Progranulin enhances neural progenitor cell proliferation through glycogen synthase kinase 3β phosphorylation

Progranulin (PGRN) is an estrogen-inducible growth factor thought to affect multiple processes in the CNS, including brain sexual differentiation, adult neurogenesis in the hippocampus, and development of neurodegenerative diseases. However, the precise physiological functions of PGRN in individual nerve cells are not fully understood. The aim of the present study was to enhance the understanding of PGRN function in the CNS by investigating the effects of PGRN on neural progenitor cells (NPCs). We found that significant amounts of endogenous PGRN were secreted from isolated NPCs in cultures. To assess the bioactivities of endogenous and exogenous PGRN, we studied NPCs derived from wild-type mice (WT-NPCs) and PGRN-deficient mice (KO-NPCs). We found that proliferation of KO-NPCs was significantly enhanced by PGRN treatment; however, PGRN treatment apparently did not affect proliferation of WT-NPCs perhaps because of the high levels of endogenous PGRN expression. NPC death and asymmetric cellular division of KO-NPCs and WT-NPCs, which results in production of neural stem cells, astrocytes, or oligodendrocytes, were not affected by PGRN treatment. We also investigated the signaling mechanism(s) that mediate PGRN-induced NPC proliferation and found that phosphorylation of serine 9 (S9) of glycogen synthase kinase 3-beta (GSK3β), which was dependent on phosphatidylinositol 3-kinase (PI3K) activity, was induced by PGRN treatment. In addition, a GSK3β-specific inhibitor enhanced NPC proliferation. Taken together, our observations indicate that PGRN enhanced NPC proliferation, at least in part, via inducing GSK3β phosphorylation.

Hemodynamic studies of intracranial dural arteriovenous fistulas using arterial spin-labeling MR imaging

Arterial spin-labeling (ASL) magnetic resonance imaging (MRI) enables non-invasive acquisition of the brain perfusion information in cerebrovascular disease. We investigated hemodynamic changes in intracranial dural arteriovenous fistulas (DAVFs) using ASL-MRI. ASL-MRI by a Q2TIPS sequence on a 3.0-Tesla MRI was performed for three patients with Cognard's IIa+b type of DAVFs before and after treatment. Perfusion images obtained by ASL-MRI (ASL images) before treatment were visually compared with those by single-photon emission computed tomography images (SPECT images). Increasing rates of temporal changes of regional perfusion values in ASL images (ASL values) before and after treatment were also calculated. In all three patients, ASL images before treatment demonstrated high perfusion in regions around the shunting areas, where normal or low perfusion were detected on SPECT images; thus, ASL images might have demonstrated the abundant arterial shunting flow via the fistulas. On days eight to 20 after treatment, ASL values around the shunt areas remained the same or decreased, and those in the regions other than the shunt areas increased in all three patients. This might have been due to a combination of the following: a decrease in shunt flow volume, an amelioration of venous congestion, and a sustained an upward shift in the autoregulation of the brain perfusion pressure. All regional ASL values decreased on days 112 and 120 after treatment in two patients, which possibly reflects a reduction in the upward shift in autoregulation. ASL-MRI might be useful for identifying the hemodynamic behavior of DAVFs before and after treatment.

Vital microscopic analysis of polymeric micelle extravasation from tumor vessels: macromolecular delivery according to tumor vascular growth stage

Particles larger than a specific size have been thought to extravasate from tumor vessels but not from normal vessels. Therefore, various nanoparticles incorporating anticancer drugs have been developed to realize selective drug delivery to solid tumors. However, it is not yet clear whether nanoparticles extravasate readily from all tumor vessels including vessels of microtumors. To answer this question, we synthesized new polymeric micelles labeled with fluorescein isothiocyanate (FITC) and injected them into the tail vein of rats with implanted skinfold transparent chambers. We also analyzed, by means of time-lapse vital microscopy with image analysis, extravasation of FITC micelles from tumor vessels at different stages of growth of Yoshida ascites sarcoma LY80. Polymeric micelles readily leaked from vessels at the interface between normal and tumor tissues and those at the interface between tumor tissues and necrotic areas. The micelles showed negligible extravasation, however, from the vascular network of microtumors less than 1 mm in diameter and did not accumulate in the microtumor. Our results suggest that we must develop a novel therapeutic strategy that can deliver sufficient nanomedicine to microtumors.

