Tilmicosin modulates the innate immune response and preserves casein production in bovine mammary alveolar cells during Staphylococcus aureus infection.

Tilmicosin is an antimicrobial agent used to treat intramammary infections against Staphylococcus aureus and has clinical anti-inflammatory effects. However, the mechanism by which it modulates the inflammatory process in the mammary gland is unknown. We evaluated the effect of tilmicosin treatment on the modulation of the mammary innate immune response after S. aureus infection and its effect on casein production in mammary epithelial cells. To achieve this goal, we used immortalized mammary epithelial cells (MAC-T), pretreated for 12 h or treated with tilmicosin after infection with S. aureus (ATCC 27543). Our data showed that tilmicosin decreases intracellular infection (P < 0.01) and had a protective effect on MAC-T reducing apoptosis after infection by 80% (P < 0.01). Furthermore, tilmicosin reduced reactive oxygen species (ROS) (P < 0.01), IL-1ß (P < 0.01), IL-6 (P < 0.01), and TNF-α (P < 0.05) production. In an attempt to investigate the signaling pathways involved in the immunomodulatory effect of tilmicosin, mitogen-activated protein kinase (MAPK) phosphorylation was measured by fluorescent-activated cell sorting. Pretreatment with tilmicosin increased ERK1/2 (P < 0.05) but decreased P38 phosphorylation (P < 0.01). In addition, the anti-inflammatory effect of tilmicosin helped to preserve casein synthesis in mammary epithelial cells (P < 0.01). This result indicates that tilmicosin could be an effective modulator inflammation in the mammary gland. Through regulation of MAPK phosphorylation, ROS production and pro-inflammatory cytokine secretion tilmicosin can provide protection from cellular damage due to S. aureus infection and help to maintain normal physiological functions of the bovine mammary epithelial cell.

Genes involved in pathogenesis, persistence, and excretion of Salmonella in animal models / Genes involucrados en la patogénesis, persistencia y excreción de Salmonella en modelos animales / Genes envueltos em patogênese, persistencia e excreção de Salmonella em modelos animais

Infectious diseases can be studied from different perspectives; from the global epidemiology to the detailed interactions between the pathogen and the host cell. Central to a complete understanding of any disease is the ability to integrate information from different points of view into a coherent model that fully explains the disease process. In vivo infections have been studied mainly in murine models, in which the possibility of genetically manipulating either the bacterium or the host allows variations in the severity of the host–pathogen combination and facilitates the evaluation of individual bacterial and host traits. Gross parameters, such as host mortality, clinical signs, overall bacterial numbers in the tissues, pathological changes, shedding patterns, production of immune mediators, as well as fluctuations and phenotypic profiles of cell populations have been widely used in the descriptive analysis of in vivo infection pathogenesis. However, key factors, such as bacterial location, spatiotemporal patterns of spread and tissue distribution, as well as sites of microbial persistence, have not been sufficiently studied despite their importance in terms of targeted medical intervention. This review aims to give a broad overview of the molecular basis associated with Salmonella infection in murine and other experimental animal models, focusing on organ location, and bacteria spread and distribution. The special conditions that promote bacteria retention and excretion in asymptomatic animals are also highlighted. It aims to gain a better understanding of the infectious process, so that comprehensive reassessment of pathogen behavior allow the establishment of preventive medicine programs in both humans and domestic or wild animals.

