Expression and regulation of transmembrane transporters in healthy intestine and gastrointestinal diseases

Transmembrane transporters mediate energy dependent or independent translocation of drugs, potentially toxic compounds, and of various endogenous substrates such as bile acids and bilirubin across membranes. In this thesis the focus is on two classes of transporters, the ATPbinding cassette (ABC) transporters, which mediate ATP dependent transport and the solute carriers (SLC) which use electrochemical gradients for their transport. The transporters are expressed on membranes of cells of excretory organs (e.g. kidney, liver) and protective barriers (e.g. intestine, blood brain barrier) and influence therefore the absorption, distribution and elimination of compounds. They may reduce the intracellular concentration of drugs. Transport activity of transmembrane transporters in the intestine depends on the expression level and distribution along the intestine. Transport activity of transporters might be influenced by other factors such as genetic variations, which may present with a dysfunctional phenotype (e.g. single nucleotide polymorphisms; SNPs), or certain disease states, which might adaptively regulate transporter expression on the transcriptional and posttranscriptional level. The first aim of this thesis was a systematic site-specific analysis of the expression of several ABC transporters and solute carriers along the intestinal tract. Following that, regulation of hepatobiliary transporters in the human intestine during obstructive cholestasis was evaluated. Studies were performed in close collaboration with the Department of Gastroenterology (University Hospital of Basel). As described in Chapter 2, transporter mRNA expression was analyzed by real time PCR (Taqman), a method that was previously developed in our laboratory to quantify the expression of transporters using standard curves. Protein expression was assessed by immunohistochemistry, bile acids plasma concentrations were measured by capillary gas chromatography (U. Beuers, Munich). The results presented in this thesis include systematic site specific analysis of quantitative expression of the human multidrug resistance transporters, such MDR1 (ABCB1), breast cancer resistance transporter (BCRP; ABCG2) and multidrug resistance associated transporters (MRP1-5; ABCC1-5) as well as the apical sodium dependent bile acid transporter ASBT (SLC10A2) along the the intestinal tract. These data are shown in Chapter 3. As the mRNA expression levels of the investigated transporters change along the intestinal tract, these findings might be of interest to develop target strategies for orally administered drugs. Also, this systematic site specific analysis of MDR transporters serves as a preparation for a prospective clinical study in patients with Inflammatory Bowel Disease (IBD), which will investigate MDR transporter gene expression in intestinal biopsies (intestinal epithelial cells, intestinal macrophages) in newly diagnosed IBD patients compared to treatment refractory IBD patients, patients in remission and disease free controls. This study design will help to evaluate, if MDR transporters vary due to interindividual differences, inflammatory processes and/or pharmacological treatment and might serve as an explanation for patients with IBD not responding to drug treatment. Intestinal macrophages play a central role in the orchestration of innate immune response reactions in the gut. As anti-inflammatory as well as immunosuppresive drugs such as glucocorticoids, methotrexate, cyclosporine, 6-mercaptopurine and sulfasalazine, which all of them are used in the treatment of IBD patients, are substrates of MDR transporters, a method for isolation of CD14+ peripheral blood cells (monocytes), their ex vivo cultivation and differentiation into macrophages was established. In Chapter 4, first results demonstrate the influence of the differentiation process of monocytes into monocyte derived macrophages (MDM) and the stimulation of MDM with bacterial products (LPS) on MDR transporter expression. At present, the effect of budesonide, methotrexate, 6-mercaptopurine and sulfasalazine on the transporter expression in ex vivo cultivated human MDM is evaluated. Adaptive regulation of hepatobiliary transport systems during obstructive cholestasis with a disrupted enterohepatic circulation has been demonstrated in the intestine only for rodents before. The results presented in Chapter 3 showed, that ASBT, which contributes substantially to the enterohepatic circulation of bile acids by their reabsorption from the intestine, is adaptivelly regulated in the human duodenum during obstructive cholestasis. Our findings are of clinical importance as we have shown for the first time that ASBT is expressed in the human duodenum. These results may indicate species specific differences to rodents, and that changes in the ASBT gene expression can be measured in the duodenum during obstructive cholestasis. Adaptive regulation of ASBT in the intestine has clinical implications for the bile acid homeostasis and also for the lipid metabolism. BCRP mediates energy dependent efflux of drugs and potentially toxic compounds, and of various endogenous substrates such as bile acids. Here, expression of human BCRP mRNA was shown to be highest in the duodenum with a continuos decrease along the intestinal tract down to the rectum. BCRP mRNA and protein expression in the duodenum was found to be decreased during obstructive cholestasis when compared to control subjects and BCRP expression increased after reconstitution of bile flow. In consequence, reduced intestinal BCRP expression during obstructive cholestasis might influence the accumulation of bile acids, foodderived carcinogens and the pharmacokinetics of various drugs that are transported by BCRP. In an isolated project with the background of observed therapy resistance to antibiotics in the treatment of patients with chronic prostatitis, MDR expression in prostatic tissue in regard to inflammation was evaluated in 50 patients that underwent transurethral resection of prostate. In this study group, neither inflammation nor localization of inflammation in prostate tissue (acinar versus interstitial) influenced MDR transporter expression

Liver Cirrhosis Affects the Pharmacokinetics of the Six Substrates of the Basel Phenotyping Cocktail Differently.

