Post-transcriptional regulation of OATP2B1 transporter by a microRNA, miR-24

A Comprehensive Review of Membrane Transporters and MicroRNA Regulation in Alzheimer's Disease

Alzheimer's disease (AD) is a distressing neurodegenerative condition characterized by the accumulation of amyloid-beta (Aβ) plaques and tau tangles within the brain. The interconnectedness between membrane transporters (SLCs) and microRNAs (miRNAs) in AD pathogenesis has gained increasing attention. This review explores the localization, substrates, and functions of SLC transporters in the brain, emphasizing the roles of transporters for glutamate, glucose, nucleosides, and other essential compounds. The examination delves into the significance of SLCs in AD, their potential for drug development, and the intricate realm of miRNAs, encompassing their transcription, processing, functions, and regulation. MiRNAs have emerged as significant players in AD, including those associated with mitochondria and synapses. Furthermore, this review discusses the intriguing nexus of miRNAs targeting SLC transporters and their potential as therapeutic targets in AD. Finally, the review underscores the interaction between SLC transporters and miRNA regulation within the context of Alzheimer's disease, underscoring the need for further research in this area. This comprehensive review aims to shed light on the complex mechanisms underlying the causation of AD and provides insights into potential therapeutic approaches.

Organic anion transporting polypeptide 3a1 is a novel influx pump for Perfluorooctane sulfonate in Sertoli cells and contributes to its reproductive toxicity

Persistent organic pollutant perfluorooctane sulfonate (PFOS) is strongly associated with male reproductive disorders, but the related mechanisms are still not fully understood. In this study, we used in vivo and in vitro models to explore the role of organic anion transporting polypeptide 3a1 (Oatp3a1) on PFOS-induced male reproductive injury. Thirty male C57BL/6 (B6) mice were orally given PFOS (0-10 mg/kg/bw) for 28 days. Body weight, organ index, sperm count, histology, and blood-testis barrier (BTB) integrity were evaluated. Primary Sertoli cells were used to describe the related molecular mechanisms of male reproductive injury caused by PFOS. Our results showed that PFOS induced a decrease in sperm count, morphological damage to testicular Sertoli cells, and disruption of BTB. In the in vitro model, exposure to PFOS significantly increased Oatp3a1 mRNA and protein levels and decreased miR-23a-3p expression in Sertoli cells, accompanied by reduced trans-epithelial electrical resistance (TEER) value. By performing the 14C-PFOS uptake experiment, we showed that 14C-PFOS uptake in HEK293-Oatp3a1 cells was apparently higher than in HEK293-MOCK cells. Meanwhile, treating Sertoli cells with Oatp3a1 siRNA significantly decreased Oatp3a1 expression and rescued PFOS-induced decreases in TEER value. As such, the present study highlights that Oatp3a1 may play an important role in the toxic effect of PFOS on Sertoli cells, advancing our understanding of molecular mechanisms for PFOS-induced male reproductive disorders.

Apple-derived extracellular vesicles modulate the expression of human intestinal bile acid transporter ASBT/SLC10A2 via downregulation of transcription factor RARα

PURPOSE

Plant-derived extracellular vesicles (EVs) have been reported to exert biological activity on intestinal tissues by delivering their contents into intestinal cells. We previously reported that ASBT/SLC10A2 mRNA was downregulated by apple-derived extracellular vesicles (APEVs). ASBT downregulation is effective in the treatment of cholestasis and chronic constipation, similar to the beneficial effects of apples. Therefore, this study aimed to establish the mechanism of ASBT downregulation by APEVs, focusing on microRNAs present in APEVs.

RESULTS

APEVs downregulated the expression of ASBT, but no significant effect on SLC10A2-3'UTR was observed. Proteomics revealed that APEVs decreased the expression of RARα/NR1B1. The binding of RARα to SLC10A2 promoter was also decreased by APEVs. The stability of NR1B1 mRNA was attenuated by APEVs and its 3'UTR was found to be a target for APEVs. Apple microRNAs that were predicted to interact with NR1B1-3'UTR were present in APEVs, and their mimics suppressed NR1B1 mRNA expression.

CONCLUSIONS

Suppression of ASBT by APEVs was indirectly mediated by the downregulation of RARα, and its stability was lowered by microRNAs present in APEVs. This study suggested that macromolecules in food directly affect intestinal function by means of EVs that stabilize them and facilitate their cellular uptake.

Recent Advances in Novel Recombinant RNAs for Studying Post-transcriptional Gene Regulation in Drug Metabolism and Disposition

Drug-metabolizing enzymes and transporters are major determinants of the absorption, disposition, metabolism, and excretion (ADME) of drugs, and changes in ADME gene expression or function may alter the pharmacokinetics/ pharmacodynamics (PK/PD) and further influence drug safety and therapeutic outcomes. ADME gene functions are controlled by diverse factors, such as genetic polymorphism, transcriptional regulation, and coadministered medications. MicroRNAs (miRNAs) are a superfamily of regulatory small noncoding RNAs that are transcribed from the genome to regulate target gene expression at the post-transcriptional level. The roles of miRNAs in controlling ADME gene expression have been demonstrated, and such miRNAs may consequently influence cellular drug metabolism and disposition capacity. Several types of miRNA mimics and small interfering RNA (siRNA) reagents have been developed and widely used for ADME research. In this review article, we first provide a brief introduction to the mechanistic actions of miRNAs in post-transcriptional gene regulation of drug-metabolizing enzymes, transporters, and transcription factors. After summarizing conventional small RNA production methods, we highlight the latest advances in novel recombinant RNA technologies and applications of the resultant bioengineered RNA (BioRNA) agents to ADME studies. BioRNAs produced in living cells are not only powerful tools for general biological and biomedical research but also potential therapeutic agents amenable to clinical investigations.

