Is there a possibility that P-glycoprotein reduces reproductive toxicity in males but breast cancer resistance protein does not?

In traditional understanding, P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP) are regarded as efflux transporters that can decrease the concentration of their substrates in the testis, thereby reducing reproductive toxicity in males (RTM) and protecting spermatogenesis. However, there is currently no direct pharmacological evidence demonstrating that P-gp and BCRP can reduce the occurrence of drug-induced RTM. In this study, we chose small molecule targeted anti-tumor agents as model drugs and systematically retrieved and collected information on the transporters and RTM for these drugs, followed by correlation analysis. The results showed a lower incidence of RTM for P-gp substrate drugs, which aligns with previous knowledge. Surprisingly, BCRP substrate drugs exhibited higher rates of RTM in various dimensions, contradicting previous notions. This discrepancy may be attributed to the differential distribution and transport directions of P-gp and BCRP on the blood-testis barrier (BTB). For the first time, this study may provide clues that BCRP may facilitate the passage of exogenous compounds across the BTB, increasing the occurrence of RTM, rather than protecting spermatogenesis as traditionally believed. Furthermore, this study provides the first direct verification of the role of P-gp in reducing RTM and protecting spermatogenesis.

Bisecting GlcNAc modification reverses the chemoresistance via attenuating the function of P-gp.

Rationale: Chemoresistance is a key factor contributing to the failure of anti-breast cancer chemotherapy. Although abnormal glycosylation is closely correlated with breast cancer progression, the function of glycoconjugates in chemoresistance remains poorly understood. Methods: Levels and regulatory roles of bisecting N-acetylglucosamine (GlcNAc) in chemoresistant breast cancer cells were determined in vitro and in vivo. Glycoproteomics guided identification of site-specific bisecting GlcNAc on P-glycoprotein (P-gp). Co-immunoprecipitation coupled mass spectrometry (Co-IP-MS) and proximity labelling MS identified the interactome of P-gp, and the biological function of site-specific bisecting GlcNAc was investigated by site/truncation mutation and structural simulations. Results: Bisecting GlcNAc levels were reduced in chemoresistant breast cancer cells, accompanied by an enhanced expression of P-gp. Enhanced bisecting GlcNAc effectively reversed chemoresistance. Mechanical study revealed that bisecting GlcNAc impaired the association between Ezrin and P-gp, leading to a decreased expression of membrane P-gp. Bisecting GlcNAc suppressed VPS4A-mediated P-gp recruitment into microvesicles, and chemoresistance transmission. Structural dynamics analysis suggested that bisecting GlcNAc at Asn494 introduced structural constraints that rigidified the conformation and suppressed the activity of P-gp. Conclusion: Our findings highlight the crucial role of bisecting GlcNAc in chemoresistance and suggest the possibility of reversing chemoresistance by modulating the specific glycosylation in breast cancer therapy.

A phase I drug-drug interaction study to assess the effect of futibatinib on P-gp and BCRP substrates and of P-gp inhibition on the pharmacokinetics of futibatinib.

Futibatinib, an inhibitor of fibroblast growth factor receptor 1-4, is approved for the treatment of patients with advanced cholangiocarcinoma with FGFR2 fusions/rearrangements. In this phase I drug-drug interaction study, the effects of futibatinib on P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) substrates, and of P-gp inhibition on futibatinib pharmacokinetics (PK) were investigated in healthy adults aged 18-55 years. In part 1, 20 participants received digoxin (P-gp substrate) and rosuvastatin (BCRP substrate). Following a ≥10-day washout, futibatinib was administered for 7 days, with digoxin and rosuvastatin coadministered on the third day. In part 2, 24 participants received futibatinib. Following a ≥3-day washout, quinidine (P-gp inhibitor) was administered for 4 days, with futibatinib coadministered on day 4. Blood samples were collected predose and for 24 (futibatinib), 72 (rosuvastatin), and 120 h (digoxin) postdose. Urine samples (digoxin) were collected predose and for 120 h postdose. PK parameters were compared between treatments using analysis of variance. Coadministration with futibatinib had no effect on the PK of digoxin and rosuvastatin, and coadministration with quinidine had minimal effects on the PK of futibatinib. Differences in Cmax and AUC with and without futibatinib and quinidine, respectively, were <20%. The most common treatment-emergent adverse events were diarrhea (80%) and increased blood phosphorous (75%) in part 1 and prolonged electrocardiogram QT interval (38%) in part 2. The data show that futibatinib has no clinically meaningful effects on the PK of P-gp or BCRP substrates and that the effect of P-gp inhibition on futibatinib PK is not clinically relevant.

