DNA Damage and Radiosensitivity in Blood Cells from Subjects Undergoing 45 Days of Isolation and Confinement: An Explorative Study.

The effect of confined and isolated experience on astronauts' health is an important factor to consider for future space exploration missions. The more confined and isolated humans are, the more likely they are to develop negative behavioral or cognitive conditions such as a mood decline, sleep disorder, depression, fatigue and/or physiological problems associated with chronic stress. Molecular mediators of chronic stress, such as cytokines, stress hormones or reactive oxygen species (ROS) are known to induce cellular damage including damage to the DNA. In view of the growing evidence of chronic stress-induced DNA damage, we conducted an explorative study and measured DNA strand breaks in 20 healthy adults. The participants were grouped into five teams (missions). Each team was composed of four participants, who spent 45 days in isolation and confinement in NASA's Human Exploration Research Analog (HERA). Endogenous DNA integrity, ex-vivo radiation-induced DNA damage and the rates of DNA repair were assessed every week. Our results show a high inter-individual variability as well as differences between the missions, which cannot be explained by inter-individual variability alone. The ages and sex of the participants did not appear to influence the results.

Dermatitis during Spaceflight Associated with HSV-1 Reactivation.

Human alpha herpesviruses herpes simplex virus (HSV-1) and varicella zoster virus (VZV) establish latency in various cranial nerve ganglia and often reactivate in response to stress-associated immune system dysregulation. Reactivation of Epstein Barr virus (EBV), VZV, HSV-1, and cytomegalovirus (CMV) is typically asymptomatic during spaceflight, though live/infectious virus has been recovered and the shedding rate increases with mission duration. The risk of clinical disease, therefore, may increase for astronauts assigned to extended missions (>180 days). Here, we report, for the first time, a case of HSV-1 skin rash (dermatitis) occurring during long-duration spaceflight. The astronaut reported persistent dermatitis during flight, which was treated onboard with oral antihistamines and topical/oral steroids. No HSV-1 DNA was detected in 6-month pre-mission saliva samples, but on flight day 82, a saliva and rash swab both yielded 4.8 copies/ng DNA and 5.3 × 104 copies/ng DNA, respectively. Post-mission saliva samples continued to have a high infectious HSV-1 load (1.67 × 107 copies/ng DNA). HSV-1 from both rash and saliva samples had 99.9% genotype homology. Additional physiological monitoring, including stress biomarkers (cortisol, dehydroepiandrosterone (DHEA), and salivary amylase), immune markers (adaptive regulatory and inflammatory plasma cytokines), and biochemical profile markers, including vitamin/mineral status and bone metabolism, are also presented for this case. These data highlight an atypical presentation of HSV-1 during spaceflight and underscore the importance of viral screening during clinical evaluations of in-flight dermatitis to determine viral etiology and guide treatment.

Alterations in Saliva and Plasma Cytokine Concentrations During Long-Duration Spaceflight.

Long-duration spaceflight is known to cause immune dysregulation in astronauts. Biomarkers of immune system function are needed to determine both the need for and effectiveness of potential immune countermeasures for astronauts. Whereas plasma cytokine concentrations are a well-established biomarker of immune status, salivary cytokine concentrations are emerging as a sensitive indicator of stress and inflammation. For this study, to aid in characterizing immune dysregulation during spaceflight, plasma and saliva cytokines were monitored in astronauts before, during and after long-duration spaceflight onboard the International Space Station. Blood was collected from 13 astronauts at 3 timepoints before, 5 timepoints during and 3 timepoints after spaceflight. Saliva was collected from 6 astronauts at 2 timepoints before spaceflight, 2 timepoints during and 3 timepoints following spaceflight. Samples were analyzed using multiplex array technology. Significant increases in the plasma concentration of IL-3, IL-15, IL-12p40, IFN-α2, and IL-7 were observed during spaceflight compared to before flight baseline. Significant decreases in saliva GM-CSF, IL-12p70, IL-10 and IL-13 were also observed during spaceflight as compared to compared to before flight baseline concentrations. Additionally, plasma TGFß1 and TGFß2 concentrations tended to be consistently higher during spaceflight, although these did not reach statistical significance. Overall, the findings confirm an in-vivo hormonal dysregulation of immunity, appearing pro-inflammatory and Th1 in nature, persists during long-duration orbital spaceflight. These biomarkers may therefore have utility for monitoring the effectiveness of biomedical countermeasures for astronauts, with potential application in terrestrial research and medicine.

