Surface reaction of stoichiometric and calcium-deficient hydroxyapatite in simulated body fluid

In the present study, the immersion behavior of two kinds of sintered HA with different Ca/P ratios in two different extracellular simulated solutions (Tris buffer and Hank's solutions) was investigated and compared. Results indicated that an as-received Ca-deficient HA (FHA) had a lower Ca/P ratio, larger linear shrinkage and higher density than a stoichiometric HA (MHA). When FHA powder was calcined at 900 degrees C, its Ca-deficient apatite structure was unstable and a significant amount of beta-TCP phase was formed. When heated to 1250 degrees C in air, the highly crystalline apatite structure of MHA was still stable without any noticeable decomposition. The FTIR spectra indicated that both immersed MHA and FHA in Hank's solution were gradually covered with a layer of precipitated apatite during immersion. When immersed in Tris buffer solution, neither HA showed significant changes in their FTIR spectra. SEM observation indicated that the precipitation rate on immersed FHA surface was much higher than that on MHA surface when immersed in Hank's solution. The weight loss and pH data confirmed the higher dissolution rate of FHA than MHA in Hank's solution.

P-glycoprotein-mediated efflux of indinavir metabolites in Caco-2 cells expressing cytochrome P450 3A4

The role of P-glycoprotein in secretion of indinavir metabolites produced by CYP3A4 was evaluated in Caco-2 cells expressing CYP3A4. Metabolism of indinavir by CYP3A4 expressing Caco-2 cells grown on filters resulted in the formation of N-dealkylation products (M5 and M6) and hydroxylation of indinavir, which were preferentially secreted into the apical compartment. Apical secretion of the metabolites was inhibited by cyclosporin A (CsA) with all three classes of metabolites showing similar sensitivity to CsA, suggesting that they are all secreted by the same pathway. M6 stimulated P-glycoprotein (Pgp)-ATPase activity in a concentration-dependent manner. This stimulation was inhibited by the Pgp-specific monoclonal antibody C219. A method was developed to specifically inhibit Pgp using the monoclonal antibody UIC2 to determine whether Pgp efflux accounts for a significant proportion of the apical secretion of indinavir metabolites. UIC2 recognizes an extracellular transient conformational epitope that is stabilized by some Pgp substrates or by ATP depletion. Incubation of Caco-2 cells with UIC2 in the presence of 1 microM CsA resulted in 50 to 80% inhibition of Pgp-mediated vinblastine efflux, with no significant inhibition observed by UIC2 or CsA alone. Inhibition of Pgp in CYP3A4-expressing Caco-2 cells by UIC2 and 1 microM CsA resulted in a significant decrease in the apical secretion of M6, M5, and OH-indinavir and an increase in the amount of the metabolites secreted in the basolateral compartment and retained in the cytosol. These results are consistent with a role of Pgp in elimination of CYP3A4-generated metabolites and indicate that even relatively polar metabolites may be secreted from the cell by Pgp.

Interindividual variability in inhibition and induction of cytochrome P450 enzymes

Drug interactions have always been a major concern in medicine for clinicians and patients. Inhibition and induction of cytochrome P450 (CYP) enzymes are probably the most common causes for documented drug interactions. Today, many pharmaceutical companies are predicting potential interactions of new drug candidates. Can in vivo drug interactions be predicted accurately from in vitro metabolic studies? Should the prediction be qualitative or quantitative? Although some scientists believe that quantitative prediction of drug interactions is possible, others are less optimistic and believe that quantitative prediction would be very difficult. There are many factors that contribute to our inability to quantitatively predict drug interactions. One of the major complicating factors is the large interindividual variability in response to enzyme inhibition and induction. This review examines the sources that are responsible for the interindividual variability in inhibition and induction of cytochrome P450 enzymes.