BACKGROUND Activities of hepatic cytochrome P450 enzymes (CYPs) are relevant for hepatic clearance of drugs and known to be decreased in patients with liver cirrhosis. Several studies have reported the effect of liver cirrhosis on CYP activity, but the results are partially conflicting and for some CYPs lacking. OBJECTIVE In this study, we aimed to investigate the CYP activity in patients with liver cirrhosis with different Child stages (A-C) using the Basel phenotyping cocktail approach. METHODS We assessed the pharmacokinetics of the six compounds and their CYP-specific metabolites of the Basel phenotyping cocktail (CYP1A2: caffeine, CYP2B6: efavirenz, CYP2C9: flurbiprofen, CYP2C19: omeprazole, CYP2D6: metoprolol, CYP3A: midazolam) in patients with liver cirrhosis (n = 16 Child A cirrhosis, n = 15 Child B cirrhosis, n = 5 Child C cirrhosis) and matched control subjects (n = 12). RESULTS While liver cirrhosis only marginally affected the pharmacokinetics of the low to moderate extraction drugs efavirenz and flurbiprofen, the elimination rate of caffeine was reduced by 51% in patients with Child C cirrhosis. For the moderate to high extraction drugs omeprazole, metoprolol, and midazolam, liver cirrhosis decreased the elimination rate by 75%, 37%, and 60%, respectively, increased exposure, and decreased the apparent systemic clearance (clearance/bioavailability). In patients with Child C cirrhosis, the metabolic ratio (ratio of the area under the plasma concentration-time curve from 0 to 24 h of the metabolite to the parent compound), a marker for CYP activity, decreased by 66%, 47%, 92%, 73%, and 43% for paraxanthine/caffeine (CYP1A2), 8-hydroxyefavirenz/efavirenz (CYP2B6), 5-hydroxyomeprazole/omeprazole (CYP2C19), α-hydroxymetoprolol/metoprolol (CYP2D6), and 1'-hydroxymidazolam/midazolam (CYP3A), respectively. In comparison, the metabolic ratio 4-hydroxyflurbiprofen/flurbiprofen (CYP2C9) remained unchanged. CONCLUSIONS Liver cirrhosis affects the activity of CYP isoforms differently. This variability must be considered for dose adjustment of drugs in patients with liver cirrhosis. CLINICAL TRIAL REGISTRATION NCT03337945

IL-20 subfamily cytokines impair the oesophageal epithelial barrier by diminishing filaggrin in eosinophilic oesophagitis.

OBJECTIVE Disruption of the epithelial barrier plays an essential role in developing eosinophilic oesophagitis (EoE), a disease defined by type 2 helper T cell (Th2)-mediated food-associated and aeroallergen-associated chronic inflammation. Although an increased expression of interleukin (IL)-20 subfamily members, IL-19, IL-20 and IL-24, in Th2-mediated diseases has been reported, their function in EoE remains unknown. DESIGN Combining transcriptomic, proteomic and functional analyses, we studied the importance of the IL-20 subfamily for EoE using patient-derived oesophageal three-dimensional models and an EoE mouse model. RESULTS Patients with active EoE have increased expression of IL-20 subfamily cytokines in the oesophagus and serum. In patient-derived oesophageal organoids stimulated with IL-20 cytokines, RNA sequencing and mass spectrometry revealed a downregulation of genes and proteins forming the cornified envelope, including filaggrins. On the contrary, abrogation of IL-20 subfamily signalling in Il20R2 -/- animals resulted in attenuated experimental EoE reflected by reduced eosinophil infiltration, lower Th2 cytokine expression and preserved expression of filaggrins in the oesophagus. Mechanistically, these observations were mediated by the mitogen-activated protein kinase (MAPK); extracellular-signal regulated kinases (ERK)1/2) pathway. Its blockade prevented epithelial barrier impairment in patient-derived air-liquid interface cultures stimulated with IL-20 cytokines and attenuated experimental EoE in mice. CONCLUSION Our findings reveal a previously unknown regulatory role of the IL-20 subfamily for oesophageal barrier function in the context of EoE. We propose that aberrant IL-20 subfamily signalling disturbs the oesophageal epithelial barrier integrity and promotes EoE development. Our study suggests that specific targeting of the IL-20 subfamily signalling pathway may present a novel strategy for the treatment of EoE

