Lipoic acid-mediated oral drug delivery system utilizing changes on cell surface thiol expression for the treatment of diabetes and inflammatory diseases.

Lipoic acid (LA), which has good safety and oral absorption, is obtained from various plant-based food sources and needs to be supplemented through human diet. Moreover, substances with a disulfide structure can enter cells through dynamic covalent disulfide exchange with thiol groups on the cell membrane surface. Based on these factors, we constructed LA-modified nanoparticles (LA NPs). Our results showed that LA NPs can be internalized into intestinal epithelial cells through surface thiols, followed by intracellular transcytosis via the endoplasmic reticulum-Golgi pathway. Further mechanistic studies indicated that disulfide bonds within the structure of LA play a critical role in this transport process. In a type I diabetes rat model, the oral administration of insulin-loaded LA NPs exhibited a more potent hypoglycemic effect, with a pharmacokinetic bioavailability of 5.42 ± 0.53%, representing a 1.6 fold enhancement compared to unmodified PEG NPs. Furthermore, a significant upregulation of surface thiols in inflammatory macrophages was reported. Thus, we turned our direction to investigate the uptake behavior of inflammatory macrophages with increased surface thiols towards LA NPs. Inflammatory macrophages showed a 2.6 fold increased uptake of LA NPs compared to non-inflammatory macrophages. Surprisingly, we also discovered that the antioxidant resveratrol facilitates the uptake of LA NPs in a concentration-dependent manner. This is mainly attributed to an increase in glutathione, which is involved in thiol uptake. Consequently, we employed LA NPs loaded with resveratrol for the treatment of colitis and observed a significant alleviation of colitis symptoms. These results suggest that leveraging the variations of thiol expression levels on cell surfaces under both healthy and diseased states through an oral drug delivery system mediated by the small-molecule nutrient LA can be employed for the treatment of diabetes and certain inflammatory diseases.

CENPA functions as a transcriptional regulator to promote hepatocellular carcinoma progression via cooperating with YY1.

The centromere proteins (CENPs), a critical mitosis-related protein complexes, are involved in the kinetochore assembly and chromosome segregation. In this study, we identified that CENPA was significantly up-regulated in HCC and highly expressed CENPA correlated with poor prognosis for HCC patients. Knockdown of CENPA inhibited HCC cell proliferation and tumor growth in vitro and in vivo. Mechanistically, CENPA transcriptionally activated and cooperated with YY1 to drive the expression of cyclin D1 (CCND1) and neuropilin 2 (NRP2). Moreover, we identified that CENPA can be lactylated at lysine 124 (K124). The lactylation of CENPA at K124 promotes CENPA activation, leading to enhanced expression of its target genes. In summary, CENPA function as a transcriptional regulator to promote HCC via cooperating with YY1. Targeting the CENPA-YY1-CCND1/NRP2 axis may provide candidate therapeutic targets for HCC.

Qiangguyin inhibited fat accumulation in OVX mice through the p38 MAPK signaling pathway to achieve anti-osteoporosis effects.

Postmenopausal osteoporosis (PMOP) is a common bone disease characterized by decreased bone density and increased bone fragility due to decreased estrogen levels. Qiangguyin (QGY) is transformed from the famous traditional Chinese medicine BuShen Invigorating Blood Decoction. In this study, we used QGY to treat PMOP. We observed that QGY significantly reduced fat accumulation in the chondro-osseous junction. However, its specific mechanism of action remains unclear. To determine the specific molecular mechanism of QGY, we explored the pharmacological mechanism by which QGY reduces fat accumulation in the chondro-osseous junction through network pharmacological analysis. The active components and targets related to PMOP and QGY were screened from different databases, forming a composition-target-disease network. Next, a comprehensive analysis platform including protein-protein interaction (PPI) network, Gene Ontology (GO) enrichment analysis, and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were established. The results revealed that QGY inhibits adipogenic differentiation by activating the mitogen-activated protein kinase (MAPK) signaling pathway, thus reducing the accumulation of fat in the chondro-osseous junction. For further verification. In vitro and in vivo experiments were carried out. Our data showed that QGY significantly reversed the high expression of fatty acid binding protein 4 (FABP4) and peroxisome proliferator-activated receptor γ (PPARγ). Further, QGY prevents fat accumulation by inhibiting the expression of p38. In summary, the results of this study suggested that QGY-induced phenotypic changes are related to the activation of the p38 MAPK signaling pathway.

