Late Inflammation Induced by Asbestiform Fibers in Mice Is Ameliorated by a Small Molecule Synthetic Lignan

Exposure to Libby amphibole (LA) asbestos-like fibers is associated with increased risk of asbestosis, mesothelioma, pulmonary disease, and systemic autoimmune disease. LGM2605 is a small molecule antioxidant and free radical scavenger, with anti-inflammatory effects in various disease models. The current study aimed to determine whether the protective effects of LGM2605 persist during the late inflammatory phase post-LA exposure. Male and female C57BL/6 mice were administered daily LGM2605 (100 mg/kg) via gel cups for 3 days before and 14 days after a 200 µg LA given via intraperitoneal (i.p.) injection. Control mice were given unsupplemented gel cups and an equivalent dose of i.p. saline. On day 14 post-LA treatment, peritoneal lavage was assessed for immune cell influx, cytokine concentrations, oxidative stress biomarkers, and immunoglobulins. During the late inflammatory phase post-LA exposure, we noted an alteration in trafficking of both innate and adaptive immune cells, increased pro-inflammatory cytokine concentrations, induction of immunoglobulin isotype switching, and increased oxidized guanine species. LGM2605 countered these changes similarly among male and female mice, ameliorating late inflammation and altering immune responses in late post-LA exposure. These data support possible efficacy of LGM2605 in the prolonged treatment of LA-associated disease and other inflammatory conditions.

Phase II Trial of Flaxseed to Prevent Acute Complications After Chemoradiation for Lung Cancer

Background: Thoracic radiotherapy is complicated by acute radiation-induced adverse events such as radiation pneumonitis (RP) and radiation esophagitis (RE). Based on preclinical work and a randomized pilot trial from our laboratory, this single-arm phase II trial investigated administering flaxseed as a radioprotector in patients receiving definitive chemoradiation for nonsmall cell lung cancer (NSCLC). Methods: Between June 2015 and February 2018, 33 patients with locally advanced or metastatic NSCLC with planned definitive chemoradiation were enrolled. Finely-ground Linum usitatissimum L. (Linaceae; flaxseed or linseed) in 40-g packets were provided for daily consumption in any patient-desired formulation 1 week before radiotherapy and throughout radiotherapy as tolerated. The primary outcomes were overall adverse events, with particular focus on Grade ≥3 RP, and flaxseed tolerability. Adverse events were graded according to CTCAE v4.0. Results: Of the 33 patients enrolled, 5 patients (15%) did not receive chemoradiation, 4 (12%) withdrew promptly after enrollment, 4 (12%) did not return a flaxseed consumption log, and 1 patient had irritable bowel syndrome (3%). The remaining 19 patients (57%) had chemoradiation and flaxseed ingestion with a mean completion and standard deviation of the intended flaxseed course of 62% ± 8.3%. Nine (50%) of these 19 patients reported difficulties with flaxseed consumption, citing nausea, constipation, odynophagia, or poor taste or texture. One patient (5%), with unverifiable flaxseed consumption, developed Grade 3 RP. There were no cases of Grade 2 RP. Six patients (32%) developed Grade 2 RE, but no patients developed Grade ≥3 RE. Median overall and progression-free survival were 31 and 12 months, respectively. Conclusions: Despite the low incidence of acute radiation-induced complications reported, significant treatment-related gastrointestinal toxicities and subsequently low flaxseed tolerability inhibit accurate determination of flaxseed effect in patients receiving concurrent thoracic chemoradiation. Thus, further investigations should focus on optimizing flaxseed formulation for improved tolerability and evaluation. CTR #: NCT02475330, https://clinicaltrials.gov/ct2/show/study/NCT02475330.

Assessment of a Small Molecule Synthetic Lignan in Enhancing Oxidative Balance and Decreasing Lipid Accumulation in Human Retinal Pigment Epithelia

Visual function depends on the intimate structural, functional and metabolic interactions between the retinal pigment epithelium (RPE) and the neural retina. The daily phagocytosis of the photoreceptor outer segment tips by the overlaying RPE provides essential nutrients for the RPE itself and photoreceptors through intricate metabolic synergy. Age-related retinal changes are often characterized by metabolic dysregulation contributing to increased lipid accumulation and peroxidation as well as the release of proinflammatory cytokines. LGM2605 is a synthetic lignan secoisolariciresinol diglucoside (SDG) with free radical scavenging, antioxidant and anti-inflammatory properties demonstrated in diverse in vitro and in vivo inflammatory disease models. In these studies, we tested the hypothesis that LGM2605 may be an attractive small-scale therapeutic that protects RPE against inflammation and restores its metabolic capacity under lipid overload. Using an in vitro model in which loss of the autophagy protein, LC3B, results in defective phagosome degradation and metabolic dysregulation, we show that lipid overload results in increased gasdermin cleavage, IL-1 β release, lipid accumulation and decreased oxidative capacity. The addition of LGM2605 resulted in enhanced mitochondrial capacity, decreased lipid accumulation and amelioration of IL-1 β release in a model of defective lipid homeostasis. Collectively, these studies suggest that lipid overload decreases mitochondrial function and increases the inflammatory response, with LGM2605 acting as a protective agent.

Radiation activates myeloperoxidase (MPO) to generate active chlorine species (ACS) via a dephosphorylation mechanism - inhibitory effect of LGM2605

BACKGROUND

Radiation exposure of tissues is associated with inflammatory cell influx. Myeloperoxidase (MPO) is an enzyme expressed in granulocytes, such as neutrophils (PMN) and macrophages, responsible for active chlorine species (ACS) generation. The present study aimed to: 1) determine whether exposure to γ-irradiation induces MPO-dependent ACS generation in murine PMN; 2) elucidate the mechanism of radiation-induced ACS generation; and 3) evaluate the effect of the synthetic lignan LGM2605, known for ACS scavenging properties.

