The effect of oral quercetin on UVB-induced tumor growth and local immunosuppression in SKH-1.

The effects of quercetin (4%) on UVB-induced carcinogenesis and immunosuppression were studied in hairless SKH-1 mice exposed daily to suberythemal UVB for 12/13 and 16/17 weeks. Macroscopic and microscopic examinations showed that quercetin did not affect the onset and growth of UVB-induced non-melanoma skin tumors. Quercetin prevented the UV-induced suppression of the contact hypersensitivity (CHS) and the reduction of the percentage of CD8-positive cells in spleen and lymph nodes. Other immunological parameters were not affected. Thus, the results indicate that oral intake of a high dose of quercetin does not prevent UVB-induced carcinogenesis, although it restores the skin-associated CHS response.

The SCID-ra mouse: rat T-cell differentiation in the severe combined immunodeficient mouse.

The SCID-hu mouse model offers the possibility to study the human thymus in vivo in an isolated xenogeneic environment. Whilst studying the toxicology of the human thymus using the SCID-hu model, a "control" model to test for differences in toxicokinetics due to the different localization of the thymus is desirable when SCID-hu data have to be extrapolated to the normal human situation. For this reason, SCID-ra mice were constructed by implanting rat fetal or postnatal thymus and liver explants under the renal capsule of severe combined immunodeficient (SCID) mice. Implantation of rat fetal thymus in combination with fetal liver resulted in thymus grafts with a histological appearance that was virtually identical to that of normal age-matched rat thymus. T cells of rat origin were found in the circulating blood and lymphoid organs of the recipient mice. After implantation of postnatal thymus and liver, the thymus grafts showed a dysplastic morphology. These grafts were devoid of thymocytes and consisted mainly of thymic microenvironmental components and large numbers of thymic macrophages. Some SCID-ra mice showed signs of graft-versus-host (GVH) reactions in the skin. The incidence of GVH reactions was higher with increasing developmental stage of the donor material used for implantation.

Quercetin prevents UV-induced local immunosuppression, but does not affect UV-induced tumor growth in SKH-1 hairless mice.

Ultraviolet is thought to induce skin tumors by its dual activity as a mutagenic agent and a suppressor of cell-mediated immunity. In the present study the effects of quercetin, a flavonoid-containing compound, on carcinogenesis and immunosuppression were studied in SKH hairless mice exposed to suberythemal doses of UV for up to 17 weeks. It was found that quercetin did not affect the onset or growth of non-melanoma skin tumors resulting from UV exposure. In contrast, it prevented the suppression in contact hypersensitivity (CHS) to picryl chloride induced by UV. The mechanism of this prevention might be explained by the observation that the decreased number of epidermal Langerhans' cells is partly prevented by the quercetin. Quercetin did not alter the effects of UV in increasing numbers of spleen and lymph node cells, only partly in decreasing the CD8-positive cells in spleen cell populations and decreasing the lymphoproliferative response of spleen cells to the mitogens concanavalin A and phytohemagglutinin. Thus oral quercetin did not prevent UV-induced carcinogenesis although it restored the skin-associated CHS response probably by protecting the antigen-presenting cells in the skin.

An enzyme-linked immunosorbent assay of anti-sheep red blood cell antibodies of the classes M, G, and A in the rat.

In order to investigate the immune system as a possible target for toxicity by chemicals, functional assays of the immune system are required. Sheep red blood cells (SRBC) are widely used as an antigen to study the immune competence of animals. Since routine toxicology includes data mainly provided with rat toxicity studies, there is a need for easy, specific, and reproducible assays of antibody responses to sheep erythrocytes in the rat. This report describes an enzyme-linked immunosorbent assay (ELISA) of anti-SRBC antibodies of the classes M, G and A in the serum of rats. Antigen preparations, prepared from ghosts of sheep erythrocytes by extraction with KCl, were used to coat the bottom of wells in 96 well microtiter plates. Serum samples from rats, that were immunized with sheep erythrocytes, were titrated on these plates, using specific polyclonal antibodies to rat immunoglobulins M and G, to which peroxidase was conjugated. Immunoglobulin A was assayed, using monoclonal anti-rat IgA antibodies, and polyclonal rat anti-mouse IgG that was conjugated with peroxidase. The results indicate that the ELISA of serum titers of IgM, G and A to sheep erythrocytes is an easy and reliable method, that can be used to detect the effects of chemicals on the immune system of the rat.

