Proteomic analysis reveals increased abundance of inflammation-related proteins in adipose tissues from postpartum dairy cows treated with sodium salicylate

Abstract Text: The objective was to investigate the effects of sodium salicylate (SS) on the proteome of adipose tissue in early lactating dairy cows. Holstein cows in parity 3+ were assigned alternately at time of calving to either control or SS treatments. CON treatment received a molasses carrier in drinking water while the SS received 2.5 g/L SS with the molasses carrier in drinking water for 7 d after parturition. Adipose tissue biopsies were obtained from control cows (n = 5) and cows treated with SS (n = 5) at 7 DIM. Proteins were analyzed by intensity based, label-free quantitative shotgun proteomics at Weizmann Institute of Science (Rehovot, Israel). Proteins were extracted and subjected to in-solution tryptic digestion, followed by nanoflow liquid chromatography coupled to high-resolution tandem mass spectrometry (nanoLC-MS/MS). Quantitative data was extracted using Genedata Expressionist data analysis package and proteins identified using Mascot search engine. PCA analysis revealed two distinctive clusters, therefore proteomics data, after logarithmic transformation, were analyzed by two-way ANOVA for effects of treatment (control vs. SS), cluster (1 vs. 2) and their interaction. Only proteins that were different at P < 0.05 for effect of treatment and P > 0.05 for effect of interaction, as well as having a fold change (FC) of ± 1.5 were further considered. Proteomic analysis quantified 1422 proteins in adipose tissue, from which the abundance of 80 (5.6%) proteins differed in SS vs. control. The top canonical pathways affected by SS treatment (IPA, Ingenuity) were the complement system, IL-10 signaling and acute phase response signaling. The abundance of several proteins related to these pathways was altered; for example, complement C1q subcomponent subunit B (C1QB, FC = 360, P < 0.002), complement component 1-r subcomponent (C1R, FC = 1.6, P < 0.04), flavin reductase (NADPH; BLVRB, FC = 1.6, P< 0.05) and lipopolysaccharide-binding protein (LBP, FC = 2.3, P < 0.004) were increased in SS adipose compared to controls. These findings imply that SS treatment up-regulates some inflammation-related proteins in adipose tissue, perhaps in order to maintain the desired inflammatory tone during the subacute inflammation in postpartum cows.

Keywords: adipose, immune, proteomics, sodium salicylate