The Inhibitory Effects of Low-Dose Ionizing Radiation in IgE-Mediated Allergic Responses

Preventive and therapeutic effects of low-dose whole-body irradiation on collagen-induced rheumatoid arthritis in mice

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by progressive joint inflammation, resulting in cartilage destruction and bone erosion. It was reported that low-dose radiation modulates immune disease. Here, we investigated whether low-dose whole-body irradiation has preventive and therapeutic effects in collagen-induced RA (CIA) mouse models. Fractionated low-dose irradiation (0.05 Gy/fraction, total doses of 0.1, 0.5 or 0.8 Gy) was administered either concurrently with CIA induction by Type II collagen immunization (preventive) or after CIA development (therapeutic). The severity of CIA was monitored using two clinical parameters, paw swelling and redness. We also measured total Immunoglobulin G (IgG) and inflammatory cytokines (interleukine (IL)-6, IL-1β and tumor necrosis factor-alpha (TNF-α)) in the serum by enzyme-linked immunosorbent assay, and we evaluated histological changes in the ankle joints by immunohistochemistry and hematoxylin and eosin staining. Low-dose irradiation reduced CIA clinical scores by up to 41% in the preventive model and by 28% in the therapeutic model, while irradiation in the preventive model reduced the typical CIA incidence rate from 82 to 56%. In addition, low-dose irradiation in the preventive model decreased total IgG by up to 23% and decreased IL-1β and TNF-α by 69 and 67%, and in the therapeutic model, decreased total IgG by up to 35% and decreased IL-1β and IL-6 by 59 and 42% with statistical significance (P < 0.01, 0.05 and 0.001). Our findings demonstrate that low-dose radiation has preventive and therapeutic anti-inflammatory effects against CIA by controlling the immune response, suggesting that low-dose radiation may represent an alternative therapy for RA, a chronic degenerative immune disease.

Interplay of immune modulation, adaptive response and hormesis: Suggestive of threshold for clinical manifestation of effects of ionizing radiation at low doses?

The health impacts of low-dose ionizing radiation exposures have been a subject of debate over the last three to four decades. While there has been enough evidence of "no adverse observable" health effects at low doses and low dose rates, the hypothesis of "Linear No Threshold" continues to rule and govern the principles of radiation protection and the formulation of regulations and public policies. In adopting this conservative approach, the role of the biological processes underway in the human body is kept at abeyance. This review consolidates the available studies that discuss all related biological pathways and repair mechanisms that inhibit the progression of deleterious effects at low doses and low dose rates of ionizing radiation. It is pertinent that, taking cognizance of these processes, there is a need to have a relook at policies of radiation protection, which as of now are too stringent, leading to undue economic losses and negative public perception about radiation.

Mesenchymal stem cell exosomes differentially regulate gene expression of mast cells

Emerging evidence indicates that the immunomodulatory effect of mesenchymal stem cells (MSCs) is primarily attributed to the paracrine pathway. As a key paracrine effector, MSC-derived exosomes are small vesicles that play an important role in cell-to-cell communication by carrying bioactive substances. We previously found that exosomes derived from tonsil-derived mesenchymal stem cells (T-MSCs) were able to effectively attenuate inflammatory responses in mast cells. Here we investigated how T-MSC exosomes impact mast cells in steady state, and how exposure of T-MSCs to Toll-like receptors (TLRs) ligands changes this impact. Transcriptomic analysis of HMC-1 cells, a human mast cell line, using DNA microarrays showed that T-MSC exosomes broadly regulate genes involved in the normal physiology of mast cells. TLR3 or TLR4 primed T-MSC exosomes impacted fewer genes involved in specific functions in mast cells. This distinguishable regulation also was apparent in the analysis of related gene interactions. Our results suggest that MSC exosomes maintain immune homeostasis in normal physiology and impact the inflammatory state by modulating mast cell transcription.

Mesenchymal Stem Cell-Derived Exosomes Attenuate TLR7-Mediated Mast Cell Activation

BACKGROUND

Mast cells are immune sentinels in the skin that respond to a wide range of pathological and environmental stimuli; they owe their function to the expression of Toll-like receptors (TLRs). We previously found that tonsil-derived mesenchymal stem cells (T-MSCs) were able to effectively attenuate TLR7-mediated skin inflammation in mice, which was accompanied by an increase in mast cell number. The present study investigated whether T-MSC extracellular vesicles, such as exosomes, are able to regulate mast cell activation in response to TLR7 stimulation.

