Integrated -omics approach reveals persistent DNA damage rewires lipid metabolism and histone hyperacetylation via MYS-1/Tip60

Although DNA damage is intricately linked to metabolism, the metabolic alterations that occur in response to DNA damage are not well understood. We use a DNA repair-deficient model of ERCC1-XPF in Caenorhabditis elegans to gain insights on how genotoxic stress drives aging. Using multi-omic approach, we discover that nuclear DNA damage promotes mitochondrial β-oxidation and drives a global loss of fat depots. This metabolic shift to β-oxidation generates acetyl-coenzyme A to promote histone hyperacetylation and an associated change in expression of immune-effector and cytochrome genes. We identify the histone acetyltransferase MYS-1, as a critical regulator of this metabolic-epigenetic axis. We show that in response to DNA damage, polyunsaturated fatty acids, especially arachidonic acid (AA) and AA-related lipid mediators, are elevated and this is dependent on mys-1. Together, these findings reveal that DNA damage alters the metabolic-epigenetic axis to drive an immune-like response that can promote age-associated decline.

Tumor Necrosis Factor Alpha Regulates Skeletal Myogenesis by Inhibiting SP1 Interaction with cis-Acting Regulatory Elements within the Fbxl2 Gene Promoter

FBXL2 is an important ubiquitin E3 ligase component that modulates inflammatory signaling and cell cycle progression, but its molecular regulation is largely unknown. Here, we show that tumor necrosis factor alpha (TNF-α), a critical cytokine linked to the inflammatory response during skeletal muscle regeneration, suppressed Fbxl2 mRNA expression in C2C12 myoblasts and triggered significant alterations in cell cycle, metabolic, and protein translation processes. Gene silencing of Fbxl2 in skeletal myoblasts resulted in increased proliferative responses characterized by activation of mitogen-activated protein (MAP) kinases and nuclear factor kappa B and decreased myogenic differentiation, as reflected by reduced expression of myogenin and impaired myotube formation. TNF-α did not destabilize the Fbxl2 transcript (half-life [t1/2], ∼10 h) but inhibited SP1 transactivation of its core promoter, localized to bp -160 to +42 within the proximal 5' flanking region of the Fbxl2 gene. Chromatin immunoprecipitation and gel shift studies indicated that SP1 interacted with the Fbxl2 promoter during cellular differentiation, an effect that was less pronounced during proliferation or after TNF-α exposure. TNF-α, via activation of JNK, mediated phosphorylation of SP1 that impaired its binding to the Fbxl2 promoter, resulting in reduced transcriptional activity. The results suggest that SP1 transcriptional activation of Fbxl2 is required for skeletal muscle differentiation, a process that is interrupted by a key proinflammatory myopathic cytokine.IMPORTANCE Skeletal muscle regeneration and repair involve the recruitment and proliferation of resident satellite cells that exit the cell cycle during the process of myogenic differentiation to form myofibers. We demonstrate that the ubiquitin E3 ligase subunit FBXL2 is essential for skeletal myogenesis through its important effects on cell cycle progression and cell proliferative signaling. Further, we characterize a new mechanism whereby sustained stimulation by a major proinflammatory cytokine, TNF-α, regulates skeletal myogenesis by inhibiting the interaction of SP1 with the Fbxl2 core promoter in proliferating myoblasts. Our findings contribute to the understanding of skeletal muscle regeneration through the identification of Fbxl2 as both a critical regulator of myogenic proliferative processes and a susceptible gene target during inflammatory stimulation by TNF-α in skeletal muscle. Modulation of Fbxl2 activity may have relevance to disorders of muscle wasting associated with sustained proinflammatory signaling.

