ROS Function in Redox Signaling and Oxidative Stress

Reactive oxygen species (ROS) are key signaling molecules that play an important role in the progression of inflammatory disorders. An enhanced ROS generation by polymorphonuclear neutrophils (PMNs) at the site of inflammation causes endothelial dysfunction and tissue injury. The vascular endothelium plays an important role in passage of macromolecules and inflammatory cells from the blood to tissue. Under the inflammatory conditions, oxidative stress produced by PMNs leads to the opening of inter-endothelial junctions and promotes the migration of inflammatory cells across the endothelial barrier. The migrated inflammatory cells not only help in the clearance of pathogens and foreign particles but also lead to tissue injury. The current review compiles the past and current research in the area of inflammation with particular emphasis on oxidative stress-mediated signaling mechanisms that are involved in inflammation and tissue injury.

Reactive Oxygen Species in Inflammation and Tissue Injury

Physiological roles of mitochondrial reactive oxygen species.

Although historically viewed as purely harmful, recent evidence suggests that reactive oxygen species (ROS) function as important physiological regulators of intracellular signaling pathways. The specific effects of ROS are modulated in large part through the covalent modification of specific cysteine residues found within redox-sensitive target proteins. Oxidation of these specific and reactive cysteine residues in turn can lead to the reversible modification of enzymatic activity. Emerging evidence suggests that ROS regulate diverse physiological parameters ranging from the response to growth factor stimulation to the generation of the inflammatory response, and that dysregulated ROS signaling may contribute to a host of human diseases.

/pdf/signal-transduction-by-reactive-oxygen-species-4u5h0ykwov.pdf

Signal transduction by reactive oxygen species

Reactive oxygen species (ROS), which were originally characterized in terms of their harmful effects on cells and invading microorganisms, are increasingly implicated in various cell fate decisions and signal transduction pathways. The mechanism involved in ROS-dependent signalling involves the reversible oxidation and reduction of specific amino acids, with crucial reactive Cys residues being the most frequent target. In this Review, we discuss the sources of ROS within cells and what is known regarding how intracellular oxidant levels are regulated. We further discuss the recent observations that reduction-oxidation (redox)-dependent regulation has a crucial role in an ever-widening range of biological activities - from immune function to stem cell self-renewal, and from tumorigenesis to ageing.

Cellular mechanisms and physiological consequences of redox-dependent signalling

Reactive oxygen species (ROS) have an established role in inflammation and host defense, as they kill intracellular bacteria and have been shown to activate the NLRP3 inflammasome. Here, we find that ROS generated by mitochondrial respiration are important for normal lipopolysaccharide (LPS)-driven production of several proinflammatory cytokines and for the enhanced responsiveness to LPS seen in cells from patients with tumor necrosis factor receptor-associated periodic syndrome (TRAPS), an autoinflammatory disorder caused by missense mutations in the type 1 TNF receptor (TNFR1). We find elevated baseline ROS in both mouse embryonic fibroblasts and human immune cells harboring TRAPS-associated TNFR1 mutations. A variety of antioxidants dampen LPS-induced MAPK phosphorylation and inflammatory cytokine production. However, gp91(phox) and p22(phox) reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits are dispensable for inflammatory cytokine production, indicating that NADPH oxidases are not the source of proinflammatory ROS. TNFR1 mutant cells exhibit altered mitochondrial function with enhanced oxidative capacity and mitochondrial ROS generation, and pharmacological blockade of mitochondrial ROS efficiently reduces inflammatory cytokine production after LPS stimulation in cells from TRAPS patients and healthy controls. These findings suggest that mitochondrial ROS may be a novel therapeutic target for TRAPS and other inflammatory diseases.

https://rupress.org/jem/article-pdf/208/3/519/1206216/jem_20102049.pdf

Mitochondrial reactive oxygen species promote production of proinflammatory cytokines and are elevated in TNFR1-associated periodic syndrome (TRAPS)

The combined treatment of aspirin and radiation induces apoptosis by the regulation of bcl-2 and caspase-3 in human cervical cancer cell

Background

Vascular endothelial growth factor (VEGF) is a potent mediator of angiogenesis and tumor growth in solid tumors. Therefore, to induce tumor regression, antiangiogenic agents to block VEGF need to be administered repeatedly.



Method

We constructed the recombinant mammalian expression vector bearing an antisense-VEGF cDNA, pZeoVEGFa. We examined the effect of pZeoVEGFa on the growth of SK-HEP1 hepatoma cells, bovine capillary endothelial (BCE) cells, and tubule formation of BCE cells in fibrin gel. To evaluate the function of pZeoVEGFa in vivo, we implanted SK-HEP1 hepatoma cells subcutaneously into nude mice.