METHODS

The HMC-1 human mast cell line was treated with a TLR7 agonist in the presence or absence of T-MSC exosomes, and the levels of expressed inflammatory cytokines were assessed. Additionally, mice were repeatedly injected with a TLR7 agonist with or without interval treatments with T-MSC exosomes and assessed dermal distribution of mast cells and related immune cells.

RESULTS

We showed that T-MSC exosomes containing microRNAs that target inflammatory cytokines significantly reduced the expression of inflammatory cytokines in TLR7 agonist-treated HMC-1 cells. In addition, T-MSC exosomes inhibited the increase in the number of both dermal mast cells and CD14-positive cells in TLR7 agonist-treated mice.

CONCLUSION

Our data suggest that T-MSC exosomes have regulatory effects on mast cell activation under inflammatory conditions, including TLR7 stimulation.

Hepatoprotective effect of ferulic acid and/or low doses of γ-irradiation against cisplatin-induced liver injury in rats

The therapeutic efficacy of cisplatin (CIS) is limited owing to its hepatotoxic side effects. The current study aimed to investigate the protective impact of ferulic acid (FA) and low-doses of γ-irradiation (LDR) against CIS-prompted hepatotoxicity in rats. Adult male Swiss albino rats were divided into eight groups: untreated group; FA, LDR, and CIS treated groups; and combinations of one or more of the above treatments. Post-treatment analyses included measuring redox markers like SOD and CAT activity, NO free radical content, and lipid peroxidation in liver tissue. Serum aminotransferase activities were also determined. Additionally, gene transcript levels of liver NF-ҡB-P65, caspase-1, COX-2, and IL-1β were quantified. Moreover, immunohistochemistry for caspase-3 and histopathological examinations were estimated in liver tissue. Our findings revealed increased levels of oxidative stress along with a significant reduction in anti-oxidative responses and a significant increase in serum aminotransferase activities in the CIS-intoxicated group. A similar increase was also observed in COX-2 and IL-1β transcript levels and caspase-3 enzyme activity, besides a decrease in transcript levels of NF-ҡB-p65 and caspase-1, indicating an overall inflammatory trend and an increase in the apoptotic shift. The co-administration of FA and/or treatment with LDR has ameliorated the hepatotoxic effect induced by CIS. The histopathological investigation of liver tissues confirmed this ameliorating action of these adjuvant therapies against CIS toxicity. In conclusion, it is plausible to suggest that the hepatoprotective effects of co-administration of FA and/or LDR against CIS-induced hepatotoxicity are attributed to the possession of anti-oxidative, anti-inflammatory, and anti-apoptotic capabilities.

Chronic exposure to low doses of ionizing radiation impacts the processing of glycoprotein N-linked glycans in Medaka (Oryzias latipes)

PURPOSE

Ionizing radiation is found naturally in the environment. Low doses of IR may have beneficial applications, yet there is also potential for detrimental long-term health effects. Impacts following exposure to low levels of IR have been refractory to identification and quantification. Glycoprotein glycosylation is vital to cell-cell communication and organismal function, and sensitive to changes in an organism's macro- and cellular environment. We investigated whether accumulated low doses of IR (LoDIR) affect the N-linked glycoprotein glycans using Medaka fish (Oryzias latipes).

MATERIALS AND METHODS

State-of-the-art methods in radiation exposure and glycan analysis were applied to study N-glycan changes after 190 day exposure at three different rates of gamma irradiation (2.25, 21.01, and 204.3 mGy/day) in wild-type adult Medaka. Tissue N-glycans were analyzed following enzymatic release from extracted proteins.

RESULTS

N-linked glycan profiles are dominated by complex type N-glycans modified with terminal sialic acid and core fucose. Fucosylation and sialylation of N-linked glycoprotein glycans are affected by LoDIR and a subset of N-glycans are involved in the organismal radio-response.

CONCLUSION

This is the first indication that the glycome can be interrogated for biomarkers that report the impact of chronic exposure to environmental stressors, such as low-level IR.

