Gene Knockout and Metabolome Analysis of Carnitine/Organic Cation Transporter OCTN1

Abstract

Purpose: Solute carrier, OCTN1 (SLC22A4) is an orphan transporter, the physiologically important substrate of which is still unidentified. The aim of the present study was to examine physiological roles of OCTN1. Methods:We first constructed octn1 gene knockout (octn1 -/-) mice. Metabolome analysis was then performed to identify substrates in vivo. The possible association of the substrate identified with diseased conditions was further examined. Results:The metabolome analysis of blood and several organs indicated complete deficiency of a naturally occurring potent antioxidant ergothioneine in octn1 -/-mice among 112 metabolites examined.Pharmacokinetic analyses after oral administration revealed the highest distribution to small intestines and extensive renal reabsorption of [ 3 H]ergothioneine, both of which were much reduced in octn1 -/-mice.The octn1 -/-mice exhibited greater susceptibility to intestinal inflammation under the ischemia and reperfusion model. The blood ergothioneine concentration was also much reduced in Japanese patients with Crohn's disease, compared with healthy volunteers and patients with another inflammatory bowel disease, ulcerative colitis. 4Conclusions: These results indicate that OCTN1 plays a pivotal role for maintenance of systemic and intestinal exposure of ergothioneine which could be important for protective effect against intestinal tissue injuries, providing a possible diagnostic tool to distinguish the inflammatory bowel diseases.

Functional expression of carnitine/organic cation transporter OCTN1 in mouse brain neurons: Possible involvement in neuronal differentiation

“…ERGO is known to be present in mammal brain in vivo at the level of 0.2 to 1.0 mg per 100 g tissue ( Fig. 2A; Kato et al, 2010;Cheah et al, 2011) and may protect neurons from cytotoxicity induced by a variety of neurotoxins, including N-methyl-D-aspartate, -amyloid and cisplatin (Moncaster et al, 2002;Jang et al, 2004;Song et al, 2010). Thus, OCTN1 may transport antioxidant into neurons and consequently reduce the intracellular ROS level, resulting in suppression of neuronal proliferation.…”

Localization of Xenobiotic Transporter OCTN1/SLC22A4 in Hepatic Stellate Cells and Its Protective Role in Liver Fibrosis

“…The octn1 -/-mice [8] and littermates were of a mixed genetic background (C57BL/6J and 129Sv/Ev), produced by intercrossing octn1 +/-mice. They had free access to food (Sankyo-labo, Toyama, Japan), which contained approximately 0.2 µg ERGO/g chaw and water, except during the oral administration study of ERGO-rich feed.…”

“…OCTN1/SLC22A4 is multispecific transporter which accepts various types of therapeutic agents as substrates [5,6]. Metabolome analysis using cell lines transfected with SLC22A4 gene in vitro and octn1/slc22a4 gene knockout (octn1 -/-) mice in vivo have demonstrated that OCTN1 most efficiently transports a naturally occurring 5 food-derived antioxidant, ergothioneine (ERGO) [7,8]. ERGO is highly hydrophilic, and its uptake through plasma membranes is primarily mediated by OCTN1, as evidenced by the fact that food-derived ERGO is detected at µM to sub-mM level in almost all organs in wild-type mice, but minimally detected in octn1 -/-mice [8].…”

“…Metabolome analysis using cell lines transfected with SLC22A4 gene in vitro and octn1/slc22a4 gene knockout (octn1 -/-) mice in vivo have demonstrated that OCTN1 most efficiently transports a naturally occurring 5 food-derived antioxidant, ergothioneine (ERGO) [7,8]. ERGO is highly hydrophilic, and its uptake through plasma membranes is primarily mediated by OCTN1, as evidenced by the fact that food-derived ERGO is detected at µM to sub-mM level in almost all organs in wild-type mice, but minimally detected in octn1 -/-mice [8]. After oral ingestion, ERGO is efficiently absorbed in the gastrointestinal tract by OCTN1, then almost completely taken up by the liver and apparently not metabolized in the body [8,9].…”

“…ERGO is highly hydrophilic, and its uptake through plasma membranes is primarily mediated by OCTN1, as evidenced by the fact that food-derived ERGO is detected at µM to sub-mM level in almost all organs in wild-type mice, but minimally detected in octn1 -/-mice [8]. After oral ingestion, ERGO is efficiently absorbed in the gastrointestinal tract by OCTN1, then almost completely taken up by the liver and apparently not metabolized in the body [8,9]. Thus, ERGO is mainly delivered to the liver after oral ingestion.…”