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Induction of Pituitary Cytokine Transcripts by Peripheral Lipopolysaccharide
Author(s) -
Whiteside Mb,
Ning Quan,
M Herkenharn
Publication year - 1999
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1046/j.1365-2826.1999.00297.x
Subject(s) - medicine , endocrinology , anterior pituitary , in situ hybridization , cytokine , posterior pituitary , lipopolysaccharide , biology , receptor , receptor antagonist , pituitary gland , glial fibrillary acidic protein , messenger rna , interleukin , antagonist , immunohistochemistry , hormone , gene , biochemistry
Systemically administered lipopolysaccharide (LPS) elicits profound changes in pituitary hormone secretion. Pro‐inflammatory cytokines have been proposed as mediators of these responses. In this study, we used in‐situ hybridization histochemistry to investigate LPS‐induced cytokine gene expression in the rat pituitary. After i.p. or i.v. injection of various doses of LPS, mRNA for the immediate‐early gene IκBu (an inhibitor of NF‐κB, a transcription factor that regulates the expression of many pro‐inflammatory cytokines) was induced in the anterior lobe as early as 0.5 h. The induced IκBα mRNA expression peaked at 1 h. In the posterior lobe, IκBα mRNA was first induced at 0.5 h and peaked at 2 h. A similar spatiotemporal pattern of interleukin‐1b (IL‐1) mRNA induction was observed. In addition, at 2 h after injection, TNFα, IL‐1β converting enzyme (ICE), and IL‐1 receptor antagonist (IL‐1RA) mRNAs were induced in both anterior and posterior lobes. Type 1 IL‐1 receptor (IL‐1R1) mRNA was constitutively expressed in the pituitary, and its expression level did not change after the LPS injection. Interestingly, the mRNA coding for glial fibrillary acidic protein (GFAP), an astrocyte marker, was selectively induced in the posterior lobe at 2 h after LPS injection, suggesting that LPS affects pituicyte function. Together, these results suggest that LPS acts directly on the pituitary to rapidly induce cytokine expression. Locally synthesized cytokines may activate cytokine receptor bearing cells to modulate the endocrine activities of the pituitary.