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BackgroundWith evidence of warming climates, it is important to understand the effects of heat stress in farm animals in order to minimize production losses. Studying the changes in the brain proteome induced by heat stress may aid in understanding how heat stress affects brain function. The hypothalamus is a critical region in the brain that controls the pituitary gland, which is responsible for the secretion of several important hormones. In this study, we examined the hypothalamic protein profile of 10 pigs (15 ± 1 kg body weight), with five subjected to heat stress (35 ± 1 °C; relative humidity = 90%) and five acting as controls (28 ± 3 °C; RH = 90%).ResultThe isobaric tags for relative and absolute quantification (iTRAQ) analysis of the hypothalamus identified 1710 peptides corresponding to 360 proteins, including 295 differentially expressed proteins (DEPs), 148 of which were up-regulated and 147 down-regulated, in heat-stressed animals. The Ingenuity Pathway Analysis (IPA) software predicted 30 canonical pathways, four functional groups, and four regulatory networks of interest. The DEPs were mainly concentrated in the cytoskeleton of the pig hypothalamus during heat stress.ConclusionsIn this study, heat stress significantly increased the body temperature and reduced daily gain of body weight in pigs. Furthermore, we identified 295 differentially expressed proteins, 147 of which were down-regulated and 148 up-regulated in hypothalamus of heat stressed pigs. The IPA showed that the DEPs identified in the study are involved in cell death and survival, cellular assembly and organization, and cellular function and maintenance, in relation to neurological disease, metabolic disease, immunological disease, inflammatory disease, and inflammatory response. We hypothesize that a malfunction of the hypothalamus may destroy the host physical and immune function, resulting in decreased growth performance and immunosuppression in heat stressed pigs.

Background Various stressors alter the 'brain-gut axis' and contribute to many gastrointestinal disorders such as inflammatory bowel disease. However, the pathological mechanisms of these perturbations are poorly understood. Here, we report on the induction of intestinal inflammation in heat-stressed pigs and apply fecal microbiota transplantation from pigs to mice to elucidate the role of intestinal microbiota in TLR4/NF-κB signaling pathway activation. Results Twelve healthy adult pigs were subjected to heat stress (34 ± 1 °C and 75–85% relative humidity) and compared with 12 control pigs exposed to 25 ± 3 °C and the same humidity level. The pigs were sacrificed on days 1, 7, 14, and 21. Their colonic contents were collected for microbiome analyses and their colonic epithelia underwent transcriptome analyses. Pseudo-germ-free mice were gavaged with fecal bacteria from heat-stressed and control pigs on the collection days to determine whether gut microbiomes and immune responses resembling those in the pigs could be induced in the mice. Heat-stressed pigs presented with fever and diarrhea from day 7 and their colonic villus length, crypt depth/width, and goblet cell number were significantly lower than those of the controls. Their TLR4, TRAF6, and nuclear p65 were upregulated at the RNA and protein levels. Their proinflammatory IL-6, IL-8, and IL-17 were also upregulated. Colonic microflora composition in the heat-stressed pigs markedly differed from that of the controls. By day 14, the former presented with substantial increases in opportunistic pathogens such as Campylobacterales , Veillonellaceae , and Megasphaera . Intestinal lipopolysaccharide concentrations were higher in the heat-stressed than the control pigs. Mice administered fecal transplantation from heat-stressed pigs had a distinctly different colonic microflora composition from those receiving control pig fecal transplantation. Bacteroides were significantly diminished and Akkermansia were significantly augmented in mice administered feces from heat-stressed pigs for 14 d. In the colonic tissues of mice given feces from heat-stressed pigs, the TLR4/NF-κB signaling pathway was activated and there was a mild inflammatory response. Conclusion Heat stress promotes changes in gut microflora composition which, in turn, activates the TLR4/NF-κB signaling pathway and causes inflammatory bowel disease in pigs.

Heat stress (HS) and its associated pathologies are major challenges facing the pig industry in southern China, and are responsible for large economic losses. However, the molecular mechanisms governing the abnormal secretion of HS-responsive hormones, such as glucocorticoids, are not fully understood. The goal of this study was to investigate differentially expressed proteins (DEPs) in the adrenal glands of pigs, and to elucidate changes in the immune neuroendocrine system in pigs following HS. Through a functional proteomics approach, we identified 1202 peptides, corresponding to 415 proteins. Of these, we found 226 DEPs between heat-stressed and control porcine adrenal gland tissue; 99 of these were up-regulated and 127 were down-regulated in response to HS. These DEPs included proteins involved in substrate transport, cytoskeletal changes, and stress responses. Ingenuity Pathway Analysis was used to identify the subcellular characterization, functional pathway involvement, regulatory networks, and upstream regulators of the identified proteins. Functional network and pathway analyses may provide insights into the complexity and dynamics of HS-host interactions, and may accelerate our understanding of the mechanisms of HS., Highlights • This is first time to investigate differentially expressed proteins (DEPs) in the adrenal glands of pigs by proteomics. • Total 226 DEPs involve in substrate transport, cytoskeletal changes, and stress responses were detected in heat stressed pigs. • Functional network and pathway analyses may provide insights into the complexity and dynamics of HS-host interactions.

Hyperthermia in pigs induces suppressor of cytokine signaling (SOCS) 3 and SOCS4 expression in intestinal gut and causes disruption of inflammation cytokine production. These changes may affect the development of inflammatory bowel disease in heat-stressed pigs. However, the mechanisms are not well understood. Accordingly, in this study, we examined the roles of SOCS members in regulation of the nuclear factor (NF)-κB pathway and heat shock protein (HSP) 70-mediated cytokine induction in 293T human embryonic kidney cells and IPEC-J2 porcine small intestinal epithelial cells. Ectopic expression of HSP70 significantly modulated NF-κB activity (p ≤ .05). Moreover, co-expression of SOCS3 or SOCS4 with HSP70 reduced NF-κB activity, which was abolished by SOCS3 or SOCS4 knockdown with short hairpin RNA. Interestingly, MyD88-adaptor-like (Mal) protein was downregulated in cells expressing SOCS3 but not in cells expressing SOCS4. In addition, SOCS3 but not SOCS4 negatively regulated the activity of NF-κB induced by HSP70 overexpression via degradation of Mal. These findings may facilitate the development of novel SOCS3-based therapeutic strategies to control heat stress-related disorders in pigs.