Functional variants of OCTN cation transporter genes are associated with Crohn disease

Non-heme iron enzyme-catalyzed complex transformations: Endoperoxidation, cyclopropanation, orthoester, oxidative C-C and C-S bond formation reactions in natural product biosynthesis

Non-heme iron enzymes catalyze a wide range of chemical transformations, serving as one of the key types of tailoring enzymes in the biosynthesis of natural products. Hydroxylation reaction is the most common type of reactions catalyzed by these enzymes and hydroxylation reactions have been extensively investigated mechanistically. However, the mechanistic details for other types of transformations remain largely unknown or unexplored. In this paper, we present some of the most recently discovered transformations, including endoperoxidation, orthoester formation, cyclopropanation, oxidative C-C and C-S bond formation reactions. In addition, many of them are multi-functional enzymes, which further complicate their mechanistic investigations. In this work, we summarize their biosynthetic pathways, with special emphasis on the mechanistic details available for these newly discovered enzymes.

Multiplex gene expression profile in inflamed mucosa of patients with Crohn’s disease ileal localization: A pilot study

BACKGROUND

Crohn’s disease (CD) is a complex disorder resulting from the interaction of genetic, environmental, and microbial factors. The pathogenic process may potentially affect any segment of the gastrointestinal tract, but a selective location in the terminal ileum was reported in 50% of patients.

AIM

To characterize clinical sub-phenotypes (colonic and/or ileal) within the same disease, in order to identify new therapeutic targets.

METHODS

14 consecutive patients undergoing surgery for ileal CD were recruited for this study. Peripheral blood samples from each patient were collected and the main polymorphisms of the gene Card15/Nod2 (R702W, G908R, and 1007fs) were analyzed in each sample. In addition, tissue samples were taken from both the tract affected by CD and from the apparently healthy and disease-free margins (internal controls). We used a multiplex gene assay in specimens obtained from patients with ileal localization of CD to evaluate the simultaneous expression of 24 genes involved in the pathogenesis of the disease. We also processed surgery gut samples with routine light microscopy (LM) and transmission electron microscopy (TEM) techniques to evaluate their structural and ultrastructural features.

RESULTS

We found a significant increase of Th17 (IL17A and IL17F, IL 23R and CCR6) and Th1 (IFN-γ) gene expression in inflamed mucosa compared to non-inflamed sites of 14 CD patients. DEFB4 and HAMP, two genes coding for antimicrobial peptides, were also strongly activated in inflamed ileal mucosa, suggesting the overwhelming stimulation of epithelial cells by commensal microbiota. IFN-γ and CCR6 were more expressed in inflamed mucosa of CD patients with ileal localization compared with patients with colonic localization suggesting a more aggressive inflammation process in this site. Morphological analysis of the epithelial lining of Lieberkün crypts disclosed enhanced release activity from goblet mucocytes, whereas the lamina propria contained numerous cells pertaining to various lines.

CONCLUSION

We observed that the expression of ileal genes related to Th1 and Th17 activity is strongly activated as well as the expression of genes involved in microbiota regulation.

Crystal Structure of the Ergothioneine Sulfoxide Synthase from Candidatus Chloracidobacterium thermophilum and Structure-Guided Engineering To Modulate Its Substrate Selectivity

Ergothioneine is a thiohistidine derivative with potential benefits on many aging-related diseases. The central step of aerobic ergothioneine biosynthesis is the oxidative C-S bond formation reaction catalyzed by mononuclear nonheme iron sulfoxide synthases (EgtB and Egt1). Thus far, only the Mycobacterium thermoresistibile EgtB (EgtB _Mth ) crystal structure is available, while the structural information for the more industrially attractive Egt1 enzyme is not. Herein, we reported the crystal structure of the ergothioneine sulfoxide synthase (EgtB _Cth ) from Candidatus Chloracidobacterium thermophilum. EgtB _Cth has both EgtB- and Egt1-type of activities. Guided by the structural information, we conducted Rosetta Enzyme Design calculations, and we biochemically demonstrated that EgtB _Cth can be engineered more toward Egt1-type of activity. This study provides information regarding the factors governing the substrate selectivity in Egt1- and EgtB-catalysis and lays the groundwork for future sulfoxide synthase engineering toward the development of an effective ergothioneine process through a synthetic biology approach.

The SLC22 Transporter Family: A Paradigm for the Impact of Drug Transporters on Metabolic Pathways, Signaling, and Disease

The SLC22 transporter family consists of more than two dozen members, which are expressed in the kidney, the liver, and other tissues. Evolutionary analysis indicates that SLC22 transporters fall into at least six subfamilies: OAT (organic anion transporter), OAT-like, OAT-related, OCT (organic cation transporter), OCTN (organic cation/carnitine transporter), and OCT/OCTN-related. Some-including OAT1 [SLC22A6 or NKT (novel kidney transporter)] and OAT3 (SLC22A8), as well as OCT1 (SLC22A1) and OCT2 (SLC22A2)-are widely studied drug transporters. Nevertheless, analyses of knockout mice and other data indicate that SLC22 transporters regulate key metabolic pathways and levels of signaling molecules (e.g., gut microbiome products, bile acids, tricarboxylic acid cycle intermediates, dietary flavonoids and other nutrients, prostaglandins, vitamins, short-chain fatty acids, urate, and ergothioneine), as well as uremic toxins associated with chronic kidney disease. Certain SLC22 transporters-such as URAT1 (SLC22A12) and OCTN2 (SLC22A5)-are mutated in inherited metabolic diseases. A new systems biology view of transporters is emerging. As proposed in the remote sensing and signaling hypothesis, SLC22 transporters, together with other SLC and ABC transporters, have key roles in interorgan and interorganism small-molecule communication and, together with the neuroendocrine, growth factor-cytokine, and other homeostatic systems, regulate local and whole-body homeostasis.

SLC22A5 polymorphism associated with risk of extra-articular manifestations in rheumatoid arthritis patients

Objectives

Rheumatoid arthritis (RA), the most common autoimmune disease, is thought to be a complex disease in which a combination of risk alleles from different susceptibility genes predisposes to development of the disease, following exposure to as yet unknown environmental factors. An important component of the carnitine system is the plasma membrane carnitine transporters, also called organic cation transporters, i.e. OCTN1 and OCTN2 encoded by the SLC22A4 and SLC22A5 genes, respectively. The aim of this study was to investigate the association between SLC22A5 polymorphism and RA.

Material and methods

The study was carried out on 404 patients diagnosed with RA according to the criteria of the American College of Rheumatology and 560 healthy subjects. The single nucleotide polymorphism (SNP) within the SLC22A5 gene – 207C>G (rs 2631367) was genotyped using pre-validated TaqMan genotyping assays.

