Biodistribution characteristics of mannosylated, fucosylated, and galactosylated liposomes in mice

The in vivo disposition behavior and pharmacokinetic characteristics of galactosylated (Gal), mannosylated (Man) and fucosylated (Fuc) liposomes were compared in this study. For the preparation of the glycosylated liposomes, cholesten-5-yloxy-N-(4-((1-imino-2-beta-D-thiogalactosyle thyl)amino)a lkyl)formamide (Gal-C4-Chol) (Kawakami et al., Biochem. Biophys. Res. Commun. 252 (1998) 78-83) and its mannosylated and fucosylated derivatives (Man-C4-Chol and Fuc-C4-Chol, respectively) were synthesized. The glycosylated liposomes are composed of distearoylphosphatidylcholine (DSPC), cholesterol (Chol), and Gal-C4-Chol (or Man-C4-Chol or Fuc-C4-Chol) with the molar ratio of 60:35:5. After intravenous injection in mice, these three types of [(3)H]cholesteryl hexadecyl ether-labeled glycosylated liposomes were rapidly eliminated from the circulating blood and preferentially recovered in the liver. In contrast, DSPC/Chol (60:40) liposomes without glycosylation were retained for a long time in the circulating blood. The uptake ratios by parenchymal cells (PC) and nonparenchymal cells (NPC) (PC/NPC ratios) for 0.5% Gal, Man and Fuc liposomes were found to be 15.1, 0.6 and 0.2, respectively. The effect of predosing glycosylated proteins and liposomes on the hepatic uptake of 0.5% (3)H-labeled Gal, Man, and Fuc liposomes was investigated and the results support the conclusion that Gal, Man, and Fuc liposomes are taken up by the liver via asialoglycoprotein receptors in PC, mannose receptors in NPC, and fucose receptors in NPC, respectively. Interestingly, Gal liposomes were taken up by NPC rather than by PC at a high dose (5%). Together with the finding that 5% Gal liposomes inhibit the hepatic uptake of (3)H-labeled Fuc liposomes, this suggests that Gal-liposomes administered at a high dose will also be taken up by fucose receptors in NPC, that are considered to act as galactose particle receptors.

Disposition characteristics of emulsions and incorporated drugs after systemic or local injection

Lipid emulsions are useful tools for controlling the in vivo disposition of drugs and plasmid DNA. The dispositions of lipid emulsions are determined by their tissue interaction depending on the anatomical and physiological characteristics of each tissue and the physicochemical and biological properties of lipid emulsions. In addition, the retention of drugs is another issue, as too rapid a release of the drug would lead to failure of exerting its therapeutic potency. This review presents an overview about the disposition profiles and various physicochemical properties of lipid emulsions and incorporated drugs after systemic or local injection. Controlled biodistribution of lipid emulsions and incorporated drugs are also discussed.

Controlled biodistribution of galactosylated liposomes and incorporated probucol in hepatocyte-selective drug targeting

Two types of galactosylated liposomes containing cholesten-5-yloxy-N-(4-((1-imino-2-beta-D-thiogalactosyle thyl)amino)b utyl)formamide (Gal-C4-Chol) as a homing device were prepared to study the biodistribution of liposomal carriers and the incorporated drug. Distearoylphosphatidylcholine (DSPC)/cholesterol (Chol)/Gal-C4-Chol (60:35:5) (Gal DSPC), DSPC/Chol (60:40) (DSPC), egg yolk phosphatidylcholine (eggPC)/Chol/Gal-C4-Chol (60:35:5) (Gal eggPC), and eggPC/Chol (60:40) (eggPC) liposomes labeled with [(3)H]cholesteryl hexadecyl ether (CHE) were tested and [(14)C]probucol, with a partition coefficient between octanol and water (PC(oct)) of 10(10.8), was selected as a model drug with lipophilicity suitable for liposomal incorporation. After intravenous injection of the combination of [(14)C]probucol and [(3)H]liposomes, the liver uptake of [(3)H]CHE was the highest in Gal DSPC liposomes, followed by Gal egg PC liposomes, egg PC liposomes, and DSPC liposomes in that order. [(14)C]Probucol incorporated in Gal DSPC liposomes exhibited lower liver uptake than [(3)H]CHE, suggesting that substantial release from liposomes had taken place. In contrast, [(14)C]probucol incorporated in Gal eggPC liposomes was more stably incorporated under in vivo conditions. Co-administration with galactosylated bovine serum albumin significantly inhibited the liver uptake of [(14)C]probucol in both types of galactosylated liposomes, suggesting that the hepatic uptake of liposomes should be mediated by asialoglycoprotein receptors being [(14)C]probucol incorporated in them.

