Potential role of organic anion transporting polypeptide 1B1 (OATP1B1) in the selective hepatic uptake of hematoporphyrin monomethyl ether isomers

MSNs-loaded HMME and Erastin-mediated ferroptosis combined with sonodynamic therapy for HCC treatment

BACKGROUND

Ferroptosis can have a major impact on the development and advancement of hepatocellular carcinoma (HCC) due to its clear association with heightened vulnerability to the disease. This study aimed to develop a novel nanoplatform to evaluate its effectiveness in in vivo and in vitro models of HCC.

METHODS

Erastin, a compound that induces iron-dependent cell death, and HMME, a sonosensitizer, were enclosed within mesoporous silica nanoparticles (MSNs). The nanoparticles were engineered to exhibit a responsive assembly-disassembly mechanism. Hydrophilic hyaluronic acid (HA) was utilized for conjugation modification to synthesize Erastin/HMME@MSNs-HA. In vivo and in vitro experiments were conducted to elucidate the antitumor mechanisms of this nanomaterial.

RESULTS

In the in vitro cellular experiments, Erastin/HMME@MSNs-HA was rapidly degraded by hyaluronidase, leading to increased endocytosis of the cancer cells. Cellular breakdown led to the generation of harmful reactive oxygen species (ROS), decreased glutathione levels, and increased lipid peroxidation, resulting in a decrease in mitochondrial membrane potential, dysfunctional mitochondria, reduced cell growth, and increased cell death. Additionally, the Erastin/HMME@MSNs-HA nanotherapy platform, when combined with ultrasound (US) treatment, exhibited significant therapeutic effectiveness against tumors in vivo. It induced significant cell death in cancerous tissues, decreased tumor growth, worsened tissue oxygen deprivation, and exhibited good compatibility with the body.

CONCLUSION

These findings indicate that the nanoplatform can effectively alleviate tumor hypoxia while inducing apoptosis and ferroptosis, laying the foundation for enhancing the efficacy of ROS-mediated HCC therapy.

Structure-activity relationship of isoprenoid triazole bisphosphonate-based geranylgeranyl diphosphate synthase inhibitors: Effects on pharmacokinetics, biodistribution, and hepatic transporters

Geranylgeranyl diphosphate synthase produces the isoprenoid geranylgeranyl diphosphate, which is used in protein geranylgeranylation. Our previous work illustrates that geranylgeranyl diphosphate synthase inhibitors (GGSIs) disrupt Rab-mediated protein trafficking in cells, inducing the unfolded protein response pathway and apoptosis. Structure-function studies of our GGSIs, which are isoprenoid triazole bisphosphonates, have revealed a complex relationship between GGSI structure and enzymatic, cellular, and in vivo activities. The dose-limiting toxicity of this family of GGSIs is hepatic, and the mechanisms underlying their hepatic uptake are unexplored. Here, we evaluate the pharmacokinetics (PK) and biodistribution of a pair of potent GGSIs that are olefin isomers (homogeranyl [HG] and homoneryl [HN]). We investigate whether these isomers, as well as their a-methylated analogs (HG-me and HN-me), are substrates for key hepatic transporters and explore the effects of these GGSIs on the expression of a panel of hepatic transporters and cytochrome P450s. The PK/biodistribution studies revealed that both systemic exposure and liver levels of HG were significantly higher than that of HN across multiple time points. Conversely, HN was present at 4-fold higher concentrations in the bile at 2 hours postinjection relative to HG. HG-me and HN-me, but not HG or HN, were determined to be substrates of hepatic transport proteins OATP1B1 and OATP1B3. While the hepatic expression of several transporters and cytochrome P450 were altered by GGSI treatment, no significant differences in expression patterns between pairs of olefin isomers were observed. Collectively, these studies reveal that GGSI structure, including olefin stereochemistry, impacts PK profile, biodistribution, and hepatic transporter affinity. SIGNIFICANCE STATEMENT: Our understanding of the in vivo structure-activity relationship of our novel geranylgeranyl diphosphate synthase inhibitors has expanded, demonstrating that isoprenoid olefin stereochemistry impacts pharmacokinetic and biodistribution patterns and that other modifications impact transporter affinity. These studies reveal the underlying complexity of the mechanisms regulating hepatic exposure to these agents. Future studies will focus on optimizing tumor-directed geranylgeranyl diphosphate synthase inhibitor delivery while minimizing hepatic uptake.

