Association between DNA methylation in the miR-328 5'-flanking region and inter-individual differences in miR-328 and BCRP expression in human placenta

Profiling the cell-specific small non-coding RNA transcriptome of the human placenta

The human placenta is the composite of multiple cell types, each which contributes uniquely to placental function. Small non-coding RNAs (sncRNAs) are regulators of gene expression and can be cell-specific. The sncRNA transcriptome of individual placental cell types has not yet been investigated due to difficulties in their procurement and isolation. Using a custom sequencing method, we explored the expression of seven sncRNA species (miRNA, piRNA, rRNA, scaRNA, snRNA, snoRNA, tRNA) from whole chorionic villi and four major sample-matched FACS-sorted cell type (cytotrophoblast, stromal, endothelial, Hofbauer) samples from 9 first trimester and 17 term placentas. After normalization for technical variables, samples clustered primarily by cell type lineage. No sncRNAs were uniquely expressed by cell type, however, mean expression differed by cell type for 115 sncRNAs. Known placentally-expressed sncRNAs showed differing expression by cell type and trimester. Expression of few sncRNAs varied by sex. Lastly, sample-matched sncRNA expression and DNA methylation correlation was not significant, although high correlation (> R 2  ± 0.6) was observed for some sncRNA-CpG pairs. This study represents the first exploration of the sncRNA transcriptome of bulk placental villi and placental cell types, informing about the expression and regulatory patterns underlying human placental development.

The miRNA Landscape in Crohn's disease: Implications for novel therapeutic approaches and interactions with Existing therapies

MicroRNAs (miRNAs), which are non-coding RNAs consisting of 18-24 nucleotides, play a crucial role in the regulatory pathways of inflammatory diseases. Several recent investigations have examined the potential role of miRNAs in forming Crohn's disease (CD). It has been suggested that miRNAs serve as diagnostics for both fibrosis and inflammation in CD due to their involvement in the mechanisms of CD aggravation and fibrogenesis. More information on CD pathophysiology could be obtained by identifying the miRNAs concerned with CD and their target genes. These findings have prompted several in vitro and in vivo investigations into the putative function of miRNAs in CD treatment. Although there are still many unanswered questions, the growing body of evidence has brought miRNA-based therapy one step closer to clinical practice. This extensive narrative study offers a concise summary of the most current advancements in CD. We go over what is known about the diagnostic and therapeutic benefits of miRNA mimicry and inhibition so far, and we see what additional miRNA family targets could be useful for treating CD-related inflammation and fibrosis.

Heterogeneous graph inference with range constrainted L2,1-collaborative matrix factorization for small molecule-miRNA association prediction

MicroRNAs (miRNAs) play a vital role in regulating gene expression and various biological processes. As a result, they have been identified as effective targets for small molecule (SM) drugs in disease treatment. Heterogeneous graph inference stands as a classical approach for predicting SM-miRNA associations, showcasing commendable convergence accuracy and speed. However, most existing methods do not adequately address the inherent sparsity in SM-miRNA association networks, and imprecise SM/miRNA similarity metrics reduce the accuracy of predicting SM-miRNA associations. In this research, we proposed a heterogeneous graph inference with range constrained L2,1-collaborative matrix factorization (HGIRCLMF) method to predict potential SM-miRNA associations. First, we computed the multi-source similarities of SM/miRNA and integrated these similarity information into a comprehensive SM/miRNA similarity. This step improved the accuracy of SM and miRNA similarity, ensuring reliability for the subsequent inference of the heterogeneity map. Second, we used a range constrained L2,1-collaborative matrix factorization (RCLMF) model to pre-populate the SM-miRNA association matrix with missing values. In this step, we developed a novel matrix decomposition method that enhances the robustness and formative nature of SM-miRNA edges between SM networks and miRNA networks. Next, we built a well-established SM-miRNA heterogeneous network utilizing the processed biological information. Finally, HGIRCLMF used this network data to infer unknown association pair scores. We implemented four cross-validation experiments on two distinct datasets, and HGIRCLMF acquired the highest areas under the curve, surpassing six state-of-the-art computational approaches. Furthermore, we performed three case studies to validate the predictive power of our method in practical application.

