Effect of PRX-1 Downregulation in the Type 1 Diabetes Microenvironment

Type 1 diabetes (T1D) is caused by dysregulation of the immune system in the pancreatic islets, which eventually leads to insulin-producing pancreatic β-cell death and destabilization of glucose homeostasis. One of the major characteristics of T1D pathogenesis is the production of inflammatory mediators by macrophages that result in destruction or damage of pancreatic β-cells. In this study the inflammatory microenvironment of T1D was simulated with RAW264.7 cells and MIN6 cells, acting as macrophages and pancreatic β-cells respectably. In this setting, peroxiredoxin-1, an anti-oxidant enzyme was knocked down to observe its functions in the pathogenesis of T1D. RAW264.7 cells were primed with lipopolysaccharide and co-cultured with MIN6 cells while PRX-1 was knocked down in one or both cell types. Our results suggest that hindrance of PRX-1 activity or the deficiency of this enzyme in inflammatory conditions negatively affects pancreatic β-cell survival. The observed decrease in viability of MIN6 cells seems to be caused by nitric oxide production. Additionally, it seems that PRX-1 affects previously reported protective activity of IL-6 in pancreatic β cells as well. These results signify new, undiscovered roles for PRX-1 in inflammatory conditions and may contribute toward our understanding of autoimmunity.     

Study of cobalt doping control via various routes in thoroughbred horses

Cobalt is a substance that has been abused for athletic performance enhancement and has thus been prohibited by human and animal sports doping control authorities. However, because cobalt is present in humans and animals as a trace element, a certain level of cobalt is naturally present in their excretions. In the racing industry, cobalt is a controlled substance with a threshold concentration specified by the International Agreement on Breeding, Racing and Wagering (IABRW) for international harmonization. Due to environmental and feed consumption differences among countries, regional cobalt concentration trends should be evaluated before cobalt testing is introduced. In this study, we conducted a preliminary evaluation of the urinary concentration of cobalt among a population of racehorses in Korea using inductively coupled plasma mass spectrometry (ICP-MS) analysis, followed by analysis of the urinary release of cobalt after the administration of cobalt chloride in various situations. The normal distribution for the Korea-based racehorses was used to determine a urine concentration limit (96.5 ng/ml, risk factor of 1 in 10,000). After the intravenous (IV) administration of CoCl₂, the initial elimination of cobalt was rapid. A high concentration (over 2,000 ng/ml) and a slow excretion pattern were observed during the final 2 weeks of the 3-week observation period. When CoCl₂ was administered orally, maximum concentration (C_max, 92–992 ng/ml) was observed at 6–8 h.     

Novel transparent collagen film patch derived from duck’s feet for tympanic membrane perforation

Abstract

To increase healing rate of tympanic membrane (TM) perforations, patching procedure has been commonly conducted. Biocompatible, biodegradable patching materials which is not limited across cultures is needed. The authors evaluated the effectiveness of novel transparent duck’s feet collagen film (DCF) patch in acute traumatic TM perforation. This procedure was compared with spontaneous healing and paper patching. Cell proliferation features were observed in paper and DCF patches. Forty-eight TMs of 24 rats were used for animal experiment, perforations were made on each TMs, and divided into three groups according to treatment modality. Sixteen were spontaneously healed, 16 were paper patched and 16 were DCF patched. The gross and histological healing results were analyzed. Both paper and DCF patch showed no cytotoxicity, but cell proliferations were more active in DCF than paper in early stage. In animal study, the healing of TM perforations were completed within 14 days in all three groups, but found to be faster in DCF patch group than paper patch or spontaneous healing group. The DCF patches were transparent and size of DCF patches were gradually decreased, so there were no need to remove the DCF patches to check the wound status or after the completion of healing. According to this result, authors concluded that DCF patch is transparent, biocompatible and biodegradable material, and can induce fast healing in acute traumatic TM perforations.     

Mutational analysis of DNMT3A gene in acute leukemias and common solid cancers

DNMT3A, a DNA methyltransferase that functions for de novo methylation, is important in development and many cellular processes related to tumorigenesis. Somatic mutations of DNMT3A gene, including recurrent mutations in its Arg‐882, were recently reported in acute myelogenous leukemia (AML), strongly suggesting its role in development of AML. To see whether DNMT3A mutation occurs in other malignancies as well, we analyzed DNMT3A in 916 cancer tissues from 401 hematologic malignancies (AML, acute lymphoblastic leukemias (ALL), multiple myelomas and lymphomas) and 515 carcinomas (lung, breast, prostate, colorectal and gastric carcinomas) using a single‐strand conformation polymorphism (SSCP) assay. We identified DNMT3A mutations, especially the Arg‐882 mutations, in adulthood AML (9.4%). In addition, we found DNMT3A mutations in pre‐B‐ALL and three lung cancers at lower frequencies. Allelic loss of DNMT3A was frequently observed in most cancer types analyzed, including lymphomas (48.1%), gastric cancers (23.5%) and lung cancers (18.3%) irrespective of DNMT3A mutation. Also, loss of DNMT3A expression was common in lung cancers (46.4%), and was associated with the allelic loss. Our data indicate that DNMT3A gene is mutated mainly in AML, but it occurs in other cancers, such as ALL and lung cancer, despite the lower incidences. Also, the data suggest that DNMT3A is altered in many cancer types by various ways, including somatic mutations, allelic loss and loss of expression that might play roles in tumorigenesis.     

Acute Hypoxia Activates an ENaC-like Channel in Rat Pheochromocytoma (PC12) Cells

Cells can resist and even recover from stress induced by acute hypoxia, whereas chronic hypoxia often leads to irreversible damage and eventually death. Although little is known about the response(s) to acute hypoxia in neuronal cells, alterations in ion channel activity could be preferential. This study aimed to elucidate which channel type is involved in the response to acute hypoxia in rat pheochromocytomal (PC12) cells as a neuronal cell model. Using perfusing solution saturated with 95% N₂ and 5% CO₂, induction of cell hypoxia was confirmed based on increased intracellular Ca²⁺ with diminished oxygen content in the perfusate. During acute hypoxia, one channel type with a conductance of about 30 pS (2.5 pA at -80 mV) was activated within the first 2~3 min following onset of hypoxia and was long-lived for more than 300 ms with high open probability (P_o, up to 0.8). This channel was permeable to Na⁺ ions, but not to K⁺, Ca⁺, and Cl^- ions, and was sensitively blocked by amiloride (200 nM). These characteristics and behaviors were quite similar to those of epithelial sodium channel (ENaC). RT-PCR and Western blot analyses confirmed that ENaC channel was endogenously expressed in PC12 cells. Taken together, a 30-pS ENaC-like channel was activated in response to acute hypoxia in PC12 cells. This is the first evidence of an acute hypoxia-activated Na⁺ channel that can contribute to depolarization of the cell.