ISOPTWPO Today

A PRIL 2015, N O 15

ISOPTWPO Today

BIOGRAPHY Dr.Maria Klawe became president of Harvey Mudd College in July 2006. Before joining Harvey Mudd College, she served as dean of engineering and a professor of computer science at Princeton University, and held several positions at the University of British Columbia, including dean of science, vice-president of student and academic services, and head of computer science. She has also worked at IBM Research in California, the University of Toronto, and Oakland University. She received her doctorate and Bachelor of Science degrees in mathematics from the University of Alberta.

Dr. Klawe has made significant research contributions in several areas of mathematics and computer science including functional analysis, discrete mathematics, theoretical computer science, and the design and use of interactive-multimedia for mathematics education. Her current research interests include discrete mathematics, serious games and assistive technologies.

One of her lifelong passions is to increase the participation of women and other under-represented groups in science and engineering, especially in areas such as computer science where their participation has significantly declined over the past three decades. She was the first woman to serve on the board of the Computing Research Association and co-founded CRA-W, the highly successful Committee on the Status of Women. She has served on the board of Anita Borg Institute for Women and Technology since its inception and as chair from 2003-2008. From 1997-2002 she held the IBM-NSERC Chair for Women in Science and Engineering for British Columbia and the Yukon, and led several research studies and projects related to increasing the participation of women in computing.

Dr. Klawe joined the Microsoft Board in March 2009. She also serves on the board of Broadcom Corporation. She is a past president of the Association of Computing Machinery (ACM), a trustee of the Mathematical Sciences Research Institute at Berkeley, and a member of the board of Math for America. She is a fellow of the ACM and the Canadian Information Processing Society, and the recipient of numerous awards including the Computing Research AssociationĹ s Nico Habermann Award. Dr. Klawe holds several honorary doctorate degrees in the areas of science and mathematics.

Follow Dr.Maria Klawe @mariaklawe — Image Credit:Microsoft.

ISOPTWPO The International Space Agency (ISA) was founded by Mr. Rick Dobson, Jr., a U.S. Navy Veteran, and established as a non-profit corporation for the purpose of advancing Man’s visionary quest to journey to other planets and the stars.

ISOPTWPO(International Space Flight & Operations - Personnel Recruitment, Training, Welfare, Protocol Programs Office) is part of ISA, which support research on Human Space Flight and its complications. ISOPTWPO will research on NASA’S Human Research Roadmap. It will also research on long duration spaceflight and publish special issues on one year mission at ISS and twin study.

Mr. Martin Cabaniss is director and Mr. Abhishek Kumar Sinha is Assistant Director of ISOPTWPO. Ad Astra ! To The Stars! In Peace For All Mankind !

Mr. Rick R. Dobson, Jr.(Veteran U.S Navy) — International Space Agency (ISA)

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IN THIS EDITION

Acute - 7: What are the most effective biomedical or dietary countermeasures to mitigate acute radiation risks?

Biological countermeasures under development for use in clinical practice and against radiological threats are expected to provide risk reduction for low-LET radiation delivered at high doses and dose rates. However, their effectiveness at low dose rates and for high-LET solar particle radiation are less clear and may be distinct from those required for the other space radiation risks of cancer, CNS, and degenerative tissue effects. Mechanistic studies of possible biochemical routes for countermeasure actions must be combined with approaches to extrapolate model system results to humans for such countermeasures to be used operationally by NASA. Read More:NASA

Contents 1.Biomedical or Dietary countermeasures to mitigate Acute Radiation Risks

2.EX-RAD, THE U.S. MILITARY’S RADIATION WONDER DRUG

3.Radiation and Normal Tissue Complications

4.CLT-008: FIGHTING ACUTE RADIATION SYNDROME

5.Îł-Tocotrienol Protects against Mitochondrial Dysfunction and Renal Cell Death 6.TOCOTRIENOL AS A POTENTIAL ANTICANCER AGENT

