Effects of Hizikia fusiforme polysaccharides on innate immunity and disease resistance of the mud crab Scylla paramamosain.

In this study, we extracted the polysaccharides from Hizikia fusiforme (HFPs) and evaluated their effects on the immune response of the mud crab Scylla paramamosain. Compositional analysis revealed that HFPs were composed mainly of mannuronic acid (49.05%) and fucose (22.29%) as sulfated polysaccharides, and the sugar chain structure was ß-type. These results indicated that HFPs have potential antioxidant and immunostimulation activity in vivo or in vitro assays. Through this research, we found that HFPs inhibited viral replication in white spot syndrome virus (WSSV)-infected crabs and promoted phagocytosis of Vibrio alginolyticus by hemocytes. Quantitative PCR results showed that HFPs up-regulated the expression levels of astakine, crustin, myosin, MCM7, STAT, TLR, JAK, CAP, and p53 in crab hemocytes. HFPs also promoted the activities of superoxide dismutase and acid phosphatase and the hemolymph antioxidant activities of crabs. HFPs maintained peroxidase activity after WSSV challenge, thereby providing protection against oxidative damage caused by the virus. HFPs also promoted apoptosis of hemocytes after WSSV infection. In addition, HFPs significantly enhanced the survival rate of WSSV-infected crabs. All results confirmed that HFPs improved the innate immunity of S. paramamosain by enhancing the expression of antimicrobial peptides, antioxidant enzyme activity, phagocytosis, and apoptosis. Therefore, HFPs have potential for use as therapeutic or preventive agents to regulate the innate immunity of mud crabs and protect them against microbial infection.

Inhibitory effects of ketoconazole and rifampin on OAT1 and OATP1B1 transport activities: considerations on drug-drug interactions.

Ketoconazole and rifampin are the most widely used compounds examined in recent drug-drug interaction (DDI) studies, and they have multiple roles in modulating drug metabolizing enzymes and transporters. To determine the underlying mechanisms of DDI, this study was performed to investigate the inhibitory effects of ketoconazole and rifampin on the functions of OAT1 and OATP1B1, and to evaluate the potential of ketoconazole and rifampin for DDI with substrate drugs for these transporters in a clinical setting. Ketoconazole inhibited OATP1B1-mediated transport activity, while rifampin inhibited OAT1 and OATP1B1. Inhibition by rifampin and ketoconazole of the uptake of olmesartan, a substrate for OAT1 and OATP1B1, was evaluated in oocytes overexpressing these transporters. The K(i) values for rifampin on OAT1 and OATP1B1-mediated olmesartan uptake were 62.2 and 4.42 µM, respectively, and the K(i) value for ketoconazole on OATP1B1-mediated olmesartan uptake was 66.1 µM. As measured plasma concentrations of rifampin and ketoconazole were 7.29 and 6.4-13.3 µM, respectively, the likelihood of an OATP1B1-mediated drug-drug interaction between rifampin and olmesartan is thought to be possible, whereas OAT1 or OATP1B1-mediated DDI between rifampin or ketoconazole and olmesartan appears unlikely in the clinical setting.

Increased affinity to canalicular P-gp via formation of lipophilic ion-pair complexes with endogenous bile salts is associated with mw threshold in hepatobiliary excretion of quaternary ammonium compounds.

OBJECTIVES: We intended to elucidate the mechanism of the molecular weight (Mw) threshold (i.e., 200 +/- 50) for appreciable hepatobiliary excretion of quaternary ammonium compounds (QACs) in rats. METHODS: We measured the effect of ion-pair complexation of QACs with taurodeoxycholate (TDC), an endogenous anionic bile salt, on the apparent partition coefficients (APC) of QACs between n-octanol and phosphate buffer, and the inhibition of organic cation transporter1 (OCT1)- and P-glycoprotein (P-gp)-mediated transport of representative substrates. RESULTS: By measuring the APC, we demonstrated that there is a Mw threshold of 200 +/- 50 in the ion-pair complexation of QACs with an endogenous bile salt, TDC. We also demonstrated, by measuring the inhibition of relevant transports, that a Mw threshold of 200 +/- 50 exists for the binding of QACs to canalicular P-gp, but not for sinusoidal OCT1. The Mw threshold values for ion-pair formation and P-gp binding were identical and consistent with the reported Mw threshold value for appreciable biliary excretion of QACs in rats. CONCLUSIONS: Mw-dependent binding of QACs to canalicular P-gp contributes in part to the mechanism of the Mw threshold of 200 +/- 50. The formation of lipophilic ion-pair complexes with bile salts, followed by stronger binding to canalicular P-gp, appears to accelerate biliary excretion of QACs with a high Mw.

