Miller, Muska; (2022) The role of antibiotics, catecholamines and sedatives on immune cell functionality and mitochondrial activity. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Introduction and aim: Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. In the absence of host-modulating therapies, specific management is focussed upon eradication of the pathogen by antibiotics ± source control, organ support, and prevention of iatrogenic harm. The use of antibiotics, catecholamines and sedatives is associated with off-target effects including immunomodulation. These drugs are routinely used together in critically ill patients with sepsis so there may be cumulative effects. Mechanisms underlying immunomodulation are still to be fully elaborated, however there is increasing interest in the role of mitochondria in organ dysfunction and drug-induced immunomodulation. My aim was to investigate the role of ciprofloxacin, propofol and norepinephrine (NE), alone and in combination, on immune cell functionality and mitochondrial activity in septic and healthy peripheral blood mononuclear cells (PBMCs). Methods: PBMCs isolated from healthy volunteers were incubated with either ciprofloxacin (100 µg/mL), propofol (50 µg/mL), NE (10 µg/mL) or all three drugs combined, in the presence and absence of endotoxin (100 ng/mL) for 6 or 24 hours. Comparison was made against untreated cells. Measurements were made of IL-6, IL-10 and TNF- production (ELISA), cell viability, phagocytosis, HLA-DR, mitochondrial membrane potential and reactive oxygen species production (flow cytometry), and mitochondrial O2 consumption (Seahorse respirometry). This was repeated in PBMCs from healthy volunteers co-incubated with serum from ED patients with suspected sepsis or septic ICU patients. Immune and metabolic pathways were investigated in PBMCs from healthy volunteers co-incubated in septic or healthy volunteer serum using Nanostring technology to identify potential pathways that may explain underlying mechanisms. Results and conclusion: While the exemplar antibiotic, sedative and catecholamine reduced TNF-, IL-6 and phagocytosis in PBMCs isolated from septic ICU patients and from healthy volunteers co-incubated with septic serum, no cumulative effect was seen with the combination. No consistent changes were seen in PBMCs’ mitochondrial functionality. Similarly, gene expression analysis did not highlight any involvement of specific immune or metabolic pathways as underlying mechanisms. Further studies are required to fully characterise immune dysfunction caused by these drugs and whether these in-vitro findings translate to the in-vivo situation.

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