7.Phytochemicals as radioprotective agents

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Biomedical or Dietary countermeasures to mitigate Acute Radiation Risks Human acute radiation syndrome (ARS) follows intense, acute whole-body or significant partial-body radiation, of doses > 1 Gy, delivered at relatively high rates. Clinical components of ARS include the hematopoietic sub-syndrome (H-ARS, 2 – 6 Gy),gastrointestinal sub-syndrome (GIS; 6 – 8 Gy) and the cerebrovascular (> 8 Gy)sub-syndrome [1]. Dividing ARS into these ’sub-syndromes’ oversimplifies the clinical reality of ARS as it often involves complex, concurrent and multi-organ dysfunctions.

Cerebrovascular sub-syndrome is considered incurable, whereas H-ARS alone or in combination with GIS, are more likely to be amenable to countermeasures; therefore, the later two sub-syndromes are specific targets for the development of novel medical countermeasures (MCM). There are several biologics at different developmental stages to be considered as MCM for ARS[2].

There are several biologics under development as radiation MCM for ARS (Tables 1 and 2). Neupogen and two others, entolimod and HemaMax, have considerable efficacy and safety profiles and have received FDA Investigational New Drug status for clinical investigation. Mechanistic studies have suggested that the various countermeasures for ARS have different modes of action (Figure).

Radiation countermeasures fall into three broad classes: protectors, mitigators and therapeutics. Radioprotectors are administered before exposure to prevent damage. Radiation mitigators are administered shortly after radiation exposure, before exposure symptoms manifest, to accelerate recovery or repair. Radiation therapeutics or treatments are given after symptoms manifest to stimulate repair or regeneration. Numerous candidate radiation countermeasures (specifically radioprotectants and radiomitigators) have been identified and are currently being developed largely for US FDA approval and licensing. Some agents have recently been applied for and received patents (Table 5).

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E X-R AD , THE U.S. M ILITARY ’ S R ADIATION W ONDER D RUG U. S. military has developed a radiation protection drug known as Ex-Rad that can give protection through DNA repair against otherwise lethal dosages of radiation. Ex-Rad, which is administered as an injection or orally, can be given either before or after exposure. While Ex-Rad officials are continuing to work with the FDA, it has successfully cleared two clinical studies showing it is safe.

Ex-Rad’s life-saving utility isn’t limited to countering radiation exposure near a compromised nuclear facility. From potentially enabling cancer patients to withstand greater levels of radiation to protecting soldiers deployed into radioactive "hot zones," this drug delivers critical help and hope.

During most of the last decade, U.S. military scientists at the Armed Forces Radiobiology Research Institute have worked with some of the best scientists in the American private sector to develop this radiation protection wonder drug.

About Ex-RAD Ex-RAD (recilisib sodium, ON 01210.Na) is a medical countermeasure that protects cells from the harmful effects of ionizing radiation. Ex-RAD is not a free-radical scavenger, chelator, or cell cycle arrestor. Four clinical trials of Ex-RAD have been successfully completed in healthy adults and have demonstrated acceptable tolerability with minimal adverse events in healthy volunteers. Current development efforts for Ex-RAD include both prophylactic (i.e. use prior to exposure to harmful radiation) as well as therapeutic (use after exposure) applications. Ex-RAD is being ˇ which permits mardeveloped in collaboration with the U.S. Department of Defense under the FDA S ¸Animal Rule,T keting approval after demonstrating safety in clinical trials in healthy human volunteers and evidence of efficacy in animals when human efficacy studies are not ethical or feasible. The molecule’s novel mode of action involves the enhancement of cellular DNA repair pathways and key elements of the DNA damage cascade in response to harmful radiation. Ex-RAD is available by injection and oral administration for convenient use and rapid distribution.

Ex-RAD is a registered trademark of Onconova Therapeutics, Inc.

By Van D. Hipp Jr.,Former Deputy Assistant Secretary,U.S. Army.