Influence of admission functional status on functional gain and efficiency of rehabilitation in first time stroke patients

The purpose of this study was to determine whether the admission functional status influences the functional gain and efficiency of stroke rehabilitation. We prospectively studied 105 first time stroke patients consecutively admitted to the inpatient rehabilitation department of a university hospital during 1997. Functional status was assessed with the Functional Independence Measure (FIM) instrument on admission and discharge of inpatient rehabilitation program. The patients were stratified into three groups according to their FIM total scores on admission, i.e., 18 to 36, 37 to 72, and 73 to 126. One-way ANOVA with Tukey's studentized range tests indicated that patients with FIM total scores of > or = 73 at admission were significantly younger (58.2 +/- 12.3 yr) and scored lower functional gain (16.6 +/- 11.7) than those who scored of < or = 36 (66.3 +/- 9.4 yr) of age and functional gain of (27.6 +/- 23.3). However, there were no significant differences on rehabilitation efficiency among the three groups. The findings of this study suggest that the functional groups stratified by admission FIM score seem to predict the degree of functional gain for first time stroke patients after inpatient rehabilitation.

Ginseng flowers stimulate progesterone production from bovine luteal cells

Our previous report first showed evidence that polysaccharides isolated from ginseng leaves obtained from Jilin, China possess luteotropic activities. In this study, we made further investigations on the root and flowers of Korean ginseng by means of the same bioassay system described briefly as follows. Frozen-thawed bovine luteal cells (1 x 10(5) cells/ml/well) in M199 were incubated in 24-well culture plates at 37 degrees C in a 5 % CO2 incubator. Ten microl of tested drugs with 1, 10 and 100 microg/ml were added into each well. After 4- and 24-hr incubation, the media were harvested and assayed for progesterone by an enzyme immunoassay. The production of progesterone from cells is the indicator for evaluating the action of tested drugs. Results showed that hot water extracts ofginseng flowers (GF-1) with 10 to 100 microg/ml significantly increased progesterone production, whereas those from ginseng root (GR-1) could not. Crude polysaccharides (GF-2) isolated from GF-1 is the active component and the small molecules (mw < 10,000 dalton) are excluded, indicating that the ginseng root has no luteotropic activities, but the polysaccharides of ginseng flowers have.

Tpl-2 induces apoptosis by promoting the assembly of protein complexes that contain caspase-9, the adapter protein Tvl-1, and procaspase-3

The Tpl-2 proto-oncoprotein promotes cellular proliferation when overexpressed in a variety of tumor cell lines. Here, we present evidence that when overexpressed in immortalized non-transformed cells, Tpl-2 induces apoptosis by promoting the activation of caspase-3 via a caspase-9-dependent mechanism, and that apoptosis is enhanced when Tpl-2 is co-expressed with the newly identified ankyrin repeat protein Tvl-1. The activation of caspase-3 by caspase-9 is known to depend on the assembly of a multimolecular complex that includes Apaf-1 and caspase-9. Data presented here show that co-expression of Tpl-2 with Tvl-1 promotes the assembly of a complex that involves several proteins that bind Apaf-1 including Tvl-1, itself, Tpl-2 and phosphorylated procaspase-9. More important, procaspase-3, which under normal growth conditions is not associated with the complex, binds Tvl-1 conditionally in response to Tpl-2-generated apoptotic signals. The conditional association of procaspase-3 with Tvl-1 promotes the in vivo proteolytic maturation of procaspase-3 by caspase-9, a process casually linked to apoptosis.

