Strategy for prevention of local recurrence of pancreatic cancer after pancreatectomy: antitumor effect of gemcitabine mixed with fibrin glue in an orthotopic nude mouse model

BACKGROUND

Pancreatic cancer frequently recurs after operative treatment, resulting in a poor prognosis. Inhibition of proliferation of residual cancer cells is important for improved survival of patients with pancreatic cancer. Fibrin glue (FG) is a biocompatible, adherent hemostat that can deliver high concentrations of anticancer drugs to residual cancer cells. The aim of this study was to evaluate the local antitumor effect of a mixture of gemcitabine (GEM) and FG on pancreatic cancer cells implanted orthotopically in nude mice.

METHODS

SUIT-2 human pancreatic cells were injected into the tail of the pancreas of nude mice. Seven days later, groups of mice were treated with 80 mg/kg GEM mixed with 0.5 mL fibrin glue (GEM + FG), 0.5 mL FG alone (FG), single intraperitoneal (i.p.) injection of 80 mg/kg GEM (GEM1), i.p. injection of 80 mg/kg GEM weekly for 3 weeks (GEM1,2,3), GEM + FG followed by weekly GEM injections for 2 weeks (GEM + FG + GEM2,3), or i.p. injection of PBS weekly for 3 weeks (controls).

RESULTS

Twenty-eight days after cell injections, tumor volumes of groups treated with GEM + FG + GEM2,3, GEM1,2,3, GEM + FG, GEM1, and FG were decreased by 84%, 70%, 62%, 37%, and 10%, respectively, compared to that of control mice. GEM + FG + GEM2,3 had the strongest anticancer effect compared to all other groups (P < .05). Additionally, GEM + FG showed a more potent antitumor effect compared to GEM1 (P < .05). Survival of mice treated with GEM + FG + GEM2,3 was longer than that of mice in all other groups (P < .05).

CONCLUSIONS

A mixture of GEM and FG was effective in inhibiting the growth of orthotopically implanted pancreatic neoplasms in nude mice. This procedure may be useful clinically to prevent the local recurrence of pancreatic cancer after pancreatectomy.

Physiological and Anatomical Properties of Mouse Medial Vestibular Nucleus Neurons Projecting to the Oculomotor Nucleus

Neurons in the medial vestibular nucleus (MVN) vary in their projection patterns, responses to head movement, and intrinsic firing properties. To establish whether neurons that participate in the vestibulo-ocular reflex (VOR) have distinct intrinsic physiological properties, oculomotor nucleus (OMN)–projecting neurons were identified in mouse brainstem slices by fluorescent retrograde labeling from the oculomotor complex and targeted for patch-clamp recordings. Such neurons were located in the magnocellular portion of the MVN contralateral to tracer injection, were mostly multipolar, and had soma diameters of around 20 μm. They fired spontaneous action potentials at rates higher than those of other MVN neurons and their spikes were of unusually short duration. OMN-projecting neurons responded to 1-s intracellular current injection with exceptionally high firing rates of >500 spikes/s. Their current–firing relationship was highly linear, with weak firing response adaptation during steady depolarization and little postinhibitory rebound firing after membrane hyperpolarization. Their firing responses were approximately in phase with sinusoidal current injection. The response dynamics of OMN-projecting neurons could be simulated with a simple integrate-and-fire model modified with the addition of small adaptation and rebound conductances. These findings indicate that the membrane properties of OMN-projecting neurons allow them to respond to head movements reliably and with high sensitivity but without substantially altering input dynamics.

Candida glabrata PDR1, a transcriptional regulator of a pleiotropic drug resistance network, mediates azole resistance in clinical isolates and petite mutants

Candida glabrata, a yeast with intrinsically low susceptibility to azoles, frequently develops increased azole resistance during prolonged treatment. Transposon mutagenesis revealed that disruption of CgPDR1 resulted in an 8- to 16-fold increase in fluconazole susceptibility of C. glabrata. CgPDR1 is a homolog of Saccharomyces cerevisiae PDR1, which encodes a transcriptional regulator of multidrug transporters. Northern blot analyses indicated that CgPDR1 regulated both constitutive and drug-induced expression of CgCDR1, a multidrug transporter gene. In agreement with the Northern analysis, the Cgpdr1 mutant had increased rhodamine accumulation, in contrast to the decreased accumulation in the CgPDR1-overexpressing strain. Northern analyses also indicated the importance of CgPDR1 in fluconazole resistance arising during therapy. Two clinically resistant isolates had higher expression of CgPDR1 and CgCDR1 compared to their paired susceptible isolates. Integrative transformation of CgPDR1 from the two resistant isolates converted the Cgpdr1 mutant into azole-resistant strains with upregulated CgPDR1 expression. Two different amino acid substitutions, W297S in one isolate and F575L in the other, accounted for the upregulated CgPDR1 expression and the resistance. Finally, CgPDR1 was shown to be required for the azole resistance due to mitochondrial deficiency. Thus, CgPDR1 encodes a transcriptional regulator of a pleiotropic drug resistance network and contributes to the azole resistance of clinical isolates and petite mutants.

P-Glycoprotein expression in human retinal pigment epithelium cell lines

P-Glycoprotein (P-gp), an active efflux transporter encoded by the MDR1 gene, has recently been identified in the human and pig retinal pigment epithelium (RPE) in situ. Efflux pumps such as P-gp are major barriers to drug delivery in several tissues. We wished to establish whether human RPE cell lines express P-gp under the culture conditions recommended for each cell line so as to determine their suitability as in vitro models for predicting drug transport across the outer blood-retinal barrier. Three human RPE cell lines, ARPE19, D407 and h1RPE were investigated. Reverse transcriptase-polymerase chain reaction (RT-PCR) was carried out to determine the expression of MDR1 mRNA. Immunocytochemistry using the P-gp-specific antibody C219 was undertaken to investigate the presence of P-gp protein in each cell type. Uptake of rhodamine 123, a P-gp substrate, in the presence or absence of pre-treatment with a P-gp inhibitor, verapamil, was measured in each cell line to determine functional expression of P-gp. For all experiments, MDCK cells stably transfected with the human MDR1 gene (MDCK-MDR1) were used as a positive control. ARPE19 cells were consistently negative for P-gp as assessed by RT-PCR and immunocytochemistry. By contrast, RT-PCR of D407 and h1RPE samples yielded weak bands corresponding to MDR1; P-gp protein expression, as demonstrated by C219 immunoreactivity, was also present. Rhodamine uptake after treatment with verapamil was significantly greater in D407 and MDCK-MDR1, indicating functional expression of P-gp in these two cell lines. No evidence of functional P-gp was found in ARPE19 and h1RPE. In conclusion, D407 and h1RPE cells express P-gp, though functional activity was demonstrable only in D407 cells. ARPE19 cells do not express P-gp. Of these human RPE cells lines D407 could be considered as a suitable model for in vitro drug transport studies, particularly those involving P-gp substrates, without modification of their usual culture conditions.

In vivo transduction of murine cerebellar Purkinje cells by HIV-derived lentiviral vectors

Cerebellar Purkinje cells are key elements in motor learning and motor coordination, and therefore, it is important to clarify the mechanisms by which Purkinje cells integrate information and control cerebellar function. Gene transfer into neurons, followed by the assessment of the effects on neural function, is an effective approach for examining gene function. However, this method has not been used fully in the study of the cerebellum because adenovirus vectors, the vectors most commonly used for in vivo gene transfer, have very low affinity for Purkinje cells. In this study, we used a human immunodeficiency virus (HIV)-derived lentiviral vector and examined the transduction profile of the vector in the cerebellum. A lentiviral vector carrying the GFP gene was injected into the cerebellar cortex. Seven days after the injection, Purkinje cells were efficiently transduced without significant influence on the cell viability and synaptic functions. GFP was also expressed, though less efficiently, in other cortical interneurons and Bergmann glias. In contrast to reported findings with other viral vectors, no transduced cells were observed outside of the cerebellar cortex. Thus, when HIV-derived lentiviral vectors were injected into the cerebellar cortex, transduction was limited to the cells in the cerebellar cortex, with the highest tropism for Purkinje cells. These results suggest that HIV-derived lentiviral vectors are useful for the study of gene function in Purkinje cells as well as for application as a gene therapy tool for the treatment of diseases that affect Purkinje cells.

Drug delivery to the cochlea using PLGA nanoparticles

OBJECTIVES

This study aimed to investigate the efficacy of encapsulating therapeutic molecules in poly lactic/glycolic acid (PLGA) nanoparticles for drug delivery to the cochlea.

STUDY DESIGN

An experimental study.

METHODS

We examined the distribution of rhodamine, a fluorescent dye, in the cochlea, liver, and kidney of guinea pigs. Intravenous injection of rhodamine or rhodamine-encapsulated PLGA nanoparticles was used to target the fluorescent dye systemically to the liver, kidney, and cochlea, and these molecules were applied locally to the round window membrane (RWM) of the cochlea. The localization of rhodamine fluorescence in each region was quantitatively analyzed.

