GLYCITEIN ATTENUATES LPS-INDUCED NEUROINFLAMMATION IN MICROGLIAL CELLS AND SELECTIVELY PROMOTES RESOLUTION-ASSOCIATED IL-10 SECRETION: EVIDENCE FROM A MULTI-CELL-LINE PANEL
Keywords:
GlyciteinAbstract
Background: Glycitein, the 6-methoxy-substituted soybean isoflavone, has been characterized primarily
outside the central nervous system. Its behaviour in microglial cells under inflammatory load remains
poorly defined, despite evidence that soy isoflavones as a class modulate neuroinflammatory pathways
relevant to Alzheimer's disease and related dementias. The present study provides the first systematic
evaluation of glycitein's anti-inflammatory activity in a panel of microglial cell lines. Methods: Cytotoxicity
was profiled in four microglial cell lines — BV-2 (murine), N9 (murine), HAPI (rat), and HMO6 (human) and
one non-neural reference (human dermal fibroblasts, HDF) using MTT and LDH-release assays. Based on
established safe concentration windows, the effect of glycitein pre-treatment (1, 10, and 50 µM; 1 h pre
treatment) on LPS-stimulated (1 µg/mL, 6 h) inflammatory responses was characterized at the transcript
level by qRT-PCR for TNF-α, IL-1β, IL-6, and IL-10, and at the secreted protein level by sandwich ELISA at
24 h. Data were analysed by one-way ANOVA with Tukey's HSD post-hoc correction. Results: Glycitein
was well tolerated in all lines, with cytotoxic IC₅₀ values of 175–260 µM, yielding a therapeutic window
approximately one order of magnitude above the functionally active range. LPS challenge induced 22- to
46-fold elevation of pro-inflammatory cytokine transcripts. Pre-treatment with 50 µM glycitein suppressed
these responses by 67–82% for IL-6, 65–76% for IL-1β, and 67–73% for TNF-α across all four lines (all
comparisons p < 0.001). Concordant suppression was observed at the protein level (62–85% for IL-6, 65
76% for IL-1β, 62–73% for TNF-α at 50 µM). In contrast, glycitein dose-dependently elevated IL-10
transcript 4.5- to 5.5-fold (mouse and rat lines) and 3.9-fold (HMO6) above vehicle, alongside a 3- to 4.7
fold protein-level induction over LPS-only baseline. The divergent direction of effect on pro-inflammatory
versus anti-inflammatory cytokines was conserved across all four lines irrespective of species origin.
Conclusions: Glycitein selectively tilts the microglial cytokine program toward a resolution-favouring
phenotype at concentrations well within its non-cytotoxic window. The consistent IL-10 induction across
species backgrounds argues against generic transcriptional suppression and is consistent with
engagement of an upstream regulatory circuit most plausibly the NF-κB/MAPK axis that biases microglial
polarization. These findings establish a quantitative in vitro baseline for glycitein's microglial pharmacology
and support its candidacy for further mechanistic and translational evaluation in neuroinflammatory
disease models.
KEY WORDS
Glycitein; soy isoflavone; neuroinflammation; microglia; cytokine; IL-10; LPS; NF-κB; BV-2; HAPI
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