Journal of Toxicology and Environmental Health, Part A, 78:671–684, 2015 Copyright © Taylor & Francis Group, LLC ISSN: 1528-7394 print / 1087-2620 online DOI: 10.1080/15287394.2015.1020977
IN VIVO EFFECTS OF NAPROXEN, SALICYLIC ACID, AND VALPROIC ACID ON THE PHARMACOKINETICS OF TRICHLOROETHYLENE AND METABOLITES IN RATS Mouna Cheikh Rouhou1, Ginette Charest-Tardif2, Sami Haddad2 1
Sciences Biologiques, Université du Québec à Montréal, Montréal, Quebec, Canada Environmental and Occupational Health, IRSPUM, Université de Montréal, Montréal, Quebec, Canada 2
It was recently demonstrated that some drugs modulate in vitro metabolism of trichloroethylene (TCE) in humans and rats. The objective was to assess in vivo interactions between TCE and three drugs: naproxen (NA), valproic acid (VA), and salicylic acid (SA). Animals were exposed to TCE by inhalation (50 ppm for 6 h) and administered a bolus dose of drug by gavage, equivalent to 10-fold greater than the recommended daily dose. Samples of blood, urine, and collected tissues were analyzed by headspace gas chromatography coupled to an electron capture detector for TCE and metabolites (trichloroethanol [TCOH] and trichloroacetate [TCA]) levels. Coexposure to NA and TCE significantly increased (up to 50%) total and free TCOH (TCOHtotal and TCOHfree, respectively) in blood. This modulation may be explained by an inhibition of glucuronidation. VA significantly elevated TCE levels in blood (up to 50%) with a marked effect on TCOHtotal excretion in urine but not in blood. In contrast, SA produced an increase in TCOHtotal levels in blood at 30, 60, and 90 min and urine after coexposure. Data confirm in vitro observations that NA, VA, and SA affect in vivo TCE kinetics. Future efforts need to be directed to evaluate whether populations chronically medicated with the considered drugs display greater health risks related to TCE exposure.
than 30 ppb (Agency for Toxic Substances and Disease Registry [ATSDR], 2013). Despite increasing evidence of the possible health risk of this chemical at relevant concentrations (Clewell et al., 2000), humans are still frequently exposed to TCE. Besides this possible simple exposure to TCE, coexposure situations to this chemical in combination with other substances do occur. The ever-increasing consumption of drugs reinforces concerns regarding a possible modulating effect resulting from TCE coexposures with potentially interacting medications. Pharmaceuticals, which are biologically active, may influence metabolism of TCE in liver and consequently affect its pharmacokinetics and/or its pharmacodynamics and therefore its toxicity in target tissue.
Various industries use trichloroethylene (TCE), a volatile chlorinated hydrocarbon solvent, in a large spectrum of applications (Wu and Berger, 2007; U.S. Environmental Protection Agency [EPA], 1985). Workers may be exposed by inhalation to high levels of TCE, ranging from approximately 1 to 100 ppm, while the general population might be exposed by inhalation of contaminated ambient air and/or ingestion of polluted drinking water. Across the United States, TCE concentrations in ambient air ranging from 0.01 to 0.3 ppb have been measured. Although concentrations as high as 3.4 ppb were reported, between 4.5 and 18% of the drinking-water supply sources in the United States, which are tested on a yearly basis by the U.S. EPA, have measurable levels of TCE: typically lower
Received 16 October 2014; accepted 16 February 2015. Address correspondence to Prof. Sami Haddad, Environmental and Occupational Health, IRSPUM, Université de Montréal, PO Box 6128, Main Station, Roger-Gaudry Building, Montréal, Quebec, HC3 3J7, Canada. E-mail: [email protected] 671
672