Restoration of miR-328a-5p function curtails hypoxic pulmonary hypertension through a mechanism involving PIN1/GSK3β/β-catenin axis

Recent evidence has highlighted the involvement of microRNAs (miRs) in hypoxic pulmonary hypertension (PH), which can be induced under hypoxic conditions. We intend to explore whether the miR-328a-5p/PIN1 axis affects hypoxic PH by regulating the GSK3β/β-catenin signaling pathway. The GEO database was retrieved to single out key miRs affecting hypoxic PH. It was observed that downregulation of miR-328a-5p occurred in hypoxia-induced PH samples. The binding affinity between miR-328a-5p to PIN1 was predicted by a bioinformatics tool and verified using a dual luciferase reporter gene assay. Rat primary pulmonary artery smooth muscle cells (PASMCs) were exposed to hypoxia for in vitro cell experiments. miR-328a-5p could target and downregulate PIN1 expression, leading to suppressed GSK3β/β-catenin activation. In addition, GSK3β/β-catenin inactivation curtailed hypoxia-induced vascular inflammatory responses and proliferation and migration in PASMCs in vitro. A hypoxic PH model was established in SD rats to observe the effects of miR-328a-5p on hemodynamic parameters and right heart remodeling. It was demonstrated in vivo that miR-328a-5p downregulated PIN1 expression to suppress GSK3β/β-catenin signaling, thereby reducing the vascular inflammatory response and alleviating disease progression in hypoxia-induced PH rats. The evidence provided by our study highlighted the involvement of miR-328a-5p in the translational suppression of PIN1 and the blockade of the GSK3β/β-catenin signaling pathway, resulting in attenuation of hypoxic PH progression.

Extracellular Vesicles and Cancer Multidrug Resistance: Undesirable Intercellular Messengers?

Cancer multidrug resistance (MDR) is one of the main mechanisms contributing to therapy failure and mortality. Overexpression of drug transporters of the ABC family (ATP-binding cassette) is a major cause of MDR. Extracellular vesicles (EVs) are nanoparticles released by most cells of the organism involved in cell-cell communication. Their cargo mainly comprises, proteins, nucleic acids, and lipids, which are transferred from a donor cell to a target cell and lead to phenotypical changes. In this article, we review the scientific evidence addressing the regulation of ABC transporters by EV-mediated cell-cell communication. MDR transfer from drug-resistant to drug-sensitive cells has been identified in several tumor entities. This was attributed, in some cases, to the direct shuttle of transporter molecules or its coding mRNA between cells. Also, EV-mediated transport of regulatory proteins (e.g., transcription factors) and noncoding RNAs have been indicated to induce MDR. Conversely, the transfer of a drug-sensitive phenotype via EVs has also been reported. Additionally, interactions between non-tumor cells and the tumor cells with an impact on MDR are presented. Finally, we highlight uninvestigated aspects and possible approaches to exploiting this knowledge toward the identification of druggable processes and molecules and, ultimately, the development of novel therapeutic strategies.

Expression profiling of human milk derived exosomal microRNAs and their targets in HIV-1 infected mothers

Despite the use of antiretroviral therapy (ART) in HIV-1 infected mothers approximately 5% of new HIV-1 infections still occur in breastfed infants annually, which warrants for the development of novel strategies to prevent new HIV-1 infections in infants. Human milk (HM) exosomes are highly enriched in microRNAs (miRNAs), which play an important role in neonatal immunity. Furthermore, HM exosomes from healthy donors are known to inhibit HIV-1 infection and transmission; however, the effect of HIV-1 on HM exosomal miRNA signatures remains unknown. In this study, we used nCounter NanoString technology and investigated miRNAs expression profiles in first week postpartum HM exosomes from HIV-1 infected and uninfected control mothers (n = 36). Our results indicated that HIV-1 perturbed the differential expression patterns of 19 miRNAs (13 upregulated and 6 downregulated) in HIV-1 infected women compared to healthy controls. DIANA-miR functional pathway analyses revealed that multiple biological pathways are involved including cell cycle, pathways in cancer, TGF-β signaling, FoxO signaling, fatty acid biosynthesis, p53 signaling and apoptosis. Moreover, the receiver operating characteristics (ROC) curve analyses of miR-630 and miR-378g yielded areas under the ROC curves of 0.82 (95% CI 0.67 to 0.82) and 0.83 (95% CI 0.67 to 0.83), respectively highlighting their potential to serve as biomarkers to identify HIV-1 infection in women. These data may contribute to the development of new therapeutic strategies in prevention of mother-to-child transmission (MTCT) of HIV-1.

