The mpn668 gene of Mycoplasma pneumoniae encodes a novel organic hydroperoxide resistance protein.

Mycoplasma pneumoniae (M. pneumoniae), as an obligate parasite, has evolved a protective strategy for coping with oxidative challenges caused by M. pneumoniae itself as well as the host immune system. However, to date, few antioxidant enzymes have been identified in mycoplasmas. In this report, we identified a protein encoded by the mpn668 gene from M. pneumoniae with a putative function as an organic hydroperoxide reductase (Ohr). The results indicated that the recombinant 140 amino acid protein, designated rMPN668, displayed hydroperoxidase activity towards both organic (tert-butyl hydroperoxide) and inorganic (hydrogen peroxide) hydroperoxides in the presence of a reducing agent such as dithiothreitol. Moreover, the expression of mpn668 in M. pneumoniae is upregulated in response to oxidative stress. Additionally, homology modeling of MPN668 and a molecular dynamics simulation suggest that both Cys55 and Cys119 form part of the active site of the protein. Mutants in which Cys55 or Cys119 were replaced with a serine lack antioxidant activity, indicating that MPN668 is a Cys-based peroxidase, consistent with it representing a new member of the Ohr family.

Mycoplasma pneumoniae capsular polysaccharides inhibit phagocytosis and membrane molecules expression of dendritic cells / 中国免疫学杂志

Objective:To study the influences of Mycoplasma penumoniae capsular polysaccharide (CPS) on the phagocytosis and membrane molecules expression of the human peripheral blood mononuclear cells derived dendritic cells by binding to dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN),so as to know the effect of CPS on the maturation of dendritic cells.Methods:M.pneumoniae strain was cultivated and CPS was extracted.Human peripheral blood mononuclear cells were separated and induced to dendritic cells,then identified the cells by flow cytometry and observation under the microscope.CPS was used to treat dendritic cells or cells pretreated with DC-SIGN monoclonal antibody,and then FITC-dextran phagocytosis and surface markers CD83,HLA-DR,CD80 and CD86 were detected by flow cytometry.Results:The dendritic cells tended to form colony groups.The positive rate of CD11c molecule in the cultured dendritic cells was about 86.27％.After stimulated by CPS,the FITC-dextran fluorescence mean intake by dendritic cells were increased (P＜0.05),while the cell surface membrane molecules CD83,HLA-DR,CD80 and CD86 were decreased significantly when compared with the PBS treated control cells(P＜0.05).When blocked DC-SIGN with the monoclonal antibody,the FITC-dextran fluorescence mean and membrane molecules expression had no statistical difference with the control cells(P＞0.05).Conclusion:M.pneumoniae CPS can promote the phagocytic function of DC and inhibit the expression of CD83,HLA-DR,CD80 and CD86.

Long-term outcome of changes in cognitive function of young rats after various/different doses of whole brain irradiation.

OBJECTIVE: To characterize the early delayed and late-delayed cognitive dysfunction induced by various doses of whole brain irradiation in young rats. METHODS: One-month-old Sprague-Dawley male rats were divided randomly into the 0 (control), 0 (anesthesia control), 2, 10, 20, and 30-Gy groups. Each group was then subdivided into 4 groups according to the experimental intervals: 1, 2, 3, and 6 months after radiation. Rats were irradiated using a 4-MeV electron beam, which was generated by a linear accelerator. Sequential behavioral tests, including open field, novel location and novel object recognition and Morris water maze were performed after radiation. Changes in gross neurological symptoms, body weight, topical skin response, and histopathology were observed. RESULTS: In the open field test, there were no radiation-induced alterations found. In the novel location and novel object recognition tests, rats of the 20-Gy group spent less time exploring the novel object and novel location 3 months after irradiation. During the place navigation test, the spatial working memory of the 30 and 20-Gy irradiated rats were impaired from 1 to 2 months after irradiation, respectively. In the spatial probe test, the 20 and 30-Gy irradiated rats spent less time in the critical region compared to control rats at 3 and 6 months post-irradiation. Morphological changes, including edema, vascular dilation, focal necrosis, demyelination, and adjacent reactive gliosis were observed in the 30-Gy irradiation group. CONCLUSION: More than 20 Gy of whole brain irradiation dose can cause significant cognitive dysfunction in young rats.