Chitosan-based microneedle arrays for dermal delivery of Centella asiatica.

Centella asiatica, a medicinal herb used for wound healing, has a limited effect when delivered as an ointment. Centella asiatica's active component asiatic acid (AA) increases extracellular matrix development and reduces inflammation but cannot penetrate the stratum corneum to access deeper skin layers. To bypass the stratum corneum, we formulated two types of AA-loaded microneedle arrays. We fabricated, characterised and optimised a dissolving array made from chitosan and PVA and a hydrogel array made from chitosan and PVP. Both needles were strong and long enough to pierce the epidermis without breaking. Both were biocompatible with keratinocytes and fibroblasts (>75% viability at 100% concentration) and showed a sustained drug release over 48 h. The hydrogel microneedle released more AA (52.2%) than the dissolving formulation (26.4%); thus, we evaluated them in an excisional rat model. The hydrogel microneedle arrays significantly increased the rate of wound closure compared to the control. This research has shown that the chitosan-PVA hydrogel microneedles could penetrate the epidermis, effectively release AA, and increase the wound closure rate. This AA-loaded delivery system shows promise as a natural treatment for wound healing and may be applied to other bioactive compounds with similar physiochemical properties in the future.

Advancements in Skin Delivery of Natural Bioactive Products for Wound Management: A Brief Review of Two Decades.

Application of modern delivery techniques to natural bioactive products improves their permeability, bioavailability, and therapeutic efficacy. Many natural products have desirable biological properties applicable to wound healing but are limited by their inability to cross the stratum corneum to access the wound. Over the past two decades, modern systems such as microneedles, lipid-based vesicles, hydrogels, composite dressings, and responsive formulations have been applied to natural products such as curcumin or aloe vera to improve their delivery and efficacy. This article reviews which natural products and techniques have been formulated together in the past two decades and the success of these applications for wound healing. Many cultures prefer natural-product-based traditional therapies which are often cheaper and more available than their synthetic counterparts. Improving natural products' effect can provide novel wound-healing therapies for those who trust traditional compounds over synthetic drugs to reduce medical inequalities.

N-trimethyl chitosan coated nano-complexes enhance the oral bioavailability and chemotherapeutic effects of gemcitabine.

N-trimethyl chitosan (TMC) is a multifunctional polymer that can be used in various nanoparticle forms in the pharmaceutical, nutraceutical and biomedical fields. In this study, TMC was used as a mucoadhesive adjuvant to enhance the oral bioavailability and hence antitumour effects of gemcitabine formulated into nanocomplexes composed of poly(lactic-co-glycolic acid) nanoparticles (PLGA NPs) conjugated with d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS). A central composite design was applied to achieve the optimal formulation. Cellular uptake and drug transportation studies revealed the nanocomplexes permeate over the intestinal cells via adsorptive-mediated and caveolae-mediated endocytosis. Pharmacokinetic studies demonstrated the oral drug bioavailability of the nanocomplexes was increased 5.1-fold compared with drug solution. In pharmacodynamic studies, the formulation reduced tumour size 3.1-fold compared with the drug solution. The data demonstrates that TMC modified nanocomplexes can enhance gemcitabine oral bioavailability and promote the anticancer efficacy.

The Molecular Mechanisms of Regulating Oxidative Stress-Induced Ferroptosis and Therapeutic Strategy in Tumors.