Inhibition of miR-328-3p Impairs Cancer Stem Cell Function and Prevents Metastasis in Ovarian Cancer

Cancer stem cells (CSC) play a central role in cancer metastasis and development of drug resistance. miRNA are important in regulating CSC properties and are considered potential therapeutic targets. Here we report that miR-328-3p (miR-328) is significantly upregulated in ovarian CSC. High expression of miR-328 maintained CSC properties by directly targeting DNA damage binding protein 2, which has been shown previously to inhibit ovarian CSC. Reduced activity of ERK signaling in ovarian CSC, mainly due to a low level of reactive oxygen species, contributed to the enhanced expression of miR-328 and maintenance of CSC. Inhibition of miR-328 in mouse orthotopic ovarian xenografts impeded tumor growth and prevented tumor metastasis. In summary, our findings provide a novel mechanism underlying maintenance of the CSC population in ovarian cancer and suggest that targeted inhibition of miR-328 could be exploited for the eradication of CSC and aversion of tumor metastasis in ovarian cancer. SIGNIFICANCE: These findings present inhibition of miR-328 as a novel strategy for efficient elimination of CSC to prevent tumor metastasis and recurrence in patients with epithelial ovarian cancer.

[Epigenetic Regulation of Pharmacokinetic-related Genes in Human Tissues]

The translocation of drugs across biological membranes not only occurs via passive diffusion but also by transporter-mediated processes. Knowledge of tissue-specific drug transporter expression, as well as characterization of substrate drugs of individual transporters, leads to a better understanding of the role of these transporters in the pharmacokinetics of drugs. The ATP-binding cassette transporter family member breast cancer resistance protein (BCRP) is one of the most important intestinal efflux transporters involved in the intestinal absorption or permeability of drugs. A genetic variant in the BCRP, 421C>A, is a useful biomarker for explaining large interindividual differences in the pharmacokinetics of sulfasalazine (SASP), a BCRP substrate. However, large intragenotypic differences remain in spite of the incorporation of this genotype into the pharmacokinetics of SASP. Epigenetic regulation alters gene expression without changing DNA sequences. In epigenetic regulation, microRNAs (miRNAs) appear to be the most extensively investigated due to their important roles in the posttranscriptional regulation of mRNAs. Our study showed that miR-328 negatively regulates BCRP expression in human tissues, and the intestine-derived exosomal miR-328 levels positively correlated with the SASP area under the blood concentration-time curve. These results suggest that circulating intestine-derived exosomal miR-328 in plasma has potential as a possible biomarker for estimating BCRP function in human intestines. A clearer understanding of epigenetic mechanisms regulating the expression of drug transporters will provide insights into novel approaches to individualized drug therapy.

An update on expression and function of P-gp/ABCB1 and BCRP/ABCG2 in the placenta and fetus

INTRODUCTION

P-glycoprotein (P-gp)/ABCB1 and breast cancer resistance protein (BCRP)/ABCG2 are highly expressed in the placenta and fetus throughout gestation and can modulate exposure and toxicity of drugs and xenobiotics to the vulnerable fetus during the sensitive times of growth and development. We aim to provide an update on current knowledge on placental and fetal expressions of the two transporters in different species, and to provide insight on interpreting transporter expression and fetal exposure relative to the concept of fraction of drug transported. Areas covered: Comprehensive literature review through PubMed (primarily from July 2010 to February 2018) on P-gp and BCRP expression and function in the placenta and fetus of primarily human, mouse, rat, and guinea pig. Expert opinion: While there are many commonalities in the expression and function of P-gp and BCRP in the placenta and fetal tissues across species, there are distinct differences in expression levels and temporal changes. Further studies are needed to quantify protein abundance of these transporters and functionally assess their activities at various gestational stages. Combining the knowledge of interspecies differences and the concept of fraction of drug transported, we may better predict the magnitude of impact these transporters have on fetal drug exposure.