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Radiation and Normal Tissue Complications Initial studies of radioprotectors and mitigators typically involve investigation of the acute effects of total-body irradiation(TBI) in rodents, using survival as the end-point.While TBI affects multiple organ systems, death in humans and rodents in the first 30 days is mainly due to two mechanisms: (1) Gastrointestinal (GI) syndrome,which often leads to death within 10-12 days after exposure to 8-20Gy of Îł -rays, due to fluid and electrolyte imbalance and bacterial translocation (sepsis); (2) Hematopoietic syndrome,which leads to death within 30 days after exposure to 3 - 8Gy, due to neutropenia and thrombocytopenia.

The effects of radiation within the first 30 days are called "acute radiation syndrome (ARS)" or "radiation sickness."

ARS follows a similar pattern in humans and rodents, except that the LD50/30 values (dose of whole body exposure required to reduce survival to 50% by day 30, without medical support) are lower in humans (ca.3.5-4Gy) than in rodents (ca. 7 - 9Gy).

An effective radioprotector/mitigator should improve a 30-day survival in rodents by protecting against GI syndrome, hematopoietic syndrome, or both. It should also have a convenient mode of delivery (e.g., by oral, subcutaneous, or intramuscular routes).

For hematopoietic syndrome, it is thought that death within the first 30 days is due to depletion of hematopoietic progenitor cells (HPCs) for white blood cell and megakaryocyte lineages, leading to neutropenia and thrombocytopenia. HPCs are more radiosensitive than pluripotent stem cells (HSCs).

However, irradiated HSCs take a long time (30 days or so) to be recruited into the cell cycle and reconstitute neutrophils and platelets. Thus, if an individual survives for 30 days,HSCs will have sufficient time to reconstitute the various bone marrow lineages, and further hematological support is not required.

Gastrointestinal syndrome is due to depletion of intestinal stem cells(ISCs)located at or near the base of the intestinal crypts .These cells die rapidly after exposure to a high dose of radiation by apoptosis. PUMA (p53 up-regulated modulator of apoptosis) appears to be a crucial mediator of apoptosis in ISCs. Crypts become progressively denuded as apical cells are shed and ISCs die or enter cell cycle arrest due to DNA damage.The villus length,number of villi percircumference,and mitotic index decrease starting about four days after irradiation. Death due to GI syndrome in mice usually occurs within 10-15 days, depending upon the mouse strain and radiation dose.However,in surviving animals(e.g.,due to treatment with a radioprotector), crypts begin to regenerate(as indicated by an increase in DNA synthesis) by day 15 or so.

Although the GI system and bone marrow are rapidly reacting systems that contribute to ARS following TBI,high dose partial body radiation that includes the lungs can result in delayed tox icity that occurs 3-10 months after exposure. This syndrome is related to repeated cycles of inflammation,eventually resulting in pulmonary fibrosis and death,depending on the dose and vol ume of lung irradiated . The skin and kidneys are also "radiosensitive" tissues in which severe effects can be observed in individuals who receive high dose partial body irradiation. ARS is the best understood consequence of TBI. Less is known about the later effects of high dose partial body irradiation and the late consequences of ARS. Much of what we know about the sensitivity of specific tissues and organs to radiation comes from early experience with radiation therapy,before the radiation toler ances of the set issues andorgans were established and before the introduction of skin sparing megavoltage radiation.

Although IR can directly target critical cellular macromolecules such as DNA, water (H2 O) is by far the most abundant molecule within cells and is thus the most likely target for radiolysis by high energy photons. As shown in Figure 1, molecular oxygen (O2 ) is a central component involved in the formation of highly reactive free radicals; and so it is not surprising that high concentrations of O2 potentiate the effects of IR, while low concentrations of O2 (hypoxia) protect cells and tissues from IR, the so-called "oxygen effect".

The most damaging species of free radical is the hydroxyl radical (OH). DNA is the most critical target for cell survival, but significant damage to other cellular molecules such as proteins and lipids is also produced . These oxidative radicals produce two major forms of DNA damage, double-strand breaks (DSBs) (the most lethal form of damage) and base lesions (which are repaired by the base excision repair pathway).

