Non-irradiated Mice Research Articles

Long-term effects of continuous low dose-rate gamma-ray irradiation on mouse hematopoietic cells.

The present work investigates the long-term effects of continuous low dose-rate (20mGy/day to total doses of 1-8Gy) gamma-ray exposure on the hematopoietic cells of specific pathogen-free C3H/HeN mice. Peripheral white blood cell (WBC) counts decreased on days 206, 471, and 486, with no significant changes in red blood cell (RBC) and platelet (PLT) counts. The number of colony forming units (CFU-S and CFU-GM) in the bone marrow and spleen from irradiated mice decreased with increasing total dose on day-12 and day-7. The decrease in bone marrow CFU-S persisted throughout the 400-day irradiation period and did not show any recovery up to 210days postirradiation. These findings suggest that the effects of low-dose-rate (LDR) radiation on the hematopoietic system remain long after the 400-day irradiation was completed. Further investigation showed no significant difference in life spans of non-irradiated W/Wv (c-kit-deficient) mice inoculated with hematopoietic stem cells from irradiated (20mGy/day for 400days) or nonirradiated wild-type mice. These results suggest that the effects of continuous low-dose-rate irradiation are more pronounced in hematopoietic stromal cells than in HSCs themselves.

Does environmental enrichment mitigate the adverse effects of chronic low dose-rate radiation exposure on mice?

The purpose of the study was to determine whether environmental enrichments (EE) can mitigate the adverse effects of chronic low-dose-rate radiation exposure in mice. Female B6C3F1 mice were continuously exposed to 20mGyd-1 gamma-rays under specific-pathogen-free conditions since 8weeks of age for 400d. After completion of the radiation exposure, OV3121 cells, derived from an ovarian granulosa cell tumor, were inoculated subcutaneously alongside age-matched non-irradiated control mice. Irradiated mice were shown to have a significantly reduced ability to eliminate inoculated tumors. The results indicate that EE may be able to mitigate the adverse effects of low-dose-rate radiation exposure, but the effects vary greatly and are complex depending on the type of EE.

Hepatic Stellate Cell-mediated Increase in CCL5 Chemokine Expression after X-ray Irradiation Determined In Vitro and In Vivo.

Radiation exposure causes hepatitis which induces hepatic steatosis and fibrosis. Although hepatic stellate cells (HSCs) have been considered potential pathological modulators for the development of hepatitis due to viral and microbial infections, their involvement in radiation-induced hepatitis is yet to be determined. This study aimed to clarify the relationship between radiation exposure and expressions of inflammatory cytokines and chemokines in HSCs in vitro and invivo. HSCs were obtained from 1-week-old mice, known to be highly sensitive to radiation-induced hepatocellular carcinoma, using a newly established method combining liver perfusion, cell dissociation, and density gradient centrifugation, followed by magnetic negative selection of hematopoietic and endothelial cells with anti-CD45.2 and CD146 antibodies. The isolated HSCs were confirmed by the expression of desmin and glial fibrillary acidic protein (GFAP). We demonstrated that primary cultured HSCs, exposed to X-ray irradiation (0, 1.9, and 3.8 Gy) and cultured for 3 and 7 days, produced elevated levels of C-C motif chemokine ligand 5 (CCL5, also known as RANTES) inflammatory chemokine in a dose-dependent manner. An invivo immunofluorescence method confirmed that increased CCL5 signals were observed in GFAP-positive HSCs in mouse livers 7 days after whole-body X-ray irradiation (1.9 and 3.8 Gy). Adequate expression of C-C motif chemokine receptor 5 (Ccr5), a receptor for CCL5, was also detected using real-time PCR in the liver of both irradiated and non-irradiated mice. Taken together, our data suggest that HSCs may drive hepatitis via CCL5/CCR5 axis in the liver under radiation-induced stress. Furthermore, this newly established experimental protocol can help evaluate the expression of other inflammatory cytokines in primary cultures of HSCs isolated from infant mice.

Models of Patient Derived Hematopoietic Stem Cell Xenografts for Assessing Individual Human Radiosensitivity

There are different approaches to assessing the human individual radiosensitivity. In this study, individual radiosensitivity was assessed in terms of survival and recovery of human hematopoietic stem cells (HSC) after acute gamma irradiation of humanized mice. Immunodeficient NOD SCID mice were transplanted with cord blood HSC intravenously, peripheral or umbilical cord blood HSC intraosseously. The estimated D0 value for human HSCs was 1.19 Gy (95٪ CI 0.90 to 1.74), 0.99 Gy (95٪ CI 0.87 to 1.15), and 0.93 Gy (95٪ CI 0.61 to 1.91) for the three methods of obtaining humanized mice, respectively. For all three methods of mouse humanization, statistically similar models that describe the dependence of HSC survival on the acute gamma irradiation dose in the range of 0.5—1.5 Gy were obtained. Thus, intraosseous administration of peripheral blood HSCs to immunodeficient mice can be effectively used to assess the response of human HSCs to radiation exposure. Comparison of the HSC number (CD34+ cells) and their descendants (CD45+ cells) in non-irradiated and irradiated mice humanized with cells from the same donor on days 3 and 14 after irradiation makes it possible to evaluate the processes of radiation-induced death and recovery of HSCs. A coefficient calculated as the ratio of the proportion of HSCs among all human cells in the bone marrow of humanized mice on the 14th day to the proportion of HSCs on the 3rd day after irradiation was proposed to assess the response to radiation exposure. This coefficient had an inverse linear dependence on the radiation dose, differed in mice with increased and normal radiosensitivity, and increased with the use of the radioprotector cysteamine in humanized mice. We propose to use this coefficient for a comparative assessment of human radiosensitivity.

