Cellular events during radiation-induced thymic leukemogenesis in mice: abnormal T cell differentiation in the thymus and defect of thymocyte precursors in the bone marrow after split-dose irradiation

Cellular events during the development of thymic lymphomas in young B10.BR mice given leukemogenic split-dose irradiation were studied by examining the differentiation of functional T lymphocyte precursors in the regenerating thymus. It was found that leukemogenic radiation treatment resulted in a sustained depression of the level of thymic cytotoxic T lymphocyte precursors (CTLp) and of mixed lymphocyte reactivity of thymus cells when assessed between 1 and 4 mo after irradiation, in spite of the fact that the total number of thymocytes was restored to the normal level within 2 mo and continued to increase thereafter. In vitro mixing studies of normal thymocytes with thymus cells from split-dose irradiated mice provided no evidence for active suppression as a mechanism for this depressed activity. The ability of bone marrow cells from split-dose irradiated mice to regenerate the thymus and to differentiate into functional CTLp was examined by use of supralethally irradiated Thy-1 congenic recipients. Reconstitution of supralethally irradiated B10.BR Thy-1.2 mice with normal bone marrow from B10.BR Thy-1.1 mice resulted in the complete repopulation of host-thymus with donor-derived cells when assessed at 4 wk after reconstitution. Lymphocytes from the regenerating thymus of these animals were shown to contain high levels of CTLp which were donor-derived. On the other hand, when the recipient mice were reconstituted with bone marrow cells from donor mice which had been split-dose irradiated 1 mo earlier, regeneration of the recipient thymus was severely depressed when assessed at 4 wk to 3 mo after reconstitution. Although variable but small numbers of donor-derived Thy-1+ cells were detected, CTL activity for alloantigen could not be induced in these donor-derived cells. The results suggest that T cell precursors derived from split-dose irradiated donor mice were unable to undergo active proliferation and differentiation into functional CTLp. The significance of these findings on radiation-induced thymic leukemogenesis is discussed.     

Effects of treatment with interleukin-1 receptor antagonist on endogenous interleukin-1 levels in normal and irradiated mice

The in vivo effects of recombinant human interleukin-1 receptor antagonist (rhIL-1Ra) administration on endogenous IL-1 levels in the circulation and conditioned media (CM) from different immunohematopoietic organ/tissues were studied in CBA mice under steady state and postirradiation conditions. In normal mice, constitutive IL-1 levels were demonstrated in the plasma, CM of peritoneal exudate cells and full-thickness skin explants with low or undetectable levels in CM of splenic and bone marrow cell suspensions. In irradiated mice (2 Gy, X rays) on day 3 post exposure a significant increase of IL-1 levels was seen in the circulation and CM of peritoneal exudate cells, with no significantly different levels in postirradiation bone marrow, spleen and skin. After rhIL-1Ra treatment of the animals (2 x 50 microg/mouse, i.p.), significantly elevated IL-1 levels were observed in the skin and CM of peritoneal exudate cells in normal mice, whereas slightly increased levels were detected in CM of splenic cells. The rhIL-1Ra administration in irradiated mice led to decreased IL-1 concentrations in the circulation, and CM of peritoneal exudate cells and skin. The results pointed out the importance of IL-1 secretion and receptor expression in the maintenance of homeostasis in steady state, as well as during recovery after irradiation. Modulatory effects of IL-1Ra on IL-1 production were dependent on basic endogenous IL-1 concentration.     

Mentha piperita (Linn.) leaf extract provides protection against radiation induced chromosomal damage in bone marrow of mice