Inhibitory activity of narirutin on RBL-2H3 cells degranulation

Context: It is an efficient strategy to apply inhibition of mast cell degranulation for evaluating anti-allergic effects of compounds. Previous works confirmed that narirutin had anti-allergic activity in OVA induced allergic asthma murine model. However, the mechanism is not clear. Objective: Here, inhibitory mechanism of narirutin on RBL-2H3 cells degranulation was investigated. Materials and methods: Cell viability was analyzed by CCK-8 kits, cell degranulation was analyzed by ELISA methods, morphology and ultrastructure of cells was observed by atomic force microscopy, intracellular Ca ²⁺ concentration was measured by fluorescence microscopre, mRNA expression were measured by PCR, and signaling pathways were measured by WB. Results: The results showed that narirutin have no direct effects on mRNA expression of FcεRI subunit. However, it inhibited Ca²⁺ influx by suppressing the phosphorylation of Syk, LAT and PLCγ1 signaling pathway transduction. Subsequently, the inhibition of Ca²⁺ influx directly leads to NF-κB signaling pathway transduction decreased. Narirutin can also suppress the phosphorylation of MAPK signaling pathways by decreasing the expression of P-p38, P-ERK and P-JNK, inhibit the synergistic effect for Ca²⁺ influx, and then reduce the release of IL-4, TNF-α, histamine and β-HEX. Conclusion: Our study suggested that the inhibitory mechanism of narirutin on RBL-2H3 cells degranulation could be related to regulate MAPK, NF-κB and Tyrosine kinase signaling pathway.

Organ-Specific Effects of Low Dose Radiation Exposure: A Comprehensive Review

Ionizing radiation (IR) is a high-energy radiation whose biological effects depend on the irradiation doses. Low-dose radiation (LDR) is delivered during medical diagnoses or by an exposure to radioactive elements and has been linked to the occurrence of chronic diseases, such as leukemia and cardiovascular diseases. Though epidemiological research is indispensable for predicting and dealing with LDR-induced abnormalities in individuals exposed to LDR, little is known about epidemiological markers of LDR exposure. Moreover, difference in the LDR-induced molecular events in each organ has been an obstacle to a thorough investigation of the LDR effects and a validation of the experimental results in in vivo models. In this review, we summarized the recent reports on LDR-induced risk of organ-specifically arranged the alterations for a comprehensive understanding of the biological effects of LDR. We suggested that LDR basically caused the accumulation of DNA damages, controlled systemic immune systems, induced oxidative damages on peripheral organs, and even benefited the viability in some organs. Furthermore, we concluded that understanding of organ-specific responses and the biological markers involved in the responses is needed to investigate the precise biological effects of LDR.

Preventative and Therapeutic Effects of Low-dose Ionizing Radiation on the Allergic Response of Rat Basophilic Leukemia Cells

The prevalence of allergies has increased over the last four decades. In allergic reactions, mast cells induce a hypersensitive immune response to a substance that is normally harmless. Ionizing radiation has different biological effects depending on the dose and dose rate. In this study, we investigated whether low-dose irradiation before (preventative effect) or after (therapeutic effect) an antigen-antibody reaction has an anti-allergic effect. To test this, we activated rat basophilic leukemia (RBL-2H3) mast cells with anti-2,4-dinitrophenyl IgE (antibody) and 2,4-dinitrophenyl human serum albumin, which served as an antigen. To test for both the potential of a preventative effect and a therapeutic effect, we irradiated mast cells both before and after mast cell activation, and we measured mediator release and signaling pathway activity. Low-dose ionizing radiation suppressed mediator release from RBL-2H3 mast cells activated by the antigen-antibody reaction regardless of when the mast cells were irradiated. These results were due to the suppression of FcεRI expression. Therefore, we suggest that low-dose ionizing radiation has a preventative and therapeutic effect in allergic reactions via the FcεRI-mediated RBL-2H3 mast cell activation system.

