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In neurons, a highly regulated microtubule cytoskeleton is essential for many cellular functions. These include axonal transport, regional specialization and synaptic function. Given the critical roles of microtubule-associated proteins (MAPs) in maintaining and regulating microtubule stability and dynamics, we sought to understand how this regulation is achieved. Here, we identify a novel LisH/WD40 repeat protein, tentatively named nemitin (neuronal enriched MAP interacting protein), as a potential regulator of MAP8-associated microtubule function. Based on expression at both the mRNA and protein levels, nemitin is enriched in the nervous system. Its protein expression is detected as early as embryonic day 11 and continues through adulthood. Interestingly, when expressed in non-neuronal cells, nemitin displays a diffuse pattern with puncta, although at the ultrastructural level it localizes along the microtubule network in vivo in sciatic nerves. These results suggest that the association of nemitin to microtubules may require an intermediary protein. Indeed, co-expression of nemitin with microtubule-associated protein 8 (MAP8) results in nemitin losing its diffuse pattern, instead decorating microtubules uniformly along with MAP8. Together, these results imply that nemitin may play an important role in regulating the neuronal cytoskeleton through an interaction with MAP8. [ABSTRACT FROM AUTHOR]

While the potential impact of magnetic nanoparticles (MNPs) has been widely explored in almost all medical fields, including cardiology, one question remains; that is whether MNPs interfere with cardiac physiological processes such as the expression and function of ion channels, especially in vivo. KCNQ(1) channels are richly expressed in cardiac myocytes and are critical to the repolarization of cardiac myocytes. In this study, we evaluated the effects of Fe(3)O(4)-magnetic nanoparticles (MNPs-Fe(3)O(4)) on the expression of KCNQ(1) in cardiac muscle of mice at rest and at different times following a single bout of swimming (SBS). Firstly, we demonstrated that the expression levels of KCNQ(1) channels are significantly up-regulated in mice following a SBS by means of reverse transcription polymerase chain reaction (RT-PCR) and western-blot. After treating mice with normal saline or pure MNPs-Fe(3)O(4) separately, we studied the potential effect of MNPs-Fe(3)O(4) on the expression profile of KCNQ(1) in mouse cardiac muscle following a SBS. A SBS increased the transcription of KCNQ(1) at 3 hours post exercise (3PE) 164% +/- 24% and at 12 hours post exercise (12PE) by 159% +/- 23% (P < 0.05), and up-regulated KCNQ(1) protein 161% +/- 27% at 12PE (P < 0.05) in saline mice. In MNPs-Fe(3)O(4) mice, KCNQ(1) mRNA increased by 151% +/- 14% and 147% +/- 12% at 3 and 12 PE, respectively (P <0.05). Meanwhile, an increase of 152% +/- 14% in KCNQ(1) protein was also detected at by 12PE. These results indicated that the administration of MNPs-Fe(3)O(4) did not cause any apparent effects on the expression profile of KCNQ(1) in rested or exercised mice cardiac muscle. Our studies suggest a novel path of KCNQ(1) current adaptations in the heart during physical exercise and in addition provide some useful information for the biomedical application of MNPs which are imperative to advance nanomedicine.

This study aims to evaluate the multidrug resistance (MDR) reversal activity by magnetic nanoparticles of Fe3O4 (MNPs-Fe3O4) and 5-bromotetrandrine (BrTet) MDR cell line K562/A02 solitarily or symphysially. The proliferation of K562 and K562/A02 cells and the cytotoxicity on peripheral blood mononuclear cells (PMBCs) were evaluated by MTT assay. Cellular accumulation of daunorubicin (DNR) was analyzed by flow cytometry. Real-time polymerase chain reaction and Western blotting analyses were performed to examine the mRNA and protein levels of mdr1, respectively. The results showed that the combination of MNPs-Fe3O4 and BrTet with effective concentrations significantly increased cytotoxicity against MDR cell line K562/A02. Both BrTet and MNPs-Fe3O4 increased the intracellular DNR accumulation in the K562/A02 cell line, and downregulated the level of mdr1 gene and expression of P-glycoprotein. Furthermore, the combination did not have significant cytotoxicity in PMBCs. We propose that MNPs-Fe3O4 conjugated with DNR and BrTet probably have synergetic effects on MDR reversal.