Toxicokinetic interactions with TCE have been reported for a few drugs, specifically aspirin and acetaminophen (Plewka et al., 2000; Zieliñska-Psuja et al., 2001). However, no other apparent toxicokinetic interactions data have been found for other drugs in the literature. Recently Cheikh Rouhou et al. (2012) showed that some pharmaceuticals, among a tested selection of 14 widely consumed drugs, modulate in vitro metabolism of TCE in rat hepatocytes and rat liver microsomes. Cheikh Rouhou and Haddad (2013) also reported that such in vitro interactions occurred in human hepatocytes and human liver microsomes. In humans and rats, in vitro naproxen (NA) competitively inhibited trichloroethanol (TCOH) glucuronidation with Ki = 2.329 mM and Ki = 211.6 μM, respectively. In the case of salicylic acid (SA), the observed interactions in hepatocytes were not detected in microsomes, both in humans and in rats. Finally, for valproic acid (VA) the observed interactions were not found in human microsomes and were characterized as partial noncompetitive inhibition in rat for both TCA and TCOH formation with Ki = 1215.8 μM and Ki = 932.8 μM, respectively. Similarities between human and rat responses, either for absence or for observed interactions, were noted. Based upon these human and rat in vitro investigations, three drugs that were found to interfere with TCE metabolism, naproxen (NA), salicylic acid (SA), and valproic acid (VA), were selected for the present study TCE is metabolized in the liver, mainly by oxidation. In this pathway, TCE is first biotransformed into chloral hydrate (CHO), predominantly by the action of CYP2E1 (Lipscomb et al., 1997; Nakajima et al., 1992; Lash et al., 2006) and secondarily by isoforms CYP1A1/2, CYP2B1/2, and CYP2C11/6 (Lash et al., 2000a, 2006; Chiu et al., 2007). Chloral hydrate is then transformed either by oxidation to trichloroacetic acid (TCA) by aldehyde oxidase, or by reduction to trichloroethanol (TCOH), mainly by CYP2E1 (Ni et al., 1996) and secondarily by alcohol dehydrogenase (Larson and Bull, 1989; Müller et al., 1975;
M. CHEIKH ROUHOU ET AL.
Yoo et al., 2015). Glutathione (GSH) conjugation is the other route of biotransformation. This pathway is secondary, taking place also in the liver (Lash et al., 2000b). In the first step, a GSH conjugate that is the S-(1,2dichlorovinyl) glutathione (DCVG) is formed with catalytic action of glutathione S-transferase (GST). The DCVG is then metabolized by γglutamyltransferase (GGTP) to free glutamic acid and cysteine conjugate form (Dekant et al., 1990; Lash et al., 2000a; Chiu et al., 2007; Yoo et al., 2015). Naproxen (NA) is a propionic acid derivative related to the arylacetic acid group of nonsteroidal anti-inflammatory drugs (NSAIDs). This pharmaceutical possesses analgesic and antipyretic properties, and is rapidly and completely absorbed from the gastrointestinal tract (GIT) with an in vivo bioavailability of 95%. The range of elimination half-life of NA is 12 to 17 h (Niazi et al., 1996). This drug is extensively metabolized in the liver to 6O-desmethyl NA by CYP2C9, CYP 2C8, and CYP 1A2 (DrugBank, 2015). Both parent compound and metabolites do not induce metabolizing enzymes. Naproxen and 6-O-desmethyl NA are further biotransformed to their respective acyl glucuronide conjugated metabolites (Toothaker et al., 2000). Naproxen and its metabolites are excreted primarily in urine. About 10% of the absorbed dose is eliminated unchanged, 40% as glucuronide conjugates, 5% as desmethyl naproxen, 12% as glucuronide of desmethyl NA, and approximately 30% as unknown conjugates of NA and desmethyl NA (Sevelius et al., 1980). Acetylsalicylic acid (ASA) is a nonsteroidal anti-inflammatory drug (NSAID), with analgesic and antipyretic properties. This pharmaceutical is rapidly hydrolyzed to salicylic acid (2hydroxybenzoic acid, SA) in the intestinal wall, liver, and red blood cells (Patel et al., 1990). Approximately 80% of the resulting SA is further biotransformed in the liver by conjugation with either glycine or glucuronic acid, or by oxidation. The salicyluric acid, which is the glycine conjugate, is the most abundant metabolite in the urine of individuals who
DRUG–TCE IN VIVO METABOLIC INTERACTIONS
received a therapeutic dose of SA. The glucuronide conjugates of SA, that is, salicylic acid phenolic glucuronide (SAPG) and salicylic acid acyl glucuronide (SAAG) (Caldwell et al., 1980; Cummings et al., 1966), represent between 0.8 and 42% of the administered dose (Hutt et al., 1986). Small amounts of SA are hydroxylated to gentisic acid. Salicylates are excreted mainly by the kidney as salicyluric acid (75%), free salicylic acid (10%), salicylic acid phenolic glucuronide (10%), salicylic acid acyl glucuronide (5%), and gentisic acid (