Oral administration of M. piperita (1 g/kg body weight/day) before exposure to gamma radiation was found to be effective in protecting against the chromosomal damage in bone marrow of Swiss albino mice. Animals exposed to 8 Gy gamma radiation showed chromosomal aberrations in the form of chromatid breaks, chromosome breaks, centric rings, dicentrics, exchanges and acentric fragments. There was a significant increase in the frequency of aberrant cells at 6 hr after irradiation. Maximum aberrant cells were observed at 12 hr post-irradiation autopsy time. Further, the frequency of aberrant cells showed decline at late post-irradiation autopsy time. However, in the animals pretreated with Mentha extract, there was a significant decrease in the frequency of aberrant cells as compared to the irradiated control. Also significant increase in percentage of chromatid breaks, chromosome breaks, centric rings, dicentrics, exchanges, acentric fragments, total aberrations and aberrations/damaged cell was observed at 12 hr post-irradiation autopsy time in control animals, whereas Mentha pretreated irradiated animals showed a significant decrease in percentage of such aberrations. A significant decrease in GSH content and increase in LPO level was observed in control animals, whereas Mentha pretreated irradiated animals exhibited a significant increase in GSH content and decrease in LPO level but the values remained below the normal. The radioprotective effect of Mentha was also demonstrated by determining the LD(50/30) values (DRF = 1.78). The results from the present study suggest that Mentha pretreatment provides protection against radiation induced chromosomal damage in bone marrow of Swiss albino mice.     

大豆异黄酮对辐射小鼠造血系统损伤防护作用的实验研究

研究大豆异黄酮(SoybeanIsoflavone,SI)对辐射损伤小鼠造血系统功能的影响。雄性昆明小鼠照射前补充SI,经4Gyγ射线照射,观察补充SI对电离辐射损伤小鼠内源性脾结节(CFU-S)数、骨髓细胞粒、巨噬系细胞集落形成单位(CFU-GM)数、骨髓细胞DNA含量及外周血淋巴细胞DNA损伤程度的影响。结果显示SI提高了辐射损伤小鼠CFU-S数,增加了骨髓有核细胞CFU-GM数,降低外周血淋巴细胞DNA损伤程度,对骨髓细胞DNA含量也有一定的增加趋势。表明SI可以提高辐射损伤小鼠造血干祖细胞的增殖能力,减轻辐射对骨髓细胞和外周血淋巴细胞DNA的损害,SI对辐射小鼠的造血系统有一定的防护作用。     

Antioxidant activity of brahma rasayana

Free oxygen radical scavenging activity of brahma rasayana (BR) was studied by in vitro and in vivo models. Addition of aqueous extract of BR was found to scavenge the lipid peroxides already present in rat liver homogenate (IC50 700 micrograms/ml) and inhibit the lipid peroxide generated by Fe(2+)-ascorbate (IC50 2600 micrograms/ml) and Fe(3+)-ADP-ascorbate system (IC50 1200 micrograms/ml). BR was found to scavenge the hydroxyl radical generated by Fenton reaction (IC50 7400 micrograms/ml) and superoxide generated by photoreduction of riboflavin (IC50 180 micrograms/ml). BR was also found to inhibit the nitric oxide radical generated in vitro from sodium nitroprusside (IC50 5.5 micrograms/ml). Oral administration of BR (50 mg/dose/animal) was found to inhibit the PMA induced superoxide generation in mice peritoneal macrophages. Oral administration of BR; 10 and 50 mg/dose/animal was also found to inhibit the nitrite production in peritoneal macrophages and percentage inhibition was 25.2% and 37.8% respectively. These results indicate significant antioxidant activity of BR in vitro and in vivo.     

Administration of human recombinant IL-7 to normal and irradiated mice increases the numbers of lymphocytes and some immature cells of the myeloid lineage.

In vitro experiments performed by several investigators have demonstrated that IL-7 is a growth factor for immature B lymphocytes, thymocytes, and mature T lymphocytes. To evaluate the potential therapeutic use for human rIL-7 (rhuIL-7) as a hematopoietin, we have studied the in vivo hematopoietic effects of rhuIL-7 in mice. In these experiments, sublethally irradiated and normal mice were treated with or without rhuIL-7 for up to 26 days. Administration of rhuIL-7 significantly increased the white blood cell count in the peripheral blood and spleen in both normal and irradiated mice. Treatment with rhuIL-7 also accelerated lymphocytic recovery in irradiated mice. Precursor and mature B lymphocytes showed the greatest expansion in response to rhuIL-7 administration, with smaller increases in T lymphocytes being observed. In mice recovering from high dose irradiation, rhuIL-7 treatment resulted in preferential expansion of CD8+ T lymphocytes and more rapid normalization of the CD4/CD8 ratios. Differential analysis of peripheral blood smears demonstrated that rhuIL-7 also increased the numbers of immature granulocytes in both normal and irradiated mice. Moreover, administration of rhuIL-7 to normal, irradiated, cyclophosphamide-pretreated, or 5-fluorouracil-pretreated mice increased the number of acetylcholinesterase-positive megakaryocytes in the spleen, but not the bone marrow. Therefore, although the major in vivo effects of rhuIL-7 were on cells of the lymphocytic lineage, rhuIL-7 also increased the numbers of some immature cells of the myeloid lineage.     