Anti-Ferroptosis Drug Enhances Total-Body Irradiation Mitigation by Drugs that Block Apoptosis and Necroptosis

Mitigation of total-body irradiation (TBI) in C57BL/6 mice by two drugs, which target apoptosis and necroptosis respectively, increases survival compared to one drug alone. Here we investigated whether the biomarker (signature)directed addition of a third anti-ferroptosis drug further mitigated TBI effects. C57BL/6NTac female mice (30-33 g) received 9.25 Gy TBI, and 24 h or later received JP4-039 (20 mg/kg), necrostatin-1 (1.65 mg/kg) and/or lipoxygenase-15 inhibitor (baicalein) (50 mg/kg) in single-, dual- or three-drug regimens. Some animals were sacrificed at days 0, 1, 2, 3, 4 or 7 postirradiation, while the majority in each group were maintained beyond 30 days. For those mice sacrificed at the early time points, femur bone marrow, intestine (ileum), lung and blood plasma were collected and analyzed for radiation-induced and mitigator-modified levels of 33 pro-inflammatory and stress response proteins. Each single mitigator administered [JP4-039 (24 h), necrostatin-1 (48 h) or baicalein (24 h)] improved survival at day 30 after TBI to 25% (P = 0.0432, 0.2816 or 0.1120, respectively) compared to 5% survival of 9.25 Gy TBI controls. Mice were administered the drug individually based on weight (mg/kg). Drug vehicles comprised 30% cyclodextrin for JP4-039 and baicalein, and 10% Cremphor-EL/10% ethanol/80% water for necrostatin-1; thus, dual-vehicle controls were also tested. The dual-drug combinations further enhanced survival: necrostatin-1 (delayed to 72 h) with baicalein 40% (P = 0.0359); JP4-039 with necrostatin-1 50% (P = 0.0062); and JP4-039 with baicalein 60% (P = 0.0064). The three-drug regimen, timed to signature directed evidence of onset after TBI of each death pathway in marrow and intestine, further increased the 30-day survival to 75% (P = 0.0002), and there was optimal normalization to preirradiation levels of inflammatory cytokine and stress response protein levels in plasma, intestine and marrow. In contrast, lung protein levels were minimally altered by 9.25 Gy TBI or mitigators over 7 days. Significantly, elevated intestinal proteins at day 7 after TBI were reduced by necrostatin-1-containing regimens; however, normalization of plasma protein levels at day 7 required the addition of JP4-039 and baicalein. These findings indicate that mitigator targeting to three distinct cell death pathways increases survival after TBI.

Fatty acid transporter 2 regulates the suppressive functions of PMN-MDSC in cancer

Polymorphonuclear myeloid derived suppressor cells (PMN-MDSC) are critically important for the regulation of immune responses in cancer, promotion of tumor progression, and metastases. PMN-MDSC contribute to the failure of cancer therapies and their presence in cancer patients correlates with a poor prognosis. However, despite the recent advances in understanding of the PMN-MDSC biology, the mechanisms responsible for their suppressive functions are not well defined. The understanding of these mechanisms is critical important for the development of therapeutic strategies for the specific targeting of PMN-MDSC in cancer. Here, we report a massive accumulation of lipids in PMN-MDSC from tumor bearing mice and from cancer patients, compared to normal neutrophils from tumor free mice and healthy donors, respectively. The content of lipids was much higher in PMN-MDSC infiltrating the tumor. The accumulation of lipids was mediated by the exclusive up-regulation of the fatty acid transporter 2 (FATP2) in PMN-MDSC. The deletion of FATP2 abrogated the suppressive activity of PMN-MDSC in spleens and tumors. The selective pharmacological inhibition of FATP2 altered the activity of PMN-MSC and delayed tumor progression in mice. Importantly, FATP2 inhibition in PMN-MDSC favored tumor regression in mice when combined with checkpoint inhibitors. In conclusion, we show that FATP2 regulates the immune suppressive activity of PMN-MDSC and may represent a new target to selectively inhibit the functions of PMN-MDSC and to improve the effect of immunotherapy.