Structure and immersion behavior of plasma-sprayed apatite-matrix coatings

The microstructure and properties of a series of plasma-sprayed coatings from sinter-granulated powders fabricated from SiO2, CaO, P2O5 and Na2O-containing HA composite powders on Ti-6Al-4V substrate were reported. The immersion behavior of these coatings in a simulated body fluid (SBF) was also investigated. The results showed that sinter-granulated apatite-matrix powders were irregularly shaped and appeared quite similar. XRD patterns showed that during fabrication of the powders, P2O5 and SiO2 enhanced the decomposition of HA structure, while CaO and Na2O did not. Reasonably high bond strengths (45-50 MPa) were obtained from all coatings. The plasma spray process itself enhanced the decomposition of apatite and chemical reactions among different phases. When immersed in SBF, the intensities of such phases as alpha- and beta-TCP in all coatings decreased with immersion time and an apatite precipitation took place on all coating surfaces. The immersed SiO2- and CaO-containing HA (HSC) coating had the highest rate of apatite precipitation among all coatings. The variations in calcium ion concentration in simulated body fluid indicated that the HSC-immersed solution reached its maximal Ca concentration the earliest, while the HSCP (HA, SiO2, CaO and P2O5)-immersed solution reached its maximum the latest.

Heart transplantation and the Batista operation for children with refractory heart failure

Medically refractory heart failure may be present in children with cardiomyopathy (CMP) or complex congenital heart disease (CHD). In adults, the surgical management of this condition is either heart transplantation or the Batista operation. From March 1995 to January 2000, a total of 6 children, aged from 1 to 16 years, with medically refractory heart failure associated with CMP or complex CHD underwent cardiac transplantation and one of them also had the Batista operation as a bridge to transplantation. One of the 6 patients died of intractable sepsis 17 days after the operation, but the other 5 were discharged with satisfactory hemodynamics. Immunosuppressive agents, including azathioprine, cyclosporin or FK-506, were given. One patient experienced moderate acute rejection, but it was controlled by FK-506, OKT-3 and solumedrol. However, another suffered from lymphoproliferative disease 8 months after transplant, but it was controlled by intravenous immunoglubulin, alpha-interferon and acyclovir. Cardiac function during serial follow-up (range, 1 month to 5 years) revealed normal systolic and diastolic function and none received any anticongestive medications. Almost all patients received an oversized donor heart. The left ventricle (LV) mass was remodeled, initially as an decrease and later as an increase. The patient who underwent the Batista operation was discharged 1 month after the operation with an increased LV ejection fraction (from 10% to 22%). She was successfully bridged to heart transplantation 7 months after the Batista operation. The results of cardiac transplantation in growing children are satisfactory and remain the mainstay of surgical treatment for medically refractory heart failure in these patients. However, with a shortage of donor hearts, the Batista operation may be adopted as a bridge to heart transplant with a fair response.

[The outcomes of restraint reduction program in nursing homes]

One of the problems in nursing home care in Taiwan is resident restraint, including physical and chemical restraints. This pre-experimental study was conducted to investigate whether a restraint reduction program could reduce the prevalence of restraint in nursing homes. Three registered nursing homes were randomly selected from nursing homes in the Kaohsiung area. Staff and residents of these nursing homes were educated in restraint alternatives, balance training and managing behavior problems in one month of interventions. Three days before and after interventions, prevalence of restraints, falls, and of pressure sores, balance reaction, frequency of agitation, use of psychotic drugs, as well as the restraint knowledge of the nursing staff, was measured. After the restraint reduction program, the prevalence of restraint and frequency of resident agitation decreased significantly. The prevalence of falls and pressure sores of residents was not changed significantly. The restraint knowledge of the nursing staff significantly increased after the restraint reduction program. The information from this study led to a better strategy to reduce restraint for the elderly in nursing homes. The results could also provide a model to improve the quality of care in nursing homes in Taiwan.

[Analysis of HLA-DQB1 polymorphism by PCR-SSO in Yichu of Yunnan Province]

HLA-DQB1 genes from 76 individuals of Yichu ethnic group in Yunnan Province were investigated, using PCR-SSO genotyping method. Of the 38 DQB1 alleles detected, DQB1 * 0301 (gene frequency: 36.18%-36.84%) was the most common gene. The frequencies of DQB1 * 0502(10.53%-11.18%), DQB1 * 0401 (9.21%), DQB1 * 0302(8.55%-9.21%), DQB1 * 0601(7.89%), DQB1 * 05031(6.58%), and DQB1 * 03032(5.92%-6.58%) are more than 5%. While DQB1 * 0504, DQB1 * 0604, DQB1 * 06052, DQB1 * 0606, DQB1 * 0607, DQB1 * 0608, DQB1 * 06112, DQB1 * 0613, DQB1 * 0615, DQB1 * 0203, DQB1 * 0305, DQB1 * 0306, DQB1 * 0307, and DQB1 * 0308 were not observed. Comparison of HLA-DQB1 allele frequencies of Yichu with those of 13 other Chinese ethnic groups showed some significant differences, suggesting Yichu is unique in the distribution of HLA alleles.

