Am Massart-Leen

Modulation of the inflammatory reaction and neutrophil defense of the bovine lactating mammary gland by growth hormone

This review is focused on the possible interactions of prolactin and somatotrope hormone in the modulation of inflammation of the mammary gland. Several different models are examined: Escherichia coli, Streptococcus uberis, and endotoxin mastitis. Subsequently, the release of growth hormone and insulin-like growth factor during fever and mastitis, the immunophysiological effects of GH on E. coli mastitis, S. uberis and endotoxin mastitis, the galactopoietic action of rBST on healthy and mastitis cows as well as the immunologic effects of GH on leukocytes in healthy and diseased cows are discussed. It can be concluded that the underlying regulation of the neuro-endocrine network is fundamental in the normal function of the immune system.

Diapedesis across mammary epithelium reduces phagocytic and oxidative burst of bovine neutrophils.

The effect of diapedesis on the phagocytic and oxidative burst activity of polymorphonuclear neutrophil (PMN) was examined, using an in vitro cell culture model consisting of a monolayer of primary mammary epithelial cells. Isolated blood PMN from 10 cows were added to the basal side of the epithelial cell monolayer. Diapedesis was induced by the addition of complement factor C5a to the apical side of the monolayer. PMN phagocytosis of Staphylococcus aureus and oxidative burst were measured before diapedesis on PMN that were non-activated and activated by incubation with C5a and on PMN after diapedesis, using flow cytometry. The percentages of PMN fluorescing due to phagocytosis of S. aureus and oxidative burst were reduced by 21.2 and 14.4%, respectively, after diapedesis. Pre-incubation in the presence of C5a had no effect on percentage PMN fluorescing due to phagocytosis or oxidative burst. The capacity for individual migrated PMN to phagocytose S. aureus and to produce an oxidative burst, as measured by the intensity of fluorescence, decreased by 34.2 and 30.3%. Activation of PMN with C5a increased intensity due to the oxidative burst, but had no effect on intensity due to phagocytosis. These data show that PMN diapedesis across mammary epithelium results in decreased phagocytosis and oxidative burst of the PMN.

Adhesion receptor CD11b/CD18 contributes to neutrophil diapedesis across the bovine blood-milk barrier.

epithelium. Neutrophil migration across mammary arterial endothelial cells was almost completely dependent on CD18, the beta-chain of the beta(2) integrins, and to a lesser extent on CD11b, one of the alpha-chains of the beta(2) integrins. Neutrophil migration across collagen was partially blocked by monoclonal antibodies to CD18. No inhibition was observed by monoclonal antibodies to CD11b. Conversely, neutrophil diapedesis across mammary epithelial cells was dependent to a greater extent on CD11b. These results provide evidence for different CD11b/CD18-dependent mechanisms for neutrophil diapedesis across the various cell layers of the blood-milk barrier.

Partial prostaglandin-mediated mechanism controlling the release of cortisol in plasma after intravenous administration of endotoxins

In a first series of experiments we studied the influence of E. coli endotoxins or lipopolysaccharides (LPS) administered either intravenously (i.v.) or intramammarily (i.mam.) to lactating goats on plasma cortisol and rectal temperature (RT). Differences in the magnitude of the cortisol release and shape of the fever curve were observed. In both models maximal pyrexia and fever index (FI) were comparable. In a second series of experiments the influence of LPS on the plasma cortisol and RT was studied after i.v. injection of increasing doses of LPS:low (25 ng/kg), moderate (200 ng/kg) and relatively high (500 ng/kg). Although the cortisol response was dose dependent, the effect was not correlated with FI. The administration of flurbiprofen, a non steroidal antiinflammatory drug (NSAID), resulted in a complete inhibition of fever at all LPS doses and the cortisol release after administration of low doses LPS. This indicates a prostaglandin mediation. With moderate and high doses LPS the cortisol release was only partially inhibited and delayed suggesting a non prostaglandin mediated mechanism. In a third series of experiments the influence of flurbiprofen on fever and cortisol release was studied after i.mam. LPS administration. The observed increase of plasma cortisol and RT were completely abolished after flurbiprofen treatment. It is concluded that: 1) the increase of plasma cortisol after LPS administration in lactating goats is not related to hyperthermia per se, 2) the control of fever and cortisol release may, to some extent, differ according to the LPS dose and method of administration, 3) the cortisol release observed after moderate and high doses of LPS is probably controlled by two phenomena. The first being induced by cyclo-oxygenase metabolites, the second by intermediary mediators other than prostaglandins or by LPS itself. 4) Although an eight-fold higher dose of LPS was given i.mam., a cortisol release comparable to the lowest dose of LPS (25 ng/kg) was observed. These differences in cortisol release can be ascribed to 1) a detoxification of LPS at the level of the mammary gland or 2) a slower resorption of LPS from the mammary gland.

ROLE OF FEVER ON THE ENDOTOXIN-INDUCED SOMATOTROPIN RELEASE IN THE LACTATING GOAT

Publisher Summary This chapter elaborates the role of fever on the endotoxin-induced somatotropin release in the lactating goat. Somatotropin (STH) blood concentrations increased during the fever of infection and artificial hyperthermia in man. The effects of i.v. LPS were compared in goats before and after pretreating the animals with the nonsteroidal, anti-inflammatory agent flurbiprofen. Plasma levels of nonesterified fatty acids were also measured. Fifty six experiments were carried out on 6 goats weighing between 49 and 63 kg. Goats were kept in individual standings and were well adapted to experimental manipulations. I.v. injection of increasing doses of LPS to goats caused fever, characterized by a striking triphasic response after the highest LPS dose, with peaks occurring at 1.5 and 4.5 h after injection. Fever response was dose-dependent, but only to low and moderate doses of LPS. High doses of LPS also induced fever, but peak values were below those seen after a dose of 100 ng/kg. Fever was accompanied by clinical symptoms including piloerection, depression, miosis, and loss of appetite. Endotoxin also caused a dose-dependent rise in plasma NEFA. Peak values were observed 2 h after injection and occurred before fever peak. Plasma STH levels significantly increased in a dose-dependent way.