Jennifer S. Kullmann

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.

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.

Visceral sensitivity correlates with decreased regional gray matter volume in healthy volunteers: A voxel-based morphometry study

Summary Increased visceral sensitivity correlates with decreased gray matter volumes in pain‐relevant brain regions in healthy volunteers. ABSTRACT Regional changes in brain structure have been reported in patients with altered visceral sensitivity and chronic abdominal pain, such as in irritable bowel syndrome. It remains unknown whether structural brain changes are associated with visceral sensitivity. Therefore, we present the first study in healthy individuals to address whether interindividual variations in gray matter volume (GMV) in pain‐relevant regions correlate with visceral sensitivity. In 92 healthy young adults (52 female), we assessed rectal sensory and pain thresholds and performed voxel‐based morphometry (VBM) to compute linear regression models with visceral sensory and pain thresholds, respectively, as independent variable and GMV in a priori‐defined regions of interest (ROIs) as dependent variable. All results were familywise error (FWE) corrected at a level of PFWE < .05 and covaried for age. The mean (±SEM) rectal thresholds were 14.78 ± 0.46 mm Hg for first sensation and 33.97 ± 1.13 mm Hg for pain, without evidence of sex differences. Lower rectal sensory threshold (ie, increased sensitivity) correlated significantly with reduced GMV in the thalamus, insula, posterior cingulate cortex, ventrolateral and orbitofrontal prefrontal cortices, amygdala, and basal ganglia (all PFWE < .05). Lower rectal pain threshold was associated with reduced GMV in the right thalamus (PFWE = .051). These are the first data supporting that increased visceral sensitivity correlates with decreased gray matter volume in pain‐relevant brain regions. These findings support that alterations in brain morphology not only occur in clinical pain conditions but also occur according to normal interindividual variations in visceral sensitivity.

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.

Salivary α-amylase response to endotoxin administration in humans

Salivary α-amylase (sAA) is a digestive enzyme that plays also an important role in mucosal immunity. Secretion of the sAA is largely under the control of the autonomic nervous system and increases in sAA activity have repeatedly been observed in response to various stressors. The present study aimed at investigating whether and to what extent sAA activity levels are affected during systemic inflammation. Fourteen healthy male volunteers received intravenous injections of either bacterial endotoxin or placebo at two different occasions in a randomized and double-blinded manner. sAA activity was monitored over a period of 6h together with inflammatory markers, plasma norepinephrine (NE) and salivary cortisol levels, vital parameters, and state anxiety. Endotoxin administration elicited a transient inflammatory response reflected by increases in body temperature, whole blood cell counts, and circulating levels of interleukin (IL)-6. The immune changes were accompanied by a transient increase in sAA activity, elevations in salivary cortisol and plasma NE concentrations, as well as increases in heart rate and state anxiety. Although sAA and plasma NE responses showed distinct time courses, a significant positive correlation over the total observation period was found. Whether the observed sAA response is driven by an increase in sympathetic activity or more generally reflects inflammation induced changes in sympathetic-parasympathetic balance remains to be elucidated.

Low dose LPS does not increase TLR4 expression on monocytes in a human in vivo model.

BACKGROUND AND PURPOSE Toll like receptor 4 (TLR4) is the major recognition receptor for lipopolysaccharides and plays a major role in the inflammatory response. CD11b is expressed on the surface of many leukocytes including monocytes. The CD11b/CD18 complex is involved in the inflammatory response by mediating migration and adhesion of leukocytes. The aim of this human in vivo study was to investigate the expression of TLR4 and CD11b on the surface of human monocytes after in vivo low-dose LPS stimulation. METHODS We performed a double-blind, randomized crossover study with 16 healthy males who received a bolus injection of bacterial lipopolysaccharide (LPS; 0.4ng/kg) or normal saline. Vital parameters, blood counts, serum cytokine levels, the expression of TLR4, and CD11b on CD14 positive cells were analyzed. RESULTS The experimentally induced inflammatory response was reflected by transient increases in body temperature, circulating leukocyte numbers, and plasma levels of pro- (TNF-α, IL-6) and anti-inflammatory cytokines (IL-10, IL-1ra). In contrast to a significant increase in CD11b expression, no changes in TLR4 expression on circulating monocytes were detectable. CONCLUSION Early changes in TLR4 expression on circulating monocytes are not necessarily part of the inflammatory response to low dose LPS in humans whereas the detected increase of CD11b expression might already be sufficient for optimized recognition and signalling.