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Gap’s in NASA Human Reserach Roadmap During the processing of base lesions, single-strand DNA breaks (SSBs) are generated, which are then repaired by one of several mechanisms that involves a scaffolding protein, DNA polymerase, and a DNA ligase. If two base lesions on opposite strands are close enough, the result can be a DSB. In DSB repair, a DNA-damaging signaling/repair complex accumulates at and around the DSB site. The "MRN" complex of three proteins (MRE11-RAD50-NBS1) senses the damage and binds to the broken DNA ends. Following MRN, ataxia telangiectasia mutated (ATM), a nuclear serine/threonine protein kinase, is recruited to the MRN complex and activated through autophosphorylation, after which it phosphorylates a number of substrate proteins on SQ/TQ motifs. The eventual result is the coating of DNA surrounding the break with a set of proteins that orches- trates the DNA repair process. These events are reviewed elsewhere.

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Gap’s in NASA Human Reserach Roadmap DSB repair can proceed by two pathways: (1) Homology- directed repair (HDR) (orchestrated by ATM/BRCA1/BRCA2 sig- naling), which is an error-free process; (2) Non-homologous end joining (NHEJ), which can be accurate or can lead to significant sequence deletions and translocations [orchestrated by DNA-dependent protein kinase (DNA-PK)].

HDR occurs only in S-phase and G2, since it requires a sister chromatid as a template for DNA repair synthesis, while NHEJ can occur in any phase of the cell cycle, but preferably occurs during G1.

In addition to mediating DNA repair, ATM signaling also results in activation of DNA damage-dependent cell cycle checkpoints (e.g., S and G2/M), which allows time for damaged cells to repair their damage, so that it is not passed on to daughter cells (Figure 1). ATM also orchestrates the "cell fate" decision. Cells that have too much damage to repair are pushed into rapid death by apoptosis or, alternatively, permanent cell cycle arrest ("senescence") or delayed death through mitotic catastrophe. ATM can also stimulate cell survival pathways (e.g., the anti-apoptotic transcription factor NF-κ B). If cells protected by NF-κ B signaling have not fully repaired their DNA damage, this can result in cells with genomic instability, which can result in the accumulation of mutations and, eventually, carcinogenesis, a late effect that usually occurs at a minimum of 3-5 years after radiation exposure.

Depending on the dose and proportion of the body exposed to radiation, the relative apoptotic vs. surviving GI and hematopoietic stem/progenitor cell populations may result in ARS (described above), which can lead to death or survival and recovery.

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CLT-008: F IGHTING A CUTE R ADIATION S YNDROME Cellerant Therapeutics’ CLT-008 (myeloid progenitor cells for infusion) has the potential to rescue a substantial number of ARS victims. Derived from adult blood-forming stem cells, CLT-008 has been shown in animal models to be effective in preventing lethal bacterial and fungal infections after radiation exposure. CLT-008 is an off-the-shelf frozen product which can be shipped to the disaster site, thawed, and infused into patients through a standard IV line. Once infused, CLT-008 rapidly proliferates into infection-fighting neutrophils and platelets necessary for blood clotting.

CLT-008 is designed for use even if administered several days after exposure. It can be stockpiled in a secure location, ready for rapid delivery to the site of an attack. CLT-008 acts as a temporary therapy until the individual’s own blood-forming system recovers and begins to generate its own infection-fighting and clotting cells. And it works synergistically with growth factors like G-CSF to provide protection quickly.

CLT-008 Offers Several Unique Characteristics Once approved for use, CLT-008 should provide life-saving therapy following exposure to radiation. As an off-theshelf cell-based medicine, it offers several advantages over traditional cell transplants and non-cellular approaches to radiation exposure: 1. CLT-008 is designed to be an off-the-shelf cell-based medicine. CLT-008 should not require tissue matching, in contrast to stem cell transplants, which require a matched donor.