Parathyroid Hormone Administration Improves Bone Marrow Microenvironment and Partially Rescues Haematopoietic Defects in Bmi1-Null Mice

The epigenetic regulator Bmi1 is key in haematopoietic stem cells, and its inactivation leads to defects in haematopoiesis. Parathyroid hormone (PTH), an important modulator of bone homeostasis, also regulates haematopoiesis, so we asked whether PTH administration improves bone marrow microenvironment and rescues the haematopoietic defects in Bmi1-null mice. The mice were treated with PTH1-34 (containing the first 34 residues of mature PTH), an anabolic drug currently used for treating osteoporosis, and compared with the vehicle-treated Bmi1 ^-/- and wild-type littermates in terms of skeletal and haematopoietic phenotypes. We found that the administration significantly increased all parameters related to osteoblastic bone formation and significantly reduced the adipocyte number and PPARγ expression. The bone marrow cellularity, numbers of haematopoietic progenitors and stem cells in the femur, and numbers of lymphocytes and other white blood cells in the peripheral blood all increased significantly when compared to vehicle-treated Bmi1^-/- mice. Moreover, the number of Jagged1-positive cells and percentage of Notch intracellular domain-positive bone marrow cells and protein expression levels of Jagged1 and NICD in bone tissue were also increased in Bmi1 ^-/- mice upon PTH1-34 administration,whereas the up-regulation of PTH on both Notch1 and Jagged1 gene expression was blocked by the Notch inhibitor DAPT administration. These results thus indicate that PTH administration activates the notch pathway and partially rescues haematopoietic defects in Bmi1-null mice, further suggesting that haematopoietic defects in the animals are not only a result of reduced self-renewal of haematopoietic stem cells but also due to impaired bone marrow microenvironment.     

Effect of Bilirubin on Lipid Peroxidation, Sphingomyelinase Activity, and Apoptosis Induced by Sphingosine and UV Irradiation

The effect of bilirubin (BR) on sphingomyelin cycle activity, lipid peroxidation (LPO), and apoptosis induced by sphingosine and UV irradiation has been studied in vivo. Neutral Mg²⁺-dependent sphingomyelinase (SMase) activity and LPO level were monitored in heart, kidney, and liver of mice after administration of BR. BR inhibited both LPO and SMase activities in heart and kidney. BR induced a mild increase in LPO level and moderate increase in lipid contents in liver, consistent with the functional role of liver in both BR and lipid metabolism. BR injected to mice causes simultaneous and unidirectional alterations in both LPO level and SMase activity with a significant (p < 0.05) positive linear correlation between these two parameters. Sphingosine administration results in increased lipid peroxidation in murine liver. Data on DNA fragmentation indicate that exogenous BR may effectively protect thymus cells against sphingosine- and UV-mediated apoptosis. These results have revealed a biochemical association between oxidative stress and BR on one hand and the sphingomyelin cycle and apoptotic cell death on the other hand. Our data show that BR as an antioxidant, due to its effect on the sphingomyelin cycle, can protect membrane lipids against peroxidation and cells against apoptosis induced by various factors.     