Low-dose ionizing radiation attenuates mast cell migration through suppression of monocyte chemoattractant protein-1 (MCP-1) expression by Nr4a2

Purpose: The aim of this study was to investigate whether low-dose ionizing radiation attenuates mast cell migration by modulating migration-associated signaling pathways and the expression of chemotactic cytokines.Materials and methods: IgE-sensitized RBL-2H3 mast cells were exposed with ionizing radiation at 0.01, 0.05, 0.1, or 0.5 Gy using a ¹³⁷Cs γ-irradiator and stimulated with 2,4-dinitrophenol-human serum albumin. Cell migration was determined using a transwell assay system, F-actin distribution using Alex Fluor 488-conjugated phalloidin, expression of various signaling proteins by Western blotting, mRNA expression by RT-PCR.Results: Low-dose ionizing radiation significantly suppressed mast cell migration induced by IgE-mediated mast cell activation. Furthermore, low-dose ionizing radiation altered cell morphology, as reflected by changes in F-actin distribution, and inhibited the activation of PI3K, Btk, Rac1, and Cdc42. These effects were mediated by Nr4a2, an immune-modulating factor. Knockdown of Nr4a2 reduced mast cell migration, inhibited the PI3K and Btk signaling pathways, and reduced expression of the chemotactic cytokine monocyte chemoattractant protein-1 (MCP-1). We further demonstrated that direct blockade of MCP-1 using neutralizing antibodies inhibits mast cell migration.Conclusion: Low-dose ionizing radiation inhibits mast cell migration through the regulation production of MCP-1 by Nr4a2 in the activated mast cell system.

Receptor-destroying enzyme (RDE) from Vibrio cholerae modulates IgE activity and reduces the initiation of anaphylaxis

IgE plays a key role in allergies by binding to allergens and then sensitizing mast cells through the Fc receptor, resulting in the secretion of proinflammatory mediators. Therefore, IgE is a major target for managing allergies. Previous studies have reported that oligomannose on IgE can be a potential target to inhibit allergic responses. However, enzymes that can modulate IgE activity are not yet known. Here, we found that the commercial receptor-destroying enzyme (RDE) (II) from Vibrio cholerae culture fluid specifically modulates IgE, but not IgG, and prevents the initiation of anaphylaxis. RDE (II)-treated IgE cannot access its binding site on bone marrow-derived mast cells, resulting in reduced release of histamine and cytokines. We also noted that RDE (II)-treated IgE could not induce passive cutaneous anaphylaxis in mouse ears. Taken together, we concluded that RDE (II) modulates the IgE structure and renders it unable to mediate allergic responses. To reveal the mechanism by which RDE (II) interferes with IgE activity, we performed lectin microarray analysis to unravel the relationship between IgE modulation and glycosylation. We observed that RDE (II) treatment significantly reduced the binding of IgE to Lycopersicon esculentum lectin, which recognizes poly-N-acetylglucosamine and poly-N-acetyllactosamine. These results suggest that RDE (II) specifically modulates branched glycans on IgE, thereby interfering with its ability to induce allergic responses. Our findings may provide a basis for the development of drugs to inhibit IgE activity in allergies.

Effects of Gamma and Electron Radiation on the Structural Integrity of Organic Molecules and Macromolecular Biomarkers Measured by Microarray Immunoassays and Their Astrobiological Implications

High-energy ionizing radiation in the form of solar energetic particles and galactic cosmic rays is pervasive on the surface of planetary bodies with thin atmospheres or in space facilities for humans, and it may seriously affect the chemistry and the structure of organic and biological material. We used fluorescent microarray immunoassays to assess how different doses of electron and gamma radiations affect the stability of target compounds such as biological polymers and small molecules (haptens) conjugated to large proteins. The radiation effect was monitored by measuring the loss in the immunoidentification of the target due to an impaired ability of the antibodies for binding their corresponding irradiated and damaged epitopes (the part of the target molecule to which antibodies bind). Exposure to electron radiation alone was more damaging at low doses (1 kGy) than exposure to gamma radiation alone, but this effect was reversed at the highest radiation dose (500 kGy). Differences in the dose-effect immunoidentification patterns suggested that the amount (dose) and not the type of radiation was the main factor for the cumulative damage on the majority of the assayed molecules. Molecules irradiated with both types of radiation showed a response similar to that of the individual treatments at increasing radiation doses, although the pattern obtained with electrons only was the most similar. The calculated radiolysis constant did not show a unique pattern; it rather suggested a different behavior perhaps associated with the unique structure of each molecule. Although not strictly comparable with extraterrestrial conditions because the irradiations were performed under air and at room temperature, our results may contribute to understanding the effects of ionizing radiation on complex molecules and the search for biomarkers through bioaffinity-based systems in planetary exploration.

