Central Injection of Exogenous IL-1β in the Control Activities of Hypothalamic-Pituitary-Gonadal Axis in Anestrous Ewes

This study was performed to determine the effect of intracerebroventricular (icv) injection of interleukin (IL)-1 beta on the gene expression, translation and release of gonadotropin-releasing hormone (GnRH) and the GnRH receptor (GnRHR) gene expression in the hypothalamus of anestrous ewes. In the anterior pituitary gland (AP), the expression of genes encoding: GnRHR, beta subunits of luteinizing hormone (LH) and folliculotropic hormone (FSH) was determined as well as the effect of IL-1 beta on pituitary gonadotropins release. The relative mRNA level was determined by real-time PCR, GnRH concentration in the cerebrospinal fluid (CSF) was assayed by ELISA and the plasma concentration of LH and FSH were determined by radioimmunoassay. Our results showed that icv injection of IL-1 beta (10 or 50 mu g/animal) decreased the GnRH mRNA level in the pre-optic area (POA) (35% and 40% respectively; p = 0.01) and median eminence (ME) (75% and 70% respectively; p = 0.01) and GnRHR gene expression in ME (55% and 50% respectively; p = 0.01). A significant decrease in GnRHR mRNA level in the AP in the group treated with the 50 mu g (60%; p = 0.01) but not with the 10 mu g dose was observed. The centrally administrated IL-1 beta lowered also GnRH concentration in the CSF (60%; p = 0.01) and reduced the intensity of GnRH translation in the POA (p = 0.01). It was not found any effect of icv IL-1 beta injection upon the release of LH and FSH. However, the central injection of IL-1 beta strongly decreased the LH beta mRNA level (41% and 50%; p = 0.01; respectively) and FSH beta mRNA in the case of the 50 mu g dose (49%; p = 0.01) in the pituitary of anestrous ewes. These results demonstrate that the central IL-1 beta is an important modulator of the GnRH biosynthesis and release during immune/inflammatory challenge.