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`PHARMACOLOGY
`
`REVIEW ARTICLE
`published: 10 February 2012
`doi: 10.3389/fphar.2012.00008
`
`Immunological response as a source to variability in drug
`metabolism and transport
`
`Hege Christensen* and Monica Hermann
`
`Department of Pharmaceutical Biosciences, School of Pharmacy, University of Oslo, Oslo, Norway
`
`Through the last decades it has become increasingly evident that disease-states involving
`cytokines affect the pharmacokinetics of drugs through regulation of expression and activ-
`ity of drug metabolizing enzymes, and more recently also drug transporters. The clinical
`implication is however difficult to predict, since these effects are dependent on the degree
`of inflammation and may be changed when the diseases are treated. This article will give
`an overview of the present understanding of the effects of cytokines on cytochrome P450
`enzymes and drug transporters, and highlight the importance of considering these issues
`in regard to increasing use of the relatively new class of drugs, namely therapeutic proteins.
`
`Keywords: cytokines, cytochrome P450 enzymes, P-glycoprotein, therapeutic proteins
`
`Edited by:
`Jaime Kapitulnik, The Hebrew
`University of Jerusalem, Israel
`
`Reviewed by:
`Gert Fricker, University of Heidelberg,
`Germany
`Stanislav Yanev, Bulgarian Academy of
`Sciences, Bulgaria
`
`*Correspondence:
`Hege Christensen, Department of
`Pharmaceutical Biosciences, School
`of Pharmacy, University of Oslo, P.O.
`Box 1068 Blindern, N-0316 Oslo,
`Norway.
`e-mail: h.s.christensen@farmasi.
`uio.no
`
`INTRODUCTION
`
`Differences in drug response among individuals are a great chal-
`lenge in order to optimize drug dosage regimen for a patient. The
`reason for this variability is multifactorial and include genetic,
`environmental, and disease related factors, which may affect
`both pharmacodynamics and pharmacokinetics. Understanding
`the factors contributing to inter-individual variability in drug
`response is of crucial importance both in the development of
`new drugs and in optimization of the use of drugs already on
`the market.
`Factors contributing to determining the pharmacokinetic pro-
`file of a drug include drug metabolizing enzymes and drug trans-
`porting proteins. The most important drug metabolizing enzymes
`are the phase I enzymes belonging to the cytochrome P450 (CYP)
`enzyme family which metabolize many structurally different xeno-
`biotics (drug, chemicals), as well as endobiotics (steroids, fatty
`acids, prostaglandins; Gonzalez, 1990). There are several CYP sub-
`families, of which CYP1, CYP2, and CYP3 are mainly involved
`in drug metabolism, and in humans 50% of the overall elimina-
`tion of commonly used drugs is performed by these subfamilies
`(Wilkinson, 2005). Liver, the principal organ of drug elimination,
`is the organ with the highest abundance of CYP enzymes, while
`the small intestinal mucosa has been described to be the most
`important extra hepatic site of biotransformation (Lin and Lu,
`2001). Inter-individual variability in the expression and activity of
`CYP enzymes is recognized as significant contributor to variation
`in drug response. CYP3A4 is the most prominent CYP enzyme,
`mainly because it is highly expressed in organs involved in drug
`disposition, such as liver, gastrointestinal tract, and kidney (Shi-
`mada et al., 1994; Paine et al., 2006) and because of the broad
`substrate specificity. The expression of this isoenzyme displays
`a 30- to 60-fold variability in human liver and intestine biop-
`sies (Thummel et al., 1994; Paine et al., 1997). The reason for
`inter-individual variability in the expression and activity of CYP
`
`enzymes is multifactorial, but may to some degree be explained by
`genetic, environmental, and disease related factors.
`The most studied drug transporter is the transmembrane efflux
`transporter P-glycoprotein (P-gp), a human ABC-transporter
`encoded by the ABCB1 gene (Higgins, 1992). P-gp was discov-
`ered in 1976 (Juliano and Ling, 1976) as an important multi-drug
`resistance (MDR) mechanism in cancer treatment. It is expressed
`and distributed in the luminal surface membrane of the ente-
`rocytes in the small intestine, renal proximal tubular cells, the
`bile canalicular membrane of hepatocytes, the capillary endothe-
`lial cells in the blood–brain barrier (BBB) and in different cell
`types involved in the immune response (Thiebaut et al., 1987;
`Sugawara et al., 1988; Cordon-Cardo et al., 1989; Klimecki et al.,
`1994). Based on its localization, the function of P-gp is sus-
`pected to be protection of the cells against various toxicants,
`among these therapeutically active drugs. As P-gp is abundant
`in the intestinal epithelium, one important function is to restrict
`oral bioavailability of drugs, and since the substrate specificity
`of P-gp is to a great deal overlapping with that of CYP3A4, the
`general view is that P-gp and CYP3A4 work together in restrict-
`ing the intestinal bioavailability of drugs (Benet and Cummins,
`2001).
