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Leptin induces cyclooxygenase‐2 via an interaction with interleukin‐1β in the rat brain
Author(s) -
Inoue Wataru,
Poole Stephan,
Bristow Adrian F.,
Luheshi Giamal N.
Publication year - 2006
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2006.05105.x
Subject(s) - leptin , endocrinology , medicine , leptin receptor , lipopolysaccharide , inflammation , cyclooxygenase , hypothalamus , appetite , receptor , downregulation and upregulation , interleukin , receptor antagonist , antagonist , biology , cytokine , enzyme , biochemistry , gene , obesity
In addition to its central effects on appetite regulation, leptin has been implicated in immune function and inflammation. Previous data suggested that leptin acts as an inflammatory signal within the brain, as exogenously administered leptin induced fever, a typical brain‐regulated inflammatory response. The present study aimed to delineate the inflammatory actions and cellular targets of leptin in the brain by examining its effects on the expression of interleukin (IL)‐1β and cyclooxygenase (COX)‐2, two important inflammatory components of the fever response. Intracerebroventricular injection of leptin (5 µg/rat) induced IL‐1β and COX‐2 mRNA and protein in the hypothalamus between 1 and 3 h after treatment as determined by reverse transcription‐polymerase chain reaction and immunohistochemistry. Coinjection of IL‐1 receptor antagonist (100 µg/rat, intracerebroventricular) attenuated leptin‐induced COX‐2, whereas IL‐1 receptor antagonist had no effect on endogenous IL‐1β levels, suggesting that leptin induces COX‐2 via, at least partly, IL‐1β action. IL‐1β protein expression was induced in macrophages in the meningis and perivascular space after leptin treatment, whereas COX‐2 induction was observed in endothelial cells, indicating the roles for these non‐neuronal cells in mediating inflammatory actions of leptin. In addition, neutralization of endogenous circulating leptin with anti‐leptin antiserum attenuated intraperitoneal lipopolysaccharide (100 µg/kg)‐induced brain IL‐1β and COX‐2 upregulation, suggesting that leptin indeed acts as an inflammatory signal to the brain during systemic inflammation. These findings are in contrast to the effects of leptin on appetite regulation where it is believed to act primarily on neurons, thus presenting a distinct anatomical basis for the inflammatory and appetite regulatory actions of leptin in the brain.