Development of a novel method for predicting human volume of distribution at steady-state of basic drugs and comparative assessment with existing methods

The parameters characterizing tissue distribution refer to the tissue/plasma partition coefficients (Kp), which can be used to derive volume of distribution at steady-state (V_ss). The effort for predicting drug distribution in human has been further expanded to calculation methods using in vitro-based algorithms. The objective of the present study was to develop a novel prediction method to estimate human V_ss for moderate-to-strong bases. The predictive performance of the novel method was compared with other well established in vitro-based methods available in the literature. Relevant information collected from previous prediction studies of V_ss facilitated the development of the novel method. This was based on the calculation of V_ss from data on Kp, which were estimated by correlating the unbound tissue/plasma ratio in vivo (Kpu) with the unbound red blood cells partitioning (RBCu) determined in vitro. The comparative assessment of the novel correlation method with existing prediction methods of human V_ss was done using a literature dataset of 61 basic drugs (at least one pK_a ≥ 7). The five existing V_ss prediction methods published in the literature are comprised of four versions of tissue composition-based models along with the model of Lombardo using the principle of Oie-Tozer. The statistical analysis of the prediction performance indicated that the novel method demonstrated a greater degree of accuracy compared to all other published methods. The maximum percentage of predicted values that fall within a twofold-error range is 77% for the basic drugs tested. Overall, the present study describes the development and the assessment of the predictive performance of the novel prediction method of human V_ss based upon in vitro data, which appears to be superior based on the current dataset studied for basic drugs.     

Prediction of clinical pharmacokinetic parameters of linezolid using animal data by allometric scaling: applicability for the development of novel oxazolidinones

1.?Allometric scaling has previously been used as an effective tool for the prediction of human pharmacokinetic data. The pharmacokinetic data for linezolid, a novel oxazolidinone to treat Gram-positive pathogens, in mice, rats and dogs were subjected to simple allometric scaling. Generated allometric equations for parameters such as clearance (CL), volume of distribution (V_ss) and elimination rate constant (K₁₀) were used to predict human pharmacokinetic parameters including elimination half-lives. In addition, the human plasma concentration–time curve was simulated using a one-compartmental model.

2.?Application of simple allometry (Y?=?aW^b) for animal parameters such as CL, V_ss, and K₁₀ showed excellent allometric fit (r?≥?0.98). The allometric equations for CL, V_ss, and K₁₀ were??0.5465W^0.6595,??0.1369W^0.9246, and??0.4117W^–0.3139, respectively. The confidence in predictability of CL and V_ss parameters was particularly high since the allometric exponents of CL and V_ss almost approached the suggested values of 0.75 and 1.00, respectively.

3.?Animal pharmacokinetic parameters generated in the present authors’?laboratories for linezolid were in close agreement with reported literature values. The predicted human values for CL (4.68?l?h^?1), V_ss (37.07 litres), and K₁₀ (0.10?h^?1) were within the range observed for linezolid in the literature (CL?=?4?10.5 l?h^?1; V_ss?=?21???53 litres; K₁₀?=?0.09???0.3?h^?1). The human half-life (t_1/2) predicted using allometry (6.9?h) was similar to reported values in humans of 5?h. In summary, the retrospective analysis for linezolid suggests that allometric scaling can be used as a prospective tool for predicting human pharmacokinetic parameters of novel oxazolidinones.     