Results

The distribution of SLC22A5 genotypes and alleles in RA patients did not differ significantly from that in healthy controls. Moreover, there were no significant associations between SLC22A5 genotypes and age at time of disease diagnosis, rheumatoid factor, erosive disease and response to treatment with methotrexate. Extra-articular manifestations were diagnosed in 16.7% of SLC22A5 GG homozygous patients, in 9.4% with the GC genotype and in 7.2% of homozygous CC patients. The frequency of extra-articular manifestations was two-fold greater in homozygous GG patients as compared with carriers of the C allele (GG vs. GC + CC), OR = 2.06 (95% CI: 1.11–3.85, p = 0.022).

Conclusions

The results of the present study suggest that the SLC22A5 polymorphism may be associated with the development of extra-articular manifestations of RA but the distribution of SLC22A5 genotypes and alleles in studied RA patients did not significantly differ from healthy subjects.

Cellular and Molecular Therapeutic Targets in Inflammatory Bowel Disease-Focusing on Intestinal Barrier Function

The human gut relies on several cellular and molecular mechanisms to allow for an intact and dynamical intestinal barrier. Normally, only small amounts of luminal content pass the mucosa, however, if the control is broken it can lead to enhanced passage, which might damage the mucosa, leading to pathological conditions, such as inflammatory bowel disease (IBD). It is well established that genetic, environmental, and immunological factors all contribute in the pathogenesis of IBD, and a disturbed intestinal barrier function has become a hallmark of the disease. Genetical studies support the involvement of intestinal barrier as several susceptibility genes for IBD encode proteins with key functions in gut barrier and homeostasis. IBD patients are associated with loss in bacterial diversity and shifts in the microbiota, with a possible link to local inflammation. Furthermore, alterations of immune cells and several neuro-immune signaling pathways in the lamina propria have been demonstrated. An inappropriate immune activation might lead to mucosal inflammation, with elevated secretion of pro-inflammatory cytokines that can affect the epithelium and promote a leakier barrier. This review will focus on the main cells and molecular mechanisms in IBD and how these can be targeted in order to improve intestinal barrier function and reduce inflammation.

OCTN: A Small Transporter Subfamily with Great Relevance to Human Pathophysiology, Drug Discovery, and Diagnostics

OCTN is a small subfamily of membrane transport proteins that belongs to the larger SLC22 family. Two of the three members of the subfamily, namely, OCTN2 and OCTN1, are present in humans. OCTN2 plays a crucial role in the absorption of carnitine from diet and in its distribution to tissues, as demonstrated by the occurrence of severe pathologies caused by malfunctioning or altered expression of this transporter. These findings suggest avoiding a strict vegetarian diet during pregnancy and in childhood. Other roles of OCTN2 are related to the traffic of carnitine derivatives in many tissues. The role of OCTN1 is still unclear, despite the identification of some substrates such as ergothioneine, acetylcholine, and choline. Plausibly, the transporter acts on the control of inflammation and oxidative stress, even though knockout mice do not display phenotypes. A clear role of both transporters has been revealed in drug interaction and delivery. The polyspecificity of the OCTNs is at the base of the interactions with drugs. Interestingly, OCTN2 has been recently exploited in the prodrug approach and in diagnostics. A promising application derives from the localization of OCTN2 in exosomes that represent a noninvasive diagnostic tool.

Pharmacogenetics of treatments for inflammatory bowel disease

INTRODUCTION

Inflammatory bowel disease is a chronic inflammation of the gut whose pathogenesis is still unclear. Although no curative therapy is currently available, a number of drugs are used in induction and maintenance therapy; however, for most of these drugs, a high inter-individual variability in response is observed. Among the factors of this variability, genetics plays an important role. Areas covered: This review summarizes the results of pharmacogenetic studies, considering the most important drugs used and in particular aminosalycilates, glucocorticoids, thiopurines, monoclonal antibodies and thalidomide. Most studies used a candidate gene approach, even if significant breakthroughs have been obtained recently from applying genome-wide studies. When available, also investigations considering epigenetics and pharmacogenetic dosing guidelines have been included. Expert opinion: Only for thiopurines, genetic markers identified as predictors of efficacy or adverse events have allowed the development of dosing guidelines. For the other drugs, encouraging results are available and great expectations rely on the study of epigenetics and integration with pharmacokinetic information, especially useful for biologics. However, to improve therapy of IBD patients with these drugs, for implementation in the clinics of pharmacogenetics, informatic clinical decision support systems and training about pharmacogenetics of health providers are needed.

Prolonging healthy aging: Longevity vitamins and proteins

It is proposed that proteins/enzymes be classified into two classes according to their essentiality for immediate survival/reproduction and their function in long-term health: that is, survival proteins versus longevity proteins. As proposed by the triage theory, a modest deficiency of one of the nutrients/cofactors triggers a built-in rationing mechanism that favors the proteins needed for immediate survival and reproduction (survival proteins) while sacrificing those needed to protect against future damage (longevity proteins). Impairment of the function of longevity proteins results in an insidious acceleration of the risk of diseases associated with aging. I also propose that nutrients required for the function of longevity proteins constitute a class of vitamins that are here named "longevity vitamins." I suggest that many such nutrients play a dual role for both survival and longevity. The evidence for classifying taurine as a conditional vitamin, and the following 10 compounds as putative longevity vitamins, is reviewed: the fungal antioxidant ergothioneine; the bacterial metabolites pyrroloquinoline quinone (PQQ) and queuine; and the plant antioxidant carotenoids lutein, zeaxanthin, lycopene, α- and β-carotene, β-cryptoxanthin, and the marine carotenoid astaxanthin. Because nutrient deficiencies are highly prevalent in the United States (and elsewhere), appropriate supplementation and/or an improved diet could reduce much of the consequent risk of chronic disease and premature aging.

Pharmacogenetics-based population pharmacokinetic analysis of gabapentin in patients with chronic pain: Effect of OCT2 and OCTN1 gene polymorphisms

Gabapentin (GAB) is eliminated unchanged in urine, and organic cation transporters (OCT2 and OCTN1) have been shown to play a role in GAB renal excretion. This prospective clinical study aimed to evaluate the genetic polymorphisms effect on GAB pharmacokinetic (PK) variability using a population pharmacokinetic approach. Data were collected from 53 patients with chronic pain receiving multiple doses of GAB. Patients were genotyped for SLC22A2 c.808G>T and SLC22A4 c.1507C>T polymorphisms. Both polymorphisms' distribution followed the Hardy-Weinberg equilibrium. An one-compartment model with first-order absorption and linear elimination best described the data. The absorption rate constant, volume of distribution, and clearance estimated were 0.44 h^-1 , 86 L, and 17.3 × (estimated glomerular filtration ratio/89.58)^1.04  L/h, respectively. The genetic polymorphism SLC22A4 c.1507C>T did not have a significant influence on GAB absorption, distribution or elimination. Due to the low minor allelic frequency of SLC22A2 c.808G>T, further studies require higher number of participants to confirm its effect on GAB renal elimination. In conclusion, GAB clinical pharmacokinetics are strongly influenced by renal function and absorption process, but not by the OCTN1 (SLC22A4 c.1507C>T) polymorphism.

