Neuronal overexpression of cyclooxygenase-2 does not alter the neuroinflammatory response during brain innate immune activation.
Neuroinflammation is a critical component in the progression of several neurological and neurodegenerative diseases and cyclooxygenases (COX)-1 and -2 are key regulators of innate immune responses. We recently demonstrated that COX-1 deletion attenuates, whereas COX-2 deletion enhances, the neuroinflammatory response, blood-brain barrier permeability and leukocyte recruitment during lipopolysaccharide (LPS)-induced innate immune activation. Here, we used transgenic mice, which overexpressed human COX-2 via neuron-specific Thy-1 promoter (TgCOX-2), causing elevated prostaglandins (PGs) levels. We tested whether neuronal COX-2 overexpression affects the glial response to a single intracerebroventricular injection of LPS, which produces a robust neuroinflammatory reaction. Relative to non-transgenic controls (NTg), 7 month-old TgCOX-2 did not show any basal neuroinflammation, as assessed by gene expression of markers of inflammation and oxidative stress, neuronal damage, as assessed by Fluoro-JadeB staining, or systemic inflammation, as assessed by plasma levels of IL-1beta and corticosterone. Twenty-four hours after LPS injection, all mice showed increased microglial activation, as indicated by Iba1 immunostaining, neuronal damage, mRNA expression of cytokines (TNF-alpha, IL-6), reactive oxygen expressing enzymes (iNOS and NADPH oxidase subunits), endogenous COX-2, cPLA(2) and mPGES-1, and hippocampal and cortical IL-1beta levels. However, the increases were similar in TgCOX-2 and NTg. In NTg, LPS increased brain PGE(2) to the levels observed in TgCOX-2. These results suggest that PGs derived from neuronal COX-2 do not play a role in the neuroinflammatory response to acute activation of brain innate immunity. This is likely due to the direct effect of LPS on glial rather than neuronal cells.
Aid
Saba
S
Molecular Neuroscience Unit, Brain Physiology and Metabolism Section, National Institute on Aging, NIH, Bethesda, MD 20892, USA.
Parikh
Nishant
N
Palumbo
Sara
S
Bosetti
Francesca
F
D000818:Animals; D001921:Brain / Q000276:immunology* / Q000378:metabolism* / Q000473:pathology; D003345:Corticosterone / Q000097:blood; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D004660:Encephalitis / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D053583:Interleukin-1beta / Q000097:blood; D008070:Lipopolysaccharides / Q000276:immunology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D017628:Microglia / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D015213:Neuroimmunomodulation / Q000502:physiology; D009474:Neurons / Q000378:metabolism* / Q000473:pathology; D018384:Oxidative Stress / Q000502:physiology; D011453:Prostaglandins / Q000378:metabolism*; D011458:Prostaglandins E / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism
D053583:Interleukin-1beta; D008070:Lipopolysaccharides; D011453:Prostaglandins; D011458:Prostaglandins E; D012333:RNA, Messenger; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D003345:Corticosterone
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