Continuous One Year Oral Administration of the Radiation Mitigator, MMS350, after Total-Body Irradiation, Restores Bone Marrow Stromal Cell Proliferative Capacity and Reduces Senescence in Fanconi Anemia (Fanca-/-) Mice

Inhibition of tyrosine kinase Fgr prevents radiation-induced pulmonary fibrosis (RIPF)

Cellular senescence is involved in the development of pulmonary fibrosis as well as in lung tissue repair and regeneration. Therefore, a strategy of removal of senescent cells by senolytic drugs may not produce the desired therapeutic result. Previously we reported that tyrosine kinase Fgr is upregulated in ionizing irradiation-induced senescent cells. Inhibition of Fgr reduces the production of profibrotic proteins by radiation-induced senescent cells in vitro; however, a mechanistic relationship between senescent cells and radiation-induced pulmonary fibrosis (RIPF) has not been established. We now report that senescent cells from the lungs of mice with RIPF, release profibrotic proteins for target cells and secrete chemotactic proteins for marrow cells. The Fgr inhibitor TL02-59, reduces this release of profibrotic chemokines from the lungs of RIPF mice, without reducing numbers of senescent cells. In vitro studies demonstrated that TL02-59 abrogates the upregulation of profibrotic genes in target cells in transwell cultures. Also, protein arrays using lung fibroblasts demonstrated that TL02-59 inhibits the production of chemokines involved in the migration of macrophages to the lung. In thoracic-irradiated mice, TL02-59 prevents RIPF, significantly reduces levels of expression of fibrotic gene products, and significantly reduces the recruitment of CD11b+ macrophages to the lungs. Bronchoalveolar lavage (BAL) cells from RIPF mice show increased Fgr and other senescent cell markers including p16. In human idiopathic pulmonary fibrosis (IPF) and in RIPF, Fgr, and other senescent cell biomarkers are increased. In both mouse and human RIPF, there is an accumulation of Fgr-positive proinflammatory CD11b+ macrophages in the lungs. Thus, elevated levels of Fgr in lung senescent cells upregulate profibrotic gene products, and chemokines that might be responsible for macrophage infiltration into lungs. The detection of Fgr in senescent cells that are obtained from BAL during the development of RIPF may help predict the onset and facilitate the delivery of medical countermeasures.

Combined injury: irradiation with skin or bone wounds in rodent models

A radiation combined injury is defined as an injury that occurs in the setting of irradiation, such as those expected after a nuclear accident, radiation dispersal device release (a 'dirty bomb'), or a nuclear weapon detonation. There is much research on irradiation-associated burns and their healing, but there is less known about other injuries sustained in the context of irradiation. Animal models are limited in their correlations to clinical situations but can support research on specific questions about injuries and their healing. Mouse models of irradiation with skin or bone wounds are validated as highly reproducible and quantitative. They show dose-dependent impairment of wound healing, with later recovery. Irradiation-induced delay of bone wound healing was mitigated to different extents by single doses of gramicidin S-nitroxide JP4-039, a plasmid expressing manganese superoxide dismutase, amifostine/WR2721, or the bifunctional sulfoxide MMS-350. These models should be useful for research on mechanisms of radiation dermal and osseous damage and for further development of new radioprotectors. They also provide information of potential relevance to the effects of clinical radiation therapies.

Ionizing irradiation-induced Fgr in senescent cells mediates fibrosis

The role of cellular senescence in radiation-induced pulmonary fibrosis (RIPF) and the underlying mechanisms are unknown. We isolated radiation-induced senescent tdTOMp16 positive mesenchymal stem cells, established their absence of cell division, then measured levels of irradiation-induced expression of biomarkers of senescence by RNA-seq analysis. We identified a Log2 6.17-fold upregulation of tyrosine kinase Fgr, which was a potent inducer of biomarkers of fibrosis in target cells in non-contact co-cultures. Inhibition of Fgr by shRNA knockdown did not block radiation-induced senescence in vitro; however, both shRNA knockdown, or addition of a specific small-molecule inhibitor of Fgr, TL02-59, abrogated senescent cell induction of profibrotic genes in transwell-separated target cells. Single-cell RNA-seq (scRNAseq) analysis of mouse lungs at day 150 after 20 Gy thoracic irradiation revealed upregulation of Fgr in senescent neutrophils, and macrophages before detection of lung fibrosis. Thus, upregulated Fgr in radiation-induced senescent cells mediates RIPF and is a potential therapeutic target for the prevention of this radiation late effect.

