Selective and cytokine-dependent regulation of hepatic transporters and bile acid homeostasis during infectious colitis in mice

Inflammation Induces Changes in the Functional Expression of P-gp, BCRP, and MRP2: An Overview of Different Models and Consequences for Drug Disposition

The ATP-binding cassette (ABC) transporters play a key role in drug pharmacokinetics. These membrane transporters expressed within physiological barriers can be a source of pharmacokinetic variability. Changes in ABC transporter expression and functionality may consequently affect the disposition of substrate drugs, resulting in different drug exposure. Inflammation, present in several acute and chronic diseases, has been identified as a source of modulation in drug transporter expression leading to variability in drug response. Its regulation may be particularly dangerous for drugs with a narrow therapeutic index. In this context, numerous in vitro and in vivo models have shown up- or downregulation in the expression and functionality of ABC transporters under inflammatory conditions. Nevertheless, the existence of contradictory data and the lack of standardization for the models used have led to a less conclusive interpretation of these data.

Therapeutic Drug Monitoring of Second- and Third-Generation Antipsychotic Drugs-Influence of Smoking Behavior and Inflammation on Pharmacokinetics

Both inflammation and smoking can influence a drug’s pharmacokinetic properties, i.e., its liberation, absorption, distribution, metabolism, and elimination. Depending on, e.g., pharmacogenetics, these changes may alter treatment response or cause serious adverse drug reactions and are thus of clinical relevance. Antipsychotic drugs, used in the treatment of psychosis and schizophrenia, should be closely monitored due to multiple factors (e.g., the narrow therapeutic window of certain psychotropic drugs, the chronicity of most mental illnesses, and the common occurrence of polypharmacotherapy in psychiatry). Therapeutic drug monitoring (TDM) aids with drug titration by enabling the quantification of patients’ drug levels. Recommendations on the use of TDM during treatment with psychotropic drugs are presented in the Consensus Guidelines for Therapeutic Drug Monitoring in Neuropsychopharmacology; however, data on antipsychotic drug levels during inflammation or after changes in smoking behavior—both clinically relevant in psychiatry—that can aid clinical decision making are sparse. The following narrative review provides an overview of relevant literature regarding TDM in psychiatry, particularly in the context of second- and third-generation antipsychotic drugs, inflammation, and smoking behavior. It aims to spread awareness regarding TDM (most pronouncedly of clozapine and olanzapine) as a tool to optimize drug safety and provide patient-tailored treatment.

Therapeutic Drug Monitoring of Second- and Third-Generation Antipsychotic Drugs—Influence of Smoking Behavior and Inflammation on Pharmacokinetics

Both inflammation and smoking can influence a drug’s pharmacokinetic properties, i.e., its liberation, absorption, distribution, metabolism, and elimination. Depending on, e.g., pharmacogenetics, these changes may alter treatment response or cause serious adverse drug reactions and are thus of clinical relevance. Antipsychotic drugs, used in the treatment of psychosis and schizophrenia, should be closely monitored due to multiple factors (e.g., the narrow therapeutic window of certain psychotropic drugs, the chronicity of most mental illnesses, and the common occurrence of polypharmacotherapy in psychiatry). Therapeutic drug monitoring (TDM) aids with drug titration by enabling the quantification of patients’ drug levels. Recommendations on the use of TDM during treatment with psychotropic drugs are presented in the Consensus Guidelines for Therapeutic Drug Monitoring in Neuropsychopharmacology; however, data on antipsychotic drug levels during inflammation or after changes in smoking behavior—both clinically relevant in psychiatry—that can aid clinical decision making are sparse. The following narrative review provides an overview of relevant literature regarding TDM in psychiatry, particularly in the context of second- and third-generation antipsychotic drugs, inflammation, and smoking behavior. It aims to spread awareness regarding TDM (most pronouncedly of clozapine and olanzapine) as a tool to optimize drug safety and provide patient-tailored treatment.

Therapeutic Drug Monitoring of Second- and Third-Generation Antipsychotic Drugs-Influence of Smoking Behavior and Inflammation on Pharmacokinetics