METHODS

MPO-dependent ACS generation was determined by using hypochlorite-specific 3'-(p-aminophenyl) fluorescein (APF) and a highly potent MPO inhibitor, 4-aminobenzoic acid hydrazide (ABAH), and confirmed in PMN derived from MPO-/- mice. Radiation-induced MPO activation was determined by EPR spectroscopy and computational analysis identified tyrosine, serine, and threonine residues near MPO's active site.

RESULTS

γ-radiation increased MPO-dependent ACS generation dose-dependently in human MPO and in wild-type murine PMN, but not in PMN from MPO-/- mice. LGM2605 decreased radiation-induced, MPO-dependent ACS. Protein tyrosine phosphatase (PTP) and protein serine/threonine phosphatase (PSTP) inhibitors decreased the radiation-induced increase in ACS. Peroxidase cycle results demonstrate that tyrosine phosphorylation blocks MPO Compound I formation by preventing catalysis on H2O2 in the active site of MPO. EPR data demonstrate that γ-radiation increased tyrosyl radical species formation in a dose-dependent manner.

CONCLUSIONS

We demonstrate that γ-radiation induces MPO-dependent generation of ACS, which is dependent, at least in part, by protein tyrosine and Ser/Thr dephosphorylation and is reduced by LGM2605. This study identified for the first time a novel protein dephosphorylation-dependent mechanism of radiation-induced MPO activation.

Synthetic secoisolariciresinol diglucoside (LGM2605) inhibits Libby amphibole fiber-induced acute inflammation in mice

BACKGROUND

Exposure to the Libby amphibole (LA) asbestos-like fibers found in Libby, Montana, is associated with inflammatory responses in mice and humans, and an increased risk of developing mesothelioma, asbestosis, pleural disease, and systemic autoimmune disease. Flaxseed-derived secoisolariciresinol diglucoside (SDG) has anti-inflammatory, anti-fibrotic, and antioxidant properties. We have previously identified potent protective properties of SDG against crocidolite asbestos exposure modeled in mice. The current studies aimed to extend those findings by evaluating the immunomodulatory effects of synthetic SDG (LGM2605) on LA-exposed mice.

METHODS

Male and female C57BL/6 mice were given LGM2605 via gavage initiated 3 days prior to and continued for 3 days after a single intraperitoneal dose of LA fibers (200 μg) and evaluated on day 3 for inflammatory cell influx in the peritoneal cavity using flow cytometry.

RESULTS

LA exposure induced a significant increase (p < 0.0001) in spleen weight and peritoneal influx of white blood cells, all of which were reduced with LGM2605 with similar trends among males and females. Levels of peritoneal PMN cells were significantly (p < 0.0001) elevated post LA exposure, and were significantly (p < 0.0001) blunted by LGM2605. Importantly, LGM2605 significantly ameliorated the LA-induced mobilization of peritoneal B1a B cells.

CONCLUSIONS

LGM2605 reduced LA-induced acute inflammation and WBC trafficking supporting its possible use in mitigating downstream LA fiber-associated diseases.

SUMMARY

Following acute exposure to Libby amphibole (LA) asbestos-like fibers, synthetic SDG (LGM2605), a small synthetic molecule, significantly reduced the LA-induced increase in spleen weight and peritoneal inflammation in C57BL/6 male and female mice. Our findings highlight that LGM2605 has immunomodulatory properties and may, thus, likely be a chemopreventive agent for LA-induced diseases.

Applications of Out of Body Lung Perfusion

RATIONALE AND OBJECTIVES

Out of body organ perfusion is a concept that has been around for a long time. As technology has evolved, so have the systems available for out of body perfusion making whole organ preservation for extended evaluation, resuscitation, and discovery routine.

MATERIALS AND METHODS

Clinical use of ex vivo lung perfusion (EVLP) systems has continued to expand as evidence has accumulated to suggest EVLP transplants experience similar mortality, ICU length of stay, length of mechanical ventilation, hospital length of stay, and rates of primary graft dysfunction as conventional lung transplants. In 2017, more lung transplants were performed than any previous year in the US history.

RESULTS

Early success of EVLP has motivated groups to evaluate additional donor types and methods for expanding the donor pool. The ability to keep a lung alive in a physiologically neutral environment opens the ability to better understand organ quality, define pathophysiology in certain disease conditions, and provides a platform for interventions to prevent or repair injury.

CONCLUSION

The next several years will usher in significant changes in understanding and interventions focused on lung injury. This manuscript highlights applications of EVLP to clarify how this system can be used for basic and translational research.

LGM2605 Reduces Space Radiation-Induced NLRP3 Inflammasome Activation and Damage in In Vitro Lung Vascular Networks

Updated measurements of charged particle fluxes during the transit from Earth to Mars as well as on site measurements by Curiosity of Martian surface radiation fluxes identified potential health hazards associated with radiation exposure for human space missions. Designing mitigation strategies of radiation risks to astronauts is critical. We investigated radiation-induced endothelial cell damage and its mitigation by LGM2605, a radioprotector with antioxidant and free radical scavenging properties. We used an in vitro model of lung vascular networks (flow-adapted endothelial cells; FAECs), exposed to gamma rays, low/higher linear energy transfer (LET) protons (3⁻4 or 8⁻10 keV/µm, respectively), and mixed field radiation sources (gamma and protons), given at mission-relevant doses (0.25 gray (Gy)⁻1 Gy). We evaluated endothelial inflammatory phenotype, NLRP3 inflammasome activation, and oxidative cell injury. LGM2605 (100 µM) was added 30 min post radiation exposure and gene expression changes evaluated 24 h later. Radiation induced a robust increase in mRNA levels of antioxidant enzymes post 0.25 Gy and 0.5 Gy gamma radiation, which was significantly decreased by LGM2605. Intercellular cell adhesion molecule-1 (ICAM-1) and NOD-like receptor protein 3 (NLRP3) induction by individual or mixed-field exposures were also significantly blunted by LGM2605. We conclude that LGM2605 is a likely candidate to reduce tissue damage from space-relevant radiation exposure.

