Disruption of Intranasal GnRH Neuronal Migration Route into the Brain Induced by Proinflammatory Cytokine IL-6: Ex Vivo and In Vivo Rodent Models

Maternal immune activation results in altered levels of cytokines in the maternal–fetal system, which has a negative impact on fetal development, including the gonadotropin-releasing hormone (GnRH) system, which is crucial for the reproduction. Suppression of GnRH–neuron migration may be associated with cytokine imbalances, and primarily with proinflammatory cytokine interleukin (IL)-6. This study aimed to determine the effects of IL-6 and monoclonal antibody to IL-6 or IL-6R or polyclonal IgG on the formation of migration route of GnRH–neurons in ex vivo and in vivo rodent models on day 11.5 of embryonic development. The increased level of IL-6 in mouse nasal explants suppressed peripherin-positive fiber outgrowth, while this led to an increase in the number of GnRH–neurons in the nose and olfactory bulbs and a decrease in their number in the fetal brain. This effect is likely to be realized via IL-6 receptors along the olfactory nerves. The suppressive effect of IL-6 was diminished by monoclonal antibodies to IL-6 or its receptors and by IgG.