Kinetics of changes in gene and microRNA expression related with muscle inflammation and protein degradation following LPS-challenge in weaned piglets

Abstract

To test the dynamic changes of the expression of genes and microRNA in the gastrocnemius muscle after LPS challenge, 36 piglets were assigned to a control group (slaughtered 0 h after saline injection) and LPS groups (slaughtered at 1 h, 2 h, 4 h, 8 h, and 12 h after LPS treatment, respectively). After LPS treatment, the mRNA expression of IL-1β, IL-6, and TNF-α reached maximal levels at 1 h, 2 h, and 1 h, respectively (P < 0.05), and mRNA expression of TLR4, NODs, muscle-specific ring finger 1, and muscle atrophy F-box peaked at 12 h (P < 0.05). Moreover, the expression of miR-122, miR-135a, and miR-370 reduced at 1 h, 1 h, and 2 h, respectively (P < 0.05), and miR-34a, miR-224, miR-132, and miR-145 reached maximum expression levels at 1 h, 1 h, 2 h, and 4 h, respectively (P < 0.05). These results suggested that mRNA expression of pro-inflammatory cytokines was elevated in the early stage, mRNA expression of genes related to TLR4 and NODs signaling pathways and protein degradation increased in the later phase, and the expression of microRNA related to muscle inflammation and protein degradation changed in the early stage after LPS injection.

Keywords: MicroRNAs; inflammation; lipopolysaccharide; muscle; piglet; protein degradation.

Figure 1.

Effect of LPS on mRNA abundance of pro-inflammatory cytokines in muscle. Piglets were injected with 100 g/kg body mass (BM) or the equivalent amount of sterile saline. The piglets in the control group were slaughtered 0 h after saline injection. The piglets in LPS treatments were slaughtered at 1 h, 2 h, 4 h, 8 h, and 12 h after LPS injection. Values are single-point determinations and represent each of the time points listed above.

Figure 2.

Effect of LPS on mRNA abundance of key genes in TLR4 and NOD signaling pathway in muscle. Piglets were injected with 100 g/kg body mass (BM) or the equivalent amount of sterile saline. The piglets in the control group were slaughtered 0 h after saline injection. The piglets in LPS treatments were slaughtered at 1 h, 2 h, 4 h, 8 h, and 12 h after LPS injection. Values are single-point determinations and represent each of the time points listed above.

Figure 3.

Effect of LPS on mRNA abundance of key genes in forkhead box O1 (FOXO)/ muscle atrophy F-box (MAFbx)-muscle-specific ring finger 1 (MuRF1) signaling pathway in muscle. Piglets were injected with 100 g/kg body mass (BM) or the equivalent amount of sterile saline. The piglets in the control group were slaughtered 0 h after saline injection. The piglets in LPS treatments were slaughtered at 1 h, 2 h, 4 h, 8 h, and 12 h after LPS injection. Values are single-point determinations and represent each of the time points listed above.