Pharmacokinetic interaction between liquiritigenin (LQ) and DDB: Increased glucuronidation of LQ in the liver possibly due to increased hepatic blood flow rate by DDB

It has been reported that both liquiritigenin (LQ) and dimethyl-4,4′-dimethoxy-5,6,5′,6′-dimethylenedioxybiphenyl-2,2′-dicarboxylate (DDB) have a hepatoprotective effect, and administration of both drugs together shows additive protective effect against acute liver injuries. Therefore, the pharmacokinetic interaction between LQ and DDB in rats was studied. LQ (20 and 50 mg/kg for the i.v. and p.o. administration, respectively), DDB (10 mg/kg for both i.v. and p.o. administration), and both drugs together were once administered intravenously or orally to rats. After the i.v. administration of both drugs together, the Cl_nr and AUC of LQ were significantly faster (by 30.5%) and smaller (by 22.5%), respectively, than those of without DDB due to the faster hepatic blood flow rate by DDB. After the p.o. administration of both drugs together, the AUC of LQ was comparable to that of without DDB due to negligible effect of DDB on intestinal metabolism of LQ. The pharmacokinetic parameters of DDB after both i.v. and p.o. administration were not altered by LQ, indicating that LQ did not considerably affect the pharmacokinetics of DDB in rats.     

Application of pharmacokinetic/pharmacodynamic modelling and simulation for the prediction of target attainment of ceftobiprole against meticillin-resistant Staphylococcus aureus using minimum inhibitory concentration and time–kill curve based approaches

The purpose of this report was to compare two different methods for dose optimisation of antimicrobials. The probability of target attainment (PTA) was calculated using Monte Carlo simulation to predict the PK/PD target of fT_>MIC or modelling and simulation of time–kill curve data. Ceftobiprole, the paradigm compound, activity against two MRSA strains was determined, ATCC 33591 (MIC = 2 mg/L) and a clinical isolate (MIC = 1 mg/L). A two-subpopulation model accounting for drug degradation during the experiment adequately fit the time–kill curve data (concentration range 0.25–16× MIC). The PTA was calculated for plasma, skeletal muscle and subcutaneous adipose tissue based on data from a microdialysis study in healthy volunteers. A two-compartment model with distribution factors to account for differences between free serum and tissue interstitial space fluid concentration appropriately fit the pharmacokinetic data. Pharmacodynamic endpoints of fT_>MIC of 30% or 40% and 1- or 2-log kill were used. The PTA was >90% in all tissues based on the PK/PD endpoint of fT_>MIC >40%. The PTAs based on a 1- or 2-log kill from the time–kill experiments were lower than those calculated based on fT_>MIC. The PTA of a 1-log kill was >90% for both MRSA isolates for plasma and skeletal muscle but was slightly below 90% for subcutaneous adipose tissue (both isolates ca. 88%). The results support a dosing regimen of 500 mg three times daily as a 2-h intravenous infusion. This dose should be confirmed as additional pharmacokinetic data from various patient populations become available.     

A new and simple HPLC method for determination of etamsylate in human plasma and its application to pharmacokinetic study in healthy adult male volunteers

A new and simple HPLC assay method was developed and validated for the determination of etamsylate in human plasma. After protein precipitation with 6% perchloric acid, satisfactory separation was achieved on a HyPURITY C₁₈ column (250 mm × 4.6 mm, 5 μm) using a mobile phase comprising 20 mM sodium dihydrogen phosphate-2 hydrate (pH was adjusted to 3.5 by phosphoric acid) and acetonitrile at a ratio of 95:5 v/v. The elution was isocratic at ambient temperature with a flow rate of 0.75 ml/min. Allopurinol was used as internal standard. The calibration curve was linear over the range from 0.25 to 20 μg/ml (r² = 0.999). The limit of quantification for etamsylate in plasma was 0.25 μg/ml. The within day coefficient of variance (%CV) ranged from 3.9% to 10.2%, whereas the between-day %CV ranged from 3.1% to 8.7%. The assay method has been successfully used to estimate the pharmacokinetics of etamsylate after oral administration of a 500 mg tablet under fasting conditions to 24 healthy Egyptian human male volunteers. Various pharmacokinetic parameters including AUC_0–t, AUC_0–∞, C_max, T_max, t_1/2, MRT, Cl/F, and V_d/F were determined from plasma concentration–time profile of etamsylate.     

