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Exogenous pathogen and plant 15-lipoxygenase initiate endogenous lipoxin A4 biosynthesis.

Bannenberg GL, Aliberti J, Hong S, Sher A, Serhan C - J. Exp. Med. (2004)

Bottom Line: Hence, we incubated STAg itself with arachidonic acid and found using LC-UV-MS-MS-based lipidomics that STAg produced both 15-HETE and 5,15-diHETE, indicating that T. gondii carries 15-lipoxygenase activity.Local administration of a plant (soybean) lipoxygenase itself reduced neutrophilic infiltration in murine peritonitis, demonstrating that 15-lipoxygenase possesses antiinflammatory properties.Together, these results indicate that 15-lipoxygenase expressed by a pathogen as well as exogenously administered 15-lipoxygenase can interact with host biosynthetic circuits for endogenous "stop signals" that divert the host immune response and limit acute inflammation.

View Article: PubMed Central - PubMed

Affiliation: Center for Experimental Therapeutics and Reperfusion Injury, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.

ABSTRACT
Lipoxin A4 (LXA4) is a potent endogenous lipoxygenase-derived eicosanoid with antiinflammatory and proresolving properties. Supraphysiological levels of LXA4 are generated during infection by Toxoplasma gondii, which in turn reduces interleukin (IL) 12 production by dendritic cells, thus dampening Th1-type cell-mediated immune responses and host immunopathology. In the present work, we sought evidence for the structural basis of T. gondii's ability to activate LXA4 biosynthesis. Proteomic analysis of T. gondii extract (soluble tachyzoite antigen [STAg]), which preserves the immunosuppressive and antiinflammatory activity of the parasite, yielded several peptide matches to known plant lipoxygenases. Hence, we incubated STAg itself with arachidonic acid and found using LC-UV-MS-MS-based lipidomics that STAg produced both 15-HETE and 5,15-diHETE, indicating that T. gondii carries 15-lipoxygenase activity. In addition, T. gondii tachyzoites (the rapidly multiplying and invasive stage of the parasite) generated LXA4 when provided with arachidonic acid. Local administration of a plant (soybean) lipoxygenase itself reduced neutrophilic infiltration in murine peritonitis, demonstrating that 15-lipoxygenase possesses antiinflammatory properties. Administration of plant 15-lipoxygenase generated endogenous LXA4 and mimicked the suppression of IL-12 production by splenic dendritic cells observed after T. gondii infection or STAg administration. Together, these results indicate that 15-lipoxygenase expressed by a pathogen as well as exogenously administered 15-lipoxygenase can interact with host biosynthetic circuits for endogenous "stop signals" that divert the host immune response and limit acute inflammation.

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LXA4 formation by T. gondii tachyzoites. T. gondii tachyzoites (107 organisms/well) were incubated for 30 min in the presence or absence of 5 μM A23187 and 20 μM arachidonic acid. LXA4 was monitored (see Materials and Methods) and expressed as mean values ± SEM (n = 3). Student's t test; *, P < 0.05; **, P < 0.005.
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fig3: LXA4 formation by T. gondii tachyzoites. T. gondii tachyzoites (107 organisms/well) were incubated for 30 min in the presence or absence of 5 μM A23187 and 20 μM arachidonic acid. LXA4 was monitored (see Materials and Methods) and expressed as mean values ± SEM (n = 3). Student's t test; *, P < 0.05; **, P < 0.005.

Mentions: Having established that STAg produces 15-HETE, a potential substrate for lipoxin biosynthesis, and 5,15-diHETE, which is associated with the activation of lipoxin pathways, we next addressed whether intact T. gondii tachyzoites were capable of forming LXA4. Tachyzoites were incubated with or without the substrate arachidonic acid and an agonist, calcium ionophore A23187. T. gondii tachyzoites formed LXA4 in the presence of added arachidonic acid (Fig. 3). The formation of LXA4 was further enhanced by simultaneous activation of the tachyzoites with calcium ionophore. Tachyzoites alone did not form appreciable amounts of LXA4 in the absence of added arachidonic acid, or with calcium ionophore alone. These results indicate that intact T. gondii tachyzoites can generate LXA4, but only when supplied with exogenous sources of arachidonic acid.