Both inflammation and smoking can influence a drug's pharmacokinetic properties, i.e., its liberation, absorption, distribution, metabolism, and elimination. Depending on, e.g., pharmacogenetics, these changes may alter treatment response or cause serious adverse drug reactions and are thus of clinical relevance. Antipsychotic drugs, used in the treatment of psychosis and schizophrenia, should be closely monitored due to multiple factors (e.g., the narrow therapeutic window of certain psychotropic drugs, the chronicity of most mental illnesses, and the common occurrence of polypharmacotherapy in psychiatry). Therapeutic drug monitoring (TDM) aids with drug titration by enabling the quantification of patients' drug levels. Recommendations on the use of TDM during treatment with psychotropic drugs are presented in the Consensus Guidelines for Therapeutic Drug Monitoring in Neuropsychopharmacology; however, data on antipsychotic drug levels during inflammation or after changes in smoking behavior-both clinically relevant in psychiatry-that can aid clinical decision making are sparse. The following narrative review provides an overview of relevant literature regarding TDM in psychiatry, particularly in the context of second- and third-generation antipsychotic drugs, inflammation, and smoking behavior. It aims to spread awareness regarding TDM (most pronouncedly of clozapine and olanzapine) as a tool to optimize drug safety and provide patient-tailored treatment.

Downregulation of Renal MRPs Transporters in Acute Lymphoblastic Leukemia Mediated by the IL-6/STAT3/PXR Signaling Pathway

Purpose

Considering prior investigations on reductions of renal multidrug resistance-associated protein (MRP) 2 and 4 transporters in mice with acute lymphoblastic leukemia (ALL), we sought to characterize the underlying mechanisms responsible for IL-6/STAT3/PXR-mediated changes in the expression of MRP2 and MRP4 in ALL.

Subjects and Methods

ALL xenograft models were established and intravenously injected with methotrexate (MTX) of MRPs substrate in NOD/SCID mice. Protein expression of MRPs and associated mechanisms were detected by Western blotting and immunocytochemistry. Plasma concentrations of MTX were determined using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS).

Results

Plasma IL-6 levels in patients with newly diagnosed ALL were increased compared to children with pneumonia. Similarly, plasma IL-6 levels in ALL, ALL-tocilizumab (TCZ, an IL-6 receptor inhibitor) and ALL-S3I-201 (a selective inhibitor of STAT3) mice were increased compared to the control group. The MRP2, MRP4, and PXR expression in HK-2 cells treated with IL-6 were decreased, whereas the p-STAT3 expression was significantly increased compared to the control group results. These results are consistent with clearance of MRPs-mediated MTX in the ALL group. These effects were attenuated by blocking IL-6/STAT3/PXR signaling pathway.

Conclusion

Inflammation-mediated changes in pharmacokinetics are thought to be executed through pathways IL-6-activated pathways, which can facilitate a better understanding of the potential for the use of IL-6 to predict the severity of adverse outcomes and the major implications on potential ALL treatments.

Breast cancer resistance protein (Bcrp/Abcg2) is selectively modulated by lipopolysaccharide (LPS) in the mouse yolk sac

Bacterial infection alters placental ABC transporters expression. These transporters provide fetal protection against circulating xenobiotics and environmental toxins present in maternal blood. We hypothesized that lipopolysaccharide (LPS-bacterial mimic) alters the yolk sac morphology and expression of key ABC transporters in a gestational-age dependent manner. Yolk sac samples from C57BL/6 mice were obtained at gestational ages (GD) 15.5 and GD18.5, 4 or 24 h after LPS exposure (150ug/kg; n = 8/group). Samples underwent morphometrical, qPCR and immunohistochemistry analysis. The volumetric proportions of the histological components of the yolk sac did not change in response to LPS. LPS increased Abcg2 expression at GD15.5, after 4 h of treatment (p < 0.05). No changes in Abca1, Abcb1a/b, Abcg1, Glut1, Snat1, Il-1β, Ccl2 and Mif were observed. Il-6 and Cxcl1 were undetectable in the yolk sac throughout pregnancy. Abca1, breast cancer resistance protein (Bcrp, encoded by Abcg2) and P-glycoprotein (P-gp/ Abcb1a/b) were localized in the endodermal (uterine-facing) epithelium and to a lesser extent in the mesothelium (amnion-facing), whereas Abca1 was also localized to the endothelium of the yolk sac blood vessels. LPS increased the labeling area and intensity of Bcrp in the yolk sac's mesothelial cells at GD15.5 (4 h), whereas at GD18.5, the area of Bcrp labeling in the mesothelium (4 and 24 h) was decreased (p < 0.05). Bacterial infection has the potential to change yolk sac barrier function by affecting Bcrp and Abcg2 expression in a gestational-age dependent-manner. These changes may alter fetal exposure to xenobiotics and toxic substances present in the maternal circulation and in the uterine cavity.