Increased aquaglyceroporin 9 expression disrupts arsenic resistance in human lung cancer cells

Resistance to chemotherapy is one of the major problems in treatment responses of lung cancer. This study explored the mechanism underlying the arsenic resistance of lung cancer. Four lung cancer cells with different proliferation activity were characterized for cytotoxicity, arsenic influx/efflux, and arsenic effects on intracellular glutathione and 8-hydroxy-2′-deoxyguanosine (8-OHdG) production. Our data revealed that relative proliferation potency of these cells was H1299 > A549 > CL3 > H1355. Moreover, A549, H1299, and H1355 were markedly resistant to As₂O₃ with IC50 ≈ 100 μM, whereas CL3 was sensitive to As₂O₃ with IC50 ≈ 11.8 μM. After treatment with the respective As₂O₃ at IC50, arsenic influx/efflux activity in CL3 was comparable to those in the other three arsenic-resistant cells. However, differences in glutathione levels and 8-OHdG production were also detected either before or after arsenic treatment, indicating that a certain degree of variation in anti-oxidative systems and/or 8-OHdG repair activity existed in these cell lines. By transfection of an aquaglyceroporin 9 (AQP9) gene, we showed that increased AQP9 expression significantly enhanced arsenic uptake and disrupted arsenic resistance of A549. The present study strongly suggests that membrane transporters responsible for arsenic uptake, such as AQP9, may play a critical role in development of arsenic resistance in human lung cancer cells.     

Meta-analysis of inter-patient pharmacokinetic variability of liposomal and non-liposomal anticancer agents

A meta-analysis was conducted to evaluate the inter-patient pharmacokinetic (PK) variability of liposomal and small molecule (SM) anticancer agents. Inter-patient PK variability of 9 liposomal and SM formulations of the same drug was evaluated. PK variability was measured as coefficient of variance (CV%) of area under the plasma concentration versus time curve (AUC) and the fold-difference between AUC_max and AUC_min (AUC range). CV% of AUC and AUC ranges were 2.7-fold (P < 0.001) and 16.7-fold (P = 0.13) greater, respectively, for liposomal compared with SM drugs. There was an inverse linear relationship between the clearance (CL) of liposomal agents and PK variability with a lower CL associated with greater PK variability (R² = 0.39). PK variability of liposomal agents was greater when evaluated from 0-336 h compared with 0-24 h. PK variability of liposomes is significantly greater than SM. The factors associated with the PK variability of liposomal agents need to be evaluated.From the Clinical EditorIn this meta-analysis, the inter-patient pharmacokinetic variability of 9 liposomal and small molecule anti-cancer agents was studied. The authors determined that several parameters are in favor of the liposomal formulation; however, the PK variability of the formulation was higher compared with small molecule agents, the reason for which remains to be determined in future studies.     

Pharmacokinetic properties and metabolism of a new potent antimalarial N-alkylamidine compound,M64, and its corresponding bioprecursors

Antimalarial activities and pharmacokinetics of the bis-alkylamidine, M64, and its amidoxime, M64-AH, and O-methylsulfonate, M64-S-Me, derivatives were investigated. M64 and M64-S-Me had the most potent activity against the Plasmodium falciparum growth (IC₅₀ < 12 nM). The three compounds can clear the Plasmodium vinckei infection in mice (ED₅₀ < 10 mg/kg). A liquid chromatography–mass spectrometry method was validated to simultaneously quantify M64 and M64-AH in human and rat plasma. M64 is partially metabolized to M64-monoamidoxime and M64-monoacetamide by rat and mouse liver microsomes. The amidoxime M64-AH undergoes extensive metabolism forming M64, M64-monoacetamide, M64-diacetamide and M64-monoamidoxime. Strong interspecies differences were observed. The pharmacokinetic profiles of M64, M64-AH and M64-S-Me were studied in rat after intravenous and oral administrations. M64 is partially metabolized to M64-AH; while M64-S-Me is rapidly and totally converted to M64 and M64-AH. M64-AH is mostly oxidized to the inactive M64-diacetamine while its N-reduction to the efficient M64 is a minor metabolic pathway. Oral dose of M64-AH was well absorbed (38%) and converted to M64 and M64-diacetamide. This study generated substantial information about the properties of this class of antimalarial drugs. Other routes of synthesis will be explored to prevent oxidative transformation of the amidoxime and to favour the N-reduction.     