Las enfermedades infecciosas pueden ser estudiadas desde diferentes puntos de vista, por ejemplo, el aspecto epidemiológico global o bien el que detalla las interacciones entre el agente patógeno y la célula hospedero. Para tener un entendimiento completo, resulta necesario, por lo tanto, integrar la información de todos los puntos de vista, conformando un modelo coherente que explique completamente el proceso de enfermedad. El seguimiento de las infecciones in vivo ha sido estudiada principalmente en modelos murinos, los cuales ofrecen la posibilidad de manipulación genética tanto en las bacterias como en el hospedero, variando de esta manera la severidad de la enfermedad y facilitando la evaluación de su comportamiento. Los parámetros epidemiológicos o anatomopatológicos, tales como mortalidad, semiología clínica, evidencias bacterianas en tejidos, cambios histopatólogicos, patrones de excreción, producción de mediadores inmunes y fluctuaciones y cambios fenotípicos en poblaciones celulares, han sido ampliamente utilizados para el análisis descriptivo de la patogenia de las infecciones in vivo. De cualquier forma, los puntos clave, como patrones espaciotemporales de diseminación en tejidos, y sitios anatómicos de persistencia microbiana, no han sido profundamente estudiados, a pesar de la importancia que esto implica en el desarrollo de políticas de intervención sanitaria. Esta revisión pretende dar un amplio panorama sobre las bases moleculares asociadas a la infección por Salmonella en modelos murinos, así como en otros modelos animales experimentales, considerado desde el nivel celular, localización, diseminación y distribución de la bacteria en órganos y rescatando aquellas condiciones especiales que promueven su permanencia y excreción en el organismo animal asintomático. Se pretende abordar este proceso infeccioso desde una visión que oriente hacia un mejor entendimiento, de tal manera que, una reevaluación integral del comportamiento del agente patógeno, permitirá el establecimiento de programas de medicina preventiva tanto en seres humanos como en animales domésticos o silvestres.

As doenças infecciosas podem ser estudadas desde diferentes pontos de vista, como por exemplo: o aspecto epidemiológico global ou as interacções entre o agente patogênico e a célula hospedeira. Para ter um entendimento completo, é necessário, integrar a informação de todos os pontos de vista, formando um modelo coerente e que explique completamente o processo de a doença. Geralmente os modelos das infecções in vivo são estudados principalmente em modelos murinos, os quais oferecem a possibilidade de manipulação genética, tanto nas bactérias como no hospedeiro, variando desta maneira a severidade da doença e facilitando a avaliação de seu comportamento. Os parâmetros epidemiológicos ou anatomopatológicos como: mortalidade, semiología clínica, evidências bacterianas em tecidos, mudanças histopatólogicos, padrões de excrecão, produção de mediadores imunes, flutuações e mudanças fenotípicos em populações celulares foram amplamente utilizados para a análise descritiva da patogenia das infecçõesin vivo. De qualquer forma, os pontos chaves como padrões espaco-temporais de disseminacão em tecidos, e lugares anatômicos de persistencia microbiana não foram profundamente estudados, apesar da importância que isto implica no desenvolvimento de políticas de intervenção sanitária. Esta revisão tem como objetivo dar um amplo panorama sobre as bases moleculares da infecção por Salmonella em modelos murinos, bem como, em outros modelos animais experimentais, considerando desde o nível celular, localização, diseminação e distribuição da bactéria em órgãos e demonstrando as aquelas condições especiais que promovem sua permanência e excreção no organismo animal assintomático. O processo infeccioso foi abordado de maneira que proponha um melhor entedimento do mesmo, uma reavaliação integral do comportamento do agente patogénico que permita o estabelecimento de programas de medicina preventiva, tanto em seres humanos, como em animais domésticos ou silvestres.

The same cellular signaling pathways mediate survival in sensory neurons that switch their trophic requirements during development.

A distinct subpopulation of rat dorsal root sensory (DRG) neurons, termed P-neurons, switch their trophic requirements for survival during development from nerve growth factor (NGF) at embryonic stages to basic fibroblast growth factor (bFGF) just after birth. We investigated in cultured P-neurons the intracellular signaling pathways mediating survival before and after this switch. The NGF-induced survival was completely blocked by either wortmannin (100 nM) or PD98059 (25-50 nM), which selectively inhibit the phosphatidylinositol 3-kinase-AKT (PI3 kinase-AKT) and mitogen-activated kinase kinase extracellular regulated kinase (MEK-ERKs) pathways, respectively. NGF activated AKT and ERKs in single embryonic P-neurons, as assayed by immunofluorescence of phosphorylated proteins. In concordance with the survival assays, wortmannin and PD98059 blocked AKT and ERKs activation, respectively. Following the trophic switch, bFGF used the same signaling pathways to promote survival of post-natal P-neurons, as either wortmannin or PD98059 blocked its effect. Also, bFGF activated AKT and ERKs in single P-neurons, and this activation was blocked by the same inhibitors. These results strongly suggest that both pathways concurrently mediate the action of NGF and bFGF during embryonic and post-natal periods, respectively. Thus, we report the novel result that the switch in trophic requirements occurs with conservation of the signaling pathways mediating survival.