The Drug Transporter P-Glycoprotein and Its Impact on Ceramide Metabolism-An Unconventional Ally in Cancer Treatment.

The tumor-suppressor sphingolipid ceramide is recognized as a key participant in the cytotoxic mechanism of action of many types of chemotherapy drugs, including anthracyclines, Vinca alkaloids, the podophyllotoxin etoposide, taxanes, and the platinum drug oxaliplatin. These drugs can activate de novo synthesis of ceramide or stimulate the production of ceramide via sphingomyelinases to limit cancer cell survival. On the contrary, dysfunctional sphingolipid metabolism, a prominent factor in cancer survival and therapy resistance, blunts the anticancer properties of ceramide-orchestrated cell death pathways, especially apoptosis. Although P-glycoprotein (P-gp) is famous for its role in chemotherapy resistance, herein, we propose alternate interpretations and discuss the capacity of this multidrug transporter as a "ceramide neutralizer", an unwelcome event, highlighting yet another facet of P-gp's versatility in drug resistance. We introduce sphingolipid metabolism and its dysfunctional regulation in cancer, present a summary of factors that contribute to chemotherapy resistance, explain how P-gp "neutralizes" ceramide by hastening its glycosylation, and consider therapeutic applications of the P-gp-ceramide connection in the treatment of cancer.

Anti-Inflammatory and Anti-(Lymph)angiogenic Properties of an ABCB5+ Limbal Mesenchymal Stem Cell Population.

Corneal transparency and avascularity are essential for vision. The avascular cornea transitions into the vascularized conjunctiva at the limbus. Here, we explore a limbal stromal cell sub-population that expresses ABCB5 and has mesenchymal stem cell characteristics. Human primary corneal stromal cells were enriched for ABCB5 by using FACS sorting. ABCB5+ cells expressed the MSC markers CD90, CD73, and CD105. ABCB5+ but not ABCB5- cells from the same donor displayed evidence of pluripotency with a significantly higher colony-forming efficiency and the ability of trilineage differentiation (osteogenic, adipogenic, and chondrogenic). The ABCB5+ cell secretome demonstrated lower levels of the pro-inflammatory protein MIF (macrophage migration inhibitory factor) as well as of the pro-(lymph)angiogenic growth factors VEGFA and VEGFC, which correlated with reduced proliferation of Jurkat cells co-cultured with ABCB5+ cells and decreased proliferation of blood and lymphatic endothelial cells cultured in ABCB5+ cell-conditioned media. These data support the hypothesis that ABCB5+ limbal stromal cells are a putative MSC population with potential anti-inflammatory and anti-(lymph)angiogenic effects. The therapeutic modulation of ABCB5+ limbal stromal cells may prevent cornea neovascularization and inflammation and, if transplanted to other sites in the body, provide similar protective properties to other tissues.

In Vivo Detection of Multidrug-Resistance Related Proteins in Locally Advanced Breast Cancer Using 99mTc-MIBI SPECT/CT Imaging: Correlation with Clinical Outcomes.