Targeted delivery of prostaglandin E1 to hepatocytes using galactosylated liposomes

Prostaglandin E(1) (PGE(1) ) was incorporated in galactosylated liposomes containing cholesten-5-yloxy-N-(4-((1-imino-2-beta-D-thiogalactosyle thyl)amino)b utyl)formamide (Gal-C4-Chol) intended for hepatocyte-selective delivery. Liposomes composed of distearoylphosphatidylcholine (DSPC)/cholesterol (Chol)/Gal-C4-Chol (60∶35∶5) were prepared and compared with DSPC/Chol (60∶40) liposomes. After intravenous injection of [(3) H]-labeled PGE(1) or cholesteryl hexadecyl ether (CHE) with the liposomal formulation, mice were sacrificed at a series of times, and the radioactivity in tissues was determined. Up to about 80% of [(3) H]CHE in galactosylated liposomes had accumulated in the liver 10 min after intravenous injection and the liver accumulation of the incorporated [(3) H]PGE(1) was significantly higher than that in control liposomes during the entire test period. The pharmacological activity was examined in mice with fulminant hepatitis induced by peritoneal injection of carbon tetrachloride. Intravenous injection of PGE(1) incorporated in DSPC/Chol/Gal-C4-Chol (60∶35∶5) liposomes significantly suppressed the GPT increase, whereas PGE(1) (dissolved in saline) and PGE(1) incorporated in DSPC/Chol (60∶40) liposomes had little effect.

Effect of vehicle properties on skin penetration of emedastine

We investigated sorption and permeation of emedastine with 11 different vehicles, composed of single or binary solvents, in excised rat skin. In the sorption study, partition parameters of the drug with each vehicle were obtained by dividing the drug amount in skin at equilibrium by its donor concentration. When the logarithm of the partition parameters for the stratum corneum/vehicle partitioning (Ks') was plotted against the dielectric constants of the vehicles, a bi-linear relationship was obtained. The skin flux of emedastine largely differ among the vehicles. A quasi-steady-state flux of emedastine exhibited a good linear relationship with Ks', except for ethanol (EtOH)/isopropyl myristate (IPM) systems, indicating that the partitioning process is critical in determining the permeation rate. Delineation of the EtOH/IPM systems would be due to an increase in the diffusivity of the drug in the stratum corneum, as indicated by the analysis using a two-layer diffusion model. Thus, differential evaluation of partitioning and diffusion processes by both sorption and permeation studies would give further insights into the effects of vehicles on skin permeation of drugs.

Chemotherapy for hepatocellular carcinoma with portal hypertension due to tumor thrombus

A case of hepatocellular carcinoma (HCC) complicated by tumor thrombosis of the main trunk is presented. Four courses of hepatic arterial infusion therapy, via a subcutaneously implanted injection port, were performed using cisplatin (10 mg for 1 hour on days 1-5) and 5-fluorouracil (250 mg for 5 hours on days 1-5). After four courses of the chemotherapy, marked reduction in size of HCC and the tumor markers were noted. The esophageal varices and ascites were improved after the chemotherapy with a recanalization of the left branch of the portal vein. The patient was doing well with a survival period of 28 months after the chemotherapy. These encouraging results suggested that the present therapy, based on the biochemical modulation, was a useful option for advanced HCC with portal hypertension due to tumor thrombosis of the main portal vein.

