DMA, a Bisbenzimidazole, Offers Radioprotection by Promoting NFκB Transactivation through NIK/IKK in Human Glioma Cells

BACKGROUND: Ionizing radiation (IR) exposure often occurs for human beings through occupational, medical, environmental, accidental and/or other sources. Thus, the role of radioprotector is essential to overcome the complex series of overlapping responses to radiation induced DNA damage. METHODS AND RESULTS: Treatment of human glioma U87 cells with DMA (5- {4-methylpiperazin-1-yl}-2-[2'-(3, 4-dimethoxyphenyl)-5'-benzimidazolyl] in the presence or absence of radiation uncovered differential regulation of an array of genes and proteins using microarray and 2D PAGE techniques. Pathway construction followed by relative quantitation of gene expression of the identified proteins and their interacting partners led to the identification of MAP3K14 (NFκB inducing kinase, NIK) as the candidate gene affected in response to DMA. Subsequently, over expression and knock down of NIK suggested that DMA affects NFκB inducing kinase mediated phosphorylation of IKKα and IKKβ both alone and in the presence of ionizing radiation (IR). The TNF-α induced NFκB dependent luciferase reporter assay demonstrated 1.65, 2.26 and 3.62 fold increase in NFκB activation at 10, 25 and 50 µM DMA concentrations respectively, compared to control cells. This activation was further increased by 5.8 fold in drug + radiation (50 µM +8.5 Gy) treated cells in comparison to control. We observed 51% radioprotection in control siRNA transfected cells that attenuated to 15% in siRNA NIK treated U87 cells, irradiated in presence of DMA at 24 h. CONCLUSIONS: Our studies show that NIK/IKK mediated NFκB activation is more intensified in cells over expressing NIK and treated with DMA, alone or in combination with ionizing radiation, indicating that DMA promotes NIK mediated NFκB signaling. This subsequently leads to the radioprotective effect exhibited by DMA

The cytoprotective drug amifostine modifies both expression and activity of the pro-angiogenic factor VEGF-A

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Analysing the mechanism of mitochondrial oxidation-induced cell death using a multifunctional iridium(III) photosensitiser

Mitochondrial oxidation-induced cell death, a physiological process triggered by various cancer therapeutics to induce oxidative stress on tumours, has been challenging to investigate owing to the difficulties in generating mitochondria-specific oxidative stress and monitoring mitochondrial responses simultaneously. Accordingly, to the best of our knowledge, the relationship between mitochondrial protein oxidation via oxidative stress and the subsequent cell death-related biological phenomena has not been defined. Here, we developed a multifunctional iridium(III) photosensitiser, Ir-OA, capable of inducing substantial mitochondrial oxidative stress and monitoring the corresponding change in viscosity, polarity, and morphology. Photoactivation of Ir-OA triggers chemical modifications in mitochondrial protein-crosslinking and oxidation (i.e., oxidative phosphorylation complexes and channel and translocase proteins), leading to microenvironment changes, such as increased microviscosity and depolarisation. These changes are strongly related to cell death by inducing mitochondrial swelling with excessive fission and fusion. We suggest a potential mechanism from mitochondrial oxidative stress to cell death based on proteomic analyses and phenomenological observations. Mitochondrial oxidation-induced cell death is an important physiological process activated by cancer therapeutics, but its investigation is challenging. Here, the authors report a multifunctional iridium(III) photosensitiser, Ir-OA, able to induce mitochondrial oxidative stress and monitor the corresponding changes in mitochondrial properties

Administration of rat acute-phase protein α2-macroglobulin before total-body irradiation initiates cytoprotective mechanisms in the liver

Previously, we showed that administration of the acute-phase protein α(2)-macroglobulin (α(2)M) to rats before total-body irradiation with 6.7 Gy (LD(50/30)) of X-rays provides the same level of radioprotection as amifostine. Here, we compare the cytoprotective effects of α(2)M and amifostine on rat liver. The potential of the liver to replenish cells destroyed by ionizing radiation was assessed by immunoblot analysis with antibody to proliferating cell nuclear antigen (PCNA). After irradiation, in unprotected rats PCNA decreased 6-fold from the basal level. In rats pretreated with either α(2)M or amifostine, PCNA was increased throughout a 4 week follow-up period, indicating that hepatocyte proliferation was unaffected. Since PCNA is an important component of the repair machinery, its increased expression was accompanied by significantly lower DNA damage in α(2)M- and amifostine-treated rats. At 2 weeks after irradiation, the Comet assay revealed a 15-fold increase in DNA damage in unprotected rats, while in α(2)M- and amifostine-treated rats we observed 3- and 4-fold rise in damage, respectively. The improved protection to DNA damage was supported by elevated activity of the antioxidant systems. Compared to untreated rats, pretreatments with α(2)M and amifostine led to similar increases in levels of the inflammatory cytokine IL-6 and the redox-sensitive transcription factor NFκB, promoting upregulation of MnSOD, the major component of the cell's antioxidant axis, and subsequent increases in Mn/CuZnSOD and catalase enzymatic activities. The results show that α(2)M induces protein factors whose interplay underlies radioprotection and support the idea that α(2)M is the central effector of natural radioprotection in the rat