The pharmacokinetics of orally administered S-carboxymethyl-l-cysteine in the dog,calf and sheep

The aim of this study was to investigate the feasibility of employing S-carboxymethyl-l-cysteine as a treatment of chronic obstructive pulmonary disease in dogs. To this end the pharmacokinetic parameters of orally administered S-carboxymethyl-l-cysteine were determined in the dog, cow and sheep. Six healthy beagle dogs, six endogenous Greek sheep and four Holstein Fresian calves were orally dosed with 10 mg/kg body weight of S-carboxymethyl-l-cysteine. No significant differences in T_max and T_1/2 were reported between the species. However, significantly higher AUC_(0–last), 21.56 ± 6.67 μg h ml^?1 and AUC_(0–∞), 21.63 ± 6.68 μg h ml^?1 were seen in the dogs compared to the sheep and calves. The calculated V_D was significantly higher in the sheep (10.4 ± 2.7 L kg^?1) and the calves (3.8 ± 0.7 L kg^?1) compared to the dogs (1.0 ± 0.6 L kg^?1). The rank order of increasing C_L was sheep (3.4 ± 2.7 L h^?1 kg^?1) > calves (2.7 ± 0.4 L h^?1 kg^?1) > dogs (0.5 ± 0.2 L h^?1 kg^?1). The result for the dogs was significantly lower that the calculated C_L for the sheep and calves.All these results indicate that the oral administration of S-carboxymethyl-l-cysteine may be useful during the therapeutic management of chronic obstructive pulmonary disease in dogs.     

Comparative in vitro and ex-vivo myelotoxicity of aflatoxins B1 and M1 on haematopoietic progenitors (BFU-E,CFU-E,and CFU-GM): Species-related susceptibility

Haemato- and myelotoxicity are adverse effects caused by mycotoxins. Due to the relevance of aflatoxins to human health, the present study, employing CFU-GM-, BFU-E- and CFU-E-clonogenic assays, aimed at (i) comparing, in vitro, the sensitivity of human vs. murine haematopoietic progenitors to AFB1 and AFM1 (0.001–50 μg/ml), (ii) assessing whether a single AFB1 in vivo treatment (0.3–3 mg/kg b.w.) alters the ability of murine bone marrow cells to form myeloid and erythroid colonies, and (iii) comparing the in vitro with the in vitro ex-vivo data.We demonstrated (i) species-related sensitivity to AFB1, showing higher susceptibility of human myeloid and erythroid progenitors (IC₅₀ values: about 4 times lower in human than in murine cells), (ii) higher sensitivity of CFU-GM and BFU-E colonies, both more markedly affected, particularly by AFB1 (IC₅₀: 2.45 ± 1.08 and 1.82 ± 0.8 μM for humans, and 11.08 ± 2.92 and 1.81 ± 0.20 μM for mice, respectively), than the mature CFU-E (AFB1 IC₅₀: 12.58 ± 5.4 and 40.27 ± 6.05 μM), irrespectively of animal species, (iii) regarding AFM1, a species- and lineage-related susceptibility similar to that observed for AFB1 and (iv) lack of effects after AFB1 in vivo treatment on the proliferation of haematopoietic colonies.     