Convection-enhanced delivery of a synthetic retinoid Am80, loaded into polymeric micelles, prolongs the survival of rats bearing intracranial glioblastoma xenografts

Prognosis for the patients with glioblastoma, the most common malignant brain tumor, remains dismal. A major barrier to progress in treatment of glioblastoma is the relative inaccessibility of tumors to chemotherapeutic agents. Convection-enhanced delivery (CED) is a direct intracranial drug infusion technique to deliver chemotherapeutic agents to the central nervous system, circumventing the blood-brain barrier and reducing systemic side effects. CED can provide wider distribution of infused agents compared to simple diffusion. We have reported that CED of a polymeric micelle carrier system could yield a clinically relevant distribution of encapsulated agents in the rat brain. Our aim was to evaluate the efficacy of CED of polymeric micellar Am80, a synthetic agonist with high affinity to nuclear retinoic acid receptor, in a rat model of glioblastoma xenografts. We also used systemic administration of temozolomide, a DNA-alkylating agent, which has been established as the standard of care for newly diagnosed malignant glioma. U87MG human glioma cells were injected into the cerebral hemisphere of nude rats. Rats bearing U87MG xenografts were treated with CED of micellar Am80 (2.4 mg/m(2)) on day 7 after tumor implantation. Temozolomide (200 mg/m(2)/day) was intraperitoneally administered daily for 5 days, starting on day 7 after tumor implantation. CED of micellar Am80 provided significantly longer survival than the control. The combination of CED of micellar Am80 and systemic administration of temozolomide provided significantly longer survival than single treatment. In conclusion, temozolomide combined with CED of micellar Am80 may be a promising method for the treatment of malignant gliomas.

Possible involvement of microglia containing cyclooxygenase-1 in the accumulation of gonadotrophin-releasing hormone in the preoptic area in female rats

Prostaglandins (PGs), especially PGE(2), are involved in the hypothalamic control of gonadotrophin-releasing hormone (GnRH) release, acting at least in part on the terminal of GnRH axons in the median eminence. The present study aimed: (i) to clarify the role of PG(s) in regulating GnRH cell function at the level of the perikarya in the preoptic area; (ii) to determine the cyclooxygenase (COX) isozyme responsible for producing PG(s) that regulates GnRH perikarya; and (iii) to identify cell types that contain the responsible COX isozyme in female rats. A surge of luteinising hormone (LH) secretion was induced by oestrogen and progesterone in ovariectomised rats. Treatment of the rat before the LH surge with indomethacin, a nonselective COX inhibitor, or NS-398, a selective COX-2 inhibitor, did not interfere with the surge. However, treatment with indomethacin or flurbiprofen, a selective COX-1 inhibitor, significantly reduced the number of GnRH-immunoreactive cells in the preoptic area at the time of peak LH secretion during the surge. NS-398 did not affect the GnRH immunoreactivity. Double-labelled immunofluorescent histochemistry revealed COX-1 immunoreactivity in the vicinity of, but not within, GnRH containing neurones in the preoptic area. COX-2 immunoreactivity was not found in the same area. The COX-1 immunoreactivity was almost entirely localised in microglia in the preoptic area, but not in neurones or astrocytes. These results suggest that microglia in the preoptic area containing COX-1 are responsible for producing PG(s), which, in turn, facilitates the accumulation of GnRH during the gonadotrophin surge in female rats.

