Possible Involvement of Protein Binding Inhibition in Changes in Dexmedetomidine Concentration in Extracorporeal Circuits during Midazolam Use.

It was recently reported that the dexmedetomidine concentration within the extracorporeal circuit decreases with co-administration of midazolam. In this study, we investigated whether displacement of dexmedetomidine by midazolam from the binding site of major plasma proteins, human serum albumin (HSA) and α1-acid glycoprotein (AAG), would increase levels of free dexmedetomidine that could be adsorbed to the circuit. Equilibrium dialysis experiments indicated that dexmedetomidine binds to a single site on both HSA and AAG with four times greater affinity than midazolam. Midazolam-mediated inhibition of the binding of dexmedetomidine to HSA and AAG was also examined. The binding of dexmedetomidine to these proteins decreased in the presence of midazolam. Competitive binding experiments suggested that the inhibition of binding by midazolam was due to competitive displacement at site II of HSA and due to non-competitive displacement at the site of AAG. Thus, our present data indicate that free dexmedetomidine displaced by midazolam from site II of HSA or from AAG is adsorbed onto extracorporeal circuits, resulting in a change in the dexmedetomidine concentration within the circuit.

Preparation and in Vitro Characterization of Fatty-Acid Modified Pirarubicin Nanosuspensions Stabilized by Albumin.

Pirarubicin (THP) shows more rapid intracellular uptake, more effective antitumor activity, and less cardiac toxicity, compared to doxorubicin. However, THP is distributed to both tumor and normal tissues indiscriminately. This study aimed to develop a nanosuspension to deliver THP to tumor tissues more efficiently. Fatty-acid-modified THPs (FA-THPs; octanoic acid, dodecanoic acid, palmitic acid-THPs) were synthesized to increase the hydrophobicity of THP. Nanosuspensions of these FA-THPs were then prepared using an antisolvent precipitation technique. Among the FA-THPs, the most efficiently drug-loaded nanosuspension was obtained from palmitic acid-THP (pal-THP) using an aqueous antisolvent containing bovine serum albumin as a stabilizer. The pal-THP nanoparticles in the nanosuspension were confirmed to be of optimal size (100-125 nm) for delivery to tumor tissues using dynamic light scattering and transmission electron microscopy. The pal-THP nanosuspension showed cytotoxicity in colon 26 cells. The nanosuspension was shown to disintegrate in the presence of surfactants such as lecithin, liberating pal-THP, which was converted to free THP in acidic media. It is therefore proposed that pal-THP nanoparticles that reach tumor cells after intravenous administration would exert antitumor effect by liberating pal-THP (i.e., disintegration of nanoparticles by the interaction with cell membrane), followed by the release of free THP in the acidic milieu of tumor cells. These findings indicate that FA-THP nanosuspensions, particularly pal-THP nanosuspension, hold promise as a candidate for cancer treatment. However, further in vivo studies are necessary.

Study of the Structural Chemistry of the Inclusion Complexation of 4-Phenylbutyrate and Related Compounds with Cyclodextrins in Solution: Differences in Inclusion Mode with Cavity Size Dependency.

4-phenylbutyrate (PB) and structurally related compounds hold promise for treating many diseases, including cancers. However, pharmaceutical limitations, such as an unpleasant taste or poor aqueous solubility, impede their evaluation and clinical use. This study explores cyclodextrin (CD) complexation as a strategy to address these limitations. The structural chemistry of the CD complexes of these compounds was analyzed using phase solubility, nuclear magnetic resonance (NMR) spectroscopic techniques, and molecular modeling to inform the choice of CD for such application. The study revealed that PB and its shorter-chain derivative form 1:1 αCD complexes, while the longer-chain derivatives form 1:2 (guest:host) complexes. αCD includes the alkyl chain of the shorter-chain compounds, depositing the phenyl ring around its secondary rim, whereas two αCD molecules sandwich the phenyl ring in a secondary-to-secondary rim orientation for the longer-chain derivatives. ßCD includes each compound to form 1:1 complexes, with their alkyl chains bent to varying degrees within the CD cavity. γCD includes two molecules of each compound to form 2:1 complexes, with both parallel and antiparallel orientations plausible. The study found that αCD is more suitable for overcoming the pharmaceutical drawbacks of PB and its shorter-chain derivative, while ßCD is better for the longer-chain derivatives.