`Through the last decade, there has been an increasing awareness
`on drug transporters other than P-gp and their role in bioavail-
`ability, elimination, and tissue distribution of drugs. These include
`other ABC transporters such as multidrug-resistance associated
`proteins (MRPs), the SLC transporters [e.g., organic anion trans-
`porting polypeptides (OATPs), organic anion transporters (OATs),
`and organic cation transporters (OCTs)]. Similar to drug metab-
`olizing enzymes, there is also a considerable variability in the
`expression and activity of drug transporters. This variability is only
`to a minor extent explained by genetic polymorphism and other
`causes, such as environmental influence (e.g., drug interactions)
`and disease-state also play a role.
`
`www.frontiersin.org
`
`February 2012 | Volume 3 | Article 8 | 1
`
`

`

`Christensen and Hermann
`
`Cytokines influence drug metabolism and transport
`
`Immunological response and the release of cytokines is part of
`the pathophysiology of various diseases like autoimmune diseases,
`infections, brain injuries, and cancer. It has been known for sev-
`eral decades that cytokines regulate the expression and activity
`of drug metabolizing enzymes and thus, may affect the phar-
`macokinetics of drugs. More recently it has become evident that
`this applies to drug transporters as well. This article will give an
`overview of the present understanding of the effects of cytokines
`on CYP enzymes and transporters involved in drug pharmaco-
`kinetics, and also point out the importance of considering these
`issues in regard to the increasing use of the relatively new class
`of drugs, namely therapeutic proteins and their involvement in
`drug–drug interactions.
`
`IMMUNOLOGICAL RESPONSE AND CYP METABOLISM
`
`Several clinical studies have reported alterations in drug pharma-
`cokinetics in patients with inflammations, infectious diseases, and
`cancer as well as in critically ill patients (Aitken et al., 2006; Morgan
`et al., 2008; Morgan, 2009). Already in 1978 acute virus infec-
`tions in asthmatic children were shown to significantly increase
`the terminal half-life of theophylline (Chang et al., 1978). Also
`during an influenza B out break asthmatic children developed
`a sudden decrease in theophylline clearance and were hospital-
`ized with toxicity problems (Kraemer et al., 1982). Already in
`1976 it was shown that agents causing inflammation and infection
`depressed hepatic CYP enzymes in rats (Renton and Mannering,
`1976a,b) and thus, the decreased theophylline clearance could be
`explained by a down-regulation of the CYP enzyme responsible
`for the metabolism of theophylline (CYP1A2). Several viruses,
`e.g., Herpes simplex, adenovirus, and HIV, have since then been
`identified to depress CYP metabolism and reduce drug clearance
`(Anolik et al., 1982; Forsyth et al., 1982; Lee et al., 1993). Also
`acute hepatitis virus A infection has been shown to decrease the
`excretion of 7-hydroxycoumarin in children and adults, indicating
`a depressed CYP2A6 activity during virus infection (Pasanen et al.,
`1997). CYP2D6 and CYP3A4 activities have been reported to be
`significantly lower in patients with chronic hepatitis C compared
`to in healthy volunteers (Becquemont et al., 2002). Interestingly,
`HIV patients genotyped as CYP2D6 extensive metabolizers (EM)
`expressed a shift toward a poor metabolizer (PM) CYP2D6 phe-
`notype which correlated with disease activity (O’Neil et al., 2000).
`Also bacterial infections cause impaired drug clearance in humans.
`Administration of low doses of bacterial lipopolysaccharide (LPS)
`to healthy volunteers has been reported to cause reduced clearance
`of theophylline, antipyrine, and hexobarbitone (Shedlofsky et al.,
`1994, 1997). In rats CYP-mediated drug metabolism is suppressed
`during polymicrobial sepsis, particularly in the late phase (Lee and
`Lee, 2005).
