0486 Bioinformatics analysis of mammary gland and liver transcriptome in response to an intramammary Escherichia coli lipopolysaccharide challenge in early-lactation dairy cattle.

Abstract:

During mastitis, pathogens are detected by the receptors on the epithelial cells of the mammary tissue and an acute phase response activates the immune system to eliminate the pathogens. The liver is a central organ during inflammation and synthesizes the necessary components for immediate defense at the site of tissue damage. The objective of this study was to determine gene expression patterns in mammary and liver tissue in response to an intramammary E. coli lipopolysaccharide (LPS) challenge in early lactating dairy cattle. Fourteen Holstein cows were used. At~ 7 d in milk, 7 cows served as controls (CTR) and 7 cows (LPS) received an intramammary E. coli LPS challenge (200 µg in sterile saline). For transcript profiling the mammary and liver tissue were sampled by biopsy 2 h after the challenge. A bovine oligonucleotide (70-mers) microarray with> 13,000 annotated sequences was used for profiling. Data were analyzed using the MIXED procedure of SAS (SAS Inst. Inc., Cary, NC) and a threshold of 1.5-fold change and a P value of 0.05 were considered to define differentially expressed genes (DEG). Bioinformatics analyses was conducted using the dynamic impact approach (DIA) and ingenuity pathway analysis (IPA; Ingenuity Systems, Inc.). In mammary tissue, a total of 189 DEG (20 downregulated, 169 upregulated) were observed in LPS vs. CTR cows. The most-impacted and activated KEGG pathways highlighted by the DIA analysis were NOD-like receptor signaling, RIGI-like receptor signaling, apoptosis, cytosolic DNA-sensing, and chemokine signaling. The IPA analysis underscored the presence of 13 transcription …

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