Inflammation is a major regulator of drug metabolizing enzymes and transporters: Consequences for the personalization of drug treatment

Inflammation is an evolutionary process that allows survival against acute infection or injury. Inflammation is also a pathophysiological condition shared by numerous chronic diseases. In addition, inflammation modulates important drug-metabolizing enzymes and transporters (DMETs), thus contributing to intra- and interindividual variability of drug exposure. A better knowledge of the impact of inflammation on drug metabolism and its related clinical consequences would help to personalize drug treatment. Here, we summarize the kinetics of inflammatory mediators and the underlying transcriptional and post-transcriptional mechanisms by which they contribute to the inhibition of important DMETs. We also present an updated overview of the effect of inflammation on the pharmacokinetic parameters of most of the drugs that are DMET substrates, for which therapeutic drug monitoring is recommended. Furthermore, we provide opinions on how to integrate the inflammatory status into pharmacogenetics, therapeutic drug monitoring, and population pharmacokinetic strategies to improve the personalization of drug treatment for each patient.

Impact of Viral Inflammation on the Expression of Renal Drug Transporters in Pregnant Rats

Inflammation impacts the expression and function of drug transporters at term-gestation; however, the impact of inflammation on the expression of drug transporters at mid-gestation is largely unknown. Since renal drug transporters play a key role in the clearance of many drugs prescribed during pregnancy, our objective was to study the impact of the viral mimetic poly I:C on the expression of renal transporters in pregnant rats at mid-gestation. Poly I:C (10 mg/kg) or saline was administered intraperitoneally to pregnant Sprague-Dawley rats on gestational day 14. Expression of renal transporters was measured at 6, 24, and 48 h by qRT-PCR and Western blot. The mRNA levels of Mdr1a, Mrp4, Oct2, Octn1, Octn2, Mate1, Oat1-3, Urat1, Oatp4c1, Ent1, and Pept2 were significantly lower in the poly I:C group at 6 h. At 24 h, only the mRNA levels of Oct2, Oatp4c1, and Ent1 were decreased compared to saline. Poly I:C significantly decreased protein expression of Urat1 at 24 h, and P-gp, Oct2, Mate1, Oat1, Oat3 at 48 h,. Poly I:C imposed significant reductions in the expression of several key renal transporters at mid-gestation in pregnant rats. Thus, viral infection may impact renal excretion of drug transporter substrates, potentially leading to drug-disease interactions.

Liver infiltrating T cells regulate bile acid metabolism in experimental cholangitis

BACKGROUND & AIMS

T cells are central mediators of liver inflammation and represent potential treatment targets in cholestatic liver disease. Whereas emerging evidence shows that bile acids (BAs) affect T cell function, the role of T cells for the regulation of BA metabolism is unknown. In order to understand this interplay, we investigated the influence of T cells on BA metabolism in a novel mouse model of cholangitis.

METHODS

Mdr2-/- mice were crossed with transgenic K14-OVAp mice, which express an MHC class I restricted ovalbumin peptide on biliary epithelial cells (Mdr2-/-xK14-OVAp). T cell-mediated cholangitis was induced by the adoptive transfer of antigen-specific CD8+ T cells. BA levels were quantified using a targeted liquid chromatography-mass spectrometry-based approach.

RESULTS

T cell-induced cholangitis resulted in reduced levels of unconjugated BAs in the liver and significantly increased serum and hepatic levels of conjugated BAs. Genes responsible for BA synthesis and uptake were downregulated and expression of the bile salt export pump was increased. The transferred antigen-specific CD8+ T cells alone were able to induce these changes, as demonstrated using Mdr2-/-xK14-OVAp recipient mice on the Rag1-/- background. Mechanistically, we showed by depletion experiments that alterations in BA metabolism were partly mediated by the proinflammatory cytokines TNF and IFN-γ in an FXR-dependent manner, a process that in vitro required cell contact between T cells and hepatocytes.

CONCLUSION

Whereas it is known that BA metabolism is dysregulated in sepsis and related conditions, we have shown that T cells are able to control the synthesis and metabolism of BAs, a process which depends on TNF and IFN-γ. Understanding the effect of lymphocytes on BA metabolism will help in the design of combined treatment strategies for cholestatic liver diseases.

LAY SUMMARY

Dysregulation of bile acid metabolism and T cells can contribute to the development of cholangiopathies. Before targeting T cells for the treatment of cholangiopathies, it should be determined whether they exert protective effects on bile acid metabolism. Herein, we demonstrate that T cell-induced cholangitis resulted in decreased levels of harmful unconjugated bile acids. T cells were able to directly control synthesis and metabolism of bile acids, a process which was dependent on the proinflammatory cytokines TNF and IFN-γ. Understanding the effect of lymphocytes on bile acid metabolism will help in the design of combined treatment strategies for cholestatic liver diseases.

