Strategies and Mechanism in Reversing Intestinal Drug Efflux in Oral Drug Delivery

Human organotypic colon in vitro microtissue: unveiling a new window into colonic drug disposition

The purpose of this study was to evaluate EpiColon, a novel human organotypic 3D colon microtissue prototype, developed to assess colonic drug disposition, with a particular focus on permeability ranking, and compare its performance to Caco-2 monolayers. EpiColon was characterized for barrier function using transepithelial electrical resistance (TEER), morphology via histology and immunohistochemistry, and functionality through drug transport studies measuring apparent permeability (Papp). Cutoff thresholds for the permeability of FITC-dextran 4 kDa (FD4), FITC-dextran 10 kDa (FD10S), and [14C]mannitol were established to monitor microtissue integrity. Permeability of EpiColon for 20 benchmark drugs was compared with Caco-2 data, and the activity of pivotal efflux transporters, including multidrug resistance protein 1/P-glycoprotein (MDR1/P-gp), along with multidrug resistance protein 2 (MRP2) and breast cancer resistance protein (BCRP), was evaluated using selective substrates. EpiColon exhibited a physiological barrier function (272.0 ± 53.05 Ω x cm2) and effectively discriminated between high (e.g., budesonide and [3H]metoprolol) and low permeable compounds (e.g., [3H]atenolol and [14C]mannitol). The model demonstrated functional activity for key efflux transporters, with efflux ratios of 2.32 for [3H]digoxin (MDR1/P-gp) and 3.34 for sulfasalazine (MRP2 and BCRP). Notably, EpiColon showed an enhanced dynamic range in the low permeability range, differentiating Papp between FD4 and FD10S, in contrast to Caco-2 monolayers. Significant positive correlations were observed between human fraction absorbed (fabs) and logarithmically transformed Papp [AP-BL] values for both EpiColon (rs = 0.68) and Caco-2 (rs = 0.68). Furthermore, EpiColon recapitulates some essential phenotypic and cellular features of the human colon, including the expression of critical marker genes (Pan-Cytokeratin+: epithelial/colonocytes, Vimentin+: mesenchymal/fibroblast, and Alcian Blue+: goblet cell/mucus). In conclusion, EpiColon is a promising platform that offers a valuable complement to conventional Caco-2 monolayers for studying colonic drug disposition. However, the presence of flat and some cuboidal cells, along with low throughput, must be addressed to improve its applicability in both academic research and pharmaceutical industry.

The role of ABCG2 in health and disease: Linking cancer therapy resistance and other disorders

All biological systems have adenosine triphosphate (ATP) binding cassette (ABC) transporters, one of the significant protein superfamilies involved in transport across membranes. ABC transporters have been implicated in the etiology of diseases like metabolic disorders, cancer, and Alzheimer's disease. ATP-binding cassette superfamily G member 2 (ABCG2), one of the ABC transporters, is necessary for the ATP-dependent efflux of several endogenous and exogenous substances. Consequently, it maintained cellular homeostasis and shielded tissue from xenobiotic substances. ABCG2 was initially identified in an Adriamycin-selected breast cancer cell line (MCF-7/AdrVp) and was linked to the emergence of multidrug resistance (MDR) in cancerous cells. Under many pathophysiological conditions, including inflammation, disease pathology, tissue injury, infection, and in response to xenobiotics and endogenous substances, the expression of ABCG2 undergoes alterations that result in modifications in its function and activity. Genetic variants in the ABCG2 transporter can potentially impact its expression and function, contributing to the development of many disorders. This review aimed to illustrate the impact of ABCG2 expression and its variants on oral drug bioavailability, MDR in specific cancer cells, explore the relationship between ABCG2 expression and other disorders such as gout, Alzheimer's disease, epilepsy, and erythropoietic protoporphyria, and demonstrate the influence of various synthetic and natural compounds in regulating ABCG2 expression.

Human enteroid monolayers as a potential alternative for Ussing chamber and Caco-2 monolayers to study passive permeability and drug efflux

After oral administration, the intestine is the first site of drug absorption, making it a key determinant of the bioavailability of a drug, and hence drug efficacy and safety. Existing non-clinical models of the intestinal barrier in vitro often fail to mimic the barrier and absorption of the human intestine. We explore if human enteroid monolayers are a suitable tool for intestinal absorption studies compared to primary tissue (Ussing chamber) and Caco-2 cells. Bidirectional drug transport was determined in enteroid monolayers, fresh tissue (Ussing chamber methodology) and Caco-2 cells. Apparent permeability (Papp) and efflux ratios for enalaprilat (paracellular), propranolol (transcellular), talinolol (P-glycoprotein (P-gp)) and rosuvastatin (Breast cancer resistance protein (BCRP)) were determined and compared between all three methodologies and across intestinal regions. Bulk RNA sequencing was performed to compare gene expression between enteroid monolayers and primary tissue. All three models showed functional efflux transport by P-gp and BCRP with higher basolateral to apical (B-to-A) transport compared to apical-to-basolateral (A-to-B). B-to-A Papp values were similar for talinolol and rosuvastatin in tissue and enteroids. Paracellular transport of enalaprilat was lower and transcellular transport of propranolol was higher in enteroids compared to tissue. Enteroids appeared show more region- specific gene expression compared to tissue. Fresh tissue and enteroid monolayers both show active efflux by P-gp and BCRP in jejunum and ileum. Hence, the use of enteroid monolayers represents a promising and versatile experimental platform to complement current in vitro models.