`Several studies have reported decreased theophylline and
`aminopyrine clearance following influenza virus and bacillus
`Calmette–Guerin (BCG) vaccination in healthy volunteers (Ren-
`ton et al., 1980; Kramer and McClain, 1981; Gray et al., 1983). The
`effect was shown to be largest in individuals with high theophylline
`clearance before vaccination (Meredith et al., 1985), probably
`those with high CYP1A2 activity. On the other hand, influenza
`immunization did not significantly change CYP3A4 or CYP2E1
`activities, as measured by the erythromycin breath test (ERMBT)
`
`and chlorzoxazone clearance (Kim and Wilkinson, 1996; Hayney
`et al., 2001). However, an inverse correlation between interferon-γ
`(IFN-γ) production and changes in ERMBT has been reported
`after administration of influenza vaccine to healthy volunteers
`(Hayney and Muller, 2003). In this respect it is interesting to note
`that in vitro studies with hepatocytes cultured with IFN-γ showed
`a decreased CYP3A4 expression and activity (Donato et al., 1997).
`The observed discrepancies in effect of vaccines might be due
`to different purity of vaccines, variable vaccination protocols or
`differences in response on the various CYP enzymes.
`Additionally altered pharmacokinetics is observed in patients
`with inflammatory diseases and cancer. The largest effect of
`inflammatory disease on the pharmacokinetics of drugs has been
`reported for patients with rheumatoid arthritis, which showed a
`three and fourfold higher systemic exposure of verapamil and sim-
`vastatin compared to healthy volunteers (Mayo et al., 2000; Zhang
`et al., 2009). Also in patients with advanced cancer, all genotyped
`as EM of CYP2C19, a reduction in omeprazole metabolism was
`observed, and all patients had a slower metabolic CYP2C19 phe-
`notype compared to healthy volunteers (Williams et al., 2000).
`Similarly decreased CYP3A4-dependent CsA metabolism has been
`reported in bone marrow transplanted patients, and interestingly
`an association between high interleukin 6 (IL-6) plasma concen-
`trations and increased CsA concentrations were found (Chen et al.,
`1994). Later, Frye et al. (2002) studied the relationship between
`plasma concentrations of IL-6 and tumor necrosis factor alpha
`(TNF-α) and CYP enzyme activities in patients with congestive
`heart failure. IL-6 and TNF-α concentrations were negatively cor-
`related to the activities of CYP1A2 and CYP2C19, investigated by
`use of caffeine and mephenytoin as probe substrates. There was
`no significant relationship between the cytokine level and CYP2D6
`and CYP2E1 activities in these patients (Frye et al., 2002). In this
`respect it is interesting to note that increased adverse events and
`discontinuing treatment of the CYP2C19 substrate imipramine
`has been reported in heart failure patients (Glassman et al., 1983).
`To summarize, depression of metabolic capacity through CYP
`enzymes seems to be a common feature of a variety of diseases
`involving an immune response with the release of cytokines.
`The different CYP enzymes are to a variable degree affected, and
`increases in drug exposure from less than 50 to up to 400% have
`been observed. The potential effects of cytokines on the phar-
`macokinetics of a large number of drugs accounts for increased
`awareness in treating patients with diseases involving an immune
`response. Also, there are indications of differential effects, with
`larger effects on patients with initially high clearance through the
`enzyme in question. Thus, depression of CYP activity is a consid-
`erable factor contributing to inter-individual variability in drug
`exposure.
`
`IMMUNOLOGICAL RESPONSE AND DRUG TRANSPORT
`
`Similar to the drug metabolizing enzymes, a variety of diseases
`have also been shown to influence on the expression of drug trans-
`porters. P-gp is in this area by far the most extensively studied drug
`transporter. For example, several studies have shown intestinal P-
`gp to be inversely correlated with inflammatory disease activity.
