Cytokines disrupt intracellular patterns of Parkinson's disease-associated proteins alpha-synuclein, tau and ubiquitin in cultured glial cells

Abstract

The purpose of this study was to determine the effects of specific proinflammatory cytokines interleukin-6 (Il-6), interleukin-1β (Il-1β), interferon-gamma (IFN), and tumor necrosis factor-alpha (TNFα), on content and distribution of alpha-synuclein (α-synuclein), tau and ubiquitin in human derived cultured glial cells. Exposure paradigms mimicked acute (2 h), intermediate (18 h) and prolonged time frames (96 h); consisting of single or repeated low doses (10 ng/ml) or high doses (50 ng/ml), consistent with either mild or serious systemic infectious/inflammatory responses. Images of intracellular protein content and distribution were reconstructed from emission patterns generated by fluorescence deconvolution microscopy. Minor alterations were seen in protein content with IFN; Il-1β decreased α-synuclein and tau at 18 and 96 h; TNFα inversely reduced α-synuclein and increased ubiquitin content. Combinations of Il-1β and IFN produced a robust increase of α-synuclein and tau at 2 h. Consecutive low doses of Il-6 produced only minor increases in α-synuclein and ubiquitin after 4 h, whereas a single high dose resulted in major increases for all three proteins over the first 18 h. Protein localization patterns were distinctly different and were altered dependent upon cytokine treatment. A high dose exposure (2 × 50 ng/ml) with Il-6 and IFN demonstrated that protein increases and dispersals could be sustained and that the normal perinuclear tau and peripheral α-synuclein patterns were disrupted. These results support the postulate that specific cytokines affect temporal protein changes with concomitant pattern disruptions, possibly reflecting a mechanism of cell dysfunction in Parkinson's degeneration.