Dysregulation of placental ABC transporters in a murine model of malaria-induced preterm labor

Malaria in Pregnancy (MiP) is characterized by placental accumulation of Plasmodium-infected erythrocytes, intrauterine growth restriction (IUGR) and preterm delivery (PTD). Placental ATP-binding cassette (ABC) transporters mediate the efflux of nutrients, cytokines and xenobiotics. The expression and activity of these transporters are highly responsive to infection. We hypothesized that MiP would perturb the expression of placental ABC transporters, promoting PTD. Peripheral blood, spleens, livers and placentas of pregnant mice, infected with Plasmodium berghei ANKA on gestational day (GD) 13.5, were collected and analyzed on GD18.5. The primary consequences of human MiP, including IUGR, PTD (20%) and placental inflammation, were recapitulated in our mouse model. Electron microscopy revealed attenuated presence of labyrinthine microvilli and dilated spongiotrophoblasts -granular endoplasmic reticulum cisternae. Additionally, a decrease in placental Abca1 (ABCA1), Abcb1b (P-glycoprotein), Abcb9 and Abcg2 (BCRP) expression was observed in MiP mice. In conclusion, MiP associated with PTD impairs placental ABC transporters’ expression, potentially modulating placental nutrient, environmental toxin and xenobiotic biodistribution within the fetal compartment, and may, at some degree, be involved with pregnancy outcome in MiP.

Interaction of glucocorticoids with FXR/FGF19/FGF21-mediated ileum-liver crosstalk

At high doses, glucocorticoids (GC) have been associated with enhanced serum bile acids and liver injury. We have evaluated the effect of GC, in the absence of hepatotoxicity, on FXR/FGF91(Fgf15)/FGF21-mediated ileum-liver crosstalk. Rats and mice (wild type and Fxr^-/-, Fgf15^-/- and int-Gr^-/- strains; the latter with GC receptor (Gr) knockout selective for intestinal epithelial cells), were treated (i.p.) with dexamethasone, prednisolone or budesonide. In both species, high doses of GC caused hepatotoxicity. At a non-hepatotoxic dose, GC induced ileal Fgf15 down-regulation and liver Fgf21 up-regulation, without affecting Fxr expression. Fgf21 mRNA levels correlated with those of several genes involved in glucose and bile acid metabolism. Surprisingly, liver Cyp7a1 was not up-regulated. The expression of factors involved in transcriptional modulation by Fxr and Gr (p300, Drip205, CBP and Smrt) was not affected. Pxr target genes Cyp3a11 and Mrp2 were not up-regulated in liver or intestine. In contrast, the expression of some Pparα target genes in liver (Fgf21, Cyp4a14 and Vanin-1) and intestine (Vanin-1 and Cyp3a11) was altered. In mice with experimental colitis, liver Fgf21 was up-regulated (4.4-fold). HepG2 cells transfection with FGF21 inhibited CYP7A1 promoter (prCYP7A1-Luc2). This was mimicked by pure human FGF21 protein or culture in medium previously conditioned by cells over-expressing FGF21. This response was not abolished by deletion of a putative response element for phosphorylated FGF21 effectors present in prCYP7A1. In conclusion, GC interfere with FXR/FGF19-mediated intestinal control of CYP7A1 expression by the liver and stimulate hepatic secretion of FGF21, which inhibits CYP7A1 promoter through an autocrine mechanism.

Repression of intestinal transporters and FXR-FGF15 signaling explains bile acids dysregulation in experimental colitis-associated colon cancer

Bile acids (BAs) are important endogenous signaling molecules that play vital roles in the pathological development of various diseases including colitis-associated cancer (CAC). BAs were previously found dysregulated under conditions of CAC; however, the exact patterns and underlying molecular mechanisms remain largely elusive. Based on the development of a method for comprehensive analysis of BAs, this study aims to elucidate the dysregulation patterns and involved mechanisms in a typical CAC model induced by azoxymethane (AOM)/dextran sodium sulfate (DSS). CAC mice showed decreased BAs transformation in gut and glucuronidation in colon, leading to accumulation of primary BAs but reduction of secondary BAs in colon. CAC mice were characterized by an accumulation of BAs in various compartments except ileum, which is in line with repressed ileal FXR-FGF15 feedback signaling and the increased expression of hepatic CYP7A1. The compromised ileal FXR-FGF15 signaling was caused in part by the reduced absorption of FXR ligands including free and tauro-conjungated BAs due to the downregulation of various transporters of BAs in the ileum of CAC mice.