IN VIVO EFFECTS OF NAPROXEN, SALICYLIC ACID, AND VALPROIC ACID ON THE PHARMACOKINETICS OF TRICHLOROETHYLENE AND METABOLITES IN RATS Mouna Cheikh Rouhou1, Ginette Charest-Tardif2, Sami Haddad2 1
Sciences Biologiques, Université du Québec à Montréal, Montréal, Quebec, Canada Environmental and Occupational Health, IRSPUM, Université de Montréal, Montréal, Quebec, Canada 2
It was recently demonstrated that some drugs modulate in vitro metabolism of trichloroethylene (TCE) in humans and rats. The objective was to assess in vivo interactions between TCE and three drugs: naproxen (NA), valproic acid (VA), and salicylic acid (SA). Animals were exposed to TCE by inhalation (50 ppm for 6 h) and administered a bolus dose of drug by gavage, equivalent to 10-fold greater than the recommended daily dose. Samples of blood, urine, and collected tissues were analyzed by headspace gas chromatography coupled to an electron capture detector for TCE and metabolites (trichloroethanol [TCOH] and trichloroacetate [TCA]) levels. Coexposure to NA and TCE significantly increased (up to 50%) total and free TCOH (TCOHtotal and TCOHfree, respectively) in blood. This modulation may be explained by an inhibition of glucuronidation. VA significantly elevated TCE levels in blood (up to 50%) with a marked effect on TCOHtotal excretion in urine but not in blood. In contrast, SA produced an increase in TCOHtotal levels in blood at 30, 60, and 90 min and urine after coexposure. Data confirm in vitro observations that NA, VA, and SA affect in vivo TCE kinetics. Future efforts need to be directed to evaluate whether populations chronically medicated with the considered drugs display greater health risks related to TCE exposure.
than 30 ppb (Agency for Toxic Substances and Disease Registry [ATSDR], 2013). Despite increasing evidence of the possible health risk of this chemical at relevant concentrations (Clewell et al., 2000), humans are still frequently exposed to TCE. Besides this possible simple exposure to TCE, coexposure situations to this chemical in combination with other substances do occur. The ever-increasing consumption of drugs reinforces concerns regarding a possible modulating effect resulting from TCE coexposures with potentially interacting medications. Pharmaceuticals, which are biologically active, may influence metabolism of TCE in liver and consequently affect its pharmacokinetics and/or its pharmacodynamics and therefore its toxicity in target tissue.
Various industries use trichloroethylene (TCE), a volatile chlorinated hydrocarbon solvent, in a large spectrum of applications (Wu and Berger, 2007; U.S. Environmental Protection Agency [EPA], 1985). Workers may be exposed by inhalation to high levels of TCE, ranging from approximately 1 to 100 ppm, while the general population might be exposed by inhalation of contaminated ambient air and/or ingestion of polluted drinking water. Across the United States, TCE concentrations in ambient air ranging from 0.01 to 0.3 ppb have been measured. Although concentrations as high as 3.4 ppb were reported, between 4.5 and 18% of the drinking-water supply sources in the United States, which are tested on a yearly basis by the U.S. EPA, have measurable levels of TCE: typically lower
Received 16 October 2014; accepted 16 February 2015. Address correspondence to Prof. Sami Haddad, Environmental and Occupational Health, IRSPUM, Université de Montréal, PO Box 6128, Main Station, Roger-Gaudry Building, Montréal, Quebec, HC3 3J7, Canada. E-mail: [email protected] 671
672