Effect of millimeter waves on cyclophosphamide induced suppression of the immune system

The effect of millimeter electromagnetic waves (MWs) on cyclophosphamide (CPA) induced toxicity to leukocytes, bone marrow cells, and T-cell-mediated immunity was examined. For studying the effect of MWs on CPA induced leukopenia and myelosuppression, BALB/C mice were irradiated for 3 days, 30 min each day, prior to administration of CPA (200 mg/kg). MWs were produced with a Russian made YAV-1 generator. The device produced 42.2 +/- 0.2 GHz modulated wave radiation through a 10 mm x 20 mm rectangular output horn. The animals were irradiated on the nose area. Peak SAR and incident power density were measured as 622 +/- 100 W/kg and 31 +/- 5 mW/cm(2), respectively. For studying the effect of MWs on CPA induced suppression of T-cell mediated immunity, a delayed type hypersensitivity (DTH) assay in mouse skin was used. The DTH reaction in mouse skin was induced by topical application of dinitrochlorobenzene (DNCB) and quantified by measuring the increase in ear thickness and by histological examination. Treatment of animals with CPA significantly (P < 0.05) reduced leukocyte and bone marrow cell population, but MW irradiation did not show any significant protection from the immunosuppressive effects of CPA. Furthermore, MW irradiation did not protect the animals from CPA induced suppression of T-cell mediated immunity.     

Immunostimulatory action of AC II--an ayurvedic formulation useful in HIV

Immunostimulatory activity of AC II, a registered ayurvedic preparation prepared at Amala Ayurvedic Research Centre for treating HIV and AIDS is reported. AC II administration could significantly enhance the mitogen-induced proliferation of lymphocytes of spleen cells. It was also found to increase cell-mediated immune responses in normal and tumor-bearing control animals. Oral administration of AC II significantly enhanced Natural Killer cell activity in normal and tumor-bearing animals on the 7th day, which was observed earlier than the tumor-bearing control animals and normal animals. Antibody dependent cellular cytotoxicity (ADCC) was also increased in AC II treated normal and tumor-bearing animals. An early enhancement of antibody-dependent complement-mediated cytotoxicity was also observed by the administration of AC II in normal as well as tumor-bearing animals. Treatment with AC II elevated the levels of IL-2, TNF-alpha and IFN-gamma in normal mice. Administration of AC II was also found to increase the cytotoxic T lymphocyte production in EL4 treated mice. These studies support the use of this immune stimulatory preparation in HIV patients.     

The influence of IL-1 treatment on the reconstitution of the hemopoietic and immune systems after sublethal radiation

The influence of IL-1 administration on the recovery of the hemopoietic and immune systems from sublethal irradiation was assessed. Mice were irradiated (750 R) and injected twice daily with purified recombinant derived IL-1 beta (200 ng/injection). At various times after irradiation, the functional capacity of the hemopoietic and immune systems was determined. It was found that IL-1 therapy resulted in a significantly greater number of granulocyte-macrophage-CSF responsive colony-forming cells in the bone marrow of the irradiated mice on days 5 and 11 postirradiation but not at later times. In addition the radiation induced neutropenia recovered quicker in the IL-1-treated mice with significantly greater numbers of peripheral blood granulocytes being seen on days 15 and 20 after irradiation. The influence of IL-1 therapy on the recovery of the immune system was also assessed. Of note was the observation that mice receiving IL-1 therapy had chronically hypoplastic thymi. Although thymic cellularity increased with time after irradiation in the control mice, there was no such increase in the IL-1-treated mice. Similarly, the number of pre-B cells in the marrow of these mice was also diminished. Thus, in the IL-1-treated mice the regeneration of the peripheral immune function was retarded, characterized by a general lymphopenia and decreased splenic responses to mitogenic stimuli.     

Diltiazem does not increase the in vivo sensitivity of murine hemopoietic progenitor cells to doxorubicin

The effect of doxorubicin and the calcium antagonist, diltiazem, on murine hemopoietic progenitor cells was studied in vivo. Dose-survival curves of murine bone marrow colony forming units (CFU)--spleen and granulocyte macrophage--were determined by in vivo and in vitro methods in DBA/2NCr/BR mice treated with doxorubicin alone or by simultaneous administration of doxorubicin (DX) and diltiazem (DTZ). Time response of bone marrow hematopoietic progenitor cells (HPC) was followed in mice similarly treated. Combination of DTZ with DX did not change the toxic effect of the latter on hemopoietic cells, either in the dose-survival model or in the time-related experiment.     