RESULTS

After systemic application of rhodamine nanoparticles, fluorescence was identified in the liver, kidney, and cochlea. The systemic application of nanoparticles had a significant effect on targeted and sustained delivery of rhodamine to the liver but not the kidney or cochlea. Rhodamine nanoparticles placed on the RWM were identified in the scala tympani as nanoparticles, indicating that the PLGA nanoparticles can permeate through the RWM. Furthermore, the local application of rhodamine nanoparticles to the RWM was more effective in targeted delivery to the cochlea than systemic application.

CONCLUSIONS

These findings indicate that PLGA nanoparticles can be an useful drug carrier to the cochlea via local application.

Interaction of a mitochondrial membrane potential-sensitive dye, rhodamine 800, with rat mitochondria, cells, and perfused hearts

Fluorescence, absorbance, and binding of a mitochondrial membrane potential-sensitive probe, rhodamine 800 (rhod800), were measured in isolated rat mitochondria, hepatocytes, cardiomyocytes, and hearts in the presence or absence of mitochondrial uncouplers. Excitation of rhod800 was achieved with laser diodes (690 or 670 nm) and resulted in a fluorescence peak at 720 nm. Greater than 99% of rhod800 (1 microM) was taken up from the buffer by energized mitochondria. This resulted in a fluorescence decrease by 77% (13% in de-energized mitochondria). Sixty-seven percent of rhod800 was taken up by cardiomyocytes and 75% by hepatocytes resulting in the fluorescence decrease by 16% and 37%, respectively, which were reversed by approximately 10% upon cell uncoupling. In hearts, binding, absorbance, and fluorescence were almost uncoupler-insensitive possibly due to rhod800 interaction outside of mitochondria. Fluorescence of the hearts perfused with 27.5 and 55 nM rhod800 was measured in orthogonal and reflection modes. The former provided deep tissue penetration (approximately a centimeter); however, nonlinearity between absorbance and fluorescence was evident. In the latter setting, depth of tissue penetration was approximately a millimeter, which eliminated an inner filter effect and restored linearity. We concluded that excessive hydrophobicity of rhod800 complicates detection of energy-dependent fluorescence changes in myocardium.

Toxicity and tissue distribution of magnetic nanoparticles in mice

The development of technology enables the reduction of material size in science. The use of particle reduction in size from micro to nanoscale not only provides benefits to diverse scientific fields but also poses potential risks to humans and the environment. For the successful application of nanomaterials in bioscience, it is essential to understand the biological fate and potential toxicity of nanoparticles. The aim of this study was to evaluate the biological distribution as well as the potential toxicity of magnetic nanoparticles to enable their diverse applications in life science, such as drug development, protein detection, and gene delivery. We recently synthesized biocompatible silica-overcoated magnetic nanoparticles containing rhodamine B isothiocyanate (RITC) within a silica shell of controllable thickness [MNPs@SiO2(RITC)]. In this study, the MNPs@SiO2(RITC) with 50-nm thickness were used as a model nanomaterial. After intraperitoneal administration of MNPs@SiO2(RITC) for 4 weeks into mice, the nanoparticles were detected in the brain, indicating that such nanosized materials can penetrate blood-brain barrier (BBB) without disturbing its function or producing apparent toxicity. After a 4-week observation, MNPs@SiO2(RITC) was still present in various organs without causing apparent toxicity. Taken together, our results demonstrated that magnetic nanoparticles of 50-nm size did not cause apparent toxicity under the experimental conditions of this study.

Fluorescent Kabiramides: New Probes to Quantify Actin in Vitro and in Vivo

We present the design, synthesis, and biochemical and spectroscopic characterization of five functional fluorescent conjugates of kabiramide C (KabC), a small molecule biomimetic of gelsolin. The tetramethylrhodamine (TMR), rhodol green (RG), IC5, dapoxyl (DAP), and fluorescein diester (FDE) conjugates of KabC bind specifically to actin at the barbed end in a 1:1 complex. These probes are shown to function in an indistinguishable manner to the unmodified KabC. Various modalities of the fluorescence emission of these KabC probes, including fluorescence anisotropy and fluorescence resonance energy transfer, are used for the development of assays for the rapid determination of G-actin concentration in solution. The TMR-KabC and FDE-KabC probes are cell permeable and provide unique imaging information on the distribution and dynamics of actin filament within living cells.

Live-cell imaging methods for the study of vagal afferents within the nucleus of the solitary tract

Substantial evidence suggests that vagal afferent functions are modulated by agonists acting on afferent terminals in the solitary nucleus (NST). Actions of these agonists are implied through intracellular recordings from cultured nodose ganglion cells or second order NST neurons. While high-quality data have been obtained using these methods, techniques in which physiological measurements can be made directly on the afferent terminal fields, in situ, in the NST, would eliminate several potential interpretive problems inherent in these less direct approaches. This paper describes methods developed to directly measure changes in presynaptic cytoplasmic calcium in vagal afferents using time-lapse laser confocal microscopy on the in vitro brainstem slice. Calcium green dextran (CG) transported from the nodose ganglion clearly demonstrates vagal afferent fibers ramifying throughout the NST in the in vitro brainstem slice. CG-labeled vagal afferents can be repeatedly activated by focal electrical stimulation, by agonists acting on presynaptic ligand-gated ion channels, and by molecules that are presumed to act directly on vagal afferents based on previous physiological and immunocytochemical studies. Image and preparation stability are a challenge to the success of the experiment; however, methods described here should assist direct studies of transduction events within other afferent terminal fields in the CNS.

Flavonoid structure-activity studies identify 6-prenylchrysin and tectochrysin as potent and specific inhibitors of breast cancer resistance protein ABCG2

Overexpression of breast cancer resistance protein ABCG2 confers multidrug resistance in cancer cells. The GF120918-sensitive drug efflux activity of human wild-type (R482) ABCG2-transfected cells was used for rational screening of inhibitory flavonoids and establishment of structure-activity relationships. Flavones were found more efficient than flavonols, isoflavones, and flavanones. Differentially substituted flavone derivatives indicated positive OH effects at position 5, in contrast to positions 3 and 7. A methoxy at position 7 was slightly positive in tectochrysin, whereas a strong positive effect was produced by prenylation at position 6. The potency of 6-prenylchrysin was comparable with that of GF120918 (IC50 = 0.3 micromol/L). Both 6-prenylchrysin and tectochrysin seemed specific for ABCG2 because no interaction was detected with either P-glycoprotein or MRP1. The ABCG2 resistance profile in vitro is altered by mutation at amino acid 482. The R482T mutation limited the effect of prenylation on ABCG2 inhibition. Whereas GF120918 strongly inhibited the ATPase activity of wild-type ABCG2, neither 6-prenylchrysin nor tectochrysin altered the activity. In contrast, all three inhibitors stimulated the ATPase activity of mutant ABCG2. 6-Prenylchrysin at 0.5 micromol/L efficiently sensitized the growth of wild-type ABCG2-transfected cells to mitoxantrone, whereas higher concentrations were required for the mutant ones. In contrast, 1 micromol/L tectochrysin was sufficient to fully sensitize mutant ABCG2-transfected cells, whereas higher concentrations were required for the wild-type ones. Both flavones exhibited a lower intrinsic cytotoxicity than GF120918 and were apparently not transported by ABCG2. 6-Prenylchrysin and tectochrysin therefore constitute new and promising inhibitors for the reversal of ABCG2-mediated drug transport.

Confocal laser scanning microscopy imaging of dynamic TMRE movement in the mitochondria of epithelial and superficial cortical fiber cells of bovine lenses

PURPOSE

Recent confocal laser scanning microscopy studies of the mitochondria of vertebrate lenses show a striking difference in the distribution and morphology of the mitochondria of lens epithelial and superficial cortical cells. This study, using confocal microscopy, was undertaken to image the movement of the mitochondria specific dye tetramethylrhodamine ethyl ester (TMRE) in the epithelium and superficial cortex of whole live bovine lens.

METHODS

Cultured bovine lenses were loaded with 5 microg/ml TMRE for 15 min at room temperature. TMRE fluorescence was acquired with a Zeiss 510 (configuration META 18) confocal laser scanning microscope for 10 to 15 min using 488 nm Argon laser excitation and 505 nm long pass emission filter settings. The uncoupler of the electron transport chain potential, carbonyl cyanide m-chlorophenylhydrazone (CCCP, 32.5 microM), was used to demonstrate the fluorescent specificity of TMRE.

RESULTS

Multidirectional dynamic movement of TMRE was observed in epithelial cells and bidirectional dynamic movement was seen in the superficial cortical fiber cells of live bovine lenses. In the epithelium, the movement of TMRE fluorescence was up to 5 microm/min whereas in the superficial cortex the observed movement was up to 18.5 microm/min. The movement of TMRE fluorescence was abolished with treatment with the uncoupler, CCCP.