Effekte Akuter Entzündungsreaktionen auf Gedächtnisleistungen, Befindlichkeiten und Neurale Aktivitäten

Zusammenfassung Infektionserkrankungen, Sepsis und chronisch-entzundliche Autoimmunerkrankungen induzieren eine systemische Entzundungsreaktion, die mit der Ausschuttung von pro-inflammatorischen Zytokinen und endo krinen Botenstoffen einhergeht. Eine Beteiligung dieser Faktoren wird auch bei der Entstehung von neuropsychiatrischen Erkrankungen wie Depression und Schizophrenie vermutet. Pro-inflammatorische Zytokine aus der Peripherie gelangen auf Ebene der zirkumventrikularen Organe direkt ins ZNS oder geben ihre Information uber andere Signalwege an das Gehirn weiter. Dort wirken sie auf neuropsychologische Funktionen, Verhalten und Befinden. Diese Verhaltensanderungen und unspezifischen Krankheits symptome werden unter dem Oberbegriff „Sickness Behavior“ zusammengefasst. Um die Effekte einer systemischen Immunreaktion experimentell zu untersuchen, kann durch die Gabe eines Endotoxins beim Menschen eine akute Inflammation kontrolliert induziert und ihre Effekte auf neuropsyc hologische Funktionen untersucht werden. Diese Arbeit gibt eine Ubersicht uber die bisher durchgefuhrten humanexperimentellen Studien, welche die Effekte einer experimentell induzierten Entzundungsreaktion auf kognitive und emotionale Parameter sowie korrespondierende neurale Aktivitaten im ZNS untersucht haben. Zudem werden die bislang bekannten Signalwege, uber die wahrend einer Entzundungsreaktion Informationen aus dem peripheren Immunsystem ans ZNS ubermittelt werden, zusammengefasst.

Sub-septic systemic inflammation does not impair performance in social cognition tasks

250 Sub-septic systemic inflammation does not impair performance in social cognition tasks J.S. Grigoleit , J.S. Kullmann , O.T. Wolf , H. Engler , E.R. Gizewski , J.R. Oberbeck , M. Schedlowski a a Institute of Medical Psychology and Behavioral Immunobiology, Medical Faculty, University of Duisburg-Essen, Hufelandstrasse 55, Essen 45122, Germany b Department of Cognitive Psychology, Ruhr-University Bochum, Germany c Institute for Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Germany d Clinic for Trauma Surgery, University Hospital Essen, Germany Clinical and experimental evidence document, that increased cytokine plasma levels evoked by cytokine therapy, chronic diseases or acute experimental immune activation with lipopolysaccharide (LPS) are associated with depression-like symptoms and neuropsychological disturbances in humans. In contrast, the effects of increased peripheral cytokine levels on emotional and social cognition are largely unknown. Thus, we employed a human endotoxemia model to analyze the impact of low-grade inflammation on social cognitive performance. In a randomized, placebo-controlled cross-over-designed study 18 male volunteers received either LPS (0.4 ng/kg) or NaCl. Body temperature, and plasma levels of cortisol, Interleukin(IL)-6, IL-10, IL1ra and Tumor Necrosis Factor(TNF)-alpha were analyzed before and 1, 2, 3, 4, 6 and 24 h after injection. In addition, the ability to assess facial expressions (‘‘Reading the Mind in the Eyes”) and social cognition performance (‘‘Movie for the Assessment of Social Cognition”/ MASC) was analyzed. LPS administration induced a clear-cut immune activation characterized by significant increases in body temperature, plasma cytokine and cortisol levels. In addition, volunteers reported increased fatigue, feelings of anxiety and impaired mood during low grade inflammation. In contrast, LPS-induced cytokine increases did neither affect performance in the facial expression task nor in the MASC. Theses data indicate that increased peripheral cytokine levels affect mood and anxiety but are not associated with alterations in social or emotional cognition. doi:10.1016/j.bbi.2010.07.044

Mood, working memory and brain activity during experimental human endotoxemia

237 Neuroinflammation and parkinson’s disease: Quantitative analysis of gene expression alterations in the substantia nigra of mice exposed to MPTP or LPS with a custom qPCR array N.M. Filipov , R.B. Pringle , S. Lee b a Physiology and Pharmacology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, United States of America b Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762, United States of America Neuroinflammation is a risk factor for Parkinson’s disease (PD) and it has been observed in animal models of PD, i.e. the MPTP (1methyl-4-phenyl-1,2,3,6-tetrahydropyridine) and peripheral lipopolysaccharide (LPS) mouse models. Most of the previous studies focusing on gene expression alterations associated with PD, including inflammatory, have investigated few genes at a time or used global proteomic/genomic approaches that either require large sample volume or are semi-quantitative in nature. Here, we used custom quantitative real-time PCR (qPCR) array. The array contains 84 genes and includes inflammation-related genes, genes important for dopamine (DA) synthesis/metabolism, DA receptors, transcription factors, oxidative stress genes, and representative genes from other neurotransmitter systems. Male C57BL/6 mice were treated with MPTP (4 10 mg/kg, i.p.; 2 h apart), or LPS (1.5 mg/kg, i.p.) and sacrificed 7 days or 4 h later. Out of the 84 genes, 19 genes were significantly up/down-regulated by MPTP, including an upregulation of inflammation-related genes, such as F4/80, Gfap, IL-6, Fos, and Jun. At 4 h after the LPS challenge, 24 genes were significantly up/down-regulated by LPS; more than half of them were inflammatory genes and they were all upregulated. Interestingly, similar to the increase observed in the MPTP-treated mice, IL-6, Fos and Jun expression was increased in the substantia nigra of LPS-treated mice, suggesting possible common pathway(s) to basal ganglia degeneration. (Support: NIH; ES011654 and ES016965). doi:10.1016/j.bbi.2010.07.034