Solvo Biotechnology (Hungary)

Background/Objectives: Ochratoxin A (OTA) is a widespread foodborne mycotoxin linked to chronic kidney disease of unknown etiology. Despite evidence from animal models showing OTA accumulation in the kidney, the molecular mechanisms underlying its renal disposition in humans remain only partially understood. Here, we identify human renal transporters responsible for OTA kidney accumulation, elimination, and establish Michaelis–Menten kinetics under matched conditions to directly compare transport mechanisms. We also aim to identify inhibition potential of these transport mechanisms with common dietary polyphenols. Methods: Mammalian cells and membrane vesicles overexpressing human renal transporters were used to screen and profile the uptake and efflux of OTA. Miquelianin, (-)-Epicatechin-3-O-gallate, myricetin, luteolin, and caffeic acid were tested as potential concentration-dependent transporter inhibitors. Results: We demonstrate that OTA is a substrate for human organic anion transporter (hOAT) 1 (Km: 2.10 ± 0.50 μM, Vmax: 396.9 ± 27.0 pmol/mg/min), hOAT3 (Km: 2.58 ± 0.83 μM, Vmax: 141.4 ± 30.3 pmol/mg/min), hOAT4 (Km: 6.38 ± 1.45 μM, Vmax: 96.9 ± 18.8 pmol/mg/min), and human organic anion transporting polypeptide (hOATP) 1A2 (Km: 37.3 ± 6.2 μM, Vmax: 801.0 ± 133.9 pmol/mg/min). Among efflux transporters, OTA was transported only by human breast cancer resistance protein (hBCRP), which has minimal renal expression. While none of the uptake transporters were potently inhibited (>90%) by polyphenols at 10 μM, luteolin inhibited hBCRP-mediated transport of OTA with an IC50 of 22 μM and caffeic acid stimulated hBCRP-mediated efflux with an EC50 of 713.8 μM, both of which are physiologically relevant intestinal lumen concentrations. Conclusions: Our results confirm that exposure to OTA will lead to renal accumulation and increased health risks in affected populations, necessitating increased scrutiny of our food sources.

Δ9-Tetrahydrocannabinol (THC) is the primary psychoactive component of cannabis which is being increasingly consumed by pregnant people. In humans, THC is sequentially metabolized in the liver to its circulating metabolites 11-hydroxy-THC (11-OH-THC, psychoactive) and 11-nor-9-carboxy-THC (THC-COOH, non-psychoactive). Human and macaque data show that fetal exposure to THC is considerably lower than the corresponding maternal exposure. Through perfused human placenta studies, we showed that this is due to the active efflux of THC (fetal-to-maternal) by a placental transporter(s) other than P-glycoprotein or breast cancer resistance protein. The identity of this placental transporter(s) as well as whether THC or its metabolites are substrates or inhibitors of hepatic solute carrier transporters is unknown. Therefore, we investigated whether 5 μM THC, 0.3 μM 11-OH-THC, and 2.5 μM THC-COOH are substrates and/or inhibitors of placental or hepatic solute carrier transporters at their pharmacologically relevant concentrations. Using HEK cells overexpressing human OATP1B1, OATP1B3, OATP2B1, OCT1, OCT3, OAT2, OAT4, or NTCP, and prototypic substrates/inhibitors of these transporters, we found that THC and THC-COOH were substrates but not inhibitors of OCT1. THC-COOH was a weak substrate of OCT3 and a weak inhibitor of OAT4. THC, 11-OH-THC, and THC-COOH were found not to be substrates/inhibitors of the remaining transporters investigated.

ABCB4 is almost exclusively expressed in the liver, where it plays an essential role in bile formation by transporting phospholipids into the bile. ABCB4 polymorphisms and deficiencies in humans are associated with a wide spectrum of hepatobiliary disorders, attesting to its crucial physiological function. Inhibition of ABCB4 by drugs may lead to cholestasis and drug-induced liver injury (DILI), although compared with other drug transporters, there are only a few identified substrates and inhibitors of ABCB4. Since ABCB4 shares up to 76% identity and 86% similarity in the amino acid sequence with ABCB1, also known to have common drug substrates and inhibitors, we aimed to develop an ABCB4 expressing Abcb1-knockout MDCKII cell line for transcellular transport assays. This in vitro system allows the screening of ABCB4-specific drug substrates and inhibitors independently of ABCB1 activity. Abcb1KO-MDCKII-ABCB4 cells constitute a reproducible, conclusive, and easy to use assay to study drug interactions with digoxin as a substrate. Screening a set of drugs with different DILI outcomes proved that this assay is applicable to test ABCB4 inhibitory potency. Our results are consistent with prior findings concerning hepatotoxicity causality and provide new insights for identifying drugs as potential ABCB4 inhibitors and substrates.

