J.C. Pompe

Differential ex vivo and in vivo endotoxin tolerance kinetics following human endotoxemia.

Objectives:Endotoxin (lipopolysaccharide) tolerance is characterized by a transient refractory state to a subsequent lipopolysaccharide challenge. Following human endotoxemia, ex vivo tolerance of circulating leukocytes to lipopolysaccharide resolves within 24 hrs. However, the duration of in vivo tolerance, assumed to be primarily mediated by tissue-resident macrophages, is unknown. Design, Setting, Subjects, and Interventions:Clinical experimental study in 16 healthy male volunteers at an intensive care research unit. To compare ex vivo and in vivo tolerance kinetics, whole blood from healthy volunteers was stimulated with lipopolysaccharide before, 4 hrs after, and 1, 2, 3, and 4 wks following in vivo endotoxin (2 ng/kg; lipopolysaccharide derived from Escherichia coli O:113) administration. Furthermore, we compared the inflammatory response during two subsequent endotoxemia experiments in healthy volunteers with an interval of 2 wks. The cytokines tumor necrosis factor-&agr;, interleukin-6, interleukin-10, interleukin-1 receptor antagonist, and transforming growth factor-&bgr; were measured. Measurements and Main Results:Four hours after in vivo lipopolysaccharide administration, production of tumor necrosis factor-&agr;, interleukin-6, and interleukin-10, but not interleukin-1 receptor antagonist in ex vivo lipopolysaccharide-stimulated whole blood was diminished. Ex vivo lipopolysaccharide tolerance completely resolved within 1 week. In contrast, in vivo lipopolysaccharide tolerance was still apparent after 2 wks. Compared to the first lipopolysaccharide administration, plasma peak levels of tumor necrosis factor-&agr;, interleukin-6, interleukin-10, interleukin-1 receptor antagonist, and transforming growth factor-&bgr; were attenuated by 46%, 36%, 45%, 10%, and 14%, respectively (all p < .05). Conclusions:While ex vivo lipopolysaccharide tolerance quickly resolves, in vivo lipopolysaccharide tolerance persists for at least 2 wks. These findings strengthen the notion that the in vivo response to lipopolysaccharide is mediated by tissue-resident macrophages and that ex vivo stimulation does not accurately reflect the in vivo innate immune response. Intervention studies utilizing the human endotoxemia model should be performed using parallel groups rather than a crossover design.

Effects of the alpha7 nicotinic acetylcholine receptor agonist GTS-21 on the innate immune response in humans

The vagus nerve can reflexively attenuate the innate immune response via binding of the vagal neurotransmitter acetylcholine (ACh) to the &agr;7 nicotinic ACh receptor (&agr;7nAChR). We recently reported potent anti-inflammatory effects of the &agr;7nAChR agonist GTS-21 in human leukocytes. In the present work, we investigated the anti-inflammatory effects of GTS-21 on the innate immune response during experimental human endotoxemia. We performed a double-blind placebo-controlled pilot study in 14 healthy nonsmoking male volunteers. Subjects received 150 mg GTS-21 (n = 7) or placebo (n = 7) orally three times per day during 3 days before endotoxin administration and on the day of the human endotoxemia experiment. This GTS-21 dosage scheme is the highest reported to be safe in humans. Subsequently, subjects were i.v. administered 2 ng/kg endotoxin (LPS derived from Escherichia coli O:113). Serial blood withdrawals were performed to determine GTS-21 plasma concentrations and inflammatory mediators. Plasma concentrations of GTS-21 and its active metabolite 4-OH-GTS-21 were highly variable between subjects. LPS administration resulted in a transient inflammatory response. There were no differences in the LPS-induced cytokine response between the GTS-21- and placebo-treated groups. However, within the GTS-21-treated group, higher GTS-21 plasma concentrations correlated with lower levels of TNF-&agr; (r = −0.78, P = 0.03), IL-6 (r = −0.76, P = 0.04), and IL-1RA (r = −0.86, P = 0.01), but not IL-10 (r = −0.35, P = 0.25). In conclusion, although higher GTS-21 plasma concentrations significantly correlated with lower cytokine levels, the highest dose tested to be safe in humans did not result in significant differences in inflammatory mediators between the GTS-21- and placebo-treated groups.

