Deok Ryong Kim

Neurotoxicity of microglial cathepsin D revealed by secretome analysis

Microglia‐driven inflammatory responses have both neuroprotective and neurotoxic effects in the CNS. The excessive and chronic activation of microglia, however, may shift the balance towards neurotoxic effects. In this regard, proteins secreted from activated microglia likely play a key role in the neurotoxic effects. To characterize secreted proteins of activated microglia, conditioned media obtained from BV‐2 mouse microglia cells were analyzed by two‐dimensional gel electrophoresis or liquid chromatography coupled with tandem mass spectrometry. Among many proteins identified in the secretome of activated microglia, an aspartic endoprotease cathepsin D has been found to mediate microglial neurotoxicity based on the following results: (i) the expression of cathepsin D protein was markedly increased in lipopolysaccharide/interferon‐γ‐stimulated microglia compared with resting microglia as determined by western blot analysis of conditioned media; (ii) knockdown of cathepsin D expression in microglia using short hairpin RNA diminished the neurotoxicity in the coculture of microglia and neuroblastoma cells and (iii) recombinant procathepsin D protein exerted cytotoxic effects toward cultured neurons. In conclusion, cathepsin D appears to play a central role in the microglial neurotoxicity, and could be a potential biomarker or drug target for the diagnosis and treatment of neurodegenerative diseases that are associated with excessive microglial activation and subsequent neurotoxic inflammation.

Autophagy protects the rotenone-induced cell death in α-synuclein overexpressing SH-SY5Y cells

Loss of dopaminergic cells induced by alpha-synuclein accumulation in substantia nigra causes the development of Parkinsons disease (PD). To date, although autophagy has been implicated in the pathology of PD, the molecular mechanism is still unclear. To study the role of autophagy in PD pathogenesis, we established stable SH-SY5Y cell lines overexpressing wild-type or mutant alpha-synuclein proteins (A30P or A53T). Overexpression of mutant alpha-synuclein induced some protein aggregates and cell death in the absence of drug. LC3-II protein, a critical marker for autophagy, was produced in an autophagy-dependent manner. The rotenone-induced cell death was interrupted by autophagy stimulation. Autophagy activation also restored the mitochondrial membrane potential (MMP) impaired by rotenone in mutant alpha-synuclein expressing cells. Additionally, autophagy activation significantly relieved rotenone-induced ROS accumulation and HIF-1alpha expression in neuronal cells expressing mutant alpha-synuclein proteins. These findings indicate that autophagy plays an important scavenger role against harmful influence of toxic protein aggregates produced in rotenone-treated cells.

Cathepsin D inhibits oxidative stress-induced cell death via activation of autophagy in cancer cells

Cathepsin D (CatD), a lysosomal aspartic protease, plays an essential role in tumor progression and apoptosis. However, the function of CatD in cell death is not yet fully understood. In this study, we identified CatD as one of up-regulated proteins in human malignant glioblastoma M059J cells that lack the catalytic subunit of DNA-PK compared with its isogenic M059K cells with normal DNA-PK activity. M059J cells were relatively more resistant to genotoxic stress than M059K cells. Overexpression of wild-type CatD but not catalytically inactive mutant CatD (D295N) inhibited H(2)O(2)-induced cell death in HeLa cells. Furthermore, knockdown of CatD expression abolished anti-apoptotic effect by CatD in the presence of H(2)O(2). Interestingly, high expression of CatD in HeLa cells significantly activated autophagy: increase of acidic autophagic vacuoles, LC3-II formation, and GFP-LC3 puncta. These results suggest that CatD can function as an anti-apoptotic mediator by inducing autophagy under cellular stress. In conclusion, inhibition of autophagy could be a novel strategy for the adjuvant chemotherapy of CatD-expressing cancers.

Propofol protects the autophagic cell death induced by the ischemia/reperfusion injury in rats

Autophagy has been implicated in cardiac cell death during ischemia/reperfusion (I/R). In this study we investigated how propofol, an antioxidant widely used for anesthesia, affects the autophagic cell death induced by the myocardial I/R injury. The infarction size in the myocardium was dramatically reduced in rats treated with propofol during I/R compared with untreated rats. A large number of autophagic vacuoles were observed in the cardiomyocytes of I/R-injured rats but rarely in I/R-injured rats treated with propofol. While LC3-II formation, an autophagy marker, was up-regulated in the I/R-injured myocardium, it was significantly down-regulated in the myocardial tissues of I/R-injured and propofol-treated rats. Moreover, propofol inhibited the I/R-induced expression of Beclin-1, and it accelerated phosphorylation of mTOR during I/R and Beclin-1/Bcl-2 interaction in cells, which indicates that it facilitates the inhibitory pathway of autophagy. These data suggest that propofol protects the autophagic cell death induced by the myocardial I/R injury.

Gangliosides induce autophagic cell death in astrocytes

Background and purpose:  Gangliosides, sialic acid‐containing glycosphingolipids, abundant in brain, are involved in neuronal function and disease, but the precise molecular mechanisms underlying their physiological or pathological activities are poorly understood. In this study, the pathological role of gangliosides in the extracellular milieu with respect to glial cell death and lipid raft/membrane disruption was investigated.

