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Immune system stimulation by repeated lipopolysaccharide injection alters liver cytoplasmic protein profile in pigs
Defining the changes in the liver protein profile of pigs in response to immune system stimulation (ISS) will provide insight into how animals handle immunological stress. Therefore, the purpose of this study was to investigate and define the effects of ISS and selection for residual feed intake (RFI) on the liver protein profile of pigs. Pigs divergently selected for low RFI (10 generations) are more efficient than their high RFI contemporaries (5 generations), providing a model to study the biology underpinning feed efficiency. Six (3/line) of 12 gilts (BW 63 ±4 kg) were injected intramuscularly every 48 h, for 7 d, with increasing amounts of E.coli lipopolysaccharide (LPS). Remaining six pigs were injected with saline (3/line). Pigs were then euthanized and liver tissue collected. The liver cytoplasmic protein fraction was isolated and two-dimensional difference in gel electrophoresis (2D-DIGE) was utilized to determine changes in the protein profile. A total of 563 protein spots were resolved on the 2D-DIGE gel. Seventy-eight protein spots were different in response to ISS (P < 0.05). Thirty-six protein spots were different between RFI selection lines (P < 0.05). Twenty-two spots from the two analyses were selected for identification through MALDI-TOF mass spectrometry. Three proteins affected by LPS were heat shock protein (HSP) 60, HSP70, and Peroxiredoxin (PRDX) 2 (Table). Identities of these proteins were independently confirmed through two-dimensional western blots. In this experiment, the identified proteins were not influenced by RFI line. Heat shock proteins 60 and 70 are known for their cytoprotective effects during stress. We predict the oxidative stress incurred during ISS causes HSP60 and HSP70 to increase in abundance due to their innate responsibilities to protect cells during times of stress. Peroxiredoxin-2 has been shown to eliminate peroxides during times of stress. A decrease in PRDX2 in the liver could indicate consumption, depletion or movement of PRDX2 throughout the body during an ISS. These data show that ISS altered cytoplasmic protein profile in the liver, specifically with a response by cellular rescue proteins.
Protein |
Coverage (%) |
Change (%) *with LPS stimulation |
P-Value |
Heat Shock Protein 60 |
6 |
27 |
0.019 |
Heat Shock Protein 70 |
7 |
20 |
0.0026 |
Peroxiredoxin-2 |
15 |
-42 |
0.00021 |
* A positive value indicates an increase in protein abundance in LPS-stimulated pigs; a negative value indicates a decrease in protein abundance in LPS-stimulated pigs.
Keywords: 2D-DIGE, heat shock protein, immune system stimulation, protein profile