Effect of Fatty Acids and Uremic Toxins on the Binding of Nateglinide, an Insulin Secretagogue, to Site II on Human Serum Albumin.

Nateglinide (NAT) is used to treat diabetes, stimulating pancreatic islet ß-cells with residual insulin secretory capacity to increase insulin secretion. NAT has been reported to bind to human serum albumin (HSA), but the detail is still unclear. In the current study, we investigated the location and the affinity for the binding of NAT to HSA. Quantitative analysis data from the ultrafiltration experiment indicated that NAT binds strongly to a primary site on HSA with a high affinity. The presence of diazepam (DZP) or ibuprofen (IB), the specific site II ligands of HSA, decreased the binding constants of NAT respectively, without the significant changes in the number of binding sites. Whereas warfarin (WF), a site I specific ligand, did not affect the binding of NAT. Fluorescent replacement experiment showed that NAT replaced dansylsarcosine (DNSS), a site II probe of HSA, but not WF. An increasing level of myristate and uremic toxins, indoxyl sulphate (IS), indoxyl acetate (IA) and p-cresyl sulphate (PCS), during renal disease significantly increased the concentration of unbound NAT. These findings suggest that NAT specifically binds to site II of HSA and the binding capacity and pharmacokinetics of NAT change in renal diseases.

Interaction of Benzbromarone with Subdomains IIIA and IB/IIA on Human Serum Albumin as the Primary and Secondary Binding Regions.

Benzbromarone has been used for the treatment of gout for more than 30 years. Although it shows a high level of binding to plasma proteins (>99%), our knowledge of this binding is not sufficiently extensive to permit us to understand its pharmacokinetics and pharmacodynamics. To address this issue in more detail, we characterized the binding of benzbromarone to human serum albumin (HSA), the most abundant protein in plasma. Equilibrium dialysis and circular dichroism findings indicated that benzbromarone binds strongly to one primary as well as to multiple secondary sites on HSA and that the bromine atoms of benzbromarone play important roles in this high affinity binding. An X-ray crystallographic study revealed that benzbromarone molecules bind to hydrophobic pockets within subdomains IB, IIA, and IIIA. Inhibition experiments using site specific ligands (subdomain IB; fusidic acid, IIA; warfarin, IIIA; diazepam) indicated that the primary and secondary binding sites that benzbromarone binds to are within subdomains IIIA and IB/IIA, respectively. Lastly, a study of the effect of fatty acids on the benzbromarone-HSA interaction suggested that benzbromarone, when displaced from subdomain IIIA by sodium oleate, could transfer to subdomains IB or IIA. Thus, these data will permit more relevant assessments of the displacement interactions of benzbromarone especially in cases of co-administered drugs or endogenous compounds that also bind to subdomain IIIA. In addition, the findings presented herein will also be useful for designing drug combination therapy in which pharmacokinetic and pharmacodynamic performance need to be controlled.

Possible Role of Electrolytes on the Formation of Precipitates during the Infusion of Nafamostat Mesilate in Hemodialysis.

Nafamostat mesilate (NFM) is used as an anticoagulant during hemodialysis in patients who have had complications due to hemorrhages. The formation of precipitates, which could lead to the interruption of hemodialysis has been reported when NFM is infused into blood during hemodialysis. We report herein on an examination of possible factors that could cause this. The effects of electrolytes such as phosphates, citrates or succinates on the formation of precipitates were examined by mixing NFM with aqueous solutions or plasma that contained these electrolytes. The formation of precipitates was observed in all electrolyte solutions when higher concentrations of NFM were mixed at around physiological pH. In the case of plasma, precipitates were observed when solutions containing higher concentrations of NFM were mixed with plasma that contained phosphate and citrate. In addition, the formation of precipitates under dynamic conditions where NFM was infused into flowing electrolyte solutions was also evaluated. The data suggested that such precipitates might be formed and disrupt the blood flow and/or an NFM infusion when NFM is infused into blood flowing in the hemodialysis circuit. The findings presented herein suggest the serum levels of anionic electrolytes (e.g., phosphate), the type of excipients present in pharmaceutical products (e.g., succinic acid or citric acid), the concentration of NFM used for the infusion or the rates of NFM infusion and blood flow are all factors that could affect precipitate formation during NFM infusions for hemodialysis.

