We report a novel drug delivery system composed of layer-by-layer (LBL) milk protein casein (CN) coated iron oxide nanoparticles. Doxorubicin (DOX) and indocyanine green (ICG) were selected as model drug molecules, which were incorporated into the inner polymeric layer, and subsequently coated with casein. The resulting casein coated iron oxide nanoparticles (CN-DOX/ICG-IO) were stable in the acidic gastric condition with the presence of gastric protease. On the other hand, the loaded drugs were released when the casein outer layer was gradually degraded by the intestinal protease in the simulated intestine condition. Such unique properties enable maintenance of the bioactivity of the drugs and thus enhance the drug delivery efficiency. Ex vivo experiments showed that the LBL CN-DOX-IO improved the translocation of DOX across microvilli and its absorption in the small intestine sacs. In vivo imaging of mice that were orally administered with these LBL CN-ICG-IO nanostructures further confirmed that the reported drug delivery vehicles could pass the stomach without significant degradation, and then accumulated in the small intestine. In addition, the magnetic iron oxide nanoparticle core offered an MRI contrast enhancing capability for in vivo imaging guided drug delivery. Therefore, the reported LBL CN-DOX/ICG-IO is a promising oral drug delivery nanoplatform, especially for drugs that are poorly soluble in water or degradable in the gastric environment.

Astrocytes are vital structures that support and/or protect neighboring neurons from pathology. Although it is generally accepted that glutamate receptors mediate most astrocyte effects, acid-evoked currents have recently attracted attention for their role in this regard. Here, we identified the existence and characteristics of acid-sensing ion channels (ASICs) and the transient receptor potential vanilloid type 1 (TRPV1) in astrocytes. There were two types of currents recorded under the application of acidic solution (pH 6.0) in cultured rat astrocytes. Transient currents were exhibited by 10% of the astrocytes, and sustained currents were exhibited by the other 90%, consistent with the features of ASIC and TRPV1 currents, respectively. Western blotting and immunofluorescence confirmed the expression of ASIC1, ASIC2a, ASIC3, and TRPV1 in cultured and in situ astrocytes. Unlike the ASICs expressed in neurons, which were mainly distributed in the cell membrane/cytoplasm, most of the ASICs in astrocytes were expressed in the nucleus. TRPV1 was more permeable to Na(+) in cultured astrocytes, which differed from the typical neuronal TRPV1 that was mainly permeable to Ca(2+). This study demonstrates that there are two kinds of acid-evoked currents in rat astrocytes, which may provide a new understanding about the functions of ligand-gated ion channels in astrocytes.

Microglia, the major immune cells in central nervous system, act as the surveillance and scavenger of immune defense and inflammatory response. Previous studies suggest that there might be close relationship between acid-sensing ion channels (ASICs) and inflammation, however, the exact role of ASICs in microglia during inflammation remains elusive. In the present study, we identified the existence of ASICs in the primary cultured rat microglia and explored their functions. By using reverse transcriptase polymerase chain reaction (RT-PCR), quantitative real-time PCR (qPCR), western blotting, and immunofluorescence experiments, we demonstrated that ASIC1, ASIC2a, and ASIC3 were existed in cultured and in situ rat microglia. After lipopolysaccharide (LPS) stimulation, the expressions of microglial ASIC1 and ASIC2a were upregulated. Meanwhile, ASIC-like currents and acid-induced elevation of intracellular calcium were increased, which could be inhibited by the nonspecific ASICs antagonist amiloride and specific homomeric ASIC1a blocker PcTx1. In addition, both inhibitors reduced the expression of inflammatory cytokines, including inducible nitric oxide synthase and cyclooxygenase 2 stimulated by LPS. Furthermore, we also observed significant increase in the expression of ASIC1 and ASIC2a in scrape-stimulated microglial migration. Amiloride and PcTx1 prevented the migration by inhibiting ERK phosphorylation. Taken together, these results suggest that ASICs participate in neuroinflammatory response, which will provide a novel therapeutic strategy for controlling the inflammation-relevant neuronal diseases.

The growth factor hepatocyte growth factor (HGF), also known as scatter factor, and its tyrosine kinase receptor c-Met play important roles in medulloblastoma malignancy. The transcription factor c-Myc is another contributor to the malignancy of these most common pediatric brain tumors. In the present study, we observed strong morphological similarities between medulloblastoma xenografts overexpressing HGF and medulloblastoma xenografts overexpressing c-Myc. We therefore hypothesized a biologically significant link between HGF/c-Met and c-Myc in medulloblastoma malignancy and studied the molecular and functional interactions between them. We found that HGF induces c-Myc mRNA and protein in established and primary medulloblastoma cells. HGF regulated c-Myc levels via transcriptional and posttranscriptional mechanisms as evidenced by HGF induction of c-Myc promoter activity and induction of c-Myc protein levels in the setting of inhibited transcription and translation. We also found that HGF induces cell cycle progression, cell proliferation, apoptosis and increase in cell size in a c-Myc-dependent manner. Activation of MAPK and PI3K, inhibition of GSK-3b and translocation of b-catenin to the nucleus as well as Tcf/Lef transcriptional activity were involved in mediating c-Myc induction by HGF. Induction of Cdk2 kinase activity was involved in mediating the cell cycle progression effects, and downregulation of Bcl-XL was involved in mediating the proapoptotic effects of HGF downstream of c-Myc. All molecules that mediated the effects of HGF on c-Myc expression, cell proliferation and apoptosis were expressed in human large-cell medulloblastoma tissues. We therefore established for the first time a functional cooperation between HGF/c-Met and c-Myc in human medulloblastoma and elucidated the molecular mechanisms of this cooperation. The findings provide a potential explanation for the high frequency of c-Myc overexpression in medulloblastoma and suggest a cooperative role for c-Met and c-Myc in large-cell anaplastic medulloblastoma formation.