Combination Metabolomics Approach for Identifying Endogenous Substrates of Carnitine/Organic Cation Transporter OCTN1

PURPOSE

Solute carrier SLC22A4 encodes the carnitine/organic cation transporter OCTN1 and is associated with inflammatory bowel disease, although little is known about how this gene is linked to pathogenesis. The aim of the present study was to identify endogenous substrates that are associated with gastrointestinal inflammation.

METHODS

HEK293/OCTN1 and mock cells were incubated with colon extracts isolated from dextran sodium sulfate-induced colitis mice; the subsequent cell lysates were mixed with the amino group selective reagent 3-aminopyridyl-N-hydroxysuccinimidyl carbamate (APDS), to selectively label OCTN1 substrates. Precursor ion scanning against the fragment ion of APDS was then used to identify candidate OCTN1 substrates.

RESULTS

Over 10,000 peaks were detected by precursor ion scanning; m/z 342 had a higher signal in HEK293/OCTN1 compared to mock cells. This peak was detected as a divalent ion that contained four APDS-derived fragments and was identified as spermine. Spermine concentration in peripheral blood mononuclear cells from octn1 gene knockout mice (octn1^-/-) was significantly lower than in wild-type mice. Lipopolysaccharide-induced gene expression of inflammatory cytokines in peritoneal macrophages from octn1^-/- mice was lower than in wild-type mice.

CONCLUSIONS

The combination metabolomics approach can provide a novel tool to identify endogenous substrates of OCTN1.

Dietary Supplementation of Selenoneine-Containing Tuna Dark Muscle Extract Effectively Reduces Pathology of Experimental Colorectal Cancers in Mice

Selenoneine is an ergothioneine analog with greater antioxidant activity and is the major form of organic selenium in the blood, muscles, and other tissues of tuna. The aim of this study was to determine whether a selenoneine-rich diet exerts antioxidant activities that can prevent carcinogenesis in two types of colorectal cancer model in mice. We administrated selenoneine-containing tuna dark muscle extract (STDME) to mice for one week and used azoxymethane (AOM) and dextran sodium sulfate (DSS) for inducing colorectal carcinogenesis. Next, we examined the incidence of macroscopic polyps and performed functional analysis of immune cells from the spleen. In the AOM/DSS-induced colitis-associated cancer (CAC) model, the oral administration of STDME significantly decreased tumor incidence and inhibited the accumulation of myeloid-derived suppressor cells (MDSCs) while also inhibiting the downregulation of interferon-γ (IFN-γ) production during carcinogenesis. These results suggest that dietary STDME may be an effective agent for reducing colorectal tumor progression.

IBD risk loci are enriched in multigenic regulatory modules encompassing putative causative genes

GWAS have identified >200 risk loci for Inflammatory Bowel Disease (IBD). The majority of disease associations are known to be driven by regulatory variants. To identify the putative causative genes that are perturbed by these variants, we generate a large transcriptome data set (nine disease-relevant cell types) and identify 23,650 cis-eQTL. We show that these are determined by ∼9720 regulatory modules, of which ∼3000 operate in multiple tissues and ∼970 on multiple genes. We identify regulatory modules that drive the disease association for 63 of the 200 risk loci, and show that these are enriched in multigenic modules. Based on these analyses, we resequence 45 of the corresponding 100 candidate genes in 6600 Crohn disease (CD) cases and 5500 controls, and show with burden tests that they include likely causative genes. Our analyses indicate that ≥10-fold larger sample sizes will be required to demonstrate the causality of individual genes using this approach.

Ergothioneine production using Methylobacterium species, yeast, and fungi

Ergothioneine (EGT) is a sulfur-containing, anti-oxidative amino acid derived from histidine. EGT is synthesized in bacteria and fungi but not in animals and plants, and is now recognized as important for human health. Its cost-effective fermentative production has not been elucidated due to the lack of information for productive microorganisms. In this study, we doubled the gene copy for EGT synthesis and deleted the histidine ammonia-lyase gene in a potent EGT-producing methylotrophic bacterium Methylobacterium aquaticum strain 22A, and optimized its culture conditions, resulting in increased EGT production of 7.0 mg EGT/g dry cell weight and 100 μg EGT/5 mL/7 days. In addition, through screening we found EGT-producing eukaryotic strains of Aureobasidium pullulans and Rhodotorula mucilaginosa, which can produce 1.0 and 3.2 mg EGT/g dry cell weight, 70 and 120 μg EGT/5 mL/7 days, respectively. This study proposes practical uses of potent EGT-producing recombinant Methylobacterium species and non-recombinant yeast and fungal strains.

Mini-Review: Ergothioneine and Ovothiol Biosyntheses, an Unprecedented Trans-Sulfur Strategy in Natural Product Biosynthesis

As one of the most abundant elements on earth, sulfur is part of many small molecular metabolites and is key to their biological activities. Over the past few decades, some general strategies have been discovered for the incorporation of sulfur into natural products. In this review, we summarize recent efforts in elucidating the biosynthetic details for two sulfur-containing metabolites, ergothioneine and ovothiol. Their biosyntheses involve an unprecedented trans-sulfur strategy, a combination of a mononuclear non-heme iron enzyme-catalyzed oxidative C-S bond formation reaction and a PLP enzyme-mediated C-S lyase reaction.

The potential therapeutic effects of ergothioneine in pre-eclampsia

Ergothioneine (ERG), is a water-soluble amino acid that is derived entirely from dietary sources. It has received much attention as a therapeutic agent due to its anti-oxidant properties, and there are claims of preferential accumulation within high oxidative stress organs. Pre-eclampsia, a condition accompanied by increased oxidative stress, is one of the leading causes of maternal morbidity and mortality. Despite intense research efforts, its aetiologies remain somewhat unclear and there are still no effective treatment options. Clinical trials of the anti-oxidants vitamin C and vitamin E have proven largely ineffective with little improvement in clinical outcome or even a negative response. This could be explained in part by their inability to permeate the plasma and mitochondrial membranes and scavenge mitochondria-derived superoxide species, and for the former by the fact that it is actually a pro-oxidant in the presence of unliganded iron. ERG accumulates within tissues through the action of a specific organic cation transporter, SLC22A4 (previously referred to as OCTN1), which is possibly also expressed in mammalian mitochondria. Mitochondrial dysfunction has been implicated in a variety of vascular diseases including pre-eclampsia. This review discusses the use of ERG as a possibly mitochondrial-targeted anti-oxidant, focusing on its physical properties, potential mechanisms of action, safety profile and administration in relation to pregnancies complicated by pre-eclampsia.