Transitory presence of myeloid-derived suppressor cells in neonates is critical for control of inflammation

Myeloid-derived suppressor cells (MDSC) are pathologically activated and relatively immature myeloid cells, which are implicated in the immune regulation of many pathologic conditions^1,2. Phenotypically and morphologically MDSC are similar to neutrophils (PMN-MDSC) and monocytes (M-MDSC). However, they have potent suppressive activity, a distinct gene expression profile, and biochemical characteristics³. None or very few MDSC are observed in steady state physiological conditions. Therefore, until recently, accumulation of MDSC was considered as a consequence of pathological process or pregnancy. Here, we report that MDSC with a potent ability to suppress T cells are present during the first weeks of life in mice and humans. MDSC suppressive activity was triggered by lactoferrin and mediated by nitric oxide, PGE2, and S100A9/A8 proteins. Newborn MDSC had a transcriptome similar to that of tumor MDSC, but with a strong up-regulation of an antimicrobial gene network and had potent antibacterial activity. MDSC played a critical role in control of experimental necrotizing enterocolitis (NEC) in newborn mice. MDSC in infants with very low-weight, which are prone to the development of NEC, had lower MDSC levels and suppressive activity than infants with normal weight. Thus, the transitory presence of MDSC may be critical for regulation of inflammation in newborns.

Improved Total-Body Irradiation Survival by Delivery of Two Radiation Mitigators that Target Distinct Cell Death Pathways

The acute lethality of total-body irradiation (TBI) involves damage to multiple organs, including bone marrow and intestine. Ionizing radiation mitigators that are effective when delivered 24 h or later after TBI include the anti-apoptotic drug, JP4-039 and the anti-necroptotic drug, necrostatin-1. In contrast to effective delivery of JP4-039 at 24 h after TBI, necrostatin-1 is most effective when delivery is delayed until 48 h, a time that correlates with the elevation of necroptosis-inducing inflammatory cytokines and necroptosis-induced serine phosphorylation of receptor-interacting serine/threonine-protein kinase-3 (RIP3) in tissues. The goal of this work was to determine whether administration of JP4-039 influenced the optimal delivery time for necrostatin-1. We measured daily levels of 33 proteins in plasma compared to intestine and bone marrow of C57BL/6NTac female mice over a 7-day time period after 9.25 Gy TBI (LD50/30). Protein responses to TBI in plasma were different from those measured in intestine or bone marrow. In mice that were given JP4-039 at 24 h after TBI, we delayed necrostatin-1 delivery for 72 h after TBI based on measured delay in RIP-3 kinase elevation in marrow and intestine. Sequential delivery of these two radiation mitigator drugs significantly increased survival compared to single drug administration.

Preferential Generation of 15-HETE-PE Induced by IL-13 Regulates Goblet Cell Differentiation in Human Airway Epithelial Cells

Type 2-associated goblet cell hyperplasia and mucus hypersecretion are well known features of asthma. 15-Lipoxygenase-1 (15LO1) is induced by the type 2 cytokine IL-13 in human airway epithelial cells (HAECs) in vitro and is increased in fresh asthmatic HAECs ex vivo. 15LO1 generates a variety of products, including 15-hydroxyeicosatetraenoic acid (15-HETE), 15-HETE-phosphatidylethanolamine (15-HETE-PE), and 13-hydroxyoctadecadienoic acid (13-HODE). In this study, we investigated the 15LO1 metabolite profile at baseline and after IL-13 treatment, as well as its influence on goblet cell differentiation in HAECs. Primary HAECs obtained from bronchial brushings of asthmatic and healthy subjects were cultured under air-liquid interface culture supplemented with arachidonic acid and linoleic acid (10 μM each) and exposed to IL-13 for 7 days. Short interfering RNA transfection and 15LO1 inhibition were applied to suppress 15LO1 expression and activity. IL-13 stimulation induced expression of 15LO1 and preferentially generated 15-HETE-PE in vitro, both of which persisted after removal of IL-13. 15LO1 inhibition (by short interfering RNA and chemical inhibitor) decreased IL-13-induced forkhead box protein A3 (FOXA3) expression and enhanced FOXA2 expression. These changes were associated with reductions in both mucin 5AC and periostin. Exogenous 15-HETE-PE stimulation (alone) recapitulated IL-13-induced FOXA3, mucin 5AC, and periostin expression. The results of this study confirm the central importance of 15LO1 and its primary product, 15-HETE-PE, for epithelial cell remodeling in HAECs.