2. CLT-008 is being optimized for administration in mass casualty situations. Because damage to the hematopoietic (blood-forming) system typically does not appear until after 3-7 days of exposure, there will be time to triage and identify those in need of CLT-008 therapy. The practical utility of most small molecule therapies is limited, as they must be administered either before exposure or within hours after exposure.

3. CLT-008 can be stockpiled. Current cell therapies for neutropenia are not amenable to large-scale production or long-term storage. CLT-008, however, can be manufactured and stockpiled: hundreds of doses could be stored on nuclear-powered ships and submarines, and thousands of doses could be stored in regional stockpiles for national emergencies.

4. A single infusion of CLT-008 should provide extended protection. A single infusion of CLT 008 is designed to yield an extended period of therapeutic coverage, in contrast to the multiple doses required with other treatments.

Safety Study of Human Myeloid Progenitor Cells (CLT-008) After Chemotherapy for Leukemia Ex vivo expanded human myeloid progenitor cells (hMPCs; CLT-008) have the potential to accelerate neutrophil recovery and decrease the risk of febrile neutropenia and infection in patients receiving chemotherapy for acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), chronic myeloid leukemia (CML), or high-risk myelodysplasia (MDS). In this study, the safety, tolerability and activity of CLT-008 administered after "standard of care" cytarabine-based consolidation or induction/re-induction chemotherapy will be determined by monitoring for adverse reactions, infusion reactions, graft-versus host disease (GVHD), neutrophil and platelet recovery, hMPC persistence, infections and complications.

References: 1.Cellerant Therapeutics, Inc. 2.National Cancer Institute

Gap’s in NASA Human Reserach Roadmap γ Tocotrienol Protects against Mitochondrial Dysfunction and Renal Cell Death Vitamin E is composed of naturally occurring α−, β−, γ−, and δ -tocopherols and α−, β−, γ−, and δ-tocotrienols that are synthesized exclusively by photosynthetic organisms. Tocopherols are commonly found in high concentrations in a wide variety of foods, whereas tocotrienols are relatively rare and found only in a few fruit and vegetable oils, including palm oil. Vitamin E isomers are well known for their antioxidant properties that prevent oxidative damage to polyunsaturated fatty acids and other events driven by free radicals.

The γ− tocotrienol (GT3) has significant antiproliferative, proapoptotic, and anti-invasive activities in different types of neoplastic cells at concentrations that have little or no effect on normal cell growth and function . Although the exact mechanisms mediating GT3 actions are unknown, postulated mechanisms include the inhibition of prosurvival signaling downstream of the tyrosine kinase receptor mediated by c-Src and phosphoinositide-3 kinase. The antiproliferative effects of GT3 may result, at least in part, from its inhibitory effects on mitogenic signaling from the epidermal growth factor receptor, resulting in the reduction of Akt and nuclear factor κB activities.

Recent data have also shown potent radioprotective effects of tocotrienols, GT3 in particular. GT3 ameliorates intestinal injury, enhances recovery of the intestine after irradiation, decreases vascular oxidative stress, and improves survival in animals subjected to total body irradiation . GT3- conferred protection and reduction of mortality are associated with accelerated recovery of hematopoietic progenitor and white blood cells, neutrophils, monocytes, platelets, and reticulocytes after lethal radiation doses in mice . It is noteworthy that the radioprotective action of GT3 against vascular injury is mediated through a HMG-CoA reductase-dependent mechanism. Chronic treatment of rats with a tocotrienol-rich fraction from palm oil decreases K2 2Cr2 O7 - induced kidney injury by decreasing morphological damage to renal proximal tubules and improving renal proximal tubular function, glomerular filtration rate, and cellular redox status. However, it is unknown which component of the tocotrienol-rich fraction is responsible for renal protection against K2 2Cr2 O7 - induced toxicity. Chronic supplementation with GT3, one of the components of the tocotrienol-rich fraction, protects the heart against ischemia and reperfusion. Furthermore, GT3 protects astrocytes from H2 O2 -induced oxidative stress and apoptosis. γ Tocotrienol Blocks ROS Production in Oxidant- Injured RPTC TBHP(tert-butyl hydroperoxide), a model oxidant, was used to produce oxidative stress in RPTCs(renal proximal tubular cell). Reactive oxygen/nitrogen species production increased to 300% of controls after TBHP-induced injury (Fig. 2A). Pretreatment with 1 and 2µM GT3 reduced TBHP-induced ROS(reactive oxygen species) production to 215 and 226% of controls, respectively, but did not block ROS generation in injured RPTCs (Fig. 2A).

