The development of the neuroendocrine system, including the hypothalamic–pituitary–gonadal (HPG) axis, is sensitive to environmental impacts during critical developmental periods. Maternal immune system activation by bacterial or viral infection may be one of the negative impacts. This study focused on the effect of systemic inflammation induced by lipopolysaccharides (LPS E. coli) on the HPG axis development in male rat offspring, corrected by the anti-inflammatory action of polyclonal IgG and monoclonal anti-interleukin (IL)-6 receptor antibodies (IL-6RmAbs). A single LPS exposure on the 12th embryonic day (ED) led to a decrease in the number of afferent synaptic inputs on gonadotropin-releasing, hormone-producing neurons in adult male offspring. LPS exposure on ED18 did not lead to such disruptions. Moreover, after the LPS injections on ED12, circulating follicle-stimulating hormone and sex steroid levels were reduced, and the gonadal structure was disrupted. A prenatal IL-6R blockade with IL-6RmAbs and polyclonal IgG reduced the negative effects of inflammation on fetal HPG axis development. Overall, the data obtained confirm the morphogenetic effect of inflammation on fetal HPG development and IL-6 involvement in these processes.

This review analyzes data on the effect of cytokines on the development of the hypothalamic–pituitary–gonadal (HPG) axis at all levels during pre- and postnatal ontogenesis under physiological and pathological conditions in humans and other mammals. Changes in cytokine physiological balance, associated with stress, inflammation, aging, and metabolic syndromes, affect the secretion of gonadotropin-releasing hormone, a key regulator of the HPG axis, as well as the secretion of pituitary gonadotropins, gonadal steroidogenesis, and gametogenesis in both males and females. Special attention is given to proinflammatory cytokines, the levels of which increase under the influence of infectious agents. Their impact on the development of the fetal brain and HPG axis is examined, as are the ensuing long-term consequences for HPG axis function. The study of cytokine contribution to the development and function of the HPG axis opens up broad prospects for reproductive disorder prevention during early ontogenesis.

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.