Disease-specific Proteins from Rheumatoid Arthritis Patients

Rheumatoid arthritis (RA) is a chronic inflammatiory disease that mainly destroys cartilages or bones at the joints. This inflammatory disorder is initiated by self-attack using own immune system, but the detail of pathological mechanism is unclear. Features of autoantigens leading to autoimmune disease are also under veil although several candidates including type II collagen have been suggested to play a role in pathogenesis. In this report, we tried to identify proteins responding to antibodies purified from RA patients and screen proteins up-regulated or down-regulated in RA using proteomic approach. Fibronectin, semaphorin 7A precursor, growth factor binding protein 7 (GRB7), and immunoglobulin µ chain were specifically associated with antibodies isolated from RA synovial fluids. In addition, some metabolic proteins such as adipocyte fatty acid binding protein, galectin-1 and apolipoprotein A1 precursor were overexpressed in RA synovium. Also, expression of peroxiredoxin 2 was up-regulated in RA. On the contrary, expression of vimentin was severely suppressed in RA synoviocytes. Such findings might give some insights into understanding of pathological mechanism in RA.

Fermented mushroom milk‐supplemented dietary fibre prevents the onset of obesity and hypertriglyceridaemia in Otsuka Long‐Evans Tokushima fatty rats

Aim:  Fermented milk product containing edible mushroom water extracts (mushroom yogurt; MY) has been reported to have glycaemic control and triglyceride‐lowering effects in streptozotocin (STZ)‐induced diabetic rats and Zucker diabetic fatty (ZDF) rats. Here, we investigated how MY‐supplemented dietary fibre (10 and 20%, v/w) influences the onset of obesity and hypertriglyceridaemia in Otsuka Long‐Evans Tokushima fatty (OLETF) rats.

Cytosolic accumulation of γH2AX is associated with tropomyosin-related kinase A-induced cell death in U2OS cells

Tropomyosin-related kinase A (TrkA) plays an important role in cell survival, differentiation, and apoptosis in various neuronal and nonneuronal cell types. Here we show that TrkA overexpression by the Tet-On system mimics NGF-mediated activation pathways in the absence of nerve growth factor (NGF) stimulation in U2OS cells. In addition, p53 upregulation upon DNA damage was inhibited by TrkA, and p21 was upregulated by TrkA in a p53-independent manner. TrkA overexpression caused cell death by interrupting cell cycle progression, and TrkA-induced cell death was diminished in the presence of its specific inhibitor GW441756. Interestingly, TrkA-mediated cell death was strongly related to γH2AX production and poly (ADP-ribose) polymerase cleavage in the absence of DNA damage inducer. In this study, we also reveal that γH2AX production by TrkA is blocked by TrkA kinase inhibitors K-252a and GW441756, and it is also significantly inhibited by JNK inhibitor SP600125. Moreover, reduction of cell viability by TrkA was strongly suppressed by SP600125 treatment, suggesting a critical role of JNK in TrkA-induced cell death. We also found that γH2AX and TrkA were colocalized in cytosol in the absence of DNA damage, and the nuclear localization of γH2AX induced by DNA damage was partly altered to cytosol by TrkA overexpression. Our results suggest that the abnormal cytosolic accumulation of γH2AX is implicated in TrkA-induced cell death in the absence of DNA damage.

In Vitro Osteogenic Differentiation of Cultured Human Dental Papilla-Derived Cells

PURPOSE This study examined the osteogenic phenotypes and mineralization of cultured human dental papilla-derived cells. MATERIALS AND METHODS Dental papillae were harvested from mandibles during surgical extraction of lower impacted third molars from 3 patients aged 13 to 15 years. The dental papilla-derived cells were introduced into the cell culture. After passage 3, the dental papilla-derived cells were further cultured for 42 days in an osteogenic inductive culture medium containing dexamethasone, ascorbic acid, and beta-glycerophosphate. We examined the histochemical detection of alkaline phosphatase (ALP), the reverse transcriptase-polymerase chain reaction (RT-PCR) analysis for ALP and osteocalcin, and von Kossa staining in the dental papilla-derived cells. RESULTS It was observed that ALP was strongly expressed in the earlier stage of osteoblastic differentiation, whereas osteocalcin was mainly expressed and secreted into the medium at the later stage. Von Kossa-positive mineralization nodules were first observed on day 14, which increased in number during the entire culture period. CONCLUSIONS These results suggest that dental papilla-derived cell have osteogenic potential and could be used as an additional source of cells for bone tissue engineering.

Tissue-engineered bone formation using periosteal-derived cells and polydioxanone/pluronic F127 scaffold with pre-seeded adipose tissue-derived CD146 positive endothelial-like cells.

The aim of this study was to generate tissue-engineered bone formation using periosteal-derived cells seeded into a polydioxanone/pluronic F127 (PDO/Pluronic F127) scaffold with adipose tissue-derived CD146 positive endothelial-like cells. Considering the hematopoietic and mesenchymal phenotypes of adipose tissue-derived cells cultured in EBM-2 medium, CD146 positive adipose tissue-derived cells was sorted to purify more endothelial cells in characterization. These sorted cells were referred to as adipose tissue-derived CD146 positive endothelial-like cells. Periosteum is a good source of osteogenic cells for tissue-engineered bone formation. Periosteal-derived cells were found to have good osteogenic capacity in a PDO/Pluronic F127 scaffold, which could provide a suitable environment for the osteoblastic differentiation of these cells. Through the investigation of capillary-like tube formation on matrigel and the cellular proliferation of adipose tissue-derived CD146 positive endothelial-like cells cultured in different media conditions, we examined these cells could be cultured in EBM-2 with osteogenic induction factors. We also observed that the osteogenic activity of periosteal-derived cells could be good in EBM-2 with osteogenic induction factors, in the early period of culture. The experimental results obtained in the miniature pig model suggest that tissue-engineered bone formation using periosteal-derived cells and PDO/Pluronic F127 scaffold with pre-seeded adipose tissue-derived CD146 positive endothelial-like cells can be used to restore the bony defects of the maxillofacial region when used in clinics.