CONCLUSIONS

The observed dynamics of TMRE fluorescence movement may represent actual mitochondrial movement, indicating the dynamic state of the mitochondria in both lens epithelium and superficial cortex. That this activity is found not only in the epithelium but also in the superficial cortex indicates that the superficial cortical fiber cells play a much more active role in lens metabolism than previously suspected. Alternatively, the observed movement of TMRE across a mitochondrial network could represent change in the distribution of potential across the inner membrane, presumably allowing energy transmission across the cell from regions of low to regions of high ATP demand.

Latent fluorophore based on the trimethyl lock

Fluorescent molecules are essential for basic research in the biological sciences and have numerous practical applications. Herein is described the synthesis and use of a new class of latent fluorophores based on a novel design element, the trimethyl lock, that confers distinct advantages over extant fluorophores and pro-fluorophores. A diacetyl version of the latent fluorophore is stable in a biological environment, but rapidly yields rhodamine 110 upon acetyl-group hydrolysis by pig liver esterase or endogenous esterases in the cytosol and lysosomes of human cells. This design element is general and, hence, provides access to an ensemble of useful latent fluorophores.

Permeability of the Nuclear Envelope at Isolated Xenopus Oocyte Nuclei Studied by Scanning Electrochemical Microscopy

In interphase eukaryotic cells, molecular transport between the cytoplasm and the nucleus is mediated by the nuclear pore complex (NPC), which perforates the double-membraned nuclear envelope (NE). Local permeability of the NE at large intact nuclei (approximately 400 microm in diameter) isolated from Xenopus laevis oocytes was studied by scanning electrochemical microscopy (SECM). Steady-state tip current versus tip-nucleus distance curves (approach curves) were measured with 10- and 2-microm-diameter Pt disk microelectrodes at the nuclei in isotonic buffer solutions containing redox-active molecules. The approach curves in the normalized form are independent of the tip diameter, indicating diffusion-limited membrane transport of the redox molecules. SECM chronoamperometry demonstrated that a decrease in the steady-state tip current at short tip-nucleus distances is due to smaller diffusion coefficients and concentrations of the redox molecules in the nucleus than those in the buffer solution. The experimental approach curves fit very well with theoretical ones for freely permeable membranes, yielding the NE permeability to the molecules that is at least 2 orders of magnitude larger than permeability of bilayer lipid membranes and cell membranes. This result indicates that passive transport of the redox molecules across the NE is facilitated by open NPC pores. The flux of the redox molecules sustainable by a single NPC channel (>9.8 x 10(6) molecules per NPC per second) and the diameter of the channel pore (>15 nm) were estimated from the SECM data by assuming the NE as an array of nanometer-sized NPC pores. The effects of the redox molecules on the nucleus and the NPC function were examined by studying signal-mediated nuclear import of rhodamine-labeled bovine serum albumin with and without nuclear localization signals by fluorescence microscopy.

[Reversal of multidrug resistance of tumor cells by FG020327 and its mechanism]

BACKGROUND & OBJECTIVE

Over-expression of P-glyco-protein (P-gp) in tumor cells results in multidrug resistance (MDR), and failure of chemotherapy. Combined therapy of MDR-related cytotoxins plus MDR modulators is a promising strategy to overcome clinical MDR. This study was to explore MDR reversal activity of a novel compound FG020327, and its mechanism.

METHODS

MTT assay was used to evaluate MDR reversal activity of FG020327 in 2 P-gp expressing tumor cell lines, KBv200 and MCF-7/ADR. Adriamycin (ADM) accumulation in MCF-7/ADR cells was detected by fluorescence spectrophotometry. The effect of FG020327 on P-gp function was showed by rhodamine 123 (Rh123) accumulation and efflux in KBv200 cells.

RESULTS

FG020327 significantly enhanced sensitivity of MDR cells to anti- tumor drugs. Five mumol/L of FG020327 enhanced sensitivity of KBv200 cells to vincristine (VCR) by 44.9 folds, the reversal activity of which was 3 times that of verapamil (VRP). However, FG020327 had little effect on drug-sensitive MCF-7 cells and KB cells. FG020327 of 2.5, 5, and 10 mumol/L also enhanced ADM accumulation in MCF-7/ADR cells by 2.3, 2.7, and 3.7 folds, respectively, but didn't affect ADM accumulation in MCF-7 cells. FG020327 enhanced Rh123 accumulation in KBv200 cells,but not in KB cells.

CONCLUSIONS

FG020327 is an efficient modulator. The reversal of drug-resistance by FG020327 is probably related to enhanced anti-tumor drug accumulation, and inhibition of P-gp function in MDR tumor cells.

Screening novel, potent multidrug-resistant modulators from imidazole derivatives

The overexpression of P-glycoprotein (P-gp) by tumor cells results in multidrug resistance (MDR) to structurally unrelated anticancer drugs. Combined therapy with MDR-related cytotoxins and MDR modulators is a promising strategy to overcome clinical MDR. This study was designed to screen potent MDR modulators from imidazole derivatives. Cytotoxicity was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The intracellular accumulation of doxorubicin (Dox) was detected by fluorescence spectrophotometry. The function of P-gp was examined by Rhodamine 123 accumulation detected with flow cytometry (FCM). Among imidazole derivatives, FG020326, FG020327, and FG020318 were found to possess three- to fourfold stronger reversal MDR activity than verapamil, a well-known positive MDR modulator. Imidazole derivatives significantly increased the Dox accumulation and inhibited P-gp function exhibited by the increase of Rhodamine accumulation in MDR cells. The fold reversal of MDR was relative with the increase of Rhodamine accumulation. FG020326, FG020327, and FG020318 showed potent MDR reversal activity in vitro. Their mechanism of MDR reversal is associated with the inhibition of P-gp function and the increase of anticancer accumulation. These results suggest FG020326, FG020327, and FG020318 are promising to further study and develop.

Cyclosporin A inhibits calcineurin (phosphatase 2B) and P-glycoprotein activity in Entamoeba histolytica

Cyclosporin A (CsA) inhibits the proliferation of several protozoan parasites through blocking the activity of calcineurin (Cn) or P-glycoproteins (Pgp). We report here, that inhibition of the proliferation of Entamoeba histolytica trophozoites, the causal agent of human amebiasis, is due to interference of the phosphatase activity of Cn, in a similar fashion to the effect of this immunosuppressive drug on T lymphocytes. The non-immunosuppressive CsA analog PSC-833, which binds Pgp without interfering the function of Cn, did not inhibit the proliferation of HM1:IMSS trophozoites. Moreover, phosphatase activity of amebic Cn, detected using the phosphopeptide RII, was drastically affected by incubation with CsA, but not with PSC-833. On the other hand, both drugs were also tested on clone C2 trophozoites, which grow in the presence of emetine due to over-expression of Pgp. The effect of CsA was similar to that observed on HM1:IMSS trophozoites, whereas PSC-833 only affected the proliferation and viability of clone C2 when the trophozoites were grown in the presence of 40 microM of emetine, suggesting an interference of the Pgp activity. This suggestion was confirmed by results from experiments of Pgp-dependent effux of rhodamine from pre-loaded trophozoites, in the presence of either of these drugs. Therefore, CsA inhibition of E. histolytica trophozoite proliferation is more likely due to Cn than Pgp activity inhibition.

A role for scavenger receptor B-I in selective transfer of rhodamine-PE from liposomes to cells

We investigated the potential role of scavenger receptor B-I (SR-BI) in the selective removal of liposomal markers from blood by hepatocytes. Liposomes were labeled with [(3)H]cholesteryloleyl-ether ([(3)H]COE), 1,2-di[1-(14)C]palmitoyl-phosphatidylcholine ([(14)C]PC), and N-(lissamine rhodamine-B sulfonyl)-phosphatidylethanolamine (N-Rh-PE). The radiolabels were eliminated at identical rates from plasma, while N-Rh-PE was cleared twice as fast. Involvement of SR-BI in the selective removal of N-Rh-PE from liposomes was studied in transfected Chinese hamster ovary cells over-expressing SR-BI. Uptake of N-Rh-PE from liposomes containing phosphatidylserine was higher than [(3)H]COE, and was further enhanced by apolipoprotein A-I, confirming involvement of SR-BI in the selective uptake of liposomal N-Rh-PE by cells.

