[Involvement of the global regulators GrrS, RpoS, and SplIR in formation of biofilms in Serratia plymuthica]

Most bacteria exist in the natural environment as biofilms, multicellular communities attached to hard surfaces. Biofilms have a characteristic architecture and are enclosed in the exopolymer matrix. Bacterial cells in biofilms are extremely resistant to antibacterial factors. It was shown in this work that the GrrA/GrrS system of global regulators of gene expression and the sigma S subunit of RNA polymerase (RpoS) play a significant role in positive regulation of biofilm formation in the rhizospheric bacterium Serratia plymuthica IC1270. Inactivation of grrS and rpoS genes resulted in an up to six-to-sevenfold and four-to-fivefold reduction in biofilm formation, respectively. Mutations in the grrS gene decreased the capacity of the bacterium for swarming motility. The splIR Quorum Sensing (QS) system was shown to negatively influence the biofilm formation. Transfer of the recombinant plasmid containing cloned genes splI/splR of S. plymuthica HRO-C48 into S. plymuthica IC1270 cells led to a twofold decrease of their ability to form biofilms. Inactivation of the splI gene coding for the synthase of N-acyl-homoserine lactones in S. plymuthica HRO-C48 resulted in a 2-2.5-fold increase in the level of biofilm formation, whereas the inclusion of plasmid carrying the cloned splI/splR genes into these mutant cells restored the biofilm formation to the normal level. The results obtained demonstrate that the formation of biofilms in S. plymuthica is positively regulated by the GrrA/GrrS and RpoS global regulators and is negatively regulated by the SplIR QS system.

Effects of adenoviral-mediated coexpression of bone morphogenetic protein-7 and insulin-like growth factor-1 on human periodontal ligament cells

BACKGROUND AND OBJECTIVE

Bone morphogenetic protein-7 (BMP-7) and insulin-like growth factor-1 (IGF-1) are important in periodontal reconstruction. However, their synergistic effect in periodontal regeneration by gene delivery has not been reported. In this study, gene delivery of these two growth factors to human periodontal ligament cells (hPDLCs) was examined for its effects on cell proliferation and differentiation.

MATERIAL AND METHODS

Recombinant adenoviruses containing both human BMP-7 and IGF-1 cDNA created by introducing the internal ribosome entry site (IRES) sequence were used to transfer the genes into hPDLCs. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and cell cycle analysis were used to observe their effects on cell proliferation, while alkaline phosphatase activity measurement, RT-PCR and in vivo tests were conducted to investigate their effects on cell differentiation.

RESULTS

The proliferation of hPDLCs transduced by adenoviruses coexpressing BMP-7 and IGF-1 was suppressed while their differentiation ability was enhanced. There was a synergism of BMP-7 and IGF-1 in up-regulating alkaline phosphatase activity and mRNA levels of collagen type I and Runx2. Implantation in vivo with scaffolds illustrated that the transduced cells exhibited osteogenic differentiation and formed bone-like structures.

CONCLUSION

The combined delivery of BMP-7 and IGF-1 genes using an IRES-based strategy synergistically enhanced differentiation of hPDLCs. It is suggested that this could be a new potential method in gene therapy for periodontal reconstruction.

Biological control of postharvest sour rot of citrus by two antagonistic yeasts

AIMS

To investigate antifungal effects of two antagonistic yeasts on postharvest sour rot caused by Geotrichum citri-aurantii in citrus and evaluate possible mechanisms.

METHODS AND RESULTS

Cell suspension of Cryptococcus laurentii at 10(8) to 10(9) cells per ml effectively reduced sour rot incidence from 55.6% among untreated control fruit to 29.9-20.7% after 5 days of incubation at 26 degrees C. Application of cell-free culture filtrate of C. laurentii was effective in reducing the sour rot, but the effectiveness was lower than that of the cell suspension (1 x 10(8) cells per ml). In addition, C. laurentii multiplied more rapidly than Rhodosporidium paludigenum at 26 degrees C. The fruit inoculated with the two yeasts demonstrated changes in peroxidase and superoxide dismutase activity. Cryptococcus laurentii, in particular, was capable of inducing a striking response in treated citrus fruits.

