Mapping the Effect of (neuro)inflammation on Stress Sensitivity in the Brain of Healthy Men

BOLD fMRI responses to the Montreal Imaging Stress Task (MIST) after administration of LPS compared to saline

The change in [18F]-DPA-714 binding potential with and without LPS administration (%∆BPND)

Serum samples will be used for the quantification of inflammatory cytokines tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), interferon-γ (IFN-γ), IL-6, IL-8, IL-1 receptor agonist (RA), IL-4, and IL-10 using the Meso Scale Discovery (MSD) electrochemiluminescence validated (V-PLEX) system.

Serum samples will be used to analyze high sensitive CRP (hs-CRP) levels using latex-enhanced immunonephelometric test.

Serum samples will be used to analyze the concentration of free cortisol in the circulation using electrochemiluminescence.

Plasma samples will be used to analyze the concentration of ACTH in the circulation using electrochemiluminescence.

To monitor the participants' condition and response to the treatment, pulse rate will be recorded every hour. Pulse rate will be measured using a pulse oximeter and/or digital sphygmomanometer and recorded in beats per minute.

To monitor the participants' condition and response to the treatment, systolic blood pressure will be recorded every hour. Systolic blood pressure will be measured using a digital sphygmomanometer and recorded in millimeters of mercury (mmHg).

To monitor the participants' condition and response to the treatment, diastolic blood pressure will be recorded every hour. Diastolic blood pressure will be measured using a digital sphygmomanometer and recorded in millimeters of mercury (mmHg).

To monitor the participants' condition and response to the treatment, body temperature will be recorded every hour. Temperature will be taken in the ear using a tympanic thermometer and recorded in degrees of Celsius (°C).

General side effects will be assessed and recorded in a structured, validated approach using the Generic Assessment of Side Effects (GASE). The GASE consists of 36 items asking for most frequently reported side effects for drugs based on the FDA adverse event reporting system database from all countries. Symptoms of all body parts during the last seven days will be self-reported and rated based on severity from 0 (not present) to 3 (severe).

To comprehensively measure sickness behaviour during the test day, the Sickness Questionnaire (SicknessQ) will be used. The SicknessQ is a brief and psychometrically sound assessment instrument to measure perceived sickness behaviour. It is sensitive to LPS challenge and was developed based on acute sickness response to LPS endotoxemia in healthy individuals. The SicknessQ score was significantly increased by LPS challenge compared to placebo at 1.5 hours post-injection and subsided to non-significant levels after 4.5 hours. In addition, the increase in SicknessQ score was partly mediated by the relative increase in inflammatory cytokines.

To measure momentary anxiety during the test day, the STAI-S will be used. This inventory is part of the State-Trait Anxiety Inventory (STAI). The STAI is a psychological inventory that measures two types of anxiety - state anxiety and trait anxiety. State anxiety is anxiety about an event, while trait anxiety is the level of anxiety related to an individual's character. The inventory consists of 40 questions, with 20 questions specifically for state anxiety, rated on a 4-point scale. State anxiety is rated with anxiety absent and anxiety present questions. Anxiety absent questions constitute the absence of anxiety in a statement like, "I feel secure." Anxiety present questions represent the presence of anxiety in a statement like "I feel worried." The 4-point scale are as follows: 1 'not at all', 2 'somewhat', 3 'moderately so', and 4 'very much so'.

The State-Trait Anxiety-Depression Inventory aims to recognize and differentiate symptoms of anxiety and depression. It consists of 40 self-report items that distinguish between temporary (state) and chronic conditions (trait). The rating scale consists of a 4-point Likert-type scale ranging from 1 (not at all) to 4 (very much). The STADI has a 4-factor structure of anxiety and depression including emotionality, worry, dysthymia, and anhedonia.

The Stanford Sleepiness Scale (SSS) is a self-report questionnaire that aims to quickly assess the levels of sleepiness throughout the day and track overall alertness at each hour of the day. It is commonly used in research and clinical settings to assess the effectiveness of a specific treatment. The scale is rated from 1 to 7 with 1 being wide awake and 7 being sleep onset. A rate of X is given if the respondent is asleep.

The PANAS consists of two 10-item mood scales and was developed to provide brief measures of negative affect (NA) and positive affect (PA). NA and PA reflect dispositional dimensions, with high-NA epitomized by subjective distress and unpleasurable engagement, and low-NA by the absence of these feelings. By contrast, PA represents the extent to which an individual experiences pleasurable engagement with the environment. Thus, emotions such as enthusiasm and alertness are indicative of high-PA, whilst lethargy and sadness characterize low-PA. Respondents are asked to rate the extent to which they have experienced each particular emotion within a specified time period, on a 5-point scale. The scale points are: 1 'very slightly or not at all', 2 'a little', 3 'moderately', 4 'quite a bit', and 5 'very much'.

The MDMQ is a well-validated 24-item questionnaire commonly used to quickly evaluate the mental state and mood of a respondent. It consists of 24 items to measure three current psychological states in bipolar dimensions of: good vs. bad, awake vs. tired, and calm vs. nervous. Each item is rated with a 5-point rating scale. The results range between 1 (feeling bad, tired, nervous) and 40 points (feeling good, awake, calm) for each dimension, summing up to an overall maximum count of 120 points (maximum scores for feeling good, awake, and calm) for the whole questionnaire.

Serum blood will be used to quantify SCFA levels using gas chromatography/mass spectrometry (GC-MS) for exploratory analysis.

Quantitative microbiota profiling will be performed using metagenomic shotgun sequencing and/or 16s sequencing for exploratory analysis.

Self-report of the Bristol Stool Score will be recorded to determine fecal consistency for exploratory analysis.