A Retrospective 30 Years After Discovery of the Enhanced Permeability and Retention Effect of Solid Tumors: Next-Generation Chemotherapeutics and Photodynamic Therapy--Problems, Solutions, and Prospects.

Solid tumor has unique vascular architecture, excessive production of vascular mediators, and extravasation of macromolecules from blood vessels into the tumor tissue interstitium. These features comprise the phenomenon named the EPR effect of solid tumors, described in 1986. Our investigations on the EPR revealed that many mediators, such as bradykinin, NO, and prostaglandins, are involved in the EPR effect, which is now believed to be the most important element for cancer-selective drug delivery. However, tumors in vivo manifest great diversity, and some demonstrate a poor EPR effect, for example, because of impaired vascular flow involving thrombosis, with poor drug delivery and therapeutic failure. Another important element of this effect is that it operates in metastatic cancers. Because few drugs are currently effective against metastases, the EPR effect offers a great advantage in nanomedicine therapy. The EPR effect can also be augmented two to three times via nitroglycerin, ACE inhibitors, and angiotensin II-induced hypertension. The delivery of nanomedicines to tumors can thereby be enhanced. In traditional PDT, most PSs had low MW and little tumor-selective accumulation. Our hydroxypropylmetacrylamide-polymer-conjugated-PS, zinc protoporphyrin (apparent MW >50 kDa) showed tumor-selective accumulation, as revealed by fluorescent imaging of autochthonous cancers. After one i.v. injection of polymeric PS followed by two or three xenon light irradiation/treatments, most tumors regressed. Thus, nanoprobes with the EPR effect seem to have remarkable effects. Enhancing the EPR effect by using vascular modulators will aid innovations in PDT for greater tumor-targeted drug delivery.

Pronounced Cellular Uptake of Pirarubicin versus That of Other Anthracyclines: Comparison of HPMA Copolymer Conjugates of Pirarubicin and Doxorubicin.

Many conjugates of water-soluble polymers with biologically active molecules were developed during the last two decades. Although, therapeutic effects of these conjugates are affected by the properties of carriers, the properties of the attached drugs appear more important than the same carrier polymer in this case. Pirarubicin (THP), a tetrahydropyranyl derivative of doxorubicin (DOX), demonstrated more rapid cellular internalization and potent cytotoxicity than DOX. Here, we conjugated the THP or DOX to N-(2-hydroxypropyl)methacrylamide copolymer via a hydrazone bond. The polymeric prodrug conjugates, P-THP and P-DOX, respectively, had comparable hydrodynamic sizes and drug loading. Compared with P-DOX, P-THP showed approximately 10 times greater cellular uptake during a 240 min incubation and a cytotoxicity that was more than 10 times higher during a 72-h incubation. A marginal difference was seen in P-THP and P-DOX accumulation in the liver and kidney at 6 h after drug administration, but no significant difference occurred in the tumor drug concentration during 6-24 h after drug administration. Antitumor activity against xenograft human pancreatic tumor (SUIT2) in mice was greater for P-THP than for P-DOX. To sum up, the present study compared the biological behavior of two different drugs, each attached to an N-(2-hydroxypropyl)methacrylamide copolymer carrier, with regard to their uptake by tumor cells, body distribution, accumulation in tumors, cytotoxicity, and antitumor activity in vitro and in vivo. No differences in the tumor cell uptake of the polymer-drug conjugates, P-THP and P-DOX, were observed. In contrast, the intracellular uptake of free THP liberated from the P-THP was 25-30 times higher than that of DOX liberated from P-DOX. This finding indicates that proper selection of the carrier, and especially conjugated active pharmaceutical ingredient (API) are most critical for anticancer activity of the polymer-drug conjugates. THP, in this respect, was found to be a more preferable API for polymer conjugation than DOX. Hence the treatment based on enhanced permeability and retention (EPR) effect that targets more selectively to solid tumors can be best achieved with THP, although both polymer conjugates of DOX and THP exhibited the EPR effects and drug release profiles in acidic pH similarly.

