Factors effecting the Th2-like immune response after gamma-irradiation: low production of IL-12 heterodimer in antigen-presenting cells and small expression of the IL-12 receptor in T cells

Radiotherapy Improves the Disability in Patients with Secondary Progressive Multiple Sclerosis

Background

Multiple sclerosis (MS) as a complex neurological abnormality is marked with loss of myelin and axons due to chronic inflammatory and autoimmune responses. The modulatory properties of the low dose radiation (LDR) on inflammatory and immune responses have well known.

Objective

The current research aimed to assess the impacts of LDR on the disability in patients suffering from MS.

Material and Methods

This experimental pilot study was done on 10 patients with secondary progressive multiple sclerosis (SPMS). After magnetic resonance imaging, the SPMS patients were treated by LDR at a daily dose of 2 Gray for 5 consecutive days (totally 10 Gray dose) using a linear accelerator. The extent of the disability was evaluated one week after the completion of radiotherapy using expanded disability status scale (EDSS).

Results

After receiving radiotherapy, the patients had a feeling of wellbeing of some sort. The mean of EDSS was significantly reduced after radiotherapy compared with before irradiation (7.4±0.45 vs 6.35±1.18; P<0.017). EDSS more decreased in younger SPMS patients (P=0.0001), and in the women after LDR (P=0.027).

Conclusion

Radiotherapy can reduce fatigue and EDSS in patients with SPMS. The age and gender of patients may influence the LDR efficacy.

Effects of low dose radiation on immune cells subsets and cytokines in mice

Whole-body exposure to low-dose radiation due to diagnostic imaging procedures, occupational hazards and radiation accidents is a source of concern. In this study, we analyzed the effects of single and long-term low-dose irradiation on the immune system. Male Balb/c mice received a single whole-body dose of irradiation (0.01, 0.05, 0.2, 0.5 or 1 Gy). For long-term irradiation, mice were irradiated 10 times (total dose of 0.2, 0.5 or 1 Gy) over a period of 6 weeks. Two days after single or long-term irradiation, the numbers of splenic macrophages, natural killer cells and dendritic cells were reduced, and the spleen organ coefficient was decreased. At 2 Days after long-term low-dose irradiation, the number of white blood cells in the peripheral blood of the mice decreased. Between 7 and 14 Days after long-term low-dose irradiation, the number of immune cells in the thymus and spleen began to increase and then stabilized. Th1/Th2 cytokines and reactive oxygen species-related proteins first decreased and then increased to a plateau. Our results show a significant difference in the effects of single and long-term low-dose irradiation on the immune system.

The interplay between cancer associated fibroblasts and immune cells in the context of radiation therapy

Fibroblasts are a key component of the tumor microenvironment (TME) that can serve as a scaffold for tumor cell migration and augment the tumor's ability to withstand harsh conditions. When activated by external or endogenous stimuli, normal fibroblasts become cancer associated fibroblasts (CAFs), a heterogeneous group of stromal cells in the tumor that are phenotypically and epigenetically different from normal fibroblasts. Dynamic crosstalk between cancer cells, immune cells, and CAFs through chemokines and surface signaling makes the TME conducive to tumor growth. When activated, CAFs promote tumorigenesis and metastasis through several phenomena including regulation of tumor immunity, metabolic reprogramming of the TME, extracellular matrix remodeling and contraction, and induction of therapeutic resistance. Ionizing radiation (radiation theraphy [RT]) is a potent immunological stimulant that has been shown to increase cytotoxic Teff infiltration and IFN-I stimulated genes. RT, however, is unable to overcome the infiltration and activation of immunosuppressive cells which can contribute to tumor progression. Another paradox of RT is that, while very effective at killing cancer cells, it can contribute to the formation of CAFs. This review examines how the interplay between CAFs and immune cells during RT contributes to organ fibrosis, immunosuppression, and tumor growth. We focus on targeting mechanistic pathways of CAF formation as a potentially effective strategy not only for preventing organ fibrosis, but also in hampering tumor progression in response to RT.

Effects of various radiation doses on induced T-helper cell differentiation and related cytokine secretion

