Summary auto-generated
This study investigates the synergistic toxicity between Verotoxin 2 (VT2) and lipopolysaccharide (LPS) in mice. Researchers administered various doses of VT2 alone or in combination with LPS to determine mortality rates and examine underlying mechanisms. Results showed that VT2 alone caused dose-dependent lethality, with higher doses producing greater mortality. When LPS was administered after VT2 treatment, significant synergistic effects were observed, with combined treatment producing markedly increased mortality compared to either toxin alone. The study examined serum VT2 concentrations and TNF-α responses at different timepoints. Data indicated that LPS administration timing relative to VT2 exposure critically influenced outcome, with LPS given 9-12 hours post-VT2 producing maximal synergy. The researchers analyzed inflammatory cytokine production and bacterial lipopolysaccharide-induced responses in the context of Shiga toxin exposure. Findings suggest that the combination of Shiga toxin and gram-negative bacterial endotoxin creates a more severe systemic response than either agent independently, likely through enhanced inflammatory mechanisms. This research clarifies the pathogenic interaction between these two toxins relevant to hemolytic uremic syndrome and related infectious diseases.
Key findings
- VT2 alone produced dose-dependent mortality in mice, with higher toxin doses causing progressively greater lethality
- LPS administration after VT2 treatment produced synergistic lethality, with combined toxins far exceeding mortality from either toxin alone
- Timing of LPS administration relative to VT2 exposure was critical, with 9-12 hours post-VT2 producing maximal synergistic effects
- Serum VT2 concentrations and TNF-α inflammatory responses were significantly altered in co-treated animals compared to single-toxin controls
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Abstract
In Escherichia coli O157 infections, verotoxins (VT) play a critical role in causing the disease, although other factors such as lipopolysaccharide (LPS) and inflammatory cytokines may affect the progression and course of the disease. The present study examined the roles of VT and LPS in induction of serum cytokines and lethality in mice. LD50 of VT2 (13 ng) was c. 104-fold smaller than that of LPS (400 µg). Although the lethal toxicity of these toxins was examined in several experimental conditions, such as VT2 (5, 10, 20, 40 ng/mouse) alone or in combination with LPS (100 µg/mouse) at various times (-2 days to +2 days), no evidence of synergy was observed. VT2 did not augment LPS-induced tumour necrosis factor-α (TNF-α) or interleukin-6 production, and conversely suppressed TNF-α production when it was injected 2 days before LPS challenge. The data failed to indicate either synergic or additive effects of VT and LPS on cytokine production or lethality in mice. In contrast, antagonistic interactions were clearly observed in cytokine production in certain conditions. The results suggested that these toxins may be co-operatively involved in the pathology of VT-related diseases, but not through synergic interactions.