Sitagliptin attenuates metformin-mediated AMPK phosphorylation through inhibition of organic cation transporters.

To assess potential interactions between sitagliptin and metformin, we sought to characterize the in vitro inhibitory potency of sitagliptin on the uptake of MPP(+) and metformin, representative substrates for OCTs, and to evaluate the pharmacological pathways that may be affected by the combination of metformin and sitagliptin. Among the OATs and OCTs screened, OAT3-mediated salicylate uptake and OCT1- and OCT2-mediated MPP(+) uptake were inhibited by sitagliptin. The K(i) values of sitagliptin for OCT1- and OCT2-mediated metformin uptake were 34.9 and 40.8 µM, respectively. As OCT1 is the gate protein for metformin action in the liver, we investigated whether sitagliptin-mediated OCT1 inhibition affected metformin-induced activation of AMPK signalling. Treatment with sitagliptin in MDCK-OCT1 and HepG2 cells resulted in a reduced level of phosphorylated AMPK, with K(i) values of 38.8 and 43.3 µM, respectively. These results suggest that the inhibitory potential of sitagliptin on OCT1 may attenuate the first step of metformin action, that is, the phosphorylation of AMPK. Nevertheless, the likelihood of a drug-drug interaction between sitagliptin and metformin is believed to be remote in usual clinical setting.

Amplification of tumor antigen presentation by NLGplatin to improve chemoimmunotherapy.

Oxaliplatin is a chemotherapeutic agent widely used in cancer treatment whereas its immunosuppressive effect hinders the progress of immunotherapy. Here we have synthesized a new compound NLGplatin constructed by combining oxaliplatin (OXA) and indoleamine 2,3-dioxygenase (IDO) inhibitor NLG919. The NLGplatin acquires chemotherapeutic properties of OXA and can activate the immune system, and also retains the ability to inhibit IDO enzyme activity without affecting the proliferation of immune cells. This difunctional drug has a great potential to achieve effective cancer chemoimmunotherapy.

Regulating the Golgi apparatus by co-delivery of a COX-2 inhibitor and Brefeldin A for suppression of tumor metastasis.

Finding a cure for breast cancer currently remains a medical challenge in due to the failure of common treatment methods to inhibit invasion and metastasis of cancer cells, which eventually leads to recurrence of breast cancer. Many secreted proteins are overexpressed and play crucial roles in tumorigenesis and development. The Golgi apparatus is a key protein processing and secretion factory in which metastasis-associated proteins are modified, transported and secreted; thus, regulating the Golgi apparatus of tumor cells is a viable strategy to inhibit tumor metastasis. Herein, celecoxib (CLX) and Brefeldin A (BFA) were encapsulated into the biocompatible polymer PLGA-PEG to form nanoparticles that act on the Golgi apparatus to treat metastatic breast cancer; CLX is a specific COX-2 inhibitor which accumulates in the Golgi apparatus, and BFA is a protein transport inhibitor fusing the Golgi apparatus into endoplasmic reticulum. The optimized CLX and BFA co-loaded nanoparticles (CBNPs) possessed good physicochemical properties. CBNPs efficiently damaged the Golgi apparatus within 30 min and showed enhanced cytotoxicity of CLX and BFA toward murine metastatic breast cancer 4T1 cells. The migration and invasion abilities of the cells were dramatically suppressed by the CBNPs. Further, the expression and secretion of metastasis-associated proteins such as matrix metalloproteinase-9 (MMP-9) and vascular endothelial growth factor (VEGF) were remarkably decreased. Our findings showed that co-delivering CLX and BFA to regulate the Golgi apparatus may be an efficient strategy to inhibit breast cancer growth and suppress tumor cell metastasis.

Upregulation of COX-2 in the lung cancer promotes overexpression of multidrug resistance protein 4 (MRP4) via PGE2-dependent pathway.