Ferroptosis is an atypical form of regulated cell death, which is different from apoptosis, necrosis, pyroptosis, and autophagy. Ferroptosis is characterized by iron-dependent oxidative destruction of cellular membranes following the antioxidant system's failure. The sensitivity of ferroptosis is tightly regulated by a series of biological processes, the metabolism of iron, amino acids, and polyunsaturated fatty acids, and the interaction of glutathione (GSH), NADPH, coenzyme Q10 (CoQ10), and phospholipids. Elevated oxidative stress (ROS) level is a hallmark of cancer, and ferroptosis serves as a link between nutrition metabolism and redox biology. Targeting ferroptosis may be an effective and selective way for cancer therapy. The underlying molecular mechanism of ferroptosis occurrence is still not enough. This review will briefly summarize the process of ferroptosis and introduce critical molecules in the ferroptotic cascade. Furthermore, we reviewed the occurrence and regulation of reduction-oxidation (redox) for ferroptosis in cancer metabolism. The role of the tumor suppressor and the epigenetic regulator in tumor cell ferroptosis will also be described. Finally, old drugs that can be repurposed to induce ferroptosis will be characterized, aiming for drug repurposing and novel drug combinations for cancer therapy more efficiently and economically.

Antioxidant activity and bioaccessibility of size-different nanoemulsions for lycopene-enriched tomato extract.

Lycopene nanoemulsions were prepared to protect the antioxidant activity and improve the bioaccessibility of lycopene-enriched tomato extract (containing 6% of lycopene) by an emulsification-evaporation method. Lycopene nanoemulsions, with droplet sizes between 100 and 200 nm, exhibited higher anti-radical efficiency and antioxidant activity, than did those smaller than 100 nm. Strong protectability of lycopene in droplets smaller than 100 nm was associated with relatively slower rates of DPPH and ABTS reactions. In vitro bioaccessibility values of lycopene-enriched tomato extract, lycopene nanoemulsions with droplets larger than 100 nm (approximately 150 nm on average), and lycopene nanoemulsions with droplets smaller than 100 nm (69 nm on average) were 0.01, 0.53, and 0.77, respectively. Interestingly, nanoemulsions with droplets smaller than 100 nm showed the highest in vitro bioaccessibility, which could be interpreted as evidence of nanoemulsification enhancing the in vitro bioaccessibility of lycopene.

Oral Delivery of Bovine Lactoferrin Using Pectin- and Chitosan-Modified Liposomes and Solid Lipid Particles: Improvement of Stability of Lactoferrin.

A critical problem associated with delivery of bovine lactoferrin (bLf) by the oral route is low bioavailability, which is derived from the enzymatic degradation in the gastrointestinal tract and poor permeation across the intestinal epitheliums. Particulate carrier systems have been identified to protect bLf against proteolysis via encapsulation. This study aimed to evaluate the physico-chemical stability of bLf-loaded liposomes and solid lipid particles (SLPs) modified by pectin and chitosan when exposed to various stress conditions. Transmission electron microscopy results showed liposomes and SLPs had a classic shell-core structure with polymer layers surrounded on surface, but the structure appeared to be partially broken after digestion in simulated intestinal fluid (SIF). Although HPLC and sodium dodecyl sulphate-polyacrylamide gel electrophoresis methods qualitatively and quantitatively described either liposomes or SLPs could retain intact bLf against proteolysis in SIF to some extent, all liposome formulations showed rapid rate of lipolysis mediated by pancreatic enzymes. On the other hand, all SLP formulations showed higher heat resistance and greater electrolyte tolerance compared to liposome formulations. After 180 days storage time, liposome-loaded bLf was completely degraded, whereas almost 30% of intact bLf still remained in SLP formulations. Overall, SLPs are considered as primary choice for oral bLf delivery.

Preparation, optimization and characterization of bovine lactoferrin-loaded liposomes and solid lipid particles modified by hydrophilic polymers using factorial design.