Characterization of Exosomal SLC22A5 (OCTN2) carnitine transporter

Exosomes are extracellular vesicles involved in cell-to-cell communication. Previous large scale proteomics revealed that they contain SLC proteins. However, no data on the function of exosomal SLCs is available, so far. An SLC localized in exosomes was here characterized for the first time: the carnitine transporter OCTN2 (SLC22A5). The protein was detected by Western Blot analysis in HEK293 exosomes. To investigate the functional properties of the exosomal OCTN2, the proteins extracted from vesicles were reconstituted into proteolipsomes and the transport function was measured as uptake of ³H-carnitine. Transport was stimulated by sodium and was dependent on pH. ³H-carnitine uptake was inhibited by Acetyl-carnitine, but not by Asn, Gln and Arg thus excluding interference by ATB^0,+, an amino acid transporter which also recognizes carnitine. Cardiolipin failed to stimulate transport, excluding the activity of the mitochondrial Carnitine/acylcarnitine transporter. Increased level of exosomal OCTN2 was induced by treatment of HEK293 with the pro-inflammatory cytokine INFγ. All data concurred to demonstrate that OCTN2 present in exosomes is fully functional and is in its native conformation. Functional OCTN2 was detected also in human urinary exosomes, thus suggesting the OCTN2 exosomal protein as a candidate biomarker for inflammation related pathologies.

Crohn's Disease Candidate Gene Alleles Predict Time to Progression from Inflammatory B1 to Stricturing B2, or Penetrating B3 Phenotype

AIM

Crohn's disease (CD) patients are mostly diagnosed with the uncomplicated inflammatory form of disease; however, the majority will progress to complicated stricturing or penetrating disease over time. It is important to identify patients at risk for disease progression at an early stage. The aim of our study was to examine the role of 33 candidate CD genes as possible predictors of disease progression and their influence on time to progression from an inflammatory to a stricturing or penetrating phenotype.

METHODS

Patients with an inflammatory phenotype at diagnosis were followed for 10 years and 33 CD-associated polymorphisms were genotyped. To test for association with CD, 449 healthy individuals were analyzed as the control group.

RESULTS

Ten years after diagnosis, 39.1% of patients had not progressed beyond an inflammatory phenotype, but 60.9% had progressed to complicated disease, with average time to progression being 5.91 years. Association analyses of selected single nucleotide polymorphisms (SNPs) confirmed associations with CD for 12 SNPs. Furthermore, seven loci were associated with disease progression, out of which SNP rs4263839 in the gene TNFSF15 showed the strongest association with disease progression and the frameshift mutation rs2066847 in the gene NOD2 showed the strongest association with time to progression.

CONCLUSIONS

The results of our study identified specific genetic biomarkers as useful predictors of both disease progression and speed of disease progression in patients with CD.

Integrative expression quantitative trait locus-based analysis of colorectal cancer identified a functional polymorphism regulating SLC22A5 expression

Multiple single nucleotide polymorphisms (SNPs) have been found to be highly correlated with colorectal cancer (CRC) risk. However, the variants identified thus far only explain a small part of the cases, suggesting the existence of many uncharacterised genetic determinants. In this study, using the multilevel 'omics' data provided in The Cancer Genome Atlas, we systematically performed expression quantitative trait locus (eQTL) analysis for CRC and identified nine SNPs with significant effects on mRNA expression (correlation |r| > 0.3 and FDR < 0.01). Then we conducted a two-stage case-control study consisting of 1528 cases and 1528 controls to examine the associations between candidate SNPs and CRC risk. We found that rs27437 in SLC22A5 was significantly correlated with CRC risk in both stages and the combined study (additive model, OR = 1.31, 95%CI = 1.17-1.47, P = 1.97 × 10^-6). eQTL analysis showed that rs27437 GG and GA genotypes were associated with lower expression of SLC22A5 compared with the AA genotype. Dual-luciferase reporter assays confirmed that the G risk allele could decrease the expression of luciferase. SLC22A5 was significantly decreased in CRC tumour tissues compared with adjacent normal tissues, indicating that SLC22A5 may play important roles in CRC, and rs27437 in SLC22A5 might serve as a novel biomarker for early detection and prevention of CRC.

The SLC2A14 gene, encoding the novel glucose/dehydroascorbate transporter GLUT14, is associated with inflammatory bowel disease

Background: Variations in intestinal antioxidant membrane transporters are implicated in the initiation and progression of inflammatory bowel disease (IBD). Facilitated glucose transporter member 14 (GLUT14), encoded by the solute carrier family 2 member 14 (SLC2A14) gene, is a putative transporter for dehydroascorbic acid and glucose. Although information on the gene is limited, shorter and longer GLUT14 isoforms have been identified. We hypothesized that GLUT14 mediates glucose and dehydroascorbic acid uptake. If this function could be validated, then genetic variations may associate with IBD.Objective: This study aimed to determine the substrate(s) for the GLUT14 protein and interrogated genetic associations of SLC2A14 with IBD.Design: The uptake of radiolabeled substrates into Xenopus laevis oocytes expressing the 2 GLUT14 isoforms was assessed. Examination of gene-targeted genetic association in the Manitoba Inflammatory Bowel Disease Cohort Study was conducted through the genotyping of single nucleotide polymorphisms (SNPs) representing linkage blocks of the SLC2A14 gene.Results: Both GLUT14 isoforms mediated the uptake of dehydroascorbic acid and glucose into X. laevis oocytes. Three alleles in the SLC2A14 gene associated independently with IBD. The odds of having ulcerative colitis (UC) or Crohn disease (CD) were elevated in carriers of the SLC2A14 SNP rs2889504-T allele (OR: 3.60; 95% CI: 1.95, 6.64 and OR: 4.68; 95% CI: 2.78, 8.50, respectively). Similarly, the SNP rs10846086-G allele was associated with an increased risk of both UC and CD (OR: 2.91; 95% CI: 1.49, 5.68 and OR: 3.00; 95% CI: 1.55, 5.78, respectively). Moreover, the SNP rs12815313-T allele associated with increased susceptibility to CD and UC (OR: 2.12; 95% CI: 1.33, 3.36 and OR: 1.61; 95% CI: 1.01, 2.57, respectively).Conclusion: These findings strengthen the hypothesis that genetically determined local dysregulation of dietary vitamin C or antioxidants transport contributes to IBD development. These transporter proteins are targetable by dietary interventions, opening the avenue to a precision intervention for patients of specific genotypes with IBD. This trial was registered at clinicaltrials.gov as NCT03262649.