Pharmacokinetics and in vivo gene transfer of plasmid DNA complexed with mannosylated poly(L-lysine) in mice

To achieve mannose receptor-mediated, cell-specific, in vivo gene transfer by intravenous injection of plasmid DNA, mannosylated poly(L-lysine) (Man-PLL) was synthesized as a carrier molecule, and mixed with a plasmid DNA encoding chloramphenicol acetyltransferase (CAT) gene to form DNA/Man-PLL complex. The particle size and zeta potential of DNA/Man-PLL (prepared at 1:0.7 on a weight basis) were determined to be 220 nm and +12 mV, respectively. The pharmacokinetics of the DNA/Man-PLL complex was assessed in mice using 32P-labeled DNA ([32P]DNA). After intravenous injection of [32P]DNA/Man-PLL, the radioactivity in plasma fell rapidly and was recovered mainly in the liver nonparenchymal cells. The amount in the liver reached more than 80% of the dose. Radioactivity observed in kidney, lung, and spleen was very low compared to that in the liver. Then, the in vivo gene expression after intravenous injection of DNA/Man-PLL was examined by a CAT assay. Highest CAT activity was detected in the liver, but no activity was detected in the lung, kidney, and spleen. These results clearly indicate that a cell-specific gene delivery system can be developed by regulating the biodistribution of DNA/carrier complex through the control of its physicochemical properties.

Effect of cationic liposomes on intracellular trafficking and efficacy of antisense oligonucleotides in mouse peritoneal macrophages

We have investigated the intracellular fate and antisense effect of oligonucleotide/cationic liposome complexes using phosphorothioate oligonucleotides (S-Oligo) targeted to inducible nitric oxide synthase in mouse peritoneal macrophages. Confocal laser microscopic analysis revealed that, after application of fluorescein isothiocyanate (FITC)-labeled S-Oligo alone, the intracellular localization of fluorescence exhibited a punctate pattern in the cytoplasm, suggesting that the oligonucleotides were mainly confined to the endosomal and/or lysosomal compartments. In the case of complexation with Lipofectin and DMRIE-C liposomes, cellular uptake of FITC-S-Oligo was not greatly enhanced and the fluorescence localization in the cells was similar to that of FITC-S-Oligo alone. LipofectAMINE slightly enhanced cellular uptake of FITC-S-Oligo; however, the intracellular localization profile of FITC-S-Oligo remained largely unchanged. The antisense effect was slightly enhanced by LipofectAMINE under only very limited experimental conditions. It was concluded that cationic liposomes are not a potential carrier for S-Oligo in peritoneal macrophages because of their inability to promote the release of S-Oligo from the endosomal compartments to the cytosol over a non-toxic concentration range.

Rates of protein transport across rat alveolar epithelial cell monolayers

The transport of model proteins, ranging from 12,300 to 150,000 Da, across tight rat alveolar epithelial cell monolayers (> 2000omegacm2) grown on polycarbonate filters, was studied. Model proteins were 14C-cytochrome c, 14C-ovalbumin, granulocyte-colony stimulating factor (G-CSF), 14C-bovine serum albumin (BSA), 125I-transferrin, and 14C-immunoglobulin G. Cytochrome c was extensively metabolized, as indicated by < 10% of the dose being translocated in intact form. This contrasts with 20-80% for the other model proteins studied. The flux of cytochrome c and G-CSF was symmetric in the apical-to-basolateral (ab) and basolateral-to-apical (ba) directions. By contrast, the flux of intact ovalbumin, BSA, transferrin and immunoglobulin G showed asymmetry, with the ab flux being higher by 2-5 times. There was no relationship between ab or ba fluxes and the molecular weights of these four model proteins. Since some of the proteins were translocated at much greater rates than are consistent with restricted diffusion or pinocytosis, receptor-mediated or adsorptive transcytosis may be involved.