Bioadhesive liposomes and solid lipid particles (SLPs) modified by pectin and chitosan for oral administration of bovine lactoferrin (bLf) were prepared using a 2(4) full-factorial design to identify the key formulation variables influencing particle size and drug entrapment efficiency (EE). Netlike structures of the polymer-particle mixture consisting of a polymeric network in which multiple particles were imbedded were observed by scanning electron microscopy (SEM). Chemical stability of bLf after encapsulation into pectin- and chitosan-modified liposomes and SLPs was confirmed by Fourier transform infrared spectra (FTIR). Bovine lactoferrin was located within phospholipid bilayer, whereas in SLPs bLf was within the matrix. The crystalline nature of bLf after encapsulation was investigated by differential scanning calorimetry (DSC) of drug-loaded particles, indicating amorphous dispersion of bLf in the polymer-lipid matrix of pectin- and chitosan-modified liposomes and SLPs. In vivo pharmacokinetic investigation of bLf in pectin- and chitosan-modified liposomes and SLPs showed prolonged mean residence time (MRT) of bLf in rat blood and increased the relative bioavailability (Fbio %) by 1.95- to 2.69-fold compared with free bLf. The developed carrier systems are considered to be promising vehicles for oral delivery.

Development of a novel niosomal system for oral delivery of Ginkgo biloba extract.

BACKGROUND: The aim of this study was to develop an optimal niosomal system to deliver Ginkgo biloba extract (GbE) with improved oral bioavailability and to replace the conventional GbE tablets. METHODS: In this study, the film dispersion-homogenization method was used to prepare GbE niosomes. The resulting GbE niosome suspension was freeze-dried or spray-dried to improve the stability of the niosomes. GbE-loaded niosomes were formulated and characterized in terms of their morphology, particle size, zeta potential, entrapment efficiency, and angle of repose, and differential scanning calorimetry analysis was performed. In vitro release and in vivo distribution studies were also carried out. RESULTS: The particle size of the optimal delivery system prepared with Tween 80, Span 80, and cholesterol was about 141 nm. There was a significant difference (P < 0.05) in drug entrapment efficiency between the spray-drying method (about 77.5%) and the freeze-drying method (about 50.1%). The stability study revealed no significant change in drug entrapment efficiency for the GbE niosomes at 4°C and 25°C after 3 months. The in vitro release study suggested that GbE niosomes can prolong the release of flavonoid glycosides in phosphate-buffered solution (pH 6.8) for up to 48 hours. The in vivo distribution study showed that the flavonoid glycoside content in the heart, lung, kidney, brain, and blood of rats treated with the GbE niosome carrier system was greater than in the rats treated with the oral GbE tablet (P < 0.01). No flavonoid glycosides were detected in the brain tissue of rats given the oral GbE tablets, but they were detected in the brain tissue of rats given the GbE niosomes. CONCLUSION: Niosomes are a promising oral system for delivery of GbE to the brain.

Development of an isocratic HPLC method for catechin quantification and its application to formulation studies.

The aim of this study was to develop a simple, rapid and accurate isocratic HPLC analytical method to qualify and quantify five catechin derivatives, namely (+)-catechin (C), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG), (-)-epicatechin (EC) and (-)-epigallocatechin gallate (EGCG). To validate the analytical method, linearity, repeatability, intermediate precision, sensitivity, selectivity and recovery were investigated. The five catechin derivatives were completely separated by HPLC using a mobile phase containing 0.1% TFA in Milli-Q water (pH 2.0) mixed with methanol at the volume ratio of 75:25 at a flow rate of 0.8 ml/min. The method was shown to be linear (r²>0.99), repeatable with instrumental precision<2.0 and intra-assay precision<2.5 (%CV, percent coefficient of variation), precise with intra-day variation<1 and inter-day variation<2.5 (%CV, percent coefficient of variation) and sensitive (LOD<1 µg/mL and LOQ<3 µg/mL) over the calibration range for all five derivatives. Derivatives could be fully recovered in the presence of niosomal formulation (recovery rates>91%). Selectivity of the method was proven by the forced degradation studies, which showed that under acidic, basic, oxidation temperature and photolysis stresses, the parent drug can be separated from the degradation products by means of this analytical method. The described method was successfully applied in the in vitro release studies of catechin-loaded niosomes to manifest its utility in formulation characterization. Obtained results indicated that the drug release from niosomal formulations was a biphasic process and a diffusion mechanism regulated the permeation of catechin niosomes.

Role of P-glycoprotein in the intestinal absorption of tanshinone IIA, a major active ingredient in the root of Salvia miltiorrhiza Bunge.

