Infections with
Shiga toxin (Stx)-producing bacteria are associated with bloody
diarrhea and postdiarrheal sequelae, including
hemolytic uremic syndrome and central nervous system (CNS) abnormalities. Stx-induced intestinal, renal, and CNS vascular lesions may involve a localized production of proinflammatory
cytokines in target organs, as
tumor necrosis factor-alpha (
TNF-alpha) and
interleukin-1beta (IL-1beta) up-regulate Stx receptor
globotriaosylceramide (Gb(3)) expression on vascular endothelial cells. However, leukocyte recruitment to injured sites may also exacerbate vascular damage. A
cytokine macroarray analysis of transcripts derived from macrophage-like THP-1 cells treated with Stx1,
lipopolysaccharides (LPS), or both demonstrated a consistent up-regulation of
TNF-alpha, IL-1beta, and four genes encoding the
chemokines interleukin-8 (IL-8), macrophage inflammatory protein-1alpha (MIP-1alpha),
MIP-1beta, and growth-related oncogene beta (GRO-beta). Real-time PCR analysis verified the macroarray results. Northern blot analyses after the addition of the transcriptional inhibitor
actinomycin D revealed increased
IL-8 mRNA stability in THP-1 cells treated with Stx1 or Stx1 plus LPS. Finally,
enzyme-linked
immunosorbent assay data for Stx1- plus LPS-treated cells demonstrated a poor correlation between
IL-8,
MIP-1alpha,
MIP-1beta, and GRO-beta
mRNA levels and
protein production, indicating a posttranscriptional regulatory effect. Our data suggest that in response to Stx1 and LPS, macrophages may be a source of
chemokines that promote tissue damage through leukocyte recruitment and activation.