Opposing effects of pituitary leukemia inhibitory factor and SOCS-3 on the ACTH axis response to inflammation.

We have shown that leukemia inhibitory factor (LIF) and suppressor of cytokine signaling (SOCS)-3 are expressed in the hypothalamus and pituitary and that LIF induces proopiomelanocortin (POMC) and ACTH, whereas SOCS-3 abrogates corticotroph POMC gene transcription and ACTH secretion. Here, we determined the role of pituitary LIF and SOCS-3 in regulating hypothalamo-pituitary-adrenal (HPA) axis inflammatory responses. Murine pituitary LIF expression was induced up to eightfold after intraperitoneal injection of lipopolysaccharide or tumor necrosis factor-alpha, concordant with elevated plasma levels of ACTH and corticosterone.

cAMP neuropeptide agonists induce pituitary suppressor of cytokine signaling-3: novel negative feedback mechanism for corticotroph cytokine action.

The hypothalamo-pituitary-adrenal (HPA) axis maintains a homeostatic response to stress, infection, or neoplasia. Inflammatory cytokines, including leukemia inhibitory factor (LIF), stimulate the HPA axis either directly at the pituitary corticotroph, or indirectly through induction of CRH or sympathetic noradrenergic neurons, and mediate the immuno-neuroendocrine interface. Unrestrained HPA axis activation leads, however, to immunosuppression.

Inhibitory roles for SHP-1 and SOCS-3 following pituitary proopiomelanocortin induction by leukemia inhibitory factor.

Leukemia inhibitory factor (LIF) is a pleiotropic cytokine that stimulates the hypothalamo-pituitary-adrenal (HPA) axis through JAK-STAT activation. We show here that LIF-induced JAK2 and STAT3 tyrosine phosphorylation is transient, disappearing within 20 and 40 minutes, respectively. LIF activates the SH2 domain-containing tyrosine phosphatase, SHP-1, with maximal stimulation observed at 30 minutes.

Frequent loss of heterozygosity at the retinoblastoma susceptibility gene (RB) locus in aggressive pituitary tumors: evidence for a chromosome 13 tumor suppressor gene other than RB.

Mice bearing retinoblastoma susceptibility gene (RB) germ-line mutations almost invariably develop pituitary neoplasms. We therefore tested 17 patients with pituitary tumors for loss of heterozygosity (LOH) using an RB sequence polymorphism and 5 polymorphic microsatellite markers surrounding the RB gene on the long arm of chromosome 13. In all of the 13 malignant or highly invasive pituitary tumor cases, and in 4 of their respective metastases, a RB allele was lost.