Synthesis and therapeutic effect of styrene-maleic acid copolymer-conjugated pirarubicin.

Previously, we prepared a pirarubicin (THP)-encapsulated micellar drug using styrene-maleic acid copolymer (SMA) as the drug carrier, in which active THP was non-covalently encapsulated. We have now developed covalently conjugated SMA-THP (SMA-THP conjugate) for further investigation toward clinical development, because covalently linked polymer-drug conjugates are known to be more stable in circulation than drug-encapsulated micelles. The SMA-THP conjugate also formed micelles and showed albumin binding capacity in aqueous solution, which suggested that this conjugate behaved as a macromolecule during blood circulation. Consequently, SMA-THP conjugate showed significantly prolonged circulation time compared to free THP and high tumor-targeting efficiency by the enhanced permeability and retention (EPR) effect. As a result, remarkable antitumor effect was achieved against two types of tumors in mice without apparent adverse effects. Significantly, metastatic lung tumor also showed the EPR effect, and this conjugate reduced metastatic tumor in the lung almost completely at 30 mg/kg once i.v. (less than one-fifth of the maximum tolerable dose). Although SMA-THP conjugate per se has little cytotoxicity in vitro (1/100 of free drug THP), tumor-targeted accumulation by the EPR effect ensures sufficient drug concentrations in tumor to produce an antitumor effect, whereas toxicity to normal tissues is much less. These findings suggest the potential of SMA-THP conjugate as a highly favorable candidate for anticancer nanomedicine with good stability and tumor-targeting properties in vivo.

Development of α-Cyclodextrin-Based Orally Disintegrating Tablets for 4-Phenylbutyrate.

Despite major improvements brought about by the introduction of taste-masked formulations of 4-phenylbutyrate (PB), poor compliance remains a significant drawback to treatment for some pediatric and dysphagic patients with urea cycle disorders (UCDs). This study reports on the development of a cyclodextrin (CD)-based orally disintegrating tablet (ODT) formulation for PB as an alternative to existing formulations. This is based on previous reports of the PB taste-masking potential of CDs and the suitability of ODTs for improving compliance in pediatric and dysphagic populations. In preliminary studies, the interactions of PB with α and ßCD in the solid state were characterized using X-ray diffraction, scanning electron microscopy, dissolution, and accelerated stability studies. Based on these studies, lyophilized PB-CD solid systems were formulated into ODTs after wet granulation. Evaluation of the ODTs showed that they had adequate physical characteristics, including hardness and friability and good storage stability. Notably, the developed αCD-based ODT for PB had a disintegration time of 28 s and achieved a slightly acidic and agreeable pH (≈5.5) in solution, which is suitable for effective PB-CD complexation and taste masking. The developed formulation could be helpful as an alternative to existing PB formulations, especially for pediatric and dysphagic UCD patients.

Characterization of carotenoid fatty acid esters from the peels of the persimmon Diospyros kaki.

Separation and structural determination of the chloroform-soluble components obtained from the peels of the persimmon (Diospyros kaki Thunb.) were performed. ß-Carotene, lycopene, ß-cryptoxanthin mono-myristic acid ester, zeaxanthin di-myristic acid ester, the latter two of which were accompanied by a small amount of palmitoleic acid in the fatty acid moiety, and oleanolic acid were identified. Among these components, the mono-fatty acid ester of ß-cryptoxanthin and the di-fatty acid ester of zeaxanthin were characterized for the first time.

Extracellular and intracellular productions of lysophosphatidic acids and cyclic phosphatidic acids by lysophospholipase D from exogenously added lysophosphatidylcholines to cultured NRK52E cells.

