Deletion of organic cation transporter Oct3 promotes hepatic fibrosis via upregulation of TGFβ

Fraxin alleviates oral lichen planus by suppressing OCT3-mediated activation of FGF2/NF-κB pathway

Oral lichen planus (OLP) is a carcinogenic chronic inflammatory oral disease, which lacks effective treatments. Fraxin is an active ingredient of the traditional Chinese medicine Qin Pi, which has an anti-inflammatory effect, but its effect on OLP is unclear. The aim of this study was to investigate the therapeutic effect of fraxin on OLP and the underlying mechanism. Human immortalized keratinocytes (HaCat) were incubated with fraxin (10, 20, or 40 µM) for 48 h and then treated with 10 µg/mL LPS for 24 h. Cell viability and apoptosis were detected. Next, the interaction between OCT3 and FGF2 was predicted by online database and verified by Co-IP analysis. Fraxin, Ad-OCT3, sh-OCT3, and sh-FGF2 were, respectively, applied to treat LPS-incubated HaCat cells, and cell viability, apoptosis, and secretion of inflammatory factors were detected with MTT, flow cytometry, and ELISA assays. Then, the involvement of OCT3 and FGF2 in the prevention of fraxin on HaCat cells from LPS-induced cell apoptosis and inflammation was investigated through multiple rescue experiments. In addition, OLP models were constructed in VDR-/- mice and NOD/SCID mice by injecting with human OLP pathological tissue homogenates to verify the therapeutic effect of fraxin on OLP. Fraxin treatment increased cell viability and reduced cell apoptosis and the secretion of IL-6 and TNF-α in a dose-dependent manner. OCT3 was significantly upregulated in oral mucosa tissues of OLP mice. OCT3 silencing inhibited LPS-induced cell apoptosis and secretion of inflammatory factors. Fraxin incubation reduced the expression of OCT3, and OCT3 interacted with FGF2 to upregulate FGF2 protein. FGF2 silencing reduced the expression of p-p65/NF-κB protein and improved LPS-induced cell apoptosis and secretion of inflammatory factors. OCT3 overexpression increased the expression of FGF2 and p-p65/NF-κB proteins, rh-FGF2 aggravated this effect, while FGF2-Neu-Ab reversed this effect. The results of in vivo experiments showed that fraxin alleviated cell apoptosis and inflammation in oral buccal mucosa tissues of OLP mice. Fraxin inhibited cell apoptosis and inflammation by suppressing OCT3-mediated activation of the FGF2/NF-κB pathway, alleviating the progression of OLP.

Targeted mutagenesis of negatively charged amino acids outlining the substrate translocation path within the human organic cation transporter 3

Recently published cryo-EM structures of human organic cation transporters of the SLC22 family revealed seven, sequentially arranged glutamic and aspartic acid residues, which may be relevant for interactions with positively charged substrates. We analyzed the functional consequences of removing those negative charges by creating D155N, E232Q, D382N, E390Q, E451Q, E459Q, and D478N mutants of OCT3. E232Q, E459Q, and D478N resulted in a lack of localization in the outer cell membrane and no relevant uptake activity. However, D155N and E451Q showed a substrate-specific loss of transport activity, whereas E390Q had no remaining activity despite correct membrane localization. In contrast, D382N showed almost wild-type-like uptake. D155 is located at the entrance to the substrate binding pocket and could, therefore be involved in guiding cationic substrates towards the inside of the binding pocket. For E390, we confirm its critical function for transporter function as it was recently shown for the corresponding position in OCT1. Interestingly, E451 seems to be located at the bottom of the binding pocket in the outward-open confirmation of the transporter. Substrate-specific loss of transport activity of the E451Q variant suggests an essential role in the transport cycle of specific substances as part of an opportunistic binding site. In general, our study highlights the impact of the cryo-EM structures in guiding mutagenesis studies to understand the molecular level of transporter-ligand interactions, and it also confirms the importance of testing multiple substrates in mutagenesis studies of polyspecific OCTs.

SLC22A3 rs2048327 Polymorphism Is Associated with Diabetic Retinopathy in Caucasians with Type 2 Diabetes Mellitus

