Paclitaxel delivery systems: the use of amino acid linkers in the conjugation of paclitaxel with carboxymethyldextran to create prodrugs

Paclitaxel was bound via its hydroxyl group to carboxymethyldextran (CMDex, 150 kDa) by means of an amino acid linker; the linker was introduced into the 2'- or 7-hydroxyl group of the paclitaxel through an ester bond. These conjugates--CMDex-2'-paclitaxel and CMDex-7-paclitaxel--were designed to be water-soluble with a paclitaxel content between 6-8% (w/w) with a degree of subsititution (DS) of the CM groups at 0.6 per sugar residue. The release of the paclitaxel from the conjugates was influenced by the hydroxyl group (2'- or 7-) of paclitaxel to which the amino acid linker was introduced, and by what amino acid was used as the linker. In mouse plasma incubated at 37 degrees C for 72 h, the most paclitaxel was released using CMDex-paclitaxel conjugate with 2'gly followed by, in descending order, 2'-ala, 2'-leu, 2'-ile, and 7-gly as the amino linkers. Colon 26, a Taxol resistant cancer, was introduced into mice and the conjugates were intravenously administered by bolus injection for a tumor distribution study, and intermittently intravenously administered for a tumor growth regression study. In both studies the highest amount of paclitaxel release was found in the CMDex-2'-gly-paclitaxel followed by CMDex-2'-ala-paclitaxel, CMDex-2'-leu-paclitaxel and paclitaxel. There was a direct correlation between the amount of paclitaxel released and the observed efficacy. CMDex-2'-ile-paclitaxel and CMDex-7-gly-paclitaxel did not show any anti-tumor activity. These results clearly demonstrate that a CMDex-paclitaxel with an appropriate amino acid linker has significant anti-tumor activity against colon 26, and that these anti-tumor effects appear to correlate with the amounts of paclitaxel released in the tumor.     

Enhancement of cellular adenosine triphosphate levels in PC12 cells by extracellular adenosine

To elucidate the biological significance of extracellular adenine compounds, the effects of adenosine (Ado) on cellular levels of adenine compounds, especially adenosine triphosphate (ATP), in PC12 cells were studied. Ado and inosine but not adenosine 5'-monophosphate, adenosine 5'-diphosphate, ATP, guanosine, cytosine, thymidine, and uridine, significantly enhanced cellular ATP levels in PC12 cells in time- and dose-dependent manners. Various P1 receptor agonists of Ado did not enhance the ATP level. In addition, theophylline, an antagonist of P1 receptors, did not inhibit the Ado-evoked ATP enhancement. These results suggest that the Ado receptor is not involved in the augmentation of the cellular ATP level induced by Ado in PC12 cells. The ATP-enhancing effect of Ado was potentiated by dipyridamole, an inhibitor of Ado uptake, or coformycin, an inhibitor of Ado deaminase. The effect of Ado on the ATP level was also observed when PC12 cells were incubated in glucose-free medium. Together these results suggest that enhancement of cellular ATP levels in PC12 cells by extracellular Ado might be acceleration of ATP synthesis through the Ado salvage system using hypoxanthine-guanine phosphoribosyltransferase rather than Ado kinase since 5'-iodotubercidin, an inhibitor of Ado kinase, had no effect on the enhancement elicited by Ado.     

Transfollicular drug delivery: penetration of drugs through human scalp skin and comparison of penetration between scalp and abdominal skins in vitro

