Background: Missense mutations have been identified in the HIF2A gene in patients with erythrocytosis. Results: A mouse knock-in line that models the first described HIF2A mutation exhibits erythrocytosis and pulmonary hypertension. Conclusion:The missense mutation is the cause of erythrocytosis, and is accompanied by pulmonary hypertension. Significance: The study demonstrates sequelae of global Hif-2␣ gain of function.

Abstract:The interaction of asbestos fibers with macrophages generates harmful reactive oxygen species (ROS) and subsequent oxidative cell damage that are key processes linked to malignancy. Secoisolariciresinol diglucoside (SDG) is a non-toxic, flaxseed-derived pluripotent compound that has antioxidant properties and may thus function as a chemopreventive agent for asbestos-induced mesothelioma. We thus evaluated synthetic SDG (LGM2605) in asbestos-exposed, elicited murine peritoneal macrophages as an in vitro model of tissue phagocytic response to the presence of asbestos in the pleural space. Murine peritoneal macrophages (MFs) were exposed to crocidolite asbestos fibers (20 µg/cm 2 ) and evaluated at various times post exposure for cytotoxicity, ROS generation, malondialdehyde (MDA), and levels of 8-iso Prostaglandin F2α (8-isoP). We then evaluated the ability of LGM2605 to mitigate asbestos-induced oxidative stress by administering LGM2605 (50 µM) 4-h prior to asbestos exposure. We observed a significant (p < 0.0001), time-dependent increase in asbestos-induced cytotoxicity, ROS generation, and the release of MDA and 8-iso Prostaglandin F2α, markers of lipid peroxidation, which increased linearly over time.LGM2605 treatment significantly (p < 0.0001) reduced asbestos-induced cytotoxicity and ROS generation, while decreasing levels of MDA and 8-isoP by 71%-88% and 41%-73%, respectively. Importantly, exposure to asbestos fibers induced cell protective defenses, such as cellular Nrf2 activation and the expression of phase II antioxidant enzymes, HO-1 and Nqo1 that were further enhanced by LGM2605 treatment.LGM2605 boosted antioxidant defenses, as well as reduced asbestos-induced ROS generation and markers of oxidative stress in murine peritoneal macrophages, supporting its possible use as a chemoprevention agent in the development of asbestos-induced malignant mesothelioma.

Secoisolariciresinol diglucosides (SDGs) (S,S)-SDG-1 (major isomer in flaxseed) and (R,R)-SDG-2 (minor isomer in flaxseed) were synthesized from vanillin via secoisolariciresinol (6) and glucosyl donor 7 through a concise route that involved chromatographic separation of diastereomeric diglucoside derivatives (S,S)-8 and (R,R)-9. Synthetic (S,S)-SDG-1 and (R,R)-SDG-2 exhibited potent antioxidant properties (EC50 = 292.17 ± 27.71 μM and 331.94 ± 21.21 μM, respectively) which compared well with that of natural (S,S)-SDG-1 (EC50 = 275.24 ± 13.15 μM). These values are significantly lower than those of ascorbic acid (EC50 = 1129.32 ± 88.79 μM) and α-tocopherol (EC50 = 944.62 ± 148.00 μM). Compounds (S,S)-SDG-1 and (R,R)-SDG-2 also demonstrated powerful scavenging activities against hydroxyl [natural (S,S)-SDG-1: 3.68 ± 0.27; synthetic (S,S)-SDG-1: 2.09 ± 0.16; synthetic (R,R)-SDG-2: 1.96 ± 0.27], peroxyl [natural (S,S)-SDG-1: 2.55 ± 0.11; synthetic (S,S)-SDG-1: 2.20 ± 0.10; synthetic (R,R)-SDG-2: 3.03 ± 0.04] and DPPH [natural (S,S)-SDG-1: EC50 = 83.94 ± 2.80 μM; synthetic (S,S)-SDG-1: EC50 = 157.54 ± 21.30; synthetic (R,R)-SDG-2: EC50 = 123.63 ± 8.67] radicals. These results confirm previous studies with naturally occurring (S,S)-SDG-1 and establish both (S,S)-SDG-1 and (R,R)-SDG-2 as potent antioxidants and free radical scavengers for potential in vivo use.

Exposure to asbestos is causally associated with the development of malignant mesothelioma (MM), a cancer of cells lining the internal body cavities. MM 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 MM. 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 activates a signaling cascade resulting in release of mature IL-1β and recruitment of inflammatory cells. To determine if inflammasome-mediated inflammation contributes to asbestos-induced MM, 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 MM incidence compared to wild-type animals. We also tested whether inflammation-related release of IL-1β contributes to tumor development in an accelerated mouse model of asbestos-induced MM. Nf2+/−;Cdkn2a+/− mice exposed to asbestos in the presence of anakinra, an IL-1 receptor (IL-1R) antagonist, showed a marked delay in the median time of MM onset compared to similarly exposed mice given vehicle control (33.1 weeks versus 22.6 weeks, respectively). Collectively, these studies provide evidence for a link between inflammation-related IL-1β/IL-1R signaling and the development of asbestos-induced MM. Furthermore, these findings provide rationale for chemoprevention strategies targeting IL-1β/IL-1R signaling in high risk, asbestos-exposed populations.

While dietary wholegrain Flaxseed (FS) has potent anti-inflammatory, anti-fibrotic and antioxidant properties in murine models of acute and chronic lung injury, the main bioactive ingredient that contributes to these protective effects remains unknown. This study evaluated the lignan complex of FS (FLC) enriched in secoisolariciresinol diglucoside with respect to lung radioprotective and tumor radiosensitizing efficacy using a mouse model of thoracic radiation-induced pneumonopathy. C57/Bl6 mice were fed 0% FS, 10% FS, 10% FLC or 20% FLC for 3 weeks, then irradiated with a single fraction (13.5 Gy) of X-ray radiation treatment (XRT). Mouse survival was monitored for 4 months after irradiation and inflammatory lung parameters were evaluated in bronchoalveolar lavage (BAL) fluid. Gene and protein levels of protective antioxidant and phase II enzymes were evaluated in lung tissue using qPCR and protein levels were verified by immunoblotting. Prolonged administration of the FLC diet was well tolerated and was not associated with any toxicity. Importantly, comparable to the whole grain 10% FS diet, irradiated mice fed 10% and 20% FLC diets displayed improved survival. Improved hemodynamic measurements were also recorded in irradiated mice fed 10% FS or 10% FLC diet compared to irradiated 0% FS fed mice. Flaxseed lignan complex diet also attenuated polymorphonuclear infiltration and overall lung inflammation to levels comparable to those in nonirradiated mice. Flaxseed lignan complex, similarly to FS, up-regulated gene expression as well as protein levels of protective antioxidant enzymes such as heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidoreductase 1 (NQO1). Dietary FLC induced radiosensitizing effects in our murine model of metastatic lung cancer. Importantly, protection of normal tissue does not thwart tumor cell death by radiation treatment. The dietary lignan complex of FS, mainly consisting of the phenolic secoisolariciresinol, is protective against radiation pneumonopathy in vivo while not hindering the tumoricidal effects of radiotherapy.