Effect of DNA/liposome mixing ratio on the physicochemical characteristics, cellular uptake and intracellular trafficking of plasmid DNA/cationic liposome complexes and subsequent gene expression

In order to identify the important factors involved in cationic liposome-mediated gene transfer, in vitro transfection efficiencies by plasmid DNA complexed with DOTMA/DOPE liposomes at different DNA/liposome mixing ratios were evaluated using four types of cultured cells with respect to their physicochemical properties. Significant changes were observed in the particle size and zeta potential of the complexes as well as in their structures, assessed by atomic force microscopy, which depended on the mixing ratio. In transfection experiments, except for RAW 264.7 cells (mouse macrophages), efficient gene expression was obtained in MBT-2 cells (mouse bladder tumor), NLH3T3 cells (mouse fibroblasts) and HUVEC (human umbilical vein endothelial cells) at an optimal ratio of 1:5, 1:7.5 or 1:5, respectively. On the other hand, cellular uptake of the [32P]DNA/liposome complexes increased in all cell types with an increase in the mixing ratio, which was not reflected by the transfection efficiency. The cellular damage determined by MTT assay was minimal even at the highest DNA/liposome ratio (1:10), indicating that the lower gene expression level at the higher ratio was not due to cytotoxicity induced by the complex. An ethidium bromide intercalation assay showed that the release of plasmid DNA from the complex, following the addition of negatively charged liposomes, was restricted as the mixing ratio increased. Furthermore, confocal microscopic studies using HUVEC showed that the 1:5 complexes exhibited a dispersed distribution in the cytoplasm whereas a punctuate intracellular distribution was observed for the 1:10 complexes. This suggests that there was a significant difference in intracellular trafficking, probably release from the endosomes or lysosomes, of the plasmid DNA/cationic liposome complexes between these mixing ratios. Taken together, these findings suggest that the DNA/liposome mixing ratio significantly affects the intracellular trafficking of plasmid DNA complexed with the cationic liposomes, which is an important determinant of the optimal mixing ratio in cationic liposome-mediated transfection.

Intratumoral pharmacokinetics of oligonucleotides in a tissue-isolated tumor perfusion system

The intratumoral pharmacokinetics of model oligonucleotides were studied in Walker 256 tissue-isolated tumor preparations using an in situ single-pass vascular perfusion technique. A 20-mer phosphodiester (PO) oligonucleotide, its fully phosphorothioated (PS) oligonucleotide counterpart, and an 18-mer phosphorothioated oligonucleotide containing four 2'-O-methylribonucleosides at both the 3'-end and 5'-end (PS-OMe) were used. These oligonucleotides were administered to the tumor in two ways, by constant arterial infusion and by direct intratumoral injection. In the case of constant arterial infusion, the experiments were carried out using perfusate with or without 4.7% bovine serum albumin (BSA). The protein binding of PO, PS, and PS-OMe to BSA was 46%, 87%, and 94%, respectively. No marked difference was observed between the degree of accumulation of the three types of oligonucleotides in the tumor when BSA was present in the perfusate. PS and PS-OMe showed higher degrees of accumulation in tumors compared with PO when no BSA was present. These results indicate that free (i.e., protein unbound) PS-OMe and PS have superior tumor accumulation characteristics. In the intratumoral injection experiments, PS-OMe was retained longer in tumor tissue compared with PS, suggesting that it might be useful for direct local injection into solid tumors. Thus, the present study provides useful information about the basic disposition characteristics of oligonucleotides in solid tumors.

In vivo gene delivery to the liver using novel galactosylated cationic liposomes

PURPOSE

The purpose of this study is to elucidate the in vivo gene transfer for galactosylated liposomes containing cholesten-5-yloxy-N-(4-((1-imino-2-beta-D-thiogalactosyle thyl)amino)butyl)formamide(Gal-C4-Chol) in relation to lipid composition and charge ratio.