Exposure to ionizing radiation often induces T helper (Th) cell differentiation, resulting in an imbalance of Th1 and Th2 cellular subtypes, which can affect the efficacy of cancer radiotherapy. The aim of this study was to analyze differential expression of Th1, Th2 and Th3/Type 1 regulatory T cell (Tr1) subtype-related genes and cytokines in mouse thymocytes after high- and low-dose systemic radiation, using functional classification gene arrays and Elisa assays, and to explore the molecular mechanisms underlying radiation's immune effects and their relationship with Th1/Th2 immunity. We found that expression of 8 genes was upregulated after LDR, while expression of 5 genes was downregulated. After HDR, 54 genes were upregulated and 3 genes were downregulated, including genes related to Th1, Th2 and Th3/Tr1 cellular subtypes, Th1/Th2-type immune response genes and transcription factor-related genes. In the foregoing results, LDR and HDR in the thymus induced opposite patterns of expression for Th1-, Th2- and Th3-type related cytokines TGF-β, C/EBP-β and TNF-α. We also found that expression of Interferon-γ (IFN-γ) and Interleukin-2 (IL-2), which have a moderating effect on immune function, was upregulated after LDR. Furthermore, the secretion of negative regulatory factors Interleukin-1β (IL-1β), Interleukin-4 (IL-4), transforming growth factor-β (TGF-β) and Interleukin-21 (IL-21) was reduced after LDR, but HDR produced the opposite effect and stimulated their expression. These findings suggest that LDR may induce a Th1-type immune response, while HDR may lead to a Th2-type immune response.

Polydatin alleviated radiation-induced lung injury through activation of Sirt3 and inhibition of epithelial-mesenchymal transition

Radiation-induced lung injury (RILI) is one of the most common and fatal complications of thoracic radiotherapy. It is characterized with two main features including early radiation pneumonitis and fibrosis in later phase. This study was to investigate the potential radioprotective effects of polydatin (PD), which was shown to exert anti-inflammation and anti-oxidative capacities in other diseases. In this study, we demonstrated that PD-mitigated acute inflammation and late fibrosis caused by irradiation. PD treatment inhibited TGF-β1-Smad3 signalling pathway and epithelial-mesenchymal transition. Moreover, radiation-induced imbalance of Th1/Th2 was also alleviated by PD treatment. Besides its free radical scavenging capacity, PD induced a huge increase of Sirt3 in culture cells and lung tissues. The level of Nrf2 and PGC1α in lung tissues was also elevated. In conclusion, our data showed that PD attenuated radiation-induced lung injury through inhibiting epithelial-mesenchymal transition and increased the expression of Sirt3, suggesting PD as a novel potential radioprotector for RILI.

Radiation-induced decrease of CD8+ dendritic cells contributes to Th1/Th2 shift

Exposure to ionizing radiation (IR) often reduce the helper T (Th) 1 like function, resulting in a Th1/Th2 imbalance, which could affect the efficacy of cancer radiotherapy. As the most potent antigen presenting cells, dendritic cells (DC) can be divided into several subsets with specialized function. However, there is no literature covering the changes of DC subsets and their roles in immune regulation in response to IR. In the present study, we were aimed to investigate the changes of DC subsets after IR and its relationship with Th1/Th2 immunity. We found a significant decrease of BDCA3+DC in the blood of patients treated with radiotherapy. CD8+DC, a mouse equivalent of human BDCA3+DC, was also found decreased in mice spleen, peripheral blood and lymph node tissues after irradiation. As CD8+DC mainly induce Th1 immunity, we tested the changes of Th1/Th2 response and found that IR caused a repression of Th1 immunity, indicating a possible role of CD8+DC in radiation-induced Th1/Th2 imbalance. We also found that a CD8+DC-inducing cytokine, Fms-like tyrosine kinase 3 ligand (FLT3 ligand), restored CD8+DC and reversed Th1/Th2 shift. And then we found that bone marrow cells from irradiated mice differentiated into less CD8+DC, which was also protected by FLT3 ligand. In conclusion, our data showed that IR induced a decrease of CD8+DC and Th1/Th2 shift, which was reversed by Flt3 ligand treatment, suggesting a novel mechanism for radiation-induced immunosuppression.

Randomized comparison of single dose of recombinant human IL-12 versus placebo for restoration of hematopoiesis and improved survival in rhesus monkeys exposed to lethal radiation

Background

The hematopoietic syndrome of the acute radiation syndrome (HSARS) is a life-threatening condition in humans exposed to total body irradiation (TBI); no drugs are approved for treating this condition. Recombinant human interleukin-12 (rHuIL-12) is being developed for HSARS mitigation under the FDA Animal Rule, where efficacy is proven in an appropriate animal model and safety is demonstrated in humans.

Methods

In this blinded study, rhesus monkeys (9 animals/sex/dose group) were randomized to receive a single subcutaneous injection of placebo (group 1) or rHuIL-12 at doses of 50, 100, 250, or 500 ng/kg (groups 2–5, respectively), without antibiotics, fluids or blood transfusions, 24–25 hours after TBI (700 cGy).

Results

Survival rates at Day 60 were 11%, 33%, 39%, 39%, and 50% for groups 1–5, respectively (log rank p < 0.05 for each dose vs. control). rHuIL-12 also significantly reduced the incidences of severe neutropenia, severe thrombocytopenia, and sepsis (positive hemoculture). Additionally, bone marrow regeneration following TBI was significantly greater in monkeys treated with rHuIL-12 than in controls.