Tap Water Shorts the Lifespan of Mice with Prolonged Exposure to Fractionated γ-Radiation

Assessing the role of social factors in the formation of radioresistance in chronic exposure and finding ways to increase it are important for understanding the mechanisms of the damaging effects of radiation and developing practical methods for reducing radiation risk in professionals exposed to ionizing radiation and patients undergoing radiation therapy. In this work, we investigated the ability to influence the lifespan of animals exposed to γ-radiation fractionally for a long time by replacing drinking water from tap water to distilled water. Female ICR mice (CD-1) were exposed to total 60Co γ radiation weekly in fractions for 33 weeks starting at 9 weeks of age. The dose of a single irradiation was 50 mGy, the average dose rate was 2 mGy/sec. The total radiation dose was 1.65 Gy. Control non-irradiated mice and irradiated animals were divided into 2 groups. The first received tap water, and the second received distilled water throughout the experiment. Non-irradiated animals kept on tap water showed a statistically insignificant (log-rank test, p = 0.483) reduction in average life expectancy compared to mice kept on distilled water. In animals after exposure to 60Co γ-radiation, a statistically significant (p = 0.0013) decrease in life expectancy was noted when kept on tap water and statistically insignificant (p = 0.1511) when kept on distilled water. Tap water and irradiation showed a clear synergy with a combined effect on the body of mice, expressed in a more than threefold decrease in the period of post-radiation shortening of life expectancy. Distilled water reduced the rate of death of irradiated animals and modified the rate of death of non-irradiated animals. Our data demonstrate that the reduction in life expectancy of mice kept on tap water caused by long-term fractionated irradiation can be reduced when animals are kept on distilled water.

Differential plasma cytokine variation following X-ray or proton brain irradiation using machine-learning approaches

PurposeX-ray and proton irradiation have been reported to induce distinct modifications in cytokine expression in vitro and in vivo, suggesting a dissimilar inflammatory response between X-rays and protons. We aimed to investigate the differences in cytokine profiles early following fractionated brain irradiation with X-rays or protons and their relationship with leukocyte subpopulations in rodents. Materials and methodsOur study utilized data from 80 tumor-free mice subjected to X-ray or proton brain irradiation in four fractions of 2.5Gy. Sixteen non-irradiated mice were used as the controls. Blood was collected 12h postirradiation to examine the profile of 13 cytokines. Correlation analysis, principal component analysis (PCA), and tree-based modeling were used to investigate the relationship between cytokine levels and leukocyte subpopulation variations following irradiation in the blood. ResultsRegardless of the irradiation type, brain irradiation resulted in a notable elevation in the plasma levels of IFN-γ and MCP-1. The use of either X-ray or proton beam had differential effect on plasma cytokine levels following brain irradiation. Specifically, X-ray irradiation was associated with significantly increased plasma levels of IFN-β, IL-12p70, and IL-23, along with a decreased level of IL-1α, in comparison to proton irradiation. Correlation analysis revealed distinct cytokine regulatory patterns between X-ray and proton brain irradiation. PCA highlighted the association of MCP-1, IL-6, TNF-α, IL-17A, and IFN-γ with neutrophils, monocytes, and naïve T-cells following X-ray irradiation. TNF-α and IL-23 levels correlated with naïve CD4+-cells following proton irradiation. Tree-based models demonstrated that high TNF-α level resulted in an increase in naïve T-cells, neutrophils, and monocytes, whereas low IL-6 level was associated with decreases in these cell counts. ConclusionOur findings revealed distinct inflammatory responses induced by X-ray irradiation in contrast to proton brain irradiation, as demonstrated by the differential regulation of cytokines in the bloodstream. Moreover, the study highlighted the association between specific cytokine levels and various leukocyte subpopulations. Further investigation is essential to accurately determine the impact of proton and X-ray brain irradiation on the inflammatory response and the efficacy of radiotherapy treatment.

Space-Like Irradiation Exacerbated Cognitive Deficits and Amyloid Pathology in CRND8 Mouse Model of Alzheimer's Disease.