METHODS

Galactosylated cationic liposomes containing N-[1-(2,3-dioleyloxy)propyl]-n,n,n-trimethylammonium chloride(DOTMA), Gal-C4-Chol and cholesterol(Chol), and similar liposomes were prepared. Plasmid DNA complexed with a galactosylated liposome preparation was injected intraportally into mice. The mice were sacrificed after 6 hours. The tissues were subjected to luciferase assay.

RESULTS

A markedly higher gene expression in the liver following injection of plasmid DNA that has been complexed with DOTMA/ Chol/Gal-C4-Chol(1:0.5:0.5) and DOTMA/Gal-C4-Chol(1:1) liposomes was observed. The effect was one order of magnitude higher than naked DNA and DOTMA/Chol(1:1) liposomes. Pre-exposing with galactosylated bovine serum albumin significantly reduced the hepatic gene expression. By comparison, the gene expression for galactosylated cationic liposomes containing 3beta[N-(N',N'-dimethylaminoethane)carbamoyl]cholesterol, Gal-C4-Chol and dioleoylphosphatidylethanolamine was 10 times lower. As far as the charge ratio of DOTMA/ Chol/Gal-CA-Chol(1:0.5:0.5) liposomes to plasmid DNA(1.6-7.0) was concerned, complexes with charge ratios of 2.3-3.1 produced maximal gene expression in the liver. Whereas, higher ratios resulted in enhanced expression in the lung.

CONCLUSIONS

By optimizing lipid composition and charge ratio, galactosylated liposome/DNA complexes allow superior in vivo gene transfection in the liver via asialoglycoprotein receptor-mediated endocytosis.

Design of polymeric prodrugs of PGE1 for cell-specific hepatic targeting

Based on the relationship between in vivo disposition of macromolecules and their physicochemical and biological characteristics obtained through clearance concept-based pharmacokinetic analysis, polymeric prodrugs of prostaglandin E1 (PGE1) were designed stepwise and evaluated on their targeting and therapeutic efficiencies. Although galactosylated poly-L-glutamic acid with a ethylene diamine (ED) spacer (Gal-ED-PLGA) showed good targeting efficacy in mice, its PGE1 conjugate synthesized by the carbonyldiimidazole method failed to show therapeutic effects probably due to inactivation of PGE1 during conjugation and lack of release in the tissue. In order to overcome these problems, PGE1 was conjugated to galactosylated poly-(L-glutamic acid) hydrazide (Gal-HZ-PLGA) via hydrazone bond. The PGE1-Gal-HZ-PLGA conjugate labeled with [111In] or [3H]PGE1 rapidly accumulated in the liver parenchymal cells after intravenous injection. In addition, PGE1 conjugate effectively inhibited the increase of GPT level in plasma, while free PGE1 indicated no therapeutic efficacy even at more than ten times higher doses, in carbon tetrachloride-induced hepatitis mice. These findings suggest potentials of polymeric targeting systems of PGE1 to hepatocyte utilizing galactose recognition.

Lipoprotein(a), left atrial appendage function and thromboembolic risk in patients with chronic nonvalvular atrial fibrillation

Lipoprotein(a) (Lp(a)) has a prothrombotic effect by modulating the fibrinolytic system. The purpose of the present study was to determine whether serum Lp(a) levels are associated with an increased risk of thromboembolism in chronic nonvalvular atrial fibrillation (NVAF). Clinical, laboratory and transesophageal echocardiographic data were collected in 172 consecutive, non-anticoagulated patients with chronic NVAF. Thirty-four patients (thromboembolic group) had a recent (<1 month) embolic event and/or a left atrial thrombus on transesophageal echocardiography. The thromboembolic group had a higher frequency of spontaneous echo contrast (94 vs. 58%, p<0.0001), increased concentrations of Lp(a) (median: 31.5 vs. 15.5 mg/dl, p<0.0001) and fibrinogen (median: 352 vs. 314 mg/dl, p = 0.0015), larger left atrial dimensions (median: 5.1 vs. 4.8cm, p = 0.0078), and reduced left atrial appendage (LAA) flow velocities (median: 9.5 vs. 21.2 cm/s, p<0.0001) than the nonthromboembolic group. Multivariate analysis identified 3 independent predictors of thromboembolism: Lp(a) level > or =30 mg/dl (odds ratio (OR) 9.5, 95% confidence interval (CI) 4.4-20.4, p<0.0001), LAA flow velocity of <20 cm/s (OR 8.7, 95% CI 3.3-23.0, p = 0.0003) and a fibrinogen concentration of <377mg/dl (OR 3.2, 95% CI 1.5-6.9, p = 0.0201). The Lp(a) elevations and reduced LAA flow velocities are independently associated with thromboembolism in chronic NVAF.