The Solute Carrier Family 22 Member 3 (SLC22A3) is a high-capacity, low-affinity transporter for the neurotransmitters norepinephrine, epinephrine, dopamine, serotonin, and histamine. SLC22A3 plays important roles in interorgan and interorganism small-molecule communication, and also regulates local and overall homeostasis in the body. Our aim was to investigate the association between the rs2048327 gene polymorphism and diabetic retinopathy (DR) in Slovenian patients with type 2 diabetes mellitus (T2DM). We also investigated SLC22A3 expression in the fibrovascular membranes (FVMs) of patients with proliferative DR (PDR). Our study involved 1555 unrelated Caucasians with T2DM with a defined ophthalmologic status: 577 of them with DR as the study group, and 978 without DR as the control group. The investigated polymorphisms were genotyped using the KASPar genotyping assay. The expression of SLC22A3 (organic cation transporter 3-OCT3) was examined via immunohistochemistry in human FVM from 16 patients with PDR. The C allele and CC genotype frequencies of the rs2048327 polymorphism were significantly higher in the study group compared to the controls. The logistic regression analysis showed that the carriers of the CC genotype in the recessive genetic models of this polymorphism have a 1.531-fold increase (95% CI 1.083-2.161) in the risk of developing DR. Patients with the C allele of rs2048327 compared to the homozygotes for the wild type T allele exhibited a higher density of SLC22A3 (OCT3)-positive cells (10.5 ± 4.5/mm2 vs. 6.1 ± 2.7/mm2, respectively; p < 0.001). We showed the association of the rs2048327 SLC22A3 gene polymorphism with DR in a Slovenian cohort with type 2 diabetes mellitus, indicating its possible role as a genetic risk factor for the development of this diabetic complication.

Bile duct ligation differently regulates protein expressions of organic cation transporters in intestine, liver and kidney of rats through activation of farnesoid X receptor by cholate and bilirubin

Body is equipped with organic cation transporters (OCTs). These OCTs mediate drug transport and are also involved in some disease process. We aimed to investigate whether liver failure alters intestinal, hepatic and renal Oct expressions using bile duct ligation (BDL) rats. Pharmacokinetic analysis demonstrates that BDL decreases plasma metformin exposure, associated with decreased intestinal absorption and increased urinary excretion. Western blot shows that BDL significantly downregulates intestinal Oct2 and hepatic Oct1 but upregulates renal and hepatic Oct2. In vitro cell experiments show that chenodeoxycholic acid (CDCA), bilirubin and farnesoid X receptor (FXR) agonist GW4064 increase OCT2/Oct2 but decrease OCT1/Oct1, which are remarkably attenuated by glycine-β-muricholic acid and silencing FXR. Significantly lowered intestinal CDCA and increased plasma bilirubin levels contribute to different Octs regulation by BDL, which are confirmed using CDCA-treated and bilirubin-treated rats. A disease-based physiologically based pharmacokinetic model characterizing intestinal, hepatic and renal Octs was successfully developed to predict metformin pharmacokinetics in rats. In conclusion, BDL remarkably downregulates expressions of intestinal Oct2 and hepatic Oct1 protein while upregulates expressions of renal and hepatic Oct2 protein in rats, finally, decreasing plasma exposure and impairing hypoglycemic effects of metformin. BDL differently regulates Oct expressions via Fxr activation by CDCA and bilirubin.

Structural basis of organic cation transporter-3 inhibition

Organic cation transporters (OCTs) facilitate the translocation of catecholamines, drugs and xenobiotics across the plasma membrane in various tissues throughout the human body. OCT3 plays a key role in low-affinity, high-capacity uptake of monoamines in most tissues including heart, brain and liver. Its deregulation plays a role in diseases. Despite its importance, the structural basis of OCT3 function and its inhibition has remained enigmatic. Here we describe the cryo-EM structure of human OCT3 at 3.2 Å resolution. Structures of OCT3 bound to two inhibitors, corticosterone and decynium-22, define the ligand binding pocket and reveal common features of major facilitator transporter inhibitors. In addition, we relate the functional characteristics of an extensive collection of previously uncharacterized human genetic variants to structural features, thereby providing a basis for understanding the impact of OCT3 polymorphisms.

Novel small molecular inhibitor of Pit-Oct-Unc transcription factor 1 suppresses hepatocellular carcinoma cell proliferation

Hepatocellular carcinoma (HCC) is one of the most prevalent fatal malignancies in the Chinese population, due to high rates of hepatitis virus infection. Molecular targeted drugs such as sorafenib are the anti-tumor agents of choice for HCC treatment, but their results are generally unsatisfactory. In the present study the use of Pit-Oct-Unc transcription factor 1 (OCT1/POU2F1) as a potential therapeutic target for HCC was investigated, and a novel small molecular inhibitor of OCT1 (SMIO-1) was designed and its therapeutic efficacy against HCC was assessed. OCT1 expression was higher in HCC specimens than in corresponding non-tumor tissues, and higher OCT1 was associated with poorer prognosis in advanced HCC patients undergoing sorafenib treatment. For the first time, the novel SMIO-1 was investigated in conjunction with OCT1 via molecular docking. Interaction between SMIO-1 and OCT1 was confirmed via OCT1 point mutation. Treatment with SMIO-1 repressed OCT1 transcription factor activation by disrupting the interaction between OCT1 and its cofactors. It also repressed the proliferation and metastasis of HCC cells, and inhibited proliferation-related and metastasis-related genes downstream of OCT1. Therefore, SMIO-1 is a promising strategy for HCC treatment.