Space radiation was linked to neurological damage and behavioral deficits which raised concerns of increased degenerative risk on the brain and development of Alzheimer's disease following space travel. In this study, we investigated the effects of irradiation by 56Fe and 28Si in CRND8 mice, an Alzheimer's disease mouse model. Six-month-old CRND8 mice were exposed to whole body irradiation by 56Fe and 28Si at 0.5 Gy and 2 Gy doses. Behavior tests were administered 1-month to 3-months post-irradiation. Amyloid deposition and other pathological changes were analyzed 3-months and/or 6-months post-irradiation. The Novel Object Recognition test showed some decline in 8-month-old mice compared to non-irradiated CRND8 mice. Male mice also showed a loss of freezing behavior in the fear conditioning contextual test following irradiation. Golgi staining revealed a loss of spines in hippocampal neurons after irradiation. Total amyloid immunohistochemistry showed a robust increase in 3-months post-irradiation 56Fe groups which became normalized to non-irradiated group by 6-months post-irradiation. However, 2 Gy 28Si caused a trend towards increased plaque load at 3-months post-irradiation which became significant at 6-months post irradiation only in male CRND8 mice. While 0.5 Gy Fe did not induce obvious changes in the total number of iba-1 positive microglia, more hippocampal microglia were found to express PCNA after 0.5 Gy Fe treatment, suggesting potential involvement of microglial dysfunction. Overall, our study provides new evidence of gender-specific and ion-dependent effects of space radiation on cognition and amyloid pathology in AD models.

Restoration of thymic T-cell development by bone marrow transplantation in mouse radiation lymphomagenesis.

Fractionated total body irradiation (TBI) with X-rays induces thymic lymphoma/leukemia (TL) in C57BL/6 mice. Radiation-induced mouse TL (RITL) can be prevented by bone marrow transplantation (BMT) of unirradiated BM cells. However, the mechanisms underlying the prevention of RITL with BMT remain unclear. Here, we show that BMT restores thymic T-cell differentiation in mice subjected to TBI. TBI (four times of 1.8Gy X-rays weekly) was conducted with C57BL/6 mice. BMT was performed immediately after the last irradiation of TBI in mice by transplantation of BM cells isolated from enhanced green fluorescence protein (eGFP) transgenic mice. Thymic cell numbers were drastically decreased in TBI and TBI + BMT mice compared to those in non-irradiated mice. Flow cytometry showed a dramatic decrease in double negative (DN, CD4-CD8-) thymocytes, especially DN2 (CD25+CD44+) and DN3 (CD25+CD44-) subpopulations, in the TBI mice on Day 10 after the last irradiation. In contrast, the DN2 and DN3 populations were recovered in TBI + BMT mice. Interestingly, these restored DN2 and DN3 cells mainly differentiated from eGFP-negative recipient cells but not from eGFP-positive donor cells, suggesting that transplanted BM cells may interact with recipient cells to restore thymic T-cell development in the RITL model. Taken together, our findings highlight the significance of restoring thymic T-cell differentiation by BMT in RITL prevention.

Non-pigmented laser hair removal mediated via sepia melanin nanoparticles: in vivo study on albino mice

Objectives Melanin is considered the main chromophore for laser hair removal. Due to a lack of laser-absorbing chromophores, removing non-pigmented hair with laser is quite problematic with unsatisfactory outcomes. This problem could be solved by delivering more melanin to the area around the hair follicle and enhancing that area as a target for light absorption. The insolubility of Sepia melanin as an exogenous dye, in most solvents, limits its bioavailability and thus its clinical use. Methods In our study, to overcome the solubility problems and increase the bioavailability of melanin for biomedical and cosmetic applications, natural sepia melanin was loaded in different nano-delivery systems (spanlastics and transfersomes) to be delivered to the hair follicles. The different formulations of melanin were prepared and characterized. In vivo skin deposition and histopathological studies were conducted on albino mice. Results Transmission electron microscopy (TEM) showed the spherical shape of the prepared vesicles with an average particle size of 252 and 262 nm and zeta potential of −22.5 and −35 mV for melanin spanlastics and melanin transfersomes, respectively. Histopathological examination of hair follicles and pilosebaceous glands for the irradiated and non-irradiated albino mice skin was studied post the application of the prepared formulations topically and subcutaneously. Qualitative statistical analysis was conducted and melanin transfersomes and melanin spanlastics showed significant damage to pilosebaceous glands and hair follicles with a p-value of 0.031 and 0.009 respectively. Conclusion Melanin nanovesicles as transfersomes and spanlastics could be considered a promising approach for the removal of non-pigmented hair.

Low to moderate dose 137Cs (γ) radiation promotes M2 type macrophage skewing and reduces atherosclerotic plaque CD68+ cell content in ApoE(−/−) mice