Histological study on side effects and tumor targeting of a block copolymer micelle on rats

Histological examinations were performed with polymeric micelle-injected rats for evaluations of possible toxicities of polymeric micelle carriers. Weight of major organs as well as body weight of rats was measured after multiple intravenous injections of polymeric micelles forming from poly(ethylene glycol)-b-poly(aspartate) block copolymer. No pathological toxic side effects were observed at two different doses, followed only by activation of the mononuclear phagocyte system (MPS) in the spleen, liver, lung, bone marrow, and lymph node. This finding confirms the absence of--or the very low level of--in vivo toxicity of the polymeric micelle carriers that were reported in previous animal experiments and clinical results. Then, immunohistochemical analyses with a biotinylated polymeric micelle confirmed specific accumulation of the micelle in the MPS. The immunohistochemical analyses also revealed, first, very rapid and specific accumulation of the micelle in the vasculatures of tumor capsule of rat ascites hepatoma AH109A, and second, the micelle's scanty infiltration into tumor parenchyma. This finding suggests a unique tumor-accumulation mechanism that is very different from simple EPR effect-based tumor targeting.

Therapeutic efficacy of a polymeric micellar doxorubicin infused by convection-enhanced delivery against intracranial 9L brain tumor models

Convection-enhanced delivery (CED) with various drug carrier systems has recently emerged as a novel chemotherapeutic method to overcome the problems of current chemotherapies against brain tumors. Polymeric micelle systems have exhibited dramatically higher in vivo antitumor activity in systemic administration. This study investigated the effectiveness of CED with polymeric micellar doxorubicin (DOX) in a 9L syngeneic rat model. Distribution, toxicity, and efficacy of free, liposomal, and micellar DOX infused by CED were evaluated. Micellar DOX achieved much wider distribution in brain tumor tissue and surrounding normal brain tissue than free DOX. Tissue toxicity increased at higher doses, but rats treated with micellar DOX showed no abnormal neurological symptoms at any dose tested (0.1-1.0 mg/ml). Micellar DOX infused by CED resulted in prolonged median survival (36 days) compared with free DOX (19.6 days; p = 0.0173) and liposomal DOX (16.6 days; p = 0.0007) at the same dose (0.2 mg/ml). This study indicates the potential of CED with the polymeric micelle drug carrier system for the treatment of brain tumors.

Particle size-dependent triggering of accelerated blood clearance phenomenon

A repeat-injection of polyethylene glycol-modified liposomes (PEGylated liposomes) causes a rapid clearance of them from the blood circulation in certain cases that is referred to as the accelerated blood clearance (ABC) phenomenon. In the present study, we examined whether polymeric micelles trigger ABC phenomenon or not. As a preconditioning treatment, polymeric micelles (9.7, 31.5, or 50.2 nm in diameter) or PEGylated liposomes (119, 261 or 795 nm) were preadministered into BALB/c mice. Three days after the preadministration [(3)H]-labeled PEGylated liposomes (127 nm) as a test dose were administered into the mice to determine the biodistribution of PEGylated liposomes. At 24h after the test dose was given, accelerated clearance of PEGylated liposomes from the bloodstream and significant accumulation in the liver was observed in the mice preadministered with 50.2-795 nm nanoassemblies (PEGylated liposomes or polymeric micelles). In contrast, such phenomenon was not observed with 9.7-31.5 nm polymeric micelles. The enhanced blood clearance and hepatic uptake of the test dose (ABC phenomenon) were related to the size of triggering nanoassemblies. Our study provides important information for developing both drug and gene delivery systems by means of nanocarriers.

A Cost-Effective Method for the Optical Transduction of Chemical Reactions. Application to Hyaluronidase Inhibitor Screening with Polyarginine−Counteranion Complexes in Lipid Bilayers