Regulation of Drug Transport Proteins-From Mechanisms to Clinical Impact: A White Paper on Behalf of the International Transporter Consortium

Membrane transport proteins are involved in the absorption, disposition, efficacy, and/or toxicity of many drugs. Numerous mechanisms (e.g., nuclear receptors, epigenetic gene regulation, microRNAs, alternative splicing, post‐translational modifications, and trafficking) regulate transport protein levels, localization, and function. Various factors associated with disease, medications, and dietary constituents, for example, may alter the regulation and activity of transport proteins in the intestine, liver, kidneys, brain, lungs, placenta, and other important sites, such as tumor tissue. This white paper reviews key mechanisms and regulatory factors that alter the function of clinically relevant transport proteins involved in drug disposition. Current considerations with in vitro and in vivo models that are used to investigate transporter regulation are discussed, including strengths, limitations, and the inherent challenges in predicting the impact of changes due to regulation of one transporter on compensatory pathways and overall drug disposition. In addition, translation and scaling of in vitro observations to in vivo outcomes are considered. The importance of incorporating altered transporter regulation in modeling and simulation approaches to predict the clinical impact on drug disposition is also discussed. Regulation of transporters is highly complex and, therefore, identification of knowledge gaps will aid in directing future research to expand our understanding of clinically relevant molecular mechanisms of transporter regulation. This information is critical to the development of tools and approaches to improve therapeutic outcomes by predicting more accurately the impact of regulation‐mediated changes in transporter function on drug disposition and response.

Vitamin D Deficiency Impacts Exposure and Response of Pravastatin in Male Rats by Altering Hepatic OATPs

This study aimed to determine the effect of vitamin D (VD) deficiency on the efficacy and pharmacokinetics of pravastatin and clarify whether the effects are mediated by Organic anion-transporting polypeptides (OATPs). Experiments were conducted in rats to explore the effect of VD deficiency on the pharmacodynamics and pharmacokinetics of pravastatin. In the pharmacodynamic study, rats were fed a VD-free or VD-supplement high-fat diet for 25–30 days, and plasma 25(OH)VD was dynamically monitored. The response of pravastatin (changes in blood lipids) on rats were then examined after 15 days of pravastatin treatment. In the pharmacokinetic study, rats were fed a VD-free or VD-supplement diet for 25–30 days. The pharmacokinetics of single oral dose pravastatin was then studied, and intestinal and hepatic Oatp1a1 and Oatp2b1 expression was determined using quantitative polymerase chain reaction (qPCR) and western blot. Furthermore, OATP1B1 and OATP2B1 expression in Huh7 cells with or without 1.25(OH)₂D were assessed via qPCR and western blot. For the pharmacodynamic study, the decrease of total cholesterol and increase of high-density lipoprotein cholesterol in VD-deficient rats were smaller than in VD-sufficient rats, indicating that VD deficiency reduced the response of pravastatin in rats. For the pharmacokinetic study, the plasma exposure slightly increased, and liver exposure decreased in VD-deficient rats, but not significantly. VD deficiency decreased the Oatp1a1 and Oatp2b1 expression in the liver, but not in the small intestine. Similarly, OATP1B1 and OATP2B1 protein levels in Huh7 cells were reduced when 1.25(OH)₂D was absent. In conclusion, VD deficiency can decrease the response of pravastatin in rats by reducing the liver pravastatin exposure and expression of hepatic OATPs, consistent with the extended hepatic clearance model theory.

MicroRNAs in Apple-Derived Nanoparticles Modulate Intestinal Expression of Organic Anion-Transporting Peptide 2B1/SLCO2B1 in Caco-2 Cells

Plant-derived nanoparticles exert cytoprotective effects on intestinal cells by delivering their cargo to intestinal tissues. We previously reported that apple-derived nanoparticles (APNPs) downregulate the mRNA of the human intestinal transporter organic anion-transporting peptide 2B1 (OATP2B1)/SLCO2B1 and that the 3'-untranslated region (3'UTR) is required for the response to APNPs. Here, we investigated the involvement of microRNAs (miRNAs) in APNPs in suppressing OATP2B1 expression to demonstrate that APNP macromolecules directly interact with intestinal tissues. Using in silico analysis, seven apple miRNAs were predicted as candidate miRNAs that interact with the SLCO2B1-3'UTR. The APNP-mediated decrease in luciferase activity of pGL3/SLCO2B1-3'UTR was abrogated by inhibitors of mdm-miR-160a-e, -7121a-c, or -7121d-h. Each miRNA mimic reduced the endogenous expression of SLCO2B1 mRNA in Caco-2 cells. The luciferase activity of the truncated pGL3/SLCO2B1-3'UTR, which contains approximately 200 bp around each miRNA recognition element (MRE), was decreased by the miR-7121d-h mimic but decreased little by the other mimics. APNP also reduced the luciferase activity of truncated pGL3/SLCO2B1-3'UTR containing an MRE for miR-7121d-h. Thus, we demonstrated that mdm-miR-7121d-h contributes to the APNP-mediated downregulation of intestinal OATP2B1. Accordingly, plant macromolecules, such as miRNAs, may directly interact with intestinal tissues via nanoparticles. SIGNIFICANCE STATEMENT: This study demonstrates that mdm-miR7121d-h contained in apple-derived nanoparticles downregulated the mRNA expression of SLCO2B1 by interacting with SLCO2B1-3'-untranslated region directly and that SLCO2B1 mRNA might also be decreased by mdm-miR160a-e and -7121a-c indirectly. This finding that the specific apple-derived microRNAs influence human intestinal transporters provides a novel concept that macromolecules in foods directly interact with and affect the intestinal function of the host.