The effects of low doses of ionizing radiation on atherosclerosis remain uncertain, particularly as regards the generation of pro- or anti-inflammatory responses, and the time scale at which such effects can occur following irradiation. To explore these phenomena, we exposed atheroprone ApoE(−/−) mice to a single dose of 0, 0.05, 0.5 or 1 Gy of 137Cs (γ) administered at a 10.35 mGy min−1 dose rate and evaluated short-term (1–10 days) and long-term consequences (100 days). Bone marrow-derived macrophages were derived from mice 1 day after exposure. Irradiation was associated with a significant skewing of M0 and M2 polarized macrophages towards the M2 phenotype, as demonstrated by an increased mRNA expression of Retnla, Arg1, and Chil3 in cells from mice exposed to 0.5 or 1 Gy compared with non-irradiated animals. Minimal effects were noted in M1 cells or M1 marker mRNA. Concurrently, we observed a reduced secretion of IL-1β but enhanced IL-10 release from M0 and M2 macrophages. Effects of irradiation on circulating monocytes were most marked at day 10 post-exposure, when the 1 Gy dose was associated with enhanced numbers of both Ly6CHigh and Ly6Low cells. By day 100, levels of circulating monocytes in irradiated and non-irradiated mice were equivalent, but anti-inflammatory Ly6CLow monocytes were significantly increased in the spleen of mice exposed to 0.05 or 1 Gy. Long term exposures did not affect atherosclerotic plaque size or lipid content, as determined by Oil red O staining, whatever the dose applied. Similarly, irradiation did not affect atherosclerotic plaque collagen or smooth muscle cell content. However, we found that lesion CD68+ cell content tended to decrease with rising doses of radioactivity exposure, culminating in a significant reduction of plaque macrophage content at 1 Gy. Taken together, our results show that short- and long-term exposures to low to moderate doses of ionizing radiation drive an anti-inflammatory response, skewing bone marrow-derived macrophages towards an IL-10-secreting M2 phenotype and decreasing plaque macrophage content. These results suggest a low-grade athero-protective effect of low and moderate doses of ionizing radiation.

FSL-1: A Synthetic Peptide Increases Survival in a Murine Model of Hematopoietic Acute Radiation Syndrome.

In the current geopolitical climate there is an unmet need to identify and develop prophylactic radiation countermeasures, particularly to ensure the well-being of warfighters and first responders that may be required to perform on radiation-contaminated fields for operational or rescue missions. Currently, no countermeasures have been approved by the U.S. FDA for prophylactic administration. Here we report on the efficacious nature of FSL-1 (toll-like receptor 2/6 agonist) and the protection from acute radiation syndrome (ARS) in a murine total-body irradiation (TBI) model. A single dose of FSL-1 was administered subcutaneously in mice. The safety of the compound was assessed in non-irradiated animals, the efficacy of the compound was assessed in animals exposed to TBI in the AFRRI Co-60 facility, the dose of FSL-1 was optimized, and common hematological parameters [complete blood cell (CBC), cytokines, and bone marrow progenitor cells] were assessed. Animals were monitored up to 60 days after exposure and radiation-induced damage was evaluated. FSL-1 was shown to be non-toxic when administered to non-irradiated mice at doses up to 3 mg/kg. The window of efficacy was determined to be 24 h prior to 24 h after TBI. FSL-1 administration resulted in significantly increased survival when administered either 24 h prior to or 24 h after exposure to supralethal doses of TBI. The optimal dose of FSL-1 administration was determined to be 1.5 mg/kg when administered prior to irradiation. Finally, FSL-1 protected the hematopoietic system (recovery of CBC and bone marrow CFU). Taken together, the effects of increased survival and accelerated recovery of hematological parameters suggests that FSL-1 should be developed as a novel radiation countermeasure for soldiers and civilians, which can be used either before or after irradiation in the aftermath of a radiological or nuclear event.

Pharmacokinetics and Biodistribution of 16,16 dimethyl Prostaglandin E2 in Non-Irradiated and Irradiated Mice and Non-Irradiated Non-Human Primates.

Exposure to high-dose ionizing radiation can lead to life-threatening injuries and mortality. Bone marrow is the most sensitive organ to radiation damage, resulting in the hematopoietic acute radiation syndrome (H-ARS) with the potential sequelae of infection, hemorrhage, anemia, and death if untreated. The development of medical countermeasures (MCMs) to protect or mitigate radiation injury is a medical necessity. In our well-established murine model of H-ARS we have demonstrated that the prostaglandin E2 (PGE2) analog 16,16 dimethyl-PGE2 (dmPGE2) has survival efficacy as both a radioprotectant and radiomitigator. The purpose of this study was to investigate the pharmacokinetics (PK) and biodistribution of dmPGE2 when used as a radioprotector in irradiated and non-irradiated inbred C57BL/6J mice, PK in irradiated and non-irradiated Jackson Diversity Outbred (JDO) mice, and the PK profile of dmPGE2 in non-irradiated non-human primates (NHPs). The C57BL/6J and JDO mice each received a single subcutaneous (SC) dose of 35 ug of dmPGE2 and were randomized to either receive radiation 30 min later or remain non-irradiated. Plasma and tissue PK profiles were established. The NHP were dosed with 0.1 mg/kg by SC administration and the PK profile in plasma was established. The concentration time profiles were analyzed by standard non-compartmental analysis and the metrics of AUC0-Inf, AUC60-480 (AUC from 60-480 min), Cmax, and t1/2 were evaluated. AUC60-480 represents the postirradiation time frame and was used to assess radiation effect. Overall, AUC0-Inf, Cmax, and t1/2 were numerically similar between strains (C57BL/6J and JDO) when combined, regardless of exposure status (AUC0-Inf: 112.50 ng·h/ml and 114.48 ng·h/ml, Cmax: 44.53 ng/ml and 63.96 ng/ml; t1/2: 1.8 h and 1.1 h, respectively). PK metrics were numerically lower in irradiated C57BL/6J mice than in non-irradiated mice [irradiation ratio: irradiated values/non-irradiated values = 0.71 for AUC60-480 (i.e., 29% lower), and 0.6 for t1/2]. In JDO mice, the radiation ratio was 0.53 for AUC60-480 (i.e., 47% lower), and 1.7 h for t1/2. The AUC0-Inf, Cmax, and t1/2 of the NHPs were 29.20 ng·h/ml, 7.68 ng/ml, and 3.26 h, respectively. Despite the numerical differences seen between irradiated and non-irradiated groups in PK parameters, the effect of radiation on PK can be considered minimal based on current data. The biodistribution in C57BL/6J mice showed that dmPGE2 per gram of tissue was highest in the lungs, regardless of exposure status. The radiation ratio for the different tissue AUC60-480 in C57BL/6J mice ranged between 0.5-1.1 (50% lower to 10% higher). Spleen, liver and bone marrow showed close to twice lower exposures after irradiation, whereas heart had a 10% higher exposure. Based on the clearance values from mice and NHP, the estimated allometric scaling coefficient was 0.81 (95% CI: 0.75, 0.86). While slightly higher than the current literature estimates of 0.75, this scaling coefficient can be considered a reasonable estimate and can be used to scale dmPGE2 dosing from animals to humans for future trials.