Correction to "Design and Synthesis of a Mitochondria-Targeted Mimic of Glutathione Peroxidase, MitoEbselen-2, as a Radiation Mitigator"

[This corrects the article DOI: 10.1021/ml5003635.].

Intraoral Mitochondrial-Targeted GS-Nitroxide, JP4-039, Radioprotects Normal Tissue in Tumor-Bearing Radiosensitive Fancd2(-/-) (C57BL/6) Mice

We evaluated normal tissue specific radioprotection of the oral cavity in radiosensitive Fanconi Anemia (FA) Fancd2(-/-) mice with orally established tumors using mitochondrial-targeted GS-nitroxide (JP4-039). Adult (10-12 weeks old) Fancd2(+/+), Fancd2(+/-) and Fancd2(-/-) mice (C57BL/6 background) and subgroups with orally established TC-1 epithelial cell tumors received a single fraction of 28 Gy or four daily fractions of 8 Gy to the head and neck. Subgroups received JP4-039 in F15 emulsion (F15/JP4-039; 0.4 mg/mouse), 4-amino-Tempo in F15 emulsion (F15/4-amino-Tempo; 0.2 mg/mouse) or F15 emulsion alone prior to each irradiation. Oral mucosa of Fancd2(-/-) mice showed baseline elevated RNA transcripts for Sod2, p53, p21 and Rad51 (all P < 0.0012) and suppressed levels of Nfkb and Tgfb, (all P < 0.0020) compared with Fancd2(+/+) mice. The oral mucosa in tumor-bearing mice of all genotypes showed decreased levels of p53 and elevated Tgfb and Gadd45a (P ≤ 0.0001 for all three genotypes). Intraoral F15/JP4-039, but not F15/4-amino-Tempo, modulated radiation-induced normal tissue transcript elevation, ameliorated mucosal ulceration and reduced the depletion of antioxidant stores in oral cavity tissue of all genotypes, but did not radioprotect tumors. Mitochondrial targeting makes F15/JP4-039 an effective normal tissue radioprotector for Fancd2(-/-) mice, as well as wild-type mice.

The brown adipocyte protein CIDEA promotes lipid droplet fusion via a phosphatidic acid-binding amphipathic helix

Maintenance of energy homeostasis depends on the highly regulated storage and release of triacylglycerol primarily in adipose tissue, and excessive storage is a feature of common metabolic disorders. CIDEA is a lipid droplet (LD)-protein enriched in brown adipocytes promoting the enlargement of LDs, which are dynamic, ubiquitous organelles specialized for storing neutral lipids. We demonstrate an essential role in this process for an amphipathic helix in CIDEA, which facilitates embedding in the LD phospholipid monolayer and binds phosphatidic acid (PA). LD pairs are docked by CIDEA trans-complexes through contributions of the N-terminal domain and a C-terminal dimerization region. These complexes, enriched at the LD–LD contact site, interact with the cone-shaped phospholipid PA and likely increase phospholipid barrier permeability, promoting LD fusion by transference of lipids. This physiological process is essential in adipocyte differentiation as well as serving to facilitate the tight coupling of lipolysis and lipogenesis in activated brown fat.

