Kinetics of Physiological and Behavioural Responses in Endotoxemic Pigs with or without Dexamethasone Treatment

Transcriptome analysis of porcine PBMCs reveals lipopolysaccharide-induced immunomodulatory responses and crosstalk of immune and glucocorticoid receptor signaling

The current level of knowledge on transcriptome responses triggered by endotoxins and glucocorticoids in immune cells in pigs is limited. Therefore, in the present study, we treated porcine peripheral blood mononuclear cells (PBMCs) with lipopolysaccharide (LPS) and dexamethasone (DEX) separately or combined for 2 hours. The resultant transcriptional responses were examined by mRNA sequencing. We found that the LPS treatment triggered pronounced inflammatory responses as evidenced by upregulation of pro-inflammatory cytokines, chemokines, and related signaling pathways like NF-κB. Concurrently, a series of downregulated pro-inflammatory and upregulated anti-inflammatory molecules were identified. These are involved in the inhibition of TLR, NF-κB, and MAPK cascades and activation of signaling mediated by Tregs and STAT3, respectively. These findings suggested that LPS initiated also an anti-inflammatory process to prevent an overwhelming inflammatory response. The transcriptome responses further revealed substantial crosstalk of immune responses and glucocorticoid receptor (GR) signaling. This was apparent in four aspects: constitutive inhibition of T cell signaling by DEX through a subset of genes showing no response to LPS; inhibition of LPS-induced inflammatory genes by DEX; attenuation of DEX action by LPS paralleled by the regulation of genes implicated in cytokine and calcium signaling; and DEX-induced changes in genes associated with the activation of pro-inflammatory TLR, NF-κB, iNOS, and IL-1 signaling. Consequently, our study provides novel insights into inflammatory and GR signaling in pigs, as well as an understanding of the application of glucocorticoid drugs for the treatment of inflammatory disorders.

In utero heat stress alters the postnatal innate immune response of pigs

The effects of in utero heat stress (IUHS) range from decreased growth performance to altered behavior, but the long-term impact of IUHS on postnatal innate immune function in pigs is unknown. Therefore, the study objective was to determine the effects of early gestation IUHS on the immune, metabolic, and stress response of pigs subjected to an 8 hr lipopolysaccharide (LPS) challenge during postnatal life. Twenty-four pregnant gilts were exposed to thermoneutral (TN; n = 12; 17.5 ± 2.1 °C) or heat stress (HS; n = 12; cyclic 26 to 36 °C) conditions from days 6 to 59 of gestation, and then TN conditions (20.9 ± 2.3 °C) from day 60 of gestation to farrowing. At 12 wk of age, 16 IUHS and 16 in utero thermoneutral (IUTN) pigs were selected, balanced by sex and given an intravenous injection of LPS (2 µg/kg BW mixed with sterile saline [SAL] and injected at 2 µL/kg BW) or SAL (2 µL/kg BW). Body temperature was monitored every 30 min, and blood was obtained at 0, 1, 2, 3, 4, 6, and 8 hr following the LPS challenge. Blood samples were analyzed for glucose, insulin, non-esterified fatty acids (NEFA), cortisol, and cytokine concentrations. In addition, white blood cell counts were determined at 0 and 4 hr. Hour 0 data were used as covariates. Body temperature was increased (P < 0.01) in LPS (40.88 ± 0.08 °C) vs. SAL (39.83 ± 0.08 °C) pigs. Eosinophils tended to be decreased overall (P = 0.09; 43.9%) in IUHS vs. IUTN pigs. Glucose concentrations were reduced overall (P = 0.05; 5.9%) in IUHS vs. IUTN pigs. The NEFA concentrations tended to be greater (P = 0.07; 143.4%) in IUHS-LPS pigs compared with all other treatments, and IUTN-LPS pigs tended to have greater (127.4%) circulating NEFA concentrations compared with IUTN-SAL and IUHS-SAL pigs. Cortisol was increased (P = 0.04) in IUHS-LPS compared with IUTN-LPS pigs at 3 hr (21.5%) and 4 hr (64.3%). At 1 hr, tumor necrosis factor α was increased (P = 0.01; 115.1%) in IUHS-LPS compared with IUTN-LPS pigs. Overall, interleukin-1β (IL-1β) and interleukin-6 (IL-6) were greater (P < 0.04; 281.3% and 297.8%, respectively) in IUHS-LPS pigs compared with all other treatments, and IUTN-LPS pigs had increased IL-1β and IL-6 concentrations compared with IUTN-SAL and IUHS-SAL pigs. In summary, IUHS altered the postnatal cytokine, metabolic, and physiological stress response of pigs during postnatal life, which may have negative implications toward the innate immune response of IUHS pigs to pathogens.