OBJECTIVE: Neoadjuvant chemotherapy (NACT) is widely used for treating locally advanced Breast cancer (LABC). However, development of multidrug resistance (MDR) is the main underlying factor for chemoresistance. Technetium-99m methoxyisobutylisonitrile (99mTc-MIBI) is a substrate for MDR. This study aimed to analyze the relationship between expression of MDR-related proteins (P-gp and Bcl-2) and 99mTc-MIBI uptake and retention in BC tumor cells, pathologic response to NACT, disease free survival (DFS) and overall survival (OS). METHODS: prospective analysis recruited 31 patients with LABC who received NACT between January 2019 and March 2020. 99mTc-MIBI planar and SPECT/CT imaging was conducted before and after NACT. Qualitative and quantitative analyses were performed, pre and post-NACT early and delayed lesion to non-lesion (LNL) ratios, and retention index (RI) of 99mTc-MIBI were calculated. Expression of P-gp and Bcl-2 in tumor cells was determined by immunohistochemistry. RESULTS: Quantitively, inter-reader ICC for SPECT/CT based quantification was consistently higher than that of planar images. Post-NACT LNL ratios were significantly higher in patients with pathologic persistent disease (PPD). A change in RI between pre- and post-NACT scans demonstrated a significant association with DFS with a hazard ratio of 0.7 (95%CI: 06-1.0). Qualitatively, SPECT/CT was significantly more accurate compared to planar imaging in identifying residual viable tumor (81% compared to 57%).  Her2neu positivity and high post-operative Bcl-2 and P-gp were associated with worse DFS. A significant association was found between increased expression of post-NACT Bcl-2 and PPD, advanced tumor stage and poor OS. CONCLUSION: 99mTc-MIBI SPECT/CT based qualitative evaluation of BC response to NACT is more accurate than planar imaging. Post-NACT MIBI retention is positively correlated with P-gp and Bcl-2 expression. 99mTc-MIBI SPECT/CT may predict MDR development. High post-NACT Bcl-2 expression is significantly associated with advanced tumor stage and OS. High post-NACT P-gp expression has a worse impact on pathologic response and DFS.

Plant-Based Products Originating from Serbia That Affect P-glycoprotein Activity.

Our review paper evaluates the impact of plant-based products, primarily derived from plants from Serbia, on P-glycoprotein (P-gp) activity and their potential in modulating drug resistance in cancer therapy. We focus on the role and regulation of P-gp in cellular physiology and its significance in addressing multidrug resistance in cancer therapy. Additionally, we discuss the modulation of P-gp activity by 55 natural product drugs, including derivatives for some of them, based on our team's research findings since 2011. Specifically, we prospect into sesquiterpenoids from the genera Artemisia, Curcuma, Ferula, Inula, Petasites, and Celastrus; diterpenoids from the genera Salvia and Euphorbia; chalcones from the genera Piper, Glycyrrhiza, Cullen, Artemisia, and Humulus; riccardins from the genera Lunularia, Monoclea, Dumortiera, Plagiochila, and Primula; and diarylheptanoids from the genera Alnus and Curcuma. Through comprehensive analysis, we aim to highlight the potential of natural products mainly identified in plants from Serbia in influencing P-gp activity and overcoming drug resistance in cancer therapy, while also providing insights into future perspectives in this field.

Effect of midostaurin on the pharmacokinetics of P-gp, BCRP, and CYP2D6 substrates: assessing potential drug-drug interactions in healthy participants : Brief title: Drug-drug interaction of midostaurin.

PURPOSE: Midostaurin, approved for FLT3-mutated acute myeloid leukemia and advanced systemic mastocytosis, is mainly metabolized by cytochrome P450 (CYP) 3A4. Midostaurin exhibited potential inhibitory effects on P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), organic anion-transporting polyprotein 1B1, and CYP2D6 in in vitro studies. This study investigated the pharmacokinetic (PK) effects of midostaurin on P-gp (digoxin), BCRP (rosuvastatin) and CYP2D6 (dextromethorphan) substrates in healthy adults. METHODS: This was an open-label, single-sequence, phase I clinical study evaluating the effect of single-dose midostaurin (100 mg) on the PK of digoxin and rosuvastatin (Arm 1), and dextromethorphan (Arm 2). Participants were followed up for safety 30 days after last dose. In addition, the effect of midostaurin on the PK of dextromethorphan metabolite (dextrorphan) was assessed in participants with functional CYP2D6 genes in Arm 2. RESULTS: The effect of midostaurin on digoxin was minor and resulted in total exposure (AUC) and peak plasma concentration (Cmax) that were only 20% higher. The effect on rosuvastatin was mild and led to an increase in AUCs of approximately 37-48% and of 100% in Cmax. There was no increase in the primary PK parameters (AUCs and Cmax) of dextromethorphan in the presence of midostaurin. The study treatments were very well tolerated with no occurance of severe adverse events (AEs), AEs of grade ≥ 2, or deaths. CONCLUSION: Midostaurin showed only a minor inhibitory effect on P-gp, a mild inhibitory effect on BCRP, and no inhibitory effect on CYP2D6. Study treatments were well tolerated in healthy adults.