DOI:http://dx.doi.org/10.7554/eLife.07485.001

If other energy sources become unavailable, cells fall back on stores of fatty molecules called lipids. These are held in membrane-enclosed compartments in the cell called lipid droplets, which in mammals are particularly abundant in fat cells called adipocytes. There are two main types of adipocytes: white adipocytes have a single giant lipid droplet, whereas brown adipocytes contain many smaller droplets.

Proteins embedded in the membrane that surrounds a lipid droplet help to control the droplet’s growth and when it releases lipids. For example, a protein called CIDEA, which is only found in brown adipocytes, helps lipid droplets to grow by enabling one droplet to transfer its contents to another droplet. However, little is known about how this occurs.

By combining cell biology, biophysical and computer modelling approaches, Barneda et al. investigated how normal and mutant forms of CIDEA affect the growth of lipid droplets. These experiments identified a helix in the structure of CIDEA that embeds it in the membrane, from where it can then interact with CIDEA proteins on other lipid droplets to hold the droplets together. In addition, the helix interacts with a molecule in the lipid droplet membrane called phosphatidic acid. Barneda et al. suggest that this interaction helps to transfer the contents of one droplet to another by making it easier for lipids to move through the droplets’ membranes.

The next challenge is to characterize the mechanisms that control CIDEA activity to influence the formation of the multiple lipid droplets that distinguish brown and BRITE (brown-in-white) adipocytes from white adipocytes. The lipid droplets in brown adipocytes are an important target for research to combat obesity, due to the 'burning' rather than storing of lipids that occurs in these cells.

DOI:http://dx.doi.org/10.7554/eLife.07485.002

Antioxidant Approaches to Management of Ionizing Irradiation Injury

Ionizing irradiation induces acute and chronic injury to tissues and organs. Applications of antioxidant therapies for the management of ionizing irradiation injury fall into three categories: (1) radiation counter measures against total or partial body irradiation; (2) normal tissue protection against acute organ specific ionizing irradiation injury; and (3) prevention of chronic/late radiation tissue and organ injury. The development of antioxidant therapies to ameliorate ionizing irradiation injury began with initial studies on gene therapy using Manganese Superoxide Dismutase (MnSOD) transgene approaches and evolved into applications of small molecule radiation protectors and mitigators. The understanding of the multiple steps in ionizing radiation-induced cellular, tissue, and organ injury, as well as total body effects is required to optimize the use of antioxidant therapies, and to sequence such approaches with targeted therapies for the multiple steps in the irradiation damage response.

Design and Synthesis of a Mitochondria-Targeted Mimic of Glutathione Peroxidase, MitoEbselen-2, as a Radiation Mitigator

Ionizing radiation (IR) triggers mitochondrial overproduction of H₂O₂ and accumulation of lipid hydroperoxides leading to the induction of apoptotic and necroptotic cell death pathways. Given the high catalytic efficiency of the seleno-enzyme glutathione peroxidase (Gpx) toward reduction of lipid hydroperoxides and H₂O₂, we tested the potential of mitochondria-targeted derivatives of ebselen to mitigate the deleterious effects of IR. We report that 2-[[2-[4-(3-oxo-1,2-benzoselenazol-2-yl)phenyl]acetyl]amino]ethyl-triphenyl-phosphonium chloride (MitoPeroxidase 2) was effective in reducing lipid hydroperoxides, preventing apoptotic cell death, and, when administered 24 h postirradiation, increased the survival of mice exposed to whole body γ-irradiation.

