Overexpression of carboxylesterase contributes to the attenuation of cyanotoxin microcystin-LR toxicity

• Published in: Comparative biochemistry and physiology. Toxicology & pharmacology 2017-04, Vol.194, p.22-27
• Main Authors: Takumi, Shota, Shimono, Tai, Ikema, Satoshi, Hotta, Yuki, Chigwechokha, Petros K., Shiozaki, Kazuhiro, Sugiyama, Yasumasa, Hashimoto, Mitsuru, Furukawa, Tatsuhiko, Komatsu, Masaharu
• Format: Article
• Language: English
• Subjects: Absorption, Physiological - drug effects; Bacterial Toxins - antagonists & inhibitors; Bacterial Toxins - metabolism; Bacterial Toxins - toxicity; Binding Sites; Carboxylesterase; Carboxylesterase - antagonists & inhibitors; Carboxylesterase - chemistry; Carboxylesterase - genetics; Carboxylesterase - metabolism; Carcinogens, Environmental - chemistry; Carcinogens, Environmental - metabolism; Carcinogens, Environmental - toxicity; 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; Irinotecan; Microcystin-LR; Microcystins - antagonists & inhibitors; Microcystins - metabolism; Microcystins - toxicity; Nitrophenols - pharmacology; OATP1B3; Organic Anion Transporters, Sodium-Independent - genetics; Organic Anion Transporters, Sodium-Independent - metabolism; Overexpression; Recombinant Fusion Proteins - metabolism; Recombinant Proteins - chemistry; Recombinant Proteins - metabolism; Solute Carrier Organic Anion Transporter Family Member 1B3; Substrate Specificity
• ISSN: 1532-0456; 1878-1659
• DOI: 10.1016/j.cbpc.2017.01.008

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.