Mastitis Resistance to Enhance Dairy Food Safety

NON-TECHNICAL SUMMARY: A cell culture system will be used as a simplified model of the cells lining the bovine mammary gland. This layer of cells is a physical barrier that protects the cow from micro-organisms and secretes each of the constituents present in milk. This laboratory has developed techniques to mimic the changes that these cells go through during pregnancy and at birth. We will use this simplified cell system to determine how the cell layer responds to inflammation that might occur when the body detects micro-organisms in the milk. A second line of investigation will focus on two classes of drugs that are used to treat systemic infections. Experiments will be conducted to determine the chemical characteristics of drugs that will minimize accumulation in milk. Outcomes from these studies will enhance animal health and improve milk quality. <P>APPROACH: Researchers at Kansas State University will take advantage of resources that have been developed for in vitro evaluation of bovine mammary epithelial functions. The cultured BME-UV cell line will be grown on permeable substrates to form a confluent cell layer that mimics the in vivo geometry separating the interstitial and blood compartments from the milk compartment. In some experiments, cultures of freshly isolated bovine mammary epithelial cells will be employed. This cell layer is the physical barrier to pathogens, responds to inflammatory mediators, and secretes milk components. Particular focus will be placed on excluding environmental toxins or pharmaceuticals from the milk. Cells will be grown in media supplemented with varying concentrations of corticosteroids, progesterone and estradiol to mimic the pre-and peri-parturant condition. Further, media of different electrolyte concentrations will be employed on the apical and basolateral aspects of the cells to mimic the compositions of milk and blood, respectively. We showed that these conditions result in the most complete epithelial barrier as assessed either electrically or with tagged solutes. Experiments will focus on two aspects of mammary epithelial function, responses of the epithelial barrier to cytokines (e.g., TNF alpha, IL1-beta, IL6, and IL8) and determining the physico-chemical parameters that influence the accumulation in or exclusion from milk of tetracycline and beta-lactam antibiotics. Techniques similar to those previously employed in the laboratory will be used including the modified Ussing flux chamber to assess epithelial ion transport and barrier integrity, gradient-driven flux of tagged solutes to assess barrier integrity, and unidirectional flux of tagged solutes to differentiate gradient-driven flux from active transport mechanisms.

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PROGRESS: 2007/01 TO 2007/12<BR>
OUTPUTS: An in vitro bovine mammary epithelial system (BME-UV cells) is being employed as a model to assess modulation of the epithelial barrier by both host and pathogens. The epithelila barrier is sensitive to the concentration of electrolytes in the solution bathing the milk or apical side of the cells. Furthermore, the amount of electrolytes in this solution can be modified by the cells. The cells can, under the control of physiological hormones, regulate the expression and/or activity of channels that reduce the sodium concentration in the milk compartment. Results from ongoing work suggests that selected co-expressor proteins of the p160 gene family are required for corticosteroid hormones to have their effect. Ongoing work is designed to develop and validate an in vitro model using cultured BME-UV cell monolayers to study the mechanisms and factors affecting the rate of drug movement between plasma and milk. This model is expected to be an important tool in the study of the pharmacokinetics of drugs used to treat mastitis and other diseases in lactating dairy cattle. Ultimately, this model will contribute to improving the efficacy and safety of drugs used in these animals, for the lactating dam, as well as the suckling off-spring and human consumer. <BR>PARTICIPANTS: Dr. Ronette Gehring <BR>TARGET AUDIENCES: NONE

<P>IMPACT: 2007/01 TO 2007/12<BR>
Results indicate that new or alternative therapies targeted to modulate transepithelial ion transport might be implemented to prevent or cure mastitis. In the second aspect of this study, the results suggest that therapeutic drugs are not passiviely distributed across the mammary epithelium. Thus, drug selection within a class of compounds can dramatically affect the level of exposure for nursing offspring or consumers.