Results

In SK-HEP1 hepatoma cells, we showed that the synthesis of VEGF protein was suppressed by the stable and transient transfection of pZeoVEGFa. pZeoVEGFa inhibited the proliferation of BCE cells and significantly suppressed tubule formation of BCE cells. pZeoVEGFa inhibited a morphological change from a round shape to an elongated spindle shape in fibrin gel. When pZeoVEGFa was injected peritumorally by liposomes, tumor growth was inhibited.



Conclusion

Endothelial cell proliferation, tubule formation and tumor growth may be diminished by down-regulation of endogenous VEGF expression in tumor cells or tissue. These findings indicate that the efficient down-regulation of the VEGF produced by tumor cells using antisense strategies has an antitumor effect. We suggest that VEGF-targeted antiangiogenic gene therapy could be an effective strategy to treat VEGF-producing tumors. Copyright © 2000 John Wiley & Sons, Ltd.

The growth inhibition of hepatoma by gene transfer of antisense vascular endothelial growth factor.

The early diagnosis of colorectal cancer and the early detection of recurrence are central to effective treatment, as prognosis is directly related to the stage of the disease. When colorectal cancer is diagnosed at an early, localized stage, 5-year survival is 90%. There is substantial interest in the identification of circulating human tumor-derived proteins in serum for the purposes of early cancer diagnosis. We have implemented an approach based on the analysis of microarray data for the identification of tumor proteins that may have utility as biomarkers in colon cancer. Expression analysis of microarray data obtained from a variety of 290 tumors and normal tissues revealed that galanin was maximally expressed in colon cancer. These findings were corroborated by real-time quantitative PCR, in which the colon cancer cell lines LOVO, HCT15, SW480, and SW620 cell showed significantly higher levels of galanin expression than did noncolon cancer cell lines. To evaluate galanin as a potential biomarker of colon cancer, a preliminary "training" set of serum from 40 healthy donors and 55 colon cancer patients was analyzed by ELISA. The data pattern was confirmed by an independent set of 90 masked serum samples: 24 from healthy donors and 66 from colon cancer patients. This result yielded a sensitivity of 69.7% [95% confidence interval (95% CI), 57.1-80.4], specificity of 75.0% (95% CI, 53.3-90.2), and positive predictive value of 88.5% (95% CI, 76.6-95.7). The galanin expression level was significantly increased with tumor size and tumor stage. These findings justify a prospective assessment of serum galanin protein as a screening tool for colon cancer.

https://cebp.aacrjournals.org/content/cebp/16/11/2373.full.pdf

Galanin Is Up-Regulated in Colon Adenocarcinoma

Prostaglandin E2 (PGE2) plays an important role in protection of the gastric mucosa against various damaging agents and growth-inhibitory activity on tumor cells. However, the precise regulation mechanism of PGE2 in gastric cancer cells is still unclear. In this study, we isolated a gene, which is regulated by PGE2 in SNU-1, human gastric adenocarcinoma cells, using differential display RT-PCR (DD RT-PCR) and characterized the function of the gene induced by PGE2. The full-length cDNA of the gene was cloned by the rapid amplification of cDNA ends method. The 1659 base pair cDNA consists of a 30-nt 5′-noncoding region, an 891-nt open reading frame and a 738-nt 3′noncoding region that includes a poly (A) signal. As a result of protein motif search, we found that it has a conserved thioredoxin-active site, Cys-Gly-Pro-Cys and a Myb-DNA binding domain repeat signature. Thus, we designated this gene product as thioredoxin-related protein-1, TRP-1. TRP-1 was expressed in a lower extent in renal, gastric and colon cancer tissues and is translated into 33 kDa protein in nuclear and cytoplasmic fractions. TRP-1 has a thioredoxin activity, which was detected using the insulin disulfide reduction assay. Another potential role of TRP-1 is repression of B-Myb activity through direct binding to B-Myb, a transcriptional factor induced at G1–S transition. Finally, TRP-1 overexpression inhibits mammalian cell proliferation and specifically predispose to G0/G1 phase arrest. In conclusion, these results imply that TRP-1 is a mammalian thioredoxin and plays as a transcriptional repressor through direct binding to the transcription factor B-Myb. © 2005 Wiley-Liss, Inc.

Kye Young Kim

Papers

Mitochondrial reactive oxygen species promote production of proinflammatory cytokines and are elevated in TNFR1-associated periodic syndrome (TRAPS)

The combined treatment of aspirin and radiation induces apoptosis by the regulation of bcl-2 and caspase-3 in human cervical cancer cell

The growth inhibition of hepatoma by gene transfer of antisense vascular endothelial growth factor.

Galanin Is Up-Regulated in Colon Adenocarcinoma

Expression of a thioredoxin-related protein-1 is induced by prostaglandin E2