Syntheses of hydrated molybdenum bronzes by reduction of MoO3 with NaBH4

Hydrated molybdenum bronzes have been prepared by reduction reaction of MoO3 with NaBH4 in ethanol and DMSO. The reduction reactions in both solvents occur smoothly; thus, the layered structure of MoO3 is maintained in the product. Divalent cation Ca2+ has been intercalated between the MoO3 layers, which leads to highly reduced molybdenum bronze (Mo5.26+). Solvated molybdenum bronze catalyzes the reduction reaction of DMSO by NaBH4, producing CH3SCH3. The structure model of hydrated sodium molybdenum bronze has also been reinvestigated by using the Rietveld analysis. The hydrated molybdenum bronze crystallizes in an orthorhombic structure, in which the structure of Mo octahedron layers is closely related to that in MoO3. However, the structure refinement reveals that the Mo octahedron in the MoO3 layers is axially distorted, which is different from that in MoO3 but similar to an isoelectron compound H0.33MoO3.

Differential inhibition of progesterone synthesis in bovine luteal cells by estrogens and androgens

We investigated the roles of estrogens and androgens in the progesterone biosynthesis of bovine luteal cells. The responsiveness of primary luteal cells to the stimulation of tropic agents was observed in a dose-dependent manner. Estrogens and androgens significantly inhibited tropic agent-induced progesterone secretions, but glucocorticoids did not, which indicated the inhibitions were specific. The failure of exogenous 8-Br-cAMP to prevent these inhibitions suggested that took place at the post-cAMP steps. The immunoblot showed that testosterone remarkably decreased the amount of induced P450scc protein after 6-hour treatment, yet 17beta-estradiol did not. The 3beta-HSD activity assays demonstrated that both 17beta-estradiol and testosterone efficiently blocked induced 3beta-HSD activities. Both inhibitory effects of E2 and T on progesterone synthesis were observed one hour after treatment and accompanied with suppressed 3beta-HSD activities. This study presents that estrogens and androgens specifically inhibit bovine luteal function through different mechanisms.

Nitric oxide synthase isoforms during fracture healing

We have shown previously that nitric oxide (NO) has regulatory effects on fracture healing. Our aim here was to investigate the temporal expression patterns of the three NO synthase (NOS) isoforms that are responsible for the generation of NO by semiquantitative competitive polymerase chain reaction (PCR) and immunoblot analysis after femoral fractures in rats. We found that 4 days after fracture, there were increases in the levels of messenger RNA (mRNA) for all three NOS isoforms, with peaks for the inducible NOS (iNOS; 35-fold increase, p < 0.05) at day 4, the endothelial NOS (eNOS; 5-fold increase, p < 0.05) at day 7, and the neuronal NOS (bNOS; 16-fold increase, p < 0.05) at day 21. At a protein level, the time course expression of NOS isoforms was consistent with the results of those at the mRNA level. In addition, we have previously reported a 2.5-fold increase in NOS activity detected by [3H]arginine to [3H]citrulline conversion at day 15 compared with that at day 4 after fracture. The findings that the expression of NOS isoforms during fracture healing is type specific and time dependent are important and may have clinical applications in the regulation of bone repair by NOS inhibitors or stimulators at different stages after injury.