Radioprotective action of extracellular adenosine on bone marrow cells in mice exposed to gamma rays as assayed by the micronucleus test

The frequency of micronucleated polychromatic erythrocytes (PCEs) in mouse bone marrow was assessed after administration of dipyridamole and/or adenosine monophosphate (AMP) to nonirradiated mice or to mice irradiated 15 min later with a sublethal dose of 6.5 Gy gamma rays. In nonirradiated mice, the administration of the drugs increased the frequency of micronucleated PCEs significantly (by 108%). In contrast, in irradiated mice, the number of radiation-induced micronucleated PCEs was significantly decreased if the mice had been pretreated with dipyridamole or AMP alone (by 24% after administration of each of the compounds) and in particular after administration of the drugs in combination (by 36%).     

The direct profibrotic and indirect immune antifibrotic balance of blocking the cannabinoid 2 receptor

Cannabinoid 2 (CB2) receptors expressed on immune cells are considered to be antifibrogenic. Hepatic stellate cells (HSCs) directly interact with phagocytosis lymphocytes, but the nature of this interaction is obscure. We aimed to study the effects of CB2 receptors on hepatic fibrosis via their role in mediating immunity. Hepatic fibrosis was induced by carbon-tetrachloride (CCl(4)) administration in C57BL/6 wild-type (WT) and CB2 knockout (CB2(-/-)) mice. Irradiated animals were reconstituted with WT or CB2(-/-) lymphocytes. Lymphocytes from na?ve/fibrotic WT animals and healthy/cirrhotic hepatitis C virus were preincubated in vitro with or without CB2 antagonist, evaluated for proliferation and apoptosis, and then cocultured with primary mouse HSCs or a human HSC line (LX2), respectively. Lymphocyte phagocytosis was then evaluated. Following CCl(4)-administration, CB2(-/-) mice developed significant hepatic fibrosis but less necroinflammation. WT mice harbored decreased liver CD4(+) and NK(+) cells but increased CD8(+) subsets. Na?ve CB2(-/-) mice had significantly decreased T cell subsets. Adoptive transfer of CB2(-/-) lymphocytes led to decreased fibrosis in the irradiated WT recipient compared with animals receiving WT lymphocytes. Moreover, necroinflammation also tended to decrease. In vitro, a CB2-antagonist directly increased human HSC activation and increased apoptosis and decreased proliferation of mice/human T cells (healthy/fibrotic) and their phagocytosis. We concluded that CB2(-/-) lymphocytes exert an antifibrotic activity, whereas lack of CB2 receptor in HSCs promotes fibrosis. These findings broaden our understanding of cannabinoid signaling in hepatic fibrosis beyond their activity solely in HSCs.     

Influence of thymic humoral factor(s) on haemopoiesis in mice

Postirradiation administration of Leukotrophin to whole-body irradiated mice was associated with increased LD50/30 and DRF. As indicated by 59Fe uptake and ESC number, haemopoiesis was significantly stimulated in spleen and bone marrow after Leukotrophin application to irradiated mice. DNA content and the uptake of 3H-thymidine in DNA was significantly enhanced in the thymus and bone marrow of irradiated and Leukotrophin-treated mice. The micronucleus test confirmed that Leukotrophin is a therapeutic agents, while administered before irradiation it does not influence the initial radio-lesions.     

Differential effect of Bacillus firmus on immune response and enterocyte brush-border enzyme levels in BALB/c and B10.BR mice

