H. van der Vliet

9-and 13-hydroxy-linoleic acid posses chemotactic activity for bovine and human polymorphonuclear leukocytes

The presence of polymorphonuclear leukocytes (PMNs) within the airways is a characteristic feature of a variety of lung diseases. Pulmonary alveolar macrophages (PAMs) and epithelial cells release many different factors which contribute to the recruitment of inflammatory cells into infected airways. PAMs and tracheal epithelial cells are able to produce linoleic acid metabolites (9-HODE and 13-HODE) besides arachidonic acid metabolites. The objective of the present study was to determine whether 9-HODE and 13-HODE possess chemotactic activity for isolated PMNs. It was found that 9-HODE and 13-HODE induced a chemotactic response of both human and bovine PMNs in vitro. The HODEs evoked chemotaxis with a linear dose response from 10(-10) to 10(-6) M to the same extent as the arachidonic acid metabolite 15-HETE. At 10(-8) M, 9-HODE and 13-HODE were approximately half as potent in inducing chemotaxis as compared to LTB4.

Functional characterization of muscarinic receptors in murine airways.

1 The effects of muscarinic receptor antagonists considered to be selective for M1 receptors (pirenzepine; PZ), M2 receptors (AFDX‐116), and for M3 receptors (4‐diphenyl acetoxy N‐methylpiperidine (4‐DAMP)) were used to investigate the existence of muscarinic receptor subtypes in murine airways. Atropine was used as a nonselective antagonist. The effects of these antagonists were studied upon tracheal contractions induced either by EFS (electric field stimulation) or by application of an exogenous cholinoceptor agonist (arecoline). 2 The muscarinic receptor antagonists tested inhibited arecoline‐induced tracheal contractions with the following rank order of potency: 4‐DAMP = atropine > pirenzepine = AFDX‐116. The rank order of potency of the muscarinic antagonists used in inhibiting EFS‐induced tracheal contractions was: 4‐DAMP = atropine > PZ > AFDX‐116. The pA2 values for these antagonists were similar when compared to the pA2 values determined in guinea‐pig and bovine airway smooth muscle. 3 In addition to in vitro studies, the effects of inhalation of the different muscarinic antagonists on lung function parameters in vivo were investigated. Inhalation of 4‐DAMP induced a decrease in airway resistance and an increase in lung compliance. In contrast, inhalation of AFDX‐116 induced an increase in airway resistance and almost no change in lung compliance. Apart from some minor effects of atropine on airway resistance, atropine, PZ, and pilocarpine failed to induce changes in lung mechanics as determined by in vivo lung function measurements. 4 The results provide evidence for the existence of M3 receptors on murine tracheae that are involved in the contraction of tracheal smooth muscle. This is in agreement with other animal species such as the guinea‐pig and bovine. In vivo experiments also demonstrated that in the mouse, M3 receptors play an important role in bronchial smooth muscle contraction and thus in bronchoconstriction. Interestingly we have also demonstrated that M2 receptors can play a role in bronchodilatation. Inhalation of an M2 receptor antagonist induced an increase in airway resistance whereas inhalation of an M3 receptor antagonist induced a decrease in airway resistance. It is therefore likely that an M3/M2 receptor balance plays an important role in the regulation of airway function.

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.

Polymorphonuclear leucocyte function: Relationship between induced migration into the bovine mammary gland and in vitro cell activity

Low doses of 10(-7) mg Escherichia coli endotoxin applied as intramammary infusion into single bovine quarters induced a rise in milk cell count without other inflammatory signs. Significantly fewer quarters responded in early lactation than in mid lactation. Maximum cell count was also somewhat later and less pronounced in early lactation. The rise in milk cell count after infusion of E. coli endotoxin was related to in vitro chemotactic activity of blood polymorphonuclear leucocytes (PMN). PMN isolated from cows which did not respond with a rise in milk cell count upon endotoxin infusion showed a diminished chemotactic activity in vitro as compared to PMN isolated from animals which did respond to an intramammary endotoxin infusion with a rise in milk cell count. No differences in phagocytic and metabolic activity were observed in vitro between the PMN isolated from the two groups of animals.

A procedure for parallel isolation of white blood cells, granulocyte and purified neutrophil suspensions from the peripheral blood of cattle

A rapid method is described for parallel isolation of white blood cells, granulocytes and purified neutrophils from peripheral blood of normal cattle. The mean recovery (+/- S.D.) of white blood cells, granulocytes and purified neutrophils isolated from peripheral blood of 13 cows was 66.4 +/- 12.6%, 68.7 +/- 20.0% and 38.0 +/- 20.9%, respectively. The mean purity of the isolated granulocyte and neutrophil suspensions was 94.0 +/- 3.8% and 95.0 +/- 6.0%, respectively. Viability of isolated cells was more than 97%.

A role for cellular immunity in the induction of airway hyperresponsiveness induced by small molecular weight compounds.