Mass spectrometry imaging identifies palmitoylcarnitine as an immunological mediator during Salmonella Typhimurium infection

Salmonella Typhimurium causes a self-limiting gastroenteritis that may lead to systemic disease. Bacteria invade the small intestine, crossing the intestinal epithelium from where they are transported to the mesenteric lymph nodes (MLNs) within migrating immune cells. MLNs are an important site at which the innate and adaptive immune responses converge but their architecture and function is severely disrupted during S. Typhimurium infection. To further understand host-pathogen interactions at this site, we used mass spectrometry imaging (MSI) to analyse MLN tissue from a murine model of S. Typhimurium infection. A molecule, identified as palmitoylcarnitine (PalC), was of particular interest due to its high abundance at loci of S. Typhimurium infection and MLN disruption. High levels of PalC localised to sites within the MLNs where B and T cells were absent and where the perimeter of CD169⁺ sub capsular sinus macrophages was disrupted. MLN cells cultured ex vivo and treated with PalC had reduced CD4⁺CD25⁺ T cells and an increased number of B220⁺CD19⁺ B cells. The reduction in CD4⁺CD25⁺ T cells was likely due to apoptosis driven by increased caspase-3/7 activity. These data indicate that PalC significantly alters the host response in the MLNs, acting as a decisive factor in infection outcome.

Importance of the novel organic cation transporter 1 for tyrosine kinase inhibition by saracatinib in rheumatoid arthritis synovial fibroblasts

Recent therapeutic approaches of rheumatoid arthritis (RA) address the use of small molecules such as tyrosine kinase inhibitors (TKIs). However, the TKIs developed to date have important side effects and/or scarce efficacy in inflammatory diseases such as RA. Since intracellular effective TKIs must enter the cell to reach their intracellular targets, here we investigated the interaction of the TKI saracatinib, a dual inhibitor of c-Src and c-Abl signaling, with transporters for organic cations as well as the role of these transporters for the biological effect of saracatinib in human RA-synovial fibroblasts (hRASF). Saracatinib significantly reduced proliferation of hRASF. The cellular saracatinib uptake was mainly dependent on the human novel organic cation transporter 1 (hOCTN1), which showed the highest apparent affinity for saracatinib among all other transporters for organic cations analyzed here. In hRASF, saracatinib biologic function was dependent on hOCTN1. Further analysis showed that disease specific factors (pH, inflammatory cytokines such as TNFα) regulated saracatinib uptake in hRASF. The knowledge of which transporters mediate the specific uptake of TKIs in target cells and of how the expression and function of such transporters are regulated in RA is of highest priority to develop effective drugs for successful therapy with minimal side-effects.

Inflammatory arthritis complicated by inflammatory bowel disease: two case reports

Coexistence of inflammatory arthritis disease and inflammatory bowel disease (IBD) is often considered to be relatively rare, and the underlying mechanisms of the association between them remain unclear. Herein, we report two cases of IBD which occurred during the course of inflammatory arthritis disease. The first case had psoriatic arthritis (PsA) for two and a half years complicated by Crohn's disease and accompanied by inactive carrier state of hepatitis B. The second case had rheumatoid arthritis (RA) complicated by ulcerative colitis four years after the onset of RA. In both cases, colonoscopy was performed, and their clinical presentations improved with a multidisciplinary approach. In the event of complaints related to the gastrointestinal tract in patients with PsA or RA, IBD should be kept in mind, and the clinical evaluation and multidisciplinary interventions should be planned to control the underlying autoimmune process.

Analysis of the human monocyte-derived macrophage transcriptome and response to lipopolysaccharide provides new insights into genetic aetiology of inflammatory bowel disease

The FANTOM5 consortium utilised cap analysis of gene expression (CAGE) to provide an unprecedented insight into transcriptional regulation in human cells and tissues. In the current study, we have used CAGE-based transcriptional profiling on an extended dense time course of the response of human monocyte-derived macrophages grown in macrophage colony-stimulating factor (CSF1) to bacterial lipopolysaccharide (LPS). We propose that this system provides a model for the differentiation and adaptation of monocytes entering the intestinal lamina propria. The response to LPS is shown to be a cascade of successive waves of transient gene expression extending over at least 48 hours, with hundreds of positive and negative regulatory loops. Promoter analysis using motif activity response analysis (MARA) identified some of the transcription factors likely to be responsible for the temporal profile of transcriptional activation. Each LPS-inducible locus was associated with multiple inducible enhancers, and in each case, transient eRNA transcription at multiple sites detected by CAGE preceded the appearance of promoter-associated transcripts. LPS-inducible long non-coding RNAs were commonly associated with clusters of inducible enhancers. We used these data to re-examine the hundreds of loci associated with susceptibility to inflammatory bowel disease (IBD) in genome-wide association studies. Loci associated with IBD were strongly and specifically (relative to rheumatoid arthritis and unrelated traits) enriched for promoters that were regulated in monocyte differentiation or activation. Amongst previously-identified IBD susceptibility loci, the vast majority contained at least one promoter that was regulated in CSF1-dependent monocyte-macrophage transitions and/or in response to LPS. On this basis, we concluded that IBD loci are strongly-enriched for monocyte-specific genes, and identified at least 134 additional candidate genes associated with IBD susceptibility from reanalysis of published GWA studies. We propose that dysregulation of monocyte adaptation to the environment of the gastrointestinal mucosa is the key process leading to inflammatory bowel disease.

Macrophages are immune cells that form the first line of defense against pathogens, but also mediate tissue damage in inflammatory disease. Macrophages initiate inflammation by recognising and responding to components of bacterial cells. Macrophages of the wall of the gut are constantly replenished from the blood. Upon entering the intestine, newly-arrived cells modulate their response to stimuli derived from the bacteria in the wall of the gut. This process fails in chronic inflammatory bowel diseases (IBD). Both the major forms of IBD, Crohn’s disease and ulcerative colitis, run in families. The inheritance is complex, involving more than 200 different regions of the genome. We hypothesised that the genetic risk of IBD is associated specifically with altered regulation of genes that control the development of macrophages. In this study, we used the comprehensive transcriptome dataset produced by the FANTOM5 consortium to identify the sets of promoters and enhancers that are involved in adaptation of macrophages to the gut wall, their response to bacterial stimuli, and how their functions are integrated. A reanalysis of published genome-wide association data based upon regulated genes in monocytes as candidates strongly supports the view that susceptibility to IBD arises from a primary defect in macrophage differentiation.