A nonpathogenic bacterium of external environment possessing remarkable immunomodulatory activity, Bacillus firmus (BF) inactivated with formaldehyde, was given intragastrically to two genetically different mouse strains BALB/c (H-2d) and B10.BR/SnPh (B10.BR, H-2k) reared in conventional (CV) and B10.BR strain also in germ-free (GF) conditions. Repeated intragastric administration of BF (500 micrograms every other day over two weeks, starting at the age of 3 months) significantly enhanced intestinal IgA levels in CV BALB/c mice but did not affect intestinal IgA in CV B10.BR mice. In GF B10.BR mice, IgG levels in sera and intestinal washings increased after BF administration compared to CV B10.BR mice. In CV BALB/c mice, specific activity of enterocyte brush-border enzymes (lactase, gamma-glutamyltransferase, alkaline phosphatase) decreased after BF treatment; sucrase (sucrose alpha-glucosidase) activity was not affected. On the other hand, in B10.BR mice, specific activity of gamma-glutamyltransferase and dipeptidyl peptidase IV were higher after administration of BF in both CV and GF groups relative to untreated controls. The activities of lactase and glucoamylase (glucan 1,4-alpha-glucosidase) were significantly stimulated only in the group of GF B10.BR mice treated with formolized BF. The stimulation of immunoglobulin production after BF treatment was accompanied by changes in the levels of enterocyte brush-border enzymes; this responsiveness to BF treatment was genetically regulated.     

Radioprotective effects of ginsan,an immunomodulator

We previously reported that ginsan, a purified polysaccharide isolated from Panax ginseng, had a mitogenic activity, induced LAK cells, and increased levels of several cytokines. In an effort to identify other immunostimulatory effects, we evaluated the protective effects of ginsan injected in vivo against radiation by measuring its effects on the CFU-S bone marrow cells and spleen cells. Ginsan was found to significantly increase the number of bone marrow cells, spleen cells, granulocyte-macrophage colony-forming cells (GM-CFC), and circulating neutrophils, lymphocytes and platelets in irradiated mice. In addition, ginsan induced the endogenous production of cytokines such as Il1, Il6, Ifng and Il12, which are required for hematopoietic recovery, and was able to enhance Th1 function while interfering with the Th2 response in irradiated mice. We demonstrated that pretreatment with ginsan protected mice from the lethal effects of ionizing radiation more effectively than when it was given immediately after or at various times after irradiation. A significant increase in the LD(50/30) from 7.54 Gy for PBS injection to 10.93 Gy for mice pretreated with 100 mg/kg ginsan was observed. These findings indicate that ginsan may be a useful agent to reduce the time necessary for reconstituting hematopoietic cells after irradiation.     

Effect of a neutrophilia-inducing tumor on hemopoietic stem cells in mice

The influence of neutrophilic stimulation on hemopoietic stem cells was studied in mice with tumor-induced neutrophilia. Transfusions of marrow cells from normal and neutrophilic tumor-bearing mice into lethally irradiated normal and tumor-bearing mice were performed. The number and the erythroid:granuloid (E:G) ratio of day 7 colonies in the recipient spleens and bones as well as the size of spleen colonies of recipient animals were determined. The E:G ratio of spleen and bone marrow colonies between normal and tumor-bearing mouse recipients and the number of spleen colonies did not differ significantly in either experiment. However, spleen colonies which developed in tumor-bearing irradiated mice were significantly larger than those which developed in normal recipients in both experiments. These studies indicated that while the line of differentiation taken by hemopoietic stem cells was not affected by the neutrophilic influence of the tumor, the tumor-bearing host environment appeared to enhance proliferation of transfused stem cells and/or their descendants. The stimulators of granulocytopoiesis in this model of neutrophilia appear to act on a population of progenitor cells more mature than the stem cells capable of forming 7-day colonies in the spleen and bone marrow of irradiated recipient mice.     

Effect of brahma rasayana on antioxidant system after radiation

Oral administration of brahma rasayana (BR; 50 mg/animal for 10 and 30 days) significantly increased the liver antioxidant enzymes such as superoxide dismutase (SOD), catalase(CAT) and tissue and serum levels of reduced glutathione (GSH). Whole body irradiation suppressed the levels of SOD, CAT and GSH. Reduced activity of SOD, CAT and GSH was significantly elevated by treatment with BR after radiation treatment. Similarly radiation exposure induced increase in serum and liver lipid peroxides was significantly reduced by further treatment with BR. The results indicate that BR could ameliorate the oxidative damage produced in the body by radiation and may be useful as an adjuvant during radiation therapy.