Investigating the contribution of IL-17A and IL-17F to the host response during Escherichia coli mastitis

Mastitis remains a major disease of cattle with a strong impact on the dairy industry. There is a growing interest in understanding how cell mediated immunity contributes to the defence of the mammary gland against invading mastitis causing bacteria. Cytokines belonging to the IL-17 family, and the cells that produce them, have been described as important modulators of the innate immunity, in particular that of epithelial cells. We report here that expression of IL-17A and IL-17F genes, encoding two members of the IL-17 family, are induced in udder tissues of cows experimentally infected with Escherichia coli. The impact of IL-17A on the innate response of bovine mammary epithelial cells was investigated using a newly isolated cell line, the PS cell line. We first showed that PS cells, similar to primary bovine mammary epithelial cells, were able to respond to agonists of TLR2 and to LPS, provided CD14 was added to the culture medium. We then showed that secretion of CXCL8 and transcription of innate immunity related-genes by PS cells were increased by IL-17A, in particular when these cells were stimulated with live E. coli bacteria. Together with data from the literature, these results support the hypothesis that IL-17A and IL-17 F could play an important role in mediating of host-pathogen interactions during mastitis

Mobilization of neutrophils and defense of the bovine mammary gland

The leucocytes present in normalmilk are not very efficient in preventing infection, because very small numbers of bacteria are able to induce infection experimentally. The mobilization of phagocytes from the blood to milk appears crucial in coping with the expansion of the bacterial population in the mammary gland. Important parameters for the outcome of mammary infections are the bactericidal efficiency of neutrophils and the antiphagocytic and cytotoxic properties of the invading bacteria, but several studies have shown that the promptness and the magnitude of the initial recruitment of neutrophils by the infected mammary gland have a profound influence on the severity and the outcome of mastitis. This is an incentive for studying the mechanisms behind the mobilization of neutrophils to the mammary gland. Although milk macrophages may play a role in the triggering of the inflammatory response, studies on several responses to infections at various epithelium sites strongly suggest that epithelial cells are capable of responding to bacterial intrusion and play a major part in the initiation of inflammation. A better knowledge of the effector cells and of the mediators involved in the mobilization of neutrophils could help in devising strategies to modulate this important determinant of milk quality and udder defense

Recrutement des polynucléaires neutrophiles lors d'une mammite bovine (rôle des cellules épithéliales mammaires et étude des récepteurs de l'interleukine-8)

Actually, cellular and molecular effectors implicated in the initiation of the recruitment of neutrophils to infected mammary gland are not well understood. In the first section of doctoral work, we have found that bovin mammary epithelial cells (bMEC) were able to release neutrophil-mobilizing chemokines and proinflammatory cytokines upon bacterial stimulation, strongly suggesting that bMEC are active contributors to immune and inflammatory responses of mammary gland. In addition, the clinical characteristics and resolution of mastitis may be partly determined by the responses of bMEC according to S. aureus strains and bacteria Gram type. In the second section of doctoral work, we have identified a novel interleukine-8 receptor in bovine specie. In addition, we showed that both bovine IL-8R are functional. In conclusion, the doctoral work constitute a basis to improve our understanding of the molecular mechanisms implicated in the recruitment of bovine neutrophils.Les médiateurs cellulaires et moléculaires impliqués dans l initiation du recrutement des PMN vers la mamelle sont mal connus. Dans la première partie de la thèse, nous avons étudié la réponse inflammatoire et immunitaire des cellules épithéliales mammaires bovines (CEMb). Dans la deuxième partie de la thèse nous avons caractérisé les récepteurs de l interleukine-8 (IL-8R) chez les bovins. A l issue de ce travail, il apparaît que les CEMb sont capables d induire une réponse inflammatoire et immunitaire pour initier le recrutement des PMN dans la mamelle infectée. Cette réponse varie en fonction de la souche de S. aureus et du Gram bactérien et ainsi pourrait déterminer partiellement la sévérité et la résolution de l infection mammaire. L étude de l implication des récepteurs CXCR1 et CXCR2 dans le recrutement des neutrophiles nous a conduit à identifier un nouvel IL-8R, à corriger l annotation du CXCR2 publié et à démontrer que les deux IL-8R bovins sont fonctionnels.TOURS-BU Sciences Pharmacie (372612104) / SudocSudocFranceF

Lycopene attenuates LPS-induced TNF-alpha secretion in macrophages and inflammatory markers in adipocytes exposed to macrophage-conditioned media

International audienceScope Adipose tissue is infiltrated by an increasing number of macrophages during the development of obesity. These immune cells are suspected to be a major source of TNF-a that interferes with adipocyte function. Because lycopene possesses anti-inflammatory properties, we hypothesize that lycopene could reduce the production of TNF-a by macrophages and thus interfere in the cross-talk between macrophages and adipocytes. Methods and results We demonstrated that physiological concentrations of lycopene were able to attenuate the lipopolysaccharide (LPS)-mediated induction of TNF-a in RAW 264.7 macrophages, at both the mRNA and protein levels. The molecular mechanism was studied. It appeared that the LPS-activation of both JNK and NF-?B signaling pathways was modulated by lycopene. The anti-inflammatory effects of lycopene on macrophages were accompanied by a decrease in LPS-stimulated macrophage migration in the presence of lycopene. Furthermore, lycopene decreased macrophage conditioned medium-induced proinflammatory cytokine, acute phase protein, and chemokine mRNA expression in 3T3-L1 adipocytes. Conclusion These data indicate that lycopene displayed an anti-inflammatory effect on macrophages that beneficially impacted adipocyte function. Thus, these results suggest that lycopene could block the vicious cycle that occurs between adipocytes and macrophages in adipose tissue during obesity