Secretion into Milk of the Main Metabolites of the Anthelmintic Albendazole Is Mediated by the ABCG2/BCRP Transporter

Albendazole (ABZ) is an anthelmintic with a broad-spectrum activity, widely used in human and veterinary medicine. ABZ is metabolized in all mammalian species to albendazole sulfoxide (ABZSO), albendazole sulfone (ABZSO2) and albendazole 2-aminosulphone (ABZSO2-NH2). ABZSO and ABZSO2 are the main metabolites detected in plasma and all three are detected in milk. The ATP-binding cassette transporter G2 (ABCG2) is an efflux transporter that is involved in the active secretion of several compounds into milk. Previous studies have reported that ABZSO was in vitro transported by ABCG2. The aim of this work is to correlate the in vitro interaction between ABCG2 and the other ABZ metabolites with their secretion into milk by this transporter. Using in vitro transepithelial assays with cells transduced with murine Abcg2 and human ABCG2, we show that ABZSO2 and ABZSO2-NH2 are in vitro substrates of both. In vivo assays carried out with wild-type and Abcg2−/− lactating female mice demonstrated that secretion into milk of these ABZ metabolites was mediated by Abcg2. Milk concentrations and milk-to-plasma ratio were higher in wild-type compared to Abcg2−/− mice for all the metabolites tested. We conclude that ABZ metabolites are undoubtedly in vitro substrates of ABCG2 and actively secreted into milk by ABCG2.S

In vitro interaction of the pesticides flupyradifurone, bupirimate and its metabolite ethirimol with the ATP-binding cassette transporter G2 (ABCG2)

[EN] ABCG2 is an ATP-binding cassette efflux transporter that is expressed in absorptive and excretory organs such as liver, intestine, kidney, brain and testis where it plays a crucial physiological and toxicological role in protecting cells against xenobiotics, affecting pharmacokinetics of its substrates. In addition, the induction of ABCG2 expression in mammary gland during lactation is related to active secretion of many toxicants into milk. In this study, the in vitro interactions between ABCG2 and three pesticides flupyradifurone, bupirimate and its metabolite ethirimol were investigated to check whether these compounds are substrates and/or inhibitors of this transporter. Using in vitro transepithelial assays with cells transduced with murine, ovine and human ABCG2, we showed that ethirimol and flupyradifurone were transported efficiently by murine Abcg2 and ovine ABCG2 but not by human ABCG2. Bupirimate was not found to be an in vitro substrate of ABCG2 transporter. Accumulation assays using mitoxantrone in transduced MDCK-II cells suggest that none of the tested pesticides were efficient ABCG2 inhibitors, at least in our experimental conditions. Our studies disclose that ethirimol and flupyradifurone are in vitro substrates of murine and ovine ABCG2, opening the possibility of a potential relevance of ABCG2 in the toxicokinetics of these pesticides.S

Transporters in the Mammary Gland—Contribution to Presence of Nutrients and Drugs into Milk

[EN] A large number of nutrients and bioactive ingredients found in milk play an important role in the nourishment of breast-fed infants and dairy consumers. Some of these ingredients include physiologically relevant compounds such as vitamins, peptides, neuroactive compounds and hormones. Conversely, milk may contain substances—drugs, pesticides, carcinogens, environmental pollutants—which have undesirable effects on health. The transfer of these compounds into milk is unavoidably linked to the function of transport proteins. Expression of transporters belonging to the ATP-binding cassette (ABC-) and Solute Carrier (SLC-) superfamilies varies with the lactation stages of the mammary gland. In particular, Organic Anion Transporting Polypeptides 1A2 (OATP1A2) and 2B1 (OATP2B1), Organic Cation Transporter 1 (OCT1), Novel Organic Cation Transporter 1 (OCTN1), Concentrative Nucleoside Transporters 1, 2 and 3 (CNT1, CNT2 and CNT3), Peptide Transporter 2 (PEPT2), Sodium-dependent Vitamin C Transporter 2 (SVCT2), Multidrug Resistance-associated Protein 5 (ABCC5) and Breast Cancer Resistance Protein (ABCG2) are highly induced during lactation. This review will focus on these transporters overexpressed during lactation and their role in the transfer of products into the milk, including both beneficial and harmful compounds. Furthermore, additional factors, such as regulation, polymorphisms or drug-drug interactions will be described.S

Ivermectin reduces secretion of meloxicam into milk by inhibition of ABCG2 transporter in sheep