The extracts from the roots of Salvia miltiorrhiza Bunge (Danshen) are widely and traditionally used in the treatment of angina pectoris, acute myocardial infarct, hyperlipidemia and stroke in China and other Asian countries. In this study, we have investigated the role of P-glycoprotein (P-gp) in the intestinal absorption of tanshinone IIA (TSA), a major active constituent of Danshen, using several in vitro and in vivo models. The oral bioavailability of TSA was about 2.9-3.4% in rats, with non-linear pharmacokinetics when its dosage increased. In a single pass rat intestinal perfusion model, the permeability coefficients (P(app)) based on TSA disappearance from the luminal perfusates (P(lumen)) were 6.2- to 7.2-fold higher (P < 0.01) than those based on drug appearance in mesenteric venous blood (P(blood)). The P(blood), but not P(lumen), was significantly increased when co-perfused with verapamil, or quinidine (both P-gp inhibitors). The uptake and efflux of TSA in confluent Caco-2 cells were significantly altered in the presence of verapamil, quinidine, MK-571, or probenecid. The transport of TSA across Caco-2 monolayers was pH-, temperature- and ATP-dependent. Furthermore, the transport from the apical (AP) to basolateral (BL) side of the Caco-2 monolayers was 3.3- to 8.5-fold lower than that from the BL to AP side, but such a polarized transport was attenuated by co-incubated verapamil or quinidine. A polarized transport was also observed in the control MDCKII cells and more apparent in MDR1-MDCKII monolayers, with the P(app) values of TSA in the BL-AP direction being 7- to 9-fold higher in MDR1-MDCKII monolayers than those in the control MDCKII cells. Moreover, TSA significantly inhibited P-gp-mediated transport of digoxin in P-gp-overexpressing membrane vesicles with an IC(50) of 2.6 microM, but stimulated vanadate-sensitive P-gp ATPase activity with estimated K(m) and V(max) values of 10.70 +/- 0.69 microM and 67.65 +/- 1.31 nmol/min/mg protein, respectively. TSA was extensively metabolized to tanshinone IIB (TSB), and two other oxidative metabolites in rat liver microsomes, but the formation rate of TSB in rat intestinal microsomes was only about 1/10 of that in liver microsomes. These findings indicate that TSA is a substrate and reversing agent for P-gp; and P-gp-mediated efflux of TSA into the gut lumen and the first-pass metabolism contribute to the low oral bioavailability. Further studies are needed to explore the role of other drug transporters and first-pass metabolism in the low bioavailability of TSA.

Transport of cryptotanshinone, a major active triterpenoid in Salvia miltiorrhiza Bunge widely used in the treatment of stroke and Alzheimer's disease, across the blood-brain barrier.

Cryptotanshinone (CTS), a major constituent from the roots of Salvia miltiorrhiza (Danshen), is widely used in the treatment of coronary heart disease, stroke and less commonly Alzheimer's disease. Our recent study indicates that CTS is a substrate for P-glycoprotein (PgP/MDR1/ABCB1). This study has investigated the nature of the brain distribution of CTS across the brain-blood barrier (BBB) using several in vitro and in vivo rodent models. A polarized transport of CTS was found in rat primary microvascular endothelial cell (RBMVEC) monolayers, with facilitated efflux from the abluminal side to luminal side. Addition of a PgP (e.g. verapamil and quinidine) or multi-drug resistance protein 1/2 (MRP1/2) inhibitor (e.g. probenecid and MK-571) in both luminal and abluminal sides attenuated the polarized transport. In a bilateral in situ brain perfusion model, the uptake of CTS into the cerebrum increased from 0.52 +/- 0.1% at 1 min to 11.13 +/- 2.36 ml/100 g tissue at 30 min and was significantly greater than that of sucrose. Co-perfusion of a PgP/MDR1 (e.g. verapamil) or MRP1/2 inhibitor (e.g. probenecid) significantly increased the brain distribution of CTS by 35.1-163.6%. The brain levels of CTS were only about 21% of those in plasma, and were significantly increased when coadministered with verapamil or probenecid in rats. The brain levels of CTS in rats subjected to middle cerebral artery occlusion and rats treated with quinolinic acid (a neurotoxin) were about 2- to 2.5-fold higher than the control rats. Moreover, the brain levels in mdr1a(-/-) and mrp1(-/-) mice were 10.9- and 1.5-fold higher than those in the wild-type mice, respectively. Taken collectively, these findings indicate that PgP and Mrp1 limit the brain penetration of CTS in rodents, suggesting a possible role of PgP and MRP1 in limiting the brain penetration of CTS in patients and causing drug resistance to Danshen therapy and interactions with conventional drugs that are substrates of PgP and MRP1. Further studies are needed to explore the role of other drug transporters in restricting the brain penetration of CTS and the clinical relevance.