CONCLUSIONS

The antifungal ability of C. laurentii can be attributed to the competitions of nutrients and space, defensive responses and possible secretion of antibiotic compounds.

SIGNIFICANCE AND IMPACT OF THE STUDY

The use of such antagonists may constitute an important alternative to synthetic fungicides for controlling postharvest sour rot in citrus.

Syntaxin 3B is essential for the exocytosis of synaptic vesicles in ribbon synapses of the retina

Ribbon synapses of the vertebrate retina are specialized synapses that release neurotransmitter by synaptic vesicle exocytosis in a manner that is proportional to the level of depolarization of the cell. This release property is different from conventional neurons, in which the release of neurotransmitter occurs as a short-lived burst triggered by an action potential. Synaptic vesicle exocytosis is a calcium regulated process that is dependent on a set of interacting synaptic proteins that form the so-called SNARE (soluble N-ethylmaleimide sensitive factor attachment protein receptor) complex. Syntaxin 3B has been identified as a specialized SNARE molecule in ribbon synapses of the rodent retina. However, the best physiologically-characterized neuron that forms ribbon-style synapses is the rod-dominant or Mb1 bipolar cell of the goldfish retina. We report here the molecular characterization of syntaxin 3B from the goldfish retina. Using a combination of reverse transcription (RT) polymerase chain reaction (PCR) and immunostaining with a specific antibody, we show that syntaxin 3B is highly enriched in the plasma membrane of bipolar cell synaptic terminals of the goldfish retina. Using membrane capacitance measurements we demonstrate that a peptide derived from goldfish syntaxin 3B inhibits synaptic vesicle exocytosis. These experiments demonstrate that syntaxin 3B is an important factor for synaptic vesicle exocytosis in ribbon synapses of the vertebrate retina.

Helminth infection inhibits airway allergic reaction and dendritic cells are involved in the modulation process

Several previous studies have demonstrated that some helminth infections can inhibit allergic reactions, but the examination on the effect of live Schistosoma japonicum (SJ) infection on allergic inflammation remains limited. The aim of this study was to examine the effect and mechanism of chronic SJ infection on airway allergic inflammation in a murine model. The data showed that chronic SJ infection suppressed airway eosinophilia, mucus production and antigen-specific IgE responses induced by ovalbumin (OVA) sensitization and challenge. Cytokine production analysis showed that chronic SJ infection reduced allergen-driven interleukin (IL)-4 and IL-5 production, but had no significant effect on IFN-gamma production. More importantly, we found that the adoptive transfer of dendritic cells (DCs) from SJ-infected mice dramatically decreased airway allergic inflammation in the recipients, which was associated with significant decrease of IL-4/IL-5 production and increase of IL-10 production. The results suggest that SJ infection may inhibit the development of allergy and that DCs may be involved in the process of helminth infection-mediated modulation of allergic inflammation.

Indoleamine 2,3-dioxygenase, an emerging target for anti-cancer therapy

The inability of the host immune system to control tumor growth appears to result from dominant mechanisms of immune suppression that prevent the immune system from effectively responding in a way that consistently results in tumor rejection. Among the many possible mediators of tumoral immune escape, the immunoregulatory enzyme, indoleamine 2,3-dioxygenase (IDO), has recently gained considerable attention. IDO is a heme-containing, monomeric oxidoreductase that catalyzes the first and rate-limiting step in the degradation of the essential amino acid tryptophan to N formyl-kynurenine. Tryptophan depletion as well as the accumulation of its metabolites results in a strongly inhibitory effect on the development of immune responses by blocking T cell activation, inducing T cell apoptosis and promoting the differentiation of naïve T cells into cells with a regulatory phenotype (T(regs)). Recent data obtained from preclinical tumor models demonstrate that IDO inhibition can significantly enhance the antitumor activity of various chemotherapeutic and immunotherapeutic agents. These results, coupled with data showing that increased IDO expression is an independent prognostic variable for reduced overall survival in cancer patients, suggest that IDO inhibition may represent an effective strategy to treat malignancies, either alone or in combination with chemotherapeutics or other immune based therapies. This review will focus on the role of IDO as a mediator of peripheral immune tolerance, evidence that IDO becomes dysregulated in human cancers, and the latest progress on the development of IDO inhibitors as a novel anti-cancer therapy.

