Reiner Oberbeck

Dose-Dependent Effects of Endotoxin on Neurobehavioral Functions in Humans

Clinical and experimental evidence document that inflammation and increased peripheral cytokine levels are associated with depression-like symptoms and neuropsychological disturbances in humans. However, it remains unclear whether and to what extent cognitive functions like memory and attention are affected by and related to the dose of the inflammatory stimulus. Thus, in a cross-over, double-blind, experimental approach, healthy male volunteers were administered with either placebo or bacterial lipopolysaccharide (LPS) at doses of 0.4 (n = 18) or 0.8 ng/kg of body weight (n = 16). Pro- and anti-inflammatory cytokines, norephinephrine and cortisol concentrations were analyzed before and 1, 1.75, 3, 4, 6, and 24 h after injection. In addition, changes in mood and anxiety levels were determined together with working memory (n-back task) and long term memory performance (recall of emotional and neutral pictures of the International Affective Picture System). Endotoxin administration caused a profound transient physiological response with dose-related elevations in body temperature and heart rate, increases in plasma interleukin (IL)-6, IL-10, tumor necrosis factor (TNF)-α and IL-1 receptor antagonist (IL-1ra), salivary and plasma cortisol, and plasma norepinephrine. These changes were accompanied by dose-related decreased mood and increased anxiety levels. LPS administration did not affect accuracy in working memory performance but improved reaction time in the high-dose LPS condition compared to the control conditon. In contrast, long-term memory performance was impaired selectively for emotional stimuli after administration of the lower but not of the higher dose of LPS. These data suggest the existence of at least two counter-acting mechanisms, one promoting and one inhibiting cognitive performance during acute systemic inflammation.

Adrenergic Modulation of Survival and Cellular Immune Functions during Polymicrobial Sepsis

Objective: An immunomodulatory effect of epinephrine has been reported that is supposed to be mediated via β-adrenergic receptors. The effect of epinephrine and/or β-adrenergic blockade on cellular immune functions during systemic inflammation has not yet been investigated. Methods: Male NMRI mice were treated with either an infusion of epinephrine (0.05 mg/kg/h i.p.), administration of the nonselective β-adrenoceptor antagonist propranolol (0.5 mg/kg s.c.), or a combination of epinephrine and propranolol after induction of a polymicrobial sepsis by cecal ligation and puncture. Forty-eight hours thereafter survival and cellular immune functions (splenocyte proliferation, splenocyte apoptosis and cytokine release, distribution of leukocyte subsets) were determined. Results: Infusion of epinephrine did not affect lethality of septic mice but induced alterations of splenocyte apoptosis, splenocyte proliferation and IL-2 release and was associated with profound changes of circulating immune cell subpopulations. Treatment with propranolol augmented the epinephrine-induced increase of splenocyte apoptosis, did not affect the decrease of splenocyte proliferation and IL-2 release, augmented the release of IL-6 and antagonized the mobilization of natural killer cells observed in epinephrine-treated animals. Furthermore, these immunologic alterations were accompanied by a significant increase of sepsis-induced mortality. Coadministration of propranolol and epinephrine augmented the propranolol-induced changes of splenocyte apoptosis and IL-6 release and was associated with the highest mortality of septic mice. Conclusion: Epinephrine infusion modulated cellular immune functions during systemic inflammation without an impact on survival. A pharmacologic β-adrenergic blockade partly augmented the epinephrine-induced immune alterations and was associated with a pronounced increase of mortality. This effect was further augmented by a combination of epinephrine infusion and β-adrenergic blockade. These data indicate that adrenergic mechanisms modulate cellular immune functions and survival during sepsis, with these effects being mediated via α- and β-adrenergic pathways.

Acute experimental endotoxemia induces visceral hypersensitivity and altered pain evaluation in healthy humans

Summary A systemic, endotoxin‐induced immune activation leads to decreased visceral sensory and pain thresholds and altered subjective pain ratings in healthy humans. Abstract Growing evidence suggests that systemic immune activation plays a role in the pathophysiology of pain in functional bowel disorders. By implementing a randomized crossover study with an injection of endotoxin or saline, we aimed to test the hypothesis that endotoxin‐induced systemic inflammation increases visceral pain sensitivity in humans. Eleven healthy men (mean ± standard error of the mean age 26.6 ± 1.1 years) received an intravenous injection of either lipopolysaccharide (LPS; 0.4 ng/kg) or saline on 2 otherwise identical study days. Blood samples were collected 15 min before and 1, 2, 3, 4, and 6 h after injection to characterize changes in immune parameters including proinflammatory cytokines. Rectal sensory and pain thresholds and subjective pain ratings were assessed with barostat rectal distensions 2 h after injection. LPS administration induced an acute inflammatory response indicated by transient increases in tumor necrosis factor alpha, interleukin 6, and body temperature (all P < .001). The LPS‐induced immune activation increased sensitivity to rectal distensions as reflected by significantly decreased visceral sensory and pain thresholds (both P < .05) compared to saline control. Visceral stimuli were rated as more unpleasant (P < .05) and inducing increased urge to defecate (P < .01). Pain thresholds correlated with interleukin 6 at +1 h (r = 0.60, P < .05) and +3 h (r = 0.67, P < .05) within the LPS condition. This report is novel in that it demonstrates that a transient systemic immune activation results in decreased visceral sensory and pain thresholds and altered subjective pain ratings. Our results support the relevance of inflammatory processes in the pathophysiology of visceral hyperalgesia and underscore the need for studies to further elucidate immune‐to‐brain communication pathways in gastrointestinal disorders.