Time course of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced thymic atrophy in the Wistar rat.

Exposure to sublethal doses of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in Wistar rats results in thymic atrophy and reduced thymic cellularity. In a first experiment, rats were once orally intubated with 0, 1, 5, 25, 50, and 150 micrograms TCDD/kg body wt and sacrificed at Day 10. The dose that produced one-half of the maximal thymic involution was estimated at about 10-20 micrograms/kg. The time course (Days 0-21) of thymic atrophy induced by a single oral intubation of 25 micrograms TCDD/kg body wt revealed four phases. In phase 1 (initiation phase, Days 0-2) a decrease in proliferative activity was seen in cortical thymocytes, whereas no changes occurred in thymic cellularity. Phase 2 (lymphodepletion phase, Days 2-8) was characterized by an initial strong depletion of immature CD4+CD8+ double-positive (DP) cells (Day 4), followed by a more gradual decrease in the number of mature thymocytes (Day 6). On Day 8 the lymphodepletion was maximal. In phase 3 (stationary phase, Days 8-13) no changes occurred in thymic cellularity. Although the first signs of recovery were already seen on Day 6, indicated by a recovery in proliferative activity in the thymus cortex, an increase in thymic cellularity was observed first after Day 13 (phase 4, recovery phase, Day 13 onward). Reversibility of thymic atrophy is therefore observed within the estimated half-life of TCDD in the rat thymus (> 16 days). We conclude that TCDD exerts a rapidly reversible effect on an intrathymic cortical target cell population.

The balloon technique: a convenient method to measure exhaled NO in epidemiological studies.

OBJECTIVES: The aim of the present study was to evaluate the balloon procedure to measure exhaled nitric oxide (NO). METHODS: This was performed by comparing the procedure with the well-established on-line measurement of NO (direct exhalation into the NO module). Using both procedures exhaled NO was measured in 16 healthy subjects on two days with different level of air pollution. RESULTS: Exhaled NO measured on-line was 3.8-4.5 times lower than exhaled NO obtained using the balloon technique but the two sets of values correlated linearly (r 0.93-0.97). Mean NO level on day 1 with low air pollution and day 2 with high air pollution was 6.6 and 8.1 parts per billion (ppb; on-line measurement) and 25.2 and 36.9 ppb (balloon method), respectively. The day 1 to day 2 ratio differed per subject but was independent of the technique of measurement. Mean day-to-day ratio of exhaled NO using the balloon technique (1. 65 +/- 0.13) was not different (P < 0.05) from the ratio of NO levels measured on-line (1.49 +/- 0.13). Based on these ratios the increase in level of outdoor air pollution appears to be associated with a 49-65% increase in exhaled NO. CONCLUSION: Exhaled NO is proposed as a de novo individual biomarker to monitor the adverse effects of air pollution. The balloon procedure offers a sound and convenient alternative for the on-line procedure to measure exhaled NO in large populations as required in epidemiological studies.

Pathological and immunological effects of respirable coal fly ash in male Wistar rats.

In this study the effects of inhalatory exposure to coal fly ash on lung pathology and the immune system in rats were examined. Rats were exposed to 0, 10, 30, or 100 mg/m(3) coal fly ash (6 h/day, 5 days/wk) for 4 wk, or to 0 and 100 mg/m(3) for 1 wk, and for 1 wk followed by a recovery in clean air of 3 wk. A concentration-related increase in lung weight was found starting from 30 mg/m(3) coal fly ash. After exposure to 100 mg/m(3), a time-related deposition of free particles in the lungs was observed as well as a time-related number of coal fly ash particles phagocytized in alveolar macrophages. Histological examination revealed increased cellularity in alveolar septa, consisting mainly of mononuclear cell infiltrate, proliferated type II cells, and a slight fibrotic reaction. After a recovery period of 3 wk the histological picture was identical to that after 1 wk of exposure, indicating no significant recovery. No toxicological significant changes were found in the hematological, clinical chemistry, or urine parameters. Effects both on nonspecific defense mechanisms and on specific immune responses were noted. With regard to the immune function in the draining lymph nodes of the lung, a significantly increased number of both T and B lymphocytes was observed. The ratio of both cell types was not changed in either of the groups. In serum of exposed rats a significant increase of up to 150% of the immunoglobulin A (IgA) content was found. The number and phagocytic capacity of macrophages were significantly increased, while the killing of Listeria bacteria per cell ex vivo/in vitro remained unchanged. Natural killer (NK) activity in pulmonary cell suspensions was slightly stimulated in rats exposed for 4 wk to 10 and 30 mg/m(3), whereas an exposure to 100 mg/m(3) resulted in a slight decrease; however, both changes were not significant. In conclusion, the alterations in lung histopathology and immunity, observed in a dose and exposure time relation at concentrations up to and including 100 mg/m(3) coal fly ash, may be considered an adverse response of the host to inhalation of particulate matter. Whether these observed alterations may effect the host resistance must be learned from infection studies.