Tanshinone IIB, a primary active constituent from Salvia miltiorrhza, exhibits neuro-protective activity in experimentally stroked rats.

Tanshinone IIB (TSB) is a major active constituent of the root of Salvia miltiorrhiza (Danshen) used in the treatment of acute stroke. Danshen extracts and TSB have shown marked neuron-protective effects in mouse studies but there is a lack of clinical evidence for the neuron-protective effects of Danshen and its active ingredients. This study investigated the neuron-protective effects of TSB in experimentally stroked rats. TSB at 5 and 25 mg/kg by intraperitoneal injection significantly reduced the focal infarct volume, cerebral histological damage and apoptosis in rats subjected to middle cerebral artery occlusion (MCAO) compared to MCAO rats receiving vehicle. This study demonstrated that TSB was effective in reducing stroke-induced brain damage and may represent a novel drug candidate for further development. Further mechanistic studies are needed for the neuron-protective activity of TSB.

A mechanistic study on altered pharmacokinetics of irinotecan by St. John's wort.

Irinotecan (CPT-11) is an important anticancer drug in management of advanced colon cancer. A marked protective effect on CPT-11-induced blood and gastrointestinal toxicity is obtained by combination of St. John's wort (SJW) in recent clinical and rat studies. However, the mechanism is unclear. This study aimed to explore the effects of SJW on the pharmacokinetics of CPT-11 and its major metabolites (SN-38 and SN-38 glucuronide) in rats and the underlying mechanisms using several in vitro models. Short-term (3 days) and long-term (14 days) pretreatment with SJW were conducted in rats to examine the effects of co-administered SJW on the plasma pharmacokinetics of CPT-11, SN-38 and SN-38 glucuronide. Rat liver microsomes and a rat hepatoma cell line, H4-II-E cells, were utilized to study the effects of aqueous and ethanolic extracts (AE and EE) and major active components (hyperforin, hypericin and quercetin) of SJW on CPT-11 and SN-38 metabolism and intracellular accumulation. Co-administered SJW for consecutive 14 days significantly decreased the initial plasma concentration (C0) of CPT-11, the area under the concentration-time curve (AUC(0-10hr)) and maximum plasma concentration (Cmax) of SN-38. The ethanolic extracts (EE) of SJW at 5 microg/ml significantly decreased SN-38 glucuronidation by 45% (P < 0.05) in rat hepatic microsomes. Pre-incubation of aqueous SJW extracts (AE) at 10 microg/ml, SJW EE at 5 microg/ml, and quercetin at 10 microM significantly increased the glucuronidation of SN-38 in H4-II-E cells. A 2-hr pre-incubation of quercetin (100 microM) significantly increased the intracellular accumulation of CPT-11 (P < 0.05). However, pre-incubation of hypericin (20 nM and 200 nM) and hyperforin (1 microM) significantly decreased the intracellular accumulation of CPT-11. In addition, pre-incubation of hypericin, SJW EE and quercetin significantly increased the intracellular accumulation of SN-38. Aqueous and ethanolic SJW extracts and its major active components did not alter the plasma protein binding of CPT-11 and SN-38. These results indicated that the aqueous and ethanolic extracts of SJW and its major active components could markedly alter glucuronidation of SN-38 and intracellular accumulation of CPT-11 and SN-38, which probably provides partial explanation for the altered plasma pharmacokinetics of CPT-11 and SN-38 and the antagonizing effects on the toxicities of CPT-11. Further studies are needed to explore the role of both pharmacokinetic and pharmacodynamic components in the protective effect of SJW against the toxicities of CPT-11.