PSA-specific and non-PSA-specific conversion of a PSA-targeted peptide conjugate of doxorubicin to its active metabolites

Tumor-selective delivery of doxorubicin by a prostate-specific antigen (PSA)-targeted peptide conjugate prodrug of doxorubicin was demonstrated in a nude mouse xenograft model of human prostate cancer. The prodrug (referred to as doxorubicin conjugate) contains doxorubicin linked to a seven-amino acid peptide conjugate that was designed to increase delivery of doxorubicin to tumor sites through the hydrolytic properties of PSA, which prostate tumors express in high amounts. Following i.p. administration of the doxorubicin conjugate to mice, tumor exposure to doxorubicin was increased 2.5-fold as compared with that achieved after an equimolar dose of doxorubicin itself. However, in heart tissue, the site of clinical dose-limiting toxicity, doxorubicin concentrations observed after administration of doxorubicin conjugate were substantially lower than those in mice that received doxorubicin itself. While the prodrug provided selective delivery of doxorubicin to tumor tissue, there was substantial non-PSA-specific formation of doxorubicin in laboratory animals, a factor that would limit the extent of therapeutic gain of the prodrug. Following i.v. administration to mice, rats, dogs, and monkeys, about one-third of the dose was metabolized to doxorubicin. In tumor-bearing mice, the fraction of the dose metabolized to doxorubicin appeared even higher. This is likely the result of conjugate conversion to doxorubicin by both PSA-specific (in tumor) and non-PSA-specific proteolytic activities. In vitro studies provided further support for the PSA specificity of metabolism; LNCaP cells mediated rapid metabolism of the conjugate, while DuPRO-1 cells, which are deficient in PSA, were incapable of metabolism.

Enzyme kinetics of cytochrome P450-mediated reactions

The most common drug-drug interactions may be understood in terms of alterations of metabolism, associated primarily with changes in the activity of cytochrome P450 (CYP) enzymes. Kinetic parameters such as Km, Vmax, Ki and Ka, which describe metabolism-based drug interactions, are usually determined by appropriate kinetic models and may be used to predict the pharmacokinetic consequences of exposure to one or multiple drugs. According to classic Michaelis-Menten (M-M) kinetics, one binding site models can be employed to simply interpret inhibition (pure competitive, non-competitive and uncompetitive) or activation of the enzyme. However, some cytochromes P450, in particular CYP3A4, exhibit unusual kinetic characteristics. In this instance, the changes in apparent kinetic constants in the presence of inhibitor or activator or second substrate do not obey the rules of M-M kinetics, and the resulting kinetics are not straightforward and hamper mechanistic interpretation of the interaction in question. These unusual kinetics include substrate activation (autoactivation), substrate inhibition, partial inhibition, activation, differential kinetics and others. To address this problem, several kinetic models can be proposed, based upon the assumption that multiple substrate binding sites exist at the active site of a particular P450, and the resulting kinetic constants are, therefore, solved to adequately describe the observed interaction between multiple drugs. The following is an overview of some cytochrome P450-mediated classic and atypical enzyme kinetics, and the associated kinetic models. Applications of these kinetic models can provide some new insights into the mechanism of P450-mediated drug-drug interactions.

In vitro substrate identification studies for p-glycoprotein-mediated transport: species difference and predictability of in vivo results

Two different cellular assay models were assessed as in vitro systems for P-glycoprotein (P-gp) substrate identification: cellular accumulation studies with KB-V1, a human MDR1 P-gp-overexpressing multidrug-resistant human epidermoid carcinoma cell line; and transcellular transport studies with L-MDR1 (or L-mdr1a), a human MDR1 (or mouse mdr1a)-transfected porcine renal epithelial cell line. The in vitro-in vivo correlation for P-gp-mediated transport activity was also examined by comparing in vitro data obtained from L-mdr1a cell studies and in vivo data from mdr1a (-/-)/(+/+) CF-1 mice studies for several compounds. The results are summarized as follows: 1) two in vitro assay systems routinely identified the substrate for human MDR1 P-gp-mediated transport with similar quantitative results; 2) in vitro studies with L-MDR1 and L-mdr1a cells demonstrated that the P-gp substrate susceptibility is different between human and mouse for certain compounds (species difference); and 3) in vivo brain concentration ratios of mdr1a (-/-) to (+/+) CF-1 mice, either at a certain time point or up to 60 min, correlated well with the in vitro transcellular transport ratios from L-mdr1a cells (r(2) = 0.968 and 0.926, respectively). This indicates that, at least in mice, the in vitro data are valid predictors of the in vivo contribution of P-gp: the contribution of P-gp to the distribution of the compound to the brain up to 60 min post i.v. administration. These results provide a rationale for predicting in vivo relevance of P-gp in human from in vitro data using human P-gp-expressing cells.