Mannose receptor-mediated gene transfer into macrophages using novel mannosylated cationic liposomes

A novel mannosylated cholesterol derivative, cholesten-5-yloxy-N-(4-((1-imino-2-beta-D-thiomannosyl -ethyl)amino)bu tyl) formamide (Man-C4-Chol), was synthesized in order to perform mannose receptor-mediated gene transfer with liposomes. Plasmid DNA encoding luciferase gene (pCMV-Luc) complexed with liposomes, consisting of a 6:4 mixture of Man-C4-Chol and dioleoylphosphatidylethanolamine (DOPE), showed higher transfection activity than that complexed with 3beta[N-(N', N'-dimethylaminoethane)-carbamoyl]cholesterol (DC-Chol)/DOPE(6:4) and N-[1-(2,3-dioleyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTMA)/DOPE(1:1) liposomes in mouse peritoneal macrophages. The presence of 20 mM mannose significantly inhibited the transfection efficiency of pCMV-Luc complexed with Man-C4-Chol/DC- Chol/DOPE(3:3:4) and Man-C4-Chol/DOPE(6:4) liposomes. High gene expression of pCMV-Luc was observed in the liver after intravenously injecting mice with Man-C4-Chol/DOPE(6:4) liposomes, whereas DC-Chol/DOPE(6:4) liposomes only showed marked expression in the lung. The gene expression with Man-C4-Chol/DOPE(6:4) liposome/ DNA complexes in the liver was observed preferentially in the non-parenchymal cells and was significantly reduced by predosing with mannosylated bovine serum albumin. The gene expression in the liver was greater following intraportal injection. These results suggest that plasmid DNA complexed with mannosylated liposomes exhibits high transfection activity due to recognition by mannose receptors both in vitro and in vivo. Gene Therapy (2000) 7, 292-299.

Design of polymeric prodrugs of prostaglandin E(1) having galactose residue for hepatocyte targeting

Based on the relationship between in vivo disposition of macromolecules and their physicochemical and biological characteristics obtained through clearance concept-based pharmacokinetic analysis, polymeric prodrugs of prostaglandin E(1)(PGE(1)) were designed stepwise and evaluated on their targeting and therapeutic efficiencies. First poly-L-lysine (PLL) and poly-L-glutamic acid (PLGA) with an ethylenediamine (ED) spacer were modified with 2-imino-2-methoxyethyl 1-thiogalactoside to obtain galactosylated derivatives. After intravenous injection in mice, Gal-ED-PLGA was selectively taken up by the liver parenchymal cells via receptor-mediated endocytosis, while Gal-PLL accumulated in the liver as well as PLL mostly due to electrostatic interaction. Although Gal-ED-PLGA showed good targeting efficacy, its PGE(1) conjugate synthesized with activated PGE(1) by carbonyldiimidazole method failed to show therapeutic effects probably due to inactivation of PGE(1) during conjugation and lack of release in the tissue. In order to overcome these problems, we next conjugated PGE(1) to galactosylated poly-(L-glutamic acid) hydrazide (Gal-HZ-PLGA) in which PGE(1) was easily coupled to Gal-HZ-PLGA via a hydrazone bond in weak acidic solution (pH 5) at room temperature. The PGE(1)-Gal-HZ-PLGA conjugate labeled with [(111)In] or [(3)H]PGE(1) rapidly accumulated in the liver parenchymal cells. In addition, the PGE(1) conjugate effectively inhibited the increase of the GPT level in plasma, while free PGE(1) indicated no therapeutic efficacy even at more than ten times higher doses, in carbon tetrachloride-induced hepatitis mice. These findings suggest potentials of polymeric targeting systems of PGE(1) to hepatocyte utilizing galactose recognition.

