New method for the detection of reactive oxygen species in anti-tumoural activity of adriamycin: a comparison between hypoxic and normoxic cells

Advances in hyperbaric oxygen to promote immunotherapy through modulation of the tumor microenvironment

Hyperbaric oxygen therapy is a relatively safe treatment method that has been used for a long time in the clinic. It has been proven that it can enhance the sensitivity of radiotherapy and photodynamic therapy for cancer. However, there are few studies on hyperbaric oxygen and immunotherapy. In this article, we summarize that hyperbaric oxygen therapy regulates the tumor microenvironment through various pathways such as improving tumor hypoxia, targeting hypoxia-inducing factors, and generating reactive oxygen species. The change in the tumor microenvironment ultimately affects the curative effect of immunotherapy. Therefore, hyperbaric oxygen can influence immunotherapy by regulating the tumor microenvironment, providing a direction for the future development of immunotherapy.

Functional Imaging of Hypoxia: PET and MRI

Molecular and functional imaging have critical roles in cancer care. Existing evidence suggests that noninvasive detection of hypoxia within a particular type of cancer can provide new information regarding the relationship between hypoxia, cancer aggressiveness and altered therapeutic responses. Following the identification of hypoxia inducible factor (HIF), significant progress in understanding the regulation of hypoxia-induced genes has been made. These advances have provided the ability to therapeutically target HIF and tumor-associated hypoxia. Therefore, by utilizing the molecular basis of hypoxia, hypoxia-based theranostic strategies are in the process of being developed which will further personalize care for cancer patients. The aim of this review is to provide an overview of the significance of tumor hypoxia and its relevance in cancer management as well as to lay out the role of imaging in detecting hypoxia within the context of cancer.

Metabolic Rate and Oxygen Radical Levels Increase But Radical Generation Rate Decreases with Male Age in Drosophila melanogaster Sperm

Oxidative damage increases with age in a variety of cell types, including sperm, which are particularly susceptible to attack by reactive oxygen species (ROS). While mitochondrial respiration is the main source of cellular ROS, the relationship between the rates of aerobic metabolism and ROS production, and how this relationship may be affected by age, both in sperm and in other cell types, is unclear. Here, we investigate in Drosophila melanogaster sperm, the effects of male age on (i) the level of hydrogen peroxide in the mitochondria, using a transgenic H2O2 reporter line; (ii) the in situ rate of non-H2O2 ROS production, using a novel biophysical method; and (iii) metabolic rate, using fluorescent lifetime imaging microscopy. Sperm from older males had higher mitochondrial ROS levels and a higher metabolic rate but produced ROS at a lower rate. In comparison, a somatic tissue, the gut epithelium, also showed an age-related increase in mitochondrial ROS levels but a decrease in metabolic rate. These results support the idea of a tissue-specific optimal rate of aerobic respiration balancing the production and removal of ROS, with aging causing a shift away from this optimum and leading to increased ROS accumulation. Our findings also support the view that pathways of germline and somatic aging can be uncoupled, which may have implications for male infertility treatments.

Hypoxia as a target for drug combination therapy of liver cancer

Hepatocellular carcinoma (HCC) is the third most frequent cause of cancer deaths worldwide. The standard of care for intermediate HCC is transarterial chemoembolization, which combines tumour embolization with locoregional delivery of the chemotherapeutic doxorubicin. Embolization therapies induce hypoxia, leading to the escape and proliferation of hypoxia-adapted cancer cells. The transcription factor that orchestrates responses to hypoxia is hypoxia-inducible factor 1 (HIF-1). The aim of this work is to show that targeting HIF-1 with combined drug therapy presents an opportunity for improving outcomes for HCC treatment. HepG2 cells were cultured under normoxic and hypoxic conditions exposed to doxorubicin, rapamycin and combinations thereof, and analyzed for viability and the expression of hypoxia-induced HIF-1α in response to these treatments. A pilot study was carried out to evaluate the antitumour effects of these drug combinations delivered from drug-eluting beads in vivo using an ectopic xenograft murine model of HCC. A therapeutic doxorubicin concentration that inhibits the viability of normoxic and hypoxic HepG2 cells and above which hypoxic cells are chemoresistant was identified, together with the lowest effective dose of rapamycin against normoxic and hypoxic HepG2 cells. It was shown that combinations of rapamycin and doxorubicin are more effective than doxorubicin alone. Western Blotting indicated that both doxorubicin and rapamycin inhibit hypoxia-induced accumulation of HIF-1α. Combination treatments were more effective in vivo than either treatment alone. mTOR inhibition can improve outcomes of doxorubicin treatment in HCC.

Synthetic Sensors for Reactive Oxygen Species Detection and Quantification: A Critical Review of Current Methods

SIGNIFICANCE

Redox reactions play important roles in both physiological and pathological processes, highlighting the importance of quantifying and localizing intracellular redox-active components. Most research has focused on direct investigation of reactive oxygen species (ROS). Intensity-based fluorescent methods are very sensitive and easy to use, but they lack specificity and can produce artifacts. In this article, we focus on synthetic sensors, describing experimental pitfalls associated with their use. We also present alternative methods for the detection of free radicals.

RECENT ADVANCES

New approaches have been developed to overcome the main artifact of intensity-based methods: spurious changes in fluorescence intensity caused by oxidation. These new approaches are based on analytical measurements of the oxidized sensors or techniques that are not susceptible to oxidation, such as electron spin resonance and fluorescence lifetime-based methods. Regardless of the approach, the need for detection of ROS on the subcellular level, especially in the mitochondria, has motivated the development of new probes.

CRITICAL ISSUES

Flow cytometry systems and confocal microscopes are now available to the majority of biologists, and commercially available probes are, therefore, more widely used. The fact that these new applications are cited in thousands of publications makes these sensors even more attractive.