Countermeasures-based Improvements in Stress, Immune System Dysregulation and Latent Herpesvirus Reactivation onboard the International Space Station - Relevance for Deep Space Missions and Terrestrial Medicine.

The International Space Station (ISS) has continued to evolve from an operational perspective and multiple studies have monitored both stress and the immune system of ISS astronauts. Alterations were ascribed to a potentially synergistic array of factors, including microgravity, radiation, psychological stress, and circadian misalignment. Comparing similar data across 12 years of ISS construction and operations, we report that immunity, stress, and the reactivation of latent herpesviruses have all improved in ISS astronauts. Major physiological improvements seem to have initiated approximately 2012, a period coinciding with improvements onboard ISS including cargo delivery and resupply frequency, personal communication, exercise equipment and protocols, food quality and variety, nutritional supplementation, and schedule management. We conclude that spaceflight associated immune dysregulation has been positively influenced by operational improvements and biomedical countermeasures onboard ISS. Although an operational challenge, agencies should therefore incorporate, within vehicle design limitations, these dietary, operational, and stress-relieving countermeasures into deep space mission planning. Specific countermeasures that have benefited astronauts could serve as a therapy augment for terrestrial acquired immunodeficiency patients.

Immune System Dysregulation During Spaceflight: Potential Countermeasures for Deep Space Exploration Missions.

Recent studies have established that dysregulation of the human immune system and the reactivation of latent herpesviruses persists for the duration of a 6-month orbital spaceflight. It appears certain aspects of adaptive immunity are dysregulated during flight, yet some aspects of innate immunity are heightened. Interaction between adaptive and innate immunity also seems to be altered. Some crews experience persistent hypersensitivity reactions during flight. This phenomenon may, in synergy with extended duration and galactic radiation exposure, increase specific crew clinical risks during deep space exploration missions. The clinical challenge is based upon both the frequency of these phenomena in multiple crewmembers during low earth orbit missions and the inability to predict which specific individual crewmembers will experience these changes. Thus, a general countermeasure approach that offers the broadest possible coverage is needed. The vehicles, architecture, and mission profiles to enable such voyages are now under development. These include deployment and use of a cis-Lunar station (mid 2020s) with possible Moon surface operations, to be followed by multiple Mars flyby missions, and eventual human Mars surface exploration. Current ISS studies will continue to characterize physiological dysregulation associated with prolonged orbital spaceflight. However, sufficient information exists to begin consideration of both the need for, and nature of, specific immune countermeasures to ensure astronaut health. This article will review relevant in-place operational countermeasures onboard ISS and discuss a myriad of potential immune countermeasures for exploration missions. Discussion points include nutritional supplementation and functional foods, exercise and immunity, pharmacological options, the relationship between bone and immune countermeasures, and vaccination to mitigate herpes (and possibly other) virus risks. As the immune system has sentinel connectivity within every other physiological system, translational effects must be considered for all potential immune countermeasures. Finally, we shall discuss immune countermeasures in the context of their individualized implementation or precision medicine, based on crewmember specific immunological biases.

SIRT2 Deacetylates and Inhibits the Peroxidase Activity of Peroxiredoxin-1 to Sensitize Breast Cancer Cells to Oxidant Stress-Inducing Agents.

SIRT2 is a protein deacetylase with tumor suppressor activity in breast and liver tumors where it is mutated; however, the critical substrates mediating its antitumor activity are not fully defined. Here we demonstrate that SIRT2 binds, deacetylates, and inhibits the peroxidase activity of the antioxidant protein peroxiredoxin (Prdx-1) in breast cancer cells. Ectopic overexpression of SIRT2, but not its catalytically dead mutant, increased intracellular levels of reactive oxygen species (ROS) induced by hydrogen peroxide, which led to increased levels of an overoxidized and multimeric form of Prdx-1 with activity as a molecular chaperone. Elevated levels of SIRT2 sensitized breast cancer cells to intracellular DNA damage and cell death induced by oxidative stress, as associated with increased levels of nuclear FOXO3A and the proapoptotic BIM protein. In addition, elevated levels of SIRT2 sensitized breast cancer cells to arsenic trioxide, an approved therapeutic agent, along with other intracellular ROS-inducing agents. Conversely, antisense RNA-mediated attenuation of SIRT2 reversed ROS-induced toxicity as demonstrated in a zebrafish embryo model system. Collectively, our findings suggest that the tumor suppressor activity of SIRT2 requires its ability to restrict the antioxidant activity of Prdx-1, thereby sensitizing breast cancer cells to ROS-induced DNA damage and cell cytotoxicity. Cancer Res; 76(18); 5467-78. ©2016 AACR.