Regeneration of unmyelinated and myelinated sensory nerve fibres studied by a retrograde tracer method

Regeneration of myelinated and unmyelinated sensory nerve fibres after a crush lesion of the rat sciatic nerve was investigated by means of retrograde labelling. The advantage of this method is that the degree of regeneration is estimated on the basis of sensory somata rather than the number of axons. Axonal counts do not reflect the number of regenerated neurons because of axonal branching and because myelinated axons form unmyelinated sprouts. Two days to 10 weeks after crushing, the distal sural or peroneal nerves were cut and exposed to fluoro-dextran. Large and small dorsal root ganglion cells that had been labelled, i.e., that had regenerated axons towards or beyond the injection site, were counted in serial sections. Large and small neurons with presumably myelinated and unmyelinated axons, respectively, were classified by immunostaining for neurofilaments. The axonal growth rate was 3.7 mm/day with no obvious differences between myelinated and unmyelinated axons. This contrasted with previous claims of two to three times faster regeneration rates of unmyelinated as compared to myelinated fibres. The initial delay was 0.55 days. Fewer small neurons were labelled relative to large neurons after crush and regeneration than in controls, indicating that regeneration of small neurons was less complete than that of large ones. This contrasted with the fact that unmyelinated axons in the regenerated sural nerve after 74 days were only slightly reduced.

Penetration into solid tumor tissue of fluorescent latex microspheres: a mimic of liposome particles

BACKGROUND

Using liposomes as a vehicle to transport anticancer drugs to cancer cells, to increase their effectiveness and decrease their toxicity, has been studied for many years. However, due to technical difficulties, the path of penetration for liposome particles into solid tumor tissue is still not clear.

MATERIALS AND METHODS

In this report, rhodamine-labeled fluorescent latex microspheres were used as a model of liposome particles, combined with fluorescent staining of blood vessel CD31 and tumor cell nuclei. The penetration of microspheres from blood vessels in L1210JF solid tumors of mice was observed. After fluorescent latex microspheres were injected into tail vein, tumor tissue samples were collected at various times and cryosections were then made for fluorescent staining.

RESULTS

Under fluorescence microscopy, the red fluorescent latex microspheres, the green fluorescent blood vessels and the blue tumor cells in the cancer tissue were seen clearly. The leaking of microspheres out from blood vessels was seen directly.

CONCLUSION

The results confirmed that the tiny particles can only leak out through the holes of the broken blood vessels and spread out through the space in between the cells of the solid tumor.

KINETIC CHARACTERIZATION OF P-GLYCOPROTEIN-MEDIATED EFFLUX OF RHODAMINE 6G IN THE INTACT RABBIT LUNG

P-Glycoprotein (P-gp) is an ATP-dependent drug efflux transporter involved in multidrug resistance and drug disposition in many organ systems. A majority of P-gp substrates are lipophilic amine drugs which also exhibit rapid extensive accumulation in lung tissue. P-gp is expressed in lung tissue, and the very nature of this drug efflux mechanism suggests a moderating role in pulmonary drug disposition. Little is known about P-gp-mediated efflux out of lung tissue or its kinetic characteristics as they may relate to the impact of P-gp on pulmonary drug accumulation. The present study develops an experimental and kinetic model to characterize the kinetics of P-gp-mediated efflux of rhodamine 6G dye (R6G) out of the intact rabbit lung. The perfusate concentration of R6G with time during recirculation through an isolated perfused rabbit lung was measured, and 66.6 +/- 2.6% (S.E.) of the perfusate R6G was taken up by the lung. In the presence of P-gp inhibitors, R6G uptake increased significantly to 87.5 +/- 1.1% (P < 0.002), indicating a functional pulmonary P-gp efflux transporter. Fractional lung accumulation of R6G increased with increasing R6G perfusate concentration, a result consistent with saturation of an efflux transporter. A parsimonious three-compartment kinetic model of R6G pulmonary disposition was used to interpret data sets from experiments with different perfusion variables and to estimate parameters descriptive of the dominant kinetic processes involved in R6G pulmonary accumulation. The estimated value of the kinetic parameter, k(pgp), rate constant for P-gp-mediated R6G efflux, indicates that this transporter plays a significant role in moderating R6G pulmonary disposition.

Transforming Growth Factor- 1 Upregulates the Tight Junction and P-glycoprotein of Brain Microvascular Endothelial Cells

1. The present study was aimed at elucidating effects of transforming growth factor-beta (TGF-beta) on blood-brain barrier (BBB) functions with mouse brain capillary endothelial (MBEC4) cells. 2. The permeability coefficients of sodium fluorescein and Evans blue albumin for MBEC4 cells and the cellular accumulation of rhodamine 123 in MBEC4 cells were dose-dependently decreased after a 12-h exposure to TGF-beta1 (0.01-10 ng/mL). 3. The present study demonstrates that TGF-beta lowers the endothelial permeability and enhances the functional activity of P-gp, suggesting that cellular constituents producing TGF-beta in the brain may keep the BBB functioning.

Impact of micropatterned surfaces on neuronal polarity

Experimental control over cellular polarity in a neuronal network is a promising tool to study synapse formation and network behavior. We aimed to exploit a mechanism described by Stenger et al. [J. Neurosci. Methods 82 (1998) 167] to manipulate the direction of axonal versus dendritic outgrowth on a micropattern. The group had used laser ablation to create patterns of aminated silanes for cell attachment on a background of repellent fluorinated silanes. The pattern offered continuous adhesive pathways for axonal and interrupted pathways for dendritic outgrowth. By microcontact printing, we created similar patterns containing continuous and interrupted pathways consisting of extracellular matrix proteins on a background of polystyrene. Neuronal polarity was determined on the functional level through double patch clamp measurements, detecting synapses and their orientation. Although our pattern reproduced the properties that were assumed to be critical for the described effect, namely contrasting pathways of different adhesiveness, we failed to reproduce the above results. It is indicated that other qualities of alternative pathways than mere differences in adhesiveness are required to orient neuronal polarity in vitro. We suggest that the effect observed by Stenger et al. has to be attributed to less universal characteristics of the micropattern, e.g. to the specific chemical groups that were utilized.

Synthesis and multidrug resistance reversal activity of 1,2-disubstituted tetrahydroisoquinoline derivatives

BACKGROUND

Cancer treatment often fails due to multidrug resistance (MDR) of the tumor cells. One of the major causes is overexpression of P-glycoprotein (P-gp).

MATERIALS AND METHODS

By N-substitution reactions of diamine, amino acid and amino alcohol derivatives with 1-substituted tetrahydroisoquinoline skeleton, structurally diverse 1,2-disubstituted 1,2,3,4-tetrahydroisoquinolines were synthesized. The compounds were assayed as P-gp inhibitors using a standard functional assay with rhodamine (6G) on MCF-7/Adr cells. Cytotoxicity was investigated on HeLa cells using an antiproliferative assay.

RESULTS

Five of the 24 compounds showed greater P-gp inhibition than the control compound verapamil with AC50 values (concentration of the compound eliciting 50% of the maximal rhodamine 6G accumulation) significantly lower than that of verapamil.

CONCLUSION

Novel compounds were synthesized that showed MDR-reversal effect. One of them, (1'R*,2R*)-2-[2'-[2''-hydroxy-3''-(alpha-naphthyloxy)propyl]-6',7'-dimethoxy-1',2',3',4'-tetrahydro-1'-isoquinolyl]propan-1-ol hydrochloride, showed two times higher efficacy than verapamil at 10 times lower concentrations. The outcome makes this molecule an attractive subject for further investigation and development.

A novel gene delivery system for mammalian cells

Although gene therapy holds great promise for the treatment of both acquired and genetic diseases, its development has been limited by practical considerations. Non-viral efficacy of delivery remains quite poor. We are investigating the feasibility of a novel lipid-based delivery system, cochleates, to deliver transgenes to mammalian cells. Rhodamine-labelled empty cochleates were incubated with two cell-lines (4T1 adenocarcinoma and H36.12 macrophage hybridoma) and primary macrophages in vitro and in vivo. Cochleates containing green fluorescent protein (GFP) expression plasmid were incubated with 4T1 adenocarcinoma cells. Cellular uptake of labelled cochleates or transgene GFP expression were visualised with fluorescence microscopy. 4T1 and H36.12 lines showed 39% and 23.1% uptake of rhodamine-cochleates, respectively. Human monocyte-derived macrophages and mouse peritoneal macrophages had 48+/-5.38% and 51.46+/-15.6% uptake of rhodamine-cochleates in vitro. In vivo 25.69+/-0.127% of peritoneal macrophages were rhodamine-positive after intra-peritoneal injection of rhodamine-cochleates. 19.49+/-10.12% of 4T1 cells expressed GFP. Cochleates may therefore be an effective, non-toxic and non-immunogenic method to introduce transgenes in vitro and in vivo.