Deconvolution analysis for absorption and metabolism of aspirin in microcapsules

We have previously proposed a novel deconvolution method, which can estimate first-pass metabolism of orally administered drugs. In the present study, we examined whether this deconvolution method is useful for evaluating oral dosage forms. The absorption and first-pass metabolism of orally administered aspirin formulated in several forms were analyzed. Two types of microcapsules consisting of Eudragit L100 alone and Eudragit L100/ethylcellulose (4:6) were prepared as sustained release formulations, for comparison with aspirin in powder form. The deconvolution analysis revealed that absorption of aspirin was sustained by encapsulating it in microcapsules. Interestingly, it also revealed that the percentage metabolized during absorption was different among the three types of formulations. Thus, the deconvolution method has enabled a comprehensive analysis of orally administered drugs. This method is believed to contribute to the evaluation of oral drug formulations.

Organic cation transport in rabbit alveolar epithelial cell monolayers

PURPOSE

To characterize organic cation (OC) transport in primary cultured rabbit alveolar epithelial cell monolayers, using [14C]-guanidine as a model substrate.

METHODS

Type II alveolar epithelial cells from the rabbit lung were isolated by elastase digestion and cultured on permeable filters precoated with fibronectin and collagen. Uptake and transport studies of [14C]-guanidine were conducted in cell monolayers of 5 to 6 days in culture.

RESULTS

The cultured alveolar epithelial cell monolayers exhibited the characteristics of a tight barrier. [14C]-Guanidine uptake was temperature dependent, saturable, and inhibited by OC compounds such as amiloride, cimetidine, clonidine, procainamide, propranolol, tetraethylammonium, and verapamil. Apical guanidine uptake (Km = 129 +/- 41 microM, Vmax = 718 +/- 72 pmol/mg protein/5 min) was kinetically different from basolateral uptake (Km = 580 +/- 125 microM, Vmax = 1,600 +/- 160 pmol/mg protein/5 min). [14C]-Guanidine transport across the alveolar epithelial cell monolayer in the apical to basolateral direction revealed a permeability coefficient (Papp) of (7.3 +/- 0.4) x 10(-7) cm/sec, about seven times higher than that for the paracellular marker [14C]-mannitol.

CONCLUSIONS

Our findings are consistent with the existence of carrier-mediated OC transport in cultured rabbit alveolar epithelial cells.

Pharmacokinetic analysis of 123I-labeled medium chain fatty acid as a radiopharmaceutical for hepatic function based on beta-oxidation

Beta-oxidation is the most important pathway to provide energy for the liver. Our recent findings indicated that radiolabeled medium chain fatty acid analogs could be used as radiopharmaceuticals in the liver, allowing us to monitor alterations in energy metabolism on the cellular level. In the present study, pharmacokinetical analysis of a radioiodinated medium chain fatty acid analog, 6-[123I]iodophenylenanthic acid ([123I]IPEA), was carried out in normal and hepatitis model rats to investigate the index for the measurement of beta-oxidation activity in hepatocytes. The rate constant for metabolism of [123I]IPEA in the liver showed a strong correlation with the ATP level, which was determined as an indicator of beta-oxidation activity in hepatocytes. The radioactivity profile in the liver after [123I]IPEA administration provided important information regarding hepatic viability, and the metabolic rate constant of [123I]IPEA calculated by a pharmacokinetic method was a useful criterion for hepatic diagnosis based on hepatic cellular energy metabolism.