[EN] The ATP-binding cassette transporter G2 (ABCG2) is an efflux protein involved in the bioavailability and secretion into milk of several compounds including anti- inflammatory drugs. The aim of this work was to determine the effect in sheep of an ABCG2 inhibitor, such as the macrocyclic lactone ivermectin, on the secretion into milk of meloxicam, a non-steroidal anti-inflammatory drug widely used in veterinary medicine, and recently reported as an ABCG2 substrate in mice. In vitro meloxicam transport assays in ovine ABCG2-transduced cells have shown that meloxicam is a substrate of ovine ABCG2 and that ivermectin is an efficient inhibitor of in vitro transport of meloxicam mediated by ovine ABCG2. In addition, the role of ovine ABCG2 in secretion into milk of meloxicam was corroborated using Assaf lactating sheep coadministered with ivermectin. Animals were administered subcutaneously with meloxicam (0.5 mg/kg) with or without ivermectin (0.2 mg/kg). A significantly lower concentration of meloxicam in milk was detected when ivermectin was coadministered, revealing a major role of ABCG2 in the secretion into milk of meloxicam and a relevant drug-drug interaction affecting this process. These results will contribute to the understanding of the potential factors that modulate the transfer of anti-inflammatory drugs into milk, opening their potential use in lactating ruminants, and the effect of drug coadministration on the presence of milk residues of these compounds.S

The ABCG2 protein in vitro transports the xenobiotic thiabendazole and increases the appearance of its residues in milk

[EN] Thiabendazole (2–(4–thiazolyl)benzimidazole, TBZ) is a broad–spectrum anthelmintic widely used in humans and cattle. It is also used as post–harvest agricultural fungicide, thus preserving crop quality and marketability (Hajikhani et al., 2024). Adverse effects after TBZ exposure including endocrine, nephrogenic, hepatogenic, teratogenic and neurological effects have been reported in mammals (Ekman et al., 2014). Etiological factors behind TBZ toxicity remain ambiguous; however, it has been hypothesized that it may be due to its bioactivation to 5OH–TBZ by the cytochrome P450 1A2 (CYP1A2) (Coulet et al., 1998a; Jamieson et al., 2011) (Fig. 1). Therefore, National and International Food Safety Authorities have established regulations for the usage of TBZ on food products setting maximum residue limits (MRLs) for the sum of TBZ and its metabolites in both agricultural and animal products ranging from 0.01 to 7 mg/kg depending on the product (European Food Safety Authority (EFSA) et al., 2021; U.S. Food and Drug Administration (FDA), 2021). Unfortunately, MRLs derived from pesticide use are equal to or higher than veterinary MRLs for all commodities, and the possible aggregated exposure from TBZ residues has not been studied, making it impossible to rule out an overexposure to TBZ through the food chain.SIPublicación en abierto financiada por el Consorcio de Bibliotecas Universitarias de Castilla y León (BUCLE), con cargo al Programa Operativo 2014ES16RFOP009 FEDER 2014-2020 DE CASTILLA Y LEÓN, Actuación:20007-CL - Apoyo Consorcio BUCL

Coadministration of ivermectin and abamectin affects milk pharmacokinetics of the antiparasitic clorsulon in Assaf sheep

[EN] In veterinary field, drug exposure during milk production in dairy cattle is considered a major health problem which concerns dairy consumers. The induced expression of the ABC transporter G2 (ABCG2) in the mammary gland during lactation plays a significant role in the active secretion of many compounds into milk. The main objective of this study was to determine the involvement of ABCG2 in the secretion into milk of the antiparasitic clorsulon in sheep as well as the possible effect of the coadministration of model ABCG2 inhibitors such as macrocyclic lactones on this process. Cells transduced with the ovine variant of ABCG2 were used to carry out in vitro transepithelial transport assays in which we showed that clorsulon is a substrate of the ovine transporter. In addition, ivermectin and abamectin significantly inhibited clorsulon transport mediated by ovine ABCG2. In vivo interactions were studied in Assaf sheep after coadministration of clorsulon (in DMSO, 2 mg/kg, s.c.) with ivermectin (Ivomec®, 0.2 mg/kg, s.c.) or abamectin (in DMSO, 0.2 mg/kg, s.c.). After ivermectin and abamectin treatment, no relevant statistically significant differences in plasma levels of clorsulon were reported between the experimental groups since there were no differences in the area under the plasma concentration-curve (AUC) between clorsulon treatment alone and coadministration with macrocyclic lactones. With regard to milk, total amount of clorsulon, as percentage of dose excreted, did not show statistically significant differences when macrocyclic lactones were coadministered. However, the AUC for clorsulon significantly decreased (p < 0.05) after coadministration with ivermectin (15.15 ± 3.17 μg h/mL) and abamectin (15.30 ± 3.25 μg h/mL) compared to control group (20.73 ± 4.97 μg h/mL). Moreover, milk parameters such as half- life (T1/2) and mean residence time (MRT) were significantly lower (p < 0.05) after coadministration of macrocyclic lactones. This research shows that the milk pharmacokinetics of clorsulon is affected by the coadministration of ABCG2 inhibitors, reducing drug persistence in milk.S

The Breast Cancer Resistance Protein (BCRP/ABCG2) influences the levels of enterolignans and their metabolites in plasma, milk and mammary gland

