ULK1 (unc-51 like kinase 1) is a serine/threonine protein kinase that plays a key role in regulating the induction of autophagy. Recent studies using autophagy-defective mouse models, such as atg5- or atg7-deficient mice, revealed an important function of autophagy in adipocyte differentiation. Suppression of adipogenesis in autophagy-defective conditions has made it difficult to study the roles of autophagy in metabolism of differentiated adipocytes. In this study, we established autophagy defective-differentiated 3T3-L1 adipocytes, and investigated the roles of Ulk1 and its close homolog Ulk2 in lipid and glucose metabolism using the established adipocytes. Through knockdown approaches, we determined that Ulk1 and Ulk2 are important for basal and MTORC1 inhibition-induced autophagy, basal lipolysis, and mitochondrial respiration. However, unlike other autophagy genes (Atg5, Atg13, Rb1cc1/Fip200, and Becn1) Ulk1 was dispensable for adipogenesis without affecting the expression of CCAAT/enhancer binding protein α (CEBPA) and peroxisome proliferation-activated receptor gamma (PPARG). Ulk1 knockdown reduced fatty acid oxidation and enhanced fatty acid uptake, the metabolic changes that could contribute to adipogenesis, whereas Ulk2 knockdown had opposing effects. We also found that the expression levels of insulin receptor (INSR), insulin receptor substrate 1 (IRS1), and glucose transporter 4 (SLC2A4/GLUT4) were increased in Ulk1-silenced adipocytes, which was accompanied by upregulation of insulin-stimulated glucose uptake. These results suggest that ULK1, albeit its important autophagic role, regulates lipid metabolism and glucose uptake in adipocytes distinctly from other autophagy proteins.
ULK1; ULK2; mTORC1; adipogenesis; adipocytes; lipid metabolism
Simultaneous improvement in respiratory maintenance and bleeding control increases survival of patients with life-threatening hemoptysis. Endobronchial blockade is an effective method and is preferred for emergency hemostasis. However, when the volume of hemoptysis is high, emergency hemostasis and airway maintenance are impossible due to flooding of blood into the airway. We used extracorporeal membrane oxygenation (ECMO) to overcome these limitations in a patient with massive hemoptysis due to severe blunt trauma and succeeded in saving the life by inducing a near-total airway obstruction.
Hemoptysis; extracorporeal membrane oxygenation (ECMO); hemostasis; trauma
Amino acids stimulate cell growth and suppress autophagy through activation of mTORC1. The activation of mTORC1 by amino acids is mediated by Rag guanosine triphosphatase (GTPase) heterodimers on the lysosome. The molecular mechanism by which amino acids regulate the Rag GTPase heterodimers remains to be elucidated. Here, we identify SH3BP4 (SH3 domain-binding protein 4) as a binding protein and a negative regulator of Rag GTPase complex. SH3BP4 binds to the inactive Rag GTPase complex through its Src homology 3 (SH3) domain under conditions of amino acid starvation and inhibits the formation of active Rag GTPase complex. As a consequence, the binding abrogates the interaction of mTORC1 with Rag GTPase complex and the recruitment of mTORC1 to the lysosome, thus inhibiting amino acid-induced mTORC1 activation and cell growth and promoting autophagy. These results demonstrate that SH3BP4 is a negative regulator of the Rag GTPase complex and amino acid-dependent mTORC1 signaling.
Interventional lung assist (iLA) effectively reduces CO2 retention and allows protective ventilation in cases of life-threatening hypercapnia. Despite the clinical efficacy of iLA, there are a few major limitations associated with the use of this approach, such as bleeding, thrombosis, and catheter-related limb ischemia. We presented two cases in which thrombotic complications developed during iLA. We demonstrated the two possible causes of thrombotic complications during iLA; stasis due to low blood flow and inadequate anticoagulation.
Lung; Complications; Thrombosistal
We hypothesized that pretreatment with sivelestat therapy could attenuate ventilator-induced lung injury (VILI) and lung inflammation in a rat model.
