Cellular and chemical mediators of type 1 hypersensitivity in calves infected with Ostertagia ostertagi: histamine, prostaglandin D2, prostaglandin E2 and leukotriene C4

Ethanol extracts of Saururus chinensis suppress ovalbumin-sensitization airway inflammation

AIM OF THE STUDY

The aerial part of Saururus chinensis has been used in folk medicine to treat several inflammatory diseases in China and Korea. Previously, our group reported that anti-asthmatic activity of an ethanol extract of Saururus chinensis (ESC) might occur, in part, via the inhibition of prostaglandin D(2) (PGD(2)) and leukotriene C(4) (LTC(4)) production, and degranulation reaction in vitro, as well as through the down-regulation of interleukin (IL)-4 and eotaxin mRNA expression in an in vivo ovalbumin-sensitization animal model. However, the effects of Saururus chinensis on eicosanoid generation, as well as Th2 cytokines and eotaxin production in an in vivo asthma model, have not been fully investigated. Moreover, it has not been determined whether ESC can ameliorate airway inflammation in vivo. In the present study, we investigated the therapeutic activity of Saururus chinensis on ovalbumin (OVA)-sensitized airway inflammation and its major phytochemical compositions.

MATERIALS AND METHODS

Asthma was induced in BALB/c mice by ovalbumin-sensitization and inhalation. ESC (10-100 mg/kg) or dexamethasone (5 mg/kg), a positive control, was administered 7 times orally every 12 h from one day before the first challenge to 1 h before the second challenge. The recruitment of inflammatory cells and hyperplasia of goblet cells were evaluated by H&E and PAS staining. Levels of Th2 cytokines, eotaxin, PGD(2) and LTC(4) were measured to evaluate the anti-inflammatory activity of ESC in OVA-sensitized mice. Contents of major components were analyzed by HPLC using a reversed-phase C18 column.

RESULTS

ESC (10 mg/kg) suppressed allergic airway inflammation by inhibition of the production of IL-4 (P<0.001), IL-5 (P<0.05), IL-13 (P<0.001), eotaxin (P<0.001), PGE(2) (P<0.001), LTC(4) (P<0.001) in lung extract and IgE level (P<0.001) in the serum. In addition, ESC (50 mg/kg) reduced the infiltration of inflammatory cells and hyperplasia of goblet cells in the lung tissues. The anti-inflammatory effect of ESC was comparable to that of the positive control drug, dexamethasone. Its major phytochemical composition includes manassantin A, B and sauchinone.

CONCLUSIONS

These results suggest that ESC decreased inflammation and mucus secretion in the OVA-induced bronchial asthma model, and its anti-asthmatic activity may occur in part via the inhibition of Th2 cytokines and eotaxin protein expression, as well as through prostaglandin E(2) (PGE(2)) and leukotriene C(4) (LTC(4)) generation. This effects may be attributed particularly to the presence of manassantin A, B and sauchinone major component evidenced by a HPLC analysis.

Antiasthmatic activity of luteolin-7-O-glucoside from Ailanthus altissima through the downregulation of T helper 2 cytokine expression and inhibition of prostaglandin E2 production in an ovalbumin-induced asthma model

Previously, we reported that an ethanol extract of Ailanthus altissima has antiinflammatory activity in an ovalbumin (OVA)-sensitized murine asthmatic model. To determine the biological compounds from this plant, luteolin-7-O-glucoside (L7G) was isolated and its antiasthmatic activity was evaluated in an in vivo murine asthmatic model. L7G (10 to 100 mg/kg, per os (p.o.)) reduced the amount of eosinophil infiltration in bronchoalveolar lavage (BAL) fluid in a dose-dependent manner. In comparison, dexamethasone (5 mg/kg, p.o.), which was used as a positive control, also strongly inhibited the number of infiltrating eosinophils. L7G inhibited both the prostaglandin E(2) (PGE(2)) and serum immunoglobulin E level in BAL fluid in a dose-dependent manner. In addition, L7G inhibited the transcript profiles of interleukin (IL)-4, IL-5, and IL-13 mRNA expression levels in the murine asthma model, as determined using reverse transcription-polymerase chain reaction (RT-PCR). These results suggest that the antiasthmatic activity of L7G in OVA-induced lung inflammation may occur in part via the downregulation of T helper 2 cytokine transcripts as well as the inhibition of PGE(2) production.

Immunoglobulin E-mediated hypersensitivity in food-producing animals

Type I hypersensitivity has been described as a cause of allergic reactivity to inhalants, injectables, endoparasites, and ectoparasites in food animal species. In addition, IgE is credited with showing some host-sparing effect when produced in response to certain gastrointestinal and other parasites. Recently, the sophistication of diagnostic procedures has increased with the elucidation of epsilon heavy chain sequences, expressed protein, development of chimeric IgE antibodies, and production of species-specific anti-IgE reagents. Application of ELISA and Western blotting has replaced the passive cutaneous anaphylaxis test for demonstration of antigen-specific IgE in serum. Regulation of the IgE response is complex, and its dependence on induction of T helper cell type 2 cytokines is now established. The next frontier in IgE research, as for many inherited diseases, lies in understanding the genetic make-up of the animal and which genes are important in controlling the IgE response.

