<b>Evaluating Systemic Inflammation by Comparing Lipid Mediators and the Platelet and Plasma Proteome of Postpartum Dairy Cows</b>
Creators: name: Grantz, Jillian Michaela
Publisher: name: Purdue University Graduate School
Year: 2024
Subjects: classificationCode: 300999
subject: Veterinary sciences not elsewhere classified

description: Inflammation is a vital aspect of the immune response and functions to maintain homeostasis and protect the host against tissue injury or infection. However, excessive or prolonged inflammation can lead to health disorders and production losses in dairy cows. inflammation is a normal part of the tissue response during parturition. However, exacerbated systemic inflammation in the early postpartum has been associated with decreased milk production, decreased reproductive efficiency, and increased disease severity. Several processes contribute to systemic inflammation in dairy cows, such as liver oxidative stress, bacterial or endotoxin translocation during increased gastrointestinal permeability (e.g., lipopolysaccharide; LPS), and postpartum adipose tissue and skeletal muscle mobilization. However, there is limited knowledge of the mechanisms underlying systemic inflammation in postpartum dairy cows. Several studies have identified potent lipid mediators known as oxylipins as direct mediators of inflammation. Some differences have been identified in dairy cows when comparing the oxylipin profile throughout lactation and between cows suffering from different disorders. In our first study, we evaluated the plasma oxylipin profile of dairy cows suffering from systemic inflammation in the first week after parturition. Cows were classified into one of four systemic inflammation categories based on plasma haptoglobin (Hp) concentrations and plasma oxylipin profiles were identified by mass spectrometry. The results from this study identified several oxylipins of interest that warrant further research to confirm their presence in dairy cows with systemic inflammation and to evaluate their biological function associated with the postpartum inflammatory process. Endocannabinoids are soluble mediators associated with inflammation in humans, mouse models, and, more recently, dairy cows. While studies have demonstrated endocannabinoids to contribute to inflammation in the adipose tissue of dairy cows, no studies have evaluated the circulating presence of these mediators in cows suffering from systemic inflammation. Therefore, our second study sought to further evaluate the plasma oxylipin and endocannabinoid profiles of dairy cows suffering from systemic inflammation. In this study, we compared the oxylipin and endocannabinoid profiles of dairy cows categorized into high- and low-inflammation groups based on plasma Hp concentrations. We identified oxylipins associated with inflammation and found differences in the plasma endocannabinoid profile of high-inflammation cows compared to low-inflammation cows. Platelets are well understood for their function in hemostasis, though more recently, they have been studied for their ability to modulate the immune and inflammatory response. Presently, no studies exist elucidating the role of platelets on systemic inflammation in dairy cows. In addition to evaluating plasma oxylipin and endocannabinoid profiles in our second study, we determined if changes in platelets are associated with systemic inflammation in postpartum dairy cows. Proteomic analysis was completed on isolated platelets and plasma collected from dairy cows with high and low inflammation based on plasma Hp concentrations. Results from this study provide the first evidence demonstrating differences in the platelet and plasma proteomes between cows suffering from high inflammation and cows with low inflammation. The lipidomic and proteomic profiles described in these studies identified differences between cows suffering from systemic inflammation and apparently healthy cows. The results from these studies suggest platelets could contribute to an inflammatory state and have identified specific oxylipins, endocannabinoids, and proteins that may contribute to systemic inflammation in dairy cows by impairing the immune response or directly exerting an inflammatory function. More research is needed to fully understand the <i>in vitro </i>and <i>in vivo </i>function of the many lipid mediators and proteins identified in these studies and their ability to contribute to an exacerbated systemic inflammatory response in dairy cows.