Neural response to emotional stimuli during experimental human endotoxemia

Increases in peripheral cytokines during acute inflammation may affect various neuropsychological functions. The aim of this functional magnetic resonance imaging (fMRI) study was to investigate the effects of acute endotoxemia on mood and the neural response to emotionally aversive visual stimuli in healthy human subjects. In a double‐blind, randomized crossover study, 18 healthy males received a bolus injection of bacterial lipopolysaccharide (LPS; 0.4 ng/kg) or saline. Plasma levels of pro‐ and anti‐inflammatory cytokines and cortisol as well as mood ratings were analyzed together with the blood‐oxygen‐level dependent (BOLD) response during the presentation of aversive versus neutral pictures. Endotoxin administration induced pronounced transient increases in plasma levels of TNF‐α, IL‐1ra, IL‐6, IL‐10, and cortisol. Positive mood was decreased and state anxiety increased. In addition, activation of right inferior orbitofrontal cortex (OFC) in response to emotional visual stimuli was significantly increased in the LPS condition. Increased prefrontal activation during the presentation of emotional material may reflect enhanced cognitive regulation of emotions as an adaptive response during an acute inflammation. These findings may have implications for the putative role of inflammatory processes in the pathophysiology of depression. Hum Brain Mapp 34:2217–2227, 2013.

A civilian perspective on ballistic trauma and gunshot injuries

BackgroundGun violence is on the rise in some European countries, however most of the literature on gunshot injuries pertains to military weaponry and is difficult to apply to civilians, due to dissimilarities in wound contamination and wounding potential of firearms and ammunition. Gunshot injuries in civilians have more focal injury patterns and should be considered distinct entities.MethodsA search of the National Library of Medicine and the National Institutes of Health MEDLINE database was performed using PubMed.ResultsCraniocerebral gunshot injuries are often lethal, especially after suicide attempts. The treatment of non space consuming haematomas and the indications for invasive pressure measurement are controversial. Civilian gunshot injuries to the torso mostly intend to kill; however for those patients who do not die at the scene and are hemodynamically stable, insertion of a chest tube is usually the only required procedure for the majority of penetrating chest injuries. In penetrating abdominal injuries there is a trend towards non-operative care, provided that the patient is hemodynamically stable. Spinal gunshots can also often be treated without operation. Gunshot injuries of the extremities are rarely life-threatening but can be associated with severe morbidity.With the exception of craniocerebral, bowel, articular, or severe soft tissue injury, the use of antibiotics is controversial and may depend on the surgeons preference.ConclusionThe treatment strategy for patients with gunshot injuries to the torso mostly depends on the hemodynamic status of the patient. Whereas hemodynamically unstable patients require immediate operative measures like thoracotomy or laparotomy, hemodynamically stable patients might be treated with minor surgical procedures (e.g. chest tube) or even conservatively.

Prolactin modulates survival and cellular immune functions in septic mice

BACKGROUND The immunomodulatory properties of the pituitary hormone prolactin have been demonstrated. It was proposed that prolactin is important in maintaining normal immune response in several pathological states. We investigated the effect of prolactin administration on the survival and cellular immune functions during systemic inflammation. MATERIALS AND METHODS Male NMRI mice were subjected to laparotomy (LAP) or sepsis induced by cecal ligation and puncture (CLP). Mice were treated with either saline (LAP/saline; CLP/saline) or prolactin (LAP/PRL, CLP/RPL; 4 mg/kg s.c.). Survival of septic mice was determined 24 and 48 h after CLP. Forty-eight hours after the septic challenge, the proliferative capacity, cytokine release (IL-2, IL-6, IFN-gamma) and apoptosis of splenocytes were determined. Additionally, monitoring of circulating leukocyte distribution was performed (WBC; CD3+, CD4+, CD8+, B220+, NK1.1+, F4/80+ cells by FASCan). RESULTS CLP was accompanied by a mortality of 47% and induced a decrease in splenocyte proliferation and apoptosis rate. Administration of prolactin significantly increased the mortality of septic mice (81%). This was paralleled by a further decrease of splenocyte proliferation and an increased splenocyte apoptosis. In addition, administration of prolactin augmented the sepsis-induced inhibition of IL-2 release, attenuated the sepsis-induced inhibition of IFN-gamma release, and did not affect the release of IL-6. However, prolactin did not affect the sepsis-induced changes of circulating leukocyte subpopulations. CONCLUSIONS We conclude that prolactin has profound immunomodulatory properties and that administration of prolactin in pharmacological doses is associated with a decreased survival and an inhibition of cellular immune functions in septic mice.