Radiation-Induced Senescence in p16+/LUC Mouse Lung Compared to Bone Marrow Multilineage Hematopoietic Progenitor Cells

We defined the time course of ionizing radiation-induced senescence in lung compared to bone marrow of p16+/LUC mice in which the senescence-induced biomarker (p16) is linked to a luciferase reporter gene. Periodic in situ imaging revealed increased luciferase activity in the lungs of 20 Gy thoracic irradiated, but not 8 Gy total-body irradiated (TBI) mice beginning at day 75 and increasing to day 170. In serial sections of explanted lungs, senescent cells appeared in the same areas as did fibrosis in the 20 Gy thoracic irradiated, but not the 8 Gy TBI group. Lungs from 8 Gy TBI mice at one year did show increased RNA levels for p16, p21, p19 and TGF-β. Individual senescent cells in 20 Gy irradiated mouse lung included those with epithelial, endothelial, fibroblast and hematopoietic cell biomarkers. Rare senescent cells in the lungs of 8 Gy TBI mice at one year were of endothelial phenotype. Long-term bone marrow cultures (LTBMCs) were established at either day 60 or one year after 8 Gy TBI. In freshly removed marrow at both times after irradiation, there were increased senescent cells. In LTBMCs, there were increased senescent cells in both weekly harvested single cells and in colonies of multilineage hematopoietic progenitor cells producing CFU-GEMM (colony forming unit-granulocyte, erythrocyte, monocyte/macrophage, megakaryocyte) that were formed in secondary cultures when these single cells were plated in semisolid media. LTBMCs from TBI mice produced fewer CFU-GEMM; however, the relative percentage of senescent cell-containing colonies was increased as measured by both p16-luciferase and β-galactosidase. Therefore, 20 Gy thoracic radiation, as well as 8 Gy TBI, induces senescent cells in the lungs. With bone marrow, 8 Gy TBI induced senescence in both hematopoietic cells and in colony-forming progenitors. The p16+/LUC mouse strain provides a valuable system in which to compare the kinetics of radiation-induced senescence between organs in vivo, and to evaluate the potential role of senescent cells in irradiation pulmonary fibrosis.

Targets for protection and mitigation of radiation injury

Protection of normal tissues against toxic effects of ionizing radiation is a critical issue in clinical and environmental radiobiology. Investigations in recent decades have suggested potential targets that are involved in the protection against radiation-induced damages to normal tissues and can be proposed for mitigation of radiation injury. Emerging evidences have been shown to be in contrast to an old dogma in radiation biology; a major amount of reactive oxygen species (ROS) production and cell toxicity occur during some hours to years after exposure to ionizing radiation. This can be attributed to upregulation of inflammatory and fibrosis mediators, epigenetic changes and disruption of the normal metabolism of oxygen. In the current review, we explain the cellular and molecular changes following exposure of normal tissues to ionizing radiation. Furthermore, we review potential targets that can be proposed for protection and mitigation of radiation toxicity.

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.

Amelioration of Mucositis in Proton Therapy of Fanconi Anemia Fanca-/- Mice by JP4-039

BACKGROUND/AIM

We tested JP4-039, a GS-nitroxide radiation damage mitigator in proton therapy of Fanconi anemia (FA) mice.

MATERIALS AND METHODS

Fanca^-/- and Fanca^+/+ bone marrow stromal cells were pre-treated with JP4-039 and irradiated with either protons or photons (0-10 GyRBE) followed by clonogenic survival and β-Galactosidase senescence analysis. Fanca^-/- and Fanca^+/+ mice were pretreated with JP4-039 for 10 min prior to oropharyngeal irradiation with either protons or photons (0 or 30 GyRBE) followed by sacrifice and measurement of oral cavity ulceration, distant hematopoietic suppression, and real-time polymerase chain reaction analysis.

RESULTS

JP4-039 reduced oral cavity ulceration in Fanca^-/- mice, transcripts Nfkb, Ap1, Sp1, and Nrf2, and proton therapy induced distant marrow suppression.

CONCLUSION

JP4-039 protected Fanca^-/- and Fanca^+/+ cells and mouse oral cavity from both proton and photon radiation.