Distinct glutamate receptors govern differential levels of nitric oxide production in a layer-specific manner in the rat cerebellar cortex

To evaluate roles of nitric oxide (NO) in neural functions, it is critical to know how neural inputs activate neuronal NO synthase in individual sites. Although NMDA receptor-dependent mechanism well explains postsynaptic, robust NO production, this sole mechanism does not explain some aspects of NO production in the brain, such as the low-level production of NO and the mechanism for presynaptic NO production. We hypothesized that the glutamate receptor involved in NO production is site-specific and controls the initial NO concentration in each site. We visualized NO production mediated by NMDA, AMPA and type-1 metabotropic glutamate (mGlu-1) receptors in rat cerebellar slices and granule cells in culture, with an NO-specific fluorescent indicator, diaminofluorescein-2. AMPA receptor, but not NMDA or mGlu-1 receptor, was responsible for NO production at parallel fiber terminals, which was blocked by CNQX, tetrodotoxin or voltage-dependent calcium channel blockers. More numbers of electrical stimulation were required for NO production in the molecular layer than in other layers, suggesting that AMPA receptor activation generates NO at lower concentrations through a remote interaction with NO synthase. Although Purkinje cell does not express NO synthase, we detected NO production in Purkinje cell layer following electrical stimulation in the white matter at 50 Hz, but not at 10 Hz. This NO production was tetrodotoxin-sensitive, suggesting occurrence in the basket cell terminals, and required synergistic activation of mGlu-1 and NMDA receptors. In the granule cell layer, activation of AMPA or mGlu-1 receptor produced NO uniformly, while NMDA receptor activation produced NO in discontinuous areas of this layer. Thus, distinct glutamate receptors, including non-NMDA receptors, govern occurrence and level of NO production in a layer-specific manner.

Effect of time of day and rabbit strain on patterns of aortic wall permeability

Lipid deposits occur more frequently downstream of branch points than upstream in immature rabbit and human aortas but the opposite pattern is seen in mature vessels. These distributions correlate spatially with age-related patterns of aortic permeability, observed in rabbits, and may be determined by them. The mature but not the immature pattern of permeability is dependent on endogenous nitric oxide synthesis. Although the transport patterns have hitherto seemed robust, recent studies have given the upstream pattern in some mature rabbits but the downstream pattern in others. Here we show that transport in mature rabbits is significantly skewed to the downstream pattern in the afternoon compared with the morning (P < 0.05), and switches from a downstream to an upstream pattern at around 21 months in rabbits of the Murex strain, but at twice this age in Highgate rabbits (P < 0.001). The effect of time of day was not explained by changes in nitric oxide production, assessed from plasma levels of nitrate and nitrate, nor did it correlate with conduit artery tone, assessed from the shape of the peripheral pulse wave. The effect of strain could not be explained by variation in nitric oxide production nor by differences in wall structure. The effects of time of day and rabbit strain on permeability patterns explain recent discrepancies, provide a useful tool for investigating underlying mechanisms and may have implications for human disease.

Selective uptake of indocyanine green by reticulocytes in circulation

PURPOSE

Hyperfluorescent cells labeled with indocyanine green (ICG) have been observed in retinal and choroidal circulation using scanning laser ophthalmoscopy. It has been suggested that ICG labels leukocytes and that ICG can be used to track leukocyte movement in vivo. The purpose of this study is to identify the cell population that takes up ICG and to study their trafficking pattern in vivo by confocal fluorescence microscopy.

METHODS

ICG was injected into the mouse tail vein, and images were taken by in vivo confocal microscopy. The trafficking pattern of ICG-labeled cells was compared with that of rhodamine 6G-labeled leukocytes. In vitro labeling of human blood cells with antibodies against cell lineage markers and with DNA stains was further used to identify the ICG-labeled cells. Antibodies against the following cell surface markers were used: CD45 (leukocytes), CD3 (T lymphocytes), CD19 (B lymphocytes), CD16 (Fc receptor), glycophorin A (erythroid lineage cells), and CD71 (transferrin receptor).

RESULTS

The ICG-labeled cells were made up of two blood cell populations with distinct levels of ICG uptake. The strongly ICG-labeled cells did not roll on dermal vascular endothelium in vivo, in contrast to rhodamine 6G-labeled leukocytes. They were identified as reticulocytes because antibody staining showed that they were CD 45(-), glycophorin A(+) and CD 71(+). The weakly ICG-labeled cells were identified as neutrophils because they were CD45(+), CD16(+), CD3(-), and CD19(-).

CONCLUSIONS

ICG strongly labels reticulocytes and weakly labels neutrophils. To the authors' knowledge, this is the first report of selective staining of reticulocytes by ICG.

Intracellular proton mobility and buffering power in cardiac ventricular myocytes from rat, rabbit, and guinea pig

Intracellular pH (pHi) is an important modulator of cardiac function. The spatial regulation of pH within the cytoplasm depends, in part, on intracellular H+ (Hi+) mobility. The apparent diffusion coefficient for Hi+, DHapp, was estimated in single ventricular myocytes isolated from the rat, guinea pig, and rabbit. DHapp was derived by best-fitting predictions of a two-dimensional model of H+ diffusion to the local rise of intracellular [H+], recorded confocally (ratiometric seminaphthorhodafluor fluorescence) downstream from an acid-filled, whole cell patch pipette. Under CO2/HCO3--free conditions, DHapp was similar in all three species (mean values: 8-12.5 x 10-7 cm2/s) and was over 200-fold lower than that for H+ in water. In guinea pig myocytes, DHapp was increased 2.5-fold in the presence of CO2/HCO3- buffer, in agreement with previous observations in rabbit myocytes. Hi+ mobility is therefore low in cardiac cells, a feature that may predispose them to the generation of pHi gradients in response to sarcolemmal acid/base transport or local cytoplasmic acid production. Low Hi+ mobility most likely results from H+ shuttling among cytoplasmic mobile and fixed buffers. This hypothesis was explored by comparing the pHi dependence of intrinsic, intracellular buffering capacity, measured for all three species, and subdividing buffering into mobile and fixed fractions. The proportion of buffer that is mobile will be the main determinant of DHapp. At a given pHi, this proportion appeared to be similar in all three species, consistent with a common value for DHapp. Over the pHi range of 6.0-8.0, the proportion is expected to change, predicting that DHapp may display some pHi sensitivity.

Inhibition of preadipocyte proliferation by mitochondrial reactive oxygen species

Preadipocytes are present and can proliferate to increase fat mass throughout adult life. The importance of mitochondria in these cells has never been investigated, although we recently reported that mitochondrial oxidative metabolism is non-negligible in white preadipocytes. Mitochondrial reactive oxygen species generation is intimately associated with respiratory chain function. An increasing number of reports support their role as signalling molecules. The aim of this work was to study the effects of mitochondrial reactive oxygen species on proliferation of white preadipocytes. Rotenone and oligomycin, inhibitors of complex I and of ATP synthase respectively, increased H(2)O(2) and inhibited cell growth of preadipocytes (without inducing necrosis or apoptosis). These effects were partly prevented by addition of radical scavengers. A chemical uncoupler had opposite effects on reactive oxygen species generation and cell growth. Propofol, which inhibits complex I but also scavenges free radicals, had effects similar to those of the uncoupler on both parameters. Thus, mitochondrial reactive oxygen species can influence development of adipose tissue by affecting the size of the white preadipocyte pool.

Ocular drug delivery targeting the retina and retinal pigment epithelium using polylactide nanoparticles

PURPOSE

To study the kinetics of polylactide (PLA) nanoparticle (NP) localization within the intraocular tissues and to evaluate their potential to release encapsulated material.

METHODS

A single intravitreous injection (5 micro L) of an NP suspension (2.2 mg/mL) encapsulating either Rh-6G (Rh) or Nile red (Nr) was performed. Animals were killed at various times, and the NPs localization within the intraocular tissues was studied by environmental scanning electron microscopy (ESEM), confocal microscopy, light microscopy histology, fluorescence microscopy, and immunohistochemistry. Eyes injected with blank NPs, free Rh, or PBS solution were used as the control.

RESULTS

ESEM showed the flow of the NPs from the site of injection into the vitreous cavity and their rapid settling on the internal limiting membrane. Histology demonstrated the anatomic integrity of the injected eyes and showed no toxic effects. A mild inflammatory cell infiltrate was observed in the ciliary body 6 hours after the injection and in the posterior vitreous and retina at 18 to 24 hours. The intensity of inflammation decreased markedly by 48 hours. Confocal and fluorescence microscopy and immunohistochemistry showed that a transretinal movement of the NPs was gradually taking place with a later localization in the RPE cells. Rh encapsulated within the injected NPs diffused and stained the retina and RPE cells. PLA NPs were still present within the RPE cells 4 months after a single intravitreous injection.

CONCLUSIONS

Intravitreous injection of PLA NPs appears to result in transretinal movement, with a preferential localization in the RPE cells. Encapsulated Rh diffuses from the NPs and stains the neuroretina and the RPE cells. The findings support the idea that specific targeting of these tissues is feasible. Furthermore, the presence of the NPs within the RPE cells 4 months after a single injection shows that a steady and continuous delivery of drugs can be achieved.