P-glycoproteins in anthelmintic safety, efficacy, and resistance.

P-glycoprotein (PGP) is a pivotal transmembrane transporter governing the cellular flux of diverse substances shielding mammals from toxics. It can thwart the effectiveness of medicines such as ivermectin (IVM) and other macrocyclic lactone (ML) anthelmintics, undermining therapeutic efforts. We analyze the role of PGPs in limiting the toxicity of these drugs in hosts, and their potential contribution to anthelmintic resistance in nematodes. Targeting nematode PGPs to increase drug sensitivity to MLs seems interesting, but is hampered by the lack of selective inhibitors. The nuclear hormone receptor (NHR)-8 should be seriously considered as a target because it upregulates multiple PGPs involved in anthelmintic resistance and it is specific to nematodes. This would advance our understanding of host-pathogen dynamics and foster innovative therapeutic strategies.

Strategy to Improve the Oral Pharmacokinetics of Cyclin-Dependent Kinase 4/6 Inhibitors: Enhancing Permeability and CYP450 Inhibition by a Natural Bioenhancer.

Palbociclib and ribociclib an orally bioavailable, potent cyclin-dependent kinase 4/6 inhibitors, with low oral bioavailability due to substrate specificity towards CYP3A and P-glycoprotein. Thus, current research aims to examine the effect of a bioenhancer (naringin), on oral pharmacokinetics of palbociclib and ribociclib. Naringin's affinity for CYP3A4 and P-glycoprotein was studied using molecular docking; its impact on palbociclib/ribociclib CYP3A metabolism and P-glycoprotein-mediated efflux was examined using in vitro preclinical models; and its oral pharmacokinetics in rats were assessed following oral administration of palbociclib/ribociclib in presence of naringin (50 and 100 mg/kg). Naringin binds optimally to both proteins with the highest net binding energy of - 1477.23 and - 1607.47 kcal/mol, respectively. The microsomal intrinsic clearance of palbociclib and ribociclib was noticeably reduced by naringin (5-100 µM), by 3.0 and 2.46-folds, respectively. Similarly, naringin had considerable impact on the intestinal transport and efflux of both drugs. The pre-treatment with 100 mg/kg naringin increased significantly (p < 0.05) the oral exposure of palbociclib (2.0-fold) and ribociclib (1.95-fold). Naringin's concurrent administration of palbociclib and ribociclib increased their oral bioavailability due to its dual inhibitory effect on CYP3A4 and P-glycoprotein; thus, concurrent naringin administration may represent an innovative strategy for enhancing bioavailability of cyclin-dependent kinase inhibitors.

The Effect of Concomitant Administration of Proton Pump Inhibitors on the Pharmacokinetics of CDK4/6 Inhibitors in Rats: Implications for the Evaluation of Hepatic and Transporter-Mediated Drug-Drug Interactions.

BACKGROUND AND OBJECTIVES: Numerous clinical concerns have been expressed regarding the potential worsening of cyclin-dependent kinase 4/6 inhibitor effects in breast cancer patients because of co-administration of proton pump inhibitors. Hence, this study evaluated the effects of proton pump inhibitors on the pharmacokinetics of palbociclib and ribociclib in terms of  cytochrome P450 (CYP) 3A4 and P-glycoprotein involvement. METHODS: The effects of omeprazole and rabeprazole on drug metabolism and efflux of these drugs were investigated using molecular docking, metabolic stability assay in rat liver microsomes, human recombinant CYP3A4 (rCYP3A4) enzymes, and Caco-2 cell monolayers, and in vivo pharmacokinetics with omeprazole and rabeprazole in (5 and 10 mg/kg) 30 min and 7 days before orally dosing palbociclib and ribociclib (10 mg/kg). RESULTS: Omeprazole and rabeprazole inhibited CYP3A4 enzyme activity in rCYP3A4 baculosomes with a 50-60% inhibition at 30 µM. Additionally, both omeprazole and rabeprazole (10 µm) significantly reduced the P-glycoprotein-mediated drug efflux of palbociclib and ribociclib. The 7-day pretreatment of omeprazole at a dose of 10 mg/kg resulted in 24% and 26% reductions in palbociclib's mean maximum plasma concentration) Cmax and area under the plasma concentration-time curve (AUC0-24 h), respectively. Palbociclib's pharmacokinetics were not significantly altered by the pretreatment with rabeprazole; however, ribociclib pharmacokinetics exhibited an 83.94% increase in AUC0-24 h. CONCLUSION: The findings indicate that long-term treatment with therapeutic doses of both omeprazole and rabeprazole can alter the pharmacokinetics of palbociclib and ribociclib. The co-administration of rabeprazole may alter the pharmacokinetics of palbociclib and ribociclib via CYP enzyme and P-glycoprotein inhibition.