Effects of gastrointestinal nematode infection on the ruminant immune system

Gastrointestinal (GI) nematodes of ruminants evoke a wide variety of immune responses in their hosts. In terms of specific immune responses directed against parasite antigens, the resulting immune responses may vary from those that give strong protection from reinfection after a relatively light exposure (e.g. Oesophagostomum radiatum) to responses that are very weak and delayed in their onset (e.g. Ostertagia ostertagi). The nature of these protective immune responses has been covered in another section of the workshop and the purpose of this section will be to explore the nature of changes that occur in the immune system of infected animals and to discuss the effect of GI nematode infections upon the overall immunoresponsiveness of the host. The discussion will focus primarily on Ostertagia ostertagi because this parasite has received the most attention in published studies. The interaction of Ostertagia and the host immune system presents what appears to be an interesting contradiction. Protective immunity directed against the parasite is slow to arise and when compared to some of the other GI nematodes, is relatively weak. Although responses that reduce egg output in the feces or increase the number of larvae undergoing inhibition may occur after a relatively brief exposure (3-4 months), immune responses which reduce the number of parasites that can establish in the host are not evident until the animal's second year. Additionally, even older animals that have spent several seasons on infected pastures will have low numbers of Ostertagia in their abomasa, indicating that sterilizing immune responses against the parasite are uncommon. In spite of this apparent lack of specific protective immune responses, infections with Ostertagia induce profound changes in the host immune system. These changes include a tremendous expansion of both the number of lymphocytes in the local lymph nodes and the number of lymphoid cells in the mucosa of the abomasum. This expansion in cell numbers involves a shift away from a predominant classic T cell population (CD2 and CD3 positive), to a population where T cell percentages are decreased and B cells (immunoglobulin-bearing) and gamma-delta cells are increased. At the same time the expression of messenger RNAs for T cell cytokines (IL2, IL4, IL10 and gamma-interferon) is changed to that of increased expression of IL4 and IL10 and decreased expression of IL2 and perhaps of gamma-interferon. The reasons for these changes remain to be elucidated, but it is evident that the lack of protective immune responses is not the result of a poor exposure of the host to parasite products, or to the stomach being an immunoprivileged site. In fact, a superficial look at the responses elicited indicates that Ostertagia induces responses (the so-called TH2 mediated responses) that are widely considered to be the type of responses necessary for protection against GI nematodes. There are many factors that could lead to this apparent lack of immunity in the face of a strong stimulation of immune responses including: (1) the elicitation of suboptimal responses; (2) the failure of the abomasum to function as an efficient effector organ; (3) active evasion of the functional immune response by the parasite; and (4) that these classic responses are not protective in this particular ruminant-parasite system and that novel protective mechanisms may be required. The strong stimulation of the host gut immune system by Ostertagia and perhaps by other GI nematode infections, raises questions about the potential effects of such infections on the overall well-being of the host. A number of authors have indicated that Ostertagia infections may diminish the host's ability to mount subsequent immune responses to antigenic challenges such as vaccination against other infectious organisms. In addition, recent studies have indicated that infections with GI nematodes may result in increased circulatory levels of stress-related hormo

Investigations into the production and function of leukotrienes during histotropic development of Oesophagostomum dentatum

The dynamics of production and excretion of leukotrienes by parasitic larvae of Oesophagostomum dentatum and their role for the development of the larvae were studied. Larvae were cultured in vitro to the fourth stage (L4). Leukotriene B4 (LTB4) was detected in homogenates and in supernatant of larvae, with the homogenate-protein-based values steadily decreasing during development. The homogenate-protein-based values of peptidyl leukotrienes (pepLT) remained fairly stable in both homogenates and supernatants, whereas the wormcount-based pepLT values increased significantly. The addition of diethylcarbamazine (DEC) to the culture medium straight from the beginning of culturing (12.8 or 25.5 mmol/l) reversibly hampered growth and development to L4. Application of DEC at 12.8 mmol/l beginning on day 13 of in vitro cultivation exerted no significant effect on further development to L4. LTB4 appeared to counteract the inhibition of development by DEC. The results of this study indicate that endogenous LTs participate in regulation of the growth and development of O. dentatum.

Local eosinophil- and mast cell-related responses in abomasal nematode infections of lambs

Eosinophil numbers in peripheral blood and eosinophil potentiating activity (EPA) and sheep mast cell protease (SMCP) in efferent gastric lymph were monitored in lambs during infections with Ostertagia circumcincta. Worm burdens, eosinophil numbers in bone marrow, abomasal mucosa and gastric lymph node, as well as mast cell numbers and SMCP concentrations in mucosa and mucus, were determined in post mortem samples. In naive lambs, high and relatively uniform worm burdens were present 10 days after primary infection and these were associated with only mild blood and tissue eosinophilia. By day 21 worm burdens were markedly lower and more variable. There was more evidence of eosinophil and mast cell accumulation in mucosa, and numbers in bone marrow were also higher than on day 10. However, neither EPA nor SMCP were detectable in lymph. By contrast, EPA and SMCP were present in substantial amounts in draining lymph within 48 h of challenge (secondary) infection of previously exposed lambs. EPA was inversely related to worm burdens recovered on day 10, as were abomasal mucosal and mucus SMCP concentrations. Elevated eosinophil numbers were also consistently detected in blood, bone marrow, mucosa and gastric lymph node. The results suggest that host immune defence against secondary, but not primary, exposure to O. circumcincta involves a rapidly mobilised local inflammatory component.

Cellular and chemical mediators of type 1 hypersensitivity in calves infected with Ostertagia ostertagi: mast cells and eosinophils

Abomasal mucosal mast cell and eosinophil accumulation was morphometrically evaluated in 26 Holstein steers after natural or experimental infection with Ostertagia ostertagi. Results showed that following infection, accumulation of mast cells and eosinophils in abomasal tissue was dependent on infection pattern. Eosinophilia was greater in steers with type 1 ostertagiosis, while mastocytes was more pronounced in steers with type 2 ostertagiosis.