Attenuation of Fever At Near Term: Is Interleukin‐6–STAT3 Signalling Altered?

Publisher Website
Google Scholar
Abstract
Pregnant rats in late gestation show a reduced fever response after stimulation with lipopolysaccharide (LPS). This can result from either an increased action of endogenous antipyretics or a reduction in the production or action of endogenous pyrogens. Nonpregnant rats given LPS release interleukin (IL)‐6, which causes nuclear translocation of the signal transducer and activator of transcription 3 (STAT3) in the vascular organ of the lamina terminalis (OVLT), followed by a significant increase in core body temperature. The present study investigated whether the reduced fever response in near‐term pregnant rats is associated with a reduced nuclear STAT3 response. Rats at gestation day 15 (G15), gestation day 21 (G21, near term) and at lactation day 5 (L5) were injected with LPS (50 µg/kg, i.p.) or vehicle. Only near‐term pregnant rats responded with an attenuated body temperature during the fever response. Immunohistological analysis indicated no significant difference in nuclear STAT3 in the OVLT of the different animal groups 2 h after LPS. Measurement of total and phosphorylated STAT3 protein in the OVLT with semiquantitative western blot revealed no significant differences of this protein among these immune challenged animal groups. IL‐6 concentrations were also similar at G15, G21 and L5 2 h after injection of LPS. These results lead to the conclusion that the attenuation of the fever response at near‐term pregnancy is not associated with a reduced amount of nuclear STAT3 in the OVLT, indicating a maintained IL‐6–STAT3 signalling pathway in the OVLT.