Pathogenesis of Inflammatory Bowel Disease and Recent Advances in Biologic Therapies

Inflammatory bowel disease (IBD) is a chronic intestinal inflammatory disorder with an unknown etiology. IBD is composed of two different disease entities: Crohn's disease (CD) and ulcerative colitis (UC). IBD has been thought to be idiopathic but has two main attributable causes that include genetic and environmental factors. The gastrointestinal tract in which this disease occurs is central to the immune system, and the innate and the adaptive immune systems are balanced in complex interactions with intestinal microbes under homeostatic conditions. However, in IBD, this homeostasis is disrupted and uncontrolled intestinal inflammation is perpetuated. Recently, the pathogenesis of IBD has become better understood owing to advances in genetic and immunologic technology. Moreover, new therapeutic strategies are now being implemented that accurately target the pathogenesis of IBD. Beyond conventional immunesuppressive therapy, the development of biological agents that target specific disease mechanisms has resulted in more frequent and deeper remission in IBD patients, with mucosal healing as a treatment goal of therapy. Future novel biologics should overcome the limitations of current therapies and ensure that individual patients can be treated with optimal drugs that are safe and precisely target IBD.

Intestinal Autophagy and Its Pharmacological Control in Inflammatory Bowel Disease

Intestinal mucosal barrier, mainly composed of the intestinal mucus layer and the epithelium, plays a critical role in nutrient absorption as well as protection from pathogenic microorganisms. It is widely acknowledged that the damage of intestinal mucosal barrier or the disturbance of microorganism balance in the intestinal tract contributes greatly to the pathogenesis and progression of inflammatory bowel disease (IBD), which mainly includes Crohn’s disease and ulcerative colitis. Autophagy is an evolutionarily conserved catabolic process that involves degradation of protein aggregates and damaged organelles for recycling. The roles of autophagy in the pathogenesis and progression of IBD have been increasingly studied. This present review mainly describes the roles of autophagy of Paneth cells, macrophages, and goblet cells in IBD, and finally, several potential therapeutic strategies for IBD taking advantage of autophagy.

Pharmacogenetics of ustekinumab in patients with moderate-to-severe plaque psoriasis

Aim/Materials & methods: Few studies have evaluated the influence of pharmacogenetics in psoriatic patients treated with ustekinumab. We evaluated 121 polymorphisms to study a possible association between these SNPs and the response to ustekinumab (PASI75 at 4 months; n = 69). Results/Conclusion: The adjusted results (false discovery rate) showed an association between five SNPs in TNFRSF1A, HTR2A, NFKBIA, ADAM33 and IL13 genes, and poor response to ustekinumab. Furthermore, six SNPs in CHUK, C17orf51, ZNF816A, STAT4, SLC22A4 and Corf72 genes were associated with better response to ustekinumab. However, there was no significant association between response to ustekinumab and SNPs in HLA-C as it has been recently described. Finally, a higher weight was obtained in nonresponders than responders (p = 0.018). Further studies would be necessary to be closer to personalized medicine.

Association study between OCTN1 functional haplotypes and Crohn's disease in a Korean population

Crohn's disease (CD) is a chronic inflammatory bowel disease with multifactorial causes including environmental and genetic factors. Several studies have demonstrated that the organic cation/carnitine transporter 1 (OCTN1) non-synonymous variant L503F is associated with susceptibility to CD. However, it was reported that L503F is absent in Asian populations. Previously, we identified and functionally characterized genetic variants of the OCTN1 promoter region in Koreans. In that study, four variants demonstrated significant changes in promoter activity. In the present study, we determined whether four functional variants of the OCTN1 promoter play a role in the susceptibility to or clinical course of CD in Koreans. To examine it, the frequencies of the four variants of the OCTN1 promoter were determined by genotyping using DNA samples from 194 patients with CD and 287 healthy controls. Then, associations between genetic variants and the susceptibility to CD or clinical course of CD were evaluated. We found that susceptibility to CD was not associated with OCTN1 functional promoter variants or haplotypes showing altered promoter activities in in vitro assays. However, OCTN1 functional promoter haplotypes showing decreased promoter activities were significantly associated with a penetrating behavior in CD patients (HR=2.428, p=0.009). Our results suggest that the OCTN1 functional promoter haplotypes can influence the CD phenotype, although these might not be associated with susceptibility to this disease.

Immunopathogenesis of Crohn's Disease

This review highlights the huge advances made in the understanding of Crohn's disease in the last 15 years. The pathogenic immune response in the gut wall is a highly polarised T helper cell type 1 response, probably directed against antigens of the commensal flora. There is marked over-expression of pro-inflammatory cytokines such as tumor necrosis factor (TNF)-alpha and increased production of matrix degrading enzymes by fibroblasts and macrophages, which are probably responsible for ulceration and fistula formation. Crohn's disease runs in families and the susceptibility genes identified so far are associated with innate recognition of microbial products (Nod2) or epithelial barrier function (OCTN cation transporter genes and DLG5). Endogenous healing pathways mediated by transforming growth factor (TGF)-beta1 are inhibited because mucosal inflammatory cells express Smad7, the endogenous intracellular inhibitor of TGF-beta signalling. This makes it unlikely that enteral feeds containing TFG-beta are therapeutic by means of direct anti-inflammatory effects, however TGF-beta may still be involved because it is a well known epithelial motogen and may promote mucosal healing, in synergy with changes in mucosal bacterial populations as a result of the change in the diet.

Identification of the Main Intermediate Precursor of l-Ergothioneine Biosynthesis in Human Biological Specimens

A capillary electrophoresis coupled to tandem mass spectrometry (CE–MS/MS) has been used to make a qualitative determination of hercynine—the main precursor of l-ergothioneine biosynthesis—in some key human biological specimens, such as urine, whole blood, plasma, and saliva. From semiquantitative analysis results, the highest concentrations of hercynine were detected in saliva and whole blood, whereas much lower concentrations were measured in urine and plasma. Whole blood was the biological matrix with the highest concentration of l-ergothioneine followed by plasma, saliva, and urine. The antioxidant effects attributed to l-ergothioneine, along with its peculiar antioxidant mechanism, offer a possible explanation for the presence of the hercynine, as well as its concentration, in the considered biological matrices.

Periodontal manifestations of inflammatory bowel disease: emerging epidemiologic and biologic evidence

Inflammatory bowel disease and periodontitis are both described as a disproportionate mucosal inflammatory response to a microbial environment in susceptible patients. Moreover, these two conditions share major environmental and lifestyle-related risk factors. Despite this intriguing pathogenic parallel, large-scale studies and basic research have only recently considered periodontal outcomes as relevant data. There are mounting and consistent arguments, from recent epidemiologic studies and animal models, that these two conditions might be related. This article is a comprehensive and critical up-to-date review of the current evidence and future prospects in understanding the biologic and epidemiologic relationships between periodontal status and inflammatory bowel disease.