Exogenous pathogen and plant 15-lipoxygenase initiate endogenous lipoxin A4 biosynthesis.

Bannenberg GL, Aliberti J, Hong S, Sher A, Serhan C - J. Exp. Med. (2004)

LXA4 formation by T. gondii tachyzoites. T. gondii tachyzoites (107 organisms/well) were incubated for 30 min in the presence or absence of 5 μM A23187 and 20 μM arachidonic acid. LXA4 was monitored (see Materials and Methods) and expressed as mean values ± SEM (n = 3). Student's t test; *, P < 0.05; **, P < 0.005.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2211821&req=5

fig3: LXA4 formation by T. gondii tachyzoites. T. gondii tachyzoites (107 organisms/well) were incubated for 30 min in the presence or absence of 5 μM A23187 and 20 μM arachidonic acid. LXA4 was monitored (see Materials and Methods) and expressed as mean values ± SEM (n = 3). Student's t test; *, P < 0.05; **, P < 0.005.
Mentions: Having established that STAg produces 15-HETE, a potential substrate for lipoxin biosynthesis, and 5,15-diHETE, which is associated with the activation of lipoxin pathways, we next addressed whether intact T. gondii tachyzoites were capable of forming LXA4. Tachyzoites were incubated with or without the substrate arachidonic acid and an agonist, calcium ionophore A23187. T. gondii tachyzoites formed LXA4 in the presence of added arachidonic acid (Fig. 3). The formation of LXA4 was further enhanced by simultaneous activation of the tachyzoites with calcium ionophore. Tachyzoites alone did not form appreciable amounts of LXA4 in the absence of added arachidonic acid, or with calcium ionophore alone. These results indicate that intact T. gondii tachyzoites can generate LXA4, but only when supplied with exogenous sources of arachidonic acid.

Bottom Line: Hence, we incubated STAg itself with arachidonic acid and found using LC-UV-MS-MS-based lipidomics that STAg produced both 15-HETE and 5,15-diHETE, indicating that T. gondii carries 15-lipoxygenase activity.Local administration of a plant (soybean) lipoxygenase itself reduced neutrophilic infiltration in murine peritonitis, demonstrating that 15-lipoxygenase possesses antiinflammatory properties.Together, these results indicate that 15-lipoxygenase expressed by a pathogen as well as exogenously administered 15-lipoxygenase can interact with host biosynthetic circuits for endogenous "stop signals" that divert the host immune response and limit acute inflammation.

View Article: PubMed Central - PubMed

Affiliation: Center for Experimental Therapeutics and Reperfusion Injury, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.

ABSTRACT
Lipoxin A4 (LXA4) is a potent endogenous lipoxygenase-derived eicosanoid with antiinflammatory and proresolving properties. Supraphysiological levels of LXA4 are generated during infection by Toxoplasma gondii, which in turn reduces interleukin (IL) 12 production by dendritic cells, thus dampening Th1-type cell-mediated immune responses and host immunopathology. In the present work, we sought evidence for the structural basis of T. gondii's ability to activate LXA4 biosynthesis. Proteomic analysis of T. gondii extract (soluble tachyzoite antigen [STAg]), which preserves the immunosuppressive and antiinflammatory activity of the parasite, yielded several peptide matches to known plant lipoxygenases. Hence, we incubated STAg itself with arachidonic acid and found using LC-UV-MS-MS-based lipidomics that STAg produced both 15-HETE and 5,15-diHETE, indicating that T. gondii carries 15-lipoxygenase activity. In addition, T. gondii tachyzoites (the rapidly multiplying and invasive stage of the parasite) generated LXA4 when provided with arachidonic acid. Local administration of a plant (soybean) lipoxygenase itself reduced neutrophilic infiltration in murine peritonitis, demonstrating that 15-lipoxygenase possesses antiinflammatory properties. Administration of plant 15-lipoxygenase generated endogenous LXA4 and mimicked the suppression of IL-12 production by splenic dendritic cells observed after T. gondii infection or STAg administration. Together, these results indicate that 15-lipoxygenase expressed by a pathogen as well as exogenously administered 15-lipoxygenase can interact with host biosynthetic circuits for endogenous "stop signals" that divert the host immune response and limit acute inflammation.

Show MeSH
Related in: MedlinePlus