Neuroinflammatory response to lipopolysaccharide is exacerbated in mice genetically deficient in cyclooxygenase-2

<p>Abstract</p> <p>Background</p> <p>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).</p> <p>Methods</p> <p>In this study, we investigated the role of COX-2 in the neuroinflammatory response to intracerebroventricular-injected LPS (5 μg), 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.</p> <p>Results</p> <p>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-1β, NADPH oxidase subunit p67^phox, 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).</p> <p>Conclusion</p> <p>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.</p

Therapeutic versus neuroinflammatory effects of passive immunization is dependent on Abeta/amyloid burden in a transgenic mouse model of Alzheimer's disease

Abstract Background Passive immunization with antibodies directed to A&#946; decreases brain A&#946;/amyloid burden and preserves memory in transgenic mouse models of Alzheimer's disease (AD). This therapeutic strategy is under intense scrutiny in clinical studies, but its application is limited by neuroinflammatory side effects (autoimmune encephalitis and vasogenic edema). Methods We intravenously administered the monoclonal A&#946; protofibril antibody PFA1 to aged (22 month) male and female 3 &#215; tg AD mice with intermediate or advanced AD-like neuropathologies, respectively, and measured brain and serum A&#946; and CNS cytokine levels. We also examined 17 month old 3 &#215; tg AD female mice with intermediate pathology to determine the effect of amyloid burden on responses to passive immunization. Results The 22 month old male mice immunized with PFA1 had decreased brain A&#946;, increased serum A&#946;, and no change in CNS cytokine levels. In contrast, 22 month old immunized female mice revealed no change in brain A&#946;, decreased serum A&#946;, and increased CNS cytokine levels. Identical experiments in younger (17 month old) female 3 &#215; tg AD mice with intermediate AD-like neuropathologies revealed a trend towards decreased brain A&#946; and increased serum A&#946; accompanied by a decrease in CNS MCP-1. Conclusions These data suggest that passive immunization with PFA1 in 3 &#215; tg AD mice with intermediate disease burden, regardless of sex, is effective in mediating potentially therapeutic effects such as lowering brain A&#946;. In contrast, passive immunization of mice with a more advanced amyloid burden may result in potentially adverse effects (encephalitis and vasogenic edema) mediated by certain proinflammatory cytokines.http://deepblue.lib.umich.edu/bitstream/2027.42/78261/1/1742-2094-7-57.xmlhttp://deepblue.lib.umich.edu/bitstream/2027.42/78261/2/1742-2094-7-57.pdfPeer Reviewe

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

Quantitative real time-PCR analysis of (A), (B) and mRNA (C) for COX-2and COX-2mice 24 h after icv injection of LPS or vehicle

(D) Quantification of phosphorylated STAT3 (Tyr 705) protein levels, relative to the total STAT3 in the brain nuclear fraction. (E) Representative immunoblot of P-STAT3 expression in COX-2and COX-2mice 24 h after icv injection of LPS or vehicle. Data are presented as mean ± SEM (= 4-6). *< 0.05, **< 0.01, ***< 0.001 compared to the corresponding vehicle-injected mice; < 0.01 compared to the LPS-injected COX-2mice.<p><b>Copyright information:</b></p><p>Taken from "Neuroinflammatory response to lipopolysaccharide is exacerbated in mice genetically deficient in cyclooxygenase-2"</p><p>http://www.jneuroinflammation.com/content/5/1/17</p><p>Journal of Neuroinflammation 2008;5():17-17.</p><p>Published online 19 May 2008</p><p>PMCID:PMC2409311.</p><p></p

Quantitative real time-PCR analysis of (A) and (B) for COX-2and COX-2mice 24 h after icv injection of LPS or vehicle

(C) Quantification of COX-1 protein levels, relative to GAPDH internal loading control in the whole brain. (D) Representative immunoblot of COX-1 expression in COX-2and COX-2mice 24 h after icv injection of LPS or vehicle. Data are presented as mean ± SEM (= 4-6). ***< 0.001 compared to the corresponding vehicle-injected mice; < 0.05 compared to the LPS-injected COX-2mice.<p><b>Copyright information:</b></p><p>Taken from "Neuroinflammatory response to lipopolysaccharide is exacerbated in mice genetically deficient in cyclooxygenase-2"</p><p>http://www.jneuroinflammation.com/content/5/1/17</p><p>Journal of Neuroinflammation 2008;5():17-17.</p><p>Published online 19 May 2008</p><p>PMCID:PMC2409311.</p><p></p