Lysophosphatidic acid (LPA) is a bioactive lysophospholipid that is a notable biomarker of kidney injury. However, it is not clear how LPA is produced in renal cells. In this study, we explored LPA generation and its enzymatic pathway in a rat kidney-derived cell, NRK52E cells. Culturing of NRK52E cells with acyl lysophosphatidylcholine (acyl LPC), or lyso-platelet activating factor (lysoPAF, alkyl LPC) was resulted in increased extracellular level of choline, co-product with LPA by lysophospholipase D (lysoPLD). Their activities were enhanced by addition of calcium ions to the cell culture medium, but failed to be inhibited by S32826, an autotaxin (ATX)-specific inhibitor. Liquid chromatography-tandem mass spectrometric analysis revealed the small, but significant extracellular production of acyl LPA/cyclic phosphatidic acid (cPA) and alkyl LPA/cPA. The mRNA expression of glycerophosphodiesterase (GDE) 7 with lysoPLD activity was elevated in confluent NRK52E cells cultured over 3 days. GDE7 plasmid-transfection of NRK52E cells augmented both extracellular and intracellular productions of LPAs (acyl and alkyl) as well as extracellular productions of cPAs (acyl and alkyl) from exogenous LPCs (acyl and alkyl). These results suggest that intact NRK52E cells are able to produce choline and LPA/cPA from exogenous LPCs through the enzymatic action of GDE7 that is located on the plasma membranes and intracellular membranes.

Structural Basis of the Change in the Interaction Between Mycophenolic Acid and Subdomain IIA of Human Serum Albumin During Renal Failure.

Mycophenolic acid (MP) is an active metabolite of mycophenolate mofetil, a widely used immunosuppressive drug. MP normally exhibits high plasma protein binding (97-99%), but its binding rate is decreased in patients with renal insufficiency. This decreased protein binding is thought to be associated with leukopenia, a side effect of MP. In this study, we characterized the change in protein binding of MP in renal failure patients. Our findings indicate that MP binds strongly to subdomain IIA of human serum albumin. X-ray crystallographic data indicated that the isobenzofuran group of MP forms a stacking interaction with Trp214, and the carboxyl group of MP is located at a position that allows the formation of hydrogen bonds with Tyr150, His242, or Arg257. Due to the specific binding of MP to subdomain IIA, MP is thought to be displaced by uremic toxin (3-carboxy-4-methyl-5-propyl-2-furan-propionic acid) and fatty acids (oleate or myristate) that can bind to subdomain IIA, resulting in the decreased plasma protein binding of MP in renal failure.

Study of the inclusion complexes formed between 4-phenylbutyrate and α-, ß- and γ-cyclodextrin in solution and evaluation on their taste-masking properties.

OBJECTIVES: 4-Phenylbutyrate (PB), which is used in the management of urea cycle disorders, has an unpleasant taste leading to poor patient compliance. Existing PB formulations though helpful, have some limitations in their use. This study reports on attempts to mask this unpleasant taste by complexing PB with cyclodextrins (CDs) to improve patient compliance. METHODS: α, ß and γCD were used as CDs. Phase solubility studies, circular dichroism, 1H-NMR spectroscopy, including ROESY, and molecular modelling were used to investigate and characterize the PB-CD interactions in solution. The taste-masking effect of the CDs was evaluated using in vitro taste sensor measurements. KEY FINDINGS: PB interacts with α, ß and γCD in solution to form 1:1, 1:1 and 1:2 CD: PB inclusion complexes, respectively, with stability constants in the order αCD > ßCD > γCD. Taste evaluation revealed that the CDs significantly mask the taste of PB through the formation of the inclusion complexes. Notably, αCD masked the bitter taste of PB to 30% of the initial taste at a 1:1 molar ratio. CONCLUSION: αCD significantly masks the unpleasant taste of PB in solution and can be used to formulate PB to address the limitations of existing formulations and improve patient compliance and quality of life.

Carbon monoxide, generated by heme oxygenase-1, mediates the enhanced permeability and retention effect in solid tumors.

