Breed-specific differences in the immune response to lipopolysaccharide in ewes

Abstract

Innate immune response to a lipopolysaccharide (LPS) challenge varies among sheep breeds. How different breeds respond to bacterial infections impacts management practices of sheep producers. Hence, clinical response, acute-phase response, and gene expression of pro- and anti-inflammatory markers in peripheral white blood cells (WBCs) were examined after an LPS challenge in Dorset and Suffolk ewes. Ewes received either PBS or 2.5 µg/kg LPS (i.v.) 4 to 5 d after onset of synchronized estrus. Blood was collected via jugular venipuncture intermittently for 24 h to determine WBC counts. Rectal temperatures and observations of behavioral/physical appearances were recorded hourly. After LPS, WBCs decreased the first hour (P = 0.0001) and rectal temperatures (P < 0.0001) increased through 4 h; both returned toward normal 6 h after challenge. Suffolk ewes exhibited greater changes in temperature (P = 0.03) and behavioral/physical responses (P < 0.0001) than Dorset ewes and had an enhanced acute-phase response demonstrated by increased concentrations of plasma haptoglobin (P = 0.04), as well as cortisol concentrations (P = 0.03). Real-time PCR was completed on buffy coat homogenates for expression of pro-inflammatory [CXCL8, IL-6, interferon gamma (IFNG), complement component 3 (C3), toll-like receptor 4 (TLR4), prostaglandin synthase 2 (PTGS2)] and anti-inflammatory [IL-10, superoxide dismutase 2 (SOD2), forkhead box P3 (FOXP3), peroxisome proliferator-activated receptor gamma (PPARG), mannose receptor C type 1 (MRC1), transforming growth factor β (TGFβ)] genes. After LPS treatment, gene expressions increased for CXCL8 (P = 0.0003), TLR4 (P = 0.004), SOD2 (P < 0.0001), and C3 (P = 0.003), while PPARG (P = 0.006) and MRC1 (P = 0.003) decreased. Overall, Dorset ewes had greater expression of TLR4 (P = 0.003), IL-10 (P = 0.045), PPARG (P = 0.002), FOXP3 (P = 0.001), and SOD2 (P = 0.0002), whereas Suffolk ewes had greater expression of IL-6 (P = 0.0007), IFNG (P = 0.02), PTGS2 (P = 0.0002), and C3 (P = 0.008). Suffolk ewes also displayed greater expression of IL-6 (P = 0.002) and C3 (P = 0.0004) in response to LPS. In conclusion, differences in gene expression may explain the enhanced inflammatory response in Suffolk ewes and may predispose Suffolk ewes to be more responsive to bacterial infection than Dorset ewes.

Protective Effect of Resveratrol Improves Systemic Inflammation Responses in LPS-Injected Lambs

“…To reveal the mechanism of inflammatory disease and to find effective counter-measures for the chronic diseases, LPS, as a non-pathogenic immune activator, is being used to establish animal models. An intrajugular injection of 2.5 μg/kg LPS resulted in different expressions of inflammation-related genes in ewes [2]. Yates et al [27] reported that an intrajugular injection of 0.75 and 1.5 μg/kg LPS caused a dose-dependent inflammatory response, manifested as an increase in rectal temperature, serum cortisol, and serum insulin.…”

“…Yates et al [27] reported that an intrajugular injection of 0.75 and 1.5 μg/kg LPS caused a dose-dependent inflammatory response, manifested as an increase in rectal temperature, serum cortisol, and serum insulin. A single injection of LPS in animals only induced a short-term acute immune stress, which caused a sharp increase in plasma concentrations of inflammatory cytokines that returned to the pre-injection levels after 4 to 8 h [2,27,28]. Therefore, to reduce the tolerance and avoid the risk of mortality due to LPS in lambs in the present study, an initial dose of 0.25, 1.25, or 2.5 μg/kg LPS was injected every other day with a dose increase of 20% each time to examine the putative effect of resveratrol on inflammatory responses.…”

“…The complement component C3 is the central factor in all three activation pathways (classical, alternative, and lectin) [31]. Hadfield et al [2] reported that the mRNA level C3 in blood of ewes increased for 6 h after LPS administration, but there was no change in C3 at 0–4 h. In this study, LPS had a tendency to increase the expression level of C3 when compared to the control group, whereas lambs treated with resveratrol had a tendency to reduce the level of C3 . It was reported that the enhanced transcription of the C3 gene induced by LPS is targeted by the c-jun transcription factor [32].…”

“…Air temperature was maintained at 13 ± 1.4 °C and relative humidity at 81% ± 9.5%. After 5 days of adaptation to the conditions, each lamb received a jugular injection of LPS isolated from Escherichia coli O111:B4 (Sigma, St. Louis, MO, USA) at 08:00 on days 1, 3, 5, 7 and 9 to induce a chronic inflammatory response [2,4]. Initial doses of 0 (control group, n = 4), 0.25 (LPSL group, n = 4), 1.25 (LPSM group, n = 4) and 2.5 (LPSH group, n = 4) µg LPS/kg BW were injected, which were increased by 20% at each subsequent injection.…”

“…Intravenous injection of bacterial lipopolysaccharides (LPS) simulates infection in livestock and can be used for the study of immune inflammatory responses without the risk of using a live pathogen [2,3,4]. LPS is a major component of the outer membrane of gram-negative bacteria such as Escherichia coli and a chief member of the pathogen-associated molecular patterns [5].…”