Mucosal Interactions between Genetics, Diet, and Microbiome in Inflammatory Bowel Disease

Numerous reviews have discussed gut microbiota composition changes during inflammatory bowel diseases (IBD), particularly Crohn’s disease (CD). However, most studies address the observed effects by focusing on studying the univariate connection between disease and dietary-induced alterations to gut microbiota composition. The possibility that these effects may reflect a number of other interconnected (i.e., pantropic) mechanisms, activated in parallel, particularly concerning various bacterial metabolites, is in the process of being elucidated. Progress seems, however, hampered by various difficult-to-study factors interacting at the mucosal level. Here, we highlight some of such factors that merit consideration, namely: (1) the contribution of host genetics and diet in altering gut microbiome, and in turn, the crosstalk among secondary metabolic pathways; (2) the interdependence between the amount of dietary fat, the fatty acid composition, the effects of timing and route of administration on gut microbiota community, and the impact of microbiota-derived fatty acids; (3) the effect of diet on bile acid composition, and the modulator role of bile acids on the gut microbiota; (4) the impact of endogenous and exogenous intestinal micronutrients and metabolites; and (5) the need to consider food associated toxins and chemicals, which can introduce confounding immune modulating elements (e.g., antioxidant and phytochemicals in oils and proteins). These concepts, which are not mutually exclusive, are herein illustrated paying special emphasis on physiologically inter-related processes.

Early Neolithic genomes from the eastern Fertile Crescent

We sequenced Early Neolithic genomes from the Zagros region of Iran (eastern Fertile Crescent), where some of the earliest evidence for farming is found, and identify a previously uncharacterized population that is neither ancestral to the first European farmers nor has contributed substantially to the ancestry of modern Europeans. These people are estimated to have separated from Early Neolithic farmers in Anatolia some 46,000 to 77,000 years ago and show affinities to modern-day Pakistani and Afghan populations, but particularly to Iranian Zoroastrians. We conclude that multiple, genetically differentiated hunter-gatherer populations adopted farming in southwestern Asia, that components of pre-Neolithic population structure were preserved as farming spread into neighboring regions, and that the Zagros region was the cradle of eastward expansion.

Transportome Profiling Identifies Profound Alterations in Crohn's Disease Partially Restored by Commensal Bacteria

BACKGROUND AND AIMS

Several transport alterations have been described in intestinal inflammatory diseases. This is relevant because the primary function of the intestine is nutrient and mineral absorption. However, analysis of the transportome as a whole and the effect of commensal bacteria on it have not been addressed so far.

METHODS

Five healthy and 6 Crohn's disease (CD) samples were hybridized to human HT-12 V4 Illumina GeneChip. Results were validated by reverse transcription-polymerase chain reaction (RT-PCR) analysis and with additional array data. Organ culture assays were performed from mucosa ileal wall specimens collected at surgery. Samples were incubated with or without commensal bacteria for 4 hours. Finally, RNA was isolated for microarray processing.

RESULTS

The analysis of CD versus healthy ileal mucosa demonstrated upregulation of previously described genes involved in immunity and the inflammatory response in this disease. Interestingly, whole transcriptional analysis revealed profound alterations in the transportome profile. Sixty-two solute carrier (SLC) transporters displayed different expression patterns, most of them being downregulated. Changes were confirmed by RT-PCR in a randomly chosen subset of SLCs. A large number of amino acid transporters and most members of the enteric purinome were found to be altered. Most of these proteins were found at the apical membrane of the enterocyte, which could impair both amino acid absorption and purinergic signalling. Treatment of ileum specimen explants with commensal bacteria restored almost all CD transportome alterations.

CONCLUSIONS

These results describe the altered transportome profile in CD and open the possibility of restoring transportome complications with commensal bacteria.

Phytochemicals Mediate the Expression and Activity of OCTN2 as Activators of the PPARγ/RXRα Pathway

Many phytochemicals exert activities as agonists of peroxisome proliferator-activated receptor gamma (PPARγ). This study aims to investigate whether phytochemicals are agonists of the PPARγ/RXRα pathway and modulate the target gene OCTN2. In this study, a luciferase reporter gene system was used to screen novel OCTN2 activators from 39 phytochemicals. Kaempferol, curcumin, and puerarin were found to show the significant PPRE-mediated luciferase activities (>150%) at 20 μM and showed a dose-dependent manner. Phytochemicals also elevated the mRNA and protein expression of OCTN2 in a dose-dependent fashion in colorectal cancer SW480 cells. These induction effects were gradually inhibited by PPARγ antagonist GW9662 in the luciferase reporter gene system and in SW480 cells. Moreover, the results of cell viability assay imply that three phytochemicals probably induce OCTN2 expression leading to the enhanced uptake of its substrate, oxaliplatin, thereby making cells more sensitive to oxaliplatin. The molecular docking study showed the possible binding sites of phytochemicals in PPARγ protein, and all of the docked phytochemicals fitted the same active pocket in PPARγ as troglitazone. All three phytochemicals exhibited hydrogen bonds between their polar moieties and the amino acid residues. Thus, we identified three phytochemicals as PPARγ ligands, which potentiated the expression and activity of OCTN2.

L503F variant of carnitine/organic cation transporter 1 efficiently transports metformin and other biguanides

Objectives

Carnitine/organic cation transporter 1 (OCTN1) is involved in gastrointestinal absorption and mitochondrial toxicity of biguanides in rodents, but its pharmacokinetic roles in humans are largely unknown. The purpose of this study was to clarify the transport activities of two major OCTN1 variants, L503F and I306T, for gabapentin and three biguanide drugs, metformin, buformin and phenformin.

Methods

HEK293 cells were transfected with OCTN1 gene, its variants, or vector alone, and the uptake and cytotoxicity of each drug were examined.

Key findings

Buformin was identified to be an OCTN1 substrate. Uptake of biguanides, especially metformin, mediated by OCTN1 variant L503F, which is commonly found in Caucasians, was much higher than that by the wild-type transporter (WT-OCTN1). Cytotoxicity of metformin was also greater in HEK293 cells expressing the L503F variant, compared with WT-OCTN1. Uptake of gabapentin mediated by OCTN1 variant I306T, which is commonly found in both Asians and Caucasians, was lower than that by WT-OCTN1, although uptake of the typical OCTN1 substrate ergothioneine was similar.

Conclusion

Organic cation transporter 1 variant L503F transports biguanides, especially metformin, more efficiently than WT-OCTN1, whereas the I306T variant transports gabapentin less efficiently than WT-OCTN1, suggesting that the common OCTN1 variants may alter pharmacokinetics of these drugs.

