Marked induction of inducible nitric oxide synthase and tumor necrosis factor-α in rat CD40+ microglia by comparison to CD40− microglia

There may be two subtypes of microglia (MG) at least in the CNS. We separated the two types from rat mixed glial culture. mRNAs and proteins for inducible nitric oxide synthase (iNOS) and tumor necrosis factor-α (TNFα) were more induced in CD40+ MG than CD40− MG after LPS stimulation. Although the expression level of LPS receptors showed a little difference between the subtypes, LPS-induced degradation of phosphorylated IκBα was marked in CD40+ MG. These results strongly suggest that CD40+ MG produce larger amount of NO and TNFα to exhibit neurotoxic action under certain pathological conditions in brains.