The neutrophil elastase inhibitor was administered intraperitoneally 30 min before and at the initiation of ventilation. The rats were categorized as (I) sham group; (II) VILI group; (III) sivelestat group; (IV) early sivelestat group. Wet-to-dry weight ratio, bronchoalveolar lavage fluid (BALF) neutrophil and protein, tissue malondialdehyde (MDA) and histologic VILI scores were investigated.
The ratio of wet-to-dry weight, BALF neutrophil and protein, tissue MDA and VILI scores were significantly increased in the VILI group compared to the sham group [3.85±0.32 vs. 9.05±1.02, P<0.001; (0.89±0.93)×104
vs. (7.67±1.41)×104 cells/mL, P<0.001; 2.34±0.47 vs. 23.01±3.96 mg/mL, P<0.001; 14.43±1.01 vs. 36.56±5.45 nmol/mg protein, P<0.001; 3.78±0.67 vs. 7.00±1.41, P<0.001]. This increase was attenuated in the early sivelestat group compared with the sivelestat group [wet-to-dry ratio: 6.76±2.01 vs. 7.39±0.32, P=0.032; BALF neutrophil: (5.56±1.13)×104
vs. (3.89±1.05)×104 cells/mL, P=0.021; BALF protein: 15.57±2.32 vs. 18.38±2.00 mg/mL, P=0.024; tissue MDA: 29.16±3.01 vs. 26.31±2.58, P=0.049; VILI scores: 6.33±1.41 vs. 5.00±0.50, P=0.024].
Pretreatment with a neutrophil elastase inhibitor attenuates VILI in a rat model.
Ventilator-induced lung injury (VILI); neutrophil elastase
Castleman's disease is a rare disorder characterized by benign tumors that may develop in the lymph node tissue throughout the body. Castleman's disease associated with myasthenia gravis is an especially rare disease. Only less than 10 cases have been reported in the world literature. The cause of Castleman's disease is associated with immune mediated reaction, and myasthenia gravis also develops due to an antibody-mediated process. The cause of myasthenia gravis is the immune activity of Castleman's disease, which may be the promoter of the antibody-mediated process. We report here a case of Castleman's disease, which was incidentally found in a patient diagnosed with myasthenia gravis.
Myasthenia gravis; Thymectomy; Retroperitoneal neoplasms
A 70-year-old male visited urgent care due to coughing for 1 month and left chest pain. He had no history of trauma. The initial chest computed tomography (CT) showed the 7th left intercostal lung herniation. A follow-up CT showed an intercostal lung herniation combined with a bowl herniation, which had developed due to a Morgagni's hernia. An emergency operation was performed due to the incarceration of the bowl and lung. The primary repair of the diaphragm was performed and the direct approximation of the 7th intercostal space was determined. We concluded that the defect of the diaphragm and the intercostal muscle was a congenital lesion, and the recurrent coughing was the aggravating factor of herniation.
Morgagni's hernia; Hernia, lung
ULK1 (Unc51-like kinase, hATG1) is a Ser/Thr kinase that plays a key role in inducing autophagy in response to starvation. ULK1 is phosphorylated and negatively regulated by the mammalian target of rapamycin complex 1 (mTORC1). Previous studies have shown that ULK1 is not only a downstream effector of mTORC1 but also a negative regulator of mTORC1 signaling.1–3 Here, we investigated how ULK1 regulates mTORC1 signaling, and found that ULK1 inhibits the kinase activity of mTORC1 and cell proliferation. Deficiency or knockdown of ULK1 or its homolog ULK2 enhanced mTORC1 signaling, cell proliferation rates and accumulation of cell mass, whereas overexpression of ULK1 had the opposite effect. Knockdown of Atg13, the binding partner of ULK1 and ULK2, mimicked the effects of ULK1 or ULK2 deficiency or knockdown. Both insulin and leucine stimulated mTORC1 signaling to a greater extent when ULK1 or ULK2 was deficient or knocked down. In contrast, Atg5 deficiency did not have a significant effect on mTORC1 signaling and cell proliferation. The stimulatory effect of ULK1 knockdown on mTORC1 signaling occurred even in the absence of tuberous sclerosis complex 2 (TSC2), the negative regulator of mTORC1 signaling. In addition, ULK1 was found to bind raptor, induce its phosphorylation, and inhibit the kinase activity of mTORC1. These results demonstrate that ULK1 negatively regulates the kinase activity of mTORC1 and cell proliferation in a manner independent of Atg5 and TSC2. The inhibition of mTORC1 by ULK1 may be important to coordinately regulate cell growth and autophagy with optimized utilization of cellular energy.