Conclusions

Data from this study demonstrate that a single injection of rHuIL-12 delivered one day after TBI can significantly increase survival and reduce radiation-induced hematopoietic toxicity and infections. These data significantly advance development of rHuIL-12 toward approval under the Animal Rule as an effective stand-alone medical countermeasure against the lethal effects of radiation exposure.

Exacerbation of lung radiation injury by viral infection: the role of Clara cells and Clara cell secretory protein

Viral infections have been associated with exacerbation of disease in human cases of idiopathic pulmonary fibrosis. Since pulmonary fibrosis is a common outcome after irradiation to the lung, we hypothesized that viral infection after radiation exposure would exacerbate radiation-induced lung injury. Epithelial injury, a frequent outcome after infection, has been hypothesized to contribute to the pathogenesis of pulmonary fibrosis and bronchiolar epithelial Clara cells participate in epithelial repair. Therefore, it was further hypothesized that altered responses after irradiation involve the bronchiolar epithelial Clara cells. C57BL/6J or CCSP(-/-) mice were irradiated with 0 (sham), 5, 10 or 15 Gy to the whole thorax. At ten weeks post-irradiation, animals were mock infected or infected with influenza A virus and body weight and survival were monitored. Pulmonary function was assessed by whole-body plethysmography. The Clara cell markers, CCSP and Cyp2f2, were measured in the lung by qRT-PCR, and protein expression was visualized in the lung by immunofluorescence. Following pulmonary function tests, mice were sacrificed and tissues were collected for pathological analysis. In 15 Gy irradiated animals infected with influenza A virus, accelerated respiratory rates, reduced pulmonary function, and exacerbated lung pathology occurred earlier post-irradiation than previously observed after irradiation alone, suggesting infection accelerates the development of radiation injury. After irradiation alone, CCSP and Cyp2f2 mRNA levels were reduced, correlating with reductions in the number of Clara cells lining the airways. When combined with infection, these markers further declined and an apparent delay in recovery of mRNA expression was observed, suggesting that radiation injury leads to a chronic reduction in the number of Clara cells that may potentiate the epithelial injury observed after influenza A virus infection. This novel finding may have considerable therapeutic implications with respect to both thoracic tumor patients and recipients of bone marrow transplants.

Antioxidant capacity of calendula officinalis flowers extract and prevention of radiation induced oropharyngeal mucositis in patients with head and neck cancers: a randomized controlled clinical study

This study was designed to determine the effect of Calendula officinalis flowers extract mouthwash as oral gel on radiation-induced oropharyngeal mucositis (OM) in patients with head-and-neck cancer. Forty patients with neck and head cancers under radiotherapy or concurrent chemoradiotherapy protocols were randomly assigned to receive either 2% calendula extract mouthwash or placebo (20 patients in each group). Patients were treated with telecobalt radiotherapy at conventional fractionation (200 cGy/fraction, five fractions weekly, 30–35 fractions within 4–7 weeks). The oropharyngeal mucositis was evaluated by two clinical investigators (a radiation oncologist and a dentist), using the oral mucositis assessment scale (OMAS). Trying to find out the possible mechanism of action of the treatment, total antioxidant, polyphenol and flavonoid contents, and quercetin concentration of the mouth wash were measured. Calendula mouthwash significantly decreased the intensity of OM compared to placebo at week 2 (score: 5.5 vs. 6.8, p = 0.019), week 3 (score: 8.25 vs. 10.95, p < 0.0001) and week 6 (score: 11.4 vs. 13.35, p = 0.031). Total antioxidant, polyphenol and flavonoid contents and quercetin concentration of the 2% extract were 2353.4 ± 56.5 μM, 313.40 ± 6.52 mg/g, 76.66 ± 23.24 mg/g, and 19.41 ± 4.34 mg/l, respectively. Calendula extract gel could be effective on decreasing the intensity of radiotherapy- induced OM during the treatment and antioxidant capacity may be partly responsible for the effect.

Effects of ionizing radiation on the immune system with special emphasis on the interaction of dendritic and T cells

Dendritic cells (DCs), as professional antigen-presenting cells, are members of the innate immune system and function as key players during the induction phase of adaptive immune responses. Uptake, processing, and presentation of antigens direct the outcome toward either tolerance or immunity. The cells of the immune system are among the most highly radiosensitive cells in the body. For high doses of ionizing radiation (HD-IR) both immune-suppressive effects after whole body irradiation and possible immune activation during tumor therapy were observed. On the other hand, the effects of low doses of ionizing radiation (LD-IR) on the immune system are controversial and seem to show high variability among different individuals and species. There are reports revealing that protracted LD-IR can result in radioresistance. But immune-suppressive effects of chronic LD-IR are also reported, including the killing or sensitizing of certain cell types. This article shall review the current knowledge of radiation-induced effects on the immune system, paying special attention to the interaction of DCs and T cells.