`In a study by Ufer et al. (2009), P-pg mRNA and protein expres-
`sion were decreased in patients with ulcerative colitis compared
`
`Frontiers in Pharmacology | Drug Metabolism and Transport
`
`February 2012 | Volume 3 | Article 8 | 2
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`

`

`Christensen and Hermann
`
`Cytokines influence drug metabolism and transport
`
`to healthy volunteers and P-gp mRNA was inversely correlated
`with disease activity. Also, while expression of breast cancer resis-
`tance protein (BCRP) and P-gp in inflamed mucosa is reduced in
`patients with ulcerative colitis, expression of these transporters is
`comparable in unaffected mucosa from ulcerative colitis patients
`and healthy volunteers (Gutmann et al., 2008). Accordingly, a
`post mortem study of seropositive HIV patients showed that P-gp
`in brain microvascular endothelial cells was decreased compared
`to HIV-negative controls (Langford et al., 2004). However, this
`picture is more complicated as different parts of the brain were dif-
`ferently affected; i.e., in contrast to the aforementioned decrease of
`P-gp in endothelial cells, P-gp immunoreactivity was increased in
`astroglial cells in AIDS patients with HIV encephalitis compared
`to HIV encephalitis-negative patients and seronegative controls
`(Langford et al., 2004).
`Many in vitro studies have examined the effect of inflammatory
`mediators on expression and activity of P-gp in the brain (Bauer
`et al., 2005; Miller et al., 2008; Roberts and Goralski, 2008). Several
`studies show a difference in effect after short-term versus long-
`term exposure to inflammatory mediators; whereas P-gp activity
`is initially depressed, long-term exposure to inflammatory media-
`tors seems to upregulate P-gp expression and activity (Hartz et al.,
`2006; Bauer et al., 2007). Not surprisingly, the magnitude and
`direction of changes in drug transport activity is dependent on
`both the specific cytokine and model examined (as reviewed by
`Roberts and Goralski, 2008). This is exemplified by the diverg-
`ing results of two separate rat models. Seelbach et al. (2007)
`reported that P-gp expression in brain microvessels increased 3 h
`after induction of inflammatory pain. These results were accompa-
`nied by in situ brain perfusion studies and antinociceptive studies
`that showed decreased brain uptake and decreased analgesia of
`morphine, a P-gp substrate (Seelbach et al., 2007). In contrast,
`Goralski et al. (2003) showed that LPS-induced CNS inflammation
`decreased P-gp expression and activity. In this study radioactive
`labeled digoxin was increased both in the brain and liver following
`intracranial ventricle administration of LPS in male rats (Goralski
`et al., 2003). Accordingly, P-gp mRNA in the brain and mRNA
`of both P-gp and OATP1B1 in liver were reduced. The diverging
`results of in vitro and animal models call for more in vivo studies
`to explore the effect of inflammatory disease on drug transport
`in patients. So far, altered pharmacokinetics of drugs relative to
`disease activity has been observed by Roberts et al. (2009). This
`group showed that patients with acute inflammatory brain injury
`obtained increased levels of the morphine metabolites morphine-
`3-glucuoronide and morphine-6-glucuronide with increasing IL-
`6, while no linkage between the P-gp substrate morphine and CSF
`IL-6 was observed. These data suggests an inhibition or down-
`regulation of drug efflux transporters specific to these metabolites
`other than P-gp in the BBB, possibly OATPs, as postulated by the
`authors (Roberts et al., 2009). Taken together, data on the effect
`of inflammatory mediators/disease on drug exposure in the brain
`are not conclusive and more in vivo studies are needed to explore
`this issue.
`There is increasing evidence for differential ability of cytokines
`to influence on the regulation of expression and activity of drug
`transporters in immune cells compared to other tissue (Liptrott
`and Owen, 2011). While most studies suggest a depression or
`
`down-regulation of P-gp upon an inflammatory response, a recent
`study showed that P-gp expression on lymphocytes in patients with
`systemic lupus erythematosus (SLE) correlated positively with dis-
`ease activity (Tsujimura and Tanaka, 2011). Up-regulation of P-gp
`in peripheral blood mononuclear cells has previously been shown
`for a variety of diseases, by far most studied in malignant dis-
`eases, where it causes the problem of MDR (Kantharidis et al.,
`2000; Shtil, 2002), but also in rheumatoid arthritis (Suzuki et al.,
`2010), HIV (Langford et al., 2004), and in solid organ transplan-
`tation (Donnenberg et al., 2001). This observation is supported
`by in vitro studies where P-gp in lymphocytes is induced by var-
`ious stimuli such as IL-2 (Tsujimura et al., 2004; Liptrott et al.,
`2009). Up-regulation of P-gp and other drug transporters result-
`ing is a problem in the use of drugs which are P-gp substrates
`and have their site of action within the immune cells, where an
`up-regulation of P-gp leads to reduced levels of drugs at their
`site of action. This applies to drugs such as antiviral agents used
`in HIV, immunosuppressants used in autoimmune diseases and
`solid organ transplantation, among others.
