Magnetite nanoparticles as a kinetically favorable source of iron to enhance GBM response to chemoradiosensitization with pharmacological ascorbate.

Ferumoxytol (FMX) is an FDA-approved magnetite (Fe3O4) nanoparticle used to treat iron deficiency anemia that can also be used as an MR imaging agent in patients that can't receive gadolinium. Pharmacological ascorbate (P-AscH-; IV delivery; plasma levels ≈ 20 mM) has shown promise as an adjuvant to standard of care chemo-radiotherapy in glioblastoma (GBM). Since ascorbate toxicity mediated by H2O2 is enhanced by Fe redox cycling, the current study determined if ascorbate catalyzed the release of ferrous iron (Fe2+) from FMX for enhancing GBM responses to chemo-radiotherapy. Ascorbate interacted with Fe3O4 in FMX to produce redox-active Fe2+ while simultaneously generating increased H2O2 fluxes, that selectively enhanced GBM cell killing (relative to normal human astrocytes) as opposed to a more catalytically active Fe complex (EDTA-Fe3+) in an H2O2 - dependent manner. In vivo, FMX was able to improve GBM xenograft tumor control when combined with pharmacological ascorbate and chemoradiation in U251 tumors that were unresponsive to pharmacological ascorbate therapy. These data support the hypothesis that FMX combined with P-AscH- represents a novel combined modality therapeutic approach to enhance cancer cell selective chemoradiosentization in the management of glioblastoma.

Avasopasem manganese (GC4419) protects against cisplatin-induced chronic kidney disease: An exploratory analysis of renal metrics from a randomized phase 2b clinical trial in head and neck cancer patients.

Head and neck squamous cell carcinoma (HNSCC) patients treated with high-dose cisplatin concurrently with radiotherapy (hdCis-RT) commonly suffer kidney injury leading to acute and chronic kidney disease (AKD and CKD, respectively). We conducted a retrospective analysis of renal function and kidney injury-related plasma biomarkers in a subset of HNSCC subjects receiving hdCis-RT in a double-blinded, placebo-controlled clinical trial (NCT02508389) evaluating the superoxide dismutase mimetic, avasopasem manganese (AVA), an investigational new drug. We found that 90 mg AVA treatment prevented a significant reduction in estimated glomerular filtration rate (eGFR) three months as well as six and twelve months after treatment compared to 30 mg AVA and placebo. Moreover, AVA treatment may have allowed renal repair in the first 22 days following cisplatin treatment as evidenced by an increase in epithelial growth factor (EGF), known to aid in renal recovery. An upward trend was also observed in plasma iron homeostasis proteins including total iron (Fe-blood) and iron saturation (Fe-saturation) in the 90 mg AVA group versus placebo. These data support the hypothesis that treatment with 90 mg AVA mitigates cisplatin-induced CKD by inhibiting hdCis-induced renal changes and promoting renal recovery.

Quantum chemical insight into the effects of the local electron environment on T2*-based MRI.

T2* relaxation is an intrinsic magnetic resonance imaging (MRI) parameter that is sensitive to local magnetic field inhomogeneities created by the deposition of endogenous paramagnetic material (e.g. iron). Recent studies suggest that T2* mapping is sensitive to iron oxidation state. In this study, we evaluate the spin state-dependence of T2* relaxation using T2* mapping. We experimentally tested this physical principle using a series of phantom experiments showing that T2* relaxation times are directly proportional to the spin magnetic moment of different transition metals along with their associated magnetic susceptibility. We previously showed that T2* relaxation time can detect the oxidation of Fe2+. In this paper, we demonstrate that T2* relaxation times are significantly longer for the diamagnetic, d10 metal Ga3+, compared to the paramagnetic, d5 metal Fe3+. We also show in a cell culture model that cells supplemented with Ga3+ (S = 0) have a significantly longer relaxation time compared to cells supplemented with Fe3+ (S = 5/2). These data support the hypothesis that dipole-dipole interactions between protons and electrons are driven by the strength of the electron spin magnetic moment in the surrounding environment giving rise to T2* relaxation.

