Oxidative stress signalling: a potential mediator of tumour necrosis factor α-induced genomic instability in primary vascular endothelial cells

Abstract

Studying the potential role of tumour necrosis factor (TNF)alpha in the initiation of genomic instability is necessary to understand whether TNFalpha can serve as a signalling mediator of radiation-induced genomic instability in non-irradiated bystander cells. In this study, we examined whether TNFalpha could initiate processes through oxidative stress signalling that lead to DNA damage and genomic instability in primary vascular endothelium. In these cells, low linear energy transfer (LET) radiation (0.1-2 Gy) induced the secretion of TNFalpha into the culture medium. When added ectopically, TNFalpha at concentrations ranging from 0.1 ng ml(-1) to 10 ng ml(-1) increased (twofold to threefold) intracellular oxidative stress. Next, to examine whether TNFalpha induces genetic damage, cells were treated with TNFalpha for 5 h and analysed immediately using the single cell gel electrophoresis assay or after 3 days, 12 days and 20 days using solid stain chromosomal analysis. Cells exposed to 0.1 Gy, 1 Gy or 2 Gy or treated with 100 microM H2O2 were used as positive controls. The results showed that TNFalpha as low as 0.1 ng ml(-1) could initiate increased DNA damage compared with untreated controls. When examined in the progeny cells after several generations, the chromosomal instability appeared to be carried over even after day 12 and day 20. The increased genetic damage is inhibited in cells that are pre-incubated with the antioxidant enzyme catalase, the antioxidant N-acetyl-L-cysteine or the metal chelator pyrrolidine dithiocarbamate. These results clearly indicate that TNFalpha at concentrations at which no cytotoxicity is observed could induce genetic damage through free radical generation, which could, in turn, lead to the delayed events associated with genomic instability.

Gene Polymorphisms of Tumor Necrosis Factor Alpha and Antioxidant Enzymes in Bronchial Asthma

“…The presence of the polymorphic TNF-308A allele is considered to be associated with increased TNF-α production [28]. Cell stimulation by TNF-α maintains increased ROS levels and increases MnSOD activity, while the presence of the MnSOD 16Val allele is associated with decreased MnSOD activity [29,30]. In relation to these findings, in the absence of TNF-α-308A allele, the stimulatory effect of TNF-α on MnSOD activity in asthmatics could be intermitted and, together with the concurrent presence of polymorphic MnSOD 16Val and CAT-21T alleles, could lead to increased oxidative stress due to a lower defense capacity against ROS.…”

Role of Oxidative Stress in the Colonic Complications of Murine Syngeneic Graft-versus-host Disease

“…Along with increases in oxidative stress, our group has shown increased levels of TNF-α and cellular adhesion molecules (CAM) in the colons of CsA treated mice compared to control BMT at early time points during and after CsA therapy [40]. The SGVHD induction regimen can trigger oxidative stress in many cell types and reports show that pathological changes associated with TNF-α signaling is associated with increased oxidative stress [41,42]. …”

Persistent Circulating Immune Complexes: Potential Source of Epimutation and Cancer Poor Prognosis

“…TNFR signalling induces NADPH oxidase and iNOS, alters glutathione levels and causes mitochondrial disruption, all of which have the capacity to produce RONS and induce DNA damage. Earlier research demonstrated that NF-κB signalling is involved in induction of DNA damage [47]. We hypothesized that persistence Immune complexes can mediate the translocation of NF-kB into the nucleus by inducing the generation of cytokines (IL-1, TNF-α) that can cause phosphrylation of IkBs kinase and subsequent release of NFkB from the cytosol into the nucleus.…”

“…DNA single-and double-stranded breaks measured by the alkaline comet assay and immunostaining for γH2AX foci were significantly higher in T cells; however, only DNA double strand breaks were significantly higher in CD19 + B cells T-cell lymphomas, due to persistent systemic genotoxicity to T cells and peripheral lymphoid organs, which manifested significant amounts of DNA damage [46]. Research has shown that elevated levels of circulating cytokines characteristic to intestinal inflammation such as TNF-α and their downstream mediators are partially responsible for inducing DNA damage [47]. In this review, we maintain that the persistent circulation of immune complexes is encompassing.…”