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Healthy mammary quarters neighboring LPS-infused quarters undergo hypogalactia associated with transcriptional changes in immune and metabolic genes.

E. M. Shangraw

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06-24-2020

Abstract:

377
Healthy mammary quarters neighboring LPS-infused quarters undergo hypogalactia associated with transcriptional changes in immune and metabolic genes.
E. M. Shangraw*1, R. O. Rodrigues1, R. K. Choudhary2, F.-Q. Zhao2, T. B. McFadden1. 1University of Missouri Columbia, MO, 2University of Vermont Burlington, VT.

Infusion of lipopolysaccharides (LPS) into a mammary gland can provoke symptoms in healthy neighboring glands, termed the systemic effect. Our aim was to determine how localized mastitis affects the mammary transcriptome of neighboring glands in lactating dairy cows, focusing on the early progression of the inflammatory response. Ten multiparous cows were paired based on milk yield, parity, and SCC. Within pair, cow treatments were randomly assigned: 1) LPS treatment (T) or 2) control (C). Within cow, udder-halves were randomly assigned to sub-treatments: in T cows, ipsilateral front and rear quarters received an infusion of 50�g LPS in 10mL saline (TL); contralateral quarters received 10mL saline (TS). In C cows, udder-halves received either 10mL saline (CS) or no infusion (CN). Rear quarters were biopsied at 0, 3 and 12h post-infusions. Total RNA isolated from TL, TS, and CS mammary tissue at 3 and 12h was sequenced to a depth of 44.1 � 2.4 million reads per sample. Transcripts were declared significant at FDR P < 0.05, log2 fold change > |1.0|, and were annotated to KEGG pathways. Comparing mammary transcriptomes of T and C cows revealed 2,779 and 1,363 differentially expressed (DE) genes at 3 and 12h, respectively. Of these genes, > 95% were DE only in TL and represented classic LPS immune responses at both times. Interestingly, despite the relatively weak response, TS quarters underwent hypogalactia to a similar extent as TL, as 12h milk yields of non-biopsied front quarters declined to 47 � 5% and 52 � 9% of 0h for TS and TL, respectively. To determine if a systemic mediator was the cause, we focused on genes DE in both TL and TS. At 3h, TNF, NF-κβ and NOD-like receptor signaling pathways were identified. At 12h, PPAR signaling and arachidonic acid metabolism were identified. Two genes, FKBP5 and LYVE1, were upregulated in TS and TL at both times. In summary, neighboring glands are initially affected by a transient systemic immune response triggered in the infused gland. Later responses shifted to changes in cellular metabolism, perhaps explaining the decline in milk yield.

Keywords: mastitis, mammary, transcriptome.