ABSTRACT
An 11-year-old boy was referred to our department with the chief complaint of acute urinary retention. He had had a history of viral enteritis a few days before the onset of dysuria. He presented with a slight fever, mild headache and weakness of the extremities. A cerebrospinal fluid examination showed the elevation of cell number (cell number : 158/3, polynuclear cells : 29/3, and mononuclear cells : 129/3). Although spinal magnetic resonance imaging (MRI) did not show abnormal findings, fluid attenuated inversion recovery (FLAIR) image of the brain MRI showed a high signal area on the cerebral cortex. Acute disseminated encephalomyelitis (ADEM) was suspected from the clinical course, the cerebrospinal fluid examination, and brain MRI findings. A urethral catheter was indwelled for urinary retention, and steroid pulse therapy was promptly started. After removal of the urethral catheter seven days after the therapy initiation, normal urination without residual urine was observed. Findings of a cerebrospinal fluid test and brain MRI also showed improvement.
Subject(s)
Encephalomyelitis, Acute Disseminated/diagnostic imaging , Urinary Retention/complications , Child , Encephalomyelitis, Acute Disseminated/etiology , Humans , Magnetic Resonance Imaging , Male , Urinary Retention/therapyABSTRACT
Microcystin-LR is a hepatotoxin produced by several cyanobacteria. Its toxicity is mainly due to a inhibition of protein phosphatase, PP1 and PP2A. Previously, we used a cell line stably expressing uptake transporter for microcystin-LR, OATP1B3 (HEK293-OATP1B3 cells). In this study, to determine whether overexpression of carboxylesterase (CES), which degrades ester-group and amide-group, attenuates the cytotoxicity of microcystin-LR, we generated the HEK293-OATP1B3/CES2 double-transfected cells. HEK293-OATP1B3/CES2 cells showed high hydrolysis activity of p-nitrophenyl acetate (PNPA), which is an authentic substrate for esterase. CES activity in HEK293-OATP1B3/CES2 cells was approximately 3-fold higher than that in the HEK293-OATP1B3 cells. HEK293-OATP1B3/CES2 cells (IC50: 25.4±7.7nM) showed approximately 2.1-fold resistance to microcystin-LR than HEK293-OATP1B3 cells (IC50: 12.0±1.5nM). Moreover, the CES inhibition assay and microcystin-agarose pull down assay showed the possibility of the interaction between CES2 and microcystin-LR. Our results indicated that the overexpression of CES2 attenuates the cytotoxicity of microcystin-LR via interaction with microcystin-LR.
Subject(s)
Bacterial Toxins/toxicity , Carboxylesterase/metabolism , Carcinogens, Environmental/toxicity , Microcystins/toxicity , Absorption, Physiological/drug effects , Bacterial Toxins/antagonists & inhibitors , Bacterial Toxins/metabolism , Binding Sites , Carboxylesterase/antagonists & inhibitors , Carboxylesterase/chemistry , Carboxylesterase/genetics , Carcinogens, Environmental/chemistry , Carcinogens, Environmental/metabolism , Cell Survival/drug effects , Drug Resistance , Enzyme Induction/drug effects , Enzyme Inhibitors/pharmacology , Green Fluorescent Proteins/genetics , Green Fluorescent Proteins/metabolism , HEK293 Cells , Hep G2 Cells , Humans , Inactivation, Metabolic/drug effects , Marine Toxins , Microcystins/antagonists & inhibitors , Microcystins/metabolism , Nitrophenols/pharmacology , Organic Anion Transporters, Sodium-Independent/genetics , Organic Anion Transporters, Sodium-Independent/metabolism , Recombinant Fusion Proteins/metabolism , Recombinant Proteins/chemistry , Recombinant Proteins/metabolism , Solute Carrier Organic Anion Transporter Family Member 1B3 , Substrate SpecificityABSTRACT
Microcystin-LR is a cyclic peptide released by several bloom-forming cyanobacteria. Understanding the mechanism of microcystin-LR toxicity is important, because of the both potencies of its acute cytotoxicity and tumor-promoting activity in hepatocytes of animals and humans. Recently, we have reported that the expression of human hepatocyte uptake transporter OATP1B3 was critical for the selective uptake of microcystin-LR into hepatocytes and for induction of its fatal cytotoxicity. In this study, we demonstrated a novel function of microcystin-LR which induced bipotential changes including anoikis resistance and cytoskeleton reorganization to OATP1B3-transfected HEK293 cells (HEK293-OATP1B3). After exposure to microcystin-LR, HEK293-OATP1B3 cells were divided to the floating cells and remaining adherent cells. After collection and reseeding the floating cells into a fresh flask, cells were confluently proliferated (HEK293-OATP1B3-FL) under the microcystin-LR-free condition. Both the proliferated HEK293-OATP1B3-FL and remaining adherent HEK293-OATP1B3-AD cells changed the character with down- and up-regulation of E-cadherin, respectively. Additionally, these cells acquired resistance to microcystin-LR. These results suggest that microcystin-LR could be associated with not only tumor promotion, but also epithelial-mesenchymal transition-mediated cancer metastasis. Furthermore, microcystin-LR might induce the cytoskeleton reorganization be accompanied epithelial-mesenchymal transition.