Elaeocarpusin Inhibits Mast Cell-Mediated Allergic Inflammation

Mast cells are major effector cells for allergic responses that act by releasing inflammatory mediators, such as histamine and pro-inflammatory cytokines. Accordingly, different strategies have been pursued to develop anti-allergic and anti-inflammatory candidates by regulating the function of mast cells. The purpose of this study was to determine the effectiveness of elaeocarpusin (EL) on mast cell-mediated allergic inflammation. We isolated EL from Elaeocarpus sylvestris L. (Elaeocarpaceae), which is known to possess anti-inflammatory properties. For this study, various sources of mast cells and mouse anaphylaxis models were used. EL suppressed the induction of markers for mast cell degranulation, such as histamine and β-hexosaminidase, by reducing intracellular calcium levels. Expression of pro-inflammatory cytokines, such as tumor necrosis factor-α and IL-4, was significantly decreased in activated mast cells by EL. This inhibitory effect was related to inhibition of the phosphorylation of Fyn, Lyn, Syk, and Akt, and the nuclear translocation of nuclear factor-κB. To confirm the effect of EL in vivo, immunoglobulin E-mediated passive cutaneous anaphylaxis (PCA) and ovalbumin-induced active systemic anaphylaxis (ASA) models were induced. EL reduced the PCA reaction in a dose dependent manner. In addition, EL attenuated ASA reactions such as hypothemia, histamine release, and IgE production. Our results suggest that EL is a potential therapeutic candidate for allergic inflammatory diseases that acts via the inhibition of mast cell degranulation and expression of proinflammatory cytokines.

Proactive strategy for long-term biological research aimed at low-dose radiation risk in Korea

PURPOSE

Since the 2011 Fukushima nuclear power plant accident, Korean radiation experts have agreed that reliable data on health risks of low-dose radiation (LDR) are needed to ease the anxiety of lay people. The intent of this study was to devise a sustainable biological program suited for the research environment in Korea and aimed at the health effects of radiation exposures <100 millisieverts (mSv). To address pressing public concerns over LDR risk, we investigated the current understanding of LDR effects by analyzing the previous reports of international authorities for radiation protection and research publications that appeared after the Chernobyl accident. A research program appropriate for societal and scientific inclinations of Korea was then devised based on input from Korean radiation scientists.

CONCLUSIONS

After review by our advisory committee, program priorities were set, calling for an agenda that focused on dose-response relationships in carcinogenesis, health span responses to lifestyle variations, and systemic metabolic changes. Our long-term biological research program may contribute scientific evidence to reduce the uncertainties of LDR health risks and help stakeholders formulate policies for radiation protection.

Chronic irradiation with low-dose-rate 137Cs-γ rays inhibits NGF-induced neurite extension of PC12 cells via Ca2+/calmodulin-dependent kinase II activation

Chronic irradiation with low-dose-rate 137Cs-γ rays inhibits the differentiation of human neural progenitor cells and influences the expression of proteins associated with several cellular functions. We aimed to determine whether such chronic irradiation influences the expression of proteins associated with PC12 cells. Chronic irradiation at 0.027 mGy/min resulted in inhibition of NGF-induced neurite extension. Furthermore, irradiation enhanced the nerve growth factor (NGF)-induced increase in the phosphorylation of extracellular signal-regulated kinase (ERK), but did not affect the phosphorylation of NGF receptors, suggesting that irradiation influences pathways unassociated with the activation of ERK. We then examined whether irradiation influenced the Akt-Rac1 pathway, which is unaffected by ERK activation. Chronic irradiation also enhanced the NGF-induced increase in Akt phosphorylation, but markedly inhibited the NGF-induced increase in Rac1 activity that is associated with neurite extension. These results suggest that the inhibitory effect of irradiation on neurite extension influences pathways unassociated with Akt activation. As Ca2+/calmodulin-dependent kinase II (CaMKII) is known to inhibit the NGF-induced neurite extension in PC12 cells, independent of ERK and Akt activation, we next examined the effects of irradiation on CaMKII activation. Chronic irradiation induced CaMKII activation, while application of KN-62 (a specific inhibitor of CaMKII), attenuated increases in CaMKII activation and recovered neurite extension and NGF-induced increases in Rac1 activity that was inhibited by irradiation. Our results suggest that chronic irradiation with low-dose-rate γ-rays inhibits Rac1 activity via CaMKII activation, thereby inhibiting NGF-induced neurite extension.