Evaluation of potential ionizing irradiation protectors and mitigators using clonogenic survival of human umbilical cord blood hematopoietic progenitor cells

We evaluated the use of colony formation (colony-forming unit-granulocyte macrophage [CFU-GM], burst-forming unit erythroid [BFU-E], and colony-forming unit-granulocyte-erythroid-megakaryocyte-monocytes [CFU-GEMM]) by human umbilical cord blood (CB) hematopoietic progenitor cells for testing novel small molecule ionizing irradiation protectors and mitigators. The following compounds were added before (protection) or after (mitigation) ionizing irradiation: GS-nitroxides (JP4-039 and XJB-5-131), the bifunctional sulfoxide MMS-350, the phosphoinositol-3-kinase inhibitor LY29400, triphenylphosphonium-imidazole fatty acid, the nitric oxide synthase inhibitor (MCF-201-89), the p53/mdm2/mdm4 inhibitor (BEB55), methoxamine, isoproterenol, propranolol, and the adenosine triphosphate-sensitive potassium channel blocker (glyburide). The drugs XJB-5-131, JP4-039, and MMS-350 were radiation protectors for CFU-GM. JP4-039 was also a radiation protector for CFU-GEMM. The drugs XJB-5-131, JP4-039, and MMS-350 were radiation mitigators for BFU-E, MMS-350 and JP4-039 were mitigators for CFU-GM, and MMS350 was a mitigator for CFU-GEMM. In contrast, other drugs were effective in murine assays; TTP-IOA, LY294002, MCF201-89, BEB55, propranolol, isoproterenol, methoxamine, and glyburide but showed no significant protection or mitigation in human CB assays. These data support the testing of new candidate clinical radiation protectors and mitigators using human CB clonogenic assays early in the drug discovery process, thus reducing the need for animal experiments.

Blast exposure in rats with body shielding is characterized primarily by diffuse axonal injury

Blast-induced traumatic brain injury (TBI) is the signature insult in combat casualty care. Survival with neurological damage from otherwise lethal blast exposures has become possible with body armor use. We characterized the neuropathologic alterations produced by a single blast exposure in rats using a helium-driven shock tube to generate a nominal exposure of 35 pounds per square inch (PSI) (positive phase duration ∼ 4 msec). Using an IACUC-approved protocol, isoflurane-anesthetized rats were placed in a steel wedge (to shield the body) 7 feet inside the end of the tube. The left side faced the blast wave (with head-only exposure); the wedge apex focused a Mach stem onto the rat's head. The insult produced ∼ 25% mortality (due to impact apnea). Surviving and sham rats were perfusion-fixed at 24 h, 72 h, or 2 weeks post-blast. Neuropathologic evaluations were performed utilizing hematoxylin and eosin, amino cupric silver, and a variety of immunohistochemical stains for amyloid precursor protein (APP), glial fibrillary acidic protein (GFAP), ionized calcium-binding adapter molecule 1 (Iba1), ED1, and rat IgG. Multifocal axonal degeneration, as evidenced by staining with amino cupric silver, was present in all blast-exposed rats at all time points. Deep cerebellar and brainstem white matter tracts were most heavily stained with amino cupric silver, with the morphologic staining patterns suggesting a process of diffuse axonal injury. Silver-stained sections revealed mild multifocal neuronal death at 24 h and 72 h. GFAP, ED1, and Iba1 staining were not prominently increased, although small numbers of reactive microglia were seen within areas of neuronal death. Increased blood-brain barrier permeability (as measured by IgG staining) was seen at 24 h and primarily affected the contralateral cortex. Axonal injury was the most prominent feature during the initial 2 weeks following blast exposure, although degeneration of other neuronal processes was also present. Strikingly, silver staining revealed otherwise undetected abnormalities, and therefore represents a recommended outcome measure in future studies of blast TBI.

Strategies for discovery of small molecule radiation protectors and radiation mitigators

Mitochondrial targeted radiation damage protectors (delivered prior to irradiation) and mitigators (delivered after irradiation, but before the appearance of symptoms associated with radiation syndrome) have been a recent focus in drug discovery for (1) normal tissue radiation protection during fractionated radiotherapy, and (2) radiation terrorism counter measures. Several categories of such molecules have been discovered: nitroxide-linked hybrid molecules, including GS-nitroxide, GS-nitric oxide synthase inhibitors, p53/mdm2/mdm4 inhibitors, and pharmaceutical agents including inhibitors of the phosphoinositide-3-kinase pathway and the anti-seizure medicine, carbamazepine. Evaluation of potential new radiation dose modifying molecules to protect normal tissue includes: clonogenic radiation survival curves, assays for apoptosis and DNA repair, and irradiation-induced depletion of antioxidant stores. Studies of organ specific radioprotection and in total body irradiation-induced hematopoietic syndrome in the mouse model for protection/mitigation facilitate rational means by which to move candidate small molecule drugs along the drug discovery pipeline into clinical development.

