title: Impact of melatonin receptor deletion on intracellular signaling in spleen cells of mice after polymicrobial sepsis.
abstract: OBJECTIVE
  Melatonin is known to influence immune functions and to ameliorate outcome after septic challenge but it is unknown whether this is mediated by melatonin receptor activation. This study aimed to elucidate molecular differences in spleen and ex vivo splenocytes of wild-type (WT) and melatonin receptor double knockout mice (KO) after polymicrobial sepsis.
  
  
  METHODS
  C3H/HeN wild-type and MT1-/-/MT2-/- mice underwent sham operation or cecum ligation and incision (CLI) and remained anesthetized for 1 h. Splenocytes were isolated and treated in culture with physiological melatonin concentrations (1 nM).
  
  
  RESULTS
  Plasma TNFα levels were consistently high after 1 h of CLI. Basal circulating leukocyte numbers were slightly higher in KO animals. We detected transcriptional differences in splenocytes of the knockout strain concerning proinflammatory mediators. Expression levels of IL-1β, IL-2, CXCR2, L-Selectin, TNFα, CXCL2 and ICAM-1 were strongly increased in splenocytes of KO mice. Splenocytes of KO mice displayed reduced ERK and p38 as well as increased JNK phosphorylation. None of the analyzed factors were influenced by melatonin in the culture medium.
  
  
  CONCLUSIONS
  The results of this study indicate an increased proinflammatory status of mice deficient in both membrane-bound melatonin receptors reflected by altered activation of MAPK cascades and transcriptional activation of proinflammatory mediators.
authors.affiliation: Department of Anaesthesiology, Intensive Care and Pain Therapy, Saarland University Medical Center, Kirrbergerstrasse 57, 66421, Homburg/Saar, Germany, astrid.kleber@uks.eu.
authors.forename: Astrid
authors.initials: A
authors.lastname: Kleber
authors.forename: Sarah
authors.initials: S
authors.lastname: Altmeyer
authors.forename: Beate
authors.initials: B
authors.lastname: Wolf
authors.forename: Alexander
authors.initials: A
authors.lastname: Wolf
authors.forename: Thomas
authors.initials: T
authors.lastname: Volk
authors.forename: Tobias
authors.initials: T
authors.lastname: Fink
authors.forename: Darius
authors.initials: D
authors.lastname: Kubulus
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D017931:DNA Primers / Q000737:chemistry; D004797:Enzyme-Linked Immunosorbent Assay; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D017353:Gene Deletion; D020869:Gene Expression Profiling; D007107:Immune System; D007249:Inflammation; D007958:Leukocyte Count; D008550:Melatonin / Q000378:metabolism; D051379:Mice; D008809:Mice, Inbred C3H; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D010766:Phosphorylation; D044122:Receptor, Melatonin, MT1 / Q000235:genetics*; D044123:Receptor, Melatonin, MT2 / Q000235:genetics*; D018805:Sepsis / Q000378:metabolism* / Q000382:microbiology*; D015398:Signal Transduction; D013154:Spleen / Q000166:cytology / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D017931:DNA Primers; D044122:Receptor, Melatonin, MT1; D044123:Receptor, Melatonin, MT2; D014409:Tumor Necrosis Factor-alpha; D048049:Extracellular Signal-Regulated MAP Kinases; D008550:Melatonin