Photoperiod Affects Leptin Action on the Choroid Plexus in Ewes Challenged with Lipopolysaccharide-Study on the mRNA Level.

The ovine choroid plexus (ChP) expresses the long isoform of the leptin receptor, which makes this structure a potential target for leptin action. In sheep, leptin concentration in plasma is higher during long days (LD) than short days (SD). This study evaluates the influence a of photoperiod on leptin impact on the gene expression of Toll-like receptor 4 (), proinflammatory cytokines (, ), their receptors (, , , , ) and inflammasome components necessary for pro-IL-1β activation (, , ), chemokine (), leptin receptor isoforms (, ) and a suppressor of cytokine signalling () in the ChP of ewes treated or not with lipopolysaccharide (LPS). Studies were conducted on adult female sheep divided into four groups ( = 6 in each): control, leptin (20 μg/kg), LPS (400 ng/kg), and LPS and leptin injected under SD and LD photoperiods. The leptin alone did not affect the gene expression but in co-treatment with LPS increased ( < 0.05) IL1B but only during SD, and , , , and only during LD, and decreased ( < 0.05) the expression only during SD photoperiod. This indicates that the immunomodulatory action of leptin on the ChP is manifested only under the LPS challenge and is photoperiodically dependent.