GTS-21 inhibits pro-inflammatory cytokine release independent of the Toll-like receptor stimulated via a transcriptional mechanism involving JAK2 activation

The vagus nerve can limit inflammation via the alpha7 nicotinic acetylcholine receptor (alpha7nAChR). Selective pharmacological stimulation of the alpha7nAChR may have therapeutic potential for the treatment of inflammatory conditions. We determined the anti-inflammatory potential of GTS-21, an alpha7nAChR-selective partial agonist, on primary human leukocytes and compared it with nicotine, the nAChR agonist widely used for research into the anti-inflammatory effects of alpha7nAChR stimulation. Furthermore, we investigated whether the effects of both nicotinic agonists were restricted to specific Toll-like receptors (TLRs) stimulated and explored the mechanism behind the anti-inflammatory effect of GTS-21. GTS-21 and nicotine inhibited the release of pro-inflammatory cytokines in peripheral blood mononuclear cells (PBMCs), monocytes and whole blood independent of the TLR stimulated, with higher potency/efficacy for GTS-21 compared to nicotine. The anti-inflammatory cytokine IL-10 was relatively unaffected by both nicotinic agonists. The effects of GTS-21 and nicotine could not be reversed by nAChR antagonists, while the JAK2 inhibitor AG490 abolished the anti-inflammatory effects. GTS-21 downregulated monocyte cell-surface expression of TLR2, TLR4 and CD14. qPCR analysis demonstrated that the anti-inflammatory effect of GTS-21 is mediated at the transcriptional level and involves JAK2-STAT3 activation. In conclusion, GTS-21 has a profound anti-inflammatory effect in human leukocytes and that GTS-21 is more potent/efficacious than nicotine. The absence of a blocking effect of nAChR antagonists in human leukocytes might indicate different pharmacological properties of the alpha7nAChR in human leukocytes compared to other cell types. GTS-21 may be promising from a therapeutic perspective because of its suitability for human use.

α7 Nicotinic acetylcholine receptor agonist GTS-21 attenuates ventilator-induced tumour necrosis factor-α production and lung injury

BACKGROUND Mechanical ventilation (MV) induces an inflammatory response that can lead to lung injury. The vagus nerve can limit the inflammatory response through the cholinergic anti-inflammatory pathway. We evaluated the effects of stimulation of the cholinergic anti-inflammatory pathway with the selective partial α7 nicotinic acetylcholine receptor (α7nAChR) agonist GTS-21 on inflammation and lung injury induced by MV using clinically relevant ventilator settings. Furthermore, we investigated whether altering endogenous cholinergic signalling, by administration of the non-specific nAChR antagonist mecamylamine and the peripherally acting acetylcholinesterase inhibitor neostigmine, modulates the MV-induced inflammatory response. METHODS C57BL6 mice were injected i.p. with either the selective α7nAChR agonist GTS-21 (8 mg kg(-1)), the acetylcholinesterase inhibitor neostigmine (80 μg kg(-1)), the nAChR antagonist mecamylamine (1 mg kg(-1)), or a placebo; followed by 4 h of MV (8 ml kg(-1), 1.5 cm H(2)O PEEP). RESULTS MV resulted in release of cytokines in plasma and lungs compared with unventilated mice. Lung and plasma levels of tumour necrosis factor (TNF)-α, but not of interleukin-10, were lower in GTS-21-treated animals compared with placebo (P<0.05). In addition, GTS-21 lowered the alveolar-arterial gradient, indicating improved lung function (P=0.04). Neither neostigmine nor mecamylamine had an effect on MV-induced inflammation or lung function. CONCLUSIONS MV with clinically relevant ventilator settings results in pulmonary and systemic inflammation. Stimulation of the cholinergic anti-inflammatory pathway with GTS-21 attenuates MV-induced release of TNF-α, which was associated with reduced lung injury. Modulation of endogenous cholinergic signalling did not affect the MV-induced inflammatory response. Selective stimulation of the cholinergic anti-inflammatory pathway may represent new treatment options for MV-induced lung injury.

Increased vagal tone accounts for the observed immune paralysis in patients with traumatic brain injury.

Traumatic brain injury (TBI) is a leading cause of death and disability, especially in the younger population. In the acute phase after TBI, patients are more vulnerable to infection, associated with a decreased immune response in vitro. The cause of this immune paralysis is poorly understood. Apart from other neurologic dysfunction, TBI also results in an increase in vagal activity. Recently, the vagus nerve has been demonstrated to exert an anti-inflammatory effect, termed the cholinergic anti-inflammatory pathway. The anti-inflammatory effects of the vagus nerve are mediated by the α7 nicotinic acetylcholine receptor present on macrophages and other cytokine-producing cells. From these observations, we hypothesize that the immune paralysis observed in patients with TBI may, at least in part, result from augmented vagal activity and subsequent sustained effects of the cholinergic anti-inflammatory pathway. This pathway may counteract systemic proinflammation caused by the release of endogenous compounds termed alarmins as a result of tissue trauma. However, sustained activity of this pathway may severely impair the bodys ability to combat infection. Since the cholinergic anti-inflammatory pathway can be pharmacologically modulated in humans, it could represent a novel approach to prevent infections in patients with TBI.