Interindividual Regulation of the Breast Cancer Resistance Protein/ABCG2 Transporter in Term Human Placentas

The breast cancer resistance protein (BCRP/ABCG2) is a maternally-facing efflux transporter that regulates the placental disposition of chemicals. Transcription factors and gene variants are important regulatory factors that influence transporter expression. In this study, we sought to identify the genetic and transcriptional mechanisms underlying the interindividual expression of BCRP mRNA and protein across 137 term placentas from uncomplicated pregnancies. Placental expression of BCRP and regulatory transcription factor mRNAs was measured using multiplex-branched DNA analysis. BCRP expression and ABCG2 genotypes were determined using Western blot and Fluidigm Biomark genetic analysis, respectively. Placentas were obtained from a racially and ethnically diverse population, including Caucasian (33%), African American (14%), Asian (14%), Hispanic (15%), and mixed (16%) backgrounds, as well as unknown origins (7%). Between placentas, BCRP mRNA and protein varied up to 47-fold and 14-fold, respectively. In particular, BCRP mRNA correlated significantly with known transcription factor mRNAs, including nuclear factor erythroid 2-related factor 2 and aryl hydrocarbon receptor. Somewhat surprisingly, single-nucleotide polymorphisms (SNPs) in the ABCG2 noncoding regions were not associated with variation in placental BCRP mRNA or protein. Instead, the coding region polymorphism (C421A/Q141K) corresponded with 40%-50% lower BCRP protein in 421C/A and 421A/A placentas compared with wild types (421C/C). Although BCRP protein and mRNA expression weakly correlated (r = 0.25, P = 0.040), this relationship was absent in individuals expressing the C421A variant allele. Study results contribute to our understanding of the interindividual regulation of BCRP expression in term placentas and may help to identify infants at risk for increased fetal exposure to chemicals due to low expression of this efflux protein.

DNA methylation mediated silencing of microRNA-874 is a promising diagnosis and prognostic marker in breast cancer

MicroRNA-874 (miR-874) is downregulated in several human cancers and has been suggested to be a tumor suppressor gene. However, the molecular mechanism of miR-874 downregulation in breast cancer has not been well elucidated. Here we aimed to study the aberrant hyper-methylation of CpG sites with the utility of miR-874 downreregulation in breast cancer and evaluate the clinical function of miR-874 as a prognostic marker. The miR-874 expressions in cells and tissues of two breast cancer lines were measured by real-time PCR. The DNA methylation status of the miR-874 promoter region in 19 pairs of breast cancer and adjacent normal samples was analyzed with Sequenom EpiTYPER MassArray. To evaluate whether miR-874 is a potential prognostic marker in breast cancer, we also explored the clinical long-time follow-up records from The Cancer Genome Atlas (TCGA). We found miR-874 expression was downregulated in 47 pairs of breast cancer tissues. Moreover, univariate and multivariate analysis revealed miR-874 expression may be a prognostic biomarker of overall survival in breast cancer patients. Preconditioning with 5-Aza-CdR in two cell lines elevated miR-874 expressions. The data from Sequenom EpiTYPER MassArray showed that DNA methylation of the promoter region of miR-874 was upregulated and accompanied by decreased miR-874 expression, which was further confirmed by TCGA. After comprehensive considerations, we think miR-874, which might be served as a prognostic biomarker, is mediated by DNA methylation.

Relationship between DNA Methylation in the 5' CpG Island of the SLC47A1 (Multidrug and Toxin Extrusion Protein MATE1) Gene and Interindividual Variability in MATE1 Expression in the Human Liver

Multidrug and toxin extrusion protein 1 (MATE1), which is encoded by solute carrier 47A1 (SLC47A1), mediates the excretion of organic cations into bile and urine. Some genetic variants in human MATE1 altered its transport function in in vitro experiments; however, differences in the pharmacokinetics of substrate drugs cannot be explained by genetic variations in humans. In this study, we investigated whether DNA methylation was involved in interindividual variability in MATE1 expression in the human liver. Approximately 20-fold interindividual variability in MATE1 mRNA expression levels was observed in liver samples and mRNA expression levels negatively correlated with methylation levels of the CpG island in the 27 kb upstream of SLC47A1 DNA demethylation by treatment with 5-aza-2'-deoxycytidine increased MATE1 mRNA expression in MATE1-negative cell lines. The luciferase reporter assay showed that the CpG island increased the transcriptional activity of the SLC47A1 promoter. MATE1 mRNA expression levels were significantly lower in CpG island knockout HepG2 cells than in control cells. These results suggest that the 5' CpG island of SLC47A1 acts as an enhancer for SLC47A1, and DNA methylation in the CpG island plays an important role in interindividual differences in hepatic MATE1 expression.

