Endotoxemia

Short-chain fatty acids (SCFAs) are substances produced by gut bacteria when they ferment dietary fiber. They can act as signals between the gut and the brain and may help regulate the body's immune and stress responses. Earlier work has shown that delivering SCFAs to the colon can lower the stress hormone response to a mental stress task in healthy people, and laboratory studies suggest SCFAs can reduce inflammation. However, it is not yet known whether SCFAs can reduce inflammation in humans, or whether doing so protects mental performance. This study uses a controlled, acute, and short-lasting challenge. Healthy adults receive a single, low dose of a bacterial substance called lipopolysaccharide (LPS) through a vein. LPS briefly activates the immune system and causes mild, flu-like symptoms (such as fatigue, headache, and feeling unwell) that pass on their own within a few hours. It does not cause a real infection. Participants are randomly assigned to take either SCFA capsules or inactive placebo capsules on the morning of the test day, before the LPS challenge. Neither the participants, the researchers running the visit, nor the researchers analyzing the results know who received which capsules until the study is complete (triple-blind). The main goal of the study is to test whether SCFAs, compared with placebo, reduce the inflammatory response to LPS, measured by markers of inflammation in the blood. The study also examines whether SCFAs reduce the associated sickness symptoms and whether they protect performance on tasks that measure core executive functions: the ability to keep relevant information in mind (working memory), the ability to hold back automatic responses or thoughts (inhibition), and the ability to switch flexibly between tasks or rules (cognitive flexibility). Blood, saliva, and stool samples are collected to measure inflammation markers, SCFA levels, stress hormones, and gut bacteria. Participants attend a screening visit, a test day with monitoring for several hours, and a short follow-up visit the next day.

The goal of this clinical trial is to investigate the immunomodulatory effects of the drugs dexamethasone, tocilizumab and anakinra in healthy male subjects aged 18 to 35 undergoing experimental endotoxemia. The main questions it aims to answer are: * What are the effects of these drugs on the development of immunoparalysis in a repeated human endotoxemia model? * What is the extent of the neuroinflammatory response and how do these drugs affect neuroinflammation in a repeated human endotoxemia model? Researchers will compare these drugs to a placebo (a look-alike substance that contains no drug). Participants will visit the Intensive Care research department on two or five occasions (screening included): * The intervention group will receive an LPS challenge twice, with a week in between. Before the first LPS challenge, one of the described drugs will be administered. Blood, saliva and tear fluid will be collected regularly during the LPS challenge. Cerebrospinal fluid will also be collected through a catheter in the spinal cord. * The control group will not receive an LPS challenge or drug administration and will have only one study day. During this day, blood, saliva, tear fluid and cerebrospinal fluid will be collected as regularly as during the LPS challenge of the intervention group. During an LPS challenge, the investigators mimic blood poisoning by giving an endotoxin, also called LPS. This is a small part of the cell wall of a bacteria. This will cause transient flu-like symptoms for 3-4 hours.