Functional inhibition of Oct leads to HNF4α upregulation

Organic cation transporters (human, OCT; mouse, Oct) are responsible for the intracellular uptake and detoxification of a broad spectrum of endogenous and exogenous substrates. The OCT1 gene SLC22A1 (human; mouse, Scl22a1) is transactivated by hepatocyte nuclear factor 4α (human, HNF4α; mouse, Hnf4α). HNF4α is a master regulator of hepatocyte differentiation and is frequently associated with hepatocellular carcinoma (HCC). In addition, the downregulation of HNF4α is associated with enhanced fibrogenesis. Our recent study revealed that hepatocarcinogenesis and fibrosis were enhanced with the loss of Oct3 (gene, Slc22a3). Notably, differences in Hnf4α expression, and in cholestasis and fibrosis were also detected in Oct3-knockout (FVB.Slc22a3tm10pb, Oct3^-/-) mice. To the best of our knowledge, no data exists on an interaction between Oct3 and Hnf4α. We hypothesised that loss of Oct3 may have an impact on Hnf4α expression. In the present study, gene expression analyses were performed in liver tissue from untreated Oct3^-/- and wild type (FVB, WT) mice. C57BL/6, Oct3^-/- and WT mice were treated with pro-fibrotic carbon tetrachloride (CCl₄) or thioacetamide (TAA) for 6 weeks to chemically induce liver fibrosis. Cholestasis-associated fibrosis was mechanically generated in Oct3^-/- and WT mice by bile duct ligation (BDL). Finally, stably OCT1- and OCT3-transfected tumour cell lines and primary murine hepatocytes were treated with the non-selective OCT inhibitor quinine and Hnf4α expression was quantified by qPCR and immunofluorescence. The results revealed that Hnf4α is one of the top upstream regulators in Oct3^-/- mice. Hnf4α mRNA expression levels were downregulated in Oct3^-/- mice compared with in WT mice during cholestatic liver damage as well as fibrogenesis. The downregulation of Hnf4α mRNA expression in fibrotic liver tissue was reversible within 4 weeks. In stably OCT1- and OCT3-transfected HepG2 and HuH7 cells, and primary murine hepatocytes, functional inhibition of OCT led to the upregulation of Hnf4α mRNA expression. Hnf4α was revealed to be located in the cytosol of WT hepatocytes, whereas Oct3^-/- hepatocytes exhibited nuclear Hnf4α expression. In conclusion, Hnf4α was downregulated in response to cholestasis and fibrosis, and functional inhibition of Oct may lead to the upregulation of Hnf4α.

Establishment and application of a predictive model for gefitinib-induced severe rash based on pharmacometabolomic profiling and polymorphisms of transporters in non-small cell lung cancer

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A total of 346 patients were enrolled in this study.

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Severe rash (grade 3&4) did not gain more bonification compare to grade 1&2 rash.

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Gefitinib and its four metabolites were detected in patients’ plasma.

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A specific and sensitive predictive model were established based on pharmacometabolomic profiling and pharmacogenomics approach.

Background

Rash is a well-known predictor of survival for patients with gefitinib therapy with non-small cell lung cancer (NSCLC). However, whether patients with more severe rash obtain the more survival benefits from gefitinib is still unknown, and predicted model for severe rash is needed.

Methods

The relationship between gefitinib-induced rash and progression free survival (PFS) was primarily explored in the retrospective cohort. The association between rash and gefitinib/metabolites concentration and genetic polymorphisms were determined by pharmacometabolomic and pharmacogenomics methods in the exploratory cohort and validated in an external cohort.

Results

The survival for patients with rash was significantly higher than that of patients without rash (p = 0.0002, p = 0.0089), but no difference was found between grade 1/2 or grade 3/4. Only the concentration of gefitinib, but not its metabolites, was found to be associated with severe rash, and the cutoff value of gefitinib was 204.6 ng/mL conducted by ROC curve analysis (AUC=0.685). A predictive model for severe rash was established: gefitinib concentration (OR = 11.523, 95% CI = 2.898-64.016, p = 0.0016), SLC22A8 rs4149179(CT vs CC, OR = 3.156, 95% CI = 0.958–11.164, p = 0.0629), SLC22A1 rs4709400(CG vs CC, OR = 10.267, 95% CI = 2.067–72.465, p = 0.0087; GG vs CC, OR = 5.103, 95% CI = 1.032–33.938, p = 0.061). This model was confirmed in the validation cohort with an excellent predictive ability (AUC = 0.749, 95% CI = 0.710–0.951).