Loss of the branched-chain amino acid transporter CD98hc alters the development of colonic macrophages in mice

Comprehensive development is critical for gut macrophages being essential for the intestinal immune system. However, the underlying mechanisms of macrophage development in the colon remain elusive. To investigate the function of branched-chain amino acids in the development of gut macrophages, an inducible knock-out mouse model for the branched-chain amino acid transporter CD98hc in CX3CR1+ macrophages was generated. The relatively selective deletion of CD98hc in macrophage populations leads to attenuated severity of chemically-induced colitis that we assessed by clinical, endoscopic, and histological scoring. Single-cell RNA sequencing of colonic lamina propria macrophages revealed that conditional deletion of CD98hc alters the "monocyte waterfall"-development to MHC II+ macrophages. The change in the macrophage development after deletion of CD98hc is associated with increased apoptotic gene expression. Our results show that CD98hc deletion changes the development of colonic macrophages

Decreased expression of breast cancer resistance protein in the duodenum in patients with obstructive cholestasis

Background/Aims: The expression of transporters involved in bile acid homeostasis is differentially regulated during obstructive cholestasis. Since the drug efflux transporter breast cancer resistance protein (BCRP) is known to transport bile acids, we investigated whether duodenal BCRP expression could be altered during cholestasis. Methods: Using real-time RT-PCR analysis we determined mRNA expression levels in duodenal tissue of 19 cholestatic patients. Expression levels were compared to 14 healthy subjects. BCRP protein staining was determined in biopsies of 6 cholestatic and 6 healthy subjects by immunohistochemistry. Results: We found that in patients with obstructive cholestasis mean duodenal BCRP mRNA levels were significantly reduced to 53% and mean protein staining was reduced to 57%. Conclusions: BCRP, a transporter for bile acids and numerous drugs, appears to be down-regulated in the human duodenum during cholestasis. The clinical impact of these results has to be investigated in further studies. Copyright (c) 2006 S. Karger AG, Basel

Multidisciplinary recommendations for essential baseline functional and laboratory tests to facilitate early diagnosis and management of immune-related adverse events among cancer patients.

Immune checkpoint inhibitors (ICIs) have fundamentally changed the treatment landscape of various cancers. While ICI treatments result in improved survival, quality of life and are cost-effective, the majority of patients experience at least one immune-related adverse event (irAE). Many of these side effects cause little discomfort or are asymptomatic; however, irAEs can affect any organ and are potentially life-threatening. Consequently, early diagnosis and appropriate treatment of irAEs are critical for optimizing long-term outcomes and quality of life in affected patients. Some irAEs are diagnosed according to typical symptoms, others by abnormal findings from diagnostic tests. While there are various guidelines addressing the management of irAEs, recommendations for the early recognition of irAEs as well as the optimal extent and frequency of laboratory tests are mostly lacking. In clinical practice, blood sampling is usually performed before each ICI administration (i.e., every 2-3 weeks), often for several months, representing a burden for patients as well as health care systems. In this report, we propose essential laboratory and functional tests to improve the early detection and management of irAEs and in cancer patients treated with ICIs. These multidisciplinary expert recommendations regarding essential laboratory and functional tests can be used to identify possible irAEs at an early time point, initiate appropriate interventions to improve patient outcomes, and reduce the burden of blood sampling during ICI treatment

Budesonide orodispersible tablets for induction of remission in patients with active eosinophilic oesophagitis: A 6-week open-label trial of the EOS-2 Programme