It is apparent that lung cancer is associated with inflammation, with accompanying hallmark elevations of cyclooxygenase 2 (COX-2) and prostaglandin E2 (PGE2) levels. However, the effects of these changes on MRP efflux transporters have not been thoroughly investigated before. Here, we report that upregulation of COX-2 can induce overexpression of MRP4 in both A549 non-small-cell lung cancer cell lines and mouse lung cancer models. In A549 cells, phorbol 12-myristate 13-acetate (PMA) treatment induced upregulation of COX-2 and MRP4 together, but not other MRP transporters. Transient overexpression of human COX-2 cDNA also specifically increased COX-2 and MRP4. Moreover, COX inhibitor treatment and COX-2-specific siRNA significantly inhibited the upregulation of MRP4. Additionally, PMA-treatment increased extracellular PGE2 levels, likely due to increased MRP4 function. Likewise, COX-2-specific siRNA reduced extracellular PGE2 levels. Furthermore, COX-2 upregulation resulted in an increase in mPGES-1, an enzyme responsible for PGE2 production. Finally, metastasized lung cancer model mice exhibited increased expression levels of COX-2 and MRP4, as well as mPGES-1. In conclusion, the present study suggests that overexpression of MRP4 in lung cancer may be attributable to COX-2 upregulation via a PGE2-dependent pathway.

Correlation of fibroblast growth factor 21 serum levels with metabolic parameters in Japanese subjects.

OBJECTS: Since serum level of fibroblast growth factor 21 (FGF21) has been implicated as a potential biomarker for the early detection of the metabolic syndrome and type 2 diabetes, we examined how FGF21 serum levels are correlated with metabolic parameters in Japanese subjects. METHODS: FGF21 levels were analyzed by enzyme-linked immunosorbent assays. Spearman's correlation and multiple stepwise regression analyses were used to examine the relationship between serum FGF21 and other factors. A Mann-Whitney U test was performed between the normal and high groups for triglycerides and systolic blood pressure (BP) respectively. RESULTS: By univariate correlation analysis, serum FGF21 levels were significantly associated with triglyceride levels, systolic BP, diastolic BP, pulse pressure, body mass index (BMI), age, fasting plasma glucose (FPG) levels, and total cholesterol levels. Multiple regression analysis (adjusted for age, gender, and BMI) showed that serum FGF21 levels were independently and significantly associated with triglyceride levels and systolic BP. Serum FGF21 levels were significantly higher in subjects with high triglyceride levels and high systolic BP compared with those who had normal triglyceride levels and normal systolic BP respectively. CONCLUSIONS: This study found that FGF21 levels might be a biomarker for some metabolic disorders associated with metabolic syndrome.

Development of a LC-MS method for quantification of FK-3000 and its application to in vivo pharmacokinetic study in drug development.

FK-3000 can inhibit proliferation of carcinomas and arrest the growth of carcinoma cells through cytotoxic (apoptosis induction) and cytostatic (cell cycle arrest) effects. A rapid and sensitive assay was developed and validated using liquid chromatography-mass spectrometry (LC-MS) for FK-3000 in rat plasma. FK-3000 was extracted with ethyl acetate from rat plasma samples, and the residue containing the FK-3000 was dried in a gentle stream of nitrogen and reconstituted with acetonitrile. The FK-3000 was quantified using high-performance liquid chromatography (HPLC; Waters Alliance 2695) with a reversed phase Gemini column (3 mm × 150 mm, 5 µm; Phenomenex, USA) and a Waters Micromass ZQ detector. FK-3000 and phenazine, an internal standard (IS), were analyzed by selected ion monitoring (SIM) at m/z transitions of 418.45 and 256, respectively. A lower limit of quantification (LLOQ) of 10 ng/mL was observed, with a linear dynamic range from 10 to 10,000 ng/mL (R>0.999). The accuracy, precision, recovery, matrix effects, and stability of the assay were deemed acceptable according to the FDA guidance for industry (bioanalytical method validation). The FK-3000 concentration was measured in plasma samples up to 6 h following FK-3000 administration at an oral dose of 20 mg/kg. The findings indicate that the assay method is suitable for routine pharmacokinetic (PK) studies of FK-3000 in rats.

Quantification of oltipraz using liquid chromatography-tandem mass spectrometry and its application to a pharmacokinetic study in rat plasma.

An assay method for the determination of oltipraz, a candidate drug for the treatment of liver fibrosis and liver cirrhosis, was developed in rat plasma using a fast-flow protein precipitation (FF-PPT) method coupled with LC-MS/MS for quantification to reduce the labor and to improve the speed of analysis. The applicability of the assay to pharmacokinetic studies was also evaluated. Oltipraz and ethyl-oltipraz, an internal standard (IS), were analyzed by multiple reaction monitoring (MRM) at m/z transitions of 227→193 and 241→174, respectively. A lower limit of quantification (LLOQ) of 20 ng/mL was observed, with a linear dynamic range from 20 to 4000 ng/mL (R>0.997). The accuracy, precision, dilution, recovery, and stability of the assay were deemed acceptable according to FDA guidelines. Oltipraz concentrations were measured successfully in plasma samples up to 12h post-dose in rats that had received an oral dose of 60 mg/kg. The findings indicate that the assay method is rapid and sensitive to oltipraz, showing applicability for pharmacokinetics (PK) studies of oltipraz in other small animals, including rats.