Enhanced cell gap junctions promotes the radiosensitivity in triple negative breast cancer cells / 实用肿瘤学杂志

Objectvi e To investigate whether promoting gap junctions may contribute to the radiosensi-tivity in triple negative breast cancer( TNBC)cells.Methods HCC70(triple-negative),MCF-7(ER-posi-tive)or SK-BR3(HER2-positive )cells were transfected with pcDNA/5 -Cx43 expression plasmid using liposome 2000.The transfected cells were treated with various doses of radiation(0,5,10,15 Gy),and the level of Cx43 protein was determined by Western blot and the cell connectivity was determined by fluorescent tracer technique. Cell proliferation inhibition,clone formation ability and apoptosis were detected using MTT,clone formation assay, AnnexinV-FITC/PI double staining and flow cytometer,respectively.Results The level of Cx43 protein signifi-cantly increased in HCC 70 -Cx43 ,MCF-7 -Cx43 and SK-BR3 -Cx43 cells.After transfection the cells were treated with various doses of radiation,level of Cx43protein was gradually enhanced in dose dependent fashion .The re-sults form fluorescent tracer technique showed that fluorescence intensity was gradually elevated with increase of radiation doses.Cell viability and clone formation ability were decreased gradually in dose dependent manner in HCC70-Cx43 ,MCF-7 -Cx43 and SK-BR3-Cx 43 cells.Unexpectedly,the inhibitive effect of proliferation ability and clone formation ability in HCC70 -Cx43 cell was higher than in MCF-7 -Cx43 and SK-BR3 -Cx43 cells under same conditions.The results from AnnexinV-FITC/PI and flow cytometer showed that apoptosis rate was enhanced gradually accompanying with increase of radiation doses.Conclu sion Enhancing the function of cell gap junc-tions promoted radiosensitivity of breast cancer cells,particularly in TNBC cells.Radiation can strengthen cell gap junctions in breast cancer cell and cytotoxicity of TNBC cell can be enhanced by both synergistic effects.

Effects of expression level of DNA repair-related genes involved in the NHEJ pathway on radiation-induced cognitive impairment.

Cranial radiation therapy can induce cognitive decline. Impairments of hippocampal neurogenesis are thought to be a paramountly important mechanism underlying radiation-induced cognitive dysfunction. In the mature nervous system, DNA double-strand breaks (DSBs) are mainly repaired by non-homologous end-joining (NHEJ) pathways. It has been demonstrated that NHEJ deficiencies are associated with impaired neurogenesis. In our study, rats were randomly divided into five groups to be irradiated by single doses of 0 (control), 0 (anesthesia control), 2, 10, and 20 Gy, respectively. The cognitive function of the irradiated rats was measured by open field, Morris water maze and passive avoidance tests. Real-time PCR was also used to detect the expression level of DNA DSB repair-related genes involved in the NHEJ pathway, such as XRCC4, XRCC5and XRCC6, in the hippocampus. The influence of different radiation doses on cognitive function in rats was investigated. From the results of the behavior tests, we found that rats receiving 20 Gy irradiation revealed poorer learning and memory, while no significant loss of learning and memory existed in rats receiving irradiation from 0-10 Gy. The real-time PCR and Western blot results showed no significant difference in the expression level of DNA repair-related genes between the 10 and 20 Gy groups, which may help to explain the behavioral results, i.e. DNA damage caused by 0-10 Gy exposure was appropriately repaired, however, damage induced by 20 Gy exceeded the body's maximum DSB repair ability. Ionizing radiation-induced cognitive impairments depend on the radiation dose, and more directly on the body's own ability to repair DNA DSBs via the NHEJ pathway.