Prolactin (PRL) up-regulates Indoleamine 2,3-dioxygenase (IDO) expression in CD14+ cells

Dysregulated expression of IDO may cause unexplained recurrent spontaneous abortion through suppression of trophoblast cell proliferation and migration

In pregnancy, trophoblast proliferation, migration and invasion are important for the establishment and maintenance of a successful pregnancy. Impaired trophoblast function has been implicated in recurrent spontaneous abortion (RSA), a major complication of pregnancy, but the underlying mechanisms remain unclear. Indoleamine 2,3-dioxygenase (IDO), an enzyme that catabolizes tryptophan along the kynurenine pathway, is highly expressed in the placenta and serum during pregnancy. Here, we identified a novel function of IDO in regulating trophoblast cell proliferation and migration. We showed that IDO expression and activity were decreased in unexplained recurrent spontaneous abortion (URSA) compared to normal pregnancy. Furthermore, blocking IDO in human trophoblast cells led to reduced proliferation and migration, along with decreased STAT3 phosphorylation and MMP9 expression. Increased STAT3 phosphorylation reversed the IDO knockdown-suppressed trophoblast cell proliferation and migration. In addition, the overexpression of IDO promoted cell proliferation and migration, which could be abolished by the STAT3 signaling inhibitor (AG490). Finally, we observed similar reductions of STAT3 phosphorylation and MMP9 expression in URSA patients. These results indicate that the level of IDO expression may be associated with pregnancy-related complications, such as URSA, by affecting trophoblast cell proliferation and migration via the STAT3 signaling pathway.

The importance of toxoplasma gondii infection in diseases presenting with headaches. Headaches and aseptic meningitis may be manifestations of the Jarisch-Herxheimer reaction

Worldwide, approximately 2 billion people are chronically infected with T. gondii with largely unknown consequences. This review presents clinical symptoms, differential diagnosis, triggering factors, treatment, and pathomechanisms responsible for idiopathic intracranial hypertension, pseudotumor cerebri, and aseptic meningitis. Literature cited in this work illustrates that immune state and other biologic mediator imbalances due to various endogenous and exogenous triggering factors may markedly affect latent central nervous system T. gondii infection/inflammation intensity, and cause reactivation of cerebral toxoplasmosis (CT). Irregularities in pro- and anti-inflammatory processes may markedly disturb the host and/or T. gondii defense mechanisms important for immune control of the parasite thereby manifesting as a wide range of neurologic symptoms and signs observed in some patients with migraine, epilepsy, celiac disease, Henoch-Schönlein purpura, and other brain disorders. This is consistent with reactivation of CT in mice after treatment with dexamethasone associated with depression of type T(H)1 immune response, and development of CT after administration of etanercept or other bioproducts. It seems that various types of headaches, epilepsy, aseptic meningitis, systemic adverse reactions to drugs or other substances represent the Jarisch-Herxheimer reaction due to apoptosis of T. gondii tachyzoites. Also development of some brain tumors, such as ependymoma and glioma may be associated with a chronic course of CT. Thus, all these patients should be tested for T. gondii infection.

Priming of peripheral monocytes with prolactin (PRL) sensitizes IFN-gamma-mediated indoleamine 2,3-dioxygenase (IDO) expression without affecting IFN-gamma signaling

Prolactin (PRL) was originally identified by its ability to stimulate mammary development and lactation, and its essential roles other than lactation have recently been implicated in female reproduction. However, little is known about PRL-mediated events in pregnancy. The tryptophan catabolism enzyme indoleamine 2,3-dioxygenase (IDO) is interferon-gamma (IFN-gamma)-inducible and has recently become a focus for maternal-fetal tolerance for successful pregnancy. Based on recognition that PRL is one of the up-regulated hormones in pregnancy, in a previous study we have shown that PRL induces IDO expression in monocytes in cooperation with a suboptimal concentration of IFN-gamma. Here, we demonstrate that PRL sensitizes monocytes to induce IDO expression in response to low doses of IFN-gamma without affecting the typical IFN-gamma signaling events, such as STAT1 phosphorylation and IRF-1 induction. In addition, IDO induction in these cell cultures was observed only after 24 h pre-exposure to PRL. These results indicate a priming effect of PRL on monocytes that occurs before IFN-gamma signaling and increases their sensitivity to IFN-gamma for IDO induction, rather than a synergistic effect of PRL and IFN-gamma on IDO induction. These results offer new insights into the roles of PRL in female reproduction, as well as provide a better understanding as to how IDO expression is regulated and achieved in pregnancy.

p-Coumaric acid inhibits indoleamine 2, 3-dioxygenase expression in murine dendritic cells

Indoleamine 2, 3-dioxygenase (IDO), a key enzyme that catalyses the initial and rate-limiting step in the degradation of the tryptophan, is simultaneously expressed in murine dendritic cells and macrophages stimulated with interferon-gamma (IFN-gamma). In the present study, we investigated whether p-Coumaric acid (CA), which is suggested to exhibit antioxidant properties, could suppress the functional expression of IDO in murine bone marrow-derived dendritic cells (BMDCs) stimulated with IFN-gamma. Treatment with CA reduced intracellular expression of IDO mRNA and protein levels in IFN-gamma-activated murine BMDCs in vitro and in CD11c(+)CD8alpha(+) DCs of tumor-draining lymph node (TDLN) of tumor-bearing mice in vivo. Consequently, we obtained evidence that CA suppresses the functional activity of IDO, which catalyses oxidative catabolism of tryptophan, and significantly recovers the IDO-dependent T cell suppression. Activation of the signal transducer and activator of transcription 1 (STAT1) is important to be express IDO in IFN-gamma-stimulated murine BMDCs. To determine whether these inhibitory effects of CA are associated with the alteration of the signal transducer and activator of transcription 1 (STAT1) and IFN-gamma-inducible, dsRNA-activated serine/threonine protein kinase (PKR), BMDCs were pretreated with various concentrations of CA. We found that CA inhibited the activation of STAT1 in response to IFN-gamma. Based on our results, this study may account that CA could inhibit IDO expression by down-regulation of STAT1 activation in IFN-gamma-stimulated murine DCs.