Pharmacokinetics of garenoxacin in elderly patients with respiratory tract infections

The pharmacokinetics of the new oral des-fluoroquinolone antimicrobial garenoxacin (GRNX) was investigated in elderly patients with respiratory tract infections. Patients were treated with GRNX (200 mg or 400 mg) once daily for 7 days. Plasma GRNX concentrations were determined and pharmacokinetic parameters were estimated by Bayesian predictions using reported population pharmacokinetic parameters. At each dose, the maximum plasma concentration (C_max) and the area under the concentration–time curve (AUC) were comparable with those reported in young subjects, except that the estimated C_max and AUC values in one patient receiving the 200 mg dose whose body weight and creatinine clearance rate (CL_Cr) were 38 kg and 17 mL/min, respectively, were higher than those of the other patients given 200 mg GRNX and were comparable with those of patients who received the 400 mg dose. These results suggest that the recommended dose of GRNX should be 400 mg for most elderly and young patients, but only 200 mg in patients whose body weight and CL_Cr are <40 kg and <30 mL/min, respectively.     

Cylindrospermopsin,a blue-green algal toxin,inhibited human luteinised granulosa cell protein synthesis in vitro

The blue-green algal toxin cylindrospermopsin (CYN) inhibits protein synthesis, and CYP450 enzymes metabolise CYN to cytotoxic endproducts. Human chorionic gonadotrophin (hCG) stimulates the de novo synthesis of StAR and CYP450 aromatase. Human IVF-derived granulosa cells (GC) (n = 7) were exposed to 0–5 μM CYN ± 1 IU/ml hCG for 2–24 h. After 24 h pre-culture GC responded to hCG by increasing estradiol 17β (E₂) and progesterone (P₄) synthesis. Three micromolar of CYN ± 1 IU/ml hCG for 24 h was not cytotoxic and did not affect basal or hCG-stimulated E₂ or P₄ production, but did inhibit protein synthesis (p < 0.05, n = 4). hCG-stimulated steroidogenesis was not reduced by CYN, suggesting a lack of effect on StAR or CYP450 aromatase protein synthesis. hCG enhanced the effects of CYN on GC protein synthesis. Twenty four hours exposure to 0.1 μM CYN did not affect GC, supporting the establishment of a 0.0024 μM Guideline level for CYN in public water supplies.     

Interspecies pharmacokinetic scaling of a new carbapenem,DA-1131, in mice,rats, rabbits and dogs,and prediction of human pharmacokinetics

The total body clearance (Cl), renal clearance (Cl_r), and apparent volume of distribution at steady state (V_ss) of DA-1131, a new carbapenem, after intravenous (iv) administration of the drug, 50 mg kg⁻¹, to mice, rats, rabbits, and dogs were analysed as a function of species body weight (W) using the allometric equation for interspecies scaling, and were used to predict these parameters in humans. Significant linear relationships were obtained between log[Cl (L h⁻¹)] and log[W (kg)] (r = 0.995; p = 0.00503), log[Cl_r (L h⁻¹)] and log[W (kg)] (r = 0.998; p = 0.0429), and log[V_ss (L)] and log[W (kg)] (r = 0.987; p = 0.0126). The corresponding allometric equations were Cl = 0.706W^0.811, Cl_r = 0.318W^0.888, and V_ss = 0.194W^0.981. These allometric equations were extrapolated to predict the Cl and V_ss for DA-1131 in humans based on 70 kg body weight. The Cl and V_ss for humans predicted from the four animal data well fitted to regression lines of animal data. Interspecies scale-up of plasma concentration–time data for the four species using a complex Dedrick plot resulted in similar profiles. In addition, the concentration in plasma–time profile predicted using the four animal data well fitted to a complex Dedrick plot of animal data. Our results indicate that the DA-1131 data obtained from laboratory animals could be utilized to generate preliminary estimates of the pharmacokinetic parameters in humans. These parameters can serve as guidelines for better planning of clinical studies. © 1998 John Wiley & Sons, Ltd.     

