Beneficial Effects of Exogenous Melatonin in Acute Staphylococcus aureus and Escherichia coli Infection-Induced Inflamma
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ORIGINAL ARTICLE
Beneficial Effects of Exogenous Melatonin in Acute Staphylococcus aureus and Escherichia coli Infection-Induced Inflammation and Associated Behavioral Response in Mice After Exposure to Short Photoperiod Biswadev Bishayi,1,2 Rana Adhikary,1 Ajeya Nandi,1 and Sahin Sultana1
Abstract—The administration of melatonin during acute bacterial infection was evaluated in this study. Mice pre-exposed to normal photoperiodic (NP), short photoperiodic (SP), and long photoperiodic (LP) day lengths were infected separately with live Staphylococcus aureus (5 × 106 cells/ml) or Escherichia coli (2.5 × 107 colony-forming units/ml) and treated with melatonin (10 mg/kg body weight). Behavioral studies were performed before bacterial infection and after melatonin administration. In mice preexposed to SP, exogenous melatonin administration resulted in better clearance of bacteria from blood and behavioral improvement. Reduced glutathione content and superoxide dismutase activities were increased, with concomitant decrease in lipid peroxidation content and catalase activities in the liver, brain, and spleen after exogenous melatonin administration. The overproduction of tumor necrosis factor-α, interferon-γ, and interleukin-6 during acute bacterial infection in mice exposed to different photoperiods was probably regulated by the administration of exogenous melatonin, by reducing neutrophil recruitment to spleen, expression of inducible nitric oxide synthase and cyclooxygenase-2 in hypothalamus, and C-reactive protein in the serum, and was also associated with improved behavioral response. Photoperiodic variations in inflammatory and oxidative stress markers might be correlated to serum melatonin and corticosterone levels. This study suggests that the administration of melatonin during SP exposure is protective in infection-induced inflammation than NP and LP exposure. KEY WORDS: antioxidants; bacterial infection; cytokines; inflammation; melatonin; photoperiod. 1
Department of Physiology, Immunology Laboratory, University of Calcutta, University Colleges of Science and Technology, 92 APC Road, Calcutta, 700009, West Bengal, India 2 To whom correspondence should be addressed at Department of Physiology, Immunology Laboratory, University of Calcutta, University Colleges of Science and Technology, 92 APC Road, Calcutta, 700009, West Bengal, India. E-mail: [email protected] Abbreviations: C/EBP, CCAAT/enhancer binding protein; CAT, Catalase; CFU, Colony-forming units; COX-2, Cyclooxygenase-2; CPCSEA, Committee for the Purpose of Control and Supervision of Experiments on Animals; CRP, C-Reactive protein; DTNB, 5,5′-Dithio-bis(2-nitrobenzoic acid); GSH, Reduced glutathione; IFN-γ, Interferon-γ; IL, Interleukin; iNOS, Inducible nitric oxide synthase; LP, Long photoperiod; LPO, Lipid peroxidation; NF-kB, Nuclear factor-kB; NP, Normal photoperiod; SDSPAGE, Sodium dodecyl sulfate-polyacrylamide gel electrophoresis; SOD, Superoxide dismutase; SP, Short photoperiod; STAT-3, Signal transducer and activator of transcription-3;
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