Fractionated irradiations lead to chronic allergic airway inflammation through increasing the influx of macrophages

OBJECTIVE

In our previous study, repeated irradiations showed persistent depression of immune response, especially Th1-related immune response. Here, we hypothesized and determined that irradiation may exacerbate development of allergic airway inflammation.

METHODS

C57BL/6 mice were irradiated repeatedly at 1 Gy or 0.5 Gy. At 6 months after irradiation, mice were sensitized and challenged short-term with OVA. Antigen-specific immunoglobulins, the percentages of inflammatory cells, chemokine expression, cytokine levels, and collagen deposition were tested.

RESULTS

In irradiated mice, IgG2a in serum was lower when compared with that of control mice, while IgG1 was significantly higher. Interestingly, the percentages of macrophages in bronchoalveolar lavage fluid (BALF) and the lung of irradiated mice were significantly higher. Conversely, the percentages of neutrophil were significantly lower in BALF of irradiated mice. In the lung of irradiated mice, MCP-1 and IP-10 for attraction of macrophages showed the higher expression level, but KC expression for neutrophils showed no difference. Next, TGF-β1 and IL-17A in BALF were higher in irradiated mice. In addition, phosphorylated-Smad2/3 was increased in irradiated mice. Finally, the deposition of collagen was increased in irradiated mice.

CONCLUSION

Our study showed that fractionated irradiation lead to the chronic allergic airway inflammation through increasing the influx of macrophages and active TGF-β levels.

HemoHIM ameliorates the persistent down-regulation of Th1-like immune responses in fractionated γ-irradiated mice by modulating the IL-12p70-STAT4 signaling pathway

Whole body irradiated mice appear to experience a down-regulation of the helper T (Th)1-like immune response, and maintain a persistent immunological imbalance. In the current study, we evaluated the effect of HemoHIM (an herbal product made from Angelica Radix, Cnidium officinale , and Paeonia japonica cultivated in Korea) to ameliorate the immunological imbalance induce in fractionated γ-irradiated mice. The mice were exposed to γ rays twice a week (0.5 Gy fractions) for a total dose of 5 Gy, and HemoHIM was administrated orally from 1 week before the first irradiation to 1 week before the final analysis. All experiments were performed 4 and 6 months after their first exposure. HemoHIM ameliorated the Th1- and Th2-related immune responses normally occur in irradiated mice with or without dinitrophenylated keyhole limpet hemocyanin immunization. HemoHIM also restored the natural killer cell activities without changing the percentage of natural killer cells in irradiated mice. Furthermore, the administration of HemoHIM prevented the reduction in levels of interleukin-12p70 in irradiated mice. Finally, we found that HemoHIM enhanced the phosphorylation of signal transducer and activator of transcription (STAT) 4 that was reduced in irradiated mice. Our findings suggest that HemoHIM ameliorates the persistent down-regulation of Th1-like immune responses by modulating the IL-12p70/pSTAT4 signaling pathway.

Chronic effects of single and fractionated γ-irradiation on an impairment of Th1-related immune response

PURPOSE

We already reported that levels of interferon (IFN)-γ have been shown to be markedly reduced in mice seven weeks after irradiation, resulting in a T helper (Th) 1/Th2 imbalance. To investigate whether the single or fractionated γ-irradiation induced an immune imbalance, we analysed the Th1-related immune response profile until six months after the fractionated whole-body irradiation.

METHODS AND MATERIALS

Mice were exposed to γ-rays at a fractionated 5 Gy cumulative dose for five weeks. At two, four and six months later from the first exposure, experiments were performed. Cell populations in the spleen, the production of IFN-γ, interleukin (IL)- 4 and IL-12p70, natural killer (NK) cell activity and the expression of IL-12 receptors, signal transducer and activator of transcription (STAT) 4 and suppressors of cytokine signaling (SOCS) 3 were detected.

RESULTS

The IFN-γ was lower in the mice exposed by all irradiation conditions than in normal control mice, but the IL-4 had increased in all the irradiated mice. To investigate Th1 profile, NK cell activity, IL-12p70 level and its receptor expression was confirmed. In all fractionated irradiation groups, the NK cell activity as well as the absolute numbers of NK cells was much decreased. Also, all the irradiated mice showed a lower IL-12p70 level. However, the expression of IL-12 receptor β2 was lower in the irradiated mice except the 0.2 Gy × 10 mice group. The phosphoylated STAT4 was lower in all the irradiated mice. This suppression was associated with an overexpression of SOCS3.