Tauroursodeoxycholic acid protects bile acid homeostasis under inflammatory conditions and dampens Crohn's disease-like ileitis

Bile acids regulate the expression of intestinal bile acid transporters and are natural ligands for nuclear receptors controlling inflammation. Accumulating evidence suggests that signaling through these receptors is impaired in inflammatory bowel disease. We investigated whether tauroursodeoxycholic acid (TUDCA), a secondary bile acid with cytoprotective properties, regulates ileal nuclear receptor and bile acid transporter expression and assessed its therapeutic potential in an experimental model of Crohn's disease (CD). Gene expression of the nuclear receptors farnesoid X receptor, pregnane X receptor and vitamin D receptor and the bile acid transporters apical sodium-dependent bile acid transporter and organic solute transporter α and β was analyzed in Caco-2 cell monolayers exposed to tumor necrosis factor (TNF)α, in ileal tissue of TNF^ΔARE/WT mice and in inflamed ileal biopsies from CD patients by quantitative real-time polymerase chain reaction. TNF^ΔARE/WT mice and wild-type littermates were treated with TUDCA or placebo for 11 weeks and ileal histopathology and expression of the aforementioned genes were determined. Exposing Caco-2 cell monolayers to TNFα impaired the mRNA expression of nuclear receptors and bile acid transporters, whereas co-incubation with TUDCA antagonized their downregulation. TNF^ΔARE/WT mice displayed altered ileal bile acid homeostasis that mimicked the situation in human CD ileitis. Administration of TUDCA attenuated ileitis and alleviated the downregulation of nuclear receptors and bile acid transporters in these mice. These results show that TUDCA protects bile acid homeostasis under inflammatory conditions and suppresses CD-like ileitis. Together with previous observations showing similar efficacy in experimental colitis, we conclude that TUDCA could be a promising therapeutic agent for inflammatory bowel disease, warranting a clinical trial.

Alterations in Enterohepatic Fgf15 Signaling and Changes in Bile Acid Composition Depend on Localization of Murine Intestinal Inflammation

BACKGROUND

Fibroblast growth factor (FGF) 15/19 is part of the gut-liver crosstalk accounting for bile acid (BA) metabolism regulation. Dysregulation of fibroblast growth factor 15/19 signaling is observed in different pathological conditions, for example, in gastrointestinal diseases such as inflammatory bowel disease (IBD). To understand the molecular bases, we analyzed the enterohepatic regulation of Fgf15-mediated pathway in 2 different inflammatory bowel disease mouse models.

METHODS

Target genes of the BA-farnesoid-X-receptor (Fxr)-Ffg15 axis were quantified by RT-PCR or western blotting in gut and liver of dextran sulfate sodium (DSS)-treated and IL10 mice. Serum Fgf15 levels were analyzed by ELISA. Biliary and fecal BA composition was differentiated by HPLC-MS/MS.

RESULTS

Dextran sulfate sodium-treated mice with ileum-sparing colitis showed higher Fgf15 serum levels. In contrast, IL10 mice with ileitis had a trend toward decreased Fgf15 serum levels compared with controls and increased expression of Asbt as a negative Fxr-target gene. In hepatic tissue of both models, no histological changes, but higher interleukin 6 (IL-6) mRNA expression and down-regulation of Fxr and Cytochrom P450 7a1 mRNA expression were observed. Fibroblast growth factor receptor 4 up-regulation was in line with higher Fgf15 serum levels in dextran sulfate sodium-treated mice. A distinct fecal BA profile was observed in both models with significantly higher levels of taurine-conjugated BA in particular tauro-β-muricholic acid in IL10 mice.

CONCLUSIONS

Ileum-sparing colitis is characterized by activation of Fxr-Fgf15 signaling with higher expression of Fxr-target gene Fgf15, whereas ileal inflammation showed no signs of Fxr-Fgf15 activation. Abundance of BA such as T-β-MCA may be important for intestinal Fxr activation in mice.

The role of transporters in toxicity and disease

The significance of transporters in the disposition, metabolism, and elimination of drugs is well recognized. One gap in our knowledge is a comprehensive understanding of how drug transporters change functionality (their amount and activity) in response to disease and how disease and its inevitable pathology change transporter expression. In this issue of Drug Metabolism and Disposition a series of review and primary research articles are presented to highlight the importance of transporters in toxicity and disease. Because of the central role of the liver in drug metabolism, many of the articles in this theme issue focus on transporters in the liver and how pathology or alterations in physiology affects transporter expression. The contributing authors have also considered the role of transporters in drug interactions as well as drug-induced liver injury. Noninvasive approaches to assessing transporter function in vivo are also described. Several articles highlight important issues in oncology where toxicity must be balanced against efficacy. In total, this theme issue will provide a stepping-stone to future studies that will establish a more comprehensive understanding of transporters in disease.