BACKGROUND A novel budesonide orodispersible tablet (BOT) has been proven effective in adult patients with active eosinophilic oesophagitis (EoE) in a 6-week placebo-controlled trial (EOS-1). AIMS To report the efficacy of an open-label induction treatment with BOT in a large prospective cohort of EoE patients within the EOS-2 study. METHODS Patients with clinico-histological active EoE were treated with BOT 1 mg BID for 6 weeks. The primary endpoint was clinico-histological remission (≤2 points on numerical rating scales [0-10] each for dysphagia and odynophagia, and peak eosinophil count <16 eos/mm$^{2}$ hpf (corresponds to <5 eos/hpf)). Further study endpoints included clinical and histological remission rates, change in the EEsAI-PRO score, change in peak eosinophil counts, and deep endoscopic remission using a modified Endoscopic Reference Score. RESULTS Among 181 patients enrolled, 126 (69.6%) achieved clinico-histological remission (histological remission 90.1%, clinical remission 75.1%). The mean peak eosinophil counts decreased by 283 eos/mm$^{2}$ hpf (i.e., by 89.0%). Mean EEsAI-PRO score decreased from baseline by 29 points and deep endoscopic remission was achieved in 97 (53.6%) patients. The majority of patients judged tolerability as good or very good (85.6%) and compliance was high (96.5%). Local candidiasis was suspected in 8.3% of patients; all were of mild severity, resolved with treatment and none led to premature withdrawal from the study. CONCLUSIONS In this large prospective trial, a 6-week open-label treatment with BOT 1 mg BID was highly effective and safe in achieving clinico-histological remission of active EoE and confirmed the results of the placebo-controlled EOS-1 trial

Budesonide orodispersible tablets maintain remission in a randomized, placebo-controlled trial of patients with eosinophilic esophagitis

Background & Aims: Eosinophilic esophagitis (EoE) is a chronic inflammatory disorder. Swallowed topical-acting corticosteroids are effective in bringing active EoE into remission. However, it is not clear whether these drugs are effective for long-term maintenance of remission. Methods: We performed a double-blind trial to compare the efficacy and safety of 2 dosages of a budesonide orodispersible tablet (BOT) vs placebo in maintaining remission of EoE. Maintenance of remission was defined as absence of clinical and histologic relapse and no premature withdrawal for any reason. Two hundred and four adults with EoE in clinical and histologic remission, from 29 European study sites, were randomly assigned to groups given BOT 0.5 mg twice daily (n = 68), BOT 1.0 mg twice daily (n = 68), or placebo twice daily (n = 68) for up to 48 weeks. Results: At end of treatment, 73.5% of patients receiving BOT 0.5 mg twice daily and 75% receiving BOT 1.0 mg twice daily were in persistent remission compared with 4.4% of patients in the placebo group (P < .001 for both comparisons of BOT with placebo). Median time to relapse in the placebo group was 87 days. The frequency of adverse events was similar in the BOT and placebo groups. Morning serum levels of cortisol were in the normal range at baseline and did not significantly change during treatment. Four patients receiving BOT developed asymptomatic, low serum levels of cortisol. Clinically manifested candidiasis was suspected in 16.2% of patients in the BOT 0.5 mg group and in 11.8% of patients in the BOT 1.0 mg group; all infections resolved with treatment. Conclusions: In a phase 3 trial, up to 48 weeks of treatment with BOT (0.5 mg or 1.0 mg twice daily) was superior to placebo in maintaining remission of EoE. Both dosages were equally effective and well tolerated. EudraCT number; 2014-001485-99; ClinicalTrials.gov number, NCT02434029

Efficacy of Budesonide Orodispersible Tablets as Induction Therapy for Eosinophilic Esophagitis in a Randomized Placebo-Controlled Trial.

BACKGROUND & AIMS: Swallowed topical-acting corticosteroids are recommended as first-line therapy for eosinophilic esophagitis (EoE). Asthma medications not optimized for esophageal delivery are sometimes effective, although given off-label. We performed a randomized, placebo-controlled trial to assess the effectiveness and tolerability of a budesonide orodispersible tablet (BOT), which allows the drug to be delivered to the esophagus in adults with active EoE. METHODS: We performed a double-blind, parallel study of 88 adults with active EoE in Europe. Patients were randomly assigned to groups that received BOT (1 mg twice daily; n = 59) or placebo (n = 29) for 6 weeks. The primary end point was complete remission, based on clinical and histologic factors, including dysphagia and odynophagia severity ≤2 on a scale of 0-10 on each of the 7 days before the end of the double-blind phase and a peak eosinophil count <5 eosinophils/high power field. Patients who did not achieve complete remission at the end of the 6-week double-blind phase were offered 6 weeks of open-label treatment with BOT (1 mg twice daily). RESULTS: At 6 weeks, 58% of patients given BOT were in complete remission compared with no patients given placebo (P < .0001). The secondary end point of histologic remission was achieved by 93% of patients given BOT vs no patients given placebo (P < .0001). After 12 weeks, 85% of patients had achieved remission. Six-week and 12-week BOT administration were safe and well tolerated; 5% of patients who received BOT developed symptomatic, mild candida, which was easily treated with an oral antifungal agent. CONCLUSIONS: In a randomized trial of adults with active EoE, we found that budesonide oral tablets were significantly more effective than placebo in inducing clinical and histologic remission. Eudra-CT number 2014-001485-99; ClinicalTrials.gov ID NCT02434029