Quantitative real time-PCR analysis of astrocyte marker (A) and microglia marker mRNA (B) in COX-2and COX-2mice 24 h after icv injection of LPS or vehicle

Data are presented as mean ± SEM (= 4-6). ***< 0.001 compared to the corresponding vehicle-injected mice; < 0.05 compared to the LPS-injected COX-2mice. (C) Effects of COX-2 deficiency on LPS-induced activation of microglia. Representative photomicrographs of SRA immunohistochemistry in the striatum/caudate putamen and hippocampal area for COX-2and COX-2mice 24 h after icv injection of LPS or vehicle. Bars represent 100 μm.<p><b>Copyright information:</b></p><p>Taken from "Neuroinflammatory response to lipopolysaccharide is exacerbated in mice genetically deficient in cyclooxygenase-2"</p><p>http://www.jneuroinflammation.com/content/5/1/17</p><p>Journal of Neuroinflammation 2008;5():17-17.</p><p>Published online 19 May 2008</p><p>PMCID:PMC2409311.</p><p></p

Quantitative real time-PCR analysis of (A), B) and mRNA (C) for COX-2and COX-2mice that received icv injection of LPS or vehicle 24 h before sacrifice

(D) Quantification of p67protein levels, relative to GAPDH internal loading control in the whole brain. (E) Representative immunoblot of p67expression in COX-2and COX-2mice 24 h after icv injection of LPS or vehicle. Data are presented as mean ± SEM (= 4-6). ***< 0.001 compared to the corresponding vehicle-injected mice; < 0.05, < 0.01 compared to the LPS-injected COX-2mice.<p><b>Copyright information:</b></p><p>Taken from "Neuroinflammatory response to lipopolysaccharide is exacerbated in mice genetically deficient in cyclooxygenase-2"</p><p>http://www.jneuroinflammation.com/content/5/1/17</p><p>Journal of Neuroinflammation 2008;5():17-17.</p><p>Published online 19 May 2008</p><p>PMCID:PMC2409311.</p><p></p

Quantitative real time-PCR analysis of (A), (B), (C), and CCL3/MIP-1α and CCL2/(E) for COX-2and COX-2mice 24 h after icv injection of LPS or vehicle

(D) ELISA-based quantification of IL-1β protein levels in the brain of COX-2and COX-2mice 24 h after icv injection of LPS or vehicle. Data are presented as mean ± SEM (= 4-6). ***< 0.001 compared to the corresponding vehicle-injected mice; < 0.05, < 0.01, < 0.001 compared to the LPS-injected COX-2mice.<p><b>Copyright information:</b></p><p>Taken from "Neuroinflammatory response to lipopolysaccharide is exacerbated in mice genetically deficient in cyclooxygenase-2"</p><p>http://www.jneuroinflammation.com/content/5/1/17</p><p>Journal of Neuroinflammation 2008;5():17-17.</p><p>Published online 19 May 2008</p><p>PMCID:PMC2409311.</p><p></p

Cyclooxygenase-1 and -2 differentially modulate lipopolysaccharide-induced blood–brain barrier disruption through matrix metalloproteinase activity

Cyclooxygenases (COX) -1 and -2 are key regulators of innate immune responses. We recently demonstrated that the expression of proinflammatory cytokines and chemokines is reduced in COX-1 null (−/−), and increased in COX-2−/− mice compared with their respective wild type controls during lipopolysaccharide (LPS)-induced innate immune activation. As chemokines are involved in leukocyte recruitment into the inflamed brain, we hypothesized that COX-1 and COX-2 deletion will differentially modulate blood–brain barrier (BBB) permeability in response to LPS. In the present study, using quantitative magnetic resonance imaging, we found that LPS-induced BBB disruption was exacerbated in COX-2−/− versus COX-2+/+ mice. In the hippocampus and cortex of LPS-treated mice, matrix metalloproteinase (MMP)-3 activity was significantly decreased in COX-1−/− mice, whereas in COX-2−/− mice the activity of both MMP-9 and MMP-3, known to mediate BBB breakdown, was increased. Brain mRNA expression of the leukocyte attracting chemokine Cxcl10, the intercellular interaction molecule Icam-1, the pan-leukocyte marker Cd45 was increased in COX-2−/− versus COX-2+/+ mice, whereas Cxcl10 and Cd45 mRNA expression was decreased in COX-1−/− versus COX-1+/+ mice after LPS. Altogether, these results indicate that COX-2 activity modulates MMP-9 and-3 activities and is necessary to maintain BBB integrity during toll-like receptor 4-dependent innate immune activation