ULK1; ULK2; Atg5; raptor; mTOR
Nutrient starvation induces autophagy in eukaryotic cells through inhibition of TOR (target of rapamycin), an evolutionarily-conserved protein kinase. TOR, as a central regulator of cell growth, plays a key role at the interface of the pathways that coordinately regulate the balance between cell growth and autophagy in response to nutritional status, growth factor and stress signals. Although TOR has been known as a key regulator of autophagy for more than a decade, the underlying regulatory mechanisms have not been clearly understood. This review discusses the recent advances in understanding of the mechanism by which TOR regulates autophagy with focus on mammalian TOR (mTOR) and its regulation of the autophagy machinery.
mTOR; Atg1; ULK1; ULK2; Atg13
Block copolymers composed of poly(3-hydroxyoctanoate) (PHO) and methoxy poly(ethylene glycol) (PEG) were synthesized to prepare paclitaxel-incorporated nanoparticle for antitumor drug delivery. In a 1H-NMR study, chemical structures of PHO/PEG block copolymers were confirmed and their molecular weight (M.W.) was analyzed with gel permeation chromatography (GPC). Paclitaxel as a model anticancer drug was incorporated into the nanoparticles of PHO/PEG block copolymer. They have spherical shapes and their particle sizes were less than 100 nm. In a 1H-NMR study in D2O, specific peaks of PEG solely appeared while peaks of PHO disappeared, indicating that nanoparticles have core-shell structures. The higher M.W. of PEG decreased loading efficiency and particle size. The higher drug feeding increased drug contents and average size of nanoparticles. In the drug release study, the higher M.W. of PEG block induced the acceleration of drug release rate. The increase in drug contents induced the slow release rate of drug. In an antitumor activity study in vitro, paclitaxel nanoparticles have practically similar anti-proliferation activity against HCT116 human colon carcinoma cells. In an in vivo animal study using HCT116 colon carcinoma cell-bearing mice, paclitaxel nanoparticles have enhanced antitumor activity compared to paclitaxel itself. Therefore, paclitaxel-incorporated nanoparticles of PHO/PEG block copolymer are a promising vehicle for antitumor drug delivery.
Nanoparticles; Block copolymer; Poly(3-hydroxyoctanoate); Drug delivery
In this study, the effect of chlorin e6-based photodynamic therapy (Ce6-PDT) was investigated in human intrahepatic (HuCC-T1) and extrahepatic (SNU1196) cholangiocarcinoma (CCA) cells. The amount of intracellular Ce6 increased with increasing Ce6 concentration administered, or with incubation time, in both cell lines. The ability to take up Ce6 and generate reactive oxygen species after irradiation at 1.0 J/cm2 did not significantly differ between the two CCA cell types. However, after irradiation, marked differences were observed for photodamage and apoptotic/necrotic signals. HuCC-T1 cells are more sensitive to Ce6-PDT than SNU1196 cells. Total glutathione (GSH) levels, glutathione peroxidase and glutathione reductase activities in SNU1196 cells were significantly higher than in HuCC-T1 cells. With inhibition of enzyme activity or addition of GSH, the phototoxic effect could be controlled in CCA cells. The intracellular level of GSH is the most important determining factor in the curative action of Ce6-PDT against tumor cells.