Synthetic secoisolariciresinol diglucoside (LGM2605) inhibits myeloperoxidase activity in inflammatory cells

BACKGROUND

Myeloperoxidase (MPO) generates hypochlorous acid (HOCl) during inflammation and infection. We showed that secoisolariciresinol diglucoside (SDG) scavenges radiation-induced HOCl in physiological solutions. However, the action of SDG and its synthetic version, LGM2605, on MPO-catalyzed generation of HOCl is unknown. The present study evaluated the effect of LGM2605 on human MPO, and murine MPO from macrophages and neutrophils.

METHODS

MPO activity was determined fluorometrically using hypochlorite-specific 3'-(p-aminophenyl) fluorescein (APF). The effect of LGM2605 on (a) the peroxidase cycle of MPO was determined using Amplex Red while the effect on (b) the chlorination cycle was determined using a taurine chloramine assay. Using electron paramagnetic resonance (EPR) spectroscopy we determined the effect of LGM2605 on the EPR signals of MPO. Finally, computational docking of SDG was used to identify energetically favorable docking poses to enzyme's active site.

RESULTS

LGM2605 inhibited human and murine MPO activity. MPO inhibition was observed in the absence and presence of Cl-. EPR confirmed that LGM2605 suppressed the formation of Compound I, an oxoiron (IV) intermediate [Fe(IV)O] containing a porphyrin π-radical of MPO's catalytic cycle. Computational docking revealed that SDG can act as an inhibitor by binding to the enzyme's active site.

CONCLUSIONS

We conclude that LGM2605 inhibits MPO activity by suppressing both the peroxidase and chlorination cycles. EPR analysis demonstrated that LGM2605 inhibits MPO by decreasing the formation of the highly oxidative Compound I. This study identifies a novel mechanism of LGM2605 action as an inhibitor of MPO and indicates that LGM2605 may be a promising attenuator of oxidant-dependent inflammatory tissue damage.

Siderophore-mediated iron removal from chrysotile: Implications for asbestos toxicity reduction and bioremediation

Asbestos fibers are highly toxic (Group 1 carcinogen) due to their high aspect ratio, durability, and the presence of iron. In nature, plants, fungi, and microorganisms release exudates, which can alter the physical and chemical properties of soil minerals including asbestos minerals. We examined whether exudates from bacteria and fungi at environmentally relevant concentrations can alter chrysotile, the most widely used asbestos mineral, and lower its toxicity. We monitored the release of iron from chrysotile in the presence of organic acid ligands and iron-specific siderophores derived from bacteria and fungi and measured any change in fiber toxicity toward peritoneal macrophages harvested from mice. Both fungal and bacterial siderophores increased the removal of iron from asbestos fibers. In contrast, organic acid ligands at environmentally relevant concentrations neither released iron from fibers nor helped in siderophore-mediated iron removal. Removal of plant-available or exchangeable iron did not diminish iron dissolution by both types of siderophores, which indicates that siderophores can effectively remove structural iron from chrysotile fibers. Removal of iron by siderophore lowered the fiber toxicity; fungal siderophore appears to be more effective than bacterial siderophore in lowering the toxicity. These results indicate that prolonged exposure to siderophores, not organic acids, in the soil environment decreases asbestos fiber toxicity and possibly lowers the health risks. Thus, bioremediation should be explored as a viable strategy to manage asbestos-contaminated sites such as Brownfield sites, which are currently left untreated despite dangers to surrounding communities.

Radiation Mitigating Properties of Intranasally Administered KL4 Surfactant in a Murine Model of Radiation-Induced Lung Damage

The threat of exposure to ionizing radiation from a nuclear reactor accident or deliberate terrorist actions is a significant public health concern. The lung is particularly susceptible to radiation-induced injury from external sources or inhalation of radioactive particles from radioactive fallout. Radiation-induced lung disease can manifest with an acute radiation pneumonitis and/or delayed effects leading to pulmonary fibrosis. As prior warning of radiation exposure is unlikely, medical countermeasures (MCMs) to mitigate radiation-induced lung disease that can be given in mass-casualty situations many hours or days postirradiation are needed to prevent both early and late lung damage. In this study, KL₄ surfactant (lucinactant) was evaluated as a radiation mitigator in a well-characterized mouse model of targeted thoracic radiation exposure, for its effect on both early (several weeks) and late (18 weeks) lung damage. Here, 120 mg/kg total phospholipid of KL₄ surfactant was administered twice daily intranasally, (enabling intrapulmonary inhalation of drug) to C57BL/6 mice 24 h after a single 13.5 Gy dose of thoracic irradiation (LD₅₀ dose). Both early and chronic phase (2 and 4 weeks and 18 weeks postirradiation, respectively) assessments were performed. Mice were evaluated for evidence of reduced arterial blood oxygenation and early and chronic lung and systemic inflammation, lung fibrosis and oxidative stress. Analysis was done by performing lung function/respiration dynamics and measuring cellular protein content of bronchoalveolar lavage fluid (BALF), and levels of cytokines, 8-iso-prostaglandin F2α, hydroxyproline in lung and plasma, along with evaluating lung histology. The results of this study showed that intranasal delivery of KL₄ surfactant was able to preserve lung function as evidenced by adequate arterial oxygen saturation and reduced lung inflammation and oxidative stress; total white count and absolute neutrophil count was decreased in BALF, as were plasma pro-inflammatory cytokine levels and biomarker of oxidative stress. KL₄ surfactant is a promising MCM for mitigation of lung tissue damage after targeted, thoracic irradiation and has the potential to be developed as a broad-spectrum, multi-use MCM against chemical, biological, radiological or nuclear threat agents with potential to cause lung injury.