Nanomedicine: Patuletin-conjugated with zinc oxide exhibit potent effects against Gram-negative and Gram-positive bacterial pathogens

With the emergence of drug-resistance, there is a need for novel anti-bacterials or to enhance the efficacy of existing drugs. In this study, Patuletin (PA), a flavanoid was loaded onto Gallic acid modified Zinc oxide nanoparticles (PA-GA-ZnO), and evaluated for antibacterial properties against Gram-positive (Bacillus cereus and Streptococcus pneumoniae) and Gram-negative (Samonella enterica and Escherichia coli) bacteria. Characterization of PA, GA-ZnO and PA-GA-ZnO' nanoparticles was accomplished utilizing fourier-transform infrared spectroscopy, efficiency of drug entrapment, polydispersity index, zeta potential, size, and surface morphology analysis through atomic force microscopy. Using bactericidal assays, the results revealed that ZnO conjugation displayed remarkable effects and enhanced Patuletin's effects against both Gram-positive and Gram-negative bacteria, with the minimum inhibitory concentration observed at micromolar concentrations. Cytopathogenicity assays exhibited that the drug-nanoconjugates reduced bacterial-mediated human cell death with minimal side effects to human cells. When tested alone, drug-nanoconjugates tested in this study showed limited toxic effects against human cells in vitro. These are promising findings, but future work is needed to understand the molecular mechanisms of effects of drug-nanoconjugates against bacterial pathogens, in addition to in vivo testing to determine their translational value. This study suggests that Patuletin-loaded nano-formulation (PA-GA-ZnO) may be implicated in a multi-target mechanism that affects both Gram-positive and Gram-negative pathogen cell structures, however this needs to be ascertained in future work.

Pharmacokinetics and pharmacodynamics of cyclodextrin-based oral drug delivery formulations for disease therapy

Oral drug administration has become the most common and preferred mode of disease treatment due to its good medication adherence and convenience. For orally administered drugs, the safety, efficacy, and targeting ability requirements have grown as disease treatment research advances. It is difficult to obtain prominent efficacy of traditional drugs simply via oral administration. Numerous studies have demonstrated that cyclodextrins (CDs) can improve the clinical applications of certain orally administered drugs by enhancing their water solubility and masking undesirable odors. Additionally, deeper studies have discovered that CDs can influence disease treatment by altering the drug pharmacokinetics (PK) or pharmacodynamics (PD). This review highlights recent research progress on the PK and PD effects of CD-based oral drug delivery in disease therapy. Firstly, the review describes the characteristics of current drug delivery modes in oral administration. Besides, we minutely summarized the different CD-containing drugs, focusing on the impact of CD-based alterations in PK or PD of orally administered drugs in treating diseases. Finally, we deeply discussed current challenges and future opportunities with regard to PK and PD of CD-based oral drug delivery formulations.

Inhibition of P-glycoprotein-mediated efflux by thiolated cyclodextrins

Overcoming P-glycoprotein (P-gp)-mediated efflux poses a significant challenge for the pharmaceutical industry. This study investigates the potential of thiolated β-cyclodextrins (β-CD-SHs) as inhibitors of P-gp-mediated efflux in Caco-2 cells. Through a series of transport assays, intracellular accumulation, and efflux of the P-gp substrates Rhodamine 123 (Rh123) and Calcein-AM with and without co-administration of β-CD-SHs were assessed. The results revealed that the cellular uptake of Rh123 and Calcein-AM were enhanced up to 7- and 3-fold, compared to the control, respectively. In efflux studies an up to 2.5-fold reduction of the Rh123 efflux was reached compared the control, indicating a substantial decrease of Rh123 efflux by β-CD-SHs. Furthermore, it was observed that β-CD-SHs led to a decrease in the reactivity of fluorescence-labeled anti-P-gp, suggesting additional effects on the conformation of P-gp. Overall, this study demonstrates the potential of β-CD-SHs as effective modulator of P-gp-mediated drug efflux in Caco-2 cells.

Screening of anti-functional dyspepsia compounds in Cynanchum auriculatum: A spectrum-effect relationship analysis, and ATP-binding cassette transporters inhibitor evaluation

ETHNOPHARMACOLOGICAL RELEVANCE

Functional dyspepsia (FD) is a disorder caused by abnormal gut-brain axis regulation and is highly prevalent in China. Cynanchum auriculatum (CA) is often used to treat FD in the ethnic minority areas of Guizhou. Although several CA-based products are currently available in the market, it is unclear which components of CA are efficacious and what their oral absorption mechanism is.