Anti-Leukemic Effects of CK1α Degrader As Monotherapy and in Combination with Targeted Drugs

CK1⍺ is a member of casein kinase 1 (CK1) family, a multifunctional serine/threonine kinase conserved in eukaryotes from yeast to humans. Substrates of CK1⍺ include various proteins important in cancer and regulate multiple survival pathways such as p53, Wnt, autophagy and NF-B signaling pathways. In particular, CK1- serves as an upstream regulator of p53 pathway through regulation of MDM2 and MDMX and degradation of CK1- may prevent MDM2 and/or MDMX mediated inactivation of p53 function, thus facilitate cell death. We identified an early hit compound, distinct from known immunomodulatory imide drugs (IMiDs) such as lenalidomide or thalidomide. In order to identify compounds having distinct characteristic with previously published IMiDs, we designed multiple compounds with a wide range of glue effect based on the binding mode analysis and binding structure of CRBN and known IMiDs. Among them, PinA1 (early lead compound) selectively degraded CK1-, in the nanomolar range with the highest potency. PinA1 induced expression of p53 which led to apoptosis in AML cell lines with wild-type TP53 (MV4-11, MOLM-13, and MOLM-14), but not in TP53 mutated cells (KASUMI-1, and KG-1). Of note, in TP53 wild-type cells, expression of MDM2 and p21 increased as well, which may limit p53-induced apoptosis in these cells. PinA1 also induced CK1- degradation and p53-dependent apoptosis in primary AML cells in vitro. On the other hand, PinA1 had marginal effects on the viability of human peripheral blood mononuclear cells and CD34+ cells, with minimal activation of the p53 pathway at an efficacious dose range for MV4-11 compared to MDM2 inhibitors. PinA1 enhanced apoptosis in combination with FLT3, BCL-2, or MDM2 inhibitors in AML cell lines (MV4-11, MOLM-14) and primary AML cells in vitro. To test the efficacy of PinA1 in vivo, we injected MOLM-14/ luc/GFP or MV4-11/ luc/Thy1.1 into nonirradiated NGS mice. Five or Six days after cell injection, mice were randomized into 4 groups: vehicle, PinA1, and PinA1 plus AMG232 (MDM2 inhibitor), venetoclax, or gilteritinib. Bioluminescence imaging (BLI) demonstrated significantly less leukemia burden in all treated groups than vehicles; leukemia progression was lowest with combination therapy. Flow cytometry with sacrificed mice revealed the lowest leukemia burden in combination therapy, consistent with those from BLI. Western blotting with sorted leukemic cells from bone marrow and spleen revealed CK1- degradation in vivo. PinA1- and other single drug-treated mice had prolonged survival compared with vehicles, and combination therapy extended survival even further. Patient-derived xenograft models from two FLT3-ITD-mutated AML patients also showed potent anti-leukemic effects of PinA1 as monotherapy and in combination with gilteritinib. In conclusion, our study showed that PinA1 selectively degrades CK1α, enhancing expression of p53, which then induces apoptosis in TP53-wild-type AML cells, but not in TP53-mutated AML cells, thereby producing anti-leukemic effects as monotherapy or in combination with targeted therapies. The minimal effect of PinA1 on normal hematopoietic cells may positively contribute to safety in future clinical trials. This novel targeting approach may improve the current targeted therapies in combination once validated.

