Effects of genotype and transportation stress on cytokine gene expression in steers
The objective of this study was to determine effects of transportation stress and single nucleotide polymorphisms (SNP) in the coding sequence of two stress indicators, cytochrome P450 and the prolactin promoter region (C994G and C1286T, respectively), on gene expression of the prolactin receptor (PRLR) and three cytokines: monocyte chemoattractant protein (MCP-1 or CCL2), interleukin-8, and tumor necrosis factor (TNF)-α. Relative gene expression was quantified by real-time reverse transcription PCR using custom-made TaqMan assays for each gene of interest (Applied Biosystems, LifeTechnologies, Carlsbad, CA) in peripheral blood mononuclear cells of Gelbvieh x Angus crossbred steers (n = 47; mean body weight = 303 ± 39 kg; mean age = 294 ± 19 d). Three time points relative to transport (T): 27 h before (T−27), and 6 and 20 h after transport (T+6 and T+20, respectively) from Booneville, AR to Stillwater, OK (386 km) were evaluated. Time relative to transport, genotype, and their interaction affected (P < 0.05) gene expression. A C1286T x time interaction affected (P < 0.01) CCL2 expression: lowest level was in CT steers at T+6. Time affected (P < 0.01) PRLR and TNF-α expression in both C994G and C1286T genotypes: highest level was at T+20, whereas expression at earlier time points was similar. Genotype affected CCL2 expression on both C994G and C1286T genotypes: expression levels were lowest (P < 0.0001) when steers were CT for the C1286T SNP, or CC (P < 0.01) for the C994G SNP. Genotype effects on PRLR and TNF-α expression were evident only in C1286T genotypes: greatest (P < 0.01) expression of both genes was in CC steers. Our findings suggest that genotypes at C994G and C1286T SNP sites influence cytokine gene expression and may therefore be used as biomarkers for animal tolerance to shipping stress. Investigating effects of other stressors prior to and/or after transport on the expression of other stress response genes will help identify critical control points when developing practical and/or therapeutic measures to reduce transport stress.
Keywords: cytochrome P450, cytokine, prolactin