Continuous administration of enteral lipid- and protein-rich nutrition limits inflammation in a human endotoxemia model

Objective:An overzealous inflammatory response is an important cause of morbidity and mortality in surgical, trauma, and critically ill patients. Enteral administration of lipid-rich nutrition was previously shown to attenuate inflammation and reduce organ damage via a cholecystokinin-1 receptor–mediated vagovagal reflex in animal studies. The current preclinical study investigates the immunomodulatory potential of a custom-made enteral nutrition during systemic inflammation in man. Design:Double-blind, randomized controlled trial. Setting:Intensive care research unit. Subjects:Male volunteers. Interventions:After an overnight fast, 18 healthy male subjects received an IV bolus of Escherichia coli lipopolysaccharide (2 ng/kg). Subjects in the fasted group (n = 6) were deprived of food throughout the study, while subjects in the intervention groups were fed either custom-made lipid- and protein-rich nutrition (n = 6) or isocaloric control nutrition (n = 6) via nasojejunal tube, starting 1 hour prior to lipopolysaccharide administration until 6 hours afterward. Measurements and Main Results:Bolus lipopolysaccharide administration resulted in a marked inflammatory response. Continuous postpyloric administration of nutrition significantly increased plasma cholecystokinin levels throughout the lipopolysaccharide-induced inflammatory response. Lipid- and protein-rich nutrition attenuated circulating levels of the proinflammatory cytokines tumor necrosis factor-&agr; and interleukin-6 and the interleukin-1 receptor antagonist compared with control nutrition (all p < 0.05) and fasted subjects (all p < 0.05). In additional, lipid- and protein-rich nutrition augmented the anti-inflammatory response, reflected by increased plasma levels of interleukin-10 compared with fasted subjects (p < 0.0001). Conclusions:The current preclinical study expands the immunomodulating effects of enteral nutrition as previously observed in rodents to man. Continuous administration of enteral nutrition resulted in a rapid anti-inflammatory effect. Furthermore, enrichment of the nutritional composition with lipid and protein was shown to enhance the anti-inflammatory potential. Therefore, continuous enteral administration of lipid- and protein-rich nutrition is a promising intervention to modulate the immune response in the early course of systemic inflammation in man.

Interplay between the acute inflammatory response and heart rate variability in healthy human volunteers.

The autonomic nervous system and the inflammatory response are intimately linked. Heart rate variability (HRV) analysis is a widely used method to assess cardiac autonomic nervous system activity, and changes in HRV indices may correlate with inflammatory markers. Here, we investigated whether baseline HRV predicts the acute inflammatory response to endotoxin. Second, we investigated whether the magnitude of the inflammatory response correlated with HRV alterations. Forty healthy volunteers received a single intravenous bolus of 2 ng/kg endotoxin (LPS, derived from Escherichia coli O:113). Of these, 12 healthy volunteers were administered LPS again 2 weeks later. Heart rate variability was determined at baseline (just before LPS administration) and hourly thereafter until 8 h after LPS administration. Plasma cytokine levels were determined at various time points. Baseline HRV indices did not correlate with the magnitude of the LPS-induced inflammatory response. Despite large alterations in HRV after LPS administration, the extent of the inflammatory response did not correlate with the magnitude of HRV changes. In subjects who were administered LPS twice, inflammatory cytokines were markedly attenuated after the second LPS administration, whereas LPS-induced HRV alterations were similar. Heart rate variability indices do not predict the acute inflammatory response in a standardized model of systemic inflammation. Although the acute inflammatory response results in HRV changes, no correlations with inflammatory cytokines were observed. Therefore, the magnitude of endotoxemia-related HRV changes does not reflect the extent of the inflammatory response.

Intestinal Obstruction after Colostomy Closure

(See pages 1030–1 for the Photo Quiz) Figure 1. The dimensions and the unilateral, flattened shape of the longitudinally sectioned structures clearly identify these as eggs of Enterobius vermicularis (thin arrows). The thick arrow indicates an elongated structure protruding from 1 of the eggs; this represents a hatching larva trapped in the inflammatory mass (original magnification, ϫ40). Diagnosis: inflammatory mass surrounding eggs of Entero-bius vermicularis. The hematoxylin-eosin–stained sections (figures 1 and 2) show multiple eggs of E. vermicularis at the site of anastomosis. The eggs are embedded in necrotic tissue, surrounded by an area of fibrosis with a histiocytic infiltrate and frequent eosin-ophils. E. vermicularis are roundworm parasites that live on the mucosa in the distal parts of the colon. Females migrate to the perianal area to deposit their eggs on the skin. This results in pruritis, with subsequent transmission via the fecal-oral route. In patients with a colostomy, the eggs may be deposited on the protruding colonic mucosa. In this patient, the restoration of the bowel continuity involved the mobilization of the colon from the abdominal wall. Subsequently, the proximal and distal parts of the colon were joined together with a stapler. During the stapling procedure, eggs (some of which were in the process of hatching) must have been trapped in the sutures, resulting in a foreign body reaction and the formation of a large ob-Figure 2. At higher magnification, the cellular structure of the intact Enterobius vermicularis larva can be recognized (original magnification, ϫ100). structing inflammatory mass. The patient was treated with me-bendazole, and treatment was repeated after 14 days. Unfortunately , the second anastomosis was complicated by leakage. At present, the patient has a permanent end colostomy because of the persistent rectal fistulae.