Molecular and functional changes in voltage-dependent Na(+) channels following pilocarpine-induced status epilepticus in rat dentate granule cells

Status epilepticus (S.E.) is known to lead to a large number of changes in the expression of voltage-dependent ion channels and neurotransmitter receptors. In the present study, we examined whether an episode of S.E. induced by pilocarpine in vivo alters functional properties and expression of voltage-gated Na(+) channels in dentate granule cells (DGCs) of the rat hippocampus. Using patch-clamp recordings in isolated DGCs, we show that the voltage-dependent inactivation curve is significantly shifted toward depolarizing potentials following S.E. (half-maximal inactivation at -43.2+/-0.6 mV) when compared with control rats (-48.2+/-0.8 mV, P<0.0001). The voltage-dependent activation curve is significantly shifted to more negative potentials following S.E., with half-maximal activation at -28.6+/-0.8 mV compared with -25.8+/-0.9 mV in control animals (P<0.05). The changes in voltage dependence resulted in an augmented window current due to increased overlap between the activation and inactivation curve. In contrast to Na(+) channel voltage-dependence, S.E. caused no changes in the kinetics of fast or slow recovery from inactivation. The functional changes were accompanied by altered expression of Na(+) channel subunits measured by real-time reverse transcription-polymerase chain reaction in dentate gyrus microslices. We investigated expression of the pore-forming alpha subunits Na(v)1.1-Na(v)1.3 and Na(v)1.5-Na(v)1.6, in addition to the accessory subunits beta(1) and beta(2). The Na(v)1.2 and Na(v)1.6 subunit as well as the beta(1) subunit were persistently down-regulated up to 30 days following S.E. The beta(2) subunit was transiently down-regulated on the first and third day following S.E. These results indicate that differential changes in Na(+) channel subunit expression occur in concert with functional changes. Because coexpression of beta subunits is known to robustly shift the voltage dependence of inactivation in a hyperpolarizing direction, we speculate that a down-regulation of beta-subunit expression may contribute to the depolarizing shift in the inactivation curve following S.E.

Facilitative role of prolactin-releasing peptide neurons in oxytocin cell activation after conditioned-fear stimuli

Emotional stress activates oxytocin neurons in the hypothalamic supraoptic and paraventricular nuclei and stimulates oxytocin release from the posterior pituitary. Oxytocin neurons in the hypothalamus have synaptic contact with prolactin-releasing peptide (PrRP) neurons. Intracerebroventricular administration of PrRP stimulates oxytocin release from the pituitary. These observations raise the possibility that PrRP neurons play a role in oxytocin response to emotional stress. To test this hypothesis, we first examined expression of Fos protein, an immediate early gene product, in the PrRP neurons in the medulla oblongata after conditioned-fear stimuli. Conditioned-fear stimuli increased the number of PrRP cells expressing Fos protein especially in the dorsomedial medulla. In order to determine whether PrRP cells projecting to the supraoptic nucleus are activated after conditioned-fear stimuli, we injected retrograde tracers into the supraoptic nucleus. Conditioned-fear stimuli induced expression of Fos protein in retrogradely labeled PrRP cells in the dorsomedial medulla. Finally we investigated whether immunoneutralization of endogenous PrRP impairs oxytocin release after emotional stimuli. An i.c.v. injection of a mouse monoclonal anti-PrRP antibody impaired release of oxytocin but not of adrenocorticotrophic hormone or prolactin and did not significantly change freezing behavior in response to conditioned-fear stimuli. From these data, we conclude that PrRP neurons in the dorsomedial medulla that project to the hypothalamus play a facilitative role in oxytocin release after emotional stimuli in rats.

Regulation of ipsilateral visual information within the tectofugal visual system in zebra finches

The eyes of zebra finches are placed laterally, the foveae are looking into different directions. It is unlikely that the birds are able to process different images from both eyes simultaneously. A neural mechanism might therefore be necessary to guide the birds' attention to one of the two eyes and to reduce the processing of information of the other. Previous studies revealed that information from the ipsilateral eye is indeed suppressed on its way to the telencephalon by the activity of the contralateral eye. It has been suggested that two nuclei of the tecto-thalamic tract, nucleus subpraetectalis and nucleus interstitio praetecto subpraetectalis, are a central part of such a suppressive mechanism. Using electrophysiological recordings, we investigated the influence of these two nuclei and nucleus rotundus on the processing of binocular visual information by treating the nuclei with picrotoxin or electrolytic lesions. Deactivation of inhibitory neurons within SP/IPS leads to a significant increase of the ectostriatal responses to ipsilateral and bilateral stimulation, the responses to contralateral stimulation remain unaffected. Lesioning SP/IPS does not alter the responses to visual stimuli. Treatment of nucleus rotundus with picrotoxin increases contralaterally and bilaterally, but not ipsilaterally evoked responses. A wiring diagram is presented which interprets these findings.

Gap junctional coupling in the olfactory organ of zebrafish embryos

Intercellular communication through gap junctions is vital for many developmental processes, including cell division and synaptogenesis. This study is the first demonstration that olfactory organ cells are functionally coupled by gap junctions. Cell coupling was examined during development in the olfactory organ using gap junction permeable dyes in live zebrafish embryos. At 1 day post-fertilization (dpf), cells of the olfactory organ were not coupled by gap junctions. At 2 and 3 dpf, olfactory organ cells passed dye from one cell to another, indicating functional coupling via gap junctions. Coupled cell cohorts included combinations of all three olfactory cell types: basal cells, support cells, and olfactory receptor cells. As the olfactory organ matured, the number of cells per coupled cell cohort increased. Gap junctional coupling corresponded with maturation of the olfactory organ and indicates that functional gap junctions may be involved in proper development of the olfactory organ.

Hypertonicity-induced p38MAPK activation elicits recovery of corneal epithelial cell volume and layer integrity

In hypertonicity-stressed (i.e., 600 mOsm) SV40-immortalized rabbit and human corneal epithelial cell layers (RCEC and HCEC, respectively), we characterized the relationship between time-dependent changes in translayer resistance, relative cell volume and modulation of MAPK superfamily activities. Sulforhodamine B permeability initially increased by 1.4- and 2-fold in RCEC and HCEC, respectively. Subsequently, recovery to its isotonic level only occurred in RCEC. Light scattering revealed that in RCEC 1) regulatory volume increase (RVI) extent was 20% greater; 2) RVI half-time was 2.5-fold shorter. However, inhibition of Na-K-2Cl cotransporter and Na/K-ATPase activity suppressed the RVI response more in HCEC. MAPK activity changes were as follows: 1) p38 was wave-like and faster as well as larger in RCEC than in HCEC (90- and 18-fold, respectively); 2) increases in SAPK/JNK activity were negligible in comparison to those of p38; 3) Erk1/2 activity declined to 30-40% of their basal values. SB203580, a specific p38 inhibitor, dose dependently suppressed the RVI responses in both cell lines. However, neither U0126, which inhibits MEK, the kinase upstream of Erk, nor SP600125, inhibitor of SAPK/JNK, had any effect on this response. Taken together, sufficient activation of the p38 limb of the MAPK superfamily during a hypertonic challenge is essential for maintaining epithelial cell volume and translayer resistance. On the other hand, Erk1/2 activity restoration seems to be dependent on cell volume recovery.

Optimizing chemotherapy by measuring reversal of P-glycoprotein activity in plasma membrane vesicles

The appearance of multidrug resistance (MDR) of cancer cells is a major obstacle to successful chemotherapy. Several proteins have been identified that pump chemotherapeutic drugs out of cells, thus bringing about MDR. One representative pump is the P-glycoprotein, whose function can be inhibited by blockers (also known as reversers, modulators or chemosensitizers). In clinical application, many of these blockers are often not effective because they become bound to the plasma of the patients. The extent of plasma binding of the blocker varies in different persons and we have developed a 96-well kit to assay such inter-person differences. The assay uses membrane vesicles isolated from a human lymphoblastoid cell line (CEM Col1000). Uptake of rhodamine into the vesicles was measured with different concentrations of the blockers verapamil and XR9576 in presence of human plasma. The reverser XR9576 is nearly 30 times more effective than the classical blocker verapamil, the relevant K(m) values ranging from 2.66 to 45 nM for XR 9576 and 0.7 to 5.5 microM for verapamil. An even greater difference between these two drugs, nearly 1,000-fold, could be shown also in intact cells by calcein AM uptake experiments.

Visualization of oleic acid-induced transdermal diffusion pathways using two-photon fluorescence microscopy

In a novel application of dual-channel high-speed two-photon fluorescence microscopy, the skin autofluores-cence and the transdermal fluorescent model drug spatial distributions were imaged simultaneously over precisely the same spatial coordinates. The dual channels enable the detection of the fluorescence emission wavelengths characteristic of the endogenous (intrinsic) skin fluorophores, as well as of the rhodamine-based model drug intensity emission at a different wavelength range of the fluorescence emission spectrum. These fluorescent model drugs delineate the oleic acid induced changes in permeant diffusion with respect to the skin structural features over the 0.3 mm by 0.3 mm skin area imaged per skin sample. The dual-channel high-speed two-photon fluorescence microscopy studies presented here provide evidence for the existence of intracorneocyte diffusion in addition to the commonly cited lipid multilamellar transdermal pathway. The image quantification analysis methodology introduced in this paper reveals that intracorneocyte diffusion exists for the hydrophobic (rhodamine B hexyl ester) and for the hydrophilic (sulforhodamine B) model drugs, in the absence of oleic acid chemical enhancer action. The mechanism of oleic acid chemical enhancer action, however, depends on the model drug physicochemical properties, where the oleic acid induces hydrophobic model drug localization to the lipid multilamellar region, while increasing the hydrophilic model drug lipid to corneocyte partitioning.

