title: Melatonin and structurally similar compounds have differing effects on inflammation and mitochondrial function in endothelial cells under conditions mimicking sepsis.
abstract: BACKGROUND
  Development of organ dysfunction associated with sepsis is due in part to oxidative damage to mitochondria. Melatonin regulates the sleep-wake cycle and also has potent antioxidant activity. The aim of this study was to determine the effects of melatonin and other structurally related compounds on mitochondrial function, endogenous glutathione (GSH), and control of cytokine expression under conditions mimicking sepsis.
  
  
  METHODS
  Human endothelial cells were treated with lipopolysaccharide (LPS) plus peptidoglycan G (PepG) to simulate sepsis, in the presence of melatonin, 6-hydroxymelatonin, tryptamine, or indole-3-carboxylic acid. Nuclear factor κB (NFκB) activation, interleukin (IL)-6 and IL-8, total glutathione, mitochondrial membrane potential, and metabolic activity were measured.
  
  
  RESULTS
  LPS and PepG treatment resulted in elevated IL-6 and IL-8 levels preceded by activation of NFκB (all P<0.0001). Treatment with all four compounds resulted in lower IL-6 and IL-8 levels, and lower NFκB activation (P<0.0001). Loss of mitochondrial membrane potential and endogenous glutathione was seen when cells were exposed to LPS/PepG, but these were maintained in cells co-treated with melatonin, tryptamine, or 6-hydroxymelatonin (P<0.05), but not indole-3-carboxylic acid. Metabolic activity decreased after exposure to LPS/PepG and was maintained by melatonin and 6-hydroxymelatonin at the highest concentrations only.
  
  
  CONCLUSIONS
  We have shown that in addition to melatonin, other structurally related indoleamine compounds have effects on NFκB activation and cytokine expression, GSH, mitochondrial membrane potential, and metabolic activity in endothelial cells cultured under conditions mimicking sepsis. Further work is needed to determine whether these compounds represent therapeutic approaches for disrupting the oxidative stress-inflammatory response signalling pathway in sepsis.
authors.affiliation: Academic Unit of Anaesthesia and Intensive Care, School of Medicine and Dentistry, University of Aberdeen, UK.
authors.forename: D A
authors.initials: DA
authors.lastname: Lowes
authors.forename: A M
authors.initials: AM
authors.lastname: Almawash
authors.forename: N R
authors.initials: NR
authors.lastname: Webster
authors.forename: V L
authors.initials: VL
authors.lastname: Reid
authors.forename: H F
authors.initials: HF
authors.lastname: Galley
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects*; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D007249:Inflammation / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D015850:Interleukin-6 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D008550:Melatonin / Q000494:pharmacology*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects / Q000502:physiology; D008928:Mitochondria / Q000187:drug effects*; D016328:NF-kappa B / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D018805:Sepsis / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
chemical_list: D000975:Antioxidants; D015850:Interleukin-6; D016209:Interleukin-8; D016328:NF-kappa B; D005978:Glutathione; D008550:Melatonin