Inducible Prostaglandin E 2 Synthesis Interacts in a Temporally Supplementary Sequence with Constitutive Prostaglandin-Synthesizing Enzymes in Creating the Hypothalamic–Pituitary–Adrenal Axis Response to Immune Challenge

• Published in: The Journal of neuroscience 2009-02, Vol.29 (5), p.1404-1413
• Main Authors: Elander, Louise, Engström, Linda, Ruud, Johan, Mackerlova, Ludmila, Jakobsson, Per-Johan, Engblom, David, Nilsberth, Camilla, Blomqvist, Anders
• Format: Article
• Language: English
• Subjects: ACTH; corticosterone; CRH; Fos; LPS; MEDICIN; MEDICINE; mPGES-1
• ISSN: 0270-6474; 1529-2401; 1529-2401
• DOI: 10.1523/JNEUROSCI.5247-08.2009

Inflammation-induced activation of the hypothalamic–pituitary–adrenal (HPA) axis has been suggested to depend on prostaglandins, but the prostaglandin species and the prostaglandin-synthesizing enzymes that are responsible have not been fully identified. Here, we examined HPA axis activation in mice after genetic deletion or pharmacological inhibition of prostaglandin E 2 -synthesizing enzymes, including cyclooxygenase-1 (Cox-1), Cox-2, and microsomal prostaglandin E synthase-1 (mPGES-1). After immune challenge by intraperitoneal injection of lipopolysaccharide, the rapid stress hormone responses were intact after Cox-2 inhibition and unaffected by mPGES-1 deletion, whereas unselective Cox inhibition blunted these responses, implying the involvement of Cox-1. However, mPGES-1-deficient mice showed attenuated transcriptional activation of corticotropin-releasing hormone (CRH) that was followed by attenuated plasma concentrations of adrenocorticotropic hormone and corticosterone. Cox-2 inhibition similarly blunted the delayed corticosterone response and further attenuated corticosterone release in mPGES-1 knock-out mice. The expression of the c- fos gene, an index of synaptic activation, was maintained in the paraventricular hypothalamic nucleus and its brainstem afferents both after unselective and Cox-2 selective inhibition as well as in Cox-1, Cox-2, and mPGES-1 knock-out mice. These findings point to a mechanism by which (1) neuronal afferent signaling via brainstem autonomic relay nuclei and downstream Cox-1-dependent prostaglandin release and (2) humoral, CRH transcription-dependent signaling through induced Cox-2 and mPGES-1 elicited PGE 2 synthesis, shown to occur in brain vascular cells, play distinct, but temporally supplementary roles for the stress hormone response to inflammation.