Dynamic biomechanical model of the hand and arm in pistol grip power handtool usage

The study considers the dynamic nature of the human power handtool operator as a single degree-of-freedom mechanical torsional system. The hand and arm are, therefore, represented as a single mass, spring and damper. The values of these mechanical elements are dependent on the posture used and operator. The apparatus used to quantify these elements measured the free vibration frequency and amplitude decay of a known system due to the external loading of the hand and arm. Twenty-five subjects participated in the investigation. A full factorial experiment tested the effects on the three passive elements in the model when operators exerted maximum effort for gender, horizontal distance (30, 60, 90 cm), and vertical distance (55, 93, 142 190 cm) from the ankles to the handle. The results show that the spring element stiffness and mass moment of inertia changed by 20.6 and 44.5% respectively with vertical location (p<0.01), and 23.6 and 41.2% respectively with horizontal location (p<0.01). Mass moment of inertia and viscous damping for males were 31.1 and 38.5% respectively greater than for females (p<0.01). Tool handle displacement and hand force during torque build-up can, therefore, be predicted based on this model for different tool and workplace parameters. The biomechanical model was validated by recalling five subjects and having them operate a power handtool for varying horizontal distances (30, 60, 90 cm), vertical distances (55, 93, 142 cm), and two torque build-up times (70, 200 ms). Tool reaction displacement was measured using a 3D-motion analysis system. The predictions were closely correlated with these measurements (R = 0.88), although the model underpredicted the response by 27%. This was anticipated since it was unlikely that operators used maximal exertions for operating the tools.

Involvement of apoptosis during deciduomal regression in pseudopregnant hamsters effect of progesterone

We determined whether fragmentation of genomic DNA, apoptosis, occurs during deciduomal regression in pseudopregnant hamsters and the effect of progesterone on the apoptotic processes. Artificially induced deciduoma were obtained on different days of pseudopregnancy and separated into mesometrial and antimesometrial tissues. The deciduomal cell cycle progression and population profiles of both sides were compared by flow cytometry. The proportion of sub-G1 peak, which was correlated with the apoptotic cells, were about 10% on day 8 and reached to 40% in both tissues on day 10. Exogenous progesterone treatment by daily injection (2 mg; s.c.) on and after day 8 reduced the percentage of low molecular weight DNA in both tissues on day 10 and day 12 as compared to the nontreated control one, respectively. The appearance of DNA ladder was also delayed at least 24 h by progesterone administration. The intensity of DNA fragmentation was more pronounced in antimesometrial deciduoma. In situ 3'-end labeling of apoptotic cells further substantiated the apoptotic process. The apoptotic cells first appeared in the luminal region in antimesometrial deciduoma on day 8 and spreaded all over the entire deciduomal tissue on day 10. Progesterone treatment stimulated deciduomal proliferating cell nuclear antigen (PCNA) expression, maintained deciduoma until day 14 and retarded the differentiation and regeneration of the uterine epithelium.