Reversal of multidrug resistance: lessons from clinical oncology

Modulation of P glycoprotein (Pgp) in clinical oncology has had limited success. Contributing factors have included the limitation in our understanding of the tumours in which Pgp overexpression is mechanistically important in clinical drug resistance; the failure to prove that concentrations of modulators achieved in patients were sufficient to inhibit Pgp; and the inability to conclusively prove that Pgp modulation was occurring in tumours in patients. New approaches are needed to determine the clinical settings in which Pgp overexpression plays a major role in resistance. (Clinical trials with third generation modulators are ongoing, including trials with the compounds LY335979, R101933 and XR9576. Using the Pgp substrate Tc-99m Sestamibi as an imaging agent, increased uptake has been seen in normal liver and kidney after administration of PSC 833, VX710 and XR9576. These studies confirm that the concentrations of modulator achieved in patients are able to increase uptake of a Pgp substrate. Furthermore, CD56+ cells obtained from patients treated with PSC 833 demonstrate enhanced rhodamine retention in an ex vivo assay after administration of the antagonist. Finally, a subset of patients treated with Pgp antagonists show enhanced Sestamibi retention in imaged tumours. These results suggest that Pgp modulators can increase drug accumulation in Pgp-expressing tumours and normal tissues in patients. Using third generation Pgp antagonists and properly designed clinical trials, it should be possible to determine the contribution of modulators to the reversal of clinical drug resistance.

In vitro human scleral permeability of fluorescein, dexamethasone-fluorescein, methotrexate-fluorescein and rhodamine 6G and the use of a coated coil as a new drug delivery system

PURPOSE

To determine the in vitro human scleral permeability of several dyes and drugdye combinations with varying molecular weights (MW) and lipid solubilities (fluorescein, dexamethasone-fluorescein, methotrexate-fluorescein, and rhodamine). Coils coated with rhodamine were also evaluated for scleral permeability and sustained release.

METHODS

Scleral sections excised from moist chamber stored human globes were mounted in a 2-compartment perfusion chamber. A small depot of drug/dye (100 microl of 10(-4) M fluorescein, dexamethasone-fluorescein, methotrexate-fluorescein or rhodamine) or a coated coil in 100 microl of BSS was added to the episcleral surface while perfusing BSS to the choroidal side. The perfusate was collected and measured for fluorescence. Permeability was calculated as Ktrans from the flux measurements.

RESULTS

Ktrans values (cm/sec, mean +/- SE) for the studied dyes and drug-dye combinations were 5.21 +/- 0.71 x 10(-6) for fluorescein, 1.64 +/- 0.17 x 10(-6) for dexamethasone-fluorescein, 3.36 +/- 0.62 x 10(-6) for methotrexate-fluorescein, 1.86 +/- 0.39 x 10(-6) for rhodamine and 2.18 +/- 0.23 x 10(-6) for the rhodamine from the coils. We found a significant difference between the permeability of the sclera to fluorescein and dexamethasone-fluorescein (P < 0.001), methotrexate-fluorescein (P < 0.05) and rhodamine (P < 0.001). Steady state flux was observed from the rhodamine coil.

CONCLUSION

The rank order of scleral permeability to the studied dyes is as follows: fluorescein > methotrexate-fluorescein > rhodamine coil > rhodamine 6G > dexamethasone-fluorescein. Differences in scleral permeability are related to MW and lipid solubility. Prolonged transscleral diffusion of rhodamine delivered by solution and by coil are similar.

Forskolin-induced clearance of the fluorescent dye sulforhodamine from rat parotid intralobular duct lumen: visualization of the secretory function under a confocal laser scanning microscope

Cyclic AMP evokes fluid secretion with bicarbonate in exocrine ducts. Clearance of fluorescent dyes from rat parotid intralobular ducts by forskolin was visualized as a fluorescence change in the duct luminal space by optical sectioning under a confocal laser scanning microscope to clarify the secretory function in the ducts. When the isolated rat parotid intralobular duct segments were superfused with membrane-impermeable fluorescent dyes during the experimental period, fluorescent dyes were passively moved into the duct space. Forskolin and isobutylmethylxanthine decreased the fluorescence of anionic dye, sulforhodamine B, and neutral dye, dextran tetramethyl-rhodamine, in the duct space, suggesting that the forskolin-induced clearance of fluorescent dyes might be the result of fluid secretion in the ducts. Methazolamide inhibited a forskolin-induced sustained decrease in duct fluorescence and intracellular acidification. Low concentrations of external Cl?, DIDS, bumetanide and amiloride did not markedly inhibit a forskolin-induced decrease in duct fluorescence. These findings suggest that a major portion of the steady decrease in duct fluorescence by forskolin was related to intracellular HCO3? production, not the uptake mechanism of external Cl?. Glibenclamide, NPPB, DPC and DMA inhibited the forskolin-induced decrease. Forskolin evokes the clearance of fluorescent dyes from duct space possibly due to fluid secretion in rat parotid ducts, associated with secretion through CFTR and DPC-sensitive anion channels of carbonic anhydrase-dependent bicarbonate linked with the Na+/H+ exchange mechanism.

Visualization of ?Water Secretion? by Confocal Microscopy in Rat Salivary Glands: Possible Distinction of Para- and Transcellular Pathway

Visualization of water transport in cells, tissues and organs is an important, yet still difficult, task in morphological science. By using confocal microscopy and the fluid-phase fluorescent tracer technique, we visualized water secretion and estimated the routes of water transport across the acinar epithelia in rat parotid and submandibular glands. Confocal microscopy of whole glands perfused arterially with Lucifer yellow revealed a bright fluorescence at the basolateral space of acini. Luminal space was devoid of fluorescence, but revealed it after isoproterenol pretreatment, ductal infusion of fluorescent dextrans into the lumen, or tissue dissociation by collagenase. Under these conditions, stimulation of fluid secretion with carbachol caused a rapid decline of the luminal fluorescence intensity, indicating that the secreted water washed out the fluorescent probes in the acinar lumen. In the stimulated dissociated acini, the luminal fluorescence disappeared by 15 sec, but reappeared at 30-45 sec to maintain a low plateau level. By assuming that the tight junction was 'paralyzed' by the collagenase digestion and that the paracellular fluid transport could not influence the dilution of Lucifer yellow, we estimated that the initial water secretion by CCh occurs via the transcellular pathway, while later than 30-45 sec the additional water permeates through the paracellular pathway.

Measurement of the activity of multixenobiotic resistance mechanism in the common carp Cyprinus carpio

The multixenobiotic resistance (MXR) mechanism, mediated by activity of the transmembrane P-glycoprotein, represents a basic biological defence system in aquatic organisms. Here we investigate the MXR transport activity in an aquatic vertebrate, the common carp (Cyprinus carpio). We measured the accumulation rate of a model MXR substrate, the fluorescent dye rhodamine B (RB), in gills, lateral muscles, liver and bile. Results obtained using this method showed a significant increase of RB accumulation in tissues of fish exposed for I h to 3 microM RB in the presence of the model MXR inhibitors cyclosporin A (CA, 5 microM) or verapamil (VER, 10 microM), when compared with specimens exposed without inhibitors. The highest increase in RB accumulation detected in the liver (VER 54%, CA 170%) indicates that among the tissues analysed within this study, liver is the most prominent candidate organ for the functional detection of MXR activity in C. carpio.

Rhodamine exclusion activity in primary cultured turbot (Scophthalmus maximus) hepatocytes

Cellular detoxification by direct processes has been investigated in fish by studying the ability of hepatocytes prepared from juvenile aquarium-reared turbot (Scophthalmus maximus) to actively exclude the fluorescent dye rhodamine B (RB). Cell viability was studied by measurements of non-specific esterase activity using fluorescein diacetate. This revealed that turbot hepatocytes can be cultured for a few days with a viability decreasing to 38% after 24 h. The 24-h cultured cells have been used to study the rhodamine B exclusion activity using confocal laser microscopy. Hepatocytes accumulated the dye in a competitive manner with verapamil, thus suggesting that they express a transport system similar to the P-glycoprotein-mediated multixenobiotic resistance process. Incubation of cells with 1 microM RB and 20 microM verapamil led to a 26% increase of cellular fluorescence as compared to the accumulation in absence of competitor. Rhodamine B accumulated in the whole cytoplasm, with more concentrated areas that might correspond to the lysosomal compartment and the cell membrane.