Intraoral Gavage of Second-Generation Probiotic Lactobacillus Reuteri Releasing IFN-β (LR-IFN-β) Mitigates Intestinal Irradiation Toxicity and Improves Survival During Whole Abdomen Irradiation (WAI)

We sought to establish a method by which to overcome the toxicity of WAI to facilitate clinical application in Ovarian Cancer patients. We irradiated C57BL/6J mice to 19.75 Gy WAI and assessed the primary endpoint of overall survival (OS). In a separate experiment, mice were irradiated to 12 Gy WAI and intestinal barrier integrity was compared between groups: control (0 Gy), irradiation only, 12 Gy + LR, 12 Gy + IFN-β, and 12 Gy + LR-IFN-β. Luminex assay of plasma and intestinal cells were also assayed at day 5 after WAI for radiation-induced inflammatory cytokines, and fecal matter was analyzed for LR-IFN-β clearance and levels of the LR-derived IFN-β gene from day 1 to 5 in control non-irradiated mice. Moreover, fluorescent beads were intraorally administered three hours prior to sacrifice at days 2 or 5 after WAI, and blood was assayed for beads. Mice receiving LR-IFN-β (109 bacteria in 100 mL of saline) 24-hours following a single fraction of 19.75 Gy WAI showed improved OS compared to control irradiated mice (p = 0.03). LR-IFN-β gavage maintained intestinal barrier integrity (p < 0.05) by stimulating intestinal stem cells regenerations (improved levels of Lgr5+ cells, occludin, and I-CAM; p < 0.05), and reduced levels of intestinal pro-inflammatory cytokines, including IFN-γ (p = 0.0261), IL-3 (p < 0.0020) and IL-17 (p < 0.0070). There was no significant effect of control LR or intraperitoneal injection of IFN-β protein at 24 hours after WAI. Detectable levels of LR-IFN-β bacteria were also cleared from fecal matter by day three via colony assay and rt-PCR, with no detectable growth of LR-IFN-β in blood from gavaged irradiated mice (13.5 Gy WAI). LR-IFN-β is both a feasible and effective radiation mitigator that could potentially improve the management of ovarian cancer patients. Furthermore, the subsequent addition of platinum/taxane-based chemotherapy to the combination of WAI and LR-IFN-β should reduce tumor volume while protecting the intestine and thus improve overall survival in ovarian cancer patients.

Irradiated Extramedullary Acute Myeloid Leukemia Increases Survival in a Leukemic Mouse Model

The systemic nature of AML likely limits their immunogenicity because antigen presentation is primarily mediated by splenic dendritic cells, which induces immune tolerance. Since antigen presentation in tissue draining lymph nodes can induce anti-tumor immune responses, we hypothesized that local irradiation of cutaneous, extramedullary leukemias will increase immunogenic cell death, dendritic cell maturation and improved survival. A murine AML cell line C1498 was assessed for immunogenic markers calreticulin (CALR), HMGB1 and cGAS-STING pathway using fluorescence cytometry and qRT-PCR. Syngeneic mice were injected with C1498 subcutaneously to model extramedullary lesions and intravenously to model systemic leukemias. Cells and subcutaneous tumor were focally irradiated with 2 Gy or 8 Gy. Two-way ANOVA and Student's t-test were used for paired-wise comparisons. Survival was estimated by Kaplan-Meier plot and groups were compared using log-rank test. C1498 cells or tumors irradiated with 2 Gy or 8 Gy showed increased CALR and HMGB1 as well as (cGAS/Md21b1; 5-fold; p<0.001) and interferon alpha (Ifna; 3-fold; p<0.001) after 48h (18- and 4-fold, respectively; p<0.05) compared to not treated controls (NTC). Irradiated C1498 subcutaneous tumors displayed increased CD11b-positive cells (9-fold; p<0.001), CD11c (6-fold; p<0.001), and MHCII-positive CD11c cells (4-fold; p<0.01) in irradiated tumors compared to NTC. Irradiation of subcutaneous C1498 tumors increased median survival in mice also injected with C1498 cells intravenously compared to non-irradiated mice bearing systemic leukemias (46 vs. 25 days; p<0.01). Irradiation of C1498 tumors combined with anti-PDL1 treatment further increased median survival in our leukemia model compared to untreated controls (>50 vs. <30 days; p<0.001). Irradiated extramedullary AML increased immunogenic markers and activation of immune effector cells that correlated with increased survival in mice also bearing systemic leukemia. These results suggest focal irradiation of extramedullary AML may facilitate eradiation of systemic leukemias.

Inhibition of p38MAPK signalling pathway alleviates radiation-induced testicular damage through improving spermatogenesis.

Damage to the testis following exposure to ionizing radiation has become an urgent problem to be solved. Here we have investigated if inhibition of p38 mitogen-activated protein kinase (p38MAPK) signalling could alleviate radiation-induced testicular damage. In mice exposed to whole body radiation (2-6 Gy), morphological changes of the epididymis and testis was measured by histochemical staining. immunohistochemical and immunofluorescence procedures and western blotting were used to monitor expression and cellular location of proteins. Expression of genes was assessed by qPCR and RNA-Seq was used to profile gene expression. Exposure to ionizing radiation induced dose-dependent damage to mouse testis. The sperm quality decreased at 6 and 8 weeks after 6 Gy X-ray radiation. Radiation decreased PLZF+ cells and increased SOX9+ cells, and affected the expression of 969 genes, compared with data from non-irradiated mice. Expression of genes related to p38MAPK were enriched by GO analysis and were increased in the irradiated testis, and confirmed by qPCR. Levels of phospho-p38MAPK protein increased at 28 days after irradiation. In irradiated mice, SB203580 treatment increased spermatozoa, SOX9+ cells, the area and diameter of seminiferous tubules, sperm movement rate and density. Furthermore, SB203580 treatment increased SCP3+ cells, accelerating the process of spermatogenesis. Exposure to ionizing radiation clearly changed gene expression in mouse testis, involving activation of p38MAPK signalling pathways. Inhibition of p38MAPK by SB203580 partly alleviated the testicular damage caused by radiation and accelerated the recovery of sperms through promoting spermatogenesis.