In order to quantitatively investigate the importance of transfollicular pathway for drug delivery, drug penetration through human scalp skin was investigated using liquid formulations containing lipophilic and hydrophilic drugs in vitro. The penetration pathway for drugs through the scalp skin was examined using fluorescent probes. Additionally, the drug penetration through the scalp skin was compared with that via human abdominal skin to clarify the usefulness of intrafollicular delivery. Lipophilic melatonin (MT) and ketoprofen (KP) showed high permeabilities through the scalp skin, although the flux of KP was much higher. Absorption enhancers, N-methyl-2-pyrrolidone and isopropylmyristate, only slightly increased the fluxes. Hydrophilic fluorouracil (5FU) and acyclovir (ACV) penetrated through the scalp skin with relatively large fluxes. However, there was large variability in the fluxes of these drugs across scalp skin from different sources. When the relationship between the flux and hair follicle density was estimated, there was good correlation between the two (r = 0.651 for MT and r = 0.666 for ACV, P < 0.05). The histologic examination of the scalp skin, following application of the formulation with nile red or sodium fluorescein, indicated that the probes permeated into the junction of the internal and external root sheath of follicles and diffused into the dermis via the outer root sheath at the initial times. The penetration of nile red, a lipophilic probe, via the stratum corneum of scalp skin was later than that via the follicles. The permeation of MT and 5FU through the scalp skin was much higher than that via the abdominal skin, being 27 and 48 times as high as the abdominal skin, respectively. These results indicate that the drug delivery through the scalp skin will offer an available delivery means for drugs, particularly for hydrophilic drugs.     

Dissociation of E-4031 from the HERG channel caused by mutations of an amino acid results in greater block at high stimulation frequency

OBJECTIVE: We have reported identification of the amino acid whose mutation reduces effects of quinidine on the HERG channel. Although the residue (isoleucine at 647) is not in the recently reported methanesulfonanilide binding site, a single concentration of E-4031 (10 microM) was less effective to I647 mutant channels than wild type HERG channel. We designed the present experiment to further investigate influence of mutations at 647 on the effects of methanesulfonanilides. METHODS AND RESULTS: HERG channels were expressed in Xenopus oocytes and their currents were measured by a two-microelectrode voltage clamp method. Of the two mutations initially studied (I647A and I647F), the I647F had a greater influence and differentially affected the effects of dofetilide and E-4031. The IC(50) for dofetilide of the two mutant channels (I647A and I647F) was increased only 2-fold, but the IC(50) for E-4031 was increased 6-fold (I647A) and 14-fold (I647F). Aromatic residues other than phenylalanine were then substituted for I647, and found to reduce the effects of E-4031. Whereas E-4031 dissociated from the mutant channels during rested state, dofetilide little dissociated. The mutant channels that showed recovery from E-4031 block were inhibited greater at 1 Hz than at 0.1 Hz. CONCLUSIONS: The present results indicate that dissociation of a drug from the HERG channel results in greater block at high frequency. Although the mechanism by which the mutations cause the dissociation of E-4031 is uncertain, it is noteworthy that one methanesulfonanilide dissociates from the channel more easily than another.     

Dermatomes and the central organization of dermatomes and body surface regions in the spinal cord dorsal horn in rats

Dermatomes and the associated central projection fields were studied with the application of fluorescent neurotracer, 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI), to 21 reference points on rat trunk and hindlimb skin. Segmental distribution and rostrocaudal central level of dorsal root ganglion (DRG) neurons innervating reference points were examined and DiI-induced fluorescent areas were mapped in the horizontal plane through lamina II of the dorsal horn. Segmental levels of DRG neurons innervating reference points were generally identical to the level determined using dye-extravasation methods. However, innervation of the first digit was situated in the L4 dermatome, not the L3 reported previously using those methods. Generally, afferents from a reference point projected to a single field in the ipsilateral dorsal horn. Reference points on ventral and dorsal median lines of the trunk were represented bilaterally. Afferents from reference points located on the ventral median line of the hindlimb projected to two separate fields: one on the medial margin of spinal cord segments L2-L5 and the other on the medial half of spinal cord segment L5. From the distribution of central projection fields of reference points, central projection fields of dermatomes were revealed as even in shape and located within corresponding spinal cord segments. The arrangement of peripheral and central fields of dermatomes and body surface regions suggests that peripheral and central projection fields of cutaneous afferent fibers are reshaped from the common prototypical pattern that exhibits an orderly and evenly sequenced arrangement.     