The enhanced permeability and retention (EPR) effect is a unique pathophysiological phenomenon of solid tumors that sees biocompatible macromolecules (>40 kDa) accumulate selectively in the tumor. Various factors have been implicated in this effect. Herein, we report that heme oxygenase-1 (HO-1; also known as heat shock protein 32) significantly increases vascular permeability and thus macromolecular drug accumulation in tumors. Intradermal injection of recombinant HO-1 in mice, followed by i.v. administration of a macromolecular Evans blue-albumin complex, resulted in dose-dependent extravasation of Evans blue-albumin at the HO-1 injection site. Almost no extravasation was detected when inactivated HO-1 or a carbon monoxide (CO) scavenger was injected instead. Because HO-1 generates CO, these data imply that CO plays a key role in vascular leakage. This is supported by results obtained after intratumoral administration of a CO-releasing agent (tricarbonyldichlororuthenium(II) dimer) in the same experimental setting, specifically dose-dependent increases in vascular permeability plus augmented tumor blood flow. In addition, induction of HO-1 in tumors by the water-soluble macromolecular HO-1 inducer pegylated hemin significantly increased tumor blood flow and Evans blue-albumin accumulation in tumors. These findings suggest that HO-1 and/or CO are important mediators of the EPR effect. Thus, anticancer chemotherapy using macromolecular drugs may be improved by combination with an HO-1 inducer, such as pegylated hemin, via an enhanced EPR effect.

An in-vitro comparative study of the binding of caspofungin and micafungin to plasma proteins.

OBJECTIVES: Echinocandins are widely used for the treatment of invasive fungal diseases. While they bind strongly to plasma proteins, our knowledge of this process is not sufficient to permit their pharmacokinetics and pharmacodynamics targets to be discussed. In this study, we characterized the binding of two echinocandins, caspofungin and micafungin, to plasma proteins, human serum albumin (HSA) and human α 1-acid glycoprotein (AAG). METHODS: The binding parameters, number of binding sites (n) and association constant (K) for caspofungin and micafungin to HSA and AAG were determined by equilibrium dialysis. The binding site on HSA for these echinocandins was identified by conducting inhibition experiments. KEY FINDINGS: Caspofungin was found to bind strongly to a single site on HSA (n = 1.26, K = 0.45 × 106 M-1) and AAG (n = 0.99, K = 0.29 × 106 M-1). Micafungin was found to bind more strongly to HSA (n = 1.35, K = 1.44 × 106 M-1) and AAG (n = 1.32, K = 1.16 × 106 M-1). The binding site for these drugs on HSA appears to be within subdomain IA. CONCLUSIONS: Free fraction of caspofungin and micafungin in patients may not be substantially affected due to the contribution of AAG to the overall protein binding and the binding to subdomain IA on HSA, which is different from the major drug-binding sites within subdomains IB, IIA and IIIA.

The Nitrated Form of Nateglinide Induces Apoptosis in Human Pancreatic Cancer Cells Through a Caspase-dependent Mechanism.

BACKGROUND/AIM: Nitric oxide (NO) has antitumor activity against various solid tumor cell types in addition to its vasodilatory effect. In the current study, we investigated the effect and mechanism of the synthetic nitrated form (NO2-NAT) of nateglinide, a hypoglycemic agent, on the induction of cell death in human pancreatic cancer cells. MATERIALS AND METHODS: NO production was evaluated by measuring nitrite (NO2) and nitrate (NO3) (NOx). Apoptotic cell numbers were determined using annexin V. RESULTS: NO2-NAT released nitrate and nitrite ions immediately upon dissolving in aqueous solution. NO2-NAT caused significant extracellular leakage of lactate dehydrogenase (LDH) in the human pancreatic cancer cell lines AsPC1 and BxPC3, and increased annexin-positive cells in a time- and concentration-dependent manner. NO2-NAT also significantly increased the activity of caspases 3 and 7. Exposure to Z-VAD-FMK, a caspase inhibitor, significantly suppressed NO2-NAT-induced cell death. CONCLUSION: These results indicated that NO2-NAT induces apoptosis in human pancreatic cancer cells and may serve as a new NO-based chemotherapeutic agent for the treatment of pancreatic cancer.

In Vitro and In Vivo Assessment of Atemoya Fruit (Annona atemoya) for Food-Drug Interactions.