Toxicokinetic interactions with TCE have been reported for a few drugs, specifically aspirin and acetaminophen (Plewka et al., 2000; Zieliñska-Psuja et al., 2001). However, no other apparent toxicokinetic interactions data have been found for other drugs in the literature. Recently Cheikh Rouhou et al. (2012) showed that some pharmaceuticals, among a tested selection of 14 widely consumed drugs, modulate in vitro metabolism of TCE in rat hepatocytes and rat liver microsomes. Cheikh Rouhou and Haddad (2013) also reported that such in vitro interactions occurred in human hepatocytes and human liver microsomes. In humans and rats, in vitro naproxen (NA) competitively inhibited trichloroethanol (TCOH) glucuronidation with Ki = 2.329 mM and Ki = 211.6 μM, respectively. In the case of salicylic acid (SA), the observed interactions in hepatocytes were not detected in microsomes, both in humans and in rats. Finally, for valproic acid (VA) the observed interactions were not found in human microsomes and were characterized as partial noncompetitive inhibition in rat for both TCA and TCOH formation with Ki = 1215.8 μM and Ki = 932.8 μM, respectively. Similarities between human and rat responses, either for absence or for observed interactions, were noted. Based upon these human and rat in vitro investigations, three drugs that were found to interfere with TCE metabolism, naproxen (NA), salicylic acid (SA), and valproic acid (VA), were selected for the present study TCE is metabolized in the liver, mainly by oxidation. In this pathway, TCE is first biotransformed into chloral hydrate (CHO), predominantly by the action of CYP2E1 (Lipscomb et al., 1997; Nakajima et al., 1992; Lash et al., 2006) and secondarily by isoforms CYP1A1/2, CYP2B1/2, and CYP2C11/6 (Lash et al., 2000a, 2006; Chiu et al., 2007). Chloral hydrate is then transformed either by oxidation to trichloroacetic acid (TCA) by aldehyde oxidase, or by reduction to trichloroethanol (TCOH), mainly by CYP2E1 (Ni et al., 1996) and secondarily by alcohol dehydrogenase (Larson and Bull, 1989; Müller et al., 1975;
M. CHEIKH ROUHOU ET AL.
Yoo et al., 2015). Glutathione (GSH) conjugation is the other route of biotransformation. This pathway is secondary, taking place also in the liver (Lash et al., 2000b). In the first step, a GSH conjugate that is the S-(1,2dichlorovinyl) glutathione (DCVG) is formed with catalytic action of glutathione S-transferase (GST). The DCVG is then metabolized by γglutamyltransferase (GGTP) to free glutamic acid and cysteine conjugate form (Dekant et al., 1990; Lash et al., 2000a; Chiu et al., 2007; Yoo et al., 2015). Naproxen (NA) is a propionic acid derivative related to the arylacetic acid group of nonsteroidal anti-inflammatory drugs (NSAIDs). This pharmaceutical possesses analgesic and antipyretic properties, and is rapidly and completely absorbed from the gastrointestinal tract (GIT) with an in vivo bioavailability of 95%. The range of elimination half-life of NA is 12 to 17 h (Niazi et al., 1996). This drug is extensively metabolized in the liver to 6O-desmethyl NA by CYP2C9, CYP 2C8, and CYP 1A2 (DrugBank, 2015). Both parent compound and metabolites do not induce metabolizing enzymes. Naproxen and 6-O-desmethyl NA are further biotransformed to their respective acyl glucuronide conjugated metabolites (Toothaker et al., 2000). Naproxen and its metabolites are excreted primarily in urine. About 10% of the absorbed dose is eliminated unchanged, 40% as glucuronide conjugates, 5% as desmethyl naproxen, 12% as glucuronide of desmethyl NA, and approximately 30% as unknown conjugates of NA and desmethyl NA (Sevelius et al., 1980). Acetylsalicylic acid (ASA) is a nonsteroidal anti-inflammatory drug (NSAID), with analgesic and antipyretic properties. This pharmaceutical is rapidly hydrolyzed to salicylic acid (2hydroxybenzoic acid, SA) in the intestinal wall, liver, and red blood cells (Patel et al., 1990). Approximately 80% of the resulting SA is further biotransformed in the liver by conjugation with either glycine or glucuronic acid, or by oxidation. The salicyluric acid, which is the glycine conjugate, is the most abundant metabolite in the urine of individuals who
DRUG–TCE IN VIVO METABOLIC INTERACTIONS
received a therapeutic dose of SA. The glucuronide conjugates of SA, that is, salicylic acid phenolic glucuronide (SAPG) and salicylic acid acyl glucuronide (SAAG) (Caldwell et al., 1980; Cummings et al., 1966), represent between 0.8 and 42% of the administered dose (Hutt et al., 1986). Small amounts of SA are hydroxylated to gentisic acid. Salicylates are excreted mainly by the kidney as salicyluric acid (75%), free salicylic acid (10%), salicylic acid phenolic glucuronide (10%), salicylic acid acyl glucuronide (5%), and gentisic acid (
