Differential expression of various cytokine receptors in the brain after stimulation with LPS in young and old mice.

The effect of lipopolysaccharides (LPS) on the expression of cytokine receptors was examined in the spleen, brain and pituitary gland, and compared in young and old mice. The level of mRNA for various cytokine receptors (IL-1RI, IL-2Ralpha, IL-3Ralpha, IL-6R, TNFalphaR and IFNgammaR) was found to be increased in the spleen of young but not in old mice within 2-6h of stimulation with LPS. Similar enhancement of cytokine receptor mRNA was also observed in the brain after LPS stimulation, but the magnitude varied according to the type of cytokine receptor, the site of brain and the age of the mice. In the hypothalamus, the level of mRNA for IL-1R, IL-3R, IL-6R and IFNgammaR increased in young but not in old mice. Reciprocally, in the cerebral cortex, mRNA for TNFalphaR and IFNgammaR increased in old but not in young mice. In the hippocampus, TNFalphaR mRNA expression, increased in young but not in old mice, and expression of the other cytokine receptors did not change greatly in either. In the pituitary gland, mRNA for IL-6R, TNFalphaR and IFNgammaR increased in both young and old mice, but IL-2Ralpha increased only in young mice.Thus, various cytokines produced by immune cells might directly or indirectly influence brain functions through the various cytokine receptors expressed in the brain. Moreover, interactions between the immune system and the brain at the time of infection would be expected to be different in young and old mice, because cytokine production changes with age, as does the expression of their receptors in the brain.