Abstract 2502: Swallowed small molecule GS-nitroxide, JP-4-039, protects the irradiated esophagus

Irradiation induced esophagitis is a dose limiting factor in the treatment of lung cancer, and limits irradiation dose escalation. Intraesophageal manganese superoxide dismutase plasmid liposomes has been shown to protect against irradiation esophagitis (Tarhini, et.al. Human Gene Therapy, in press). A new small molecule drug recently has shown irradiation protection and mitigation in vitro. The new drug (JP4-039) is a nitroxide attached to a mitochondrial targeting sequence. Drug was delivered to the top of the esophagus and the mouse swallowed the F15 formulation, consisting of soy PC: Tween-80: L-glutamyl dioleylamide (4:1:1 w/w) and 8 mg/ml of JP4-039 in PBS. C57BL/6NHsd mice swallowed 100 µl water followed by 100 µl F15-JP4-039 (0.4 mg/mouse) ten minutes before 28 Gy to the upper body. F15-JP4-039 resulted in a significant increase in survival compared to irradiated controls. F15-JP4-039 produced a 30 day survival of 75% compared to 30% for irradiation control (p = 0.0315). The JP4-039 nitroxide signal, detected by EPR, allowed demonstration that drug was in whole esophagus and in the esophageal stem cells. F15-JP4-039 intraorally treated mice were sacrificed at 10 min, 30 min, 1 hr or 5 hr after swallowing the F15-JP4-039, esophagus removed, single cell suspensions made, frozen, and analyzed by EPR. At 10 min, 2971.3 fmoles of JP4-039/million cells were detected, and still detected out to 5 hours, 1081 fmoles/million cells, after irradiation. Sorted side population cells (SP), enriched for stem cells, and nonside population cells (NSP) isolated by flow cytometer were analyzed at 10 min after swallow, by EPR for JP4-039 uptake. The SP cells had 3666.7 fmoles per million cells and the NSP cells had 73.7 fmoles nitroxide per million cells demonstrating that drug had reached stem cells. Thus, intraesophageal administration of small molecule antioxidant GS-nitroxide reduces murine radiation esophagitis, and may be a valuable translational radiation protector to ameliorate clinical esophagitis in lung cancer patients.

Supported by 2U19A1068021-06 and RO1-CA83876-06

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2502. doi:10.1158/1538-7445.AM2011-2502

Intraesophageal administration of GS-nitroxide (JP4-039) protects against ionizing irradiation-induced esophagitis

BACKGROUND/AIM

this study evaluated esophageal radioprotection by the Gramicidin S (GS) derived-nitroxide, JP4-039, a mitochondrial targeting peptide-isostere covalently-linked to 4-amino-Tempo, delivered in a novel swallowed oil-based (F15) formulation.

MATERIALS AND METHODS

C57BL/6HNsd female mice received intraesophageal F15 formulation containing JP4-039 (4 mg/ml in 100 microl volumes) 10 minutes before 28 or 29 Gy upper body irradiation compared to MnSOD-PL (100 microl containing 100 microg plasmid) 24 hours prior to irradiation. Subgroups received 1 × 10(7) C57BL/6HNsd, GFP(+) male bone marrow cells intravenously 5 days after irradiation.

RESULTS

JP4-039/F15 or MnSOD-PL increased survival compared to irradiated controls (p<0.0001 for either). Marrow injection further increased survival (p=0.0462 and 0.0351, respectively). Esophagi removed at 1, 3, 7, 14, 24, or 60 days showed bone marrow-derived cells in the esophagi.