Acute and late effects of combined internal and external radiation exposures on the hematopoietic system

Purpose: Incidents, such as nuclear facility accidents and the release of a 'dirty bomb', might result in not only external irradiation of personnel, but additional internal exposures through concomitant inhalation and/or ingestion of radioactive particulates. The purpose of this study was to define the impact of such a combination of radiation injuries on the hematopoietic niche.Material and methods: To assess changes in the murine hematopoietic system, we used a combined exposure of total body irradiation (TBI, 6 Gy) followed immediately by an internal (intraperitoneal) administration of 100 µCi of soluble ¹³⁷Cs. We then evaluated acute survival in combined versus single modality exposure groups, as well as assessing hematopoietic function at 12 and 26 week time points.Results: Acutely, the combination of external and internal exposures led to an unexpected delay in excretion of ¹³⁷Cs, increasing the absorbed dose in the combined exposure group and leading to mortality from an acute hematopoietic syndrome. At 12 weeks, all exposure paradigms resulted in decreased numbers of phenotypic hematopoietic stem cells (HSCs), particularly the short-term HSCs (ST-HSC); long-term HSCs (LT-HSC) were depleted only in the internal and combined exposure groups. At 26 weeks, there was significant anemia in both the TBI alone and combined exposure groups. There were decreased numbers in both the LT- and ST-HSCs and decreased functionality, as measured by competitive repopulation, was seen in all radiation groups, with the greatest effects seen in the internal and combined exposure groups.Conclusions: Our data indicate that a combined injury of sublethal external irradiation with internal contamination induces significant and persistent changes in the hematopoietic system, as may have been predicted from the literature and our own group's findings. However, a novel observation was that the combined exposure led to an alteration in the excretion kinetics of the internal contamination, increasing the acute effects beyond those anticipated. As a result, we believe that a combined exposure poses a unique challenge to the medical community during both the acute and, possibly, delayed recovery stages.

Radioresistance of Serpinb3a-/- Mice and Derived Hematopoietic and Marrow Stromal Cell Lines

Serpins are a group of serine-proteases involved in multiple signal transduction pathways in mammalian cells. In particular, Serpinb3a is involved in the lysosomal necrosis cell death pathway with components that overlap with radiation-induced apoptosis. We investigated the radiation response of Serpinb3a^-/- mice compared to Serpinb3a^+/+ mice on the Balb/c background. Serpinb3a^-/- mice showed significant radioresistance to a dose of 8.0 Gy total-body irradiation, compared to Serpinb3a^+/+ Balb/c mice. Long-term bone marrow cultures from Serpinb3a^-/- mice showed increased longevity. In clonogenic survival assays, fresh bone marrow hematopoietic progenitors, as well as clonal interleukin-3 (IL-3)-dependent hematopoietic progenitor and bone marrow stromal cell lines from Serpinb3a^-/- mice were radioresistant. Serpinb3a^-/- mouse bone marrow-derived stromal cell lines had increased baseline and postirradiation antioxidant capacity. Serpinb3a^-/- bone marrow stromal cells showed increased radiation-induced RNA transcripts for MnSOD and p21, and decreased levels of p53 and TGF-b. Both irradiated Serpinb3a^-/- mouse bone marrow stromal cell lines and plasma removed from total-body irradiated mice had decreased levels of expression of stress response and inflammation-associated proteins. Abrogation of Serpinb3a may be a potential new target for mitigation of radiation effects.

Amelioration of Amyotrophic Lateral Sclerosis in SOD1G93A Mice by M2 Microglia from Transplanted Marrow

Background/Aim: The cause of fatal neuromuscular amyotrophic lateral sclerosis (ALS) is not known. Materials and Methods: Ninety-day-old superoxide-dismutase-1 G93A (SOD1 G93A ) mice demonstrating level 1 paralysis, received 9.0 Gy total body irradiation (TBI) from a cesium source at 340 cGy per minute, and intravenous transplantation with 1×10 6 C57BL/6 green fluorescent protein (GFP)+ donor bone marrow cells. Results: Paralysis-free survival was prolonged in TBI and bone marrow-transplanted SOD1 G93A mice from 100 to over 250 days (p=0.0018). Other mice transplanted with SOD1 G93A marrow or marrow treated with the free-radical scavenger MMS350 showed no therapeutic effect. GFP+ macrophage-2 (M2) microglial cells of bone marrow origin, were seen at sites of degenerating anterior horn motor neurons. SOD1 G93A mice had a disruption in the blood-brain barrier permeability which was reversed by marrow transplant from C57BL/6 mice. SOD1 G93A marrow showed unexpected robust hematopoiesis in vitro, and radioresistance. Conclusion: After TBI, M2 microglial cells from transplanted donor marrow extended the paralysis-free interval in SOD1 G93A mice.