Abstract 842: The NALP3 inflammasome and IL-1â signaling link asbestos-induced inflammation with the development of malignant mesothelioma

Exposure to asbestos is causally associated with the development of malignant mesothelioma (MM), a cancer of cells lining the internal body cavity. MM is an aggressive cancer that is resistant to all current therapies. Once inhaled or ingested, asbestos causes inflammation in and around tissues that come in contact with these carcinogenic fibers. Recent studies suggest that inflammation is a major contributing factor in the development of many types of cancer, including MM. The NALP3 inflammasome, including the component ASC, is an important mediator of inflammation that senses extracellular insults, such as infection or asbestos, and activates a signaling cascade resulting in release of mature IL-1â and recruitment of inflammatory cells. To determine if inflammasome-mediated inflammation contributes to asbestos-induced MM, we chronically exposed Asc-deficient mice to asbestos and evaluated tumor incidence, latency and overall survival. Asc-deficient mice showed a significant delay in tumor onset compared to wild-type animals, suggesting that the NALP3 inflammasome plays a role in MM carcinogenesis. We also tested whether inflammation-related release of IL-1â promotes tumor development in an accelerated mouse model of asbestos-induced MM. Nf2+/-;Cdkn2a+/- mice exposed to asbestos in the presence of the IL-1â antagonist, anakinra, showed a 50% longer disease-free survival than in similarly exposed mice given vehicle control, consistent with IL-1â signaling contributing significantly to MM development. Collectively, these studies provide evidence for a link between asbestos-associated inflammation/IL-1â signaling and the development of MM; furthermore, these findings provide rationale for chemoprevention strategies targeting inflammation-related IL-1â signaling in high risk, asbestos-exposed populations.

Citation Format: Yuwaraj Kadariya, Craig W. Menges, Jacqueline Talarchek, Qi Cai, Andres J. Klein-Szanto, Ralph A. Pietrofesa, Melpo Christofidou-Solomidou, Brooke T. Mossman, Arti Shukla, Joseph R. Testa. The NALP3 inflammasome and IL-1â signaling link asbestos-induced inflammation with the development of malignant mesothelioma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 842.

Abstract 1665: Piperlongumine (PPLGM) has potent tumor-radiosensitizing properties in a mouse model of lung cancer

Background: Although over half of all lung cancer patients receive radiation therapy as part of their treatment plan, the therapeutic window of radiation is quite small, and it is difficult to deliver tumoricidal doses of radiation without the development of severe adverse effects in the nearby normal tissues. An agent that could sensitize lung cancer tissue to radiotherapy while sparing damage to normal tissues is still an unmet need. Piperlongumine (PPLGM), a natural product of the plant Piper longum has shown potent anti-carcinogenic properties through an ROS-inducing mechanism. Our hypothesis is that PPLGM will sensitize tumor cells to radiation-induced cell death in an orthotopic murine model of lung cancer. Methods: 7-week old female C57BL/6 mice were injected intravenously with 1×106 Lewis lung carcinoma (LLC) cells. Mouse cohorts (n = 30/group) were administered PPLGM (1 mg/kg of body weight) or vehicle daily by oral gavage initiated 7 days post-LLC injection. At 14 days post-LLC injection, 15 mice per treatment cohort were exposed to 12 Gy thoracic X-ray radiation treatment (XRT). Administration of PPLGM or vehicle continued 7 days post-XRT. Mice were euthanized 14 days post-XRT and evaluated for total lung weight and tumor burden using morphometric analysis. Additionally, we assessed the potential for a dual role of PPLGM (0.1-2.5μM) as a radiosensitizer of cancer cells (LLC) and a radioprotector of normal lung cells (pulmonary microvascular endothelial cells (PMVEC)) via clonogenic survival assays. Results: Using LC/MS/MS we were able to detect significantly elevated levels of PPLGM above baseline in mouse plasma and lung tissue. We observed a significant (p&lt;0.01) increase in lung weight (from 0.14 g to 0.36 g), an indicator of tumor burden, that was significantly (p&lt;0.01) reduced by exposure to a tumoricidal dose of XRT. Importantly, while thoracic XRT-alone reduced tumor burden by 48%, administration of PPLGM+XRT radiosensitized tumor and enhanced tumor killing by XRT, leading to a significant (p&lt;0.05) 56% reduction in lung weight. Morphometric analysis of lung sections confirmed that PPLGM-alone significantly (p&lt;0.01) reduced tumor area relative to vehicle, irrespective of radiation exposure. While exposure to XRT significantly (p&lt;0.01) reduced tumor volume by 65% (from 44.4 ± 7.6% to 15.4 ± 4.5% tumor area), lung sections from mice exposed to PPLGM+XRT significantly (p&lt;0.05) potentiated radiation-induced tumor eradication (reduction in tumor area to 5.6 ± 3.0%) above XRT-only exposure. Furthermore, PPLGM significantly (p&lt;0.05) radiosensitized LLC dose-dependently to gamma-radiation killing, while trending towards radioprotecting normal lung cells. Conclusion: These findings provide evidence that PPLGM is a potent radiosensitizing agent that could aid in the eradication of irradiated tumors in the clinical setting.

Funding: Funded in part by NIH-1R21CA178654-01

Citation Format: Anastasia Velalopoulou, Ralph A. Pietrofesa, Raymond Luke, Katie Reindl, Melpo Christofidou-Solomidou. Piperlongumine (PPLGM) has potent tumor-radiosensitizing properties in a mouse model of lung cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1665.