cholangiocarcinoma; chlorin e6; photodynamic therapy; reactive oxygen species; glutathione; heme oxygenase-1
Cell cycles, ordered series of events modulating cell growth and division, are tightly regulated by complexes containing cyclin-dependent kinases (CDKs) and cyclins. Cyclin O is a novel cyclin family protein which interacts with CDK2. However, the molecular effects of cyclin O on the activity of CDK2 have not been fully evaluated. In this study, an interaction between cyclin O and CDK2 was identified by co-immunoprecipitation and the effect of cyclin O on the kinase activity of CDK2 was investigated using cyclin O point mutants. Co-immunoprecipitation was achieved using using HEK293 human embryonic kidney cells which were transiently transfected with vectors expressing cyclin O and CDK2, which revealed that cyclin O interacted with CDK2, particularly with the active form of endogenous CDK2. Cyclin O was expressed as several different bands with molecular weights between 45 and 50 kDa, possibly due to different post-translational modifications. When co-expressed with CDK2, cyclin O appeared as a band with a molecular weight of 50 kDa. Treatment with calf intestinal phosphatase reduced the intensity of the uppermost band. Mass spectroscopic analysis of cyclin O co-expressed with CDK2 revealed that the 81st serine residue of cyclin O was phosphorylated. The in vitro kinase activity of CDK2 phosphorylating histone H1 was markedly increased in the cells overexpressing cyclin O. This activity was reduced in cells overexpressing cyclin O, in which the 81st serine had been replaced with alanine (S81A). These results suggest that cyclin O is a novel cyclin family protein that regulates CDK2 kinase activity, which is mediated by the phosphorylation of the 81st serine residue of cyclin O.
cyclin-dependent kinase 2; cyclin O; phosphorylation; kinase activity
Autophagy, the starvation-induced degradation of bulky cytosolic components, is up-regulated in mammalian cells when nutrient supplies are limited. Although mammalian target of rapamycin (mTOR) is known as the key regulator of autophagy induction, the mechanism by which mTOR regulates autophagy has remained elusive. Here, we identify that mTOR phosphorylates a mammalian homologue of Atg13 and the mammalian Atg1 homologues ULK1 and ULK2. The mammalian Atg13 binds both ULK1 and ULK2 and mediates the interaction of the ULK proteins with FIP200. The binding of Atg13 stabilizes and activates ULK and facilitates the phosphorylation of FIP200 by ULK, whereas knockdown of Atg13 inhibits autophagosome formation. Inhibition of mTOR by rapamycin or leucine deprivation, the conditions that induce autophagy, leads to dephosphorylation of ULK1, ULK2, and Atg13 and activates ULK to phosphorylate FIP200. These findings demonstrate that the ULK-Atg13-FIP200 complexes are direct targets of mTOR and important regulators of autophagy in response to mTOR signaling.
Macroautophagy is an evolutionarily conserved cellular process involved in the clearance of proteins and organelles. Although the cytoplasmic machinery that orchestrates autophagy induction during starvation, hypoxia, or receptor stimulation has been widely studied, the key epigenetic events that initiate and maintain the autophagy process remain unknown. Here we show that the methyltransferase G9a coordinates the transcriptional activation of key regulators of autophagosome formation by remodeling the chromatin landscape. Pharmacological inhibition or RNA interference (RNAi)-mediated suppression of G9a induces LC3B expression and lipidation that is dependent on RNA synthesis, protein translation, and the methyltransferase activity of G9a. Under normal conditions, G9a associates with the LC3B, WIPI1, and DOR gene promoters, epigenetically repressing them. However, G9a and G9a-repressive histone marks are removed during starvation and receptor-stimulated activation of naive T cells, two physiological inducers of macroautophagy. Moreover, we show that the c-Jun N-terminal kinase (JNK) pathway is involved in the regulation of autophagy gene expression during naive-T-cell activation. Together, these findings reveal that G9a directly represses genes known to participate in the autophagic process and that inhibition of G9a-mediated epigenetic repression represents an important regulatory mechanism during autophagy.
Acupuncture as an ancient Chinese treatment has proven effective and is utilized worldwide. Although it is generally believed to be a safe clinical procedure, serious lethal complications including death have been reported. We present a rare case of life-threatening cardiac tamponade due to penetration of an acupuncture needle directly into the right ventricle.