BACKGROUND AND OBJECTIVES: Atemoya (Annona atemoya) is increasingly being consumed worldwide because of its pleasant taste. However, only limited information is available concerning possible atemoya-drug interactions. In the present study, the issue of whether atemoya shows food-drug interactions with substrate drugs of the major drug-metabolizing cytochrome P450s (i.e., CYP1A2, CYP2C9, and CYP3A) is addressed. METHODS: The ability of atemoya juice to inhibit the activities of phenacetin O-deethylase (CYP1A2), diclofenac 4'-hydroxylase (CYP2C9), and midazolam 1'-hydroxylase (CYP3A) was examined in vitro using human and rat liver microsomes. The in vivo pharmacokinetics of phenacetin and metabolites derived from it in rats when atemoya juice or fluvoxamine (a CYP1A2 inhibitor) was preadministered were also investigated. RESULTS: Atemoya juice significantly inhibited CYP1A2 activity in human liver microsomes, but not the activities of CYP2C9 and CYP3A. In spite of this inhibition, preadministration of atemoya had no effect on the pharmacokinetics of phenacetin, a CYP1A2 substrate, in rats. Meanwhile, preadministration of fluvoxamine significantly extended the time needed for the elimination of phenacetin, possibly due to the inhibition of CYP1A2. This suggests that the intake of an excess amount of atemoya juice is necessary to cause a change in the pharmacokinetics of phenacetin when the IC50 values for CYP1A2 inhibition by atemoya and fluvoxamine are taken into account. CONCLUSION: The results indicate that a daily intake of atemoya would not change the pharmacokinetics of CYP1A2 substrates such as phenacetin as well as CYP2C9- and CYP3A-substrate drugs.

Therapeutic potential of pegylated hemin for reactive oxygen species-related diseases via induction of heme oxygenase-1: results from a rat hepatic ischemia/reperfusion injury model.

Many diseases and pathological conditions, including ischemia/reperfusion (I/R) injury, are the consequence of the actions of reactive oxygen species (ROS). Controlling ROS generation or its level may thus hold promise as a standard therapeutic modality for ROS-related diseases. Here, we assessed heme oxygenase-1 (HO-1), which is a crucial antioxidative, antiapoptotic molecule against intracellular stresses, for its therapeutic potential via its inducer, hemin. To improve the solubility and in vivo pharmacokinetics of hemin for clinical applications, we developed a micellar hemin by conjugating it with poly(ethylene glycol) (PEG) (PEG-hemin). PEG-hemin showed higher solubility in water and significantly prolonged plasma half-life than free hemin, which resulted from its micellar nature with molecular mass of 126 kDa in aqueous media. In a rat I/R model, administration of PEG-hemin significantly elevated HO-1 expression and enzymatic activity. This induction of HO-1 led to significantly improved liver function, reduced apoptosis and thiobarbituric acid reactive substances of the liver, and decreased inflammatory cytokine production. PEG-hemin administration also markedly improved hepatic blood flow. These results suggest that PEG-hemin exerted a significant cytoprotective effect against I/R injury in rat liver by inducing HO-1 and thus seems to be a potential therapeutic for ROS-related diseases, including I/R injury.

Synthesis and In Vitro Assessment of pH-Sensitive Human Serum Albumin Conjugates of Pirarubicin.

In a previous study, we reported on the development of a synthetic polymer conjugate of pirarubicin (THP) that was formed via an acid-labile hydrazone bond between the polymer and the THP. However, the synthetic polymer itself was non-biodegradable, which could lead to unexpected adverse effects. Human serum albumin (HSA), which has a high biocompatibility and good biodegradability, is also a potent carrier for delivering antitumor drugs. The objective of this study was to develop pH-sensitive HSA conjugates of THP (HSA-THP), and investigate the release of THP and the cytotoxicity under acidic conditions in vitro for further clinical development. HSA-THP was synthesized by conjugating maleimide hydrazone derivatives of THP with poly-thiolated HSA using 2-iminothiolane, via a thiol-maleimide coupling reaction. We synthesized two types of HSA-THP that contained different amounts of THP (HSA-THP2 and HSA-THP4). Free THP was released from both of the HSA conjugates more rapidly at an acidic pH, and the rates of release for HSA-THP2 and HSA-THP4 were similar. Moreover, both HSA-THPs exhibited a higher cytotoxicity at acidic pH than at neutral pH, which is consistent with the effective liberation of free THP under acidic conditions. These findings suggest that these types of HSA-THPs are promising candidates for further development.