Pretreatment of RPTC with either 5, 10, or 20 µ M GT3 blocked TBHP-induced ROS generation (Fig. 2A; data not shown). In contrast, pretreatment with 5 and 10µM AT did not block ROS generation after TBHP exposure in RPTCs (Fig. 2B). These data show that GT3 prevents TBHP-induced ROS production in a dose-dependent manner and that 5 to 20µM GT3 is the most effective in blocking ROS production. In contrast, at the same concentrations, AT is not an effective antioxidant in TBHP-injured RPTCs. γ Tocotrienol Prevents Oxidant-Induced RPTC Lysis and Death LDH release is a measure of RPTC lysis and a marker of cell death by oncosis. LDH release was 3.2 ± 0.4% in controls, suggesting that approximately 3% of RPTCs treated with the diluent (dimethyl sulfoxide) had undergone lysis during the duration of the experiment, which most likely reflects cell turnover (Fig. 3A; 0% is equivalent to no cell lysis; 100% is equivalent to lysis of all cells). GT3 treatment had no effect on LDH release and morphology in noninjured RPTCs up to the concentration of 20µM (Fig. 3A; data not shown).

However, the exposure of RPTCs to 50µM GT3 for 24 h caused changes in mitochondrial morphology without producing apparent changes in cell viability and mitochondrial respiration (data not shown). Furthermore, pretreatment with 50µM GT3 did not protect against the damage in oxidant-injured RPTC monolayers (data not shown).

LDH release increased to 26.0±1.9 and 54.0±2.7% at 4 and 24 h after TBHP-induced injury, respectively, demonstrating that more than 50% of cells were lethally injured and lysed within 24 h after the exposure to oxidant (Fig. 3A). Pretreatment with 5 and 10µM GT3 blocked the increase in LDH release at 4 h after TBHP exposure (Fig. 3A).

Furthermore, GT3 reduced LDH release from 54.0±2.7 to 11.8± 0.6% at 24 h after TBHP-induced injury (Fig. 3A).

No increase in apoptosis was found in TBHP-treated RPTCs (3.6±0.8 versus 5.3± 0.7% in TBHP-injured and control RPTCs, respectively) or RPTCs treated with GT3 and TBHP (data not shown).

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In contrast, pretreatment with 5 and 10µM AT decreased cell lysis to 22 and 21%, respectively, at 4 h after TBHP exposure (Fig. 3B). These data show that GT3 blocks RPTC lysis at 4 h after oxidant-induced injury and markedly decreases RPTC lysis at a later time point after injury, whereas γ -tocopherol is only partially protective at the same concentrations.

γ-Tocotrienol Improves Mitochondrial Respiration in RPTCs Injured by Oxidant State 3 respiration was used to assess the effects of GT3 and AT on the respiratory capacity of mitochondria in injured RPTCs. At 4 h after TBHP exposure, state 3 respiration in TBHP-injured RPTCs decreased to 50% of controls, which demonstrates significant impairment of mitochondrial electron transport chain and respiratory capacity (Fig. 4). Pretreatment of RPTCs with 1 and 2µM GT3 did not improve state 3 respiration in TBHP injured RPTCs, whereas pretreatment with 5 and 10 MGT3 blocked TBHP-induced decreases in state 3 respiration (Fig. 4A). Likewise, pretreatment with 5 and 10µM AT prevented the decreases in state 3 respiration in oxidant-injured RPTCs(Fig. 4B).