FUTURE DIRECTIONS

The field of ROS detection by synthetic sensors continues to expand, bringing needed additional research to the development of robust techniques that are applicable both in vitro and in vivo. Antioxid. Redox Signal. 25, 520-533.

Adriamycin dose and time effects on cell cycle, cell death, and reactive oxygen species generation in leukaemia cells

We investigate the relative importance of the different mechanisms of Adriamycin, an anthracycline, and their interrelations, in particular the link between cell cycle arrest, cell death, and generation of reactive oxygen species (ROS) that is suspected to be the origin of cardiotoxic side-effects. We introduced a lifetime fluorescence based technology and used videomicrofluorometry, two efficient analytical methods. We show that depending on the doses and time after incubation, ADR will not reach the same compartments (nucleus, mitochondria, cytosol) in the cells, having consequences on the production of ROS, growth arrest pathways and cell death pathways.

Reduced metabolic rate and oxygen radicals production in stored insect sperm

Females of internally fertilizing species can significantly extend sperm lifespan and functionality during sperm storage. The mechanisms for such delayed cellular senescence remain unknown. Here, we apply current hypotheses of cellular senescence developed for diploid cells to sperm cells, and empirically test opposing predictions on the relationship between sperm metabolic rate and oxygen radical production in an insect model, the cricket Gryllus bimaculatus. Using time-resolved microfluorimetry, we found a negative correlation between metabolic rate (proportion of protein-bound NAD[P]H) and in situ intracellular oxygen radicals production in freshly ejaculated sperm. In contrast, sperm stored by females for periods of 1 h to 26 days showed a positive correlation between metabolic rate and oxygen radicals production. At the same time, stored sperm showed a 37 per cent reduced metabolic rate, and 42 per cent reduced reactive oxygen species (ROS) production, compared with freshly ejaculated sperm. Rank differences between males in ROS production and metabolic rate observed in ejaculated sperm did not predict rank differences in stored sperm. Our method of simultaneously measuring ROS production and metabolic rate of the same sample has the advantage of providing data that are independent of sperm density and any extracellular antioxidants that are proteins. Our method also excludes effects owing to accumulated hydrogen peroxide. Our results unify aspects of competing theories of cellular ageing and suggest that reducing metabolic rate may be an important means of extending stored sperm lifespan and functionality in crickets. Our data also provide a possible explanation for why traits of ejaculates sampled from the male may be rather poor predictors of paternity in sexual selection studies and likelihood of pregnancy in reproductive medicine.

Over-expression of metallothionein predicts chemoresistance in breast cancer

Metallothionein (MT) plays a role in fundamental cellular processes such as proliferation, apoptosis and differentiation. We examined MT expression in women with invasive breast ductal carcinoma who underwent mastectomy/lumpectomy without neo-adjuvant treatment. We showed that MT was over-expressed in 87.9% of breast cancer tissues examined, with the mean percentage of positive cells at 30%. There were two patterns of MT expression: predominantly cytoplasmic in 75.9% and nuclear in 24.1% of MT-positive cases. Higher MT scores were associated with poorer histological grade (p = 0.009) but were independent of age, tumour size and oestrogen receptor status. For patients who were treated with adjuvant chemotherapy (cyclophosphamide/methotrexate/5 fluorouracil- or doxorubicin-based regimes), those with high MT expression had a significantly lower recurrence-free survival (p = 0.048), suggesting a role of MT in predicting disease recurrence. Down-regulation of MT in MCF-7 cells by silencing the MT-2A gene (the most abundantly expressed of the 10 known functional MT isoforms) increased chemosensitivity of the cells to doxorubicin. To examine the mechanisms underlying these clinical data, we used siRNAs to decrease MT-2A mRNA expression and protein expression. In MT down-regulated cells challenged with the IC(50) concentration of doxorubicin, we observed a significant reduction in cell viability. Cell cycle analysis also revealed a corresponding increase in apoptosis in the MT down-regulated cells following doxorubicin exposure, showing that down-regulation of MT increased susceptibility to doxorubicin cytotoxicity. The data suggest that MT could be a potential marker of chemoresistance and a molecular therapeutic target.

Hydrogen peroxide enhances osteopontin expression and matrix metalloproteinase activity in aortic vascular smooth muscle cells

1. Restenosis after percutaneous coronary intervention (PCI) is a major clinical complication. However, the underlying mechanisms remain poorly understood. The present aim of the present study was to test the hypothesis that reactive oxygen species (ROS) enhance osteopontin (OPN) expression and increase matrix metalloproteinase (MMP)-2 activity (two major factors that contribute to restenosis) in aortic vascular smooth muscle cells (VSMC), thus facilitating restenosis. 2. Primary cultured rat aortic VSMC were exposed to different concentrations (10, 50 and 100 micromol/L) of H(2)O(2). The expression of OPN mRNA and protein was determined by reverse transcription-polymerase chain reaction and Western blotting, respectively. The activity of MMP-2 was determined by gelatin zymography. 3. The expression of OPN mRNA and protein in VSMC was enhanced by H(2)O(2) in a dose-dependent manner. In addition, H(2)O(2) at all concentrations tested (which are comparable to those seen in diabetic vascular tissues) significantly increased MMP-2 activity in VSMC. 4. Because vascular ROS production is significantly increased in patients with ischaemic disease and OPN and MMP-2 have been shown to play critical role in restenosis, the results of the present study strongly suggest that a ROS-initiated and OPN- and MMP-2-mediated signalling pathway may play an important role in accelerated restenosis after PCI in patients with ischaemic disease. Therefore, the H(2)O(2)-OPN/MMP-2 system may be a new therapeutic target in reducing restenosis in patients undergoing PCI.