CONCLUSIONS

The fractionated whole-body irradiations of a dose of 5 Gy appear to be the down-regulation of the Th1-like immune response. These changes, in turn, maintain an immunological imbalance that persists in the long term.

Ionising radiation triggers fat accumulation in white adipose tissue

PURPOSE

To investigate changes in gonadal white adipose tissue and lipogenesis-related gene expression induced by radiation exposure.

MATERIALS AND METHODS

Groups of two-month-old C57BL/6 mice were exposed whole-body to ¹³⁷Cs γ-rays at a single dose (5 gray [Gy]) or fractionated doses (1 Gy x 5 times, 0.5 Gy x 10 times, or 0.2 Gy x 25 times). Six months after irradiation, gonadal white adipose tissue was isolated from mice. Two and 25-month-old mice were used as young and old study references. Real-time reverse transcriptase-polymerase chain reaction (RT-PCR) was used to measure messenger RNA (mRNA) expression of genes related to: (i) Primary lipid metabolism (ATP-citrate lyase [ACL], malic enzyme1 [ME1] and glucose-6-phosphate dehydrogenase 2 [G6PD2]), (ii) glucose uptake (glucose transporter 4 [GLUT4]), (iii) fatty acid synthesis (sterol regulatory element binding transcription factor 1 [SREBP-1c], fatty acid synthetase [FAS] and acetyl-coenzyme A carboxylase beta [ACC]), (iv) triglyceride synthesis (diacylglycerol O-acyltransferase 1 [DGAT1] and diacylglycerol O-acyltransferase 2 [DGAT2]), and (v) adipose-derived hormones (leptin [LEP]).

RESULTS

The weight of gonadal white adipose tissue in the irradiated groups tended to increase compared to the non-irradiated group though the radiation-induced increase in white adipose tissue was only significant for the 5 x 1 Gy group. The mRNA levels of SREBP-1c, ACC, FAS, ACL, GLUT4, ME1 and G6PD2 were relatively lower in γ-irradiated groups than in non-irradiated groups. The mRNA levels of leptin and DGAT were relatively higher than non-irradiated groups. The changes in expression of these lipogenesis-related genes caused by γ-irradiation showed a very similar pattern to changes caused by ageing.

CONCLUSIONS

A physical agent such as γ-rays can trigger biological responses resulting in fat accumulation of gonadal white adipose tissue in mice.

Attenuation of radiation- and chemoradiation-induced mucositis using gamma-D-glutamyl-L-tryptophan (SCV-07)

OBJECTIVE

To evaluate the efficacy of a novel immunomodulating peptide (SCV-07) in attenuating the course of radiation-induced mucositis in an established animal model of oral mucositis (OM).

MATERIAL AND METHODS

In three separate experiments, golden Syrian hamsters received either an acute radiation challenge to the buccal mucosa of eight fractionated doses of 7.5 Gy of radiation over a 2-week-period, or a combination of acute radiation and cisplatin. In each experiment, animals were treated with varying doses or schedules of SCV-07 or placebo. OM was scored in a blinded fashion using digital images obtained during the experimental period.

RESULTS

We found that SCV-07 reduced the severity and duration of both acute and fractionated radiation-induced OM. Similarly, when radiation and chemotherapy were used to induce OM, treatment with SCV-07 significantly reduced the duration of ulcerative OM. The therapeutic benefit was dependent on both dose and schedule of administration.

CONCLUSION

Taken together, we found SCV-07 was able to modify the duration and severity of oral mucositis and was dependent on schedule and dose.

2-Gy whole-body irradiation significantly alters the balance of CD4+ CD25- T effector cells and CD4+ CD25+ Foxp3+ T regulatory cells in mice

CD4(+)CD25(+) T regulatory (Treg) cells are critical in inducing and maintaining immunological self-tolerance as well as transplant tolerance. The effect of low doses of whole-body irradiation (WBI) on CD4(+)CD25(+)Foxp3(+) Treg cells has not been determined. The proportion, phenotypes and function of CD4(+)CD25(+) Treg cells were investigated 0.5, 5 and 15 days after euthymic, thymectomized or allogeneic bone marrow transplanted C57BL/6 mice received 2-Gy γ-rays of WBI. The 2-Gy WBI significantly enhanced the ratios of CD4(+)CD25(+) Treg cells and CD4(+)CD25(+)Foxp3(+) Treg cells to CD4(+) T cells in peripheral blood, lymph nodes, spleens and thymi of mice. The CD4(+)CD25(+) Treg cells of the WBI-treated mice showed immunosuppressive activities on the immune response of CD4(+)CD25(-) T effector cells to alloantigens or mitogens as efficiently as the control mice. Furthermore, 2-Gy γ-ray WBI significantly increased the percentage of CD4(+)CD25(+)Foxp3(+) Treg cells in the periphery of either thymectomized mice or allogeneic bone marrow transplanted mice. The in vitro assay showed that ionizing irradiation induced less cell death in CD4(+)CD25(+)Foxp3(+) Treg cells than in CD4(+)CD25(-) T cells. Thus, a low dose of WBI could significantly enhance the level of functional CD4(+)CD25(+)Foxp3(+) Treg cells in the periphery of naive or immunized mice. The enhanced proportion of CD4(+)CD25(+)Foxp3(+) Treg cells in the periphery by a low dose of WBI may make hosts more susceptible to immune tolerance induction.