Exercise promotes growth and rescues volume deficits in the hippocampus after cranial radiation in young mice.

Human and animal studies suggest that exercise promotes healthy brain development and function, including promoting hippocampal growth. Childhood cancer survivors that have received cranial radiotherapy exhibit hippocampal volume deficits and are at risk of impaired cognitive function, thus they may benefit from regular exercise. While morphological changes induced by exercise have been characterized using magnetic resonance imaging (MRI) in humans and animal models, evaluation of changes across the brain through development and following cranial radiation is lacking. In this study, we used high-resolution longitudinal MRI through development to evaluate the effects of exercise in a pediatric mouse model of cranial radiation. Female mice received whole-brain radiation (7 Gy) or sham radiation (0 Gy) at an infant equivalent age (P16). One week after irradiation, mice were housed in either a regular cage or a cage equipped with a running wheel. In vivo MRI was performed prior to irradiation, and at three subsequent timepoints to evaluate the effects of radiation and exercise. We used a linear mixed-effects model to assess volumetric and cortical thickness changes. Exercise caused substantial increases in the volumes of certain brain regions, notably the hippocampus in both irradiated and nonirradiated mice. Volume increases exceeded the deficits induced by cranial irradiation. The effect of exercise and irradiation on subregional hippocampal volumes was also characterized. In addition, we characterized cortical thickness changes across development and found that it peaked between P23 and P43, depending on the region. Exercise also induced regional alterations in cortical thickness after 3 weeks of voluntary exercise, while irradiation did not substantially alter cortical thickness. Our results show that exercise has the potential to alter neuroanatomical outcomes in both irradiated and nonirradiated mice. This supports ongoing research exploring exercise as a strategy for improving neurocognitive development for children, particularly those treated with cranial radiotherapy.

Preliminary Results of the Effects of Localized High-Dose Radiotherapy Combined with Total Body Low-Dose Irradiation on Tumor Growth and Stimulating the Immune System in Tumor-Bearing Mice.

The immune system plays an extensive role in eliminating tumor cells. On the other hand, low-dose irradiation stimulates the immune system. The present study aimed to investigate the therapeutic outcomes of localized high-dose radiotherapy (LH) alone and combined with total body low-dose irradiation (TB). In this experimental study, B16F0 tumor cells were injected into the right flank of C57JL/6 mice. The mice were treated with LH alone (13 Gy X-rays to the tumor surface) (LH group) or combined with TB (85 mGy X-rays at the skin) (TB+LH group). Then the tumor volume, the mice's lifespan, the number of lymphocytes extracted from the spleen, and interferon gamma (IFN-γ) production were measured. Reduced number of lymphocytes, compared to non-irradiated mice (control group), was observed in LH and TB+LH groups. However, the identical number of cultured lymphocytes produced a higher level of IFN-γ in irradiated groups. Comparing the irradiated groups, the number of lymphocytes and their IFN-γ production, tumor growth control, and the mice's lifespan were statistically higher in TB+LH group. Observing a higher level of IFN-γ in TB+LH group compared to LH group indicates that low-dose radiation enhanced the stimulating effects of high-dose radiation on the immune system. It caused the mice in TB+LH group to have a more prolonged lifespan and a lower tumor growth rate. Therefore, it is worth our attention for future studies to investigate whether total body low-dose irradiation can be utilized before radiotherapy to enhance its efficiency.

Human Adipose-Derived Endothelial Progenitor Cells Accelerate Epithelialization of Radiation Ulcers in Nude Mice.

Cotransplantation of adipose-derived stem cells (ASCs) and endothelial progenitor cells has shown superior angiogenic effects compared with ASCs alone in recent animal studies. However, endothelial progenitor cells could only be collected from blood vessels or bone marrow. Thus, the authors have established a method for purifying adipose-derived endothelial progenitor cells (AEPCs). The authors hypothesized that AEPCs would enhance the therapeutic effect of ASCs on radiation ulcers. Seven-week-old male nude mice (BALB/cAJcl-nu/nu) were irradiated on the dorsal skin (total 40 Gy); 12 weeks later, 6-mm-diameter wounds were created. The mice were then treated with subcutaneous injection of human ASCs [1 × 10 5 ( n = 4)], human AEPCs [2 × 10 5 or 5 × 10 5 ( n = 5)], combinations of those [ASCs 1 × 10 5 plus AEPCs 2 × 10 5 ( n = 4) or 5 × 10 5 ( n = 5)], or only vehicle ( n = 7). The nonirradiated group was also prepared as a control ( n = 6). The days required for macroscopic epithelialization was compared, and immunostaining for human-derived cells and vascular endothelial cells was performed at day 28. AEPC-ASC combination-treated groups healed faster than the ASC-treated group (14 ± 0 days versus 17 ± 2 days; P < 0.01). Engraftment of the injected cells could not be confirmed. Only the nonirradiated mice had significantly higher vascular density (0.988 ± 0.183 × 10 -5 /µm -2 versus 0.474 ± 0.092 × 10 -5 /µm 2 ; P = 0.02). The results suggested therapeutic potentials of AEPCs and an enhanced effect of combination with ASCs. This study is a xenogenic transplantation model, and further validation in an autologous transplantation model is needed. Human AEPCs and their combination with ASCs accelerated epithelialization of radiation ulcers in nude mice. The authors suggest that administration of humoral factors secreted from AEPCs (eg, treatment with culture-conditioned media) could be used for the same purpose.