We report the systematic elaboration of a cost-effective, interference-minimized assay for the label-free optical transduction of chemical reactions. Recently, we have found that certain complexes formed by arginine-rich cell-penetrating peptides (CPPs) and amphiphilic counteranions can act as synergistic anion carriers in lipid bilayer membranes. Application of this discovery to rapid and reversible cytosolic CPP delivery has been described (Futaki, S.; et al. ACS Chem. Biol. 2006, 1, 299). Here, we report the complementary use of polyarginine (pR)-counteranion complexes as general optical transducers of chemical reactions. Counterion screening revealed dodecyl phosphate (DP) as an ideal pR activator. Carboxyfluorescein (CF)-loaded vesicles with a shelf life of 3.5 years served best for the detection of fluorogenic CF release by pR-DP complexes with the naked eye. Inactivation of pR-DP complexes by counterion exchange with hyaluronan (HA) caused no CF emission, while HA removal by hyaluronidase (HAase) did. pR-DP complexes were further compatible with the optical detection of HA immobilization on solid support as well as inhibitor screening for HAase (cromolyn, heparin) with and without substrate immobilization. Controls concerning binary ATP/ADP discrimination for naked-eye kinase detection are mentioned to delineate scope but also limitations of this simple and quite universal method.

Arginine magic with new counterions up the sleeve

The elusive questions how arginine-rich sequences allow peptides and proteins to penetrate cells or to form voltage-gated ion channels are controversial topics of current scientific concern. The possible contributions of exchangeable counterions to these puzzling processes remain underexplored. The objective of this report is to clarify scope and limitations of certain counteranions to modulate cellular uptake and anion carrier activity of oligo/polyarginines. The key finding is that the efficiency of counteranion activators depends significantly on many parameters such as activator-membrane and activator-carrier interactions. This finding is important because it suggests that counteranions can be used to modulate not only efficiency but also selectivity. Specifically, activator efficiencies are found to increase with increasing aromatic surface of the activator, decreasing size of the transported anion, increasing carrier concentration as well as increasing membrane fluidity. Efficiency sequences depend on membrane composition with coronene > pyrene >>fullerene > calix[4]arene carboxylates in fluid and crystalline DPPC contrasting to fullerene > calix[4]arene approximately coronene > pyrene carboxylates in EYPC with or without cholesterol or ergosterol. In HeLa cells, the efficiency of planar activators (pyrene) exceeds that of spherical activators (fullerenes, calixarenes). Polyarginine complexes with pyrene and coronene activators exhibit exceptional excimer emission. Decreasing excimer emission with increasing ionic strength reveals dominant hydrophobic interactions with the most efficient carboxylate activators. Dominance of ion pairing with the inefficient high-affinity sulfate activators is corroborated by the reversed dependence on ionic strength. These findings on activator-carrier and activator-membrane interactions are discussed as supportive of arene-templated guanidinium-carboxylate pairing and interface-directed translocation as possible origins of the superb performance of higher arene carboxylates as activators.

Anionic Fullerenes, Calixarenes, Coronenes, and Pyrenes as Activators of Oligo/Polyarginines in Model Membranes and Live Cells

We report that the efflux of 5(6)-carboxyfluorescein anions from neutral egg yolk phosphatidylcholine vesicles is mediated by oligo/polyarginines only in the presence of activating amphiphilic anions. Screening of anion activators reveals best synergism for amphiphilic carboxylates (fullerene > calix[4]arene approximately coronene > pyrene > calix[6]arene > alkyl), whereas amphiphilic sulfates show less satisfactory activation despite often lower effective concentrations. The analogous alcohols and one calix[4]arene diphosphate were inactive. These results are discussed in the context of a tentative anion carrier mechanism, where interactions with bilayer (interface-directed translocation) and carrier (arene-templated carboxylate-guanidinium pairing) contribute to activator efficiencies. Applied to HeLa cells, pyrenebutyrate is shown to significantly increase the uptake of a fluorescently labeled octaarginine in a concentration-dependent manner.

The depth of molecular recognition: voltage-sensitive blockage of synthetic multifunctional pores with refined architecture

Voltage-sensitive blockage by ADP, ATP and phytate (IP6) demonstrates that active-site contraction toward the middle of newly synthesized rigid-rod beta-barrels provides a general strategy to rationally create and modulate the voltage sensitivity (and to increase the efficiency) of molecular recognition by synthetic multifunctional pores.