Floating matrix dosage form for dextromethorphan hydrobromide based on gas forming technique: In vitro and in vivo evaluation in healthy volunteers

The objective of this study was to develop the dextromethorphan hydrobromide sustained-release (DMB-SR) tablets using floating technique to prolong the gastric residence time and compared their pharmacokinetic behavior with conventional sustained release tablets. DMB-SR floating tablets were prepared employing hydroxypropyl methylcellulose (HPMC) as hydrophilic gel material, sodium bicarbonate as gas-generating agent and hexadecanol as floating assistant agent. An orthogonal experiment design method was used to select the optimized formulation. The floating tablets were evaluated for uniformity of weight, hardness, friability, drug content, floating characteristics, in vitro release and in vivo bioavailability. The optimized tablets were prepared with HPMC K4M 25 mg, sodium bicarbonate 20 mg and hexadecanol 18 mg. The prepared tablets could float within 3 min and maintain for more than 24 h. The data of physical parameters were all lie within the limits. Drug release at 12 h was more than 85%. The comparative pharmacokinetic study was performed by administration of the DMB-SR floating tablets and conventional DMB-SR tablets. The area under curve of plasma concentration–time (AUC) of floating tablets was slightly higher than that of reference tablets, T_max was prolonged apparently. The results showed the floating tablets are a feasible approach for the sustained-release preparation of drugs, which have limited absorption sites in the stomach.     

Postmarketing In Vitro/In Vivo Assessment of Fixed Dose Combination Products of First Line Antiretrovirals

The purpose of this study was to evaluate the postmarket pharmaceutical equivalence, stability and bioequivalence of generic and innovator fixed dose combination products of lamivudine (3TC) and zidovudine (AZT) 150/300 mg tablets available in Nigeria. An isocratic HPLC-UV method was developed and validated for the quantitative determination of 3TC and AZT in human plasma and pharmaceutical samples. The model independent f₂ similarity factor was used to compare the dissolution profiles of the two products stored at accelerated and longterm stability conditions for 6 months. The f₂ values for 3TC and AZT in both products were found to be greater than 51. Also, the tablets were stable according to the USP potency and drug dissolution criteria with more than 80% of drug dissolution in 30 min indicating the pharmaceutical equivalence of the two products. The 90% confidence interval for the ratios of generic/innovator pharmacokinetic parameters for 3TC/AZT were 73.5–112.6/63.4–95.8 (C_max); 68.5–105.6/68.0–114.8 (AUC_0–t); and 64.2–106.2/80.1–120.3 (AUC_0–∞) respectively. The pharmacokinetic parameters failed to fully demonstrate bioequivalence between the products. The results underscored the importance of assessing the quality of the combination drug products that would ensure the safety and efficacy of the generic drug products available in the market.     

Effect of total and partial nephrectomy on the elimination of ciprofloxacin in humans

BackgroundRenal cell carcinoma (RCC) is the most common form of kidney cancer. Surgery is a standard procedure to resect the tumor during total (TN) or partial (nephron-sparing) nephrectomy (PN). Ciprofloxacin is most often administered at the usual intravenous dose of 100–400 mg/12 h. The application of such low doses of ciprofloxacin as 200 mg/24 h carries the risk of achieving subtherapeutic concentrations even in patients with limited renal function. The aim of the study was a comparison of concentrations and pharmacokinetics for ciprofloxacin at steady-state in patients after total and partial nephrectomy and evaluation of the effectiveness of the iv dose 200 mg/24 h against the theoretical value of MIC, 0.5 μg/ml.MethodsThe research was carried out on two groups of patients after nephrectomy: total (group 1, n = 21; mean [SD], age, 62.9 [14.4] years; weight, 76.0 [14.6] kg; creatinine clearance, clcr, 90.7 [22.2] ml/min) and partial (group 2, n = 15; 61.7 [9.3] years; 87.8 [16.4] kg; CL_CR, 107.8 [36.4] ml/min). The patients were treated with ciprofloxacin in the dose of 200 mg/24 h (iv). Plasma concentrations of ciprofloxacin at steady state were measured with validated HPLC method with UV detection.ResultsThe mean values of plasma concentrations of ciprofloxacin at steady state in group 1 and 2 were: C^ss_max, 2.012 and 1.345; C^ss_min, 0.437 and 0.244 μg/ml, respectively. The main pharmacokinetic parameters for ciprofloxacin in group 1 and 2 were as follows: AUC_(0–last), 30.9 [17.9] and 19.5 [8.7] μg h/ml; AUMC_(0–last), 177.91 [11.1] and 91.9 [66.5] μg h²/ ml; _t1/2β, 13.9 [7.7] and 9.8 [3.3] h; MRT, 16.5 [12.1] and 9.77 [5.4] h; V_d, 115.0 [67.2] and 142.2 [78.7] l; CL, 6.2 [3.3] and 10.8 [5.7] l/h, respectively. With the assumed MIC = 0.5 μg/ml, the values of C^ss_max/MIC < 10 and AUC/MIC < 125 were obtained in all the patients.ConclusionIn our patients we observed significant differences in some pharmacokinetic parameters of ciprofloxacin after two types of nephrectomy.     