Association of phosphorylation site of tau protein with neuronal apoptosis in Alzheimer's disease

In addition to neuritic changes and amyloid deposits, neuronal and glial cell apoptosis is an important pathological feature of Alzheimer's disease (AD). Several factors have been postulated as causes or triggers of cellular apoptotic change. This study focused on a quantifiable relationship between phosphorylation sites of tau protein in the neurofibrillary tangles (NFT) and neuronal apoptosis. Five monoclonal anti-tau antibodies (AT180, AT8, HT7, Tau2 and Tau5) for NFT labeling and TdT-mediated UTP nick-end labeling (TUNEL) for localizing apoptotic change were employed. TUNEL-stained neuronal nuclei showed significantly high density in the entorhinal cortex, cornu ammonis (CA) and the parietal cortex. In all regions, density of TUNEL-stained neuronal nuclei showed significantly direct correlation with that of AT8-, AT180- and Tau2-positive neurons. Correlation of TUNEL-stained neuronal nuclei with tau-positive neurons differed depending on the cerebral regions. Density of TUNEL-stained neuronal nuclei showed inverse correlation with that of both AT8-positive and Gallyas-stained NFT in the CA and showed significantly direct correlation with AT8- and HT7-positive neurons in the frontal cortex. Density of tau-positive and Gallyas-stained NFT was higher than that of TUNEL-stained nuclei. We conclude that phosphorylation sites of tau, 159-163 and 202-205, are probably associated with neuronal apoptosis and apoptotic change follows abnormal phosphorylation of tau.     

Changes in serum macrophage-related factors in patients with chronic inflammatory demyelinating polyneuropathy caused by intravenous immunoglobulin therapy

Chronic inflammatory demyelinating polyneuropathy (CIDP) is a slowly progressive or recurrent neuropathy accompanied by infiltration of macrophages in the peripheral nerves. Macrophage colony-stimulating factor (M-CSF) and monocyte chemoattractant protein-1 (MCP-1) are a macrophage-related cytokine and chemokine, respectively. Although, intravenous immunoglobulin (IVIg) infusion therapy has been used for treating CIDP patients, not all CIDP patients have responded to IVIg infusion therapy. To determine the mechanisms of the action of IVIg, we examined serum M-CSF and MCP-1 levels during and after IVIg infusion therapy in 19 CIDP patients treated with IVIg (0.4 g/kg/day for 5 days). Ten of the 19 patients (52.6%) responded to IVIg therapy. Both M-CSF and MCP-1 concentrations in IVIg responders were significantly higher on day 1 postinfusion than those in nonresponders, but decreased to their pretreatment values on day 5 postinfusion. The results suggest that immunomodulation through M-CSF and MCP-1 is involved in the mechanisms underlying the effect of IVIg infusion therapy in CIDP patients.     

Analysis of longterm survivors with expandable metallic stent inserted for malignant biliary stenosis

Background/Purpose. Some patients with unresectable malignant biliary stenosis can survive for more than 1 year after the insertion of self-expandable metallic stents (SEMS). The aim of this study was to analyze the background of the longterm survivors.Methods. In our study, 111 patients with inserted SEMS were divided into two groups: patients who died within 1 year and patients still alive for more than 1 year. The parameters analyzed were survival rate, survival period, patent period of the inserted SEMS, adjuvant therapy, and complications.Results. The number of those who survived for more than 1 year totaled 24 (21.6%). Their diagnoses were bile duct carcinoma (15/31; 48.4%) and pancreas carcinoma (9/28; 32.9%). There were no survivors with other diseases. The survival period and stent-patent period of the patients with bile duct carcinoma (429.2 days and 589.7 days, respectively) and pancreas carcinoma (270.1 days and 336.4 days, respectively) were significantly longer than those of the patients with other diseases. The specific complication of the longterm survivors was duodenal obstruction.Conclusions. Many patients with bile duct carcinoma and pancreas carcinoma survived for more than 1 year and adjuvant therapy should be performed to improve the survival of those patients.