Heat stress protects against lung injury in the neutropenic, endotoxemic rat

The Evidence for a Causal Link Between Disease and Damaging Behavior in Pigs

Damaging behaviors (DB) such as tail and ear biting are prevalent in pig production and reduce welfare and performance. Anecdotal reports suggest that health challenges increase the risk of tail-biting. The prevalence of tail damage and health problems show high correlations across batches within and between farms. There are many common risk factors for tail-biting and health problems, notably respiratory, enteric and locomotory diseases. These include suboptimal thermal climate, hygiene, stocking density and feed quality. The prevalence of tail damage and health problems also show high correlations across batches within and between farms. However, limited evidence supports two likely causal mechanisms for a direct link between DB and health problems. The first is that generalized poor health (e.g., enzootic pneumonia) on farm poses an increased risk of pigs performing DB. Recent studies indicate a possible causal link between an experimental inflammation and an increase in DB, and suggest a link between cytokines and tail-biting. The negative effects of poor health on the ingestion and processing of nutrients means that immune-stimulated pigs may develop specific nutrient deficiencies, increasing DB. The second causal mechanism involves tail-biting causing poor health. Indirectly, pathogens enter the body via the tail lesion and once infected, systemic spread of infection may occur. This occurs mainly via the venous route targeting the lungs, and to a lesser extent via cerebrospinal fluid and the lymphatic system. In carcasses with tail lesions, there is an increase in lung lesions, abscessation, arthritis and osteomyelitis. There is also evidence for the direct spread of pathogens between biters and victims. In summary, the literature supports the association between poor health and DB, particularly tail-biting. However, there is insufficient evidence to confirm causality in either direction. Nevertheless, the limited evidence is compelling enough to suggest that improvements to management and housing to enhance pig health will reduce DB. In the same way, improvements to housing and management designed to address DB, are likely to result in benefits to pig health. While most of the available literature relates to tail-biting, we suggest that similar mechanisms are responsible for links between health and other DB.

Postprandial insulin and nutrient concentrations in lipopolysaccharide-challenged growing pigs reared in thermoneutral and high ambient temperatures1

The aim of this study was to evaluate the associated effects of ambient temperature and inflammation caused by repeated administration of Escherichia coli lipopolysaccharide (LPS) on insulin, energy, and AA metabolism. Twenty-eight pigs were assigned to one of the two thermal conditions: thermoneutral (24 °C) or high ambient temperature (30 °C). The experimental period lasted 17 d, which was divided into a 7-d period without LPS (days -7 to -1), and a subsequent 10-d LPS period (days 1 to 10) in which pigs were administered 5 repeated injections of LPS at 2-d intervals. Postprandial profiles of plasma insulin and nutrients were evaluated through serial blood samples taken on days -4 (P0), 4 (P1), and 8 (P2). Before the LPS-challenge (P0), postprandial concentrations of glucose, lactate, Gln, Ile, Leu, Phe, Tyr, and Val were greater in pigs kept at 24 °C than at 30 °C (P < 0.05). In contrast, Arg, Asp, Gly, His, and Met postprandial concentrations at P0 were lower at 24 °C than at 30 °C (P < 0.05). At both 24 and 30 °C conditions, pigs had greater postprandial concentrations of insulin (P < 0.01) and lower concentrations of NEFA (P < 0.01) and α-amino nitrogen (P < 0.05) at P1 and P2 than at P0. Compared with P0, postprandial concentrations of glucose were greater (P < 0.05) at P1 in pigs kept at 24 °C, and at P1 and P2 in pigs kept at 30 °C. At both ambient temperatures, pigs had lower (P < 0.05) postprandial concentrations of Ala, Gly, His, Ile, Leu, Pro, Ser, Thr, Trp, and Val at P1 and P2 than at P0. Arginine postprandial concentration at P1 was lower than at P0 in pigs kept at 24 °C (P < 0.05), whereas no difference was observed in pigs at 30 °C. Relative to P0, Gln and Tyr concentrations were lower at P1 and P2 in pigs kept at 24 °C (P < 0.01), whereas lower Gln concentration was observed only at P2 (P < 0.01) and lower Tyr only at P1 (P < 0.01) in pigs kept at 30 °C. Our study shows a hyperglycemic and hyperinsulinemic state in LPS-challenged pigs and a greater magnitude of this response in pigs kept at 30 °C. Furthermore, LPS caused important changes in BCAA, His, Thr, and Trp profiles, suggesting the role these AA in supporting the inflammatory response. Finally, our results suggest that LPS-induced effects on postprandial profiles of specific AA (Arg, Gln, Phe, and Tyr) may be modulated by ambient temperature.

Heat stress prevents lipopolysaccharide-induced apoptosis in pulmonary microvascular endothelial cells by blocking calpain/p38 MAPK signalling

Pulmonary microvascular endothelial cells (PMECs) injury including apoptosis plays an important role in the pathogenesis of acute lung injury during sepsis. Our recent study has demonstrated that calpain activation contributes to apoptosis in PMECs under septic conditions. This study investigated how calpain activation mediated apoptosis and whether heat stress regulated calpain activation in lipopolysaccharides (LPS)-stimulated PMECs. In cultured mouse primary PMECs, incubation with LPS (1 μg/ml, 24 h) increased active caspase-3 fragments and DNA fragmentation, indicative of apoptosis. These effects of LPS were abrogated by pre-treatment with heat stress (43 °C for 2 h). LPS also induced calpain activation and increased phosphorylation of p38 MAPK. Inhibition of calpain and p38 MAPK prevented apoptosis induced by LPS. Furthermore, inhibition of calpain blocked p38 MAPK phosphorylation in LPS-stimulated PMECs. Notably, heat stress decreased the protein levels of calpain-1/2 and calpain activities, and blocked p38 MAPK phosphorylation in response to LPS. Additionally, forced up-regulation of calpain-1 or calpain-2 sufficiently induced p38 MAPK phosphorylation and apoptosis in PMECs, both of which were inhibited by heat stress. In conclusion, heat stress prevents LPS-induced apoptosis in PMECs. This effect of heat stress is associated with down-regulation of calpain expression and activation, and subsequent blockage of p38 MAPK activation in response to LPS. Thus, blocking calpain/p38 MAPK pathway may be a novel mechanism underlying heat stress-mediated inhibition of apoptosis in LPS-stimulated endothelial cells.