`In vitro studies in human hepatocytes also suggest a role for
`proinflammatory cytokines in the regulation of a wide range of
`drug transporters other than P-gp, such as OATPs, MRPs, OATs,
`and OCTs (Le Vee et al., 2008, 2011; Vee et al., 2009). However,
`in vivo data is lacking, and more studies are needed to explore the
`role of immune response in the regulation of drug transporters
`and its effect on the pharmacokinetics of drugs.
`
`MECHANISMS OF CYP AND TRANSPORTER REGULATION BY
`
`CYTOKINES
`
`In response to infections and inflammatory diseases, cytokines like
`interferons (IFNs), interleukins (IL-1 and IL-6), and TNFα are
`produced and released from monocytes, macrophages, and stro-
`mal cells. The mechanisms by which they affect drug metabolism
`and transport is not fully understood, but in brief cytokines bind to
`receptors on the cell surface in target organs and activate intracel-
`lular signal systems regulating gene transcription of enzymes and
`transporters. Such receptors include Toll-like receptors (TLRs),
`which are presented on the surface of Kupffer cells in the liver
`and are involved in mediating inflammatory response. In patients
`with sepsis, TLR2 and TLR4 expression has been found to be sig-
`nificantly up-regulated in several organs (Cinel and Opal, 2009).
`It has been shown that CYP enzyme expression was regulated by
`a TLR4-dependent mechanism in a LPS-induced inflammation
`model (Ghose et al., 2008). Several animal studies have shown that
`individual CYP enzymes and transporters are down-regulated by
`cytokines at the level of gene transcription with decreases in mRNA
`and protein expression (Renton, 2004, 2005; Aitken et al., 2006;
`Morgan et al., 2008; Roberts and Goralski, 2008; Miller, 2010). The
`major mechanistic explanation involve the transcription factors
`pregnane X receptor (PXR) and constitutive androstane receptor
`(CAR), which both are involved in the expression of genes asso-
`ciated with drug metabolism and transport (Chang and Waxman,
`2006).
`For CYP3A4 and P-gp transcriptional activation is mediated by
`PXR and NF-κB (Bentires-Alj et al., 2003; Gu et al., 2006; Kojima
`et al., 2007). Moreover cytokines have been shown to induce
`the production of NF-κB, which directly disrupt binding of the
`
`www.frontiersin.org
`
`February 2012 | Volume 3 | Article 8 | 3
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`

`

`Christensen and Hermann
`
`Cytokines influence drug metabolism and transport
`
`PXR–retinoid X receptor (RXR) complex to its response element,
`leading to suppression of CYP3A4 expression (Gu et al., 2006).
`Recently suppression of CYP3A4 by IL-6 was shown to occur after
`the decrease of PXR in human hepatocytes (Yang et al., 2010).
`Several additional transcription factors may be responsible for
`regulation of P-gp expression. Heat-shock transcription factor 1
`(HSF-1) and stimulatory protein 1 (SP-1) both have binding sites
`within the ABCB1 promoter (Rohlff and Glazer, 1998; Vilaboa
`et al., 2000), and in tumor cells P-gp expression is regulated by
`Y-box protein (YB-1; Ohga et al., 1998).
`Studies in human hepatocytes indicate that the effect of vari-
`ous cytokines is gene-specific. While IL-1 down-regulated CYP2C8
`and CYP3A4 mRNA expression by 75 and 95%, respectively, there
`was no effect on CYP2C9 or CYP2C19 (Aitken and Morgan, 2007).
`IL-6, on the other hand, caused a decrease in CYP2C8, CYP2C9,
`CYP2C19, and CYP3A4 mRNA expression. Recently IL-6 was also
`shown to suppress the activities of CYP3A4 and CYP1A2 in human
`primary hepatocytes, while anti-IL-6 monoclonal antibody par-
`tially blocked this suppression (Dickmann et al., 2011). The effects
`of various cytokines on individual CYP isoenzyme expression and
`activity investigated in vitro are summarized in Table 1. With
`respect to P-gp, in vitro studies in human hepatoma cells and
`human colon carcinoma (Caco-2) cells as well as in vivo studies
`in mice have shown that IL-6 and IL-2 down-regulate its expres-
`sion (Piquette-Miller et al., 1998; Hartmann et al., 2001; Belliard
`et al., 2002; Hosten et al., 2008). On the other hand induction of
`P-gp by TNF-α or IL-2 has been shown in mice (Hartmann et al.,
`2001), human lymphocytes (Liptrott et al., 2009), and rat brain
`capillaries (Bauer et al., 2007). Thus, for P-gp there seems to be
`organ- and cytokine-specific effects. The response of cytokines on
`CYP protein expression correlated generally well with the effect on
`mRNA expression (Aitken and Morgan, 2007), while P-gp expres-
`sion was strongly decreased with no change in mRNA expression
`in patients with inflammatory gastrointestinal disorders (Blokzijl
`et al., 2007).