Asbestos Fiber Preparation Methods Affect Fiber Toxicity

To measure the toxic potential of asbestos fibers-a known cause of asbestosis, lung cancer, and malignant mesothelioma-asbestos minerals are generally first ground down to small fibers, but it is unknown whether the grinding condition itself changes the fiber toxicity. To evaluate this, we ground chrysotile ore with or without water for 5-30 min and quantified asbestos-induced reactive oxygen species generation in elicited murine peritoneal macrophages as an indicator of fiber toxicity. The toxicity of dry-ground fibers was higher than the toxicity of wet-ground fibers. Grinding with or without water did not materially alter the mineralogical properties. However, dry-ground fibers contained at least 7 times more iron than wet-ground fibers. These results indicate that grinding methods significantly affect the surface concentration of iron, resulting in changes in fiber-induced reactive oxygen species generation or toxicity. Therefore, fiber preparation conditions should be accounted for when comparing the toxicity of asbestos fibers between reported studies.

Novel Double-Hit Model of Radiation and Hyperoxia-Induced Oxidative Cell Damage Relevant to Space Travel

Spaceflight occasionally requires multiple extravehicular activities (EVA) that potentially subject astronauts to repeated changes in ambient oxygen superimposed on those of space radiation exposure. We thus developed a novel in vitro model system to test lung cell damage following repeated exposure to radiation and hyperoxia. Non-tumorigenic murine alveolar type II epithelial cells (C10) were exposed to >95% O₂ for 8 h only (O₂), 0.25 Gy ionizing γ-radiation (IR) only, or a double-hit combination of both challenges (O₂ + IR) followed by 16 h of normoxia (ambient air containing 21% O₂ and 5% CO₂) (1 cycle = 24 h, 2 cycles = 48 h). Cell survival, DNA damage, apoptosis, and indicators of oxidative stress were evaluated after 1 and 2 cycles of exposure. We observed a significant (p < 0.05) decrease in cell survival across all challenge conditions along with an increase in DNA damage, determined by Comet analysis and H2AX phosphorylation, and apoptosis, determined by Annexin-V staining, relative to cells unexposed to hyperoxia or radiation. DNA damage (GADD45α and cleaved-PARP), apoptotic (cleaved caspase-3 and BAX), and antioxidant (HO-1 and Nqo1) proteins were increased following radiation and hyperoxia exposure after 1 and 2 cycles of exposure. Importantly, exposure to combination challenge O₂ + IR exacerbated cell death and DNA damage compared to individual exposures O₂ or IR alone. Additionally levels of cell cycle proteins phospho-p53 and p21 were significantly increased, while levels of CDK1 and Cyclin B1 were decreased at both time points for all exposure groups. Similarly, proteins involved in cell cycle arrest was more profoundly changed with the combination challenges as compared to each stressor alone. These results correlate with a significant 4- to 6-fold increase in the ratio of cells in G2/G1 after 2 cycles of exposure to hyperoxic conditions. We have characterized a novel in vitro model of double-hit, low-level radiation and hyperoxia exposure that leads to oxidative lung cell injury, DNA damage, apoptosis, and cell cycle arrest.

Gamma-irradiation produces active chlorine species (ACS) in physiological solutions: Secoisolariciresinol diglucoside (SDG) scavenges ACS - A novel mechanism of DNA radioprotection

Background

Secoisolariciresinol diglucoside (SDG), the main lignan in whole grain flaxseed, is a potent antioxidant and free radical scavenger with known radioprotective properties. However, the exact mechanism of SDG radioprotection is not well understood. The current study identified a novel mechanism of DNA radioprotection by SDG in physiological solutions by scavenging active chlorine species (ACS) and reducing chlorinated nucleobases.

Methods

The ACS scavenging activity of SDG was determined using two highly specific fluoroprobes: hypochlorite-specific 3′-(p-aminophenyl) fluorescein (APF) and hydroxyl radical-sensitive 3′-(p-hydroxyphenyl) fluorescein (HPF). Dopamine, an SDG structural analog, was used for proton ¹H NMR studies to trap primary ACS radicals. Taurine N-chlorination was determined to demonstrate radiation-induced generation of hypochlorite, a secondary ACS. DNA protection was assessed by determining the extent of DNA fragmentation and plasmid DNA relaxation following exposure to ClO⁻ and radiation. Purine base chlorination by ClO⁻ and γ-radiation was determined by using 2-aminopurine (2-AP), a fluorescent analog of 6-aminopurine. Results: Chloride anions (Cl⁻) consumed >90% of hydroxyl radicals in physiological solutions produced by γ-radiation resulting in ACS formation, which was detected by ¹H NMR. Importantly, SDG scavenged hypochlorite- and γ-radiation-induced ACS. In addition, SDG blunted ACS-induced fragmentation of calf thymus DNA and plasmid DNA relaxation. SDG treatment before or after ACS exposure decreased the ClO⁻ or γ-radiation-induced chlorination of 2-AP. Exposure to γ-radiation resulted in increased taurine chlorination, indicative of ClO⁻ generation. NMR studies revealed formation of primary ACS radicals (chlorine atoms (Cl^•) and dichloro radical anions (Cl₂^−•)), which were trapped by SDG and its structural analog dopamine.

Conclusion

We demonstrate that γ-radiation induces the generation of ACS in physiological solutions. SDG treatment scavenged ACS and prevented ACS-induced DNA damage and chlorination of 2-aminopurine. This study identified a novel and unique mechanism of SDG radioprotection, through ACS scavenging, and supports the potential usefulness of SDG as a radioprotector and mitigator for radiation exposure as part of cancer therapy or accidental exposure.