Acupuncture; Complications; Cardiac tamponade
Mammalian target of rapamycin complex 1 (mTORC1) is a master regulator of cell growth and autophagy. Its activity is regulated by the availability of amino acids and growth factors. The activation of mTORC1 by growth factors, such as insulin and insulin-like growth factor-1 (IGF-1), is mediated by tuberous sclerosis complex (TSC) 1 and 2 and Rheb GTPase. Relative to the growth factor-regulated mTORC1 pathway, the evolutionarily ancient amino acid-mTORC1 pathway remains not yet clearly defined. The amino acid-mTORC1 pathway is mediated by Rag GTPase heterodimers. Several binding proteins of Rag GTPases were discovered in recent studies. Here, we discuss the functions and mechanisms of the newly-identified binders of Rag GTPases. In particular, this review focuses on SH3 binding protein 4 (SH3BP4), the protein recently identifed as a negative regulator of Rag GTPases.
mTOR; mTORC1; Rag GTPases; SH3BP4
Heart rate variability (HRV) changes as a function of psychiatric illness. This study aimed to evaluate HRV among patients with various psychiatric disorders.
The present study recruited patients with schizophrenia (n=35), bipolar disorder (n=41), post-traumatic stress disorder (PTSD; n=34), or major depressive disorder (n=34) as well as healthy controls (n=27). The time-domain analysis (the standard deviation of all RR intervals [SDNN] and the square root of the mean squared differences of successive normal sinus intervals [RMSSD]), the frequency-domain analysis (very low frequency, low frequency [LF], high frequency [HF], and total power [TP]), and a non-linear complexity measure the approximate entropy were computed.
SDNN and HF were significantly reduced in patients with schizophrenia compared with healthy controls. SDNN, RMSSD, TP, LF, and HF were significantly reduced in bipolar patients compared with healthy controls. HF was significantly reduced in PTSD patients compared with healthy controls.
Our findings indicate that HRV is not sufficiently powerful to discriminate among various psychiatric illnesses. However, our results suggest that HRV, particularly HF, could be used as a tool for discriminating between psychiatric patients and healthy controls.
Heart rate variability; Schizophrenia; Bipolar disorder; Post traumatic stress disorder; Major depressive disorder
Vacuum-assisted closure therapy is an alternative method for a massive subcutaneous emphysema treatment. It is easily applicable and shows rapid effectiveness in massive subcutaneous emphysema, intractable with chest tube drainage.
Subcutaneous emphysema; Device; Negative pressure
Nanoparticles based on stimuli-sensitive drug delivery have been extensively investigated for tumor targeting. Among them, pH-responsive drug targeting using pH-sensitive polymers has attracted attention because solid tumors have an acidic environment. A dextran-b-poly(L-histidine) (DexPHS) copolymer was synthesized and pH-responsive nanoparticles were fabricated for drug targeting.
Methods and results
A DexPHS block copolymer was synthesized by attaching the reductive end of dextran to the amine groups of poly(L-histidine). pH-responsive nanoparticles incorporating doxorubicin were fabricated and studied in HuCC-T1 cholangiocarcinoma cells. Synthesis of DexPHS was confirmed by 1H nuclear magnetic resonance spectroscopy, with specific peaks of dextran and PHS observed at 2–5 ppm and 7.4–9.0 ppm, respectively. DexPHS nanoparticles showed changes in particle size with pH sensitivity, ie, the size of the nanoparticles increased at an acidic pH and decreased at a basic pH. DexPHS block copolymer nanoparticles incorporating doxorubicin were prepared using the nanoprecipitation dialysis method. The doxorubicin release rate was increased at acidic pH compared with basic pH, indicating that DexPHS nanoparticles have pH-sensitive properties and that drug release can be controlled by variations in pH. The antitumor activity of DexPHS nanoparticles incorporating doxorubicin were studied using HuCC-T1 cholangiocarcinoma cells. Viability was decreased in cells treated with nanoparticles at acidic pH, whereas cell viability in response to treatment with doxorubicin did not vary according to changes of pH.