Folate-mediated poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) nanoparticles for targeting drug delivery

A novel targeting drug delivery system (TDDS) has been developed. Such a TDDS was prepared by W₁/O/W₂ solvent extraction/evaporation method, adopting poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) [P(HB-HO)] as the drug carrier, folic acid (FA) as the targeting ligand, and doxorubicin (DOX) as the model anticancer drug. The average size, drug loading capacity and encapsulation efficiency of the prepared DOX-loaded, folate-mediated P(HB-HO) nanoparticles (DOX/FA–PEG–P(HB-HO) NPs) were found to be around 240 nm, 29.6% and 83.5%. The in vitro release profile displayed that nearly 50% DOX was released in the first 5 days. The intracellular uptake tests of the nanoparticles (NPs) in vitro showed that the DOX/FA–PEG–P(HB-HO) NPs were more efficiently taken up by HeLa cells compared to non-folate-mediated P(HB-HO) NPs. In addition, DOX/FA–PEG–P(HB-HO) NPs (IC₅₀ = 0.87 μM) showed greater cytotoxicity to HeLa cells than other treated groups. In vivo anti-tumor activity of the DOX/FA–PEG–P(HB-HO) NPs showed a much better therapeutic efficacy in inhibiting tumor growth, and the final mean tumor volume was 178.91 ± 17.43 mm³, significantly smaller than normal saline control group (542.58 ± 45.19 mm³). All these results have illustrated that our techniques for the preparing of DOX/FA–PEG–P(HB-HO) NPs developed in present work are feasible and these NPs are effective in selective delivery of anticancer drug to the folate receptor-overexpressed cancer cells. The new TDDS may be a competent candidate in application in targeting treatment of cancers.     

Sulfation of melatonin: Enzymatic characterization,differences of organs,species and genders,and bioactivity variation

Exogenous melatonin (Mel) is widely used in clinic for multiple therapeutic purposes. In metabolism pathways of Mel, 6-hydroxymelatonin-sulfate (S-O-Mel) and N-acetylserotonin sulfate (S-NAS) are the most abundant metabolites account for over 90% of total Mel metabolites in humans, indicating that sulfation plays an important role in reflecting the functions and clearance of Mel in vivo. In the present study, we characterized Mel sulfation using various human organ cytosols (liver, lung, kidney, small intestine and brain), liver cytosols from five different animal species, and cDNA-expressed human sulfotransferase (SULT) for the first time. Our results demonstrated that liver, lung, kidney and small intestine of humans had high catalytic efficiency for Mel sulfation, however, brain contained a very low reaction rate. Interestingly, organ cytosols prepared from females exhibited higher sulfation activity than those of males. SULT isoforms 1A1, 1A2, 1A3, 1B1 and 1E1 exhibited metabolic activities toward Mel. According to kinetic parameters (K_m and V_max), chemical inhibition, correlation analysis, molecular docking and sulfation assays with recombinant human SULTs isoforms, SULT1A1 was determined as the major enzyme responsible for Mel sulfation. Furthermore, considerable species differences in Mel sulfation were observed, and the total intrinsic clearance rate of Mel sulfation was as follows: monkey > rat > dog > human > pig > mouse. Additionally, the anti-inflammatory effects of Mel and its sulfated metabolites were evaluated by inhibiting nitric oxide (NO) production in RAW264.7 cells, and S-O-Mel as a bioactive form, exhibited potent bioactivity. Our investigation provided a global view of the enzyme-dependent sulfation of Mel that can guide biomedical research on Mel.     

