Peripheral challenge with double-stranded RNA elicits global up-regulation of cytokine gene expression in the brain.
It is well established that mediators of peripheral inflammation are relayed to the brain and elicit sickness behavior via neuroinflammatory agents that target neuronal substrates. In the present study, we used double-stranded RNA (dsRNA), a viral replication intermediate, to mimic the acute phase of viral infection. C57BL/6 mice were injected intraperitoneally with 12 mg/kg of synthetic dsRNA, i.e., polyinosinic-polycytidylic acid (PIC). The treatment induced severe sickness behavior in the animals as revealed by the burrowing test performed 6 hr postinjection. PIC challenge also induced up-regulation of mRNA for several cytokines in the brain as determined by real-time quantitative RT-PCR. In all brain regions, i.e., the forebrain, brainstem, and cerebellum, the gene encoding the CXCL2 chemokine featured the most robust up-regulation over the basal level (saline-injected animals), followed by the genes encoding the CCL2 chemokine, interferon-beta (IFNbeta), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNFalpha), and interleukin-1beta (IL-1beta). The forebrain featured the highest extent of up-regulation of the Ifnb gene, whereas the other genes attained the highest expression in the cerebellum. Most of the genes featured transient up-regulation, with peaks occurring 3-6 hr after PIC challenge. The TNFalpha, CCL2, CXCL2, IFNbeta, and IL-1beta messages remained profoundly up-regulated even at 24 hr. The expression of genes encoding inducible and neuronal nitric oxide synthase (NOS) in the brain was not affected by the peripheral PIC challenge. However, the endothelial NOS message was initially down-regulated and subsequently up-regulated, indicating stimulation of cerebral vasculature.
Konat
Gregory W
GW
Department of Neurobiology and Anatomy, West Virginia University School of Medicine, Morgantown, West Virginia 26506-9128, USA. gkonat@wvu.edu
Borysiewicz
Elizabeth
E
Fil
Daniel
D
James
Isaac
I
D000818:Animals; D001921:Brain / Q000378:metabolism*; D020805:Central Nervous System Viral Diseases / Q000276:immunology; D018932:Chemokine CCL2 / Q000378:metabolism; D054426:Chemokine CXCL2 / Q000378:metabolism; D016207:Cytokines / Q000235:genetics* / Q000378:metabolism; D004195:Disease Models, Animal; D005260:Female; D016899:Interferon-beta / Q000378:metabolism; D053583:Interleukin-1beta / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D011070:Poly I-C / Q000008:administration & dosage*; D012330:RNA, Double-Stranded / Q000008:administration & dosage*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D015854:Up-Regulation
C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; D054426:Chemokine CXCL2; C404915:Cxcl2 protein, mouse; D016207:Cytokines; D053583:Interleukin-1beta; D015850:Interleukin-6; D012330:RNA, Double-Stranded; D014409:Tumor Necrosis Factor-alpha; D016899:Interferon-beta; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; C496321:Nos1 protein, mouse; C496317:Nos2 protein, mouse; D011070:Poly I-C