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Bacterial magnetosomes (BMs) are commonly used as vehicles for certain enzymes, nucleic acids and antibodies, although they have never been considered drug carriers. To evaluate the clinical potential of BMs extracted from Magnetospirillum gryphiswaldense in cancer therapy, doxorubicin (DOX) was loaded onto the purified BMs at a ratio of 0.87 +/- 0.08 mg/mg using glutaraldehyde. The DOX-coupled BMs (DBMs) and BMs exhibited uniform sizes and morphology evaluated by TEM. The diameters of DBMs and BMs obtained by AFM were 71.02 +/- 6.73 and 34.93 +/- 8.24 nm, respectively. The DBMs released DOX slowly into serum and maintained at least 80% stability following 48 h of incubation. In vitro cytotoxic tests showed that the DBMs were cytotoxic to HL60 and EMT-6 cells, manifested as inhibition of cell proliferation and suppression in c-myc expression, consistent with DOX. These observations depicted in vitro antitumor property of DBMs similar to DOX. The approach of coupling DOX to magnetosomes may have clinical potential in anti-tumor drug delivery.

We report the identification and characterization of a new ischemia/reperfusion-inducible protein (IRIP), which belongs to the SUA5/YrdC/YciO protein family. IRIP cDNA was isolated in a differential display analysis of an ischemia/reperfusion-treated kidney RNA sample. Mouse IRIP mRNA was expressed in all tissues tested, the highest level being in the testis, secretory, and endocrine organs. Besides ischemia/reperfusion, endotoxemia also activated the expression of IRIP in the liver, lung, and spleen. The transporter regulator RS1 was identified as an IRIP-interacting protein in yeast two-hybrid screening. The interaction between IRIP and RS1 was further confirmed in coimmunoprecipitation assays. A possible role of IRIP in regulating transporter activity was subsequently investigated. IRIP overexpression inhibited endogenous 1-methyl-4-phenylpyridinium (MPP ؉ ) uptake activity in HeLa cells. The activities of exogenous organic cation transporters (OCT2 and OCT3), organic anion transporter (OAT1), and monoamine transporters were also inhibited by IRIP. Conversely, inhibition of IRIP expression by small interfering RNA or antisense RNA increased MPP ؉ uptake. We measured transport kinetics of OCT2-mediated uptake and demonstrated that IRIP overexpression significantly decreased V max but did not affect K m . On the basis of these results, we propose that IRIP regulates the activity of a variety of transporters under normal and pathological conditions.

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BackgroundC-1027, produced by Streptomyces globisporus C-1027, is one of the most potent antitumoral agents. The biosynthetic gene cluster of C-1027, previously cloned and sequenced, contains at least three putative regulatory genes, i.e. sgcR1, sgcR2 and sgcR3. The predicted gene products of these genes share sequence similarities to StrR, regulators of AraC/XylS family and TylR. The purpose of this study was to investigate the role of sgcR3 in C-1027 biosynthesis.ResultsOverexpression of sgcR3 in S. globisporus C-1027 resulted in a 30–40% increase in C-1027 production. Consistent with this, disruption of sgcR3 abolished C-1027 production. Complementation of the sgcR3-disrupted strain R3KO with intact sgcR3 gene could restore C-1027 production. The results from real time RT-PCR analysis in R3KO mutant and wild type strain indicated that not only transcripts of biosynthetic structural genes such as sgcA1 and sgcC4, but also putative regulatory genes, sgcR1 and sgcR2, were significantly decreased in R3KO mutant. The cross-complementation studies showed that sgcR1R2 could functionally complement sgcR3 disruption in trans. Purified N-terminal His10-tagged SgcR3 showed specific DNA-binding activity to the promoter region of sgcR1R2.ConclusionThe role of SgcR3 has been proved to be a positive regulator of C-1027 biosynthesis in S. globisporus C-1027. SgcR3 occupies a higher level than SgcR1 and SgcR2 in the regulatory hierarchy that controls C-1027 production and activates the transcription of sgcR1 and sgcR2 by binding directly to the promoter region of sgcR1R2.

BackgroundTuberculosis is a serious global health problem. Its paradigms are shifting through time, especially in rapidly developing countries such as China. Health providers in China are at the forefront of the battle against tuberculosis; however, there are few empirical studies on health providers' perspectives on the challenges they face in tuberculosis control at the county level in China. This study was conducted among health providers to explore their experiences with tuberculosis control in order to identify bottlenecks and emerging challenges in controlling tuberculosis in rural China.MethodsA qualitative approach was used. Semi-structured, in-depth interviews were conducted with 17 health providers working in various positions within the health system of one rural county (ZJG) of China. Data were analyzed based on thematic content analysis using MAXQDA 10 qualitative data analysis software.ResultsHealth providers reported several problems in tuberculosis control in ZJG county. Migrant workers and the elderly were repeatedly documented as the main obstacles in effective tuberculosis control in the county. At a personal level, doctors showed their frustration with the lack of new drugs for treating tuberculosis patients, and their opinions varied regarding incentives for referring patients.ConclusionThe results suggest that several problems still remain for controlling tuberculosis in rural China. Tuberculosis control efforts need to make reaching the most vulnerable populations a priority and encourage local health providers to adopt innovative practices in the local context based on national guidelines to achieve the best results. Considerable changes in China's National Tuberculosis Control Program are needed to tackle these emerging challenges faced by health workers at the county level.

Mycobacterium tuberculosis kills about 2 million people annually and antibiotic resistance is a cause of increased mortality. Therefore, development of new antituberculosis drugs is urgent for the control of widespread tuberculosis infections. For this purpose, we performed an innovative screen to identify new agents that disrupt the function of ribosomes in M. tuberculosis. Two bacterial ribosomal proteins L12 and L10 interact with each other and constitute the stalk of the 50S ribosomal subunit, which recruits initiation and elongation factors (EFs) during translation. Therefore, the L12-L10 interaction should be essential for ribosomal function and protein synthesis. We established a yeast two-hybrid system to identify small molecules that block the interaction between L12 and L10 proteins from M. tuberculosis. Using this system, we identified two compounds T766 and T054 that show strong bactericidal activity against tuberculosis but with low toxicity to mice and other bacterial strains. Moreover, using surface plasmon resonance (SPR) assay, we have demonstrated that these compounds bind specifically to L12 to disrupt L12-L10 interaction. Overproduction of L12 protein, but not L10, lowers the antibacterial activity of T766 and T054, indicating that the ribosome is likely the cellular target. Therefore, our data demonstrate that this yeast two-hybrid system is a useful tool to identify unique antituberculosis agents targeting the ribosomal protein L12-L10 interaction.