Syndecan-1 (SDC-1) is a heparan sulfate (HS)/chondroitin sulfate proteoglycan (PG) of the cell surface and the extracellular matrix (ECM), which regulates a broad spectrum of physiological and pathological processes such as cell proliferation, migration, inflammation, matrix remodeling, wound healing, and tumorigenesis. Syndecan-1 represents the major PG of the liver, expressed by hepatocytes and cholangiocytes, and its elevated expression is a characteristic feature of liver diseases. The highest syndecan-1 expression is found in liver cirrhosis and in hepatocellular carcinoma (HCC) developed in cirrhotic livers. In addition, as being a hepatitis C receptor, hepatitis C virus (HCV)-infected livers produce extremely large amounts of syndecan-1. The serum levels of the cleaved (shedded) extracellular domain have clinical significance, as their increased concentration reflects on poor prognosis in cirrhosis as well as in cancer. In vivo experiments confirmed that syndecan-1 protects against early stages of fibrogenesis mainly by enhanced clearance of transforming growth factor β1 (TGFβ1) and thrombospondin-1 (THBS1) via circulation, and against hepatocarcinogenesis by interfering with several signaling pathways and enhancing cell cycle blockade. In addition, syndecan-1 is capable to hinder lipid metabolism and ribosomal biogenesis in induced cancer models. These observations together with its participation in the uptake of viruses (e.g., HCV and SARS-CoV-2) indicate that syndecan-1 is a central player in liver pathologies.

To assess efficacy and toxicity of a drug in humans, it is important to measure the tissue concentration of a drug at the target site. For a drug that is transported into or out of the tissue, the tissue unbound steady-state concentration can be dramatically different from its corresponding unbound steady-state plasma concentration. Because routine measurement of drug tissue concentrations is not possible, using rosuvastatin as a model transporter substrate drug, we compared the ability of the proteomics-informed relative expression factor (REF) approach and sandwich-cultured human hepatocytes (SCH) to accurately predict rosuvastatin human hepatobiliary clearances and hepatic concentrations. REF-predicted rosuvastatin biliary clearance (CLbile ), estimated using BCRP-overexpressing, MDR1-overexpressing, and MRP2-overexpressing vesicles, together with our previously published REF-predicted rosuvastatin hepatic sinusoidal uptake clearance (CLuptake ) and physiologically scaled sinusoidal passive uptake and efflux clearance (CLs,efflux ), were used to predict rosuvastatin hepatic concentrations. For SCH, the estimated rosuvastatin CLbile , CLuptake , and CLs,efflux were scaled using physiological scaling. The REF-predicted CLbile (6.39±1.56mL/minute) and hepatic rosuvastatin area under the concentration-time curve (AUC) fell within our a priori defined success criterion, i.e., within twofold of the observed positron emission tomography-imaged values. In contrast, as expected, SCH dramatically overpredicted (predicted/observed ratio P/O=8.38-10.41) rosuvastatin CLbile , and underpredicted hepatic AUC (P/O=0.08-0.14). For both approaches, predictions were improved by using the parallel tube model vs. well-stirred model. Overall, using rosuvastatin as a model drug, this study demonstrates the success of the REF approach in predicting in vivo CLbile and hepatic concentration of drugs, and highlights the shortcomings of the SCH approach in making such predictions.

Abstract Angiogenesis and vasculogenesis are not only indispensable for normal tissue growth and regeneration but also particularly vital for tumors. As without sufficient blood supply that provides nutrients, tumor cells cannot proliferate. Tumors may employ several strategies to receive sufficient blood supply: they can promote the development of new blood vessels, engulf already existing arteries, or induce the splitting or glomeruli-like proliferation of pre-existing blood vessels. The outcome depends on the equilibrium of pro- and antiangiogenic factors that regulate these events. The most potent stimulatory factor is VEGF, but several other growth factors, cytokines, chemokines, and miRNAs have a stimulatory potential, whereas specific proteolytic breakdown products and other miRNAs can inhibit angiogenesis. Like tumor cells, newly generated tumor vasculature also displays deregulated behavior: blood vessels created upon the angiogenic switch differ from their normal counterparts in both structure and function. Perlecan, a large extracellular matrix heparan sulfate/chondroitin sulfate (HS/CS) proteoglycan, is a ubiquitous component of basement membranes, including vascular basement membranes of both normal and tumorous blood vessels. Besides its structural role, perlecan regulates angiogenesis by interacting with a large number of partner molecules, mainly with growth factors and cytokines bound to its HS chains. Whereas intact perlecan promotes angiogenesis, a tryptic fragment of its domain V called endorepellin exerts anti-angiogenic action and triggers tumor autophagy, whose potentials may be exploited in the future management of cancer.KeywordsStrategies of tumor angiogenesisStructural compartmentsRegulatory factorsPerlecan in basement membrane and tumor angiogenesisEndorepellin and autophagy

During the COVID-19 pandemic, several repurposed drugs have been proposed to alleviate the major health effects of the disease. These drugs are often applied with analgesics or non-steroid anti-inflammatory compounds, and co-morbid patients may also be treated with anticancer, cholesterol-lowering, or antidiabetic agents. Since drug ADME-tox properties may be significantly affected by multispecific transporters, in this study, we examined the interactions of the repurposed drugs with the key human multidrug transporters present in the major tissue barriers and strongly affecting the pharmacokinetics. Our in vitro studies, using a variety of model systems, explored the interactions of the antimalarial agents chloroquine and hydroxychloroquine; the antihelmintic ivermectin; and the proposed antiviral compounds ritonavir, lopinavir, favipiravir, and remdesivir with the ABCB1/Pgp, ABCG2/BCRP, and ABCC1/MRP1 exporters, as well as the organic anion-transporting polypeptide (OATP)2B1 and OATP1A2 uptake transporters. The results presented here show numerous pharmacologically relevant transporter interactions and may provide a warning on the potential toxicities of these repurposed drugs, especially in drug combinations at the clinic.