`
`DRUG INTERACTION WITH THERAPEUTIC PROTEINS
`
`Therapeutic proteins are a group of drugs currently extensively
`used in the treatment of autoimmune diseases (e.g., rheumatoid
`
`arthritis), cancer, and HIV. These drugs include monoclonal
`antibodies, interferons, and other cytokines among others. Ther-
`apeutic proteins are macromolecules, and compared to small-
`molecule drugs there is still
`limited knowledge about their
`pharmacokinetics. For small-molecule drugs problems related to
`metabolism-based drug–drug interactions have gained extensive
`attention as a major cause of adverse drug reactions and toxi-
`city problems in general. There are however major differences
`regarding clearance mechanisms for small-molecule drugs and
`therapeutic proteins. Proteins are mainly cleared by renal filtration
`or receptor-mediated clearance, and since they are not metabolized
`by CYP enzymes, drug–drug interactions involving CYP enzymes
`have been considered not to be relevant for therapeutic proteins.
`However, it has recently been clear that these drugs, due to altering
`the immunological state in patients, can affect the pharmacokinet-
`ics of a variety of other drugs by interferences with CYP-mediated
`metabolism and drug transport (Table 2).
`
`INTERFERONS AND INTERACTIONS WITH CYP METABOLISM
`
`Interferons (IFNs), produced by the immune system in response
`to infections and inflammations, have antiviral, antiproliferative,
`and immunoregulatory effects. INF therapy is extensively used in
`the treatment of chronic hepatitis C, multiple sclerosis and can-
`cer. In addition to the effect of endogenous cytokines on drug
`metabolism, therapeutic use of cytokines may therefore addition-
`ally contribute to the decreased metabolic ability. Williams et al.
`(1987) reported already in 1987 that 1 day after a single intramus-
`cular injection of IFN-α in five patients with chronic hepatitis B
`and four healthy volunteers, clearance of the CYP1A2 substrate
`theophylline was significantly reduced (30–80%). A 26% reduc-
`tion in clearance of theophylline was also observed in patients with
`hepatitis C after IFN-β treatment, with a corresponding increase in
`terminal half-life of about 40% (Okuno et al., 1993). Additionally
`IFN-α administration in patients with hepatitis B has been shown
`to cause a minor decrease of erythromycin metabolism (15%), as
`determined by ERMBT (Craig et al., 1993), and patients moni-
`tored on warfarin needed a dose reduction when IFN-α-2b and
`IFN-β were given (Adachi et al., 1995).
`
`Table 1 | Effects of various cytokines on individual drug metabolizing CYP enzyme expression (mRNA or protein) and activity in vitro (no
`
`available data for CYP2D6).
`
`Cytokines
`
`CYP enzymes
`
`CYP1A2
`
`CYP2B6
`
`CYP2C8
`
`CYP2C9
`
`CYP2C19
`
`CYP2E1
`
`CYP3A4
`
`IFN-γ
`
`TGF-β1
`
`TNF-α
`
`IL-1β
`
`IL-2
`
`IL-4
`
`IL-6
`
`IL-10
`
`⇓
`
`⇓
`
`⇓
`
`⇓
`
`⇓
`
`⇓
`
`⇓
`
`⇑⇓
`
`⇑⇓
`
`⇓
`
`⇓
`
`⇑
`
`⇓
`
`⇔
`
`⇓
`
`⇓
`
`⇓
`
`⇓
`
`⇓
`
`⇓⇔
`
`⇓
`
`⇓⇔
`
`⇓⇔
`
`⇔
`
`⇓
`
`⇓⇔
`
`⇔
`
`⇓
`
`⇓
`
`⇓
`
`⇓
`
`⇑
`
`⇓
`
`⇓⇔
`
`⇓
`
`⇓
`
`⇓
`
`⇓
`
`⇑⇔
`
`⇓
`
`⇑
`
`Two arrows indicate that studies show diverging results (Abdel-Razzak et al., 1993, 1994; Donato et al., 1997; Sunman et al., 2004; Aitken and Morgan, 2007; Liptrott
`
`et al., 2009).