In a murine model it was shown that during a T help-1 cell dependent immune reaction, i.e. delayed type hypersensitivity (DTH), directed against the small molecular weight compound picryl chloride (PCI), altered lung functions are induced. Skin sensitization with PCI followed by intranasal hapten challenge resulted in an increment of pulmonary resistance and airway hyperresponsiveness which are general features of asthma. Whether this is also true for low molecular weight compounds, such as toluene diisocyanate, that can induce asthmatic complaints in humans, in addition to T help-2 cell dependent immune responses, remains to be clarified in future studies.

The effect of Pasteurella haemolytica cytotoxin on bovine polymorphonuclear leukocytes can be attenuated by β-adrenoceptor antagonists

It was investigated whether beta-adrenoceptor antagonists could disturb the interaction between cytotoxin preparations isolated from Pasteurella haemolytica and bovine polymorphonuclear leukocytes (PMNs). The toxicity of the cytotoxin preparation was evaluated by measuring the chemiluminescence response and the viability of the cells after incubation with the cytotoxin. No effect on cell viability was detected when PMNs were incubated with 63 micrograms cytotoxin per ml while the chemiluminescence response was diminished by approximately 30%. The beta-adrenoceptor antagonists alprenolol (10(-5) M) and propranolol (5 X 10(-7) - 5 X 10(-6) M) were able to attenuate this effect of cytotoxin on the chemiluminescence response of PMNs. It seemed unlikely that propranolol and alprenolol diminished the effect of cytotoxin on the chemiluminescence response of PMNs by their beta-adrenoceptor blocking potency because other beta-adrenoceptor antagonists used were without effect. Also, the membrane stabilizing characteristics of the beta-adrenoceptor antagonists used were probably not responsible for the diminished interaction between PMNs and the cytotoxin. Whether beta-adrenoceptor antagonists could be used in vivo to prevent or treat P. haemolytica infections in bovines remains to be examined.

The relationship between phagocytic activity of polymorphonuclear leukocytes and mastitis in cattle

Polymorphonuclear leukocytes (PMNs) have a major role in preventing or eliminating infections in the bovine udder. These cells migrate from the blood circulation into the milk by chemotaxis. Variation in the speed and magni tude of the influx of PMNs into the udder may largely determine the extent to which individual cattle can resist or eliminate bacteria [1, 2]. Experimental models have been established to study the inf lammatory reactions in the udder of cattle after bacterial inoculation. After inoculat ion of an inf lammatory agent into a lactating mammary gland, increased numbers of leukocytes can be detected in the milk. However, it is of more interest to know the capability of PMNs for handling infections before any bacterial stimulation. The aim of the present work was to investigate the relat ionship between the in vivo reaction to a non-specific inf lammatory irritant and in vitro phagocytic cell activity of b lood PMNs.

The generation of chemiluminescence by alveolar macrophages is affected by 9-hydroxy-linoleic acid

Alveolar macrophages (AMs) are the primary defenders in the lung against inhaled particles. These cells exhibit a variety of biological activities, like phagocytosis and killing of micro-organisms and secretion of enzymes, reactive oxygen metabolites, prostaglandins, leukotrienes and other mediators [1]. The activities of phagocytic cells are not always beneficial to the host because reactive oxygen species and enzymes may also inflict considerable damage to host tissues [2]. Recently, we demonstrated that guinea pig AMs synthesize substantial amounts of the linoleic acid metabolite, 9-hydroxylinoleic acid (9-HODE) under non-stimulated conditions [3]. In the present study, we investigated the effects of 9-HODE and its precursor 9-hydroperoxy-linoleic acid (9-HPODE) on the phagocytic and metabolic activity of guinea pig AMs.

Oxygen metabolism and eicosanoid formation of alveolar macrophages ofHaemophilus influenzae-treated guinea pigs

In an animal model it has been shown that Gramnegative bacteria may modulate airway function through an effect on smooth muscle receptors mediating contraction and relaxation [1]. In this atopic model, treatment of guinea pigs with Haemophilus influenzae or endotoxin results in a reduction of the number of fl-adrenergic receptors in the lung as well as in a diminished function of fl-adrenergic receptors involved in respiratory smooth muscle relaxation [1]. The decreased fl-adrenergic receptor function of the airways found in guinea pigs four days after intraperitoneal administration of H. influenzae might be caused by products released by phagocytic cells in the lung. This hypothesis has been studied by Engels et al. [2] in in vitro experiments in which isolated tracheal spirals were incubated with alveolar macrophages (AMs). AMs incubated with sera obtained from control and H. influenzae-treated animals had detrimental effects on airway smooth muscle fl-adrenergic receptor function [2]. By using scavengers and inhibitors of activated oxygen metabolites it was indirectly shown that the attenuation of fl-adrenoceptor function was due to hydroxyl radicals produced by the AMs [2]. Besides the antimicrobial action, reactive oxygen species produced by phagocytic cells can contribute to structural damage of tissues and cell structures [3]. The aim of the present study was to directly measure the production of oxygen metabolites and eicosanoid mediators by AMs during incubation with sera. In addition, we investigated if there are differences in action of AMs isolated from H. influenzae-treated and control guinea pigs.