Alterations in acetylcholine,PGE2 and IL6 release from urothelial cells following treatment with pyocyanin and lipopolysaccharide

The effects of pseudomonal virulence factor pyocyanin, and LPS from Pseudomonas aeruginosa and Escherichia coli on urothelial mediator release and cytokine production were examined. RT4 urothelial cells were treated with pyocyanin (1–100 μM) or LPS (1–100 ng/mL) for 24-h. Effects were measured in terms of changes in cell viability, basal and stretch-induced acetylcholine (Ach) and PGE₂ release, and inflammatory cytokines (IL-6 and IL-12) production. Twenty-four hour pyocyanin (100 μM) treatment significantly decreased urothelial cell viability, while stretch-induced Ach release response was inhibited. E. coli LPS (100 ng/mL) produced a similar response with an additional significant increase in basal Ach release. All three virulence factors significantly increased urothelial PGE₂ release; under basal release for pyocyanin (100 μM), stretch-induced release for pseudomonal LPS (?10 ng/mL) and both basal and stimulated release for E. coli LPS (?10 ng/mL). IL-6 and IL-12 were not detected in control samples, however 24 h treatment with pyocyanin (100 μM) or LPS (100 ng/mL) resulted in IL-6 release from urothelial cells. The changes in urothelial Ach and PGE₂, and release of inflammatory cytokine IL-6 induced by exposure to the bacterial virulence factors may play a role in the symptoms of pain and urinary urgency experienced with urinary tract infections.     

Variants of glutathione s-transferase pi 1 exhibit differential enzymatic activity and inhibition by heavy metals

Nonsynonymous single nucleotide polymorphisms in glutathione s-transferase pi 1 (GSTP1; Ile/Val 105, Ala/Val 114) have been associated with altered toxicant metabolism in epidemiological cohorts. We explored the impact of GSTP1 genotype on enzyme kinetics and heavy metal inhibition in vitro. Four GSTP1 allozymes (105/114: Ile/Ala, Val/Ala, Ile/Val, Val/Val) were expressed in and purified from Escherichia coli. Enzyme activity assays quantifying the rate of glutathione conjugation with 1-chloro-2,4-dinitrobenzene (CDNB) revealed significant differences in kinetic parameters depending on genotype (p < 0.01). Allozymes with Ile105 had better catalytic efficiency and greater affinity for CDNB (mean ± SEM: Ile105 Ala114 K_m = 0.33 ± 0.07 mM vs. Val105 Ala114 K_m = 1.15 ± 0.07 mM). Inhibition of GSTP1 activity by heavy metals was assessed following treatment with mercury (inorganic-HgCl₂, methylmercury-MeHg), selenium, cadmium, lead, arsenic, and manganese. All allozymes were inhibited by HgCl₂ (IC₅₀ range: 24.1–172 μM), MeHg (93.9–480 μM), and selenium (43.7–62.8 μM). Genotype significantly influenced the potency of mercury with GSTP1 Ile105 Val114 the least sensitive and Val105 Ala114 the most sensitive to inhibition by HgCl₂ and MeHg. Overall, genotype of two nonsynonymous polymorphisms in GSTP1 influenced enzyme kinetics pertaining to an electrophilic substrate and inhibition by two mercury species.