The reproductive system at the neuroendocrine-immune interface: focus on LHRH, estrogens and growth factors in LHRH...

Bidirectional communication between the neuroendocrine and immune systems plays a pivotal role in health and disease. Signals generated by the hypothalamic-pituitary-gonadal (HPG) axis (i.e. luteinizing hormone-releasing hormone, LHRH, and sex steroids) are major players coordinating the development immune system function. Conversely, products generated by immune system activation exert powerful and longlasting effects on HPG axis activity. In the central nervous system (CNS), one chief neuroendocrine-immune (NEI) compartment is represented by the astroglial cell population and its mediators. Of special interest, the major supporting cells of the brain and the thymus, astrocytes and thymic epithelial cells, share a similar origin and a similar set of peptides, transmitters, hormones and cytokines functioning as paracrine/autocrine regulators. This may explain some fundamental analogies in LHRH regulation of both cell types during ontogeny and in adult life. Hence, the neuropeptide LHRH significantly modulates astrocyte and thymic cell development and function. Here we focus this work on LHRH neuron-glial signaling cascades which dictate major changes during LHRH neuronal differentiation and growth as well as in response to hormonal manipulations and pro-inflammatory challenges. The interplay between LHRH, growth factors, estrogens and pro-inflammatory mediators will be discussed, and the potential physiopathological implications of these findings summarized. The overall study highlights the plasticity of this intersystem cross-talk and emphasize neuron-glial interactions as a key regulatory level of neuroendocrine axes activity.