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.

Synergistic enhancement: Exploring the potential of piperine in cancer therapeutics through chemosensitization and combination therapies.

Despite significant advancements in chemotherapy, effective treatments for advanced cancer stages remain largely elusive due to chemoresistance. Resistance to anticancer agents in cancer cells can arise through various mechanisms, including multi-drug resistance, inhibition of apoptosis, modification of drug targets, and enhancement of DNA repair capabilities. Consequently, there is a critical need for agents that can suppress the molecular signatures responsible for drug resistance. Piperine, an active alkaloid extracted from Piper nigrum L. (black pepper), is one such agent that has been extensively studied for its potential in addressing chronic diseases, including cancer. Piperine's antineoplastic properties are mediated through the regulation of numerous key cellular signaling pathways and the modulation of various biological processes. Its capability to enhance drug bioavailability and counteract mechanisms of drug resistance, such as the inhibition of P-glycoprotein (P-gp) and multidrug resistance-associated protein 1 (MRP-1), emphasizes its potential as an adjunct in cancer therapy. Research across various cancer types has demonstrated piperine's role in chemosensitization by targeting P-gp and MRP-1 and altering drug-metabolizing enzymes. This review provides a comprehensive analysis of piperine's pharmacological characteristics and its capacity to modulate several cellular signaling pathways involved in drug resistance. Furthermore, the review emphasizes how piperine, when used in conjunction with other chemotherapeutic agents or natural compounds, can enhance therapeutic effects, leading to improved outcomes in cancer treatment.

Temperature Self-Limited Intelligent Thermo-chemotherapeutic Lipid Nanosystem for P-gp Reversal Time Window Matched Pulse Treatment of MDR Tumor.

Mild photothermal therapy (PTT) shows the potential for chemosensitization by tumor-localized P-glycoprotein (P-gp) modulation. However, conventional mild PTT struggles with real-time uniform temperature control, obscuring the temperature-performance relationship and resulting in thermal damage. Besides, the time-performance relationship and the underlying mechanism of mild PTT-mediated P-gp reversal remains elusive. Herein, we developed a temperature self-limiting lipid nanosystem (RFE@PD) that integrated a reversible organic heat generator (metal-phenolic complexes) and metal chelator (deferiprone, DFP) encapsulated phase change material. Upon NIR irradiation, RFE@PD released DFP for blocking ligand-metal charge transfer to self-limit temperature below 45 °C, and rapidly reduced P-gp within 3 h via Ubiquitin-proteasome degradation. Consequently, the DOX·HCl-loaded thermo-chemotherapeutic lipid nanosystem (RFE@PD-DOX) led to dramatically improved drug accumulation and 5-fold chemosensitization in MCF-7/ADR tumor models by synchronizing P-gp reversal and drug pulse liberation, achieving a tumor inhibition ratio of 82.42%. This lipid nanosystem integrated with "intrinsic temperature-control" and "temperature-responsive pulse release" casts new light on MDR tumor therapy.

Formononetin Defeats Multidrug-Resistant Cancers by Induction of Oxidative Stress and Suppression of P-Glycoprotein.

