Upregulation of α-synuclein by lipopolysaccharide and interleukin-1 in human macrophages.

α-Synuclein was originally identified as the presynaptic nerve terminal protein. Recently, we reported that α-synuclein is also expressed in cultured human astrocytes and that its levels are increased by stimulation with interleukin-1β, suggesting that it may be involved in inflammatory processes. We therefore investigated the effect of inflammatory stimuli on α-synuclein expression in human macrophages. α-Synuclein mRNA and protein were detected in cultured human macrophages and levels of α-synuclein protein were increased by stimulation with lipopolysaccharide and interleukin-1β in a time- and concentration-dependent manner. Immunofluorescent staining showed that α-synuclein protein was expressed within the cytoplasm and nucleus. Furthermore, α-synuclein immunoreactivity was present in alveolar macrophages from human lung tissues. These findings suggest that the function of α-synuclein is not exclusive to the nervous system and that α-synuclein may play a role in inflammatory processes and immune responses. [ABSTRACT FROM AUTHOR]