagia. A chest computed tomography scan showed the mass to have a smooth surface and heterogeneous contents. Magnetic resonance imaging demonstrated the morphology of the vascular tumor to be a hyperintense mass on a T2-weighted image. Using thoracoscopic surgery, the tumor was completely extirpated and confirmed histologically to be a venous hemangioma. In this case, thoracoscopic surgery provided a satisfactory view and facilitated correct handling for the mediastinal venous hemangioma.

Thoracoscopic resection for a pulmonary nodule with the infiltrate of IgG4-positive plasma cells.

This report describes a rare case of IgG4‐related lung disease that was difficult to distinguish from lung cancer. CT revealed a well‐demarcated round tumor in S10 of the right lung of a 56‐year‐old man suspected of having lung cancer. PET revealed high fluorodeoxyglucose uptake with a maximum standardized uptake value of 14.0. Because primary lung cancer was strongly suspected, lower lobectomy was performed via the thoracoscopic approach without mini‐thoracotomy. Histopathology showed lymphoplasmacytic infiltration. Immunostaining revealed numerous IgG4‐positive plasma cells diffusely infiltrating the tumor. Serum IgG4 levels increased, thereby confirming the diagnosis of IgG4‐related lung disease.

Thoracoscopic thymectomy is a feasible and less invasive alternative for the surgical treatment of large thymomas

OBJECTIVES Thoracoscopic surgery is widely used for the surgical treatment of thymoma. However, large-sized thymomas are typically treated using open surgery. This study evaluated the feasibility of performing thoracoscopic thymectomy (TT) for thymoma ≥50 mm. METHODS A retrospective review was conducted on 135 patients who underwent TT or open thymectomy (OT) for Masaoka stage I-IVa thymoma between 1996 and 2014. RESULTS Patients were first divided into two groups based on thymoma size: thymoma ≥50 mm and thymoma <50 mm groups. There was no significant difference in the 5-year disease-free survival (DFS) between the groups ( P  = 0.5352). Patients in the thymoma ≥50 mm group were further subdivided into TT and OT groups. The length of postoperative hospital stay was significantly shorter in the TT group than in the OT group (5 vs 14 days, P  < 0.0001), with significantly fewer postoperative complications (6 patients vs 14 patients, P  = 0.0008). There was no significant difference in the 5-year DFS between patients with thymoma ≥50 mm in the TT and OT groups ( P  = 0.3501). Finally, patients undergoing TT were further subdivided into thymoma ≥50 mm and thymoma <50 mm groups and, no significant difference in the 5-year DFS was found between these groups ( P  = 0.6661). Masaoka stages III-IV, but not thymoma size, were an independent prognostic factor for DFS. CONCLUSIONS These results demonstrate the decreased invasiveness and feasibility of TT for large-sized thymomas.

A step-by-step development of real-size chest model for simulation of thoracoscopic surgery

OBJECTIVES For the purpose of simulating thoracoscopic surgery, we have conducted stepwise development of a life-like chest model including thorax and intrathoracic organs. METHODS First, CT data of the human chest were obtained. First-generation model: based on the CT data, each component of the chest was made from a 3D printer. A hard resin was used for the bony thorax and a rubber-like resin for the vessels and bronchi. Lung parenchyma, muscles and skin were not created. Second-generation model: in addition to the 3D printer, a cast moulding method was used. Each part was casted using a 3D printed master and then assembled. The vasculature and bronchi were casted using silicon resin. The lung parenchyma and mediastinum organs were casted using urethane foam. Chest wall and bony thorax were also casted using a silicon resin. Third-generation model: foamed polyvinyl alcohol (PVA) was newly developed and casted onto the lung parenchyma. The vasculature and bronchi were developed using a soft resin. A PVA plate was made as the mediastinum, and all were combined. RESULTS The first-generation model showed real distribution of the vasculature and bronchi; it enabled an understanding of the anatomy within the lung. The second-generation model is a total chest dry model, which enabled observation of the total anatomy of the organs and thorax. The third-generation model is a wet organ model. It allowed for realistic simulation of surgical procedures, such as cutting, suturing, stapling and energy device use. This single-use model achieved realistic simulation of thoracoscopic surgery. CONCLUSIONS As the generation advances, the model provides a more realistic simulation of thoracoscopic surgery. Further improvement of the model is needed.