Role of P-glycoprotein in the intestinal absorption of glabridin, an active flavonoid from the root of Glycyrrhiza glabra.

Glabridin is a major constituent of the root of Glycyrrhiza glabra, which is commonly used in the treatment of cardiovascular and central nervous system diseases. This study aimed to investigate the role of P-glycoprotein (PgP/MDR1) in the intestinal absorption of glabridin. The systemic bioavailability of glabridin was approximately 7.5% in rats, but increased when combined with verapamil. In single-pass perfused rat ileum with mesenteric vein cannulation, the permeability coefficient of glabridin based on drug disappearance in luminal perfusates (P(lumen)) was approximately 7-fold higher than that based on drug appearance in the blood (P(blood)). Glabridin was mainly metabolized by glucuronidation, and the metabolic capacity of intestine microsomes was 1/15 to 1/20 of that in liver microsomes. Polarized transport of glabridin was found in Caco-2 and MDCKII monolayers. Addition of verapamil in both apical (AP) and basolateral (BL) sides abolished the polarized transport of glabridin across Caco-2 cells. Incubation of verapamil significantly altered the intracellular accumulation and efflux of glabridin in Caco-2 cells. The transport of glabridin in the BL-AP direction was significantly higher in MDCKII cells overexpressing PgP/MDR1 than in the control cells. Glabridin inhibited PgP-mediated transport of digoxin with an IC(50) value of 2.56 microM, but stimulated PgP/MDR1 ATPase activity with a K(m) of 25.1 microM. The plasma AUC(0-24h) of glabridin in mdr1a(-/-) mice was 3.8-fold higher than that in wild-type mice. These findings indicate that glabridin is a substrate for PgP and that both PgP/MDR1-mediated efflux and first-pass metabolism contribute to the low oral bioavailability of glabridin.

Involvement of P-glycoprotein and multidrug resistance associated protein 1 in the transport of tanshinone IIB, a primary active diterpenoid quinone from the roots of Salvia miltiorrhiza, across the blood-brain barrier.

Tanshinone IIB (TSB) is a major constituent of Salvia miltiorrhiza, which is widely used in treatment of cardiovascular and central nervous system (CNS) diseases such as coronary heart disease and stroke. This study aimed to investigate the role of various drug transporters in the brain penetration of TSB using several in vitro and in vivo mouse and rat models. The uptake and efflux of TSB in rat primary microvascular endothelial cells (RBMVECs) were ATP-dependent and significantly altered in the presence of a P-glycoprotein (P-gp) or multidrug resistance associated protein (Mrp1/2) inhibitor. A polarized transport of TSB was found in RBMVEC monolayers with facilitated efflux from the abluminal to luminal side. Addition of a P-gp inhibitor (e.g. verapamil) in both abluminal and luminal sides attenuated the polarized transport. In an in situ rat brain perfusion model, TSB crossed the blood-brain barrier (BBB) and blood-cerebrospinal fluid barrier at a greater rate than that for sucrose, and the brain penetration was increased in the presence of a P-gp or Mrp1/2 inhibitor. The brain levels of TSB were only about 30% of that in the plasma and it could be increased to up to 72% of plasma levels when verapamil, quinidine, or probenecid was co-administered in rats. The entry of TSB to CNS increased by 67-97% in rats subjected to middle cerebral artery occlusion or treatment with the neurotoxin, quinolinic acid, compared to normal rats. Furthermore, The brain levels of TSB in mdr1a(-/-) and mrp1(-/-) mice were 28- to 2.6-fold higher than those in the wild-type mice. TSB has limited brain penetration through the BBB due to the contribution of P-gp and to a lesser extent of Mrp1 in rodents. Further studies are needed to confirm whether these corresponding transporters in humans are involved in limiting the penetration of TSB across the BBB and the clinical relevance.