Utilization of redox modulating small molecules that selectively act as pro-oxidants in cancer cells to open a therapeutic window for improving cancer therapy.

There is a rapidly growing body of literature supporting the notion that differential oxidative metabolism in cancer versus normal cells represents a metabolic frailty that can be exploited to open a therapeutic window into cancer therapy. These cancer cell-specific metabolic frailties may be amenable to manipulation with non-toxic small molecule redox active compounds traditionally thought to be antioxidants. In this review we describe the potential mechanisms and clinical applicability in cancer therapy of four small molecule redox active agents: melatonin, vitamin E, selenium, and vitamin C. Each has shown the potential to have pro-oxidant effects in cancer cells while retaining antioxidant activity in normal cells. This dichotomy can be exploited to improve responses to radiation and chemotherapy by opening a therapeutic window based on a testable biochemical rationale amenable to confirmation with biomarker studies during clinical trials. Thus, the unique pro-oxidant/antioxidant properties of melatonin, vitamin E, selenium, and vitamin C have the potential to act as effective adjuvants to traditional cancer therapies, thereby improving cancer patient outcomes.

Thermal stress and the disruption of redox-sensitive signalling and transcription factor activation: possible role in radiosensitization.

In spite of ongoing research efforts, the specific mechanism(s) of heat-induced alterations in the cellular response to ionizing radiation (IR) remain ambiguous, in part because they likely involve multiple mechanisms and potential targets. One such group of potential targets includes a class of cytoplasmic signalling and/or nuclear transcription factors known as immediate early response genes, which have been suggested to perform cytotoxic as well as cytoprotective roles during cancer therapy. One established mechanism regulating the activity of these early response elements involves changes in cellular oxidation/reduction (redox) status. After establishing common alterations in early response genes by oxidative stress and heat exposure, one could infer that heat shock may have similarities to other forms of environmental antagonists that induce oxidative stress. In this review, recent evidence supporting a mechanistic link between heat shock and oxidative stress will be summarized. In addition, the hypothesis that one mechanism whereby heat shock alters cellular responses to anticancer agents (including hyperthermic radiosensitization) is through heat-induced disruption of redox-sensitive signalling factors will be discussed.

Heat shock and the activation of AP-1 and inhibition of NF-kappa B DNA-binding activity: possible role of intracellular redox status.

The early response genes comprising the AP-1 and NF-kappa B transcription factors are induced by environmental stress and thought to modulate responses to injury processes through the induction of target genes. Exposure to heat and ionizing radiation (IR) has been shown to affect signalling machinery involved in AP-1 and NF-kappa B activation. Furthermore, regulation of the signalling pathways leading to the activation of these transcription factors has been linked to changes in intracellular oxidation/reduction (redox) reactions. The hypothesis is proposed that exposure to thermal stress and/or IR might alter metabolic processes impacting upon cellular redox state and thereby modify the activity of redox-sensitive transcription factors such as AP-1 and NF-kappa B. Gel electromobility shift assays (EMSA) demonstrated that heat shock-induced AP-1 DNA-binding activity but inhibited IR-induced activation of NF-kappa B. A time course showed that activation of the AP-1 complex occurs between 4 and 5 h following thermal stress, and inhibition of IR-induced NF-kappa B activation also occurs during this time interval. Using a redox-sensitive fluorescent probe [5-(and -6)-carboxy-2',7'-dichlorodihydrofluorescein diacetate], a shift to 40% less intracellular dye oxidation was observed in HeLa cells 0-4 h post-heat shock (45 degrees C, 15 min) relative to cells held at 37 degrees C. This was followed by a shift to greater dye oxidation between 4 and 12 h after treatment (about 1.8-fold) that returned to control levels by 24 h post-heating. These results show changes in DNA-binding activity closely paralleled apparent heat-induced changes in the intracellular redox state. Taken together, these results provide correlative evidence for disruption of redox-sensitive IR-induced signalling pathways by heat shock and support the hypothesis that this mechanism might play a role in heat-induced alterations in radiation response.