Efflux and uptake of androgen sulfates using transporter-overexpressing HEK293 cells and membrane vesicles

Hydrophilic steroid conjugates require active and facilitated transport mechanisms for their distribution into tissues and excretion from the body. The ATP-binding cassette (ABC) and solute carrier organic anion (SLCO) transporters involved in androgen sulfate (-S) disposition have been poorly characterized. In this study, we investigated the in vitro transport of testosterone-S, epitestosterone-S, dehydroepiandrosterone-S (DHEA-S), androsterone-S, and etiocholanolone-S by the multidrug resistance-associated proteins 2-4 (MRP2-4, ABCC2-4), breast cancer resistance protein (BCRP, ABCG2), and organic anion-transporting polypeptides (OATP) 1B1, 1B3, and 2B1 (SLCO1B1, SLCO1B3, and SLCO2B1) using human transporter-overexpressing HEK293 cells and membrane vesicles. We found testosterone-S, epitestosterone-S, and DHEA-S to be selectively transported by BCRP and/or MRP4, whereas all studied androgen sulfates were substrates of MRP3, OATP1B1, OATP1B3, and OATP2B1. MRP2 did not transport any of the studied compounds. Evaluation of transport kinetics revealed MRP4 to interact with its substrates at high to moderate affinity, whereas the observed affinities towards MRP3, BCRP, and OATPs were mostly moderate. These results help to build a better mechanistic understanding of the disposition of androgen sulfates in the human body. Additionally, this data may be used to assess the feasibility of androgen sulfates as additional biomarkers in doping detection.

Transport of Bupropion and its Metabolites by the Model CHO and HEK293 Cell Lines

BACKGROUND

Bupropion (BUP) is widely used as an antidepressant and smoking cessation aid. There are three major pharmacologically active metabolites of BUP, Erythrohydrobupropion (EB), Hydroxybupropion (OHB) and Threohydrobupropion (TB). At present, the mechanisms underlying the overall disposition and systemic clearance of BUP and its metabolites have not been well understood, and the role of transporters has not been studied.

OBJECTIVE

The goal of this study was to investigate whether BUP and its active metabolites are substrates of the major hepatic uptake and efflux transporters.

METHOD

CHO or HEK293 cell lines or plasma membrane vesicles that overexpress OATP1B1, OATP1B3, OATP2B1, OATP4A1, OCT1, BCRP, MRP2 or P-gp were used in cellular or vesicle uptake and inhibition assays. Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) was used to quantify transport activity.

RESULTS

BUP and its major active metabolites were actively transported into the CHO or HEK293 cells overexpressing OATP1B1, OATP1B3 or OATP2B1; however, such cellular active uptake could not be inhibited at all by prototypical inhibitors of any of the OATP transporters. These compounds were not transported by OCT1, BCRP, MRP2 or P-gp either. These results suggest that the major known hepatic transporters likely play a minor role in the overall disposition and systemic clearance of BUP and its active metabolites in humans. We also demonstrated that BUP and its metabolites were not transported by OATP4A1, an uptake transporter on the apical membrane of placental syncytiotrophoblasts, suggesting that OATP4A1 is not responsible for the transfer of BUP and its metabolites from the maternal blood to the fetal compartment across the placental barrier in pregnant women.

CONCLUSION

BUP and metabolites are not substrates of the major hepatic transporters tested and thus these hepatic transporters likely do not play a role in the overall disposition of the drug. Our results also suggest that caution should be taken when using the model CHO and HEK293 cell lines to evaluate potential roles of transporters in drug disposition.