Exhaled NO level and number of eosinophils in nasal lavage as markers of pollen-induced upper and lower airway inflammation in children sensitive to grass pollen.

OBJECTIVES: This study investigates the upper and lower inflammatory response induced by natural exposure to grass pollen in atopic and non-atopic children. METHODS: After children's atopic profile had been assessed, their nasal lavage fluid (NAL) and exhaled air was sampled once before and once during the pollen season. Level of nitric oxide (NO) was determined in exhaled air, and the following mediators were measured in NAL: ECP, IL-6, IL-8, albumin, uric acid, and urea. The number of eosinophils in NAL was determined after Giemsa staining. During the experiment ozone and pollen levels were measured continuously. RESULTS: During the pollen season the level of grass pollen was 95 pollen grains per cubic metre. At baseline, 8.0% and 5.4% of total cells in NAL of children sensitive to, respectively, house dust mite (HDM) and pollen + HDM were eosinophils, whereas virtually no eosinophils were observed in NAL of non-atopic children. In contrast to the non-atopic and HDM groups, in children sensitive only to grass pollen, grass pollen induced a threefold increase in the percentage of NAL eosinophils and a 2.5-fold increase in the NAL level of ECP ( P<0.05). In all groups, the NAL levels of albumin, uric acid, urea, IL-6 and IL-8 were not significantly increased by pollen exposure. At baseline, children sensitive to HDM showed significantly higher exhaled nitric oxide (eNO) values than non-atopic subjects and children sensitive only to pollen (79 to 141% increase). During pollen exposure eNO of children sensitive only to pollen increased from 35.8 to 64.5 ppb ( P<0.05), whereas no increase in eNO was observed in the other children. CONCLUSION: Pollen-sensitive children show a season-dependent upper and lower airway inflammatory response, resembling the continuous inflammation in HDM-sensitive children.

Acute effect of air pollution on respiratory complaints, exhaled NO and biomarkers in nasal lavages of allergic children during the pollen season.

During 2 months of the pollen season, the acute and putative adjuvant effect of traffic-related air pollution on respiratory health was investigated in children sensitised to grass pollen or house dust mite (HDM). Respiratory complaints were objectified via measurement of exhaled NO and inflammatory mediators in nasal lavage (NAL). During the study children, skin prick negative (n = 31) or positive to grass pollen (n = 22), HDM (n = 34) or grass pollen + HDM (n = 32), kept a daily diary on respiratory symptoms, and NAL and exhaled air was sampled twice a week. The level of air pollutants and pollen was monitored continuously. Like children sensitised to HDM, those sensitised to pollen reported respiratory complaints (shortness of breath, itchy eyes or blocked nose) more frequently than non-sensitised children during (but not before) the pollen season; the respiratory complaints of sensitised children were independent of the pollen level. In addition, exposure to increased levels of PM(10) induces 'shortness of breath' in pollen- and HDM-sensitised children, whereas ozone induces a blocked nose in HDM-sensitised children. Combined exposure to PM(10) + pollen and O(3) + pollen induces a blocked nose in both HDM-sensitised children and children sensitised to pollen + HDM. Significant positive associations were found between eNO and the levels of NO(2), CO, PM(2.5) and pollen in both sensitised and non-sensitised children. At the start of the pollen season, the NAL concentration of eosinophils and ECP in pollen-sensitised children was increased compared to winter, but their levels were not further affected by increased exposure to pollen or air pollution. In conclusion, during the pollen season, sensitised children continuously report a high prevalence of respiratory complaints which coincides with increased levels of upper and lower airway inflammatory markers. No additional pro-inflammatory effect of air pollution was observed, which indicates that air pollution does not facilitate allergen-induced inflammatory responses.