Inflammation-Related IL1β/IL1R Signaling Promotes the Development of Asbestos-Induced Malignant Mesothelioma

Exposure to asbestos is causally associated with the development of malignant mesothelioma, a cancer of cells lining the internal body cavities. Malignant mesothelioma is an aggressive cancer resistant to all current therapies. Once inhaled or ingested, asbestos causes inflammation in and around tissues that come in contact with these carcinogenic fibers. Recent studies suggest that inflammation is a major contributing factor in the development of many types of cancer, including malignant mesothelioma. The NALP3/NLRP3 inflammasome, including the component ASC, is thought to be an important mediator of inflammation in cells that sense extracellular insults, such as asbestos, and activate a signaling cascade resulting in release of mature IL1β and recruitment of inflammatory cells. To determine if inflammasome-mediated inflammation contributes to asbestos-induced malignant mesothelioma, we chronically exposed Asc-deficient mice and wild-type littermates to asbestos and evaluated differences in tumor incidence and latency. The Asc-deficient mice showed significantly delayed tumor onset and reduced malignant mesothelioma incidence compared with wild-type animals. We also tested whether inflammation-related release of IL1β contributes to tumor development in an accelerated mouse model of asbestos-induced malignant mesothelioma. Nf2(+/-);Cdkn2a(+/-) mice exposed to asbestos in the presence of anakinra, an IL1 receptor (IL1R) antagonist, showed a marked delay in the median time of malignant mesothelioma onset compared with similarly exposed mice given vehicle control (33.1 weeks vs. 22.6 weeks, respectively). Collectively, these studies provide evidence for a link between inflammation-related IL1β/IL1R signaling and the development of asbestos-induced malignant mesothelioma. Furthermore, these findings provide rationale for chemoprevention strategies targeting IL1β/IL1R signaling in high-risk, asbestos-exposed populations. Cancer Prev Res; 9(5); 406-14. ©2016 AACR.

Flaxseed lignans enriched in secoisolariciresinol diglucoside prevent acute asbestos-induced peritoneal inflammation in mice

Following acute exposure to crocidolite asbestos fibers, flaxseed lignans, enriched in secoisolariciresinol diglucoside (SDG), significantly reduced peritoneal inflammation, proinflammatory/profibrogenic cytokine release and oxidative/nitrosative stress in mice. Our findings support the potential role of SDG, which is safe and well-tolerated, in the chemoprevention of malignant mesothelioma.

Malignant mesothelioma (MM), linked to asbestos exposure, is a highly lethal form of thoracic cancer with a long latency period, high mortality and poor treatment options. Chronic inflammation and oxidative tissue damage caused by asbestos fibers are linked to MM development. Flaxseed lignans, enriched in secoisolariciresinol diglucoside (SDG), have antioxidant, anti-inflammatory and cancer chemopreventive properties. As a prelude to chronic chemoprevention studies for MM development, we tested the ability of flaxseed lignan component (FLC) to prevent acute asbestos-induced inflammation in MM-prone Nf2^+/mu mice. Mice (n = 16–17 per group) were placed on control (CTL) or FLC-supplemented diets initiated 7 days prior to a single intraperitoneal bolus of 400 µg of crocidolite asbestos. Three days post asbestos exposure, mice were evaluated for abdominal inflammation, proinflammatory/profibrogenic cytokine release, WBC gene expression changes and oxidative and nitrosative stress in peritoneal lavage fluid (PLF). Asbestos-exposed mice fed CTL diet developed acute inflammation, with significant (P < 0.0001) elevations in WBCs and proinflammatory/profibrogenic cytokines (IL-1ß, IL-6, TNFα, HMGB1 and active TGFß1) relative to baseline (BL) levels. Alternatively, asbestos-exposed FLC-fed mice had a significant (P < 0.0001) decrease in PLF WBCs and proinflammatory/profibrogenic cytokine levels relative to CTL-fed mice. Importantly, PLF WBC gene expression of cytokines (IL-1ß, IL-6, TNFα, HMGB1 and TGFß1) and cytokine receptors (TNFαR1 and TGFßR1) were also downregulated by FLC. FLC also significantly (P < 0.0001) blunted asbestos-induced nitrosative and oxidative stress. FLC reduces acute asbestos-induced peritoneal inflammation, nitrosative and oxidative stress and may thus prove to be a promising agent in the chemoprevention of MM.

Metformin use and risk of colorectal adenoma after polypectomy in patients with type 2 diabetes mellitus

BACKGROUND

Existing literature suggests that metformin, the most commonly used biguanide, may lower colorectal cancer risk. Because most colorectal cancers originate in precancerous adenomas, we examined whether metformin use lowered colorectal adenoma risk after polypectomy in patients with type-2 diabetes.

METHODS

Retrospective cohort study of 40- to 89-year-old Kaiser Permanente Northern California patients who had type 2 diabetes, and ≥1 adenoma detected at baseline colonoscopy during 2000 to 2009 and a repeat colonoscopy 1 to 10 years from baseline adenoma diagnosis through 2012. Cox models evaluated the association between metformin use during follow-up and subsequent adenoma diagnoses, controlling for age, race/ethnicity, sex, body mass index, and repeat examination indication.

RESULTS

Study included 2,412 patients followed for a median of 4.5 years; cumulatively, 1,117 (46%) patients had ≥1 adenoma at repeat colonoscopy. Compared with patients not receiving diabetes medications (n = 1,578), metformin-only use (n = 457) was associated with lower adenoma recurrence risk [adjusted HR, 0.76; 95% confidence interval (CI), 0.65-0.89], and the association was stronger with increasing total metformin dose [quartile (Q) 1: HR, 0.90; 95% CI, 0.72-1.12; Q2: HR, 0.89; 95% CI, 0.70-1.12; Q3: HR, 0.80; 95% CI, 0.63-1.01; Q4: HR, 0.50; 95% CI, 0.42-0.60, Ptrend < 0.001]. Findings were unchanged in sensitivity analyses, including evaluating only outcomes during the 3- to 10-year period from baseline.

CONCLUSION

Our study suggests a potential benefit of metformin use in lowering the risk of subsequent adenomas after polypectomy in patients with type 2 diabetes.

IMPACT

Metformin may lower colorectal cancer risk by reducing the formation of precancerous lesions, reinforcing the potential additional benefits of its use.