A Safety Evaluation of a Nature-Identical l-Ergothioneine in Sprague Dawley Rats

l-(+) Ergothioneine is a naturally occurring thiol amino acid with antioxidant properties and potential benefits as a dietary supplement. Despite its century-old identification and wide distribution in human food, little is known of its mechanism of action and safety. The nature-identical biomimetic of l-(+) ergothioneine, produced by Mironova Labs and supplied as Mironova (EGT+), has been investigated in the present studies for its mutagenic and toxicologic potential. In a plate incorporation and preincubation assay with Salmonella typhimurium strains TA98, 100, 1,535, and 1,537 and Escherichia coli WP2uvrA strain, at dose concentrations of 1.58, 5, 15.8, 50, 158, 500, 1,580, and 5,000 μg/plate with and without metabolic activation, no cytotoxicity or mutagenicity was observed. Following a preliminary 28-day study, a repeated dose 90-day gavage study at dose levels of 0, 400, 800, and 1,600 mg/kg body weight (bw)/d in Sprague Dawley rats, in which dose-proportional systemic absorption was confirmed by plasma analysis, no adverse clinical, body weight/gain, food consumption and efficiency, clinical pathology, or histopathological changes associated with the administration of the nature-identical ergothioneine were observed. In conclusion, EGT+ administered over 90 days was well tolerated with a no adverse effect level at 1,600 mg/kg bw/d, the highest dose tested for male and female rats. In addition, the nature-identical test substance, EGT+ was not mutagenic in a bacterial reverse mutation assay at plate concentrations of up to 5,000 μg/mL in the presence or absence of metabolic activation.

A mutation in SLC22A4 encoding an organic cation transporter expressed in the cochlea strial endothelium causes human recessive non-syndromic hearing loss DFNB60

The high prevalence/incidence of hearing loss (HL) in humans makes it the most common sensory defect. The majority of the cases are of genetic origin. Non-syndromic hereditary HL is extremely heterogeneous. Genetic approaches have been instrumental in deciphering genes that are crucial for auditory function. In this study, we first used NADf chip to exclude the implication of known North-African mutations in HL in a large consanguineous Tunisian family (FT13) affected by autosomal recessive non-syndromic HL (ARNSHL). We then performed genome-wide linkage analysis and assigned the deafness gene locus to ch:5q23.2-31.1, corresponding to the DFNB60 ARNSHL locus. Moreover, we performed whole exome sequencing on FT13 patient DNA and uncovered amino acid substitution p.Cys113Tyr in SLC22A4, a transporter of organic cations, cosegregating with HL in FT13 and therefore the cause of ARNSHL DFNB60. We also screened a cohort of small Tunisian HL families and uncovered an additional deaf proband of consanguineous parents that is homozygous for p.Cys113Tyr carried by the same microsatellite marker haplotype as in FT13, indicating that this mutation is ancestral. Using immunofluorescence, we found that Slc22a4 is expressed in stria vascularis (SV) endothelial cells of rodent cochlea and targets their apical plasma membrane. We also found Slc22a4 transcripts in our RNA-seq library from purified primary culture of mouse SV endothelial cells. Interestingly, p.Cys113Tyr mutation affects the trafficking of the transporter and severely alters ergothioneine uptake. We conclude that SLC22A4 is an organic cation transporter of the SV endothelium that is essential for hearing, and its mutation causes DFNB60 form of HL.

Metabolomics in epidemiology: from metabolite concentrations to integrative reaction networks

Metabolomics is becoming feasible for population-scale studies of human disease. In this review, we survey epidemiological studies that leverage metabolomics and multi-omics to gain insight into disease mechanisms. We outline key practical, technological and analytical limitations while also highlighting recent successes in integrating these data. The use of multi-omics to infer reaction rates is discussed as a potential future direction for metabolomics research, as a means of identifying biomarkers as well as inferring causality. Furthermore, we highlight established analysis approaches as well as simulation-based methods currently used in single- and multi-cell levels in systems biology.

Wide tolerance to amino acids substitutions in the OCTN1 ergothioneine transporter

BACKGROUND

Organic cation transporters transfer solutes with a positive charge across the plasma membrane. The novel organic cation transporter 1 (OCTN1) and 2 (OCTN2) transport ergothioneine and carnitine, respectively. Mutations in the SLC22A5 gene encoding OCTN2 cause primary carnitine deficiency, a recessive disorders resulting in low carnitine levels and defective fatty acid oxidation. Variations in the SLC22A4 gene encoding OCTN1 are associated with rheumatoid arthritis and Crohn disease.

METHODS

Here we evaluate the functional properties of the OCTN1 transporter using chimeric transporters constructed by fusing different portion of the OCTN1 and OCTN2 cDNAs. Their relative abundance and subcellular distribution was evaluated through western blot analysis and confocal microscopy.

RESULTS

Substitutions of the C-terminal portion of OCTN1 with the correspondent residues of OCTN2 generated chimeric OCTN transporters more active than wild-type OCTN1 in transporting ergothioneine. Additional single amino acid substitutions introduced in chimeric OCTN transporters further increased ergothioneine transport activity. Kinetic analysis indicated that increased transport activity was due to an increased V(max), with modest changes in K(m) toward ergothioneine.

CONCLUSIONS

Our results indicate that the OCTN1 transporter is tolerant to extensive amino acid substitutions. This is in sharp contrast to the OCTN2 carnitine transporter that has been selected for high functional activity through evolution, with almost all substitutions reducing carnitine transport activity.

GENERAL SIGNIFICANCE

The widespread tolerance of OCTN1 to amino acid substitutions suggests that the corresponding SLC22A4 gene may have derived from a recent duplication of the SLC22A5 gene and might not yet have a defined physiological role.

Identification of OCTN2 variants and their association with phenotypes of Crohn's disease in a Korean population

Crohn’s disease (CD) is a chronic inflammatory bowel disease and a genetic variant in the OCTN2, g.-207G > C is significantly associated with CD susceptibility. This study was aimed to identify novel OCTN2 functional promoter variants and their roles in transcriptional regulation using various in vitro assays. In addition, we investigated the association between OCTN2 genotypes and CD through genetic analysis using DNA samples from 193 patients with CD and 281 healthy controls. Among the three major promoter haplotypes of OCTN2 identified, one haplotype, H3, showed a significant decrease in promoter activity: two polymorphisms in H3 were associated with a significant reduction in promoter activity. In particular, we found that the reduced transcriptional activity of those two polymorphisms results from a reduction in the binding affinity of the activators, NF-E2 and YY1, to the OCTN2 promoter. The functional haplotype of the OCTN2 promoter was associated with clinical course of CD such as the disease behavior and need for surgery. However, genetic variants or haplotypes of OCTN2 did not affect the susceptibility to CD. Our results suggest that a common promoter haplotype of OCTN2 regulates the transcriptional rate of OCTN2 and influences the clinical course of CD.