Conclusions

Our finding demonstrated that the incidence, not the severity, of gefitinib-induced rash predicted improved survival, the gefitinib concentration and polymorphisms of SLC22A8 and SLC22A1 were recommended to manage severe rash.

Deletion of Protein Kinase D3 Promotes Liver Fibrosis in Mice

BACKGROUND AND AIMS

Liver fibrosis (LF) is a central pathological process that occurs in most types of chronic liver diseases. Advanced LF causes cirrhosis, hepatocellular carcinoma, and liver failure. However, the exact molecular mechanisms underlying the initiation and progression of LF remain largely unknown.

APPROACH AND RESULTS

This study was designed to investigate the role of protein kinase D3 (PKD3; gene name Prkd3) in the regulation of liver homeostasis. We generated global Prkd3 knockout (Prkd3^-/- ) mice and myeloid-cell-specific Prkd3 knockout (Prkd3^∆LysM ) mice, and we found that both Prkd3^-/- mice and Prkd3^∆LysM mice displayed spontaneous LF. PKD3 deficiency also aggravated CCl₄ -induced LF. PKD3 is highly expressed in hepatic macrophages (HMs), and PKD3 deficiency skewed macrophage polarization toward a profibrotic phenotype. Activated profibrotic macrophages produced transforming growth factor beta that, in turn, activates hepatic stellate cells to become matrix-producing myofibroblasts. Moreover, PKD3 deficiency decreased the phosphatase activity of SH2-containing protein tyrosine phosphatase-1 (a bona-fide PKD3 substrate), resulting in sustained signal transducer and activator of transcription 6 activation in macrophages. In addition, we observed that PKD3 expression in HMs was down-regulated in cirrhotic human liver tissues.

CONCLUSIONS

PKD3 deletion in mice drives LF through the profibrotic macrophage activation.

Organic Cation Transporters in Human Physiology, Pharmacology, and Toxicology

Individual cells and epithelia control the chemical exchange with the surrounding environment by the fine-tuned expression, localization, and function of an array of transmembrane proteins that dictate the selective permeability of the lipid bilayer to small molecules, as actual gatekeepers to the interface with the extracellular space. Among the variety of channels, transporters, and pumps that localize to cell membrane, organic cation transporters (OCTs) are considered to be extremely relevant in the transport across the plasma membrane of the majority of the endogenous substances and drugs that are positively charged near or at physiological pH. In humans, the following six organic cation transporters have been characterized in regards to their respective substrates, all belonging to the solute carrier 22 (SLC22) family: the organic cation transporters 1, 2, and 3 (OCT1–3); the organic cation/carnitine transporter novel 1 and 2 (OCTN1 and N2); and the organic cation transporter 6 (OCT6). OCTs are highly expressed on the plasma membrane of polarized epithelia, thus, playing a key role in intestinal absorption and renal reabsorption of nutrients (e.g., choline and carnitine), in the elimination of waste products (e.g., trimethylamine and trimethylamine N-oxide), and in the kinetic profile and therapeutic index of several drugs (e.g., metformin and platinum derivatives). As part of the Special Issue Physiology, Biochemistry, and Pharmacology of Transporters for Organic Cations, this article critically presents the physio-pathological, pharmacological, and toxicological roles of OCTs in the tissues in which they are primarily expressed.

Cigarette smoke extract combined with lipopolysaccharide reduces OCTN1/2 expression in human alveolar epithelial cells in vitro and rat lung in vivo under inflammatory conditions

Organic cation transporter 1/2 (OCTN1/2) play important roles in the transport of drugs related to pulmonary inflammatory diseases. Nevertheless, the involvement of inflammation induced by cigarette smoke extract (CSE) combined with lipopolysaccharide (LPS) in the regulation of OCTN1/2 is not fully understood. In this study, CSE combined with LPS was used to establish inflammation models in vitro and in vivo. Our study found that the expression of OCTN1/2 was downregulated in rat lung in vivo and in a human alveolar cell line in vitro after treatment with CSE and LPS compared with the control group, while the expression of inflammatory factors was upregulated. After treatment with ipratropium bromide (IB) or dexamethasone (DEX), the expression of OCTN1/2 was upregulated compared with that in the CSE-LPS model group, while the expression of inflammatory factors was significantly downregulated. After administration of the NF-κB inhibitor PDTC on the basis of the inflammatory status, the expression of OCTN1/2 was upregulated in the treated group compared with the CSE-LPS model group, while the expression of phospho-p65, phospho-IκBα and inflammatory factors was significantly downregulated. We further added the NF-κB agonist HSP70 and found a result that the exact opposite of that observed with PDTC. Our findings show that CSE combined with LPS can downregulate the expression of OCTN1/2 under inflammatory conditions, and that the downregulation of OCTN1/2 expression may partially occur via the NF-κB signaling pathway.