These data show that both GT3 and AT protect the respiratory capacity of mitochondria in RPTCs after oxidantinduced injury.

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γ-Tocotrienol Prevents Mitochondrial Uncoupling and Loss of Mitochondrial Membrane Potential in OxidantInjured RPTCs The respiratory control ratio (RCR) is used as a measure of coupling of mitochondrial respiration and oxidative phosphorylation. RCR in noninjured RPTCs was 5.9±0.60 (Fig. 5A), demonstrating tight coupling of mitochondrial respiration and oxidative phosphorylation. RCR decreased by 47% after the exposure of RPTCs to TBHP (Fig. 5A).

Pretreatment with 1 and 2µM GT3 improved RCR in TBHP-injured RPTCs.Pretreatment of TBHP-injured RPTCs with 5 and 10µM GT3 restored RCR in TBHP injured RPTCs (Fig. 5A). Pretreatment with 5 and 10µM AT resulted in RCR in oxidant-injured RPTCs equivalent to 82% of controls (Fig. 5B). These data show that GT3 prevents and AT decreases mitochondrial uncoupling induced by an oxidant in RPTCs. ∆Ψm is created by mitochondrial respiration using energy released from the oxidation of substrates to support the translocation of protons from the matrix across the inner mitochondrial membrane. The percentage of RPTCs with depolarized mitochondria was used to assess changes in ∆Ψm (Fig. 5C). Treatment of noninjured RPTCs with 5µ M GT3 had no effect on ∆Ψm . Exposure to TBHP induced mitochondrial depolarization in 56% of RPTCs (Fig. 5C).

Treatment of RPTCs with 5µ M GT3 before TBHP injury restored the number of RPTCs with polarized mitochondria to control levels at both 4 and 24 h after oxidant exposure (Fig. 5C). These data show that GT3 prevents the loss of mitochondrial membrane potential in RPTCs injured by an oxidant.

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γ-Tocotrienol Maintains the Function and Activity of F0 F1 -ATPase in Oxidant-Injured RPTCs Oligomycin is a specific inhibitor of F0 F1 -ATPase and thus blocks oxidative phosphorylation and ATP synthesis.

Oligomycin-sensitive respiration represents the amount of oxygen consumed by oxidative phosphorylation and is used as an indirect measure of oxidative phosphorylation and the function of F0 F1 -ATPase in RPTCs. Oligomycinsensitive respiration in RPTCs decreased by 63% at 4 h after TBHP treatment (Fig. 6, A and B). Pretreatment of RPTCs

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Gap’s in NASA Human Reserach Roadmap with 1 and 2 M GT3 before TBHP injury reduced the decreases in oligomycin-sensitive respiration. Pretreatment with 5 and 10µM GT3 restored oligomycin-sensitive respiration in TBHP-injured RPTCs (Fig. 6A). Pretreatments with 5 and 10µM AT resulted in the oligomycin-sensitive respiration in oxidant-injured RPTCs equivalent to 82 and 75% of controls (Fig. 6C).

Exposure of RPTCs to TBHP decreased F0 F1 -ATPase activity by 42% 4 h after the exposure (Fig. 6C). GT3 had no effect on F0 F1 -ATPase activity in noninjured RPTCs. Pretreatment of RPTCs with 5µM GT3 blocked TBHP-induced decreases in F0 F1 -ATPase activity (Fig. 6C). These data show that GT3 blocks oxidant-induced decreases in the activity and function of F0 F1 -ATPase and suggest that GT3 prevents the decreases in oxidative phosphorylation in RPTCs injured by oxidant. Although AT improved the function of F0 F1 - ATPase, its protective actions were not as potent as those of GT3.