Integrative Data Mining, Scaffold Analysis, and Sequential Binary Classification Models for Exploring Ligand Profiles of Hepatic Organic Anion Transporting Polypeptides

Hepatocellular organic anion transporting polypeptides (OATP1B1, OATP1B3, and OATP2B1) are important for proper liver function and the regulation of the drug elimination process. Understanding their roles in different conditions of liver toxicity and cancer requires an in-depth investigation of hepatic OATP–ligand interactions and selectivity. However, such studies are impeded by the lack of crystal structures, the promiscuous nature of these transporters, and the limited availability of reliable bioactivity data, which are spread over different data sources in the open domain. To this end, we integrated ligand bioactivity data for hepatic OATPs from five open data sources (ChEMBL, the UCSF–FDA TransPortal database, DrugBank, Metrabase, and IUPHAR) in a semiautomatic KNIME workflow. Highly curated data sets were analyzed with respect to enriched scaffolds, and their activity profiles and interesting scaffold series providing indication for selective, dual-, or pan-inhibitory activity toward hepatic OATPs could be extracted. In addition, a sequential binary modeling approach revealed common and distinctive ligand features for inhibitory activity toward the individual transporters. The workflows designed for integrating data from open sources, data curation, and subsequent substructure analyses are freely available and fully adaptable. The new data sets for inhibitors and substrates of hepatic OATPs as well as the insights provided by the feature and substructure analyses will guide future structure-based studies on hepatic OATP–ligand interactions and selectivity.

Coproporphyrins I and III as Functional Markers of OATP1B Activity: In Vitro and In Vivo Evaluation in Preclinical Species

Inhibition of organic anion-transporting polypeptide (OATP)1B function can lead to serious clinical drug-drug interactions, thus a thorough evaluation of the potential for this type of interaction must be completed during drug development. Therefore, sensitive and specific biomarkers for OATP function that could be used in conjunction with clinical studies are currently in demand. In the present study, preclinical evaluations were conducted to characterize the suitability of coproporphyrins (CPs) I and III as markers of hepatic OATP functional activity. Active uptake of CPs I and III was observed in human embryonic kidney (HEK) 293 cells singly expressing human OATP1B1 (hOATP1B1), hOATP1B3, cynomolgus monkey OATP1B1 (cOATP1B1), or cOATP1B3, as well as human and monkey hepatocytes. Cyclosporin A (100 mg/kg, oral) markedly increased the area under the curve (AUC) plasma concentrations of CPs I and III by 2.6- and 5.2-fold, while rifampicin (15 mg/kg, oral) increased the AUCs by 2.7- and 3.6-fold, respectively. As the systemic exposure increased, the excretion of both isomers in urine rose from 1.6- to 4.3-fold in monkeys. In agreement with this finding, the AUC of rosuvastatin (RSV) in cynomolgus monkeys increased when OATP1B inhibitors were coadministered. In Oatp1a/1b gene cluster knockout mice (Oatp1a/1b(-/-)), CPs in plasma and urine were significantly increased compared with wild-type animals (7.1- to 18.4-fold; P < 0.001), which were also in agreement with the changes in plasma RSV exposure (14.6-fold increase). We conclude that CPs I and III in plasma and urine are novel endogenous biomarkers reflecting hepatic OATP function, and the measurements have the potential to be incorporated into the design of early clinical evaluation.

Transmembrane transport of steviol glucuronide and its potential interaction with selected drugs and natural compounds

Steviol glucuronide (SVG) is the major metabolite derived from steviol, the aglycone of stevioside and rebaudioside A. After the ingestion of stevioside and rebaudioside A, SVG is formed and excreted into the urine in humans. In the present study, transporter mediated efflux and uptake of SVG was investigated in order to understand molecular mechanisms underlying its renal clearance. Results showed that SVG was not a substrate of efflux transporters BCRP, MRP2, MATE1 or P-gp. In contrast, OAT3 played a predominant role in the uptake of SVG in comparison to OATP1B1, OATP1B3, or OATP2B1. Quercetin, telmisartan, diclofenac, and mulberrin displayed a relatively strong inhibition against OAT3 mediated uptake of SVG with IC50 values of 1.8, 2.9, 8.0, and 10.0 μM, respectively. Because OAT3 is a major uptake transporter in the kidney, inhibition of OAT3 activity may alter SVG's renal clearance by drugs and natural compounds that are used concomitantly with stevia leaf extracts.