Our results indicated that DexPHS polymeric micelles are promising candidates for antitumor drug targeting.
pH-responsive drug targeting; nanoparticles; block copolymer; poly(L-histidine); dextran
The aim of this study was to investigate the effect of the combination of vorinostat and epigallocatechin-3-gallate against HuCC-T1 human cholangiocarcinoma cells. A novel chemotherapy strategy is required as cholangiocarcinomas rarely respond to conventional chemotherapeutic agents. Both vorinostat and EGCG induce apoptosis and suppress invasion, migration, and angiogenesis of tumor cells. The combination of vorinostat and EGCG showed synergistic growth inhibitory effects and induced apoptosis in tumor cells. The Bax/Bcl-2 expression ratio and caspase-3 and -7 activity increased, but poly (ADP-ribose) polymerase expression decreased when compared to treatment with each agent alone. Furthermore, invasion, matrix metalloproteinase (MMP) expression, and migration of tumor cells decreased following treatment with the vorinostat and EGCG combination compared to those of vorinostat or EGCG alone. Tube length and junction number of human umbilical vein endothelial cells (HUVECs) decreased as well as vascular endothelial growth factor expression following vorinostat and EGCG combined treatment. These results indicate that the combination of vorinostat and EGCG had a synergistic effect on inhibiting tumor cell angiogenesis potential. We suggest that the combination of vorinostat and EGCG is a novel option for cholangiocarcinoma chemotherapy.
5-Aminolevulinic acid (ALA)-based photodynamic therapy (PDT) has the potential to kill cancer cells via apoptotic or necrotic signals that are dependent on the generation of intracellular reactive oxygen species (ROS). Celecoxib is an anti-inflammatory drug that induces intracellular ROS generation. We investigated whether the combined application of celecoxib and ALA-PDT improved the efficacy of PDT in human cholangiocarcinoma cells and in tumor bearing mice. In vitro, combined treatment of celecoxib and ALA-PDT increased phototoxicity and intracellular ROS levels after irradiation with 0.75 J/cm2 when compared to ALA-PDT alone. Even though ROS levels increased with 0.25 J/cm2 of irradiation, it did not influence phototoxicity. When heme oxygenase-1, a defensive protein induced by oxidative stress, was inhibited in the combined treatment group, phototoxicity was increased at both 0.25 J/cm2 and 0.75 J/cm2 of irradiation. We identified the combined effect of ALA-PDT and celecoxib through the increase of oxidative stress such as ROS. In vivo, about 40% tumor growth inhibition was observed with combined application of ALA-PDT and celecoxib when compared to ALA-PDT alone. The combined application of ALA-PDT and celecoxib could be an effective therapy for human cholangiocarcinoma. Moreover, use of a heme oxygenase-1 inhibitor with PDT could play an important role for management of various tumors involving oxidative stress.
celecoxib; aminolevulinic acid; reactive oxygen species; photodynamic therapy; human cholangiocarcinoma
The prognosis of acute lung injury (ALI) after pneumonectomy is poor, with reported mortality rates of 30-100%. Neutrophil elastase inhibitor (NEI) is known to prevent lung injury caused by neutrophil elastase and improve lung function in ALI. We evaluated the effect of NEI on ALI after pneumonectomy.
We analyzed nine patients who required ventilator care due to ALI after pneumonectomy. Five of these patients underwent conventional ventilator care (group I), and four patients underwent ventilator care and were administrated NEI (group II). We retrospectively analyzed the lung injury score (LIS) for 10 days after intubation.
The LIS before intubation satisfied the diagnostic criteria of ALI or acute respiratory distress syndrome (ARDS) in all patients. After intubation, the LIS improved in both groups. But, as times went on, the mean value of the LIS in group II was lower compared to group I. In group I, only one patient underwent extubation. In group II, extubation was possible in three patients. Mortality rates were 80% in group I and 25% in group II.