`
`Frontiers in Pharmacology | Drug Metabolism and Transport
`
`February 2012 | Volume 3 | Article 8 | 4
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`

`

`Christensen and Hermann
`
`Cytokines influence drug metabolism and transport
`
`Table 2 | Examples of drug interactions caused by therapeutic proteins.
`
`Therapeutic protein
`
`Affected drug
`
`Effect
`
`Reference
`
`INTERFERONS
`
`INF-α
`
`INF-β
`
`INF-α
`
`INF-α-2b, INF-β
`
`INF-α
`
`IFN-α-2b
`
`IFN-α-2b
`
`INTERLEUKINS
`
`IL-2
`
`Theophylline
`
`Theophylline
`
`Erythromycin
`
`Warfarin
`
`Cyclophosphamide
`
`Caffeine
`
`Mephenytoin
`
`30–80% reduced clearance
`
`26% reduced clearance
`
`15% decreased CYP3A4 activity
`
`Increased concentration
`
`60% reduced clearance
`140% increased t 1/2
`60% decreased CYP1A2 activity
`
`40% decreased CYP2C19 activity
`
`Williams et al. (1987)
`
`Okuno et al. (1993)
`
`Craig et al. (1993)
`
`Adachi et al. (1995)
`
`Hassan et al. (1999)
`
`Islam et al. (2002)
`
`Islam et al. (2002)
`
`Erythromycin
`
`50% decreased CYP3A4 activity
`
`Elkahwaji et al. (1999)
`
`MONOCLONAL ANTIBODIES
`
`Muromonab-CD3
`
`Basiliximab
`
`Basiliximab
`
`Tocilizumab
`
`Tocilizumab
`
`Tocilizumab
`
`Cyclosporine
`
`Cyclosporine
`
`Tacrolimus
`
`Omeprazole
`
`Simvastatin
`
`Simvastatin
`
`Increased concentration
`
`Increased concentration
`
`60% increased concentration
`
`30% decreased AUC
`
`60% decreased AUC
`
`40–60% decreased AUC
`
`Vasquez and Pollak (1997)
`
`Strehlau et al. (2000)
`
`Sifontis et al. (2002)
`
`Zhang et al. (2009)
`
`Zhang et al. (2009)
`
`Schmitt et al. (2011)
`
`In cancer patients with multiple myeloma, administration of
`IFN-α before treatment with cyclophosphamide caused about
`60% decreased clearance and 140% increased peak concentra-
`tion and half-life, accompanied by a decreased concentration of
`the CYP3A4 metabolite 4-hydroxycyclophosphamide, compared
`to when IFN-α was administered after cyclophosphamide (Hassan
`et al., 1999). Also a study in 17 patients with melanoma showed
`that the activities of CYP1A2 and CYP2C19, measured by the
`probe drugs caffeine and mephenytoin, were 60 and 40% reduced,
`respectively, after treatment with high-dose IFN-α-2b (Islam et al.,
`2002).
`On the other hand when administered in lower doses to hepati-
`tis C patients, IFN has been shown to induce a small, statistically
`non-significant increase in activity of CYP3A4 and CYP2D6 after
`1 month of exposure, when administered in combination with rib-
`avirin as antiviral therapy (Becquemont et al., 2002). It is however
`important to note that these patients had significantly lower pre-
`treatment CYP3A4 and CYP2D6 activities than healthy volunteers.