Monitoring of biodistribution and persistence of conditionally replicative adenovirus in a murine model of ovarian cancer using capsid-incorporated mCherry and expression of human somatostatin receptor subtype 2 gene.

A significant limiting factor to the human clinical application of conditionally replicative adenovirus (CRAd)-based virotherapy is the inability to noninvasively monitor these agents and their potential persistence. To address this issue, we proposed a novel imaging approach that combines transient expression of the human somatostatin receptor (SSTR) subtype 2 reporter gene with genetic labeling of the viral capsid with mCherry fluorescent protein. To test this dual modality system, we constructed the Ad5/3Δ24pIXcherry/SSTR CRAd and validated its capacity to generate fluorescent and nuclear signals in vitro and following intratumoral injection. Analysis of 64Cu-CB-TE2A-Y3-TATE biodistribution in mice revealed reduced uptake in tumors injected with the imaging CRAd relative to the replication-incompetent, Ad-expressing SSTR2 but significantly greater uptake compared to the negative CRAd control. Optical imaging demonstrated relative correlation of fluorescent signal with virus replication as determined by viral genome quantification in tumors. Positron emission tomography/computed tomography studies demonstrated that we can visualize radioactive uptake in tumors injected with imaging CRAd and the trend for greater uptake by standardized uptake value analysis compared to control CRAd. In the aggregate, the plasticity of our dual imaging approach should provide the technical basis for monitoring CRAd biodistribution and persistence in preclinical studies while offering potential utility for a range of clinical applications.

Synthesis and radiopharmacological evaluation of a high-affinity and metabolically stabilized 18F-labeled bombesin analogue for molecular imaging of gastrin-releasing peptide receptor-expressing prostate cancer.

INTRODUCTION: Bombesin (BBN) and BBN analogues have attracted much attention as high-affinity ligands for selective targeting of the gastrin-releasing peptide (GRP) receptor. GRP receptors are overexpressed in a variety of human cancers including prostate cancer. Radiolabeled BBN derivatives are promising diagnostic probes for molecular imaging of GRP receptor-expressing prostate cancer. This study describes the synthesis and radiopharmacological evaluation of various metabolically stabilized fluorobenzoylated bombesin analogues (BBN-1, BBN-2, BBN-3). METHODS: Three fluorobenzoylated BBN analogues containing an aminovaleric (BBN-1, BBN-2), or an aminooctanoic acid linker (BBN-3) were tested in a competitive binding assay against (125)I-[Tyr(4)]-BBN for their binding potency to the GRP receptor. Intracellular calcium release in human prostate cancer cells (PC3) was measured to determine agonistic or antagonistic profiles of fluorobenzoylated BBN derivatives. Bombesin derivative BBN-2 displayed the highest inhibitory potency toward GRP receptor (IC50 = 8.7 ± 2.2 nM) and was subsequently selected for radiolabeling with fluorine-18 ((18)F) through acylation with N-succinimidyl-4-[(18)F]fluorobenzoate ([(18)F]SFB). The radiopharmacological profile of (18)F-labeled bombesin [(18)F]BBN-2 was evaluated in PC3 tumor-bearing NMRI nude mice involving metabolic stability studies, biodistribution experiments and dynamic small-animal PET studies. RESULTS: All fluorobenzoylated BBN derivatives displayed high inhibitory potency toward the GRP receptor (IC50=8.7-16.7 nM), and all compounds exhibited antagonistic profiles as determined in an intracellular calcium release assay. The (18)F-labeled BBN analogue [(18)F]BBN-2 was obtained in 30% decay-corrected radiochemical yield with high radiochemical purity >95% after semi-preparative HPLC purification. [(18)F]BBN-2 showed high metabolic stability in vivo with 65% of the radiolabeled peptide remaining intact after 60 min p.i. in mouse plasma. Biodistribution experiments and dynamic small-animal PET studies demonstrated high tumor uptake of [(18)F]BBN-2 in PC3 xenografts (2.75 ± 1.82 %ID/g after 5 min and 2.45 ± 1.25 %ID/g after 60 min p.i.). Specificity of radiotracer uptake in PC3 tumors was confirmed by blocking experiments. CONCLUSION: The present study demonstrates that (18)F-labeled BBN analogue [(18)F]BBN-2 is a suitable PET radiotracer with favorable metabolic stability in vivo for molecular imaging of GRP receptor-positive prostate cancer.