Suppression of RAGE and TLR9 by Ketamine Contributes to Attenuation of Lipopolysaccharide-Induced Acute Lung Injury

The present study aimed to investigate the protective role of ketamine in lipopolysaccharide (LPS)-induced acute lung injury (ALI) by the inhibition of the receptor for advanced glycation end products (RAGE) and toll-like receptor 9 (TLR9). ALI was induced in rats by intratracheal instillation of LPS (5 mg/kg), and ketamine (5, 7.5, and 10 mg/kg) was injected intraperitoneally 1 h after LPS administration. Meanwhile, A549 alveolar epithelial cells were incubated with LPS in the presence or absence of ketamine. After 24 h, bronchoalveolar lavage fluid (BALF) and lung tissue were collected. Ketamine posttreatment at doses of 5, 7.5, and 10 mg/kg decreased LPS-induced evident lung histopathological changes, lung wet-to-dry weight ratio, and lung myeloperoxidase activity. In addition, posttreatment with ketamine-inhibited inflammatory cells and inflammatory mediators including tumor necrosis factor-α, interleukin-6, and high-mobility group box 1 in BALF. Furthermore, we demonstrated that ketamine-inhibited LPS-induced RAGE and TLR9 protein up-expressions and the phosphorylation of I-κB-α and nuclear factor-κB (NF-κB) p65 in vivo and in vitro. The results presented here suggest that the protective mechanism of ketamine may be attributed partly to decreased production of inflammatory mediators through the inhibition of RAGE/TLR9-NF-κB pathway.

Heat stress pretreatment decreases lipopolysaccharide-induced apoptosis via the p38 signaling pathway in human umbilical vein endothelial cells

The present study aimed to investigate vascular endothelial apoptosis, and the regulatory molecules involved in the condition of heatstroke caused by direct hyperthermia due to high core temperature and gut‑derived endotoxemia. Human umbilical vascular endothelial cells (HUVECs) were isolated and treated with heat stress (43˚C for 1 h), lipopolysaccharide (LPS; 1 µg/ml), or a combination of heat stress pretreatment followed by LPS. Caspase‑3 activity, DNA fragmentation, and cell viability, determined using a 3‑(4, 5‑dimethyl thiazol‑2‑yl)‑2,5‑diphenyl tetrazolium bromide assay, were measured to examine cellular apoptosis. Changes in the expression levels of heat shock protein (HSP) 27, HSP90 and B‑cell lymphoma 2 (Bcl‑2), and the phosphorylation of p38 were detected using Western blot assays. The specific inhibitor of p38, SB203580, was also used. LPS induced endothelial apoptosis, as indicated by increased caspase‑3 activity, a high level of DNA fragmentation and low cell viability. LPS also increased p38 phosphorylation and decreased the expression levels of HSP27, HSP90 and Bcl‑2. Heat stress pretreatment inhibited LPS‑induced cellular apoptosis, increased the phosphorylation of p38, and increased the expression levels of HSP27, HSP90 and Bcl‑2. Pretreatment with SB203580 had effects similar to those of heat stress in the amelioration of LPS‑induced effects. These findings demonstrated that heat stress pretreatment decreased LPS‑induced Bcl‑2‑associated apoptosis in HUVECs by attenuating p38 activation, thereby increasing the expression levels of HSP27 and HSP90.

Lidocaine attenuates lipopolysaccharide-induced acute lung injury through inhibiting NF-kappaB activation

BACKGROUND AND OBJECTIVES

Lidocaine has been reported to attenuate the inflammatory response in addition to its anesthetic activity, but the mechanisms are poorly understood. The objective of this study is to determine if lidocaine prior to endotoxemia diminishes pulmonary dysfunction by blocking the NF-kappaB activation.

METHODS

Rats were assigned to: (1) control (0.9% sodium chloride); (2) lipopolysaccharides (LPS); (3) LPS + lidocaine 1 mg/kg; (4) LPS + lidocaine 2 mg/kg, and (5) LPS + lidocaine 4 mg/kg. The LPS and LPS + lidocaine 4 mg/kg groups were subjected to 1-, 3-, 6- and 12-hour time points. To investigate the activation of NF-kappaB, the expression of NF-kappaB in the nuclear and I kappaB alpha in the cytosol extracts were analyzed by Western blot. The concentration of TNF-alpha and IL-6 in serum was detected by ELISA. The pathologic changes of the lung were observed using HE staining.

RESULTS

After i.p. injection of LPS, the expression of NF-kappaB in the nuclear extracts was significantly increased and I kappaB alpha in the cytosol extracts was markedly decreased. The concentration of TNF-alpha and IL-6 in serum was increased. Pathological examination showed that the normal structure of the lung was destroyed badly. However, lidocaine reversed the above results.

CONCLUSION

Lidocaine attenuates LPS-induced lung injury via mechanisms involving inhibiting NF-kappaB activation and cytokine release, which implies that lidocaine may be a potential anti-inflammatory agent in endotoxemia.