Comparative proteomic analysis of proteins expression changes in the mammary tissue of cows infected with Escherichia coli mastitis

Cows infected with Escherichia (E.) coli usually experience severe clinical symptoms, including damage to mammary tissues, reduced milk yield, and altered milk composition. In order to investigate the host response to E. coli infection and discover novel markers for mastitis treatment, mammary tissue samples were collected from healthy cows and bovines with naturally occurring severe E. coli mastitis. Changes of mammary tissue proteins were examined using two-dimensional gel electrophoresis and label-free proteomic approaches. A total of 95 differentially expressed proteins were identified. Of these, 56 proteins were categorized according to molecular function, cellular component, and biological processes. The most frequent biological processes influenced by the proteins were response to stress, transport, and establishment of localization. Furthermore, a network analysis of the proteins with altered expression in mammary tissues demonstrated that these factors are predominantly involved with binding and structural molecule activities. Vimentin and alpha-enolase were central "functional hubs" in the network. Based on results from the present study, disease-induced alterations of protein expression in mammary glands and potential markers for the effective treatment of E. coli mastitis were identified. These data have also helped elucidate defense mechanisms that protect the mammary glands and promote the pathogenesis of E. coli mastitis.

Role of neutrophils in protection of udder from infection in high yielding dairy cows

Protection of the mammary gland against mastitis-causing pathogens is mediated by many factors in the gland and blood circulation. The professional phagocytic cells of bovine udder, polymorphonuclear neutrophils [PMN] and macrophages, comprise the first line of defense against invading mastitis pathogens. Most researchers now accept that the PMN is a key factor in the cows' defense against intramammary infections. The PMN are the only leukocytes in the milk compartment that are capable of producing large amounts of reactive oxygen species [ROS] to kill phagocytosed bacteria. In this review, the role of PMN function as an effective defense against intramammary pathogens in dairy cows and physiopathological influencing factors on blood and milk PMN functions are discussed. Apart from playing a crucial role in the first line of defense mechanism, the PMN can also, indirectly, interfere with the complex interactions of second line of defense against pathogens. To minimize mammary tissue damage caused by bacterial toxins and oxidative products released by PMN, elimination of invading bacteria should proceed quickly. This can provide balance among inflammation reactions, bactericidal activity and tissue damage. The good balance between host-pathogen interactions might be affected by the physiological [e.g., stage and number of lactation] and pathological [e.g., local-systemic effect of mastitis] status of dairy cows. Hormones, metabolites and acute phase proteins also influence PMN functions, thereby affecting the outcome of mastitis. This is especially the case around parturition. PMN function in healthy cows after parturition is highly heritable and has been related to the cow's susceptibility to clinical mastitis. Despite advances in veterinary science, nutrition and molecular biology, mastitis is still a very big problem in high yielding dairy cows. The long-term and fundamental solution for mastitis affecting high yielding dairy cows is to strengthen cows' immune systems by means of attainable physio-immunological approaches. This requires a comprehensive study on the immunophysiological alterations throughout lactation and during mastitis. This review focuses on some factors affecting PMN functions during the lactation cycle and mastitis in high yielding dairy cows