Brief report: incidence of and risk factors for autistic disorder in neonatal intensive care unit survivors

We investigated prospectively the incidence of autistic disorder (AD) in the neonatal intensive care unit and the risk factors associated with autistic development. The study population included the 5,271 children at St. Mary's Hospital and the diagnosis of AD was performed using DSM-III-R criteria. A total of 36 prenatal, perinatal, and postnatal factors were evaluated in the patients with AD, 57 cerebral palsy (CP), and 214 controls. AD was identified in 18 of the 5,271 children and the incidence was 34 per 10,000 (0.34%). This value was more than twice the highest prevalence value previously reported in Japan. Children with AD had a significantly higher history of the meconium aspiration syndrome (p = .0010) than the controls. Autistic patients had different risk factors than CP.

Characterization of plasmid DNA binding and uptake by peritoneal macrophages from class A scavenger receptor knockout mice

PURPOSE

Plasmid DNA (pDNA) has become an important class of macromolecular agent suitable for non-viral gene therapy as well as DNA vaccination. Our recent study has suggested that pDNA is taken up by mouse peritoneal macrophages via a specific mechanism mediated by a receptor similar to the scavenger receptor (SR). This study was designed to further characterize the pDNA uptake by macrophages in order to elucidate the mechanism.

METHODS

The binding and uptake of pDNA labeled with 32P or a fluorescent marker were studied in vitro using cultured Chinese hamster ovary (CHO) cells expressing the class A scavenger receptor (SRA) and peritoneal macrophages from SRA-knockout mice.

RESULTS

pDNA binding and uptake by CHO(SRA) cells were minimal and almost identical to that by wild-type CHO cells. Macrophages from the knockout mice showed pronounced pDNA binding and uptake as did the control macrophages. In both types of macrophage, pDNA binding was significantly inhibited by cold pDNA, polyinosinic acid and dextran sulfate but not by polycytidylic acid or Ac-LDL. These results provide direct evidence that SRA is not responsible for the significant binding and subsequent uptake of pDNA by mouse peritoneal macrophages. Further binding experiments revealed that, in addition to polyinosinic acid and dextran sulfate, heparin was a potent inhibitor among a variety of polyanionic compounds such as polynucleotides, anionic polysaccharides and modified proteins including Ox-LDL.

CONCLUSIONS

The present study suggest that pDNA binding and uptake by mouse peritoneal macrophages are mediated by a specific mechanism to some defined polyanions not by scavenger receptors. The finding would be an important basis for further studies to elucidate the mechanism(s) of pDNA uptake by macrophages.

Theoretical analysis of the effect of cutaneous metabolism on skin permeation of parabens based on a two-layer skin diffusion/metabolism model

The effect of cutaneous metabolism on the skin penetration of drugs was analyzed based on a two-layer skin diffusion/metabolism model. In vitro permeation studies of propylparaben and butylparaben with or without an esterase inhibitor, diisopropyl fluorophosphate (DFP), were performed. Pretreatment of the skin with DFP prolonged the lag time for the penetration of intact parabens. Additionally, DFP significantly decreased the total flux of butylparaben, but not that of propylparaben. Model analysis of the penetration profiles revealed that DFP inhibits the cutaneous metabolism without affecting any other processes. To comprehensively understand the relationships among lipophilicity, metabolic rate, and skin permeation of drugs, simulation studies were performed with newly derived equations concerning the permeability coefficient and the lag time for the penetration of both intact and metabolite forms. The analysis revealed that the lag time for the penetration of both intact and metabolite forms becomes shorter with increasing metabolic rate. As the metabolic rate of the drug increases, skin penetration of the intact form decreases whereas that of the metabolite increases. The total flux of intact and metabolite forms increases with increasing metabolic rate, being more obvious for highly lipophilic drugs. This indicates that the permeation of lipophilic compounds such as butylparaben is more highly affected by cutaneous metabolism in the viable layer because these compounds easily penetrate the stratum corneum layer. Consequently, the balance between the permeability of drug across the stratum corneum and the dermis has been implicated to impose a significant influence on the percutaneous absorption of drugs subjected to cutaneous metabolism.