Effects of low-dose X-ray irradiation on activated macrophages and their possible signal pathways

Low-dose irradiation (LDI) has been used in clinics to treat human diseases, including chronic inflammation. This study assessed the effects of LDI on the inflammatory response of activated mouse primary peritoneal macrophages, and the underlying signal pathways. Primary peritoneal macrophages were isolated from mice and then incubated with lipopolysaccharide (LPS)-coated Ti microparticles (Ti-positive control) with or without brief exposure to LDI (X-ray, 0.5 Gy) 1 h later (Ti-LDI group) or left untreated in culture medium (Ti-negative control). The macrophages were then subjected to qRT-PCR, Western blot, cell viability CCK-8 assay, and ELISA. qRT-PCR analysis revealed the Ti-LDI group expressed significantly lower levels of IL-1β, IL-6, and TNF-α mRNA than those of the Ti-positive control group, while the ELISA data showed that Ti-LDI group had significantly lower secretion of IL-1β, IL-6, and TNF-α proteins. The most significant reduction associated with LDI was the secretion TNF-α protein, which barely increased from 13 to 25 h after treatment. Western blot data demonstrated that phosphorylation of p65 and ERK was much lower in the Ti-LDI group than in the controls. The data from the current study suggests that LDI of activated mouse macrophages was associated with significantly lower inflammation responses, compared with non-exposed activated macrophages, which was possibly through inhibition of the NF-κB and ERK pathways.

Th17 cell-mediated immune responses promote mast cell proliferation by triggering stem cell factor in keratinocytes

Although mast cells are traditionally thought to function as effector cells in allergic responses, they have increasingly been recognized as important regulators of various immune responses. Mast cells mature locally; thus, tissue-specific influences are important for promoting mast cell accumulation and survival in the skin and the gastrointestinal tract. In this study, we determined the effects of keratinocytes on mast cell accumulation during Th17-mediated skin inflammation. We observed increases in dermal mast cells in imiquimod-induced psoriatic dermatitis in mice accompanied by the expression of epidermal stem cell factor (SCF), a critical mast cell growth factor. Similar to mouse epidermal keratinocytes, SCF was highly expressed in the human HaCaT keratinocyte cell line following stimulation with IL-17. Further, keratinocytes promoted mast cell proliferation following stimulation with IL-17 in vitro. However, the effects of keratinocytes on mast cells were significantly diminished in the presence of anti-CD117 (stem cell factor receptor) blocking antibodies. Taken together, our results revealed that the Th17-mediated inflammatory environment promotes mast cell accumulation through keratinocyte-derived SCF.

Sinomenine potentiates P815 cell degranulation via upregulation of Ca2+ mobilization through the Lyn/PLCγ/IP3R pathway

Mast cells are vital mediators of drug allergy and, therefore, studying the relationship between drug allergy and mast cells is essential. Sinomenine is the principal active component of Sinomenium acutum, which has anti-inflammatory and anti-immune effects, and is used to treat various rheumatoid diseases. However, allergic responses to sinomenine are frequently reported. Therefore, this study assessed the effects of sinomenine on mast cell activation to characterize its allergic effects and the underlying mechanisms. Enzyme-linked immunosorbent assay (ELISA), western blot analyses, and degranulation assays were performed to measure pro-inflammatory and allergic mediators in P815 cells. The allergenic effects of sinomenine were also determined in mice by using active general anaphylaxis (ASA). The results indicated that sinomenine induced inositol-1,4,5-trisphosphate (IP₃) production and the release of histamine, interleukin (IL)-6, and endoplasmic reticulum Ca²⁺ in P815 cells. Furthermore, sinomenine upregulated the phosphorylation of sarcoma (Src), phospholipase C (PLC)-γ1, and IP₃ receptor (R). Therefore, sinomenine induced concentration-dependent mast cell activation directly in vitro Furthermore, our in vivo data identified an appropriate intravenous dose that did not induce these allergic effects, thereby providing information for the potential safe clinical use of sinomenine.