Down-regulation of the placental BCRP/ABCG2 transporter in response to hypoxia signaling

INTRODUCTION

The BCRP/ABCG2 efflux transporter protects the developing fetus by limiting the transplacental transfer of drugs and chemicals and prevents the apoptosis of trophoblasts. The purpose of this study was to determine whether hypoxia-related signaling alters placental BCRP expression and function in vitro and in human pregnancies.

METHODS

Human BeWo choriocarcinoma cells were treated with the hypoxia mimetic, cobalt chloride (CoCl₂), or 3% oxygen for 24-48 h. Activation of HIF-1α signaling and regulation of BCRP was assessed using qPCR, ELISA, western blotting and a fluorescent substrate transport assay. In addition, healthy term placentas from high altitude pregnancies with chronic hypoxia were assessed for BCRP expression.

RESULTS

CoCl₂ and 3% oxygen increased HIF-1α protein signaling and decreased the mRNA and protein expression of BCRP by 30-75% in BeWo cells. Reduced BCRP expression corresponded with impaired efflux activity during hypoxia as evidenced by accumulation of the substrate Hoechst 33342. A number of transcription factors known to regulate BCRP, including AHR, NRF2 and PPARγ, were also coordinately down-regulated by 3% oxygen in BeWo cells. Moreover, women who gave birth at a high altitude (3100 m) exhibited signs of chronic placental hypoxia, including enhanced protein expression of the HIF-1α target GLUT1, and had reduced BCRP levels in microvillous membranes compared to women at a moderate altitude (1600 m).

DISCUSSION

This study provides novel insight into the regulation of the placental BCRP transporter by hypoxia, which may be important for exposure of the fetus to chemicals during early development and in hypoxia-related pregnancy disorders.

Placental ABC Transporters: Biological Impact and Pharmaceutical Significance

The human placenta fulfills a variety of essential functions during prenatal life. Several ABC transporters are expressed in the human placenta, where they play a role in the transport of endogenous compounds and may protect the fetus from exogenous compounds such as therapeutic agents, drugs of abuse, and other xenobiotics. To date, considerable progress has been made toward understanding ABC transporters in the placenta. Recent studies on the expression and functional activities are discussed. This review discusses the placental expression and functional roles of several members of ABC transporter subfamilies B, C, and G including MDR1/P-glycoprotein, the MRPs, and BCRP, respectively. Since placental ABC transporters modulate fetal exposure to various compounds, an understanding of their functional and regulatory mechanisms will lead to more optimal medication use when necessary in pregnancy.

Circulating intestine-derived exosomal miR-328 in plasma, a possible biomarker for estimating BCRP function in the human intestines

A variant in the breast cancer resistance protein (BCRP) gene, 421C> A is a useful biomarker for describing large inter-individual differences in the pharmacokinetics of sulfasalazine (SASP), a BCRP substrate. However, large intra-genotypic variability still exists in spite of the incorporation of this variant into the pharmacokinetics of SASP. Since miR-328 negatively regulates BCRP expression in human tissues, we hypothesized that exosomal miR-328 in plasma, which leaks from the intestines, is a possible biomarker for estimating BCRP activity in the human intestines. We established an immunoprecipitation-based quantitative method for circulating intestine-derived miR-328 in plasma using an anti-glycoprotein A33 antibody. A clinical study was conducted with an open-label, non-randomized, and single-arm design involving 33 healthy participants. Intestine-derived exosomal miR-328 levels positively correlated (P < 0.05) with SASP AUC_0-48, suggesting that subjects with high miR-328 levels have low intestinal BCRP activity, resulting in the high AUC of SASP. Circulating intestine-derived exosomal miR-328 in plasma has potential as a possible biomarker for estimating BCRP function in the human intestines.