Increased lipid peroxidation and impaired antioxidant enzyme function is associated with pathological liver injury in experimental alcoholic liver disease in rats fed diets high in corn oil and fish oil.

Increased hepatic oxidative stress with ethanol administration is hypothesized to be caused either by enhanced pro-oxidant production or decreased levels of antioxidants or both. We used the intragastric feeding rat model to assess the relationship between hepatic antioxidant enzymes and pathological liver injury in animals fed different dietary fats. Male Wistar rats (5 per group) were fed ethanol with either medium-chain triglycerides (MCTE), palm oil (PE), corn oil (CE), or fish oil (FE). Control animals were fed isocaloric amounts of dextrose instead of ethanol with the same diets. The following were evaluated in each group: liver pathology, lipid peroxidation, manganese superoxide dismutase (MnSOD) levels, copper-zinc SOD (CuZnSOD) levels, glutathione peroxidase (GPX) levels, and catalase (CAT) levels. All enzymes were evaluated using activity assays and immunoblots. Rats fed FE showed the most severe pathology (fatty liver, necrosis, and inflammation), those fed CE showed moderate changes, those fed PE showed fatty liver only, and those fed MCTE were normal. Parameters indicative of lipid peroxidation (conjugated dienes and thiobarbituric acid-reactive substances) were also greater in rat livers from animals fed the diets high in polyunsaturated fatty acids (CE and FE). CuZnSOD, GPX, and CAT activities showed an inverse correlation (r=-.92, P < .01) with severity of pathological injury, with the lowest levels for both enzymes found in FE-fed rats. Decreased enzyme activity in CE- and FE-fed rats was accompanied by similar decreases in immunoreactive protein. Ethanol administration did not cause significant decreases in enzyme activity in groups that showed no necroinflammatory changes (MCTE and PE). MnSOD activity showed no significant change in any ethanol-fed group. Our results show that decreases in CuZnSOD, GPX, and CAT occur in rats showing pathological liver injury and also having the highest levels of lipid peroxidation. These results suggest that feeding dietary substrates that enhance lipid peroxidation can exacerbate both ethanol-induced oxidative damage as well as necroinflammatory changes. The decrease in activity of antioxidant enzymes observed in animals fed diets high in polyunsaturated fatty acids and ethanol could possibly increase the susceptibility to oxidative damage and further contribute to ethanol-induced liver injury.

The effect of monosaturated and polyunsaturated fatty acids on oxygen toxicity in cultured cells.

The influence of oleic, linoleic (LIN), and eicosapentaenoic (EPA) acids incorporated into cellular lipids on susceptibility to O2-induced toxicity was evaluated in Chinese hamster fibroblasts (HA1) using a clonogenic cell survival assay. Fatty acid incorporation was achieved by incubating HA1 cells in 21% O2 for 72 h in the presence or absence of media supplemented with 25 microM oleic acid, 25 microM LIN, or 2, 4, and 25 microM EPA. This fatty acid incorporation period increased the percentage of composition in phospholipids 2-fold for oleic acid, 6-fold for LIN, and 6- to 20-fold for EPA. Vitamin E, total glutathione, superoxide dismutase activity, glutathione transferase activity, and catalase activity were unchanged, relative to control, in the 25-microM EPA-treated group, and only total glutathione was elevated in the LIN-treated group. After the incorporation period, the cells were placed in non-fatty acid supplemented media and exposed to 95% O2, and clonogenic survival responses were evaluated at time intervals up to 100 h. Sensitization to O2 toxicity in EPA-treated cells was apparent after 24 h of O2 exposure, whereas LIN-treated cells were significantly (p less than 0.05) sensitized to hyperoxia after 54 h of exposure, indicating that EPA was a more potent sensitizer for O2 injury. Furthermore, cells supplemented with 4 and 25 microM EPA were more sensitive to O2 toxicity than cells supplemented with 2 microM EPA. In contrast, cells treated with 25 microM oleic acid were significantly more resistant to O2 toxicity at 51, 72, and 98 h of O2 exposure.(ABSTRACT TRUNCATED AT 250 WORDS)