Interleukin-1 beta expression in the pineal gland of the rat

Increasing evidence of the neuroimmunomodulatory role of the pineal gland p rompted the present study of pineal gland expression of the immunoregulator y cytokine, interleukin (IL)-1 beta. IL-1 beta was constitutively expressed in the adult gland, with mRNA levels higher in glands collected during the photophase than in those collected during the scotophase of the light:dark cycle. IL-1 beta was up-regulated in pineal cultures, after treatment with either norepinephrine (NE) or interferon (IFN)/lipopolysaccharide (LPS). A lthough both astrocytes and microglia expressed IL-1 beta, important differ ences were found in the cellular expression of this cytokine under in vivo and in vitro conditions. Increased IL-1 beta expression by NE ex vivo and t he decline in IL-1 expression at night, when NE levels are elevated, can be explained by immunocytochemical data showing that astrocytes are the predo minant cell type expressing this cytokine in vivo, whereas IL-1 beta-positi ve cells are predominantly microglia in pineal explants and dispersed cell cultures. These results are consistent with the hypothesis that cytokines s ecreted by pineal glia (astrocytes and microglia) may have an important reg ulatory role in the pineal gland.