Expression and activity of a multixenobiotic resistance system in the Pacific oyster Crassostrea gigas

The multidrug resistance (MDR) mechanism corresponds to a defence system relying on the expression of high molecular membrane proteins that can actively lower the intracellular concentration of a wide variety of toxins, thus maintaining them below their toxic level. Using RT-PCR, expression levels of a gene belonging to the class I of mammalian mdr genes, has been assessed in different developmental stages of the oyster Crassostrea gigas. While no expression was found in the oocyte or the trocophore stage, a rise of mRNA content was observed from the veliger stage to the juvenile stage, thus indicating the induction of the system as the animal is developing in the environment. The incubation of gill fragments in the dye rhodamine B and subsequent measurements of intracellular fluorescence using a microplate reader indicates that the system can effectively decrease the accumulation of the test compound in a competitive manner with known inhibitors or environmental contaminants as observed in vertebrate cells. The oyster MXR system is thus becoming active in adult oyster and could be of importance in environmentally contaminated areas.

Bifluorophoric molecules as fluorescent beacons for antibody-antigen binding

The quenching of fluorescence (up to 98%) by anti-fluorescein antibodies is well documented in the literature. Here we report a system where, instead of quenching, bifluorophoric molecules are designed to increase in fluorescence upon binding by an anti-fluorescein antibody. Bifluorophoric molecules are made of fluorescein (F) linked to tetramethylrhodamine (T) via varying numbers of methylene units, denoted as F-(CH(2))(n)-T. These F-(CH(2))(n)-T conjugates are almost nonfluorescent when free in solution due to intramolecular dimerization and stacking. Upon binding to an anti-fluorescein antibody, however, up to 110-fold increase in fluorescence was observed from the rhodamine moiety. This increase is believed to result from intramolecular dimer dissociation that dequenches the rhodamine fluorescence. Fluorescein fluorescence, on the other hand, remains quenched due to binding and intramolecular resonance energy transfer. Moreover, the excitation wavelength was at the absorption maxima of fluorescein, giving a Stoke's shift of about 90 nm. This system couples directly molecular recognition with a concurrent increase in fluorescence emission, obviating wash and incubation steps required by most assays. It is an important molecular reporter system for developing homogeneous assays.

P-glycoprotein targeting: a unique strategy to selectively eliminate immunoreactive T cells

T lymphocytes have been found to harbor P-glycoprotein (Pgp) and to demonstrate modulation of its ion channel transporter function according to the state of activation of T lymphocytes. We hypothesized that cytotoxic chemicals that are extruded by Pgp could be used to specifically eliminate immunoreactive T-cell populations. In this study, we evaluated the capacity of 4,5-dibromorhodamine methyl ester (TH9402), a photosensitizer structurally similar to rhodamine, a dye transported by Pgp, and which becomes highly cytotoxic on activation with visible light to selectively deplete alloreactive T lymphocytes. Stimulation of T cells with mitogens or allogeneic major histocompatibility complex-mismatched cells resulted in the preferential retention of the TH9402 rhodamine-derivative in activated T cells, both CD4+ and CD8+. Photodynamic cell therapy of TH9402-exposed T cells led to the selective elimination of immunoreactive T-cell populations. In addition, this treatment preserved resting T cells and their capacity to respond to third-party cells. Inhibition of Pgp enhanced cellular trapping of the dye in nonactivated T cells and resulted in their depletion after exposure to light. Targeting of Pgp-deficient cells may therefore represent an appealing strategy for the prevention and treatment of graft-versus-host disease and other alloimmune or autoimmune disorders.

Fluorescent retrograde neuronal tracers that label the rat facial nucleus: a comparison of Fast Blue, Fluoro-ruby, Fluoro-emerald, Fluoro-Gold and DiI

Many fluorescent retrograde tracers are commercially available for neuroanatomical studies. They have been used with varying success in different models and can be very effective in the study of the facial nerve and nucleus. We compare the tracers Fast Blue (FB), Fluoro-ruby, Fluoro-emerald, Fluoro-Gold (FG), and DiI in the rat facial nucleus after application to the buccal division of the nerve. There were no significant differences between counts of cells on the left and right sides of the brain stem with any of the tracers. FB produced a lower sample variation than the other tracers, and together with DiI, demonstrated greater axonal labelling when applied to the surface of the epineurium. FB and FG resulted in strong retrograde labelling of the facial nucleus after only 2 days from injection. All the tracers produced adequate cell labelling after 1 week from nerve application. This labelling persisted for up to 8 weeks for most tracers except FG, which did not produce satisfactory labelling at 8 weeks.

Myeloid-lymphoid initiating cells (ML-IC) are highly enriched in the rhodamine-c-kit(+)CD33(-)CD38(-) fraction of umbilical cord CD34(+) cells

OBJECTIVE

The study of hematopoietic stem cells (HSC) is limited by lack of specific markers for HSC. Rhodamine 123 (Rho) is one of the substrates of P-glycoprotein (Pgp), and the presence of active Pgp can be shown by the efflux of Rho. Rho can also be used to measure the mitochondrial transmembrane potential (energy state) of a cell. We reasoned that selection of hematopoietic progenitors using a combination of Rho efflux and phenotypic markers might be superior to use of phenotypic markers alone.

MATERIALS AND METHODS

We used the myeloid-lymphoid initiating cell (ML-IC) assay as functional measure of primitive progenitors. Umbilical cord blood CD34(+)CD33(-)CD38(-), CD34(+)CD33(-)CD38(-)Rho(-), and CD34(+)CD33(-)CD38(-)Rho(-)c-kit(+) cells were sorted singly onto AFT024 feeders to assess their capacity to become ML-IC.

RESULTS

The frequency of ML-IC in CD34(+)CD33(-)CD38(-)Rho(-) cells was significantly higher (15 +/- 0.4%) than that in CD34(+)CD33(-)CD38(-) cells (6.2 +/- 0.9%, p < 0.05). However, the frequency of long-term culture-initiating cells (LTC-IC) (17 +/- 3% vs 12 +/- 1.5%) and natural killer culture-initiating cells (NK-IC) (25 +/- 3% vs 20 +/- 4%) was similar in the two populations. Following the treatment of CD34(+)CD33(-)CD38(-)Rho(-) cells with verapamil, which blocks Pgp function, no increase in ML-IC was detected compared with CD34(+)CD33(-)CD38(-) cells (6 +/- 0.7%), suggesting that differences in the energy state, which is reflected by Rho staining after verapamil treatment, cannot be used as a criterion to identify human HSC. Further selection of CD34(+)CD33(-)CD38(-)Rho(-) cells based on expression of c-kit significantly increased the frequency of ML-IC, LTC-IC and NK-IC by 1.75-, 1.3-, and 1.8-fold, respectively.

CONCLUSION

Combining the function of Pgp and phenotypic features of hematopoietic progenitors enriches the frequency of cord blood ML-IC to greater than 25%. Use of such enriched populations will allow us to characterize the biological behavior of human HSC.

Intraocular distribution of 70-kDa dextran after subconjunctival injection in mice

PURPOSE

To investigate the intraocular distribution kinetics of 70-kDa dextran after subconjunctival injection.

METHODS

The right eye of 15 mice received a single subconjunctival injection of a 1.5-microL solution of 0.25% 70-kDa tetramethylrhodamine-dextran (TMR-D). The distribution of fluorescent labeling in eye sections was examined by fluorescence microscopy at 0.25, 1, 4, 24, or 72 hours after the injection. The brightness and homogeneity of fluorescence in the sclera, choroid, and retina were scored near the injection site, on the side of the globe opposite the injection site, and adjacent to the optic nerve head. Fluorescence intensity within the sclera and choroid adjacent to the optic nerve was assessed quantitatively by imaging densitometry.

RESULTS

TMR-D readily diffused transsclerally and dispersed throughout a large portion of the sclera, uvea, and cornea. Shortly after the injection, homogenous fluorescence was observed in the sclera and choroid on the same meridian as that of the injection site. This fluorescence gradually decreased in intensity with distance from the injection site. At the opposite meridian, fluorescence in the choroid was more intense than in the adjacent sclera and could be traced up to the ciliary muscle. TMR-D was also observed in the retinal and optic nerve vessels. The intensity of scleral and choroidal fluorescence adjacent to the optic nerve reached a maxima at 1 hour, and then decreased slowly, with half-lives of approximately 16 and 100 hours, respectively. Visible fluorescence was maintained at least until 72 hours in the sclera, choroid, iris, and cornea. Specific fluorescent labeling was never found in the contralateral eyes.

CONCLUSIONS

Macromolecular 70-kDa dextran can be readily delivered to the mouse retina and uveal tissues by subconjunctival injection through transscleral diffusion, local hematogenous spread, and possibly movement through the uveoscleral outflow pathway. Subconjunctival injection may be a useful approach for delivering macromolecules to the retina and uvea.