P. 648-654Lignans are phytoestrogens widely used in dietary supplements and functional foods. After oral ingestion, these polyphenols are metabolized to enterolignans, the main gut microbiota-derived metabolites with weak estrogenic/anti-estrogenic activities. The ABCG2 transporter is highly expressed in the mammary gland and could be responsible for enterolignan accumulation. We aimed here at evaluating the levels of enterolignans and their conjugates in plasma, milk and mammary tissue from wild-type and knockout Abcg2-/- female mice after a lignan-enriched diet for one week. In vitro transepithelial transport of enterolignans was also assayed with ABCG2- transduced cells. Enterolactone and enterodiol levels were higher in plasma and lower in milk from Abcg2-/- compared with wild-type mice. Both enterolactone and enterodiol were accumulated in the mammary gland but with significant differences only for enterolactone. Our results suggest that ABCG2 may be determinant for plasma and milk levels of enterolignans whose accumulation could exert chemopreventive effects against breast cancerS

Role of the Abcg2 Transporter in Secretion into Milk of the Anthelmintic Clorsulon: Interaction with Ivermectin

[EN] Clorsulon is a benzenesulfonamide drug that is effective in treating helminthic zoonoses such as fascioliasis. When used in combination with the macrocyclic lactone ivermectin, it provides high broad-spectrum antiparasitic efficacy. The safety and efficacy of clorsulon should be studied by considering several factors such as drug-drug interactions mediated by ATP-binding cassette (ABC) transporters due to their potential effects on the pharmacokinetics and drug secretion into milk. The aim of this work was to determine the role of ABC transporter G2 (ABCG2) in clorsulon secretion into milk and the effect of ivermectin, a known ABCG2 inhibitor, on this process. Using in vitro transepithelial assays with cells transduced with murine Abcg2 and human ABCG2, we report that clorsulon was transported in vitro by both transporter variants and that ivermectin inhibited its transport mediated by murine Abcg2 and human ABCG2. Wild-type and Abcg22/2 lactating female mice were used to carry out in vivo assays. The milk concentration and the milk-to-plasma ratio were higher in wild-type mice than in Abcg22/2 mice after clorsulon administration, showing that clorsulon is actively secreted into milk by Abcg2. The interaction of ivermectin in this process was shown after the coadministration of clorsulon and ivermectin to wild-type and Abcg22/2 lactating female mice. Treatment with ivermectin had no effect on the plasma concentrations of clorsulon, but the milk concentrations and milk-to-plasma ratios of clorsulon decreased in comparison to those with treatment without ivermectin, only in wild-type animals. Consequently, the coadministration of clorsulon and ivermectin reduces clorsulon secretion into milk due to drug-drug interactions mediated by ABCG2S

Altered tissue distribution of flaxseed lignans and their metabolites in Abcg2 knockout mice

Lignans are dietary polyphenols, which are metabolized by gut microbiota into the phytoestrogenic metabolites enterolignans, mainly enterolactone and enterodiol. Breast Cancer Resistance Protein (BCRP/ABCG2) is an efflux transporter that affects the plasma and milk secretion of several drugs and natural compounds. We hypothesized here that Abcg2 could influence the levels of lignans and their derived metabolites in target tissues. Consequently, we aimed to evaluate the role of Abcg2 in the tissue distribution of these compounds. We used Abcg2−/− knockout and wild-type male mice fed with a lignan-enriched diet for one week and analysed their plasma, small intestine, colon, liver, kidneys and testicles. High levels of lignans as well as enterolignans and their glucuronide and sulfate conjugates in the small intestine and colon were detected, with higher concentrations of the conjugates in the wildtype compared with Abcg2−/− mice. Particularly relevant was the detection of 24-fold and 8-fold higher concentrations of enterolactone-sulfate and enterolactone-glucuronide, respectively, in the kidney of Abcg2−/− compared with wild-type mice. In conclusion, our study showed that lignans and their derived metabolites were in vivo substrates of Abcg2, which affected their plasma and tissue levels. These results highlight the role of Abcg2 in influencing the health-beneficial properties of dietary lignans.S

Effect of bovine ABCG2 Y581S polymorphism on concentrations in milk of enrofloxacin and its active metabolite ciprofloxacin

P. 5731-5738The ATP-binding cassette transporter G2 (ABCG2) is involved in the secretion of several drugs into milk. The bovine Y581S ABCG2 polymorphism increases the secretion into milk of the fluoroquinolone danofloxacin in Holstein cows. Danofloxacin and enrofloxacin are the fluoroquinolones most widely used in veterinary medicine. Both enrofloxacin (ENRO) and its active metabolite ciprofloxacin (CIPRO) reach milk at relatively high concentrations. The aim of this work was to study the effect of the bovine Y581S ABCG2 polymorphism on in vitro transport as well as on concentrations in plasma and in milk of ENRO and CIPRO. Experiments using cells over-expressing bovine ABCG2 showed the effects of ABCG2 on the transport of CIPRO demonstrating more efficient in vitro transport of this antimicrobial by the S581 variantS