Abstract P1-10-09: AQP4 inhibition prevents cytotoxic edema of AQP4+ astrocytes but promotes tumor growth of AQP4+ breast cancer brain metastasis

Abstract Brain edema is a complication of radiation used to treat brain metastasis (BM) in which the brain parenchyma accumulates fluid and ions, often leading to the suspension of systemic anticancer treatment. While brain edema is often attributed to disruption of the Blood Brain Barrier (BBB), RTx induces cytotoxic-edema, a premorbid cellular process whereby extracellular Na+ and other cations enter into neurons and astrocytes and accumulate intracellularly, resulting in osmotic expansion of the cells and necrotic cell death. Aquaporin 4 (AQP4) is a main regulator of osmotic expansion (water intake) in astrocytes and we have shown that RTx upregulates AQP4 in astrocytes and leads to astrocytic swelling in vitro. However, whether pharmacological modulation of AQP4 could be used to prevent cytotoxic brain edema in RTx-treated BM and its impact on metastatic tumor progression remains unknown. Goal: To determine if the FDA-approved drug Topiramate (TPM), an anti-epileptic drug able to inhibit AQP4) can prevent astrocytic swelling in vitro, reduce RTx-induced brain edema and modulate brain metastatic progression. Results: Electron microscopy of brain cortex from mice treated with 35 Gy RTx showed acute astrocytic end-feet swelling and increase in AQP4 expression compared with non-irradiated mice. A single 8 Gy dose increased astrocytic cell area of human astrocytes by 4.8 fold compared with non-irradiated cells 24 h after RTx. This increased cell-swelling did not result from senescence-associated cellular hypertrophy, as staining of senescent β-galactosidase positive (SA-β-Gal+) cells showed that Rtx-induced astrocytic area only increased significantly in non-senescent (SA-β-Gal- cells). shAQP4s reduced AQP4 levels by 60% and 50%, respectively, and significantly reduced RTx-induced astrocytic swelling. Since there are no FDA-approved AQP4 inhibitors, we tested whether the AQP4-blocking function of TPM could be sufficient to prevent cytotoxic edema, prevent BBB dysfunction and protect from necrotic cell death in vitro. TPM pretreatment did not alter radiation-induced ERK1/2 or AKT activation (a known maker of radioprotection) in astrocytes, but TPM decreased radiation-induced PARP-cleavage, pP38 and pJNK levels. TPM prevented loss of Trans-electric epithelial resistance (TEER) of Rtx-treated astrocytes, but was not able to protect astrocytes from ultimate cell death. Immunohistochemical analysis of a cohort of breast cancer BM showed heterogeneous AQP4 expression in cancer cells ranging from 1.6% to 91% AQP4+ tumoral areas and from 0.6% to 86.9% in stroma. AQP4 inhibition using shRNAs decreased proliferation and survival of AQP4 + 231BR, and EO711 cells in vitro. However, TPM did not alter survival of AQP4+ or AQP4- cells in vitro, suggesting that while AQP4 expression is important for survival of AQP4+ cells in vitro, the inhibition of AQP4 function by TPM is not sufficient to decrease their growth. To determine if TPM could decrease brain edema without negatively impacting tumor progression, female NSG mice were injected intracardially with JmT1BR3 AQP4-cells and ten days later randomized to (1) RTx + vehicle, (2) RTx + TPM (2 days prior to irradiation), (3) Non-RTx + vehicle, and (4) Non-RTx + TPM. TPM decreased brain-water content (a marker of brain edema) in irradiated mice as compared with vehicle-treated mice, without alteration of metastatic burden 21 days post-injection. However, a similar study using AQP4+ E0711 cells in C57Bl6 mice showed TPM was less effective in decreasing brain water content and resulted in a significant increase in extracranial metastatic tumor burden, suggesting that TPM can promote tumor progression by non-tumor intrinsic mechanisms. Conclusions: while TPM shows promise in preventing RTx-induced brain edema, our results show a potential pro-tumorigenic mechanism for TPM that warrants further investigation. Citation Format: Maria J. Contreras-Zarate, Karen ALvarez-Eraso, Nicole Tsuji, Peter Kabos, D.Ryan Ormond, Sana Karam, Diana Cittelly. AQP4 inhibition prevents cytotoxic edema of AQP4+ astrocytes but promotes tumor growth of AQP4+ breast cancer brain metastasis [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-10-09.