Temporal expression of nitric oxide synthase isoforms in healing Achilles tendon

We investigated the temporal expressions of the three nitric oxide synthase (NOS) isoforms by semi-quantitative polymerase chain reaction (PCR) assays and by immunoblot analysis, following Achilles tendon transection in rats. Four days after injury, there were increases in the steady-state levels of mRNA for all three NOS isoforms, with peaks for the inducible isoform (iNOS) (23-fold increase) at day 4, the endothelial isoform (eNOS) (24-fold increase) at day 7 and the neuronal isoform (bNOS) (seven-fold increase) at day 21. The temporal expression of NOS isoforms at a protein level was consistent with the results at the mRNA level. We have previously shown a five-fold increase in the NOS activity, as detected by 3H-arginine to 3H-citrulline conversion, at day 7 postinjury. These findings indicate that all three NOS isoforms are expressed during tendon healing with differential expression patterns during the various phases of tendon healing. These findings may prove clinically relevant with respect to strategies for regulating tendon healing.

P450 interaction with HIV protease inhibitors: relationship between metabolic stability, inhibitory potency, and P450 binding spectra

More than 60 human immunodeficiency virus protease inhibitors were examined for the structure-activity relationship between metabolic stability, CYP3A4 inhibitory potency, and substrate-induced binding spectra with a ferric form of P450 in human liver microsomes. A positive relationship was found between CYP3A4 inhibitory potency and metabolic stability; namely, compounds that were more potent for the CYP3A4 inhibition generally were more metabolically stable. In addition, the compounds formed two clusters defined by the distinct type of substrate-induced P450 binding spectra: the compounds with type II binding spectra were more stable metabolically and more potent for the CYP3A4 inhibition than those with type I binding spectra. The structure-activity relationship suggested that the presence and position of heterocyclic nitrogen on the pyridine moiety play an important role in determining the manner of interaction with P450 and the magnitude of CYP3A4 inhibition/metabolic stability in the series of structurally related human immunodeficiency virus protease inhibitors under development.

KIAP, a novel member of the inhibitor of apoptosis protein family

We have identified a novel human gene, kiap (kidney inhibitor of apoptosis protein) that encodes a single BIR domain and a RING zinc finger domain. kiap has been assigned to the q13.3 region of human chromosome 20 by fluorescent in situ hybridization analysis. Northern blot analysis indicates that KIAP is expressed mainly in placenta, lymph node and fetal kidney. In this report, we show that overexpression of KIAP blocks apoptosis induced by menadione or by overexpression of BAX. In addition, we show that overexpression of KIAP enhances apoptosis induced by etoposide, and, that KIAP fails to block apoptosis induced by overexpression of Fas. Thus, KIAP, a new member of the inhibitor of apoptosis protein (IAP) family, has pleiotropic effects on apoptosis induced by various stimuli.

TNF-alpha induction by LPS is regulated posttranscriptionally via a Tpl2/ERK-dependent pathway

Tpl2 knockout mice produce low levels of TNF-alpha when exposed to lipopolysaccharide (LPS) and they are resistant to LPS/D-Galactosamine-induced pathology. LPS stimulation of peritoneal macrophages from these mice did not activate MEK1, ERK1, and ERK2 but did activate JNK, p38 MAPK, and NF-kappaB. The block in ERK1 and ERK2 activation was causally linked to the defect in TNF-alpha induction by experiments showing that normal murine macrophages treated with the MEK inhibitor PD98059 exhibit a similar defect. Deletion of the AU-rich motif in the TNF-alpha mRNA minimized the effect of Tpl2 inactivation on the induction of TNF-alpha. Subcellular fractionation of LPS-stimulated macrophages revealed that LPS signals transduced by Tpl2 specifically promote the transport of TNF-alpha mRNA from the nucleus to the cytoplasm.

Intracellular delivery of membrane-impermeable hydrophilic molecules to a hepatoblastoma cell line by asialoglycoprotein-labeled liposomes

BACKGROUND AND PURPOSE

Mammalian hepatic receptors are specific for the terminal D-galactose of desialylated glycoproteins. This study used asialofetuin-labeled liposomes (AF-liposomes) to target hepatoma cells using this receptor mechanism, and investigated their efficiency in intracellular delivery of membrane-impermeable hydrophilic molecules to a hepatoblastoma cell line (HepG2).

