DHEA inhibits acute microglia-mediated inflammation through activation of the TrkA-Akt1/2-CREB-Jmjd3 pathway.

Dehydroepiandrosterone (DHEA) is the most abundant circulating steroid hormone in humans, produced by the adrenals, the gonads and the brain. DHEA was previously shown to bind to the nerve growth factor receptor, tropomyosin-related kinase A (TrkA), and to thereby exert neuroprotective effects. Here we show that DHEA reduces microglia-mediated inflammation in an acute lipopolysaccharide-induced neuro-inflammation model in mice and in cultured microglia in vitro. DHEA regulates microglial inflammatory responses through phosphorylation of TrkA and subsequent activation of a pathway involving Akt1/Akt2 and cAMP response element-binding protein. The latter induces the expression of the histone 3 lysine 27 (H3K27) demethylase Jumonji d3 (Jmjd3), which thereby controls the expression of inflammation-related genes and microglial polarization. Together, our data indicate that DHEA-activated TrkA signaling is a potent regulator of microglia-mediated inflammation in a Jmjd3-dependent manner, thereby providing the platform for potential future therapeutic interventions in neuro-inflammatory pathologies.

Toll-like receptors in endocrine disease and diabetes.

The body's ability to keep a steady homeostatic state is crucial to health and life. This involves providing an adequate response to a variety of challenges both physical and mental, such as microbial invasion and emotional distress. Interplay between the neuroendocrine and immune systems is essential in either case. Studies have demonstrated that toll-like receptors, or TLRs, play a regulatory role in both systems, and have been proposed as a possible link between the immune, hormonal and metabolic systems. As part of the innate immune system, these receptors control the identification by the body of microbial invaders and its immediate reaction in immune and inflammatory response. What are referred to as pattern recognition receptors are mostly expressed by cells involved in hematopoietic linkage, but an increasing number of studies have demonstrated their expression in other cell types such as neurons and endocrine cells on the hypothalamic-pituitary-adrenal (HPA) axis, thyrocytes, adipocytes and islets of Langerhans. Together with endocrine and metabolic dysregulation, immune system overreaction is often associated with infection and autoimmunity, clearly indicating TLR involvement at organ level which affects organ function. Several diseases such as autoimmune thyroid and pancreatic diseases, septic dysregulation of the HPA axis, diabetes and the metabolic syndrome have been linked to TLR activation and polymorphism. To gain insight into stress response and adaptation, we need to know more about TLRs and the specific physiological role they play in the endocrine and metabolic system and its processes.

The role of toll-like receptors in the immune-adrenal crosstalk.

Sepsis and septic shock remain major health concerns worldwide, and rapid activation of adrenal steroid release is a key event in the organism's first line of defense during this form of severe illness. Toll-like receptors (TLRs) are critical in the early immune response upon bacterial infection, and recent data from our lab demonstrate a novel link between the innate immune system and the adrenal stress response mediated by TLRs. Glucocorticoids and TLRs regulate each other in a bidirectional way. Bacterial toxins acting through TLRs directly activate adrenocortical steroid release. TLR-2 and TLR-4 are expressed in human and mice adrenals and TLR-2 deficiency is associated with an impaired glucocorticoid response. Furthermore, TLR-2 deficiency in mice is associated with marked cellular alterations in adrenocortical tissue. TLR-2-deficient mice have an impaired adrenal corticosterone release following inflammatory stress induced by bacterial cell wall compounds. This defect appears to be associated with a decrease in systemic and intraadrenal cytokine expression. In conclusion, TLRs play a crucial role in the immune-adrenal crosstalk. This close functional relationship needs to be considered in the treatment of inflammatory diseases requiring an intact adrenal stress response.

Pam3CSK4 and LTA-TLRs ligands associated with microdomains induce IL8 production in human adrenocortical cancer cells.

Bacterially derived ligands, Pam3CSK4 and LPS, can directly impact adrenal glands steroidogenesis through microdomain-related TLR1/2 and 4, respectively, and indirectly via immune cell-derived cytokines. The bilateral immunoadrenal relationship plays an important role in the proper functioning of both systems. CXC chemokine-dependent immune cell infiltration into adrenocortical carcinomas (ACC), which correlates with poor prognosis, is a common phenomenon. Recently, IL8 was identified in ACC and NCI-H295R cells, and was found to contribute to ACC tumour growth. The aim of this study was to clarify the role of different TLR ligands in IL8 production in NCI-H295R cells. This is the first study to demonstrate the expression of several TLRs including TLR1, 3, 6, 7 and 9 in human adrenocortical cells by using the RT-PCR approach. Only stimulation with TLR1/6 together with TLR2 ligands resulted in IL8 peptide and mRNA induction in a dose and time-dependent manner. Our data suggest that gram-positive bacteria-related TLR1/2/6 ligands might contribute to adrenal gland tumorigenesis via IL8 production.