MiR-328 targeting PIM-1 inhibits proliferation and migration of pulmonary arterial smooth muscle cells in PDGFBB signaling pathway

MicroRNAs (miRNAs) have been recognized to mediate PDGF-induced cell dysregulation, but their exact functions remain to be elucidated. By using a sensitive S-Poly(T) Plus qRT-PCR method, the expression profiling of 1,078 miRNAs were investigated in pulmonary artery smooth muscle cells (PASMCs) with or without PDGFBB stimulation. MiR-328 was found as a prominent down-regulated miRNA, displaying a specific dose- and time-dependent downregulation upon PDGFBB exposure. Functional analyses revealed that miR-328 could inhibit PASMCs proliferation and migration both with and without PDGFBB treatment. The Ser/Thr-protein kinase-1 (PIM-1) was identified as a direct target of miR-328, and functionally confirmed by a rescue experiment. In addition, the decrease of miR-328 by PDGFBB might be due to the increased expression of DNA methylation transferase 1 (DNMT1) and DNA methylation. Finally, serum miR-328 level was downregulated in PAH patients associated with congenital heart disease (CHD- PAH). Overall, this study provides critical insight into fundamental regulatory mechanism of miR-328 in PDGFBB-activited PASMCs via targeting PIM- 1, and implies the potential of serum miR-328 level as a circulating biomarker for CHD- PAH diagnosis.

Mammalian drug efflux transporters of the ATP binding cassette (ABC) family in multidrug resistance: A review of the past decade

Multidrug resistance (MDR) is a serious phenomenon employed by cancer cells which hampers the success of cancer pharmacotherapy. One of the common mechanisms of MDR is the overexpression of ATP-binding cassette (ABC) efflux transporters in cancer cells such as P-glycoprotein (P-gp/ABCB1), multidrug resistance-associated protein 2 (MRP2/ABCC2), and breast cancer resistance protein (BCRP/ABCG2) that limits the prolonged and effective use of chemotherapeutic drugs. Researchers have found that developing inhibitors of ABC efflux transporters as chemosensitizers could overcome MDR. But the clinical trials have shown that most of these chemosensitizers are merely toxic and only show limited or no benefits to cancer patients, thus new inhibitors are being explored. Recent findings also suggest that efflux pumps of the ABC transporter family are subject to epigenetic gene regulation. In this review, we summarize recent findings of the role of ABC efflux transporters in MDR.

Involvement of miRNAs in placental alterations mediated by oxidative stress

Oxidative stress (OS) is known to be strongly involved in a large number of fetal, neonatal, and adult diseases, including placental disorders, leading to pregnancy loss and stillbirths. A growing body of research links OS to preeclampsia, gestational diabetes, obesity, spontaneous abortion, recurrent pregnancy, preterm labor, and intrauterine growth restriction. While a considerable number of miRNAs have been related to physiological functions and pathological conditions of the placenta, a direct link among these miRNAs, placental functions, and OS is still lacking. This review summarizes data describing the role of miRNAs in placental pathophysiological processes and their possible impact on OS damaging responses. As miRNAs can be found in circulation, improving our understanding on their role in the pathogenesis of pregnancy related disorders could have an important impact on the diagnosis and prognosis of these diseases.

MicroRNAs as regulators of drug transporters, drug-metabolizing enzymes, and tight junctions: implication for intestinal barrier function

Drug transporters, drug-metabolizing enzymes, and tight junctions in the small intestine function as an absorption barrier and sometimes as a facilitator of orally administered drugs. The expression of these proteins often fluctuates and thereby causes individual pharmacokinetic variability. MicroRNAs (miRNAs), which are small non-coding RNAs, have recently emerged as a new class of gene regulator. MiRNAs post-transcriptionally regulate gene expression by binding to target mRNA to suppress its translation or regulate its degradation. They have been shown to be key regulators of proteins associated with pharmacokinetics. Moreover, the role of miRNAs on the expression of some proteins expressed in the small intestine has recently been clarified. In this review, we summarize current knowledge regarding the role of miRNAs in the regulation of drug transporters, drug-metabolizing enzymes, and tight junctions as well as its implication for intestinal barrier function. MiRNAs play vital roles in the differentiation, architecture, and barrier function of intestinal epithelial cells, and directly and/or indirectly regulate the expression and function of proteins associated with drug absorption in intestinal epithelial cells. Moreover, the variation of miRNA expression caused by pathological and physiological conditions as well as genetic factors should affect the expression of these proteins. Therefore, miRNAs could be significant factors affecting inter- and intra-individual variations in the pharmacokinetics and intestinal absorption of drugs. Overall, miRNAs could be promising targets for personalized pharmacotherapy or other attractive therapies through intestinal absorption of drugs.