Neuroinflammatory response to lipopolysaccharide is exacerbated in mice genetically deficient in cyclooxygenase-2.
BACKGROUND
Cyclooxygenases (COX) -1 and -2 are key mediators of the inflammatory response in the central nervous system. Since COX-2 is inducible by inflammatory stimuli, it has been traditionally considered as the most appropriate target for anti-inflammatory drugs. However, the specific roles of COX-1 and COX-2 in modulating a neuroinflammatory response are unclear. Recently, we demonstrated that COX-1 deficient mice show decreased neuroinflammatory response and neuronal damage in response to lipopolysaccharide (LPS).


METHODS
In this study, we investigated the role of COX-2 in the neuroinflammatory response to intracerebroventricular-injected LPS (5 mug), a model of direct activation of innate immunity, using COX-2 deficient (COX-2-/-) and wild type (COX-2+/+) mice, as well as COX-2+/+ mice pretreated for 6 weeks with celecoxib, a COX-2 selective inhibitor.


RESULTS
Twenty-four hours after LPS injection, COX-2-/- mice showed increased neuronal damage, glial cell activation, mRNA and protein expression of markers of inflammation and oxidative stress, such as cytokines, chemokines, iNOS and NADPH oxidase. Brain protein levels of IL-1beta, NADPH oxidase subunit p67phox, and phosphorylated-signal transducer and activator of transcription 3 (STAT3) were higher in COX-2-/- and in celecoxib-treated mice, compared to COX-2+/+ mice. The increased neuroinflammatory response in COX-2-/- mice was likely mediated by the upregulation of STAT3 and suppressor of cytokine signaling 3 (SOCS3).


CONCLUSIONS
These results show that inhibiting COX-2 activity can exacerbate the inflammatory response to LPS, possibly by increasing glial cells activation and upregulating the STAT3 and SOCS3 pathways in the brain.
Aid
Saba
S
Brain Physiology and Metabolism Section, National Institute on Aging, NIH, 9000 Memorial Drive, Bldg 9 Room 1S126, Bethesda, MD 20892, USA. aidsab@mail.nih.gov
Langenbach
Robert
R
Bosetti
Francesca
F
D000818:Animals; D000068579:Celecoxib; D051545:Cyclooxygenase 1 / Q000502:physiology; D051546:Cyclooxygenase 2 / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D052246:Cyclooxygenase 2 Inhibitors / Q000633:toxicity*; D016207:Cytokines / Q000096:biosynthesis / Q000235:genetics; D004660:Encephalitis / Q000139:chemically induced / Q000201:enzymology* / Q000276:immunology; D020869:Gene Expression Profiling; D008070:Lipopolysaccharides / Q000008:administration & dosage / Q000633:toxicity*; D008297:Male; D008565:Membrane Proteins / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009410:Nerve Degeneration / Q000209:etiology; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics; D009474:Neurons / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D011720:Pyrazoles / Q000633:toxicity; D017382:Reactive Oxygen Species; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D013449:Sulfonamides / Q000633:toxicity; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics / Q000378:metabolism
D052246:Cyclooxygenase 2 Inhibitors; D016207:Cytokines; D008070:Lipopolysaccharides; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D011720:Pyrazoles; D017382:Reactive Oxygen Species; D050796:STAT3 Transcription Factor; C491411:Socs3 protein, mouse; C494087:Stat3 protein, mouse; D013449:Sulfonamides; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; C482199:lipopolysaccharide, E coli O55-B5; C077623:Ptgs2 protein, mouse; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; C496512:Ptgs1 protein, mouse; D000068579:Celecoxib