title: Endotoxin Disrupts Circadian Rhythms in Macrophages via Reactive Oxygen Species.
abstract: The circadian clock is a transcriptional network that functions to regulate the expression of genes important in the anticipation of changes in cellular and organ function. Recent studies have revealed that the recognition of pathogens and subsequent initiation of inflammatory responses are strongly regulated by a macrophage-intrinsic circadian clock. We hypothesized that the circadian pattern of gene expression might be influenced by inflammatory stimuli and that loss of circadian function in immune cells can promote pro-inflammatory behavior. To investigate circadian rhythms in inflammatory cells, peritoneal macrophages were isolated from mPer2luciferase transgenic mice and circadian oscillations were studied in response to stimuli. Using Cosinor analysis, we found that LPS significantly altered the circadian period in peritoneal macrophages from mPer2luciferase mice while qPCR data suggested that the pattern of expression of the core circadian gene (Bmal1) was disrupted. Inhibition of TLR4 offered protection from the LPS-induced impairment in rhythm, suggesting a role for toll-like receptor signaling. To explore the mechanisms involved, we inhibited LPS-stimulated NO and superoxide. Inhibition of NO synthesis with L-NAME had no effect on circadian rhythms. In contrast, inhibition of superoxide with Tempol or PEG-SOD ameliorated the LPS-induced changes in circadian periodicity. In gain of function experiments, we found that overexpression of NOX5, a source of ROS, could significantly disrupt circadian function in a circadian reporter cell line (U2OS) whereas iNOS overexpression, a source of NO, was ineffective. To assess whether alteration of circadian rhythms influences macrophage function, peritoneal macrophages were isolated from Bmal1-KO and Per-TKO mice. Compared to WT macrophages, macrophages from circadian knockout mice exhibited altered balance between NO and ROS release, increased uptake of oxLDL and increased adhesion and migration. These results suggest that pro-inflammatory stimuli can disrupt circadian rhythms in macrophages and that impaired circadian rhythms may contribute to cardiovascular diseases by altering macrophage behavior.
authors.affiliation: Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, Georgia, United States of America.
authors.forename: Yusi
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Pharmacology, Medical College of Georgia at Augusta University, Augusta, Georgia, United States of America.
authors.forename: Paramita
authors.initials: P
authors.lastname: Pati
authors.affiliation: Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, Georgia, United States of America.
authors.forename: Yiming
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, Georgia, United States of America.|Department of Forensic Medicine, Nanjing Medical University, Nanjing, Jiangsu, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Chen
authors.affiliation: Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, Georgia, United States of America.
authors.forename: David W
authors.initials: DW
authors.lastname: Stepp
authors.affiliation: Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, Georgia, United States of America.
authors.forename: Yuqing
authors.initials: Y
authors.lastname: Huo
authors.affiliation: Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, Georgia, United States of America.
authors.forename: R Daniel
authors.initials: RD
authors.lastname: Rudic
authors.affiliation: Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, Georgia, United States of America.
authors.forename: David J R
authors.initials: DJ
authors.lastname: Fulton
mesh_terms: D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects; D002940:Circadian Rhythm / Q000187:drug effects* / Q000235:genetics; D004731:Endotoxins / Q000633:toxicity*; D005786:Gene Expression Regulation / Q000187:drug effects; D008070:Lipopolysaccharides / Q000494:pharmacology; D008077:Lipoproteins, LDL / Q000378:metabolism; D017737:Macrophages, Peritoneal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D018345:Mice, Knockout; D009569:Nitric Oxide / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D051197:Toll-Like Receptor 4 / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D004731:Endotoxins; D008070:Lipopolysaccharides; D008077:Lipoproteins, LDL; D017382:Reactive Oxygen Species; D051197:Toll-Like Receptor 4; D014157:Transcription Factors; D009569:Nitric Oxide