We conclude that NEI may improve the lung function, shorten the duration of mechanical ventilation, and reduce mortality in patients with ALI after pneumonectomy.
Background and Purpose
Dopamine agonists are first-line drugs for treating the symptoms of restless legs syndrome (RLS). However, few studies have investigated the effect of dopamine agonists on the quality of life (QoL) in RLS patients. We conducted a study to determine whether ropinirole exerts positive effects on the QoL in RLS patients and to analyze the underlying factors.
Primary RLS patients from eight medical centers were recruited in the study. They were evaluated in the baseline phase using various questionnaires including the Korean versions of the International Restless Legs Scale (K-IRLS), RLS QoL questionnaire (K-RLSQoL), and the Short Form 36 Health Survey (SF-36). After taking ropinirole for 8 weeks the same questionnaires were again completed as a re-evaluation. We analyzed the statistical difference using a paired t-test, a Pearson's correlation, and a stepwise multiple regression in order to identify the factors associated with the QoL change.
A total of 107 subjects, including 65 (60.7%) females, completed this study. They were aged 51.68±14.80 years (mean±SD) and had a symptom duration of 8.8±9.0 months. After treatment with ropinirole, there were significant improvements on the K-RLSQoL, SF-36, and K-IRLS. The Pearson's correlation analysis showed that the improvement of QoL in RLS patients was significantly correlated with the severity of RLS (r=0.236, p<0.014) at baseline.
The results from this study suggest that treatment with ropinirole can improve the QoL in RLS patients. The improvement in the QoL is more related with the improvement of RLS symptoms.
restless legs syndrome; dopamine agonists; quality of life; sleep
Autophagy, the primary recycling pathway of cells, plays a critical role in mitochondrial quality control under normal growth conditions and in the response to cellular stress. The Hsp90-Cdc37 chaperone complex coordinately regulates the activity of select kinases to orchestrate many facets of the stress response. Although both maintain mitochondrial integrity, the relationship between Hsp90-Cdc37 and autophagy has not been well characterized. Ulk1, one of the mammalian homologues of yeast Atg1, is a serine-threonine kinase required for mitophagy. Here we show that the interaction between Ulk1 and Hsp90-Cdc37 stabilizes and activates Ulk1, which in turn is required for the phosphorylation and release of Atg13 from Ulk1, and for the recruitment of Atg13 to damaged mitochondria. Hsp90-Cdc37, Ulk1 and Atg13 phosphorylation are all required for efficient mitochondrial clearance. These findings establish a direct pathway that integrates Ulk1- and Atg13- directed mitophagy with the stress response coordinated by Hsp90 and Cdc37.
Oxidative stress such as reactive oxygen species (ROS) within the inflamed joint have been indicated as being involved as inflammatory mediators in the induction of arthritis. Correlations between extracellular-superoxide dismutase (EC-SOD) and inflammatory arthritis have been shown in several animal models of RA. However, there is a question whether the over-expression of EC-SOD on arthritic joint also could suppress the progression of disease or not. In the present study, the effect on the synovial tissue of experimental arthritis was investigated using EC-SOD over-expressing transgenic mice. The over-expression of EC-SOD in joint tissue was confirmed by RT-PCR and immunohistochemistry. The degree of the inflammation in EC-SOD transgenic mice was suppressed in the collagen-induced arthritis model. In a cytokine assay, the production of pro-inflammatory cytokines such as, IL-1β, TNFα, and matrix metalloproteinases (MMPs) was decreased in fibroblast-like synoviocyte (FLS) but not in peripheral blood. Histological examination also showed repressed cartilage destruction and bone in EC-SOD transgenic mice. In conclusion, these data suggest that the over-expression of EC-SOD in FLS contributes to the activation of FLS and protection from joint destruction by depressing the production of the pro-inflammatory cytokines and MMPs. These results provide EC-SOD transgenic mice with a useful animal model for inflammatory arthritis research.
arthritis, experimental; reactive oxygen species; rheumatoid arthritis; superoxide dismutase; synovial membrane