Multidrug resistance (MDR) remains the most difficult problem facing conventional chemotherapy for cancers. Astragalus membranaceus is a historically traditional Chinese medicine. One of its bioactive components, formononetin, exhibits antitumor effects on various cancers. However, the effects of formononetin on MDR cancers have not been evaluated. Therefore, we investigated the defense's effects of formononetin on MDR. We used rhodamine 123 and doxorubicin efflux assays to analyze the inhibition kinetics of P-glycoprotein (P-gp) mediated-efflux. Cell viability was detected by sulforhodamine B assay, and the synergistic effects of formononetin combined with chemotherapeutic agents were further calculated using CompuSyn software. Molecular docking was performed with iGEMDOCK. We discovered that formononetin considerably induced oxidative stress and the disruption of mitochondrial membrane potential in MDR cancer cells. Furthermore, formononetin inhibits the P-gp efflux function by ATPase stimulation and the uncompetitive inhibition of P-gp-mediated effluxes of rhodamine 123 and doxorubicin. The molecular docking model indicates that formononetin may bind to P-gp by strong hydrogen bonds at Arginine (Arg) 489 and Glutamine (Gln) 912. Formononetin exhibits significant synergistic effects with vincristine and doxorubicin toward MDR cancer cells, and it synergistically suppressed tumor growth in vivo with paclitaxel. These results suggest that formononetin should be seen as a potential candidate for the adjuvant therapy of MDR cancers.

Ivermectin toxicokinetics in rainbow trout (Oncorhynchus mykiss) following P-glycoprotein inhibition.

Changes to ivermectin (IVM [22,23-dihydro avermectin B1a + 22,23-dihydro avermectin B1b]) toxicokinetics (TK) with and without P-glycoprotein (P-gp) inhibition by cyclosporin A (CsA) were examined in rainbow trout (Oncorhynchus mykiss). Rainbow trout were injected with 175 µg/kg 3H-IVM (8.6 µCi/mg IVM) with or without co-administration of 480 µg/kg CsA into the caudal vasculature. Fish were sacrificed at various time points (0.25, 0.5, 1, 3, 24, 48, 96, and 168 h) for organ and tissue sampling (blood, liver, kidney, gill, intestines, brain [5 regions], eye, gonad, and fat) which were analyzed for IVM-derived radioactivity. The IVM concentration decreased over time in blood, liver, kidney, and gill, while concentrations in other tissues remained constant. The highest maximum IVM concentration (Cmax) was found in kidney, followed by liver; the lowest Cmax was found in eye, followed by brain and adipose tissue. The highest % of the administered dose was found in the blood 15 min post-IVM administration, followed by the intestine at 60 min post-IVM administration. P-gp inhibition by CsA did not significantly affect calculated TK parameters (AUC [7.33 ± 0.73 - 11.5 ± 2.5 mg•h/kg], mean residence time [84.7 ± 21 - 125 ± 55 h], T1/2 [58.7 ± 15 - 86.8 ± 38 h], clearance rate [0.0152 ± 0.0033 - 0.0239 ± 0.0024 L/kg•h], or volume of distribution [1.91 ± 0.47 - 2.02 ± 0.33 L/kg]), but resulted in small but significant changes in the % administered dose found in blood and medulla. These results suggest that P-gp plays a limited role in overall IVM TK, and that its role in xenobiotic protection may be much less robust in fish than it is in mammals.

[P-glycoprotein activity in vivo in older adults: physiological, -pathophysiological and pharmacokinetic interplay at the blood-brain barrier]. / Activité de la p-glycoprotéine in vivo chez la personne âgée : intrications physiologique, physiopathologique et pharmacocinétique au niveau de la barrière hémato-encéphalique.

p-glycoprotein (P-gp) is an efflux transporter of xenobiotic and endogenous compounds across the blood-brain barrier (BBB). P-gp plays an essential role by limiting passage of these compounds into the brain tissue. It is susceptible to drug-drug interactions when interactors drugs are co-administrated. The efficiency of P-gp may be affected by the aging process and the development of neurodegenerative diseases. Studying this protein in older adults is therefore highly relevant for all these reasons. Understanding P-gp activity in vivo is essential when considering the physiological, pathophysiological, and pharmacokinetic perspectives, as these aspects seem to be interconnected to some extent. In vivo exploration in humans is based on neuroimaging techniques, which have been improving over the last years. The advancement of exploration and diagnostic tools is opening up new prospects for understanding P-gp activity at the BBB.