METHODS

Inulin was used as a model molecule. Blank liposomes consisting of phosphatidylcholine:phosphatidic acid:cholesterol in 6:1:6 molar ratio were prepared. Palmitoyl-asialofetuin was anchored onto the blank liposomes using a detergent dialysis method. 3H-inulin was entrapped in the AF-liposomes by dehydration (freeze-drying) and rehydration followed by freeze-thaw sonication. Plain liposomes (N-liposomes) were prepared by the same process but without AF. HepG2 cells were incubated for 3 hours with free 3H-inulin, N-liposomal 3H-inulin, AF-liposomal 3H-inulin, or free AF. The cellular uptake of 3H-inulin and the cell viability were then determined. Uptake of AF-liposomes in a non-hepatoma cell line, NIH3T3, was also studied for comparison.

RESULTS

Cellular uptake of free inulin was negligible while uptake of liposomal inulin, either in N-liposomes or in AF-liposomes, was significant (p < 0.01). The uptake of AF-liposomal inulin was significantly higher than that of N-liposomal inulin in HepG2 cells but not in NIH3T3 cells. Free AF and blank AF-liposomes inhibited the HepG2 cell uptake of AF-liposomal inulin.

CONCLUSIONS

These results indicate that AF-liposomes enhanced intracellular delivery of a membrane-impermeable hydrophilic drug into hepatoma cells by a receptor mechanism. AF-liposomes are a potential drug carrier for intracellular delivery of membrane-impermeable hydrophilic drugs to HepG2 cells.

Activation of the Ikappa B kinases by RIP via IKKgamma /NEMO-mediated oligomerization

To understand the mechanism of activation of the IkappaB kinase (IKK) complex in the tumor necrosis factor (TNF) receptor 1 pathway, we examined the possibility that oligomerization of the IKK complex triggered by ligand-induced trimerization of the TNF receptor 1 complex is responsible for activation of the IKKs. Gel filtration analysis of the IKK complex revealed that TNFalpha stimulation induces a large increase in the size of this complex, suggesting oligomerization. Substitution of the C-terminal region of IKKgamma, which interacts with RIP, with a truncated DR4 lacking its cytoplasmic death domain, produced a molecule that could induce IKK and NF-kappaB activation in cells in response to TRAIL. Enforced oligomerization of the N terminus of IKKgamma or truncated IKKalpha or IKKbeta lacking their serine-cluster domains can also induce IKK and NF-kappaB activation. These data suggest that IKKgamma functions as a signaling adaptor between the upstream regulators such as RIP and the IKKs and that oligomerization of the IKK complex by upstream regulators is a critical step in activation of this complex.

Sense and nonsense in the prediction of drug-drug interactions

Drug interactions are always a major concern in medicine and within the pharmaceutical industry. Fatal drug interactions have been reported, and several prominent drugs have been withdrawn from the market because of serious adverse reactions related to drug interactions. Therefore, drug interactions represent not only a medical problem for clinicians, but also an economic loss for pharmaceutical companies. Today, many pharmaceutical companies are predicting potential interactions of new drug candidates in an attempt to minimize such losses and to more effectively safeguard the welfare of patients. Can in vivo drug interactions be predicted accurately from in vitro metabolic studies? Should the prediction be qualitative or quantitative? These are the fundamental questions that industrial drug metabolism scientists must confront daily. Prediction of in vivo drug interactions from in vitro metabolic data is highly controversial, because of the complexities of factors that are involved in drug interactions. Some scientists believe that quantitative prediction of drug interaction is possible, whereas others are less optimistic, and believe that quantitative prediction is extremely difficult, if not impossible. The purpose of this review is to present and discuss the technical problems inherent in estimating in vitro Ki values and in measuring inhibitor concentration at the active-site of enzymes. Theoretic considerations are briefly reviewed, and representative examples are drawn from literature to illustrate the sense and nonsense in predicting in vivo drug interactions.