Direct inhibition of retinoblastoma phosphorylation by nimbolide causes cell-cycle arrest and suppresses glioblastoma growth.

PURPOSE: Classical pharmacology allows the use and development of conventional phytomedicine faster and more economically than conventional drugs. This approach should be tested for their efficacy in terms of complementarity and disease control. The purpose of this study was to determine the molecular mechanisms by which nimbolide, a triterpenoid found in the well-known medicinal plant Azadirachta indica, controls glioblastoma growth. EXPERIMENTAL DESIGN: Using in vitro signaling, anchorage-independent growth, kinase assays, and xenograft models, we investigated the mechanisms of its growth inhibition in glioblastoma. RESULTS: We show that nimbolide or an ethanol soluble fraction of A. indica leaves (Azt) that contains nimbolide as the principal cytotoxic agent is highly cytotoxic against glioblastoma multiforme in vitro and in vivo. Azt caused cell-cycle arrest, most prominently at the G1-S stage in glioblastoma multiforme cells expressing EGFRvIII, an oncogene present in about 20% to 25% of glioblastoma multiformes. Azt/nimbolide directly inhibited CDK4/CDK6 kinase activity leading to hypophosphorylation of the retinoblastoma protein, cell-cycle arrest at G1-S, and cell death. Independent of retinoblastoma hypophosphorylation, Azt also significantly reduced proliferative and survival advantage of glioblastoma multiforme cells in vitro and in tumor xenografts by downregulating Bcl2 and blocking growth factor-induced phosphorylation of Akt, extracellular signal-regulated kinase 1/2, and STAT3. These effects were specific because Azt did not affect mTOR or other cell-cycle regulators. In vivo, Azt completely prevented initiation and inhibited progression of glioblastoma multiforme growth. CONCLUSIONS: Our preclinical findings demonstrate nimbolide as a potent anti-glioma agent that blocks cell cycle and inhibits glioma growth in vitro and in vivo.

Thermoreversible-mucoadhesive gel for nasal delivery of sumatriptan.

The purpose of the present study was to develop intranasal delivery systems of sumatriptan using thermoreversible polymer Pluronic F127 (PF127) and mucoadhesive polymer Carbopol 934P (C934P). Formulations were modulated so as to have gelation temperature below 34 degrees C to ensure gelation at physiological temperature after intranasal administration. Gelation temperature was determined by physical appearance as well as by rheological measurement. The gelation temperatures of the formulations decreased by addition of increasing concentrations of Carbopol (ie, from 29 degrees C for 18% PF127 to 23.9 degrees C for 18% PF127, 0.5% Carbopol). The mucoadhesive force in terms of detachment stress, determined using sheep nasal mucosal membrane, increased with increasing concentration of Carbopol. The results of in vitro drug permeation studies across sheep nasal mucosa indicate that effective permeation coefficient could be significantly increased by using in situ gelling formulation with Carbopol concentration 0.3% or greater. Finally, histopathological examination did not detect any damage during in vitro permeation studies. In conclusion, the PF127 gel formulation of sumatriptan with in situ gelling and mucoadhesive properties with increased permeation rate is promising for prolonging nasal residence time and thereby nasal absorption.

Effects of gossypol on O2 consumption and CO2 production in human prostate cancer cells.

BACKGROUND: Gossypol (GP) is a potent antifertility agent contained in cottonseed and other parts of cotton plants. We have shown that GP inhibits in vitro growth of Dunning rodent prostate cancer cells (MAT-LyLu), PC3, MCF-7 and primary cultured human prostate cells, as well as the in vivo tumor growth of the MAT-LyLu cell line after implantation into Copenhagen rats. MATERIALS AND METHODS: GP's effects on O2 consumption/CO2 production of PC3 cells were studied using the Micro-Oxymax respirometer. The effects of GP on oxidative phosphorylation in PC3 cells were determined by the succinic dehydrogenase assay. RESULTS: GP at the concentration of 1.0 microM reduced DNA synthesis by 25.6%, 54.6% and 81.25% after treatment times of 24, 28, and 32 hours, respectively, while GP at 2 microM reduced DNA synthesis by 78.57%, 81.44% and 83.72% after treatment durations of 24, 28 and 32 hours, respectively. GP at the concentration of 2.0 microM decreased significantly CO2 production by 37.5%, 42.4% and 44.7% and O2 consumption by 6.4%, 6.9% and 7.9% in PC3 cells after the different periods of treatment (24, 28 and 32 hours, respectively). GP at the concentration of 1.0 microM did not significantly inhibit O2 consumption/CO2 production of PC3 cells. GP also reduced the activity of mitochondrial succinic dehydrogenase in PC3 cells to 31% of control at the concentration of 1.0 microM and 15% of control at the concentration of 2.0 microM. CONCLUSION: The inhibitory action of GP on O2 consumption/CO2 production of PC3 cells may be due to disruption of oxidative phosphorylation by inhibition of mitochondrial succinic dehydrogenase.