γ-Tocotrienol Maintains ATP Content in Oxidant-Injured RPTCs ATP content was used to evaluate the energy status of RPTCs after TBHP-induced injury. ATP content in TBHP-treated RPTCs decreased by 65% (Fig. 7).Treatment with GT3 and AT had no effect on ATP content in non injured RPTCs ISOPTWPO Today Page 19 International Space Agency(ISA)

Gap’s in NASA Human Reserach Roadmap (Fig. 7). Pretreatment of RPTCs with GT3 before TBHP exposure maintained ATP content in injured RPTCs (Fig. 7A). However, the same concentrations of AT were unable to protect against ATP decreases in TBHP injured RPTCs (Fig. 7B). These data show that GT3 maintains ATP content and energy status of oxidant-injured RPTCs and GT3 is superior to AT in protecting against oxidant-induced loss of ATP in renal proximal tubules.

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T OCOTRIENOL AS A POTENTIAL ANTICANCER AGENT Vitamin E is composed of two structurally similar compounds: tocopherols (TPs) and tocotrienols (T3). T3 is now considered to be a promising anticancer agent due to its potent effects against a wide range of cancers. A growing body of evidence suggests that in addition to its antioxidative and pro-apoptotic functions, T3 possesses a number of anticancer properties that make it superior to TP. These include the inhibition of epithelial-to-mesenchymal transitions, the suppression of vascular endothelial growth factor tumor angiogenic pathway and the induction of antitumor immunity. More recently, T3, but not TP, has been shown to have chemosensitization and anti-cancer stem cell effects, further demonstrating the potential of T3 as an effective anticancer therapeutic agent.

T3 was found to induce apoptosis in prostate and breast cancer cells but not in the non-malignant breast and prostate epithelial cells, suggesting that it has selective cancer cell-killing properties.In addition, in both studies, the hormoneindependent cell lines were found to be more sensitive to T3 than the hormone-dependent lines, which highlight the potential of T3 in targeting breast and prostate tumors at hormone refractory stage.A higher uptake of T3 by cancer cells may also account for the observed cancer cell-specific killing effect since examination of T3 distribution in vivo revealed that T3 tends to accumulate at a much higher concentration in tumor tissues when compared with other vital organs .

References: Review:Ming T. Ling, Sze U. Luk, Fares Al-Ejeh, and Kum K. Khanna,Tocotrienol as a potential anticancer agent Carcinogenesis (2012) 33 (2): 233-239 first published online November 17, 2011 doi:10.1093/carcin/bgr261

Gap’s in NASA Human Reserach Roadmap Phytochemicals as radioprotective agents Recently, many of the investigators have focused the radioprotective research towards the phytochemicals and plant extracts. A review by Arora et.al, on the present status of herbal radioprotectors and future prospectives emphasize the potential in the area of natural product based radioprotector drug discovery[7].

The efficacy of any radioprotector is expressed in terms of dose modifying factor (DMF) or dose reduction factor (DRF). DRF is evaluated by plotting the percentage survival at the end of 30 days against the different doses of

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R EFERENCES 1.Hall EJ, Giaccia AJ. Radiobiology for the Radiobiologist. 6th edition. Lippincott Williams and Wilkins; Philadelphia, PA:2006 2.Vijay K Singh, Patricia LP Romaine & Victoria L Newman,Radiation countermeasure agents: an update (2011 – 2014).

Expert Opin Ther Pat 2014;24(11):1229-55.

3.Vijay K Singh, Patricia LP Romaine & Victoria L Newman,Biologics as countermeasures for acute radiation syndrome: where are we now?,Expert Opin. Biol. Ther. (2015) 15(4):465-471.

4.Eliot M. Rosen, Regina Day and Vijay K. Singh,New approaches to radiation protection,Frontiers in oncology,January 2015,Volume 4, Article 381,doi: 10.3389/fonc.2014.00381.

5.Grazyna Nowak, Diana Bakajsova, Corey Hayes, Martin Hauer-Jensen, and Cesar M. Compadre,gamma-Tocotrienol Protects against Mitochondrial Dysfunction and Renal Cell Death,JPET February 2012 vol. 340 no. 2 330-338,doi: 10.1124/jpet.111.186882.

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