Reactive oxygen species （ROS） attack guanine bases in DNA easily and form 8-hydroxydeoxyguanosine （8-OHdG）, which can bind to thymidine rather than cytosine, based on which, the level of 8-OHdG is gen- erally rega...Reactive oxygen species （ROS） attack guanine bases in DNA easily and form 8-hydroxydeoxyguanosine （8-OHdG）, which can bind to thymidine rather than cytosine, based on which, the level of 8-OHdG is gen- erally regarded as a biomarker of mutagenesis conse- quent to oxidative stress. For example, higher levels of 8-OHdG are noted in Helicobacter pylori-associated chronic atrophic gastritis as well as gastric cancer. However, we have found that exogenous 8-OHdG can paradoxically reduce ROS production, attenuate the nuclear factor-KB signaling pathway, and ameliorate the expression of proinflammatory mediators such as interleukin （IL）-I, IL-6, cyclo-oxygenase-2, and induc- ible nitric oxide synthase in addition to expression of nicotinamide adenine dinucleotide phosphate oxidase （NOX）-I, NOX organizer-1 and NOX activator-1 in vari- ous conditions of inflammation-based gastrointestinal （GI） diseases including gastritis, inflammatory bowel disease, pancreatitis, and even colitis-associated carci- nogenesis. Our recent finding that exogenous 8-OHdG was very effective in either inflammation-based or oxidative-stress-associated diseases of stress-related mucosal damage has inspired the hope that synthetic 8-OHdG can be a potential candidate for the treatment of inflammation-based GI diseases, as well as the pre- vention of inflammation-associated GI cancer. In this editorial review, the novel fact that exogenous 8-OHdG can be a functional molecule regulating oxidative- stress-induced gastritis through either antagonizing Rac-guanosine triphosphate binding or blocking the signals responsible for gastric inflammatory cascade is introduced.展开更多
Objective： Chronic lymphocytic leukemia （CLL） and mantle cell lymphoma （MCL） cells over-express a guanine exchange factor （GEF）, Rasgrf-1. This GEF increases active Ras as it catalyzes the removal of GDP from R...Objective： Chronic lymphocytic leukemia （CLL） and mantle cell lymphoma （MCL） cells over-express a guanine exchange factor （GEF）, Rasgrf-1. This GEF increases active Ras as it catalyzes the removal of GDP from Ras so that GTP can bind and activate Ras. This study aims to study the mechanism of action of Rasgrf-1 in B-cell malignancies. Methods： N-terminus truncated Rasgrf-1 variants have a higher GEF activity as compared to the full-length transcript therefore a MCL cell line with stable over-expression of truncated Rasgrf-1 was established. The B-cell receptor （BCR） and chemokine signaling pathways were compared in the Rasgrf-I over-expressing and a control transfected cell line. Results： Cells over-expressing truncated form of Rasgrf-1 have a higher proliferative rate as compared to control transfected cells. BCR was activated by lower concentrations of anti-IgM antibody in Rasgrf-1 over-expressing cells as compared to control cells indicating that these cells are more sensitive to BCR signaling. BCR signaling also phosphorylates Rasgrf-1 that further increases its GEF function and amplifies BCR signaling. This activation of Rasgrf-1 in over-expressing cells resulted in a higher expression of phospho-ERK, AKT, BTK and PKC-alpha as compared to control cells. Besides BCR, Rasgrf-1 over-expressing cells were also more sensitive to microenvironment stimuli as determined by resistance to apoptosis, chemotaxis and ERK pathway activation. Conclusions： This GEF protein sensitizes B-cells to BCR and chemokine mediated signaling and also upregulates a number of other signaling pathways which promotes growth and survival of these cells.展开更多
基金Supported by A grant from the Ministry of Education and Science Technology,South Korea,No.2010-0002052
文摘Reactive oxygen species （ROS） attack guanine bases in DNA easily and form 8-hydroxydeoxyguanosine （8-OHdG）, which can bind to thymidine rather than cytosine, based on which, the level of 8-OHdG is gen- erally regarded as a biomarker of mutagenesis conse- quent to oxidative stress. For example, higher levels of 8-OHdG are noted in Helicobacter pylori-associated chronic atrophic gastritis as well as gastric cancer. However, we have found that exogenous 8-OHdG can paradoxically reduce ROS production, attenuate the nuclear factor-KB signaling pathway, and ameliorate the expression of proinflammatory mediators such as interleukin （IL）-I, IL-6, cyclo-oxygenase-2, and induc- ible nitric oxide synthase in addition to expression of nicotinamide adenine dinucleotide phosphate oxidase （NOX）-I, NOX organizer-1 and NOX activator-1 in vari- ous conditions of inflammation-based gastrointestinal （GI） diseases including gastritis, inflammatory bowel disease, pancreatitis, and even colitis-associated carci- nogenesis. Our recent finding that exogenous 8-OHdG was very effective in either inflammation-based or oxidative-stress-associated diseases of stress-related mucosal damage has inspired the hope that synthetic 8-OHdG can be a potential candidate for the treatment of inflammation-based GI diseases, as well as the pre- vention of inflammation-associated GI cancer. In this editorial review, the novel fact that exogenous 8-OHdG can be a functional molecule regulating oxidative- stress-induced gastritis through either antagonizing Rac-guanosine triphosphate binding or blocking the signals responsible for gastric inflammatory cascade is introduced.
文摘Objective： Chronic lymphocytic leukemia （CLL） and mantle cell lymphoma （MCL） cells over-express a guanine exchange factor （GEF）, Rasgrf-1. This GEF increases active Ras as it catalyzes the removal of GDP from Ras so that GTP can bind and activate Ras. This study aims to study the mechanism of action of Rasgrf-1 in B-cell malignancies. Methods： N-terminus truncated Rasgrf-1 variants have a higher GEF activity as compared to the full-length transcript therefore a MCL cell line with stable over-expression of truncated Rasgrf-1 was established. The B-cell receptor （BCR） and chemokine signaling pathways were compared in the Rasgrf-I over-expressing and a control transfected cell line. Results： Cells over-expressing truncated form of Rasgrf-1 have a higher proliferative rate as compared to control transfected cells. BCR was activated by lower concentrations of anti-IgM antibody in Rasgrf-1 over-expressing cells as compared to control cells indicating that these cells are more sensitive to BCR signaling. BCR signaling also phosphorylates Rasgrf-1 that further increases its GEF function and amplifies BCR signaling. This activation of Rasgrf-1 in over-expressing cells resulted in a higher expression of phospho-ERK, AKT, BTK and PKC-alpha as compared to control cells. Besides BCR, Rasgrf-1 over-expressing cells were also more sensitive to microenvironment stimuli as determined by resistance to apoptosis, chemotaxis and ERK pathway activation. Conclusions： This GEF protein sensitizes B-cells to BCR and chemokine mediated signaling and also upregulates a number of other signaling pathways which promotes growth and survival of these cells.