In this paper we establish the xenograft leukemia model with stable multidrug resistance in nude mice and to investigate the reversal effect of 5-bromotetrandrine (5-BrTet) and magnetic nanoparticle of Fe(3)O(4) (MNP-Fe(3)O(4)) combined with daunorubicin (DNR) in vivo. Two subclones of K562 and K562/A02 cells were inoculated subcutaneously into the back of athymic nude mice (1 x 10(7) cells/each) respectively to establish leukemia xenograft models. Drug-resistant and sensitive tumor-bearing nude mice were assigned randomly into five groups which were treated with normal saline; DNR; NP-Fe(3)O(4) combined with DNR; 5-BrTet combined with DNR; 5-BrTet and MNP-Fe(3)O(4) combined with DNR, respectively. The incidence of formation, growth characteristics, weight, and volume of tumors were observed. The histopathologic examination of tumors and organs were detected. For resistant tumors, the protein levels of Bcl-2, and BAX were detected by Western blot. Bcl-2, BAX, and caspase-3 genes were also detected. For K562/A02 cells xenograft tumors, 5-BrTet and MNP-Fe(3)O(4) combined with DNR significantly suppressed growth of tumor. A histopathologic examination of tumors clearly showed necrosis of the tumors. Application of 5-BrTet and MNP-Fe(3)O(4) inhibited the expression of Bcl-2 protein and upregulated the expression of BAX and caspase-3 proteins in K562/A02 cells xenograft tumor. It is concluded that 5-BrTet and MNP-Fe(3)O(4) combined with DNR had a significant tumor-suppressing effect on a MDR leukemia cells xenograft model.

Apoptosis is a common pathway that finally mediated the killing functions of anticancer drugs, which is an important cause of multidrug resistance (MDR). The aim of this study was to investigate the potential benefit of combination therapy with magnetic nanoparticle of Fe(3)O(4) (MNP(Fe(3)O(4))) and 5-bromotetrandrin (BrTet). Analysis of the apoptosis percentage showed that combination of daunorubicin (DNR) with either MNP(Fe(3)O(4)) or BrTet exerted a potent cytotoxic effect on K562/A02 cells, while MNP(Fe(3)O(4)) and BrTet cotreatment can synergistically enhance DNR-induced apoptosis. Importantly, we confirmed that the distinct synergism effect of that composite on reverse multidrug resistance may owe to the regulation of various proliferative and antiapoptotic gene products, including P53 and caspase-3. Thus our in vitro data strongly suggests a potential clinical application of MNP(Fe(3)O(4)) and BrTet combination on CML.

Drug resistance is a primary hindrance for efficiency of chemotherapy. To investigate whether Fe3O4-magnetic nanoparticles (Fe3O4-MNPs) loaded with adriamycin (ADM) and tetrandrine (Tet) would play a synergetic reverse role in multidrug resistant cell, we prepared the drug-loaded nanoparticles by mechanical absorption polymerization to act with K562 and one of its resistant cell line K562/A02. The survival of cells which were cultured with these conjugates for 48 h was observed by MTT assay. Using cells under the same condition described before, we took use of fluorescence microscope to measure fluorescence intensity of intracellular ADM at an excitation wavelength of488 nm. P-glycoprotein (P-gp) was analyzed with flow cytometer. The expression ofmdrl mRNA was measured by RT-PCR. The results showed that the growth inhibition efficacy of both the two cells increased with augmenting concentrations of Fe3O4-MNPs which were loaded with drugs. No linear correlation was found between fluorescence intensity of intracellular adriamycin and augmenting concentration of Fe3O4-MNPs. Tet could downregulate the level of mdr-1 gene and decrease the expression of P-gp. Furthermore, Tet polymerized with Fe3O4-MNPs reinforced this downregulation, causing a 100-fold more decrease in mdrl mRNA level, but did not reduce total P-gp content. Our results suggest that Fe3O4-MNPs loaded with ADM or Tet can enhance the effective accumulation of the drugs in K562/A02. We propose that Fe3O4-MNPs loaded with ADM and Tet probably have synergetic effect on reversal in multidrug resistance.