Modulation of chronic hypoxia-induced chemoreceptor hypersensitivity by NADPH oxidase subunits in rat carotid body

Previous studies in our laboratory established that reactive oxygen species (ROS) generated by NADPH oxidase (NOX) facilitate the open state of a subset of K+ channels in oxygen-sensitive type I cells of the carotid body. Thus pharmacological inhibition of NOX or deletion of a NOX gene resulted in enhanced chemoreceptor sensitivity to hypoxia. The present study tests the hypothesis that chronic hypoxia (CH)-induced hypersensitivity of chemoreceptors is modulated by increased NOX activity and elevated levels of ROS. Measurements of dihydroethidium fluorescence in carotid body tissue slices showed that increased ROS production following CH (14 days, 380 Torr) was blocked by the specific NOX inhibitor 4-(2-amino-ethyl)benzenesulfonyl fluoride (AEBSF, 3 microM). Consistent with these findings, in normal carotid body AEBSF elicited a small increase in the chemoreceptor nerve discharge evoked by an acute hypoxic challenge, whereas after 9 days of CH the effect of the NOX inhibitor was some threefold larger (P<0.001). Evaluation of gene expression after 7 days of CH showed increases in the isoforms NOX2 (approximately 1.5-fold) and NOX4 (approximately 3.8-fold) and also increased presence of the regulatory subunit p47phox (approximately 4.2-fold). Involvement of p47phox was further implicated in studies of isolated type I cells that demonstrated an approximately 8-fold and an approximately 11-fold increase in mRNA after 1 and 3 days, respectively, of hypoxia in vivo. These findings were confirmed in immunocytochemical studies of carotid body tissue that showed a robust increase of p47phox in type I cells after 14 days of CH. Our findings suggest that increased ROS production by NOX enzymes in type I cells dampens CH-induced hypersensitivity in carotid body chemoreceptors.

Trends in the exploration of anticancer targets and strategies in enhancing the efficacy of drug targeting

A number of therapeutic targets have been explored for developing anticancer drugs. Continuous efforts have been directed at the discovery of new targets as well as the improvement of therapeutic efficacy of agents directed at explored targets. There are 84 and 488 targets of marketed and investigational drugs for the treatment of cancer or cancer related illness. Analysis of these targets, particularly those of drugs in clinical trials and US patents, provides useful information and perspectives about the trends, strategies and progresses in targeting key cancer-related processes and in overcoming the difficulties in developing efficacious drugs against these targets. The efficacy of anticancer drugs directed at these targets is frequently compromised by counteractive molecular interactions and network crosstalk, negative and adverse secondary effects of drugs, and undesired ADMET profiles. Multi-component therapies directed at multiple targets and improved drug targeting methods are being explored for alleviating these efficacy-reducing processes. Investigation of the modes of actions of these combinations and targeting methods offers clues to aid the development of more effective anticancer therapies.

Trends in the exploration of anticancer targets and strategies in enhancing the efficacy of drug targeting

A number of therapeutic targets have been explored for developing anticancer drugs. Continuous efforts have been directed at the discovery of new targets as well as the improvement of therapeutic efficacy of agents directed at explored targets. There are 84 and 488 targets of marketed and investigational drugs for the treatment of cancer or cancer related illness. Analysis of these targets, particularly those of drugs in clinical trials and US patents, provides useful information and perspectives about the trends, strategies and progresses in targeting key cancer-related processes and in overcoming the difficulties in developing efficacious drugs against these targets. The efficacy of anticancer drugs directed at these targets is frequently compromised by counteractive molecular interactions and network crosstalk, negative and adverse secondary effects of drugs, and undesired ADMET profiles. Multi-component therapies directed at multiple targets and improved drug targeting methods are being explored for alleviating these efficacy-reducing processes. Investigation of the modes of actions of these combinations and targeting methods offers clues to aid the development of more effective anticancer therapies.