`Recently also Gupta et al. (2011) demonstrated that weekly admin-
`istration of IFN-α-2b to patients with chronic hepatitis C was
`associated with small increase in CYP2C8/9 and CYP2D6 activities
`in some individuals, while there was no effect on CYP3A4 activity
`and a limited inhibitory effect on CYP1A2. IFN-β treatment in
`patients with multiple sclerosis revealed unaltered CYP2D6 and
`CYP2C19 activities (Hellman et al., 2003). Several studies have
`been performed with administration of IFN-α-2b and IFN-α-2a
`and possible interaction with methadone, which is predominantly
`metabolized by CYP3A4. A minor increase in methadone exposure
`in hepatitis C patients after multiple doses of peginterferon-α-2b
`or peginterferon-α-2a have been reported, but the authors con-
`clude that this may not be of any clinical relevance (Sulkowski
`et al., 2005; Gupta et al., 2007). However several reports indicate
`that IFN could cause a clinically relevant interaction when admin-
`istered with drugs that are CYP substrates, but there might be
`
`different effect on the individual CYPs. At least IFN given in high
`doses for the treatment of cancer seems to decrease the activity of
`CYP3A4, CYP1A2, and CYP2C19, and it is important to be aware
`of possible interactions with drugs metabolized through these
`enzymes. However, a decreased CYP activity due to the disease-
`state in chronic hepatitis patients may be restored by antiviral
`therapy involving IFN.
`
`INTERLEUKIN AND INTERACTIONS WITH CYP METABOLISM
`
`Interleukins (ILs) are cytokines mainly synthesized by T lym-
`phocytes, as well as monocytes, macrophages, and endothelial
`cells. They promote the development and differentiation of T,
`B, and hematopoietic cells. Therapeutic administration of IL-2
`has shown several immunological effects, including activation of
`cellular immunity and production of cytokines (Winkelhake and
`Gauny, 1990). Recombinant IL-2 is used to treat advanced cancers
`(Vlasveld et al., 1992), but there is not much clinical data on the
`effect of IL-2 on CYP metabolism. However, high-dose admin-
`istration of IL-2 to patients with liver cancer has been shown to
`decrease expression of CYP1A2, CYP2C, CYP2E1, and CYP3A4 by
`approximately 40–60%, and also the CYP1A2 and CYP3A4 activi-
`ties were 62 and 50% reduced, respectively (Elkahwaji et al., 1999).
`Thus administration of IL-2 to cancer patients has been proposed
`to cause clinically important drug interactions (Lee et al., 2010).
`
`MONOCLONAL ANTIBODIES AND INTERACTIONS WITH CYP
`
`METABOLISM
`
`Human monoclonal antibodies are widely used for treatment of
`several diseases, e.g., autoimmune diseases (rheumatoid arthritis),
`cancer, and rejection episodes following transplantation. Since
`it is now recognized that cytokines induce alterations in CYP
`metabolism of drugs, it is also evident that cytokine modulators
`may have an effect on CYP-mediated drug metabolism. How-
`ever, the prediction of this effect is not straightforward. Use of
`
`www.frontiersin.org
`
`February 2012 | Volume 3 | Article 8 | 5
`
`

`

`Christensen and Hermann
`
`Cytokines influence drug metabolism and transport
`
`the monoclonal antibody muromonab-CD3 (OKT3), as antilym-
`phocyte induction therapy, has been shown to cause a significant
`increase in cyclosporine A (CsA) trough levels in adult renal
`transplant recipients (Vasquez and Pollak, 1997). The mecha-
`nism behind this elevated CsA levels is not known, but it has
`been hypothesized to be mediated by down-regulation of CYP
`enzymes by cytokines, because OKT3 administration has been
`reported to cause cytokine release (especially TNF-α and IFN-γ;
`Chatenoud et al., 1989). Similarly treatment with the immuno-
`suppressive agent basiliximab, a monoclonal antibody against the
`IL-2 receptor, in 24 renal transplanted children gave a substantial
`increase in the whole-blood CsA concentration compared to 15
`recipients who received placebo (Strehlau et al., 2000). Also a 63%
`higher tacrolimus concentration was reported in 12 adult renal
`transplant recipients 2 days after basiliximab induction therapy
`compared to eight patients who received antithymocyte globulin
`therapy (Sifontis et al., 2002). The mechanism for this interaction
`between basiliximab and CsA or tacrolimus is unclear, but the
`authors have suggested that the interaction may be mediated via
`cytokine-induced alterations in CYP3A4 metabolism, when basil-
`iximab binds to the IL-2 receptor on activated T-cells, circulating
`IL-2 may have an effect on intestinal epithelial cells and hepato-
`cytes and decrease the expression of CYP3A4 (Elkahwaji et al.,
`1999; Strehlau et al., 2000; Sifontis et al., 2002). Additionally, both
`tacrolimus and CsA are substrates of P-gp. As P-gp expression is
`also regulated by cytokines, the observed effect could be caused by
`a combined effect on CYP3A4 and