Lasting effects of an impairment of Th1-like immune response in γ-irradiated mice: A resemblance between irradiated mice and aged mice

Although one of the several chronic effects of ionizing radiation is aging, there are no experimental data on radiation-induced immunological aging. The most interesting change in aging was a helper T (Th) 1/Th2 imbalance. We investigated chronic effect on immune responses after ionizing radiation and its effects in irradiated mice were compared with those of aged mice. The 2-month-old mice received a whole-body irradiation of 5Gy. At 6months after irradiation, we compared the immune functions of the irradiated mice with those of normal mice of the same age and with those of older. Interferon (IFN)-γ and antigen-specific immunoglobulin (Ig)G2a level were lower in the irradiated mice than in normal mice of same age, showing similar levels to those of old normal mice. In contrast, interleukin (IL)-4 and IL-5 and antigen-specific IgG1 level were increased in irradiated mice when compared with the same aged-normal mice. Next, we investigated the low expression of IL-12p70, IL-12 receptors and IL-18 receptors in irradiated and old mice. Also, the decrease of natural killer cell activity was intensified in the irradiated mice, showing lower than values to those of old mice. Interestingly, in irradiated mice, the absolute numbers and the percentages of natural killer (NK) cells was extremely decreased. But the absolute numbers of Th cells and cytotoxic T (Tc) cells in old mice were significantly decreased. In conclusion, an immunological imbalance by the whole-body irradiation of 5Gy induces to persist in the long term, resulting in the similar results with aging. Our results suggest that the downregulation of the Th1-like immune response shown in old mice rapidly occurred through exposure of ionizing radiation.

Influence of sublethal total-body irradiation on immune cell populations in the intestinal mucosa

The intestinal immune system is the largest in the body. This study analyzed changes in intestinal immune cell populations, cytokine protein levels, and transcript profiles after total-body irradiation (TBI) in CD2F1 mice. A single dose of 8.0 Gy gamma radiation caused negligible 30-day lethality but induced significant histological damage in jejunal mucosa that was maximal at 3.5 days and that had seemingly recovered by day 21 after irradiation. These changes were accompanied by decreased numbers of mucosal macrophages, neutrophils, and B and T lymphocytes, mostly coinciding with similar reductions in peripheral blood cell counts. Recovery of mucosal macrophages occurred within 1 week, whereas mucosal granulocytes and lymphocytes remained low until 3 weeks after TBI. Maximal suppression of T-helper cell (T(H))-related transcripts occurred at 3.5 days, but there was no obvious T(H)1 or T(H)2 bias. Genome-wide transcriptional profiling revealed a preponderance of differentially regulated genes involved in cell cycle control, cell death and DNA repair between 4 h and 3.5 days after irradiation. Genes involved in tissue recovery predominated from day 7 onward. We conclude that the intestinal immune system undergoes profound changes after sublethal TBI and that these changes likely contribute to postirradiation pathophysiological manifestations.

Gamma-ray resistance of regulatory CD4+CD25+Foxp3+ T cells in mice

Abstract CD4(+)CD25(+) regulatory T cells (Treg cells) are an important subset of T cells for keeping proper immune responses and tolerance. However, the effects of gamma radiation on CD4(+)CD25(high) Foxp3(+) Treg cells have not been examined previously. In the present study, we compared the sensitivity of mouse CD4(+)CD25(high) Foxp3(+) Treg cells and CD4(+)CD25(-) T cells to gamma radiation in vitro and in vivo. After C57BL/6 mice received a whole-body dose of 5 Gy gamma rays, the numbers of lymphocyte subsets in blood, lymph nodes, spleens and thymuses clearly decreased. However, gamma radiation significantly enhanced the ratios of CD4(+)CD25(high) Treg cells and CD4(+)CD25(high) Foxp3(+) Treg cells to CD4(+) T cells in the blood, lymph nodes, spleens and thymuses of mice. More dead cells were observed in CD4(+)CD25(-) T cells than in CD4(+)CD25(high) Treg cells or CD4(+)CD25(high) Foxp3(+) Treg cells when the cells were irradiated in vitro, indicating that CD4(+)CD25(high) Foxp3(+) Treg cells are more resistant to gamma radiation than other T cells. Moreover, a higher expression of Bcl-2 in CD4(+)CD25(high) Treg cells was detected compared with that in CD4(+)CD25(-) T cells. CD4(+)CD25(+) Treg cells from irradiated mice were functional, though their immunosuppressive ability was somewhat impaired compared to those from nonirradiated mice as determined by an in vitro assay. These results indicate that mouse CD4(+)CD25(+) Treg cells and CD4(+)CD25(-) T effector cells have different sensitivities to gamma radiation in mice.