Strain-level variations of Dirofilaria immitis microfilariae in two biochemical assays.

BACKGROUND: The increase in reports of resistance to macrocyclic lactones in the canine heartworm, Dirofilaria immitis is alarming. While DNA based tests have been well-validated, they can be expensive. In a previous study, we showed that two biochemical tests adapted to a 96- well plate format and read in a spectrophotometer could detect differences among lab validated D. immitis isolates. The two tests- Resazurin reduction and Hoechst 33342 efflux-detect metabolism and P-glycoprotein activity respectively in microfilariae isolated from infected dog blood. METHODS: Our objective was to optimize the two assays further by testing various assay parameters in D. immitis isolates not tested previously. We tested microfilarial seeding density, incubation time and the effect of in vitro treatment with ivermectin and doxycycline in five other D. immitis isolates-JYD-34, Big Head, Berkeley, Georgia III and LOL. All assays were performed in 3 technical replicates and 2-4 biological replicates. To understand the molecular basis of the assays, we also performed qPCR for selected drug metabolism and elimination associated genes of the ABC transporter and cytochrome P450 gene families. RESULTS: Metabolism and ABC transporter activity as detected by these assays varied between strains. Anthelmintic status (resistant or susceptible) did not correlate with metabolism or P-gp efflux. Basal transcriptional variations were found between strains in ABC transporter and cytochrome P450 genes. CONCLUSIONS: These assays provide a greater understanding of the biochemical variation among isolates of D. immitis, which can be exploited in the future to develop in vitro diagnostic tests capable of differentiating susceptible and resistant isolates.

Pharmacokinetic Modeling of the Effect of Tariquidar on Ondansetron Disposition into the Central Nervous System.

PURPOSE: Serotonin (5-HT3) receptor antagonists are promising agents for treatment of neuropathic pain. However, insufficient drug exposure at the central nervous system (CNS) might result in lack of efficacy. The goal of this study was to evaluate the impact of administration of a Pgp inhibitor (tariquidar) on ondansetron exposure in the brain, spinal cord, and cerebrospinal fluid in a wild-type rat model. METHODS: Ondansetron (10 mg/kg) and tariquidar (7.5 mg/kg) were administered intravenously, plasma and tissue samples were collected and analyzed by HPLC. A mathematical model with brain, spinal cord, cerebrospinal fluid and two systemic disposition compartments was developed to describe the data. RESULTS: The results demonstrate that tariquidar at 7.5 mg/kg resulted in a complete inhibition of Pgp efflux of ondansetron in the brain and spinal cord. The compartmental model successfully captured pharmacokinetics of ondansetron in wild type and Pgp knockout (KO) animals receiving the drug alone or in wild type animals receiving the ondansetron and tariquidar combination. CONCLUSIONS: The study provided important quantitative information on enhancement of CNS exposure to ondansetron using co-administration of Pgp Inhibitor in a rat model, which will be further utilized in conducting a clinical study. Tariquidar co-administration resulted in ondansetron CNS exposure comparable to observed in Pgp KO rats. Results also highlighted the effect of tariquidar on plasma disposition of ondansetron, which may not be dependent on Pgp inhibition, and should be evaluated in future studies.

A hybrid evaluation of the intestinal absorption performance of compounds from molecular structure.

Intestinal absorption of compounds is significant in drug research and development. To evaluate this efficiently, a method combining mathematical modeling and molecular simulation was proposed, from the perspective of molecular structure. Based on the quantitative structure-property relationship study, the model between molecular structure and their apparent permeability coefficients was successfully constructed and verified, predicting intestinal absorption of drugs and interpreting decisive structural factors, such as AlogP98, Hydrogen bond donor and Ellipsoidal volume. The molecules with strong lipophilicity, less hydrogen bond donors and receptors, and small molecular volume are more easily absorbed. Then, the molecular dynamics simulation and molecular docking were utilized to study the mechanism of differences in intestinal absorption of drugs and investigate the role of molecular structure. Results indicated that molecules with strong lipophilicity and small volume interacted with the membrane at a lower energy and were easier to penetrate the membrane. Likewise, they had weaker interaction with P-glycoprotein and were easier to escape from it and harder to export from the body. More in, less out, is the main reason these molecules absorb well.