CONCLUSION

intraesophageal GS-nitroxide radioprotection is mediated primarily through recovery of endogenous esophageal progenitor cells.

Programmed cell clearance: molecular regulation of the elimination of apoptotic cell corpses and its role in the resolution of inflammation

Programmed cell clearance is a physiological process of elimination of apoptotic cell corpses. Recent studies have disclosed several ligand-receptor interactions that dictate the recognition or non-recognition of cells by macrophages and other phagocytes. The externalization of the anionic phospholipid, phosphatidylserine is effectively recognized by specific receptors on professional phagocytes and facilitates the clearance of apoptotic cells. Macrophage disposal of cells at sites of inflammation is believed to play an important role in the resolution of the inflammatory process, and recent studies have suggested a role for the NADPH oxidase in the process of macrophage elimination of activated neutrophils. The present review will focus on the molecular regulation of programmed cell clearance, and discuss the role of cell elimination in the resolution of inflammation.

Fat(al) attraction: oxidized lipids act as "eat-me" signals

Phagocytosis of apoptotic cell corpses is a conserved and well-regulated process and is required to maintain tissue homeostasis within an organism. Evidence suggests that apoptotic cell engulfment by macrophages is dependent upon the externalization of phosphatidylserine (PS) on the plasma membrane of the dying cell. Furthermore, oxidation of PS and other phospholipids may serve to facilitate cell corpse removal. However, our understanding of how these various lipid "eat-me" signals are recognized by macrophages has been limited. Using a combination of cellular and animal models, along with an array of biophysical methods, Hazen and his associates (Greenberg et al., J. Exp. Med., 2006, 203, 2613-2625;Li et al., Biochemistry, 2007, 46, 5009-5017) have now identified the scavenger receptor CD36 as a putative receptor for oxidized PS on apoptotic cells; moreover, they have deduced the conformation of the oxidized lipid ligand that is recognized by this receptor, thus providing structural insight into how phagocytes recognize senescent or apoptotic cells.

Effects of MnSOD-Plasmid Liposome Gene Therapy on Antioxidant Levels in Irradiated Murine Oral Cavity Orthotopic Tumors

Intraoral manganese superoxide dismutase (SOD2)-plasmid liposome (PL) radioprotective gene therapy prolongs the survival of mice with orthotopic oral cavity tumors within the irradiated field. To determine whether the mechanism involved effects in antioxidant pool, C57BL/6J mice bearing orthotopic oral cavity squamous cell carcinoma SCC-VII tumors received intraoral or intravenous MnSOD-PL gene therapy 24 h prior to 18 Gy irradiation to the head and neck region. Glutathione (GSH) levels and levels of radiation-generated nitric oxide and peroxynitrite were measured in orthotopic tumors and in adjacent oral mucosa. MnSOD-PL transfection of the SCC-VII tumor cells, but not normal embryo fibroblasts, produced acute radiosensitization. Furthermore, SCC-VII tumor cells demonstrated increased relative hydrogen peroxide (the product of MnSOD superoxide dismutation)-induced apoptosis in vitro. Radiation decreased levels of GSH and increased GPX in both tumor and normal cells in vitro, effects that were blunted by MnSOD-PL treatment. In vivo irradiation decreased GSH and GPX more effectively in tumors, and the decrease was not reversed by MnSOD-PL therapy. Intravenous but not intraoral administration of epitope-tagged hemagglutinin MnSOD-PL resulted in significant uptake in orthotopic tumors and decreased the levels of radiation-induced nitric oxide and peroxynitrite. Thus normal tissue radioprotective MnSOD-PL gene therapy radiosensitizes tumor cell lines in vitro and has a therapeutic effect on orthotopic tumors in part through its effects on tumor antioxidants.