PPARs in Irradiation-Induced Gastrointestinal Toxicity

The use of radiation therapy to treat cancer inevitably involves exposure of normal tissues. Although the benefits of this treatment are well established, many patients experience distressing complications due to injury to normal tissue. These side effects are related to inflammatory processes, and they decrease therapeutic benefit by increasing the overall treatment time. Emerging evidence indicates that PPARs and their ligands are important in the modulation of immune and inflammatory reactions. This paper discusses the effects of abdominal irradiation on PPARs, their role and functions in irradiation toxicity, and the possibility of using their ligands for radioprotection.

Enhanced antitumor efficacy of cisplatin in combination with HemoHIM in tumor-bearing mice

Background

Although cisplatin is one of the most effective chemotherapeutic agents, cisplatin alone does not achieve a satisfactory therapeutic outcome. Also cisplatin accumulation shows toxicity to normal tissues. In this study, we examined the possibility of HemoHIM both to enhance anticancer effect with cisplatin and to reduce the side effects of cisplatin in melanoma-bearing mice.

Methods

HemoHIM was prepared by adding the ethanol-insoluble fraction to the total water extract of a mixture of 3 edible herbs, Angelica Radix, Cnidium Rhizoma and Paeonia Radix. Anticancer effects of HemoHIM with cisplatin were evaluated in melanoma-bearing mice. We used a Cr⁵¹-release assay to measure the activity of NK/Tc cell and ELISA to evaluate the production of cytokines.

Results

In melanoma-bearing mice, cisplatin (4 mg/kg B.W.) reduced the size and weight of the solid tumors, and HemoHIM supplementation with cisplatin enhanced the decrease of both the tumor size (p < 0.1) and weight (p < 0.1). HemoHIM itself did not inhibit melanoma cell growth in vitro, and did not disturb the effects of cisplatin in vitro. However HemoHIM administration enhanced both NK cell and Tc cell activity in mice. Interestingly, HemoHIM increased the proportion of NK cells in the spleen. In melanoma-bearing mice treated with cisplatin, HemoHIM administration also increased the activity of NK cells and Tc cells and the IL-2 and IFN-γ secretion from splenocytes, which seemed to contribute to the enhanced efficacy of cisplatin by HemoHIM. Also, HemoHIM reduced nephrotoxicity as seen by tubular cell of kidney destruction.

Conclusion

HemoHIM may be a beneficial supplement during cisplatin chemotherapy for enhancing the anti-tumor efficacy and reducing the toxicity of cisplatin.

Acute and persisting Th2-like immune response after fractionated colorectal γ-irradiation

AIM: To investigate if an immune imbalance may account for the development and progression of chronic radiation enteritis. We analyzed the Th1/Th2 immune response profile early and 6 mo after fractionated colorectal irradiation.

METHODS: A rat model of fractionated colorectal γ-irradiation (4-Gy fractions, 3 fractions per week) was designed to investigate the effects of cumulative dose on inflammatory mediators (cytokines and chemokines) and immune response (Th1/Th2 profile and immunosuppressive mediator IL-10) during acute (early) response and 6 mo after the end of fractionated irradiation (chronic response). Analyses were performed 1 d after the cumulative doses of 16 Gy and 36 Gy and 1 d, 3 d, and 26 wk after the cumulative dose of 52 Gy.

RESULTS: Without causing histological damage, fractionated radiation induced elevated expression of IL-1β, TNFα, MCP-1, and iNOS in distal colonic mucosa during the early post-irradiation phase. At that time, a Th2 profile was confirmed by expression of both the Th2-specific transcription factor GATA-3 and the chemokine receptor CCR4 and by suppression of the Th1 cytokine IFNγ/IP-10 throughout the irradiation protocol. After 6 mo, despite the 2-fold reduction of iNOS and MCP-1 levels, the Th2 profile persisted, as shown by a 50% reduction in the expression of the Th1 transcription factor T-bet, the chemokine receptor CCXCR3, and the IFNγ/STAT1 pathway. At the same time-point, the immunosuppressive IL-10/STAT3 pathway, known to regulate the Th1/Th2 balance, was expressed, in irradiated rats, at approximately half its level as compared to controls. This suppression was associated with an overexpression of SOCS3, which inhibits the feedback of the Th1 polarization and regulates IL-10 production.