Abstract 5542: Flaxseed and its lignan component protect from asbestos-induced inflammation in mice

Introduction/Background: Malignant mesothelioma (MM) is a highly lethal form of thoracic cancer with high mortality and poor treatment options. Development of MM has been linked directly to exposure to asbestos fibers, but with a long latency period. Recent studies have indicated that the pathogenesis of asbestos-induced cancers is due, in part, to chronic inflammation and oxidative tissue damage caused by persistent asbestos fibers. Whole grain flaxseed (FS) has known antioxidant, anti-inflammatory and cancer chemopreventive properties. Rationale: As a prelude to future chemoprevention studies, we tested the ability of oral FS and its lignan component, FLC which is enriched in the lignan secoisolariciresinol diglucoside (SDG), to prevent acute asbestos-induced inflammation and inflammatory cytokine release in MM-prone Nf2+/mut;Cdkn2a+/mut mice. Methods: Mice were given a single ip bolus of 400 mM of crocidolite asbestos. They were then placed on 10% FS or 10% FLC supplemented diets 1 day prior (-1) to or after (+1) asbestos instillation. All mice were evaluated 3 days after injection of asbestos for abdominal inflammation and proinflammatory cytokine release. The Nf2+/mut;Cdkn2a+/mut model was selected as it develops an accelerated form of MM when exposed to asbestos. Results: Using liquid chromatography and tandem mass spectrometry (LC/MS/MS), we showed that systemic levels (plasma) of flaxseed lignan metabolites (such as the mammalian lignans Enterolactone (EL) and Enterodiol (ED)) were comparable to those in other mouse models where FS was shown to be an effective chemopreventive agent. The numbers of macrophages (MF) and neutrophils (PMN) in peritoneal lavage fluid indicated that both FS and FLC blunted acute abdominal inflammation induced by asbestos. In addition, the levels of pro-inflammatory cytokines TNF alpha and IL-1 beta in lavage fluid were also decreased by the dietary agents. Conclusions: Our findings suggest that the known chemopreventive properties of FS and its lignan component appear to reduce short-term asbestos-induced inflammation and may thus prove to be a promising dietary agent in the chemoprevention of MM.

Funding: This study was supported in part by Penn's SRP Center Grant (P42 ES027320), “Asbestos fate, exposure, remediation and adverse health effects” from the National Institute of Environmental Health (NIEHS) and 1R03CA180548-02 (MCS).

Citation Format: Steven M. Albelda, Ralph A. Pietrofesa, Craig W. Menges, Joseph R. Testa, Melpo Christofidou-Solomidou. Flaxseed and its lignan component protect from asbestos-induced inflammation in mice. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5542. doi:10.1158/1538-7445.AM2015-5542

Flaxseed modulates inflammatory and oxidative stress biomarkers in cystic fibrosis: a pilot study

Background

Cystic fibrosis (CF) leads to advanced lung disease despite aggressive care. Persistent inflammation and oxidative stress contribute to exacerbations and disease progression. Flaxseed (FS), a dietary botanical supplement with high fiber, lignan phenolics, and omega-3 fatty acids has anti-inflammatory and antioxidant properties in murine models of acute and chronic lung injury. This pilot study was designed to determine whether CF patients could tolerate FS, evaluate circulating FS metabolites, and study biomarkers of lung damage, as a prelude to studying clinical outcomes.

Methods

10 CF patients and 5 healthy volunteers consumed 40 g of FS daily for 4 weeks with safety and tolerability being assessed. Urine was evaluated for systemic oxidative stress and plasma for FS metabolites (enterolignans) and cytokine levels. Buccal swabs were analyzed for gene expression of Nrf2-regulated antioxidant enzymes including Heme Oxygenase-1 (HO-1) and NAD(P)H Quinone Oxidoreductase 1 (NQO1).

Results

All subjects completed the study without serious adverse events. Plasma levels of enterolignans were detectable in both healthy controls and CF volunteers. CF patients were stratified based on plasma enterolignan levels after 2 weeks of FS administration into high- (174 to 535 nM ED and 232 to 1841 nM EL) and low- (0 to 32 nM ED and 0 to 40 nM EL) plasma lignan cohorts. The low enterolignan level cohort experienced a statistically significant drop in urinary inflammatory IsoP and plasma TNFα levels, while demonstrating higher average NQO1 mRNA levels in buccal epithelium compared to high-lignan patients.

Conclusions

This pilot study demonstrated that FS is tolerated by CF patients. FS metabolites could be detected in the plasma. Future studies will assess appropriate dosing and target populations for FS, while exploring clinical outcomes.

Trial registration

ClinicalTrials.gov identifier: NCT02014181.

Space radiation-associated lung injury in a murine model

Despite considerable progress in identifying health risks to crewmembers related to exposure to galactic/cosmic rays and solar particle events (SPE) during space travel, its long-term effects on the pulmonary system are unknown. We used a murine risk projection model to investigate the impact of exposure to space-relevant radiation (SR) on the lung. C3H mice were exposed to (137)Cs gamma rays, protons (acute, low-dose exposure mimicking the 1972 SPE), 600 MeV/u (56)Fe ions, or 350 MeV/u (28)Si ions at the NASA Space Radiation Laboratory at Brookhaven National Laboratory. Animals were irradiated at the age of 2.5 mo and evaluated 23.5 mo postirradiation, at 26 mo of age. Compared with age-matched nonirradiated mice, SR exposures led to significant air space enlargement and dose-dependent decreased systemic oxygenation levels. These were associated with late mild lung inflammation and prominent cellular injury, with significant oxidative stress and apoptosis (caspase-3 activation) in the lung parenchyma. SR, especially high-energy (56)Fe or (28)Si ions markedly decreased sphingosine-1-phosphate levels and Akt- and p38 MAPK phosphorylation, depleted anti-senescence sirtuin-1 and increased biochemical markers of autophagy. Exposure to SR caused dose-dependent, pronounced late lung pathological sequelae consistent with alveolar simplification and cellular signaling of increased injury and decreased repair. The associated systemic hypoxemia suggested that this previously uncharacterized space radiation-associated lung injury was functionally significant, indicating that further studies are needed to define the risk and to develop appropriate lung-protective countermeasures for manned deep space missions.