Experimental human endotoxemia enhances brain activity during social cognition

Acute peripheral inflammation with corresponding increases in peripheral cytokines affects neuropsychological functions and induces depression-like symptoms. However, possible effects of increased immune responses on social cognition remain unknown. Therefore, this study investigated the effects of experimentally induced acute inflammation on performance and neural responses during a social cognition task assessing Theory of Mind (ToM) ability. In this double-blind randomized crossover functional magnetic resonance imaging study, 18 healthy right-handed male volunteers received an injection of bacterial lipopolysaccharide (LPS; 0.4 ng/kg) or saline, respectively. Plasma levels of pro- and anti-inflammatory cytokines as well as mood ratings were analyzed together with brain activation during a validated ToM task (i.e. Reading the Mind in the Eyes Test). LPS administration induced pronounced transient increases in pro- (IL-6, TNF-α) and anti-inflammatory (IL-10, IL-1ra) cytokines as well as decreases in mood. Social cognition performance was not affected by acute inflammation. However, altered neural activity was observed during the ToM task after LPS administration, reflected by increased responses in the fusiform gyrus, temporo-parietal junction, superior temporal gyrus and precuneus. The increased task-related neural responses in the LPS condition may reflect a compensatory strategy or a greater social cognitive processing as a function of sickness.

Single-trial conditioning in a human taste-endotoxin paradigm induces conditioned odor aversion but not cytokine responses.

Immunological responses to bacterial endotoxin can be behaviorally conditioned in rodents. However, it is unclear whether an acute systemic inflammatory response can be behaviorally conditioned in humans. Thus, in a double-blind placebo-controlled study, 20 healthy, male subjects received either a single injection of lipopolysaccharide (LPS) or saline together with a novel tasting beverage (conditioned stimulus, CS). Five days later, all subjects received a saline injection and were re-exposed to the CS. Blood was drawn prior to as well as 0.5, 1.5, 3, 4, 6, and 24 h after LPS administration or CS re-exposure. Endotoxin administration led to transient increases in plasma concentrations of interleukin (IL)-6, IL-10, and tumor necrosis factor (TNF)-α and to a significant rise in body temperature. Sole presentation of the CS during evocation did induce neither alterations in body temperature nor changes in plasma cytokine levels. However, subjects in the experimental group rated the smell of the CS significantly more aversive compared to the control group. Employing endotoxin as a US in a single trial taste-immune conditioning paradigm in humans shows a behaviorally conditioned smell aversion but no learned alterations in cytokine levels.

Pavlovian conditioning of endotoxin-tolerance in rats.

The most fascinating example of the bi-directional interaction between the central nervous system (CNS) and immune system is the behavioral conditioning of immune functions. We therefore investigated the behavioral conditioning of lipopolysaccharide (LPS)-induced endotoxin tolerance using the taste aversion paradigm. The conditioned stimulus (CS) saccharin was paired with the unconditioned stimulus (UCS) LPS over a five (CONDl) or four (COND2) days learning trial. Controls received drinking water with (SHAM) or without (UNT) LPS. Endotoxin tolerance was tested by determination of LPS-induced tumor necrosis factor (TNF)-alpha release. After the avoidance of the induced endotoxin-tolerance the CS saccharin was re-presented in all experimental groups. A the end of the re-exposure period a complete endotoxin tolerance was noticed in the CONDl- and COND2-group. In contrast, no effect of saccharin administration was observed in the SHAM- or UNT-group. Our data demonstrate for the first time the behavioral conditioning of endotoxin tolerance. Furthermore, these results contribute new aspects to the mechanisms underlying the development and modulation of endotoxin tolerance.

Improved student preparation from implementing active learning sessions and a standardized curriculum in the surgical examination course

Students’ knowledge before and preparation for courses with practical skills training or bedside teaching may be insufficient and reduce efficiency of teaching time at the bedside and in skills training. To study the effect of a new curriculum on students’ preparation for courses, a quasi-randomized study was conducted. All medical students were included who participated in the surgical examination course during a period of four semesters. In the intervention group, specified topics for every session, a course book describing only those procedures relevant for the course and a foregoing case-based active learning session were introduced as compared to the traditional way of teaching the surgical examination course. For evaluation a questionnaire for the students was used. A total of 614 questionnaires (return rate 79.6%) were included in the analysis. Student as well as teacher preparation significantly improved in the intervention group from 34.8 to 73.6% and 46.1 to 73.0%, respectively. The case-based learning session and the course book were considered helpful by 77.7 and 96.4% of the students, respectively. The introduction of a timetable with specified topics for every session, a course book and a foregoing case-based learning session significantly improved student preparation for the surgical clinical examination course.