CONCLUSION: Colorectal irradiation induces Th2 polarization, defective IL-10/STAT3 pathway activation and SOCS3 overexpression. These changes, in turn, maintain a immunological imbalance that persists in the long term.

Impairment of natural killer (NK) cells is an important factor in a weak Th1-like response in irradiated mice

In whole-body-irradiated (WBI) mice, levels of the canonical Th1 cytokine IFN-gamma (IFNG) have been shown to be markedly reduced, resulting in a Th1/Th2 imbalance. In this study, the influence of natural killer (NK) cells on the balance of this Th1/Th2 immune response was evaluated in WBI mice. Although NK cells are one of the types of cells that secreteIFN-gamma, NK cell activity tends to be minimal, even at 7 weeks after irradiation. In NK cell-depleted mice, the levels of Th1-related cytokines were lower than those of the control mice and were correlated with lower IgG2a production and elevated IgE and IgG1 production. These results indicated that NK cells have a crucial role in the final differentiation of Th cells into Th1 cells. The impairment of NK cells in the WBI mice was confirmed by the observation that NK cells from the WBI mice induced a decrease in the generation of IFN-gamma by the NK cell-depleted spleen lymphocytes from normal mice. Also, the WBI mice that received NK cells obtained from the normal mice generated more IgG2a, IL12 and IFN-gamma. Our results indicate that the impairment of NK cells is an important factor in the reduced Th1-like response in irradiated mice.

The NK1.1+T cells alive in irradiated mice play an important role in a Th1/Th2 balance

PURPOSE

Ionizing radiation is known to reduce the helper T (Th) 1 like function, resulting in a Th1/Th2 imbalance. We studied whether NK1.1+T cells which were the most resistant against gamma-irradiation impact on the imbalanced immune response after irradiation.

MATERIALS AND METHODS

C57BL/6 mice received a whole-body gamma-irradiation (WBI) of 4 Gy. The primary T cells were separated by magnetic cell sorter (MACS) using the anti-CD90.2 antibody. The apoptotic cells were detected by propidium iodide (PI) staining. To determine the Th1 and Th2 cell functions, the production of interferon (IFN)-gamma and interleukin (IL)-4 were analysed by a reverse transcriptase-polymerase chain reaction (RT-PCR) and an enzyme linked immunosorbent assay (ELISA). NK1.1+T cells were detected by flow cytometry. For depletion of the NK1.1+T cells in the WBI mice, anti-asialo GM1 antiserum was injected.

RESULTS

The CD90.2 positive cells of the WBI mice produced significantly more Th2 type cytokines and also produced Th1 type cytokines at a not lower level than normal mice, and contained a higher absolute number of NK1.1+T cells. Also, the proportion of the NK1.1+T cells increased in the WBI mice. We found that the NK1.1+T cells were resistant to radiation-induced apoptosis in comparison with the conventional T cells. The depletion of NK1.1+T cells in WBI mice resulted in higher production of IgE and IL-4 and lower secretion of IL-12p70.

CONCLUSION

Our findings revealed that NK1.1+T cells that survive at an early stage after irradiation play an important role in the balance of the immune responses at a late stage after irradiation.

Low dose radiation induced immunomodulation: effect on macrophages and CD8+ T cells

PURPOSE

The aim of the present investigation was to study the effect of fractionated whole body low dose ionizing radiation (LDR) on the functional responses of T lymphocytes, their subpopulations and macrophages.

MATERIALS AND METHODS

C57BL/6 mice were exposed to 4 cGy from a (60)Co source, at 0.31 cGy/min, at 24 h intervals for 5 days (total dose 20 cGy). Phagocytic activity was measured by flow cytometry using Bioparticles and nitric oxide generation was estimated by spectrophotometry. Proliferation of lymphocytes in response to concanavalin A (con A) and alloantigens was measured by (3)H thymidine incorporation. Expression of cell surface markers was assessed by flow cytometric analysis of antibody labeled cells. Target cell killing by cytotoxic T cells (CTL) generated against allogenic cells was assessed by flow cytometry using PKH26 labeled target cells. Cytokines were estimated by enzyme linked immunosorbent assay.

RESULTS

Exposure to LDR enhanced nitric oxide secretion and phagocytosis. The expression of early activation antigen, CD69, was enhanced in CD8(+) T lymphocytes concomitant with enhanced proliferation in response to con A. In addition, mixed lymphocyte reaction (MLR) and CTL response were augmented and secretion of interferon gamma (IFN-gamma) was suppressed following LDR exposure.

CONCLUSIONS

LDR exposure enhanced the function of macrophages and responses of CD8(+) T cells in C57BL/6 mice.