Flaxseed Mitigates Acute Oxidative Lung Damage in a Mouse Model of Repeated Radiation and Hyperoxia Exposure Associated with Space Exploration

BACKGROUND

Spaceflight missions may require crewmembers to conduct extravehicular activities (EVA). Pre-breathe protocols in preparation for an EVA entail 100% hyperoxia exposure that may last for a few hours and be repeated 2-3 times weekly. Each EVA is associated with additional challenges such as low levels of total body cosmic/galactic radiation exposure that may present a threat to crewmember health. We have developed a mouse model of total body radiation and hyperoxia exposure and identified acute damage of lung tissues. In the current study we evaluated the usefulness of dietary flaxseed (FS) as a countermeasure agent for such double-hit exposures.

METHODS

We evaluated lung tissue changes 2 weeks post-initiation of exposure challenges. Mouse cohorts (n=5/group) were pre-fed diets containing either 0% FS or 10% FS for 3 weeks and exposed to: a) normoxia (Untreated); b) >95% O₂ (O₂); c) 0.25Gy single fraction gamma radiation (IR); or d) a combination of O₂ and IR (O₂+IR) 3 times per week for 2 consecutive weeks, where 8-hour hyperoxia treatments were spanned by normoxic intervals.

RESULTS

At 2 weeks post challenge, while control-diet fed mice developed significant lung injury and inflammation across all challenges, FS protected lung tissues by decreasing bronchoalveolar lavage fluid (BALF) neutrophils (p<0.003) and protein levels, oxidative tissue damage, as determined by levels of malondialdehyde (MDA) (p<0.008) and nitrosative stress as determined by nitrite levels. Lung hydroxyproline levels, a measure of lung fibrosis, were significantly elevated in mice fed 0% FS (p<0.01) and exposed to hyperoxia/radiation or the combination treatment, but not in FS-fed mice. FS also decreased levels of a pro-inflammatory, pro-fibrogenic cytokine (TGF-β1) gene expression levels in lung.

CONCLUSION

Flaxseed mitigated adverse effects in lung of repeat exposures to radiation/hyperoxia. This data will provide useful information in the design of countermeasures to early tissue oxidative damage associated with space exploration.

Oxidative Lung Damage Resulting from Repeated Exposure to Radiation and Hyperoxia Associated with Space Exploration

BACKGROUND

Spaceflight missions may require crewmembers to conduct Extravehicular Activities (EVA) for repair, maintenance or scientific purposes. Pre-breathe protocols in preparation for an EVA entail 100% hyperoxia exposure that may last for a few hours (5-8 hours), and may be repeated 2-3 times weekly. Each EVA is associated with additional challenges such as low levels of total body cosmic/galactic radiation exposure that may present a threat to crewmember health and therefore, pose a threat to the success of the mission. We have developed a murine model of combined, hyperoxia and radiation exposure (double-hit) in the context of evaluating countermeasures to oxidative lung damage associated with space flight. In the current study, our objective was to characterize the early and chronic effects of repeated single and double-hit challenge on lung tissue using a novel murine model of repeated exposure to low-level total body radiation and hyperoxia. This is the first study of its kind evaluating lung damage relevant to space exploration in a rodent model.

METHODS

Mouse cohorts (n=5-15/group) were exposed to repeated: a) normoxia; b) >95% O₂ (O₂); c) 0.25Gy single fraction gamma radiation (IR); or d) a combination of O₂ and IR (O₂+IR) given 3 times per week for 4 weeks. Lungs were evaluated for oxidative damage, active TGFβ1 levels, cell apoptosis, inflammation, injury, and fibrosis at 1, 2, 4, 8, 12, 16, and 20 weeks post-initiation of exposure.

RESULTS

Mouse cohorts exposed to all challenge conditions displayed decreased bodyweight compared to untreated controls at 4 and 8 weeks post-challenge initiation. Chronic oxidative lung damage to lipids (malondialdehyde levels), DNA (TUNEL, cleaved Caspase 3, cleaved PARP positivity) leading to apoptotic cell death and to proteins (nitrotyrosine levels) was elevated all treatment groups. Importantly, significant systemic oxidative stress was also noted at the late phase in mouse plasma, BAL fluid, and urine. Importantly, however, late oxidative damage across all parameters that we measured was significantly higher than controls in all cohorts but was exacerbated by the combined exposure to O₂ and IR. Additionally, impaired levels of arterial blood oxygenation were noted in all exposure cohorts. Significant but transient elevation of lung tissue fibrosis (p<0.05), determined by lung hydroxyproline content, was detected as early as 2 week in mice exposed to challenge conditions and persisted for 4-8 weeks only. Interestingly, active TGFβ1 levels in +BAL fluid was also transiently elevated during the exposure time only (1-4 weeks). Inflammation and lung edema/lung injury was also significantly elevated in all groups at both early and late time points, especially the double-hit group.

CONCLUSION

We have characterized significant, early and chronic lung changes consistent with oxidative tissue damage in our murine model of repeated radiation and hyperoxia exposure relevant to space travel. Lung tissue changes, detectable several months after the original exposure, include significant oxidative lung damage (lipid peroxidation, DNA damage and protein nitrosative stress) and increased pulmonary fibrosis. These findings, along with increased oxidative stress in diverse body fluids and the observed decreases in blood oxygenation levels in all challenge conditions (whether single or in combination), lead us to conclude that in our model of repeated exposure to oxidative stressors, chronic tissue changes are detected that persist even months after the exposure to the stressor has ended. This data will provide useful information in the design of countermeasures to tissue oxidative damage associated with space exploration.