c-Abl and Arg tyrosine kinases regulate lysosomal degradation of the oncoprotein Galectin-3

Galectin-3 (Gal3) has important roles in tumor transformation and metastasis. This study shows that c-Abl and Abl-related gene (Arg) associate with and phosphorylate Gal3. The SH (Src homology)3 domains of c-Abl/Arg bind to a P(80)GPPSGP motif of Gal3, and Tyr79 and Tyr118 are the major tyrosine phosphorylation sites. A consequence of this interaction and phosphorylation is the significant impairment of chaperone-mediated autophagy of Gal3. Cells expressing Gal3 and treated with the c-Abl/Arg inhibitor STI571, Gal3-depleted cells, and Gal3-depleted cells expressing Gal3 phosphorylation mutants all display an increased sensitivity to apoptosis-inducing agents. In addition, tumor cells expressing the phosphorylation mutants show impaired tumorigenicity. These results partially explain the antiapoptotic effect of Abl and Arg. As tumors frequently overexpress Gal3, a c-Abl/Arg-specific inhibitor may potentially be applied along with other antitumor drugs to target the lysosomal degradation of Gal3 in tumor therapy.

Preliminary evaluation on the use of homing pigeons as a biomonitor in urban areas

This study evaluates the usefulness of homing pigeons as a biomonitor of polycyclic aromatic hydrocarbons (PAHs) in urban environments. The mean concentrations of total PAHs in liver and lung tissues were greater in pigeons from Beijing compared to pigeons from Chengdu, however, this difference was only statistically significant for PAH concentrations in liver tissue (P < 0.05). Similarly, the severity of anthracosis or pneumoconiosis in lung tissue and hepatitis in liver tissue was greater in pigeons from Beijing compared to pigeons from Chengdu. Low molecular weight PAHs dominated the contribution of individual PAHs in both tissues. Significant differences (P < 0.05) were observed for most low and moderate molecular weights PAHs in liver and for some low and high molecular weights PAHs in lung between the two cites. The profile patterns of individual PAHs were similar between lung tissue of pigeons and between local ambient airs in summer for both cities, whereas the profile patterns between liver tissue and pigeon food were less similar. These data suggest that homing pigeons may be of value as a biomonitor of environmental pollution in urban areas.

Cardioprotection of exogenous erythropoietin in mice with ligature-induced aortic stenosis: effects on maladaptive cardiac hypertrophy

Pre-operative treatment with recombinant human erythropoietin may improve aortic stenosis patients' condition, including anemia and/or cardiac dysfunction, for subjecting to aortic valve replacement. In this study, we tested this hypothesis in a mouse model of aortic stenosis. Adult male mice were subjected to either aortic stenosis created by aortic ligature or sham operation. Aortic stenosis for 4 weeks caused cardiac hypertrophy, pulmonary congestion and left ventricular dysfunction. It was associated with increased levels of tumor necrosis factor-alpha in serum and myocardium, and reduced levels of interleukin-10 in myocardium but not in serum. Myocyte apoptosis rate, level of cleaved caspase 3, activity of nuclear factor-kappaB and expression of p38-MAPK pathway were also elevated. Erythropoietin treatment increased hematocrit but did not prevent the development of cardiac hypertrophy. It, however, reduced the apoptosis, prevented the increases in tumor necrosis factor-alpha, nuclear factor-kappaB activation and phosphorylation of p38, and attenuated the increases in lung weight, the decreases in LVEF and LVFS, and the increases in LVDd and LVDs. In conclusion recombinant human erythropoietin has cardioprotective effects in maladaptive cardiac hypertrophy by inhibiting nuclear factor-kappaB activation, phosphorylation of p38-MAPK pathway, and production of tumor necrosis factor-alpha, together leading to a reduced apoptosis.