Enhanced electrostatic interaction between chitosan-modified PLGA nanoparticle and tumor.

In our previous study, lung tumor-specific targeting of paclitaxel was achieved in mice by intravenous administration of chitosan-modified paclitaxel-loaded PLGA nanoparticles (C-NPs-paclitaxel). Transient formation of aggregates in the blood stream followed by enhanced trapping in the capillaries was proposed as a mechanism of the lung-specific accumulation of paclitaxel. In the present study, the mechanism of tumor lung preferential accumulation of paclitaxel from C-NPs-paclitaxel was investigated. Zeta potential and in vitro cellular cytotoxicity (A549 cells and CT-26 cells) of C-NPs-paclitaxel, and in vitro uptake of coumarin 6 to these cells from chitosan-modified coumarin 6 containing PLGA nanoparticles (C-NPs-coumarin 6) were examined as a function of pH (6.8, 7.4 and 8.0). The zeta potential of C-NPs-paclitaxel increased as the medium pH became more acidic. In vitro uptake of coumarin 6 by A549 cells and CT-26 cells was enhanced at lower pH for C-NPs-coumarin 6. In vitro cytotoxicity experiment with C-NPs-paclitaxel demonstrated enhanced cytotoxicity as the pH became more acidic. Therefore, enhanced electrostatic interaction between chitosan-modified PLGA nanoparticles and acidic microenvironment of tumor cells appears to be an underlying mechanism of lung tumor-specific accumulation of paclitaxel from C-NPs-paclitaxel.

Testosterone-independent down-regulation of Oct2 in the kidney medulla from a uranyl nitrate-induced rat model of acute renal failure: effects on distribution of a model organic cation, tetraethylammonium.

Although acute renal failure (ARF) has been an area of extensive research in recent decades, our understanding of ARF is far from complete. Organic cations (OCs) are primarily excreted via vectorial transport by various renal organic cation transporters (OCTs). It is reasonable to assume that ARF may alter the expression profiles of these transporters. In a rat ARF model, induction of ARF by uranyl nitrate (UN) treatment significantly decreased the levels of Oct2 (slc22a2) mRNA and protein in the kidney medulla. mRNA expression of the other OCTs was not appreciably altered. The plasma level of testosterone, a well-known regulator of Oct2, was not changed, suggesting that the Oct2 down-regulation is testosterone-independent. The effect of reduced Oct2 expression on the distribution of a model OC, tetraethylammonium (TEA), in various rat tissues including kidney cortex and kidney medulla was investigated during steady state plasma TEA concentrations. The steady state tissue-to-plasma (T/P) TEA ratio was decreased in the kidney medulla (approximately 15-fold) during ARF. These results indicate that, in a rat model of ARF, reduced Oct2 expression in the kidney medulla results in decreased distribution of TEA to the kidney medulla, thereby reducing renal clearance of TEA in UN-ARF rats.

Effects of tetraalkylammonium compounds with different affinities for organic cation transporters on the pharmacokinetics of metformin.

The study sought to investigate the effects of tetraalkylammonium (TAA), inhibitors of the organic cation transporters (OCTs) with different affinities, on the pharmacokinetics of metformin. The inhibitory potentials of TAAs on the uptake of metformin were evaluated by determining IC(50) values in MDCK cells over-expressing OCTs and, to assess in vivo drug interactions, metformin and TAAs were coadministered to rats. Uptake of metformin was facilitated by over-expression of hOCT1 and hOCT2 and showed saturable processes, indicating that metformin is a substrate of hOCT1 and hOCT2. The IC(50) values of TAAs for hOCT2 were lower than hOCT1 and decreased with increasing alkyl chain length, indicating that the inhibitory potential of TAAs on metformin uptake was greater in hOCT2 than in hOCT1 and increased with increasing alkyl chain length. The plasma concentration of metformin was elevated by the coadministration of tetrapropylammonium (TPrA) and tetrapentylammonium (TPeA), but not by tetramethylammonium (TMA) or tetraethylammonium (TEA). However, the plasma concentrations of TMA, TEA and TPrA were not changed by the coadministration of metformin. In conclusion, in vivo drug interactions between metformin and TAAs were caused only when metformin was coadministered with TAAs showing higher affinities for OCTs.