AIM OF THE STUDY

This study aimed to screen anti-FD components of CA based on the spectrum-effect relationship. In addition, the study evaluated the intestinal absorption mechanism of these components using transporter inhibitors.

MATERIALS AND METHODS

The fingerprinting of compounds from CA extract and plasma after oral administration was conducted using ultra-high-performance liquid chromatography quadrupole-time-of-flight tandem mass spectrometry (UHPLC-Q-TOF-MS). The intestinal contractile parameters were then measured in vitro using the BL-420F Biofunctional Experiment System. Multivariate statistical analysis of the result of spectrum-effect relationship assessment was used to elucidate the correlation between prominent peaks of CA-containing plasma and intestinal contractile activity. The effect of ATP-binding cassette (ABC) transporter inhibitors, such as the P-gp inhibitor verapamil, the MRR inhibitor indomethacin, and the BCRP inhibitor Ko143, on the directional transport of the predicted active ingredients was assessed in vivo.

RESULTS

Twenty chromatographic peaks were identified in the CA extract. Of these, three were C21 steroids, four were organic acids, and one was a coumarin, and acetophenone by comparing with reference compounds. Additionally, it is discovered that there are totally 39 migratory components in CA-containing plasma, which was found to significantly promote the contractility of the isolated duodenum. Moreover, multivariate analysis of the spectrum-effect relationship demonstrated that 16 characteristic peaks (3, 6, 8, 10, 11, 13, 14, 18, 21, m1-m4, m7, m15, and m24) in CA-containing plasma were significantly associated with the anti-FD effect. These compounds included seven prototype compounds, i.e., cynanoneside A, syringic acid, deacylmetaplexigenin, ferulic acid, scopoletin, baishouwubenzophenone, and qingyangshengenin. The inhibition of ABC transporters demonstrated that the inhibitors verapamil and Ko143 significantly increased (P < 0.05) the uptake of scopoletin and qingyangshengenin. Thus, these compounds may be substrates for P-gp and BCRP.

CONCLUSIONS

The potential anti-FD components of CA and the effect of ABC transporter inhibitors on these active components were preliminarily clarified. These findings lay a foundation for subsequent in vivo studies.

Tigecycline Absorption Improved by Selected Excipients

To investigate the effects of (2,6-di-O-methyl)-β-cyclodextrin (DM-β-CD), (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD), tocopherol polyethylene glycol 1000 succinate (TPGS), sodium desoxycholate (SDOCH), trimethyl chitosan (TMC), and sodium caprate (C10) on the plasma concentration and the oral bioavailability of tigecycline in broiler chickens. To test the effects of the excipients on absorption of tigecycline, a tetracycline that is poorly absorbed from the gastrointestinal tract, broiler chickens were used as an animal model. Tigecycline (10 mg/kg body weight) was administered intravenously, orally, and orally with one of the excipients. Plasma samples were taken after administration. To measure tigecycline concentrations, high-performance liquid chromatography coupled with tandem mass spectrometry was used. Compartmental and non-compartmental analyses were used for pharmacokinetic analyses of mean plasma concentrations versus time. With the exception of sodium caprate, all the excipients significantly increased the area under the curve and bioavailability of tigecycline (p < 0.05). These parameters were approximately doubled by HP-β-CD, TPGS, and SDOCH, with 95% confidence intervals (95% CIs) for the difference that included only increases of 1.5-fold or higher (bioavailability: control, 1.67%; HP-β-CD, 3.24%; TPGS, 3.30%; and SDOCH, 3.24%). The increases in these parameters were smaller with DM-β-CD and TMC (DM-β-CD, 2.41%; TMC, 2.55%), and the 95% CIs ranged from close to no difference to nearly double the values in the control group. These results indicate that HP-β-CD, TPGS, and SDOCH substantially increase the area under the curve and oral bioavailability of tigecycline. They suggest that DM-β-CD and TMC may also substantially increase these parameters, but more research is needed for more precise estimates of their effects.

Impact of nanotechnology on the oral delivery of phyto-bioactive compounds

Nanotechnology is an advanced field that has remarkable nutraceutical and food applications. Phyto-bioactive compounds (PBCs) play critical roles in promoting health and disease treatment. However, PBCs generally encounter several limitations that delay their widespread application. For example, most PBCs have low aqueous solubility, poor biostability, poor bioavailability, and a lack of target specificity. Moreover, the high concentrations of effective PBC doses also limit their application. As a result, encapsulating PBCs into an appropriate nanocarrier may increase their solubility and biostability and protect them from premature degradation. Moreover, nanoencapsulation could improve absorption and prolong circulation with a high opportunity for targeted delivery that may decrease unwanted toxicity. This review addresses the main parameters, variables, and barriers that control and affect oral PBC delivery. Moreover, this review discusses the potential role of biocompatible and biodegradable nanocarriers in improving the water solubility, chemical stability, bioavailability, and specificity/selectivity of PBCs.